US2388666A - Burner control mechanism - Google Patents

Description

Nov. 13, 1945. s. D. BOWER BURNER CONTROL MECHANISM 7 Sheets-Sheet 1 Filed Jan. 27, 1941 NOV. 16, 1945. ow 2,388,666

BURNER CONTROL MECHANISM Filed Jan. 2'7, 1941 7 Sheets-Sheet 2 /A/ Aw/roe: 6E0 REE 0. .80 WEE) Nov. 13, 1945. e. D. BOWER BURNER CONTROL MECHANISM Filed Jan. 27, 1941 7 Sheets-Sheet 3 0 m J 0 IF w w I kQQkQUN 0 0 LU 5 MT 1 I 0 0 m M 0 WT 0 II 0 29% n m 0 a u 0 w w a 0 m 5 9 1 0 r M Q m w w M .0 J v 0 a. L w 0 w L m 4 Lkfim 2 a 9 Nov. 13, 1945. G. D. BOWER 2,388,666

BURNER CONTROL MECHANISM Filed Jan 2'1. 1941 7 Sheets-Sheet 4 OIL COLD 4rroRMe /S.

Nov. 13, 1945.- G. D. BowE R 2,388,666

BURNER CONTROL MECHANISM Filed Jan. 27, 1941 7 Sheets-Sheet 5 I66 62 /45 I 6/ w m 4 .25. we 6Z /20 55c. 1 g M5 5 STACK 5w. Cow K 7 6/ 'L 4 j 0 M0 fl?- /A/l f/VTOE: GEORGE D- .BOWER,

as 67 g wg E HTTam/E K5 v motor operable at a operate Patented Nov. 13, 1945 2,388,666 I BURNER coN'rnoL MECHANISM George D. Bower,

University City, Mo., assignor to Automatic Control Corporation, St. Louis, Mo., a corporation of Delaware Application January 27, 1941, Serial No. 376,127

38 Claims.

The present invention relates to a control mechanism for controlling a heat responsive device, and particularly a burner.

The mechanism includes generally a control given rate, a pair of relays and a plurality of cam switches operated by the motor. The several switches control, with the relays, circuits for the control motor, a burner motor or like device, an ignition device, and a fuel valve or like device.

The switches are arranged to provide a cycle, and they include a space or room thermostat with an instituting circuit, whereby the heatchange device is set into operation in'response to operation of the thermostat. The cycle includes a starting phase, a running phase, a scavenging phase, .and a lock-out phase adapted to upon failure of the starting phase to institute operation of the heat-change device.

In the starting phase, the mechanism is first under direct control of the room thermostat through the instituting circuit, and is designed to operate through a predetermined cycle if the thermostat remains closed a brief interval sufilcient to get the cycle under way by establishing holding circuits cuit. Thereafter, the complete starting cycle will be performed, regardless of displacement of the room thermostat, at the end of which the mechanism returns to control of the room thermostat for a running period. During the running period the control motor is inactive, but upon satisfying of the room thermostat, the mechanism may take up where it left off, at the end of the starting cycle, complete a closing or scavenging cycle, and be ready for a subsequent operation.

, In the starting-cycle the burner motor and control motor first begin, followed by the ignition device, and the oil supply device, with an added 011 pre-heating control interposed.-

It the starting cycle fails to cause proper operation, the lock-out circuit will operate, but

shunting the instituting cironly after an intervening. scavenging period; andthe mechanism will move to a position requiring manual reset for further operation.

If the power fails at the outset of the starting cycle, while the instituting circuit is closed, there will be merely an interruption thereof. If it fails after the-starting cycle holdingcircuit is established, upon restoration of power the mechanism will run through the interval of a complete cycle including scavenging without the fuel line open, and reinstitute the. starting phase, de

pendent upon the condition of the room thermo-.

stat when the mechanism attains the new startmg position. If power fails during the running period, upon return of power the mechanism will complete a scave ging p riod and reinstitute a starting cycle, again dependent upon the then condition of the room thermostat. If power fails during a scavenging period, upon return of ower, it will complete the scavenging period.

' Ii. ignition falls during the starting phase, the results are as above. If ignition, or flame, falls during a running period, as by breaking oi the fuel supply, the mechanism will then complete a scavenging period, by restart of the control motor, at the end of which it may reinstitute a starting cycle. If the failure was due merely to an extinguishing of the flame-or other temporary dislocation, the starting cycle, may reestablish operation. If, however, the failure is not remedied, ignition will not take place during the new starting cycle and the lock-out cycle will operate these conditions consisted of a failure to ignite at the end of an ignition or starting period, the lock-out mechanism will operate. Under all other conditions, the lock-out mechanism will not operate, and the mechanism will reinstitute a new starting cycle and automatically determine whether the failure has been corrected or can be corrected by re-ignition.

The objects of the invention are to obtain each of the above functions, severally or in combina. tion. It is a further object to accomplish the same in a relatively simple mechanism.

It is a further object to provide a manual reset device that is operated by movement to establish its circuits, but which is ineffective to alter any circuits after it has been moved, so that holding it in operating condition has no effect. More particularly, it is an object to provide a reset mechanism giving a. limited displacement of thecontrol motor cams to reset the mechanism in a desired position, wherefrom it automatically operates.

Additional objects will appear from the description to follow, with especial reference to the explanations of the operations produced by the front of the partition wall are switches, to be described.

The control motor 84 is attached to a plate or bracket 18 that is spaced somewhat from the partition wall, but is secured thereto. This plate nonrotatably supports a reset shaft II having at the end thereof a knob 12 that may rotatea limited distance, as will be described. This knob has a leaf spring I3 projecting from the back face thereof and adapted at times to register with a button I4 on the front cam. When the button drops in front of the edge of the leaf spring 18 the knob 12 may be turned counterclockwise a suflicient distance to displace the front cam and the remaining cams with it an angular distance adequate for resetting of the device, as will be described.

There are three cams I8, 11, and I8 secured in a plurality of cam spaced relation and nonrotatably mounted on the cam shaft 81. The cam sh'aft, in turn, rotates on the reset shaft-II. At its rear end between the partion wall 48 and the plate 18 it has formed on it a ratchet wheel 18. This ratchet wheel is engaged by a ratchet dog 88 (Figs. 4 and 5), spring urged into contact, and pivotally mounted on a gear 8| set within an opening in the partition wall and rotatably'on the cam shaft. A guard sheet 82 is also mounted on the cam shaft to protect the gear 8| and to cover the opening.

The gear 8I meshes with the pinion 88 that is rotated by the control motor 84. Rotation ofthe pinion 83 in forward direction causes rotation of the gear 8| and correspondingly rotation of the ratchet wheel I8 through the ratch'et dog 88 and with it the cams. The ratchet permits rotation of the cams in the forward direction, independently of the gears and motor.

I Cam switches these switches are mounted between the brackets switch 8|. Thereafter, it will ride onto the lobe 88 to produce a maximum displacement in which the switch 88 first closes, and then the switch 82 opens. Subsequently, the follower falls to the edge 81 in which the switch 82 closes, the switches 8| and 83 remaining closed. when the follower 84 subsequently falls to the edge 88, the switch 88 will open, the other two remaining closed.

The middle cam I1 (Fig. 9) has an outer edge II8 followed by a deep notch HI, after which occurs a low edge II2 followed by another deep notch I I8. Th'e notch H3 i followed by an edge II4 corresponding to the edge I I2 which, in turn, is followed by a medium edge I I8 which terminates in the edge II 8. Thiscam operates switches I I7, I I8 and H8.

It has a cam follower I28 having on it a contact I2I adapted to engage with the contact I22 on a spring blade I23 to form the switch I". A stop blade I24 limits the movement of the sprin blade I23 toward the cam.

The blade I23 has an additional contact I28 adapted to close with a contact IT! on a spring blade I28 to form the switch II8. A stop blade I28 limits the movement of the blade'l28 toward the cam. A spacer member I38 is disposed between the blade I28 and a spring blade I8I to cause them to move together. The blade I3I has a contact I32 adapted to register with the contact I83 on a, spring blade I34 to form the switch II8. A stop member I38 limits the movement of the blad I34 towards the cam.

When the follower I28 is within the deep notch II3 all of the switches are open. When the cam rotates counterclockwise lifting the follower I21 into the edge II4, this closes the switch I". Thereafter, when the follower rides onto the higher edge II8, it closes the switch II8. Subsequently, when it rides onto the high edge I I8, it

40 closes the switch- I I8 so that all of the switches 84 and 88 secured to the front of the partition wall 48. Suitable blocks of insulation separate the several switches and each has its switch blades projecting back of the blocks to provide terminal. posts.

The front cam," (Fig. 8) has an edge 81, a lower edge 88, a notch 88 and a lobe 88. There are three switches actuated by this cam. They are generally indicated at 8|, 82, and 83. There is a cam follower arm 84 having-s. contact 88 cooperating with an additional contact 88 on a spring arm 81 to form the switch 8|. A suitable stop blade 88 limits the movement of the spring arm 81 toward the cam.

A spacer member 88 secured between the spring arm 81 andanother spring. arm III will cause them to move together. The spring arm I88 has a first contact I8I adapted to engage with a contact I82 on a spring blade I 88 to form the switch 82. A stop blade I84 limits the movement of the spring arm I88 in its movement away from the cam.

The spring arm I 88 has an additional contact I88 adapted to engage with contact I88 on a spring arm I8'I to form the switch 88. The spring arm.|8| is limited in its movement toward the cam by a stop blade I88.

Inv the position shown in Fig. 8, the cam follower 84 is in the notch 88'so that theswitch 8| is open, the switch 82 is closed, and the switch 88 is open. As the cam rotates counterclockwi e, the follower arm 84 will be lifted first to close the will close. Thereafter; when the follower drops into the deep notch III all three switches open. Subsequently the edge II 2 will lift the cam follower I28 to close the switch III which remains closed until it is opened by the arm I28s dropping into the deep notch I I8.

The rear cam I8 (Fig. 10) has a lobe I48 followed by a, low edge I terminating in a notch I42. The-notch is followedby a low edge I48 corresponding to the edge I 4|; and the edge I48 is followed by a high edge I44 which extends to the lobe I48. This cam operates four switches, 8,148, I41 and I48.

There is a cam follower arm I88 having a contact I8I adapted to engage with a contact I82 on" a spring blade I88 to form the switch I48. A stop blade I84 limits movement of the blade I88 away from the cam.

The follower arm I88 has a spacer member I88 connecting it to the spring blade I81 so that they move together. The spring blade I81 has a contact I 88 adapted to engage with the contact I 88 to form the switch I48. The contact I88 is mounted upon a spring blade I 88, movement of A stop blade iii limits movement oi the blade are toward the cam.

With the follower use on the edge it i as shown, switches i 35. Ml and M8 will open and the switch M8 is closed. When the follower drops into the notch M2, the switch Mt opens and the switch its closes. Thereafter, when the follower rides onto the edge M33 the switch 9 115 is again cod, and the switch 6% closes. Subsequently, when the cam follower rides on the edge Md it additionally closes the switch. Ml. Subsequently, when the lobe Mill. lifts the follower arm ihil it further closes the switch i 33. Thereafter, the follower drops to the edge i i-i opeg the switches it? and M8, but keeping the switch its closed.

External mechanisms and connections The mechanism is adapted for use with a room 7 thermostat, an oil supply device such as a solenoid valve in the oil line, an ignition producing device and a burner device such as a blower jmo'tor, or the like. Two of the terminals, such as 59 and 6d. are connected to the room thermo= stat, two others, such as St and G2, are the two power line terminals. One of the terminals, such as 63, is connected to one lead from the oil supply valve, the other lead irom which is connected to the other power line, such as by way of the terminal 82. Another terminal, such as 6 3, is con nected to the ignition device, the other lead from which is brought from the power line such as by way of the terminal 62. Another terminal, such as the one 65, receives one lead from the burner motor, the other lead from which is carried to the power line as by way oi the terminal 82. The two remaining terminals such as so and 81 are connected to an additional control, such as an oil pro-heating means.

The particular arrangement of the terminals is not important provided the connections are in accord with the wiring diagram; In Fig. 40, one powgr line terminal is shown at at and the other at Internal connections The relay 55 and the relay to are similar.

.- The relay 55 has a coil sac operating on one double-acting armature ml, which is closed with the contact I82 when the coil ltd is deenergized.

' Upon energization of the coil, the armature Edi V gized; opens a switch new and closes a switch i853. It also opens a switch we when energized. When not energized, the coil ltd releases the switches i8? and are into closed mitlon.

One terminal of the switch ME) leads to the power line 6i. The other terminal is connected with the switch Bal with the switch its and one terminal 59 of the room thermostat. The other terminal to of the room thermostat is connected with one terminal of the switch oil, with the relay coil 580, and with the switch ill. The other end of the coil ltd leads to the other teal 62 and thence to the power line. The other lead from the coil 5% extends to the term 62.

The armature switch blade 66B is connected with the power line terminal at.

The contact 983 of the flrstrelay is connected with one side of the switch at and also with one side of the switch BM operated by the first relay aseaece and thence with the other power line, as at $2.

The contact i82 of the relay switch M35 is connected with one side of the switch M6, the other side of which is, in turn, connected with the other side of the switch ill, with the burnermo: tor terminal 65, and also with one side of each of the switches A89 and H9. The other sides of each of the switches E89 and M8 are likewise connected together and to one side of each of the switches 92 and S3, and to the to a: a1 I36 for the oil pie-heating mechanism. The switch as leads to the ignition mechanism teal 5d and thence to the terminal $2. The switch 92 is connected at its other sidewith the other terminal El 0f the pro-heating mechanism, and with the control motor which, in turn, is connected to the terminaltfi.

The manual reset The reset knob l2, as shown in Figs. 11-44, has an axial opening. therein by which it fits rotatably over the shaft 1!. This opening onlarges into a chamber receiving the operating mechanism. I

Within the chamber there is a flanged disc iQB having a notch i9! '(Fig. l2).in one edge thereof. A torsion spring H92 is anchored at one end in the disc we, and at the other end in a second flanged disc M3 at thebottom of the chamber. The second disc is nonrotatably mounted on the shaft H by fitting over a fiat I98 thereon. The

flange of the second disc W3 is cut away as at wall of the chamber by a screw E98. This key engages with low tolerance in the notch 59E of the disc IQQ, and engages also in the larger notch I of the second disc fist.

An expander segmental ring I99 engages in a groove in the knob to hold the upper disc in place in the chamber. A second contractile spring its engages around the shaft outside of the disc We to hold the knob assembly on the shaft.

The shaft H is nonrotatably mounted on the partition. The knob may be turned counterclockwise on the shaft. In this, the key i9? canries the disc ltd while the shaft holds the disc W3, causing the normal clockwise torsion of the spring I92 to be increased. The key moves in the notch ace 'until it strikes the counterclockwise end thereof, whereupon further movement is prevented. Upon release of the knob, the spring returns it to its first position.

A can 2cm closes the chamber.

Additional connections As shown in Fig. 40, a limit switch L may be inserted between the lead from the switch I85 and the switches ass and 9!. This location has advantages to be pointed out, A limit switch may be located in one power line, as at L2, which will have results to be pointed out.

As shown in Fig. 41, a slight change in the connections avoids even the potential hazard of carelessly connecting the igniter to the oil valve terminal to and the oil valve to the terminal cc. Such misconnection in the circuit of Fig. 40 would result in supplying oil prior to operation ottheigniter', I i

In Fig. 41, the terminal 84 is not connected with the control motor circuit, but is connected by two parallel circuits with the terminal 88. These circuits include two switches 88 and 288. The switch 88 provides intermittent ignition controlled as shown in the diagram of Fig. 15. The switch 288 is a screw contact switch that, when turned down, shunts the switch 88 for constant ignition, and when turned up, leaves control under the intermittent switch 88.

OPERATION At the start (Fig. 40) the switches I45, 8|, and 82 are the only cam switches closed (see Fig. This is a position represented by rotation of the cams, as shown in Figs. 8, 9, and 10, a short distance counterclockwise, the distance being such as to cause the follower arm 84 (Fig. 8) to ride out of the notch 88 into the short edge immediately preceding the lobe 80; to cause the follower I (Fig. 9) to be in more or less the middle of the notch H8, and to drop the follower arm I80 (Fig. 10) into the notch I42. At this time, the stack switch 80 is cold and hence open, as a consequence of which the coil I88 is deenergized, the switches I81 and I88 are closed, and the switch I88 is opened. The coil I80 is deenergized owing to the fact that the room thermostat T is open and the switcif I I1v is open. With this coil deenergized, the switch IN is closed against the contact I82 and the switch I84 is open.

Normal cycling: Starting If the room thermostat closes demanding heat, an instituting circuit is established, as shown in Fig. 16. This circuit extends from the terminal 8! through switch I45, the room thermostat T, and the coil I80 to the terminal 82. The results from energizing the coil I88 are shown in Fig. 1'7. The coil closes the switch I8I against the is also established a circuit to the control motor through the switch I88, switch 8i, and switch I88 (dependent upon a cold stack), switch 82 and the control motor to the terminal 82. There is further established a similar circuit to the burner motor as is clear from Fig. 17. These two devices then begin to operate, the burner motor without fuel.

After the lapse of about 3 seconds, as shown in Fig. 18, the switches H1 and 83 close. The previous circuits remain as described. Closing of the switch II1, however, shunts out the room thermostat and the stack switch as controls for the coil I88 by establishing a starting cycle holding circuit from the terminal 8|, switch I88, switch I84, switch H1 and the coil I80 to the terminal 62. The coil I80 is thereafter held in circuit as long as power continues, independently of the instituting circuit through the switch I45 and the thermostat, but dependent upon continuous power because of the power failure relay switch I84. Closing of the switch 83 puts the ignition device in circuit in parallel with the control motor and the switch 82. Ignition, however, does not take place because the oil supply means or valve is not in operation.

' I48 cannot be simultaneously closed.

power failure during the closure of the insti- After the lapse of 5 seconds, the cycle changes if the oil is not heated, as represented in Fig. 19. At this time, the. coil I88 remains energized through its three difierent circuits. The ignition mechanism continues in operation as before, but the switch 82 opens. An alternate circuit around the switch 82 is provided through the oil pro-heating control mechanism A. If the oil is cold, the pre-heating mechanism opens this alternate circuit and the control motor stops. The ignition mechanism and the burner motor continue in circuit until the oil is heated and the alternate circuit through the pro-heating mechanism is closed by the mechanism A. Hence, the cycle remains static for this interval if the oil is cold.

The condition when the oil is adequately heated at the 5 second point is represented in Fig. 20. In it. the circuits established as shown in Fig. 19, remain but the mechanism A again closes the circuit to the control motor through the alternate circuit shunting the switch 82. The control motor then again operates to continue the cycle. It will beclear that if the oil is hot the control will not stop upon opening of the switch 82.

After the lapse of 10 seconds (Fig. 21), (omitting whatever intermission may have occurred because of cold oil),.the switch I45 opens and the switches I48, H8, and 92 close. Opening the switch I 45 opens the instituting circuit, which'remains open until the beginning of a new cycle, to prevent fortuitous reenergization of the coils I80 or I88 once deenergized, and leaves the coil I80 dependent upon its two circuits through its own switches I 8I and I84, one of which circuits includes the switch I81 and the room thermostat, the other of which includes the switch I". Closing of theswitch II8 has no immediate effect. Reclosing of the switch 82 shunts out the oil temperature control mechanism and holds the control motor circuit independently thereof. Closing of the switch I48 cocks a scavenging circuit, but has no immediate efiect since the. switch Ill is not closed with the contact I82. It will be forecast, however, that the scavenging circuit and the instituting circuit cannot both be energized at once, since the switches I48 and Upon tuting circuit, there will be no following scavenging operation commencing upon restoration of power, as will be explained.

After the lapse of 20 seconds, as shown in Fig. 22, the switch II8 closes. This produces no immediate change, but provides a circuit for the control motor and ignition mechanism independently of the switch I88 and, hence, independently of the stack switch that controls the coil I88. Whereas hitherto the control motor operation has been dependent upon lack of ignition, it may be held in circuit upon closure of this switch II 8,

even though ignition occurs.

After the lapse of 30 seconds, as shown In Fig. 23, the switch I41 closes. The other cir cuits to the igniter, the control motor, and the burner motor remain as'in Fig. 22. However, the oil supply control is energized through the now closed switch I41, the circuit being switch I83, switch I84, switch II8, switch I41, the oil control to the other power line. This oil control may be a solenoid valve, or the like, through which oil is supplied to the burner. Ignition may thereafter occur.

when ignition occurs. the circuit changes as thermostat.

shown in Fig. 2d. Ignition almost instantly produces a shifting of the stack switch 59 to closed v position. This puts the second relay coil use in circuit in parallel with the coil 58d. Upon energizetion of the coil use, the switch lfil opens, the switch N38 is closed and the switch l89 opens.

Opening the switch it? breaks the circuit to the two coils 58d and see through the room However, the coils remain energized through the switch ill. Qlosing the switch its establishes an alternate circuit to the oil supply mechanism in parallel with the switch i it, this circuit being dependent upon continued ignition. Opening the switch 8% leaves the circuit to the igniter end to the control motor dependent upon the switch its.

Aiterthe lapse of 115 seconds, as shown in Fig. 25, the switch i458 'closesf This is the running period holding switch for the coils 98d and ass, sud provides an additional circuit for the coils itld and E86 as follows: switch E53, switch loll, switch ltd, switch M8, the room thermostat, through both of the coils to the other terminal. Itwill be seen that this circuit is dependent upon continuation of combustion to hold the switch to closed end, in turn, to hold the switch 588 closed. It-likewise puts the two coils back into dependence upon the room thermostat. It will be ob served that all of these circuits through the switch ass are dependent upon continuation of power, because they are dependent upon the holding circuit through the switch i8 3 which opens upon failure of power. The mechanism is thus cocked for the running period, since it is y in position to be mode d p t up the oom thermostat.

Running period switch t3 cuts the ignition device out of circuit,

regardless oi the control motor. The burner motor continues to operate.

This is the ing period. At this time, the

. circuits ere dependent upon continued combustion and continued power, which will he explained.

They are also dependent upon the condition of the room thermostat. The control motor is inoperetive, so that the cycle stops until the room thermostat opens or until-flame failure, or power failure.

Scocenging period and opens, the circuit becomes as shown in Fig. 27. It will be remembered that in the running p riod the only circuits to the two coils ore through the roomthermostat. At the instant of pening of the thermostat, the switch 5d will he closed because the heat of combustion is still presout. However, the coil ltd is instantly deenersized shifting the switch ltl against the contact I82 and opening the switch 185. Shifting of the switch it! to the contact E82 (known as switch it?) closes the circuit through the switch kid and holds the burner motor in circuit. However, the oil supply is cut ed and dome will stop.

lit the instent the room thermostat is satisfied starting period, a

essence Deenerglzetion or the coil ltd causes the switches l8? and ass to close and the switch use to open. This operation of the switches 88? and 588 has no efiect, their circuits being otherwise broken. Closing the switch H89, however, reestablishcs the circuit to the control motorthrough the switch E82, switch tilt, switch its, switch 92 to the control motor, this circuit being designated as the scavenging circuit. It will be remembered that the switch 88 is opened st the beginning of the running period, so that the ignition mechanism is not in circuit. The burner motor is in circuit to purge the furnace and connections of residual fuel. A very short time after stopping of the flame, as shown in-Fig'. 28, the stack unit cools, opening the switch 583, with no additional effect.

After 123 seconds. as shown in Fig. 29, the switch ill recloses. This has no effect on the cycle at this point. The three second son for the running period in operotion of the switch M1 is adequate to accommodate cossting oi the control motor after its deenergizstion without reclosins the switch Ml.

Thereafter, after 125 seconds, the switches lei and Mid open as shown in Fig. 30. These have no efiect on the normal cycle but heel to be clwed throughout the running period. After 175 seconds, as shown in Fig. 31, the lock-out switch 9! opens. This has no efifect on the normal cycle. After shout 178 seconds, as shown in Fig. es, the switch i ll reopens. has no edect on the normal cycle. After about 181 seconds, as shown in Fig. 33, the switch 9i recloses. This has no efiect on the normal cycle.

After about 185.5 seconds, as shown in Fig. 34, the switch use opens and the switch 665 recloses. This is the starting position as closing the switch led reestoblishes the instituting circuit-to the coil its dependent upon the room thermostat, and

opening the switch ll'dibreelrs ell circuits to the control motor and the burner motor.

L ck-mot It will be seen from the foregoing that there-is e r 11 period, and a scaven ing period. It will now be shown how the lockout mechanism operates.

Fig. 2d discloses the condition at the time ignition takes place and Fig. 25 shows the arrangement with ignition after expiration of 115 seconds.

The absence of ignition at 115 seconds is shown in Fig. 35. The switch its closes to estoblish the circuit through the room thermostat to the coil hi9 and also to establish an alternate circuit to the oil supply device, but the failure of the switch 593 to close prevents energizationoi the coil I186,

as a consequence of which the switch it? end the switch we remain closed end the switch 598 remains open. It will be seen that the circuits are cocked at this time for holding both the coil not and the control motor upon the subsequent opening of'the switches fill, M8. and M Likewise, the fact that the switch 988 remains open predicts the condition of the oil supply upon opening of the switch H8.

. With no ignition, the conditions at seconds ere shown in Fig. 36, which is the normal point for starting the running period. The switches ill, lid, li,'and Q3 own. The coil 5% is held in circuit through the switch 888, the switch its, the switch it? and the room thermostat. The oil supply remains in circuit, by being put across the room thermostat end the coil use through the switches Hill and mi. The control motor reaasaeoo the parallel switch II! opens. Opening of the switch 98 disconnects the igniter and the burner motor remains in circuit.

After 123 seconds, with no ignition, as shown in Fig. 3'7, the switch I" recloses reestablishing a holding circuit of the coil I88 independent of the room thermostat. The other circuits remain unchanged.

After 125 seconds, with no ignition, as shown in Fig, 38, the switches I41 and I48 open. Opening these switches breaks the circuits to the oil supply. The remaining circuits are not changed.

After 175 seconds, with no ignition, as shown in Fig. 39, the switch 8| opens. This breaks the circuit to the control motor and to the burner motor. The cycle, therefore, stops with the coil I88 held energized. Manual reset is required to reestablish the circuits.

the knob 12 counterclockwise as far as it will go;

The mechanism, as shown in Figs, 1 10, is in the lock-out position. The button H on the front cam 18 has just passed under the leaf spring 13 and is immediately in front thereof. Hence, rotation of the knob displaces the cams counterclockwise under the ratchet an angular maximum distance just sufficient to return the control motor switches to starting position. Release of the knob permits it to return to its original position under the influence of its spring. Further cycling will then depend upon the condition of the room thermostat.

1 It may be noted that if the manual reset is operated only partially to starting position, so as to reclose the switch 8|, the switch II! will ,be opened, causing the relay switch I83 to break and I8: to make, and establishing the scavenging circuit to return the mechanism to starting position, the coil Ill will be cut out of circuit, opening the switch I88 and shifting the switch I8I into contact with the contact I82. This will then institute the scavenging cycle represented by Figs. 28-34 inclusive, so that the mechanism returns to its starting position and will automatically recycle again upon demand by the thermostat.

It will be observed that during the lock-out period, the switch II! is closed, holding the coil I88 independently of the thermostat.

Flame failure If the flame fails during the running period, as shown in Fig. 26, the switch 80 will open deenergizing the, coil I88. This will close the switch I81 and open the switch I88. Thi will be an adequate break to release the coil I80 with the resultant opening of the switch I84 and shifting of the switch IN to the contact I82. When this occurs, the result is the same as opening of the room thermostat, and the mechanism cycles out its scavenging period and returns to its start.

Power failure Power failure at any time immediately releases the two coils. If this failure occurs during the first 10 seconds when the switch 145 is closed,

restoration of power will merely re-institute the tion. The switch II'I must break not later than opening of the switch I, as otherwise the switch I48 will not determine the starting position. On the other hand, the switch I" must hold beyond the lock-out opening of the switch 9|, in order to hold the switch I88 away from the scavenging circuit.

Fortuitous shift of the room thermostat There are only two periods in which fortuitous action of the room thermostat can have any effect. These periods are at the start and at the interval between 120 and 123 seconds, which is normally the running period, but which may come during a prelude to a lock-out.

If the room thermostat opens prior to the closure of the switch III, the mechanism will stop but will be fully prepared to start again when the thermostat recloses, and will continue the cycle. Of course, after the switch II! is closed, it is immaterial whether or not the room thermostat changes its position. If the thermostat, however, is open at the beginning of the running period, the result will be merely a completion of the cycle through the scavenging period and the return to the start. If the room thermostat opens and then recloses during the running period, the mechanism will nevertheless, upon opening, cycle through the scavenging period and ed in Fig. 35, but where there has been no ignicycle because the coil will be reenergized through the switch I 45.

If power fails thereafter, as shown in Fig. 21, the coil I will release the switch I84 to open so that the coil I88 is not subject to reenergizing. However, by this time the switch I46 is closed so that the switch I8l, upon shifting to the contact I82, establishes circuits to the control motor and to the burner motor and to the igniter which may function as in a normal starting cycle, but without oil. When the cycle reaches the running period, after seconds, it passes directly across the running period and continues with the scavenging'period, ultimately returning to the start.

In this, it is immaterial whether or not any igni-- tion has occurred, as by residual oil, as the two coils I88 and I88 cannot be energized. Note that by closing the switch I at the time switch I45 opens, a scavenging period is assured after any flame or power failure when the instituting circuit is open, whereas power failure prior to opening of switch N5 is automatically remedied upon restoration of power.

If there is power failure during the running period, the effect is the same as if the room thermostat were to open. Upon restoration of power, the mechanism cycles through the scavenging period and then restarts.

Upon power failure and restoration during the scavenging period, the mechanism starts where it left off before failure.

It will be seen that, after every possible c5 cle, whether normal or after power failure or after flame failure, there is a scavenging period insuring the complete discharge of all unconsumed fuel.

Likewise, it may be observed that, although the lookout does not come until the end of the scavenging period, whether it will occur is predetermined at the end of the starting period. In other words, whether or not the mechanism will operate into th lock-out position after seconds or whether it will return to the starting position after 175 seconds is predetermined at the end of 120 seconds, and lock-out follows only hing period.

Other abnormal operations If the switch to sticks in open position, a lockout will result, as the result is the same as a failure of ignition. Ifthe switch t sticks in hot position and fails to open, at the end of a running period the mechanism will nevertheless cycle out its scavenging period because the relays are otherwise deenergized. However, recycling cannot take place thereafter, as the relay i855 will-be energized immediately upon establishing the instituting circuit, causing the switch 989 to open and, since the switch H9 is open at the start, the control motor cannot start. Under this condition, the burner motor will operate without ignition or oil,

Likewise, if the relay ltd sticks in hot position during a running period, at the end of the running the controlmotor cannot restart owing to its dependency at that time upon the switch its. Hence, the burner motor will operate without oil. Lock-out will follow its sticking in cold position.'

essence open the switch 589, and prevent operation of the control motor, until the unit does cool. The device will be held only in starting position However, for the unit to require any such time for coolingis grossly abnormal for the present stack unit.

If the room. thermostat opens and quickly re closes during a running period, the relay use will nevertheless open the switch 886' and begin a scavenging period. If the relay 58d switches stick, or fail closed, and theroom thermostat recloses prior to cooling of the switch 51d, and

If the relay switch ltd sticks in open position,

no start can occur, because the control motor circuit is dependent upon its assuming its closed position. If it sticks in closed position during a running period, upon opening of the thermostat the scavenging circuit cannotbe instituted, as it depends upon the switch blade ltfl in open. position against contact 582. But breaking of the room thermostat will deenergize the coil E86, opening the switches H88 and are and closing the switch E87. The oil valve circuit will then be closed through switches 33, E86, 83?, M8 and Bill. But the control motor will again start, upon closing of the switch W9, with the result that shortly the switches i i? and 8 5% will open to break the oil valve circuit. Thereafter, with the look-out circuits m3, Ql, ltd closed, the mechanism will proceed to lock-out. If power fails with the switch 59 stuck closed, after ignition has occurred, upon restoration the mechanism will cycle out to starting period, since the switch is out of circuit by opening of the switch i853. Thereafter, as above, no new cycle can start.

If power fails after ignition with the relay switches ass stuck in hot position, upon its restoration the mechanism will cycle as long as the switch H9 is closed, and when that switch is open the burner motor will operate without oil.

If power falls during the starting period and the relay switch 588 sticks closed, upon its restorshop, the mechanism will resume its cycle, and reach either the running period or the loch=out, depending on ignition. And, if a running period occurs, it will nevertheless be followed by a lockout, as above. 1

If the relay iBtlsticks in lock-out position, upon manual reset, the switch l lli will be shunted, and by recycling immediately upon closing of the room thermostat, the mechanism will cycle to a running period, if ignition occurs, and ultimately to a relock-out whether or not ignition occurs.

By virtue of deenergizing the relay lab at the end of a running period, rendering the position nine out the scavenging period is concerned, that period is not interrupted by any pause to cool the prior to flame failure, the running period will continue. If" flame failure has occurred, the switch 56 will very shortly open, and a lockout circuit will be established.

If the room thermostat fails closed during a running period, the mechanism will run on the limit switch L (see Fig. d0). When the limit switch once opens, it deenergizes the relay coils, and opens their switches. Its location permits the mechanismto continue the scavenging cycle, and to restart after cooling of the limit switch. In fact, whenever the burner runs on the limit switch, it. will do so only'once for each cycle. If the'limit switch remains hot at the beginning of a subsequent cycle, upon opening of the instituting circuit switch 955, and the simultaneous closing of the scavenging switch see, the mechanism. will cycle through the scavenging operation and return to starting position.

if the limit switch be located at is (rig. to),

the relays will open when it does, but continued cycling will await cooling of the limit switch, whereupon the mechanism will cycle out through the scavenging period and restart.

Of course, the normal operation oi the limit switch, with-the thermostat closed, is substantially the same as above.

The length of the cycle may be varied as may be'the individual durations or the several phases of the switch 50 inconsequential so far as runproviding only that the cycle itself be not changed. Widening or narrowing the cycle is a matter of changing the ratio of the gears di and 83. The mechanism can be used with'any kind of fuel to be ignited, such as gas. The oiisupply control may be merged into the burner motor, or the burner motor may be merged into the oil supply mechanism, at the sacrifice of certain obvious advantages of the present arrangement.

:It is not essential that there be an igniter in the cycle, because it will have value where other ignition means, such as a pilot light, is used.

Operation of Fig. 41

supply circuit, even crossing the leads from the.

igniter and oil supply will not create a hazardous condition. If the oil supply be connected to tab minal 6d, and the igniter to the terminal 63, the result will only be that oil will stop upon estab= lishment of a running period, and there will resuit a failure of ignition, followed by scavenging out and recycling. No danger inheres in this operation.

What is claimed is:

- 1. In a mechanism of the kind described for ginning of the running period to a position of inoperation short of starting position, and means responsive to existence of the flame to select which circuit is effective, and means dependent upon the control devices being in starting position for instituting operation of the same.

2. In a mechanism of the kind described for use with a burner device, a fuel supp y means therefor, an ignition means therefor, and a space thermostat responsive to the heat produced thereby, the combination of a control device for effecting sequential operations, means operable under control of the control device to cause operation of the fuel supply means upon closing of the thermostat, means under control of the control device for effecting operation of the ignition means, means including the control device for holding the fuel supply mean's and ignition means in operation for a predetermined period independently of the thermostat, means including the .control device for returning the fuel supply means to control by the thermostat after the period, a means including the control device op-. erated upon opening of the thermostat to hold the fuel supply means inoperative for a period after opening of the thermostat, and means to lock the mechanism out at the end of said lastnamed period upon failure of ignition to be effective at the time the burner device is returned to control by the thermostat.

3. In a mechanism of the kind described for use with a burner, a pair of power operated relays, a control device to effect sequential operations, a thermostat, a burner device for producing predetermined flame conditions at the burner,

means responsive to flame conditions produced by the burner device to control the second relay.

means including the control device and the first including the control device for effecting operation of the fuel pre-heating device, said pre-heating device being adapted to prevent operation of the control device until the fuel attains a desired temperature, a switch means operated upon existence of flame, and adapted to render the control device inoperative, means including the control device for rendering the mechanism subject to control of the thermostat when ignition occurs, said means including means to hold the air supply device in operation as well as means to hold the fuel device in operation, means Operated upon change of the thermostat to shut oif the fuel supply means and to restart the control device, and means including the control device to continue operation of the air supply device for a period after the flame has ceased to exist.

5. In a mechanism of the kind described for use with a burner mechanism, a control device providing a plurality of operations of the burner mechanism, an instituting circuit for causing starting of the control device into operation, circuit means including a self-holding relay and circuit for holding the control device in operation independently of the instituting circuit, circuits controlled by said control device establishing a starting interval to cause ignition of the burner mechanism, and a running interval during which combustion exists, and means to open the instituting circuit prior to the end of the starting interval, and said relay being adapted to control said circuits providing the starting and running intervals after said instituting circuit opens, and means operated upon release of the relay during either the starting or the running interval to prevent unlimited operation of the burner mechanism.

6. In a mechanism of the kind described, a burner mechanism, a control for the burner mechanism comprising a space thermostatic means to control the operation thereof, said means being relay to start operation of the burner device,

means under control of the control device to cause operation of itself and to maintain the burner device for predetermined, limited intervals, regardless of the operating position of the first or second relay, and means operated by the second relay adapted to stop operation of the control device after one such interval when the flame conditions at the burner are at the predetermined condition.

4. In a mechanism of the kind described, a conrol device for effecting sequential operation, a fuel supply device, an air supply means, an ignition means, and a fuel pre-heating device, a space thermostat, means including the thermostat and the control device for causing the control device and the air supply device to begin operation, means for holding said operation after it starts independently of the thermostat, said control device being adaptedto cause operation of the ignition device, control device to cause operation of the fuel supply means, whereby ignition may occur. means movable to an operative position in response to demand for heat from the burner, means including a circuit adapted to be established through said thermostatic means in operative position to effect a running period of operation of the burner mechanism, means providing an operation after the running period to return the control to starting position, and means to cause the last-named means to function even if the thermostatic means remains in operative position, together with means preventing recycling by the control until the thermostatic means leaves its operative position.

'1. In a mechanism of the kind described, a fuel supply device, a space thermostatic means operable in response to demand for heat in the space, a relay controlled by said means in turn to control the operation of the fuel supply device, said relay having a switch movable to operating position, means to effect a cycling operation of the fuel supply device, comprising circuit means providing a running period of operation for the fuel supply device, through the relay switch in operating position, means providing a cycling operation after the running period, means to prevent operation of the fuel supply device if the relay switch sticks in operating position after a use with a burner mechanism including fuel supplying means, and a space thermostat, the combination ofa relay switch adapted to be connected burner mechanism, a cycling control including means providing a running period therefor, means providing a scavenging period therefor after the running period, means providing a lockout adapted to follow the scavenging period, said running period means comprising burner mechanism energizing means, including a control switch operable to running position, said energizing means being rendered effective by operation of the control switch into running position,

and .means causing the lock-out means to be effective if the control switch sticks in running position after a running period.

10. In a mechanism of the kind described, a burner mechanism, cycling control means including a thermostat subject to fortuitous displacement, switches in said control means operated by the thermostat on closing thereof, said switches being adapted to be opened if the thermostat opens, means including the thermostat in cold position and said switches closed upon closing of the thermostat to provide a running period for the burner mechanism, and means to prevent reoperation of the burner mechanism if the ther- I mostat is opened during the running period but the switches stick closed.

11. In a mechanism of the kind described for use with a fuel supply device, a cycling control therefor including a motor and a plurality of sequentially operated switches operated thereby, said control being adapted to establish a, circuit for the device including certain of said switches to provide a starting period of operation of the device during which combustion may occur, a second circuit for the device including other of said switches to provide a second period during which combustion may continue, means in the control to maintain the device inoperative for a third period after the second period, said lastnamed means being adapted to return the control to starting position at the end of the third period, from which it may recycle, means in the control to prevent recycling of the control and to lockout the device after at least a substantial part of the third period, and automatic means responsive to existence of combustion, operative at the end of the starting period to determine whether or not the look-out means shall be actuated to prevent such recycling.

12. In a mechanism of the kind described for use with a fuel supply means, a cycling timing control adapted to provide sequential operations for the fuel supply means, means to energize the timing control, means under control of the timins control to maintain the fuel supply means in operation for a first period during which combustion may occur, means to maintain the fuel supply means inoperative'for a period after combustion has stopped; said last-named means being adapted to return the control to starting position after the inoperative period, for recyclin means independent of the total time of operation of the timing control to cause the ill?! 5 9- ply means to lock-out after at least a substantial part of the inoperative period has passed, and means responsive to existence of combustion at the end of the first period to render the lockout means inefiective to prevent recycling of the control.

13. In a mechanism of the kind'described, a fuel supply means, a cycling timing control to provide sequential operations for the fuel supply means, means to energize the timing control, means under control of the timing control to maintain the fuel supply means in operation for a first period during which combustion may occur, a space thermostat, a combustion-responsive thermostat, said control being adapted to render operation of said fuel supply means subject to said space thermostat and combustion thermostat for a second period, means to restart the timing control for a third period after'sald space thermostat is satisfied, said timing control having means thereafter to maintain the fuel supply means inoperative for a fourth period during which scavenging may occur, means to lock-out the fuel supply means after at least a substantial part of the fourth period, and means under control of the combustion thermostat to render the look-out means ineffective to prevent recycling if combustion exists at the end of the first period.

14. In a mechanism of the kind described, a fuel supply means, a cycling timing control, means to effect actuation of the timing control, combustion-responsive means, means under control of the timing control to render the fuel supply means operative during a first period during which combustion may occur, a first and a second circuit for maintaining actuation of the timing control during a scavenging period after the first period, a switch in the first circuit maintained closed by the timingcontrol for a fuel scavenging period to the end of the cycle, a switch in the second circuit maintained closed by the timing control for a period less than the fuel scavenging period, means operated by the combustion-responsive means upon existence of combustion to select the first circuit, and upon lack of combustion toselect the second circuit, and means to render the timing control actuation effecting means ineffective to recycle the control upon opening of the second circuit switch.

15. In a mechanism of the kind described, a fuel supply means, a cycling timing control adapted to provide sequential operations of the fuel supply means, said timing control including means to render the fuel supply means operative during a starting period during which combustion may occur, and means to maintain itself operative and the fuel supply means inoperative during a scavenging period after the starting period, said timing control also including means to stop itself and look-out at a point between the start and the finish of the scavenging period, means responsive to lack of combustion at the end of the starting period to render the look-out means effective, and means to effect operation of the timing control, said means being ineffective to effect such operation at the point of locking-out, but being adapted to be effective at the end of a fuel scavenging period.

16. In a mechanism of the kind described, a fuel supply means, combustion-responsive 'means including relay switch means operated in response to existence of combustion, temperature-responsive means including relay switch means operated in response to existence of predetermined temperature conditions, a cycling control motor, and

switch means operated thereby, means including both relay switch means in operative positions,

and a cycling motor switch to hold the fuel supply means in operation, and means to restart the cycling motor upon release of the combustion relay switch to stop the fuel supply means if the temperature relay switch means fails in operative position.

17. In a mechanism of the kind described, a fuel supply means. a timing control therefor, a space thermostat and switch means operated under control thereof, means including the space thermostat switch incold position of the thermostat to eil'ect operation of the timing control, said timing control including means to effect operation of the fuel supply means for a starting period independent of the space thermostat, and means to render the fuel supply means subject to the thermostat switch in cold position for continued operation thereafter, means to reoperate the timing control upon movement of the thermostat switch to hot position, said timing control being adapted to continue such reoperation for a further period during which it maintains the fuel supply means inoperative, and means to cause said timing control to operate for said-further period even after the thermostat switch fails in the hot position of the thermostat.

18. In a mechanism of the kind described, a fuel supply means, a timing control therefor, a space thermostat and switch means operated under control thereof. means including the space thermostat switch in cold position to effect operation of the timing control, said timing control including means to effect operation of the fuel supply means for a starting period independent of the space thermostatand means to render the fuel supply means subject to the thermostat switch in cold position for continued operation thereafter, means to reoperate the timing control upon movement of the thermostat switch to hot said control having means to provide a period during which the fuel supply meansis held inoperative, means responsive to failure of power to render the fuel supply means inoperative at any time after it has begun operation durin the starting or the running period, and said lastnamed means being adapted to render the inoperative period means effective upon restoration of power to insure a scavenging period before the fuel supply means may again become opera ive.

21. In a mechanism of the kind described, a-

fuel supply means, a cycling timing control, means to effect operation of the timing control, said timing control having switch means operated sequentially, a first circuit for the timing control including a first switch operated by the timing control to cause said circuit to cycle the timing control back to starting position, a second circuit for the timing control including a second switch operated by the timing control to cause said circuit to cycle the timing control to cycle to a position short of the starting position, means operated by the timing control to operate the fuel supply means for a starting period beginning after closure of the first and second switches and stopping Prior to opening of the second, means operated by the timing control for enabling the fuel supply means to continue in operation for a running period after the starting period, said enabling means being adapted to render the timing control inoperative for said running period, means including a combustionresponsive means operative upon existence of combustion to maintain the fuel supply means operative during the running period, and means under control of the combustion-responsive means to select the first circuit to the timing device if combustion fails and the combustion-responsive means becomes inoperative during the position, said timing control being adapted to 1 continue such reoperation for a further period during which it maintains the fuel supply means inoperative, means to cause said timing control to operate for said further period even after the thermostat switch means fails in the hot position of the thermostat, said last means including a limit switch. and means to eii'ect said reoperation of the timing control for said further period immediately upon operation of the limit switch.

19. In a mechanism of the kind described for use with a fuel supply means. a timing control therefor, means to eifect actuation of the timing control, said control being adapted to eifect operation of the fuel supply means for a starting 1 period during which combustion may occur, and being adapted to effect a running period during which operation of the fuel supply means may continue, and said control having means to provide 'a period durlngwhich the fuel supply means is de'energised, and means to effectuate operation of said control to produce said last-named period whenever during the starting or running period, after the fuel supply means has startedoperation, the fuel supply means is deenergised, prior to its being reenergized again.

20. In a mechanism of the kind described for use with a fuel supply means, 'a timing control, means to eifect operation of the timing control. said control being adapted to effect operation of the fuel supply means for a starting period during which combustion may occur. and being adapted to effect a running'period during which operation of the fuel s pp y mm 7m"- running period, and to select the second circuit to the timing device if combustion fails at the end of the starting period, and said means to effect starting of the timing control being dependent upon cycling of the timing control back to its starting position.

22. In a mechanism of the kind described. a

fuel sup ly means, air supply means, and a timing control adapted to produce a cycle of operations of said means and return to starting position, means to start the timing control dependent upon its being in starting position, said control including means to operate both the fuel and air means for a starting period during which combustion may occur, and including means responsive to lack of combustion at the end of the starting period to maintain the fuel supply means inoperative for a period thereafter with means to maintain the air device operative during said period of inoperativeness of the fuel device, and said control including means thereafter adapted to stop the air supply means and control short of starting position.

23. In a mechanism of the kind described for use with a burner device, a control device for effecting sequential operations of the burner device including a running period, a first and a second circuit for the control device, said control device having circuit clonng means operable to open the two circuits at different times to cause the control device to stop at different times, said control device being adapted to operate the circuit closing means in both circuits during the running period, means to maintain one circuit openduringthorunningperiodandtocloseit thereafter, means responsive to existence of gredient to the burner, a cycling control device having first means to maintain the supplying means in operation for a period until the control device returns to starting position, and hav-- ing a second means to maintain the supplying means in operation for a period short of return of the control device to starting position, means operated by the control device to stop the control device prior to the end of either period, means to maintain the supplying means in operation during said stoppage, means operable upon combustion at the burner to select the first means aforesaid, and operable upon lack of combustion at the outset of the period of stoppage to select the second means aforesaid, and means dependent upon having the control device in its starting position to effect a restart of the-same.

25. In a mechanism of the kind described for use with a burner mechanism under control of a space thermostat and including fuel supplying means, a relay switch controlled by the space thermostat for controlling operation of the burner mechanism, means including the thermostat in operating position for starting the burner mechanism, means including the thermostat in operating position for maintaining the fuel supply means in operation and providing a running period for the burner mechanism, means to prevent supply of fuel after a running period if the relay switch sticks in operating position. said means comprising a second relay having switches controlling th burner mechanism, and a coil dependent upon the thermostat in its operative position to operate the said switches into position to maintain operation of the burner mechanism.

26. In a mechanism of the kind described for use with a burner mechanism under control of a space thermostat and including fuel supplying means, a relay switch controlled thereby for controlling operation of the burner mechanism, means including the thermostat in operating po sition for starting the burner mechanism, means including the thermostat in operating position for maintaining the fuel supplying means in operation and providing a running period for the burner mechanism, means to prevent supply of fuel after a running period if the relay switch sticks in operating position, said means comprising a second relay having switches controlling the burner mechanism, and a coil dependent upon thermostat in its operative position to operate the said switches into position to maintain operation of the burner mechanism, together with means dependent upon existence of combustion to maintain the coil energized.

27. In a mechanism of the kind described for use with a fuel supply means under control of a space thermostat, a cycling control device including a control motor and switch means cyclically operated thereby, a circuit for the motor, a relay under control ofthe space thermostat including a coil, and a switch means operated thereby to close the motor circuit, a circuit for the fuel supply means dependent upon operation of the space thermostat relay by movement of the said thermostat to cold position, a combustion-responsive relay and a switch means operated thereby, said last=named switch means including a switch arranged to control operation of the circuit for the fuel supply means, the space theromstat being also in series with the coils of said relays whereby if it opens, said fuel supply means is immediately deenergized even if one of said relay switches fails in closed position, and said circuit for the fuel supply means being also controlled by the control motor switch means. 7

28. In a mechanism of the kind described for use with a fuel supply device, a relay, a cycling control device, a pair of circuits for the control device, a relay switch adapted to select the first circuit when energized and the second when deenergized, a switch operated by the control device in one circuit to stop it in a locking position preventing operation of the control device, a switch operated by the control device for stopping it after return of the control device to starting position, a circuit through the relay in its locking circuit position for energizing the fuel supply device, a switch operated by the control device t open the fuel supply device prior to opening of either control device circuit, and a thermostatic means controlling energization of said relay.

29. In a mechanism of the kind described for use with a burner, a fuel supply means, and an igniter for the burner, the combination of control means to provide operation of the fuel supply means for a. starting and a running period, .circuit means under control of the control means to effect initiation of operation of the igniter during the starting period, switch means to render the igniter'operative during the running period, said last-named switch means being selectively operative independently of the control means, and means to render the igniter inoperative after the running period regardless of the circuit means and the switch means.

30. In a mechanism of the kind described for use with a fuel supply means under control of a A space thermostat and a combustion thermostat, a control motor having switch means to effect a, cycle having a starting period and a running period for the fuel supply means, and to reestablish starting conditions after the running period, a pair of relay coils, both adapted for disposal in series with the space thermostat and one in series with the combustion thermostat, a switch operated by each coil, an energizing circuit for the coils being provided through a switch of each coil closed by energization thereof, and adapted to include the space thermostat, and a running period circuit for the fuel supply means being provided through both said coil switches, and a circuit for the control motor including a switch held open upon energization of the second coil, whereby when either thermostat opens the fuel supply means will be deenergized and the control motor circuit will be rendered subject to reenergization.

31. In an apparatus of-the kind described for use with a burner and means to supply fuel to the burner, a control mechanism for controlling the fuel supply means, said control mechanism including means adapted to provide a cycle of operation for the burner including starting, running, scavenging, and lock-out thereof, followed by a return to starting position, and comprising means adapted to put the fuel supply mean in assacee operation, for a starting period, means to maintain the fuel-supply means in operation after the starting period for a running period, means to provide a period of inoperativeness of the fuel,

supply means after the running period for a scavenging period, means to cause at least a part of-the scavenging period to occur after any starting period, and then to cause a lock-out of the fuel supply means prior to return of the control to starting position during any cycle, upon ab-= sence of combustion at the end of the starting period.

32. In a mechanism of the kind described, for use with a burner, a fuel supply device and an air supply'device for the burner, the combination of a power failure circuit holding device, a pair of switches operated b said holding device, a control motor, means to operate the circuit holding device upon existence of a predetermined condition, circuit means including one of said switches operated upon energization of the circuit holding device to cause actuation of the control motor, means to cause operation of the air supply device upon operation of the control motor, means including the other of said switches to cause operation of the air supply device upon deenergization of the circuit holding device, and circuit means dependent upon energization of said one switch for energization of the fuel supply means,

33. In a mechanism of the kind described, for use with a fuel supply device, a control motor for controlling operation of the fuel supply de-' vice, and a power failure relay, with circuit means for effecting operation or the control motor when the power failure relay is either energized or deenergized, and circuit means controlled by the control motor and arranged to operate the fuel supply device only when the relay is energized.

34. In a mechanism of the kind described for use with a burner means requiring a first and bustion at the burner mechanism, and an external control device operable to demand or deny heat need from the burner mechanism, the combination of a timing control device having means to provide astarting period for the burner mechanism in response to demand for heat by the external control device, means to provide a scavenging period during which the control mechanism maintains the burner mechanism inoperative after the starting period, means adapt ed for connection with the combustion-responsive device for holding the burner mechanism in operation after the starting period and before the scavenging period, and means in the control device to lock-out the burner mechanism and hold the same against any operation, said means being rendered effective upon failure of combustion at the end of the starting period, to effect said lock-out after the beginning of the scavenging period,

36. In a mechanism of the kind described for use with a burner having a fuel ingredient supply device and anair supply device, the combination of a power operated rela switch mechanism, a control device for eifecting sequential operations of itself, the air supply device and the a second combustion ingredient, the first being air and the second being fuel, and an ignition means, the combination of a control device, said control device including means adapted to maintain itself, both combustion ingredient supply means and the ignition means in operation for a starting period, and said control including means adapted to cause the two combustion ingredient means to operate for a running period, the con-' and then to stop in a position preventing recycling, and said control device also including means operated upon flame failure as aforesaid to render the second combustion ingredient means inoperative.

[85; In a m of-thc kind described for use with a burner mechanism, a combustion-rcsponsive device operable upon existence of comfuel ingredient suppl device, to produce combustion at the burner and to maintain the same, means to operate the air supply device including both the relay switch mechanism and the control device, and means including the control de vice for operating the air supply device and the control device whatever the condition of the relay mechanism,

37. In a mechanism of the kind described, a

control device for eifecting sequential operationsincluding a plurality of switches and means for closing them in a predetermined order to eflect a cycle and to return thereafter to starting position, means dependent upon return to starting position to restart the control device, mechanism to be operated upder control of the control device, means causing the control device to become ineflective to complete the cycle for the operated mechanism, and manually movable means movable to eflect mechanical engagement with the closing means, and further manually movable to bodily displace the same and such of the switches as to reestablish the starting position.

38. In a control for use with a fuel burner including means to supply fuel, under control of a space thermostat and a combustion thermostat operated to circuit closing position upon existence of combustion, means responsive to domand by the space thermostat to cause the fuel supply means to supply fuel to be ignited, a flame-responsive relay includlnl a coil in series with the space thermostat and the combustion thermostat, and energized upon demand for heat by the space thermostat and closure of the combustion thermostat in response to existence of combustion, relay switch means closed by said coll upon energizationthereof, a circuit including said relay switch means to operate the fuel supply means when said 0011 is energized, and means to prevent the fuel supply means from supplying fuel after the space thermostat stopsdemanding heat but the relayswitch fails in circuit closing position.

.. GEORGE D. BOWIR.

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