US2684463A - Variable function voltage source - Google Patents

Description

y 1954 J. J. WILENTCHIK VARIABLE FUNCTION VOLTAGE SOURCE Filed Aug. 24, 1949 IN V EN TOR. JERZY I WILENTC/J'IK. Q

A TTORNE X Patented July 20, 1954 UNITED STATES PATENT OFFICE 12 Claims.

This invention relates to improvements in position control systems with particular reference to control systems comprising primary and final control means, wherein the position of the final control means is varied as a function of the displacement of primary control means according to any desirable law.

An object of the invention is to provide a system of the aforementioned character in which the law according to which the final control element is adjusted can be varied at will, by simple manual means and in a relatively short time.

Another object of this invention is to provide an apparatus of high sensitivity accurate follow up operation in which hunting is eliminated by operating the motor unit at a number oi speeds depending to large extent on the error position signal, and. by providing it with braking means.

Yet another object of this invention is to provide a control apparatus adapted to be used as a control, indicating or calculating device.

A more specific object of this invention is to extend appreciably the range of operation of a follow up control system Without increasing the values of. current and voltage associated with its control circuits.

A still further object of the invention is to provide simple and inexpensive means for eliminating the inertia effect of the control relay.

The invention allows use of less sensitive balancing means and/or extension of range of control without impairing the sensitivity or the instrument or requiring extremely long resistance elements, high impressed voltage or large cur-- rent intensities. Since every relay has certain inherent amount of stability which may or may not be constant, the primary control device would have to be displaced at each time some minimum distance along its respective resistance element before the relay is afiected and a corrective action started, it follows that all other circuit parameters being constant, only a limited number of positions of the final control means can be obtained from a fixed length of control resistance. The present invention allows extension of range through use of plurality of suitably interconnected resistance elements at both the controlling and the control points, step down gears being interposed between contact devices associated with said resistance elements, which results in realization of numerous positions of controlling means through relatively few resistance elements. Asan example, if "n positions of final control means were possible with one single resistance element at the controlling and the control points, with m similar elements suitably interconnected at each one of said points, 11 positions could be realized.

In the art prior to this invention, a single balancing relay controls the performance of a motor unit operating at a single speed, which may result in hunting unless the motor is adapted to operate at extremely low speeds which is objectionable because of the relatively long time necessary for the final control means to assume their correspondence position. The present invention allows the motor unit to operate at number of speeds equal to the number of relays associated with its control network, the change or speed being eifected through insertion of a suitable amount of resistance in the motor current supply circuit. The motor speed decreases in steps as the final corresponding position is being established and is stopped abruptly by braking means effective only in the balance position of all balancing relays.

The present invention enables to realize any desirable relationship between the positions of the primary and the final control means, wherein the position of the final control means is unequivocally dependent on that of the primary control means. Moreover, the invention provides manual means to vary this desirable relationship continuously, or at single and/or numerous points, with a high degree of accuracy, at a relatively short time, and by unskilled personnel, which features have been not realized in previous art on the subject.

In some embodiments of the invention electronic balancing means may replace the electromechanically balanced relay. The electronic arrangement offers the advantage of insensitivity to vibrations, lesser amount of inherent inertia associated with performance of said balancing means, higher speed of operation thereof, and no dependability as to the location of the relay.

For a better understanding of the invention, its advantages over existing art and the specific oblects attained with its use, reference should be had to the accompanying drawings and to the following specifications in which preferred embodiments of the invention have been illustrated and described.

In the drawings:

Fig. l is a diagrammatic representation of a proportioning control system with a plurality of mechanically balanced relays.

Fig. 2 is a section of Fig. 1, showing the resistance elements being connected in parallel.

Fig. 3 is a partial cross-section through a functional resistance unit employed in the invention.

Fig. 4 is a transverse section according to Fig. 3, and

Fig. 5 is a view of the intermi tent motion coupling according to Fig. 1.

To make the drawings more readily understandable, the control system can be represented generally as composed of three interconnected but separate unita'designated by Roman numerals, namely, I the input means at the control point; If bank of balancing relays and Ill the follow up control means as the controlled point.

Referring to Fig. 1 there are shown at the control point contact devices 3 and 3a linked to corresponding sha- fts 2 and 2a, adapted to be adjusted along their respective resistance elements i3 and tie by the primary control means 5. Though only two elements of each kind are shown on Fig. 1, more such elements similarly connected could be, of course, used. The primary control means are coupled operatively with shaft 2 and can be a motor unit, a measuring element, a hand lever or other device. The shaft 2 is coupled operatively with shaft 2a through a step down gear transmission 57 including an arm 58 and a toothed wheel it fixedly connected to respective shafts 2 and 2a, the arm l8 being normally sep arated from the wheel [9 except for an integral number of revolutions of shaft 2, counted from its zero displacement position, when said arm 53 becomes physically engaged with said wheel 59 and rotates it a distance corresponding to the width of one tooth. The tooth wheel, is, may be a conventionally designed gear, the arm l8, may have its tip shaped according to the teeth of gear it. The distance between 8 and it is sufiicient for the arm 58 to enter the recess between a pair of successive teeth in the wheel is and to displace the latter in a colckwise or in an anti-clockwise direction, depending on the sense of direction of shaft 2. To obtain more accurate positioning of gear iii, a conventional detent mechanism comprising a spring and a disk, i l, the latter provided with a plurality of recesses may be used.

It is understood that in a balanced position of the shaft, 212, the spring l5 escapes a respective recess in disk M. The shaft 2c can be coupled similarly with the next following one, the coupling between any two successive shafts bein similar in all respects except for gear ratios which may have the same or diiferent values for any two gear transmissions. The resistance elements 6 and 6a are wound to form regular circles with a little neutral spacing between the endings of each element at the maximum and the minimum potential levels. When the shaft 2 is in its zero displacement position, the current drawn from the voltage source is null, since the contact device 3 is associated at that time with the neutral spacing t between the resistor endings. As the shaft 2 is being rotated, the current in its associated contact device increases abruptly at first to its primary value corresponding to the minimum value of resistance in the circuit, then increases gradually to its maximum value and finally drops back to Zero which state corresponds to one complete revolution of shaft 2. Upon continuous rotation of shaft 2, the above described cycle will be repeated and parallely to it the shaft 250 will be rotated by step motion at each time that the contact device 3 crosses the neutral spacing between the endings of resistance element 6.

A substantially identical organization including contact devices 30 and 3% associated with their respective resistance elements 2%? and 29a and shafts 5| and Ma means to move the shaft El and to transmit the motion thereof to the next following one, including motor unit s3 and gear transmission of similar step down ratio, as this at the control point including an arm l3 and a toothed wheel is is provided at the controlled point which may be or may not be remotely located from the control point. The resistance ele ments at both control and controlled points are associated with a source of voltage and can be connected thereto either as potentiometers (Fig. 2) or as current rheostats having one end free and unconnected, which is illustrated in Fig. 1.

The final control means at the controlled point comprise an electrical motor 53 having two independent energization circuits 5d and 55, the direction of rotation thereof dependent on whichever of said circuits is energized, the motor unit being stationary in the absence of energizing voltage. The motor unit output shaft 53 is coupled operatively through suitable gear transmission to the final control element l2 and repositions it.

The operation of the motor unit 53 is controlled through a bank of suitably interconnected relays II. The wiper 3 is coupled with the solenoid windings 25 of balancing relay 2c comprising an armature 2% which is pivotally mounted at 22 and operatively linked to the cores 23 and 25 of a pair of solenoid windings 25 and 26. Each solenoid winding when energized tends to attract its respective core in the'direction indicated by the arrow (upward in Fig. l). The energizing circuit for solenoid winding 25 includes a source of voltage connected across input terminals 21 and 28 and may be traced from the positive terminal 28, resistance element 6, contact device 3, conductor 5, winding 25, conductor 8, to negative terminal 27. Similarly, the energizing circuit for solenoid winding 25 may be traced from positive terminal 23, conductor '3, resistance element 28, wiper 36, winding 28, conductor 8, to the negative terminal 27. In the same manner the energization circuits for solenoid windings 25a and 26m can be traced. If the resistance elements are connected as potentiometers the free end of each one of them is associated through conductors 9 and 8 with the negative voltage treminal 2'! (dotted line connection). It will be understood that when the wipers s and 35 of corresponding resistance elements 5 and 2% stand in such positions as to cause current of the same magnitude to flow through the windings 25 and the armature 2! will be in the balanced position illustrated in Fig. 1, in which the switch blades 3! and 32 operatively linked and electrically insulated from the armature 2i and connected by ire conductors to positive and negative terminals 33 and 3 respectively of motor and brake voltage supply mains, will be insulated from two pairs of stationary contacts 35 and 33. and 35 and 3?. The contacts 35 and 33 are connected via conductors as and st respectively to stationary contacts ilo and Hit of next following relay 28a and from there through tongues 553a and lso to motor input terminals 45 and :38. The contacts 3'! and 38 are joined together and connected through resistor 47 and conductor H to the input motor terminal d3. There can of course be used, accordin to design requirements any number of relays (two relays being used in our example), the actual number of relays being equal to the number of resistance elements at the control or the controlled points. Each one of said relays would be substantially similar to relayas described above, except for provision of tongues 43c and 44a linked operatively to but electrically insulated from armature Zia, connected through conductors to stationary contacts 35a and 35a and associated. with contacts 4 la and 42a. in the balance position only.

From the foregoing description it will be apparent that when the control device I operates to displace the contact device 3, so that the current through solenoid winding will differ from that flowing through winding 26, the armature 2| will be rotated in one sense or the other and the blades 32 and 3| will engage one or the other of their associated pairs of contacts 35 and 38 or 36 and 3?. If the next following relay 20a is in the balanced condition, the circuit would be completed as described above. If on the other hand, both armatures 2i and 21a are unbalanced at the same time, the tongues 53a and Ma will be insulated from contacts Ma. and 62a and no current will flow through conductors 39 and 30. Since the armature 2la is unbalanced, the current will flow now from the positive terminal 33 through blade 32a, contacts 35a and 35a, input motor terminals 5-5 or :25, motor winding or 54, input motor terminal 48, resistors 41 and 47a, either contact 3? or 38, either contact 37a or 38s, blades 3! and 31a, back to the negative terminal B l. The motor unit 53 will start to rotate in either direction as dictated by position of armature 2m and will displace the contact devices 3t and Eta until the wiper 3% assumes a position along the follow up resistance element 29a at which the currents through the two windings 25a and 26a are once again equal, upon which the armature 2m returns to its balanceposition while the relay 2!! if unbalanced assumes the control over the performance of the motor and makes it continue its rotation in the same or reverse sense of direction depending on position of unbalance of the armature 2i, until the currents in the windings 25 and 25 are equal, upon which the armature 2| is returned to balanced position and the motor unit is finally deenergized.

The change of position of contact devices 3a and Eta respective to their resistance elements, through action of associated step down gears has been of course assumed sufiiciently large as to cause unbalance of the relay 28a.

By providing the armature 21 with a depending arm which supports the blades 32, the latter may be arranged to have its center of gravity below the pivot 22 so that the armature will always remain in neutral position unless the difference in the pull of the two solenoids exceeds a predetermined value.

The resistors ll and lla are provided to prevent the hunting of the motor back and forth from the final correspondence position. If the armature 25 is unbalanced alone, which is an indication of a relatively small position error of the final control means, the motor supply current flows through resistor 4?, but when both armatures are unbalanced at the same time, which corresponds usualy to a large position error, the current flows through both resistances ll and lla connected in parallel, consequently the overall resistance decreases, the current increases and the motor operates at a higher speed. From the foregoing description it will be appar out, that the extent to Which the position of a relay can be a criterion of optimum motor speed may be misleading sometimes as in case when both armatures 2| and 2111 return to balanced position at the same or at approximately the same time. Upon balancing of armature ia, there may not be enough time left for the motor unit operating at a higher speed to reach the lower speed level yet before the armature 2i returned to its balance position, consequently the corresponding position of the final control means i2 is overshot. This results in reversal of position of armature 2i while the armature 2 Ea remains balanced, the motor unit is controlled to rotate in-a sense of direction opposite to the former one and at a lower speed level, which decreases the oscillatory tendencies of the system.

To further improve the performance of the system, an electromagnetic braking device 56 active in the balance position of the armatures 2i and Zia only may be provided to stop the motor instantly upon establi nent of the corresponding position. The bra ing device consists of a plunger 5? adapted to be moved inside two solenoid coiled windings 53 and the plunger provided with a friction surface Si; which is normally in physical engagement with a corresponding friction surface ti on motor shaft 5! through action of spring 52 but separated from said friction su face when current flows through either one of solenoid windings 5;; or 59. Each one of solenoid windings 5i) and when energized, tends to attract the plunger in the direction indicated by the arrow (Fig. 1) against the opposing force of spring 52, but when the flow of energizing current is stopped, the plunger 5'5 is returned to its normal position in which the pressure of friction surfaces to and 65 against each other exert a friction torque to stop the motor unit instantly. The two energization circuits for solenoids 58 and 59 arranged in parallel to the motor energization circuit and connected across motor and voltage source terminals and ill-36 respectively, to advantage of full voltage drop across terminals 353. The system described in Fig. 1 may be modified to control the position or a motor driven load i2 according to a desired law 31:) (x) wherein .r is the input from the controller i and y the output of the motor by provision of a pair of similar functional resistance units described with reference to Figs. 3 and 4 instead of employing linear resi. "uncles and A functional res" canoe unit shown in Fig. 3 consists of a reslstan einent connected to input voltage terminals i 25 and Wound unifcrnily on a cylindrical, Bakelite core till, the latter being placed concentrically within a slotted, non-conducting pipe 554. The slots 852 are arranged uniformly and longitudinally along the circumference of the pipe iiii, A plurality of spring loaded contact sliders are adapted to be disposed manually along the length of respective slots its in conductive engagement with the resistance its. The slots i612 serve thus as guides, while the body of the pipe its between the slots 562 provides required contact pressure between the sliders i 83 and the resistance Hit. The spacing of the slots is such as to enable displacement of individual slider contacts N53 without inteference. To facilitate manual adjustment the sliders IE3 may be provided with respective non-conducting handles ififi. The sliders m3 are connected via flexible conductors 85 to respective bars 16? of a circular commutator unit ITS. A wiping contact I69 (similar to contact 3) is adapted for displacement by a primary control means I, in engagement with the bars $67!. To ensure a correct positioning of the wiper I69 a detent mechanism similar to that shown in Fig. 1 can be employed.

The voltage signal of the contact IE9 is transferred via conductor 5 to the winding 25, similarly the voltage signal of a second functiona1 resistance unit operating in conjunction with the first one is transferred via a conductor 5a to the winding 25a (see Fig. 1). etween the shafts 2 and 2a of the first and of the second functional resist ance units, there is interposed a one to one gear transmission (not shown) which will cause the wiping contacts 169 of both above units to be displaced in unison.

The operation of a system comprising functional resistance units is substantially similar to the one described with reference to Fig. 1, except that instead of a proportional relationship between mechanical inputs and outputs a functional relationship according to any desired law 11:1 (1') can be realized. The number of possible positions of the load motor is equal to the number of bars in the commutator i it.

It should be borne in mind that the invention is applicable not merely to resistance elements but to all types of variable voltage (or current) sources comprising voltage division means having spaced taps from which voltages (or currents) of different magnitude, phase, frequency, etc. may be obtained.

What I claim as novel, and desire to secure by Letters Patent is:

1. In combination, a plurality of contact devices controlling respective sources of variable voltage, control means to move the first one of said contact devices, a plurality of couplings for transmitting the motion of said first moved contact device to the next following ones, each of said variable voltage sources comprising a respective resistance Winding, each of said couplings comprising at least one gear, a plurality of bars connected electrically to respective contact sliders, said sliders being adapted for manual displacement along the length of respective resistance windings.

2. The combination according to claim 1,

wherein said bars are insulated from each other and arranged in a circular array.

3. The combination according to claim 1, including detent mechanism for producing step motion of respective contact devices.

l. In combination, a control means, a mandrel, a multi-turn resistance coil wound on said mandrel, a source of voltage connected to said coil, a plurality of sliders adapted to cooperate electrically with said resistance coil, 2. commutator provided with a plurality of bars, electrical connections between respective sliders and bars, and

9 wiping means adapted to be displaced in electrical engagement with said bars by said control means.

5. The combination according to claim 4, wherein said sliders can be manually adjusted along the length of said resistance coil.

6. The combination according to claim 5, including a detent mechanism to produce a step motion of said Wiping means.

'7. In combination, a plurality of variable voltage sources, each of said sources comprising a resistance winding provided with a plurality of manually adjustable contact sliders connected to respective stationary contact points, a plurality of contact devices cooperating conductively with said contact points and control means to move said contact devices along the length of said contact points.

8. The combination according to claim 7 including a detent mechanism to produce step motion of respective contact devices.

9. In combination, a support, a resistance winding on said support, a voltage source connected to said winding, a plurality of contact sliders adapted to be adjusted manually along the length of said support in conductive engagement with said winding, a plurality of stationary contact-points connected to respective ones of said sliders, a wiping contactdevice displaceable along the length of said contact points and control means to move said contact device.

10. The combination according to claim 9, including a detent mechanism adapted to graduate the motion of said contact device into a series of distinct steps.

11. The combination accordin to claim 9, wherein said stationary contact points are arranged in a circular array.

12. The combination according to claim 9, including rail means on said support to facilitate the adjustment of said contact sliders.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,042,693 Kramer Oct. 29, 1912 1,268,712 l-larle June 4, 1918 1,508,796 Kaminski Sept. 16, 1924 1,586,233 Anschutz-Kaempfe May 25, 1926 usa es Tanner July 1, 1930 2,025,218 Reinken Dec. 24, 1935 2,436,172 Kent Feb. 17, 1948 2,453,462 Sellers 1 Nov. 9, 1948 2,471,843 Stamper May 31, 1949 2,494,922 Yardeny Jan. 17, 1950

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