US3871324A

US3871324A - Outboard propulsion unit exhaust discharge system

Info

Publication number: US3871324A
Application number: US795434*A
Authority: US
Inventors: Richard H Snyder
Original assignee: Brunswick Corp
Current assignee: Brunswick Corp
Priority date: 1969-01-31
Filing date: 1969-01-31
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: CA927684A

Abstract

It is disclosed for an engine driven outboard propulsion unit having a reversible propeller to selectively drive the propulsion unit in forward and reverse directions and passage means for conducting the exhaust gases from the engine through said unit, a pair of underwater discharge openings for said propulsion unit and respectively disposed fore and aft of the propeller to provide for selective exhaust discharge into the outflow of the propeller slipstream regardless of the direction of propulsion unit operation and thereby assure a solid flow of water to the propeller in both forward and reverse directions of operation of the propulsion unit.

Description

[ Mar. 18, 1975 1 OUTBOARD PROPULSION UNIT EXHAUST DISCHARGE SYSTEM [75] Inventor: Richard II. Snyder, Oshkosh, Wis.

[73] Assignee: Brunswick Corporation, Chicago,

Ill.

22 Filed: Jan. 31, 1969 21 Appl.No.:795,434

Shimanckas 416/93 Primary ExaminerTrygve M. Blix Assistant ExaminerStuart M. Goldstein Attorney, Agent, or FirmRoy Montgomery [57] ABSTRACT It is disclosed for an engine driven outboard propulsion unit having a reversible propeller to selectively drive the propulsion unit in forward and reverse directions and passage means for conducting the exhaust gases from the engine through said unit, a pair of underwater discharge openings for said propulsion unit and respectively disposed fore and aft of the propeller to provide for selective exhaust discharge into the outflow of the propeller slipstream regardless of the direction of propulsion unit operation and thereby assure a solid flow of water to the propeller in both forward and reverse directions of operation of the propulsion unit.

27 Claims, 16 Drawing Figures PATENTEUHAR 1 81975 R SHEET l I]? 5 INVENTOR. RICHARD H SNYDER BY 7 f A,f2@)Z24 Attorneys FIG -2 PATENTEU 3,871,324

sum 3 BF 5 INVENTOR RICHARD H SNYDER PMEIJTEU 1 8 i975 3. 87 l 324 SHEET u of 5 INVENTOR! RICHARD H. SNYDER BY 7 w 54%, av /M Attorneys wgmgum 1 81975 3.8

sum 5 OF 5 w /4/ J IG 2 /7 {I I I 2 #4 4'2 4 //J 1 1 w r /7 v. i F

4 i /iif gj/ry fi Ug H) A l 6/ P";

REVERSE TH RUST (LBS) A FOR A THROUGH THE HUB EXHAUST PROPELLER ENGlNE TWO BLADES, 2| PITCH SPEED (RPM) B O D REAR EXHAUST OPEN REAR EXHAUST OPEN REAR EXHAUST CLOSED NO FORWARD EXHAUST FORWARD EXHAUST OPEN FORWARD EXHAUST OPEN I500 A 20 so I I50 2000 as v 225 255 INVENTOR. FIG 16 RICHARD H. SNYDER Jinx/f Attorneys OUTBOARD PROPULSION UNIT EXHAUST DISCHARGE SYSTEM This invention relates to an exhaust discharge system for outboard propulsion units.

In the case of inboard-outboard drives for watercraft and outboard motors it has been common practice to conduct the engine exhaust gases through the drive shaft housing of the drive unit or motor for discharge underwater. The discharge is generally rearwardly of the propeller either through the propeller hub or through an exhaust snout associated with or projecting beneath the anti-cavitation plate of the propulsion unit. When the propulsion unit is operating in the forward direction, such discharge is into the outflow side of the propeller slipstream and generally does not affect the solid" flow of water to the propeller. When the propulsion unit is operated in reverse, however, the propeller blades cavitate' in the froth created by the discharge of the exhaust gases into the inflow side of the propeller slipstream to greatly impair the reverse propeller thrust. Also when operating in reverse, the exhaust passage is substantially blocked by water giving rise to a back pressure on the engine exhaust ports to adversely affect the efficiency of the engine and further impair the reverse propeller thrust. It is generally an object of this invention to provide for discharge of exhaust gases into the outflow side of the propeller slipstream during reverse operation as well as in forward operation and thereby assure solid flow of water'to the propeller in both forward and reverse directions of operation of the propulsion unit. A further object is to substantially reduce the back pressures in the exhaust system generally attendant with reverse operation of the propulsion unit.

Generally, the invention relates to an outboard propulsion unit driven by an internal combustion engine and having a reversible propeller to selectively drive the unit in forward and reverse directions and further having passage means for conducting the exhaust gases from the engine. According to the invention, the propulsion unit includes means defining an underwater exhaust discharge opening generally rearwardly of the propeller and communicating with the exhaust passage means to provide for discharge of the engine exhaust gases rearwardly of the propeller when the propeller is operating to drive the propulsion unit in the forward direction. The propulsion unit further includes means defining a second underwater exhaust discharge opening generally forwardly of the propeller and which is normally closed when the unit is operated in the forward direction. The second exhaust discharge opening is adapted to open and provide for discharge of the exhaust gases forwardly of the propeller when the propeller is operating to drive the propulsion unit in the rearward or reverse direction. The invention thus provides for solid flow of water to the propeller in both forward and reverse directions of operation of the propulsion unit.

The drawings furnished herewith illustrate the best mode of carrying out the invention as presently contemplated and described hereinafter.

In the drawings:

FIG. 1 is a side elevation of an outboard motor which embodies the invention;

FIG. 2 is an enlarged partial sectional view of the propeller and its mounting for the motor of FIG. 1 and shows a construction wherein the propeller is separable from the slip clutch mounting and wherein the propeller is positioned in the forwarddrive position;

FIG. 3 is a partial sectional view taken generally on 33 of FIG. 2;

FIG. 4 is a view generally similar to that of FIG. 2 and shows the propeller in the reverse drive position;

FIG. 5 is an enlarged partial sectional view of a propeller and its mounting wherein the propeller is separable from the slip clutch mounting but movable there with and shown in the forward drive position;

FIG. 6 is a view generally similar to that of FIG. 5 and shows the separable propeller and slip clutch in the reverse drive position;

FIG. 7 is an enlarged partial side elevational view of a propeller and its mounting wherein the propeller is not normally separable from its slip clutch mounting and shows the propeller in the forward drive position;

FIG. 8 is a view generally similar to that of FIG. 7 and shows the propeller in the reverse drive position;

FIG. 9 is a partial side elevational view of a propeller and its mounting generally similar to that of FIG. 7 but shows a different form of closure plate at the exhaust discharge opening, showing in solid lines the position of the propeller for forward drive operation and in phantom lines the position of the propeller for reverse drive operation;

FIG. 10 is a partial side elevational view of a further embodiment of the propeller and its mounting according to this invention, showing in solid lines the position of the propeller for forward drive operation and in phantom lines the position of the propeller for reverse drive operation;

FIG. 11 is a partial side elevational view of a still further embodiment -of the invention showing the propeller, its mounting and shaft, and showing in solid lines the position of the propeller for forward drive operation and in phantom lines the position of the propeller for reverse drive operation;

FIG. 12 is a view generally similar to that of FIG. 11 and shows an embodiment along with reversing gear means on the propeller shaft;

FIG. 13 is a partial side elevation of an outboard propulsion unit showing a further embodiment of the invention wherein an exhaust dischargesnout is disposed rearwardly of the propeller;

FIG. 14 is a sectional view taken generally on line 14-14 of FIG. 13;

FIG. 15 is a detail view taken generally on line 1515 of FIG. 13; and

FIG. 16 is a table setting forth data generally showing the improvement in reverse propeller thrust which results from a utilization of this invention.

Referring to the drawings, an outboard propulsion unit for watercraft such as the outboard motor 1 includes an internal combustion engine 2 within the cowl enclosure 3 at the upper end of the motor for driving a propeller 4 at the lower end thereof. Driving rotation of propeller 4 is selectively reversible by means, not shown, to provide for operation of motor I in forward and reverse directions as desired. The exhaust gases from the engine 2 are conducted through passage means 5 in the lower housing portion 6 of the motor I for underwater discharge generally rearwardly of the propeller 4 in a manner further described hereinafter.

According to the embodiment shown in FIGS. 2 through 4, the propeller 4 is independently replaceable,

if desired or when need be, relative to the slip clutch assembly 7 on which it is carried. The assembly'7 comprises inner and outer sleeve members 8 and 9 respectively, between which an elastomeric annulus 10 is sandwiched. The inner sleeve 8 is rotationally locked relative to the generally horizontal propeller shaft 11 by engagement of complementary axial splines 12 and 13 on sleeve 8 and shaft 11, respectively, and is axially secured on the shaft between the forwardly disposed annular stop collar 14 engaged with the tapered shoulder 15 on the shaft and the annular retainer member 16 disposed rearwardly on the shaft.

The propeller 4 includes an outer hub member 17 which carries the blades 18 and an inner hub member 19 spaced radially inwardly from and connected to the outer hub member 17 by a plurality of circumferentially spaced vanes 20. The several vanes 20 divide the annular space between the hub members 17 and 19 into a plurality of axially extending passages 21 which communicate with the passage means 5 through the opening 22 rearwardly of the lower housing portion 6 and serve to conduct the engine exhaust gases rearwardly for discharge underwater through the rearwardly disposed propeller hub opening 23.

The separable propeller 4 is rotationally locked onto the outer sleeve 9 of the slip clutch assembly 7 by engagement of complementary axially extending

splines

24 and 25 on the sleeve and propeller, respectively. Propeller'4 is movable axially to the slip clutch assembly 7 and shaft'll, and is biased forwardly into engagement with the stop collar 14 by the coil spring 26 disposed between the retainer member 16 and the annular shoulder seat 27 formed by the rearwardly disposed internal offset 28 on the inner propeller hub member 19. With the propeller 4 in engagement with the stop collar 14 as generally shown in FIG. 2, the outer hub 17 overlaps within the opening 22 of housing portion 6 to provide a generally continuous passage for the exhaust gases from the passage means 5 in housing portion 6 into the propeller hub passages 21. During forward drive operation, the propeller thrust as well as spring 26 tend to maintain the propeller 4 forwardly and the exhaust gases pass through the passages 21 for discharge into the outflow side of the propeller slipstream through the discharge opening 23. The retainer member 16 on the end of the propeller shaft 11 is rotationally locked on the shaft by engagement of the complementary splines 29 and 13 on the retainer member and shaft, respectively, and engages with the end of the inner sleeve 8 of the slip clutch assembly 7 to secure the assembly against the stop collar 15. Member 16 carries a peripherally disposed annular resilient valve member 30 which in the forward position of the propeller 4 is spaced from the outer hub member 17 to define the annular character of discharge opening 23. The propeller 4, slip clutch assembly 7 and retainer member 16 are secured on the propeller shaft 11 by the lock washer 31 and nut 32 disposed on the end of the shaft.

As explained, during forward drive operation of the outboard motor 1, propeller rotation develops a thrust which along with the biasing force of spring 26 tends to maintain the propeller 4 forwardly against the stop collar 14 as generally shown in FIG. 2 to provide for discharge of the engine exhaust gases into the outflow side of the propeller slipstream through the discharge opening 23. When the propeller rotation is reversed for reverse drive operation of the motor 1, the thrust developed by the propeller 4 is also reversed forcing the propeller to move rearwardly relative to the slip clutch assembly 7 and shaft 11 against the biasing pressure of spring 26 as generally shown in, FIG. 4. With rearward movement of the propeller 4 upon reverse drive operation, the inner hub member 19 of the propeller moves under thrust to engage the retainer member 16 and the valve member 30 engages with the outer hub member 17 to close the discharge opening 23 against egress of exhaust gases into what is now the inflow side of the propeller slipstream. The movement of the propeller rearwardly causes a separation between the propeller 4 and the housing portion 6 to form the radial opening 33 therebetween to provide for discharge of the engine exhaust gases. The gases passing through opening 33 during reverse drive operation enter the outflow side of the propeller slipstream so that the propeller 4 acts on a solid flow of water to the blades 18 instead of cavitating in a froth created by the exhaust gases as was heretofore the practice when the gases were discharged from the opening 23 regardless of the direction of operation for the motor 1. As a result, the thrust developed by the propeller during reverse drive operation is substantially increased to provide for better and more positive control and maneuverability in reverse for the motor 1 and watercraft driven thereby.

When the outboard motor 1 is placed in neutral, the coil spring 26 will bias the non-rotating propeller 4 to its forward position and the spring will maintain the propeller forwardly when the engine 2 is shut off. Since the spring 26 biases the propeller 4 to its forward position when the engine 2 is shut off, any corrosion or marine growth would tend to freeze" or seize the propeller in that position. and during subsequent operation, the motor 1 would still be capable of normal forward operation without exhaust leakage ahead of the propeller. Until such a freeze condition is corrected, reverse operation of the motor I will be inefficient while the exhaust flows through the propeller 4 into the inflow side of the propeller slipstream.

The embodiment of FIGS. 5 and 6 show a separable propeller 34 and slip clutch assembly 35 which though separable move together as a unit relative to the propeller shaft 36 in response to propeller thrust to provide for engine exhaust discharge into the outflow of the propeller slipstream for both forward and reverse drive operation.

Referring to FIG. 5, the slip clutch assembly 35 generally includes inner and outer

hub sleeve members

37 and 38, respectively, having an elastomeric annulus 39 sandwiched therebetween. The assembly 35 is rotationally locked on the shaft 36 by engagement of the complementary splines 40 and 41 on the inner hub member and shaft respectively. The separable propeller 34 having radially spaced inner and outer hub sleeve members 42 and 43, respectively, is rotationally locked on the slip clutch assembly 35 by engagement of the complementary splines 44 and 45 between the propeller inner hub member 42 and the slip clutch outer hub member 38. The slip clutch outer hub member 38 and the propeller inner hub member 42 are generally confined axially between the enlarged stepped forward portion 46 on the inner hub member 37 and the radial flange 47 on nut 48 threaded onto the rearward end of the member 37 to form a unitary assembly, with adequate clearance being provided for the hub member 38 to permit the slip clutch to yield in response to vibration and/or shock loading. Some axial clearance may also be provided for propeller hub member 42 to permit slight axial movement of the propeller relative to the slip clutch sleeve member 38 with changes in thrust to prevent corrosion buildup therebetween.

The radially spaced hub sleeve members 42 and 43 of propeller 34 are connected by a plurality of circumferentially spaced vanes 49 forming axially extending passages 50 for conducting engine exhaust gases through the propeller for discharge through the opening 51 rearwardly thereof. The blades 52 are carried on the outer hub member 43 of the propeller.

The unitary assembly comprising the propeller 34 and slip clutch assembly 35 is movable axially on shaft 36 and is shown biased forwardly by the coil spring 53 in FIG. 5 to place the inner hub member 37 of the slip clutch assembly into engagement with the annular tapered shoulder 54 on the shaft. In the forward position of the unitary assembly the outer sleeve member 43 of propeller 34 is overlapped within the opening 22 of the lower housing portion 6 to place the propeller hub passages 50 in communication with the passage means 5 of the lower housing portion.

The coil spring 53 is disposed between the flanged nut 48 ofthe unitary assembly and the retainer member 55 which has a forwardly facing annular recess 56 for seat-ing the rear end of the spring. The retainer member 55 is rotationally locked on the shaft 36 by engagement of the

complementary splines

57 and 41, respectively,

and carries the annular valve member 58 peripherally thereof. The lock washer 59 and nut 60 confine the retainer member 55 aftward.

In forward drive operation, the unitary assembly including propeller 34 tends to remain forwardly against the tapered shoulder 54 on the shaft 36 under the influ ence of propeller thrust and the spring 53 as generally shown in FIG. 5 so that the exhaust flow from the passage means 5 in lower housing portion 6 is conducted rearwardly through the propeller passages 50 for discharge from the opening 51 into the outflow of the propeller slipstream. When propeller rotation is reversed for reverse drive operation, the reversal in propeller thrust forces the unitary assembly rearwardly away from shoulder 54 against the pressure of spring 53 as generally shown in FIG. 6. The rearward movement of the unitary assembly upon reverse drive operation carries the outer hub member 43 of the propeller 34 into circumferential engagement with the valve member 58 to close the discharge opening 51 generally preventing the egress of exhaust gases into what is now the inflow side of the propeller slipstream. The movement of the unitary assembly rearwardly during reverse drive operation effects a separation between the propeller 34 and the lower housing portion 6 to form the radial exhaust discharge opening 61 therebetween for discharging the exhaust gases into the outflow of the propeller slipstream leaving the propeller 34 to act on a solid flow of water to the blades 52.

In the embodiment of FIGS. 7 and 8 the propeller 62 and slip clutch are considered to be non-separable and together move relative to the propeller shaft 63 in response to propeller thrust to provide for engine exhaust discharge into the outflow of the propeller slipstream for both forward and reverse drive operation.

Referring to FIG. 7, the propeller 62 is carried on the generally horizontal propeller shaft 63 and includes an inner hub sleeve member 64 rotationally locked on the shaft by engagement of

complementary splines

65 and 66 on the hub member and shaft, respectively. An intermediate hub sleeve member 67 is spaced outwardly from hub member 64 and an elastomeric annulus 68 is sandwiched therebetween to form a slip clutch. The intermediate hub member 67 is generally confined axially at the respective ends thereof by the enlarged stepped portion 69 at the forward end of the inner hub member 64 and rearwardly by the radial flange 70 on the nut member 71 threadedly engaged externally on the hub sleeve 64, though adequate clearance is provided between the

hub sleeve members

64 and 67 to permit the slip clutch to yield in response to vibration and/or shock loading.

The propeller 62 also includes an outer hub sleeve member 72 which is spaced outwardly from the hub sleeve member 67 and carries-the blades 73. A plurality of circumferentially spaced vanes 74 connect the outer and intermediate

hub sleeve members

72 and 67 to form axially extending passages 75 through the propeller 62.

The propeller 62 is axially movable on shaft 63 and is biased forwardly by the coil spring 76 placing the inner hub sleeve member 64 into engagement with the annular tapered shoulder 77 on shaft 63 with the outer hub sleeve member 72 overlapping within the opening 22 of the lower housing portion 6. The coil spring 76 is disposed between the flanged nut member 71 and a forwardly facing annular recess 78 in valve retainer member 79 spaced rearwardlyfrom the nut member 71. The retainer member 79 carries a peripherally disposed annular resilient valve member 80 which as shown in FIG. 5 is spaced from the outer hub member 72 at the exhaust discharge opening 81. Retainer member 79 is rotationally locked on shaft 63 by engagement of

complementary splines

66 and 82 on the shaft and retainer member, respectively, and is biased rearwardly by the spring 76. Retainer member 79 has a hexagonal pocket 83 into which the nut 84 fits, thus locking the nut 84 against backing off. The spring 76 biases the retaining member 79 into engagement with the nut 84, but the retaining member can be manually moved forward, thus allowing the nut to be removed without the use of special tools.

' In forward drive operation as generally shown in FIG. 7, the propeller 62 tends to remain forwardly against shoulder 77 under the influence of propeller thrust and the spring 76 so that the exhaust flow is conducted rearwardly through the propeller passages 75 for discharge from the opening 81 into the outflow of the propeller slipstream. When propeller rotation is reversed for reverse drive operation, the reversal in propeller thrust forces the propeller 62 rearwardly away from the stop shoulder 77 against the pressure of spring 76 and moves the outer hub member 72 into circumferential engagement with the valve member 80 to close the discharge opening 81 against egress of exhaust gas into what is now the inflow side of the propeller slipstream as generally shown in FIG. 8. The movement of propeller 62 rearwardly during reverse drive operation effects a separation between the propeller and the lower housing portion 6 forming the radial exhaust discharge opening 85 therebetween for discharging the exhaust gases into the outflow of the propeller slipstream leaving the propeller to act on a solid flow of water to the blades 73.

The embodiment of FIG. 9 is generally similar to that of FIGS. 7 and 8 but showing another form of valve member to close the exhaust discharge opening 81. According to FIG, 9, a metal valve plate 86 is utilized in place of the annular resilient member 80 of the previous figures and is formed integral with the retainer member 87. The retainer member 87 is rotationally locked on shaft 63 by engagement of the

complementary splines

66 and 88 on the shaft and retainer member, respectively, and an annular forwardly facing recess 89 is provided in the retainer member for seating the corresponding end of the coil spring 76.

Operation for the embodiment of FIG. 9 is generally similar to the embodiment of FIGS. 7 and 8 in that the propeller 62 is thrust sensitive and moves relative to shaft 63 to provide for engine exhaust discharge into the outflow of the propeller slipstream for both forward and reverse drive operation. However, rearward travel of the propeller 62 is halted by engagement between the outer hub member 72 and the generally rigid metal plate valve member 86 as'generally indicated by phantom lines in FIG. 9.

In the embodiments heretofore described, the propellers were thrust sensitive to provide for exhaust discharge into the outflow of the propeller slipstream in both forward and reverse drive operation. According to FIG. the propeller 90 is torque sensitive with the shaft 91 and inner hub member 92 having complementary helical splines or

screw threads

93 and 94, respectively. During forward drive operation, the rotation of shaft 91 along with the biasing pressure of spring 95 tends to force the propeller 90 in the direction of the tapered shoulder or stop 96 on the shaft. With the propeller 90 disposed forwardly, the engine exhaust gases are conducted rearwardly through the propeller passages 97 formed by the circumferentially spaced vanes 98 connecting the intermediate and outer hub sleeve members 99 and 100 for discharge rearwardly through the discharge opening 101 into the outflow of the propeller slipstream. A reversal in the rotation of shaft 91 for reverse drive operation forces the propeller 90 rearwardly against the pressure of spring 95 and in the direction of the retainer member 102 which is rotationally locked on the shaft by engagement of complementary splines 103 and 104 and carries the annular resilient valve member 105. With rearward movement of the propeller 90 as shown in phantom lines in FIG. 10, the discharge opening 101 is closed as the valve member 105 engages with the outer hub member 100 and the resultant separation between the propeller and housing portion 6 forms the radial opening 106 for discharge of the engine exhaust gases into the outflow of the reverse drive propeller slipstream.

Referring now to the embodiment of FIG. 11, the propeller 107 is carried on the generally horizontal propeller shaft 108 rotatably supported within the bore 109 of the housing portion 110. The propeller 107 is fixedly secured on its shaft 108 and together they are selectively rotatable in opposed directions in accordance with forward and reverse drive operation by the generally vertical drive shaft 111 through the meshing

bevel gears

112 and 113, with the gear 113 being rotatably locked onto the propeller shaft by engagement of the

complementary splines

114 and 115, respectively. The drive shaft 111 is driven from an engine, not shown, whose exhaust gases are conducted downwardly through the passage means 116 in the housing portion and into the bore 109 around the spoollike bearing retainer 117 for discharge underwater as hereinafter described.

The propeller 107 and its shaft 108 are movable axially relative to the bore 109 in response to propeller thrust with such movements being controlled by the spring retainer 118 fixedly secured on the shaft between the bevel gear 113 and the forwardly disposed tapered roller bearing 119. An expandable bellows type seal 120 is disposed between the shaft 108 and the rear end of the spool-like bearing retainer 117 to protect the bearings and gears against ingress of water.

During forward drive operation of the propeller 107, the propeller thrust as well as the biasing pressure of spring 121 disposed between the gear 113 and spring retainer 118 tend to maintain the propeller and its shaft 108 forwardly. In the forwardmost position of the propeller 107 and its shaft 108, the spring retainer 118 engages the inner race of the tapered roller bearing 119 as a stop while the propeller overlaps within the rearwardly facing opening 122 of the housing portion 110 as generally shown in solid lines in FIG. 11. The exhaust gases during forward drive operation, flow from the housing portion passage means 116 into the bore 109 and thence through the opening 122 into the passages 123 of the propeller 107 formed by the circumferentially spaced vanes 124 connecting the spaced

hub sleeve members

125 and 126 for discharge rearwardly through the propeller discharge opening 127 into the outflow of the propeller slipstream.

During reverse drive operation of propeller 107, the reversal in thrust forces the propeller and its shaft 108 rearwardly against the pressure of spring 121 causing a separation between the propeller and housing portion 110 to form the radial exhaust discharge opening 128 therebetween as generally shown by the phantom lines in FIG. 11. In the rearmost position of the propeller 107 and its shaft 108, the spring retainer 118 engages the bevel gear 113 as a stop and the spring 129 disposed between the spring retainer and the inner race of the tapered roller bearing 119, though weaker than the spring 121, serves to hold the inner race of the roller bearing in place. While the propeller exhaust discharge opening 127 is not closed by a valve, and water is allowed to enter the passages 123 during reverse drive operation, yet reverse propeller thrust is considerably improved as a substantial part of the exhaust gases take the route of least resistance and are discharged through the opening 128 into the outflow of the propeller slipstream. I

The embodiment of FIG. 12 is in some respects similar to FIG. 11 and shows reversing gear means 130 in combination with the axially movable propeller shaft 131 on which the propeller 132 is fixedly secured. The reversing gear means 130 comprise axially aligned, opposed forward and reverse bevel gears 133 and 134, respectively, disposed in the bore 135 of the housing portion 136 in meshing engagement with and on opposite sides of the bevel gear 137 secured on the lower end of the generally vertical drive shaft 138. The bevel gears 133 and 134 are freely rotatable on the propeller shaft 131 and are driven in opposed directions by the drive gear 137. The driven gears 133 and 134 are selectively clutched to the propeller shaft 131 to drive the shaft correspondingly by the clutch element 139 fixedly secured onto the shaft between the driven gears. A cam actuator 140 is carried at the lower end of the rotatable shift rod 141 and is engageable with the forward end of the propeller shaft 131 to provide for selective movement of the shaft and clutch element 139 within the bore 135 into forward drive, neutral, and reverse drive positions. The drive shaft 138 is driven from an engine, not shown, whose exhaust products are conducted downwardly through the drive shaft housing passage 142 and into the bore 135 around the spool-like bearing retainer 143 for discharge rearwardly through the opening 144 at the rear of the housing portion 136.

When forward drive operation is contemplated for the embodiment of FIG. 12, the cam actuator is moved to a corresponding position to permit the coil spring 145 disposed between the clutch element 139 and the reverse gear 134 to bias the clutch element into engagement with the forward gear 133. In the forward drive position, the propeller 132 is somewhat overlapped within housing opening 144 and the engine exhaust gases move through the opening into the propeller passages 146 formed between the circumferentially spaced vanes 147 connecting the-radially spaced

propeller sleeve members

148 and 149 for discharge rearwardly through the rear propeller opening 150 into. the outflow of the propeller slipstream.

When reverse drive operation is contemplated, the propeller shaft 131 together with the propeller 132 are moved axially rearwardly to the position shown in phantom lines in FIG. 12 against the pressure of coil spring 145 by the cam actuator 140 to engage the clutch element 139 with the reverse gear 134. Simultaneously the radial exhaust opening 151 is formed where the propeller 132 and housing portion 136 separate. As was the case in the embodiment of FIG. 11, the discharge opening 150 at the rear of the propeller 132 is not closed by a valve, but nevertheless propeller thrust is considerably improved as a substantial part of the exhaust gases are discharged through the radial opening 151 into the outflow of the propeller slipstream.

The embodiment of FIGS. 13-15 shows the invention as applied to an outboard propulsion unit 152 having a lower housing portion 153 from which the engine exhaust gases are discharged underwater at a location adjacent to the anti-cavitation plate 154 and generally rearwardly from the propeller 155 as by an exhaust snout 156 projecting beneath the anti-cavitation plate. The propulsion unit 152 includes reversing gear means 157 whereby the propeller 155 may be selectively driven in opposed directions corresponding to forward and reverse drive operation. The reversing means 157 are controlled by a cam actuator 158 selectively movable by the rotatable shift rod 159. The vertically disposed drive shaft 160 is driven from an engine, not shown, the exhaust products of which are conducted downwardly through the lower housing passage 161. The passage 161 divides into two

branch passages

162 and 163 above the anti-cavitation plate 154 and selectively communicated with the branch passages in accordance with operation of the flap valve member 164 carried by the shaft 165 pivotally supported within the lower housing portion 153. The shaft 165 and valve member 164 are biased by a spring 166 to close the branch passage 163 so that the housing passage 161 normally communicates with the exhaust snout 156 through branch passage 162. The branch passage 163 communicates with an opening 167 in the side of the lower housing portion 153 beneath the anti-cavitation plate 154. A flexible and/or resilient valve member 168 is disposed on the exterior of the housing portion 153 to cover the opening 167 and is secured to the housing along its forward edge. The valve member 168 may be disposed in a depressed portion 169 provided in housing portion 153 so that the streamlined contour of the housing is not unduly violated to accommodate the valve member.

During forward drive operation of propulsion unit 152, the engine exhaust gases move through passage 161 and branch passage 162 for discharge from the snout 156 into the outflow of the propeller slipstream.

When reverse drive operation of the propulsion unit 152 is contemplated, the reversing gear means 157 are engaged accordingly by corresponding rotation of the shift rod 159 and cam actuator 158. The shift rod 159 simultaneously pivots the flap valve member 164 against the biasing pressure of spring 166 to open the branch line 163 and close the branch line 162. To effect this purpose the shift rod 159 carries an actuator pin 170 which is engageable within a slot 171 of the link 172. FIG. 15 generally shows the relationship of the actuator pin 170 in the slot 171 in the neutral position of the shift rod 159 such that with clockwise rotation of the rod to the reverse drive position the link 172 is pulled and maintained forwardly by the actuator pin. Rearwardly the link 172 is pivotally connected at 173 to a lever 174 secured to the shaft 165. Thus, clockwise actuation of the lever 174 by the forward movement of link 72 actuates the flap valve member 164 correspondingly to close the branch passage 162. With the branch line 162 closed during reverse drive operation of the propulsion unit 152, the engine exhaust gases flow from passage 161 through branch passage 163 for discharge through the exhaust opening 167 past the valve member 168 into the outflow of the propeller slipstream.

When the reversing gear means 157 and shift rod 159 are returned to the neutral position the spring 166 is able to return the flap valve member 164 to the position for closure of branch passage 163. With the propulsion unit 152 underway in the forward direction, the valve member 168 is maintained closed over the exhaust opening 167 by the water flowing past the housing 153. 1 l

The test data presented in the table of FIG. 16 gives some indication of the substantial improvement in reverse propeller thrust to be derived from utilization of this invention. The data was taken in connection with an outboard motor utilizing a through the propeller hub exhaust system with the engine operating at the engine speeds indicated in column A. A two bladed, 21 pitch propeller was employed in the test. In columns B, C and D the reverse thrust in pounds is recorded under the varying test conditions indicated, namely, whether the exhaust discharge opening at the rear of the propeller was open as indicated in columns B and C or closed as in column D and whether the propeller mounting provided for a radial exhaust discharge opening forwardly of the propeller resulting from separation between the propeller and adjacent housing portion.

The data of FIG. 16 would seem to show that the solid flow of water to the propeller and the reduction in exhaust back pressures during reverse operation of the propulsion unit results in substantially improved reverse propeller thrust giving rise to better economy and improved control and manueverability in the operation of the propulsion unit.

Further, a cavitating propeller or one that is working in an exhaust and water environment can overspeed which may well lead to engine damage. A propeller provided with a solid flow of water acts as a governor on the engine to preclude overspeeding. Thus, according to the present invention, such overspeeding is prevented regardless of the direction of operation of the propulsion unit.

I claim:

1. In an outboard propulsion unit driven by an internal combustion engine and having a reversible propeller to selectively drive the unit in the forward and rearward directions, said unit further having passage means for conducting exhaust gases from the engine through said unit and a first underwater exhaust discharge opening generally rearwardly of the propeller and communicating with said passage'means to discharge the exhaust gases rearwardly of the propeller when the latter is operating to drive the propulsion unit in the forward direction, said propulsion unit having a second underwater exhaust discharge opening forwardly of the propeller and communicating with said passage means and normally closed when the unit is driven in the forward direction, said second exhaust discharge opening being adapted to open to discharge the exhaust gases forwardly of the propeller when the latter is operating to drive the propulsion unit in the rearward direction.

2. in an outboard propulsion unit driven by an internal combustion engine and havinga reversible propeller to selectively drive the unit in the forward and rearward directions, said unit further having passage means for conducting exhaust gases from the engine, means defining a first underwater exhaust discharge opening generally rearwardly of the propeller and communicating with said passage means to provide for discharge of the exhaust gases rearwardly of the propeller when the latter is operating to drive the propulsion unit in the forward direction, and means defining a second underwater exhaust discharge opening forwardly of the propeller and communicating with said passage means and normally closed when the unit is driven in the forward direction, said second exhaust discharge opening being adapted to open to provide for discharge of exhaust gases forwardly of the propeller when the latter is operating to drive the propulsion unit in the rearward direction.

3. The invention as set forth in claim 2 wherein the propeller is provided with an exhaust passage communicating with the exhaust passage means of the propulsion unit and the means defining the first underwater exhaust discharge opening is an opening from said exhaust passage at the rear of the propeller.

4. The invention as set forth in claim 3 wherein valve means are disposed in the exhaust discharge opening at the rear of the propeller to close the opening when the propulsion unit is operating in reverse.

5. The invention as set forth in claim 4 wherein the propeller is carried on a generally horizontal and selectively reversible propeller shaft rotatably supported by the propulsion unit and the valve means comprise an annular valve member carried by the propeller shaft,

said annular valve member being circumferentially en 7. The invention as set forth in claim 5 wherein the annular valve member carried by the propeller shaft comprises a metal plate member.

8. The invention as set forth in claim 2 wherein the means defining the second underwater exhaust discharge opening is a radial opening formed by a separation between the propulsion unit and propeller.

9. The invention as set forth in claim 8 wherein the radial exhaust discharge opening formed by a separation between the propulsion unit and propeller is effected by reverse propeller thrust.

10. The invention as set forth in claim 8 wherein the radial exhaust discharge opening formed by a separation between the propulsion unit and propeller is effected by reverse propeller torque.

11. The invention as set forth in claim 8 wherein the propeller is carried on a generally horizontal and selectively reversible propeller shaft rotatably supported by the propulsion unit and the radial exhaust discharge opening formed by a separation between the propulsion unit and propeller is effected by axial movement of the propeller shaft.

12. The invention as set forth in claim 2 wherein the propulsion unit includes an anti-cavitation plate and the means defining the first underwater exhaust discharge opening is an opening associated with said anticavitation plate.

13. The invention as set forth in claim 2 wherein the propulsion unit includes an anti-cavitation plate and the means defining the first underwater exhaust discharge opening is an exhaust snout projecting downwardly from the anti-cavitation plate.

14. In an outboard propulsion unit driven by an inter.- nal combustion engine and having a housing portion including passage means for receiving the exhaust gases from said engine, said housing portion having an opening rearwardly thereof communicating with said exhaust passage means, said unit having a generally horizontal propeller shaft rotatably supported in said housing portion and projecting from the opening thereof and drivingly connected to the engine for selective rotation in opposed directions in accordance with forward and reverse drive operation of the unit, a slip clutch'assembly mounted on the rearwardly projecting portion of the propeller shaft for rotation therewith, and a propeller carried on the slip clutch assembly and comprising a pair of radially spaced hub sleeves connected by a plurality of vanes to form axially extending exhaust passages in the propeller and terminating with an exhaust discharge opening rearwardly thereof, said propeller having a forward position wherein the outer hub sleeve is generally adjacent to and aligned with the opening in the housing portion to place the propeller passages in communication with the housing portion exhaust passage means whereby to conduct the engine exhaust gases rearwardly through the propeller for discharge from the exhaust discharge opening during forward drive operation of the propulsion unit, said propeller being axially movable relative to the propeller shaft and having a rearward position wherein the propeller is spaced from the housing portion to form a radial exhaust discharge opening forwardly of the propeller for discharge of exhaust gases during reverse drive operation of the propulsion unit.

15. The invention as set forth in claim 14 wherein the propeller is drivingly connected to the slip clutch assembly by engagement of complementary splines and stop means are provided on the propeller shaft at the respective ends of the slip clutch engageable by the propeller, and wherein said propeller is axially movable between the stop means in response to propeller thrust.

16. The invention as set forth in claim 14 wherein a valve retaining member is disposed on the propeller shaft rearwardly of the slip clutch assembly and serves as stop means for movement of the propeller rearwardly, and an annular flexible valve member is disposed on the periphery of said retaining member, said valve member being adapted to engage with the outer hub sleeve of the propeller to close the exhaust discharge opening at the rear of the propeller when the propeller is moved rearwardly-during reverse drive operation of the propulsion unit.

17. The invention as set forth in claim 16 wherein stop means engageable by the propeller are disposed on the propeller shaft forwardly of the slip clutch assembly, and a spring is disposed between the valve retaining member and the propeller to bias the propeller in the direction of the stop means.

18. The invention as set forth in claim 16 wherein an annular offset is provided in one of the adjacent faces of the inner hub sleeve and the valve retaining member to form a spring seat, and a coil spring is disposed on the propeller shaft between the inner hub sleeve and the valve retaining member with one end thereof seated in the offset and serves to bias the propeller in the forward direction.

19. The invention as set forth in claim 14 wherein the propeller and slip clutch assembly are secured together to form a unitary assembly which is axially movable relative to the propeller shaft.

20. ln an outboard propulsion unit driven by an internal combustion engine and having a housing portion including passage means for receiving the exhaust gases from said engine; said housing portion having an opening rearwardly thereof communicatingwith said ex haust passage means; said unit having a generally horizontal propeller shaft rotatably supported in said housing portion and projecting from the opening thereof and drivingly connected to the engine for selective rotation in opposed directions in accordance with forward and reverse drive operation of the unit; a propeller assembly comprising radially spaced first and second hub sleeves having an annular elastomeric element sandwiched therebetween to form slip clutch means, a third hub sleeve disposed radially outward from the second hub sleeve and carrying the propeller blades, and a plurality of axially extending vanes connecting the second and third hub sleeves to form exhaust passages therebetween extending through the propeller assembly and terminating with an exhaust discharge opening rearwardly of the assembly; the inner first hub sleeve of said assembly being rotationally locked on the propeller shaft to provide for rotation of the assembly with the propeller shaft; said propeller assembly having a forward position wherein the outer third hub sleeve overlaps within the opening in the housing portion to peller assembly is spaced from the housing portion to form a radial exhaust discharge opening forwardly of the propeller assembly for discharge of exhaust gases during reverse drive operation of the propulsion unit.

21. The invention as set forth in claim 20 wherein axially spaced stop means are provided on the propeller shaft and the propeller assembly is axially movable between the stop means in response to propeller thrust.

22. The invention as set forth in claim 20 wherein a valve retaining member is disposed on the propeller shaft rearwardly of the propeller assembly and serves as a stop to interrupt movement of the propeller rearwardly and an annular flexible valve member is disposed on the periphery of the retaining member, said valve member being adapted to engage with the outer third hub sleeve of the propeller assembly to close the exhaust discharge opening at the rear of the assembly when the propeller assembly is moved rearwardly during reverse drive operation of the propulsion unit.

23. The invention as set forth in claim 22 wherein stop means engageable by the propeller assembly are disposed on the propeller shaft forwardly of the assembly, and a spring is disposed between the valve retaining member and the propeller assembly to bias the as sembly in the direction of the stop means.

24. In a marine propulsion device comprising a lower unit including an exhaust gas discharge passageway terv minating in an exhaust gas discharge port, a rotatably mounted porpeller shaft extending through said port, a clutch mechanism selectively connecting said propeller shaft in forward drive and in rearward drive and a propeller mounted on said propeller shaft for rotation therewith and including a blade having a rear face and an exhaust gas passageway having an inlet communicating with said exhaust gas discharge port and an outlet rearwardly of said blade, the improvement in combination therewith comprising means for affording underwater exhaust gas discharge through said port and into the water around said lower unit forwardly of the rear face of said propeller blade when said device is in reverse drive.

25; A device in accordance with claim 24 including means for preventing exhaust gas discharge through said outlet when said device is in said reverse drive.

26. In a marine propulsion device comprising a lower unit including an exhaust gas discharge passageway terminating in an exhaust gas discharge port, a rotatably mounted propeller shaft extending through said port, and a propeller mounted on said propeller shaft for rotation therewith and including an exhaust gas duct having an inlet located in a position directly communicating with said exhaust gas discharge port, the improvement in combination therewith comprising means for affording axially shifting of said propeller relative to said discharge port between said position wherein said discharge port and said inlet are in direct communication and a second position wherein said discharge port and said inlet are in spaced relation to each other to provide an opening for exhaust gas discharge forwardly of said propeller.

27. A marine propulsion device according to claim 26 wherein said means for affording axial shifting of said propeller relative to said discharge port comprises cooperating means on said propeller shaft and on said propeller affording axial shifting of said propeller on said propeller shaft.

Claims

1. In an outboard propulsion unit driven by an internal combustion engine and having a reversible propeller to selectively drive the unit in the forward and rearward directions, said unit further having passage means for conducting exhaust gases from the engine through said unit and a first underwater exhaust discharge opening generally rearwardly of the propeller and communicating with said passage means to discharge the exhaust gases rearwardly of the propeller when the latter is operating to drive the propulsion unit in the forward direction, said propulsion unit having a second underwater exhaust discharge opening forwardly of the propeller and communicating with said passage means and normally closed when the unit is driven in the forward direction, said second exhaust discharge opening being adapted to open to discharge the exhaust gases forwardly of the propeller when the latter is operating to drive the propulsion unit in the rearward direction.

2. In an outboard propulsion unit driven by an internal combustion engine and having a reversible propeller to selectively drive the unit in the forward and rearward directions, said unit further having passage means for conducting exhaust gases from the engine, means defining a first underwater exhaust discharge opening generally rearwardly of the propeller and communicating with said passage means to provide for discharge of the exhaust gases rearwardly of the propeller when the latter is operating to drive the propulsion unit in the forward direction, and means defining a second underwater exhaust discharge opening forwardly of the propeller and communicating with said passage means and normally closed when the unit is driven in the forward direction, said second exhaust discharge opening being adapted to open to provide for discharge of exhaust gases forwardly of the propeller when the latter is operating to drive the propulsion unit in the rearward direction.

5. The invention as set forth in claim 4 wherein the propeller is carried on a generally horizontal and selectively reversible propeller shaft rotatably supported by the propulsion unit and the valve means comprise an annular valve member carried by the propeller shaft, said annular valve member being circumferentially engageable within the propeller exhaust discharge opening to substantially seal the opening.

6. The invention as set forth in claim 5 wherein the annular valve member carried by the propeller shaft comprises a resilient member.

7. The invention as set forth in claim 5 wherein the annular valve member carried by the propeller shaft comprises a metal plate member.

12. The invention as set forth in claim 2 wherein the propulsion unit includes an anti-cavitation plate and the means defining the first underwater exhaust discharge opening is an opening associated with said anti-cavitation plate.

14. In an outboard propulsion unit driven by an internal combustion engine and having a housing portion including passage means for receiving the exhaust gases from said engine, said housing portion having an opening rearwardly thereof communicating with said exhaust passage means, said unit having a generally horizontal propeller shaft rotatably supported in said housing portion and projecting from the opening thereof and drivingly connected to the engine for selective rotation in opposed directions in accordance with forward and reverse drive operation of the unit, a slip clutch assembly mounted on the rearwardly projecting portion of the propeller shaft for rotation therewith, and a propeller carried on the slip clutch assembly and comprising a pair of radially spaced hub sleeves connected by a plurality of vanes to form axially extending exhaust passages in the propeller and terminating with an exhaust discharge opening rearwardly thereof, said propeller having a forward position wherein the outer hub sleeve is generally adjacent to and aligned with the opening in the housing portion to place the propeller passages in communication with the housing portion exhaust passage means whereby to conduct the engine exhaust gases rearwardly through the propeller for discharge from the exhaust discharge opening during forward drive operation of the propulsion unit, said propeller being axially movable relative to the propeller shaft and having a rearward position wherein the propeller is spaced from the housing portion to form a radial exhaust discharge opening forwardly of the propeller for discharge of exhaust gases during reverse drive operation of the propulsion unit.

16. The invention as set forth in claim 14 wherein a valve retaining member is disposed on the propeller shaft rearwardly of the slip clutch assembly and serves as stop means for movement of the propeller rearwardly, and an annular flexible valve member is disposed on the periphery of said retaining member, said valve member being adapted to engage with the outer hub sleeve of the propeller to close the exhaust discharge opening at the rear of the propeller when the propeller is moved rearwardly during reverse drive operation of the propulsion unit.

20. In an outboard propulsion unit driven by an internal combustion engine and having a housing portion including passage means for receiving the exhaust gases from said engine; said housing portion having an opening rearwardly thereof communicating with said exhaust passage means; said unit having a generally horizontal propeller shaft rotatably supported in said housing portion and projecting from the opening thereof and drivingly connected to the engine for selective rotation in opposed directions in accordance with forward and reverse drive operation of the unit; a propeller assembly comprising radially spaced first and second hub sleeves having an annular elastomeric element sandwiched therebetween to form slip clutch means, a third hub sleeve disposed radially outward from the second hub sleeve and carrying the propeller blades, and a plurality of axially extending vanes connecting the second and third hub sleeves to form exhaust passages therebetween extending through the propeller assembly and terminating with an exhaust discharge opening rearwardly of the assembly; the inner first hub sleeve of said assembly being rotationally locked on the propeller shaft to provide for rotation of the assembly with the propeller shaft; said propeller assembly having a forward position wherein the outer third hub sleeve overlaps within the opening in the housing portion to place the propeller assembly passages in communication with the housing portion exhaust passage means whereby to conduct the engine exhaust gases rearwardly through the propeller assembly for discharge from the exhaust discharge opening during forward drive operation of the propulsion unit; said propeller assembly being axially movable relative to the propeller shaft and having a rearward position wherein the propeller assembly is spaced from the housing portion to form a radial exhaust discharge opening forwardly of the propeller assembly for discharge of exhaust gases during reverse drive operation of the propulsion unit.

23. The invention as set forth in claim 22 wherein stop means engageable by the propeller assembly are disposed on the propeller shaft forwardly of the assembly, and a spring is disposed between the valve retaining member and the propeller assembly to bias the assembly in the direction of the stop means.

24. In a marine propulsion device comprising a lower unit including an exhaust gas discharge passageway terminating in an exhaust gas discharge port, a rotatably mounted porpeller shaft extending through said port, a clutch mechanism selectively connecting said propeller shaft in forward drive and in rearward drive and a propeller mounted on said propeller shaft for rotation therewith and including a blade having a rear face and an exhaust gas passageway having an inlet communicating with said exhaust gas discharge port and an outlet rearwardly of said blade, the improvement in combination therewith comprising means for affording underwater exhaust gas discharge through said port and into the waTer around said lower unit forwardly of the rear face of said propeller blade when said device is in reverse drive.

25. A device in accordance with claim 24 including means for preventing exhaust gas discharge through said outlet when said device is in said reverse drive.