US3285221A

US3285221A - Outboard propulsion unit power tilt mechanism

Info

Publication number: US3285221A
Application number: US396147A
Authority: US
Inventors: Irving W North
Original assignee: Kiekhaefer Corp
Current assignee: Kiekhaefer Corp
Priority date: 1964-09-14
Filing date: 1964-09-14
Publication date: 1966-11-15
Anticipated expiration: 1983-11-15

Description

Nov. 15, 1966 l. w. NORTH 3,285,221

OUTBOARD PROPULSION UNIT POWER TILT MECHANISM Filed Sept. 14, 1964 5 Sheets-Sheet 1 INVENTOR. lRVl/VG W /VORTH BY (/Qndrus f rl r4 for/13315 I. W- NORTH Nov. 15, 1966 OUTBOARD PROPULSION UNIT POWER TILT MECHANISM Filed Sept. 14, 1964 5 Sheets-Sheet 2 INENTOR. W A/0RTH 5 f r/1" e Affo ne s I. W. NORTH Nov. 15, 1966 OUTBOARD PROPULSION UNIT POWER TILT MECHANISM Filed Sept. 14, 1964 5 Sheets-Sheet 3 INVENTOR. lRV/IVG M. A aRTH BY qndrus ff United States Patent M 3,285,221 OUTBOARD PROPULSION UNIT POWER TILT MECHANISM Irving W. North, Fond du Lac, Wis., assignor to Kiekhaefer Corporation, Fond du Lac, Wis., a corporation of Delaware Filed Sept. 14, 1964, Ser. No. 396,147 11 Claims. (Cl. 115-41) This invention relates to outboard propulsion units for boats and more particularly to a power tilt mechanism therefor.

The invention has been applied to outboard propulsion units wherein the drive unit is pivotally supported from a transom support member upon a generally horizontal tilt-axis and wherein the drive unit is releasably secured against tilting to the support member in the normal operating position of the drive unit.

According to one phase of the invention, the power tilt mechanism generally includes a source of fluid at a given pressure and an extendable cylinder-piston means disposed between the drive unit and its support member. The pressure source and cylinder-piston means are connected by means including pressure boosting means. The pressure boosting means is adapted to initially provide fluid to the cylinder-piston means at a pressure higher than the given pressure to initially extend the cylinderpiston means with a force adequate to tilt the drive unit and overcome the releasable securement between the drive unit and the support member. After the releasable securement is overcome, the pressure boosting means is rendered ineffective and is adapted to pass fluid at the given pressure to extend the cylinder-piston means and further tilt the drive unit upon its tilt axis. The cylinderpiston means is further adapted to damp the angular momentum of the drive unit upon striking a submerged or floating object.

According to another phase of the invention, the hydraulic power tilt mechanism is disposed between the propulsion unit and its support means in such a way that the cylinder-piston means are disposed in a vertical plane or planes substantially parallel to the propeller thrust force in all positions of steering. In accomplishing this the support means comprises a member mounted upon the boat transom by means providing for angular steering of the member relative to the boat on a substantially vertical axis. 7

The drawings furnished herewith illustrate the best mode for carrying out the invention as presently contemplated and set forth hereinafter.

In the drawings:

FIG. 1 is a side elevation of an outboard propulsion unit showing the drive unit in its normal operating position and releasably secured to its support member and in phantom lines shows the drive unit in a tilted position;

FIG. 2 is a detail sectional view showing the power tilt mechanism of this invention generally at a time when the drive unit is in the normal operating position;

FIG. 3 is a view generally similar to that of FIG. 2 and shows the power tilt mechanism at a time when the drive unit is approaching its position of maximum tilt; and

FIG. 4 is a sectional view showing an alternate cylinder-piston means for the power tilt mechanism of this invention.-

Referring to the drawings, the watercraft 1, only partially shown, is propelled by the outboard drive unit 2.

3,285,221 Patented Nov. 15, 1966 The drive unit 2 is carried upon the boat transom by sup- ,port means wherein the unit is pivotally supported on a generally horizontal tilt axis 3 by an intermediate member 4 which is in turn pivotally supported on a generally vertical steering axis 5 by the support structure 6 rigidly secured to the transom 7 of the watercraft.

The thrust of the propeller 8 is transmitted to the intermediate member 4 through abutment means in the form of a transversely extending tilt adjustment pin 9 supported in aligned openings 10 in the transversely spaced flange members 11 extending rearwardly from the intermediate member generally beneath the tilt axis 3. The tilt adjustment pin 9 is selectively movable for disposition in a corresponding pair of a series of aligned openings 10 provided in flange members 11 to establish the desired operating trim for the drive unit.

A releasable latch assembly 12 is pivotally carried by the drive unit 2 at 13 and is spr'mg-biased into engagement with the tilt adjustment pin 9. While the latch' hook 14 normally remains in engagement with the tilt adjustment pin 9 during operation of the drive unit, the hook is disengageable from the pin when a predetermined pressure is exerted on the hook to permit tilting of the drive unit 2 about the horizontal axis 3 as when the unit strikes a submerged or floating obstruction. The hook 14 re-engages the pin 9 when the drive unit returns to its normal operating position after the unit has cleared the obstruction.

According to this invention, power means are provided for driving the drive unit 2 about the tilt axis 3 from the normal operating position to the full tilt position or between intermediate positions as desired. The power means includes an extendable hydraulic cylinder-piston arrangement 15 which is interposed between the drive unit 2 and the intermediate member 4. The cylinderpiston arrangement 15 serves also to damp the angular momentum imparted to the drive unit 2 upon impact with a submerged or floating object.

As generally shown in FIG. 1, the end of cylinder 16 is pivotally mounted upon an anchor pin 17 carried rearwardly of the drive shaft housing 18 and above the anticavitation plate 19 of the drive unit 2. The opposite end of the piston rod 20 is supported within bracket means 21 pivotal-1y mounted on an outboard extension of the tilt adjustment pin 9 carried by the intermediate member 4.

The power means for operating the cylinder-piston arrangement 15 to tilt the drive unit 2 includes the gear pump 22 which is driven by a reversible electric motor 23. That which is the suction side of the pump 22 when the drive unit 2 is driven upwardly is provided with an adaptor 24 which communicates with the oil sump 25 through priming conduit 26. The flow of oil from the sump 25 through conduit 26 is controlled by check valve 27 having an upper closure seat 28 and a lower by-pass seat 29 selectively engageable by the loose ball 30 in accordance with pressure during operation of the pump.

The adaptor 24 for pump 22 further communicates with the sump 25 through conduits 31 and 32 having a valve 33 interposed therebetween. Valve 33 includes a rotatable cylindrical element 34 having a pair of angularly spaced diametrically extending through passages 35 and 36 either of which is capable of connecting conduits 31 and 32 to place the adaptor 24 in communication with the sump 25. Valve element 34 has an intermediate position wherein the valve element closes off conduits 31 and 32 as generally shown in FIG. 2.

That which is the pressure side of pump 22 when the drive unit 2 is driven upwardly is provided with an adaptor 37 which communicates with the sump 25 through the priming conduit 38. A check valve 39 similar to valve 27 is disposed in conduit 38 and has an upper closure seat 40 and a lower by-pass seat 41 selectively engageable by the loose ball 42.

When the pump 22 is not in operation, the valves 27 and 39 freely pass priming fluid from the sump 25 past the

corresponding bypass seats

29 and 41. When the pump 22 is operated to tilt up the drive unit 2, pressure at the adaptor 37 closes valve 39 by forcing the ball 42 against the upper closure seat 40 and suction at the adaptor 24 retains valve 27 open by holding the ball 30 against the corresponding lower bypass seat 29 as generally shown in FIG. 3. When the pump 22 is driven reversely to thereby alternate the pressure and suction sides of the pump and permit the drive unit 2 to return to the direction of its normal operating position, the ball 30 is forced against its closure seat 28 to close the valve 27. In the latter instance the pressure at adaptor 37 normally exceeds the suction pressure of pump 22 as the cylinder-piston assembly 15 contracts and thereby forces the ball 42 against its closure seat 40 to also close valve 39 and prevent flow from sump 25 through conduit 38.

The adaptor 37 for pump 22 also communicates with a pressure booster or multiplier 43 through conduits 44 and 45 having the valve 46 interposed therebetween. Valve 46 is similar to valve 33 and includes the rotatable cylindrical element 47. Element 47 has a pair of diametrically extending through passages 48 and 49 which are similarly angularly spaced as passages 35 and 36 in valve element 34 of valve 33 and are adapted to connect conduits 44 and 45 to place the adaptor 37 in communication with the pressure multiplier 43. Like valve element 34, element 47 of valve 46 has an intermediate position wherein the valve element closes off conduits 44 and 45.

The rotatable valve elements 34 and 47 are similarly disposed within the respective valves 33 and 46 and are always operable in unison by the cylinder-piston means 50 disposed therebetween. The piston 51 is slidably disposed in the cylinder 52 and is provided with

opposed rods

53 and 54 which extend through the opposed cylinder chambers 55 and 56 and project through the correspond ing ends of the cylinder. Outwardly of cylinder 52, the

respective rods

53 and 54 are provided with corresponding offset rack portions 57 and 58. The respective rack portions 57 and 58 meshingly engage corresponding pinions 59 and 60 drivingly associated with the corresponding rotatable valve elements 34 and 47.

When the pump 22 is not operating, the piston 51 is maintained generally centrally of cylinder 52 by the helical springs 61 and 62 disposed around the

corresponding piston rods

53 and 54 in abutting relation between the piston and the corresponding end walls of the cylinder chambers 55 and 56. As generally shown in FIG. 2, with piston 51 disposed generally centrally of the cylinder 52, the valve elements 34 and 47 of the corresponding valves 33 and 46 are rotated to an intermediate closed position isolating the pump 22 from the sump 25 through conduits 31 and 32 and from pressure multiplier 43 respectively.

Cylinder chamber 55 is placed in communication with the adaptor 24 of pump 22 through conduit 63 and chamber 56 communicates with the adaptor 37 through conduit 64. Thus, when the pump 22 is placed in operation, the pressure differential across the pump acts upon and slidably displaces the piston 51 Within cylinder 52. Operation of the pump 22 to tilt the drive unit 2 upwardly, effects movement of piston 51 to compress the spring 61 and thereby rotate the valve elements 34 and 47 in a counterclockwise direction. As generally shown in FIG. 3, movement of the piston 51 is interrupted by engagement of the shoulder 65 formed by the offset in 4 rod 54 against the end Wall of cylinder 52 at which point the valve passages 35 and 48 of corresponding valves 33 and 46 are properly aligned to open the hydraulic circuit between the sump 25 and the pump 22 via conduits 31 and 32 and between the pump and pressure multiplier 43 respectively. When the pump 22 is reversely driven, the piston 51 is moved in the opposite direction compressing spring 62 until movement is interrupted by shoulder 66 at which point the

valve passages

36 and 49 are properly aligned within the corresponding valves to open the corresponding hydraulic circuits providing for reverse flow of the pressure fluid to permit the drive unit 2 to return in the direction of its normal operating position.

To tilt the drive unit 2 upwardly, an initial pressure considerably higher than normal pump pressure is required to disengage the spring-biased latch assembly 12 on the drive unit from the tilt adjustment pin 9. This initial surge of pressure is developed Within the pressure multiplier 43 the head end of which communicates with conduit 45 extending from valve 46. Y

The pressure multiplier 43 generally comprises a closed hollow cylindrical member 67 having a cylindrical core or stationary plunger 68 extending inwardly and coaxially from the base end thereof. Core 68 is spaced radially from the inner wall of member 67 and the head 69 thereof is spaced axially from the head 70 of the cylindrical member. A plunger 71 is slidably disposed in member 67 ahead of the core 68 and is movable between the cylinder head 70 and the head 69 of core 68. The plunger 71 includes a cylindrical skirt portion 72 which telescopes upon core 68.

The head chamber 73 ahead of plunger 71 communicates with the chamber 74 disposed between the plunger and head 69 of core 68 and within the plunger skirt portion 72 through the axial passage 75 in the plunger. Flow in the corresponding direction through plunger passage 75 is controlled by the opposed

check valves

76 and 77 disposed adjacent the corresponding ends of the passage. The

balls

78 and 79 of the

respective valves

76 and 77 are constantly biased toward their corresponding seats 80 and 81 by the compression spring 82 therebetween.

When head chamber 73 is subjected to pump pressure and passage 75 is closed initially by check valve 77 and thereafter by check valve 76 due to the higher pressure in chamber 74, plunger 71 is forced in the direction of core 6 8 pushing the fluid from chamber 74 through the stepped core passage 83 and into conduit 84 connected to the cylinder-piston assembly 15. In view of the crosssectional area differential between the head chamber 73 and chamber 74, the initial pressure coursing passage 83 and conduit 84 is boosted or multiplied in the ratio of the areas so that the initial extension of the cylinder-piston assembly 15 can effect a release of the spring-biased latch assembly 12 from the tilt adjustment pin 9 on the intermediate member 4.

After the fluid is substantially displaced from chamber 74 by movement of plunger 71 effecting adequate extension of the cylinder-piston assembly 15 to effect release of the latch assembly 12, the ball 79 of check valve 77 in passage 75 engages with and is retained unseated by pin 85 extending axially from the head 69 of core 68 as generally shown in FIG. 3. Thereafter substantially normal pump pressure opens check valve 76 and courses passages 83 and conduit 84 to further extend the cylinderpiston assembly 15 and tilt the drive unit 2 upwardly relative to the intermediate member 4 as desired.

When the pump 22 is reversely driven to permit return of the drive unit 2 in the direction of its normal operating position, the ball 78 of check valve 76 in passage 75 is seated and the plunger 71 returned in the direction of the cylinder head 70 by the higher pressure in chamber 74 due to the contracting cylinder-piston assembly 15. As the plunger 71 approaches cylinder head 70, the ball 78 is unseated by the axially extending pin 86 projecting from the cylinder head to provide for return passage of the fluid to the sump 25 to permit contraction of the cylinder-piston assembly and return of the drive unit 2 in the direction of its normal operating position.

Conduit 84 communicates with the stepped passage 87 in the piston rod 20 of the cylinder-piston assembly 15. At least a portion of conduit 84 is flexible to accommodate movements of the cylinder-piston assembly 15 along with the drive unit 2 and intermediate member 4 in a generally horizontal plane about the steering axis 5. A velocity check valve 88 is disposed in conduit 84 and comprises a ball 89 biased in the direction of the cylinder-piston assembly 15 by the spring 90. The spring 90 normally biases the ball 89 away from its seat 91 and against the perforated retainer 92 and is able to withstand the pressure due 'AtO contraction of the cylinder-piston assembly 15 to permit passage of fluid from the contracting cylinderpiston assembly when the pump 22 is reversely driven.

The piston 93 is mounted on the end of rod 20 within the cylinder 16 and separates chamber 94 ahead of the piston from the chamber 95 through which the rod extends. A velocity check valve 96 is disposed in passage 97 which extends generally axially of the piston 93 and connects chamber 94 with the passage 87 in rod 20. Check valve 96 comprises a ball 98 biased in the direction of rod passage 87 by the spring 99. The spring 99 biases the ball 98 away from its seat 100 and against the open slot retainer 101. Passage 87 in rod 20 also communica-tes with chamber 95 behind piston 93 through the opening 102 in the rod.

Chambers 94 and 95 on the respective sides of piston 93 also communicate through passage 103 which extends through the piston and is offset from the rod 20. A relatively high pressure check valve 104 permits flow through passage 103 only from chamber 95 to chamber 94. Flow in the reverse direction is prevented by valve ball 105 being biased against its seat 106 by the spring washer 107.

In operation and assuming a desire to tilt the drive unit 2 upwardly about the tilt axis 3 from its normal operating position with hook 14 of latch assembly 12 engaged with the tilt adjustment pin 9 of the intermediate member 4, the initial fluid pressure as generated in chamber 74 of the pressure multiplier 43 courses passage 87 in piston rod 20, passes around the ball 98 of velocity check valve 96 and enters chamber 94. Since the fluid pressure acts on a larger piston area in chamber 94 than in chamber 95 behind the piston, the cylinder 16 is forced rearwardly with respect to the boat transom 7 under the influence of the boosted pressure a distance sufficient to effect release of the spring-biased latch assembly 12 from the tilt adjustment pin 9 of intermediate member 4. Thereafter, substantially normal pump pressure continues through passage 87 of the piston rod 20 and flows similarly as the initially boosted pressure past check valve 96 into chamber 94 to further extend cylinder 16 as desired.

If so desired, the drive unit 2 may be tilted upwardly about the axis 3 to a maximum position as determined by an appropriate stop, not shown. If the pump 22 is thereupon shut oflf, the rotatable elements 34 and 47 of valves 33 and 46 respectively return to the intermediate closed position to lock the fluid in the system and retain the drive unit in a substantially maximum tilt position. If desired, the pump 22 may be stopped at any lesser tilt position of drive unit 2, and with stoppage of the pump and consequent closure of valves 33 and 46, the drive unit will be retained in the desired position. With the fluid in the system locked, the drive unit may be retained in a given position even as against propeller thrust. Thus, the power means of this invention is particularly useful when navigating water more shallow than required for operation of the drive unit at normal operating trim.

When it is desired to return the drive unit 2 about its tilt axis 3 to some lesser tilt position or all the way to its lowermost normal operating position, reversal of pump 22 imposes a suction pressure on the system and permits the cylinder-piston assembly 15 to contract as the drive unit 2 moves downwardly under the influence of gravity. Upon return of the -unit 2 to the normal operating position, the latch assembly 12 is automatically reengaged with the tilt adpustment pin 9 of the intermediate member 4.

With the drive unit 2 underway, the cylinder-piston assembly 15 further serves as means to damp the angular momentum of the unit as when the unit strikes a submerged or floating object and swings upwardly about the tilt axis 3. Regardless of whether the underway drive unit 2 is in the normal operating position or in some other tilt position, impact with a submerged or floating object causes a pressure buildup behind piston 93 in chamber as the cylinder 16 is extended with the swinging drive unit. The suddenly increased pressure courses opening 102, rod passage 87 and conduit 84 to close the

velocity check valves

96 and 88 and trap the fluid in the cylinderpiston assembly 15. The small amount of fluid under high pressure which may initially get past velocity check valve 88 is relieved into the sump 25 past the relatively high pressure check valve 108 in conduit 109 connecting the sump and pressure multiplier 43 to protect the parts in the system. As the cylinder 16 is further extended with the swinging drive unit, the pressure in chamber 95 continues to buildup to dampen and dissipate a large portion of the energy imparted to the drive unit and upon exceeding the preset pressure of check valve 104 is relieved through passage 103 into chamber 94. When the swinging drive unit returns to its initial position, the pressure fluid in chamber 94 is forced from the chamber through passage 97 past the now open velocity check valve 96. The cross-sectional area of passage 97 is selected to provide a controlled flow from chamber 94 back to chamber 95 whereby to limit or impede the eflect of propeller thrust as the drive unit reenters the water on the return swing.

According to the embodiment of FIG. 4, the power means for driving the drive -unit 2 about the tilt axis 3 includes cylinder-piston means in the form of a pair of telescoping sleeves 110 and 111. The closed end of outer sleeve 110 is pivotally mounted upon anchor pin 17 carried by the drive shaft housing 18. The oposite closed end of inner sleeve 111 is supported within bracket means 21 pivotally mounted on an outward extension of the tilt adjustment pin 9 carried by the intermediate member 4. The stepped passage 112 extending substantially the length of inner sleeve 11 communicates with core passage 83 of the pressure multiplier 43 through conduit 113 at least a portion of which is flexible. A pair of return springs 114 and 115 are disposed one within the other within inner sleeve 111 and have one end thereof engaged over .a transverse pin 116 of the inner sleeve while the opposite spring ends are secured to the projection 117 extending inwardly from the end of outer sleeve 110.

In operation and with the drive unit 2 in the normal operating position having the releasable latch assembly 12 engaged with the tilt adjustment pin 9 of intermediate member 4, outer sleeve 110 is extended initially by the boosted pressure as generated in chamber 74 of multiplier 43 and conducted to sleeve 111 through core passage 83 and conduit 113 to tilt the unit sufliciently to etfect release of the latch assembly. Thereafter, further extension of the sleeve 110 to tilt the drive unit to the height desired is efifected by substantially normal pump pressure. Upon reversal of pump 22 and the withdrawal of fluid from the system, return movement of the drive unit is effected by gravity with assistance from return springs 114 and 115.

I claim:

1. In combination with an outboard propulsion unit pivotally supported upon a generally horizontal axis from a support member to provide for tilt movement of the unit in a generally vertical plane and said unit being releasably secured against tilting to said member in the normal operating position of the unit, power means to tilt the unit upwardly about said axis and comprising extendable cylinder-piston means disposed between the drive unit and the support member, a source of fluid at a given pressure, and means connecting the pressure source and the cylinder-piston means and including pressure boosting means to initially provide fluid to the cylinder-piston means at a pressure higher than said given pressure to initially extend the cylinder-piston means with a force adequate to tilt the drive unit and overcome the releasable securement between the drive unit and the support member, and thereafter said pressure booster means being rendered ineffective and being adapted to pass fluid at the given pressure to extend the cylinder-piston means and further tilt the drive unit.

2. The invention as set forth in claim 1 wherein the means connecting the pressure source and the cylinderpiston means includes valve means interposed between the cylinder-piston means and the pressure boosting means, said valve means-being adapted to close in response to pressure emanating within the cylinder-piston means when the latter is extended to dampen and dissipate energy imparted to the drive unit upon striking a submerged or floating object.

3. In combination with an outboard propulsion unit pivotally supported upon a generally horizontal axis from a support member to provide for tilt movement of the unit in a generally vertical plane and said unit being releasably secured against tilting to said member in the normal operating position of the unit, power means to tilt the unit upwardly about said axis and comprising extendable cylinder-piston means disposed between the drive unit and the support member, pump means to deliver fluid at a given pressure, and a pressure multiplier connected respectively to the pump means and the cylinder-piston means, said pressure multiplier being adapted to initially deliver fluid to the cylinder-piston means at a pressure higher than the given pressure delivered by the pump means to initially extend the cylinder-piston means with a force adequate to tilt the drive unit and overcome the releasable securement between the drive unit and the support member, and after release of the drive unit from the support member said pressure multiplier being adapted to pass fluid at the given pressure to extend the cylinderpiston means arid further tilt the drive unit.

4. The invention as set forth in claim 3 wherein means are provided to return the drive unit in the direction of its normal operating position when the pump means is reversely driven.

5. The invention as set forth in claim 4 wherein the return means constitute spring means within the cylinder-piston means.

6. The invention as set forth in claim 3 wherein the pressure multiplier comprises a pair of telescopingly related plungers having corresponding head chambers of varying cross-sectional area providing a pressure boost substantially in the ratio of the respective areas to initially extend the cylinder-piston means from the normal operating position of the drive unit.

7. In a power tilt mechanism for an outboard propulsion unit tiltable on a generally horizontal axis relative to support means for said unit, extendable cylinder-piston means disposed between the unit and the support means, pump means to deliver fluid at a given pressure, and a pressure multiplier connected respectively to the pump means and the cylinder-piston means, said pressure multiplier comprising a cylindrical housing having a head end and a base end, a stationary plunger projecting axially in- Wardly from the base end of said housing and spaced radially from the housing wall, a movable plunger disposed between the head end of the housing and the stationary plunger and defining a head chamber between said movable plunger and the head end of the housing communicating with said pump means, said movable plunger including skirt means adapted to telescope upon the stationary plunger and to define a pressure chamber between said plungers communicating with the cylinderpiston means, passage means in said movable plunger connecting the head chamber and the pressure chamber, valve means in said passage means adapted to close in response to said .given pressure, said movable plunger being movable in response to said given pressure to step up the pressure in the pressure chamber substantially in the ratio of the cross-sectional areas of the respective chambers to initially deliver fluid to the cylinder-piston means at a pressure higher than said given pressure to tilt the propulsion unit iupwardly a given amount, and means to open said valve means and pass fluid to the cylinder-piston means at the given pressure to tilt the propulsion unit upwardly beyond said given amount.

8. In a power tilt mechanism for an outboard propulsion unit tiltable on a generally horizontal axis relative to support means for said unit, extendable cylinder-piston means disposed between the unit and the support means, first means connected to the cylinder-piston means to deliver fluid at a given pressure, second means connected to the cylinder-piston means to deliver fluid at a pressure higher than said given pressure, said cylinder-piston means initially receiving fluid from said second means and being extended at the higher pressure to tilt the propulsion unit upwardly a given amount and thereafter receiving fluid from said first means and being further extended at the given pressure to tilt the propulsion unit upwardly beyond said given amount. 4

9. The invention as set forth in claim 8 wherein said second pressure means is interposed between said first pressure means and the cylinder-piston means.

10. In combination in an outboard propulsion means for boats, support means carried by the boat and steerable relative thereto on a substantially vertical axis, an outboard propulsion unit carried by said support means and tiltable relative thereto on a substantially horizontal axis, said propulsion unit having underwater propulsion means exerting a thrust force in the forward direction of said unit, extendable cylinder-piston means disposed between the unit and the support means and parallel to said thrust force, means to supply substantially incompressible fluid to said cylinder-piston means to actuate the same in a direction to tilt the unit upwardly, means to trap the fluid in said cylinder-piston means to lock the latter in any selected position of extension whereby to maintain the propulsion unit in a corresponding tilt position, and means to drain fluid from said cylinder-piston means to effect a return of said unit to any selected lower tilt position.

11. In combination in an outboard propulsion means for boats, support means carried by the boat and steerable relative thereto on a substantially vertical axis, an outboard propulsion unit carried by said support means and tiltable relative thereto on a substantially horizontal axis, said propulsion unit having underwater propulsion means exerting a thrust force in the forward direction of said unit, extendable cylinder-piston means disposed between the unit and the support means and parallel to said thrust force, a source of fluid, pump means, a conduit connecting the pump means with the fluid source and the cylinder-piston means respectively, said pump means being adapted to deliver fluid under pressure to the cylinder-piston means to thereby extend the latter and tilt the propulsion unit relative to the support means, and valve means inerposed in the conduit to control the flow of fluid therebetween, said valve means constituting means to trap the fluid in the cylinder-piston means to lock the latter in any desired 9 10 position of extension whereby to maintain the propulsion 3,024,758 3/ 1962 Liebef 115-41 unit in a corresponding tilt position. 3,146,755 9/ 1964 Morse 115-35 3,186,375 1/1965 Cass 11541 References Cited by the Examiner UNITED STATES PATENTS 5 MHJTON BUCHLER, Primary Examiner. 2 755 7 195 Wanzer. T. MA] OR, Assistant Examiner.

2,893,342 7/1959 Langford 11541

Claims

1. IN COMBINATION WITH AN OUTBOARD PROPULSION UNIT PIVOTALLY SUPPORTED UPON A GENERALLY HORIZONTAL AXIS FROM A SUPPORT MEMBER TO PROVIDE FOR TILT MOVEMENT OF THE UNIT IN A GENERALLY VERTICAL PLANE AND SAID UNIT BEING RELEASABLY SECURED AGAINST TILTING TO SAID MEMBER IN THE NORMAL OPERATING POSITION OF THE UNIT, POWER MEANS TO TILT THE UNIT UPWARDLY ABOUT SAID AXIS AND COMPRISING EXTENDABLE CYLINDER-PISTON MEANS DISPOSED BETWEEN THE DRIVE UNIT AND THE SUPPORT MEMBER, A SOURCE OF FLUID AT A GIVEN PRESSURE, AND MEANS CONNECTING THE PRESSURE SOURCE AND THE CYLINDER-PISTON MEANS AND INCLUDING PRESSURE BOOSTING MEANS TO INITIALLY PROVIDE FLUID TO THE CYLINDER-PISTON MEANS AT A PRESSURE HIGHER THAN SAID GIVEN PRESSURE TO INITIALLY EXTEND THE CYLINDER-PISTON MEANS WITH A FORCE ADEQUATE TO TILT THE DRIVE UNIT AND OVERCOME THE