CA1151506A - Hydraulic trim tilt system for outboard propulsion units using a pressure amplifier - Google Patents

Abstract

ABSTRACT
A hydraulic system for trimming a marine out-board drive, and wherein a single actuator for moving the propulsion unit is used for both trim and tilt. The actuator is connected to a hydraulic pump. A means for amplifying the pump pressure is connected to the actuator, The amplifier has first and second ports connecting the actuator and to the hydraulic pump. The amplifier means includes a switch for bypassing the amplifier to pass the hydraulic fluid from the pump to the actuator without amplification. The switch is operable for bypassing the amplifier for rapidly tilting the propulsion unit and operable for connecting the amplifier within the hydraulic circuit to develop increased pressure for trimming the propulsion unit, The hydraulic amplifier includes a piston movable within a cylinder. Movement of the hydraulic amplifier piston to one end of the hydraulic amplifier cylinder actuates the switch to bypass the amplifier and movement in the other direction away from that end, switches the amplifier to its amplification mode, the amplifier continuing in its amplification mode until the amplifier piston reaches a limit means switch placed in its path to bypass the amplifier hydraulic circuit.

Description

S~6 HYDRAULIC TRIM TILT SYSTEM FOR OUTBOARD
PROPULSION UNITS USING A PRESSURE AMPLIFIER

FIELD OF THE INVENTION
This invention relates to the field of hydraulic amplifiers and to the use of a hydraulic amplifier to provide higher pressure and force to move objects such as an outboard propulsion assembly in a marine drive.

BA~KGROUND OF THE XNVENTIO_ Hydraulic trim tilt systems for outboard propulsion units are well-knwon. Further, such systems' units employing a single cylinder to displace the propulsion system such as rotating them through an arc are well-known. One such example is shown in U.S. patent No.
3,799,104 which issued to L. Kurling on March 26, 1974.
U.S. patent No. 3,842,789 which issued to K. A.
Bergstedt on October 22, 1974 also shows a system for l; using a single cylinder for power trim and tilt. Patent No. 4,064,824 which issued to J. R. Draxler on December 27, 1977 and 4,096,820 which issued to C. B. Hall on June 27, 1978, both show systems for applying hydraulic forces to separate trim and tilt cylinders. Other patents showing hydraulic systems used with marine propulsion units are 3,885,517 which issued to G. M. Borst on May 27, 1975; 3,434,450 and 3,434,448 which issued to D. F.
McCormick and W.L. Woodfill, respectively, on March 25 1969.
All of the prior systems, U.S. Patent No.
3,842,789 identified above, being an example, require a particular valving arrangement to change the amount of hydraulic pressure to the actuator and to rotate the propulsion unit through the trim and tilt range. In that patent, manual adjustment of a valve in the hydraulic supply lines is required. Although the object of this patent and of other patents is to provide a higher pressure to a system when requiring greater force and less rapid movement during trim operation and a lower pressure and more rapid movement during tilt operation, the prior , , ~ .

. ,~' ' .

5~6 devices either require separate actuator cylinders to rotate the propulsion unit through trim and tilt, or require special hydraulic switching systems to change the distribution area or the hydraulic fluid in the actuator.
DISCLOSURE OF THE INVENTION
In accordance with an aspect of the invention there is provided an hydraulic amplifier for amplifying pressure of a hydraulic fluid, said hydraulic amplifier having a displaceable means movable by said fluid in a -displacement path, said displaceable means having switch means, said switch means being open to connect a first port of said amplifier to a second port of said amplifier and to provide a fluid path through said amplifier sub-stantially without amplification responsive to a pressure differential across said switch, said amplifier having retarding means in said displacement path for retarding the movement of said displaceable means, said switch means being in a closed position when said displaceable means is moved in said displacement path, movement of said displaceable means being retarded upon reaching said retarding means in said path and increasing said pressure differential to provide fluid through said amplifier substantially without amplification.
This invention is a hydraulic system for moving, displacing or rotating a load for example, such as in a marine propulsion unit through its trim range and through a tilt range. In the trim range, when the boat is underway, and the angle of propulsion unit must be adjusted, a considerably greater force is required to displace the propulsion unit then to tilt it out of the water when power is removed. The trim range is limited with respect to the range of movement for the hydraulic propulsion unit. During trim, hydraulic fluid is provided to the hydraulic cylinder actuator unit with greater pressure and force and with a resultant slower movement of the hydraulic cy:Linder and the propulsion unit.

~51S(~6 -2a-Accordingly, this invention uses a hydraulic amplifier which is connected in the hydraulic circuit between the hydraulic pump and the hydraulic cylinder actuator unit. The amplifier increases the pump pressure during the trim operation as necessary to increase the force to the hydraulic actuator connected to the propulsion unit, at the end of the trim and start of the tilt range, the amplifier is bypassed and further displacement of the propulsion unit is then in the tilt range where the propulsion unit is then rapidly lifted clear of the water.
The hydraulic amplifier includes a displaceable or movable means which may be a piston and which has a displacement proportional to the displacement of the hydraulic actuator cylinder and the propulsion unit in the trim range. Movement of the piston within the amplifier to one end of its displacement path may correspond to movement of the propulsion unit to the end of its trim range and to the start of its tilt range.

~lS~S06 At this point, a switch means such as a valve within the hydraulic amplifier and which may be mounted on the piston, bypasses the amplifier and connects the fluid from the hydraulic pump directly through to the actuator unit. m e valve may be made responsive to dif-ferential pressure. The differential pressure will be large enough to open the valve when the load placed on the actuator cylinder is reduced or removed. In the system this will occur when the piston reaches the end of its 10 displacement path and the load is removed from the actuator.
The flow of the hydraulic fluid into ~he actuator unit is then at a lower pressure, but at a faster rate. As the propulsion unit at this point is to be tilted out of the water with power to propulsion unit being removed, less 15 force is necessary and the lower hydraulic pressure moving at a higher velocity through to the actuator is s~fficient to rapidly move the hydraulic actuator and the propulsion unit through its tilt range out of the water.
When it is desired to move the propulsion unit 20 through its tilt range bacX into the water and into the trim range, the pump is reversed, displacing the fluid in the hydraulic system in the opposi e direction and causing the actuator cylinder to rotate the propulsion unit down-wards towards the water and correspondingly displacing the 25 piston within the hydraulic amplifier. As stated above, the displaceable or movable means may be a slidable piston, moving within a cylinder. Movement of the fluid under the force of the pump forces the amplifier piston and actuator piston to be displaced as the actuator forces the propul-sion unit in the opposite direction, the movement of the 30 piston within the hydraulic amplifier corresponding to the movement of the actuator piston and of the propulsion unit.
The hydraulic amplifier includes a limit means - which may be removPd from an end and placed within the path of movement of the said amplifier piston or may be, 35 but not necessarily at the oth r extreme end of its dis-placement path~ When the amplifier piston reaches that limit means, the switch corresponding to the valve is actuated causing the amplifier to be bypassed such that , iL5~

f~ fr~m the actuator ~lows directly through the ampli-fier, bypassing the amplifier and through to the pump.
The continued operation of the pump then displaces the fluid from the actuator and through the hydraulic amplifier without amplification to further displace the hydraulic cylinder and the propulsion unit down through the balance of its tilt range. Continued operation of the pump forces the propulsion unit through the trim range until the extreme of the trim range is reached where further move-10 ment is prevented.
When during this movement of the propulsion unitin the downward direction, the pump is reversed, the hy-draulic pressure in the system will force the amplifier piston to move away from the limit means and in the other 15 direction along its displacement path and towards the one end. At this point, the switch within the amplifier will be actuated connecting the amplifier within the hydraulic circ~it, and providing hydraulic fluid with increased pre~sure but at a slower velocity to the hydraulic cylinder 20 actuator.
In the contemplated use of this device, this part of the operation will take place after the system has been operated in reverse to bring the hydraulic propuLsion unit from its full tilt position downward and to a posi-25 tion where it immersed in the water and where furtherreversal of the pump and fluid flow will be for the purpose of causing a desired trim.
In a system for providing hydraulic fluid at a first higher pressure to a hydraulic cylinder to move a 30 propulsion unit through a trim rang~, and at a lower pre-ssure but at a faster rate to move the hydraulic cylinder and a propulsion unit through a tilt range, a kydraulic amplifier is provided with means for switching the ampli-fier in and out of the hydraulic circuit ~o produce a 35 change in pressure required for the respective trim and tilt operation.
Thi9 invention accomplishes its result ky means o~ a novel arrangement of a switch being a valve mounted on the piston wlthin the hydraulic ampli~ier and dispenses .

~51506 with ex~er~al switches ~nd control s~stems to alter the system from a trim to a tilt operation and visa-versa.
Additionally, this system uses a single hydrau-lic cylinder for both trim ancl tilt operations. Use of this single cylinder is made possible by the hydraulic amplifier and its internal va].ve arrangement. When the propulsion unit and the hydraulic cylinder has moved through a range corresponding to the trim range, the valve arrangement within the pressure amplifier is switched by differential fluid pressure and fluid at a lower pressure 10 is provided directly to the actuator but at a faster rate for tilt operation.
- The invention is described with xeference to its use with a load such as a marine propulsion unit and parti-cularly where the propulsion unit is tilted or rotated out 15 of the water and where the unit may also be rotated through a trimming range when immersed in the water.
As is known, a marine propulsion unit, under-drive, exhibits a strong force in one direction, tending to rotate or drive the propulsion unit towards the transom 20 of the boat. Hydraulic systems are most commonly used to displace the propulsion unit forward and backward within a trim range when the propulsion unit is immersed in the water. ~hen underdrive and to displace the propulsion unit away from the transom of the boat, a considerable force 25 must be developed within a hydraulic actuator.
Where the propulsion unit is displaced through its trim range, further rotation or movement of the hydrau-lic propulsion unit then tilts the propulsion unit out of the water. For tilt, the drive is removed from the marine 30 propulsion unit and less hydraulic pressure is required for the actuator to rotate or-displace the propulsion unit through the balance of its range of movement and particu-larly through the tilt range.
With regard to this application and for refer-35 ence purposes, movement of the propulsion unit from aposition where it is closest to the transom of the boat, through its trim range, into and through its til~ range to its other extreme position out of the water, is defined as . . .

~si~o~

movement in a first direction. The first direction then i.s identified as movement of the propulsion unit through its trim range and its tilt range rotating it in an upper direction removing the propulsion unit from the water.
Accordingly, movement of the propulsion unit in the reverse or second direction would be downward towards the transom of the boat and through its tilt range and its trim position immersing the marine propulsion unit in the water.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. la through ld show in schematic form, the system in various stages of displacement. FIG. la showing the amplifier system wi~h the piston at its limit means wherein the amplifier is bypassed. FIG. lb showing the piston movable being midway between its limit means and its opposite end position in its displacement path and wherein it provides an amplified pressure to the actuator.
FIG. lc shows the amplifier piston at its end posltion and stopped f-rom further movement and wherein the amplifier is bypassed to provide fluid to the actuator at the pump velocity and pump pressure, and FIG. ld shows movement of the piston within the amplifier to its limit means responsive to movement of the actuator from its tilt posi-tion with the pump pressure reversed from that shown in FIGS. la through lc.
FIG. 2 shows in cross section, the amplifier assembly with the piston at one end at its stopped position.
FIGS. 2a, 2b and 2c show in cross-section the surfa¢es of the piston at various positions along its axial length.
FIG. 3 shows in cross-section, a detail of the switch means, being a hydraulic valve within the ampli-fier piston.
FIG.4 (appearing on the same sheet of drawings as Fig. 2) is an end view of the amplifier assembly of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
I
FIGS. la, lb, lc and ld shows operation of the hydraulic system in a first direction, proceeding through . ..~ ,.
cl'`

~51506 the tri~ r~nge t~ the tilt x?nje to~a full extensiQn sf the hydraulic actuator cylinder where the propulsion unit is in its full tilt position.
The hydraulic unit is shown in schematic form and wherein the same numerals indicate the same and simi-larly operating parts.
As shown, a hydraulic pump 3 provides fluid to a hydraulic amplifier indicate generally as 5. m e hydrau-lic amplifier 5 has a first port 7 connected to the pump 3 and a second port 9 connected to the hydraulic actuator cylinder shown as 11. The hydraulic amplifier 5 as is well~known, has a displaceable means piston which may be a piston 13, having a first corss-section area 15 shown in FIG. 2b and a second cross-sectional area 17, shown in FIG. 2c, area 17 being an annular area represented by the difference between the area of face 15 of the piston 13 and the area of face 19 of piston 13, shown in FIG. 2a.
The piston 13 is displaced or moves within the cylinder assembly 21 of the hydraulic amplifier 5 between a first extreme position at the top of the ampli~ier cylin-der 21 shown as position B and a second extreme position shown as position A at the bottom of the amplifier 21.
It being understood that the terms top and bottom are used for reference purposes only and this invention in no way requires that the hydraulic cylinder be aligned as shown in the drawing with respect to top and bottom.
Seals 23 and 28 are provided for allowing move-ment of the amplifier piston 13 within the cylinder 21 without loss of fluid and without fluid communication between that volume bound by face 15 of piston 13 and that volume bound by face 17 of piston 13.
~ e piston 13 is shown as having a switch means 29 which may be a valve assembly as shown having a ~alve 33 and valve seat 34, a means for closing the ~alve shown as spring 3;2 and means for opening the valve shown as plunser 36 positioned to a limit means shown as bottom wall 35 of c~ylinder 21.
~le fluid may be communicated to the actuator ..

.

cylind~ 3A th~ough ~crt g of ~he Gyli..nfl~?~ ?1 c~r,d~ 3 and port 45 within the cylinder 11.
Operation in the system is described assuming that the load 49 is a~ its fully dow~wardly ex~ended posi-~ion with the hydraulic cylinder 11 and the load propulsionunit 49, being at ievel C at one end of the trim range.
Assuming now that the pump 3 is operated in a first dixection to apply pre-~sure to the system, fluid under pressure is applied to the hydraulic amplifier 5 through 10 port 7 and to that volume adjoining the sur~ace 15 of piston 13.
Although the plunger 31 in contact with the bot-tom of the amplifier cylinder 35 as shown in FIG. la, forces the valve 29 to open, communicating the volume of 15 the amplifier cylinder adjoining face 15 of piston 13 to the volume of the cylinder adjoining face 17 of the piston 13 sufficient force is developed due to the differences in affected surface area to move the piston 13 up towards position B from the position A shown in FIG la.
As shown in FIG. 15, movement of the piston from position A to position A-B between extreme positions A and B correspondingly moves the plunger 31 from the bottom 3~ of the amplifier allowing the valve 33 to close under the force of the valve closing means shown as spring 25 32.
During this time when the amplifier piston 13 is moving between end position A and end position B as shown in FIG. lb, the valve will be closed under the force or 32 and the area or volume withi~ the amplifier cylinder 30 adjoining face lS of piston 13 will be isolated from the area adjoining ace 17 of piston 13. With the valve 33 closed, movement of the amplifiar piston 19 will force rluid from the amplifier cylinder 21 through port 9 to the hydraulic actuator cylinder 11 and displace the hydraul;c 35 actuator cylinder from its initial rest position to a new position D shown as in FIG. lb.
During the time the amplifier piston is moving, the pressure within the hydraulic cylinder 5 will be an amplified prassure relative to the pressure of the pump.

, - -~51S06 g As is well-kno~.~ in hydx~ amplifie~s, t~e ~e.5sure at port 9 will be equal to the pump pressure multiplied by the ratio of the surfa~e area of face 15 of piston 13 to the sur~ace area of the annu].ar surface 17 of piston 19.
During movement of the piston, the force pro-duced by the di~ferential pressure between the volume adjoining surface 17 and the volume adjoining surface 15 will be less than the force of the valve closing means 32 within valve assembly 29 and the valve will be maintained closed as shown in FIG.'lb.
In FIG. lc, the amplifier piston 13 has been moved to one-end of its displacement path at position B.
When this point is reached, the amplifier is constructed so that further mechanical displacement of the piston 13 is not possible in the direction from A to B. At this point, 15 and assuming power ~ the propulsion unit is removed the differential pressure between the fluid in the volume bound by ~a~e 15 and the volume bound by annular face 17 will force the valve 33 to open against the force of spring 32, permitting communication between that volume bounded by face 15 and the volume bounded by face 17. The further 20 operation of the pump in the first direction, rorces fluid from the pump 3 through port 7 of amplifier 5 through the valve assembly 29 and conduit 37, through the volume of the amplifier cylinder 21 adjoining surface 17, through port 9 of amplifier 21, and conduit 43 connecting the amplifiar to 25 the hydraulic cylinder ll at port 45.
When the piston 13 of the hydraulic amplifier is moved to its extreme position B, and the differential pres-sure opens valve 33, allowing communication of the fluid through the amp,lifier 5 without amplification, the fluid is 30 then moved at a lower pressure but at the velocity of the pump further displacing the piston 47 within the hydraulic cylinder 11 from position D to position E as shown in FIG.
lc .
As explained above, where the propuLsion system 35 shown as load 49 is at its lowest position shown as C in FIG. la, initial displacement, corresponding to the dis-placement between A and B of the amplifier piston 12 will .

~5~506 b9 through the trim range oosition~ the di.splacement ~eLn~.j...
C to D of the piston 47 and the propulsion unit 49.
When the amplifier piston is at position B, and with the v21ve 33 open as explained above, the pump will be connected directly through to the hydraulic cylinder 41 bypassing the hydraulic amplifier 5. The fluid within the system will be moved at the pump velocity but at the lower pump pressure, directiy to the hydraulic actuator and will rapidly move the actuator and the propulsion unit from pos-ition D to E representing the tilt range.
Operation of the device is now shown with refer-ence to FIG. ld wherein the propulsion unit 49 shown as position 1 in Phantom at the extreme end of its tilt posi-tion, is lowered through its tilt range and its trim range, back to its extreme from position C.
As can be seen in FIG. lc, when the pump 3 is stopped or reversed, the differential pressure exist m g at face 15 of the amplifier piston 13 will no longer maintain the valve 33 in valve assembly open, valve 33 will close connecting the hydraulic amplifier S in the hydraulic 20 circuit, so the hydraulic amplifier piston 13 is displaced downwardly in a second direction from position B towards position A. As the hydraulic amplifier pistcn 13 moves from position B to A, a corresponding displacement of the actuator piston rod 47 and the propulsion unit 49 from its 25 extreme tilted position E to an intermediate position shown as F will take place corresponding to the movement of the piston within the hydraulic amplifier from B to A.
Ac explained above at position A, the force of the plunger 36 against the limit means shown as the bottom 30 35 of the cylinder 21 of the amplifier 5 will open the valve 33 allowing communication of the actuator cylinder 11 through port 9, conduit 37, the valve 29 and port 7 of the amplifier 5 through to the pump 3. As the valve will be open under the force of plunger 36, the amplifier will 35 be bypassed and switched out of the hydraulic circuit, and the piston 47 of the hydraulic actuator 11 will be moved under the direct force of the pump nd with the velocity of the pump through to its other extreme bottom and moving the ~L~5~5S~6 propulsion unit 49 to position CO
Operation of the pump in the reverse direction with the unit within its tilt range at F for example, and with piston 13 at B will cau~;e displacement of the fluid, moving the piston 47 within t:he hydraulic actuator cylinder 11 and moving the propulsion unit.
Movement of the pump in the sècond direction then displaces or rotates the propulsion unit downward towards the water, and continued move~m,ent and operation of the 10 pump displaces the propulsio~ unit 49 to the trim range be~ween positions ~ and D. When the propulsion unit is located in the trim range, operation of the pump in the first direction will cause movement of the hydraulic ampli-fier piston 19 away * om the limit means shown as the bot-15 tom wall 35, removing the force of the opening means sho~nas plunger 36 from the valve 33 closing the valve under the force of closing means shown as spring 32 and placing the amplifier within the hydraulic circuit. The amplifier then provides an amplified pressure to permit displacement of 20 the load shown as a propulsion unit 49 to ef~ect proper trimming of the propulsion unit.
Operation of the pump in the reverse direction with the unit within its tilt range at F for example, and with piston 13 at B will cause displacement of the fluid, 25 moving the piston 47 within the hydraulic actuator cylinder 11 and the propulsion unit toward position C.
The amplifier piston 13 will also experience cor-responding movement until it reaches a limit means where the valve 33 will open allowing direct communication of 30 the hydraulic actuator cylinder 11 with the pump 3 and rapid movement of the piston 47 and the associated propul-sion unit ~9 at the speed and pressuxe of the pump 3.
In the described operation o~ the amplifier S, valve 33 op~ns when the piston reaches position A. However, 3~ it should be understood that position A is not necessarily at an end or limit of the displacement path of the piston 13 within th,e amplifier.
As will be understood by one skilled in the art, a limit means for contacting a means to open valve 33 can 5~ 5~ 6 be placed within the hydraulic amplifier ~ to open the valve 33 before the piston l9 reaches position A. For ( example, a contact means can be placed within the ampli-fier 5 which contacts the plungex 36 when the piston assem-bly is somewhere between position B and A.
It should be understood that the limit means shown as bottom wall 35 in this embodiment, may ~e placed anywhere along the path of the piston 13 between position A and position B and may be any suitable means which con-tacts the actuator means shown as plunger 36 responsive to 10 movement of the piston 13 towards the limiting means, and wherein further movement of the piston 13 in the same direction towards the limiting means, forces the actuator means against the valve, opening the val~e and allowing communication between the two volumes.
Operation of the am~lifier is now shown with reference to FIGS. 2, 3 and 4 wherein a detail of the valve assembly 29 is shown.
m e valve is mounted in the displaceable piston 13 and includes a means shown as spring 32 forcing valve _ 20 body 33 ag~inst valve seat 34. An actuator means for o~ening th~ valve is shown as a plunger 36 having an end ~ 38 protruding below the surface 15 of the piston to engage a limit means such as the bottom wall 35 of cylinder 21.
Movement of the amplifier piston 13 towards posi-25 tion A places the plunger 36 in contact with the bottomwall 35 of the amplifier cylinder. The plunger 36 then displacPs valve body 33 against valve spring 32 opening the valve and permitting fluid to flow from the volume bounded by surface 17 through conduit 37, ~alve seat 34 and 30 valve body 33, through to port 7. A small annular space 24 may be left between piston 13 and the inner wall of cylinder 21 to permit fluid to flow out conduit 37.
It should be noted that it is not necessary for the piston to be displaced to the bottom or to the bottom 35 wall 35 of the amplifier cylinder 21 as any suitable means for contacting the plunger 31 and forcing the plunger against the valve body 33 and against the force of the spring 32 opening the valve may be used. For example, a .

~*~lS~6 suitable mechanical structure may be placed close to posi-tion A and removed from position B to contact the plunger extension 38 and open the valve before the valve reaches the bottom wall 35 of the cyLinder. However, the bottom wall is a convenien~ place for locating the limit means for the valve and for that reason is shown as such in the preferred embodiment.
Further, it should be known that a plunger is not required as any suitable actuating means ~ay be used, responsive to movement of the piston, to contact the valve, 10 and open the valve. For exa~lple, a structure stationarily mounted in the cylinder, and located in the path of the valve so it contacts the valve when the valve reaches a corresponding limit position, opening the valve and communicating the volume bounded by surface 15 to the 15 volume bounded by surface 17.
As hydraulic fluid is driven in a first direc-tion, the differential force against the surface 15 forces the piston to be displaced towards position B from position A, moving the piston away from bottom wall 35 and allowing 20 the valve to close. The piston is then displaced up until the point where the annular surface 17 contacts the stop 23 located in the cylinder 21. At this point, and assum-ing no power is provided to the drive unit, the differen-tial pressure on the plunger side of the valve compared to 25 the force of the spring against the valve opens the valve and provides hydraulic fluid under the speed and pressure of the pump to the hydraulic actuating cylinder 11 to dis-place the cylinder through its tilt range. r~hen the pump is stopped or reversed, the differential pressure forcing 30 the valve open is removed and spring 32 forces the valve closed.
However, if power is supplied to the propulsion drive unit, the force of the pump by itself will be insuf-ficient to displace the hydraulic cylinder against the 35 force of the propulsion unit and the system will go into hydraulic stall or fluid will be directed through a bleed valve.
With the piston of the hydraulic amplifier located ~5~5~6 at position B, operation of the hydraulic pump in the second direction, displaces fluid ~rom the hydraulic cylin-der to the amplifiex, and to the volume defined by surface 17 displacing the piston from position B to position A, S When the piston reaches the limit means, plunger 36 is forced against the valve body 33, and opens valve and permitting fluid to flow around the valve seat 34, fluid under the speed and pressure of the pump is forced to the hydraulic cylinder allowing the hydraulic cylinder to move 10 its end position where the hydraulic unit is placed to its fully lowered position in the water corresponding to posi-tion C in FIG. 1, The principles of this invention have been shown with reference to the preferred embodiment, but should not 15 be limited to the description of this embodiment as shown.
For example, the manner of opening the switch means mounted in the movable portion of the amplifier, by driving the movable means to one end of its path may be changed to any other suitable arrangement~ One possible 20 arrangement would be to place a limit means in the path of the movable means, a limit distance from the end of the path. In this way, the amplifier could have two limit means, neither at the end of the path, or one limit means which may or may not be at the end of the path, with the 25 the switch being opened by the third pressure when it is at the respective other end of th0 path, or the switch may be operated by the fluid under pressure at both ends of the path.

Claims (23)

Claims:

1. An hydraulic amplifier for amplifying pressure of a hydraulic fluid, said hydraulic amplifier having a displaceable means movable by said fluid in a displacement path, said displaceable means having switch means, said switch means being open to connect a first port of said amplifier to a second port of said amplifier and to provide a fluid path through said amplifier substantially without amplification responsive to a pressure differential across said switch, said amplifier having retarding means in said diaplacement path for retarding the movement of said displa-ceable means, said switch means being in a closed position when said displaceable means is moved in said displacement path, movement of said displaceable means being retarded upon reaching said retarding means in said path and increasing said pressure differential to provide fluid through said amplifier substantially without amplification.

2. The hydraulic amplifier of claim 1 wherein said switch means is operable to close said fluid path whereby said amplifier increases the pressure of said fluid at the said second port relative to the pressure at said first port, when said displaceable means is displaced from the said retarding means.

3. The hydraulic amplifier of claim 2 wherein said retarding means is placed at one end of said displace-ment path.

4. The hydraulic amplifier of claim 4 wherein said pressure differential opens said switch means when said displaceable means is at the said one end of said displace-ment path.

5. A hydraulic amplifier connected to a source of hydraulic fluid having a means displaceable within a path, said displaceable means including a switch means operable to connect a first port of said amplifier to a second port of the amplifier and to pass hydraulic fluid through said amplifier substantially without increasing the pressure of said fluid, said path having first and second ends defining the limits of said path and said switch means being operable in a first position in response to said fluid pressure when said displaceable means reaches said first end of said path, said switch means being operable in a second position when said displaceable means is displaced from said first end of said path, a limit means located along said path and removed from said first end and said switch means being movable from said second position to said first position when said displaceable means reaches said limit means, said switch in said first position passing fluid from said first port to said second substantially without amplification, and said switch in said second position isolating said first port from said second port for amplifying the pressure of said hydraulic fluid at second port relative to said first port.

6. The hydraulic amplifier of claim 5 where said switch means comprises a valve, said valve being open to connect said first port with said second port when said displaceable means reaches said first end.

7. The hydraulic amplifier of claim 5 where said switch means is a valve and said valve includes means to open said valve to connect said first port with said second port when said valve means to open said valve contacts said limit means.

8. The amplifier of claim 7 wherein said movement of the displaceable means towards the said second end of the path places said valve opening means in contact with said limit means and said limit means opens said valve in response to further movement of said displaceable means.

9. The amplifier of claim 8 wherein said valve includes a valve body and valve seat and said fluid forces said valve body from said valve seat when said displaceable means is at the first end of said displacement path.

10. The hydraulic amplifier of claim 8 wherein said displaceable means is a piston, said amplifier includes a cylinder and said piston is arranged to slide within said cylinder.

11. The hydraulic amplifier of claim 5 wherein said switch means is located within said path and is moved along said path in response to movement of the said displa-ceable means.

12. A system for trimming and tilting an outboard propulsion unit having a hydraulic means for developing pressure, displaceable means connected to said hydraulic means for trimming and tilting said propulsion unit in response to said hydraulic pressure, means for amplifying said pressure connected to said displaceable means and said hydraulic means, said amplifier means having a first and second port, said first port connected to said hydraulic means and said second port connected tosaid displaceable means, said amplifier means including switch means within said amplifier, and responsive to a pressure differential for bypassing said amplifier and connecting said hydraulic means to said displacement means substantially without amplification for tilting said propulsion unit substantially without increased pressure and said switch means connecting said amplifier between said displacement means and said hydraulic means to increase said pressure for trimming said propulsion unit.

13. The system of claim 12 wherein said switch means is in a first state for tilting and said switch means changes state in the absence of said pressure from said hydraulic means to enclose a volume of fluid within said amplifier, said enclosed volume of fluid holding said displaceable means against further movement.

14. The system of claim 13 wherein said switch means is a valve which opens in response to said hydraulic means developing said pressure and closes when said hydraulic means is inactive removing said pressure.

15. The system of claim 12 wherein said hydraulic amplifier includes a means movable along a path, said path having first and second ends and said switch being mounted in said movable means and operable to bypass said amplifier in response to said pressure differential across said switch means.

16. The system of claim 15 wherein said amplifier includes a limit means placed along said path, said switch means having means for engaging said limit means to operate said switch and to bypass said amplifier when said engaging means is driven against said limit means.

17. The system of claim 16 wherein said switch means in a first state isolates said first port from said second port, said amplifying means amplifying the hydraulic pressure of said fluid received at said first port, and pro-viding said amplified pressure at said second port and to said displaceable means in response to said switch means being in said first state.

18. The system of claim 17 wherein said fluid at amplified pressure is connected to said displaceable means, said displaceable means being displaced under the force of said fluid at said second port.

19. The system of claim 17 wherein said displa-ceable means is effective to trim said propulsion unit in response to said amplified hydraulic fluid pressure at said second port, when said propulsion unit is operative and effective to tilt said propulsion unit in response to said fluid at the second port of said amplified unit, when said power unit is inoperative.

20. The system of claim 18 wherein said displa-ceable means moves responsive to said fluid at the second port of said amplifier with a displacement proportional to the displacement of said movable means within said amplifier between said first end and said limit means, to trim said propulsion unit.

21. The system of claim 20 wherein said movable means moves responsive to said hydraulic fluid pressure at said second port with a displacement proportional to the displacement of said displaceable means and responsive to the pressure at said second port being higher than said pressure at said first port.

22. The system of claim 21 wherein said switch is operable to bypass said amplifier when said movable means reaches said limit means in said amplifier to provide a fluid path for said fluid through said amplifier substan-tially without amplification.

23. A hydraulic amplifier having a piston with opposed first and second faces for movement along a displa-cement path within said amplifier, said amplifier having a first port and a second port, said first and second port being located on opposite faces of said piston, said piston including a valve having an open position and a closed posi-tion, said valve in said open position establishing a hydraulic path from said first port to the said second port and sealing said first port from second port in said closed position, a cource of hydraulic fluid under pressure con-nected to said first port, said displacement path in said hydraulic amplifier having first and second ends, said piston being displaced to said first end responsive to the presence of said hydraulic fluid from said source, said switch being switched from said closed position to said open position when said piston reaches said first end and the pressure within said amplifier and is increased, a source of hydraulic fluid under pressure connected to said second port, said piston being moved from said first end when the pressure of said hydraulic fluid in said second port is higher than said pressure of said hydraulic fluid at the said first port and displacing said piston from said first end, a limit means placed in said path and displaced from said first end, said valve including means for contacting said limit means and for forcing said valve to said open position in response to further movements of said valve against said limit means and said amplifier amplifying the pressure at said second port relative to the pressure at said first port when said switch is closed and said piston is displaced to said first end.