Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
1999-08-30
2001-10-30
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
C440S055000
Reexamination Certificate
active
06309264
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lift cylinder assembly and is particularly to an improved hydraulic cylinder arrangement that is particularly well suited for use with a marine outboard propulsion unit.
2. Description of the Related Art
Many types of marine propulsion units include a hydraulic motor assembly that is interposed between the outboard drive portion of the propulsion system and the watercraft transom. This hydraulic mechanism is provided for a number of purposes. The first of these purposes is to permit the outboard drive to pop-up when an underwater obstacle is struck so as to avoid damage to the lower unit. Once the underwater obstacle is cleared, the weight of the outboard drive returns it to its previous trim adjusted position.
In addition to this shock-absorbing function, the shock-absorbing mechanism is also constructed so as to preclude the outboard motor from popping-up when operated in reverse mode. That is, the pressure at which the shock absorber valve opens is chosen to be low enough to permit adequate shock-absorbing when underwater obstacles are struck, but high enough to resist the pop-up action when operating in reverse drive.
The functions can be achieved with relatively conventional shock absorbers. It is also desirable, however, to provide an arrangement wherein the marine propulsion unit can be hydraulically trimmed when operating under power. In addition, the hydraulic mechanism may also be employed for tilting the outboard drive up out of the water when not in use or for other purposes, such as for inspection.
Obviously, in order to permit trimming when operating under power, the hydraulic motor must provide large forces. This often is accomplished by providing relatively large effective piston areas over which the hydraulic pressure operates. Although providing good hydraulic force for trim operation, these types of mechanisms are very slow in tilt up operation.
Therefore, it has been proposed to employ one hydraulic motor that operates to provide the trim adjustment. This hydraulic motor has a relatively large diameter piston and, thus, has a relatively low stroke for a given fluid displacement. In addition, a smaller bore, but longer stroke, tilt fluid motor is also coupled to the outboard drive for effecting the tilt up operation. Thus, high speed tilting can be accomplished without loss of power for trim operation. These mechanisms are, however, quite complicated and require several fluid motors and control valve arrangements so as to actuate the proper motor when trim or tilt of the outboard motor is required.
Telescopic or compound hydraulic motors provide a single external cylinder to accomplish both the tilt and trim functions. A tilt cylinder is slidably supported in this outer or trim cylinder and it itself defines an internal cavity in which a tilt piston is provided. These systems basically operate by effecting hydraulic pressure actuation of both the trim and tilt cylinders simultaneously for a portion of the stroke during which the trim movement is accomplished. The tilt cylinder is then held and the tilt piston, which has a smaller effective piston area, is operated for tilt up operation.
One exemplary hydraulic cylinder arrangement will now be described for the reader's understanding of the conventional arrangement with particular reference to
FIGS. 1A through 1E
. This arrangement is also disclosed in the U.S. Pat. No. 5,718,613, which is hereby incorporated by reference.
FIGS. 1A through 1E
illustrate in the five views the conditions at fully tilted and trimmed down position shown in
FIG. 1A
, through intermediate positions, to a fully trimmed up position shown in
FIG. 1C
, and to a fully tilted up position shown in FIG.
1
E. This prior type of mechanism is indicated generally by the reference numeral
11
in these figures and is connected between a marine outboard drive, which may either constitute the outboard drive portion of an inboard-outboard drive or an outboard motor per se.
The combined tilt and trim fluid motor
11
includes an outer cylindrical housing assembly or tilt cylinder, indicated generally by the reference numeral
12
which has an integral trunion
13
having an opening
14
to pass a pivot pin for pivotal connection to the transom of the associated watercraft.
The tilt cylinder
12
defines an internal cavity
15
in which a tilt cylinder
16
is slidably supported. The tilt cylinder
16
, in turn, divides the cylinder bore
15
of the cylinder housing
12
into an upper chamber
17
and a lower chamber
18
. Suitable connections link the chambers
17
,
18
with a hydraulic pressure circuit. Although a part of actual connections are formed at the wall portion of the outer cylinder
12
and not seen, inlet and outlet ports
19
a
,
19
b
are schematically indicated in these figures. The hydraulic pressure circuit is provided for pressurizing either the lower chamber
18
or the upper chamber
17
and depressurizing the other chamber in a known manner.
A tilt piston
20
is slidably supported within a bore
21
of the tilt cylinder
16
. The tilt piston
20
has affixed to it a piston rod
22
that extends through openings in the end of the tilt cylinder
16
and the outer cylinder
23
. A trunion
23
is provided on the exposed end of the piston rod
22
. The trunion
23
has a bore
24
that is adapted to pass a pin (not shown) for providing a pivotal connection to the outboard drive.
Positioned in the tilt cylinder bore
21
below the piston
20
is a floating piston
25
. The floating piston
25
is retained in the bore
21
below the tilt piston
20
by means that include a retainer device
26
which is urged by springs
26
a
toward the upper chamber
17
. A latch operating mechanism
27
is interposed between the retainer device
26
and the floating piston
25
and cooperates with a plurality of detent balls
28
. The detent balls
28
are adapted to engage corresponding recesses
29
in the outer cylinder
12
at the end of the trim stroke for locking the tilt cylinder
16
at this position, as FIG.
1
D.
A shock absorber valve, indicated by the reference numeral
31
, is carried by the tilt piston
20
and permits flow from the chamber formed above the tilt piston
20
within the tilt cylinder bore
21
to the area between the trim piston
19
and the floating piston
25
. When an underwater obstacle is struck, the tilt piston
20
is urged upwardly and, if sufficient force is applied to open the shock absorber
31
, fluid is displaced from the chamber in the trim piston cylinder bore
21
to the area between the tilt piston
29
and the floating piston
25
. When this occurs, less fluid will be displaced from above the tilt piston
20
than below it and the floating piston
25
may move slightly upwardly.
Displacement of fluid from the chamber above the tilt piston
20
within the tilt cylinder bore
21
is precluded by a check valved passageway
32
. This check valved passageway permits the piston
20
to act as a conventional shock absorber.
Once the underwater obstacle, which has been struck and has caused the popping up action has been cleared, the tilt piston
20
moves downwardly through the opening of a let down valve
33
which opens at a substantially lower pressure than the shock absorber valve
31
. The let down valve
33
provides no significant damping and can be opened merely by the weight of the outboard drive acting on the tilt piston
20
.
If the operator desires a trim up operation, the prior hydraulic mechanism shown in
FIGS. 1A-1B
is pressurized so that the chamber
18
below the floating piston
25
and tilt cylinder
16
will be pressurized. At the same time, the chamber
17
is depressurized by opening it to return. When the chamber
18
is pressurized, the fluid pressure acts upon the lower face of the tilt cylinder
16
and also on the floating piston
25
and on the tilt piston
20
to cause this assemblage to move upwardly as shown in
FIG. 1B
to a desired trim adjusted position. When the desired position
Knobbe Martens Olson & Bear LLP
Morano S. Joseph
Wright Andy
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