Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
1999-08-20
2003-05-06
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
C440S053000
Reexamination Certificate
active
06558212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic tilt device for a marine outboard drive and more particularly to an improved hydraulic tilt device that affords good operational performance for a relatively small outboard drive.
2. Description of Related Art
Marine outboard drives, i.e., both outboard motors and the outboard drive sections (stern drives) of inboard motors, have a wide variety of hydraulic tilt devices that support the outboard drives for tilting movement relative to an associated watercraft about a generally horizontally disposed tilt axis. The hydraulic tilt device generally comprises a cylinder, a piston slidably supported in the cylinder and defining a pair of fluid chambers and a piston rod extending from the piston through one of the fluid chambers. The fluid chambers are filled with a working fluid. Either one of the cylinder or piston rod is affixed to a cramp bracket and the other one is affixed to a swivel bracket. The cramp bracket is mounted on the associated watercraft, while the swivel bracket directly supporting the outboard drive is pivotally mounted on the cramp bracket about a tilt axis. Accordingly, when the piston rod comes out of the cylinder with the activation of the working fluid, the swivel bracket pivots about the tilt axis and the outboard drive is tilted up to a lifted position relative to the associated watercraft. When the piston rod comes into the cylinder with the reversed activation of the working fluid, then the outboard drive is tilted down to a lowered position.
Some of the hydraulic tilt devices for relatively small outboard motors have a manually operable switchover valve in a passage that connects the pair of the fluid chambers with each other and an operator of the outboard motor can switch the passage between a communication state and a non-communication state. When the passage is in the communication state, the operator may tilt up or tilt down the outboard drive without any restraint. Meanwhile, by bringing the passage to the non-communication state, the outboard drive will not be moved and stay at any position that the operator desires.
The majority of the hydraulic tilt devices contain gasses in said cylinder or an accumulation chamber, which is provided separately from the cylinder, for compensating the capacity of the working fluid being out of the cylinder, because gasses are compressive.
FIGS. 1 and 2
illustrate cross-sectional side views of some exemplary hydraulic tilt devices which are conventionally used. The tilt devices includes a cylinder
20
, a piston
22
, a piston rod
24
, a passage
26
and a switchover valve
28
which are described above. A working fluid
30
fills both chambers of the cylinder
20
. A floating piston
32
is additionally provided in the cylinder
20
. This floating piston
32
slides in the cylinder
20
with the piston
24
as a unit except under the condition that a submerged obstacle strikes the outboard motor. In addition, the tilt device shown in
FIG. 2
further has an accumulator chamber
34
communicated with a chamber
36
where the piston rod
24
does not extend. The chamber
36
, in other words, is the opposite chamber relative to the other chamber
37
where the piston rod
24
extends. Gasses
38
are contained in the chamber
36
or the accumulator chamber
34
.
The hydraulic tilt device as such constructed has a problem. When the outboard motor is operated, the thrust force is exerted upon the gasses
38
because the piston rod
24
comes into the cylinder
20
by the thrust force and pushes the unit of the piston
22
and the floating piston
32
toward the gasses
38
. Since the gasses are compressive, at some occasion they accept this thrust force and some other occasion they push back. This gives the operator a kind of “floating feeling” and the operator is likely to believe that the operational performance of the outboard motor is not so good.
FIG. 3
illustrates a cross-sectional side view showing another type of tilt device that can be proposed for resolving the problem. In this tilt device, gasses
38
exclusively exert onto the working fluid
30
in the chamber
37
where the piston rod
24
extends when the switchover valve
28
closes the passage
26
. Thus, the phenomenon coming with the tilt devices shown in
FIGS. 1 and 2
no longer occur with this tilt device. However, another problem arises particularly with this arrangement, not limited to though.
The problem tends to appear when the associated watercraft is running in shallow water. Usually, the drive unit of the outboard motor is lifted up to a tilt range and powered with a low or medium speed in this situation so that submerged obstacles might not strike it. Under the circumstances, if the operator powers up the engine of the outboard motor to run it at a full speed without lowering down the drive unit, the propeller thrust is headed downwardly as well as forwardly. Such a downward thrust, then, raises the bow of the associated watercraft. If this happens abruptly, the watercraft may lose balance.
With the tilt devices shown in
FIGS. 1 and 2
, the “floating feeling” is amplified when the operator tries to power up the engine and the operator can relatively easily notice that the situation could happen. Accordingly, the problem is not so serious with those tilt devices. However, it is desirable to avoid this problem even in using the tilt devices shown in
FIGS. 1 and 2
.
Further, the problem may appear even with hydraulic tilt devices that contain no gasses therein but have a reservoir containing surplus fluid for compensating the capacity of the piston rod. This type of hydraulic tilt devices is also conventional.
It is, therefore, a principal object of this invention to provide a hydraulic tilt device thereby a drive unit can be lowered down when an engine is powered up under the condition that the drive unit is tilted up for advancing in a shallow water.
It is another object of this invention to provide a hydraulic tilt device thereby the “floating feeling” does not occur and a drive unit can fall down in the same situation as described above even though the operator do not have the “floating feeling”.
A conventional hydraulic tilt device usually has a shock absorber mechanism thereby an underwater obstacle can be safely cleared. It is desirable to have the relief function in the shallow water running with reserving the function of the shock absorber mechanism.
It is, therefore, a further object of this invention to provide a hydraulic tilt device that can achieve the relief function in the shallow water running as well as the shock absorber function.
SUMMARY OF THE INVENTION
This invention is adapted to be embodied in a hydraulic tilt device for a marine outboard drive.
In accordance with one aspect of this invention, the hydraulic tilt device comprises a cylinder. A piston is slidably supported in the cylinder and defining a first chamber and a second chamber in the cylinder. A working fluid is contained in the first and second chambers. A piston rod extends from the piston through the first chamber. A passage is disposed outside of the piston and joins the first and second chambers together. A switchover valve is disposed in the passage for switching the passage between a communication state and a non-communication state. Gasses are contained for compensating the working fluid and pressuring the working fluid in the first chamber when the passage is in the non-communication state. Means are provided for permitting flow of the working fluid from the second chamber to the first chamber when the passage is in the non-communication state and the second chamber produces a pressure greater than a predetermined magnitude.
In accordance with another aspect of this invention, the hydraulic tilt device comprises a cylinder. A piston is slidably supported in the cylinder and defining a first chamber and a second chamber in the cylinder. The first and second chambers are filled with a working fluid. A piston rod extends from the piston through the first ch
Knobbe Martens Olson & Bear LLP
Morano S. Joseph
Sogi Kabushiki Kaisha
Wright Andy
LandOfFree
Hydraulic tilt device for marine outboard drive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic tilt device for marine outboard drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic tilt device for marine outboard drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3017172