Hydraulic tilt system for marine propulsion

Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...

Reexamination Certificate

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Reexamination Certificate

active

06273770

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a hydraulic tilt system for a marine propulsion, and more particularly to an improved hydraulic tilt system that provides a reliable tilting and holding operations of the marine propulsion.
2. Description of Related Art
A drive unit of an outboard motor is typically mounted on a transom of an associated watercraft by means of a bracket assembly which comprises a swivel bracket and a clamping bracket. The swivel bracket supports the drive unit for pivotal movement about a generally vertically extending axis. The clamping bracket is affixed to the transom of the associated watercraft and supports the swivel bracket for pivotal movement about a generally horizontally extending axis.
Usually, a hydraulic cylinder assembly is interposed between the swivel and clamping brackets to tilt up or down the drive unit. The cylinder assembly comprises a cylinder housing, a tilt piston slidably supported within the cylinder housing and defining a couple of fluid chambers. A piston rod is affixed to the tilt piston and extends therefrom through one of the fluid chambers. The cylinder housing is affixed to one of the swivel bracket and clamping bracket, while an outer end of the piston rod is affixed to the reminder of the brackets. A pressurizing mechanism including, for example, a fluid pump pressurizes fluid in the fluid chambers for causing reciprocal movement of the tilt piston within the cylinder housing so that the drive unit is tilted up or down. The hydraulic cylinder assembly and the pressurizing mechanism generally define a hydraulic tilt system.
Although various arrangements are applicable for the hydraulic tilt system, a shuttle valve assembly is one typical component that is employed in these arrangements. The shuttle valve assembly includes a shuttle cylinder housing having openings at both outer ends and a shuttle piston slidably supported within the shuttle cylinder housing. The openings are joined with each one of the fluid chambers in the cylinder housing. A pair of closure valves are provided for closing the openings of the outer ends of the cylinder housing. The shuttle piston defines a pair of shuttle chambers in the housing and has projections provided at both sides to confront the closure valves. A reversible fluid pump, for example, is joined to the shuttle chambers with its inlet-outlet ports. When one of the shuttle chambers is pressurized by the fluid pump, the closure valve at this shuttle valve is pushed out to permit fluid flow through the opening to the fluid chamber in the cylinder housing for effecting the tilt piston moves. Simultaneously, the shuttle valve moves toward the other closure valve and pushes the valve outwardly by its projection. Accordingly, the fluid in the other fluid chamber may return to the other inlet-outlet port through the opening at this side of the shuttle cylinder not to resist the movement of the tilt piston. A typical shuttle valve assembly is disclosed in U.S. Pat. No. 4,557,696.
The shuttle valve assembly is advantageous because the hydraulic tilt system can be neatly formed. However, a space for the hydraulic tilt system, which is defined in the bracket assembly and specifically between the swivel bracket and clamping bracket, is extremely narrow. In order to place the shuttle valve assembly in this space, improved shuttle valve assemblies are desirable.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a hydraulic tilt system for a watercraft and an outboard drive comprises a cylinder housing adapted to be affixed to one of the watercraft and the outboard drive. A tilt piston is slidably supported within the cylinder housing and defining a first chamber and a second chamber in the cylinder housing. A piston rod extends from the tilt piston through one of the first chamber and the second chamber for attachment to the other of the outboard drive and the watercraft. A pressurizing mechanism is arranged to selectively pressurize fluid within the first chamber and the second chamber for causing reciprocal movement of the tilt piston. The pressurizing mechanism has a pair of ports through which fluid is pushed out and received.
Shuttle housings are provided, one of which is positioned between the first chamber and one of the ports and the other one of which is positioned between the second chamber and the other one of the ports. Shuttle pistons are slidably supported within each one of the shuttle housings defining a third chamber and a fourth chamber in each one of the shuttle housings. The fourth chambers are connected to each other. Each of the shuttle pistons has a check valve arranged to permit fluid in the third chamber to flow to the fourth chamber and to preclude inverse flow of the fluid. The first chamber and the second chamber are each connected for fluid communication with one of the ports through the third chambers. A pair of shutting mechanisms are arranged to shut the communications. Each of the shutting mechanisms is rendered ineffective by pressurized fluid in the third chamber and is also rendered ineffective by the shuttle piston being moved toward the shutting mechanism by the pressurized fluid in the third chamber of the other shuttle housing. One of the shuttle pistons has a seal arranged to separate the third chamber from the fourth chamber. The other one of the shuttle pistons permits leakage from the fourth chamber to the third chamber, such as by providing no seal around the piston.
In accordance with another aspect of the present invention, a hydraulic tilt system for an outboard drive comprises a fluid motor including a lower chamber and an upper chamber. A powering device is arranged to selectively deliver pressurized fluid to the lower chamber and the upper chamber and receive the fluid from the lower chamber and the upper chamber. The powering device has a pair of ports for selectively delivering and receiving the fluid therethrough.
A first passage joins one of the ports and one of the lower chamber and the upper chamber. A second passage joins the other one of the ports and the other one of the lower chamber and the upper chamber. A first housing is disposed in the first passage and has a first actuator slidably movable within the first housing. The first actuator defines a first actuating chamber and a first pressurizing chamber. The first passage passes through the first actuating chamber. A first closure unit is arranged to primarily close the first passage and open the first passage when the first actuating chamber is pressurized. The first actuator has a projection that opens the first passage against the first closure unit when the first pressurizing chamber is pressurized. The first actuator has a check valve that permits flow of the fluid in the first actuating chamber to the first pressurizing chamber and precludes inverse flow.
A second housing is disposed in the second passage and has a second actuator slidably movable within the second housing. The second actuator defines second actuating chamber and a second pressurizing chamber. The second passage passes through the second actuating chamber. A second closure unit is arranged to primarily close the second passage and open the second passage when the second actuating chamber is pressurized. The second actuator has a projection that opens the second passage against the second closure unit when the second pressurizing chamber is pressurized. The second actuator has a check valve that permits flow of the fluid in the second actuating chamber to the second pressurizing chamber and precludes inverse flow.
A third passage joins the first pressurizing chamber to the second pressurizing chamber. An outer diameter of the first actuator is smaller than an inner diameter of the first actuator housing. An outer diameter of the second actuator is smaller than an inner diameter of the second actuator housing. A seal is provided only around one of the first actuator and the second actuator to prevent communication between the actuating chamber a

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