Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
2001-02-26
2002-05-21
Avila, Stephen (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
Reexamination Certificate
active
06390867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tilt device for a marine propulsion unit.
2. Description of the Related Art
There is a structure described in Japanese Patent No. 2945071 as a tilt device having a gas assist function for assisting a tilt up load applied to a main body of a propulsion unit by a gas pressure in a pressure accumulating chamber.
The tilt device is a single cylinder inverted type in which a piston rod protrudes to the lower side of a cylinder. A piston is fixed to the piston rod inserted to the cylinder, and a free piston for coinciding a returning position after the main body of the propulsion unit rises up due to collision of drifting wood with a staying position before rising up is provided along the piston. A switching valve for communicating a rod side chamber within the cylinder defined by the piston and the free piston with a piston side chamber and an operating portion thereof are provided in a side portion of the cylinder. Further, a pressure accumulating chamber for applying gas pressure for a gas assist to the piston side chamber is arranged within the cylinder and on the piston side chamber. Accordingly, gas pressure in the pressure accumulating chamber is applied to both sides of the piston via a working fluid when opening the switching valve, and The gas assist force corresponding to the cross sectional area of the rod can be generated in a tilting up direction.
(1) The tilt device described in Japanese Patent No. 2945071 is structured such that the pressure accumulating chamber is arranged on the piston side chamber without a gas-liquid separating means such as a partition or the like therebetween. The gas in the pressure accumulating chamber immediately moves to the rod side chamber from the piston side chamber when the switching valve opens for use. The erect type tilt device in which the protruding direction of the piston rod from the cylinder is directed to an upper side, will not allow the gas assisting function to be achieved. Accordingly, the tilt device can be mounted only in the inverted direction, and there is no freedom of the mounting direction.
(2) Since the pressure accumulating chamber is within the single cylinder type cylinder and on the piston side chamber in a recessed side of the closed end of the cylinder, it is hard to increase the capacity of the pressure accumulating chamber.
(3) Since the switching valve and the operating portion thereof are within the side portion of the cylinder, the lateral size of the tilt device becomes too large.
In Japanese Patent Application No. 11-64054, the tilt device filed by the applicant of the present invention is a plural cylinder erect type in which a piston rod protrudes to the upper side of a cylinder. The cylinder has a double pipe structure with an outer cylinder and an inner cylinder, and a pressure accumulating chamber formed between the outer cylinder and the inner cylinder. The pressure accumulating chamber communicates with a piston side chamber defined in an inner portion of the inner cylinder and below the piston so as to provide a gas assisting function. However, in this structure, since the gas-liquid separating means such as a partition or the like is not provided between the pressure accumulating chamber and the piston side chamber, the gas moves to the rod side chamber disposed above the piston after passing through the switching valve and stays in the rod side chamber when the gas in the pressure accumulating chamber is caught up in the piston side chamber due to a wave rock of the hull or the like. Therefore the gas assist is deteriorated due to the gas pressure in the pressure accumulating chamber or the tilt lock is deteriorated because the piston is accidentally moved at a time when the switching valve is closed. This state is due to existence of the working fluid constituted by mixing the gas in both side chambers of the piston.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a tilt device for a marine propulsion unit with a gas assist function which can increase the capacity of a pressure accumulating chamber while being compact and can secure an improved operability while maintaining freedom in the mounting direction.
In accordance with the present invention, there is provided a tilt device for a marine propulsion unit having a cylinder connected to one of a hull and a main body of a propulsion unit which receives a working fluid. A piston rod is connected to another and is inserted into the cylinder so as to freely compress and expand. A piston is connected to an inserted end of the cylinder of the piston rod and which defines a rod side chamber in a piston rod receiving side and a piston side chamber in a piston rod not receiving side within the cylinder. A switching valve is capable of communicating the rod side chamber with the piston side chambers, a pressure accumulating chamber is capable of applying a gas pressure to the piston side chamber.
The cylinder is constituted by a double pipe with an outer cylinder and an inner cylinder, the piston rod and the piston are received in the inner cylinder, the pressure accumulating chamber is formed in a space between the outer cylinder and the inner cylinder, and gas-liquid separating means is arranged between the pressure accumulating chamber and the piston side chamber.
REFERENCES:
patent: 5876259 (1999-03-01), Nakamura
patent: 6039617 (2000-03-01), Nakamura
patent: 2945071 (1999-06-01), None
patent: P2000255490 (2000-09-01), None
Nakamura Tamotsu
Sekikawa Shinsuke
Avila Stephen
Orum & Roth
Showa Corporation
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