Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
2000-07-14
2001-12-11
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
Reexamination Certificate
active
06328616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a trim-tilt device for a marine propulsion unit such as an outboard motor or inboard/outboard motor.
2. Description of the Related Art
Conventionally, the trim-tilt device for a marine propulsion unit has a cylinder device interposed between a hull and the propulsion unit which is tiltably supported by the hull. By controlling supply and discharge of hydraulic fluid from a hydraulic fluid supply/discharge device to a cylinder device or vise versa, the cylinder device is expanded and contracted to thereby trim and tilt the marine propulsion unit.
A prior art trim-tilt device for a marine propulsion unit is described in Japanese Patent Application No. 11-112856. This application suggests a cylinder device for a trim-tilt device for a marine propulsion unit comprising a housing connected to one of a hull and a marine propulsion unit and which forms a large-diameter trim chamber. A cylinder is telescopically inserted into the trim chamber of the housing which forms a small-diameter tilt chamber. A large-diameter trim piston is fixed to an end portion of the cylinder within the trim chamber of the housing which partitions the trim chamber into a first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side. A piston rod is connected to the other of the hull and the marine propulsion unit and is telescopically inserted into the tilt chamber of the cylinder. A small-diameter tilt piston is fixed to an end of the piston rod within the tilt chamber of the cylinder which partitions the tilt chamber into a first tilt chamber of a piston rod accommodation side and a second tilt chamber of an anti piston rod accommodation side. Additionally, in the cylinder device, a portion of the cylinder or the cylinder device which projects outward from the housing in the trim operable region is covered with a tank housing constituting a hydraulic fluid supply/discharge device. According to this embodiment, since the cylinder of the cylinder device does not touch water in the outside, it is covered with the tank housing and it can be rustproof easily and steadily by hydraulic fluid within the tank housing.
In the above mentioned trim-tilt device for a marine propulsion unit disclosed in Japanese Patent Application No. 11-112856, if the operation of the pump of the trim-tilt device stops in a trim operable region (the state in which the cylinder device does not finish the trim-up operation) during forwarding sailing and an obstacle in the water such as a floating log etc., collides with the propulsion unit such that a hydraulic fluid supply/discharge flow passage, from the hydraulic fluid supply/discharge device to the cylinder device, is locked, the piston rod and the cylinder in a body carry out a trim-stroke to the housing and the tank housing. At this time, in the trim-tilt device of the propulsion unit, due to the boosting of the hydraulic pressure at the locked state in a first tilt chamber, a buffer valve of a tilt piston is opened to transfer this hydraulic pressure to a second tilt chamber, so that an impact can be absorbed.
However, when the piston rod the cylinder transfer (trim-stroke) to the housing and the tank housing as described above, there is a possibility that the tank housing which is made of resin is destroyed due to the rapid increase of an internal pressure of the tank, or an end plate of the pump motor which is made of resin is destroyed, that covers a pump chamber provided so as to communicate to the tank.
SUMMARY OF THE INVENTION
The object of the present invention is to avoid an abnormal application of pressure of the pump by movement of a cylinder according to the collision of an obstacle in the water or the like in the case that a cylinder of a cylinder device is covered with a tank housing of a hydraulic fluid supply/ discharge device in a trim-tilt device for a marine propulsion unit.
According to the present invention, there is disclosed a trim-tilt device for a marine propulsion unit, wherein a cylinder device is mounted between a hull and the marine propulsion unit freely tiltably supported by the hull. A hydraulic fluid is supplied from a hydraulic fluid supply/discharge device into the cylinder device and is discharged from the cylinder device into the hydraulic fluid supply/discharge device to thereby expand and contract the cylinder device and thereby trim and tilt the marine propulsion unit.
The cylinder device comprises:
a housing connected to one of the hull and marine propulsion unit to form a large-diameter trim chamber;
a cylinder telescopically inserted into the trim chamber and forming a small-diameter tilt chamber;
a large-diameter trim piston fixed to an end portion of the cylinder within the trim chamber of the housing and serving to partition the trim chamber into an first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side;
a piston rod being connected to the other of the hull and the marine propulsion unit that is telescopically inserted into the tilt chamber of the cylinder; and
wherein the cylinder device has a small-diameter tilt piston comprising a buffer valve which is fixed to an end of a piston rod within a tilt chamber of the cylinder, which partitions a tilt chamber into a first tilt chamber of a piston rod accommodation side and a second tilt chamber of an anti piston rod accommodation side and which is open when hydraulic pressure of the first tilt chamber becomes higher than a fixed value, so that a hydraulic fluid of the first tilt chamber can transfer to the second tilt chamber.
A portion of the cylinder of said cylinder device which projects outward from the housing in the trim operable region is covered with a tank housing constituting a hydraulic fluid supply/discharge device, comprising relief valve which is opened when a hydraulic pressure of the tank becomes higher than a fixed value, so that hydraulic fluid of the tank can be relieved for the second trim chamber to avoid an abnormal application of pressure of the pump by movement of the cylinder due to addition of the impact in the direction that expands the cylinder device to the marine propulsion unit.
REFERENCES:
patent: 2953335 (1960-09-01), Kiekhaefer
patent: 3250240 (1966-05-01), Ziegler
patent: 5156561 (1992-10-01), Kinoshita
patent: 5975968 (1999-11-01), Nakamura
patent: 6042435 (2000-03-01), Nakamura
patent: 6062924 (2000-05-01), Nakamura
patent: 6213823 (2001-04-01), Nakamura et al.
Nakamura Tamotsu
Orihara Keiji
Takayanagi Hisao
Toyoshima Omito
Morano S. Joseph
Orum & Roth
Showa Corporation
Vasudeva Ajay
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