Patent ID: 6328616
Filing Date: 2001-12-11
Classification: B63H,F02B

Abstract:
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; and wherein 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 comprising:a housing adapted to be 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 a first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side;a piston rod adapted to be connected to the other of the hull and the marine propulsion unit that is telescopically inserted into the tilt chamber of the cylinder; andwherein the cylinder device has a small-diameter tilt piston comprising a buffer valve 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 and wherein said buffer valve is opened when hydraulic pressure of the first tilt chamber becomes higher than a fixed value, so that 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 a trim operable region being -covered with a tank housing constituting the hydraulic fluid supply/discharge device; and comprising a relief valve which is opened when hydraulic pressure of the tank housing becomes higher than a second fixed value so that hydraulic fluid of the tank housing can be relieved into the second trim chamber to avoid an abnormal application of pressure of a pump by movement of the cylinder due to addition of the import on the direction that expands the cylinder device to the marine propulsion unit.