Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1976-12-20
1978-09-05
Cohen, Irwin C.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
91 29, 91433, 91445, 91447, 137493, B66B 920, F15B 13042
Patent
active
041112830
ABSTRACT:
A two-stage regulator valve, particularly for regulating the operation of single acting hydraulic lift motors in lift trucks, which embodies a spool valve controlling first and second ports in the valve body and responsive at one end to lift motor fluid pressure. At the opposite end the valve is responsive first to the force of a first spring which closes the spool on one port when lift motor fluid is below a predetermined pressure, and secondly, following predetermined compression of the first spring during which both ports are opened to exhaust pressure fluid from the lift motor, to the added combined force of a lift motor pressure responsive piston and a second spring. The piston forms with the spool valve a differential area response to said fluid pressure and together with the second spring regulates the position of the spool valve so as to variably restrict the other port to control the exhaust from the lift motor inversely as a function of the fluid pressure therein. At a predetermined low pressure both ports are fully open, the piston and second spring are fixed in a position inoperative to effect the position of the spool valve, and the first spring is compressed to said predetermined fixed compression. The first spring is effective to close the one port below said predetermined low pressure to prevent exhaust of lift motor fluid, such as in a condition of incipient slack in lifting chains which may be adapted to connect a fork carriage to the lift motor for elevation in an upright.
REFERENCES:
patent: 2146537 (1939-02-01), Farnham
patent: 2495785 (1950-01-01), Stepaens
patent: 2603235 (1952-07-01), Kirkham
patent: 2701552 (1955-02-01), Light
patent: 2782598 (1957-02-01), Gatwood
patent: 3438308 (1969-04-01), Nutter
patent: 3456671 (1969-07-01), Stacey
patent: 3889709 (1975-06-01), Dwyer
patent: 3999462 (1976-12-01), Chamberlain
Clark Equipment Company
Cohen Irwin C.
Wiessler John C.
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