Hydraulic elevator with dynamically programmed motor-operated va

Details Hydraulic elevator with dynamically programmed motor-operated va Hydraulic elevator with dynamically programmed motor-operated va

1986-04-17

1988-02-23

Shoop, Jr., William M.

Elevator, industrial lift truck, or stationary lift for vehicle

Stationary lift for roadway vehicle or required component...

Having specific drive means for support

B66B 104

Patent

active

047264500

ABSTRACT:
The point at which pump out pressure exceeds load is sensed to provide a point for scheduling flow to an actuator in a hydraulic system. Flow is controlled by a stepper motor (28) that moves a flow control valve (27). The steps needed to achieve fixed flow changes are greater for high flow positions. When the pump (21) is turned on, the valve (27) is positioned to bypass flow; the bypass flow is then programmably decreased to the actuator. Reverse flow is regulated by the valve (27) to control actuator retraction. Reverse flow is initiated by opening a check valve (40) with an actuator (50) that opens it first to reduce pressure across the valve, then fully. The flow control valve (27) also operates to relieve excess pressure in the system. During a descent the stepper rate is started at a first stored rate for worse conditions, the car velocity is measured and successive stored rates are increased or decreased.

REFERENCES:
patent: 3977497 (1976-10-01), McMurray
patent: 4249641 (1981-02-01), Takenoshita et al.
patent: 4311212 (1982-01-01), Simpson

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