Hydraulic elevator with dynamically programmed motor-operated valve
US4726450A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 17, 1986 |
| Grant date | Feb 23, 1988 |
| Priority date | — |
| Expiry date | Apr 17, 2006 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB66B1/405
- WIPO fieldHandling
- WIPO sectorMechanical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.