Electricity: single generator systems – Automatic control of generator or driving means – Fluid pressure including wind
Patent
1987-01-13
1988-02-02
Hickey, R. J.
Electricity: single generator systems
Automatic control of generator or driving means
Fluid pressure including wind
318139, 320 61, 414529, H02P 314
Patent
active
047231076
ABSTRACT:
A hydraulic lifting mechanism, particularly suitable for a battery-powered industrial truck, including a hydraulic lifting cylinder, a hydraulic unit, operating as a pump in the load lifting operational mode, and supplying the lifting cylinder with pressure medium, and operating as a motor in the load lowering operational mode during which mode it is actuated by the pressure medium exiting from the lifting cylinder, and a DC generator coupled with the hydraulic unit operating as an electromotor in the load lifting operational mode and as a generator in the load lowering operational mode. A control valve arrangement is provided at the halfway point in the pressure path between the hydraulic cylinder and the hydraulic unit, which is controlled by a lifting mechanism control. In addition, the lifting mechanism control controls a regenerative brake circuit supplied by the DC generator in the load lowering operational mode. The control valve arrangement includes a proportional valve which is opened by the lifting mechanism control in the load lowering operational mode in accordance with a ramp-like function. The regenerative brake circuit is switched on depending on the output current of the DC generator working as a generator, if the generator output current exceeds a predetermined value. Undesirable dropping of the load in the lowering operational mode is hereby prevented during transition to regenerative braking.
REFERENCES:
patent: 3512072 (1970-05-01), Karazija et al.
patent: 3947744 (1976-03-01), Grace et al.
Hickey R. J.
Steinbock GmbH
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