Controlled electric pump drive for hydraulic lifting arrangement

Details Controlled electric pump drive for hydraulic lifting arrangement Controlled electric pump drive for hydraulic lifting arrangement

1988-10-21

1990-10-09

Look, Edward K.

Power plants

Pressure fluid source and motor

Condition responsive control of or by input to input pump...

60433, 60475, 60476, 60486, 92134, 267 6411, 187 9R, B66F 922

Patent

active

049613162

ABSTRACT:
A hydraulic lifting arrangement for a lift assembly on a materials-handling vehicle includes a working piston-cylinder device (17) for raising and lowering the lift assembly, a reversible pump assembly (40) for operating the piston-cylinder device, and an electric motor for driving the pump assembly. The piston-cylinder device (17) is a double-acting device and has two working chambers (28,29), which are connected to the pump assembly by connecting pipes (46,47). The pump assembly comprises a first and a second hydraulic pump (41,42) having fixed displacements. The pumps are so arranged in the system that together they supply hydraulic medium to and receive hydraulic medium from solely the first chamber (28) whereas only the pump motor (41) supplies and receives hydraulic medium to and from the second chamber (29). The relationship between the displacement of the first pump (41) and the sum of the displacements of both pumps (41,42) corresponds essentially to the relationship between the respective active piston areas in the second and the first chambers. Conveniently, a pressure-gas chamber (26) is arranged in the piston-cylinder device for biassing the piston (19) so as to enable the dead weight of the lift assembly and a given part of the load to be counter-balanced.

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