Duane M Anderson

US Patent:

50170945, May 21, 1991

Filed:

Mar 12, 1990

Appl. No.:

7/491776

Inventors:

Kevin J. Graf - Eden Prairie MN
James J. Hastreiter - Eden Prairie MN
Duane A. Anderson - Edina MN

Assignee:

Eaton Corporation - Cleveland OH

International Classification:

F04B 4906
F04B 126

US Classification:

417218

Abstract:

A control system (33, 41) is disclosed of the type used to control the displacement of a variable displacement pump (11) having stroking cylinders (25, 27). The control system includes a pair of ON-OFF electromagnetic valves (49, 51) and a proportional valve (85). When a first direction of operation is selected, a first direction command signal (43) is transmitted to the first ON-OFF valve (40) such that control pressure from the charge pump (17) flows through the valve (49), then through the proportional valve (85) and through the valve (51) to the reservoir (75) until the proportional valve (85), in response to an increasing displacement signal (47), moves from its minimum displacement position (FIG. 1) toward a position corresponding to the desired displacement of the pump. With the control system of the present invention, two of the three electromagnetic valves (49, 51, 85) would have to fail, such as being stuck in an open position, in order for the vehicle operator to be unable to bring the vehicle to a safe stop.