Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Cylinders parallel to rotation axis
Reexamination Certificate
1999-09-03
2001-07-17
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Cylinders parallel to rotation axis
Reexamination Certificate
active
06260468
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic units of the bent axis type. More particularly, this invention relates to a swinging yoke type bent axis hydraulic unit.
Bent axis hydraulic units have been known for many years. The most widespread or common of the bent axis designs utilizes a “tilting block” such as disclosed by Forster in U.S. Pat. No. 4,893,549. A rotatable cylindrical drum or cylinder block kit has a plurality of axial pistons therein supported on a nonrotatable swivel carriage on its axis of rotation. The swivel carriage has a convex end face positioned against a concave swivel carriage guide surface. The swivel carriage guide surface is part of the swivel carriage housing, which is attached to the machine.
Other bent axis units utilize a “swinging yoke” configuration. The cylinder block kit is carried by the yoke and swings with it to vary the displacement of the unit.
A control mechanism of the prior applications includes a stepper motor, control member with an elongated bore, an elongated hydraulic fluid control spool movably mounted in the bore and positioned by the cooperative functions of the stepper motor and the feedback signal to the spool which senses a cam on a pivotal yoke, and a pair of servo pistons operatively mechanically connected to the yoke and hydraulically connected to the fluid control spool.
The principal object of this invention is to replace the stepper motor with a proportional solenoid fluid valve which is operatively connected to a computer.
A further object of this invention is to have one end of the fluid control spool influenced by the solenoid fluid valve, and the other end influenced by a spring loaded feedback system operatively connected to the yoke or pivotal member of the system.
These and other objects will be apparent to those skilled in the art.
SUMMARY OF THE INVENTION
A variable displacement bent axis hydraulic unit has a pivotal member for carrying a cylinder block pivotally mounted to a fixed frame on the unit. A close loop control mechanism for changing the hydraulic displacement of the unit and including at least one movable servo piston is operatively connected to the pivotal member. The control mechanism includes a feedback member operatively connected to the pivotal member so as to provide feedback to the control mechanism regarding the pivotal position of the pivotal member relative to the fixed frame. The control mechanism is operative to vary the servo piston to change the pivotal position of the pivotal member. The control mechanism includes an elongated bore with a control valve mounted therein. The feedback member comprises a sleeve downstream from a spool slidably mounted within the bore with one end slidably mounted in the control bore and the other end protruding from the control housing. That end engages the pressure feedback sleeve to engage the pivotal member. A pair of spaced apart servo bores with servo pistons therein in the control housing are in hydraulic communication with the bore and the spool. The pistons are operatively connected to the pivotal member for rotating the same in one of two directions as determined by the position of the spool in the bore.
The spool is longitudinally energized in one direction by the displacement feedback sleeve on one end, and hydraulic pressure imposed on the other end. The hydraulic pressure is induced by a computer connected to a proportional solenoid fluid valve controlled by the computer and in operative fluid engagement with one end of the spool.
REFERENCES:
patent: 2931250 (1960-04-01), Ebert
patent: 3142963 (1964-08-01), Thoma
patent: 3148628 (1964-09-01), Boydell
patent: 3803987 (1974-04-01), Knapp
patent: 3958496 (1976-05-01), Wallin
patent: 4893549 (1990-01-01), Forster
patent: 5160245 (1992-11-01), Geringer
“Data Sheet for Variable Pump/Motor V20, ” Volvo Hydraulics, pp. 1-4, published prior to 1980.
“Hydrostatics for power split transmissions,” E. Skirde & M. Gigling, Industrial Vehicle Technology '98, pp.30-33, published , 1998.
Dirks David D.
Gollner Wilhelm
Kardell Doug
Ryken James D.
Lopez F. Daniel
Sauer-Danfoss Inc.
Zarley, McKee, Thomte , Vorhees & Sease
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