Motors: expansible chamber type – Fluid supply through diverse paths to single expansible chamber – One path includes restriction
Reexamination Certificate
2000-09-06
2002-07-09
Lopez, F. Daniel (Department: 3745)
Motors: expansible chamber type
Fluid supply through diverse paths to single expansible chamber
One path includes restriction
C091S006000
Reexamination Certificate
active
06415703
ABSTRACT:
TECHNICAL FIELD
The present invention concerns a method for controlling the speed of motion of a hydraulically driven machine, an operating system, and a control device of a hydraulically driven machine.
BACKGROUND ART
Hydraulic systems are known in the art, where the speed of motion of a hydraulically driven machine can be adjusted for different purposes.
Publication DE 30 10 973 discloses a control system, where the positions of the valve and the feed of the hydraulic oil to the machine to be driven are adjusted by means of a control cam. Depending on the valve position, three different feeding speeds and speeds of the machine can be provided.
Publication DE 26 08 988 discloses a system, where by using different flow resistances, the motion of the hydraulic piston operating the machine can be slowed down, e.g. when lowering a heavy load.
In the system in accordance with publication SE 376 788, the acceleration and speed of a hydraulic actuator of a pressure casting machine is controlled so that a desired speed profile can be exactly repeated. There, the main control valve is controlled by means of an auxiliary valve.
Publication DE 41 29 508 concerns a system provided with two pumps, wherein the speed of rotation of a hydraulic motor is adjusted. With a small load of the motor, only one pump is used. When necessary, the motor is also supplied with a part of the feed volume of the other pump.
DISCLOSURE OF INVENTION
The object of the present invention is to provide a control system, where the speed of a hydraulically operated device, when necessary, can be proportionally controlled.
By means of the present invention, the speed of e.g. a hydraulic cylinder-piston device of a vehicle's loading device can be controlled, when necessary, in any position of the piston. During a slow precision drive, the speed can be controlled by changing the speed of rotation of the pump.
Although the valves used in the system are on-off valves, the required controlling of the speed can be provided proportionally by means of the device in connection with starting and ending of a motion.
An on-off valve means a valve that either opens or closes certain flow channels, but by means of which the flow cannot be continuously controlled during the operation, like with an actual control valve.
A simple pump can be used in the system, whereby the flow produced by it is controlled by changing its speed of rotation. There is no need of any variable capacity pump with a complicated construction, where the change of flow is provided by changing the position of the pistons, while the speed of rotation remains the same.
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Burns Doane , Swecker, Mathis LLP
Kershteyn Igor
Multilift Oy
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