Fluid handling – Processes – Involving pressure control
Reexamination Certificate
2001-07-10
2003-11-11
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Processes
Involving pressure control
C060S427000, C060S452000, C137S112000, C137S636200
Reexamination Certificate
active
06644335
ABSTRACT:
1. TECHNICAL FIELD
This invention relates generally to the use of precision orificing that is specifically designed within a pilot control valve for a joystick, and, more particularly, to the ability to precisely determine the size, shape, and position of an orifice for improved flow response.
2. BACKGROUND
It is well known to utilize pilot control valves within a work machine, such as front end loaders and the like. The pilot control valves typically include a tiltable or rotatable joystick with a cam movable therewith. It is also conventional to provide a series of valves about the vertical axis of the cam, which, when the stems thereof are selectively depressed, allow a flow of fluid to actuate fluid motors for controlling various functions of the work machine.
It is also well known to utilize orifices within a hydraulic circuit to provide directional control of hydraulic fluid. For example, in U.S. Pat. No. 4,481,770 issued to Kenneth R. Lohbauer on Nov. 13, 1984, a fluid control system for controlling the torque of a fluid motor and varying the flow to the fluid motor is disclosed. A mechanism is used to control the torque and flow in proportion to the operator's input to a pilot operated control valve that controls the fluid pump. The mechanism controls the torque and flow of the fluid motor during both acceleration and deceleration of the fluid pump and eliminates the need for special, complicated control valves. This invention relates to the ability to change the flow characteristics of a pilot control valve through the use of various valves and orifices. However, the need to improve hydraulic flow response in a hydraulic circuit is not disclosed in the present invention. The ability to improve hydraulic flow response through the use of precision orificing provides numerous benefits. For example, a reduction of the variability of hydraulic flow response in relation to changes in hydraulic fluid temperature would be available. Additionally, different hydraulic flow responses may be achieved for different functions of the work machine controlled by a single joystick controller. Therefore, the ability to improve hydraulic flow response is important to increase efficiency and control for various functions of the work machine regardless of temperature and oil-viscosity variations.
The present invention is directed to overcoming the problems as set forth above.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a method of dampening a pressure flow between a pilot operated control valve connected with a control device and a resolver is disclosed in a fluid control system having a supply of hydraulic fluid capable of being pressurized. The dampening method comprises the step of locating an orificing device directly in the pressure flow between the pilot operated control valve and the resolver.
In another aspect of the present invention, a fluid control system with a supply of hydraulic fluid capable of being pressurized comprises a control device. A pilot operated control valve is connected with the control device and is actuated by the control device to produce a pressure flow. A resolver is connected with the pilot operated control valve for receiving the pressure flow from the pilot operated control valve. An orificing device is located directly between the pilot operated control valve and the resolver. The orificing device includes means for dampening the pressure flow between the pilot operated control valve and the resolver.
The present invention includes the ability to improve hydraulic flow response through the use of an orificing device located directly between a pilot operated control valve and a resolver. The orificing device is capable of dampening a pressure flow between the pilot operated control valve and the resolver. This capability permits different hydraulic flow responses for different functions of a work machine controlled by a single control device.
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Dvorak Paul A.
Khairallah Gabriel G.
Khaw Chin T.
Caterpillar S.A.R.L.
Charlton Diana L
Michalsky Gerald A.
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