Fluid handling – Systems – Line condition change responsive release of valve
Utility Patent
1999-09-28
2001-01-02
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Line condition change responsive release of valve
C137S625640, C137S625660
Utility Patent
active
06167909
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a slide valve in which an apertured slide block is reciprocally moved between an operative position wherein a supply line carrying supply fluid under pressure is coupled to a function line to provide power to hydraulic equipment and, in particular, to a slide valve having improved corrosion resistance and protection from the adverse effects of contaminants that might be carried into the valve from the valve return line.
Slide type valves are oftentimes mounted in inaccessible locations and thus must maintain their functional capabilities over long periods of time without the benefit of scheduled maintenance. One widely used form of this type valve contains an apertured slide that can be positioned to control the flow of a fluid from a pressurized supply line to a function line that services some type of hydraulic equipment when the slide is placed in an operative position and coupling the function line to an unpressurized return line when the slide is placed in an inoperative position.
Movement of the slide plate is typically achieved by two pistons that are arranged to act upon opposite sides of the slide block. The pistons are mounted in cylinders and are under the control of poppet or pilot valves that are activated by solenoids. To change the slide blocks position, a selected solenoid is energized for a short period of time causing a pulse of pressurized pilot fluid to be introduced into one of the piston cylinders which, in turn, causes the piston to move the slide to the desired position. Once the change of position is achieved, the solenoid is deenergized and the pressurized cylinder is coupled through the poppet valve to a return line to vent the cylinder.
The typical prior art slide valve is also equipped with a failsafe device that is usually mounted behind the valve closing piston. The failsafe device generally includes a spring actuated failsafe piston, that uses supply pressure to hold a return spring in a loaded condition as long as the pressure in the supply line is maintained above a given level. In the event of a pressure loss in the supply line, the holding force acting upon the piston is reduced to a point wherein the spring is permitted to unload. This, in turn, drives the failsafe piston into moving contact with the valve closing piston thus moving the slide to an inoperative position.
The space between the failsafe piston and the valve piston is in communication with the poppet valve control circuit. When there is low pressure in the supply line and the failsafe piston has moved against the valve closing piston, the space between the pistons becomes vented to the return line through the poppet valve. When pressure is again applied to the supply line, the failsafe piston is moved back creating a void in the space between the two pistons which causes fluid from the return line to be drawn into the void through the associated poppet valve circuit. If contamination is present in the return fluid, and it usually is, it can collect in the working parts of the poppet valve preventing it from fully closing under certain conditions. With the poppet valve partially open, pilot fluid under pressure will have an open path to the system return line and the supply of pilot fluid will be rapidly depleted. This rapid depletion of fluid is extremely costly and can produce serious operating problems with regard to the equipment being serviced by the slide valve.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to improve slide valves and, in particular, slide valves used in remote and generously inaccessible locations.
It is a further object of the present invention to enhance the ability of a slide block used in a slide valve to efficiently change position to open or close the valve.
A still further object of the present invention is to prevent the unwanted loss of pilot fluid from a slide valve.
Another object of the present invention is to provide an improved slide valve that can operate over long periods of time without the need of scheduled maintenance.
These and other objects of the present invention are attained by a slide valve mechanism that includes a housing containing a slide chamber and an apertured slide block reciprocally mounted in the chamber for movement between an operative position wherein a supply line for carrying fluid under pressure is coupled to a function line servicing hydraulic equipment and an inoperative position wherein the function line is coupled to a return line. A pair of control pistons are mounted in cylinders on opposite sides of the slide block and the pistons are selectively moved into contact with the slide block to change the valve between an operative and an inoperative state. The valve closing piston has an elongated nose section that passes through a failsafe chamber. A failsafe piston is slidably mounted upon the nose section within the failsafe chamber and a compression spring is wound about the nose section to act between the rear wall of the chamber and the failsafe piston. An elongated groove is formed about the outside of the failsafe piston to create a sealed cavity with the inside wall of the failsafe chamber. The cavity is connected to the supply line and adapted so that the failsafe piston is moved back under normal supply pressure to place the spring in a loaded condition. In the event supply pressure is lost, the spring unloads to force the failsafe piston into driving contact with the slide block, thus moving the slide block rapidly into an inoperable position. Unlike prior art slide valves, the present failsafe piston chamber is isolated from the poppet valve control circuit and thus return fluid is not drawn into the poppet valve any time the failsafe piston is cycled.
In one embodiment of the invention, the slide block is supported upon a pair of shear seals and a roller assembly is positioned between the top surface of the slide block and a roof block. The slide block, shear seals and roof block are constructed of a ceramic material with the opposing surfaces of the two blocks being held in close flat and parallel alignment.
REFERENCES:
patent: 3640146 (1972-02-01), Barnes
patent: 4041983 (1977-08-01), Bianchetta
patent: 4046165 (1977-09-01), Rose et al.
patent: 4848404 (1989-07-01), Hickok
patent: 2201227 (1987-02-01), None
Michalsky Gerald A.
Tactair Fluid Controls, Inc.
Wall Marjama & Bilinski
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