Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Reexamination Certificate
2008-03-11
2008-03-11
Fristoe, Jr., John K. (Department: 3753)
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
C251S030030, C251S038000
Reexamination Certificate
active
07341236
ABSTRACT:
A pilot operated valve has a main poppet that selectively controls flow of fluid between first and second ports in response to pressure in a control chamber on one side of the main poppet. The main poppet has an aperture extending between the control chamber and the first port. A pilot piston slides within the aperture and has the pilot passage with a pilot orifice and a first disk spring biases the pilot piston with respect to the main poppet. A pilot valve element selectively engages the pilot orifice to open and close the pilot passage and thereby controls motion of the main poppet. Forces from the first disk spring and a pressure differential between control and pilot chambers alter a position of the pilot valve seat with respect to the main poppet. The change in position compensates for effects on valve operation due to variation of the pressure at the two ports.
REFERENCES:
patent: 2575272 (1951-11-01), Harris
patent: 4174824 (1979-11-01), Kolze
patent: 4699351 (1987-10-01), Wells
patent: 5878647 (1999-03-01), Wilke et al.
patent: 6149124 (2000-11-01), Yang
patent: 6328275 (2001-12-01), Yang et al.
patent: 6736370 (2004-05-01), Crockett et al.
patent: 6742763 (2004-06-01), Kremer
patent: 6745992 (2004-06-01), Yang et al.
Hughes R. Christopher
Jackson Randall J.
Stephenson Dwight B.
Yang Xiaolong
Fristoe Jr. John K.
Haas George E.
HUSCO International Inc.
Quarles & Brady
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