Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Reexamination Certificate
2005-09-28
2008-10-07
Leslie, Michael (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
C060S488000
Reexamination Certificate
active
07430860
ABSTRACT:
Improvement in a hydrostatic valve assembly for use in a hydrostatic transmission, for controlling fluid transfer between a first, second and third line, wherein two of the lines define first and second pressure lines within a closed loop circuit. The valve assembly comprises a valve body having ports in communication with the three lines; a spool bore and valve spool reciprocating therewithin, having first and second end portions joined by a connecting portion, and first and second bypass orifices within the valve spool; and dampers for centering the valve spool in a neutral position. The bypass orifices utilize increased cross-sectional areas that permit the passage of substantially the full flow of the charge pump, without using a charge pump relief valve, at a low pressure drop. A hydraulic system utilizing this valve assembly and a method for increasing the transmission efficiency, in the neutral mode, are also set forth.
REFERENCES:
patent: 2961829 (1960-10-01), Weisenbach
patent: 3236049 (1966-02-01), Reinke
patent: 3734225 (1973-05-01), Kobald et al.
patent: 5211015 (1993-05-01), Schroeder
patent: 6263670 (2001-07-01), Gluck et al.
patent: 6837047 (2005-01-01), Dong et al.
patent: 2004/0006981 (2004-01-01), Dong et al.
Dong Xingen
Whitaker James
Clark Robert J.
Leslie Michael
Parker-Hannifin Corporation
Pophal Joseph J.
Whitman Daniel J.
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