Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Reexamination Certificate
2006-02-21
2006-02-21
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
C137S115160
Reexamination Certificate
active
07000387
ABSTRACT:
A hydraulic spool valve is provided in which two inlet bores and an outlet bore lead into a housing. A spool-valve piston which is under the influence of compression springs on both sides can be displaced longitudinally in the housing. When a difference in pressure of the hydraulic fluid in the inlet bores occurs, the inlet bore which conducts the lower pressure in each case is connected to the outlet bore. The two compression springs are pre-stressed and have an additional expansion path. During the displacement of the spool-valve piston from a neutral central position into an extended intermediate position, the two compression springs therefore remain in operative connection with the spool-valve piston, in which case the spring forces counterbalance each other until the intermediate position is reached.
REFERENCES:
patent: 3561214 (1971-02-01), Bobst
patent: 3846982 (1974-11-01), Rometsch et al.
patent: 4341133 (1982-07-01), Sakamoto
patent: 4531369 (1985-07-01), Izumi et al.
patent: 6295811 (2001-10-01), Mangano et al.
patent: 6339928 (2002-01-01), Gollner
Sauer Sundstrand, Baureihe—Series 90, Jun., 1992—16 pages.
Leslie Michael
Sauer-Danfoss (Neumunster) GmbH & Co. OHG
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