Schwartz, Jeffery, Schwaab, Mack, Blumenthal & Koch
Hydraulic power clutch control system having an inching valve
 The spool of the inching valve has first and second lands, a first portion connected to the first land and tapered or suitably formed in such a manner as to gradually increase the flow resistance of the inlet port in accordance with the axial movement of the spool into a position in which the first land fully closes the inlet port, and a second portion connected to the second land and having a reduced uniform diameter or a suitable form which initially temporarily abruptly reduces the flow resistance of the drain port and subsequently gradually reduces the flow resistance thereof in accordance with the axial movement of the spool from a position in which the second land opens the drain port. 
Nissan Motor Company, Limited
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Yasufumi Shoei
Ideta Watanabe