Manual hydraulic pump

Pumps – Expansible chamber type – Having pumping chamber pressure responsive distributor

Reexamination Certificate

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Details

C417S222100, C417S269000, C417S571000, C417S455000, C092S071000

Reexamination Certificate

active

11008102

ABSTRACT:
A manual hydraulic pump includes a cylinder block10and an end block8. The rear end of the cylinder block10and the end block8defines an end space21between them. The cylinder block10has cylinders13and oil passages23. Each oil passage23extends between the rear end of one of the cylinders13and the end space21. The end block8has a pair of cylindrical holes27opening into the end space21. The end block8also has a pair of inlet/outlet ports25each communicating with the outside of the pump and one of the cylindrical holes27. A distributing valve22is put in the end space21and spring-biased into compressive contact with the rear end of the cylinder block10. The distributing valve22substantially takes the form of a disc and has a thickness smaller than the distance between the adjacent ends of the blocks10and8. The distributing valve22has a pair of arcuate ports22aformed on its front side. The arcuate ports22acan communicate selectively with the oil passages23of the cylinder block10when this block turns. The distributing valve22also has a pair of cylindrical holes22cformed on its rear side, each of which communicates with one of the arcuate ports22a. A pair of pressing pistons31each include a rear cylindrical part31aand a front cylindrical part31b, which is smaller in diameter than the rear cylindrical part. The rear cylindrical part31ais in axially slidable engagement with one of the cylindrical holes27of the end block8, with an O-ring33interposed between this part and this block. The front cylindrical part31bis in axially slidable engagement with one of the cylindrical holes22cof the distributing valve22, with an O-ring32interposed between this part and the valve. Each pressing piston31has an axial bore31ccut through it.

REFERENCES:
patent: 6176684 (2001-01-01), Zimmermann
patent: 6659733 (2003-12-01), Takenaka et al.
patent: 6957950 (2005-10-01), Kamiya et al.
patent: 11-222197 (1999-08-01), None

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