Importance

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Abstract

A pump includes a cylindrical plunger chamber having an inward projecting radial seal. A plunger moves with a reciprocating stroke within the cylindrical plunger chamber, the plunger having a first diameter, and a second diameter less than the first diameter, the radial seal engaging the plunger at the second diameter for an entire length of the stroke of the plunger. A pressure balancing valve is in fluid communication with the pumping chamber and the hydraulic oil chamber. A fluid passage connects to the plunger chamber at a position between the radial seal and the first diameter of the plunger and leads to the pressure balancing valve. A radial clearance is between the cylinder and the second diameter, and a seal between the first portion and the cylinder having a clearance smaller than the radial clearance allows hydraulic fluid to escape past the seal during a plunger stroke.

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First Claim