Patent ID: 9243629
Filing Date: 2016-01-26
CPC Classification: F04B

Claim Text:
1. A fluid pump for use in high pressure liquid chromatography comprising: a housing having a drive case and a pump head at one end of the drive case defining an internal pump chamber communicating with an inlet and an outlet; a first piston supported by said housing for reciprocation along a first axis; a motor fixed to said housing rotating a shaft; a cam fixed to said shaft for rotation about a second axis transverse to said first axis, said cam having a peripheral edge intersecting said first axis; a first spring biasing said first piston along said first axis towards said cam; said first piston having an outer end with a plunger of lesser diameter than said first piston inward thereof movable in said pump chamber and an inner end engaging said cam edge so that said plunger may be reciprocated in said pump chamber upon rotation of said cam by said motor; a second piston supported by said housing for reciprocation along said first axis and having inner and outer ends, said cam being disposed between the inner ends of said pistons, said second piston outer end having an outer surface transverse to said first axis open to ambient atmosphere; a second spring biasing said second piston inner end towards said cam; and, wherein said second spring and atmospheric pressure in combination provide torque compensating force biasing said second piston inward against said cam opposing the inward force of said first piston on said cam.