Patent ID: 6364639
Filing Date: 2002-04-02
Classification: F04B,F16N

Abstract:
A pump for pumping a pumpable product, particularly lubricant including grease, said pump comprising:a head; an elongate member constituting a pump plunger extending outward from the head having an inner end adjacent the head and an outer end remote from the head; said plunger being fixed at its inner end with respect to the head; an elongate pump tube surrounding the plunger extending outward from adjacent the inner end of the plunger to and outward of the outer end of the plunger and reciprocable in and out through a pump stroke relative to the plunger; a motor-driven mechanism associated with the head operable to reciprocate the tube through said pump stroke between an inward position relative to the plunger and an outward position relative to the plunger; said tube having an inner end closure slidable in and out on an inner portion of the plunger adjacent the inner end of the plunger in sealed relation thereto; said tube having an outer closure slidable in and out on an outer portion of the plunger adjacent the outer end of the plunger in sealed relation thereto, closing the tube inward of its outer end; said tube being of larger internal cross-section than the cross-section of the plunger throughout the length of the tube between said closures thereby defining an elongate annular pump chamber between the plunger and tube extending from said inner end closure to said outer closure; said tube being open at its outer end and having an inlet check valve adjacent its said open outer end outside the outer end of the plunger defining in conjunction with the outer end of the plunger an expansible and contractible outer end chamber; the cross-sectional area of said inner portion of the plunger being different from the cross-sectional area of said outer portion of the plunger; the inlet check valve opening on an outward stroke of the tube for entry of the pumpable product to said outer end chamber; said pump having a passage for outflow of pumpable product from said elongate annular pump chamber to and through an outlet in the head on an outward stroke and also on an inward stroke of the tube; said pump having a passage with a check valve therein adapted to open on each inward stroke of the tube with the inlet check valve closed for delivery of pumpable product from said outer end chamber to said elongate annular pump chamber.