Patent ID: 6102676
Filing Date: 2000-08-15
Classification: F04B,F16N

Abstract:
A pump for pumping a pumpable product, particularly lubricant including grease, from a supply thereof, said pump comprising:a head adapted for placement above said supply;an elongate member constituting a pump plunger extending down from the head having an upper end and a lower end;said plunger being fixed at its upper end with respect to the head;an elongate pump tube surrounding the plunger extending down from adjacent the upper end of the plunger to and below the lower end of the plunger and reciprocable up and down through a pump stroke relative to the plunger;motor-driven means associated with the head for reciprocating the tube through said pump stroke between a raised position relative to the plunger and a lowered position relative to the plunger;said tube having an upper end closure slidable up and down on an upper portion of the plunger adjacent the upper end of the plunger in sealed relation thereto;said tube having a lower closure slidable up and down on a lower portion of the plunger adjacent the lower end of the plunger in sealed relation thereto, closing the tube above its lower 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 upper end closure to said lower closure;said tube being open at its lower end and having an inlet check valve adjacent its said open lower end below the lower end of the plunger defining in conjunction with the lower end of the plunger an expansible and contractible lower end chamber;the cross-sectional area of said upper portion of the plunger being different from the cross-sectional area of said lower portion of the plunger;the inlet check valve opening on a downstroke of the tube for entry of the pumpable product to said lower 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 a downstroke and also on an upstroke of the tube;said pump having a passage with a check valve therein adapted to open on each upstroke of the tube with the inlet check valve closed for delivery of pumpable product from said lower end chamber to said elongate annular pump chamber.