High pressure pump

Claim 1

A high pressure pump to supply liquid to a nozzle, comprising a cylinder with a liquid inlet at one end and an outlet at the other end, a reciprocating rod extending through a seal at one end of the cylinder and connected with means producing rapid reciprocation of the rod, a pair of spaced discs on the rod in the cylinder, one of said discs being adjacent the outlet and having a plurality of holes therethrough facilitating free passage of liquid, the other of said discs being adjacent the inlet and being imperforate to prohibit passage of liquid therethrough, and also being smaller than the cylinder to permit substantial liquid flow past the edge of the disc, and a piston on the rod between the discs and movable toward and away from said imperforate disc, the piston having a rodreceiving bore with a diameter greatly exceeding the size of the rod to permit free flow of liquid through the piston and to allow the piston to center itself in the cylinder, the piston having a valve seat at the exterior periphery of the bore and confronting the imperforate disc to engage the disc and prevent flow of liquid through the piston, and said disc with holes being engageable with the piston at the exterior of said bore for moving the piston and permitting flow through the holes and bore, said piston including a rigid piston body defining said bore and valve seat, said piston body having an annular exterior shoulder facing the outlet end of the cylinder and having an annular groove adjacent thereto, said piston also including a resiliently yieldable annular piston cup having an exterior periphery with a generally cylindrical cup wall bearing and sealing against the interior of the cylinder, and the inner periphery of said annular cup embracing the piston body to be mounted thereon without clamping and also including an internal bead confined in the groove of the piston body, the inner periphery of the cup including the bead being subject to the liquid pressure adjacent the outlet end of the cylinder for maintaining the cup wall in sealing relation with the interior of the cylinder regardless of lack of concentricity between the piston body and the cylinder, and said annular cup also bearing and sealing against said shoulder to be moved toward the outlet end of the cylinder thereby.