Patent ID: 7021387
Filing Date: 2006-04-04
Classification: E21B,F04B

Abstract:
1. A wellbore pump for use in a wellbore having cylindrical walls, a lower end and an upper end, the wellbore having a pressurized fluid adjacent the lower end thereof; the wellbore pump comprising: a plunger having an upper plunger end, a lower plunger end, and cylindrical plunger walls extending from the upper to the lower plunger ends, the cylindrical plunger walls having an external surface facing the cylindrical walls of the wellbore; a chamber having chamber side walls, an open end and a closed end within the plunger; a seal on the external surface of the cylindrical plunger walls and providing a seal between the plunger and the cylindrical walls of the wellbore; a passage in the plunger to permit the pressurized fluid to pass through the plunger from below the seal to above the seal; a valve in the passage movable between an open position permitting fluid to pass through the passage from below to above the seal to a closed position preventing fluid from passing through the passage from below to above the seal; a piston within and closing the open end of the chamber and being connected to the valve and mounted for reciprocating movement within the chamber to move the valve between the open and closed positions; a bias member within the chamber between the piston and the closed end of the chamber, the bias member acting upon the piston to bias the piston in a direction that moves the valve to the open position; a seal between the piston and the chamber side walls to prevent the pressurized fluid from entering the chamber around the piston and preventing the bias member from being exposed to the pressurized fluid; the pressurized fluid being exposed to the piston and acting on the piston in a direction opposite from the bias member, whereby when the pressurized fluid reaches a predetermined pressure it will move the piston against the bias of the bias member to cause the valve to move to the closed position.