Pressure relief mechanism for a dispensing device

Abstract

A pressure relief mechanism for devices such as a dispensing device, the dispensing device being of a type that includes a cylinder having a piston disposed therein, the piston including an opening which provides communication between a front portion of the cylinder and a rear portion of the cylinder. At least one driven rod is connected to the piston which extends through an end wall of the cylinder. The piston and its driven rod are driven in an ejecting direction in response to pressure provided within the rear portion of the cylinder. The pressure relief mechanism includes an elongated return rod that is actuable from outside the cylinder. The return rod has a length extending through the piston and is provided for engaging and moving the piston in a return direction. The pressure relief mechanism also includes a sealing device disposed within the rear portion of the cylinder. The sealing device is fixedly secured to an end of the return rod and normally covers the piston aperture to prevent pressure flow across the piston when driven in the ejecting direction. The return rod is actuable to remove the sealing means from the piston to uncover the piston opening thus permitting pressure to pass across the piston to the front portion of the cylinder thus enabling effortless movement of the piston in the return direction in response to actuation by the return rod.