Abstract: A dispenser for viscous fluids includes a tubular cylindrical barrel member, a dispensing nozzle on one end of the barrel member and a piston element which is sealingly received in the barrel member and slidable therein in a direction toward the nozzle for dispensing a viscous fluid from the barrel member. The barrel member and the piston element are constructed so that the piston element is freely slidable in a reverse direction in the barrel member to relieve the pressure on the fluid in the barrel member after a dispensing operation has been completed and to thereby eliminate post extrusion from the dispenser. The dispenser is operative in combination with a dispenser gun which includes a drive plunger and an advancing mechanism which is operative for advancing the drive plunger in order to advance the piston element of the dispenser in the barrel member thereof.

Abstract: A metering valve having a valving element with a valving surface; a valve head with a valve seat, an inlet passage upstream of the valving surface and an outlet passage downstream of the valving surface; a valve body which provides a predetermined small movement of the valving surface into and out of contact with the valve seat to dispense fluid, and biases the valving surface against the valve seat when fluid is not being dispensed; and a seal between the valving element and the valve head, the seal defining a dispensed fluid cavity around the valving surface and valve seat communicating with the inlet and outlet passages, and including a diaphragm in the preferred embodiment.