Fixed-volume liquid dispenser

A dispenser for dispensing a fixed volume of viscous material, said dispenser comprised of:

• a cylinder coupled to and extending from said reservoir, said cylinder having a first opening within the reservoir through which material in the reservoir can pass, and a second opening outside the reservoir through which material can exit the cylinder;
• and
• a piston assembly means for receiving material that passes through the first opening, sectioning off said material, translating the sectioned off material down a cylinder and pumping material from the second opening.

A method of dispensing viscous liquids from a dispenser having a piston assembly that translates in a cylinder, a fixed volume of material from a presurrizable reservoir to a dispensing opening, said piston assembly having first and second opposing pistons separable from each other by a piston separation spring having a first spring constant, the cylinder being provided with a piston assembly return spring having a second spring constant, the method comprising the steps of:

• selecting the first spring constant to be a value less than the value of the second spring constant whereby releasing pressure on the pressurizable reservoir causes at least some material dispensed from said dispensing opening to be drawn back into the dispensing opening.