Patent ID: 7703643
Filing Date: 2010-04-27
Classification: B05C,F16N

Abstract:
1. A method of pumping viscous materials, comprising the steps of: (1) storing a predetermined portion of driving energy for a pumping operation as elastic potential energy when said pumping operation starts; and (2) releasing said driving energy stored in step (1) when said pumping operation stops, leaving a space for filling viscous materials as said viscous materials expand after the pumping operation is terminated, whereby said viscous materials will be sucked back into an associated pumping device for preventing dripping of said viscous materials; and wherein said step of storing elastic potential energy is realized by a declined surface structure, selected from a slope and a spring, formed on a screw nut at a free end of a push rod in said pumping device, thereby a driving torque doing work to deform said spring when said pumping operation starts so as to shift said push rod for a predetermined displacement determined by a height of said slope, when said elastic potential energy is stopped to be stored and said push rod is driven directly; said spring is restored when the pumping operation stops, whereby said push rod will be drawn backward through a distance to expand with the space for filling said viscous materials left in said pumping device and therefore preventing dripping.