Liquid dispensing apparatus

A liquid dispensing apparatus to accurately dispense known volumes of liquid onto a receiving surface of a workpiece, for use in conjunction with a two axis of movement robotic table that is configured to hold a workpiece in a given position on a table member, with said robotic table having motor means for moving said table member with respect to said liquid dispensing apparatus, said apparatus comprising:

• a cartridge having a longitudinal axis and defining a reservoir for containing an amount of liquid therein, said cartridge having an outlet of known cross sectional area and an inlet for allowing said liquid to be deposited into said cartridge;
• a piston positioned within said cartridge along said longitudinal axis, the displacement of said piston with said cartridge, with respect to said outlet, defining the volume of said reservoir;
• driving means for effecting translational movement of said piston with respect to said cartridge so as to cause a change in the volume of said reservoir;
• control means for operating said driving means;
• and
• interconnection means for mechanically interconnecting said piston and said driving means, such that said driving means may rotatably drive said piston with said cartridge, said interconnection means having a threaded portion thereon;
• a first retaining means for retaining said interconnection means in threadibly engaged relation thereto;
• a second retaining means for retaining said interconnection means in freely rotatable substantially non-translatable relation thereto;
• wherein one of said first and second retaining means is securely connected to said piston and the other of said first and second retaining means is securely connected to said cartridge;
• wherein said interconnection means is longitudinally rigid between said first retaining means and said second retaining means thereby to preclude unwanted relative movement along said longitudinal axis of said piston with respect to said cartridge;
• whereby, when said piston is advanced long said cartridge towards said outlet by way of a known degree of rotation of said interconnection means, a known volume of said liquid is dispensed from said reservoir through said outlet;
• and
• wherein the rate of liquid dispensing from said reservoir is substantially proportional to the rate of change in displacement of said outlet with respect to said workpiece, in a direction substantially perpendicular to said receiving surface of said workpiece, and further varies proportionally as said rate of change in displacement varies.