Method and apparatus for rapid dispensing of minute quantities of viscous materials

摘要

A chamber (10) that communicates with a viscous material reservoir has a flexible resilient diaphragm (30) which forms an exterior wall thereof. An impact mechanism (34, 36), which may comprise a solenoid actuated hammer (34), applies a predetermined momentum to the diaphragm (30) for rapidly metering a predetermined minute blob of the viscous material from the chamber through a nozzle (38). The reservoir is pressurized with gas to force the viscous material into the chamber to refill the same. The chamber is heated to control the viscosity of the material. Dispensing rates in excess of four blobs per second can be achieved. Variations in the height of the nozzle from the surface of the workpiece are not critical to uniform rapid dispensing. An alternate embodiment eliminates the diaphragm and instead rapidly retracts a nozzle relative to a fluid feed conduit to eject very small blobs of viscous material. A strain gauge detects refill of the chamber inside the nozzle and sends a signal to control refill logic circuitry. A fiber optic droplet detector is utilized to correct dispensing defects.