Equipment for point by point application of an adhesive

Claim 1

Apparatus for the point by point application of a viscous substance, such as a thermoplastic adhesive, comprising a feeder device including a piston slidable in a cylinder, means for reciprocating said piston through a compression stroke and a return stroke in a predetermined timed work cycle, means for introducing the substance into the interior of said cylinder during the return stroke of said piston, means connecting the interior of said cylinder with an application nozzle whereby the substance is moved under pressure from said cylinder to said nozzle during the compression stroke of said piston, means blocking said connecting means except during the end phase of the compression stroke and the beginning phase of the return stroke of said piston, said connecting means including a conduit extending through said piston into the interior of said cylinder and a bore extending through said cylinder communicating with said nozzle, said conduit including a first section which extends axially through said piston and a second section extending transversely from said first section to an opening in the outer surface of said piston, said opening being defined by a slot extending axially along the surface of said piston and adapted to be positioned in communication with said bore during the end phase of the compreSsion stroke and the beginning phase of the return stroke of said piston, said slot extending for a greater axial dimension than said bore whereby the communication therebetween will be maintained during a predetermined phase of the compression stroke and the return stroke of said piston, and pressure responsive means for reducing the pressure in said cylinder during the compression stroke of each cycle.