Apparatus and method for thermoplastic material handling

Abstract

A thermoplastic material melting and dispensing apparatus includes a hopper, a melting grid, and a lid assembly which vents the interior of the hopper in an over pressure situation. Specifically, the lid assembly may be mounted with a spring-loaded hinge mechanism and may include a spring-loaded latch mechanism which each allow the lid to move upwardly away from a gas seal in the event that the gas pressure within the hopper exceeds a predetermined amount. The apparatus further includes a gas purging system which constantly circulates a gas, such as nitrogen, within the hopper interior. This gas purging system may include a solenoid valve which opens to allow exhaustion of pressurized gas from the hopper interior and the introduction of gas from a pressurized supply. A melting grid is provided which includes an surface with grooves communicating with a central outlet. The central outlet includes a plug and filter assembly which maintains solid thermoplastic material out of the outlet and filters melted thermoplastic material flowing through the outlet. A raised sealing element is provided on the lid assembly to maintain an airtight seal, and to also maintain opposed surfaces of the lid and the lid mounting portion in spaced apart relation. An advantageous flow control block with a pressure relief is connected to the thermoplastic material outlet.