Thermoplastic grid melter

Claim 1

An apparatus for converting solid thermoplastic material to molten thermoplastic material and for dispensing the molten thermoplastic material, comprising a housing including a hopper having side walls for receiving solid thermoplastic material, a flow-through grid melter secured to the lower portion of said hopper, at least one discharge opening through said grid melter, a reservoir mounted beneath said grid melter and adapted to receive molten material from said discharge opening of said grid melter, at least one seal between said hopper, grid melter, and reservoir, means for heating said grid melter, a pump adapted to supply said molten thermoplastic material from said reservoir to a dispenser, and means for preventing pressure buildup and failure of said seal upon solidification and remelt of thermoplastic material above the level of said grid melter, said pressure buildup prevention means comprising, downwardly open recesses in the bottom surface of said grid melter, said recesses being adapted to entrap air and gas and to function as gaseous accumulators during buildup of pressure in said molten material.

Claim 2

An apparatus for converting solid thermoplastic material to molten thermoplastic material and for dispensing the molten thermoplastic material, comprising a housing including a hopper having side walls for receiving solid thermoplastic material, a flow-through grid melter secured to the lower portion of said hopper, at least one discharge opening through said grid melter, a reservoir mounted beneath said grid melter and adapted to receive molten material from said discharge opening of said grid melter, at least one seal between said hopper, grid melter, and reservoir, means for heating said grid melter, a pump adapted to supply said molten thermoplastic material from said reservoir to a dispenser, and means for preventing pressure buildup and failure of said seal upon solidification and remelt of thermoplastic material above the level of said grid melter, said pressure buildup prevention means comprising, downwardly open recesses in the bottom surface of said grid melter, said recesses being adapted to entrap air and gas and to function as gaseous accumulators during buildup of pressure in said molten material.

Claim 5

A method of preventing seal failure in an apparatus for converting solid thermoplastic material to molten thermoplastic material, which apparatus comprises a housing, including a hopper, for receiving solid thermoplastic material, a flow through grid melter sealingly secured to the lower portion of said hopper, and a reservoir sealingly mounted beneath said grid melter and adapted to received molten material from said grid melter, which method comprises providing downwardly open recesses in the underside of said grid melter for entrapment of air and gas in said recesses such that the air and gas filled recesses function to prevent thermoplastic material which has backed up into the hopper in the molten state and solidified therein from creating a pressure buildup beneath the grid melter and inducing seal failure and leakage of molten material from between the hopper and the grid melter or between the grid melter and the reservoir upon remelt of this solidified material.

Claim 6

A method of preventing seal failure in an apparatus for converting solid thermoplastic material to molten thermoplastic material, which apparatus comprises a housing, including a hopper, for receiving solid thermoplastic material, a flow through grid melter sealingly secured to the lower portion of said hopper, and a reservoir sealingly mounted beneath said grid melter and adapted to received molten material from said grid melter, which method comprises providing downwardly open recesses in the underside of said grid melter for entrapment of air and gas in said recesses such that the air and gas filled recesses function to prevent thermoplastic material which has backed up into the hopper in the molten state and solidified therein from creating a pressure buildup beneath the grid melter and inducing seal failure and leakage of molten material from between the hopper and the grid melter or between the grid melter and the reservoir upon remelt of this solidified material.