Abstract: A needle valve nozzle is employed in a hot melt adhesive gun used to apply thermoplastic adhesive. Actuation of a trigger mechanism supplies pressurized gas to a nozzle chamber which urges the nozzle in an outward direction to an open position, the needle remaining stationary during operation of the nozzle. Deactuation of the trigger mechanism stops the flow of pressurized gas to the chamber and a vent allows the pressurized gas to flow from the chamber, permitting a spring-biasing mechanism to return the nozzle to a closed position. Pressure on the adhesive can also be employed to urge the nozzle to an open position.

Abstract: A hot melt adhesive gun capable of dispensing relatively large volumes of molten adhesive and comprising a hot melt chamber and a pressurized air chamber separated by a moveable element which isolates the chambers one from the other. Molten adhesive from an associated bulk supply is fed into the hot melt chamber by means of a supply nozzle temporarily plugged into a valved inlet passage of the gun only when necessary to charge the gun with a fresh supply of molten adhesive. Upon actuation of the gun trigger, pressurized air in the air chamber, drives the moveable element forward to cause adhesive to flow out of the nozzle. Upon release of the trigger, adhesive flow from the nozzle valve is discontinued. The novel gun also includes a pressure relief valve and relief port to allow the escape of trapped gas which can build up in the melted adhesive and which exceeds a predetermined pressure level.

Abstract: A hot melt adhesive gun employing a cartridge of thermoplastic adhesive contained within a chamber made of a thermally insulative non-stick material. A plunger is driven into engagement with the cartridge by a manually operative trigger actuated infinite resolution ratchet to urge the cartridge into melting contact with an electrical heater block and to provide pressure for driving the melting adhesive into a storage reservoir and out through a valved nozzle for application to a bonding surface. A partially melted portion of the cartridge deforms under the applied pressure of the plunger to form a seal against backflow of molten adhesive. Upon release of the trigger, a retraction mechanism causes the plunger to retract a predetermined amount to disengage the cartridge thereby allowing closure of the nozzle valve and arresting of adhesive flow.