Bulk unloader of solidified thermoplastic material from pails and drums

Abstract

An apparatus for unloading heat meltable material from a container including a vertically moveable platen assembly having a platen supported by a platen carriage. The weight of the platen assembly is trapped between a balance spring which urges the platen assembly upwardly and a pressure spring which exerts a downward pressure on the platen assembly. The springs are fixed about a motor driven lead screw retaining the balance spring against the platen assembly from below and a pressure adjusting nut retaining the pressure spring against the platen assembly from above. Descent of the lead screw without an equivalent movement by the platen assembly will cause a disequilibrium in spring tensions as the balance spring expands and the pressure spring compresses. A limiting switch restricts the amount the lead screw can move after platen contact with the heat meltable material prevents further platen carriage movement. As material is dispensed the platen carriage will slowly catch up with the position of the turn screw and eventually the limit switch will once again engage, allowing the lead screw to descend some preselected incremental amount determined by the limiting switch. The apparatus also contains an applicator head safety switch activated during extended periods of nonuse. When activated, the safety switch prevents lead screw movement.