Plastic sheet vacuum forming machine

Claim 1

A PLASTIC SHEET VACUUM FORMING MACHINE COMPRISING A FRAME AND CASING HAVING A TOP PLATE, A VACUUM BOX STRUCTURE SUPPORTED ON THE TOP PLATE FOR SUPPORTING ARTICLES OVER WHICH THE PLASTIC SHEET IS TO BE DRAWN, VALVECONTROLLED VACUUM PUMP MEANS SUPPORTED IN THE FRAME FOR EVACUATING THE VACUUM BOX STRUCTURE, A VERTICALLY-ADJUSTABLE PLASTIC SHEET RETAINING FRAME ASSENBLY OVERLYING THE TOP PLATE AND THE VACUUM BOX STUCTURE, AIR-OPERATED MEANS FOR RAISING AND LOWERING SAID PLASTIC SHEET RETAINING FRAME BETWEEN ELEVATED AND LOWERED POSITIONS, A HEATER BOX FOR HEATING THE PLASTIC SHEET WHEN THE RETAINING FRAME ASSEMBLY IS IN ITS ELEVATED POSITION AND ARM MEANS FOR SUPPORTING THE HEATER BOX FOR FORE AND AFT MOVEMENT BETWEEN REARWARD RETRACTED AND FORWARD HEATING POSITIONS,SAID HEATER BOX IN ITS FORWARD POSITION OVERLYING THE ELEVATED PLASTIC SHEET FRAME TO HEAT THE PLASTIC SHEET PREPARATORY TO THE LOWERING OF THE PLASTIC SHEET RETAINING FRAME ASSENBLY UPON THE ARTICLE AND THE VACUUMING OPERATION, AND SAID ARM MEANS FOR SUPPORTING SAID HEATER BOX FOR FORE AND AFT MOVEMENT INCLUDING LONG FORWARD SUPPORTING ARMS PIVOTALLY CONNECTED TO THE SIDE OF THE HEATER BOX AND PIVOTALLY CONNECTED TO THE SUPPORTING FRAME AT THE LOWER OPPOSITE SIDES THEREOF, REAR ARM SUPPORTS EXTENDING REARWARDLY FROM THE SUPPORTING FRAME, REAR HEATER SUPPORTING ARM MEANS PIVOTALLY CONNECTED TO THE REAR ENDS OF THE REARDLY EXTENDING ARM SUPPORTS AND TO THE