GB835694A - Machine for folding or bending thermoplastic sheet materials - Google Patents

Abstract

835,694. Forming thermoplastic sheets. CARFIELD (ENGINEERS) Ltd. Sept. 10, 1956 [June 9, 1955], No. 16546/55. Class 87(2). A machine for folding thermoplastic sheet material has means for supporting the sheet and heating it to soften it along the desired fold line, means for pressing the softened sheet about the heating means, and means for setting the fold by cooling. The cellulose acetate or other thermoplastic sheet S is laid on an inclined table 37, Fig. 1 above a pivoted transverse lifting bar 38, with its lower edge resting against a stop 11 on a rear folding bar 10 lying across the frame 1 of the machine. A front folding bar 12 also lies across the machine. Both folding bars are adjustable, leaving a transverse slot between them, and are of stainless steel, large enough to absorb heat rapidly. A treadle, not shown, is depressed and causes a forked arm 24, Fig. 3 carrying a pin 23, to withdraw the pin from a recess in a plate 21 and engage a toothed clutch 25. A shaft 20 is thus driven through gearing and rotates a cam 19, to which the plate 21 is attached, and cams 32 at the end of the shaft. The portion a to b of the cam 19, engaging a roller 18 supported from a cross bar joining the ends of levers 14, turns the levers about pivots 15 and causes them to lower a blade carrier 4 in slideways 3, so bringing the blade down on the sheet S. In the movement of the cam from b to c the blade dwells on the sheet and is heated by an electrical element in the blade carrier, controlled by an adjustable thermostat, the sheet thereby being softened along the line of the blade. Movement of the cam from c to d depresses the blade into the slot between the folding bars 10, 12 and the sheet is therefore folded along the softened line, the blade remaining there during the cam travel d to e while the material cools and sets. In the travel e to a the levers 14 are operated to raise the blade carrier, and the cycle is completed by the pin 23 dropping back into its recess and allowing the clutch to be disengaged by a spring 26. The folding is assisted by the lifting bar 38, which is pivoted to raise the sheet as the blade carrier descends by rods 39 thereon engaging the tail of the lifting bar side arms 40. In the last part of the cycle the cams 32 operate push rods 34 the upturned ends of which push the folding bar 12 forwards against a spring 36, so releasing the folded sheet which drops into a receptacle.