GB976281A - Apparatus and method for creasing and bending synthetic plastic sheet stock - Google Patents

Abstract

976,281. Creasing &c. plastic sheets. C. E. PALMER. Oct. 9, 1963 [Oct. 11, 1962], No. 39765/63. Heading B6J. Apparatus for creasing and bending plastic sheet stock comprises a pair of rotary discs, one having a blade edge on its periphery and the other a periphery of resilient rubber-like material. The discs are both driven in opposite directions so that their peripheries travel at the same speed, and the plastic sheets are creased and folded by being pressed by the blade edge of one disc into the resilient surface of the other disc. Fig. 4 shows apparatus for forming a rectangular tubular member from a flat plastic strip 34, there being four discs 38a, 38b, 38c, 38d with resilient peripheries, and four co-operating blade-edge discs 40a, 40b, 40c, 40d. The shafts of all the discs are power driven from drive shafts and gearing as shown, the blade discs being mounted in an elongated mandrel 42 so that their edges protrude. The plastic strip 34, as it approaches the mandrel 42, is supported by guiding rollers, and is first engaged by the discs 38a, 38b and 40a, 40b, and later by the discs 38c, 38d and 40c, 40d, further guide rollers and deflecting rollers being arranged immediately before these latter discs to shape and support the strip. The strip is now formed into rectangular tubular shape with the free ends overlapping. Triangular and other shapes may be formed by suitable mandrels, guide &c. rollers, and discs. The blade-edge disc may have an integral V-shaped edge, or an undercut edge which is shaped on one face to assist the folding of the creased plastic strip, or the edge may be a separate member secured to the disc and of frusto-conical form, and secured at an acute angle to the plane of the disc in a circumferential recess in the disc. The co-operating disc has a resilient, rubber-like material such as sponge rubber, or a synthetic organic polymer such as polyurethane, secured to its periphery, and has a rectangular , V, or other shape to suit the particular creasing &c. operation and the shape of the co-operating blade edge. The strip 34 may be biaxially oriented polystrene of five to thirteen mils. thickness, and is overfolded about twenty to forty degrees to achieve the desired shape when it leaves the discs. The creased and folded strips are further processed to produce tubular or tray-shaped containers. Specifications 906,075, 937,733, and U.S.A. Specification 2,954,725 are referred to.