Patent GB-882612-A (GB)
Title: Apparatus for forming simulated threads in plastic sheet material
IPC: B29C65/00
Filed: 1959-04-27
Abstract: 882,612. Bonding threads to synthetic resin sheeting. GENERAL TIRE & RUBBER CO. April 27, 1959 [May 12, 1958], No. 14358/59. Class 93  Apparatus for bonding thermoplastic synthetic resin threads or threads coated with thermoplastic synthetic resin to synthetic resin sheeting comprises a press having fixed and movable platens, spaced parallel electrode bars mounted on the movable platen, dielectric heating means connected between the bars and the fixed platen, thread supply means, and thread gripper members mounted on a pair of spaced roller chains moving in a controlled closed path about the movable platen and straddling the fixed platen, the gripper members gripping the threads at the supply means and positioning lengths thereof underneath the bars prior to bonding. The sheeting may be of plasticized polyvinyl or polyvinylidene chloride, or of copolymers of vinyl chloride with vinyl acetate or vinylidene chloride, or mixtures thereof. The sheeting may be backed with cotton or rayon fabric or a fabric of rayon mixed with nylon or polyethylene terephthalate, felt, or paper. The threads may be of polyvinyl or polyvinylidene chloride or of resin-coated cotton, rayon or nylon. The diameter of the threads may be 1 to 4 times the thickness of the synthetic resin layer of the sheeting, and the threads may be bonded in straight, curved or wavy lines. The threads may comprise a single monofilament or two monofilaments twisted together. As shown in Fig. 2, synthetic resin sheeting 13 is intermittently fed across a fixed platen 4 by a roller 107 of appropriate diameter and operated by rack-and-pinion mechanism 109-111, the movement of the rack being controlled by the admission of compressed air or hydraulic fluid through one of the pipes 116, 117  to the cylinder 115. The admission is controlled electromagnetically via a switch 98, the finger 121 of which is contacted by the rack 109 to reverse the motion on the up-stroke of the piston. Thread grippers 19, each comprising a shaft 48, Fig. 6, and surrounding sleeve 49 with circumferential slots normally held out of alignment by spring action, are mounted on a pair of chains 18 guided on pairs of sprockets 33, 35, 36 and 37, the sprockets 33 being driven by belt-and-pulley and chain-and-sprocket gearing from the motor 26 and the chains 18 being guided between sprockets 35 and 36 by guide bars 40. Between sprockets 33 and 37, the slots remain out of alignment, but when a gripper nears sprockets 36, the slots are aligned by the co-operation of a roller 57 connected to an extension of the sleeve 49 with a fixed cam 58. The thread 12, drawn off a spool 20, Fig. 2, passes through a hole 69 in member 68, is snubbed by toe 71 of block 70, and is picked up in the aligned slots. Member 68 swings away from toe 71 when a thread gripper is not picking up thread. On further movement of the chains, the slots tend to move out of alignment to grip the thread. A microswitch 81 contacted by the grippers keeps the length moved each time by the chains substantially uniform. The movable platen 5 is moved towards and from the sheeting 13 by piston rods 86 extending from hydraulic cylinders 85. The electrode bars are attached to the platen 5 and have U-shaped ends each with central grooves receiving the threads, the U- shaped ends pressing into the softened sheeting to form indentations alongside the welded threads and the tension on the threads being such as to cause the softened threads to break off at both ends of each bar. Switch 99 reverses the movement of the platen 5 on the down stroke, while switch 100 on the up stroke starts the movement both of the chains 18 and of the plastic sheeting 13. The high-frequency generator connected to a brass plate forming the top of the platen 4 and insulated from the body thereof is switched on when switch 99 is contacted on the down stroke of platen 5, and heating of the threads and sheeting is thereby effected.