GB940329A - Method and apparatus for producing hollow articles of thermo-plastic - Google Patents

Abstract

940,329. Seaming non-metallic sheet material. M. SCHMIDT. July 7, 1961 [July 8, 1960], No. 24731/61. Heading B5K. A method of welding thermoplastic parts by means of frictional heat produced at the surfaces to be joined, comprises producing the frictional heat by the rotation of one of the parts to be joined relative to the other, the parts being held together under pressure. A Christmas tree ball 1, Fig. 1, is formed from two thermoplastic parts 2, 3 welded together along a projecting rim 4. An opening 5 for pressure equalization is provided. Also an opening to receive a hanger may be provided. Two thermoplastic strips 6, 7 having projections 2 and depressions 3 respectively to form the parts of the balls are placed together after the contacting surface of at least one strip has been coated with a lubricating fluid, e.g. silicon oil, and are fed along a guide 9, Fig. 6, and inserted into a slotted guide tube 10. A piercing needle 12 of a device 11 moves in the direction of the arrow 13 to form the opening 5 in one projection 2. A gripping device 17, Fig. 10, enters the slot in the tube 10 and feeds the workpiece 6, 7 for one increment therealong. A device 16, Fig. 11, comprising cutting wheels 19, 20, moves in the direction of the arrow 18 to cut an individual workpiece 6, 7 from the strip. A piston 26, Fig. 12, moves clamping fingers 22, 22a of a device 21 in the direction of the arrow 25 to grip the cut workpiece. A piston-rod 35 moves a plate 32 in the direction of the arrow 38 and a rod 28 is moved upwardly by a roller 29 sliding along a cam 30. The workpiece is deposited in a lower welding die 41 and a rotating upper die 40 is lowered thereon, the dies 40, 41 having serrated contact surfaces 40a, 41a. The die 40 grips the part 6 which is then rotated and pressed upon the part 7 to produce frictional heat which welds the parts together. The die 41 is held by a slip clutch 42 until the parts 6, 7 are partly welded and is then rotated by the die 40 during the completion of the welding. The die 40 is retracted and a device 43 lifts the welded workpiece out of the die 41 and carries it to a punch 44 which punches the welded rim to the desired size. The finished article is ejected from the punch 44 by compressed air and/or a mechanical ejector and deposited in a container 48. The cut-off scrap is ejected into another container. The speed of the die 40 is adjustable. All of the operations of the movable parts of the machine are controlled by a single cam-shaft carrying a plurality of cams which actuate rocking lever valves controlling pneumatic valves. A control panel 51 is provided to adjust the valves externally. A photo-electric cell 54 and a light source 55 prevent the operation of the welding and punching apparatus if there is no workpiece present. A feeler actuated micro-switch may be provided at the end of the tube 10 for stopping the device 16 if the workpiece is not properly fed. The opening for the insertion of the hanger may be formed by an electrically heated, thermo-statically controlled, pneumatically operated cutter.