Patent IT-1001718-B (IT)
IPC: B31B1/90
Filed: 1973-11-12
Granted: 1976-04-30
Abstract: 1446325 Seaming non-metallic sheet material W R GRACE & CO 7 Nov 1973 [13 Nov 1972] 51729/73 Heading B5K A thermoplastic snap fastener element 14A is secured to a heat sealable material 29, the element 14A having a surface surrounding a raised projection, by positioning the material 29 relative to the element 14A so that the material 29 is over the raised projection of the element 14A, stretching the material 29 over the raised projection of the element 14A, cutting the material 29 around the raised projection to remove part of the material and leave an aperture to receive the projection, and heat sealing the element 14A to the material 29 at least partially around the aperture. Apparatus for heat sealing thermoplastic snap fastener elements 14 to a thermoplastic film layer 29, Figs. 1 and 2, comprises a plunger 13 for advancing intermittently the elements 14 along a delivery track 30. The plunger 13 is reciprocated horizontally by a cam 18 on a shaft 16 engaging a follower 17 on an arm 8 pivoted at 9 and connected, through a rod 10, to a plate 12 carrying the plunger 13. A spring 15 urges the plunger 13 towards its forward position. A sealing and severing head 25 is reciprocated vertically by a cam 20 on the shaft 16 engaging a follower 19 on a rocker arm 22 pivoted at 21 and at 23 to a connecting rod assembly 24 carrying the head 25. A spring 26 urges the follwer 19 into contact with the cam 20. A vibratory hopper 33, Fig. 2, supplies the elements 14 in an upright position via an inclined vibratory track 32 and a track 31 to the track 30. The head 25, Fig. 3, comprises a tubular rotary knife 40 mounted in a housing 38 and ihaving its central duct 50 connected to a suction port 51 to remove slugs of material when an aperture is formed. The knife 40 is slidable into the housing against the action of a spring 46. Heating elements 41 of nickel-chromium alloy or stainless steel are secured to a holder 43. The knife 40 is rotated by a pneumatic cylinder 54 which reciprocates a rack 52 to turn a pinion 48 having dowel pins slidable in a slot 47 in the knife. In operation, the plunger 13 feeds an element 14A below the film layer 29 into a nest 56, Fig. 7, in which it is held by suction applied through lines 57, 58, 59. The head 25 is lowered and the cutting edge of the knife 40 first stretches the film layer 29 across the projection on the element 14A and then the cylinder 54 is actuatsd to rotate the knife 40 to cut an aperture in the film. Further descent of the head 25 causes the knife 40 to be retracted into the housing 38 and the elements 41 compress the film around the aperture against the element 14A. An electrical impulse is sent to the elements 41 to effect sealing. Preferably, the film layer 29 of a folded film 27, Fig. 1, is a fold-over flap of a plastics bag, an upper film layer 28 forming the front wall portion. The second element of each fastener is sealed to the layer 28 in alignment with the element 14a, a second nest and feed track extending below the layer 28. After sealing the fastener elements to the film, the folded film is sealed and severed transversely to form individual bags. Alternatively, the fasteners may be applied to raincoats, shower curtains or canopy material. Specified materials for the snap fastener and the film are polyethylene, polypropylene or polyvinyl chloride.