Patent GB-1262901-A (GB)
Title: Heat sealing head
Inventor: PAGE DONALD JOSEPH
IPC: B29C65/00
Filed: 1969-04-24
Abstract: 1,262,901. Transversely sealing wrapper tubes. F.M.C. CORP. 24 April, 1969 [29 April, 1968], No. 20905/69. Heading B8C. [Also in Division B5] A wrapping machine 12, Fig. 1, includes a head 10, Fig. 4, for heat sealing and severing a multi-layer thermoplastic web 24, the head 10 comprising an anvil 42 mounted for rotation about a first axis at one side of the web, a heatable sealing bar 74 mounted for rotation about a second axis on the other side of the web, a pair of hollow gripper jaws 108 straddling and rotatable with the bar 74 about the second axis, drive means for rotating the anvil 42 and the bar 74 to index the anvil and the bar into alignment across the web, camming means 86 mounted for rotation about a third axis and drive means for synchronously rotating the camming means 86, the anvil 42 and the bar 74 about their respective axes, the camming means 86 being operative to move the bar 74 to heat seal and sever the web. Articles A to be wrapped are fed from a conveyer 16 on to a continuously moving conveyer 18. A polyethylene film web W is continuously fed from a spool 20 into a station 22 in which it is formed into a longitudinally sealed tube 24, Fig. 4, around the spaced articles A. A conveyer 26 moves the entubed articles A through a station 28 at which the head 10 pinches the tube 24 together between adjacent articles and transversely seals and severs the web to form individual packages P discharged by a conveyer 30 operating at a slightly higher speed than the conveyer 26. If desired, auxiliary mechanism (not shown) may tuck and seal the projecting gable ends 32 of the wrapper against the body of the package. The anvil 42, e.g. a relatively hard polytetrafluoroethylene bar having an arcuate face, is mounted in a holder 40 carried by a shaft 38 which is circumscribed by a floating cylindrical sleeve 44 of polytetrafluoroethylene impregnated glass cloth. The bar 74 is mounted in a groove 72 in a shaft 56. Each end portion of the bar 74 is connected by a pin 76 to a push rod 78. A compression spring 84 holds the bar normally retracted into the groove 72. An electrical resistance heating element 81 is mounted in the bar 74 and is energized from a low voltage source by the commutator ring and brush units 83. The space between upright walls of the bar 74 is filled with asbestos fibre cement to prevent heating the shaft 56 and the rods 78. Rollers 86 act on heads 80 on the rods 78 to project the bar 74 towards the anvil 42 to seal and sever the web. Each roller 86 is pivoted to a slotted arm 88 secured by a bolt 90 in a selected position radially of a rotatably adjustable disc 92 bolted to a hub 93 keyed to a rotatable shaft 94. Each rod 78 is slidably mounted in a bushing 102 pressed into a sleeve 104 which restricts the flow of a cooling fluid pumped through a bore 58 in the shaft 56. The jaws 108 have arcuate faces 109, are mounted on the shaft 56 and, at each end, are interconnected by pads. Each jaw 108 is provided with a passage 112 in fluid communication with the bore 58 by conduits 114, (116), the latter, Fig. 5 (not shown), and radial apertures (118) in the shaft 56. Due to the restriction of the sleeve 104 in the bore 58, portions of cooling fluid are diverted into the passages 112. In operation, the web 24 with the articles A entubed therein is advanced in timed relationship with the rotation of the shafts 38, 56, 94. The leading edge of the holder 40 and one of the jaws 108 contact the web near the trailing end of the leading article, Fig. 6 (not shown), and, subsequently, the jaws 108, the anvil 42 and the holder 40 reach full gripping position, Fig. 8 (not shown). The rollers 86 contact the heads 80 when the rods 78 and the rollers 86 are about 10 degrees out of vertical alignment and project the bar to effect sealing and severing. The bar 74 is exposed for only about 20 degrees of its rotation. Reference has been directed by the Comptroller to Specification 1,114,501.