Patent GB-1062051-A (GB)
Title: Film sealing and cutting apparatus and method
IPC: B31B19/64
Filed: 1964-02-03
Abstract: 1,062,051. Seaming non-metallic sheet material. WELDOTRON CORPORATION. Feb. 3, 1964 [March 8, 1963; Sept. 9, 1963; Dec. 10. 1963], No. 4555/64. Heading B5K. Superposed layers of thermoplastic film are cut and sealed along a predetermined line by releasably clamping the layers together along both sides of a zone including the line by two pairs of clamping members and heating the assembly within the zone by a heat source disposed out of contact with the assembly and between one pair of clamping members to simultaneously cut and seal the film layers. In one embodiment, Fig. 1, a clamping head 12 is slidable in a frame 10 and is held in its retracted position by tension springs 14. The head 12 is provided with clamping bars 18, 20 each carried by a plurality of supports 22 having guides 24 slidable in recesses 26 in the head 12 against compression springs 28. Lower clamping bars 18a, 20a are similarly carried by a stationary lower head 30. Superimposed layers 40 of thermoplastic film to be cut and sealed are placed on the bars 18a, 20a and the head 12 lowered by an eccentric 16 mounted on a shaft 17 so that the layers 40 are clamped. Heating elements comprising metal bands 42, 44, preferably of high resistance alloy, cut and seal the layers 40 by radiant heat to form sealed beaded edges. The band 42 is carried by a bracket 48 and is secured to the head 12 by a plurality of rods 46 so as to be movable therewith. A tension spring 52, Fig. 3, maintains the band 42 taut if it expands longitudinally when heated. The band 44 is preferably stationary and is similarly held taut. In another embodiment, Fig. 4 (not shown), the layers 40 are clamped by members 60, 61, 62, 63 around which additional pressing members 66, 67, 68, 69 are slidable. The members 66, 68 are movable downwardly by a plate 70 actuated by cams 71 against tension springs 72 and the members 67, 69 are similarly movable upwardly so that the beaded edges are squeezed while they are still plastic. The radiant heating member 64 is in the form of a ribbon or a flat wire similar to the ribbon 42 except that the wider face thereof is vertically disposed. In modifications, the radiant heating elements may take the form of two round wires, Fig. 9 (not shown), triangular-section members, Fig. 10 (not shown), a tapering member, Fig. 11, or members 64d, 64e, Fig. 12. In a further embodiment, Fig. 13 (not shown), the distance of the clamping bars 80, 81, 82, 83 from the radiant heaters 42a, 44a is adjustable by sliding bars 87 carrying the bars 80, 81, 82, 83 in slots 86 in frames 84, 85. Each bar 80, 81, 82, 83 is made of metal and is provided with a cushioning layer of silicone rubber or polytetrafluoroethylene. In a still further embodiment, Fig. 14 (not shown), stationary clamping members 93, 95 and movable clamping members 94, 96 are provided with bevelled sides 97. Up on retraction of the radiant heating member 98 and the members 94, 96 cooling air is introduced through a passage 104 to cool the beaded edges. A valve 106 controls the air flow and may be opened by a solenoid 108 controlled by a micro-switch 110 actuated by a member 112 carried by a bar carrying the member 94.