Patent GB-1058663-A (GB)
Title: Apparatus and method for cutting and sealing thermoplastic films
IPC: B29C65/10
Filed: 1964-02-03
Abstract: 1,058,663. Seaming non-metallic sheet material. WELDOTRON CORPORATION. Feb. 3. 1964 [March 8, 1963], No. 4556/64. Heading B5K. Superposed layers F of thermoplastic film are cut and sealed along a predetermined line or in a predetermined region by releasably clamping the layers along both sides of a zone including the line or the region and heating the clamped assembly within the zone to effect simultaneous cutting and welding thereof, the heating being effected or aided by directing a hot gaseous stream against the assembly within the zone. In the embodiment shown in Figs. 2 and 4, the film layers F to be cut and sealed are placed on a stationary metal base 10 having a groove 11 in the upper surface thereof. Clamping bars 12, 14 which are slidable in a frame 16 are lowered therewith by a rod 32 to clamp the layers F, compression springs 18 urging the bars 12, 14 towards the base 10. Means (not shown) are provided for limiting the movement of the bars 12, 14 in the frame 16. A bar 20 having a passage 22 supplied with combustible gaseous mixture or hot air at 1000 F. is provided with jets 24 to direct the flame or hot air against the layers F and is secured in the frame 16. Cooling fluid is circulated through passages 26 in the bars 12, 14. The layers F are simultaneously cut and sealed, a beaded seam being formed. A pilot light ignition device may be provided so that the flame issues from jets 24 only when the frame 16 moves to the cutting and sealing position. In modifications (not shown), the bars 12, 14 and the member 20 may be L-shaped or circular. In a second embodiment, Fig. 6 (not shown), a radiant heating cutting and sealing bar 54 of a high temperature alloy is heated to incandescence. The bar 54 is electrically insulated from its mounting member 60. Openings 64 are provided in the frame 16 to allow for the admission of air under pressure which becomes heated by the bar 54 and is directed against the layers F to accelerate the sealing and cutting thereof. After initial melting of the thermoplastic film the bar 54 moves into the space formed between the confronting edges of the film and completes the seal. In a further embodiment, Fig. 6B (not shown), the heating element comprises a metal ribbon 54a continuously heated to 1000 F. by a current passing therethrough and is mounted on a support 54b of insulation material by a fixed metal clip 55 and a movable metal clip 57 slidable in a groove 54c. The clip 57 is connected by a tension spring 57a to a pin 59 on the support 54b to maintain the ribbon 54a taut. In operation, the lower thin edge of the ribbon 54a contacts the film and on continued lowering forms beaded seals. In another embodiment, Fig. 5 (not shown), for continuous sealing and cutting, the film layers F are clamped and conveyed by metal bands 40, 42 driven by rollers 44, 46. Stationary supports 52 support the layers F firmly during their travel under the flame or hot gas to effect the sealing and issuing from a stationary tube 45. Two spaced sealers of this type may be provided to simultaneously seal and cut the side edges of superimposed films. In a still further embodiment, Fig. 8 (not shown), to form a lap seam with holes therein having beaded edges, the film layers are placed on a platen 70 having recesses 72 therein which register with holes 74 in a platen 76. A rod 84 moves the platen 76 downwardly to clamp the film F1. As the platen 76 descends a valve 98 is operated to admit gas to a chamber 86 for ignition by a pilot light on a tube 100. Air is also supplied to the chamber 86 through an inlet 92 and openings 88 direct flame downwardly through the holes 74. In another embodiment, Fig. 9, also to form a lap seam between superimposed films F2, F3 or lapped portions of the same film, the films F2, F3 are placed on a member 114 and a member 116 is moved vertically in a fixed frame 112 by a rod 124 to clamp the films F2, F3. A flame or hot air bar 126 directs jets of flame or hot air through openings 128 in the member 116 which register with openings 130 in the member 114 so that the films are sealed to each other by a number of holes each having a sealed beaded edge.