Patent GB-1391911-A (GB)
Title: Machines duitable for use in carrying out hf operations on workpieces
IPC: B29C65/04
Filed: 1971-02-19
Abstract: 1391911 Seaming non-metallic sheet material; laminating apparatus BRITISH UNITED SHOE MACHINERY CO Ltd 18 Feb 1972 [19 Feb 1971 18 Feb 1971] 4994/71 and 43616/71 Headings B5K and B5N [Also in Divisions B6 and H5] A machine for performing a H.F. operation, e.g. welding, welding and cutting, or embossing, on a workpiece, made of thermoplastic layers or non-activatable layers with a heat-activatable adhesive layer therebetween, comprises a presser member movable so as to be positioned above a selected one of at least two workpiece supporting surface portions on a lower platen of the machine, means whereby the presser member and the lower platen, which serve as electrodes, can be connected to a H.F. electrical source provided by a H.F. generator having an output tuning capacitor comprising two plates one of which is movable relative to the other, and control means whereby the position of the movable plate, and thus the power of the H.F. field to be applied, can be pre-set. In one embodiment, Figs. 1 and 2, a machine similar to that described in Specification 1,352,143, i.e. a two station welding and cutting machine, having a presser member 18 movable between two stations. The H.F. generator 20 has an output tuning capacitor comprising a fixed plate 22 and a movable plate 24, the plate 24 being urged towards the plate 22 by springs 26. The control means for pre-setting the position to which the plate 24 is to be moved and which is also operable, when the member 18 is brought above one surface portion, to automatically move the plate 24 to the pre-set position, comprises a block 28 secured to a control box 30. An actuator lever 38 is pivoted on a pin 40 guided in slots 42 formed in plates 32 which together with spacers 34 from the block 28. Rollers 44, 46 are mounted on the lever 38 and are engagable with stop faces 54, 56 on screw members 48, 50 adjustably received in a spacer 34. The pin 40 also provides a pivot for a pulley 58 about which a sheathed control cable 60 is entrained, the ends of the cable 60 are secured to the rearward spacer 34 and the plate 24. The springs 26 hold the cable taut. A resiliently mounted camming member 64 is mounted on the member 18 and acts on a roll 68 on a projecting portion 68 of the lever 38. In use, when the member 18 is at the left hand station, chain-dot line in Fig. 1, the lever 38 is moved out of the Fig. 2 position by the member 64. The lever 38 first pivots clockwise about the pin 40, which moves in the slots 42 under the influence of the springs 26 through the cable 60, until the roller 44 engages the spacer 34 and the further pivotal movement of the lever 38 is about the axis of the roller 44 until the roller 46 engages the face 56. As the lever pivots about the second axis, the pin 40 moves, against the spring 26, along the slots 42, to re-position the lever 38 and the plate 24. When the member 18 moves to the right hand station, retraction of the member 64 allows the spring 26 to return the lever 38 to the position of Fig. 2. In a modification (not shown), the member 64 is replaced by an electric control circuit. In another embodiment, Figs. 3 and 4, a machine, similar to that descirbed in Specification 1,244,655, comprises an upper presser member 42 secured by spaced insulators 40 to a plate 38 secured to a cylinder C4. A lower platen 24 is secured to a base plate 20. Strips 52, 54 connect the member 42 and the platen 24, respectively, to a generator 56. A turntable 60 is supported on a bush 62 for rotation and has a plurality of work stations, e.g. three, each having an aluminium support plate 66 with a cover 78 of polytetrafluoroethylene - coated sponge rubber. Three pneumatic trip valves V51, V52, V53 are mounted on a bracket 202 and have plungers extending along a radius of the turntable. A clamp plate 64 secures the turntable to the bush 62 and, mounted on the turntable, at equal distances about the plate 64, are three plates 204 carrying trip members 206 each associated with one of the valves V51, V52, V53. The output tuning capacitor 210 of the generator 56 comprises a movable plate 212 pivoted to a fixed wall 214 constituting the other plate. The piston rod 218 of a rolling- diaphragm piston-and-cylinder C5 receives in a bore 220 a rod 222 supported in a V-bracket 224 carried by a plate 226 on a frame 216. A trunnion block 230 is slidably received between spaced collars 228 on the rod 222 and has two spigots 232 received in bores in a bifurcated end of an arm 234 of a bell crank lever pivoted to the plate 226. The other arm 236 is pivoted to a link 240 pivoted to the plate 212. Adjustable screws 242, 244 limit the movement of the plate 212. The cylinder C5 acts against a spring 246 which normally holds the plate 212 away from the wall 214. For setting up the control means, the heightwise position of the rod 222 is adjusted by two nuts, 248, 250 arranged to abut one against each arm of the bracket according to whether or not the cylinder C5 is operated. In operation, the air pressure supplied to the cylinder C5 is controlled according to which one of the valves V51, V52, V53 is tripped, the pressure being determined by regulator valves (not shown). Thus, by varying the air pressure supplied to the cylinder C5, the amount of movement of the plate 212 by the bell crank lever is varied to vary the power output of the generator. A pneumatic circuit for the operation of the machine is described, Figs. 5a and 5b (both not shown).