Patent GB-1245050-A (GB)
Title: Device for continuous welding of plastics sheets, in particular for use in the manufacture of exploratory balloons
IPC: B29C65/08
Filed: 1969-10-14
Abstract: 1,245,050. Seaming non-metallic sheet material. CENTRE NATIONAL D'ETUDES SPATIALES. 14 Oct., 1969 [24 Oct., 1968], No. 50346/69. Heading B5K. A device for ultrasonically welding together overlapping edges of very thin films 2, 3 of thermoplastic material comprises an anvil 8, means for guiding the film edges in overlapping relation on to the anvil 8, an ultrasonic welding head 10 having a welding tool 9, clamping means operated by gravitational force to force the tool 9 and the anvil 8 towards one another to clamp the overlapping edges therebetween, means for cooling the head 10 and drive means 16, 17 for driving the welded edges downstream of the tool 9. The device is used to weld thin polyethylene terephthalate films to produce an exploratory balloon having gores and two end caps as described in Specification 1,115,686. As shown in Figs. 1 and 2, the already-welded film part 2 of a balloon is placed over a hemispherical support 1 and a film 3 to be welded is placed on a table 4. The edges of the films 2, 3 are driven to overlap by convergent rollers (5), 6, see also Fig. 3 (not shown), located in grooves 7a, 7b in a guide (7). The head 10 is fixed in height relative to the table 4 but is rotatable about a vertical axis XX<SP>1</SP>. The anvil 8 moves in a slot 4a in the table 4 and is carried by an arm 11 pivoted at 12 and containing slots 11a in which can engage a ring 13a carrying a counterweight 13. Therefore, the welding pressure exerted by the anvil 8 can be altered by adjusting the mass of and the position of the weight 13. After a welding operation, the anvil 8 is parted from the tool 9 by operating a valve 14 to lift a piston-rod 15a in a cylinder 15 to raise the weight 13. To raise the anvil for the next welding operation, the rod 15a is lowered until it is out of contact with the arm 11 to enable the weight 13 to act alone. The welded films are driven downstream of the head 10 by rollers 16, 17 having rubber peripheries. The axle of the roller 17 is fixed to a support 17a on the table 4. The axle of the roller 16 is secured to one end of a lever 18 pivoted to an arm 19 fixed to a frame 10b of the head 10, the other end of the lever 18 being urged towards the arm 19 by a spring 18a. The roller 16 is driven by a flexible drive. Cooling water or other fluid having a high specific heat is circulated through the head 10 through an input 10c and an output 10d. The tool 9 is preferably made of stainless steel or titanium and takes the form of a convex shoe, the longitudinal direction of which coincides with the direction of the weld to be formed. To weld in a direction other than that shown in Figs. 1 and 2, the frame 10b, the head 10 and the arm 19 are rotated about the axis XX<SP>1</SP>. Strips of paper (26), (27), Fig. 7 (not shown), or adhesive tapes may be located between the tool and the films to be welded and the anvil and the films. To weld the second cap 21, Fig. 6, of a balloon 22, the edges of the cap and the balloon are clamped between an anvil 8a and the tool 9 which passes through an orifice 23a in an already-welded cap 23. Subsequently, the balloon valve is fixed in the orifice 23a.