Patent GB-1094823-A (GB)
Title: Joining thermoplastic sheets
IPC: B29C65/08
Filed: 1966-02-03
Abstract: 1,094,823. Seaming non-metallic sheet material. UNIROYAL Inc. Feb. 3, 1966 [March 22, 1965], No. 4718/66. Heading B5K. Thermoplastic sheets 50, 51 are bonded by overlapping adjacent marginal portions thereof to form an area of double thickness, compressing and heating a portion of the overlapped area by application of oscillatory energy to transpose the sheets 50, 51 into a common plane and to bond them together in this portion, and at least partially cutting through an unbonded edge portion 52a, 53a of each sheet 50, 51 to facilitate removal of the portions 52a, 53a from the bonded remainder of each marginal portion. The sheets 50, 51 are seamed by ultrasonic vibratory apparatus which comprises a high frequency vibrator (10), Fig. 1A (not shown), preferably a barium titanate hollow cylinder having interior and exterior silver-coated surfaces connected to a power source (13) comprising an oscillator and an amplifier. Alternatively, a magnetostrictive or crystal vibrator may be used. The cylinder (10) is clamped or welded to an adaptor (14) bolted to a tool holder (20) having a tool (21) brazed or welded thereto. The steel or nickel holder may be a transformer or mechanical amplifier, e.g. an exponential type (20), Fig. 1A (not shown), a straight taper type (20a), Fig. 1B (not shown), or a stepped type (20b), Fig. 1C (not shown), or non-amplifying, e.g. a straight-rod type (20c), Fig. 1D (not shown). The frequency of energy transmitted to the tool holder is preferably from 10,000-500,000 c.p.s. and the amplitude of vibration of the tool (21) is preferably from 0À0005-0À015 inch. Beneath the sheets 50, 51, Fig. 2B, a tool or anvil 32 is mounted on a holder 31 on a plate 30 adjustable transversely between limits 30a, 30b. The tools 21, 32 are identical but the tool 32 is mounted in a position 180 degrees reversed to that of the tool 21 with confronting surfaces 40a, 40b overlapping to form a compacting zone. Surfaces 41a, 41b are formed normal to the surfaces 40a, 40b to form cutting edges at the intersections. Sloped surfaces (42a), Fig. 2A (not shown), 43a and 42b, (43b) are also provided on the tools 21 and 32, respectively, and further cutting edges are formed by the intersection of the surfaces 41a and 41b with the surfaces (42a), 40a and (43b), 40b, respectively. In use, one of the tools 21, 32 is vertically displaced to allow the leading edge of the overlapped sheets 50, 51 to be introduced therebetween. The tool 21 is vibrated and the gap between the tools 21, 32 is adjusted to be approximately equal to the thickness of one sheet. As the sheets 50, 51 are progressed through the apparatus they are bonded together to form a butt seam and, simultaneously, the unbonded marginal portions 52a, 53a are severed. If the sheets are of unequal thickness and the spacing between the tools 21, 32 is set to the thickness of the thicker sheet, the portions 52a, 53a are only partially severed and are removed manually or mechanically to leave a slight ridge on each side of the seam. In a modification, Figs. 9A and 9B (both not shown), the lower tool (32a) comprises a replaceable rotatably mounted cylinder having a compacting surface (62) and a surface (63) normal thereto. In a further modification, Figs. 10A and 10B (both not shown), the upper tool (21a) comprises a cylinder locked in a bracket (71) and having a compacting surface (72). A lower rotatable tool (32a) is provided. In another modification, Fig. 11 (not shown), the tools (21), (32) are each independently vibrated.