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694,379. Moulding tubular articles from thermoplastic strip material BORKLAND, G. W. Dec. 4, 1950 [Dec. 21, 1949]. No. 29658/50. Class 87 (ii). [Also in Group XI]. A flat thin strip of thermoplastic material is bent cold into the general shape of the article, the bent strip is placed in contact with a moulding surface having the same general shape but provided with one or more cavities which form protuberances on the articles, the strip is heated, and fluid pressure is applied to the hot strip to force it against the'moulding surface and into the cavities. In making a lampshade an arcuate strip 10, which may be decorated, printed, &c. is bent into frusto-conical shape 11, Fig. 3. The ends may overlap, as at 13, or may form a butt joint, and may be secured together by a strip of thermoplastic material. The bent strip is placed in a frusto-conical recess 19 in a mould 17, the recess having cavities 20 of flower, hemisphere, ribbon or other shape. An electrical heating element 33 is lowered into the bent strip to soften the latter, the parts 34, 35 thereof, which are formed of heat-resisting insulating material, engaging the bent strip 11. The softened strip is sucked on to the mould and into the cavities by a vacuum pump. The pump acts through conduit 23, annular chamber 22 and conduits 21 which open into the cavities. Embossments 43 are thus formed on the lampshade (Fig. 5). At the same time two annular grooves 44, 46 are formed in the lampshade by suction applied to annular grooves 27, 29 in the mould. The groove 44 receives a support ring 45, and the groove 46 strengthens the base of the shade. To prevent loss of vacuum, the joint 13 is covered with a strip which holds it flat against the mould. This strip may be of metal, wood or thermosetting laminated material. Instead of using vacuum, air pressure or steam pressure can be applied to the inside of the conical strip 11. The heating means may be steam or infra-red bulbs. Fig. 6 shows modified apparatus for forming embossments on the inside of a frusto-conical shade, the bent strip 11 being in this instance fitted over a mandrel 52 having cavities 54 connected by openings 55 to the interior of the mandrel which is connected to vacuum through conduit 57. The heating means comprises insulating rings 64, 65 carrying electrical heating elements 74, the rings being brought down into contact with the strip. In both of the examples shown, either the heater or the mould or both may move towards each other. The thermoplastic material may be cellulose acetate, ethyl cellulose, vinyl resin or methyl methacrylate resin.
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