Patent GB-820408-A (GB)
Title: A method and apparatus for shaping articles from thermoplastic sheet material
IPC: B29C51/18
Filed: 1956-07-19
Abstract: 820,408. Blow-moulding container covers &c. EMHART MANUFACTURING CO. July 19, 1956 [Oct. 19, 1955], No. 22438/56. Class 87(2). A method of shaping articles from thermoplastic sheet materials comprises "doming" the sheet by fluid pressure whilst the sheet is cool and moving the sheet and a heating surface relative to each other into overall surface engagement, the engagement being effected progres. sively from the centre of the sheet outwardly to expel air from between the sheet and the heating surface, heating and thus softening the sheet, moving the sheet into engagement with a shaping die and finally cooling the moulded article. The apparatus has eight main portions (A) a magazine M with a pivoted suction device 10, operated by a hydraulic ram and cylinder 15, for feeding the blanks B to the mould. (B) A stationary heating member 32, fixed to a main frame 31, with a thermocouple 38 for controlling the heat supplied by electrical elements 35, and with an air supply 40 connected via passages 43 to an annular orifice 44. (C) A movable clamping ring 46, surrounding and movable on the member 32, operated by a hydraulic ram and cylinder 52. (D) A movable mould member 33, with a fluid heating passage 70 with intake 70a and outlet 70b, operated via a tube 74 by a hydraulic ram and cylinder 78. (E) A movable clamping ring 47, with heating coils 47a, mounted on a sleeve 56 slidable over the tube 74, operated through a pivoted lever 61 by a hydraulic ram and cylinder 65 and having movable locating pegs 30, for the blanks B, operated by an air supply 92. (F) A pressing member 80, located inside the mould member 33, with an air supply 86 connected via passages 88 to the space between the pressing member 80 and the mould member 33, and operated by a tube 81, inside the tube 74, by the ram and cylinder 65. (G) A finished article stacker S, with a supply shoot 102 from the mould, and a stacking device 104, in a channel 103, operated by a hydraulic ram and cylinder 106. (H) A motor driven timer controlling the hydraulic supply to the cylinders 15, 52, 65, 78 and 106, the air supply to the mould member 32, the pressing member 80 and the pegs 30, and the vacuum to the device 10. In operation, Fig. 7, with the clamping rings 46, 47 and the mould member 33 retracted, the pegs 30 are advanced and a blank B is fed from the magazine M to rest on the pegs 30 between the mould member 33 and heating member 32. The clamping ring 46 is advanced to grip the blank B against the clamping ring 47 and to push back the pegs 30, air pressure is then admitted through the passages 88 in the pressing member 80 to "dome" the blank B. The clamping ring 47, mould member 33 and pressing member 80 are then simultaneously advanced, pushing back the clamping ring 46 and pressing the blank B against the heating member 32 whilst still "domed" under pressure through the passages 88. The clamping ring 47 and the pressing member 80 are then retracted and the clamping ring 46 advanced, at a lesser rate than the retraction, to mould the rim of the blank B over the circumferential edge of the mould member 33. The air pressure in the passage 88 is then relieved, air admitted through the annular orifice 44 and the blank is moulded against the mould member 33 and the fully retracted pressing member 80. The clamping ring 46 is then retracted, the mould member 33 retracted over the relatively stationary pressing member 80 to push the moulded cap out of the mould whereupon a stream of air from a nozzle 101, Fig. 21 (not shown), blows the cap into the stacks 5. Alternatively to "doming" the blank by air pressure, it may be advanced flat towards a convexly curved heating member. To mould a cap with an undercut rim making ejection from the mould difficult, a second embodiment is described, Figs. 24, 25 (not shown) in which the mould has spring loaded, conically guided, radial segments which move radially outwards under the action of the springs for ejection of the article and move radially inwards on conical surfaces to mould the cap.