| 摘要 |
837,485. Moulding thermoplastic sheets. MARTELLI, G., MARTELLI, N., and MARTELLI, F. Feb. 18, 1957 [Feb. 21, 1956], No. 5360/57. Class 87(2). A machine for the continuous formation of fruit packing trays by vacuum formirig thermoplastic sheet material 3 incorporates perforated moulds 1, on the periphery of a rotating drum 2, on to which the sheet 3 is fed and which are connected to distributing valve means 20, 25 which, whilst the sheet is being heated by spaced electric heaters 4, connect the lower faces of the moulds with a source of vacuum 6 and subsequently with the atmosphere after a fraction of a revolution of the drum. The longitudinal edges of sheet 3 are sealed to the walls 402 of the drum 2 during heating and vacuum forming by two endless wires 7 which extend around a great part of the drum periphery and register in grooves in the walls 402. These wires also drive the lower of two pairs of co-acting rollers 19, &c. (near the delivery station), the higher rollers 18 having a cutting edge 118 for trimming the sides of the moulded sheet. The periphery of the drum 2 comprises a number of vat-like cells into which the moulds are tightly fitted leaving chambers 30 therein into which pipes 23 open. Each of said pipes is connected to a port 22 in a disc 20 of the distributing valve and a second disc 25, having corresponding ports 28, 26 connected to the atmosphere and suction pump 6 respectively, is spring-pressed there-against. The thermoplastic sheet 3 may be pre-heated and after moulding, cool air is blown both outside the sheet and between the sheet and the mould face. Transverse heated edges may be provided on the drum to divide or indent the moulded sheet.
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