GB1005036A - Automatic vacuum forming machines for plastics material - Google Patents

Abstract

1,005,036. Vacuum forming machines. COMET INDUSTRIES Inc. Dec. 12, 1961, No. 44496/61. Heading B5A. A vacuum forming machine has platens 25, 26 movable vertically by power units comprising electric brake and gear motors 37 mounted on the platens themselves and guided by rack bars 23, a carriage 56 which is slidably mounted on a pair of parallel track rods 50, 51, and a clamping frame 73 for securing a plastic sheet 79 to the carriage. The carriage 56 is moved from a position between the platens to a position between ovens 80, 85 by means of a fluid pressure cylinder 91 acting through pivoted levers 92. An oven door 98 is opened and closed by an air cylinder 100. A plurality of electrical stop switches 108 adjustably mounted on bars 107 limit the extent of movement of the platens. In operation, lower platen 26, with a cavity die connected to an airwithdrawal line 48 is in its lower position and upper platen 25 is in its upper position. The carriage 56 and clamping means are in the forward position between the platens. A plastic sheet 79 is mounted in position and clamped by admitting air into cylinders 65 to operate the clamping frame 73. An electrical impulse introduces air into cylinder 91 causing carriage 56 to move into position between the two ovens 80, 85. Another switch closes the oven door 98 and thermostatically controlled heating elements 82 maintain the desired temperature. The plastic sheet is then moved to a position above the cavity die by reverse operation of the above mechanism. The platens are then caused to move towards each other, and a vacuum pump is operated to withdraw air from the cavity. After an interval sufficient to partially rigidify the plastic in its newly formed shape, the platens are separated and the formed plastic article removed manually or by using compressed air.