GB1088039A - Improvements in or relating to the manufacture of articles of plastics using extrusion apparatus - Google Patents

Abstract

1,088,039. Extrusion / blow - moulding. REXALL DRUG & CHEMICAL CO. Oct. 15, 1964 [Oct. 15, 1963; June 4, 1964], No. 42160/64. Heading B5A. In an extrusion/blow-moulding process the wall thickness of the extrudate is varied in accordance with a predetermined programme by control means including a detecting element responsive to the length of the extrudate. As described the extruder head of the machine is initially closed by a mandrel 4, Fig. 2. On closure of a switch 26 an electromagnet 24 is energized to actuate a control valve 19 which controls the fluid supply to a cylinder 30 to cause upward movement of the piston block 28, 17 to pivot the lever 11 clockwise so lifting the mandrel 4 and allow plastics material to leave the extruder head and enter a raised two-part neck mould 44. The switch 26 is opened and pressurized fluid is supplied to the cylnder 50 to cause the piston 51 to move downwardly with the neck mould 44. The valve 19 is now controlled by a cam and cam follower mechanism 71, 72, acting through the linkage 20, 73, to regulate the flow of pressurized fluid to the cylinder 30 of the piston 28 and so control the position of the mandrel 4 in dependence on the position of the neck mould 44 and in accordance with the profile of the cam 71. On completion of the extrusion the switch 27 is closed, e.g. manually, by timing means or by electrically or mechanically operated sensing means, to energize the electromagnet 25 so that the valve 19 moves downwardly to cause the piston block 28, 17 to move downwardly so pivoting the lever 11 counter-clockwise and closing the mandrel 4 on the seat 6. The blow mould sections 85 and 86 are then closed on the extrudate and the blowing tube 61 is supplied with air. After blowing the blow mould sections 85, 86 are separated. The gripping device 92 is moved over the sprue tail 95 which is engaged by pivoting fingers 94. The neck mould parts 45, 46 are then separated by upward movement of the member 55, 56. The blowing tube 61 is then withdrawn downwardly by movement of the piston 64 and the gripping device 92 is retracted to withdraw the moulded article. The fingers 94 are pivoted to pull the sprue from the article. The extruder mechanism is shown in Fig. 12 and comprises one screw 111 feeding a plurality of conduits 115 leading to conduits 119 each leading to two heads 117, 118. A reservoir chamber 120 extends from each conduit 119 and contains a piston the operation of which is controlled by a device 124, 123. The provision by the capacitors or reservoirs 121 normally allows continuous operation of the screw 111 but should all the reservoirs 120 become full, all the relays 125, one of which is associated with each reservoir, are operated to effect disengagement of the coupling device 112 in the drive from the motor 113 to the screw 111.