| 摘要 |
723,730. Automatic pressure control. POLYMER CORPORATION. Dec. 2, 1952 [Aug. 6, 1952], No. 30525/52. Class 38 (4). [Also in Group V] In a method of forming elongated shapes of uniform size from softened or liquified thermoplastic material in which the material is fed by a screw feed mechanism to a forming device, the speed of rotation of the screw feed mechanism is so controlled as to establish and maintain a substantially uniform pressure of the material at the inlet end of the forming device to ensure uniformity of size of the shape being formed. An extrusion cylinder 12 houses a screw 14 driven by a variable-speed electric motor 16 to force plastic material through a long forming tube 17. In a chamber 18 between the discharge end of the screw and the inlet to the tube is fixed a pressure-responsive bellows 51. The bellows communicates by way of an oil-filled line 52 with a Bourdon tube 53 arranged to shift an armature 54 in relation to windings 57 connected to a control circuit 58 coupled to the motor control unit 49. When the pressure in chamber 18 rises, the armature 54 moves and the motor slows down, whereupon the pressure drops, and vice versa. In a modification (Fig. 11, not shown) the motor is a constant-speed one and is connected to the screw through an adjustable clutch, e.g. a magnetic clutch adapted to vary the torque transmitted by variation of the current flowing through a rotor or armature; such variations of current being caused by variations of pressure on bellows 51. |
