Patent GB-574367-A (GB)
Title: Extrusion machine
IPC: B29C48/03
Filed: 1943-07-13
Abstract: 574,367. Liquid - pressure engines. MACMILLIN, H. F., and POCOCK, P. C. July 13, 1943, No. 11386. Convention date, March 10. [Class 69 (ii)] [Also in Group V] The extrusion screw is axially slidable in its cylinder, and axial thrust exerted thereon by the material being extruded is opposed hydraulically by liquid under pressure supplied from a liquid-circulating system, means being provided whereby changes in the said axial thrust cause variations in the opposed hydraulic pressure, the axial position of the screw in its cylinder being thus automatically regulated. Thus, the screw may be retained always in a predetermined position, whereby the output thereof is maintained constant. Fig. 1 shows an arrangement in which the screw shaft 35 slidably passes through and is driven by a hydraulic motor 40. The rear end of the shaft carries a piston 42 disposed in a cylinder 44, the front wall of which includes a thrust bearing 47. Pressure liquid is supplied by a variable delivery pump P through pipes 70, 96 to motor 40 and cylinder 44. If the screw encounters undue resistance (and thus tends to move to the right) the torque required by the motor is increased and the pressure in pipe 70 is increased ; the pressure in cylinder 44, being the.same as that in pipe 70, is thus increased in proportion to the increased torque, and the screw is prevented from moving to the right. The extruded article 17 is transferred on an upward blast of air from the nozzle 16 to a discharge conveyer 51 driven by another hydraulic motor 52. The conveyer 51 may move faster than the speed of discharge of the article 17, the article being thus stretched, its molecular structure oriented and its strength increased. The speeds and the relative speed of the two motors 40 and 52 are maintained substantially constant by means of a balancing valve 75 comprising two adjustable choke valves 84, 93. The extrusion cylinder and nozzle are heated by fluid chambers 21, 22, 23. The screw flights closest to motor 40 are most effective, and if an undue thrust on the screw should move the latter to the right the resulting decrease in efficiency of the screw relieves congestion near the nozzle 16. Fig. 2 shows a modification comprising a variable delivery pump 105 having a control 106. The discharge 107 from the pump leads into the discharge 72 from motor 40. When the load on motor 40 changes, the change in pressure in pipe 72 is reflected by a change in pressure in cylinder 44. The Specification as open to inspection under Sect. 91 comprises also Figs. 2, 3, 5 and 6 (all Cancelled). In Fig. 2 (Cancelled) the space 97a behind the piston 42a communicates with the valve 75, and the screw, when overloaded, moves to the right to relieve the pressure thereon. In Fig. 3 (Cancelled) a variable delivery pump 100 delivers fluid under pressure into the space 97b behind the piston 42, and a pressure control 102 allows the screw to move to the right as in the Fig. 2 (Cancelled) arrangement. Figs. 5 and 6 (Cancelled) (not shown) refer to a construction similar to that of Fig. 1 (Cancelled) but having a screw core of constant diameter. This subject-matter does not appear in the Specification as accepted.