GB633568A - Injection-moulding apparatus - Google Patents

Abstract

633,568. Injection-moulding apparatus. HARTLEY, A. W. E. June 14, 1947, No. 15733. [Class 87 (ii)] [Also in Group XXIX] Relates to apparatus of the kind having a tube 13 along which material is fed by a close-fitting archimedean screw 29 through a non-return valve to a telescopic injection chamber which is telescoped, to effect injection, by movement of the mould thereagainst; the tube is surrounded by heating means. According to the invention the heating means is spaced from the inlet end of the tube, so that powdered or granular material being dealt with by the early part of the screw will not become liquefied until it has been fed to a point nearer the outlet end of the tube. The Figures show an apparatus comprising an injection unit A and a mould carrying unit B mounted on a stand 11. An electric heater 15 surrounds the tube 13 and is spaced from the inlet 12a by a cooling chamber 14. The screw 29 is rotated manually by means of a handle 54 and feeds liquefied material through holes 37 in a plug 38 which forms a bearing for one end of the screw. A ring 39 slides on the plug and forms, with the holes 37, a non-return valve. The telescopic chamber 36 carries an electric heater 33 and a sliding valve 40. The valve 40 has a head 44 between which and the chamber is a spring 45. The nozzle 46 that engages the mould orifice is slidably mounted within the valve 40 and is backed by a spring 48. The nozzle communicates with the chamber 16 by way of an orifice 42 which is normally biased to the closed position by the spring 45. The mould-carrying part of the apparatus comprises a sleeve-like mould-holder 19 to which the mould is attached by bayonet joints 55. The holder 19 slides on a hydraulic ram 58, and is fastened to the ram by toggle links 20, 21, one of which has an operating handle 22. The ram is operated by a cylinder 18 to which pressure liquid is supplied from a reservoir 24 by means of a plunger 59 which is manually reciprocated by means of links 64 and handle 25. The suction stroke of the plunger draws liquid from the tank 23 through pipe 60, filter 61, duct 62 and non-return valve 63, and the working stroke forces liquid through valve 65, pressure conduit 66, rotary valve 67 and pipes 70, 71. The pressure of the hydraulic liquid may be limited by a ball valve 75 which is pressed to the closing position by a spring 77 acting through screw 78, bell-crank lever 76 and rod 79. When a certain pressure is reached the spring 77 yields and pressure liquid escapes from conduit 66 and returns to the tank 23. The maximum pressure may be adjusted by turning the screw 78, and may be increased by pulling downwardly on the horizontal arm of the bell-crank lever by means of pedal 81 and spring 82. Alternatively, the valve 75 can be locked in position by means of a bolt 84. In operation, the injection chamber 16 is filled by turning the handle 54, the chamber sliding outwardly on the tube 13. Then there are two alternative methods of procedure, viz:- (1) With the valve 75 locked solid by means of the bolt 84, the handle 25 is worked to force the mould into contact with the nozzle, thereby uncovering the orifice 45 and forcing back the chamber 16, whereby the mould is filled. Then the valve 67 is turned, and the mould is retracted. (2) The bolt 84 is released and the screw 78 set to give a desired released pressure, whereupon the mould is advanced and filled as before. Then the handle 52 is turned to re-extend the chamber 16, the mould being pushed back while the valve 71 lifts. During this operation the pedal may be held depressed to increase the pressure on the material in the mould. The manually-operated parts of the apparatus may be power-driven. Specification 569,155 is referred to.