GB728784A - An improved method of and apparatus for plastically shaping materials, more especially by extrusion - Google Patents

Abstract

728,784. Automatic control systems. MUNKER, T. Feb. 6, 1953 [Feb. 15, 1952], No.3379/53. Class 38 (4). [Also in Groups XXII and XL (b)] In a method of plastically shaping materials, more especially by extrusion the workpiece after deformation passes through a substantially closed chamber 7 where the radiation emanating from the workpiece is passed through an optical system to a device responsive to heat radiation, the output from which device is used for the control of the conditions of the process determining the heat radiation of the deformed workpiece. In an extrusion process the speed of extrusion is preferably controlled so that the temperature and hence the heat radiation of the, extruded workpiece leaving the extrusion die 4 is maintained substantially constant. The chamber 7, Fig. 3, is lined with bright aluminium 17 to reflect the radiation through a pair of lens 14, 15 which direct it through a revolving slotted disc 27 to a photo-cell or photo-electric resistance 16. The latter also receives through the slotted disc, a standard or comparative radiation from a standard radiation device 21 consisting of an electrically heated body controlled by a resistance 24. A movable diaphragm or filter 22 controls the standard radiation and a lens 23 directs it through the slotted disc to the photocell 16. The latter therefore receives alternate radiation impulses from the chamber 7 and the standard device 21 and thus generates electric impulses which are passed through a three-stage amplifier and phase discriminating circuit, Fig. 4 (not shown). The output of the latter controls through a relay 36, Fig. 1, a servomotor 37 which in turn controls the water pressure valve 33 of a hydraulic extrusion press 1 and thus the speed of extrusion. A device 32 connected to the output of the phase discriminating circuit indicates any difference between the chamber radiation and the standard radiation whereby an operator may control the valve 33 manually to maintain constant the temperature of the workpiece. A recording device 40, for the speed of extrusion and the temperature of the extruded work-piece, and optical or acoustical alarm signals 39 are also provided. The measuring head 13, Fig. 3, containing the radiation detecting equipment is surrounded by a water jacket 19. The extruded work-piece 8, Fig. 2, which is preferably of aluminium or aluminium alloy is tempered by water issuing from an annular jet 41. A cushion of compressed air from an annular jet 42 projects the chamber 7 from water vapour.