GB1141033A - Improvements in or relating to extruding methods and apparatus - Google Patents

Abstract

1,141,033. Ram-extrusion presses. BARWELL ENG. Ltd., J. H. BARWELL, and D. J. LANHAM. 29 March, 1966 [5 April, 1966; 29 June, 1966], Nos. 14367/65 and 27566/66. Heading B5A. [Also in Divisions F1 and G3] An extrusion moulding machine for the production of equal volume tubular or solid blanks, e.g. combined sole and heel blanks of rubber, comprises an hydraulic ram extrusion unit 3, 4, Fig. 1, which extrudes material at a constant rate through a die 6 and a cutter mechanism 2 which comprises a blade 15 rotated at equal intervals of time past and in close proximity to the face of die 6. The cutter mechanism.-Blade 15, Fig. 4, is pivotally mounted on a flyweel 16 via a holder 73. This holder is provided with a slot 76 which accommodates a block 77 mounted on a needle bearing 78 and adjustable in its position relative to the axis of rotation of flywheel 16. When the flywheel is rotated there is relative movement between slot 76 and block 77 and the arrangement is such that an additional swinging movement, the amount of which depends on the position of block 77, is imparted to blade 15 in the direction of rotation of flywheel 16 as the former moves past the die face. The rotational axis of flywheel 16 may be brought perpendicular to the face of die 6 by adjustment of bushes (33), Fig. 3 (not shown), in a fixed triangular plate (18). Movement of the blade towards or away from the die face is achieved by rotation of a sprocket (44) fixed to a threaded housing (39) which co-operates with a fixed threaded collar (35). Rotation of sprocket (44) may be effected manually by rotation of a knob (44d), Fig. 1 (not shown). Preferably blade 15 is inclined to the die face and its speed of rotation is so chosen that the underface of the blade recedes from the face of the die at a rate not less than the rate of extrusion. In an alternative arrangement (not shown) the path of movement of blade 15 may be adjusted such that it only sweeps across the die face once in every two or more rotations of flywheel 16. The extrusion die.-The composite die shown in Fig. 5 is intended for the production of combined sole and heel blanks. Cutouts 93, 100 and 101 of part 91 are so shaped that heel, instep and sole portions respectively are formed and the shaping also varies the impedance to flow so that the extrudate is appropriately non- uniform in the extrusion direction. An alternative die, Fig. 7 (not shown), for producing annular sections, is provided with a peripheral flange (108) in passageway (103) which it is said prevents the concavity usually formed at the cut surface when rubber "recovers" after extrusion and severing. In modifications, flange (108) may be on ring (102) and, to produce a solid blank, mandrel (104) may be dispensed with. Extrusion ram and hydraulic circuitry.-The hydraulic ram comprises a piston (110, 113), Fig. 8 (not shown), and cylinder (3) and a further piston (112, 114) and cylinder (109). Initially fluid from a tank is delivered by pump (8) via conduit (131), valve (122), conduit (132) and conduit (133) to cylinder (109) and the ram is thereby extended rapidly to take up slack. For extrusion at a constant volume rate, fluid is also admitted to cylinder (3) via conduits (132), (136), valve (124), conduit (137), a pre-set volume control valve (125), conduit (138) and conduit (134). Volume control valve (125) operates under a substantially constant pressure difference and this is achieved by automatic co-operation between valve (122) and a valve (126). Valve (122), Fig. 9 (not shown), comprises a spool (144) which is urged to the left, should pressure in conduit (131) and hence in passage (148) exceed a predetermined value by-passing fluid to tank via passage (147). The predetermined pressure value is set by a valve (153). The rate at which fluid is bled may also be adjusted by a hand operated valve (127), Fig. 8 (not shown), connected to valve (122) by conduit (157). Also in valve (122) the output to valve (125) is via passage (149). In valve (126), Fig. 10 (not shown), the pressure applied to the left hand side of a piston (163) is equal to the ram cylinder pressure which is equal to the pressure on the downstream side of volume control valve (125). The pressure on the right hand side of piston (163) is that in passage (160), conduit (157), Fig. 8 (not shown), and passage (150), Fig. 9 (not shown), of valve (122), and since passage (150) is linked to passage (149) the pressure value is that on the upstream side of control valve (125). A change in pressure differential across piston (163) moves it to the left to open aperture (165) and fluid is bled from passage (160) via passages (166), (177) to tank. Aperture (165) is closed when the correct pressure difference has been restored. A ball valve (169) prevents bleed of fluid when there is negligible pressure in the ram cylinder. General operation.-Die 6, Fig. 1, is mounted on a hinged head assembly 5 and initially this is swung away from barrel 4 so that it may be charged with heated rubber. On starting the hydraulic feed to the ram, trapped air is evacuated from barrel 4 by means of a vacuum pump 9. Motor 25, which drives the cutter mechanism, is then started at a pre-set speed.