GB938378A - Improvements in methods and apparatus for mixing rubber with particulate solid material - Google Patents

Abstract

938,378. Mixing rubber. DUNLOP RUBBER CO. Ltd. Feb. 15, 1960 [Feb. 16, 1959], No. 5267/59. Class 86. [Also in Group V] Rubber is mixed in specific proportions with particulate solids, e.g. carbon black, ground reclaim rubber and sulphur, by extruding the rubber as a tube and feeding the solids into the tube as it is formed, the relative rates of extrusion and feeding being controlled to obtain the required proportions, the filled tube being fed into a mixer to disintegrate and mix it into a homogeneous mass. Raw shredded rubber is supplied from hopper 4 to a worm 3 having a pitch which lessens towards the outlet; an elbow 8b conducts the rubber to a die 8c through which protrudes the tube 27 bringing the particulate solid material from an agitating unit 10, which comprises a casing 11 having heating pipes 14, 15 and inclined agitating blades 22. A feed screw 24 forces the solids into the rubber tube which is removed from the die on a conveyer belt 32 and fed to a compacting unit 31. The speed of the belt and tube is measured by a phototachoscope unit 34 which controls the speeds of the extruder screw 3 and the compacting unit 31. A freely rotatable roller 36 on a pivoted lever 37 bears on the tube and influences an electrical transducer 39 to control the speed of the motor 26 to correct variations in the diameter of the tube and hence in solid filler content. The compacting unit 31 comprises a barrel 41, a forcing screw 40 driven by a motor 43 controlled by the unit 34, and a feed pipe 44 for rubber compounding liquids, which are injected by a pump which operates once for each rotation of the screw 40. The unit 31 feeds the compacted material to a number of mixers 45-48 constructed as described in Specification 937,652, the mixing worms 51 being inclined at an angle of 30 degrees to a vertical plane normal to the axis and successively at 45 degrees to the vertical when viewed axially each being at right angles to the inclination of the preceding worm. Gas relief valves 52 are provided. A unit 49, positioned between mixers 46, 47, supplies pellets of vulcanising compounds and is also controlled by the unit 34. The final delivery is by a screw extruder 63 through a die or dies 67 on to a conveyer 68. There is an inspection hatch 66. The apparatus may be water cooled as necessary. In a modification, the particulate solids may be fed through a coaxial passage in the feed screw 3, a stationary feed screw being arranged in this passage. The feed pipe 44 may be fitted between the worm 40 and the first mixer 45; or the liquids may be introduced into the rubber tube extruding apparatus, or into the unit 10. If a mixture of natural and synthetic rubbers is being made, the mixture may be extruded as a tube, or one rubber may be extruded inside a tube of the other, and the solids in the centre.