GB1423984A - Extruders - Google Patents

Abstract

1423984 Extrusion calendering DAVID BRIDGE & CO Ltd 8 Feb 1973 [9 Feb 1972] 6045/72 Heading B5A [Also in Division G3] Rubber or plastics material is delivered from the outlet 25 of a screw extruder 16 and under extrusion pressure into the nip 52 of sheet calendering rolls 42, 46, and control means are provided for maintaining constant the thickness of the calendered sheet by automatically varying the speed of an electric or hydraulic motor which rotates the screw 18. The control means (may) comprises an electric strain gauge mounted in the roller frame for measuring the load at one, or both ends, of one or both rolls 42, 46 and in either the calendering direction or the direction perpendicular thereto, and acting by change of resistance or impedance upon resilient deflection of the roll or rolls in the frame, to vary the speed of the screw 18 through a control circuit (not shown). The upper and lower rolls 42, 46 are respectively supported in bearing blocks 36, 38 located in vertical slideways 32, 36 of frame members 28 and 30, with the spacing between the rolls fixed, or the spacing between one or both rolls being adjustable by support means for the blocks. The upper bearing blocks 38 may be located with a clearance in the slideways 32, 34 and suspended from vertical columns 50 which are resiliently deflectable in the direction of calendering under a load on the rolls in that direction, the deflection of the bearing 39, e.g. of a maximum of 0À04 inch acting, via a slidable rod 54, upon the strain gauge 55 to control the speed of the motor driving the screw to maintain constant the load on the rolls. Alternatively, the bearing block actuating the strain gauge may be supported by roller bearings for displacement under load, and against resilient means in a slideway extending in the direction of calendering. Alternatively, the strain gauge may be mounted to act in response to a load on the rolls acting perpendicularly to the calendering direction. The speed of the extruder screw or rolls, and the roller gap and the load on the rolls which is to be maintained constant, are settable by an operator. The extruder screw 18 and barrel 16 may be heated or cooled, and the calendered sheet may be transported by a conveyer to a curing oven and cooling means. Pressure in the die 24, or in the region between the outlet 25 and the rolls, may be indicated to the operator by a pressure gauge, and the load of the strain gauge may also be indicated.