EXTRUCTION CAKE APPERFECTED TO PRODUCE CONTINUED AN ALONGAGE OF TERMOPLASTICAL MATERIAL WHICH IS CONSTITUTED BY TWO COMPETITIVE CAMADES COST COST COST OF SOLDAGING SAYS ALTERNATED BETWEEN YOU

摘要

1533041 Tube extrusion head BATTENFELD MASCHINENFABRIKEN GmbH 20 Feb 1976 [6 March 1975] 06864/76 Heading B5A A tube having inner and outer layers, of the same or different thermoplastics material, is extruded by an accumulation piston 26 of a cross head die having an axially adjustable mandrel 6 to around which the material(s) is distributed extending around the mandrel on opposite sides of a sleeve 39, and via a pair of grooves 38, 12, around each of which the material flows in opposite directions from respective offset inlets and is discharged from respective annular outlet slots 42, 43, on opposite sides of the sleeve 39, in a required ratio of thicknesses, to pass through an annular slot 19 whose thickness is adjustable upon axial displacement of a sleeve 16 to effect a throttling action, the slots 42, 43 also being of a minimum thickness which is adjustable by axial displacement of sleeve 39 so that, upon adjustment of slot 19, slots 42, 43 can be maintained at the same ratio of thickness and at a total thickness equal to that of the slot 19. The ratio between the thicknesses of the slots 42, 43 and 19, is maintained by making the walls of the slots 42, 43 and 19, at angles to the axis of the sleeves, such that their sines fulfill the desired requirement by calculation. Thus, in the Fig. 2 embodiment, each slot 42, 43 and 19 comprises parallel walls and the angles are selected such that, where slots 42, 43 are of the same width, sine b = 2 sine a, and sine c = 2 sine b, the relationship providing for the requirement to be maintained upon displacing sleeve 39 by twice the amount that sleeve 16 is displaced. In the Fig. 1 embodiment, material from an extruder 2 is delivered into the head to travel in opposite directions from the mid point of a semi-circular duct 37 to discharge at one end at an inlet into the groove 12, and at the other end into the groove 38 at an inlet through an opening in the sleeve 39. The grooves 12, 38 are of a cross-section which decreases from the inlet into the location at which the material flowing in opposite directions meets. Alternative embodiments describe different arrangements of ducts for discharging material at various locations around each groove, from one or more extruders and including the discharge of different material into each groove.