Patent GB-1502267-A (GB)
Title: Extrusion dies in which at least one lip of the die orifice is adjustable
IPC: B29C48/32
Filed: 1974-06-06
Abstract: 1502267 Adjustable extrusion die lips AGFAGEVAERT 20 May 1975 [6 June 1974] 25216/74 Heading B5A An extrusion die has at least one elongate extrusion orifice defined between die lips 30, 31, Fig. 2, at least one, 31, of which is adjustably deflectable to vary the depth of the orifice across its width, by means of a plurality of rods 37 which are spaced apart in a row parallel to the orifice, and which are fixed at one of their ends to the lip and are each axially displaceable to effect the variation, by a cam acting on their other ends and comprising a circular eccentric surface 51 of a manually rotated shaft 49. The lip 31 may be carried by or, as shown, comprise an integral part of a die body part 16, which has a thinner region 35 about which the deflection is deflected. Each rod 37 is secured to the lip at its one end, by screw threading 40, upon rotation of the rod 37 by a wrench at a location 42, and is locked in position by a nut 41, the rod 37 being loaded by springs 47 against the cam surface 51, which it engages at a saddle 46 mounted at a spigot 45 for free rotation in the end of the rod 37. Each shaft 49 is axially located in the die by a set-screw engaging a circular groove 54 of the shaft 49, and is rotated at a square head piece 55 by engagement with a tool 60. Predetermined location between the shaft 49 and tool 60 is ensured by a pin and slot 55, 61, and the degree of lip adjustment is indicated by marks 62 on the tool 60 co-operating with marks (not shown) on the die surface 63. The die may be employed for the extrusion of self supporting films, e.g. of polyethylene terephthalate film base, or for the extrusion of a magnetizable layer on to a polished endless belt from which it is stripped, or the die may be employed as in the embodiment, for the coating of a pair of simultaneously extruded layers, on to a web 14 of paper or film, Fig. 1, which is delivered to the die around a roller 10. The die of the embodiment comprises a part 17 and a lip 32 of a part 18 which may be similarly adjustable, to define the orifices for the layers which slide down a surface 13 of the die to form, adjacent the moving web 14, a bead from which the layers are applied to the web by a pressure differential created by atmospheric pressure above, and a reduced pressure below the bead. The die is stabilized by bolting of the die part 16 to a beam 19, in which it locates at a tongue and groove 20, 21. For cleaning purposes, the die parts 17, 18, are mounted for pivotable displacement away from the part 16 and beam 19, effected by hydraulic motors 29, 28. The die part 17 is pivotable at 24 about the beam 19, and the part 18 is pivotable at 27 about the part 17. The motor 29 is located to the part 17, and at 64 to the beam 19, and contracts to pivot both parts 17 and 18 away from the part 16, and the motor 28 is located to the parts 17 and 18 to simultaneously expand and pivot the part 18 away from the part 17. The die may have bores, or pipes located in grooves, for the circulation of heating or cooling fluid. The die spaces corresponding to the regions of reduced thickness at locations 35, 36, may be filled with silicone rubber 58 which seals the adjusting mechanism against spillage of the extrudate. The die lips may define film extrudate having beaded edges, for gripping by clamps which orientate the film by stretching by passage along diverging paths, and uneven stretching and resultant film thickness may be compensated for by adjusting the die lip or lips to extrude a film of non-uniform thickness.