Patent GB-878135-A (GB)
Title: Method and apparatus for extruding and forming plastic, rubber or rubber like materials
IPC: B29C48/94
Filed: 1960-01-20
Abstract: 878,135. Extrusion machines. ESSO RESEARCH & ENGINEERING CO. Jan. 20, 1960 [March 31, 1959], No. 2062/60. Class 87(2). Apparatus for extruding and forming plastic, rubber or rubber-like materials, e.g. into large blocks suitable for packaging, comprises (a) an extruder tube 42 of circular cross-section with a die plate closure 48 having a plurality of passageways therethrough, (b) an expansion chamber 50 connected to the die plate 48 and having interior walls 56 flaring outwardly to an outlet end 54 of rectangular cross-section of larger area than the inlet end 52, the walls 56 having roughened surfaces, and (c) a forming chamber 58 of rectangular cross-section in communication with the outlet end 54 of the expansion chamber 50 and having roughened interior surfaces adapted to be lubricated during the passage of the extrudate. The latter is in the form of a billet 32 formed as a result of the individual extruded filaments being compressed together by the pressure head built up by the drag on the extrudate due to the roughened, e.g. corrugated, walls 56. Lubricant, e.g. an aqueous solution of a soap or detergent, is supplied to the forming chamber 58 by pump 72 through pipe 70, internal passages 64, and wall perforations 68 in order to give the billet surface a well finished and polished appearance. The billet 32 then passes over a roller table support 72a beneath a speed sensing device, Fig. 6, comprising a frame 80 carrying a pair of knurled edge wheels 82 which run on the upper surface 36 of the billet and drive an induction generator 86 via a speed changer 84 to produce a voltage signal having a magnitude which corresponds to the linear speed of the billet. This voltage is transmitted to a comparator means in which it is matched against a voltage similarly generated and corresponding to the linear speed of slot conveyer belts 92, 94 and 98 which form a four-sided conveyer means, the difference or error voltage, amplified as necessary, being used to regulate the speed of a motor 90 which drives the conveyer belts and also the carriage 102 of the block cut-off device 28 described below. During its passage from the outlet of forming chamber 58 to the slot conveyer means, elevated temperature so that it may be necessary to apply slight compression to all four surfaces of the billet 32 to reform its cross-section to the size and shape that it had on leaving the chamber 58. The slot elements should be smooth to the order of buffed and polished stainless steel. The block cut-off device 28 which follows is mounted on a platform 100 and comprises a carriage 102 reciprocatable by means of a crank and connecting rod mechanism, the crank being driven from the drive shaft of belt 94 by a sprocket chain 106. Supported on and extending above carriage 102 are stanchions 122 which guide the cutter knife 128, this being driven by a piston rod, (not shown), extending from the cylinder 130. As the billet 32 moves forward, it contacts the arm 136 of switch 134 which, after a delay period, causes the crank-shaft to turn and the connecting rod 104 to move the carriage 102 along platform 100. After about 80 degrees of crank-shaft rotation when the carriage 102 and the billet 32 are moving at the same speed, a rotary programmer meshed with a gear on the crank-shaft acts to cause the knife 128 to descend and, after remaining at the bottom of its stroke for 2-3 seconds, is caused to retract. The retraction of the knife 128 occurs after about 120 degrees of crank-shaft rotation and during the remaining 60 degrees before the carriage 102 ends its forward movement, the billet 32 is travelling faster than the carriage 102 and is thus able to push the product block 38 along an inclined portion of the upper roller surface of the carriage 102.