Patent GB-623773-A (GB)
Title: Improvements in or relating to the manufacture of reinforced concrete articles by extrusion
IPC: B28B3/26
Filed: 1946-12-07
Abstract: 623,773. Extruding articles of reinforced concrete, cement, clay &c. SNELGROVE, E. C. Dec. 7, 1946, Nos. 36245/46, 37083/46 and 606/47. [Class 87 (ii)] [Also in Groups X and XXVIII] A reinforcement-feeding member is passed rearwardly through the extrusion nozzle, through the extrusion chamber and out through an inlet opening for the reinforcement, and is then attached to the reinforcement. A pull is then applied to the member to draw the reinforcement into the chamber and out through the nozzle from which the reinforcement emerges embedded in the concrete &c. Figs. 1 to 4 show a machine comprising a drum 53 which is rotated to pull wire 30 through the extrusion chamber 1. At its rear end the chamber is closed by rubber flaps 48, 50, which allow entry of reinforcement. The wire is attached to several hair-pin-like reinforcements 46 or, as shown, to the leading reinforcement which is attached by a short wire 30a to the next reinforcement. The speed of the drum 53 is coordinated with the operation of the screws 4, 5, which feed the chamber 1 with concrete. The wire is centred by an adjustable guide 55. Fig. 3 is a sectional plan view of the extrusion nozzle 13, which is initially closed by a verticallyreciprocable shutter 14 having a slot 29 therein for the reception of the wire 30. In operation, with this shutter closed, concrete is fed into the extrusion chamber until the pressure therein reaches a certain level. which may be indicated by a gauge 43. The shutter is then raised quickly, and the column of concrete emerges. As it emerges it may be shaped, e.g. tapered to form a tapered fencing post, by means of horizontally-reciprocable jaws 15, 16. The discharged articles are received on a conveyer 56. When the desired length of article has been produced it is cut off by closing the shutter 14 or by means of a separate shear. The operation of the machine is then continued with the shutter closed, pressure building up until the shutter is again raised to form another article. When the space between the nozzle and the drum 53 has been filled with articles and part of another article is protruding from the nozzle, the apparatus is stopped, the wire is disconnected from the articles, the reinforcement between the last article and the protruding article is severed, the articles are removed from the conveyer, the wire is connected to the reinforcement of the protruding article, and the operation continued. The shutter is raised by means of a weight 21 and chain 22 attached thereto, the chain passing over a sprocket 23 which is kept locked, while the shutter is down, by a plunger. To release the weight, the plunger is withdrawn, whereupon the weight fallsuntil it is arrested by a stop 26. The plunger may be withdrawn manually or automatically by oil pressure transmitted from the chamber 1 through a pipe 25, a pressure-responsive device being provided on the chamber instead of or in addition to the gauge 43. The shutter is lowered by turning the sprocket by means of a handle 27. The shutter has a U- shaped channel 28 that imparts a corresponding shape to the end of the fencing post &c. being extruded To ensure that the shutter returns to its proper closing position on a platform 31 despite trapped concrete, the platform is pivoted at 32 and rests on a spring 33. The jaws 15, 16 are operated by a cam mechanism or by a shaft 34 having right- and left-hand threads, and may be given a steady movement towards and away from each other or a non-uniform movement or movements. Concrete is fed into the chamber 1 from a mixer 7 by way of belts 8, 9, vertical towers 11, 12, which may contain feed screws, and the feed screws 4, 5. The drive to the feed screws 4, 5 may be co-ordinated with the position of the jaws 15, 16, to obtain a constant extrusion feed. Figs. 7 and 10 show a machine modified to extrude solid or tubular articles having cage-type . reinforcements 138. A cage is supported on a mandrel 133 and its leading end is attached to a wire 115 as in the first machine. The mandrel is supported at its rear end by a pillar 134 mounted on a slide 135 which moves on rails 137. The mandrel 133 may incorporate a reciprocating auxiliary concrete-feeding plunger, especially when the extrusion chamber is fed by screws from the side as in the first machine. Two or more mandrels may be carried on a hub rotatably mounted on the pillar 134. The feed screw 102 is hollow to receive the mandrel, works in a casing 119 having a hardened steel liner 125 and is fed by a supplementary screw 126. A valve may be provided to prevent escape of concrete between the mandrel and the screw. The concrete is compacted in the chamber 101 and nozzie 103 by eight reciprocating plungers 150, 171 operated by fluid pressure ; these plungers may be covered by rubber diaphragms which are bulged inwardly by the action of the plungers. The feed to the plungers may include a compressed-air cushion to minimize shocks. The nozzle is fitted with a horizontally-reciprocable sliding shear or shutter 108 having a slot for the passage of the wire 115; this shutter may be automatically opened, to allow emergence of the concrete, by an increase in oil pressure consequent upon an increase in the resistance to the operation of the plungers 150, 171. In operation, the mandrei is run forwardly into the feed screw until its forward end is near the shutter 108, and during the latter part of its travel the screws 102, 126 and plungers 150, 171 are operated to feed and compact concrete around the front end of the mandrel and reinforcement. The shutter is then opened and the extrusion proceeds in normal fashion. If a tubular article is to be produced, a sleeve 141 of paper, waxed paper, cardboard, fabric or expanded, perforated or sheet metal is disposed on the mandrel within the cage reinforcement and forms a lining for the article.