Patent GB-1506722-A (GB)
Title: Apparatus for extruding concrete
IPC: B28B1/08
Filed: 1975-03-06
Abstract: 1506722 Building slabs; crash barriers; casting barriers F M HEWITT 6 March 1975 9432/75 Headings E1B E1G and E1S [Also in Division B5] Concrete is extruded onto a casting bed as a slab or pile, (see Division B4-5), or onto a road as a median barrier, from the open end of the moulding channel of a machine which is displaced on wheels along the bed or road to effect the extrusion, by the compaction of augers delivering the concrete into the channel, and friction between the channel walls and the concrete is reduced by vibrating each wall in its plane in the direction of extrusion, at a frequency of at least 22,000, and preferably of up to 55,000 cycles per minute. The slab of the Fig. 1 embodiment comprises an upper layer 16 extruded onto a previously extruded lower layer 12, to define bores 22, and having stressed cables 20, 14 extending longitudinally and transversely. The lower layer 12 comprises sequential square sections which have been rotated 90‹ from their extruded orientation in which bores for the cables extended longitudinally, and is extruded with indentations 18 at spaced intervals along each side, into which the concrete of the upper layer 16 affects keys. The stressed cables 20 may be incorporated into the layer 16 during extrusion, or may be inserted after extrusion through extruded bores 186, Fig. 11, by projecting a lead wire 200 through the bore 186 by means of an air gun 190, which is sealed to the bore at a rubber gasket 208 and has an air pressure inlet for projecting a head 202 secured to the lead wire 200. A pile, Fig. 21, extruded by augers 328, 330, 332, 334, comprises longitudinal reinforcements 352, 354, 356, 358, and transverse reinforcements 360 which may be "U" shaped or may comprise fabric, or mesh. A median road barrier 210, Fig 12, extruded in situ to separate traffic lanes, is anchored at its ends on a neoprene pad 212, to a cement bed 214 laid only at the ends and to which an anchorage plate 216 is secured by bolts 218. An upward extension of the plate 216 is secured to the barrier 210, at a bulkhead 226, by cable anchors 220 fixed to post tensioned cables 222 and 224. An anchorage cover 228, is removably secured to the bulkhead 226 and plate 216. The barrier 210, Fig. 13, is extruded with bores for the cables 220, 222, and with an intermediate bore as a utility duct. The concrete from a hopper 240, is extruded by five augers 242, 244, 246, 248, and 250, Fig. 16, through the moulding channel defined by walls 260, 262 and 264, within which mandrels defining the fines are supported by shafts 286, 288, 290. The mandrels are pneumatically vibrated, via their supporting shafts carried by the extruder frame, and the walls 260, 262, are vibrated by vibrators secured thereto and are mounted in ball races for sliding movement by the vibrators in the direction of extrusion e.g. the races 270, 272, Fig. 18, for the wall 260. A skid 266 is carried by each wall 260 so that it is vertically displaceable by the road surface, the displacement being permitted by the races 270, 272 being carried by a vertical member 274, which is vertically slidable in ball races 276, 278, carried by the extruder frame 238 The machine wheels are pivotably mounted in ball joints and are each provided with hydraulic steering and levelling arms. A wheel is also provided to record vertical displacements in the road surface, which are transmitted by a pneumatic system to a hydraulic system which effects adjustment of the height of the machine wheels to maintain the top of the barrier horizontal, the rear wheels being adjusted prior to a gradual readjustment of the front wheels. Levelling is similarly effected, with the vertical displacements of the extruder being accommodated by the skids 260. Concrete is delivered to the extruder hopper, from a further hopper which is displaced thereover by articulated arms of a power unit and to which the concrete has been delivered from a transit mixer.