GB1174711A - Manufacture of Hollow Concrete Planks - Google Patents

Abstract

1,174,711. Moulding hollow concrete planks. WEST ALLIS CONCRETE PRODUCTS CO. 14 March, 1968, No. 12382/68. Heading B5A. [Also in Division E1 In a method of moulding a hollow concrete plank, comprising a plurality of cavities, wherein the concrete is cast on to a bed from a machine travelling thereover and provided with cavity defining cores, bridging of the concrete in the webs between the cavities is prevented by progressively tamping the concrete over the cores with a series of elements, comprising a plurality of downwardly projecting lugs of progressively decreasing depth and the side tamping surfaces whereof one of decreasing inclination to the horizontal transversely of the cores, which tamp the concrete whereby it is progressively displaced over and forced into the webs to form a flat surface. The plank is cast on to bed 20 from a travelling machine 21, including hoppers 22, 24, 28 for depositing successive layers of concrete, and preliminary tampers 36 and 37 comprising grooved surfaces for forming in the first layer of concrete, ridges (38), Fig. 6 (not shown), over pretensioned reinforcing wires (35), and valleys (39) therebetween for receiving the cores 31 which longitudinally reciprocate on the machine 21 and are provided with tapered ends 31 for ploughing through an intermediate concrete layer deposited thereover from the hopper 24 which is provided with a tamper 40 which also controls the hopper discharge. Tampers 43, 44 and a screed 63 tamp concrete over the cores 31 and into the webs intermediate thereof, and reciprocating trowels 68 and 67 smooth the upper concrete layer. The tamper 43 comprises a first series of lugs 45 provided with bottom surfaces 46 for tamping over the cores 31, side surfaces 47 inclined at 60 degrees to the horizontal and surfaces 48 intermediate the lugs 45 for tamping the concrete intermediate the cores 31, and a second series of lugs 49 provided with bottom surfaces 50, which project lower than surfaces 47, side surfaces 51 inclined at a shallower angle of 45 degrees than surfaces 47, and which lugs 49 are either integral with the tamper or mounted on a spacer 52 whereby the surfaces 53 are lower than surfaces 48, the overall effect being to define a shallower and narrower groove between lugs 49 than between lugs 47. Tamper 44 is similarly provided with two series of lugs defining progressively shallower and narrower grooves. The tamping screed 63 is supported for vibrating or tamping motion and may be flat or preferably is provided with downwardly projecting lugs (65), Figs. 4 and 5, not-shown, which progressively taper to a flat surface towards the screed trailing edge.