US2397728A - Mold for the production of prestressed reinforced concrete sleepers - Google Patents

Description

April 946. H. L. DOWSETT ET AL 2,397,728

MOLD FOR THE PRODUCTION OF PRE-STRESSED REINFORCED CONCRETE SLEEPERS Filed March 25, 1944 2 Sheets-Sheet 1 3g 5% wgzaz za zq'ga sz gz ll l u fiur WWW Ir J fwd- W'n, I' l. 1,291 Ml "P M f WW x $2 3% 52 3% 2& 5 .222 $9 2551a r 3% H mm; brrre non DOHSETT Roan SN'NELVERNON BRRBEQ 2 I H, L, DOWSETT\ ET AL MOLD FOR THE PRODUCTION OF FEE-STRESSED REINFORCED CONCRETE SLEEPERS Filed March 23, 1944 2 Sheets-Sheet 2 HHRRI L vT'rEuon DONSETT Rmnmsnvwenvevzuou BAR BER R x Q ww wwjww Patented Apr. 2, 1946 MOLD FOR THE PRODUCTION OF PR E STRESSED REINFORCED CONCRETE SLEEPERS Harry Lyttelton Dowsett and Ronald Samuel 7 Vernon Barber, Malvern, England, assignors to Dowsett Engineering Construction Malvern; England, a British company Limited,

Application March 23, 1944, Serial No. 527,798

In Great Britain April 8, 1943 7 1 Claim.

This invention consists of improvements in the production of' pre-stressed reinforced concrete sleepers, and in this specification the term sleepers includes similar beams.

Processes have been proposed for the manufacture of articles of reinforced concrete in which reinforcing wires or like members of high tensile steel ,are subjected (prior to and during the setting of the concrete) to a high tension approaching the elastic limit of the steel so that when the concrete has'hardened and the externally-applied tension on the reinforcing wires is discontinued, the Wires apply high and permanent compression forces to the concrete. In the application of that process to the mass production of sleepers the problem arises of assembling the molds and of dismantling the molds and the cast sleepers and the object of the present invention is to provide means, for dealing with that problem. It should be explained that in a mass production scheme not only is it essential that the reinforcing wires shall pass through the end plates of each-mold so that the wires are properly located in the mold and the necessary high tension can be applied to the wires by appropriate fittings, but it is also essential that the end plates can be readily assembled in operative position and can be readily dismantled when the casting operation is complete. s r i The reinforcing wires run the whole length of the production line which accommodates a considerable number of molds in series. At each end of the production line standards are arranged in which the parallel reinforcing wires are supported and means are provided forapplying high tension to the reinforcing wires. At an appropriate assembly point the open-ended mold is placed around the wires. The operator then applies the two end plates as above described at each end of the mold so as to locate each wire and after the assembly of the mold, the mold (either before or after filling with concrete) is ready for its journey along the production line.

When the casting of the sleeper is completed and the mold is to be dismantled, it is a simple task to withdraw each end plate at each end of the mold leaving the wires ready for cutting (say 2y oxy-acetylene flame).

In the arrangement described above it will be appreciated that there is no risk of escape of concrete because the openings formed by the slots of one plate are sealed by the other plate. The use of wires of square section enables a complete seal to be obtained. v

In the arrangement above described the two end plates were detachably secured in position In an alternative arrangement one of the end plates (conveniently the one having vertical slots) is fixed to the mold while the other end plate is detachable. In the case where one end plate is secured to the mold it will be understod that the mold is brought into proper relationship with the reinforcing wires, the wires of each vertical set being introduced into the appropriate slots. In the case of detachable end plates itwil'l be understood that they can either be bolted on to the mold or they can be slid into guides at the ends of the molds.

In an embodiment of the invention found to be eminently suitable each of the two plates has a series of parallel slots extending from one edge of the plate (say the top edge) for an appropriate distance across the plate. Then each of these slots has a series of lateral extensions in the form of very short branches; or spurs adapted to accommodate the reinforcing wires in their final positions. 1

The other plate is similarly provided with a setof parallel slotsextending from its edge but in this case the lateral branches or spurs extend in the opposite direction from those in the first plate. When the ,two plates are placed with their fiat faces in contact and with their main slots coinciding, said plates are not themselves in register with one another but are slightly staggered (i. e. those edges of the plates which are parallel with the main slots are slightly displaced from' one. another). The arrangement is such that when the two plates are slid to bring them into register, the main slots are no longer in register but the two sets of short lateral branches now engage the reinforcing wires and may be caused to grip these wires securely. The slotted end plates in their first position (with the long slots coincident) may be temporarily held face to face by bolts passing through slots, and it will be understood that these slots may be laterally extended to permit the relative sliding of the two contacting plates and the bolts may be tightened up when the plates have been brought into their final position. Considering the case where each sleeper is to have ten reinforcing wires arranged in two verti cal rows of three wires and two vertical rows of two wires, each plate may have four long slots extending from the upper edge. Thev two outer and longer slots have three short lateral branches on their right-hand side at the same vertical height as the reinforcing wires which they are to receive. The two shorter slots have each two plates are then securely .ibolted together.

i the end plates.

ready to receive the other four wires. The other plate is similarly constructed but in this case the main slots are laterally displaced from those of a the first plate by rather more than. the width of g a main-slot and in this case the'branches are on the left-hand side of the main slots. As del 2 H 2,397,728 little branches (likewise on their right-hand side) scribed above certain bolt holes for the securingv bolts are in the form of oblong. horizontal slots. f

In this example the operation asfollows. The reinforcing wires are set up with light tension. The two contactingend plates with their main slots in coincidence are passed upwards so slid in relation to one another so that-all the wires are gripped on both sides by thelatcral: branches. At first the grip may be slight. Be-

fore the casting of'the concrete final tension is applied to the wires and the-end plates are then pressed firmly togetherii. 1e. .sli'd relatively to effect the finaly'gripping of the wires) and the This final gripping of the wires may be carried out before the concrete is poured into the molds or alternatively it may be carried out before the concrete sets.

Y It will be understood that during the operation of filling the mold with concrete grout, or after the mold has been filled, there is a possibility that'grout may leak betweenthe wires and Each end plate may therefore be provided at its lower end with a horizontal flange upturned at its edges-so as to form a tray or trough to catch any grout which may leak from the end of the mold. The trough at the bottom of the inner end plate may face inwardly and the trough of the outer end plate may face outwardly. i

In the accompanying drawings:

Figures 1 and .2 areend elevations of end plates embodying a preferred form of this invention;

Figure .3 is an end elevation showing the two end plates of Figures 1 and 2 in their final position gripping and locating the wires, and

Figure 41s .a'perspective view showing the reinforcing wires and a mold having attached thereto end plates with troughs at their lower ends.

Referring to Figures 1 and 2, the end late 22 shown in Figure 1 has four parallel slots 23, 24, 2.5,:26 extending from the top edge of-the plate vertically downwards for an appropriate distance across the plate. Then each of these slots 23, 24, 25, 28 has a series of lateral extensions in the formuof very short branchesor spurs I23, I24, I and 126 adapted 'to accommodate the reinforcing wires in their final positions. The other plate 21 shown in Figure 2 is similarly provided with four parallel slots 28, 2'9, '30-and 3l extending from the top edge vertically downwards for an appropriate distance across the plate but in this case the lateral branches or spurs I28, I29, I30, |3l extend in the opposite direction from those in the first plate, In this: case the bolt holes 32 are in the form of short horizontal slots. When the two plates 22 and 21 are placed with their fiat faces in contact and with their main slots coinciding, the vertical edges of the plates are slightly displaced from one another but the two plates: can'be readily passed over the reinforcing wires. When the two plates are relatively moved to bring them into register the two sets ofjshort lateral branches engage the reinforcing wires and, grip them securely.

Figure 3 shows the two end plates in their final position where the reinforcing wires are firmly gripped and located.

Referring to Figure 4, the body of the mold 33 is a hollow open-ended trough. It has horizontal flanges 34' along the upper lateral edges and these flanges carry the transverse bars 35 which support the upright pins 36 which form in the concrete sleeper the holes for the holdingdown bolts.

At each end of the mold 33 the side walls have flanges-3:1 having bolt holes to enable the end in Figure 4 are placed back to back, they can be similar in form when originally made (subject to the positioning of the bolt holes).

We claim: 7

A mold for the production of pro-stressed reinforced concrete sleepers comprising an openended trough-shaped body portion, adapted to accommodate a number of parallel reinforcing wires stretched within and extending longitudinally of said mold and at each end of the mold two end plates each havin a series of parallel slots extending from one edge of the plate, each of these slots in one plate having a series of lateral extensions in the form ofvery short branches extending in one direction while each of the slots in the second plate has very short lateral branches extending in the opposite direction from those in the first plate, means for applying the plates to the endof the mold to accommodate the wires in the slots and means to impart relative lateral movement to the end plates to bring the main slots out of register but to cause the wires to be gripped in the said'lateral extensions.

HARRY LYTTELTON DQWSETT, RONALD SAMUEL VERNON BARBER

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