This invention relates to an apparatus for manufacturing prestressed. concrete piles or beams, in particular railway ties, which apparatus comprises a casting mould which is divisible into segments each having the length of a beam to be formed, with wire tensioning devices being arranged at the ends of the casting mould for tensioning the prestressing wires running through the segments, which prestressing wires, upon hardening of the concrete poured into the casting mould, can be cut between the respective segments by means of a cutting device to obtain separate prestressed beams of a length determined by the mould segments .

In the manufacture of prestressed concrete piles or beams, it is known to use casting moulds of a length a few times the length of a beam to be manufactured. The length of the moulds can be 100-200 m. The mould is divided into segments of a desired length by means of end partitions with apertures provided therein for passing the prestressing wires therethrough. The distance between two end partitions is 25-30 cm and the end partitions are retained in this position by spacers. After the concrete has been poured into the mould segments so formed - but not, of course, into the space between adjacent end partitions - and the concrete has hardened, the prestressing wires are cut between adjacent end partitions by means of a welding torch, for instance, and the separate beams can be removed from the segments of the mould. In the case of piles or beams of a length of 20 m, for instance, and a mould of a length of 100 m, there are five mould segments and four interspaces between adjacent segments, bounded by end partitions. In that case, the loss of useful production space within the mould and prestressing wire is still limited. However, if the length of the beam is selected to be shorter, for instance about 250 cm, which is the length of railway ties, the loss of prestressing wire and production space within such a mould is considerable. The object of the invention is to provide an apparatus for manufacturing rela-

tively short beams or railway ties, in which these drawbacks are overcome and no end partitions are required.

To that end, the apparatus according to the invention is characterized in that adjacent mould segments are inter- connected by at least one open passage of trapezoidal cross- section surrounding the continuous prestressing wires, while the mould is supported by supporting means which can be moved vertically and vertically directed supporting rods are provided at each open passage between adjacent mould segments, which supporting rods extend through the bottom of the mould and can be moved in vertical direction separately from the mould, the arrangement being such that after hardening of the concrete poured into the mould, the interconnected beams remain supported by the supporting rods during mould release by downward displacement of the mould.

In contrast with the known apparatus, the beams to be manufactured are disposed in the mould with their end faces substantially in end-to-end abutment, these end faces being interconnected via a transitional area of a trapezoidal cross- section which is considerably smaller than the cross-section of the beam or tie and which includes all prestressing wires. Thus, the separate segments are in communication within the mould. Separate ties are obtained by making a saw cut in the transitional area, requiring not only the prestressing wires but also the concrete surrounding the prestressing wires to be cut. This sawing operation is performed after the ties have been released from the mould by lowering the mould while the hardened ties remain supported in the cast position by verti¬ cal supporting rods. This provides the possibility of support- ing the long "pile" built up from a plurality of intercon¬ nected ties, for instance by means of portals which can be moved in the longitudinal direction of the mould, so that the composite concrete element can be moved in the longitudinal direction to the cutting device provided at the end of the mould for sawing through the concrete element at the transi¬ tional area between two adjacent ties. In this manner, the

loss of prestressing wire and production space within the mould has been reduced to practically nil and no end parti¬ tions are required.

The characteristic feature of the ties manufactured by means of the apparatus according to the invention is that the end faces comprise projections approximately trapezoidal in cross-section. In order to reduce the amount of concrete to be sawn through, each end face may comprise two, rather than one, trapezoidal projections disposed on opposite sides of the median plane of the tie.

Further particularities of the apparatus according to the invention are described in the subclaims.

One embodiment of the apparatus according to the inven¬ tion and the tie manufactured by means of such apparatus will now be explained, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 shows a tie in cast position;

Fig. 2 is a plan view of the tie according to Fig. 1; Fig. 3 is a side elevation of a tie according to Fig. 1; Fig. 4 is a section of an apparatus according to the invention taken in the saw plane Z of Fig. 1;

Fig. 5 is a view taken on the line V-V of Fig. 4; Fig. 6 is a view taken on the line VI-VI of Fig. 4; Fig. 7 is an enlarged view of a supporting frame accord- • ing to Fig. 5; and

Fig. 8 is an enlarged view of a supporting rod according to Fig. 6.

Fig. 1 shows a tie 1 to be manufactured in the casting position. The profile of the tie is determined on the basis of the strength and rigidity requirements the tie 1 must _, meet . Shown on opposite sides of the tie 1 are adjacent ties 1 ' which are connected to tie 1 via a transitional area 3 before the ties 1, l ¹ are separated from each other by making a saw cut in planes Z. The ties 1, 1' are manufactured in a casting mould whose shape is naturally determined by the profile of the ties and which extends in longitudinal direction over the

length of a multiplicity of ties, for instance thirty-five. The mould is accordingly divided into segments of a length L which corresponds to the length of the tie to be manufactured, i.e. approximately 250 cm, said segments being interconnected via transitional areas 3. The transitional area 3 has a cross- section in the shape of a trapezoid 4, as indicated by dotted lines in the side elevation of Fig. 3. Consequently, after making the saw cuts in planes Z, the end face 7 of a tie comprises a projection 4 of trapezoidal cross-section, which includes all prestressing wires 6. To reduce the amount of concrete to be sawn through, it is preferred that instead of a- single trapezoidal projection, two trapezoidal projections 5 are provided, disposed on opposite sides of the median plane of the tie 1, as shown in solid lines in Fig. 3. It will be clear that in that case the transitional area 3 also has a cross-section in the form of the two projections 5.

Fastening devices 2 such as plugs must be cast along with tie 1, so as to permit bolts to be screwed into them for securing the rail tracks to the tie. An apparatus for manufacturing the ties according to

Figs 1-3 is shown in Figs 4-6. Fig. 4 is a section taken in the saw plane Z of Fig. 1. The elongated casting mould 16 is supported by a series of supporting frames 10 anchored to the floor by means of bolts 11. Each supporting frame 10 essen- tially consists of two side plates 12 interconnected by means of transverse connections 13, 14, 15. The transverse connec¬ tion 13 consists of a crossbeam on which the mould 16 is mounted. The dotted lines within the mould indicate the profile 17 of the tie, while the solid lines indicate the transitional area 3 in section, which section corresponds to the shape of the trapezoidal projections 5. The mould 16 is in the casting position. Mounted in the crossbeam 13 adjacent the end faces are supporting pins 18 comprising cylindrical projections 19. The projections 19 are locked in a vertical slot 20 provided in the side plates 12.

Extending on opposite sides of the mould throughout the length thereof, is a control plate 21 provided with slots 22 extending substantially obliquely (Fig. 5) in which the projection 19 is mounted. The control plate 21 can be moved to and fro in horizontal direction by means of a hydraulic cylin¬ der 23 and guide rollers 24, 25 provided at the top and the bottom of the control plate 21 in each supporting frame 10. If the hydraulic cylinder 23 is energized, the control plates 21 arranged on opposite sides of the mould 16 will move to the left in the view of Fig. 5, the obliquely extending slots 22 forcing the projections 19 received therein to move downwards in the vertical slot 20 provided in the side plates 12 of each supporting frame 10. The mould 16 which is con¬ nected to the crossbeams 13 is thereby moved downwards towards the position shown in Fig. 4 at 16' with the crossbeams 13 being in position 13' . The projections 19 are then disposed at the lower end of the vertical slots 20.

It will be clear that upon downward displacement of the mould, the hardened ties will also move downwards unless they are somehow retained in the original casting position.

The means of supporting the hardened ties in the casting position are formed by vertical rods 34, supported in each frame 10 by a supporting beam 14. These supporting rods 34 are arranged in each frame 10 adjacent the transitional area 3 (see Fig. 1) . The rods 34 extend through the crossbeam 13 and in the upper position the end faces of the rods 34 are dis¬ posed precisely at the level of the bottom surfaces of the trapezoidal projections 5. The supporting beam 14 for the rods 34 can be moved vertically in a manner corresponding to the displacement of the crossbeam 13. The end faces of the sup¬ porting beam 14 are provided with pins 30 having connected thereto a cylindrical projection 31. The projections 31 are mounted in a vertical slot 32 provided in the two side plates 12 of a frame 10. Arranged under the supporting beam 14 in each frame 10 is a pivot 15 having mounted thereon two cam discs 33 abutting on the inside against the side plates 12.

The cam discs 33 are fixedly connected to the pivot 15. The cam discs 33 (see Fig. 7) comprise a slotted curved track 35 in which the projection 31 of the supporting beam 14 is re¬ ceived. By pivoting the pivot 15, the projections 31 are forced to move vertically downwards in the slots 32, whereby the supporting rods 34 are pulled from their upper position and finally reach the retracted position shown in dotted lines in Fig. 4. The path traveled by the supporting rods 34 in vertical direction is shorter than the vertical path of travel of the mould 16.

The pivoting movement of the pivot 15 is effected by a crank 36 connected to pivot 15, the end of the crank 36 being, connected to a hydraulic cylinder (not shown) . With the assis¬ tance of this hydraulic cylinder all pivots 15 of the various supporting frames 10 can be pivoted simultaneously, so that in each supporting frame 10 the supporting rods 34 can be moved in upward or downward direction simultaneously. Fig. 6 shows the position in which the ties 1, still interconnected at the transitional areas 3, are supported in hardened condition by the supporting rods 34, while the moulds 16 (not shown) are arranged in the lower position.

The manufacture of ties of prestressed concrete using the apparatus according to the invention comprises the following steps: 1. The mould or falsework 16 is set in the upper position as are the supporting rods 34. The mould is cleaned and oiled while fastening devices 2 are arranged in the mould at the appropriate places.

2. Prestressing wires 6 are arranged in the mould 16, tautened and subsequently adjusted to the required pretension.

3. The mould is filled up with concrete which is subse¬ quently packed, the concrete is covered and allowed to harden.

4. After the hardening stage, the mould 16 can be moved downwards into the position shown in Fig. 4. The intercon- nected ties are then supported in the cast position by sup-

porting rods 34 engaging the bottom surface of the projections 5 (see also Fig. 6) .

5. In this position, the support of the still intercon¬ nected ties is taken over by means suitable for the purpose, such as portals which are movable along the mould, from which portals the ties 1 are suspended in some manner or other. Then the supporting rods 34 are moved down.

6. Then the prestressing wires are released and cut through or ground off at the two ends of the mould. 7. Using the supporting means as described hereinabove

(for instance mobile portals) , the concrete elements consist¬ ing of the interconnected ties are moved in the longitudinal direction of the mould and then cut or sawn through at the transitional areas 3, so that separate ties 1 are obtained.