The object of the invention is a stiff adjoint piece for joining concrete piles, particularly reinforced piles, end to end so that those ends of the concrete piles which are joined together comprise base plates that correspond to the cross-section of the pile, the joining means being attached to the base plate and consisting of: projecting locking bars which comprise broad ends provided with at least one stop face pointing towards the said base plate; of locking blocks on the counterpart, provided with a cavity that receives the locking bar, and with a groove transversal to the length of the locking bars, the groove extending as a toroid around the cavity, and with a hole extending from this groove at least approximately in a tangential direction; and of an insert pin which, when the pile joint is made, is driven into the hole so that it turns around the locking bar in the cavity, guided by the circumferential face of the groove, whereby it is simultaneously locked permanently in place because of plastical deformation.

In Finland and other parts of the world, long concrete piles are provided with adjoint pieces to facilitate handling and transportation.

An adjoint piece of the type defined above is described in publication FI-76169, and slightly similar joints are described in publications FI-57293 and FI-58669. All these joints employ fork-like locking means in which only very minor locking deformation takes place when they are put in place. These pile joints which are known from before and which are used for the coiresponding purpose have numerous disadvantages. First, the structure of the known joints is complex and expensive to implement, or unreliable in use because the joint tends to open under the effect of concussions that occur when the pile is driven to the ground. Consequently, material costs have been great in the constructions used earlier. Furthermore, clampjoints in these earlier constructions had to be welded to the base plate by using load-bearing seams, whereby it was necessary to use thick base plates because of thermal strain. The disengagement or loosening of the joint during driving down again caused all kinds of other problems and, thus, different costs.

The former patent application FI-852020 of the applicant tried to solve the above- mentioned problem by using a long insert pin which was bent into a doughnut- shaped channel which was jointly formed by the groove of the locking block and the groove of the locking bar opposite the former. Such a pile joint is good because of

its great length of deformation which prevents it from opening under any conditions. Because, in publication FI-852020, the joint is implemented by opposite grooves, i.e., by clamping in the direction of the toroid radius, its structure, however, has the same problem as the structures of the other publications mentioned above. All these known structures require that the base plate of the pile be carefully machined into a planar form of an accurate thickness because, otherwise, the joint will either be loose or the insert pin will possibly not go into its place. Disregarding the machining, the welding of the sheet casing of the pile end box to the base plate can cause deformation in the base plate with the consequences described above.

The object of the invention is to provide a simpler, stiff adjoint piece for reinforced piles which does not have the disadvantages of the earlier known, corresponding joints. A more detailed object of the invention is to provide a stiff joint with low material costs which can be manufactured with low labour costs. Another object of the invention is to provide a pile joint with clamping which will not become loose even after a great number of strikes. Another object of the invention is to provide a pile joint solution with clamping means to which reinforcement bars can be attached by threading or welding. Another object of the invention is to provide a pile joint solution which simply provides a tight mutual joint for the piles.

The disadvantages of the known structures can be eliminated and the objects of the invention defined above can be accomplished by a pile joint which is characterised by what is defined in the characterising clause of Claim 1.

The pile joint according to the invention can be used to obtain numerous advantages. Because of the simple construction, considerable savings are obtained in material and labour costs. A clampjoint is obtained which does not become loose even after a lot of striking because a very large locking deformation is created in the insert pin when it is installed in place. This construction also prevents disadvantages caused by water which freezes in the lock housing on the pile-driving site when the joint is made. In addition, a clampjoint is provided which creates a tight joint between the piles, both in a case where the locking block is attached to the inner face of the end part, and particularly in a case where the locking block forms a stop face or a part of it for the joint.

The invention is described in detail with reference to the appended drawings.

Fig. 1 is a general top view of the end of a reinforced concrete pile provided with the joint members according to the invention, taken in direction I of Figs. 2 and 3, and as a partly cut view along plane II-II of Figs. 2 and 3.

Fig. 2 presents a detailed view of the members providing the joint according to the invention as a longitudinal section of the pile along plane III-III of Fig. 1, as the first embodiment thereof.

Fig. 3 presents a detailed view of the members providing the joint according to the invention as a longitudinal section of the pile along plane III-III of Fig. 1, as the second embodiment thereof.

Fig. 4 presents the embodiment according to Fig. 3 as an otherwise similar but smaller view than in Fig. 3 with the ends of the pile apart.

In Figs. 1, 2, and 3, the pile joint according to the invention is generally marked reference number 1. Mutually similar joint bisegments la and lb form a double joint placed end to end, thus forming the joint between the joint ends of the piles. Joint sections la and lb is made from thick enough steel plate and of locking parts in the manner described below. Generally, each joint bisegment comprises the same amount of female joint parts and male joint parts placed symmetrically so that two pile ends provided with similar joint bisegments are placed tightly against one another. Fig. 1 shows one such embodiment comprising female joint parts in two opposite corners and male joint parts in the two other opposite corners. Other arrangements can also be used.

The end of the pile comprises, in a conventional way per se, base plate 5 with the same cross-sectional shape as the pile, for example square, from which margin collar 7 on the level of the pile outer surface generally projects to the side of the pile, whereby a box-like part is formed, covering the end of the pile, and base plate 5 constituting the end face of the pile. Furthermore, the pile comprises, inside the concrete, at least longitudinal reinforcement bars or starter bars 6.

The structure described above contains male locking bars 2 extending from base plate 5, female locking blocks 3 and insert pins 4 inside the end of the reinforced pile, according to tl e invention. Fig. 2 presents an embodiment comprising base plate 5 which is provided with holes 10 through which only locking bars 2 and particularly their wide outer ends 20 can be accommodated. Locking blocks 3 are

attached, against holes 10, to base plate 5 on its surface 21 which is inside the concrete pile and thus points away from the other joint bisegment coming to the joint. Locking block 3 is provided with a hole or cavity 9 through which locking bar 2 can go, and which is aligned with hole 10 of the base plate. In this way, the tensile stress that is caused on the locking blocks by joint 1 is exerted directly to base plate 5, which is an advantage of this embodiment. One disadvantage again is the requirement of the above-mentioned high machining accuracy. Starter bars 6 in the longitudinal direction of the pile are attached directly to locking blocks 3 by welding or threading. Correspondingly, locking bars 2 run through the holes in the base plate and are attached directly to starter bars 6 by welding or threading. In addition, the locking blocks and the locking bars are generally also welded to the base plate, as shown in the figures.

According to the invention, locking block 3 is provided with groove 8 that surrounds the entire cavity 9 in a toroid-like way on the circumferential face of the cavity, the circumference of the groove being transversal and typically peφendicular to the length of the locking bar and thus to the length of the pile. According to all the embodiments of the invention, this groove comprises annular stop face 24 which points away from end plate 5 of said joint bisegment lb, i.e., towards the interior of the pile. The stop face is preferably planar and typically peφendicular to length L of the pile. Locking bar 2 is preferably provided with groove 1 1 that is transversal to the length of the pin and thus to the length of the pile, the groove comprising annular stop face 21 which points towards the base plate to which locking bar 2 is attached. Upon the locking bar penetrating into cavity 9 when joint 1 is assembled, grooves 8 and 1 1 are placed against one another, forming a circumferential channel that surrounds locking bar 2, the cross-sectional shape of the channel corresponding to the cross-sectional shape of insert pin 4. According to the invention in particular, the cross-section of the insrt pin and the diameter and location of grooves 8 and 1 1 are dimensioned so that the insert pin is tightly placed, in grooves 8, 1 1, distinctly between stop face 24 of locking block 3 and stop face 21 of locking bar 2. In this way, when driven inside the grooves, insert pin 4 clamps joint bisegments la and lb of the piles to be joined towards one another, forming a tight pile joint 1 without clearance. The other surfaces of grooves 8 and 1 1 are only significant in shaping the locking pin when it is driven in place when the joint is made. This design provides a tight and accurate guiding for insert pin 4 and, thus, a strong joint between the ends of the piles. In locking bar 2, it is also possible to only use its head 20 which is wider than its arm and which comprises the said stop face 21 ; this embodiment not being shown in the figures, whereby the insert pin penetrates into the

circumferential channel formed by groove 8 of the locking block and stop face 21 , as described above. However, this structure is not quite as reliable as the one formed by aligned grooves 8, 1 1.

Furthermore, each locking block 3 comprises hole 12 which extends from groove 8 essentially in the tangential direction to the outer face of the pile or to the outer face formed by sheet casing 7. This hole is preferably lined, for example, with metal tube 13 with respect to the concrete. Insert pins 4 according to the invention are long or bar-like parts which are straight before installing in place. The length of the insert pin is at least as high as depth H of the hole and the essential part of the circumferential length of the locking block groove 8 together; typically, the length of the insert pin is as high as the depth of the hole and half of the said circumferential length together. The length of the insert pin is preferably as close as possible to the sum of the hole depth and the said circumferential length. The cross- sectional shape of insert pin 4 remains, at least with respect to the essential part of its length, unchanging or integral, starting from initial end 22 of the insert pin which is pushed ahead through hole 12 to groove 8. The cross-section of the insert pin is preferably unchanging along the portion of its length that corresponds to the length that bends in accordance with groove 8. For example, if the insert pin is so long that it bends and fills the entire circumferential length of groove 8, the cross-section of the pin is mainly unchanging along the length which is as long as the circumferential length. The cross-sectional shape and/or the cross-sectional area of the insert pin can vaiy to the extent of hole 12, i.e., starting from the other ram end; the pin is preferably thicker along this length. In this case, the insert pin better withstands the push exerted on the ram end which is used to place the pin in the channel. The cross-section of insert pin 4 is round, angular, or oval. The cross- section of insert pin 4 is preferably rectangular, whereby it comprises parallel, opposite surfaces 28a and 28b which are placed against said stop faces 21 and 24. The invention does not prevent the insert pin from being slightly sphenoid in the longitudinal direction, whereby the pin penetrates easier into its place and clamps the pile ends towards one another. In this case also, the cross-section remains unchanged. According to the invention, this wedge-sized property is arranged to be formed between opposite surfaces 28a and 28b of the insert pin, whereby the wedge-sized property is placed between stop face 24 of the locking block and stop face 21 of the insert pin. Generally, the wedge-sized property extends approximately evenly along the entire length of the insert pin which is bent into a toroid and is small in quantity, for example, the angle of wedge between surfaces 28a and 28b is about 10° at the most, generally even smaller, such as less than 5° _,

possibly only 3° - 4° or 1° - 2°. Generally, there is no wedge-sized property in insert pins 4 in the direction of the toroid diameter formed by grooves 8, 1 1, and thus of the plane of base plate 5, but the insert pins have even widths on the above- mentioned length, because the wedge-sized property is not advantageous here. The wedge-sized property is thus not the same as rounding or bevelling of the end of insert pin 4, which guide and facilitate the penetration of the insert pin into the grooves and which aie presented in Fig. 1. In this way, the insert pin can be used to provide the joint described below.

Piles are extended by pushing the piles provided with the above-mentioned joining parts together end to end, whereby locking bars 2 penetrate from locking blocks 9. With base plates 5 of pile joints 1 squeezing tightly together and, in the embodiments of Figs. 3 and 4, front surfaces 26 of locking blocks 3 squeezing tightly against outer surface 27a of base plate 5 of the opposite joint bisegment la, the joint is clamped by driving insert pins 4 according to the invention into each clampjoint which is comprised of a locking bar and locking blocks. When insert pin 4 is pushed in place in the direction of arrow 19 in Fig. 1 , it is shaped according to the channel formed by grooves 8 and 1 1 , particularly guided by the circumferential face of groove 8 in the locking block, into an annular strap around locking bar 2, as shown by the line of dots and dashes in the upper right hand corner in Fig. 1. As already described above, the larger the part of the circumferential length of the circumferential or toroidal channel is filled by the locking bar, the more advantageous it is. In any case, the locking bar should fill an essential part of the circumferential length surrounding locking bar 2, whereby half of the circumferential length can be considered minimum. At the same time, insert pin 4 locks joint bisegments la and lb together at said stop faces 21 and 24 in a phenoidal way, and, because of the large plastical deformation, it is locked into the joint without becoming loose, whereby the joint stays good even after numerous strokes.

Figs. 3 and 4 present a particularly preferred embodiment of the invention. It comprises holes 25 made for locking blocks 3 in base plate 5, the diameter of the holes being so dimensioned that the locking block fits through the base plate at least at the end part which points outwards from this joint bisegment lb. The locking block is welded to the base plate at a spot where front surface 26 of the locking block is flushed with outer surface 27b of the base plate. In this solution, it is not necessary to use a machined plate as the base plate of either joint bisegment la and/or lb but, generally, a piece cut from a plate can be used as such. In this case, the thickness of the base plate has no significance because distance T2 between stop

face 24 of locking block 3 and front surface 26, and distance T 1 between stop face 21 of the locking bar and shoulder 29 define the position of the stop faces in joint 1 , no matter what the thickness of base plate 5 is. Consequently, it is necessary to accurately machine only locking blocks 3 and locking bars 2 in this structure. The good clamping accuracy of joint 1 mentioned earlier can be provided by this structure in a simple and advantageous manner. Distinguished from this, a shoulder which is not presented in the figures can be provided on the outer circumference of the locking block, pressing against the above-mentioned inner surface 21 of the base plate. In this case, front surface 26 of the locking block can be arranged at such a distance from this shoulder that it is always placed at least level with outer surface 27b of the base plate or so that it slightly projects therefrom. Alternatively, base plate 5 and a slightly too long locking block 3 attached thereto can be machined from the outside, after the weldings, to form an integral surface 26, 27b, whereby the spot of welding is controlled from stop face 24. This requires machining but less than in prior art solutions, and the accuracy is very good because welding can no longer influence the accuracy.

The embodiment described above is only one advantageous embodiment of the invention and those skilled in the art understand that numerous modifications can be made thereto without deviating from the scope of the invention. For example, the insert pin can be a self-locking, annular spring. Similarly, the grooves of the locking means can have a rectangular cross-section, they can be shaped like parts of a polygon or they can be round or V-shaped and their longitudinal section can be straight or V-shaped. The insert pins have the same or slightly modified cross- section and/or longitudinal section so that a desired clamping and plastical deformation aie achieved. Thus, the scope of the invention is defined within the inventive idea described in the appended claims.