The present invention relates to an apparatus and a method for joining first and second at least partly mutually over- lapping reinforcement rods by means of a wire, and a combi¬ nation of a joint between reinforcement rods and a particular knot.

Reinforcement rods are traditionally tied together with the aid of simple, manually manipulated tools, such as pliers, by means of which, ends of a wire length or legs of a U-shaped wire clip, which have been manually positioned around the overlapping reinforcement rods or an intersection of the reinforcement rods, are intertwined.

The traditional manual tying or joining of reinforcement rods suffers from two serious drawbacks: the method is extremely time-consuming, and thereby expensive, and it is liable to cause strain injuries to the person involved. On the other hand, the manual joining of reinforcement rods is a very flexible method and it provides a number of advantages such as the ability to perform substantially uniformly joined reinforcement rods even though the reinforcement rods are of different diameters and have different shapes and different cross sections, and the ability to add substantially the same tension of the wire length or U-shaped wire clip used in the joining operations. Furthermore, the manual method will typically provide a tight joining due to the fact that it is possible to press the reinforcement rods together while arranging the wire length or the U-shaped wire clip around the reinforcement rods and while twining the ends of the wire length or the legs of the U-shaped wire clip together, re¬ spectively. Additionally, the manual joining of reinforcement rods does not require much space around the overlapping reinforcement rods or the intersection of the reinforcement rods to be manually joined. Finally, the person who performs the tying or joining will typically adjust the length of the

wire length used before joining the reinforcement rods or cut away superfluous wire after the intertwining of the ends of the wire length or the legs of U-shaped wire clips so as to prevent long wire ends to stick out from the joining. Such long wire lengths extending out of a concrete structure may cause discolouring of the concrete shuttering due to corro¬ sion of the wire lengths or even result in damage to the concrete due to the corrosion of the wire and entering of water into the concrete.

A number of automatic tying machines have been developed to replace the task of manually joining reinforcement rods but still none of the machines have been able to comply with all the above-mentioned demands to this task. Examples of known machines for joining reinforcement rods are disclosed in US 4.640.319, EP-A1-0.190.071, US 3.391.715, US 4.117.872, US

4.362.192, DE-A-2.223.099, GB-A-2.171.038, WO 88/01671 and WO 92/06260. In the following, the machines disclosed in WO 88/01671 and WO 92/06260 will be discussed in greater detail as these machines are considered to be representative of the machines disclosed in the other publications mentioned.

The machine disclosed in WO 92/06260 includes a device having a curved wire-guiding surface defined within two curved jaws which are rotatably mounted to a housing. The curved jaws should be positioned around the reinforcement rods to be joined in such a way that the guiding surface surrounds the intersection of the reinforcement rods. A wire is fed from a coil into this curved wire-guide which will bend the wire around the intersection. A wire length is cut from the coil and the free ends of the wire length are led into a rotatable twisting head and are intertwined by means thereof.

WO 88/01671 discloses a lashing machine using preformed U- shaped wire ties for joining reinforcement rods. The U-shaped wire ties are singly dispensed from a magazine in such a manner that the legs thereof embrace the intersection of the

reinforcement rods to be joined. The legs are received in a twisting head performing the intertwining operation.

All the above-mentioned machines for joining reinforcement rods use the conventional knot with a single loop.

While the known machines undoubtedly provide a number of advantages compared to the manual method, there is still a need for an apparatus which can combine the advantages of manual method, that is, inter alia, the possibility of press¬ ing together reinforcement rods prior to and during the tying operation, the possibility of working under unfavourable spatial conditions, and the possibility of effectively adapt¬ ing the process to reinforcement rods of different shapes and different cross-sections, with the obvious advantages of a fast and efficient automated operation. The present invention provides such an apparatus. The invention also relates to a method for tying together reinforcement rods in a new manner and using a new knot which confers added rigidity and strength to the resulting joined reinforcements; this method is most advantageously performed using the apparatus of the invention.

Thus, the present invention provides an apparatus and a method for joining reinforcement rods, wherein the reinforcement rods are joined in a even more stable way than is possible when manually tying or joining reinforcement rods as the present invention provides a new type of knot which is more stable and which has a higher strength than those previously used. It is almost impossible to manually tie this knot in a reasonable time period. - the reinforcement rods are pressed together while a wire length is arranged and bent around the mutually over¬ lapping reinforcement rods or around the intersection of the reinforcement rods and while the free ends of the wire length are intertwined. This ensures a tight joint of the reinforcement rods.

reinforcement rods of different diameters and with dif¬ ferent shapes and different cross-sections can be joined uniformly without the need for changing the configuration of the apparatus.

Contrary to the manual tying or joining of reinforcement rods, the present invention provides a method of joining reinforcement rods, which can be carried out in 2-3 sec. This should be compared to manual tying or joining which typically takes in the order of 20-25 sec.

In a first aspect, the invention relates to a method of joining first and second at least partly mutually overlapping reinforcement rods by means of a wire, said method comprising

arranging at least one substantially U-shaped wire length having a pair of leg parts and a connecting part, around the reinforcement rods at a mutually overlapping position thereof so that the leg parts of the wire length embrace the first and second reinforcement rods, the connecting part being arranged adjacent to the first reinforcement rod and such that the free ends of the leg parts extend in a first general direction, bending the leg parts of the U-shaped wire length in opposite directions around at least the second reinforcement rod so as to direct their free ends in a second general direction substantially opposite to the first general direc- tion, and subsequently twining the free ends of the leg parts so as to tighten the wire length around the reinforcement rods.

As will be understood especially from the following discus¬ sion of the drawings, this method results in a new type of knot which results in a number of advantages as indicated above.

The overlap of the first and second reinforcement rods is normally an intersection. In this situation it is preferred

that the leg parts of the wire length are bent around the second reinforcement rod on either side of the intersection as this results in a joint with an optimum stability. How¬ ever, the method of the invention is also useful in cases in which the reinforcement rods to be joined are arranged paral- lelly, e.g. where a reinforcement rod is to be extended.

The leg parts of the wire length are preferably bent around both the first and second reinforcement rods. This results in an very stable joint.

As will appear from the discussion of the drawings, the bending of the leg parts of the U-shaped wire length is suitably performed by forcing each of the free ends of the leg parts along a concavely curved guiding surface. The twining of the free ends of the leg parts is suitably per- formed by rotating a gripping member by which the free ends of the leg parts are held by means of holding hooks around which the ends are bent, which means that at a certain ten¬ sion of the wire as a result of the twining, the free ends will be able to overcome the fixing force resulting from the bend. Thereby, the tension of the joint can be suitably adjusted in a technically elegant manner so that the joint is sufficiently tight, but at the same time avoiding the risk of rupturing the wire.

In another aspect, the invention relates to an apparatus for joining first and second at least partly mutu¬ ally overlapping reinforcement rods by means of a wire, said apparatus comprising

means for supplying a U-shaped wire length having a pair of leg parts and a connecting part, - means for arranging the U-shaped wire length around the reinforcement rods at a mutually overlapping position thereof so that the leg parts of the wire length embrace the first and second reinforcement rod, the connecting part being arranged adjacent to the first reinforcement rod, and such

that the free ends of the leg parts extend in a first general direction, means for bending the leg parts of the U-shaped wire in opposite directions around at least the second reinforcement rod so as to direct their free ends in a second general direction substantially opposite to the first general direc¬ tion, and means for twining the free ends of the leg parts so as to tighten the wire length around the reinforcement rods.

Further details concerning the apparatus are evident from the discussion above and the following detailed discussion of the drawings.

As mentioned above, the invention provides what is believed to be a novel combination of a joint between two (or more) reinforcement rods and the particular knot with which the joint is made. In this aspect, the invention relates to an intersection of first and second reinforcement rods in which the rods are joined by means of a wire length having first and second leg parts and a connecting part and forming a knot in which

the connecting part is arranged on a part of the circum¬ ference of the first reinforcement rod substantially diametrically opposite to the intersection point between the rods, - the first leg part extends from the connecting part at a first side of the first reinforcement rod, taken relati¬ vely to the longitudinal axis of the first reinforcement rod, to the second reinforcement rod and around the second reinforcement rod in a direction transverse to the longitudinal axis of the second reinforcement rod, and from there returning to the first side of the first reinforcement rod and extending to the part of the cir¬ cumference of the first reinforcement rod which is sub¬ stantially opposite to the intersection point between the reinforcement rods, the first leg part thereby forming a

ference of the first reinforcement rod thereby crossing each other.

Thus, the present invention relates to an apparatus and a method which fulfil the above-mentioned demands. The appara- tus and the method can be used with great benefit in the above-described tying or joining operations and in all other operations joining elongated members in which the same strin¬ gent demands or less stringent demands apply. Additionally, the apparatus and the method according to the invention can also advantageously be used in joining operations in which the number of elongated members to be joined is in excess of two.

The invention will now be further described with reference to the drawings showing a preferred embodiment of an apparatus according to the invention and a joining of a pair of rein¬ forcement rods in accordance with the method according to the invention.

Fig. 1 shows a perspective partly cut away view of an em¬ bodiment of the apparatus according to the invention, Fig. 2 is a perspective view of the lower part of the appara¬ tus shown in Fig. 1 where a U-shaped wire length has been bent around an intersection of two reinforcement rods, Fig. 3 illustrates a mechanism in the apparatus shown in Fig. 1 which cuts the superfluous length of the wire length, Fig. 4 is a perspective view of the lower part of the appara¬ tus shown in Fig. 2 in which the ends of the leg parts of the wire length are twined so as to tighten the wire length around the reinforcement rods, Fig. 5 illustrates a mechanism adding a bend to free ends of a wire length and fixing the ends while intertwining,

Fig. 6 shows a pair of reinforcement rods joined in accor¬ dance with the invention, and

Fig. 7 shows in greater detail the magazine for storing U- shaped clips illustrated in Fig. 1.

Outer casing, inner casing, and bending means Fig. 1 shows a perspective partly cut away view of a pre¬ ferred embodiment of an apparatus 1 according to the inven¬ tion. The apparatus 1 comprises an outer casing 2 and an inner casing 4 telescopically displaceable in relation to the outer casing 2. The inner casing 4 is connected to the outer casing 2 via a carriage 9 which preferably has linear bear¬ ings.

The apparatus 1 comprises means for bending the leg parts of a U-shaped wire length. The means for bending the leg parts is in this preferred embodiment of the apparatus 1 a member 6 having concavely curved guiding surfaces 10 and 11 in the form of two grooves 12 and 13 into which each of the free ends of the leg parts is forced. The concavely curved guiding surfaces 10 and 11 are defined within a surface part 14 of the member 6 facing the inner casing 4. The member 6 is fastened to the lower part of the outer casing 2. The member 6 is further provided with an upwardly open rod-receiving groove 8 also defined in the surface part 14, the rod-receiv- ing groove 8 extending transversely, preferably substantially perpendicularly, to the longitudinally axis of the grooves 12 and 13. The member 6 may advantageously be of a replaceable type as constant use of the apparatus 1 may wear out the grooves defined in the upper surface side 14. Alternatively, the member 6 may be provided with replaceable parts defining the grooves. The member 6 may preferably be of a sinter compressed metal powder.

The apparatus 1 is also provided with means for pressing and keeping the reinforcement rods pressed together while the U- shaped wire length is arranged around the intersection of the reinforcement rods and the bending and the twining is performed. The inner casing 4 is lowered towards the member 6 so as to press the reinforcement rods together, thereby, fixing the reinforcement rods between the inner casing 4 and the member 6 in a suitable position for the subsequent bind¬ ing. One advantage offered by the above mentioned fixing by

the reinforcement rods (as will be described in greater detail with reference to Fig. 2, Fig. 3, and Fig. 4) and form an intertwining of the free ends of the leg parts. The length of the leg parts should, however, not be longer than that which is necessary, as long wire ends extending out of a concrete structure may cause discolouring of the concrete shuttering it may even result in damage to the concrete due to corrosion of the wire and introduction of water into the concrete. It is therefore important that superfluous wire length is removed. The mechanism providing this adjustment of the length of the wire length or wire clip will be described with reference to Fig. 3.

For the purpose of reducing the space taken up by the clips 26, the clips 26 are preferably arranged one after another in a stack of clips 28, the stack of clips 28 may be glued together or covered and kept together by plastic film in handy stacks of e.g. 100 clips. The force keeping the clips 26 together should, however, not be greater than that which allows the clips 26 to be easily separated from each other during performing of the joining. The clips 26 may be of steel, preferably with a surface treated to reduce friction forces and wear of the member 6. This surface treatment may preferably be application of a layer of cuber to the clips 26.

Clips magazine

In this preferred embodiment, the clips 26 are stored in a clips magazine 30 in a substantially vertically manner with the U-shaped part downwardly open. The clips magazine 30 is illustrated in Fig. 1 and shown in greater detail in Fig. 7. The clips magazine 30 is attached to the inner casing 4 and movable therewith. The clips magazine 30 comprises a top plate 29 for covering the clips magazine 30 and a bottom plate 31 having a hole 39 in one end. The top plate 29 does not cover the whole length of the clips magazine 30 and leaves an opening 41 in the top of the clips magazine 30 opposite the hole 39 in the bottom plate 31, so that the

piston rod 49 which is attached to the clip-supplying member 42. The pneumatic cylinder 48 is preferably a Bimba flatt-II FTM 0 19.

The clip-supplying member 42 is in its upper starting posi- tion guided by two stationary U-shaped profiles 51 and 52 located above the clips magazine 30, and is supported by two L-shaped profiles 53 and 54 when passing through the clips magazine 30 in which the clip replaces the clip being pro¬ cessed.

The length of the clip-supplying member 42 is preferably longer than the total length of the clip taken from the ends of the leg parts to the upper arch of the connecting part. This ensures that the clip-supplying member 42 is able to return to its starting position after processing a clip. The clip-supplying member 42 returns to its starting position by activation of the pneumatic cylinder 48, and a new clip is moved forward into the space left by the clip-supplying member 42 and is thereby ready for a new joining procedure.

The lower part of the clip-supplying member 42 preferably defines an substantially semicircular-shaped cut 55 corres¬ ponding to the U-shaped connecting part of the clips. To ensure that the clip does not slide aside when pushed down¬ wards, a groove (not shown in the drawings) is preferably formed in the semicircular cut 55, the groove preferably having a depth sufficient to receive about half the cross section of the clip wire in question.

As mentioned above, the movement of the clip-supplying member 42 is generated by the pneumatic cylinder 48 and the dis¬ placement of the inner casing 4 relative to the outer casing 1 is generated by the pneumatic cylinder 20. However, the force needed for the movement and the displacement may also be driven by other sources of energy, such as an electrical motor, a hydraulic cylinder, etc.

Binding assembly

One of the essential parts of the apparatus 1 according to the invention is a binding assembly 60 (see Fig. 2) which performs the intertwining of free ends 104 and 105 of the leg parts 106 and 107. Furthermore, the binding assembly 60 removes superfluous clip wire length from the leg parts 106 and 107 by cutting, and provides the leg parts 106 and 107 with a bend 90 having an angle, preferably in the order of 90°, fixing the leg parts 105 and 106 until the strength and tightness of the twined clip 108 is sufficiently large to overcome the fixing force. The binding assembly 60, shown in Fig. 1 - Fig. 5, will be described in further detail in following.

The binding assembly 60 is mounted within the inner casing 4 and displaceable therewith. The binding assembly 60 comprises a stationary part 62 and a first rotatable part 64 driven by a second rotatable part 66. The first rotatable part 64 is adapted to receive the free ends 104 and 105 of the leg parts 106 and 107 and to perform the intertwining of the leg parts when rotated. An outer surface of the first rotatable part 64 comprises a part forming a toothed wheel 68 meshing with a pinion 72 being a part of the second rotatable part 66. The pinion 72 is the output shaft of a pneumatic motor 70 mounted within the inner casing 4. The pneumatic motor 70 is pre- ferably a M 002 from Ingersoll-Rand.

The stationary part 62 comprises a central part 69 being adapted to the shape of the first rotatable part 64, bearings (not shown in the drawings) for the first rotatable part 64 and for the pinion 72, and a bottom covering plate 67 and a top covering plate 65 connected to the lower part of the inner casing 4 for partly encapsulating and protecting the elements within the binding assembly 60. The top and bottom covering plates are preferably metal plates, the first rota¬ table 64 and second rotatable 66 part are preferably of steel, and the bearing are preferably of bronze.

rod 102, the connecting part 108 and the joined parts 103 of the returning first and second leg parts extending on a part of the circumference 109 of the first reinforcement rod 101 thereby crossing each other.

The joining of the reinforcement rods 101 and 102 may be performed in the following way: the member 6 with the grooves 12 and 13 and the rod-receiving groove 8 are positioned under the intersection of the reinforcement rods 101 and 102 so that the second reinforcement rod 102 is at least partly received in the rod-receiving groove 8, the reinforcement rods 101 and 102 are pressed together by lowering of the inner casing 4, this lowering of the inner casing 4 being started by activating actuator means (not shown in the drawings) adjusted so that after the first gathering of the first and the second reinforcement rods 101 and 102 the rods are pressed together between the member 6 and the lower side of the inner casing 4 with a force of about 200 N, a U-shaped wire length of the above-mentioned type is supplied and arranged so that the leg parts of the wire length embrace the first and second reinforcement rods 101 and 102, and the connecting part is arranged adjacent to the first reinforcement rod 101 so that the free ends of the leg parts extend in a first general direction, while the U-shaped wire length is arranged around the reinforcement rods 101 and 102, the leg parts of the wire length are, from the moment they reach the grooves 12 and 13, simultaneously bent in opposite directions in the grooves 12 and 13 and around the second reinforcement rod 102 so that the free ends of the U-shaped wire length are directed in a second general direction (towards the upper part of the apparatus) in such a way that the free ends are gripped and subsequently cut to the right length and intertwined by the binding assembly, after the intertwining of the leg parts, the inner casing 2 is moved upwards so that the reinforcement rods 101 and 102 can be released from the apparatus 1.

During the above-mentioned steps, the pneumatic cylinders 20 and 48 and the pneumatic motor 80 are operated and activated in the following way: the pneumatic cylinders 20 and 48 are activated simultaneously. The pneumatic cylinder 20 is pre- ferably a single-acting pneumatic cylinder with a spring return. The lowering of the piston rod 21 of the pneumatic cylinder 20 depends on the diameter of the reinforcement rods to be joined, and is typically in the range of 5-25 mm, subsequently, the force pressing the first and the second reinforcement rods 101 and 102 together is generated. This force is preferably about 200 N, and is maintained until the joining of the reinforcement rods has been performed.

During and after the displacement of the piston rod 21, the pneumatic cylinder 48 with the piston rod 49 moves the clip- supplying member 42 and thereby forces a U-shaped clip length from the clip magazine 30 towards the intersection of the first and the second reinforcement rods 101 and 102 so that the U-shaped wire length is bent as described above. Due to its shorter displacement in relation to the pneumatic cylin- der 48, the pneumatic cylinder 20 generates the fixing and inter-pressing of the reinforcement rods before the leg parts of the U-shaped wire length reach the reinforcement rods 101 and 102 and the member 6.

At the return position of the pneumatic cylinder 48, a con- trol valve (not shown in the drawings) is activated, whereby the pneumatic cylinder 48 starts its return movement, the pneumatic cylinder 48 preferably being a double-acting cylin¬ der, and at the same time a pneumatic motor 70 is started and consequently, the rotatable parts 64 and 66 of the binding assembly are activated.

When the pneumatic cylinder 48 has returned to its starting position, another control valve (not shown in the drawings) is activated. This control valve causes the elimination of the pressure in the pneumatic cylinder 48, thereby stopping the pneumatic motor 70 and consequently the rotating parts in

the binding assembly and eliminating, the pressure in the cylinder 20, as a result of which the pneumatic cylinder 20 returns to its starting position due to it being spring biased. Thus, the pneumatic cylinder 48 is in its starting position, the inner casing 4 is in its upper position and the joint reinforcement rods 101 and 102 are released from the apparatus, which is now ready for another joining cycle.

For certain special joining operations, it may be advanta¬ geous to provide the apparatus with an extended handle so as to further improve the working conditions for the person using the apparatus in these operations.