The present invention relates to an apparatus for joining two intersecting reinforcing bars.

In spite of the fact that a number of different methods and devices were proposed through the ages for joining reinforc¬ ing bars, joining is still generally carried out in the same manner as when utilization of reinforced concrete was introduced, i.e. manually by the aid of wire and tongs.

Joining iron bars is not very meaningful labour by itself, as well as being inconvenient and exerting. It is also a price raising and delaying factor in concrete construction.

It was, thus, only natural that efforts were made to develop methods and devices to facilitate such work and to save time and costs in joining reinforcing bars.

From NO-PS No. 113 174 an apparatus is known to apply a resilient clip diagonally across the intersection of two reinforcing bars. The free end of the clip legs is hook- shaped to hook onto the lower bar. Said hooks will, however, sit at an angle relative to the bar, and since the hooks will necessarily have a limited extension they will go out of engagement if there is a certain tension between the iron bars. From NO-PS No. 91710 an apparatus is known for guiding a wire from a coil to be wound about two intersecting bars and to be twisted together. This apparatus is complicated and, thus, no doubt expensive, and it will be heavy as regards carrying.

From DE-OS No. 35 24 821 an apparatus is known for joining two intersecting reinforcement bars by the aid of a metal clamp or cramp with straight legs, comprising a magazine for a number of clamps and a guide and a piston which is movable

back and forth in said guide to advance the front clamp in the magazine in the direction of the clamp legs, an abutment with grooves for folding the legs, said grooves being curved and extending in a direction away from the clamp plane, said abutments comprising two hook shaped plates provided at a mutual distance and projecting freely from the guide end.

The apparatus according to the German publication has a structure rendering it difficult to adjust the apparatus for binding another iron bar dimension.

It is an object of the present invention to propose an apparatus which is based on the apparatus known from DE-OS No. 35 24 821, and which may in a simple manner be adjusted from one iron bar dimension to another. According to the invention this is achieved in an apparatus of the kind mentioned above, the characterizing feature of which is that the abutment consists of an inward facing projection, provided on the inside of each of the hook-shaped plates in the hook-shaped portion and, preferably, having the shape of plates, with a concave edge in which the folding grooves are received, and that the hook-shaped plates form a lateral guide for the clamp legs during advancement of said clamps, and that said plates are readily exchangeable in the hook- shaped plates.

Futher features of the invention will appear from the independent claims.

The invention is disclosed in more detail below with reference to the drawing, which shows a preferred embodiment of an apparatus according to the invetnion, a cramp for use in the apparatus, and two intersecting reinforcement bars which are joined by the aid of the method and apparatus, as well as a cramp according to the invention.

Figure 1 is a side elevation of the apparatus of the embodiment, Figure 2 shows the apparatus in a side elevation and in section, Figure 3 shows the apparatus from below, Figure 4 is a front view of the apparatus, Figures 5 and 6 show a cramp for use in the apparatus, as seen toward the cramp plane, and from the side, respectively, Figures 7a-7d show two intersecting reinforcement bars in a joined state, and as seen from different sides, Figure 8 is a perspective view of the apparatus, used for joining reinforcement bars, and Figure 9 shows the apparatus in use, and with an extension permitting the operator to use it in an upright position.

The apparatus has a shape rather like a pistol with a grip 1 and a tool portion 2 extending normally to the grip portion and being hook shaped at its free end. Across portion 2 a magazine 3 for cramps 4 is provided. By the aid of a diagrammatically indicated spring 5 cramps are automatically advanced towards front wall 6 of tool portion 2, which by the aid of said wall and lateral portions 7 forms a guide for cramps 4 during advancement of the cramps. A flat piston 8 showing the same thickness as cramps 4 is movable in the guide by the aid of reciprocating motor 9. In the shown embodiment this is a so called reluctance motor driven by a rechargeable battery 10. Motor 9 is activated by the aid of a switch (not shown) by depression of a trigger shaped control knob 11. A U-shaped plate member 12 integrally connected with two hook-shaped plates 13 and 14 is slidably provided on apparatus portion 2. The plates extend at a mutual distance permitting insertion of an upper or first reinforcing bar 15 to be joined with a second reinforcing bar 16. The distance between plates 13 and 14, thus, must be at least

equal to the diameter of iron bar 15. Inside each plate member 13, 14 plates 17 and 18 are secured to serve as abutments and are in the top face provided with outwards opening grooves 19 which guide cramp legs 4a when the latter are folded. Plates 17 and 18 are divided into an inner portion 17a and an outer portion 17b to permit adjustment of the folding grooves to the diameter of iron bars. This will be disclosed in more detail below.

Cramp 4 has straight legs 4a and an arched web 4b. The curve of the web is substantially adapted to the circumferencial curve of upper or first reinforcement bar. In order to facilitate folding of legs 4a the outer ends 4c of said legs are chamfered and the outer leg portions are provided with transversal weakening means 4d.

In Figures 7a-7d different elevational views show how two intersecting reinforcing bars 15, 16 are joined by the aid of a cramp 4 by use of the method and apparatus according to the invention.

Figure 8 shows the apparatus according to the invention in use for joining mutually intersecting reinforcing bars 15, 16.

Figure 9 also shows the apparatus according to the invention in use and with an extension 20 so that the operator of said apparatus can use it in an upright position.

The mode of operation of the apparatus according to the invention is as follows: When two reinforcing bars 15, 16 are to be joined, both hook-shaped plates 13,14 are moved over bar 15 and under bar 16. The apparatus is pushed to secure that bar 16 is in good contact with abutment plates 13 and 14, and the apparatus is activated by the aid of trigger 11. Stroke mechanism 9 forces piston 8 down towards the web of the first cramp 4 and the whole cramp 4 is urged down over

the first bar 15 and is guided below the latter by the guide and down into folding grooves 19 in plate members 17, 18. Cramp legs 4a are, thus, folded under lower bar 16, with said bar acting as an abutment, and close the fourth side of grooves 19.

U-shaped plate member 12 is provided with a slot 21 on both sides, which is controlled by a bolt 22 which may be tightened and loosened by the aid of a wheel 23, so that plate member 12 may be adjusted outwards and inwards, respectively, relative to apparatus portion 2 in order to adjust plate members 13, 14. In this manner it is possible to achieve the correct length of said hook-shaped members, i.e. the distance from the end of the cramp guide of the appar- atus, until the inward curvature of the plate members constitutes at least the sum of the diameters of both iron bars 15, 16. This value can be maximum twice the distance between the hook-shaped plate members. The curvature of the abutments and guide grooves 19 can also be adjusted to a certain degree by mutual displacement of members 17a, 17b to be adapted to the curvature of the lowermost reinforcing iron 16.

The lower edge of piston 18 has a curved recess 8a, the curvature of which is adapted to the diameter of uppermost bar 15. When a cramp is driven down, the lower portion of its legs will, as mentioned, be folded around lower bar 16, whereas the web of the cramp sits about the upper bar.

Piston 8 of the apparatus will drive the cramp downwards until the legs of the cramp are folded entirely about bar 16 and both bars 15 and 16 are clamped tightly together, if they extend at some distance originally.

Extension 20 may advantageously be used when, e.g. a cover or floor is to be cast with the iron bars placed slightly spaced from the formwork bottom, or when the reinforcement is joined

outside the casting area and is then lifted up into the formwork.

Between apparatus and extension plug/socket members may be provided, so that the extension can be provided with a separate actuating switch. The extension may also be made telescopic to permit adaption to different operators.