The present invention relates to a method for manufacturing a mesh reinforcement, in which the main bars of the mesh reinforcement, said main bars being of normal ribbed bar, are fed parallelly and step-wise to a welding station at a controlled distance from each other, and its transverse reinforcements are placed, at the welding station, indivi¬ dually in position on top of the main bars and welded together with these.

Previously, mesh reinforcements were usally welded such that each transverse reinforcement was welded simultaneous¬ ly together with all main bars by using a long welding brush, which extended across the entire mesh reinforcement. Such a method makes very large demands upon the uniformity of the reinforcement bars, and its power requirement is extremely high. Due to this matter, it has previously been possible to use only a normal rod wire with a cross-section of 12 mm at the highest, which does not provide a suffi¬ cient strength for concrete structures in all conditions. In spite of the rod wire, the contact between the transver¬ se reinforcements and the main rods is relatively uncer¬ tain, which results in that the transverse reinforcement is not properly welded together with all main rods.

The method according to the invention for manufacturing a mesh reinforcement is characterized in that the welding of the transverse reinforcements is performed with two spot welding heads, whose actuators are located on the opposite sides of a welding station, which welding heads may be controUably transferred in the transverse direction of the mesh reinforcement along the transverse reinforcement to be welded together and which are arranged to stop automatical- ly at every main bar within its moving area and to perform there the spot welding function. Since a considerably thick

ribbed bar may be used, a sufficient strength is obtained for the concrete structures by means of a simple reinforce¬ ment at the same time as it is ensured that the transverse reinforcement will certainly fix to every main bar. By means of the invention, it is possible to industrially manufacture such mesh reinforcements provided with strength properties, which cannot have been previously manufactured economically.

The other characteristics of the invention are presented in the enclosed claims 1 to 7.

The invention is next described in more detail with refe¬ rence to the accompanying drawing, in which

Fig. 1 is a principle view of an equipment to be utilized in the performance of the method according to the inven¬ tion, seen from the top, and

Fig 2 shows the equipment of Fig. 1, seen from the right, at a welding station.

According to the invention, the manufacturing of the mesh reinforcement occurs in such a way that the main bars 1 of the mesh reinforcement are fed parallelly and step-wise to a welding station 2 at a controlled distance from each other. The transverse reinforcements 3 are placed, at the welding station 2, individually in position on top of the main bars 1 and are spot welded to each main bar 1 in turn. In the method according to the invention, the main bars 1 are of a normal ribbed bar, which by its strength proper¬ ties is completely superior to a rod wire. The ribbed bars to be used as main bars 1 may have a cross-section of 8-32 mm of standard ribbed bar HW.

The spot welding of the transverse reinforcements 3 is preferably performed with two spot welding heads 4, which

are controUably transferable on guide arms 5 in the trans¬ verse direction of the mesh reinforcement. Actuators 6 of the spot welding heads 4 are located on the opposite sides of the welding station 2.

The welding station 2 has a metal table 7 supporting the main bars 1. On the upper surface of the table 7 preferably two adjacent stops 8 are placed such that a transverse reinforcement 6 to be welded and being placed against them is located accurately on the movement path of the spot welding heads 4. When a new transverse reinforcement 3 is placed on top of the main bars 1 against said stops 8, the welding functions of both spot welding heads 4 are actu¬ ated, whereby both welding heads 4 transfer from the ini- tial positions on opposite sides of the mesh reinforcement along the transverse reinforcement 3 to be welded toward the center line of the mesh reinforcement, till each spot welding head 4 reaches the outermost main bar 1 of the side concerned, whereby the horizontal movement of the spot welding head 4 automatically stops and a first actual spot welding step begins. The electrode of each welding head 4 is then pushed downward and presses the transverse reinfor¬ cement 3 toward the main bar 1 concerned at the same time as the welding voltage is connected between the electrode 9 and the welding-station table 7 such that a spot-like weld is obtained. Λfter the weld has been obtained, the electrode 9 automatically rises to its basic position, after which the spot welding head 4 moves along the trans¬ verse reinforcement 3 to the next main bar 1, whereby the spot welding step is repeated. When all main bars in turn have been spot welded onto this transverse reinforcement 3, the spot welding heads 4 return to their initial positions.

In connection with the welding function, the mesh reinfor- cements may be cut to a fixed size by means of a cutting device 10 located on the outlet end of the welding station

2 and by means of a stop 11 in cooperation therewith, which

stop 11 is controUably transferable in the longitudinal direction of the mesh reinforcement. This stop is prefera¬ bly of a lever arm type, which, after the mesh reinforce¬ ment has collided against it, is capable of sending a stopping impulse to a feeding device 12 of the main bars 1 as well as of giving a starting signal to the cutting device 10.

The distance between adjacent main bars 1 is adjusted preferably on the inlet side of the welding station by means of axially adjustably transferable guide rollers 14 pivoted around two parallel shafts 13. By arranging the guide rollers 14 on two shafts 13 such that the guide rollers 14 of two adjacent main bars 1 are located on different shafts 13, also the manufacturing of such mesh reinforcements is made possible, in which the main bars 1 are nearly in contact with each other.

The feeding device 12 for the main bars 1 is preferably a reciprocating gripping and pushing device, which during the pushing step is arranged to grip all main bars 1 by means of grip beams forming a pressing gap such that the main bars 1 move forward by one step during every pushing step. During the return movement of the pushing device 12, the grip beams are in an opened position and move freely to the initial position of the feeding device 12, in which positi¬ on they again grip the main bars 1. The distance between the transverse reinforcements 3 is thus determined easily according to the lenght of the feeding step of the main bars. The distance between the transverse reinforcements 3 may thus be of a length of either one or more feeding steps. If necessary, the machine operator may interrupt the feeding device 12 during the pushing step and start up the welding function, if the distance between the transverse reinforcements 3 is to be smaller than the feeding step of the main bars.