The invention relates to a method for the reduction of embedded torsional strain in reinforcement steel guided in between at least one set consisting of two rows of straigh- tening means having at least two straightening means in the first row for being pressed against one side of the reinfor- cement steel, and at least three straightening means in the second row for being pressed against the diametrally opposite side of the reinforcement steel and having grooves in the straightening means for receiving and guiding the reinfor- cement steel, said straightening means in a set being arranged at mutual distances and in such a way that the reinforcement steel is forced to pass them according to a straight line, and at least one of the straightening means in one row is arranged just opposite a spacing between the straightening means in the other row.

In reinforcement steel being fed through straigh- tening means of the above mentioned known type, embedded torsional strain (in the reinforcement steel) can cause unacceptable effects during subsequent bending operations on the reinforcement steel after its passage through the straightening means.

By a bending of a reinforcement steel having embedded torsional strains these will be relieved and cause the reinforcement steel to become and be left twisted in the bending zone. Such reinforcement steel which is intended subsequently to be bent in order to form an e. g. polygonal plane shape, will after its bending operation and the relieving of the embedded torsional strain thus caused, be twisted in the bending zones in such a way that the sides of the polygonal bent reinforcement steel do not all lie in the same plane or according to an intended shape or outline.

It is the object of the present invention to eliminate this drawback.

This object is achieved by the method according to the invention thereby that one of the straightening means- which in a row of straightening means is arranged opposite one of said spacings-is displaced from a neutral position and in a direction to a reinforcement steel side being different from any of the above mentioned sides, and that said one straightening means is locked into its displaced position after its displacement for the formation of a curved path for the reinforcement steel passage between the closest straightening means in the opposite row of straightening means, whereby the size as well as the direction of the said displacement of the one straightening means for the reinfor- cement steel in question has been empirically established in advance.

Thus, it is achieved that the reinforcement steel can be relieved of any embedded torsional strain which may have undesired effects on the shape or layout of the reinfor- cement steel after a subsequent bending operation.

The invention also relates to an apparatus for carrying out the method according to the invention, viz. an apparatus for use in the reduction of embedded torsional strains in reinforcement steel which is guided in between at least one set consisting of two rows of straightening means having at least two straightening means in the frist row for being pressed against the one side of the reinforcement steel, and at least three straightening means in a the second row for being pressed against the diametrally opposite side of the reinforcement steel and with grooves in the straigh- tening means for receiving and guiding the reinforcement steel, said straightening means in a set being arranged at mutual distances and in such a way that the reinforcement steel is forced to pass them according to a straight line, and at least one of the straightening means in one row is arranged opposite a spacing between the straightening means in the other row.

According to the invention the apparatus is characterized in that the straightening means consist of

straightening pulleys with grooves similarly to those in V- belt pulleys, that the straightening pulleys are arranged in the same plane with two straightening pulleys on one side of the reinforcement steel and three straightening pulleys on the diametrally opposite side of the reinforcement steel, and that the intermediate of the three straightening pulleys is arranged opposite the spacing between the two straightening pulleys on the opposite side and is displaceable along its axis and is adapted to be locked into its displaced position.

Furthermore, the apparatus according to the invention can be characterized in that a sensor can be arranged between the spool or bobbin and the apparatus for measuring of certain parameters of the reinforcement steel which parameters are indicative of the corresponding reinfor- cement steel properties.

As an advantageous embodiment the apparatus according to the invention may be characterized in that the axially displaceable straightening pulley may be provided with a shaft extending through a bearing in a plate arranged behind the apparatus, whereby the shaft extends on the opposite side of the plate as a piston rod with a piston in a hydraulic servo actuator being secured to the plate.

The invention will now be described in more detail with reference to the drawing in which: Fig. 1 shows a side view of a straightening apparatus and a spool or bobbin with wound-up reinforcement steel, Fig. 2 a top view of the straightening apparatus, and Fig. 3 a top view of the straightening apparatus and a straightening pulley displaced in its axial direction.

The drawing illustrates an embodiment of the method according to the invention for the reduction of embedded torsional strain in reinforcement steel 2 being guided in between a set consisting of two rows of straightening means 4,5 with two straightening means 4 in the first row for being pressed against the one side of the reinforcement steel 2, e. g. the upturned side, and three straightening means 5 in the second row for being pressed against the diameetrically

opposite side of the reinforcement steel 2, and having grooves in the straightening means 4,5 for receiving and guiding the reinforcement steel 2. The straightening means 4, 5 are arranged in mutual distances and in such a way that the reinforcement steel 2 is forced to pass them according to a straight line, and one of the straightening means 5, namely 5T, in one row is arranged opposite a spacing between the straightening means 4 in the other row. According the invention said straightening means 5T is displaced from a neutral position and in a direction of a reinforcement steel side being different from the above mentioned sides for the formation of a curved path for the reinforcement steel 2 passage 2A between the closest straightening means in the opposite row of straightening means, it turned out surpri- singly that the reinforcement steel 2, when the size and the direction of the displacement of the one straightening means for the relevant reinforcement steel was decided empirically in advance, was relieved of any embedded torsional strain which may otherwise have unfortunate effects on the final shape of the reinforcement steel 2 after a consecutive bending operation, e. g. that the sides of a polygonal bent reinforcement steel 2 do not all lie in the same plane or according to intended shape or outline. Said empiric estab- lishment may be prescribed from the supplier of the spool 1 or based on a previous experimental bending of a length of reinforcement steel 2 passed from the spool through the straightening means 4,5 of the straightening machine.

Fig. 1 is a side view corresponding to section A-A in Fig. 3 of a spool 1 carrying a wound-up reinforcement steel 2 which from the spool 1 is guided through an apparatus 3 for the reduction of embedded torsional strains in the reinforcement steel 2.

The apparatus 3 consists of two straightening means in the form of straightening pulleys 4 which can be pressed against the upper surface of the reinforcement steel 2, and three straightening means in the form of straightening pulleys 5 which may be pressed against the lower side of the

reinforcement steel 2.

The intermediate of the three lower straightening pulleys 5 is an axially displaceable straightening pulley 5T, which in a preferred embodiment is rotated by frictional forces between the pulley 5T and the reinforcement steel 2 during its movement forwards between the straightening pulleys 4,5 through the apparatus 3.

One or more of the remaining straightening pulleys 4,5 may be driving pulleys 4D or 5D. Frictional forces between said pulleys and the reinforcement steel 2 may drive it from the spool 1, forwards between the straightening pulleys 4,5 and further away therefrom and out of the apparatus 3.

As shown, a sensor 10 may be arranged between the spool 1 and the apparatus 3, the purpose of which sensor is the detection or measuring of certain reinforcement steel parameters being indicative of the corresponding reinfor- cement steel properties. The measuring or detection with the sensor 10 may be the basis of the adjustment of the axial displacement size and displacement direction of the straigh- tening pulley 5T, and the displacement may then take place manually and/or automatically by means of mechanical, hydraulic or electric means.

A bending apparatus not shown may be arranged at the output side of the apparatus 3.

Figure 2 shows a top view of the apparatus 3, cf. section B-B in Figure 1.

In Fig. 2 all the straightening pulleys 4,5 lie in the same plane. Except for the axially displaceable straigh- tening pulley 5T, all the straightening pulleys 4,5 are secured to said plane. The axially displaceable straightening pulley 5T is displaceable in its axial direction and can be locked or secured in a displaced position.

Figure 3 is the same picture, showing a top view of the apparatus 3 along section C-C in Figure 1, however, with the axially displaceable straightening pulley 5T being displaced along its axis and thereby parallelly displaced

compared to the remaining straightening pulleys 4,5 to a position in which it is locked.

The axially displaceable straightening pulley 5T is provided with a shaft 7 extending through a bearing in a plate arranged behind the apparatus 3. On the opposite side of the plate the shaft 7 extends as a piston rod with a piston 8 in a hydraulic servo actuator 6 being secured to the plate. The servo actuator 6,7,8 is shown in a position in which the axially displaceable straightening pulley 5T has been parallelly displaced compared to the plane in which the remaining straightening pulleys 4,5 are located.

With the axially displaceable straightening pulley 5T in its displaced position the reinforcement steel 2 is forced to follow a curved path between the straightening pulleys 4,5 during its passage over the axially displaceable straightening pulley 5T (see reference 2A in Figure 1).

During its passage in the curved path being determined on the basis of the adjustment of the size and direction of the immediate displacement, the reinforcement steel 2 is exposed to bending and torsional influences eliminating the embedded torsional strain of the reinfor- cement steel 2.

The axially displaceable straightening pulley 5T may advantageously be a freely rotatable straightening pulley.

The invention is not limited to the embodiments set forth in this application, since also other embodiments may be manufactured within the scope of the invention. Thus, the straightening pulley 5T may also be positively rotatably driven in a likewise predetermined rotational direction and with a predetermined number of revolutions, which rotation also like the above mentioned axial displacement has been empirically decided based on certain parameters/information attached to the relevant reinforcement steel or the like bar or wirelike material which according to the method should be exposed to the neutralization of embedded torsional strains.