METHOD AND DEVICE FOR CLENCHING REINFORCEMENT BARS

Abstract: The invention relates to a method and a device for producing a tie connection holding together at least two elongated elements (14). In this the tie wire (1) is fed from a wire supply by means of a wire feed mechanism (3) guided by a wire bending and wire guiding device (12) to a predetermined point, so that it describes a loop (1a) around the elements (14). At the said point the end of the wire is held in a rotation head and the wire feed mechanism is made to reverse. In so doing the wire leaves the wire bending and wire guide device (12) and the loop is tightened around the elements (14). At a predetermined tensile stress in the wire loop the wire is cut off at a point between the rotation head and the wire feed mechanism in that the rotation head begins to rotate. In so doing the ends (1b1, 1b2) of the loop (1b) are gradually twisted together, the ends being held by frictional engagement so that there is a certain tensile stress at the ends of the wire during the twisting operation.

Description: Method and Device for Clenching Reinforcement Bars. The present invention relates to a method according to the pre-characterising clause of claim 1. The invention also relates to a device according to the pre-characterising clause of claim 5 , The joining together of reinforcement rods, so-called tying, has long been one of the most demanding manual operations on construction sites. This operation has barely changed ever since reinforcement rods began to be used as reinforcement for concrete more than a century ago. Even today, the tying is performed in essentially the same way that it has always been done, that is with steel wire and tie pliers. Reinforcement workers are one of the most injury-prone categories in the construction industry. Crush injuries and cuts to the hands, and knee/back injuries associated with stooped/bent working positions contribute to a high sickness frequency resulting in high costs to the individual employer and to society. There has therefore long been a great need for labour-saving methods and equipment in this sector. The Swedish patents 226.149, 226.153, 7102619-9 and 8401155-0, the latter relating to a device solely for tying, not spacing of reinforcement, may be cited as examples of the prior art. The object of the present invention is to produce a method and a device for making the task of a reinforcement worker easier. The characteristic features of the method according to the invention will be evident from the characterising part of claim 1. The characteristics of a device for performing the method according to the invention will be evident from the characterising part of claim §. Special features of the method and the device according to the invention will be evident from the respective subordinate claims. The invention provides various advantages: The job of the reinforcement worker is made considerably easier, thereby reducing the risk of industrial injuries. Furthermore the invention means that tie wire is saved, since virtually no wastage of wire occurs. Not least important is the fact that the tying can be performed to reinforcement rods with all prevalent dimensions, as a result of which the various dimensions can be mixed with one another. The invention will be explained in more detail below with reference to the attached drawings in which figure 1 is a section through an embodiment of a device according to the invention illustrating how a tie wire runs through the device. Figure 2a is a longitudinal section through a rotation head forming part of the device and shown in figure 1. Of the figures 2b and 2c, figure 2b shows a cross-section through the rotation head in figure 2a taken in a plane A-A, whilst figure 2c shows and end view of the rotation head. The figures 3a, 3b show a cross-section through a wire guide and wire bending device shown in figure 1 at two different stages of the tying process. In the drawings 1 denotes a tie wire, which comes from a wire supply (not shown), in which the wire may be wound on to a reel, for example. The wire supply may be a replaceable part of the device or may be arranged in a housing, of which only one wall forming an attachment plate 2 is shown. A wire feed mechanism, generally denoted by 3, is pivotally mounted on a shaft 4 and is supported by a helical coil spring 5 arranged on a pin 3a formed on the wire feed mechanism. The spring 5 rests in a recess 6 in the shell 7 of the device, which is shown in section in the drawing. The purpose of the pivotable suspension of the wire feed mechanism 3 and the function of the spring 5 will be explained in a description of the operation of the device according to the invention. The wire feed mechanism 3 has two motor-driven friction rollers 3b, 3c, between which the wire 1 is intended to run, and its wall facing the wire supply is provided with a wire guide channel 8 narrowing in a funnel shape towards the friction rollers 3b, 3c. The friction roller drive is reversible, so that the wire 1 can be fed both in the direction out from the supply, that is to say the normal feed direction, and in the opposite direction. After the wire feed mechanism, viewed in the normal feed direction, there is a second wire guide channel 9, connected to the shell 7 and narrowing in a funnel shape in the normal feed direction, the narrow end of which connects with a channel 1 la through a cutter unit 11. The channel 11 a ends at a rotation head 10 rotatably supported in the shell, the rotation shaft 10a of the rotation head forming an angle α with the common direction in which the wire guide channels 8 and 9 extend. The size of the said angle α is of crucial significance for the function of the tying device, which will be apparent later in the description. Running through the rotation head 10 is a channel 10b, the direction of which is such that when the rotation head assumes a certain angular position, the channel 10b lies in the direction of the wire guide channels 8 and 9. In the said angular position the mouth of the channel 1 la connects with the corresponding (upper) mouth of the channel 10b. The mouths of the channels 11 a and 10b facing one another form a pair of scissor edges, which are designed to cut the tie wire 1 when the rotation head 10 is turned at a certain stage in the use of the device. The torsional movement of the rotation head 10 is started and stopped automatically as will be explained subsequently in the description of the operation of the device. As will be seen from figure 2b, the rotation head is designed with a wire guide opening 10c and two grippers lOd together with a stop lOe. The grippers lOd are each supported so that they can pivot about a shaft lOdl and are functionally connected to one another by means of a spring clip lOf, so that the upper gripper on the drawing is forced to rotate anticlockwise to bear against a heel 1 Og. The same applies to the lower gripper, which is pressed clockwise against its heel 1 Og by the spring 1 Of. The person skilled in the art will perceive that this construction here briefly described constitutes a holding mechanism, which is capable of gripping and holding fast a wire, which is fed by way of the wire guide opening 10c in between the grippers lOd and towards the stop lOe. The (lower) mouth of the channel 10 furthest from the wire guide channel 9 connects with a wire bending and wire guide unit 12. The latter is designed, as the wire 1 is being fed, to bend and guide this so that it describes an approximate circle, at the centre of which the reinforcement rods 14 will be situated when tying. For this purpose the unit 12, which like a hook projects out through the attachment plate 2, is designed with a channel 12a. The latter has a bottom 12al and side walls 12a2, 12a3. The side walls 12a2, 12a3 are designed to be capable of moving apart against the action of springs 12b, so as to form a slit opening 12c, which in figure 3a has a negligible width, but in figure 3b is sufficiently wide to allow the wire 1 to leave the channel 12a by way of the slit opening 12c. The force required in order to overcome the springs is produced here by the force that the wire 1 exerts on the walls 12a2, 12a3 when bent into a circular shape and subjected to tensile stress, as will be explained later. The wire 1 having passed through the channel into the bending and guide unit 12, it describes a free curve la towards an opening 2a in the attachment plate 2. Connected to the said opening 2a is a sprung guide plate 13, designed to guide the tip of the wire 1 so that when fed by way of the wire guide opening 10c it passes in between the grippers lOd before being stopped by the stop lOe. The grippers lOd are capable of holding the wire 1 when it is subjected to tensile force in a transverse direction to the rotation shaft 10a of the rotation head 10, but holding of the wire ceases if the wire is drawn in a direction parallel to the rotation shaft 10a. Referring to the figures in the drawings, the operation of the tying device according to the invention, by means of which the reinforcement rods 14 shown diagrammatically in figure 1 will be tied together, will now be explained step by step. First, the wire bending and wire guide unit 12 of the device according to the invention is brought over the reinforcement rods 14 so that these ultimately lie approximately on the rotation shaft 10a and in the centre of the unit 12. The wire 1 , which comes from the wire supply, runs through the wire guide channel 8 and is situated between the friction rollers 3b, 3c. The driving of the friction rollers 3b, 3c is started up by means of a pushbutton (not shown), so that the wire 1 reaches the rotation head 10 and the upper mouth of the channel 10b by way of the wire guide channel 9 and the channel 11 a of the cutter unit 11. The wire 1 is fed on through the channel 10b and out of its lower mouth by the wire feed mechanism 3, before entering the channel 12a of the bending and guide unit 12. This imparts an approximately circular shape to the wire 1, with the free curved section la. As feeding continues the tip of the wire 1 approaches the opening 2a and the guide plate 13. The latter guides the wire 1 so that as feeding continues its tip is introduced into the wire guide opening 10c and is forced in between the grippers lOd and held by the latter. In this way the wire forms a loop around the reinforcement rods 14. The tip is stopped by the stop lOe and the feed action presses the wire against the guide plate 13, which due to its sprung suspension folds back and thereby acts on a limit position reversing switch 15, the arm 15a of which bears against the guide plate 13. The limit position reversing switch 15 is connected to the drive of the friction rollers 3b, 3c of the wire feed mechanism 3, in such a way that the rotational movement of the drive is thereby reversed. As a result the feed direction of the wire is also reversed. Since the end of the wire is held by the grippers lOd in the rotation head 10, the wire loop will be tensioned. As the wire tension in the loop is increased, the walls 12a2, 12a3 of the channel 12a are acted upon so that the slit is widened and the wire leaves the channel 12a, see figure 3b, so that the loop now denoted by lb in figure 1 is tightened around the reinforcement rods 14. Due to the increased wire tension as a result of the reversal, the wire feed mechanism will be turned clockwise around the shaft 4 against the action of the spring 5. In a predetermined position the torsional movement of the wire feed mechanism 3 acts on limit position reversing switch 16 connected to the control for the wire feed mechanism drive motor in such a way that the motor is stopped and the reversal ceases. The limit position reversing switch 16 is also connected to the feed circuit of the drive motor of the rotation head 10, so that this is started. The wire 1 is thereby cut instantaneously by the aforementioned shears and the ends lbl, lb2 of the loop lb thus obtained are twisted together by the torsion of the rotation head 10. It is very important in this connection that approximately equal tensile stress prevails at both ends of the wire lbl, lb2. Two factors contribute to the tensile stress at the end of the wire lb2 initially situated in the channel 10b, namely the forces that are required to bring the wire over edges lOh and lOi. The force needed at the edge lOh is then dependent on the angle α. By appropriate selection of the angle α the wire tension at this end of the wire can be balanced against the tensile stress at the end of the wire lbl initially held by the grippers. During reversal this end of the wire will leave the wire guide opening 10c and be pressed down in the slit 1 Ocl . As will be seen from figure 2c, the slit 1 Ocl extends radially over more than half of the end surface of the rotation head 10. The twisting process and hence also the tie connection is completed when both ends of the wire lbl, lb2 have left the rotation head 10. Its torsional movement is automatically stopped, for example, a certain time after the limit position reversing switch 16 has commenced its torsional movement. It is easy to calculate a suitable running time for the torsional movement of the rotation head, since the ends of the wire lbl, lb2 are always of equal length regardless of the number of reinforcement bars and their dimensions. The person skilled in the art will obviously be able, within the framework of the idea of the invention, to modify both the device described above and its application. The invention can thus also be used, for example, for tying cable harnesses.

Claims: Claims 1. Method for tying together at least two elongated elements (14), for example reinforcement rods, by means of a metal wire (1), in which the wire (1) guided towards a predetermined point is fed so that it describes a loop (lal) around the elongated elements (14), the free ends of the wire (1) are held when it has reached the predetermined point, and the feed is reversed so that the loop (lal) is tightened around the elongated elements (14), when during the reversal a predetermined wire tension is attained in the loop (lb) the wire is cut and the second free end (lb2) of the loop thus occurring is fixed, the two ends of the wire (lbl, lb2) are twisted together and the tying is completed, characterised in that the wire (1) is guided towards the predetermined point by bending throughout a first part of the circumference of the loop and that the free end of the wire throughout the remainder of the circumference of the loop is fed in a free direction towards the predetermined point. 2. Method according to claim 1, characterised in that the free end of the wire (1) is given a predetermined length when it is held at the predetermined point, that the wire (1) is cut at a predetermined distance from the loop (lb) and that the second free end (lb2) of the loop thus occurring is given essentially the same length as the said first free end (lbl) of the wire (1). 3. Method according to either of the preceding claims, characterised in that the two ends of the wire (lbl, 1 b2) are twisted together whilst stretching relative to the loop (lb) and that during the twisting a tensioning of the ends of the wire (lbl, lb2) is produced by holding or fixing thereof, by means of which the ends of the wire are ultimately freed. 4. Method according to claim 3, characterised in that during twisting the ends (lbl, lb2) of the loop (lb) are held by a frictional engagement, the ends being gradually drawn out of the frictional engagement by the effect of tensile stresses in the ends of the wire occurring during the twisting. . Device for producing a tie connection holding together at least two elongated elements, comprising: a housing (2) a tie wire supply arranged on or in the housing (2) a wire feed mechanism (3) arranged in the housing (2) and designed to feed the tie wire (1) in one feed direction as a function of a manually triggered feed signal, and to reverse the feed direction as a function of an automatically generated return feed signal, elements (12) fixed to the housing (2) and designed to guide the tie wire (1) in a path around the elongated elements (14), so that the tie wire encounters an inlet opening in the housing (2), elements designed to: hold the end of the wire entering through the inlet opening (2) in one locking direction and to emit the return feed signal in order, by means of the wire feed mechanism (3) to produce tightening of the loop (lb) around the elongated elements (14); to cut the tie wire (1) at a point after the wire feed mechanism (3); to hold the cut end of the wire (lb2) of the loop (lb); and during the rotation to twist the ends (lbl, lb2) of the wire loop (lb) together during continued tightening of the loop (lb), characterised in that the said tie wire control elements (12) comprise a circular curved part projecting from the housing (2), which part has a channel (12a) defined by a bottom (12al) and walls (12a2) and designed with a longitudinal slit (12c), the function of which channel is to produce bending and guiding of the tie wire (1), that the width of the slit (12c) is less than the diameter of the tie wire (1) and that the walls (12a2) are designed to spring resiliently away from and towards one another so that when a tensile stress occurs in the tie wire (1), which due to its circular curved shape results in radial forces, the wire (1) can move out of the channel (12a) by way of the slit (12c). 6. Device according to claim 5, characterised in that the said element for holding and cutting the tie wire comprises a cylindrical rotation head ( 10) rotatably supported in the housing and designed, in a predetermined angular position, to guide the tie wire (1) in an internal channel (10b), which in the said angular position begins at the feed mechanism and ends at the channel (12a) of the wire bending and wire guide device (12), to receive and up to a predetermined limit to hold the free end (lbl) of the tie wire (1) when this has passed through the inlet opening of the housing, to cut the tie wire (1) at the beginning of the internal channel (10b) in connection with an incipient rotational movement and during continued rotation to cause the ends (lbl, lb2) of the tie wire loop (lb) to be twisted together. 7. Device according to claim 6, characterised in that the rotation head (10) has a radial slit (1 Ocl ) designed to produce a frictional engagement with the tie wire (1).

Inventors: FORSBERG BENGT, LIDMAN LENNART, FORSBERG, BENGT, LIDMAN, LENNART
Applicants: FORSBERG BENGT, LIDMAN LENNART, FORSBERG, BENGT, LIDMAN, LENNART
Application year: 1999
Main classification: E04G21
IPC codes: E04G21