Device for holding wires and method for welding wires

Abstract

The invention relates to a device (1) for holding wires, in particular for holding wires during welding, for example during welding of longitudinal wires of a mesh mat to transverse wires thereof, wherein the device (1) comprises tongs (2) for holding the wires. In order to bring wire, in particular a longitudinal wire, into an initial position which is favourable for the welding process for welding to a further wire such as a transverse wire, according to the invention the tongs (2) comprise pivotable tong elements (3) and at least one driver (4) for the tong elements (3), wherein the tong elements (3) can be moved substantially linearly from a starting position into a holding position by means of the at least one driver (4) and can be pivoted in relation to one another, in particular in a positively guided manner, in said holding position by means of the at least one driver (4) in order to hold a wire. The invention also relates to a method for welding wires, in particular by means of a device (1) according to the invention.

Description

[0001] Device for holding wires and method for welding wires

[0002] The invention relates to a device for holding wires, in particular for holding wires during welding, for example during welding of longitudinal wires of a grid mat to transverse wires thereof, wherein the device comprises a pair of pliers for holding the wires.

[0003] Furthermore, the invention relates to a method for welding wires, for example longitudinal wires and transverse wires of a grid mat such as a reinforcement mat, in particular with a device of the type mentioned above, wherein at least one wire is held with a pair of pliers during welding.

[0004] When manufacturing mesh mats with longitudinal wires and cross wires, each made of a single steel, the state-of-the-art involves feeding the longitudinal wires in the direction of production and welding them to cross wires fed perpendicular to the direction of production. For welding, appropriate devices are provided with movable welding heads, allowing a bundle of longitudinal wires at the same height to be welded to a single cross wire at different positions. A single welding head that can be moved linearly along a cross wire may be sufficient for this purpose. A group of welding heads that can only be moved vertically may also be provided.

[0005] During the production of mesh mats, the longitudinal wires are provided at a predetermined pitch, i.e., at a specific distance from each other, on an inlet side. However, it may happen that this inlet-side pitch does not correspond to the pitch in the mesh mat, for example, because a different pitch is desired on an outlet side or in the mesh mat to optimize static properties.

[0006] In order to hold the fed longitudinal wires in a suitable position when welding with a cross wire, it is known from the prior art to use V-shaped components such as angle plates, which are usually arranged on the welding head. The V-shape allows the longitudinal wires to be guided into a specific position regardless of their diameter before the welding process begins. The V-shaped components are usually actuated via pneumatic cylinders. Although angle plates, for example, allow flexibility in terms of diameter, a disadvantage is that this results in a relative movement of the longitudinal wires relative to the V-shaped component, which can lead to friction and damage to the cross wire. Another disadvantage is that a translation can be initiated without an additional position measuring system, which is detrimental to the product geometry.Finally, the pneumatic cylinders used have a high failure rate because the forces resulting from impact on the product are transmitted directly into the pneumatic cylinders.

[0007] Devices of the type mentioned above are also known from the prior art, in which, for example, longitudinal wires are gripped and handled with pliers, although this can also result in damage.

[0008] This is where the invention comes in. The object of the invention is to further develop a device of the type mentioned above so that a wire can be held securely and precisely, particularly for welding, while reducing the risk of damage to individual wires.

[0009] A further aim of the invention is to develop a method of the type mentioned at the outset in such a way that a safe and precise welding of wires is possible, whereby the risk of damage to individual wires is reduced.

[0010] The object of the invention is achieved if, in a device of the type mentioned at the outset, the pliers comprise pivotable pliers elements and at least one driver for the pliers elements, wherein the pliers elements with the at least one driver can be moved substantially linearly from an initial position into a holding position and can be pivoted relative to one another in this position, in particular in a positively guided manner, in order to hold a wire.

[0011] According to the invention, the pliers comprise pivotable pliers elements and a driver designed to pivot the pliers elements relative to one another. The device is designed such that the pliers elements, together with the driver, can be moved from a starting position into a holding position, wherein the movability is provided at least substantially along a straight line. Advantageously, the linear movement of the pliers elements is first completed, after which the pliers elements are moved relative to one another in order to grip and hold a wire, in particular a fed longitudinal wire. By means of the sequence of linear movement of the pliers elements and subsequent pivoting thereof, the gripped wire can be gripped reliably and precisely and also welded.The pivoting of the clamp elements is achieved by at least one driver, which initially moves passively with the clamp elements into the holding position and is then actuated. This also at least reduces the risk of damage to wires.

[0012] In principle, it is also possible for the clamp elements to already pivot or be initiated when the clamp elements are moved linearly. However, for design reasons, carrying out these steps of moving and pivoting the clamp elements discretely one after the other is preferred. The device is therefore advantageously designed so that the clamp elements can only pivot in the holding position. This ensures that the wire is reliably gripped and can also be released again. An introduced force can be used to first effect the translational movement up to the holding position and then, when the clamp elements can no longer be moved translationally, to initiate and complete the pivoting process. The actuating elements are thus protected because the force introduced into them is low.

[0013] Advantageously, the gripper elements can be moved essentially linearly, particularly vertically, up to a stop. The stop ensures that the gripper elements cannot be moved beyond the holding position. For this purpose, the gripper elements can be connected to a flange, which rests against the stop in the holding position. This blocks further linear movement beyond the holding position.

[0014] Although the invention is not limited thereto, the gripper elements typically grip a supplied longitudinal wire, which is, for example, placed on a cross wire and welded to this cross wire, in particular to produce a grid mat from longitudinal wires and cross wires in a horizontal plane. For linear movement, the gripper elements are suitably mounted in the device, for example, on a block that is slidably mounted on one or more associated guide rods and supports the aforementioned flange. The gripper elements can be pivotably mounted laterally on this block.

[0015] To perform the movements of the gripper elements, the device can comprise an actuator with which the gripper elements and / or the driver can be moved and / or with which the gripper elements can be pivoted. The actuator can be an electric or hydraulic actuator, for example, but a pneumatic actuator is preferably provided. A single actuator is sufficient for all movements. When the gripper elements can be moved up to a stop, they are in the holding position. The at least one driver moves along and is mounted between the gripper elements for further movement. Once the stop is reached, the pivoting movement can then follow the vertical movement by the at least one driver being moved further in a linear manner, thus initiating the pivoting movement of the gripper elements. In principle, however, several separately operating actuators can also be provided for different movements, although this is more complex.

[0016] In particular, it can be provided that the pliers elements have guides which run obliquely with respect to a vertical axis and into which a driver engages, wherein the guides are designed to move the pliers elements towards one another when the driver is moved in the holding position. Preferably, the guides are designed such that pivoting of the pliers elements is achieved by a further linear movement of the driver in the holding position. One driver is then sufficient for one pair of pliers elements. When two or possibly more pairs of pliers elements are arranged, a single driver can actuate several pairs of pliers elements or, in other words, activate a gripping action when there are several pliers.

[0017] It can also be provided that the guides have a length and / or an angle relative to the vertical axis such that, in the holding position when the tongs elements are pivoted towards each other, the contact surfaces of the tongs elements hold the wire solely through friction. In this particularly preferred variant, the wire to be welded can initially be gripped by the tongs elements with a clamping force, but can be held exclusively through friction during welding. For this purpose, the tongs elements can be designed with an opening angle downwards relative to the vertical axis, i.e., forming a downwardly open V. The tongs elements then remain in position on the wire through friction.Due to the open angle of the tong elements and the inherent self-locking, the tongs formed by the tong elements act like a guide during welding when the actuator is depressurized, and a change in the longitudinal wire in the direction of gravity (welding depth) can be compensated for during the welding process. This results in welded joints of particularly high quality. In this context, it is particularly preferred that the device comprises a preferably pneumatic actuator and a control device, wherein the control device optionally depressurizes the actuator in the holding position when the tong elements are pivoted towards each other. This makes it possible to initially grip a wire with a predetermined clamping force. For example, the actuator can be subjected to a pressure of several bar.

[0018] As soon as the wire is gripped in the holding position and ready for welding, the actuator can be depressurized. The gripper elements cannot move due to friction and, as mentioned above, act as a guide for the wire to be welded without applying additional force.

[0019] Particularly preferably, a single driver is provided for pairs of interacting pliers elements. In particular, multiple pairs of interacting pliers elements can also be provided. For example, if two pairs of interacting pliers elements are provided, a single driver can pivot four pliers elements, so that a total of four pliers elements can be pivoted with one driver, and thus two pliers can be actuated. An arrangement of two or possibly more pliers offers the advantage that a torque can be introduced into the wire. This allows for precise creation of intersection points, particularly at an angle of 90°.

[0020] The device can comprise at least one spring which presses the clamp elements into the holding position. The clamp elements can be pivotally mounted on a movable block with a flange. The flange can in turn be moved along one or more guide rods from a rest position to the stop. A spring can be mounted on one of these guide rods, so that an additional spring force is produced during the linear movement of the clamp elements from the rest position to the stop. This additional spring force ensures that, particularly in the case of pneumatic actuation, the driver does not initiate the pivoting movement before the stop or holding position is reached. Conversely, when opening, the driver is activated first before the clamp elements can be moved to the starting position by overcoming the opposing spring force.

[0021] The device can further comprise a linearly movable, particularly vertically movable, hold-down clamp. This makes it possible to easily perform double-wire welds with individual, movable welding heads, although double-wire welds are also possible without a hold-down clamp. It should be ensured that a wire to be welded on is not pushed over an already welded wire. Suitable means can be used for this purpose, if necessary, for example, suitably designed guides for the wire to be welded on.

[0022] The device can be mounted on a freely moving welding carriage or on a dedicated chassis of a welding system and preferably picks up longitudinal wire transversely to the production direction before welding. The gripper elements are generally designed to grip wires with a wire diameter of 2 mm to 26 mm, preferably 4 mm to 20 mm.

[0023] However, the use of a device according to the invention is not limited to merely welding wires. Rather, the device according to the invention can also be used, for example, for feeding wires to mesh welding systems or other systems, such as for the inlet-side feeding of longitudinal wires for the production of mesh mats with a welding device.

[0024] Furthermore, a device according to the invention can comprise, for example, a position measuring system for supplied longitudinal wires, so that the quality of a weld can be determined. This can also be achieved with other measuring systems, for example, a measuring system for secondary currents during welding, which also allows conclusions to be drawn about the weld quality. In a further aspect, the invention comprises a welding device with a plurality of devices according to the invention, wherein the devices can be operated separately from one another.

[0025] The further object of the invention is achieved if, in a method of the type mentioned at the outset, pivotable pliers elements of the pliers are moved substantially linearly from a starting position into a holding position and pivoted in this position in order to hold the at least one wire.

[0026] A method according to the invention is particularly advantageous in that a wire can be gripped and held in a defined manner during welding. A discrete sequence of linear, particularly vertical, movement of the gripper elements followed by pivoting of the gripper elements ensures high process reliability and allows for safe and precise welding of wires, significantly reducing the risk of wire damage compared to V-shaped angle plates.

[0027] The gripper elements and / or drivers, which are designed to pivot the gripper elements, can be moved electrically or hydraulically, for example. Particularly preferably, the gripper elements and / or drivers are initially moved together linearly and pneumatically. Once a holding position of the gripper elements has been reached, the drivers can be moved further linearly to initiate a pivoting movement of the gripper elements relative to one another. For this purpose, the elongated gripper elements can have lateral guides into which the drivers engage. These lateral guides are at an angle relative to the plane along which the driver is moved, in particular pneumatically. This results in a positive guide which causes the gripper elements to pivot relative to one another and thus grip a wire when the driver is moved further linearly.The lateral guides of the pliers elements are adjusted to the wire diameter and the desired clamping force.

[0028] Particularly when both the gripper elements and the driver(s) are pneumatically actuated, it is advantageous if the gripper elements are subjected to a spring force during the linear movement from the starting position to the holding position. The additional spring force ensures that the gripper elements are moved into the holding position before the driver(s) are actuated. This makes it possible to only initiate the pivoting movement once the holding position for the gripper elements has been reached. This can be the case in particular when the holding elements have moved up to a stop against which, for example, a flange connected to the gripper elements strikes. The at least one driver is mounted between the gripper elements and only moves relative to them when the gripper elements can no longer be moved linearly to grip a wire.

[0029] It is also particularly preferred, and within the scope of the method with a device according to the invention, for the wire to be gripped in the holding position with a clamping force, after which the clamping force is reduced, in particular set to substantially zero, and the wire is held by friction during welding. Thus, the wire to be welded can initially be gripped in the holding position or in a desired welding plane and brought into position. A specific clamping force is provided for this purpose. Once the wire is in this position, the clamping force can be omitted. If the tongs elements form a predetermined angle of less than approximately 5° in relation to the wire diameter when pivoted relative to one another, which results from the pivotability of the tongs elements about a common pivot axis, even when a pneumatic system is depressurized, there is no mobility for the tongs elements due to a self-locking or wedge effect.This changes the function of the gripper elements during welding with a welding head to simply guiding the wire. This results in particularly high-quality welded joints, as the wire is welded virtually without additional force.

[0030] The sequence of a movement of the linear movement of the tong elements and the closing takes approximately 200 ms. Due to the provided mechanical positive guidance, position switches and the associated position processing between the two movements can be omitted if the tong elements and the driver(s) are mechanically positively guided. A device according to the invention for carrying out the method can be used for this purpose. The method according to the invention can also be used to produce double-wire welds if, for example, a first longitudinal wire is welded to a cross wire in the manner explained, after which another longitudinal wire is grasped with the tongs and placed on the cross wire, after which the tong elements are closed so that both longitudinal wires are held, after which a hold-down device is lowered onto the longitudinal wires, after which the second longitudinal wire is welded to the cross wire.

[0031] Further features, advantages, and effects of the invention will become apparent from the following exemplary embodiments. Reference is made to the drawings, which show:

[0032] Fig. 1 is a schematic representation of a device according to the invention and of a welding process;

[0033] Fig. 2 is a schematic representation of a method for producing double wire welds;

[0034] Fig. 3 is a perspective view of a device according to the invention;

[0035] Fig. 4 shows a section through a device according to the invention;

[0036] Fig. 5 to Fig. 7 show different states when operating a device according to the invention.

[0037] Fig. 1 shows a highly schematic representation of a device 1 according to the invention and a method using the same. The device 1 comprises a pair of tongs 2 with two tong elements 3. Furthermore, a driver 4 is provided for the two tong elements 3. The tong elements 3 are mounted so as to be pivotable relative to one another about a pivot axis S. The tong elements 3, like the driver 4, are mounted so as to be linearly movable along a vertical axis V. As a rule, linear movement is possible along a vertical axis, in particular when a grid mat is produced in a horizontal plane. The tong elements 3 are connected to the driver 4, with the driver 4 engaging in the tong elements 3 such that they can be pivoted upon linear movement of the driver 4. Furthermore, an actuator 14 (not shown) is provided which is designed for the pneumatic actuation of the tong elements 3 and the driver 4.In addition, a spring 7 is provided which presses the tongs elements 3 towards a stop 5 along the arrow shown in Fig. 1. In the starting position A shown top left in Fig. 1, the actuator 14 initially holds the tongs elements 3 in a starting position A against the spring force by applying a corresponding force. In order to grip a longitudinal wire L to be welded, a force is applied in the opposite direction via the actuator 14, so that according to the second position in the top row in Fig. 1, an excitation force is produced which acts in the same direction as the spring force. As a result, the tongs elements 3 are moved linearly until the tongs elements 3 reach a holding position H because a part connected to the tongs elements 3 rests against a stop 5. The tongs elements 3 can then not be moved any further.Due to the pneumatic excitation force still present, the driver 4 can now be moved linearly and, due to the positively guided connection with the gripper elements 3, closes them or positions the gripper elements 3 relative to each other so that they grip the longitudinal wire L. Thus, the translatory extension of the gripper elements 3 is followed by a rotational closing of the same by the driver 4.

[0038] The spring force exerted by spring 7 is necessary in this context to prevent the actuation of actuator 14 from simultaneously initiating a closing movement by driver 4. Due to the spring force, closing is only possible when stop 5 or holding position H is reached.

[0039] The position visible in Fig. 1 in the top row on the far right corresponds to a situation in which the longitudinal wire L is gripped with a clamping force and brought into a welding position. For this purpose, the actuator 14 can be pneumatically pressurized with a pressure of, for example, a few bar. The longitudinal wire L is then in the welding position corresponding to the bottom row, on the far left. In this situation, the actuator 14 can be depressurized. The spring force still acts to hold the tong elements 3 in the welding position. Furthermore, the tong elements 3, in interaction with the driver 4, can be configured in such a way, in particular by means of a downwardly opening angle, that the tong elements 3 cannot move in this pressure-free situation. The longitudinal wire L is then held only by friction.This is an optimal situation for the subsequent welding process, indicated by the arrow pointing to the longitudinal wire and indicating the pressure exerted by a welding head, which allows for the creation of very high-quality welds. The process then runs in reverse. The excitation force of actuator 14 initially ensures that the driver 4 is moved linearly in the opposite direction, which, due to the positive guidance, leads to the opening of the tong elements 3. Only once this opening has occurred can the tong elements 3 be moved back to their starting position A against the spring force of spring 7.

[0040] Fig. 2 schematically shows an analogous method for producing double-wire welds, comprising steps 1 to 7. In this case, a hold-down device 9 is also required. A longitudinal wire L is placed on a cross wire in the manner explained above and welded to it using a movable welding head 10. After the first longitudinal wire L has been welded to the cross wire, the tongs 2 are opened, the welding head 10 is raised and the tongs 2 are raised, and an additional tong takes over a second longitudinal wire L. This second longitudinal wire L is placed on the cross wire next to the first longitudinal wire L. A hold-down device 9 is then lowered onto the two longitudinal wires L so that the second longitudinal wire L cannot be pushed over the first longitudinal wire L. The tongs 2 are then positioned so that both longitudinal wires L are gripped from one side each, and the second longitudinal wire L can be welded to the cross wire.

[0041] A practical embodiment of a device 1 according to the invention can be seen in Fig. 3 and the cross-section according to Fig. 4. The device 1 comprises two tongs 2, each with two pairs of tong elements 3. The tong elements 3 are pivotally mounted about a pivot axis S and can be moved linearly between a starting position A and a holding position H. Typically, the device 1 is installed in a welding system such that the tong elements 3 can be moved vertically in order to grasp a longitudinal wire L, as explained in Fig. 1 or Fig. 2, and to hold it during welding. The tong elements 3 are connected to a block with a flange 11. The block with the flange 11 can be moved linearly on guide rods 12, up to a stop 5. In the opposite direction, springs 7 are mounted on the guide rods 12 and are clamped between the flange 11 and a counterpart 13.The clamp elements 3 are actuated by a pneumatic actuator 14. In the starting position A, the excitation force of the actuator 14 counteracts the spring force of the springs 7, so that the starting position A is maintained.

[0042] As can be seen in particular from Fig. 4, the tongs elements 3 are connected to the drivers 4. When two tongs 2, each with two tongs elements 3, are designed in pairs, a single driver 4 is preferably provided for all tongs elements 3. The driver 4 then actuates four tongs elements 3. The tongs elements 3 have lateral guides 6 for this purpose. The guides 6 can be designed as elongated holes, as shown, although other types of guides 6 are also possible. Extensions of the driver 4 engage in the guides 6. This means that during a linear movement of the driver 4, the tongs elements 3 are only pivoted mechanically about the pivot axis S due to the forced guidance.

[0043] Various operating states can be seen from Fig. 5 to Fig. 7, as explained with reference to the schematic representation in Fig. 1. Fig. 5 corresponds to a situation in which the pliers elements 3 are in a starting position A. A force applied by the actuator 14 counteracts a spring force of the springs 7. If the actuator 14 is now actuated in such a way that a force acts in the other direction, the force of the actuator 14 together with the spring force of the springs 7 ensure that the pliers elements 3 are moved linearly until the flange 11 comes to rest on the stop 5. The drivers 4 are not actuated during this linear movement, but rather the state according to Fig. 6, thus the holding position H, is reached first.Only when this holding position H is reached can the drivers 4 move linearly and, due to the positive guidance in the guides 6 of the tong elements 3, ensure the desired pivoting of the same and thus the gripping of a longitudinal wire L. The longitudinal wire L is then gripped and is in a suitable welding position. In this welding position, the actuator 14 can then be depressurized so that, with a suitable design of the guides 6, the longitudinal wire L is held on the contact surfaces 8 of the tong elements 3 only by friction and movement of the tong elements 3 is prevented. An angle of less than 5° formed by the contact surfaces 8 and open downwards is indicated by a dashed line in Fig. 7. The longitudinal wire L is then in an optimal starting situation A for the production of high-quality welded joints.

[0044] A device 1 according to the invention has, among other things, the advantage that it is very simply designed with only a single actuator 14 and, due to the provided positive guidance between the tongs elements 3 and the driver 4 as well as the spring forces by the springs 7 and a discrete sequence of linear movements and pivoting movements in the application, enables high-quality production of welded joints.

Claims

Patent claims 1. Device (1) for holding wires, in particular for holding wires during welding, for example during welding of longitudinal wires (L) of a grid mat to transverse wires thereof, wherein the device (1) comprises a pair of pliers (2) for holding the wires, characterized in that the pliers (2) comprise pivotable pliers elements (3) and at least one driver (4) for the pliers elements (3), wherein the pliers elements (3) can be moved with the at least one driver (4) essentially linearly from a starting position (A) into a holding position (H) and in this position can be pivoted relative to one another with the at least one driver (4), in particular in a positively guided manner, in order to hold a wire.

2. Device (1) according to claim 1, characterized in that the pliers elements (3) are pivotable only in the holding position (H).

3. Device (1) according to claim 1 or 2, characterized in that the pliers elements (3) are substantially linear, in particular vertical, up to a stop (5) are movable.

4. Device (1) according to one of claims 1 to 3, characterized in that the device (1) comprises an actuator with which the pliers elements (3) and / or the driver (4) can be moved and / or with which the pliers elements (3) can be pivoted.

5. Device (1) according to one of claims 1 to 4, characterized in that the pliers elements (3) have guides (6) which run obliquely with respect to a vertical axis (V) and in which a driver (4) engages, wherein the guides (6) are designed to move pliers elements (3) towards one another when the driver (4) is moved into the holding position (H).

6. Device (1) according to claim 5, characterized in that the guides (6) have a length and / or an angle relative to the vertical axis (V) such that in the holding position (H) when the pliers elements (3) are pivoted towards each other, contact surfaces (8) of the pliers elements (3) hold the wire by friction.

7. Device (1) according to one of claims 1 to 6, characterized in that the device (1) comprises a preferably pneumatic actuator (14) and a control device, wherein the control device controls the actuator (14) and wherein the control device optionally depressurizes the actuator (14) in the holding position (H) when the pliers elements (3) are pivoted towards one another.

8. Device (1) according to one of claims 1 to 7, characterized in that a single driver (4) is provided for pairs of cooperating pliers elements (3).

9. Device (1) according to one of claims 1 to 8, characterized in that several pairs of cooperating pliers elements (3) are provided.

10. Device (1) according to one of claims 1 to 9, characterized in that the device (1) comprises at least one spring (7) which presses the pliers elements (3) into the holding position (H).

11. Device (1) according to one of claims 1 to 10, characterized in that the device (1) comprises a linearly movable, in particular vertically movable, hold-down device (7).

12. Device (1) according to one of claims 1 to 11, characterized in that the pliers elements (3) are designed to grip wires with a wire diameter of 2 mm to 26 mm, preferably 4 mm to 20 mm.

13. Welding device with a plurality of devices (1) according to one of claims 1 to 12, wherein the devices (1) can be actuated separately from one another.

14. Method for welding wires, for example longitudinal wires (L) and transverse wires of a grid mat such as a reinforcement mat, in particular with a device (1) according to one of claims 1 to 12, wherein at least one wire is held during welding with a pair of pliers (2), characterized in that pivotable pliers elements (3) of the pliers (2) from a starting position (A) in Essentially moved linearly into a holding position (H) and pivoted in this position in order to hold at least one wire.

15. Method according to claim 14, characterized in that the pliers elements (3) and / or drivers (4) are moved pneumatically linearly to pivot the pliers elements (3).

16. Method according to claim 14 or 15, characterized in that the clamp elements (3) are subjected to a spring force during the linear movement from the starting position (A) to the holding position (H).

17. Method according to one of claims 14 to 16, characterized in that the wire is gripped in the holding position (H) with a clamping force, after which the clamping force is reduced and the wire is held by friction during welding.

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