Welding wire conveyor device and method for operating a welding wire conveyor device

Abstract

The invention relates to a welding wire conveying device (100) for automatically conveying a welding wire (20) from a welding wire reservoir (22) to a welding location (80), comprising a first wire conveyor (30) downstream of the welding wire reservoir (22), a wire buffer arrangement (50) downstream of the first wire conveyor (30), in which a welding wire buffer loop (210) is formed during conveying operation, the amplitude (A) of which is monitored by a loop monitoring device (52), a second wire conveyor (40) downstream of the wire buffer arrangement (50), an electrically actuated welding wire cutter (60) upstream of the wire buffer arrangement (50), which cuts the welding wire (20) as required, and a system control (70) which is connected via signal connections to the loop monitoring (52) and the welding wire separator (60), and which has a separation value memory (74) in which a lower amplitude limit value (LA) is stored, at which the welding wire (20) in the wire buffer arrangement (50) forms a buffer loop (210') with a lower limit amplitude, wherein the system control (70) activates the welding wire cutter (60) when the loop monitoring (52) signals an amplitude (A) below the amplitude limit value (LA), and continues the conveying operation for at least two seconds.

Description

[0001] The invention relates to a welding wire conveying device for automatically conveying a welding wire from a welding wire reservoir to a welding location, and relates to a method for operating such a welding wire conveying device.

[0002] Welding wire conveying devices are known, for example, from EP 0 130 104 A2, US 4 572 421 A, US 4 422 583 A, CN 219944891 U, CN 117182256 A, US 4 674 668 A and WO 2005 002 775 A1.

[0003] A welding wire conveyor automatically conveys a welding wire from a welding wire reservoir to a welding location. Since the quality of the weld seam produced at the welding location depends to a large extent on the continuous conveyance of the welding wire at the welding location, a wire buffer arrangement is provided between a first wire conveyor and a second wire conveyor. This buffer arrangement compensates for minor deviations in the effective conveying speeds between the first and second wire conveyors. For this purpose, the welding wire forms a buffer loop in the wire buffer arrangement. The amplitude of the buffer loop is monitored by a loop monitoring system, whereby the wire conveyors are suddenly switched off if the amplitude of the buffer loop in the wire buffer arrangement reaches an extreme lower or upper value.One possible cause for this could be a kink or knot in the welding wire, which can lead to complications, especially in the wire feeders. The sudden shutdown abruptly interrupts the welding process, which is fundamentally undesirable.

[0004] The object of the invention is to provide a welding wire conveyor device and a method for operating a welding wire conveyor device with improved fault behavior.

[0005] This object is achieved according to the invention by a welding wire conveying device having the features of device claim 1 and a method for operating a welding wire conveying device having the features of method claim 4.

[0006] The welding wire conveying device according to the invention for automatically conveying a welding wire from a welding wire reservoir to a welding location comprises a first wire conveyor downstream of the welding wire reservoir, a wire buffer arrangement downstream of the first wire conveyor and a second wire conveyor downstream of the wire buffer arrangement.

[0007] The welding wire reservoir can be designed, for example, as a wire drum or a basket spool. The second wire feeder is preferably operated as a so-called master drive. The first wire feeder is then operated as a slave drive, since its feed speed is based on the feed speed of the second wire feeder.

[0008] The wire buffer assembly forms a welding wire buffer loop, the amplitude of which is monitored by a loop monitor. Loop monitoring can be performed contactlessly, for example, using camera surveillance. However, loop monitoring can also be implemented mechanically, for example, in the form of a pivoting rocker, with approximately the center of the welding wire buffer loop guided to its free end, so that the free end of the rocker follows the amplitude of the welding wire buffer loop. A rotation angle sensor is provided at the other end of the rocker, which determines the pivot angle of the rocker, so that the amplitude of the welding wire buffer loop can be determined from this.

[0009] An electrically actuated welding wire cutter is provided upstream of the wire buffer arrangement to cut the welding wire as required.

[0010] Furthermore, a system control system is provided, which is connected to the loop monitoring system, the welding wire cutter, and the two wire feeders via signal connections. The system control system has a cut-off value memory in which a lower amplitude limit is stored, at which the welding wire in the wire buffer arrangement forms a buffer loop with a lower limit amplitude. The system control system can have further limit value memories in which, for example, extreme values ​​for the buffer loop amplitude are stored, upon reaching which, for example, the entire welding wire conveyor device or the two wire feeders are immediately stopped. The cut-off value memory preferably does not contain a value as the lower amplitude limit at which the amplitude is already equal to zero.The amplitude limit value stored in the cut-off value memory is less extreme than the cut-off extreme value(s) that may also be stored and does not functionally require immediate cut-off.

[0011] The lower amplitude limit stored in the cutoff value memory is typically reached as soon as the feed resistance increases permanently. The feed resistance typically increases when a knot in the welding wire enters the feed path, i.e., as soon as the knot in question leaves the welding wire reservoir. Such a knot does not necessarily require an immediate shutdown of both wire feeders.

[0012] According to the invention, it is therefore provided that the system control activates the welding wire cutter when the loop monitoring signals an amplitude value below the amplitude limit value, so that the welding wire is severed before the relevant node can cause further disturbances.

[0013] Preferably, the feed operation continues for at least a few seconds after the welding wire trainer is activated. Feed operation can generally continue until the severed welding wire end reaches the first wire feeder. This allows enough time to complete the welding process at the welding location in a controlled manner, ensuring that the quality of the weld seam is not compromised. Under certain circumstances, feed operation can also continue until the severed welding wire end reaches the second wire feeder.

[0014] Preferably, the welding wire cutter is arranged between the first wire conveyor and the welding wire reservoir. This allows a knot to be severed from the conveyed welding wire before the knot reaches the first wire conveyor, where it could cause a sudden reduction in the conveying speed. The welding wire conveyor can continue to feed for at least a few seconds, for example, until the knot-free, severed end of the welding wire reaches the first wire conveyor. This allows enough time to complete the welding process at the welding location in a controlled manner.

[0015] The inventive method according to claim 4 relates to the operation of a welding wire conveyor having the structural features of claim 1.

[0016] The method initially comprises the step of activating the welding wire cutter by the system control system as soon as the loop monitoring signals an amplitude value for the welding wire buffer loop in the wire buffer arrangement below the amplitude limit. The welding wire is completely severed by the welding wire cutter, wherein the knot of the welding wire that may be responsible for activating the welding wire cutter remains upstream of the welding wire cutter, and the knot-free end of the welding wire is located downstream of the welding wire cutter.

[0017] The conveyor operation continues for at least two seconds after the welding wire cutter is activated and is therefore not stopped immediately. The welding wire feed must be stopped at the earliest when the severed welding wire end reaches the first wire feeder, but may continue to run until the severed welding wire end reaches the second wire feeder.

[0018] The figure schematically shows a welding wire conveying device according to the invention and the method according to the invention for operating the welding wire conveying device.

[0019] The figure schematically shows a welding wire conveyor device 100, which serves to continuously convey a welding wire 20 from a welding wire reservoir 22 to a welding location 80. The welding wire conveyor device 100 can be part of a welding robot that generates a weld seam 216 from the welding wire 20 at the welding location 80.

[0020] The welding wire conveyor device 100 essentially comprises a first wire conveyor 30 downstream of the welding wire reservoir 22, a wire buffer arrangement 50 downstream of the first wire conveyor 30, a second wire conveyor 40 downstream of the wire buffer arrangement 50, and an electrically actuated welding wire separator 60 between the welding wire reservoir 22 and the first wire conveyor 30.

[0021] In an interior space 59 of the wire buffer assembly 50, the welding wire 20 forms a welding wire buffer loop 210, the amplitude of which is held in a central position by appropriate control of the two wire feeders 30, 40, as long as no major disturbances occur. The wire buffer assembly 50 has a loop monitor 52, by which the amplitude A of the buffer loop 210 is monitored. In the present case, the loop monitor 52 is mechanically designed and has a swing arm 54 pivotably connected to the housing by one swing end, with a follower eye 55 at the free swing end, through which a central region of the buffer loop 210 is passed. On the housing side, the loop monitor 52 has a rotation angle sensor 58, which detects the relative or absolute rotation angle of the swing arm 54.

[0022] The wire buffer arrangement 50 is controlled and regulated by a system control 70, which is connected via signal connections to the loop monitoring system 52, the two wire feeders 30, 40, and the wire buffer arrangement 50, or to the rotation angle sensor 58. The electronic system control 70 includes, among other things, a cut-off value memory 74 and a control module 76, which intervenes in the event of a malfunction in the welding wire feed. A lower amplitude limit value LA is stored in the cut-off value memory 74, at which the welding wire 20 forms a buffer loop 210' with a lower limit amplitude in the wire buffer arrangement 50.

[0023] During conveying operation, the first wire conveyor 30 feeds the welding wire 20 from a wire supply 201 of the welding wire reservoir 22. The first welding wire section 204 between the wire supply 201 and the first wire conveyor 30 is pulled by the first wire conveyor 30. The first wire conveyor 30 pushes the downstream welding wire section 206 to the wire buffer assembly 50, where the welding wire 20 forms the buffer loop 210 with an amplitude A. The welding wire section 212 downstream of the wire buffer assembly 50 is pulled by the second wire conveyor 40. The welding wire section 214 emerging from the second wire conveyor 40 is finally fed to the welding location 80, where the weld seam 216 is generated.

[0024] The loop monitoring system 52 continuously sends a measured value for the amplitude A of the buffer loop 210 to the system control system 70. During trouble-free operation, the system control system 70 controls the two wire feeders 30, 40 such that the welding wire buffer loop 210 in the wire buffer arrangement 50 remains with its amplitude A between an upper buffer loop 210" and a lower buffer loop 210'.

[0025] As soon as a kink or knot 202 of the welding wire 20 coming from the wire supply 201 reaches the inlet opening of the conveyor path, the friction increases, so that the effective feed rate of the first wire feeder 30 decreases. As a result, the amplitude A of the buffer loop 210 in the wire buffer arrangement 50 decreases until the amplitude A reaches the amplitude limit value LA, at which the buffer loop 210' forms a lower limit amplitude.

[0026] As soon as the loop monitor 52 signals an amplitude A below the amplitude limit value LA, the system control 70 activates the welding wire cutter 60 before the welding wire knot 202 reaches the welding wire cutter 60. The welding wire cutter 60 completely severs the welding wire 20, so that the conveyance of the welding wire 20 does not have to be interrupted immediately, but initially continues without disruption for at least several seconds, since the welding wire knot 202 no longer contributes to friction. In principle, the conveying operation can be continued until the loose end of the remaining welding wire 20 reaches the second wire feeder 40. For this purpose, the loop monitor 52 is no longer observed after the activation of the welding wire cutter 60.

[0027] Alternatively, the amplitude A of the buffer loop 210' continues to be monitored after the activation of the welding wire cutter 60. Only if the amplitude A returns to a tolerable center position within 2.0 seconds will the second wire feeder 40 be or remain activated.

[0028] In this way, after the activation of the welding wire cutter 60, there is enough time to complete the welding process in a controlled manner so that the quality of the weld seam 216 is not compromised.

Claims

[1] Welding wire conveying device (100) for automatically conveying a welding wire (20) from a welding wire reservoir (22) to a welding location (80), with a first wire conveyor (30) downstream of the welding wire reservoir (22), a wire buffer arrangement (50) downstream of the first wire conveyor (30), in which a welding wire buffer loop (210) is formed during conveying operation, the amplitude (A) of which is monitored by a loop monitoring device (52), a second wire conveyor (40) downstream of the wire buffer arrangement (50), an electrically actuated welding wire cutter (60) upstream of the wire buffer arrangement (50), which cuts the welding wire (20) as required, and a system control (70) which is connected via signal connections to the loop monitoring (52) and the welding wire separator (60), and which has a separation value memory (74) in which a lower amplitude limit value (LA) is stored, at which the welding wire (20) in the wire buffer arrangement (50) forms a buffer loop (210') with a lower limit amplitude, wherein the system control (70) activates the welding wire cutter (60) when the loop monitoring (52) signals an amplitude (A) below the amplitude limit value (LA). [2] Welding wire feeding device (100) according to claim 1, wherein the welding wire separator (60) is arranged between the first electric wire feeder (40) and the welding wire reservoir (22). [3] Welding wire conveying device (100) according to claim 1 or 2, wherein after activation of the welding wire separator (60), the welding wire conveying is continued for at least 2 seconds. [4] Method for operating a welding wire conveyor device (100) for automatically conveying a welding wire (20) from a welding wire reservoir (22) to a welding location (80), wherein the welding wire conveyor device (100) has the following features: a first electric wire feeder (30) downstream of the welding wire reservoir (22), a wire buffer arrangement (50) downstream of the first wire conveyor (30), in which a welding wire buffer loop (210) is formed during conveying operation, the amplitude (A) of which is monitored by a loop monitor (52), a second electric wire feeder (40) downstream of the wire buffer arrangement (50), an electrically actuated welding wire cutter (60) upstream of the wire buffer arrangement (50) which cuts the welding wire (20) as required, and a system control (70) which is connected via signal connections to the loop monitoring (52) and the welding wire separator (60), and which has a separation value memory (74) in which a lower amplitude limit value (LA) is stored, at which the welding wire (20) in the wire buffer arrangement (50) forms a buffer loop (210') with a lower limit amplitude, with the procedural steps: Activation of the welding wire cutter (60) by the system control (70) when the loop monitoring (52) signals an amplitude (A) below the amplitude limit value (LA), and Continue conveying operation for at least two seconds. [5] A method of operating a welding wire feed device (100) according to claim 4, wherein the welding wire separator (60) is arranged between the first electric wire feeder (40) and the welding wire reservoir (22).

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