Wire feeding system

Abstract

An auxiliary wire feeder has a pushing device for advancing welding wire, a control device for controlling the pushing device, and an electric contact adapted for being in electrical connection with the welding wire. The electric contact is connected to the control device for supplying a control signal to the control device. A welding system comprises an auxiliary wire feeder of this kind and further a welding torch, a main wire feeder, a wire guide for guiding welding wire from a supply to the welding torch and a welding current contact for supplying welding current to the welding wire. For controlling an auxiliary wire feeder in a welding system having a welding torch, a main wire feeder, a wire guide for guiding welding wire from a supply to the welding torch, a welding current contact for supplying welding current to the welding wire, the control of the auxiliary welding wire feeder is responsive to an electrical signal transmitted via the welding wire.

Claims

1. A method for controlling an auxiliary wire feeder in a welding system having a welding torch, a main wire feeder, a wire guide guiding welding wire from a supply to the welding torch, a welding current contact supplying welding current to the welding wire, the auxiliary wire feeder having a pushing device advancing welding wire, a control device controlling the pushing device, and an electrical contact connected to the control device supplying a control signal to the control device and being electrically connected to the welding wire for picking up an electrical voltage signal on the welding wire, the control device being responsive to when the electrical voltage signal is supplied to the welding wire, sensing when the welding current is supplied to the welding wire, and powering the auxiliary wire feeder on and off, independently of the main wire feeder, in response to when the electrical voltage signal is picked up on the welding wire as a result of the welding current being supplied to the welding wire, wherein the control device comprises a voltmeter relay.

2. The method of claim 1 wherein the electrical voltage signal is the electrical potential present between the welding wire and ground.

3. The method of claim 2 wherein the control device interprets the electrical potential being above a predefined threshold as a signal for operating the pushing device.

4. The method of claim 1 wherein the main wire feeder applies the control signal to the welding wire.

5. The method of claim 1 wherein the control device shuts down the pushing device, after receiving a signal for stopping the pushing device, with a stop delay.

6. The method of claim 1 wherein the control device completely stops the pushing device after an adjustable lapse of time to prevent an overheated condition.

7. The method of claim 1 wherein the auxiliary wire feeder includes at least one pulley for cooperating with the welding wire, the pulley forming the electrical contact with the welding wire.

8. The method of claim 7 wherein the pulley is connected to the pushing device for advancing the welding wire.

9. The method of claim 7 wherein the pulley is a pressing pulley for pressing the welding wire against a drive pulley connected to the pushing device.

10. The method of claim 1 wherein the electrical contact is a collector ring contact.

11. The method of claim 1 wherein the pushing device comprises an electric motor.

12. The method of claim 1 wherein a slip clutch is provided in a force flow path from the pushing device to the welding wire for preventing creation of excessive torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the enclosed drawings. In the drawings,

(2) FIG. 1 schematically shows a welding system according to an embodiment of the invention in a shutdown condition,

(3) FIG. 2 shows the system of FIG. 1 during a welding operation,

(4) FIG. 3 shows the system of FIG. 1 in a different view,

(5) FIG. 4 shows at an enlarged scale the auxiliary wire feeder as used in the welding system of FIG. 1,

(6) FIG. 5 shows a detail of the auxiliary wire feeder of FIG. 4, and

(7) FIG. 6 shows a second detail of the auxiliary wire feeder of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

(8) In FIGS. 1, 2 and 3, a welding system is shown which comprises a welding torch 10 which is here mounted to a welding robot 12, a main feeder for feeding welding wire to the welding torch 10, and a welding wire supply 16. Welding wire supply 16 is here a bulk container which can comprise a coil formed from several hundred kilograms of welding wire.

(9) In view of its weight and further in view of considerations such as accessibility etc., welding wire supply 16 is usually arranged at a distance from welding torch 10. Welding wire 18 from welding wire supply 16 is guided towards main feeder 16 and welding torch 10 by means of a wire guide 20. Wire guide 20 can be any device which allows to reliably guide the welding wire from welding wire supply 16 towards welding torch 10. Preferably, wire guide 20 is formed from a plurality of interconnected bodies which each rotatably support a couple of rolls. The rolls guide the welding wire 18 in the interior of the bodies with low friction while at the same time ensuring that the wire guide 20 can follow the movements of welding torch 10.

(10) At a suitable location between welding wire supply 16 and main feeder 14 and preferably close to welding wire supply 16, an auxiliary wire feeder (also referred to as booster feeder) 22 is arranged. The purpose of auxiliary wire feeder 22 is to provide a pushing effect on welding wire 16 for pushing the welding wire towards main feeder 14, or to at least assist the effect of main feeder 14.

(11) Auxiliary wire feeder 22 comprises a pushing device (briefly shown with reference numeral 24 in FIG. 4) for advancing the welding wire. Pushing device 24 preferably comprises an electric motor which cooperates with a drive pulley 26 (please see FIG. 6).

(12) The welding wire is biased against drive pulley 26 by means of a pushing pulley 28 so that any rotational movement of drive pulley 26 generated by means of pushing device 24, is transmitted into a longitudinal movement of the welding wire, advancing the welding wire towards main feeder 14.

(13) Drive pulley 26 can be formed from PEEK. Pushing pulley 28 is preferably formed from steel or a similar, electrically conductive material.

(14) Pushing device 24 is controlled by means of a control device 30 (please see FIG. 4). Control device 30 controls operation of pushing device 24 (meaning in particular the start and the stop of pushing device 24) and can also control the speed of operation of the pushing device.

(15) Control device 30 is responsive to a control signal which is transmitted via welding wire 18. The control signal in particular is the presence of a certain electrical potential (voltage) between welding wire 18 and ground. In particular, the electrical potential is the electrical potential which is used for generating a welding arc (please see FIG. 2) at the welding torch for generating a welding seam.

(16) The electrical signal present in welding wire 18 is sensed by control device 30 by means of an electrical contact which is in electrical connection with welding wire 18. In the embodiment shown in the drawings, the electrical contact is formed by pushing pulley 28 which is connected via a transmission cable 32 to control device 30.

(17) Auxiliary wire feeder 22 is furthermore provided with electric power by means of a power connector 34. The electrical power supplied via connector 34 is in particular used for operation of pushing device 24.

(18) As long as the welding system is in the condition of FIG. 1 where no welding seam is being formed, no electrical potential is generated between welding wire 18 and ground. This is interpreted by control device 30 of auxiliary wire feeder 22 as an indication that there is no need for advancing the welding wire.

(19) When a welding seam is to be generated, an electrical potential of typically approximately 40 Volts is applied between welding wire 18 and ground. Approximately at the same time, main feeder 14 advances the welding wire, and a welding arc is generated at the tip of welding torch 10. Then, the electrical potential between the welding wire and ground drops to a value of approximately 10 Volts, and welding continues.

(20) As soon as the electrical potential is generated between welding wire 18 and ground, this is sensed by control device 30 via the electrical connection established between the welding wire and the control device by means of pushing pulley 28 and cable 32. The presence of the electrical potential is interpreted by control device 30 as a request that welding wire is being advanced, and control device 30 starts pushing device 24. Accordingly, auxiliary wire feeder 22 advances the welding wire towards main feeder 14.

(21) When the welding process is to be stopped, the electrical potential generated between welding wire 18 and ground is removed, and the welding arc extinguishes. The drop of the voltage sensed by control device 30 is interpreted as an indication that no more welding wire is to be advanced towards main feeder 14. Accordingly, control device 30 shuts down pushing device 24. This can be done with a certain delay of one or two seconds, if desired.