GB2178989A - Automatic welding device - Google Patents

Abstract

A welding device, suitable for use by relatively unskilled personnel, comprises a rigid frame 3 and a linear edge 9 fixed relative to it to locate the frame in the desired position relative to the intended wed. A welding torch 8 supported upon the frame comprises a torch nozzle 11 approximately aligned with the linear edge. Guide means 7 are provided which define a linear path of movement of the torch nozzle substantially parallel to the linear locating edge. The linear edge may be in two or more spaced-apart sections and the welding nozzle may be located between these sections, Figures 2 and 3, not shown. <IMAGE>

Description

SPECIFICATION Welding device The present invention is a novel welding device, which lends itself to the carrying out of numerous diverse welding operations by relatively unskilled personnel.

Welding is, of course, a widely used technique in all the metal construction and fabrication industries. In its many forms it is extensively practised in particular in ship-building and in the construction of modules or complete assemblies for the off-shore exploration and production of oil and gas. Welding may be used to secure components together on a permanent basis but may also be applied (as so-called "tack" welding) to secure components temporarily in correct relative alignment before welding them together permanently, or to attach features such as lifting lugs, temporarily or permanently, to facilitate erection of larger units.

Tack welding and the attachment of fixtures facilitating erection tend to be entrusted to workers who are not fully experienced skilled welders and consequently unsatisfactory welds and damage can result. The time which may be wasted in checking an rectifying such unsatisfactory tack welds or damage may amount to a serious loss of productivity overall and it is therefore desirable that such time losses be minimised.

We are aware that devices have been proposed to assist welders in improving the quality, speed or positioning of welding operations but such devices do not simplify the task of the unskilled operative and may entail heavy base structures or delicate setting operations scarcely relevant to the carrying out of relatively routine tack welding and similar welding operations in a variety of situations by operatives of limited welding skill.

The problem has been further aggravated by the increasing use of inert-gas-type welding techniques in shipbuilding, since such techniques are more difficult to control than, for example, conventional stick welding and are therefore even less adapted to unskilled operation.

It is therefore an object of the present invention to provide a welding device which is particularly suitable for operation by unskilled or relatively unskilled operators, especially but not exclusively for forming tack welds or other relatively short welding runs.

The device according to the present invention comprises a rigid frame, a linear edge fixed relative to said frame for locating the frame in a desired position relative to the intended weld, a welding torch supported upon said frame comprising a torch nozzle in approximate alignment with said linear edge, and guide means defining a linear path of movement of said torch nozzle, said linear path being substantially parallel to said linear locating edge.

As will be readily understood, in operation of the device according to the present invention, the linear locating edge may be placed in the angle of contact between the components to be welded together and, with the frame thus located and held stationary, the welding torch can traverse the linear path defined by the guide means and form the required weld in alignment with, but displaced from, the locating edge.

The locating edge may be continuous or discontinuous but in either case is preferably tapered towards the edge itself in order to maximise the accuracy with which the frame is located in the desired position.

Thus the edge may be elongated or may be formed by two or more linearly spaced sections. In the latter case, the torch nozzle may advantageously be disposed between the spaced sections.

The linear movement of the torch nozzle along the path defined by the guide means may be effected manually but it is much preferred that a suitable drive for that purpose be provided. Thus a motor, for example a mechanical or pneumatic motor but preferably an electric motor, may be housed within the device to move the nozzle along its linear path. The length of the path and/or the velocity of the nozzle along it may be variable.

The whole operation of forming the weld may be automatic such that, once the welding frame has been located in its intended position, a single step such as the pressing of a start button will initiate the welding cycle and cause the nozzle to traverse its pre-determined path at a velocity appropriate to the formation of a continuous weld of pre-determined size, the nozzle automatically coming to rest and the torch being switched off at the end of its traverse. Such automatic operation is preferably controlled by means of a solid state controller also housed within the welding device.

In a preferred form of automatically-controlled welding device according to the present invention, the nozzle is automatically returned to its start position at the completion of the welding stroke, optionally after automatic crater filling as described below. If desired, this return stroke may be effected at a greater velocity than the welding stroke.

The control may include a facility to operate the welding stroke in the reverse direction, that is to form the weld in whichever direction of movement of the nozzle is selected. In this way, in a given orientation of the welding device, it may be possible to form the weld by choice either from right or left or vice versa or, more importantly, either upwards or downwards. Since forming a vertical weld is more easily done when working downwardly, that is a uniform weld is more readily produced in that direction, the facility to choose the direction of the welding stroke may be an important consideration in the use of the device by an inexperienced operative.

The invention will now be further described with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of one embodiment of the welding device according to the present invention; Figure 2 is an elevational view of a second embodiment of the welding device according to the invention; and Figure 3 is an elevational view, partly in section, of a third embodiment of the device.

The illustrated welding device illustrated in Figure 1 has been designed to be relatively light in weight, weighing less than 3 kg, and is ergonomically styled so that it can be used by the operator in a wide range of physical working positions. Its main outline comprises a butt or body part 1, linked by a stock 2 to a torch support 3. From the butt 1 an operating handle in the shape of a pistol grip 4 extends and the support frame 3 incorporates a handle 5. Thus the whole device can be comfortably gripped and supported by means of the two handles 4 and 5.

The support frame 3 carries a housing 6 from which a pair of parallel torch guides 7 extend vertically upwards. Between the guides 7 the operating head of the welding torch 8 itself is a sliding fit.

Integral with the frame 3 are two linearly spacedapart blades 9, of which the edges 10 are aligned with each other to form the locating edge for the welding device. The contact tip at the nozzle 11 of the torch 8 projects to a point at which it is slightly rearward of that locating edge and its spacing from that edge remains constant throughout movement of the torch 8 along the guides 7, the preset spacing being adjustable to vary the wire "stickout".

The housing 6 contains the electrical drive mechanism by means of which the torch 8 is caused to traverse its linear path between the guides 7. Control of the drive mechanism, including selection of the torch path length and its traverse velocity in each direction, together with control of the welding cycle itself, is afforded by a solid state controller located in the butt 1.

Supply of the welding consumable, for example mild steel or other metal wire, to the torch nozzle is via the torch cable 12 extending generally parallel to the stock 2 and terminating at its feed end in a quick-release connector 13 to facilitate easy disconnection of the welding device.

The pistol grip 4 carries two operating buttons, namely a "start" button 14 and an "abort" or emergency stop button 15.

In operation of this device, the operator locates the blade edges 10 in the angle formed between the two components to be welded together, in such a position down the length of that angle that the contact tip of the welding torch nozzle 11 is opposite the point where it is intended that the weld should begin. He then simply presses the start button 14 and the welding cycle then takes place solely under instruction from the controller in the butt 1. That is, the arc is struck and welding begins, the torch head 8 moves at a uniform predetermined velocity along the path defined by the guides 7 and forms a continuous weld as it moves (welding metal being supplied continuously as required via the nozzle 11) and finally, at the end of the predetermined linear movement of the torch head 8, the welding operation ceases and the torch head returns to its start position (as illustrated).

In an emergency, or if it is desired to shorten the weld length, the welding operation may be terminated by the operator pressing the abort button 15.

To terminate the weld correctly, the welding current remains on for a brief final back-tracking of the torch in order to achieve crater filling of the weld.

Figure 2 shows an alternative embodiment of the welding device, which functions in a generally similar manner to the device of Figure 1. The frame 20 of this welding device is essentially in the form of an inverted 'U', with a control box 21 built into the upper end of the frame and operated by buttons or triggers 22. In this embodiment, the welding torch nozzle 23 is located between, and approximately in line with, blade edges 24. Traversing of the nozzle 23, which is fed with welding consumable by a tube 25, is achieved by a linear drive mechanism housed in a tubular crossmember 26 and driven by a linear actuator (not shown).

The form of the device illustrated in Figure 2 is a slightly more compact arrangement than that of Figure 1 and has the advantage that, particularly when the weldments may not be straight, any resulting alignment error is minimised. It is particularly useful in situations where the operator has to work in a stretched position, for example at an overhead point which is difficult of access, and has the further advantage of distancing the welder somewhat from the welding fumes.

The further form of the invention which is illustrated in Figure 3 is compact in dimensions and design and is ideal for use in a relatively confined space, wherein the devices shown in Figures 1 and 2 would not easily fit.

However, it may, of course, be used in non-confined situations and is therefore of wide applicability. This device also is based on a U-shaped frame 30 with a tubular cross-member 31.

The member 31 houses a linear drive mechanism, the shuttle 33 of which supports the welding torch through a guide slot in that member. A lead screw 32, driven by an electric motor 36, engages a threaded bore in the centre of the shuttle 33 and causes it to advance whithin the cross-member 31 and thereby cause a goose-neck welding nozzle 34 to traverse in the direction of the arrows between locating blades 35.

The devices illustrated in the drawings may be used for any of those welding systems which rely upon a stream of ionised metal particles, for example the metal inert gas (MIG), tungsten inert gas (TIG) and other low hydrogen systems. They are disigned for easy use in a wide range of locations and welding positions by an unskilled operator and are suitable for both butt welding and fillet welding tasks. The control unit may be used to reverse the direction of weld formation as described above and may, if desired, include manual controls permitting the operator to vary the weld length or torch traverse velocity.

The device has been described especially in the context of tack welding by unskilled operators buy may, of course, be used to perform other welding tasks as desired. In experimental operation, however, it has been found that totally unskilled operatives are able to produce good quality welds repeatedly after only a few minutes' operation.

Claims (14)

1. A welding device comprising a rigid frame, a linear edge fixed relative to said frame for locating the frame in a desired position relative to the intended weld, a welding torch supported upon said frame comprising a torch nozzle in approximate alignment with said linear edge, and guide means defining a linear path of movement of said torch nozzle, said linear path being substantially parallel to said linear locating edge.

2. A welding device as claimed in claim 1, wherein the linear locating edge is tapered towards said edge.

3. A welding device as claimed in either of the preceding claims, wherein the linear locating edge is formed by two or more linearly-spaced sections.

4. A welding device as claimed in claim 3, wherein the torch nozzle is disposed between said spaced sections of said locating edge.

5. A welding device as claimed in any of the preceding claims, wherein the torch nozzle is movable along its linear path by a powered drive.

6. A welding device as claimed in claim 5, wherein said powered drive is an electric motor.

7. A welding device as claimed in claim 5 or claim 6, wherein the length of path and/or the velocity of the nozzle along it is variable.

8. A welding device as claimed in any of claims 5 to 7, wherein the whole welding operation is automatic once it has been initiated.

9. A welding device as claimed in claim 8, wherein the welding operation is controlled by means of a solid state controller.

10. A welding device as claimed in either of claims 8 and 9, wherein the nozzle is automatically returned to its start position at the completion of the welding stroke.

11. A welding device as claimed in claim 10, wherein the return stroke is faster than the welding stroke.

12. A welding device as claimed in any of claims 5 to 11, wherein the welding stroke may be operated in either linear direction.

13. A welding device substantially as hereinbefore described with reference to, and as illustrated in, Figure 1 of the accompanying drawings.

14. A welding device substantially as hereinbefore described with reference to, and as illustrated in, Figure 2 or Figure 3 of the accompanying drawings.