GB2055657A - An attachment for reducing concentrations of ozone at an electric arc - Google Patents

Abstract

An attachment for an electric arc torch, for welding (e.g. MIG), cutting or hard surfacing, comprises first and second spaced tubular hoop-like members 1,2. Each member 1,2 has a plurality of orifices which communicate with a suction pump. A wire mesh extends across and depends from the member 2 to form a skirt 9. When operatively attached to a torch 15, the skirt 9 surrounds the arc generated during a working operation. The skirt 9 retains flying sparks and reduces the reflection of ultraviolet radiation from the arc thereby reducing the formation of ozone. Any ozone formed is sucked into the members 1,2 via the orifices. <IMAGE>

Description

SPECIFICATION An attachment for reducing concentrations of ozone at an electric arc The present invention relates to attachments for arc welding machines for reducing the formation of ozone when working with an electric arc and extracting at least some of any ozone produced from the vicinity of the arc during a welding, cutting or hard surfacing operation.

It is recognised in the welding industry that toxic and noxious gases and fumes are generated during an arc welding operation which gases and fumes are harmful to the health of an operator. In particular, during metal-inertgas (MIG) welding where high currents in the region of 350 to 400 amps can be used, when welding or cutting certain materials such as aluminium and stainless steel comparatively large amounts of ozone are formed which, if inhaled by an operator, could damage his health. It is believed that certain wavelengths of ultraviolet light which are generated at the arc and reflected by the workpiece cause the formation of ozone from the oxygen in the atmosphere surrounding the arc. Some of the ozone which is produced by the ultraviolet radiation decomposes when heated.It follows, therefore, that at the vicinity of the arc two reactions occur, one forming and the other decomposing the ozone. It has been found that a peak concentration of ozone is usually produced a few centimetres from the arc.

It is known to provide means for sucking oxides of nitrogen and fumes generated by the arc from the vicinity of the arc. However, it has been found that this has only exacerbated the problem of the formation of ozone since the fumes when present at the vicinity of the arc provide a blanket effect which tends to reduces the reflection of ultraviolet radiation and therefore reduce the generation of ozone. Futhermore, in MIG welding difficulties have been experienced when utilising suction means for removing unwanted gases and fumes from the vicinity of the arc in that the suction means has been known to disturb the flow of a shielding gas around the arc.

It is an aim of the present invention to provide an attachment for arc welding machines that not only seeks to extract oxides of nitrogen and fumes from the vicinity of the arc but also seeks to reduce the formation of ozone and extract any ozone which is likely to formed by ultraviolet radiation during the welding operation.

According to the present invention, an attachment for arc welding machines for reducing the formation of ozone when working with an electric arc and extracting at least some of any ozone if formed from the vicinity of the arc comprises first and second spaced, tubular, hoop like members each having a plurality of spaced orifices around its periphery, which orifices communicate via the interior of the member with a suction pump, a wire mesh extending across and depending from the periphery of the second tubular member to form a skirt, the arrangement of the first and second hoop like members and the wire mesh being such that when the attachment is operatively positioned on the welding machine, the welding torch extends first through the first hoop like member, second through the wire mesh extending across the second hoop like member, and finally through the second hoop like member so that the skirt surrounds the arc generated during a working operation, and means for attaching the attachment to the welding machine.

In a preferred embodiment, a hole is formed in the wire mesh extending across the second member to permit an operator to see the arc during a welding, cutting or hard surfacing operation.

An embodiment of the invention will now be described, by way of example, reference being made to the Figures of the accompanying diagrammatic drawings, in which: Figure 1 is a side view of an attachment for arc welding machines for reducing the formation of ozone when working with an electric arc and for extracting at least some of any ozone if formed from the vicinity of the arc, the attachment being attached to the welding torch of a welding machine; Figure 2 is an inverted plan view of the attachment of Fig. 1; and Figure 3 is a perspective view of the attachment of Fig. 1.

As shown, an attachment for reducing the formation of ozone when working with an electric arc and extracting at least some of any ozone if formed from the vicinity of the arc comprises first and second spaced, tubular, hoop-like members 1, 2. Each member 1, 2 is made from aluminium tubing which has been formed into a closed oval hoop. Each member 1, 2 has a plurality of spaced orifices 3, 4 respectively. The orifices 4 in the member 2 are of different sizes. The orifices 3, 4 communicate respectively with conduits 5, 6 which meet in a main pipe 7 communicating with a suction pump (not shown).

The member 1 rests above a wire mesh of stainless steel which extends across the upper (as shown) side of the second member 2 and depends from the periphery of the second member 2 to form a skirt 9. A hole 10 is formed in the wire mesh extending across the member 2 which permits an operator to see the welding arc during a welding, cutting or hard surfacing operation. Extending across the second member 2 is a bracket 1 2 which supports a collar 1 3. The collar 1 3 is split and can be tightened, as will be explained, around a welding torch 1 5 by means of a bolt 1 4.

In use, the attachment is attached adjustably to the welding machine by means of the collar 1 3 and bolt 1 4. The attachment is operatively positioned on the welding machine such that the welding torch 1 5 extends first through the member 1, second through the wire mesh extending across the second member 2 and finally through the second member 2 so that the skirt 9 surrounds the welding electrode 16. When the bolt 14 is tightened down the collar 1 3 will grip tightly around the welding torch 1 5.

When the MIG welding, cutting or hard surfacing operation is commenced, an arc will be generated at the tip of the welding electrode 1 6 which arc will extend downwardly towards the workpiece (not shown). The arc will be surrounded by a shielding gas such as argon. The suction pump is then operated so that noxious gases and fumes are sucked through the orifices 3, 4 of the members 1. 2 through the conduits 5, 6 and the pipe 7 away from the vicinity of the arc and the operator.

The orifices 4 are of different sizes in order to balance the suction effect of the member 2 around the arc.

It is believed that the stainless steel mesh which forms the skirt 9 not only contains flying sparks but reduces reflection of ultraviolet radiation emanating from the arc. As a consequence, the mesh reduces the formation of ozone at the arc. Any ozone that is formed and other noxious gases and fumes are sucked into the members 1, 2 via the orifices 3, 4.

The wire mesh also offers the following advantages: (a) it allows ambient air to be sucked into the space encompassed by the skirt 9 and the mesh extending across the upper side of the second member 2, thereby inhibiting the shielding gas from being sucked away; (b) it inhibits overheating in said space by permitting the drawing in of cold ambient air.

This is important for good operation of the MIG process and the suction pump and; (c) it is flexible and should any protrusion or uneven surface of a workpiece fou[ the attachment, the mesh will pass over it without damage and without movement of the welding torch 1 5.

An advantage of the attachment described above is that it provides a simple means of reducing and extracting ozone from the vicinity of an electric arc.

In tests, using the attachment described above when MIG welding, the ozone concentration around the vicinity of the arc has been below the threshold limit value of O. 1 parts per million. Furthermore, at least 95% of noxious fumes produced when welding have been removed although there has been no adverse effect on the shielding gas around the arc.

Three separate samples taken at an operators breathing zone with the attachment placed 12mm above the workpiece when MIG welding using a current between 350 and 400 amps were as follows: 1. O3 < 0.05 ppm 2. 03 < 0.05 ppm 3. 03 < 0.05 ppm Three separate samples taken 1 00mm above hole 10 were as follows: 1. 0, s = 0.3 ppm 2. 03=0.4 ppm 3. 03 =0.6 ppm One sample taken for a background reading in a gangway 2 metres from attachment when the attachment was placed 1 2m above the workpiece failed to register any ozone.

Claims (7)

1. An attachment for arc welding machines for reducing the formation of ozone when working with an electric arc and extracting at least some of any ozone is formed from the vicinity of the arc, comprising first and second spaced, tubular, hoop-like members each having a plurality of spaced orifices around its periphery which orifices communicate via the interior of the member with a suction pump, a wire mesh extending across and depending from the periphery of the second tubular member to form a skirt, the arrangement of the first and second hoop-like members and the wire mesh being such that when the attachment is operatively positioned on the welding machine, the welding torch extends first through the first hoop-like member, second through the wire mesh extending across the second hoop-like member and finally through the second hoop-like member so that the skirt surrounds the arc generated during a working operation and means for attaching the attachment to the welding ma chine.

2. An attachment as claimed in claim 1, in which a hole is formed in the wire mesh extending across the second hoop-like member to permit an operator to see the arc during a working operation.

3. An attachment as claimed in claim 1 or 2, in which some of the orifices in the second member are different sizes to permit balancing of the suction effect around the arc.

4. An attachment as claimed in claim 1, 2 or 3, in which each member communicates with the same suction pump.

5. An attachment as claimed in any one of claims 1 to 4, in which the first and second hoop-like members are made from aluminium tube and the wire mesh is made from stainless steel.

6. An attachment for arc welding ma chines for reducing the formation of ozone when working with an electric arc and extracting at least some of any ozone if formed from the vicinity of the arc, constructed and arranged substantially as hereinbefore described with reference to and illustrated in the Figures of the accompanying drawings.

7. An arc welding machine when provided with an attachment as claimed in any one of claims 1 to 6.