Background of the invention Prior to welding or high temperature cutting operations, it is known to use chalk as a marker for creating markings on a workpiece, such as the path which the weld or cut is to follow. However the mask which the operator interposes to protect the eyesight includes a dark filter to substantially attenuate the very intense electromagnetic radiation from the welding or cutting site. This can make it very difficult or impossible for the operator to see the chalk markings during the welding or cutting operation. As a result, the weld or cut is frequently inaccurate and sometimes it is necessary for the operation to be performed again to achieve the required standard of accuracy or neatness. Also, the difficulty of seeing the chalk markings often means that the operator stops the operation, removes the mask to inspect the progress of the operation before resuming. These interruptions can significantly increase the time taken for the welding or cutting operation.

Object of the invention It is an object of the present invention to provide products and methods which can enable a person carrying out a welding or high temperature cutting operation to see markings on a workpiece during the welding or cutting operation.

Summary of the Invention According to a first aspect of the invention there is provided a workpiece marker for use in a welding or high temperature cutting operation, the marker including a luminescent material in a form or medium for application to a workpiece, the luminescent material having

the property of enabling creation of markings on the workpiece which are visible during the welding or cutting operation through eyesight protecting means of the operator to thereby provide a visible aid for the welding or cutting operation.

According to a second aspect of the invention there is provided a welding or cutting aid system for aiding a welding or high temperature cutting operation, the system including: a workpiece marker which includes a luminescent material in a form or medium for application to a workpiece, the luminescent material having the property of enabling creation of markings on the workpiece which are visible during the welding or cutting operation through eyesight protecting means of the operator, and a light filter to be interposed in use between the workpiece and the operator's eyes, the light filter being translucent to a band of frequencies which includes the frequency or frequencies of visible light emission of the luminescent material of the marker, the light filter substantially attenuating radiation at frequencies spaced from said band of frequencies.

According to a third aspect of the invention there is provided a method of aiding a welding or high temperature cutting operation being carried out on a workpiece, the method including the steps of : applying to the workpiece a luminescent material so as to create markings on the workpiece at locations intended to guide or inform an operator monitoring or controlling the welding or cutting operation, the luminescent material having the property of emitting visible radiation, when excited during the welding or cutting operation, and conducting a welding or high temperature cutting operation on the workpiece while viewing the workpiece through an eyesight protector apparatus, the eyesight protector apparatus being translucent to a band of frequencies which includes the frequency or frequencies of visible light emission of the luminescent material, and controlling the welding

or cutting operation in accordance with the visible markings of luminescent material on the workpiece.

Description of the Preferred Embodiments In the embodiments of the invention, preferably the luminescent material which enables creation of markings on the workpieces emits radiation in the visible spectrum upon excitation during the welding or cutting operation. In particular, it is preferable that the welding or cutting operation generates the exciting radiation which stimulates the luminescent material to emit the visible radiation.

The products and methods of the present invention are particularly applicable to arc welding including stick welding, TIG welding and MIG welding or plasma cutting operations. It is possible that the principles of the invention may be applicable to other types of welding or cutting operations but the radiation generated in other types of welding and cutting may not be as readily amenable to stimulating or exciting a luminescent material to emit sufficient light in the visible part of the spectrum. In the preferred or expected principal field of use in which the welding or cutting operation includes generation of an electric arc, the radiation being emitted by the arc preferably constitutes the exciting radiation which impinges on the luminescent material to stimulate it to emit the visible radiation. For example, the luminescent material may be excited by ultraviolet radiation emitted by the electric arc to emit the visible radiation.

The luminescent material may be a fluorescent material, or may be a phosphorescent material.

Preferably the luminescent material emits visible radiation in the middle or higher wavelengths of the visible spectrum, particularly in the yellow to orange to red regions of the visible spectrum. The luminescent material may for example emit light predominantly in the

range of wavelengths from 580 nm to 660 nm, e. g. primarily at or around about 620 nm (orange-red). The yellow to orange to red region of the visible spectrum is preferred since it is found that these colours are more readily visible in or through the fume or smoke created during the welding or cutting operations than colours towards the blue-violet end of the spectrum.

Suitable luminescent materials can be chosen from organic and inorganic materials, and from liquid or solid formulations, having the required excitation and emission properties.

Organic dyes known as"daylight fluorescent pigments"can provide suitable markers.

Rhodamine and fluorescein dyes may be suitable, although specific and optimum fluorescent materials have not been identified at this stage of development. It is expected however that an ordinarily skilled chemist could readily identify suitable materials by reference to published properties for luminescent materials or by routine empirical testing.

The workpiece marker preferably further includes a filler mixed with the luminescent material. The filler may be a solid material whereby the workpiece marker can be held by hand and manipulated by a user to apply the markings to the workpiece. Preferably, the filler itself creates a marking on the workpiece which is visible in daylight or other illumination conditions enabling human visibility of the markings formed by the filler. The filler may comprise chalk in a particulate form mixed with the luminescent material. In the case of a luminescent material in solid solution or suspended in a solid transparent material such as an organic resin, the chalk may be mixed in a proportion of 60% by weight with 40% by weight of the resin/luminescent material particles.

The workpiece marker may further include a binder which binds the luminescent material in a solid form which can be held and manipulated by a user to apply the markings to the workpiece. The binder may comprise a resin material which is substantially

translucent to the visible radiation emitted by the luminescent material making the markings on the workpiece visible during the welding or cutting operation. A suitable resin binder may be a thermosetting or thermoplastic resin binder. Melamine sulphonamide formaldehyde resin may be suitable as a carrier or medium for the luminescent material and/or as a binder for the chalk and active material mixture.

As mentioned above in the summary of the invention, the second aspect of the invention provides a welding or cutting aid system for aiding a welding or high temperature cutting operation, the system including: a workpiece marker which includes a luminescent material in a form or medium for application to a workpiece, the luminescent material having the property of enabling creation of markings on the workpiece which are visible during the welding or cutting operation through eyesight protecting means of the operator, and a light filter to be interposed in use between the workpiece and the operator's eyes, the light filter being translucent to a band of frequencies which includes the frequency or frequencies of visible light emission of the luminescent material of the marker, the light filter substantially attenuating radiation at frequencies spaced from said band of frequencies.

The light filter preferably includes a panel of coloured light filter material to be interposed in use between the workpiece and the eyes of the operator, the panel being arranged to be mounted by the eyesight protecting means through which the operator views the welding or cutting operation. In the case of a conventional eyesight protecting means which comprises a mask having a window through which the operator views the welding or cutting operation, the window is provided with a dark filter medium interposed in the light path to reduce the intensity of light from the welding or cutting operation reaching the operator's eyes, and is also provided with the light filter additionally interposed in the light path from the site of the welding or cutting operation to the operator's eyes. The dark filter

may be the conventional dark glass which cuts out ultraviolet and infrared radiation and substantially attenuates visible radiation so as to protect the operator's eyes. The light filter can be also a panel, e. g. of the standard 180 mm by 50 mm size, to fit into the mountings provided by welder's masks for the dark filter. The light filter is desirably selected to pass light at frequencies or wavelengths which the dark filter also passes and also if desired to substantially attenuate UV and/or IR radiation. The frequencies that the light filter passes preferably match the visible emission frequencies of the luminescent material. For example for luminescent material emitting at a wavelength of about 620 nm, an orange-red light filter would be preferred.

The light filter may be a lighting gel of the kind used for projecting coloured light such as in theatre stage lighting, the lighting gel having a characteristic colour substantially matched to the colour of visible light emission of the luminescent material. For the suggested orange-red luminescent material emissions, an"Amber-rose No. 22"gel filter is suitable.

The light filter enhances the visibility of the markings on the workpiece by attenuating or cutting out other wavelengths and helping the operator's eyes be more sensitive to the wavelength of the emissions from the luminescent material.

Also as mentioned above in the summary of the invention, the third aspect of the invention provides a method of aiding a welding or high temperature cutting operation being carried out on a workpiece, the method including the steps of : applying to the workpiece a luminescent material so as to create markings on the workpiece at locations intended to guide or inform an operator monitoring or controlling the welding or cutting operation, the luminescent material having the property of emitting visible radiation, when excited during the welding or cutting operation, and conducting a welding or high temperature cutting

operation on the workpiece while viewing the workpiece through an eyesight protector apparatus, the eyesight protector apparatus being translucent to a band of frequencies which includes the frequency or frequencies of visible light emission of the luminescent material, and controlling the welding or cutting operation in accordance with the visible markings of luminescent material on the workpiece.

The most common situation for application of the method of the invention would be where the visible markings applied to the workpiece define or at least include a welding or cutting path which the welding or cutting operation is to follow. However, other marks such as prompts for the nature or location of the welds and/or cuts can also be used.

In the preferred method, the step of applying markings comprises the application of markings to the workpiece using a workpiece marker according to the first aspect of the invention.

Likewise in the preferred method the steps of applying the markings and conducting the welding or cutting operation comprises using an aid system according to the second aspect of the invention by application of markings to the workpiece using the workpiece marker of the aid system and interposing the light filter in the light path during the welding or cutting operation.

It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiment (s) of the invention as herein described without departing from the spirit and scope of the invention as defined in the following claims.