GB2034171A - Improvements in and relating to protective devices - Google Patents

Abstract

A protective helmet (10) for use when welding is described. To eliminate flash and glare a filter (26) is movable into alignment with the window (24) before a welding arc can be struck and a mechanism involving a solenoid operated device (28) is incorporated into the helmet (10) to actuate the movement of the filter (26). The helmet includes provision for attachment thereto of a flexible skirt (20) to provide further protection. In order to prevent the striking of an arc until the filter (26) is in place, a switch (30, 32) is incorporated which is only operated when the filter (26) is in position and electrical connections between the switch and an electrical control circuit prevent the flow of arc current to a welding tool until switch (30) has been closed. The electrical connection between the switch (30) and the electrical control circuits may be by way of a flexible electrical connection or by way of a radio link. <IMAGE>

Description

SPECIFICATION Improvements in and relating to protective devices FIELD OF INVENTION This invention concerns protective headgear such as welding helmets for providing protection from undesirable side effects of industrial processes and the like. Although the invention will be specifically described with reference to welding helmets and is particularly applicable to such helmets, it is by no means limited to such an application.

BACKGROUND TO THE INVENTION Many industrial processes involve undesirable side effects. Typically these involve the production of unwanted fumes and gases, the production of excess heat and light, and the production of spatter and flying particles and sparks.

In order to reduce the risk of injury or undue exposure to such hazards, recent legislation has required the provision of shields and guards for use by such operators.

Many processes involve the prior setting up of a machine or workpiece by the operator and during the setting-up procedure there is no need for protective headgear to be used since the process will not be operating and the dangerous and undesirable side effects will not be experienced by the operator. However prior to initiating the process such as the welding arc, the operator must in-state or reinstate the protective guard or shield (such as a hand-held shield or nodding helmet in the case of welding) so that when the process is established (for example the arc is struck in the case of welding) the bright light and spatter from the welding arc do not damage the operator.

Most protective headgear involves the use of a shield of some form which protects either the whole or part of the face and head from the side effects of the process. In the case of welding two forms of protective device have been provided hitherto.

The best known device is a hand-held shield or visor which includes a hand grip and a darkened window through which the operator can peer when the arc is struck. In use the welder positions his welding rod or welding tool above the workpiece with the hand-held shield to the side so that his vision is not obstructed. As soon as he is satisfied that his rod or tool is correctly located above the workpiece the shield is located directly in front of his face between his face and the workpiece and the rod or tool is moved so as to establish the arc.Once the arc has been established there is usually sufficient light for the welder to be able to see approximately what is happening and under these rather difficult conditions the welder continues to weld until either the weld is completed or the arc is accidentally extinguished or he cannot see properly and has to break off from welding to inspect the work and determine whether he is making a satisfactory weld for the job in hand.

A second form of protective headgear for welders is the nodding shield or visor which is strapped to the upper part of the head and is pivotable from a position in which the shield lies on the crown of the operator's head into a lowered position in which the shield is in front of his face.

The position of the centre of gravity in the shield is selected so that the shield is stable in both positions and can be moved from the first position in which the operator 5 vision is not obscured, into the lowered position (in which his face is completely protected and he can only see through a darkened window) by simply nodding the head in a forward and downward direction rather sharply. The effect is to cause the shield to drop into place in front of his face and in use the device is somewhat more convenient than the hand-held shield but is not applicable to all situations.In particular it is virtualJy unusable when the weld is vertically above the operator as can very often be the case in static situations and although for convenience many welders prefer to use the nodding shield it is not always possible for them to nod it into position and one hand or the other must be used to move it into the lowered, protecting position. This defeats the object of the nodding shield which is intended to represent an improvement over the hand-held shield in that it leaves (in theory) both hands of the operator free, one to hold the welding tool and the other to steady himself or the workpiece or both.

After welding or in between one weld and another the operator can rarely nod the helmet into the upper position (although it is theoretically possible to do so) and at that stage, a free hand is necessary to allow the operator to once again clear his vision and allow him to inspect the workpiece etc.

PRIOR ART In an attempt to produce an improved welding shield has been introduced by Revue Thommen A.G. of Switzerland. This shield is similar to the nodding shield in many respects except that the window design is different and is such as to allow the operator to keep the helmet in the one position (i.e. in the face-covered position) all the time.

The improvement which allows this is the use of a liquid crystal panel as the lower half of the window through which the operator looks. The upper half is an interchangeable protective welding glass of a conventional type and protective plain glasses are mounted on either side front and rear and filters are combined with the liquid crystal panel.

As is known, the liquid crystal panel becomes less transparent upon the application of an appropriate electrical current to the panel and the shield is rendered automatic by providing a photocell sensor on the front of the shield which responds to the light from the welding arc when the latter is struck and causes the appropriate electrical current to be generated and applied to the liquid crystal panel to render the latter dark as soon as the arc is established.

The problem with such a device is that arc flash is not entirely eliminated since although the response time between striking the arc and establishing the darkened panel is very small, it is nevertheless long enough for the manufacturers to have to rely on the upper half of the windows to be of permanent darkened glass or filters to provide the protection during the intitial flash-when the lower panel is not darkened.

A further disadvantage of the Revue Thommen A.G. device is that it is not a fail-safe device. In the event that the crystal fails to darken or the electrical circuit controlling it fails to generate the appropriate electrical current or in the event that the photoelectric sensor becomes covered with dirt or spatter (perhaps unknown to the operator) the protection which should follow the establishment of the arc will not be established and arc burn and arc flash can result.

With these disadvantages of the prior art in mind the Applicant has sought to produce an alternative and improved unit.

OBJECTS OF THE INVENTION The present invention has a number of objects.

(1 ) It is one object of the present invention to provide protective headgear for industrial processes which is fail-safe. To this end the present invention seeks to provide protective headgear in which the industrial process cannot be preformed without the protective nature of the headgear in an operational condition.

(2) It is another object of the present invention to provide protective headgear for an operator in industrial process which does not require movement 9f the head or hand to render operational the protective part of the headgear.

(3) It is another object of the present invention to provide protective headgear for an operator such as a welder which will allow greater flexibility of head movement that has hitherto been the case so as to improve the angle of vision and allow for a more relaxed posture particularly in confined working areas when operating the process.

(4) It is a further object of the present invention to improve the effective production time of an industrial process in which hitherto the operator has had to devote part of his total time to positioning the protective headgear or the protective parts of the headgear.

(5) Where high power is required to operate the industrial process it is an ancillary object of the invention to provide protective headgear which is such that at least the high power level to the process is inhibited except for those periods of time when the operator is in a position to perform the process from a protected point of view.

THE INVENTION According to the present invention protective headgear for an industrial process which includes a protective element which for safety must be situated between the face of the operator and the industrial process before the latter is carried out, includes first means for moving the protective element into position in response to an electrical signal derived from the process but before the process is initiated and switch means operable only when the protective element is in position for generating a second electrical signal the generation and maintenance of which is essential before the industrial process can be initiated and continued.

The means for moving the protective element into position may be electromagnetic or electropneumatic or purely pneumatic or mechanical depending on the application.

The means for generating the second electrical signal may be a simple switch for completing a circuit or may comprise a transducer unit which responds to the position of the protective element and alters the electrical characteristics of the circuit so as to cause an electrical signal corresponding to the second electrical signal to be generated.

It will be seen that by incorporating the invention into protective headgear, an industrial process cannot be carried out unless the protective element required in the headgear is correctly positioned between the operator and the process. Whilst the insertion of protective elements on apparatus and in industrial processes may have been known in the past the invention lies in the provision of such a protective element within the unit worn by the operator as headgear and the provision of means also within the headgear of the means for generating the second electrical signal without which the industrial process cannot be performed.

It will be seen that the invention is particularly applicable to the field of welding in which a window is provided in a fixed shield helmet worn by the operator and in which the window is formed from clear or slightly darkened glass and includes a movable filter which under the action of the first means is moved into position so as to completely darken the window and provide the protection needed by the operator to prevent arc burn.By providing switch means which is only operated when the darkened filter is fully in place, and by arranging that the electrical signal generated when the switch means is operated in response to the correct positioning of the darkened filter, is the signal to control the operation of a contactor the operation of which is essential before welding current is available, it will be seen that it will be impossible for the operator ever to experience arc burn providing he is wearing his helmet correctly since welding current will not be available until the darkened filter is in position across the window.

The unit can be rendered completely automatic in the case of welding very easily by providing a low voltage and low current source to the welding rod and detecting when the welding rod makes contact with the workpiece. When the latter touches the workpiece, the low voltage/low current circuit is completed and a switching device is initiated (such as a relay or electronic amplifier) to produce the operating current needed to drive the first mentioned means for moving the darkened filter into position across the window.

Once it is in position, the heavy current circuit can be made and the welding arc struck.

It will be seen that once the welding arc has been extinguished the low current/low voltage circuit will also be broken and in order to prevent rapid oscillation of the filter when a number of arcs are struck and extinguished in succession, a delay is introduced before the darkened filter will revert to its rest position to leave the operator's vision clear once again. Multiple arcing occurs when poor electrical contact between electrode and workpiece exists.

The great advantage of the invention is that the operator is left with both hands free to perform his task and there is no need to even move his face muscles let alone his head in order to introduce the darkened filter into his field of view and thereby give the necessary protection from the arc.

Although the invention has been specifically described in this context in relation to an electric arc welding set, the invention may be applied equally to any other type of welding such as argon arc welding and gas welding in which the operator has a switch on the welding gun which opens the valves to cause the gas flow to be initiated and starts the wire feed motor where this is used. In this case the gun switch may be used to initiate the first said means for moving the darkened filter into position and the gas and wire feed etc. are inhibited until the said second electrical signal is generated after the protective element has been moved into position.

Likewise the invention may be applied to any other industrial process in which a protective element has to be inserted into position between the operator's face (typically in front of his eyes) before the process can be carried out.

The invention is not limited to exposure to light or heat but is also applicable to the case where the by-products of the industrial process are fumes and gases and in which a mask containing appropriate fume extraction or filtration devices must be in position and operational before the process in initiated. Thus the invention may be applied to the fields of paint spraying and crop spraying and the like.

The invention will now be described by way of example with refere#nce to the accompanying drawings.

IN THE DRAWINGS Fig. 1 is a perspective view of an automatic welding visor helmet embodying the invention, Fig. 2 is a pe#rspective view of another automatic welding visor helmet fitted with a flexible skirt to increase protection, Fig. 3 is a wiring/circuit diagram of a control system which is linked to the automatic welding visor helmet of Figs. 1 or 2, Fig. 4 illustrates diagrammatically how the visor is connected the various parts of the wiring/circuit diagram of Fig. 3, Fig. 5 is a perspective view of an automatic welding visor helmet constructed as another embodiment of the invention which is partly cut away to reveal the internal construction of the helmet, and Fig. 6 is a similar view to Fig. 5 of the same embodiment of welding visor helmet further cut away to reveal the components used for raising and lowering the shield.

DETAILED DESCRIPTION OF FIGURES Turning first of all to Figs. 1 and 2 there is shown a protective helmet in each case generally designated by reference numeral 10 which includes a spine section 12 which extends from the rear to the front of the helmet and an integral mask 14 having a window designated 16 through which the operative can view the workpiece or machine.

The mask 14 continues to a certain extent on both sides of the main cap section 18 to provide lateral protection on both sides and in the case of the Fig. 2 embodiment a flexible skirt 20 is secured to the lower edge of the mask 14 so that complete protection from sparks and flying matter is provided both from above, from both sides and from below.

It will be seen that the flexible skirt 20 is secured to the case 10 by lacing 22 (see Fig. 1) and is thus removable so that an operative not requiring the flexible skirt can remove same to improve manoeuvrability of the helmet. (It will be appreciated that when the flexible skirt is in position manoeuvrability in the downward direction may be somewhat restricted if the skirt is not constructed from fully flexible material. The degree of flexibility of leather of simulated leather materials can vary and worsen with age and use.

To this end the skirt is made removable for replacement purposes.) The window 16 is normally closed by transparent glass or plastics material 24 through which the operative can view his workpiece or machine without difficulty. In areas of high intensity lighting or unwanted radiation the glass or clear plastics material 24 can be replaced with a less transparent medium or be coated with an appropriate filter or additional filters may be provided behind or in front of the glass or plastics window to protect the operative depending on the light level or radiation which normally exists.

Any filters or coatings or other screens permanently located or semi-permanently located, over the window 16 should not be confused with a movable radiation protection filter (not shown in Figs. 1 and 2) which is movable down into position across the window automatically when the process under control of the operator is initiated. This radiation protection screen or filter is shown in dotted outline in Figs. 1 and 2 and is designated by reference numeral 26.

The mechanis#m for automatically lowering the screen 26 into position conveniently comprises a solenoid operated device which is shown diagrammatically in dotted outline at 28 in Figs. 1 and 2.

Alternatively the screen 26 may be held in position by means of a locking device which is released when the solenoid operated device 28 is actuated, the screen 26 being lowered into position to protect the operative's eyes by the action of a spring (not shown).

The return of the screen 26 to its raised position clear of the window 16 is then rendered either manual by means for example of a lever (not shown) or may be rendered automatic by means of a second solenoid operated device or by means of an electric motor adapted to raise the screen 26 until it is once again locked in position by the solenoid released mechanism previously referred to and not shown in the drawings.

It is to be understood that the invention is not limited to any particular device for moving the screen 26 up and down and any convenient device may be used including a pneumatically operated cylinder (both single acting involving manual return of the screen or double acting for moving the screen in both directions).

In conjunction with the movable screen 26 there is a microswitch which for convenience is shown at the lower end of window 1 6 and is designated by reference numberal 30. The microswitch includes a push button 32 which is engaged by the underside of the screen 26 when it is in its lowermost position and the microswitch 30 is arranged to control the flow of current in a control circuit (to be described) and the remainder of the system incorporating the automatic welding visor helmet is arranged to be rendered inoperative until current flows in the control circuit. In this way in a welding situation, no welding arc can be struck until the screen 26 is in its lowered position and the microswitch 30 has been operated.

Although not shown in detail, access to the microswitch or at least to the microswitch operating button 32 is prevented for example by means of a fixed transparent screen so that unauthorised or accidental operation of the microswitch 30 cannot occur. It will be appreciated that were the microswitch to be operated by depression of the push button 32 the welding arc or other industrial process controlled by the control circuit could then be initiated without the need for the screen 26 to be in the lowered position.

As shown in Fig. 4 a coiled flex plugs into the underside of the spine section 12 and connects the helmet to a welding tool 34. To this end a jack plug 36 is provided although any other convenient form of plug and socket may be used.

In the welding application the control circuit is completed when the welding rod 38 which extends from the tool holder 34 touches the workpiece which is normally electrically connected to earth via a crocodiled clip 40 and a lead 42 to the oppposite side of the welding current supply. Electrical connection establishes a control circuit current (which need only be a very low current and is certainly not enough to produce a large spark) and the remainder of the apparatus serves to detect when this condition obtains and to thereafter control a contactor or circuit breaker to supply welding current.

A A further refinement which is built in to the circuit which will now be described is that the protective screen 26 does not immediately rise to expose the window 1 6 the moment that a welding current is extinguished but a time delay is built into the system so that only after welding current has been extinguished for a finite length of time can the screen 26 (or visor as it sometimes referred to) be raised to expose the window and the eyesight of the operative once again.

The welding current is obtained from a transformer 44 having a mains input socket into which is plugged a mains plug 46 at the end of a supply lead 48. The latter extends from a control box 50 the contents of which will be described in more detail with reference to Fig. 3 and a flexible lead 52 connects the control box 50 to a mains plug 54.

Welding current is provided from the welding transformer secondary output terminals labelled 56 and 58. Terminal 56 is connected to the welding electrode 38 via flexible power conductor 60 and in parallel with that power conductor 60 is a low power conductor 62 for supplying operating current via the coiled flex 64 for operating the mechanism which moves the visor screen 26 into and out of the plane of the window 1 6. A connector 66 connects the lead 62 to a lead 68 which feeds the control box 50.

The other side of the welding transformer secondary (terminal 58) is connected via lead 70 to the control box 50 and by means of a circuit breaker or contactor within the control box 50 can be connected to the earth lead 42 and clamp 40.

Normally the lead 70 is isolated from the earth lead 42 and only after the visor screen 26 is in position can the contactor or circuit breaker (to be described in more detail later) be operated and welding current established.

The sensing current for indicating when the electrode 38 is first touched on the workpiece so as to indicate that the operative wished to strike an arc is provided by means of a low current conductor pair 72 connected to the terminals 56 and 58. The earth connection for the sensing current is established at all times so that as soon as the electrode 38 touches the conductive workpiece the control current flows and as will be described hereinafter, the visor screen 26 is lowered into position. Thereafter the microswitch is operated and only then can the main contactor or circuit breaker within the control box 50 be operated so as to establish the earth connection via conductors 42 and 70 to allow the main arc to be struck.

The electrical circuit within the control box 50 is shown in Fig. 3 and the construction and operation of the circuit will best be understood by a brief description of the mode of operation of the circuit shown in Fig. 3 in relation to the various parts of the apparatus already described in relation to Fig. 4.

OPERATION DESCRIPTION 1. With the main supply ON low voltage transformer 74 produces the e.m.f. for the control circuit. This is rectified by rectifier 76.

2. With the welding transformer earth clamp 40 attached to the workpiece and all other components at rest in the normal position as shown in Fig. 4 welding transformer 44 will be OFF.

3. The operator prepares to commence the weld in the normal way by inserting the electrode 38 into the holder 34 and striking an arc by touching the tip of the electrode 38 against the workpiece (not shown) to which the earth clamp 40 has been attached. The following sequence of events then take place:~ 4. Relay 78 includes make before break changeover contacts and energising of the relay cuts out the welding leads and welding transformer from the secondary circuit whilst still maintaining the secondary circuit.

5. Relay 80 is normally closed and this also cuts out welding leads from the secondary circuit under low voltage conditions which may be experienced with poor electric contact with work when first starting the arc.

6. Contactor 82 is normally open and this closes the earth welding lead 42 to the welding transformer terminal 58.

7. Solenoid 84 energises and operates the solenoid or other drive mechanism generally designated 28 in the visor helmet so as to bring the welding visor/safety screen 26 into the safety position.

8. Microswitch 86 is normally open and when the visor safety screen 26 is moved into its fully home position microswitch 86 is operated bringing relay 88 into circuit.

9. Relay 88 contains normally open heavy duty contacts which are closed when the relay is brought into circuit so as to connect the main supply to the welding transformer thereby allowing the arc to be established.

10. Microswitch 90 contains changeover contacts and is also tripped by operation of relay 88. This brings drop resistor 92 into circuit with solenoid 84 to reduce the hold in voltage on this solenoid.

When welding ceases and the arc is broken, the increase in the welding transformer open circuit voltage causes a relay 94 to be brought into operation in the secondary circuit. Relay 94 contains normally closes contacts with a time delay on energising so that the secondary circuit is broken after this time delay. The delay on energising prevents an on/off chatter of the welding visor screen under poor arc conditions.

11. A capacitor 96 also prevents contact chatter on relay 78 when de-energising after a welding sequence.

As soon as the relay 94 has operated all the components return to the rest or OFF position the primary circuit to the low voltage transformer 74 remains ON whilst the secondary circuit is OFF.

The sequence is repeated when the next arc is struck It will be seen that by switching the primary circuit of the welding transformer 44, the normal standing current associated with on line welding equipment is in fact eliminated since the welding transformer is only connected whilst the arc is struck. This represents a saving in power and reduces the heating normally associated with such transformers.

It is to be understood that the particular circuit diagram shown in Fig. 3 is intended only to be illustrative of the principle of the circuit and solid state switching devices and/or electronic logic circuits may be used instead of the electromagnetic relays and contactors if desired.

Figs. 5 and 6 of the drawings illustrate another embodiment of the invention which is similar to that described with reference to Figs. 1 and 2 but in which the mechanism for raising and lowering the filter 24 is shown in more detail.

Although much of the content of Figs. 5 and 6 is common to that shown in Figs. 1 and 2 different reference numerals will be used for simplicity.

The helmet comprises an outer casing 110 which includes a removable flexible skirt 112 which is secured thereto by lacing 114. As shown in both Figs. 5 and 6 the skirt is cut away at 116.

The outer skin is shaped substantially as shown in Figs. 1 and 2 and is cut away at 118 to reveal the inner skin or shell 120 which is also cut away.

This latter is secured within the external shell and includes upturned lips along opposite sides such as 122 which engage against the underside of inwardly directed lips 124 provided on opposite sides of the interior of the outer shell 11 0. Front and back of the inner shell incorporates platforms 126 and 128 respectively which are secured to and provide supports for on the one hand the window and movable filter mechanism contained within a framework generally designated 130 and at the rear, the housing for a solenoid generally designated 132.

The housing 130 includes a seating 134 which is secured to the front platform 126.

The inner shell 120 is typically secured to the outer shell by means of screws (not shown) located through holes one of which is shown at 136.

The window and filter mechanism contained in the housing 130 will be described in more detail with reference to Fig. 6 as also will the operating mechanism including the solenoid contained in the housing 132.

Referring now to Fig. 6, the housing 130 includes front and back glass plates 138 and 140 between which are sandwiched the filter plate 142 which can be raised or lowered by the operating mechanism to be described.

The filter plate 142 is contained within a frame 144 the upper end of which includes two lugs which are pivotally attached to the lower ends of a scissors action mechanism generally designated 146 the upper bridging member of which (identified by reference numeral 148) is attached to the leading end of a flexible cord 150 which extends around a pulley 152 and is guided over a roller 154 and around a second pulley 156 to be attached at its far end to an armature 1 58 of a solenoid generally designated 160 housed within the housing 132 of Fig. 5.

Energisation of the solenoid 1 60 draws the armature 158 in a rearward and downward direction thereby pulling the cord 150 in a rearward direction. This in turn lifts the scissors mechanism 146 into the position shown in Fig. 6 and causes the downward movement of the frame 144 and filter 142.

On releasing the solenoid 160 the armature 158 returns in a generally forward and upward direction thereby allowing the cord 150 to move in the same direction so as to allow the scissors action mechanism 146 to revert to its rest position under the action of a return spring 162.

Reversion of the scissors action mechanism 146 causes the frame 144 to lift in a generally vertical direction until the filter 142 is well clear of the window area but leaving the window unobscured.

Slots 164 and 166 are provided in a plate 168 carried at the upper end of the assembly 130 and best seen in Fig. 5. The slots align with the heads of bolts 1 70 and 172 and the plate provides a support at its upper end for a bridging member 174 to which is attached a housing generally designated 176 (see Fig. 5) which is shown cut away in Fig. 6.

The housing 176his panel sided-and includes mountings for the pulley 152 and roller 1 54.

Between these two items is located a microswitch 178 having an actuating arm 180 and the cord 150 has threaded thereon an actuating device 182 which can be positioned accurately along the length of the cord and retained in position for example by grub screws and is adapted to engage the actuating arm 180 as the cord is moved in a rearward direction when the armature is fully retracted. This microswitch 178 takes the place of thre micro-switch 30 in the Fig. 1 embodiment Instead of connecting the protective headgear to the apparatus by means of electrical conductors, a radio link may be established between a small transmitter receiver unit in the helmet and a receiver transmitter unit mounted in the apparatus. The operation of the unit is then exactly the same as if the unit were connected to the apparatus by electrical conductors but instead of electrical currents, a first radio signal is transmitted by the apparatus and received by the protective headgear to cause the protective element to move into place and only when in position will a second radio signal be generated by the radio transmitter within the headgear for reception by the receiver unit mounted in the apparatus to initiate the industrial process, typically to establish a welding arc.

Claims (1)

1. Protective headgear for an industrial process which includes a protective element which for safety must be situated between the face of the operator and the industrial process before the latter is carried out, the protective headgear comprising first means for moving the protective element into position in response to an electrical signal derived from the process but before the process is initiated and switch means operable only when the protective element is in position for generating a second electrical signal the generation and maintenance of which is essential before the industrial process can be initiated and continued.

2. Protective headgear as claimed in claim 1 in which the means for moving the protective element into position is electromagnetically operated.

3. Protective headgear as claimed in claim 1 in which the means for moving the protective element into position is electropneumatically operated.

4. Protective headgear as claimed in claim 1 in which the means for moving the protective element into position is pneumatically operated.

5. Protective headgear as claimed in claim 1 in which the means for moving the protective element into position is mechanically operated.

6. Protective headgear as claimed in any of the preceding claims wherein the means for generating a second electrical signal comprises a switch for completing a circuit.

7. Protective headgear as claimed in any of claims 1 to 5 wherein the means for generating the second electrical signal comprises a transducer unit which responds to the position of the protective element and alters the electrical characteristic of the circuit so as to cause an electrical signal corresponding to the second electrical signal to be generated.

8. Protective headgear as claimed in any one of the preceding claims which includes electrical connections between the headgear and further electrical control circuit means for controlling the industrial process whereby the means for generating the second electrical signal is connected to the electrical control circuit means for controlling the industrial process to prevent the latter from being initiated until such time as the second electrical signal is generated.

9. Protective headgear as claimed in any one of the preceding claims which comprises a helmet having a facial mask integrally formed therewith which includes a window and the protective element comprises a filter which is movable by the said first means into alignment with the window to provide the protection needed by the operator.

10. Protective headgear as claimed in claim 9 in which the filter is of darkened glass or plastics material to reduce the transmission of light through the window whilst the industrial process is being carried out.

11. Protective headgear as claimed in any one of the preceding claims further comprising means for introducing a delay before the protective element can move out of the protecting position to prevent rapid oscillation of the protective element in the event that the industrial process can involve a number of on/off operations in rapid succession.

12. Protective headgear as claimed in any one of the preceding claims in combination with an electric arc welding set, the protective element comprising a darkened filter which is movable into the protective position before the electric arc can be struck to reduce the risk of arc burn.

13. Protective headgear as claimed in any one of claims 1 to 11 in combination with an argon arc welding or gas welding set which includes a welding gun having a switch which is used to initiate the gas and/or wire feeds and the protective element is a darkened filter which is movable into the protective position before the gas and/or wire feeds can be initiated by the operation of the said switch on the gun.

14. Protective headgear as claimed in claim 13 in which the switch on the gun causes the said first means to be operated to move the protective element into position and the said switch means operable only when the protective element is in position serves to control the gas and/or wire feeds.

15. Protective headgear as claimed in claim 1 in combination with paint spraying equipment wherein the protective element comprises a face mask for removing fumes and noxious by-products of the paint spraying process and the latter cannot be initiated until the face mask is in position.

16. Protective headgear as claimed in claim 1 in combination with crop spraying apparatus in which the protective element is a face mask for removing noxious fumes and gaseous vapours arising during spraying and the spraying apparatus is inhibited from operation until such time as the protective element is in position.

17. Protective headgear as claimed in claim 1 further comprising a radio link between the switch means and electrical control circuits for controlling the industrial process so as to obviate the need for flexible electrical leads between the protective headgear and the industrial process.

18. Protective headgear constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in Figs. 1 to 4 or Figs. 5 and 6 of drawings accompanying the application.

New claims or amendments to claims filed on 11/2/80 Superseded claims 1 New or amended claims:~

1. Protective headgear for an industrial process which includes a protective element which for safety must be situated between the face of the operator and the industrial process before the latter is carried out, the protective headgear comprising first means for moving the protective element into position in response to an electrical signal derived from the process or from first switch means associated with the process operable by the operator, before the process is initiated, and second switch means operable only when the protective element is in position for generating a second electrical signal the generation and maintenance of which is essential before the industrial process can be initiated and continued.