Welding mask with automatic obscuring of the visual field

A mask for carrying out electric arc welding by protecting the operator's eyes against both the glare and the ultraviolet rays during operation and reducing to a minimum the period of lack of visibility, which is embodied by an opaque shell with a vision window normally not obscured but provided with an oscurator means which is rendered operative upon flowing of electric current through an actuation apparatus connected to the electric welding circuit.

BACKGROUND OF THE INVENTION 
The present invention relates to a protection mask for those who carry out 
electric arc welding, which mask automatically obscures the field of 
vision when the electric arc is lighted. 
As is well-known, the electric arc emits an intense light having a high 
content of ultraviolet rays, and the eyes of the people carrying out the 
welding have to be protected against both the glare and the effect of the 
ultraviolet rays. At present time this is achieved by means of masks 
provided with a window of obscured glass which are manipulated manually by 
placing them before the face prior to welding. Such manipulation seriously 
hinders the work because of the total absence of visibility through the 
obscured glass between the moment in which the mask has been placed before 
the face and the moment in which the arc is lighted. 
To try to find a remedy for this disadvantage, masks have been proposed in 
which the obscured glass may be manually displaced out of the visual 
field; this facilitates the welding operation, but does not allow one to 
avoid a period of lack of visibility and the possibility of injuries to 
the eyes in the case of delay in operating the obscuration. In any case, 
however, the fact that the operator must hold the mask as well as the 
welding gun at the same time and trail along the electric feeding cable 
constitutes a heavy hindrance and gives rise to dangers when the welding 
has to be carried out in not very accessible places, such as for instance 
wells, stairs and the like. 
BRIEF SUMMARY OF THE INVENTION 
The object of the present invention is to provide a mask which may be put 
on permanently, for example by connecting it to a helmet or support, 
without hindering the normal visibility, and which obscures automatically 
the visual field in those periods of time only, in which the electric arc 
is lighted. In this way, the free visibility is maintained up to the 
moment in which the arc is lighted, whereupon the visibility remains 
ensured even through the obscured glass, and the normal visibility is 
restored as soon as the arc is extinguished. Moreover, the disadvantages 
and dangers inherent in the necessity to hold the mask are avoided and it 
is also possible to avoid having to hold in one's hand the heavy cable of 
the welding machine, especially during the displacements thereof. 
According to the present invention, the above object is achieved by means 
of an opaque mask provided with means for supporting it permanently before 
the operator's face and with a normally clear window whose field can be 
obscured by an absorption means controlled, directly or indirectly, by the 
welding current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The welding mask according to the embodiment shown is formed by a shell, 
which may preferably be made of moulded plastic material and which 
comprises side elements 3 connected, by pivoting means 2, to a support 
cross 1 applicable to the operator's head indicated by dashed line at 0. 
This cross will not be described in detail, as it is well-known per se and 
can be found on the market. The shell of the mask is completed, between 
the side elements 3, by a central element 4 which extends before the 
operator's face and partly over it and below the chin, when the mask is in 
its operative position shown. However, thanks to its being pivoted at 2, 
the mask can be lifted and turned over the operator's head, without 
removing the cross 1, during the time intervals between the welding 
operations, thus leaving completely free the visual field of the operator. 
At the level of the operator's eyes (when the mask is in its operative 
position), the shell of the mask is provided with a vision window limited 
by rims 5. At the level of the operator's mouth, the shell has also a 
channel-like recessing 6, extending towards the rear end, having centrally 
an aperture 7 and covered externally by a plate 8. The aperture 7 is 
located in such a manner as to receive operator's expiration, both from 
the nose and from the mouth, so that the air expired is conveyed outwards 
through the channel 6, thereby changing the air contained in the inner 
space of the mask. 
Applied onto the side rims 5 of the vision window are support brackets 9, 
preferably made of metal, which support a pair of transverse bars 10 
having hooked thereon, by means of profiled slots 11, a body 12 made of 
rubber or the like, provided with an almost rectangular window having 
restrained therein an inner glass 13. Preferably, this glass is treated by 
means of known processes in order to render it protective against infrared 
radiations. 
Inserted from the outside into the vision window, between the rims which 
delimit the latter, is a frame of plastic material 14 which hooks itself 
in position by means of hooks 15 and retains in its interior, by means of 
a retainer member 16, an outer glass 17. Preferably, this latter glass is 
of a type, for instance containing iron ions, which is adapted to absorb 
the ultraviolet radiations. In this way, the operator is permanently 
protected (even during the periods of time which are not specifically 
reserved to the welding operations) both against the infrared radiations 
(thanks to the inner glass 13) and against ultraviolet radiations (thanks 
to the outer glass 17), without any hindrance of the vision. Thus, he 
cannot be injured by radiations emitted from adjacent working stations in 
which welding operations are carried out. 
Housed in the closed chamber defined by rubber body 12 and frame 14 between 
the inner glass 13 and the outer glass 17 is a mobile frame 18 rigidly 
connected to a shaft 20 pivotally supported by the brackets 9, so that the 
frame 18 can move between a rest position shown by continuous lines in 
FIGS. 1 and 2 and an operative position shown by dashed lines in FIG. 1. 
The frame 18 carries, mounted on windows, a pair of small glasses 19, each 
of which corresponds to the visual field of one eye of the operator, when 
the frame 18 is in its operative position. The glasses 19 are of a type 
having a high degree of absorption of the rays of light, i.e. of the type 
which is usually employed for welding spectacles and masks. However, since 
the ultraviolet rays are absorbed already by the outer glass 17, said 
glasses 19 could also be made of a lighter material, as for instance a 
suitable plastic material, adapted to absorb the rays of light, but not 
the ultraviolet rays. 
Keyed on an outer end of the shaft 20 by means of an adjusting member 21 is 
a short lever 22 having connected thereto an end of a flexible cable 23 
whose sheath 24 is anchored in a suppport 25 rigidly connected to the side 
element 3 of the mask. These latter parts are shown by dashed lines in 
FIG. 1 because they are located in the mask portion which is removed by 
drawing the cross-section. Also hooked onto the lever 22 is a return 
spring 45, whose opposite end as well is fixed to the support 25. This 
return spring is disposed in such a way as to displace the frame 18, by 
means of the lever 22 and the shaft 20, towards the rest position, while 
cable 23 is connected in such a way that a traction exerted on it will 
move frame 18 towards the operative position. 
The opposite ends of the flexible cable 23 and of the sheath 24 are 
connected to an actuating device, shown in FIG. 3. This device comprises a 
housing 26, which may for example be connected to the operator's belt or 
may be located at a fixed point in the vicinity of the operator's working 
place. Housing 26 contains an electromagnet 27 whose winding 28 is 
connected to two connections 29 and 30 protruding from the housing 26. The 
electromagnet 27 acts on a mobile keeper 31 which normally is maintained 
in a rest position by a return spring 32, but is shown in FIG. 3 as 
attracted by the electromagnet. Keeper 31 in turn acts on the end of the 
flexible cable 23 applying on it a traction, when the electromagnet 27 is 
excited. 
The sheath 24 of the cable 23 rests on a stretcher 33 screwed into a ring 
nut 34, which stretcher serves for setting up the actuating device. 
Interposed between the sheath 24 and the stretcher 33 is a freely 
rotatable bush 35 which prevents sheath 24 from being accidentally 
twisted. The ring nut 34 is mounted on a neck 36 of the housing 26 and is 
fixed thereon by means of a bayonet joint engageable by a 90.degree. 
rotation of the ring nut. Furthermore, the ring nut 34 extends internally 
with a neck 38, into the end of which there is inserted a slide 39, 
movable axially but not rotatable, coupled, by means of a preloaded spring 
40, with a head 41 on which the end of the flexible cable 23 is anchored 
by means of a setscrew 42. Slide 39 is provided with shoulders 43, by 
means of which it may receive the thrust of the movable anchor 31, when it 
is in the operative position shown, but the slide 39 disengages from the 
anchor 31 when it is rotated by 90.degree.. Therefore, disengagement of 
the bayonet joint 37 produces also the disengagement of the slide 39 from 
the anchor 31, and thus allows one to detach the ring nut 34 with all the 
parts connected to the cable 23, from the housing 26; moreover, owing to 
the arrangement, the coupling can take place in the correct position only. 
Preferably, the neck 36 of the housing 26, and the ring nut 34, are 
sufficiently long to prevent any contact between the head 41 and the 
anchor 31 as long as the ring nut 34 is not mounted correctly onto the 
neck 36, whereby the insertion of the parts into one another can take 
place in the correct position only. 
The connections 29 and 30 are inserted into the circuit of the welding 
machine used by the operator. Depending on the applications it may be 
suitable to insert such connections (and, consequently, the winding 28 of 
the electromagnet 27) in series with the cable which feeds the welding 
electrodes, or in parallel; obviously, the winding must be sized suitably. 
In any case, the electromagnet is excited during the periods of time in 
which the welding current is flowing, and remains de-energized when said 
current does not flow. 
Therefore, when the operator, after having put on the mask, is on the point 
of carrying out a welding, he has a non obscured vision, because the frame 
18 with the obscured glasses 19 is in a lifted rest position. As soon as, 
after the electrode has been brought into contact, the current begins 
flowing, the electromagnet 27 attracts the anchor 31 which actuates the 
slide 39 and, by means of the spring 40 (which prevents excessive stresses 
in case of high currents), pulls the cable 23, thereby lowering the frame 
18 and obscuring the visual field of the operator. As soon as the welding 
electrode is detached, thereby switching off the current, the whole 
apparatus returns to the rest position and the operator immediately 
obtains again unobscured vision. 
The preloaded spring, intended to prevent overloads, may generally be 
mounted in any point of the kinematic system, and for example also at 44, 
between the cable 23 and the lever 22, as shown partially and by dash 
lines in FIG. 1. 
In FIG. 6 there is shown in detail, on an enlarged scale, a protection 
device having a preloaded compression spring. In this device, the head 41 
having anchored thereon the flexible cable 23 by means of the setscrew 42, 
is attached in such a way as to be axially slidable along a limited path 
with respect to the slide 39, and the compression spring 40 is lodged in 
the compressed condition between said parts. It yields only in case of a 
stress higher than its preloading. 
In the variant shown in FIG. 7, the slide 39' extends to form by itself the 
head 41' in the shape of a bracket, on which there is anchored the 
preloaded spring 40', which in this case is an extension spring, on which 
there is in turn anchored the flexible cable 23. 
In any case, at some point on the cable 23 or on the elements connected to 
it, there is disposed a rotatable joint intended to prevent twisting of 
the cable. 
In the cases in which the winding 28 has to be inserted in parallel to the 
welding circuit, for example in the case of continuous feed welding, it is 
advantageous to insert an incandescent lamp (diagrammatically shown at 46 
in FIG. 3) in series with the winding, in order to allow the initial 
passage of a high actuating current and to successively limit the 
consumption, owing to the known characteristic of variation of the 
electric resistance of an incandescence lamp. 
Obviously, instead of a lamp also other components or circuits may be used 
in view of obtaining this effect. 
In accordance with possible modifications, the obscuration of the field 
could also be obtained by the cooperation of two crossing polarizing 
filters, one of which is fixed and the other is movable, or by means of an 
element whose transparency varies as a result of the application of a 
field or of an electric current.