Light protection apparatus comprising an electrically controllable light protection filter element

The invention provides a light protection apparatus, particularly for welder's protective helmets, welder's protective eyeglasses or welder's protective shields. It comprises a light protection filter element, the optical transmission thereof being electrically controllable, and a control box connected to the light protection filter element to control the optical transmission of the light protection filter element. The control box comprises one or several light sensitive sensor to control the light transmission of the light protection filter element in dependence of the light falling onto the sensor or sensors, respectively. The light protection filter element is provided with shield elements adapted to shield the sensor against interfering light falling onto the sensor in at least one preselected direction.

FIELD OF THE INVENTION 
The present invention refers to a light protection apparatus, particularly 
for welder's protective helmets, welder's protective eyeglasses or 
welder's protective shields, comprising a light protection filter element, 
the optical transmission thereof being electrically controllable. Further, 
the invention refers to a light shield member for a light protection 
apparatus, particularly for welder's protective helmets, welder's 
protective eyeglasses or welder's protective shields. 
Prior Art 
The EPO Publication No. 0,091,514--A2 and other publications disclose light 
protection filter elements the optical transmission characteristics 
thereof being electrically controllable. Particularly, these light 
protection filter elements make use of light sensitive sensor elements 
which control the transmission ratio of the light protection filter 
element in a manner contrary to the amount of light falling onto the light 
sensitive sensor. 
Practice has shown that these sensors can be hit and, thereby, influenced 
by undesired interfering light which does not originate from the real 
welding operation with the result that the light protection filter element 
changes its transmission behaviour, particularly darkens, in an undesired 
moment. Known interfering light sorces are, for example, sodium vapour 
lamps or other similar light sources which are particularly used for the 
illumination of the place of work in manufacturing plants or factory 
buildings. This means for the user of such light protection filter 
elements, i.e. for the user of e.g. a welder's protective helmet, that the 
light sensitive sensors unwantedly react under the influence of a bright 
ambient illumination, particularly under the influence of the bright 
sodium vapour lamps used for the illumination of the place of work of a 
welder. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide a light protection apparatus, 
particularly for welder's protective helmets, welder's protective 
eyeglasses or welder's protective shields, comprising a light protection 
filter element, the optical transmission thereof being electrically 
controllable, which is designed such that interfering light coming e.g. 
from place of work illumination does not influence the sensor or sensors 
used to control the transmission of the light protection filter element. 
It is a further object of the invention to provide a light shield member 
for a light protection apparatus, particularly for welder's protective 
helmets, welder's protective eyeglasses or welder's protective shields, 
comprising a light protection filter element, the optical transmission 
thereof being electrically controllable, which is designed such that 
interfering light coming e.g. from place of work illumination does not 
influence the sensor or sensors used to control the transmission of the 
light protection filter element. 
SUMMARY OF THE INVENTION 
In order to achieve these and other objects, the invention provides, 
according to a first aspect, a light protection apparatus, particularly 
for welder's protective helmets, welder's protective eyeglasses or 
welder's protective shields, comprising a light protection filter element, 
the optical transmission thereof being electrically controllable. The 
apparatus includes a control means connected to the light protection 
filter element to control the optical transmission of the light protection 
filter element. The control means comprises a light sensitive sensor to 
control the light transmission of the light protection filter element in 
dependence of the light falling onto the sensor. The light protection 
filter element is provided with shield means adapted to shield the sensor 
against interfering light falling onto the sensor in at least one 
preselected direction. 
According to a second aspect of the invention, there is provided a light 
protection apparatus, particularly for welder's protective helmets, 
welder's protective eyeglasses or welder's protective shields, comprising 
a light protection filter element, the optical transmission thereof being 
electrically controllable. Again, the apparatus includes a control means 
connected to the light protection filter element to control the optical 
transmission of the light protection filter element. The control means 
comprises a plurality of light sensitive sensor means to control the light 
transmission of the light protection filter element in dependence of the 
light falling onto the sensors. The light protection filter element is 
provided with shield means adapted to shield each of said sensor means 
against interfering light falling onto said sensor means in at least one 
preselected direction. 
In a first embodiment, the shield means comprises a shade means having a 
first transparent part and a second non-transparent part extending 
substantially perpendicularly to the first transparent part and running 
along the length of the first transparent part. The shade means is mounted 
to the light protection filter element in front of the sensor means such 
that interfering light falling onto the sensor means in at least one 
preselected direction is shielded. 
Preferably, the shade means are pivotally connected to the light protection 
filter element by means of a hinge and are provided with an operating 
handle such that the shade means can be swivelled from an operative 
position to an inoperative position. 
In a further embodiment, the shield means comprise a shackle member 
provided with light-transparent openings. Thereby, the shackle member is 
mounted to the light protection filter element in front of the sensor 
means such that the position of the openings substantially corresponds 
with the position of the sensor means such that interfering light falling 
onto the sensor means in at least one preselected direction is shielded. 
The openings can be partially surrounded by shielding cap members. Another 
possibility is to provide the shackle member with light-transparent, 
obliquely and/or vertically and/or horizontally running apertures. 
According to a second aspect of the invention, there is provided a light 
shield member for a light protection apparatus, particularly for welder's 
protective helmets, welder's protective eyeglasses or welder's protective 
shields, such light protection apparatus comprising a light protection 
filter element, the optical transmission thereof being electrically 
controllable. The light protection apparatus comprises a control means 
connected to the light protection filter element to control the optical 
transmission of the light protection filter element. The control means 
comprises at least one light sensitive sensor to control the light 
transmission of the light protection filter element in dependence of the 
light falling onto the sensor or sensors, respectively. The light shield 
member comprises an elongated strip member having at least on bore, said 
strip member being mounted to the light protection filter element in front 
of the sensor or sensors, respectively, such that the position of the bore 
or bores substantially corresponds with the position of the sensor or 
sensors such that interfering light falling onto the sensor or sensors in 
at least one preselected direction is shielded.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS 
FIG. 1 shows a welder's protective helmet 1 with a built-in light 
protective filter element 3. As is well known in the art, the light 
transmission ratio of such a light protective filter element is 
electrically controllable. Particularly, the welder's protective helmet 1 
shown in FIG. 1 comprises the helmet housing 2, a light protection 
cassette 9, an opto-electric transducer element 4, a bridge member 7, two 
sensor elements 5 and 6 as well as the real light protection filter 
element 8. 
FIG. 2 shows a first embodiment of a shielding member 10, comprising a 
light transparent cover 11, a hinge member 12 which serves in this example 
for pivotally connecting the shielding member 10 to the light protection 
filter member, an operating handle 13 to swivel the shielding member from 
an operative position to an inoperative position, as well as a 
non-transparent part 14 which serves, in this example, as the shielding 
member to prevent interfering light to reach the sensor elements 5 and 6. 
FIG. 3 shows a second embodiment of a shielding member 20, comprising 
shackle member 21 having apertures 22 provided in the region of the outer 
ends of the shackle member 21. The distance between the apertures 22 and 
their position corresponds to the distance between and to the position of 
the sensor elements 5 and 6 provided on the bridge member 7 of the light 
protection cassette 9. The apertures 22 are designed such that they let 
pass light only under a certain predetermined angle with the result that 
interfering light is prevented to fall onto the light sensor elements 5 
and 6. Preferably, the apertures 22 are in the form of bores which are 
designed such that they are not directed perpendicularly to the surface of 
the shackle member 21, but include a certain angle. With other words, the 
central axis of the bores include a certain angle with the central optical 
axis of the related sensor member, preferably downwardly directed. 
FIG. 4 shows a third embodiment of a shielding member 30, comprising a 
shackle member 31 having apertures 22 provided in the region of the outer 
ends of the shackle member 21. The distance between the apertures 32 and 
their position corresponds to the distance between and to the position of 
the sensor elements 5 and 6 provided on the bridge member 7 of the light 
protection cassette 9. The apertures 32 are designed such that they let 
pass light only under a certain predetermined angle with the result that 
interfering light is prevented to fall onto the light sensor elements 5 
and 6. To assist this effect, the apertures are provided with shielding 
cap members 33 at least partially surrounding said apertures 32. Thus, 
interfering light coming from a certain direction is prevented to fall 
onto the sensor elements 5 and 6. 
FIG. 5 shows a fourth embodiment of a shielding member 40, comprising a 
shackle member 41 having apertures 42 provided in the region of the outer 
ends of the shackle member 41. The distance between the apertures 42 and 
their position corresponds to the distance between and to the position of 
the sensor elements 5 and 6 provided on the bridge member 7 of the light 
protection cassette 9. The apertures 42 are designed such that they let 
pas light only under a certain predetermined angle with the result that 
interfering light is prevented to fall onto the light sensor elements 5 
and 6. 
FIGS. 5a and 5b show, in an enlarged scale, two of several variants of the 
design of the light transparent apertures 42. The variant shown in FIG. 5a 
comprises a plurality of horizontally extending slits 42a while the 
variant shown in FIG. 5b comprises one horizontally extending and one 
vertically extending slit. The particular design depends on the situation 
where the welder's helmet, mask or shield is used and it is possible to 
have realized another slit pattern, e.g. including obliquely running slits 
(not shown). 
FIG. 6 shows a fifth embodiment of a shielding member 50, comprising a 
plate member 50a the center of which is equipped with a bore 51. The plate 
member 50a is mounted in front of the one sensor element 5 or 6 such that 
the center of the bore 51 corresponds with the central axis of the sensor 
element 5 or 6. In this case as well, the bores 51 can be arranged under a 
certain angle different from the perpendicular line with reference to the 
surface of the plate member 50a. 
FIGS. 7a to 7c show a sixth embodiment of a shielding member 60, comprising 
an elongated strip member 61 being equipped with two bores 62 and 63. Z1 
designates a first central symmetry plane, running in the longitudinal 
extension of the strip member 61 and parallel to the even, flat top 
surface and lower surface of the strip member 61. Z2 designates a second 
central symmetry plane, running in the centre of the strip member 61 and 
parallel to the even, flat side surfaces of the strip member 61. The 
curved front surface 64 of the strip member 61 does not have any 
functional meaning and serves only for the purpose of improving the 
aesthetical appearance of the light protection filter 3. 
In FIG. 7b, the strip member 61 is shown in outline. The reference d1 means 
the diameter of the bores 62 and 63, and the reference e1 means the 
thickness of the strip member 61 in the region of the bores 62 and 63. 
Thus, from this drawing figure, it can be seen that the bores 62 and 63 
are parallel with the central symmetry plane Z2. 
In FIG. 7c, the strip member 61 is shown in a cross sectional view along 
the line A--A (c. FIG. 7a). From this figure, it can be clarly seen that 
the axes of the bores 62 and 63 include an angle W1 with the central 
symmetry plane Z2. The result is that the sensor elements 5 and 6 arranged 
behind the bores 62 and 63 of the strip member 61 receive only light which 
essentially falls onto the sensors 5 and 6 under the aforementioned angle 
W1, as compared to the horizontal plane. The total amount of the light 
falling onto the sensors 5 and 6 arranged behind the bores 62 and 63 of 
the strip member 61 can be adjusted or preselected by the diameter d1 of 
the bores and the thickness e1 of the strip member 61. 
FIGS. 8a to 8c show a seventh embodiment of a shielding member 70, 
comprising an elongated strip member 71 being equipped with two bores 72 
and 73. Generally, the strip member 71 corresponds to the strip member 61 
shown in FIGS. 7a to 7c. Z3 designates a first central symmetry plane, 
running in the longitudinal extension of the strip member 71 and parallel 
to the even, flat top surface and lower surface of the strip member 71. Z4 
designates a second central symmetry plane, running in the centre of the 
strip member 71 and parallel to the even, flat side surfaces of the strip 
member 71. The curved front surface of the strip member 71 does not have 
any functional meaning and serves only for the purpose of improving the 
aesthetical appearance of the light protection filter 3. 
In FIG. 8b, the strip member 71 is shown in outline. The reference d2 means 
the diameter of the bores 72 and 73, and the reference e2 means the 
thickness of the strip member 71 in the region of the bores 72 and 73. 
Thus, from this drawing figure, it can be seen that the axes of the bores 
72 and 73 include an angle W2 with the central symmetry plane Z2. 
In FIG. 8c, the strip member 71 is shown in a cross sectional view along 
the line B--B (cf. FIG. 8a). From this figures, it can be clarly seen that 
he axes of the bores 72 and 63 run parallel with with the central symmetry 
plane Z4. The result is that the sensor elements 5 and 6 arranged behind 
the bores 72 and 73 of the strip member 71 receive only light which 
essentially falls onto the sensors 5 and 6 from the left and the right 
side. Again, the total amount of the light falling onto the sensors 5 and 
6 arranged behind the bores 72 and 73 of the strip member 71 can be 
adjusted or preselected by the diameter d2 of the bores and the thickness 
e2 of the strip member 62. 
It is understood that the extension of the angle of the bores, as explaines 
in connection with the FIGS. 7a to 7c and 8a to 8c, can be combined, i.e. 
the bores can be oblique in vertical as well as in horizontal direction. 
The shielding means shown in FIGS. 2 to 8 can be directly formed onto the 
light protection cassette. However, if a welder's protective helmet, for 
example, has already been sold in great numbers not having these shielding 
means, the need can arise that these shielding means have to be mounted to 
the helmet at a later date. Thus, the shielding means shown in the FIGS. 2 
to 8 and described hereinbefore can be designed such that they can be 
separately sold and mounted to the welder's helmet as needed. It is even 
possible for the user of the helmet to buy different sets of shielding 
means and to mount it to its helmet in dependence whether the interfering 
light comes from the top or from the side.