Flat Automatic Darkening Filter And Welding Protector

Abstract

An automatic darkening filter for welding protection. The automatic darkening filter has a first liquid crystal cell having two flat ultrathin glass substrates. Further, a welding protector is provided that includes the automatic darkening filter. The automatic darkening filter is lightweight and nevertheless mechanically stable and durable.

Claims

1. An automatic darkening filter for welding protection, comprising a first liquid crystal cell having two flat ultrathin glass substrates, wherein the ultrathin glass substrates have a thickness of between 30 m and 200 m.

2. The automatic darkening filter of claim 1, further comprising a first and a second flat polarizer each having a polarization direction, the first and second polarizer being arranged in an overlapping manner on opposite sides of the first liquid crystal cell, with their polarization directions oriented angularly offset to each other.

3. The automatic darkening filter of claim 2, further comprising a second liquid crystal cell having two flat ultrathin glass substrates.

4. The automatic darkening filter of claim 3, further comprising a third flat polarizer having a polarization direction, the second and the third polarizer being arranged in an overlapping manner on opposite sides of the second liquid crystal cell, wherein the first and the third polarizer are arranged with their polarization directions oriented parallel or at an angle within a range of 6 to 12 degrees relative to each other.

5. The automatic darkening filter of claim 3, wherein each of the first and second liquid crystal cell have an edge sealing which seals the liquid crystals within a space formed by the glass substrates and the edge sealing.

6. The automatic darkening filter of claim 5, wherein each of the glass substrates comprising a transparent electrode layer and an alignment layer for the liquid crystals.

7. The automatic darkening filter of claim 1, wherein the ultrathin glass substrates have a thickness of between 50 m and 150 m.

8. The automatic darkening filter of claim 4, having a third liquid crystal cell and a fourth polarizer, wherein the first, second, and third liquid crystal cell are arranged between the first and the fourth polarizer, and wherein the second polarizer is arranged between the first and the second liquid crystal cell and the third polarizer is arranged between the second and the third liquid crystal cell.

9. The automatic darkening filter of claim 8, having a fourth liquid crystal cell and a fifth polarizer, wherein the first, second, third and fourth liquid crystal cell are arranged between the first and the fifth polarizer and the fourth polarizer being arranged between the third and the fourth liquid crystal cell.

10. The automatic darkening filter of claim 9, further having a fifth liquid crystal cell and a sixth polarizer, wherein the first, second, third, fourth and fifth liquid crystal cell are arranged between the first and the sixth polarizer and the fifth polarizer being arranged between the fourth and the sixth liquid crystal cell.

11. A welding protector, such as a welding shield or welding helmet, comprising the automatic darkening filter of any of claim 1.

12. The welding protector of claim 11, further comprising electronic circuitry having a power source and a light sensor and being electrically connected to the automatic darkening filter, wherein the electronic circuitry is configured for causing the automatic darkening filter to switch dependent on light detected by the light sensor.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] FIG. 1 is a perspective view of a welding protector, in particular of a welding helmet, according to an embodiment of the invention;

[0024] FIG. 2 is a cross-sectional view of a liquid crystal cell according to an embodiment of the invention;

[0025] FIG. 3 is a perspective view of two glass substrates with an edge sealing according to an embodiment of the invention;

[0026] FIG. 4 is an exploded view of an automatic darkening filter according to an embodiment of the invention; and

[0027] FIG. 5 illustrates a measurement of a deflection of a glass substrate.

DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1 shows a welding protector 1 which in the example is a welding helmet. The invention is however not limited to a use with a welding helmet, but may likewise be used with a welding shield or welding goggles in an appropriate configuration.

[0029] The welding protector 1 has a protective shield portion 2 for protecting a welder's face (and other head portions) from radiation, dust and splashes of hot materials as these may occur during welding. The welding protector 1 further has an automatic darkening filter 3 through which the welder can observe the welding arc during welding. In the example the automatic darkening is based on two liquid crystal cells by which the automatic darkening filter assembly 3 is electrically switchable between a light-state and a dark-state. When switched in the dark-state, the automatic darkening filter assembly 3 blocks a significant amount of light from being transmitted therethrough. This enables a user to observe a welding arc by seeing through the automatic darkening filter 3 without risking to be exposed to harmful light radiation from the welding arc. In the light-state the automatic darkening filter assembly 3 permits a significant amount of light to be transmitted therethrough. Thus, the automatic darkening filter assembly 3 in the light-state allows the user to see under ambient light conditions (in the absence of the welding arc).

[0030] The automatic darkening filter 3 comprises two (or more) liquid crystal cells that are arranged optically in sequence. This provides for multiplying the darkening effect (in particular in the dark-state) and thus a sufficient eye protection from light radiation.

[0031] Further, the welding protector 1 comprises at least one light sensor 4 and electronic circuitry (not illustrated) that causes the liquid crystal cells to switch dependent on light recognized by the light sensor(s). In particular, the light sensor 4 may provide a signal to the electronic circuitry depending on the light sensed by the light sensor 4. The signal provided by the light sensor 4 can typically be correlated to the intensity of light sensed by the light sensor 4. The electronic circuitry is set up to control the switching of the automatic darkening filter to the dark-state in case the light intensity (and optionally an additional frequency or pulsation) detected by the light sensor 4 exceeds a predetermined maximum value. Further, the electronic circuitry is set up to control the switching of the automatic darkening filter to the light-state in case the light intensity detected by the light sensor 4 drops below the predetermined maximum value.

[0032] FIG. 2 shows a liquid crystal cell 10 of the invention. The liquid crystal cell 10 has two glass substrates 11. Each glass substrate has opposite major sides and a thickness T1 defined between. In the example the glass substrates have a thickness of 100 m. In addition, the liquid crystal cell 10 has a liquid crystal layer 12 which comprises liquid crystal molecules 13 and spacers 14. The liquid crystal layer 12 has a thickness T2 of 4 m. The thickness T2 of the liquid crystal layer is determined by a gap between the major sides of the glass substrates and the size of the gap is provided by the spacers 14 arranged between the glass substrates. The spacers 14 are distributed across the major sides between the glass substrates. The amount of spacers may be between 30 and 200 spacers per square mm. Thus, the thickness of the liquid crystal layer 12 can be maintained relatively uniform across the liquid crystal cell 10. Accordingly, the darkening effect can be maintained relatively uniform across the liquid crystal cell 10 particularly in the dark-state. In the example the spacers are silica beads having a diameter of 4 m.

[0033] Each glass substrate further has an electrode layer 15, which in the example is a transparent layer of indium tin oxide, as well as an alignment layer 16 for providing a default alignment of the liquid crystals.

[0034] FIG. 3 shows the two glass substrates of the liquid crystal cell shown in FIG. 2. An edge sealing 17 is provided in the margin of the glass substrate for sealing the gap between the glass substrates. The edge sealing hermetically seals the liquid crystals between the two glass substrates and provides mechanical stability (for example flexural resistance) for the liquid crystal cell.

[0035] FIG. 4 shows an exploded view of the automatic darkening filter 3. It is noted that the exploded view is a type of illustration only and that certain components that appear to be spaced from each other are normally mounted in contact to each other. The automatic darkening filter 3 comprises two liquid crystal cells 10 arranged optically in sequence with a (in the example horizontal) polarizer 21 arranged between. Further, the automatic darkening filter 3 comprises two (in the example vertical) polarizers 20 on the side of each liquid crystal cell 10 opposite of that side of the liquid crystal cell 10 on which the horizontal polarizer 21 is arranged. Thus, a sandwich arrangement is formed in which a vertical polarizer 20, a liquid crystal cell 10, a horizontal polarizer 21, a further liquid crystal cell and another vertical polarizer 20 are arranged in sequence. The skilled person will be aware that the vertical polarizers can be replaced by a horizontal polarizer and the horizontal polarizer can be replaced by a vertical polarizer as long as the polarizer in the middle is different from the outer polarizers. Further, other orientations are possible as long as the polarizer in the middle provides for a polarization which orientation is inclined relative to the orientation of the polarization provided by the outer polarizers. Hence, in absence of any liquid crystals the combination of the three polarizers blocks light through the three polarizers to a significant level.

[0036] Further, the automatic darkening filter 3 has a UV (ultraviolet light) filter that typically also includes an IR (infrared light) filter. The UV light filter blocks at least a significant amount of ultraviolet light. The UV light filter is arranged on a side of the automatic darkening filter that faces away from a person's (for example a welder's) eye 100 who uses the automatic darkening filter 3. The UV filter is preferably fixedly laminated into the automatic darkening filter.

[0037] Furthermore, the automatic darkening filter 3 may comprise an exchangeable transparent protective layer on the eye facing side of the automatic darkening filter 3 and/or on the opposite side.