Welding helmet with eye piece control

Abstract

A protective welding lens assembly is shown, as for use in the eye piece of a welding helmet, utilizing a liquid crystal together with an electrical circuit which applies a suitable electrical potential to the liquid crystal to change the same from a uniform light transmitting condition to a uniform approximately opaque condition of very small light transmission solely in response to approach to the welding electrode close to the workpiece to be welded.

What is claimed is: 
     
       1.  A protective welding lens assembly for use with an electrical welding machine having an electrical energizing circuit and having a welding electrode connected thereto by an electrical cable, said assembly being . .planar and.!. fixedly mounted in a welder's helmet, and comprising a layer of liquid crystal material sandwiched between opposing parallel plates coated . .over their entire area.!. with unbroken transparent conducting films, said films being pretreated by rubbing the same in parallel lines at right angles to each other whereby to control their polarizing effect upon said liquid crystal material, said plates with the enclosed liquid crystal material being disposed between and parallel to a pair of conventional . .cross.!. polarizers so arranged that when a suitable electrical potential is established across said conducting films and said liquid crystal layer the lens assembly will change . .from a uniform.!. .Iadd.its .Iaddend.light transmitting condition . .to a uniform high density approximately opaque condition.!..Iadd., .Iaddend.and means including a low voltage electrical circuit . .electrically associated with said electrical energizing circuit and.!. responsive . .solely.!. to . .approach of.!. .Iadd.establishment of an arc between .Iaddend.said welding electrode . .to the.!. .Iadd.and .Iaddend.work to be welded . .by the wearer of the helmet.!. for applying said suitable electrical potential across said conducting films and said liquid crystal layer . .in a period of approximately 1/500 of a second.!.. 
     
     
       2. A welding lens assembly as defined in claim 1, wherein said liquid crystal material is of the nematic type of mesophase with a positive dielectric anisotropism. 
     
     
       3. A welding lens assembly as defined in claim 2, wherein said last named means includes a switching device responsive to visible light from a welding arc struck between a welding electrode and a workpiece upon approach of said electrode close to a workpiece. 
     
     
       4. A welding lens assembly as defined in claim 2, wherein said last named means includes a switching device responsive to infra-red rays emitted from an electrode approaching a workpiece prior to the emission of actinic rays.  . .5. A welding lens assembly as defined in claim 2, wherein said welding machine utilizes a direct current, and said last named means includes a current transformer operatively associated with said electrical cable and a switching device in said electrical circuit responsive to current generated in said transformer when said electrode approaches a workpiece..!.  . .6. A welding lens assembly as defined in claim 2, wherein said welding machine utilizes alternating current and said last named means includes a capacitance type pickup operatively associated with said electrical cable and a switching device in said electrical circuit responsive to change in said capacitance when said electrode is advanced to a workpiece..!.  . .7. A welding lens assembly as defined in claim 2, for use with a welding machine utilizing direct or alternating current, wherein said last named means includes an electromagnetic-responsive ferrite core antenna operatively associated with said electrical cable, and said last named means includes a switching device in said electrical 
     
     
        circuit responsive to a signal from said antenna..!. 8. A welding lens assembly as defined in claim 2, for use with a welding machine having a high frequency welding current, wherein said last named means includes a detector responsive to high frequency, and said last named means includes a switching device in said electrical circuit responsive to a signal from 
     
     
        said detector. 9. A welding lens assembly as defined in claim 8, including a switching device in circuit with said high frequency detector, said last named switching device responsive to visible light from a welding arc struck between a welding electrode connected with said welding machine and a workpiece upon approach of said electrode close to said workpiece. . .10. A welding lens assembly as defined in claim 2, wherein said welding machine utilizes alternating current, wherein said last named means includes a voltage transformer operatively associated with said electrical cable and a switching device in said electrical circuit responsive to electrical flow from said transformer when said electrode approaches a workpiece..!.  . .11. A welding lens assembly as defined in claim 10, including a switching device in circuit with said first named switching device, said last named switching device responsive to visible light from a welding arc struck between a welding electrode connected with said welding machine and a workpiece upon approach of said electrode close to said workpiece..!.  . .12. A welding lens assembly as defined in claim 10, responsive to infra-red rays emitted between a welding electrode and a workpiece upon approach of said electrode close to a workpiece..!. .Iadd. 13. In a welding helmet, a protective welding lens assembly fixed in position within said welding helmet, said assembly comprising a layer of liquid crystal material sandwiched between spaced transparent plates, polarizers on opposite sides of said layer of liquid crystal material, means for applying an electrical potential across said layer of liquid crystal material to thereby vary the light-transmitting characteristics of said lens assembly, and means including a low voltage electrical circuit actuable in response to establishment of an arc between a welding electrode and work to be welded for applying an electric field across said liquid crystal layer to vary the light-transmitting characteristics of the lens assembly. .Iaddend..Iadd. 14. The welding lens assembly of claim 13 wherein said liquid crystal material is nematic, said lens assembly incorporating means for effecting a twisted nematic structure in said liquid crystal material. .Iaddend..Iadd. 15. The protective welding lens assembly of claim 13 wherein said low voltage electrical circuit includes means responsive to wave energy emitted by a welding arc for applying said electric field across the liquid crystal layer. .Iaddend. .Iadd. 16. A protective welding lens assembly for use with an electrical welding machine having an electrical energizing circuit and having a welding electrode connected thereto by an electrical cable, said assembly being fixedly mounted in a welder's helmet and comprising a layer of liquid crystal material sandwiched between opposing parallel plates coated with unbroken transparent conducting films, said films being pretreated by rubbing the same in parallel lines at right angles to each other whereby to control their polarizing effect upon said liquid crystal material, said plates with the enclosed liquid crystal material being disposed between and parallel to a pair of conventional polarizers so arranged that when a suitable electrical potential is established across said conducting films and said liquid crystal layer the lens assembly will change its light transmitting condition, and means including a low voltage electrical circuit responsive to a surge of current through said electrical cable upon establishment of a welding arc for applying said suitable electrical potential across said conducting films and said liquid crystal layer. .Iaddend..Iadd. 17. A welding lens assembly as defined in claim 16 wherein said welding machine utilizes direct current, and said last-named means includes a current transformer operatively associated with said electrical cable and a switching device in said electrical circuit responsive to current generated in said transformer when said electrode approaches a workpiece. .Iaddend. .Iadd. 18. A welding lens assembly as defined in claim 16 wherein said welding machine utilizes alternating current, and said last-named means includes a capacitance-type pickup operatively associated with said electrical cable, and a switching device in said electrical circuit responsive to a change in said capacitance when a welding electrode is advanced to a workpiece. .Iaddend..Iadd. 19. A welding lens assembly as defined in claim 16 for use with a welding machine utilizing direct or alternating current, wherein said last-named means includes an electromagnetic-responsive ferrite core antenna operatively associated with said electrical cable, and said last-named means includes a switching device in said electrical circuit responsive to a signal from said antenna. .Iaddend..Iadd. 20. A welding lens assembly as defined in claim 16 wherein said welding machine utilizes alternating current and said last-named means includes a voltage transformer operatively associated with said electrical cable, and a switching device in said electrical circuit responsive to electrical flow from said transformer when said electrode approaches a workpiece. .Iaddend.