Negative electrode for lead accumulators

Abstract

A negative electrode for lead accumulators has the form of a rectangular, expanded metal, grid plate 11 of copper. The grid plate serves as carrier for the active mass and for the supply and extraction of current. The direction of stretching of the expanded metal extends parallel to the edge of the rectangular grid plate at which the connection lug is arranged. A lead strip 13, which is in one piece with the connection lug, is conductively secured to the top edge of the grid plate. The lead strip 13 is cast onto the grid plate 12 (FIG. 1).

I claim: 
     
       1. In a negative electrode for lead accumulators in the form of a rectangular expanded metal grid plate of copper having upper and lower ends forming upper and lower crossing points of said grid which serves as a carrier for an active mass and for current supply and extraction, the direction of stretching of the expanded metal extending parallel to an end of the rectangular grid plate at which a connection lug is provided, and wherein a lead strip, unitary with .[.a.]. .Iadd.the .Iaddend.connection lug, is conductively secured to .[.one.]. .Iadd.said .Iaddend.end of said grid plate over the whole length thereof, .Iadd.the .Iaddend.improvement wherein .Iadd.said copper grid is covered with a galvanically applied layer of a lead-tin alloy and .Iaddend.the lead strip is cast onto the grid plate .[.and said copper grid is covered by a lead or.]. .Iadd.on top of the previously galvanically applied .Iaddend.lead-tin alloy layer.Iadd., and wherein the end regions of the grid plate which are either cast with lead or surrounded by a synthetic material, are pressed flat in a plane to form the grid plate prior to the casing of the lead and application of the synthetic material respectively.Iaddend.. 
     
     
       2. An electrode in accordance with claim 1 wherein the lower portion of the lead strip extends substantially through the outermost upper crossing points of said grid plate. 
     
     
       3. An electrode in accordance with claim 1 wherein the grid plate is cut off at its upper end just beyond the upper crossing points in such a way that short anchoring webs project beyond said upper crossing points for securing the casting of the lead of said strip around the upper portion of said grid plate. 
     
     
       4. An electrode in accordance with claim 1 wherein the openings formed by said grid immediately adjacent said lead strip are also cast full of lead. 
     
     
       5. An electrode in accordance with claim 1 wherein a termination strip is provided at the lower end of the grid plate remote from the lead strip carrying the connection lug, said termination strip comprising an acid resistant synthetic material. 
     
     
       6. An electrode in accordance with claim 5 wherein said synthetic material is injection-molded around the lower end region of the grid plate. 
     
     
       7. An electrode in accordance with claim 5 wherein the lower end region of the grid plate is pressed in heated condition into the thermoplastic synthetic material. 
     
     
       8. An electrode in accordance with claim 5 wherein said grid plate is cut off at its lower end at the level of said crossing points. 9. An electrode in accordance with claim 1 wherein the end regions of the grid plate which are either cast with lead or surrounded by synthetic material, are pressed flat in a plane to form the grid plate prior to the casting of the lead 
     
     
        and application of the synthetic material respectively..]. 10. An electrode in accordance with claim .[.5.]. .Iadd.22 .Iaddend.wherein .[.the.]. .Iadd.an acid resistance synthetic .Iaddend.termination strip is applied to the .Iadd.other end of the .Iaddend.expanded metal grid plate of copper prior to the application of the lead-tin layer and/or of the 
     
     
        lead layer. 11. An electrode in accordance with claim 10 wherein the application of the lead-tin alloy and the final lead layer take place one after the other by galvanic deposition following the attachment of the 
     
     
        termination strip. 12. An electrode in accordance with claim .[.11.]. 
     
     
        .Iadd.1 .Iaddend.wherein the lead-tin alloy contains at least 8% tin. 13. An electrode in accordance with claim .[.11.]. .Iadd.22 .Iaddend.wherein the lead layer is from about 20 μm to 40 μm thick. 
     
     
         4. An electrode in accordance with claim .[.11.]. .Iadd.22 .Iaddend.wherein the current density during galvanizing, in particular during the application of the lead layer, amounts to from about 6 to 10 
     
     
        A/dm 2 . 15. An electrode in accordance with claim 1 wherein the stretching ratio of the expanded metal amounts to from about 0.5 to 0.6. 
     
     
          . An electrode in accordance with claim 1 wherein the web width of the expanded metal amounts to from about 1.7 to 2.3 mm when the resulting 
     
     
        plate is surrounded on both sides by a positive plate. 17. An electrode in accordance with claim 1 wherein the web thickness of the expanded metal 
     
     
        amounts to from about 0.4 to 0.8 mm. 18. An electrode in accordance with claim 1 wherein the mesh length of the expanded metal amounts to from 
     
     
        about 15 to 30 mm. 19. An electrode in accordance with claim 1, wherein 
     
     
        the web width of the expanded metal is approximately 2 mm. 20. An electrode in accordance with claim 1, wherein the web thickness of the 
     
     
        expanded metal is approximately 0.6 mm. 21. An electrode according to claim 1, wherein the mesh length of the expanded metal is approximately 20 mm. .Iadd.22. An electrode in accordance with claim 1 wherein a galvanically applied layer of lead is deposited on the copper grid on top of the previously galvanically applied lead-tin alloy layer. .Iaddend. .Iadd.23. An electrode in accordance with claim 22 wherein the lead-tin 
     
     
        alloy contains at least 8% tin. .Iaddend. .Iadd.24.  An electrode in accordance with claim 22, wherein the lead-tin alloy layer is applied to the grid plate after suspending the grid plate in a cleaning and rinsing bath, and the layer of lead is subsequently deposited without intermediate rinsing. .Iaddend. .Iadd.25. An electrode in accordance with claim 12, 
     
     
        wherein the lead-tin alloy layer contains 10% tin. .Iaddend. .Iadd.26.  An electrode in accordance with claim 1, wherein the thickness of the galvanically applied lead-tin alloy is from about 7 μm to 10 μm. .Iaddend.