Patent GB-1442936-A (GB)
Title: Method and apparatus for making expanded metal lead-acid storage battery grids
IPC: B21D31/04
Filed: 1974-09-05
Abstract: 1442936 Making battery plates; angular bending; drawing; shearing GENERAL MOTORS CORP 5 Sept 1974 [20 Sept 1973 (3)] 38915/74 Headings B3A B3E B3P and B3W [Also in Division H1] A method of making lead-acid storage battery plates comprises passing a strip or ribbon of lead 40 between dies and cutters to form by expanded metal techniques two longitudinally extending reticulated strip portions connected to a central strip portion 42 and at acute angles to the plane of the portion 42, folding down the reticulated portions into substantially the same plane as the portion 42, stretching the reticulated portions to form cells 16 of a predetermined width joined by nodes 10, compressing the reticulated portions to reduce the nodes to a thickness greater than, but substantially less than twice, the thickness of the strip and applying to the reticulated portions an active paste containing lead. The strip 40 is passed between a series of reciprocating dies 72 and fixed cutters 74, both of which are spaced progressively closer together in the direction of travel of the strip, Fig. 11 (not shown). The lead strip passes over a bed or stripper plate which is fixed to the cutter holder assembly 75, but spaced from it, so as to strip the expanded portions from the dies 72 during their downward movement. Each upward motion of the dies forms one half of a cell 16 and when a border 14 is required the first increment of metal cut is only slit but not stretched appreciably. The border 14 causes the reticulated portion to curl and jam in the expander and a straightener 90 is provided to overcome this. It is located about midway along the row of dies, Fig. 10 (not shown) and its height is set to force the border upwardly thereby pulling out any curl formed. The straightener also aligns the nodes 10 in a space 93 formed between it and a retainer 82. The cutters 74 and dies 72 are made from air hardening tool steel, the cutters being machined so as to have machining marks running in the same direction as the movement of the dies thereby eliminating the need for final buffing. The cutting surfaces of the dies 72 require buffing to allow the lead to slide over them during stetching. Ordinary tap water is used as a lubricant allowing for higher work rates than when using conventional lubricants. The water also oxidises the surface of the lead thereby improving adhesion of the active paste to the grid. The V-shaped expanded strip is then passed through a plough 60, which flattens it, apart from a slight bump (102), Fig. 13 (not shown), near the centre portion 42. A drive roller 41 and its coacting roller flatten the hump (102), the rollers being knurled to grip the portion 42 and drive the strip through the apparatus. The cells are expanded between a pair of rollers 44. The lower roller is provided with truncated pyramidal projections 46, which engage in each cell 16 and pass into holes in the upper roller 48, the surface of which is made of a thick compressible polyurethane layer. The reticulated portions are then passed between roll pairs 18, which are spaced apart at least 1À3 times the thickness of the strip, and the nodes are slightly rotated and have flattened portions 22 formed on them, Figs. 4, 5 (not shown). The expanded strips are laid on strips of perforated paper 50 on a continuous belt 52 and paste dispensing apparatus 54 presses paste into the grid elements. A second layer of paper 56 is applied, the paste is dried, the pasted strips separated and finally cut into separate plates. Headers 4 and lugs 6 are formed from the centre portion 42 at a convenient point in the apparatus. The grid may be formed with a bottom border 14 for strengthening during manufacture and as support means in the battery case. The paperbound, pasted grid finally enclosed in a conventional battery separator (32), Fig. 8 (not shown), e.g. of sintered P.V.C. The grid material in addition to pure lead may comprise conventional lead alloys, especially non-antimonial alloys and particularly lead-calcium alloys.