Device for casting electrode supports for lead-acid batteries

Abstract

A device for casting electrode carriers for the production of lead grid electrodes in a continuous casting process is provided, which includes a casting drum, the surface of which has been engraved with the shape of the lead strip to be cast, and a casting shoe which rests on the outer circumference of the casting drum in the region of the horizontal axis drawn through the axis of rotation when the casting drum rotates counterclockwise, whereat the exiting liquid lead flows into the concave mold of the casting drum surface and is removable as a solidified lead strip at the lower vertex of the casting drum after three quarters of a rotation and whereat draft angles of less than 7 degrees, in particular less than 3 degrees are provided.

Claims

1. A method for casting electrode carriers for production of lead grid electrodes in a continuous casting process, comprising: (a) providing a casting drum having a surface engraving, the engraving having a trapezoidal cross-sectional shape having a draft angle of 3 to 7 degrees; (b) supplying a liquid lead into the casting drum surface from a casting shoe positioned next to an outer circumference of the casting drum, wherein the liquid lead is supplied during rotation of the casting drum; (c) allowing the liquid lead to solidify into a lead grid strip on the casting drum, wherein the casting drum allows the liquid lead to solidify before less than one rotation of the casting drum from the position of the casting shoe; and (d) releasing the solidified lead grid strip only at a lower vertex of the casting drum after after about a three quarter turn of the casting drum, wherein the releasing of the solidified lead grid strip from the casting drum is caused by a means consisting of the force of gravity acting perpendicular on the solidified lead grid strip.

2. The method of claim 1, wherein the casting drum has a radius greater than 1 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the machine described in lateral view.

(2) FIG. 2 shows typical commercial machines for continuous casting of lead grids for lead-acid battery electrodes.

DETAILED DESCRIPTION

(3) It can thus be summarized significant advantages for the continuous casting process result from the absence of punching returns and thus, as described above, corrosion-promoting lead oxides, as well as the lower Ohm resistance achieved by thicker flags and the high casting speed, regardless of the alloy. In contrast, the draft angle of the grid bars is particularly disadvantageous.

(4) A solution to avoid the asymmetric grid of the continuous casting process was surprisingly found by employing some physical processes. The prior art engineering realization is based on the unwinding of gears and timing belts, which require draft angles, covered in textbooks.

(5) By changing the running direction of today's commercial systems in accordance with FIG. 1 and an increase in the drum radius, demolding can take place with a small draft angle of less than 7 degrees. It is advantageous to use drums with a radius that is greater than 1 m, preferably greater than 1.2 m, as a result of which demolding becomes easier. In the illustrated arrangement of the casting shoe at the lower vertex, only one force component acts on the lead grid belt in the direction of gravity, after approximately 270 degrees. Thus, any weight force components that are perpendicular to the gravitational force at the lower apex will be eliminated so that the grid would fall from the engraved mold by the action of gravity, if no adhesion forces remained from the lubricant, which must be applied to the casting drum to reduce the friction between the casting shoe and the casting drum. Thus, apart from the adhesion forces resulting from the separating agent, the grid falls from the drum at a very low draft angle of less than 5 degrees, usually 3 degrees, as a result of which the bars exhibit a nearly ideal rectangular cross-sectional area.

(6) To help overcome the low adhesion forces, hot compressed air can be blown into the gap between the drum and grid, or the cast lead grid band can be suctioned by means of a parallel-running vacuum belt. A knocking device or vibration device is also suitable for overcoming the adhesion forces. Furthermore, it is proposed to introduce a separating mold coating in the engraving of the casting drum. The openings of the vacuum band are adapted to the contour of the lead grid band, whereby an effective frictional connection takes place, which pulls the lead grid tape from the engraved grid shape.

(7) A grid with such a small draft angle can be considered a rectangularly symmetrical, analog punched grid. The grids produced in continuous casting in this manner are sufficiently symmetrical and do not tend to bend during normal operation in the battery, provided that the active mass is equally applied to the bottom and top of the grid.

(8) Continuous casting machines also avoid punched parts, which have to be cleaned from lead oxides in an alloying process. The cost of the additional alloying step is at least 10% of the price of the procured lead.

(9) If the alloying process is omitted, the corrosion resistance of the grids in the batteries is reduced.

(10) The device is particularly well-suited for the manufacture of lead-electrode grids with low alloy contents as well as for pure lead-tin alloys. These alloys are particularly suitable for AGM batteries as well as hybrid applications in the automotive field. Calcium or strontium alloys are used as alloy components for strengthening the grid. Both alloys result in increased corrosion. Antimony, which was used in the past, leads to high water consumption and cannot be used for maintenance-free batteries. Pure lead-tin alloys have proven to be particularly corrosion-resistant and have extremely low water consumption. Furthermore, the soft lead grid technology prevents force effects and damage to the separators, especially of glass fleece separators, such as those used in AGM batteries.

(11) Subsequent sandblasting can on one hand roughen the surface of the lead strip and on the other hand remove any remaining release agents. Thus the surface is increased by sandblasting, which leads to a better mass grid adhesion and consequently improved current dissipation.

(12) The system will be described in more detail below with reference to a schematic drawing.

(13) FIG. 1 shows a drum 1, the surface of which has been engraved with the shape of the lead strip 3 to be cast. A so-called casting shoe 2 rests on the outer circumference of the drum, in the area of the horizontal drawn through its axis of rotation. In the present case, the shoe 2 is arranged on the right side of the drum, which rotates counterclockwise. The liquid lead exiting the casting shoe 2 runs into the concave mold in the drum surface. After three quarters of a rotation, the solidified lead strip is removed with the vacuum belt 4. The vacuum belt helps to overcome adhesion forces where necessary present.