A DEVICE FOR THE PRODUCTION OF LEAD GRID ELECTRODES FOR LEAD ACID BATTERIES IN A CONTINUOUS CASTING PROCESS

Abstract

A device for casting electrode grids for producing lead acid batteries in a continuous casting process. The device includes a casting wheel and a casting shoe which rests on an outer circumference of the casting wheel. Liquid lead exiting the casting shoe flows into a concave mold of the casting wheel surface and is removable as a solidified lead strip. The casting shoe is made up of two or more zones, at least a first hot zone with a temperature above the melting point of lead and a second, thermally separated zone with a temperature below the melting point of lead. Cooling the lead strip from two sides (the wheel side and the shoe side) avoids columnar crystal formation and increases the casting speed to 40 meter per minute and above. Thermal isolation of the lead feeding tube avoids re-flowing of lead to a lead pot, reducing PbO formation.

Claims

1-5. (canceled)

6. A device for production of lead grid electrodes for lead acid batteries in a continuous casting process, comprising a casting wheel with an engraved lead grid structure, and a casting shoe which rests on an outer circumference of the casting wheel and is configured to feed lead towards the casting wheel, wherein the casting shoe comprises a two-zone or multi-zone configuration, wherein a first zone of the two-zone or multi-zone configuration is configured to be heated up above a melting point of lead in order to melt lead for filling the engraved grid structure of the casting wheel, wherein one or more thermally separated second zones of the two-zone or multi-zone configuration, following the first zone in a direction of rotation of the casting wheel, is configured to be kept below the melting point of lead to support solidification of the previously melted lead from a shoe side of the casting wheel, and wherein the first and second zones are thermally isolated from each other by an insulator plate of low thermal conductivity.

7. The device according to claim 6, wherein in the first zone of the casting shoe heated above the melting point of lead, in which in an area the lead is flowing through, a ceramic tube with an orifice is located.

8. The device according to claim 7, wherein in the first zone of the casting shoe heated above the melting point of lead, a separate electric heater is inserted in an area of the ceramic tube.

9. The device according to claim 6, wherein the casting shoe is configured such that there is no lead flow back through the first zone heated above the melting point of lead and afterwards back into a lead pot.

10. The device according to claim 6, wherein a material of the casting shoe is an invar alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will be more clearly understood from the following description of an embodiment thereof, given by way of an example only, with reference to the accompanying drawings, in which:

[0018] FIG. 1 shows the current design of a prior art one-zone casting shoe with heaters, casting tube, ribs, orifice and thermocouples, and

[0019] FIG. 2 shows the design of a two-zone casting shoe according to the invention, with heaters, cooling liquid drill holes, thermal isolation plate, ceramic tube with orifice, ribs and thermocouples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The prior art one-zone casting shoe according to FIG. 1 is provided with heaters 11, a casting tube 12, ribs 13, an orifice 14 and thermocouples 15 in a known fashion, as explained above.

[0021] The casting shoe 7 according to the invention, shown in FIG. 2, is a two-zone casting shoe regarding temperature, with at least a first zone Z1 heated up above the melting point of lead and at least a temperature-controlled second zone Z2 with a temperature below the melting point. Essential to the functioning of the casting shoe according to the invention is that the first and second zones Z1, Z2 are thermally isolated by an insulator plate 3 of low thermal conductivity. Only the lead supply contact area 8 of the casting shoe 7 towards the casting wheel 9 is not isolated, therefore reducing the heat flow due to the greatly reduced heat transfer area between casting wheel and casting shoe. Preferably, the first zone Z1 is heated up by electrical heaters 1. Heating by heated oil or inductive heating is also possible. The temperature of the second zone Z2 must be kept below the melting point of lead. Water or other liquids, circulating in cooling liquid drill holes 2, can be used to keep the temperature to the desired value. The second zone Z2 is preferably kept at the same temperature as the casting wheel 9 shown positioned on the left side of the casting shoe 7, to achieve a symmetric cooling of the lead from both sides. To control the set temperatures, sensors to measure the temperature are used, preferably thermocouples 6.

[0022] Longitudinal wires of ribs 5 on the surface of the first zone Z1 of the casting shoe 7, facing the casting wheel 9, avoid lead flowing against the rotation direction of the casting wheel, which is counter-clockwise in FIG. 2.

[0023] Another important part of the invention is the use of a ceramic tube 4 with an orifice 4A to feed the melted lead to the orifice of the casting shoe. The ceramic tube 4 has the advantage of greatly reducing or eliminating intermetallic compounds or dross, which can agglomerate and block the filling. Agglomeration of dross and intermetallic compounds is a huge problem in existing casting shoes with the current technology, which use metal pipes with front holes towards the orifice. In the current technology, most of the lead is flowing through the pipe and goes back to the lead pot and only a portion penetrates the orifice 4A and goes to the casting wheel 9 to solidify as the lead grid. Not only does the re-circulation of the lead waste energy, but also the flow of the lead introduces more chances for buildup of dross. With the ceramic tube 4 in the casting shoe according to the invention, the agglomeration of dross from the metal tube, as well as the buildup of dross from the reflow of lead, can be greatly reduced or eliminated. It is of advantage to bring an additional electric heater 4B into the ceramic tube 4 from the opposite side of the lead inlet side of the casting shoe. With the additional heater 4B, the lead is heated up to a temperature, which can be different from the hot areas in zone Z1 of the casting shoe. Zone Z1 will be kept above the melting point of lead but the ceramic tube 4 with an additional heater inside can be kept at a lower temperature than in the current design of casting shoes as depicted in FIG. 1.

[0024] The new casting shoe according to the invention can be used for clockwise as well as counter-clockwise running casting wheels. FIG. 2 shows the design for counter-clockwise operation of the casting wheel. In this case, the first, heated zone Z1 is on the lower side. For a clockwise running casting wheel, the first, heated zone Z1 would be located on the upper side of the casting shoe.

[0025] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

LIST OF REFERENCE NUMERALS

[0026]

TABLE-US-00001 Numeral Designation 1 electrical heaters 2 cooling liquid drill holes 3 thermal isolation plate 4 ceramic tube 4A orifice 4B heater 5 ribs 6 thermocouples 7 casting shoe 8 lead supply contact area 9 casting wheel 11 heaters 12 casting tube 13 ribs 14 orifice 15 thermocouples Z1 first zone of casting shoe Z2 second zone of casting shoe