Patent Application
20170084926
The present invention generally relates to lead acid batteries, and more specifically, a battery grid for use in a lead acid battery.
Lead acid batteries are used in many fields, such as industrial applications, motive power, telecomm batteries, and more. Battery grids for use in lead acid batteries are typically produced using a book molding procedure (i.e., gravity casting). In a book molding process, molten lead is gravity-fed into a grid-shaped mold and solidified. The lead battery grid is then released, and the process is repeated to form another grid.
Book molded battery grids are produced such that their outer borders are significantly thicker and wider than their inner current-carrying wires. This is necessary to promote proper flow patterns of lead within the mold and to allow each part of the grid to become full with lead prior to solidification. The thicker outer borders permit “over-pasting” or applying battery paste on the entire grid to the thickness of the outer borders, thereby completely covering the internal current-carrying wires. Over-pasting protects the current-carrying wires from corrosion over time and with use of the finished battery. Although book molded battery grids have these desirable features, they also suffer from several disadvantages. One operation of the book mold caster produces one battery grid. Book mold machines have many disadvantages, such as slow cycle time, low production rate per machine, requirement for skilled labor, environmentally hazardous mold cleaning and corking process, and a high labor requirement. Battery grids made by book molding have a porous and non-uniform micro-structure which promotes corrosion, can be subject to grid growth, and cause high water loss in a battery. These features shorten the battery life. In addition, alloy additions, grain refiners, or both are often required to promote proper grid quality.
An alternative to producing book molded battery grids is to punch battery grids out of lead or lead alloy strip. Strip can be produced by casting, extruding, or rolling. Strip produced by certain methods can have virtually no porosity and require no additional grain refiners or alloy additions, and have a higher corrosion resistance and resistance to growth. Battery grids punched from strip can be produced at a high speed with minimal labor requirement. In certain processes, the strip can be continuously produced on a high-speed caster and continuously punched for quick production of battery grids. Thus, grids punched from strip offer several advantages over book molded grids.
However, continuously punched strip is subject to certain limitations of the punching process. The entire grid must be punched flat, so the outer borders are the same thickness as the internal current-carrying wires. In addition, punched wire widths are limited to being at least 35% of the thickness of the grid. Thus, in order to match the overall mass of the book molded grid (for comparable battery performance), the thickness of the punched grid would have to be less than the thickness of the outer borders of the book molded grid, but greater than the thickness of the internal wires of the book molded grid. Because the borders are the same thickness as the internal current-carrying wires, the amount of over-paste that can be applied to completely cover the internal wires is minimal. In addition, the volume of paste that can be applied to the grid cannot match that of the book molded grid, which means that the battery would have less reserve capacity. This is because the minimum width of the internal wires is limited in a punched grid, so the volume of void space in which paste can be applied is less overall than in a book molded grid. Alternatively, the punched grid can be made thicker (thereby permitting smaller wire widths) to increase the volume of void space in which paste can be applied. However, the greater thickness requires more lead or lead alloy, resulting in a higher material cost.
Both the industry standard book molded grids and the continuously punched grids offer several advantages and have several drawbacks.
In one aspect, a battery grid includes a first grid member having opposite first and second side frame elements and opposite first and second end frame elements extending between the first and second side frame elements. A second grid member is attached to the first grid member. The second grid member has opposite first and second side frame elements and opposite first and second end frame elements extending between the first and second side frame elements.
In another aspect, a method of making a battery grid having a thickness includes making a first grid member and making a second grid member. The first and second grid members are superposed. The first and second grid members are attached together.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Referring to
Referring to
Longitudinal wires 40 extend along a length of the first grid member 22. Each longitudinal wire 40 is substantially parallel to the longitudinal axis LA1. The longitudinal wires 40 are positioned between the first and second side frame elements 30, 32 at spaced locations. Each longitudinal wire 40 extends between the first end frame element 34 and the second end frame element 36. The longitudinal wires 40 are substantially parallel to and spaced from the first side frame element 30, the second side frame element 32, and each other. In the illustrated embodiment, the longitudinal wires 40 are equally spaced between the first and second side frame elements 30, 32. The longitudinal wires 40 are symmetrically positioned on either side of the longitudinal axis LA1. The longitudinal wires 40 each have substantially equal widths. It will be understood that the longitudinal wires 40 may have unequal spacing (not shown), and/or not be symmetrically positioned on either side of the longitudinal axis LA1 (not shown), and/or not have substantially equal widths, or have varying widths along their lengths.
The first grid member 22 includes transverse wires 42 extending along a width of the grid member. Each transverse wire 42 is substantially parallel to the transverse axis TA1. The transverse wires 42 are positioned between the first and second end frame elements 34, 36 at spaced locations. Each transverse wire 42 extends between the first side frame element 30 and the second side frame element 32. The transverse wires 42 are substantially parallel to and spaced from the first end frame element 34, the second end frame element 36, and each other. In the illustrated embodiment, the transverse wires 42 are equally spaced from each other and have substantially equal widths. The transverse wires 42 are not symmetrically positioned on either side of the transverse axis TA1. As seen in
The external wires of the first grid member 22 (i.e., the first and second side frame elements 30, 32 and the first and second end frame elements 34, 36) have widths greater than the widths of the internal wires (i.e., the longitudinal wires 40 and the transverse wires 42). In other words, the wires defining the outer border of the first grid member 22 are wider than the wires within the outer border in order to conduct electricity and provide strength and rigidity to the first grid member. However, other configurations are within the scope of the present invention. For example, the external wires can have widths the same as or smaller than the widths of the internal wires. Alternatively, all of the wires of the first grid member can have substantially identical widths.
The first and second side frame elements 30, 32, the second end frame element 36, the longitudinal wires 40, and the transverse wires 42 define openings 44. The openings 44 are each generally the same size. The first end frame element 34, the first end transverse wire 42a, and the longitudinal wires 40 define openings 46. The openings 46 are smaller than the openings 44. Specifically, the openings 46 are smaller along a dimension extending parallel to the longitudinal axis LA1 than the openings 44. The openings 46 are smaller than the openings 44 because the first end transverse wire 42a is closer to the first end frame element 34 than the second end transverse wire 42b is to the second end frame element 36.
The first grid member 22 includes at least one lug portion. In the illustrated embodiment, a first lug portion 50 extends outward from the first end frame element 34. The first lug portion 50 is positioned adjacent the first side frame element 30. A second lug portion 52 extends outward from the second end frame element 36. The second lug portion 52 is positioned adjacent the first side frame element 30. The first and second lug portions 50, 52 are symmetrically arranged on either side of the transverse axis TA1. Other configurations (not shown) are within the scope of the present invention, such as a different number, configuration, or position of lug portions. For example and without limitation, the arrangement of the lug portions 50, 52 on the first grid member 22 may not be symmetrically arranged on either side of the transverse axis TA1. Moreover, the first grid member 22 could include only one lug portion. Still further, the first grid member 22 may have more than two lug portions 50, 52 and/or the lug portions may extend from a side frame element 30, 32.
The second grid member 24 will now be described, and is best seen in
Longitudinal wires 70 extend along a length of the second grid member 24. Each longitudinal wire 70 is substantially parallel to the longitudinal axis LA2. The longitudinal wires 70 are positioned between the first and second side frame elements 60, 62 at spaced locations. Each longitudinal wire 70 extends between the first end frame element 64 and the second end frame element 66. The longitudinal wires 70 are substantially parallel to and spaced from the first side frame element 60, the second side frame element 62, and each other. In the illustrated embodiment, the longitudinal wires 70 are equally spaced between the first and second side frame elements 60, 62. The longitudinal wires 70 are symmetrically positioned on either side of the longitudinal axis LA2. The longitudinal wires 70 each have substantially equal widths. Other configurations (not shown) are within the scope of the present invention. For example and without limitation, the longitudinal wires 70 may have different spacings between each other, and/or they may not be symmetrically positioned on either side of the longitudinal axis LA2, and/or not have substantially equal widths, or having varying widths along their lengths.
The second grid member 24 includes transverse wires 72 extending along a width of the grid member. Each transverse wire 72 is substantially parallel to the transverse axis TA2. The transverse wires 72 are positioned between the first and second end frame elements 64, 66 at spaced locations. Each transverse wire 72 extends between the first side frame element 60 and the second side frame element 62. The transverse wires 72 are substantially parallel to and spaced from the first end frame element 64, the second end frame element 66, and each other. In the illustrated embodiment, the transverse wires 72 are equally spaced from each other and have substantially equal widths. The transverse wires 72 are not symmetrically positioned on either side of the transverse axis TA2. As seen in
As seen in
The first and second side frame elements 60, 62, the second end frame element 66, the longitudinal wires 70, and the transverse wires 72 define openings 74. The openings 74 are each generally the same size. The first end frame element 64, the first end transverse wire 72a, and the longitudinal wires 70 define openings 76. The openings 76 are smaller than the openings 74. Specifically, the openings 76 are smaller along a dimension extending parallel to the longitudinal axis LA2 than the openings 74. The openings 76 are smaller than the openings 74 because the first end transverse wire 72a is closer to the first end frame element 64 than the second end transverse wire 72b is to the second end frame element 66.
Referring to
The first and second grid members 22, 24 can be formed in a continuous operation in which the configuration of the grid members, including specifically the wires 40, 42, 70, 72, is formed by punching. The grid members 22, 24 are then attached together to form the battery grid 20. The first and second grid members 22, 24 can be attached in any suitable manner, such as adhesive or welding. Preferably, the first and second grid members 22, 24 are attached by spot welding. The first and second grid members 22, 24 can include structure to facilitate attachment. As seen in
The grid 20 can be formed in a continuous process in which identical grid members 22, 24 are made. To form the final grid 20, one of the grid members 22, 24 is turned over 180° about its transverse axis before the grid members are attached to each other to form the battery grid 20. As illustrated, the second grid member 24 is flipped about the transverse axis TA2 prior to attachment to the first grid member 22. Because the projections 86 are symmetrically arranged about the transverse axes TA1, TA2, the projections remain in alignment for spot welding of the grid members 22, 24. For simplicity of illustration, the longitudinal axes LA1, LA2 and the transverse axes TA1, TA2 of the grid members 22, 24 are shown as being coincident in the assembled grid 20. The first and second grid members 22, 24 are attached to each other such that the first side frame element 30 of the first grid member is aligned with the first side frame element 60 of the second grid member. The second side frame element 32 of the first grid member 22 is aligned with the second side frame element 62 of the second grid member 24. The first end frame element 34 of the first grid member 22 is aligned with the second end frame element 66 of the second grid member 24. The second end frame element 36 of the first grid member 22 is aligned with the first end frame element 64 of the second grid member 24. The side frame elements 30, 32, 60, 62 and end frame elements 34, 36, 64, 66 form an outer border of the battery grid 20.
Referring still to
Referring to
In an alternative embodiment illustrated in
In an alternative embodiment illustrated in
The grid members 22, 24, 22′, 24′ can be formed from any suitable material and by any suitable method. Preferably, the grid members 22, 24, 22′, 24′ are punched grids. The grid members 22, 24, 22′, 24′ can be formed from any suitable material, such as lead, lead alloys, carbon, carbon alloys, zinc, zinc alloys, or zinc-silver alloys. Examples of suitable lead alloys include, but are not limited to: antimony-lead alloys; calcium-lead alloys; and lead alloys including optional alloying elements such as tin, silver, arsenic, copper, selenium, tellurium, cadmium, bismuth, magnesium, lithium, sulfur, barium, zinc, iridium, or phosphorous. For example, cast, extruded, or rolled lead or lead alloy strip material can be punched (e.g., with a punch press, rotary puncher, or other die punching equipment) to form the grid members 22, 24, 22′, 24′. For speed of operation, preferably lead or lead alloy strip is continuously formed and continuously punched to form the grid members 22, 24, 22′, 24′. Examples of methods and apparatuses for continuously casting or extruding lead and lead alloy strip are disclosed in U.S. Pat. No. 5,462,109; U.S. Pat. No. 6,797,403; and U.S. Pat. No. 8,701,745, the entirety of each of which is incorporated herein by reference. Examples of methods and apparatuses for ontinuously punching lead and lead alloy strip are disclosed in U.S. Pat. No. 7,066,066; U.S. Pat. No. 7,380,484; and U.S. Publication 2007/0193009, the entirety of each of which is incorporated herein by reference.
Preferably, each grid member 22, 24, 22′, 24′ has a thickness about half the thickness of the assembled battery grid 20, 20′, 20″. The width of the wires in a punched grid is limited by the thickness of the wires. In general, the width of a wire must be at least 35% of the thickness of the wire. Thus, by punching each grid member 22, 24, 22′, 24′ separately with a thickness about half the thickness of the battery grid 20, 20′, 20″, the width of the wires of each grid member can be significantly smaller than the width of the wires of a conventional punched battery grid formed as one piece. For example, in a conventional punched battery grid formed as one piece and having a thickness of about 0.180 inches (4.572 mm), the minimum width of a wire in that grid is at least about 35% of the thickness, or about 0.063 inches (1.6002 mm). In comparison, in a battery grid 20, 20′, 20″ formed from two grid members 22, 24, 22′, 24′ each having a thickness of 0.090 inches (2.286 mm) for a total battery grid thickness of 0.180 inches (4.572 mm), the minimum width of a wire in that grid is at least about 35% of the thickness of the grid members, or about 0.0315 inches (0.8001 mm). Therefore, in a battery grid having a thickness of about 0.180 inches (4.572 mm), the minimum width of the wires in the battery grid 20, 20′, 20″ formed from two grid members 22, 24, 22′, 24′ (about 0.0315 inches (0.8001 mm)) is about half the minimum width of the wires in a conventional punched battery grid (about 0.063 inches (1.6002 mm)). It is understood that other configurations are within the scope of the present invention, such as grid members having a thickness smaller than about half the thickness of the assembled battery grid, or one grid member having a thickness greater than about half the thickness of the assembled battery grid.
The battery grid 20, 20′, 20″ as described above offers several advantages over known battery grids. The battery grid 20, 20′, 20″ is punched from strip, which permits continuous production. Thus, the battery grid 20, 20′, 20″ can be produced at a high speed and continuously, thereby offering an advantage over book molded grids which have a slow cycle time and low production rate per machine. Book molded grids typically have high porosity, which increases the potential for corrosion and weight loss over time. In addition, alloy additions and grain refiners are often necessary to promote proper finished grid quality and attributes. Using strip to form the grid members 22, 24, 22′, 24′ can reduce the porosity of the grid members and reduce the need for grain refiners and alloy additions. In addition, the battery grid 20, 20′, 20″ overcomes the limitations of current continuously produced battery grids. Specifically, by forming two grid members and attaching them together, the width of each of the longitudinal and transverse wires 40, 40′ 70, 70′ 42, 42′, 72, 72′ can be thinner than the wires of a conventional punched battery grid. The battery grid 20, 20′, 20″ offers the advantages of a continuously punched grid, but overcomes the limitations of current continuously punched grids. In overcoming these limitations, the battery grid 20, 20′, 20″ can have the desirable features of a book molded battery grid. Thus, the battery grid 20, 20′, 20″ formed from two grid members 22, 24, 22′, 24′ attached to each other, offers both the advantages of a continuously punched grid and the performance capabilities of a book molded grid.
Table 1 below shows an illustrative comparison of battery grids having a thickness of 0.180 inches (4.572 mm). Table 1 includes comparative data showing a book molded grid having a thickness of 0.180 inches (4.572 mm), a punched grid having a thickness of 0.180 inches (4.572 mm), a battery grid 20′ as described above formed from two grid members each having a thickness of 0.090 inches (2.286 mm) for a total battery grid thickness of 0.180 inches (4.572 mm), a battery grid 20 as described above formed from two grid members each having a thickness of 0.090 inches (2.286 mm) for a total battery grid thickness of 0.180 inches (4.572 mm), and a battery grid 20″ as described above formed from two grid members each having a thickness of 0.090 inches (2.286 mm) for a total battery grid thickness of 0.180 inches (4.572 mm). As seen in Table 1, based on the limitations of continuously punching battery grids, a battery grid continuously formed as one piece has a total grid weight about 90.7% higher than the total grid weight of the book molded grid. Thus, the continuously formed battery grid requires more material than a book molded grid, which increases costs. The continuously formed battery grid also has about 16.7% less volume of paste as compared to the book molded grid. Less paste volume means the continuously produced grid has less reserve capacity than the book molded grid. Although the continuously punched grid can be made relatively quickly compared to the book molded grid, the trade-off is a higher material cost and a reduction in paste volume. In comparison, the battery grid 20 formed from two grid members has approximately the same weight of material as the book molded grid (about a 0.0% reduction or increase), and about the same paste volume as the book molded grid (about a 0.1% increase). The battery grid 20 thus offers the quick production of the continuously punched grid without sacrificing the performance capabilities of the industry standard book molded grid or increasing the material cost. Likewise, the battery grid 20′ formed from two grid members has approximately the same weight of material as the book molded grid (about a 0.0% reduction or increase), and about the same paste volume as the book molded grid (about a 0.1% increase). The battery grid 20′ thus offers the quick production of the continuously punched grid without increasing the material cost, although the wires may not be optimally spaced for paste locking. In addition, the battery grid 20″ formed from two grid members has about an 18.4% increase in total grid weight and about a 3.3% reduction in paste volume, a significant improvement as compared to the continuously punched grid. As seen in Table 1, the battery grid 20″ requires additional transverse wires to support the battery paste as compared to the battery grid 20 with offset transverse wires or the battery grid 20′ with larger paste openings. Thus, battery grid 20″ does not offer the same level of improvement as the battery grid 20, but still offers a significant improvement over current continuously punched grids. The battery grid 20″ thus offers the quick production of the continuously punched grid with fewer limitations.
The battery grids 20, 20′, 20″ as described above are suitable for use in a lead acid battery, such as the battery 100 shown in
In one exemplary method, a battery grid 20, 20′, 20″ is formed by attaching first and second grid members 22, 24, 22′, 24′ together. The grid members 22, 24, 22′, 24′ are attached to each other by spot welding or other suitable method.
In another exemplary method, a battery grid 20 is formed by attaching first and second grid members 22, 24 together. One of the first and second grid members 22, 24 is flipped or turned over about its transverse axis such that the transverse wires 42, 72 of the first and second grid members are offset from each other. The first and second grid members are attached to each other by spot welding or other suitable method.
In another exemplary method, first and second grid members 22, 24, 22′, 24′ are punched from strip. The strip can be continuously cast, or produced by any other suitable method. The first and second grid members 22, 24, 22′, 24′ are attached to each other to form a battery grid 20, 20′, 20″. Optionally, one of the first and second grid members 22, 24 is turned over 180° about its transverse axis TA1, TA2 such that the transverse wires 42, 72 are offset from each other. The battery grid 20, 20′, 20″ is then pasted.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
