MXPA99001084A - Bat separator - Google Patents

Abstract

A battery separator for use in lead-acid batteries of the submerged cell type comprising a continuous back strap of porous material, resistant to acid, capable of embossing with a plurality of main ribs and sub-ribs extending through of the width of the rear continuous tape from at least one flat surface 1 C) of the rear continuous tape. The submini-ribs extend in a direction substantially parallel to the longitudinal axis of the subsequent web. The main ribs extend in a direction that is diagonal to the longitudinal axis of the subsequent web. Each main rib is a corrugated embossed structure comprising alternate ridges and notches. The separator is particularly useful in a lead acid battery of the submerged cell type having tubular plates

Description

"BATTERY SEPARATOR" BACKGROUND OF THE INVENTION This invention relates to a battery separator for use in lead acid batteries of the submerged cell type. In a submerged cell type lead acid battery, the positive and negative electrodes or "plates" are separated by a battery separator. The battery separator typically has "ribs" or protuberances extending from at least one flat face of the separator. These ribs are formed in one of several ways: the ribs can be formed integrally with the rear continuous tape of the separator; the ribs may subsequently be applied to the back web as a rim of a material equal to or different from the back web; or the ribs can be formed by embossing the subsequent web. The ribs function to provide proper spacing between the plates, and to provide a space where a free electrolyte remains. The battery separator that is currently used by most manufacturers of lead acid batteries of the submerged cell type is - of the microporous polyethylene type. This type of separator has a composition consisting essentially of an ultra-high molecular weight polyethylene, a filler or filler (typically amorphous silica), a plasticizer (typically a processing oil), and certain secondary ingredients such as an antioxidant, lubricant and carbon black. The material of the microporous polyethylene separator is commercially manufactured by passing the ingredients through a heated extrusion apparatus, passing the extruded material generated by the extrusion apparatus through a die and towards the clamping point formed by two calendering cylinders. heated to form a continuous belt, extracting a considerable amount of the processing oil from the continuous belt by the use of a solvent, drying the extracted continuous belt, cutting the strip into strips of predetermined width in strips, and winding the bands into rolls . These separators and a method of making the same are described in US Patent Number 3,351,495. The microporous polyethylene separators typically have a configuration comprising a subsequent continuous belt having a predetermined thickness, and - a plurality of parallel ribs spaced apart at a predetermined distance, and extending outward from a flat surface of the subsequent web. The ribs extend continuously in a longitudinal direction parallel to the edges of the spacer material. The thickness of the posterior continuous tape and the height and separation of the ribs is specified to the manufacturer of the separator by the battery manufacturer; The specifications are designed to maximize certain battery characteristics desired by the battery manufacturer. Lead-acid ignition lead-acid ("SLI") batteries used, for example in automobiles, tend to have separators that are thinner than "industrial" lead acid batteries used for standby power sources and traction devices. It is also known to form "mini-ribs" between these "main" ribs to add rigidity to the continuous ribbons of the separator having thinner back webs. In general, these mini-ribs have a lower height than the main ribs and are separated closer together. The height of these mini-ribs typically varies from approximately .152 millimeters and approximately. 223 mm. The separation of these mini-ribs varies between approximately 1.52 millimeters and approximately 6.35 millimeters. These ribs (both main and mini) are formed during the manufacture of the microporous polyethylene separator by providing the way for one of the two heated calendering cylinders forming the clamping point through which the extruded material is fed from the extrusion apparatus., is engraved with slots so that the ribs are formed as an integral part of the continuous strip of the separator. There are many different specifications required by battery manufacturers regarding the size of the rib and the separation of the rib. When manufacturing the separator material to meet the customer's requirements, almost every change in the size and spacing of the rib requires the separator manufacturer to paralyze its manufacturing line in order to remove the engraved cylinder that has been used to fill the previous order and insert a differently configured engraved roll capable of producing the size and spacing of the rib required for the new order to be filled. The manufacturing time is lost during this shutdown and extra scrap material is generated during the start-up of the line.

- - In addition, the ribs formed integrally in the polyethylene type separator undergo extraction together with the subsequent continuous tape and, because it has relatively more bulk than a portion of the subsequent continuous tape occupying the same flat surface area, generally the ribs retain more processing oil than the subsequent continuous belt, thus raising the total electrical resistance of the separator. In co-pending US Patent Application Serial No. 08 / 646,764, filed on May 8, 1996, a battery separator is disclosed having a longitudinal dimension, a width dimension perpendicular to the longitudinal dimension, upper and lower planar faces and a plurality of ribs (at least three) projecting from at least one planar face, the ribs extend in a direction substantially parallel to the longitudinal dimension (axis) of the spacer, each of which Ribs are formed of a plurality of individual projecting enhancements that form a corrugated structure consisting of alternate ridges and notches. The ribs may extend from one or both of the planar faces of the separator. When the ribs extend from both planar faces, the adjacent projecting enhancements (flanges) on a flat face are separated by an indentation (notch) that forms a projecting enhancement (flange) on the other flat face of the spacer. When the ribs extend from both flat sides of the separator, the ribs projecting from a flat surface may have a height equal to or different from the height of the ribs extending from the other flat surface. Even though the separator described in Patent Application Serial No. 08 / 646,764, works very well when the height of the rib does not exceed about .762 millimeter, it has been found that with rib heights in excess of about .762 millimeter, the compressive strength of the rib becomes less satisfactory. By the term "compressive strength" is meant the resistance to a compressive force applied to the upper portions of the ribs. In the co-owned Patent Application Serial No. 08 / 837,286, filed on April 11, 1997, an improvement is disclosed in the separator described in Patent Application Serial No. 08 / 646,764. The improved battery separator of Patent Application Number 08 / 837,286 employs a continuous base tape capable of embossing consisting of a rear continuous tape having a plurality of submini-ribs extending from at least one flat face of the same, with the continuous base tape being embossed with a plurality of main ribs, each main rib is essentially parallel to the longitudinal axis of the posterior continuous tape and extends towards at least one, and preferably two submini-ribs adjacent so as to form a separator having improved compressive strength. The continuous base tape capable of embossing having submini-ribs therein, is disclosed separately and US Patent Application Number 08 / 837,287 filed April 11, 1997 is claimed. The separator disclosed in Application Serial Number 08 / 646,764 and the improved spacer disclosed in the application Serial Number 08 / 837,286 has embossed (main) ribs that are placed essentially parallel to the longitudinal dimension (shaft) of the separator, and that were designed to be used in batteries that have flat plates. It has been found that when it comes to using these spacers to cover (wrap) the tubular plates, the spacer tended to fit down around the plate. In addition, the stratification of the acid (electrolyte) and the release of the gas were not satisfactory.

It is an object of this invention to provide a battery separator for use in a submerged cell lead acid battery having tubular plates, the separator having improved packing resistance, reduced or eliminated acid stratification and improved gas release.

COMPENDIUM OF THE INVENTION This invention relates to a battery separator having a longitudinal dimension, a width dimension perpendicular to the longitudinal dimension, flat top and bottom faces, a plurality of submini-ribs extending from at least one of the flat faces, and a plurality of main ribs extending diagonally across the width of the separator, the main ribs of individual projecting embossments being compressed forming a corrugated structure having alternative ridges and notches extending through at least some of the submini. -ribbing.

BRIEF DESCRIPTION OF THE DRAWINGS - Figure 1 is a partial top view of the upper planar surface of the spacer of this invention showing the relative location of one of the major ribs and submini-ribs omitted. Figure 2 is a cross-sectional enlarged partial side view of a main rib of the separator of this invention taken along line 2--2 of Figure 1. Figure 3 is a partial top perspective view of the Main planar surface of the separator of this invention, showing the relative location of both the main ribs and the submini-ribs. Figure 4 is an enlarged partial cross-sectional view of the separator of this invention, which is taken along the line 4-4 of Figure 3. Figure 5 is a partial top view of a main rib embossing in the submini-ribs. Figures 6 to 8 are partial top views of the individual main ribs illustrating different variations in the angle of the ridges and valleys of the main rib with respect to the longitudinal axis of the spacer.

DESCRIPTION OF THE PREFERRED MODALITIES - Figure 1 is a partial top view of a part of the separator 10 of this invention. Projecting from the upper flat surface 12 of the separator 10, there are a plurality of main ribs 14a to 14w. For reasons of clarity, only the main ribs 14a, 14b, 14u, 14v and 14w have been identified in Figure 1, the main ribs placed between 14v and 14u, 14c to 14t, respectively. Again, for reasons of clarity, only the main surfaces 14 have been illustrated, the submini-ribs omitted. The main ribs 14 are placed across the width of the spacer diagonally with respect to the longitudinal axis of the spacer 10. The longitudinal axis of the spacer 10 extends in the direction of the arrow and is parallel to the longitudinal edges 17 and 18 thereof. The material of the separator is manufactured in roll form with the longitudinal dimension being several thousand meters. The angle of the main ribs 14 with respect to the longitudinal axis of the spacer 10 may vary between about 6 degrees and about 45 degrees. In the preferred embodiment, the main ribs 14 do not extend completely to the edge of the spacer 10, as seen with reference to the principal ribs 14a, 14v and 14w in Figure 1. There remains a free margin of major ribs for this purpose. allow the overlap and seal of the edges of the separator, where it is formed in an envelope around a plate. In some applications, however, it may be desirable to extend the main ribs to the edges of the spacer. Also projecting from the main planar surface 12 of the separator 10, there is a larger plurality of "submini-ribs" 15, essentially essentially equally spaced apart, as can best be seen in Figure 3. For reasons of clarity, not all submini-ribs have been identified numerically in Figure 3. These ribs are called "sub-inners" because they are so-called "sub-ribs". shorter and are separated from each other more closely than the mini-ribs of the prior art. The submini-ribs 15 are positioned essentially parallel to the longitudinal axis of the spacer 10. As can be seen in Figures 2 and 4, the submini-ribs 16 extend from the lower planar surface 13 of the spacer 10. The submini-ribs 16 are of the same size and spacing as the submini-ribs 15; however, the submini-ribs 16 are preferably spaced apart so that they do not lie in the same plane as the submini-ribs 15.

- The main ribs 14 are formed by embossing the spacer ID to form a corrugated structure as will be more fully described below. Figure 2 is a partial cross-sectional side view of the separator 10, which is taken along the line 2-2 of Figure 1. The main rib 14a projects above the upper planar surface 12 of the rear continuous tape 20 and below the lower planar surface 13 thereof. The adjacent submini-ribs 15 and 16 show extending from the upper planar face 12 and the lower planar face 13, respectively, of the rear continuous tape 20. As will be further seen in Figure 2, the main rib 14a is a corrugated structure. which consists of alternate ridges and notches 22a and 23a, 22b and 23b, 22c and 23c, etc., extending respectively from the upper planar surface 12. Also, that part of the main rib 14a extending from the lower planar surface 13 is a corrugated structure consisting of ridges and notches 24a and 25a, 24b and 25b, 24c and 25c, etc. alternative, respectively. One flange on a flat surface forms the notch on the other flat surface, and vice versa. For example, the side - The lower flange 22a extending from the upper planar surface 12 forms the notch 25a of that portion of the main rib 14, which extends from the lower planar surface 13. As the main ribs 14 are being embossed towards the base sheet of the separator consisting of the rear continuous tape 20 and the submini-ribs 15 and 16, they are pressed towards the submini-ribs 15 and 16 at the intersections of the submini-ribs and the bands forming the main ribs 14. Those portions of the submini-ribs 15 and 16 thus incorporated into the main ribs 14, provide the same with increased compressive strength. The spacing and size of the main ribs 14 of the submini-ribs 15 and 16 is such that each "section" of a main rib 14 intersects diagonally at least one and preferably at least two or three submini-ribs. By a "section" of a main rib 14, it is meant that portion of a main rib between a flange and an adjacent notch and between the edges of the rib strip of the main rib extending between the flange and the rib. adjacent notch.

- - A side view illustrating the relationship between the main ribs 14 and the submini ribs 15 and 16, is illustrated in Figure 4 and a top view of this relationship is illustrated in Figure 5. In Figure 3, the various "sections" "of the main rib 14 are designated by the reference numerals 30a to 30e. Those portions of the submini-ribs 15 and 16 not incorporated in the main ribs 14, provide increased stiffness to the spacer to thereby allow thinner back webs to be used than would otherwise be possible. The ratio of the main ribs 14 and the submini-ribs 15 and 16 can be seen in cross-section by reference to Figure 4. The length dimension of the flanges 22 and 24 ie the length of the flanges 22 and 24 from a wall 26, lateral to the other side wall 28 of the main rib 14, is selected in accordance with the desired width of the rib. This dimension will generally be between approximately .508 millimeters and approximately 2.54 millimeters. The frequency of the ridges, i.e., the number of ridges per unit rib length or preferably will be between about 5 and about 25 rims per 2.54 centimeters The height of the rims 22 and 24 above the flat surfaces 12 and 13 of the subsequent continuous tape 20, is selected from the according to the height of the main ribs 14 which is specified by the battery manufacturer. This dimension will generally be between approximately .254 millimeters to approximately 2.54 millimeters. The submini-ribs 15 are particularly useful for providing improved compressive strength when the desired height of the main ribs 14 is greater than about 0.076 millimeter. The distance between adjacent main ribs 14 will generally be between about 6.35 millimeters to about 25.40 millimeters. The height of the submini-ribs above the upper planar surface of the spacer will generally be between about 0.7662 millimeters and about .2286 millimeters. The selection of an appropriate height for the submini-ribs 15 will depend on the height of the main ribs 14, and the desired compressive strength. The width of the submini-ribs will generally be between approximately .254 millimeters and approximately .508 millimeters.

The submini-ribs 15 will generally be equally spaced between approximately 6.35 millimeters and approximately 1.27 millimeters, across the width of the spacer. The width of the separator of this invention may be any width used by the battery manufacturers; generally this width will vary from approximately 5.08 centimeters to approximately 30.4 centimeters, with the lateral edges 16 and 18 remaining parallel with respect to each other. The thickness of the rear continuous tape 20 of the separator 10 will typically vary from about .0508 to .645 mm. For ease of illustration, the corrugated structure forming the rib of this invention illustrated in Figure 3 is shown as being triangular, with each individual raised projection being thus of wedge configuration. It is preferred, however, to round the wedge configuration enhancements, as seen in Figure 2. One of the advantages obtained by using the spacer of the present invention is that, since the ribs are a corrugated structure formed of ridges adjacent notches, and the main ribs are placed diagonally to the longitudinal axis of the separator, when wound around a tubular plate the separator provides an environment essentially free of barrier to the flow of electrolyte and any of the gases released during loading and unloading, since the ribs contact the plates only in the flange area. The use of submini-ribs to provide higher main rib height without loss of compressive strength also allows the separators to be manufactured with thinner back webs which means an economy in the amount of material required to manufacture a surface in specified square meters, of the separating product. Another advantage of the separator product with submini-ribs is that longer production operations can be carried out between tool changes compared to the main ribs being formed in the production line. Likewise, solvent extraction and drying of product with submini-ribs is easier and faster than a product having main ribs formed entirely therein during manufacture. Although the separator of the invention is illustrated as having main ribs 14 extending from both flat surfaces 12 and 13 of the backstop 20, the invention is intended to include a spacer wherein the main ribs extend from only one side flat When the main ribs 14 extend from both planar surfaces of the spacer 10, the height above the ribs 14 above the planar surfaces 12 and 13 respectively, the posterior continuous tape 20, may be the same or the height of the ribs in one side may be larger or smaller than the height of the ribs on the other side. The submini-ribs 15 and 16 have been described as extending from both planar surfaces of the spacer. In this configuration, the submini-ribs on the two flat surfaces can have the same or different heights. However, the spacer can be configured so that the submini-ribs extend from only one flat face. In addition, adjacent flanges of a main rib 14 can vary in height. The formation of the ribs of the present invention involves the plastic deformation of the material of the subsequent web in the place where the embossing is carried out. The plastic deformation indicates that the material had been loaded beyond its elastic limit which, by definition means that it had undergone plastic flow. It has been shown that the oxidation resistance is improved in the area of plastic deformation because the oil is driven towards the surface during the crushing of the micropores. Reference is made to co-pending applications Serial Numbers 08/646, 764 and 08 / 837,286 for the description of an apparatus suitable for __ embossing the relief the main ribs 14 in a sheet material for the separator, capable of embossing. The only change would be to place the embossing teeth of the apparatus in a pattern diagonal to the axis of the calender roll instead of perpendicular to it. All of the teachings of the copending patent applications mentioned above are incorporated herein by reference. Even though the invention has been described in relation to the formation of ribs in a microporous polyethylene separator, since this is the main type of separator material that is currently used by manufacturers of lead acid batteries of the type of submerged cell, after using any material for separator that is porous, resistant to acid and capable of being permanently embossed. These materials can generally be characterized as loaded or uncharged films and nonwoven webs of thermoplastic or thermosetting polymers. Suitable thermoplastic polymers include polymers and copolymers of ethylene, propylene, butylene, vinyl chloride and styrene. Suitable thermosetting compositions include phenolics, ethylene / propylene / diene polymers, isoprene, butadiene, styrene and similar thermosetting polymers. The ribs have been illustrated in the preferred embodiment disclosed herein as having ridges and notches that are aligned perpendicularly with the longitudinal edges of the bands forming the main ribs 14. However, the alignment of the ridges and notches may be in such a way as to form an angle with respect to the longitudinal edges of the bands. In particular, the alignment may be perpendicular to the longitudinal axis of the spacer, or perpendicular to a diagonal line that lies along the specular image of the angle between the diagonal line forming the axis of the main ribs 14, and the longitudinal axis of the rib. separator. Examples of these alternative configurations are illustrated in Figures 6 to 8.

In addition, the ridges and notches may have patterns that are disclosed in copending patent application Serial No. 08 / 646,764. The disclosure of this patent application is incorporated herein by reference.

Claims (20)

1. CLAIMS: 1. A battery separator comprising: a rear continuous strip of a porous material, resistant to acid, capable of being embossed, the continuous strip having posterior longitudinal edges essentially parallel, a longitudinal axis parallel to the lateral edges, a width dimension perpendicular to the longitudinal side edges, and top and bottom flat surfaces, the spacer has a plurality of submini-ribs projecting from at least one flat surface of the subsequent web, the submini-ribs extend essentially parallel to the longitudinal axis of the subsequent continuous tape; the spacer has a plurality of main ribs extending across the width of the continuous backing strip diagonally with respect to the longitudinal axis of the rear continuous web, each main rib being embossed in a plurality of sub-ribs, each of The main ribs consist of bands of a corrugated structure having substantially parallel lateral edges with alternative ridges and notches extending therebetween.
2. 2. The battery separator of claim 1, wherein the back web is made of microporous polyethylene. The battery separator of claim 1, wherein the main ribs are at an angle of between about 6 degrees and about 45 degrees with respect to the longitudinal axis of the subsequent web. The battery separator of claim 3, wherein the ridges and notches are essentially perpendicular to the lateral edges of the bands of the main rib. The battery separator of claim 3, wherein the ridges and notches are essentially prependicular to the longitudinal edges of the rear continuous belt. The battery separator of claim 3, wherein the ridges and notches are essentially perpendicular to a line that is at an angle with respect to the longitudinal axis of the posterior continuous strip that is the mirror image of the angle formed between the longitudinal axis of the rear continuous tape and the longitudinal axis of the bands of the main rib. 7. The battery separator of claim 1, wherein the frequency of the flanges is between - approximately 5 and approximately 25 by 2.54 centimeters. The battery separator of claim 1, wherein the ridges and notches of at least some of the main ribs are at a different angle with respect to the longitudinal dimension of the ribs of the main ribs than that of the ribs and ribs. notches of the immediately adjacent main ribs. 9. The battery separator of the claim 1, wherein the ridges and notches of at least some of the ribs are in a "V" shaped pattern. "10. The battery spacer of claim 1, wherein the ridges and notches of at least some of the ribs are in a tractor tread pattern 11. The battery separator of claim 1, wherein the ridges and notches of at least some of the ribs are in a continuous sinusoidal pattern. reivitication battery 1, wherein the submini-ribs are substantially equally spaced across the width of the spacer. 13. The battery separator of claim 12, wherein the submini-ribs are separated 2. by a distance between approximately 635 mm and approximately 1,270 mm. The battery separator of claim 1, wherein the width of the main ribs and the spacing of the submini-ribs are such as to cause essentially each section of the main ribs to be embossed towards at least two adjacent submini-ribs, the section of the main ribs being the space encompassed by an adjacent flange and notch and the adjacent lateral edges of the band forming the main rib. 15. The battery separator of claim 14, wherein essentially each section of the main ribs is embossed in three adjacent submini-ribs. 16. The battery separator of claim 1, wherein the submini-ribs have a height above the rear continuous tape of between about 0.7662 millimeter and about .2286 millimeter. 17. The battery separator of claim 1, wherein the submini-ribs have a height above the posterior continuous tape of between about 0.7662 millimeters to about 1524 millimeters. 18. The battery separator of claim 1, wherein the rear continuous belt has a thickness of between about .0508 millimeter and about .2032 millimeter. 19. The battery separator of claim 1, wherein the main ribs do not extend fully to the edges of the posterior continuous tape to thereby form a margin adjacent to both of the lateral edges of the posterior continuous tape that is exempt. of these main ribs. The battery separator of claim 1, wherein the submini-ribs extend from both flat sides of the subsequent web.