US3506495A - Primary dry cell - Google Patents

Description

April 1970 T. A. REILLY ETAL 3,506,495

PRIMARY DRY CELL Filed Jan. 15, 1968 HR 4 SH E,. REM W m Y M B United States Patent 3,506,495 PRIMARY DRY CELL Thomas A. Reilly, Bay Village, and William Bemer,

North Olmsted, Ohio, assignors to Union Carbide Corporation, a corporation of New York Filed Jan. 15, 1968, Ser. No. 697,958 Int. Cl. H01m' 21 06', 1/02 U.S. Cl. 136107 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to primary dry cells.

Primary dry cells are one of the most familiar articles of commerce and are widely used in flashlights, portable radios, photofiash and other devices. One common problem that has been encountered in the use of dry cells is that of leakage of liquid exudate during and after use of the cell. This problem is a particular vexing one since the liquid exudate is corrosive and can damage the device in which the dry cells are used.

Dry cell manufacturers have adopted a more or less common approach to the solution of this problem, that is, to encase the dry cell within a closed container comprising a non-corrodible jacket made from a fibrous cellulosic material usually in the form of a multiple-ply, spirally wound tube which surrounds the cupped electrode of the cell and which is locked in engagement at its peripheral edges with a metallic top and bottom closure. An advantage derived from the use of this noncorrodible jacket or tube is that it is highly absorbent to liquid and can be employed as a liquid reservoir to retain the exudate within the cell. One drawback, however, is that the jacket or tube may become so thoroughly soaked with liquid that it will lose its strength and ability to retain the liquid and thus permit leakage from the cell.

In our US. Pat. No. 3,278,339, issued on Oct. 11, 1966, there is disclosed and claimed a primary dry cell comprising the combination of an improved jacket composed of a multiple-ply, laminated tube of a fibrous cellulosic material having an innermost layer or ply of a high strength, liquid impermeable material, and a displaceable inner seal positioned within the upper edges of the cupped electrode just below the metallic top closure of the cell. This dry cell construction represents a somewhat modified approach to the problem of cell leakage in that the innermost layer or ply of the jacket or tube constitutes a liquid impermeable barrier which liquid can not penetrate as opposed to being used as a liquid reservoir for retaining exudate within the cell.

With this dry cell construction, provision is made for containing the liquid exudate and preventing its escape in the form of leakage from the cell by means of a displaceable inner seal which defines a free space within the upper end of the cupped electrode for the collection of liquid during discharge of the cell. Broadly, the displaceable inner seal consists of a top collar fitted around the central carbon electrode and a relatively thick, soft seal of asphalt or microcrystalline wax, for example, disposed on top of the top collar. The top collar is made from a liquid impermeable material and serves as a liquid barrier to prohibit the exudate from coming into contact and corroding the top closure. If liquid exudate formed on discharge should collect and fill the free space below the displaceable inner seal, the seal is then displaced upwardly allowing additional space for the exudate and also causmg the soft seal to tightly seal oif the uppermost end of the cupped electrode, thus aiding in prohibiting leakage from the cell.

Another advantage derived from the use of the displaceable inner seal is that containment of liquid exudate is effectively accomplished but without at the same time interfering with the proper venting of gases formed within the cell.

While the concept of a displaceable inner seal has worked well and proven successful in dry cells thus far provided, it nevertheless possesses the disadvantage in that the seal occupies a relatively large space within the cell proper which might otherwise accommodate a larger vol ume of liquid or even active ingredients to increase or substantially improve upon the capacity of the cell to deliver electrical current.

The present invention contemplates the provision in a primary dry cell of the type utilizing a noncorrodible acket which is impermeable to liquid of a novel and improved seal arrangement for containing liquid exudate formed on discharge of the cell, and has for its principle ob ect to provide such a novel and improved seal arrangement which occupies a minimum amount of space within the cell.

Another object of this invention is to provide such a novel and improved seal arrangement which is capable of venting gases formed within the cell.

Still another object of this invention is to provide such a novel and improved seal arrangement which is relatively easy and inexpensive to manufacture.

Other objects and advantages of this invention will become apparent from the following description, taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is an elevational view in section of a primary dry cell embodying the invention;

FIGURE 2 is an enlarged, fragmentary view of a portion of the jacket used in the dry cell of FIGURE 1.

In accordance with the invention, a primary dry cell comprising a cupped electrode of a consumable metal having therein a depolarizer mix, electrolyte and a central porous carbon electrode embedded within the depolarizer mix, is provided with a noncorrodible jacket WhlCh is impermeable to liquid and which has locked thereto the conventional metallic top and bottom closures for the cell. Positioned within the upper open end of the cupped electrode is an inner seal composed of a top collar made from a liquid impermeable material. The top collar is fitted tightly around the central carbon electrode and defines an upper and lower free space above the depolarizer mix. Just below the top closure and spaced above the top collar is a liquid and gas impermeable seal washer. The seal washer is fitted around the carbon electrode and has its outermost peripheral edges mounted over the upper edges of the cupped electrode. A peripheral bead seal is positioned around both sides of the upper edges of the cupped electrode just beneath the seal washer and an electrode seal underlies the innermost edges of the seal washer surrounding the carbon electrode. Mounted on top of the seal washer is an absorbent layer of bibulous material for soaking up and retaining any liquid which might possibly escape past the seal washer and thus prevent the liquid from coming into contact and corroding the top closure of the cell.

In the preferred form of the invention, the noncorrodible jacket for the cell comprises a multiple-ply, laminated tube composed of a first laminate of a high strength, liquid impermeable plastic and a thermoplastic material, and a second laminate of a thermoplastic material and one or more layers or plies of a fibrous cellulosic material, e.g., kraft paper. The first and second laminates are bound together by joining the thermoplas tic material of each laminate by autogenous action under heat. The high strength, liquid impermeable plastic for use in the tube is preferably poly(ethylene terephthalate), other suitable liquid impermeable plastics including the thermoplastic polyhydroxyethers such as poly (oxyphenyl-2,2-propylenephenoxy-Z-hydroxy 1,3 propylene) which is the condensation product of equimolar amounts of epichlorohydrin and bisphenol A. The thermoplastic material used in the laminated tube is preferably a flexible plastic having a softening point lower than that of the liquid impermeable plastic and preferably is polyethylene. Other suitable thermoplastic materials include polyvinylidene chloride, polyvinyl chloride, polypropylene, polystyrene and mixtures thereof. The fibrous cellulosic material, e.g., kraft paper, may be bonded to the thermoplastic material by a polyvinyl acetate water emulsion which is commonly used in adhering paper, but other suitable adhesives and glues may be used. The multiple-ply tube may be made by spiral winding the first and second laminate together in accordance with conventional methods and then heating to bond the thermoplastic layers of each laminate to form the composite tube.

Referring now to FIGURE 1 of the drawing, a primary dry cell embodying the invention may comprise a cupped electrode of a consumable metal (e.g., zinc) having therein a depolarizer mix 12, an immobilized electrolyte 14 and a porous carbon electrode 16 embedded within the depolarizer mix 12. Both the depolarizer mix 12 and the carbon electrode 16 may be suitably provided in the form of a conventional bobbin. Separating the bobbin from the bottom of the cupped electrode 10 is a conventional bottom insulator washer 18, suitably of cardboard or paper. Atop the washer 18 is a fibrous or paper cup 20 which fits around the bottom edges of the depolarizer mix 12.

Positioned within the upper open end of the cupped electrode 10 and so placed as to define a lower free space 22 above the depolarizer mix 12 and an upper free space 24 is an inner seal composed of a liquid impermeable top collar 26. The top collar 26 is fitted tightly within the upper end of the cupped electrode 10 and around the carbon electrode 16. The top collar 26 is permeable to gas but impermeable to liquid and serves as a liquid barrier, and may be made of paper or other fibrous material which is coated with a liquid-repellent material, for example, a plastic such as polyethylene. Spaced above the top collar 26 and within the upper free space 24 is a liquid and gas impermeable seal washer 28. The seal washer 28 fits tightly around the carbon electrode 16 and rests on the upper peripheral edges of the cupped electrode 10, which peripheral edges are turned slightly inwardly as indicated at 30, The seal washer 28 is impermeable to both liquid and gas and is electrically nonconductive and may be composed of a suitable plastic material such as polystyrene. Mounted on top of the seal washer 28 is a layer 32 of a highly absorbent or bibulous material such as conventional blotting paper, for example. The seal washer 28 and absorbent layer 32 may be formed from a laminated sheet of polystyrene having adhered to one side a layer of blotting paper or other suitable bibulous material.

The top closure of the cell may comprise a one-piece metal plate 34. As clearly shown in FIGURE 1, this top closure plate 34 is shaped to fit over the top edges of the carbon electrode 16 and has its outer peripheral edges locked in liquid-tight engagement with the noncorrodible jacket 36. Similarly, the bottom closure may comprise a metal plate 38 positioned beneath the cupped electrode 10 and having its outer peripheral edges locked in liquidtight engagement with the jacket 36. The bottom closure plate 38 may also be provided with a central indentation as at 40 which makes electrical contact with the bottom of the cupped electrode 10. In the construction of the dry cell shown in FIGURE 1, the top closure plate 34 is locked in liquid but not gas-tight engagement with the jacket 36.

As shown in FIGURE 1, the juncture between the top closure plate 34 and the jacket 36 is postioned over the top of the seal washer 28 and absorbent layer 32 and just above the peripheral edges of the cupped electrode 10. By this construction, the top closure plate 34 is electrically insulated from the cupped electrode 10 and the seal washer 28 is firmly held in place. It will be noted that the seal washer 28 is slightly larger in diameter than the upper end of the cupped electrode 10 and that its outer edges abut tightly against the interior side walls of the jacket 36. Underlying the seal washer 28 in the space left by the inwardly turned edges of the cupped electrode 10 is a peripheral bead seal 42 of wax, for example. This bead seal 42 extends around the periphery of the cupped electrode 10 and adheres to both the cupped electrode 10 and the jacket 36. It will be seen that any electrolyte or exudate which may escape from within the cupped electrode 10, due to perforation of its side walls during discharge, and which passes between the cupped electrode 10 and jacket 36 is barred by the bead seal 42 from contact with the top closure plate 34.

Underlying the seal washer 28 on the opposite interior side of the cupped electrode 10 is a bead seal 44 which extends around the inner peripheral edges of the cupped electrode 10. Similarly, an electrode bead seal 46 underlies the innermost edges of the seal washer 28 surrounding the carbon electrode 16. The combination of these bead seals 44, 46 underlying the seal washer 28 assures that the seal washer 28 effectively seals off the upper open end of the cupped electrode 10, preventing liquid from coming into contact with the top closure plate 34 of the cell.

FIGURE 2 shows in enlarged detail the multiple-ply, laminated tube structure of the jacket used in the dry cell of the invention. As shown, the jacket 36 comprises a first 0r innermost ply 48 of a high strength, liquid impermeable plastic material, e.g., poly(ethylene terephthalate), which is positioned adjacent to the outer side walls of the cupped electrode 10 and which serves as liquid impermeable barrier, and a second ply 50 of a thermoplastic material, e.g., polyethylene. Both the first and second plies 48, 50 of liquid impermeable and thermoplastic material constitute the first laminate in the multiple-ply, laminated tube. The second laminate of the tube comprises a ply 52 of thermoplastic material and three plies 54, 56 and 58 of a fibrous cellulosic material, such as kraft paper.

Having described the features of a primary dry cell embodying the invention, its mode of operation may now be explained. During discharge of the cell, both liquid and gas are formed as a by-product of the cell reaction. The gas normally follows a path from within the depolarizer mix 12 directly into the porous carbon electrode 16 or into the lower free space 22 above the depolarizer mix 12. The gas that passes into the free space 22 enters the carbon electrode 16 or portions of the gas may pass through or around the top collar 26 into the upper free space 24 below the seal washer 28 from whence it also enters the carbon electrode 16. Eventually all of the gas is vented from the cell through the carbon electrode 16 by way of the locked junction between the top closure plate 34 and jacket 36.

As indicated above, this locked juncture is made liquid but not gas-tight and is capable of venting gas from the cell. The venting path so provided is maintained continuously open and free from liquid blocking the passage of gas by the novel seal arrangement of the invention. The liquid exudate passes into the lower free space 22 where it collects together with gas that is generated in the cell. Under normal conditions, the liquid exudate will be substantially confined within the free space 22 by virtue of the liquid barrier formed by the liquid impermeable top collar 26, but should the cell be subjected to severe conditions of use more liquid exudate may be formed then can be held within the free space 22. The additional liquid exudate which is formed may cause the top collar 26 to become displaced upwardly so as to allow some of the liquid to pass into the upper free space 24. This liquid which passes into the upper free space 24 is barred from contact with the top closure plate 34 (or more importantly with the locked juncture between the top closure plate 34 and jacket 36 through which gas is vented) by the novel seal arrangement composed of the combined seal washer 28 and peripheral bead seals 44, 46 formed respectively around the upper peripheral edges of the cupped electrode and the carbon electrode 16. The seal washer 28 being both liquid and gas impermeable and being held firmly in place by the top closure plate 34 as described above constitutes a permanent or nondisplaceable liquid barrier which liquid cannot penetrate, while at the same time the bead seals 44, 46 effectively prohibit liquid from passing around the edges of the seal washer 28 even under the influence of gas pressure developed with the cell. It should also be mentioned that in order to prevent the liquid exudate which collects within the free space 22 from passing into the porous carbon electrode 16, thus blocking the passage of gas, the carbon electrode 16 is preferably made of a fine grain carbon and is suitably water-proofed in order to prevent liquid penetration. A suitable water-proof treatment may be achieved by impregnation with a solution containing a microcrystalline wax dissolved in a suitable solvent, such as ethylenedichloride. It will thus be seen that the novel seal arrangement of the invention effectively retains liquid exudate which might otherwise result in leakage from the cell but without at the same time taking up a large amount of space within the cell. The novel seal arrangement also provides a continuous venting path for venting gases so that no substantial gas pressure is allowed to build up within the cell.

In the event perforation of the cupped electrode 10 should occur due to normal consumption of the zinc during discharge, the liquid exudate that escapes from within the cell is prohibited from penetrating and becoming soaked into the jacket 36 by the innermost layer or ply 48 of liquid impermeable material, e.g., poly(ethylene terephthalate), which constitutes a liquid impermeable barrier. This liquid exudate will normally collect between the jacket 36 and the side walls of the cupped electrode 10. For the purpose of retaining this liquid but without causing the jacket 36 to bulge it is generally good practice to fit the jacket 36 loosely around the cupped electrode 10 in order to provide a free space or exudate chamber for the liquid as generally indicated at 60 in FIGURE 2. If the liquid exudate should collect within this space or chamber in any significant amount, the liquid may force its way towards the top closure, thus endangering the free passage of gas through the locked juncture between the top closure plate 34 and the jacket 36. It will be noted however that in the present dry cell construction the peripheral bead seal 42, which is positioned between the jacket 36 and upper edges of the cupped electrode 10, bars the liquid from reaching the top closure plate 34 or more importantly its locked juncture with the jacket 36.

An important advantage of the dry cell jacket is that leakage of liquid exudate through the locked juncture between the top closure 34 and the jacket 36 due to so called wicking effect is eliminated. In prior dry cell constructions where the jacket has been made of a fibrous cellulosic material, or even in those cells where a liquid impermeable barrier layer has been incorporated but as an intermediate ply in the jacket, the liquid exudate would normally become soaked into the first or innermost fibrous ply of the jacket and would eventually creep into or wick through the locked juncture, resulting in blockage of the venting path and even leakage from the cell. In the 6 construction of the present dry cell, the jacket 36 incorporates a liquid impermeable barrier in the first or innermost ply 48 which the liquid cannot penetrate and additionally this first or innermost ply 48 actually forms a seal between the jacket and the top closure plate 34 as shown in FIGURE 1.

Although the construction of the dry cell of the invention is quite different from conventional construction, an advantage is that its manufacture is simple. The active elements of the cell, the cupped electrode, carbon electrode, depolarizer mix and electrolyte, are all assembled in the conventional manner. It may be mentioned that while the electrolyte may be provided in the form of a paste, an electrolyte-wet bibulous paper separator may also be used.

While the invention has been described herein with particular reference to the preferred form of multiple-ply laminated tube as illustrated in FIGURE 2, it will be understood that the invention is not so limited but is applicable to the use of most any dry cell jacket which is impermeable to liquid. Thus the invention is intended to cover the use of many different types of multiple-ply tubes having an innermost layer or ply of a liquid im permeable material as well as a jacket or tube which is composed entirely of a liquid impermeable plastic material.

Dry cells embodying the invention have been subjected to tests ranging from normal usage to severe abuse. These tests demonstrated the effectiveness of the invention, for cells of a conventional construction and not having a jacket which is impermeable liquid and the novel seal arrangement described herein, showed evidence of leakage while the cells of the invention showed little or no leakage, and where the cells did leak under abusive use, the percentage of failure was comparatively far smaller in the case of the dry cells of the invention.

It will be apparent that various modifications of the dry cell described herein may be made without departing from the spirit and scope of the invention.

We claim:

1. A primary dry cell comprising, in combination:

(a) a cupped electrode of a consumable metal having an upper open end, the peripheral edges of which are turned slightly inwardly;

(b) a depolarizer mix and an electrolyte disposed within said cupped electrode;

(c) a central porous carbon electrode embedded within said depolarizer mix and extending at its upper end beyond the upper edges of said cupped electrode;

((1) a non-corrodible liquid impermeable jacket surrounding said cupped electrode;

(e) a metallic top closure fitted over the top of said carbon electrode, said top closure having its outer edges locked in liquid-tight engagement with said jacket and having gas venting means therein;

(f) an inner seal positioned within the open end of said cupped electrode and between said top closure and said depolarizer mix and extending from around said carbon electrode to the inner side walls of said cupped electrode, defining a lower free space between said seal and said depolarizer mix for the collection of liquid from said cell and an upper free space between said seal and said top closure;

(g) a non-displaceable liquid and gas impermeable seal washer tightly fitted around said carbon electrode and over the upper peripheral edges of said cupped electrode within said upper free space, the outer edges of said seal washer abutting against the interior wall of said jacket, said seal washer being held against displacement at the outer edges thereof by the outer edges of said top closure which are locked in engagement with said jacket;

(h) an outer peripheral bead seal disposed below and in contact with said seal washer in the space left by the inwardly turned upper edges of said cupped electrode and between said cupped electrode and the interior wall of said jacket;

(i) an inner peripheral bead seal disposed below and in contact with said seal washer on the opposite side of the upper peripheral edges of said cupped electrode and an electrode bead seal underlying and in contact with the innermost edges of said seal washer around said carbon electrode; and

(i) an absorbent layer of bibulous material disposed on top of said seal washer just below said top closure of said cell.

2. The primary dry cell defined by claim 1 in which said inner seal is composed of a top collar fitted tightly within the open end of said cupped electrode and around said carbon electrode, said top collar being composed of a liquid impermeable material.

3. The primary dry cell defined by claim 1 wherein said absorbent layer is composed of a bibulous blotting paper.

4. The primary dry cell defined by claim 1 in which said noncorrodible jacket is composed of a multiple-ply, laminate tube comprising a first laminate of a high strength, liquid impermeable plastic material and a thermoplastic material and a second laminate of a thermoplastic material and a fibrous cellulosic material, the thermoplastic material of said first laminate being united to the thermoplastic material of said second laminate.

5. In a primary dry cell including a cupped electrode of a consumable metal having an upper open end, a

depolarizer mix and an electrolyte disposed within said cupped electrode, a central porous carbon electrode embedded within said depolarizer mix and extending at its upper end beyond the upper edges of said cupped electrode, a liquid impermeable jacket surrounding said cupped electrode and a metallic top closure positioned over the upper open end of said cupped electrode having its outer edges locked in engagement with said jacket, the improvement in combination therewith comprising a non-displaceable liquid and gas impermeable seal washer tightly fitted around the upper end of said carbon electrode and having its outer edges positioned over the upper edges of said cupped electrode sealing off the upper open end of said cupped electrode, said seal washer being held against displacement at the outer edges thereof by the outer edges of said top closure which are locked in engagement with said jacket, an inner peripheral bead seal disposed below and in contact with said seal washer around the interior upper edges of said cupped electrode, an electrode bead seal underlying and in contact with the innermost edges of said seal washer around said carbon electrode, and an absorbent layer of bibulous material disposed on top of said seal washer just below said top closure.

6. The primary dry cell defined by claim 5 wherein said absorbent layer is composed of a bibulous blotting paper.

References Cited UNITED STATES PATENTS 2,243,938 6/ 1941 Anthony.

2,642,470 6/1953 Reinhardt et al 136-133 2,773,926 12/1956 Glover 136 -107 3,184,341 5/1965 Reilly 136107 3,214,298 10/1965 Urry l36107 3,255,049 6/1966 Wolfe 136107 3,278,339 10/1966 Reilly et al. 136-107 3,335,031 8/1967 Kordesch 136-107 3,338,750 8/1967 Urry l36l07 FOREIGN PATENTS 851,253 10/1960 Great Britain.

WINSTON A. DOUGLAS, Primary Examiner C. F. LeFEVOUR, Assistant Examiner US. Cl. X.R. 136133

Images