US1956243A - Cell construction - Google Patents

Description

April 24, 1934. E, J, MCEAQHRON E1- AL 1,956,243

CELL CONSTRUCTION Filed NOV. 7, 1931 Patented Apr. 24, 1934 UNITED STATES PATENT OFFICE CELL CONSTRUCTION a corporation of Wisconsin Application November 7, 1931, Serial No. 573,550

5 Claims.

This invention relates to a new and improved construction for galvanicncells commonly used in assembling dry batteries, and more particularly to the type of cells known in the art as 5 dry Acells of the bag type. By the expression bag type is meant that type of cell having a central core composed of a carbon pencil and a mixture of depolarizing material, this core not being compressed directly into-a lined zinc can l as in the case of paper-lined cells, but being fabricated as a separate unit and afterwards.

put into operative relationship with the zinc can,

by means of an annular layer of gelatinous electrolyte positioned between the core and the l zinc can.

This. application is a Icontinuation in part, of applicants' copending applications 'Serial No. 395,516, filed September 27, 1929, by the applicants McEachron, Johnson, Jensen and Schroeder, and Serial No. 455,226, filed May 24, 1930,

by applicants McEachron and Schroeder.

The cores of this type of cell usually comprise a depolarizing mixture of manganese dioxide, carbonaceous material, ammonium chloride, zinc chloride, and water, prepared as a damp fairly cohering vmass which is given form by compression. However, the compressed cores are fragile, and are easily broken or deformed, by ordinary commercial methods of handling and disinte:

grate and flake off rapidly when placed into a liquid. These characteristics present numerous `problems but the use of cores is highly desirable from a commercial manufacturing stand-v point, and the general practice has therefore been to encase them in what is termed a bag, usually consisting of cheese cloth which serves to retain the shape of the core mass to prevent its disintegration and to prevent the aking off of particles when it is brought into contact with the ungelatinized electrolyte and during the time necessary to convert the electrolyte mixture from a milky uid to a relatively sti gelatinous consistency.

The maintenance of the physical form of the core and the prevention of disintegration after the core has been placed in the zinc cup, is essential to the production of a satisfactory commercial cell, as the'scaling off of any particles 0 of depolarizing material and the collection thereof adjacent the bottom of the cell between the core and the zinc cup, will cause short circuits in the cell or establish local action therein which I will entirely destroy the usefulness of the cell as a commercial product, or so materially shorten (Cl. 13G-123) its life, that it will fall below the standards now demanded for dry cells in use.

The bag or casing which has heretofore been employed in dry cells, presents certain limitations which cannot be avoided and which are based upon the following considerations:

In dry cells of the bag type, the core of depolarizing mixture is made as above described of less diameter than the zinc can and the space between the core and the can is occupied by an electrolyte mixture which is rendered nonilowable by the gelatinizing action of some suitable agent, such as starch, cereal or similar material. This is necessary in the type of cell referred to in order to eliminate the -presenceof a flowable' liquid which would leak out of the cell and cause the rapid disintegration ,of the core of depolarizing mixture in Contact with the ungelatinized electrolyte mixture.

The disintegrating action of liquid may be illustrated by placing a compressed core of the type used in the cells here referred to, in a container of water, Where it will be noted the core will rapidly'disintegrateand crumble to a powdered mass in the bottom of the container in less than sixty seconds. The necessity for the bag or casing is therefore apparent and as above mentioned, cheese cloth has been the only material which has been succesesfully used in commercial practice prior to this invention.

Cheese cloth has heretofore been considered necesary because of its absorption and porosity, whereby cheese cloth offers little or no resistance to the passage of the ungelatinized mixture and further its use largely avoids the formation of insulating pockets of air films between the core and the bag. The efficiency of a dry cell of this type depends upon the maintenance of its composing elements in proper intimate association whereby the electric functions may result Without hindrance, and also the avoidance of air films, bubbles, voids of any kind, evaporation of water, displacement of the core material or any other condition which will alterthe proper atrangement or association of the composing elements.

It is not only essential to establish this degree of perfection for a limited period of time but for increased life of cells and batteries, it is desirable to maintain this perfection to a high degree throughout substantially the entire'electrolytic life of the cell.

Whereas cheese cloth serves well as a casing for the depolarizing core, efforts have been made to find a cheaper substitute material, because the relatively high cost of cheese cloth adds materially to the expense of the cell and batteries, both as a raw material and in labor costs, due to the relatively slow and diflicult manipulation required to apply the cheese cloth casing to the core.

All efforts thus far, however, have failed to produce a satisfactory substitute with the result that allcommercial batteries of the bag type with wrapped cores manufactured at the present time, employ cheese cloth casings for the core notwithstanding the fact that it is extremely expensive, and that its installation is slow, tedious and costly. V

' Prior efforts to use paper as a substitute, have proven unsatisfactory, as it was found that the proper degree of porosity could not be obtained in a commercially satisfactory manner and further, that paper casings or bags formed in effect,

a barrier between the core and the gelatinized electrolyte which prevented the electrolyte from coming into proper intimate contact with the depolarizing mixture.

Various efforts have been made to eliminate this difficulty, but additional difficulties have been encountered. Heretofore, it has been found impracticable to commercially produce cells employing paper bags having an electric efficiency and life equal to cells employing1 cheese cloth. This was usually due to the existence of an air film between the bag casing and the depolarizing core, which is created either initially at the time the cell is assembled during manufacture or later, due to the entrapping of air, the evaporation of moisture from the space between the core and the bag, or, to other causes. This vdifculty will be better understood by the following description of the customary methods now employed for manufacturing cells of this type.

The prevailing manufacturing practice, is substantially as follows:

Zinc cans, carbon pencils and the depolarizing mix are first provided. Thereafter, by suitable machinery, a predetermined quantity,y of depolarizing mix is compressed around the carbon pencil to form the core of any desired siz'e and shape with one end of thecarbon pencil protruding a slight distance from the end of the core.

The compressing operation serves to mold the depolarizing mix so that it clings together around the imbedded carbon pencil and holds its shape by its natural coherence. Preferably before the cores are compressed, a metal cap is pressed by suitable mechanism, onto `the protruding end of the carbon pencil. Then insulating discs are placed in the bottom of the zinc cups. These are preferably made of relatively heavy waxed paper.

lAt this stage, the cores must be handled carefully, because as above mentioned, they are fragile and easily broken or deformed and will disintegrate and flake off rapidly when in contact with a liquid for a period of thirty seconds or more. It next becomes necessary to place the cores so made in the zinc cups, containing an amount of electrolyte sufficient to occupy the annular space between the core and the cup, it being understood that the core is of slightly less diameter than the cup. Thecups are usually placed in trays, a 'number in one tray,`and in each is placed the predeterminedl amount of the electrolyte lwhich is usually a solution of Zinc chloride and sal ammoniac. The electrolyte also includes a suitable gelatinizing agent, prefer ably starch, so that upon the application of suf.-

thus made are thereafter grouped together in cient heat, the liquid will be gelatinized in a relatively short period after the core has been placed in the cup, in contact with the liquid.

In order to avoid the liability of the core scaling off and particles thereof from coming in contact with the cup, such as might short circuit or otherwise damage the cell, as above described, a core wrapping is provided.

Inasmuch as cheese cloth is very expensive and involves a difficult and slow manipulation for` its application to the core, this invention is directed to a substitute core wrapping which will replace cheese cloth and yet give corresponding results in electrolytic action while permitting a much simpler and cheaperl operation for applying the wrappings to the cores in manufacture.

It is usual in commercial practice, to place small discs of insulating material in the bottom of the' cups and to thereafter introduce the electrolyte. Thereafter, cores are placed in the cups mounted in the trays and a frame having holes therein for receiving the protruding carbon pencils is placed over the cells to center the cores within the cups. Upon the introduction of the cores in the cups, the electrolyte is displaced and is caused to rise and fill the annular space between the core and the walls of the cups to the desired level.

Immediately after placing the cores in the cups, that is to say; within the period of a few seconds, the tray of cups is placed in a bath of hot water of sufficient temperature to gelatinize the starch material. This occurs almost at once, at least in a period of time, after the cores have been introduced, insufficient to permit any substantial deterioration of the cores by the liquid in contact with them. After the electrolyte is thoroughly gelatinized, the danger period has passed and the individual cells are then sealed at the top with a suitable sealing material. The seal is preferably brought to the top of the zinc cup and is designed. to leave the end of the carbon pencil, protruding slightly to enable a satisfactory electric connection to be made thereto. The cells suitable retaining cartons or the like, connected and made up into finished batteries.

The difficulty heretofore encountered in endeavoring to use cheaper substitute materials for cheesev cloth is attributable to the fact that no other material has been found which would enable the electrolyte to pass through the core wrapper in a manner required to completely expel, in the limited period of a few seconds, the air film which exists between the core and the wrapping and to expel all air bubbles which tend to cling to the wrapping itself before they become frozen in the gelatinized electrolyte.

Failure to eliminate the air in this manner results in a cell which is imperfect from the standpoint of electrical performance. In other instances, only a small quantity of electrolyte penetrates the wrapping which, after a period, evaporates leaving an undesirable air space as before.

More -specifically therefore, the present invention relates to a new and improved type ,of core wrapping of paper, which is cheap and is of such kind and is made of such form and shape in its application to the core, that it serves equally as 145 ywell as cheese cloth injthe performance of the cell v'and yet is --one whichy enables its application by Y 'mediately surrounding the core. i tom is'open, the electrolyte with the proper proeral important discoveries which are as follows:

First, that satisfactory cells having paper core wrappings may be provided when the core wrapping is omitted from the top of the core so that the upperedge of the wrapping terminates adjacent the upperedge of the core so asto leave an opening at the top of the space or crack between the core and the wrapping, and provided the paper employed is of such porosity and absorption as topermit the electrolyte solution to pass therethrough.` v It is preferable that the paper be of such fiber composition-.as-to show minute holes therethrough when held up to a strong light. It has been discovered that the elimination of the air film between the core and the wrapping is greatly assisted by leaving the top of the core uncovered in this manner.

Whereas, this feature makes for considerable improvement over all prior efforts to use paper wrappings, and standing alone, constitutes a part of this invention, the vcharacter of the cell may be further improved by adopting in addition to the open top, either one cr both of the additional improvements hereinafter described.

Secondly, it has been found that additional advantages are realized if the Wrapping does not extend completely over the bottom of the core, as with this arrangement, the electrolyte is free to enter the space between the core and the wrapping from the bottom and rise therein as the core is inserted downwardly'in the cup, so as to quickly and completely expel the air which escapes freely through the top opening.

Whereas, the top opening alone assists greatly in eliminating the air film, it is found that substantially all of th'e starch will be filtered out of the electrolyte as it passes through the paper wrapping so that the electrolyte which occupies the inner space will not be gelatinized and will therefore remain as a liquid for long periods with the liability of becoming vaporized in time, creating an air or other space, forming insulation im- Whenthe botportion of starch is permitted to freely pass into the space between the core and the wrapping whereby the electrolyte inside the Wrapping is gelatinized the same as on the outside.

In this form, the wrapping may terminate flush with the bottom edge of the core and the insulating disk will serve to prevent sh'ort circuits or local action by any particles or crumbs which may drop to the bottom in the space between the core and wrapping. However, as a precaution it 'is desirable to provide the Wrapping of a length greater than the height of the core so that the lower margin thereof may be folded a short distance at the lower edge of the core to under-lie the rim portion of the core base.

Wrappings of this type are foundgto provide sufficient opening and clearance for the `free passage of the starch and electrolyte into the space between the core and the wrappings.

Thirdly, in addition to the above discoveries, it has"been also found that if paper of the above described type is provided with a plurality of perforations therethrough of approximately, say

faf to -ll of Jan inch in diameter and from approximately 1/4 to 1/2 of an inch apart, extending in both directions, the free passage of the electrolyte and starch into the space between the core and the wrapping is materially assisted without in any way detracting from the effectiveness of the wrapper. Wrappers so provided are productive of cells which are in every respect, equal to the cells having cheese cloth wrappers, yet they may be produced at a great reduction in cost both as to material and in manufacture.

In order to more clearly illustrate this invention, reference will now be made to the accompanying drawing, in which- Figure 1 is an elevational view in cross section of a cell embodying one form of the present invention and Figure 2 is a perspective view vof the core and wrapper construction shown in Figure- 1;

Figure 3 is a view showing the wrapper before it is applied t'o the core.

Figure 4 is a perspective view of a modied form of core and wrapperconstructed in accordance with this invention and Figure 5 is asimilar view of another modified form of core and wrapper construction.

Figure 6 is a view similar to Figure l, showing a cell having a rectangular can and core, also embodying features of this invention and Figuresy 7 and 8 are perspective `views showing the rectangular core of Figure 6 and the manner of applying the core wrapper thereto.

By referring to the drawing, it will be noted that one form of thisinvention is illustrated as embodied in a cell shown in Figure 1, comprising a zinc cup 10, having an insulating disk 11 placed in the bottom thereof-with a suitable quantity of electrolyte 12, for surrounding the core. The construction of the core here used is clearly shown in Figures 1 and 2 and comprises the car,- bon pencil 13 having the metallic cap 14 on -the upper end thereof and the mass 15, of depolarizing mixture.

Surrounding the sides of the core, is a paper wrapper 16, which is formed of such length that the upper edgethereof may terminate substantially iiush with the upper edge of the core or slightly above, as shown in Figure 1 and the lower edge folded under the base of the core as at 17, shown in Figures l and 2. The wrapper preferably overlaps a short distance along its vertical edge and is held in place by a glued strip or sticker 18.

The wrapper is composed of a paper which is permeable enough to allow the electrolyte to pass therethrough in order to expel the lm of air disposed between theA wrapper and the core.`

This space is shown in Figure 1 and is designated film of air is suflicient to impair the electrolytic 1.

action of the cell unless `it is completely expelled during the cell forming operation.

The exaggerated showing in the drawing is given in order to more clearly illustrate the problems herein `referred to and the nature of the present invention in solving same.

An important feature of this construction is that the top of the core is left uncovered so that the space 20 is vented at the top whereby the electrolyte in passing into this space can displace the air upwardly and thereby efficiently eliminate the undesirable air lm referred to. 'An additional feature of this constructionis thetype of paper employed. There are several kindsof paper which may be used, preferably a vegetable fiber, but it must possess the characteristics of being porous and penneable. Examples of satisfactory paper are, paper towelllng, battery board, including sulphate pulp and ground wood, and even-cheap, sized writing paper Gli not suitable for writing in ink. One of the best -examples of satisfactory paper for the present wrapper consists of 100 per cent pulp containing no filler or sizing which has not been calendered and is preferably creped. As above mentioned, the fiber construchon of this paper should be such that minute openings may be detected in the pores thereof when placed in front of a strong light.

v Additional features of the construction of this invention are the holes 21, provided in the wrapper in such size and number that the electrolyte with its gelatinizing starch can freely pass into the space 20. The openings are preferably between one thirty-second and one sixteenth of an inch in diameter and may be placed between one quarter and one half of an inch apart in both directions.

Further, the bottom of the core is left substantially uncovered so that the electrolyte with the gelatinizing starch is free to enter the space 20 from the bottom as the core is inserted into the cup. The overlap 17, at the bottom, has substantially no retarding effect upon the passage of the liquid and starch into the space and yet it serves as a very satisfactory protection in conjunction With the insulating disk 1l, of waxed or greased paper to prevent any-possibility of short clrcuiting or local action by particles which may fall from the sides of the core downwardly in the space 20. After the core is lplaced in the cup an insulating disk 22 having a central opening'23is positioned around the pencil and in engagement with the cup in the manner shown in Figure l whereby it acts as a centering device for the core as Well as a support for the sealing material 24, placed on the top thereof. The seal 24, may be of wax or a similar material now commercially used in this art and is so applied that the metallic cap on the upper end of the carbon pencil is left exposed to an extent sufiicient to make a satisfactory electrical connection thereto.

As an alternative crm of the present invention, the core may be made as shown in Figure 5, in which case the wrapper terminates ilush with the lower edge of the core and is not provided with the under-lying fold 1'7, as shown in Figure l. Furthermore, the paper maybe made without the perforations 21 in the sides thereofleaving only the bottom and top openings together with the pores in the paper for .effecting the displacement of the air film. The form with the holes omitted is not as desirable as that shown in Figure 1, but notwithstanding, it constitutes a decided improvement over the prior art which renders it possible to use paper wrappings instead of cheese cloth.

Accordingly, this invention should be con strued sufficiently broad to cover this type of cell. In any of the forms, here illustrated, the manner of securing the wrapper may be varied according to particular circumstances, whereby if it is desired, a rubber band 25, shownT in Figure 4, may be used, instead of the paper sticker 18, shown in Figure 2.

In practice, the rubber band is found to exert suicient constricting force upon the wrapper to hold it tightly in place and yet have substantially no retarding eiect on the displacement of air in the space 20.

A further form of the invention is shown in Figures 6 to 8 inclusive, in which a rectangular core is provided, and in connection with which, is also illustrated that embodiment of thepresent invention wherein the wrapper is folded over the lower edge of the core to cover the entire bottom thereof.

As Figure 6 is the same in all essential principles as the showing in Figure 1, corresponding parts thereof will be designated by like reference numerals where this is practical.

The core shown in Figures 7 and 8 will be made in substantially the same way as the cylindrical core except that the core forming press will be suitably modified. The wrapper here shown in addition to being folded over the bottom of the core may be made with or without perforations in the sides thereof as shown in Figures 1 and 2.

Furthermore, the wrapper may be held in place by the rubber band 25, as shown, or if desired, by means of a sticker, as shown at 18, in Figure 2.

In commercial manufacture it is desirable in certain instances, to provide cores of rectangular shape. In such cases, improved results are realized by wrapping the core at the bottom in the manner shown in Figures '7 and 8. The wrappers may be either without perforations as shown in said figures, or preferably with perforations as shown in Figure 3. As a manufacturing proposition, it is less difcult to provide the folded bottom as shown in Figure 8, with rectangular cores than it is to provide the tucked-under bottom of thetype shown on the round core in Figure 2. With the type of porous paper above specified, and the open top, this form of wrapping is found to serve well.

It should be understood that any combination of the features herein described as important are contemplated for this invention and that in certain instances,l all or various combinations thereof may be embodied in a cell of commercial construction or on the other hand, certain ones alone may be utilized according to the dictates of manufacture and the type of cell desired.

We claim:

1. An electrical cell of the bag type, comprising a zinc cup, a wrapped core of compressed depolarizing mixture and an embedded carbon pencil, in said cup with a space, between said wrapped core and the sides of said cup, a gelatinized electrolyte in said space, and an insulating material between the bottom of said core and cup, the wrapper for said core being of porous, absorbent paper covering the sides of said core while leaving the top thereof uncovered whereby to provide a free and unobstructed vent at the top of said core for the escape of air ordinarily confined between said core and wrapper.

2. An electrical cell of the lbag type, comprising a zinc cup, a wrapped core of compressed depolarized mixture and an embedded carbon pencil, in said cup with a space between said wrapped core and the sides of said cup, a gelatinized electrolyte in said space, and an insulating material between the bottom of said core and cup, the wrapper for said core being of porous, absorbent paper covering the sides of said core while leaving the top thereof uncovered whereby to provide a free and unobstructed vent at the top of said core for the escape of air ordinarily confined between said core and Wrapper, said wrapper having a pluralityv of minute holes therethrough, distributed over its area to overlie at least a portion of the sides of said core, said holes being of such size as to permit the free passage of gelatinizable electrolyte while confining any free particles which may become loosened from said core.

3. An electrical cell of the bag type, comprising a zinc cup, a Wrapped core of compressed depolarizing mixture and an embedded carbon pencil, lin` said cup with a space between said wrapped core and the sides of said cup, a gelatinized electrolyte in said space, and an insulating material between the bottom of said core and cup, the wrapper for said core being of porous, absorbent papercovering the sides and marginal area of the bottom of said' core while leaving the top and the central bottom portions thereof uncovered whereby to provide a free and unobstructed vent at the top of said core and a free passage for gelatinizable electrolyte at the bottom of said core, for the ready displacement and escape of air ordinarily Aconfined between said core and wrapper.

4. An electrical cell of the bag type, comprising a zinc cup, a wrapped core of compressed depolarizing mixture andan embedded carbon pencil, in said cup with a space between said wrapped core and the sides of said cup, a gelatinized electrolyte in said space, and an insulating material between the bottom of said core and cup, the wrapper for said core being of porous, absorbent paper covering the sides and marginal area of the bottom of said core while leaving the top and the central bottom portions thereof uncovered, whereby to provide a free and unobH structed vent at'the top of said core and a free,

passage iorgelatinizable electrolyte at the bottom of said core, for the ready displacement and escape of air ordinarily conned between said core and wrapper, said wrapper having a plurality ofv minute holes therethrough, distributed over its area to overlie at least a portion of the sides oi.' said core, said holes being of such size as to permit the free passage of gelatinizable electrolyte while coniining any free particles which may become loosened from said core.

5. An electrical cell of the bag type, comprising a zinc cup, a wrapped core of compressed depolarizing mixture and an embedded carbon pencil, in said cup with a space between said wrapped core and the sides of said cup, a gelatinized electrolyte in said space, and an insulating material between the bottom of said core and cup, the wrapper for said core being of porous, absorbent paper covering the sides of said core while leaving the top thereof uncovered whereby to provide a free and unobstructed vent at the top of said core for the escape of air ordinarily confined between said core and wrapper, said wrapper extending vertically upwardly along the sides of said core with its upper edge disposed slightly above the upper edge of saidcore.

EDGAR J. MCEAC'HRON. REGINALD S. JOHNSON. HAROLD G. JENSEN. O'I'IO E. RUHOFF. GEORGE SCHROEDER. OTTO J, KRUEGER.

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