US2262734A - Method of making dry cells - Google Patents

Description

Patented Nov. 1 1, 1941 UNIT-ED STATES PATENT I OFFICE I rmrnon or MAKING ar onus consin Application September 6, 1940, Serial No. 355,677

8 Claims.

This-invention relates to a dry cell and method of making the same, and more particularly to a method of preparing the dry cell core and assembling the cell.

The primary object of the invention is to provide a simple, inexpensive and emcient method of making and assembling dry cells. Another object of the invention is to provide for the treatment of dry-cell cores to prevent disintegration thereof in the process of assembling the units. Still another object is to provide a method of treating the drycell cores whereby the same may be readily and easily handled.

Another object is-to solidify arid bond together the entire mass of a dry cell core into an integral unit which is highly resistant to disintegration. Yet another object is to provide a solid unified core wherein the mass thereof is bonded together by the freezing of the moisture therein.

Other features and advantages will appear from the following specification and drawing, in which- Fig. 1 is a vertical sectional view of a dry-cell core: Fig. 2 is a similar view of a casing for a dry cell, the casing being provided with fluid electrolyte in the lower portionthereof; Fig. 3 is a vertical sectional view of a dry cell with the core in position in the casing; and Fig. 4 is a plan view of the assembled unit.

Heretofore in the making and assembling of dry cells, the handling of the core has been a difllcult problem. The core normally consists of a carbon pencil electrode with a granular depolarizing mixture distributed thereabout, the depolarizing mixture being compressed into a suitable shape. Since the depolarizing mixture is an electrical conductor, the disintegration thereof may readily cause a, short circuit to be formed in the cell. For example, when the core is inserted into the casing, any particles which break or fall from the core may lodge in the electrolyte paste and cause such a short circuit.

Various means have been developed for avoiding this difllculty. In some instances, the core has been wrapped in cheesecloth, muslin, or other suitable material. This operation is obviously expensive.

It has also been suggested that the core be inserted into the casing before the electrolytic paste is added. However, the pouring of the paste around the core after the same is in position is a difilcult operation, and, in addition, tends to wash particles of the core into the paste.

Another means which has been used in an effort to avoid the difilculty of handling the core is to place a lining in the zinc cup casing, the lining being made of paper and being saturated with the electrolytic paste. The depolarizing mixture is then placed in the lined casing and the carbon electrode inserted in the center thereof. This method, although it avoids the problem of disintegration of the core, does not provide an entirely satisfactory cell.

This invention includes broadly the subjecting of a moist core to a temperature substantially below 32 F. until it is frozen and substantially the entire mass thereof solidified. The frozen core may be readfly handled without danger of disintegration or breaking off of particles therefrom.

In the specific embodiment of my invention described herein, a core l0 includes an electrode l I and a depolarizing mixture l2 distributed about the electrode. The electrode H is preferably of the usual carbon composition.

The depolarizing mixture I! may be composed of any suitable mixture of the type ordinarily used for this purpose. The usual composition includes a mixture of graphite, manganese dioxide, sal ammonic (ammonium chloride), and a viscous solution of zinc chloride. The first three ingredientsas normally used in the dry cell are in granular form, while the zinc chloride is used in the form of a water solution, preferably of a specific gravity of 55 B. The term granular" will be understood to include powdered or even colloidal particles. In'any event, the mixture should contain a substantial quantity of moisture preferably between 5 and 35%.

In accordance with the usual practice in the art, the depolarizing mixture may be placed in a mold (not shown) and compressed by the exertion of pressure thereon. The carbon electrode is then inserted in the mixture to form a complete core.

After the core is formed, it may be subjected to a temperature substantially below 32% F- and maintained at this temperature until the mixture therein is frozen. Because of the presence of water-soluble salts in the depolarizing mixture, it

be placed in any of the well known mechanical refrigerators. Preferably the refrigerating apparatus is arranged to provide a temperature well below the freezing temperature in order to speed up the operation. Thus a temperature of 30 F. has been found to be very satisfactory in prac- 3 tice The temperature necessary to freeze the core will, of course, vary with the composition and moisture content of, the depolarizing mixture. 1 Since the soluble electrolytes or salts in the depolarizing mixture reduce the freezing point of the solution,- the temperature required for freezing will be lower as the, concentration of xthe solution increases.

Thus when only a small percentage of moisture is present, the freezing point will be relatively low.

Similarly, when the per- 1 'centage of soluble electrolytes in the composition 3 is increased, the freezing point will be further lowered.

Although water is normally used inthe de- When the core is cooled to freeze the same, the

'depolarizing mixture becomes a substantially entire solid mass. The frozen moisture in the core 3 serves to bond the particles thereof together. 3 Since the moisture is distributed substantially uniformly throughout the depolarizing mixture, the bonding action causes the core to be retained handled.

in its original shape as an integral mass which is highly resistant to disintegration.

The frozen cores may be readily and easily It is no longer necessary to take extreme precautions to prevent disintegration of the core. or the falling or breaking oil. of. particles 7 therefrom. Where processes heretofore used have required careful hand operations in assemi bling the cells, it is now possible to mechanize these operations.

1 core.

A casing or shell I3 is provided to receive the This casing should be of an electrically f conducting material such as a suitable metal, and 3 is preferably in the form of a cylinder provided 5 with a closed bottom ll.

Within the casing may be placed a suitable quantity of a fluid electrolyte IS. The composition of such electrolytes is well known in the art and need not be described herein. The electrolyte is preferably viscous in character and may be of the consistency of paste. The purpose of the fluid electrolyte is to provide an electrolytic medium between the conducting casing l3 and the core l0.

When the cell is to be assembled, the frozen core Ill lsinserted into the casing l3 and into the fluid electrolyte IS in the lower portion thereof.

' As the core is inserted into the electrolyte, the

electrolyte wells up around the sides of the core and-along the inner surface of the casing until (Fig. 3) the electrolyte forms a layer 16 around substantially the entire cylindrical sides of the depolarizing mixture of the core Ill. By freezing the core before inserting it into the casing, sub- 1 stantially all danger of having particles break oil? from the core and fall into the electrolyte is avoided.

In the making of dry cells for special'types of service. it is desirable to have a construction in which the core is as large as possible with respect to the size of the cell. A large core permits the use of a large amount of depolarizing material and produces a more eflicient cell. By freezing the core and eliminating the danger of distintegration thereof, it is now possible to use a larger core with the same casing. Thi is possible because the distance between the core and the casing need not be so great in order to permit ready assembly of the cell. The diameter of the core, therefore, may be only slightly less than the in. side diameter of the casing.

The freezing of the core also provides certain advantages in the handling of the assembled cell. The frozen depolarizing mixture clings more firmly. to the electrode inserted therein. Accordingly, operations on the assembled cell may be carried out without taking extreme precautions to prevent the displacement or loosening of the electrode within the depolarizing mixture.

be used having a much higher percentage of' moisture than has heretoforebeen considered practical.

The foregoing specific examples have been given for the purpose of illustrating the invention and the means of practicing it. Changes and modifications may, therefore, be made in the method and product as described, particularly with respect to the composition of the various portions of the battery and in connection 'with the conditions and order of the various steps of the method, without departing from the spirit and scope of my invention as set forth in the appended claims. a

I claim:

1. In a method ofmaking dry cells, the steps of providing a solidelectrode in contact with a moist depolarizing mixture in a predetermined shape, subjecting the mixture to a temperature below 32 F. to freeze the mixture in said shape, and placing the assembly in a dry cell unit.

2. In a method of making dry cells, the steps of providing a casing and a core, said core including an electrode packed in a moist, granular,

depolarizing mixture, subjecting said core to a temperature substantially below 32 F. to freeze the assembly, and inserting the frozen'core into said casing.

3. In' a method of making dry cells, the steps v same to a temperature substantially below 32 F.,

and picking up the core by means of the electrode and insertingit into said casing, said core being separated from said casing by said electrolytic material.

5. A method of making dry cells comprising providing a casing, a core with an electrode, and a fluid'electrolyte in said casing, subjecting said core with its electrode to a temperature substantially below 32 F. for a sufllcient period of time to freeze the same, and inserting the frozen core into the casing and into the fluid therein to cause said fluid to well up between the casing and the core.

6. A method of making dry cells comprising providing a cylindrical casing having a closed bottom, a core, and a fluid electrolyte in the lower portion of said casing, said core including a moist, granular, depolarizing mixture compressed in the form of a cylinder around an electrode, the diameter of the core being slightly less than that of the casing, cooling the core to freeze the same, and inserting the frozen core into the casing and into the fluid in the lower portion thereof to cause the fluid to flow upwardly between the core and the casing.

7.A method of making dry cell cores for assembly in batteries, comprising distributing a. moist depolarizing mixture around an electrode in a predetermined shape, ar/d freezing the same to form a solid integral core prior to its assembly in a dry cell.

8. A method of preparing dry cell cores for assembly in batteries, comprising compressing a moist depolarizing mixture around an electrode in a predetermined shape, and freezing the compressed product to solidify substantially the entire mass thereof in the form of a solid integral core prior to its assembly in a cell.

HOWARD B. HILEMAN.

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