US2279575A - Dry cell - Google Patents

Description

Apri1`14,1942. H. E. LAW'SQN 2,219,515

DRY CELL.

Filed Dec. 13, 1939 @deze for.'

Patented Apr. 14,1942

UNITED STATES] PATENT ori-lcs Herbert E. Lawson, Chicago, Ill.,

Burgess Battery Company, Chicago, poration of Delaware assitnor to Ill., a cor- Appneauon December 13, 1939, serial No. 308,923

(ci. 13s- 154) 6 Claims.

This invention relates to dry cells, and particularly to improvements in the construction whereby deterioration of such cells during periods of storage and inactivity is reduced.

It is the object of the invention to provide an improved dry cell which has favorable "shelf life and intermittent drain properties.

Briefly, the improvement is obtained by associating a wood balsam with thezlnc anode of the cell in such way as to be eiective at the surface thereof which is exposed to the electrolyte. In accordance with the invention, it has been discovered that the wood balsams,'as a class of ma.-

y storage, in the plant or on the dealers shelf, for -y between the time they are Cil a considerable period manufactured and the time they are placed in use by the consumer. After they are placed in use, they may be discharged rapidly, or they mayV be discharged slowly and only intermittently, with relatively long periods of inactivity intervening between periods of use. It is highly important, therefore, that a dry cell does not deteriorate and lose its capacity to deliver 'electric energy during such inactivity. Unless steps are taken to resist such deterioration, it takesplaceat an Iappreciterials, possess the property of inhibiting the corrosion of the zinc anode, which, due to local action or other causes, occurs during periods of inactivity.

The invention will be described `in connection with the common cylindrical type of dry cell. It is not limited to this type of cell, however, and may be used with any dry cell in which a zinc anode is-employed in such manner as to have a surface thereof exposed to an electrolyte. The dry cell which is illustrated in the drawing comprises an open-top cylindrical zinc can i@ which is the negative electrode. Upon the bottom of the can is disposed a layer of electrical insulating material Il, which may be a heatfusible pitch or wax composition, a resin, or a treated fibrous material such as paper board or pulp board,

which is resistant to the electrolyte of the cell.

A carbon, rod positive electrode l2 is disposed substantially centrally of the zinc can lo and has a metal cap I3 upon its upper end. The carbon rod is electrically insulated and positively separated from the bottom of the can Ill by the insulating layer ll.- The carbon rod is surrounded by a moist, compacted mass of depolarizing material i4 which may be composed of powdered manganese dioxide ore, carbon or graphite, ammonium chloride, zinc chloride, and other wellknown ingredients. Between the depolarizing body l and zinc can l0 is a substantially solid, electrolyte-containing layer l5 which may be composed of the usual electrolyte substances, such as water, starch, usually in gelatnlzed form, ammonium chloride, zinc chloride, etc. The electrolyte is in the form of an aqueous solution when initially inserted in the can Id. A top washer i6 is arranged in spaced relation above the depolarizing body I4 to form an expansion'spce I1, and

able rate, and the dry cell industry has from the beginning striven to overcome this difficulty. This invention provides an improvedmeans for accomplishing the purpose.

In accordance with this invention, it has been discovered that wood balsams have the property ,to a remarkable degree of inhibiting corrosion of the zinc electrode during inactivity of the cell, both before and after the cell is initially placed in use. They do not, however, interfere with the delivery of energy while the cell is in operation. It is a primary feature of the invention to llncorporate a material of this character in the electrolyte layer l5 contiguous to the dry cell can' Ill. The wood balsams which are available upon the market may be used for the purpose. A large number of balsams-have been used with success, among them being the following: balsam copaiba, Oregon fir balsam, gumbo limbo balsam,

` balsam Peru, balsam Mecca, Canada balsam,

a. heat-fusible seal I8, of wax or pitch, rests upon Cil Cuban pine balsam, citrus guinosa balsam, resinoid Sandalwood and resinoid patchouli. Other wood balsams may be used, and it is understood that the invention is not limited to those specifically mentioned.

The balsams are in the form of solids or liquids, and may be incorporated in the dry cell in V several different ways. The simplest method is to deposit a small quantity of the material upon the top of the depolarizing body I4 or electrolyte paste l5. A portion of it becomes absorbed by the depolarizing body or electrolyte paste and spreads to the surface of the zinc can l0.. It becomes distributed vuniformly and protects the entire area of the zinc whichl is exposed to the electrolyte.

The balsam may also be incorporated in `the form of a suspension or dispersion thereof in the electrolyte. It may be added to the electrolyte liquid with agitation before the electrolyte is inserted in the can l0. It is adsorbed by the starch present in the electrolyte, and this promotes its uniform distribution. To'im'prove the thorough dispersion of the balsam, an emulsifying agent. such as an organic amine may be added. Triethanolamine is an example. 'A small vquantity of ammonia added-to the liquid also serves the purpose. c

Satisfactory results are also obtained by rinsing the interior surface of the zinc can with a dilute solution or emulsion of the balsam, or

by dipping the can momentarily into such a so-` lution or emulsion, before the other elements of the cell are inserted in the can.

In a. well known type of dry cell, the electrolyte layer I5 is in the form of a lining'of paper pulp sheet material which is inserted in the can I 0 and is saturated with electrolyte. The balsam may be applied to the paper pulp -sheet before it is insertedin the can, or it may be incorporated in the liquid electrolyte before the latter is inserted in the can.

'Ihe amount of balsam which should be used' `is not critical.

A relatively small lamount is all that is required. 'I'his depends upon the specific balsam used. In a dry cell adapted for heavy duty, such as meter readers service, employing a zinc can 21A inches high and 1% inches in diameter, approximately 0.16 gram oforegon r balsam has been used inthe electrolyte paste4 of each cell with satisfactory results.l However, more than this may be used and, in general, more is used in cells intended for light,.intermittent service than in those intended for heavy duty. So much balsam should not be used aswill cause the internal resistance of the cell to be exces- The reason for the remarkable beneficial results produced by the use of a Wood balsam is not fully understood. c 'Ihe balsams are partially soluble in water, and it may be thatvthe beneficial results are producedfbi? $01112 chemically active agent'which goes into solution inl the liquid of the electrolyte. It may be that they are produced by the formation of a mechanical layer or film of the balsam upon the surface of the zinc. It is`believed that the active agent, whatever it is, is physically present at the surface of the zinc and exerts its influence there. This presence may be due to migration Vfrom differcnt localities within the cell, as where the balsam is incorporated in the electrolyte; or to actual application to the zinc surface, as where lthe can is rinsed with' an emulsion or solution of the balsam. The distribution of the substance over the active surface of the zinc is thorough even when a small amount of the .natural balsam is placed directly upon the top of the depolarizing body or electrolyte paste, because in such case the entire active surface of the zinc is protected effectively against deterioration and Icorrosion. Therefore, the invention contemplates the application of the balsam to the interior of the cell in any manner whereby it has an opportunity tobecome accessible to the zinc and is eni abled to exert its beneficial effect.

sam, citrus gumosa balsam, reslnoid SandalwoodA and resinoid patchouli.

3. In a dry cell having a zinc anode, and a y non-alkaline chloride electrolyte adjacent said anode; a suspension of wood balsam at the surface of said anode exposed to said electrolyte.

4. In a dry cell having a zinc anode, and a non-alkaline chloride electrolyte adjacent said anode; a suspension of wood 'balsam at the surface of said` anode exposed to said electrolyte, said wood balsam being Ifrom the group consisting of balsamcopaiba, Oregon rbalsam, gumbo limbo balsam, balsam Peru, balsam Mecca, Canada balsam, Cuban pine balsam, citrus gumosa balsam,` resinoid Sandalwood and resinoid patchculi.

5. A non-alkaline chloride electrolyte for a dry cell containing a Wood balsam in suspension therein.

6. The method for decreasing the corrosion during inactivity of the zinc electrode of a dry cell having a non-alkaline chloride electrolyte, which comprises applying asuspensicn of wood l balsam to the' surface of the zinc exposed to the electrolyte.

HERBERT E. LAWSON.

balsam being from

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