US3338750A

US3338750A - Leak-resistant dry cell

Info

Publication number: US3338750A
Application number: US483053A
Authority: US
Inventors: Lewis F Urry
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1961-05-01
Filing date: 1965-08-27
Publication date: 1967-08-29
Anticipated expiration: 1984-08-29

Description

Aug. 29, 196 7 Y 3,338,750

LEAK-RESISTANT DRY CELL Original Filed May 1, 1961 2 Sheets-Sheet 1 INVENTOR. LEWIS F. URRY A T TORNFV Aug. 29, 1967 URRY 3,338,750

LEAK-RESISTANT DRY CELL Original Fild May 1, 1961 2 Sh 2 86 :.I: I. 2.x:

I02 C 90 1: mg .1) INVENTOR. 104 g: m LEWIS F. URRY ATTORNEY United States Patent ,3 Y LEAK-RESISTANT DRY CELL Lewis F. Urry, Cleveland, Ohio, assignor to Union Carbide Corporation, a corporation of New York Original application May 1, 1961, Ser. No. 106,760. Divided and this application Aug. 27, 1965, Ser. No. 483,053

7 Claims. (Cl. 136-107) This application is a division of application Ser. No. 106,760, filed on May 1, 1961, now abandoned;

This invention relates to leak-resistant dry cells of the type having a closed container surrounding the cell proper.

The so-called Leclanch dry cell used for flashlights, portable radios, photofiash and other devices has gone through an evolution of improvements during the past decade or more in an attempt by manufacturers to prevent leakage from the cell during and after its use. Despite the many proposals, however, that have been advanced, there still remains a need for a better leak-resistant dry cell.

One proposal that has been adopted commercially is to encase a conventional dry cell within a closed container. This dry cell construction, however, has been plagued by certain difiiculties. For example, one type of container which has ,been used comprises a metal container, but this suffers from the disadvantage that the metal is subject to corrosion by liquid exudate from the cell. To avoid this disadvantage, non-corrodible containers have also been utilized. The principal difliculty, however, with non-corrodible containers is that they do not possess the mechanical strength of metal containers and sufler from the disadvantage that they may often be damaged, and even destroyed, by the pressure which builds up from the formation of gas within the cell. Several suggestions have been advanced for overcoming this disadvantage of non-corrodible containers in which the attempt has been made to continuously vent the gas from the cell. Thus, in prior constructions, the gas has been vented, for example, through the carbon electrode, and then out through venting means provided in the top closure of the container. The difiiculty, however, with these suggestions is that the venting paths, for instance through the carbon electrode, have been prone to obstruction by cell exudate, thereby blocking the passage of gas from the cell.

In addition to obstructing the venting paths provided in the cell, this cell exudate has also given rise to other serious problems. For example, one diflicult problem has been the tendency for metal formed in solution by normal consumption of the metal electrode to deposit out from the cell exudate in the form of spongy tree-like deposits. These metal deposits have formed principally on top of the depolarizer mix between the electrodes of the cell and have been particularly troublesome from the standpoint of cell performance, for they very likely can short out the cell by establishing short-circuit paths between the cell electrodes. Thus, the cell in many instances may be drained of its power even though it is not in use.

It is therefore an important object of the invention to provide an improved gas venting path in a leak-resistant dry cell particularly of the type of construction utilizing a non-corrodible container, which gas venting path is not prone to obstruction during use of the cell.

More specifically, it is another object to provide such a ga venting path in a leak-resistant dry cell while at the same time preventing the establishment of short-circuit paths between the electrodes of the cell.

Briefly, these and other objects are achieved by the invention which comprises a partition seal between the closure and depolarizer mix of a leak-resistant dry cell defining a barrier which protects at least one of the electrodes of the cell from contact by liquid cell exudate and also providing a path for venting gas from the cell.

I In the accompanying drawings:

FIG. 1 is a vertical elevation partially in section of a leak-resistant dry cell embodying the invention;

FIG. 2 is a similar view of the top portion only of a dry cell showing another embodiment of the invention;

FIG. 3 is similar to FIG. 2 showing another embodiment of the invention;

FIG. 4 is a similar view of another dry cell construction showing another embodiment;

FIG. 5 is similar to FIG. 4 showing another embodiment;

FIG. 6 is similar to FIG. 2 showing another embodiment;

FIG. 7 is similar showing still another embodiment;

FIG. 8 is similar showing yet another embodiment;

FIG. 9 is similar showing a further embodiment; and

FIG. 10 is a vertical elevation of still another dry cell construction embodying the invention.

Referring to the drawings, a leak-resistant dry cell of a construction otherwise conventional but embodying the invention is shown in FIG. 1. The cell comprises a cup electrode 10 of a consumable metal, for instance, zinc having therein a central electrode 12 'of porous carbon embedded within a depolarizer mix 14 and an immobilized electrolyte 16 suitably in the form of a conventional paste. At the top of the cell just above the depolarizer mix 14 and so placed as to define a lower free space 18 around the carbon electrode 12 and an upper free space 20 is a partition seal comprising a truncated cone 22 fitted tightly around but not necessarily sealed to the carbon electrode 12 and firmly embedded in the depolarizer mix 14 at the junction 24. A hard rigid sealing layer 26 is applied over both the depolarizer mix 14 and electrolyte paste 16 and secures the truncated cone 22 rigidly in place by overlying at least its outermost edges. The truncated cone 22 is composed suitably of paper or other fibrous material protected against penetration of liquid by a coating of a liquid repellent material, for example, polyethylene. The sealing layer 26 preferably is composed of a hard variety of asphalt or wax, for example.

A preferred top closure for the cell comprises a flanged metal cap 28 fitted on top of the carbon electrode 12 and an insulating washer 30 carried by the cap 28 on which rests the inner peripheral edges of a metal washer 32 whose outer edges are locked in liquid-tight engagement with a jacket 34. The jacket 34 preferably is noncorrodible, it being composed, for example, of paper, and fits the cup electrode 10 rather loosely, thereby providing a supplementary chamber 36 for receiving liquid exudate from the cell. The jacket 34 also has locked to it a metallic false bottom 38 which underlies and is in contact with the bottom of the cup electrode 10.

During use of the cell, especially under severe conditions, gas is released. The .gas follows a path through or around the carbon electrode 12 in the depolarizer mix 14, into the free space 18 and then through the electrode 12, into the upper free space 20 where eventually the gas escapes from the cell, for instance, by being vented from between the displaceable edges of metal washer 32 and insulating washer 30 of the top closure. Alternatively, the gas may also be passed through the carbon electrode 12 and into the upper free space 20 or from within the free space 18 between the electrode 12 and the truncated cone 22, and then out of the cell through the top closure,

the latter being the gas venting path, for instance, when a carbon elect-rode impregnated against penetration of both liquid and gas is used. At the same time, liquid is exuded through the depolarizer mix 14 towards the cup electrode 10, but is barred from entering the upper free space 20 by the hard rigid sealing layer 26, thereby preventing the liquid exudate from blocking the passage of gas through the top closure. The junction 24 aids in preventing displacement of the truncated cone 22 by gas pressure generated within the cell, but more importantly, it provides a barrier which effectively blocks off liquid from creeping into the free space 1 8 from beneath the sealing layer 26. To establish the juncture 24, the truncated cone 22 should be firmly and rigidly embedded within the depolarizer mix 14. In a D-size dry cell, the truncated cone 22 (or any of the partition seals to be hereinafter described) should be embedded in the depolarizer mix 14 to a depth of about /a inch and in AA-size cell to a depth of about inch. Thus, it will be seen by this construction that liquid exudate is not only barred from blocking the passage of gas through the free space 18 and carbon electrode 12 or from escaping out of the cell by way of the free space 18, but also is barred from contacting the carbon electrode 12 and from establishing short-circuit paths between it and the cup electrode 10 by the deposition of spongy zinc metal over the depolarizer mix 14. An insoluble salt layer which normally forms on the surfaces of the depolarizer mix 14 during discharge protects the cell from being shorted out by these metal deposits between the depolarizer mix 14 and the cup electrode 10. It should be noted that the partition seal of this invention takes advantage of this salt layer which serves to provide a seal around the junction 22 which liquid cannot penetrate.

As shown in FIGS. 2 to 10 inclusive, the principles of the invention may be achieved in a number of ways and are applicable to a variety of dry cells. For example, referring to FIG. 2, the partition seal may comprise a tube 40 and a washer 42 so arranged as to define a lower free space 44 and an upper free space 46. The tube 40 is provided about the carbon electrode 12 and is embedded in the depolarizer mix 14 at the junction 24. The washer 42 fits rather snugly around the carbon electrode 12 and rests on the top edges of the tube 40. A hard rigid sealing layer 48 of asphalt or wax is applied over the depolarizer mix 14 and electrolyte paste 16 and secures the seal rigidly in place by overlying the outer edges of the washer 42. In FIG. 3 the washer 42 is sealed to the carbon electrode 12 by the sealing layer 48 which surmounts it, the gas venting path in this instance being solely through the electrode 12. Both the tube 40 and washer 42 suitably are composed of paper or other fibrous material rendered repellent to liquid by a coating of polyethylene, for example.

The constructions thus far desmribed have been characterized by the fact that liquid is immobilized by a hard rigid sealing layer applied to the top of the depolarizer mix and electrolyte paste of the cell. This makes it possible to utilize practically the whole of the space between the depolarizer mix and the top closure for venting gas from the cell. However, it is entirely possible to construct a dry cell embodying the principles of the invention in which the sealing layer is eliminated.

Such a. construction is shown in FIG. 4. As shown, a dry cell is constructed utilizing a partition seal similar to that just described but in which the washer 42 is of a larger diameter and rests on the upper edges of the cup electrode 1 defining an exudate chamber 50. The washer 42 is preferably sealed to both the tube 40 and cup electrode by a thin layer 52 of asphalt, for example, to prevent against exudate escaping out of the chamber 50. Alternatively, a thicker sealing layer 54 suitably of Wax may be used for the same purpose as shown in FIG. 5. Also shown in FIG. 5, an insulating washer 56 suitably of polyethylene overlies the depolarizer mix 14 and prevents spongy zinc metal from penetrating through the before mentioned salt layer, thereby preventing the cell from otherwise being shorted out between depolarizer mix 14 and cup electrode 10. The dry cell constructions shown in FIGS. 4 and 5 differ from that illustrated in FIG. 1, for example, in that a top closure comprising a one-piece metal cover 58 having an opening 60 for venting gas is utilized.

Another construction which may be used is shown in FIG. 6. Here, a dry cell incorporates a partition seal of one piece composed of a tube 62 embedded in the depolarizer mix 14 at the junction 24 as in the constructions described, but which differs in that the tube 62 extends up to the metal washer 32 of the top closure and defines an inner free space 64 and an outer exudate chamber 66. The tube 62 preferably is composed of a plastic material, polyethylene, for example, and is bonded to the metal washer 32 by a thin layer 68 of cement, a vinyl resin having been used successfully for this purpose. It will be observed in this construction that gas may be vented through the inner free space 64 and directly out the top closure of the cell. FIG. 7 shows a modification of this construction in which the tube 62 is provided with a flanged end 70 which fits over the flanged cap 28 of the top closure and replaces the insulating washer of the closure. A coating 72 suitably of vinyl resin, for example, may also be applied to the underneath side of the metal washer 32 to prevent against its being corroded. Also shown in FIG. 7, a thin layer 74 of grease, for example, to prevent ingress of oxygen may be provided over the depolarizer mix 14. This grease layer as well as the before mentioned insulating washer may be used in any of the constructions described.

Still another construction which may be used is shown in FIG. 8. A dry cell as shown is constructed with a partition seal which comprises a molded plastic washer 76 fitted rather tightly within the upper edges of the cup electrode 10 overlying the electrolyte paste 16 and having an integral depending flange 78 embedded within the depolarizer mix 14 at the junction 24. Preferably, the upper edges of the cup electrode 10 are curled over on top of the washer 76 to rigidly secure it in place within the cell. It will be noted in this construction that liquid exudate is immobilized as in the construction shown in FIGS. 2 and 3, and that the Whole of the free space above the depolarizer mix 14 is utilized for venting gas from the cell.

The constructions described in which the partition seal embodying the invention is of one piece are advantageous because placement of the seal is greatly facilitated during manufacture of dry cells. It will be understood that any of the constructions described, for example that of FIG. 4 may be embodied in one piece such as shown in FIG. 9. A dry cell thus is constructed utilizing a partition seal of a molded plastic disc 80 which is supported within the cup electrode 10 at its upper edges. The disc 80 has an aperture at its center for tightly receiving the carbon electrode 12, and also has an integral tubular flange 82 depending therefrom the lower edges of which are embedded within the depolarizer mix 14 at the junction 24. Preferably, a thin layer 84 of a sealant, for example, vinyl resin, seals the disc 80 to the metal washer 32 of the top closure.

A different version of a dry cell incorporating the invention is shown in FIG. 10. The dry cell which is shown is substantially disclosed and claimed in US. Patent No. 2,605,299 issued to J. P. Teas on July 29, 1952, and comprises a non-corrodible jacket 86 suitably of paper having a metallic one-piece top closure 88 locked to its upper edges and a cup electrode 90 of carbon molded in juxtaposition to and in adherent contact with the inner surfaces of the jacket 86 and top closure 88, the cup electrode 90 being suitably molded in place by injection molding techniques. A central electrode 92 of a consumable metal, for example, zinc having a generally X shaped cross section and provided with a conventional separator 94 of a bibulous paper is embedded within a depolarizer mix 96 Which substantially fills the cup electrode 90 but which leaves a space through which the stem of the central electrode 92 extends at the bottom open end of the cup electrode 90. A metallic bottom closure 98 is locked to the bottom edges of the jacket 86 with which makes contact the stem of the central electrode 92. Between the bottom closure 98 and depolarizer mix 96 and defining an inner free space 100 and an outer free space 102 is a partition seal comprising a tubular sleeve 104 of a diameter slightly less than that of the cup electrode 90, one end of which is embedded Within the depolarizer mix 96 at the junction 106 and the other end of which is locked in the engagement between the bottom closure 98 and jacket 86. A hard rigid sealing layer 108 suitably of wax is applied over the depolarizer mix 96 and overlies both the bottom closure 98 and tubular sleeve 104, and prevents liquid from entering the free space 100 within the bottom of the cell. With this construction, it will be seen that the dry cell functions essentially the same as previously described except that gas is vented through the outer free space 102 and then out of the cell from between the locked junction of the bottom closure 98 and jacket 86.

A number of dry cells embodying the invention have been made and tested over a wide range of conditions. These tests demonstrated the eflectiveness of the invention, for cells otherwise identical in construction but lacking the structural features of the invention showed evidence of leakage from and/ or bulging of the cell container while those cells embodying the invention showed little or no evidence of gas pressure build-up and consistently demonstrated superior leakproofness. The eilectiveness of the invention was further demonstrated by the fact that the dry cells of the invention had a longer life and did not short out during the tests.

It will be understood that many changes and modifications of the dry cell constructions described herein may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In a leak-resistant dry cell comprising a cup elec- I trode containing depolarizer mix, electrolyte and a second electrode embedded within said depolarizer mix, the combination of a closure for said cell, said closure being spaced from said depolarizer mix and having gas venting means therein, a partition seal positioned between said depolarizer mix and said closure within the space provided therebetween and defining a barrier which protects at least one of said electrodes against contact by liquid exudate from said cell, said seal being embedded within said depolarizer mix and forming a juncture which prohibits the passage of said liquid exudate beneath said seal, and a hard rigid sealing layer disposed within the space provided between said closure and said depolarizer mix, said hard rigid sealing layer being positioned over said depolarizer mix and electrolyte and overlying at least a portion of said partition seal, said seal in conjunction with said gas venting means in said closure providing a liquid-free path for venting gas from said cell.

2. A leak-resistant dry cell as defined by claim 1 in which said cup electrode is composed of a consumable metal and in which said second electrode is composed of car n,

3. A leak-resistant dry cell as defined by claim 1 in which said cup electrode is composed of carbon and in which said second electrode is composed of a consumable metal.

4. A leak-resistant dry cell as defined by claim 2 in which said partition seal comprises a truncated cone fitted around said carbon electrode and at its lower edges embedded within said depolarizer mix and in which said sealing layer overlies the embedded edges of said truncated cone.

5. A leak-resistant dry cell as defined by claim 2 in which said partition seal comprises a tube provided about said carbon electrode and at its lower edges embedded within said depolarizer mix, and a washer fitted around said carbon electrode and resting on the upper edges of said tube and in which said sealing layer overlies the peripheral edges of said washer.

6. In a leak-resistant dry cell comprising a jacket, a metal top closure locked in engagement with said jacket and a cup electrode of carbon in juxtaposition to and in adherent contact with said jacket and said top closure containing depolarizer mix and a central electrode of a consumable metal embedded within said depolarizer mix, the combination of a bottom closure locked in engagement with said jacket, said bottom closure having gas venting means therein; and a partition seal positioned between said depolarizer mix and said bottom closure providing a free space between said seal and said cup electrode and defining a barrier which protects said cup electrode from contact by liquid exudate from said cell, said seal being embedded within said depolarizer mix and forming a juncture which prohibits the passage of said liquid exudate beneath said seal and into said free space, said seal in conjunction with said gas venting means in said bottom closure providing a path for venting gas from said cell. I

7. A leak-resistant dry cell as defined by claim 6 in which said partition seal comprises a tubular sleeve embedded within said depolarizer mix and at its lower end locked in engagement between said bottom closure and said jacket.

References Cited UNITED STATES PATENTS 2,850,558 9/1958 Urry 136-433 3,016,414 1/1962 Priebe 136-107 3,051,769 8/1962 Jammet 13 6l33 3,179,537 4/1965 Reilly 136-107 X 3,214,298 1 0/ 1965 Urry 136107 FOREIGN PATENTS 1,213,467 11/1959 France.

792,152 3/1958 Great Britain.

WINSTON A. DOUGLAS, Primary Examiner. B, J. OHLENDORF, A. SKAPARS, Assistant Examiners.

Claims

1. IN A LEAK-RESISTANT DRY CELL COMPRISING A CUP ELECTRODE CONTAINING DEPOLARIZER MIX, ELECTROLYTE AND A SECOND ELECTRODE EMBEDDED WITHIN SAID DEPOLARIZER MIX, THE COMBINATION OF A CLOSURE FOR SAID CELL, SAID CLOSURE BEING SPACED FROM SAID DEPOLARIZER MIX AND HAVING GAS VENTING MEANS THEREIN, A PARTITION SEAL POSITIONED BETWEEN SAID DEPOLARIZER MIX AND SAID CLOSURE WITHIN THE SPACE PROVIDED THEREBETWEEN AND DEFINING A BARRIER WHICH PROTECTS AT LEAST ONE OF SAID ELECTRODES AGAINST CONTACT BY LIQUID EXUDATE FROM SAID CELL, SAID SEAL BEING EMBEDDED WITHIN SAID DEPOLARIZER MIX AND FORMING A JUNCTURE WHICH PROHIBITS THE PASSAGE OF SAID LIQUID EXUDATE BENEATH SAID SEAL, AND A HARD RIGID SEALING LAYER DISPOSED WITHIN THE SPACE PROVIDED BETWEEN SAID CLOSURE AND SAID DEPOLARIZER MIX, SAID HARD RIGID SEALING LAYER BEING POSITIONED OVER SAID DEPOLARIZER MIX AND ELECTROLYTE AND OVERLYING AT LEAST A PORTION OF SAID PARTITION SEAL, SAID SEAL IN CONJUNCTION WITH SAID GAS VENTING MEANS IN SAID CLOSURE PROVIDING A LIQUID-FREE PATH FOR VENTING GAS FROM SAID CELL.