GB1603552A

GB1603552A - Dry batteries

Info

Publication number: GB1603552A
Application number: GB13795/78A
Authority: GB
Original assignee: CHING WA PUN
Current assignee: CHING WA PUN
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-11-25
Also published as: DE2914028A1; JPS54142533A

Description

(54) DRY BATTERIES (71) We, CHING WA PUN AND CHING CHAU POON, both British Subjects, both of On Shing Industrial Building, 9th Floor, Fo Tan S.T.T.L. No. 7, Shatin, New Territories, Hong Kong, formerly of 289 To Kwa Wan Road, 1st Floor, Kowloon, Hong Kong, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention is concerned with dry cells and batteries, for example Lechlanche cells, alkaline dry cells and batteries containing such cells.

Such cells comprise an assembly of active components comprising an electrolyte, positive and negative electrodes and, usually, a depolariser to absorb hydrogen produced by the chemical reactions involved in cell operation.

In some cells, one electrode is so constructed as to form a case for the cell. For example, Leclanche cells are known in which the negative electrode is formed as a cylindrical cup within which the other components are contained. It is however, common practice to provide a separate jacket to minimise the risk of leakage of fluid as the electrode becomes eroded. It is also knows no described in our British Patent application No.

45042/74 (Serial No. 1,506,579Fto enclose the cell components in a sealed flexible plastics bag which relieves the electrode of its sealing function and results in a saving of materials.

According to one aspect of the presentinvention, there is provided a method of making a dry battery comprising completely enclosing the active components of at least one dry cell within a heat shrinkable plastics bag, and then heat-shrinking the bag to seal the components against leakage and hold them together in compression.

In this specification, the term battery is used to mean not only a package containing a plurality of cells, but also a package containing a single cell.

In another aspect the invention provides a dry battery comprising at least one dry cell whose active components are sealed against leakage and held together in compression by a heat shrink plastics bag completely enclosing them.

The shrunk plastics bag thus performs the dual function of sealing the cell(s) against leakage of electrolyte and of applying compressive force to the cell assembly(ies) thus tightly clasping the contents to reduce the internal resistance.

The bag may be made of any suitable plastics material which is heat shrinkable, impervious to liquid and resistant to attack by electrolyte. The number of materials which can, in the present state of the plastics art, be made heat shrinkable is limited, however, Polyvinyl chloride (PVC) is a suitable material. PVC can be treated to produce heat shrinkable properties by causing cross-linking of the polymer (e.g. by irradiation) in the extended state. The material has an elastic memory and will revert to its original dimensions upon heating. Heat shrinkable PVC is readily available commercially: for example the material marketed by Raychem Corporation under the trade mark "Thermofit PVC" which, in tubing form, can shrink by from extremely low percentages up to 50% of its supplied diameter when heated above 175"C.

It will be appreciated that other polymers such as polyethylene, polypropylene, synthetic rubber and nylon may be suitable provided they can be made heat-shrinkable.

In a preferred embodiment, connections between the terminals of the battery and the electrodes within the bag are effected by means of metal portions having pointed projections which penetrate the bag. Thus the method may include the further step of enclosing the bag and cell(s) in a jacket having a pair of terminals, and compressing the battery so that connections between the terminals are established by means of pointed metal projections or any other means which penetrate through the bag. These portions may be formed on the terminals and penetrate the bag to engage either the electrodes themselves or contact portions secured to the electrodes: alternatively the portions with projections may be formed on the electrodes, and penetrate the bag to engage the terminals.

Where an external jacket is fitted to the cell by rolling or crimping or the like, it may conveniently be arranged that compression of the battery to effect penetration of the bag by the pointed projections, and the fitting of the jacket are performed as a single operation.

The air inside the bag can be extracted before or after sealing in order to reduce the pressure inside the bag and to increase the space available for the storage of liquid generated by the cell(s).

Some exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure IA is a cross-section through a partially completed Leclanche battery according to the invention.

Figure 1B is a view similar to 1A showing the completed cell.

Figure 2A is a cross-section through a partially completed alkaline battery according to the invention.

Figure 2B is a view similar to 2A showing the completed cell.

Figure 3A is a cross-section through a single-cell Leclanche battery according to the invention.

Figure 3B shows the upper portion of a battery similar to that shown in Figure 3A.

Figure 3C shows a further embodiment of a battery similar to that of Figure 3A.

Figure 3D shows a plan and an elevation of a detail of the battery of Figure 3 C.

Figure 4 is a cross-section through a singlecell alkaline battery of the invention.

In figures 1A and 1B is shown a layer type battery (9 volt) in accordance with the present invention having six dry Leclanche cells.

Conventional cells of this type usually have a coating of a thick layer of microcrystalline wax (through which hydrogen gas can pass) for sealing and preventing leakage. But microcrystalline wax alone tends to crack and fall to pieces, and an open ended shrinkable plastics tube is usually fitted as an exterior layer to protect it. In the arrangement shown in Fig. 1A, the cells 103 are enclosed in a plastics bag 101, the upper and lower ends 102 of which are sealed up. The bag has been shrunk so that the cells are tightly clasped by the bag. There is a carbon contact plate 104 on the bottom end of the lowermost cell. On the surface of the plate, there is a thick layer of sealing material 105 such as wax, asphalt or other oil-based or gum-like substance which can solidify under normal air temperature. The negative electrode 106 of the top part of the uppermost dry cell is likewise coated with a thick layer of sealing material 105. As the dry cells 103 are completely enclosed in the bag 101, the layer of microcrystalline wax used in conventional cells is unnecessary. As a result the space thus saved can be utilized to enlarge the size of the basic dry cells thus increasing the electric capacity.

Fig. 1B shows the arrangement of Fig. 1A fitted with terminals and enclosed in an outer metal jacket. A negative terminal, button 107, has pointed projections 108. A positive terminal, button 109, is connected to a conductive strip 110 which extends to the lower end of the cell where it has pointed projections 111. The strip 110 should be insulated on both sides so as to avoid electrical contact with other parts of the cell.

The upper and lower ends of the outer metal jacket are rolled or crimped over as at 112, and at the same time axial pressure is applied to the battery whereupon projections 108 at the bottom of the button 107 penetrate the plastics bag 101 and the upper layer of sealing material 105 to make electrical contact with the negative electrode 106 of the uppermost cell. Similarly the projections 111 of the conductive strip 110 connected to the button 109 penetrate the plastics bag 101 and the lower layer of sealing material 105 to make electrical contact with the carbon contact plate 104 of the lowermost dry cell 103. Thus both electrodes can be provided with external terminals although the six layers of basic dry cells are enclosed in the bag 101. The layer of sealing material 105 around the perforations at the ends maintains an effective seal at the points of penetration.

In Figures 2A, 2B is shown a layer type 9 volt alkaline battery according to a second embodiment of the invention.

201 in the figure is the shrinkable plastics bag, and its upper and lower ends 202 are sealed up to make a tightly sealed bag, containing six dry cells in a group.

Each of the cells is contained within a plastics frame 203. Each frame 203 contains a metal tray 204 which, owing to the chemical reactions which take place in the cells is gold-plated on both the outside and inside.

An electrolyte 205 containing zinc dust and mercury is contained in the trays 204. The top of the electrolyte 205 is covered with one or more layers of paper 206, which can absorb alkaline liquids produced in the electro-chemical reactions. A laminated diaphragm 207 may be additionally placed on top of the paper 206. An inwardly and downwardly extending flange 208 is provided around the interior of each frame 203 in order to prevent the metal tray 204 from moving upwardly and to assist in retaining the electrolyte 205 within the plastics frame.

Each cell further comprises a depolarising dolly 209, the lower part of which is in electrical contact with layers 205,206 and the upper part of which is in electrical contact with the underside of the metal tray 204 of the cell above. Thus the six cells together form a 9 volt battery.

A metal contact plate 210, at least the underside of which is gold plated, is arranged on the top of the uppermost cell. The underside of plate 210 is in contact with the depolarizing dolly of the uppermost cell and the top side of the plate 210 is coated with a thick layer of sealing material 211. The underside of the tray 204 of the lowermost cell is similarly coated with a thick layer of sealing material 212. After the cells have been placed in the plastics bag 201, the bag is put into a metal jacket 213, as shown in Figure 2B. The method of enclosure within the jacket 213 is similar to that described in the embodiment of Figure 1, however the position of the two electrodes is exchanged.

As shown in Figure 2B, a positive terminal comprising a button 214 has pointed projections 215. A negative terminal comprising a button 216 is conected to a conductive strip 217 which extends to the underside of the battery. The portion of the strip 217 which extends along the underside of the battery is provided with pointed projections 218. The strip 217 is insulated on both sides so as to avoid electrical contact with other parts of the cell. The upper and lower ends of the metal jacket 213 are rolled or crimped over as at 219 and at the same time axial pressure is applied to the battery, whereupon projections 215 on the bottom of button 214 penetrate the plastics bag 201 and the layer 211 of sealing material to make electrical contact with the plate 210. Similarly, the projections 218 on the conductive strip 217 penetrate the plastic bag 201 and the layer 212 of sealing material to make electrical contact with the metal tray 204 of the lowermost cell. Thus, both electrodes are provided with external terminals, although the dry cells are enclosed in the bag 201. The layers of sealing material 211, 212 maintain an effective seal around the points at which the projections 215,218 penetrate the plastics bag 201, as in the embodiment of Figure 1.

In Figure 3A there is shown a third embodiment of the invention, in the form of a cylindrical type single cell Leclanche battery. The battery comprises a shrinkable plastics bag 301, a depolarising dolly 302 having an insulating plate 323 at the top and bottom thereof, a carbon rod 303, a layer of paper 304 impregnated with electrolytic paste and a zinc tube 305.

The upper end of the carbon rod 303 is coated with a thick layer 307 of a sealing material such as wax, asphalt or other kind of oily substance which is solid at ambient temperatures, to assist sealing. The lower end of the zinc tube 305 is extended to form a tongue 308 having a circular enlarged end 309 similar to that shown in Figure 3D. The tongue 308 is entirely coated with a thick layer 310 of sealing material to reduce corrosion and assist sealing.. The zinc tongue is folded inwardly through 90 relative to the zinc tube, so that the enlarged end 309 is positional at the centre of the lower end of the dry cell.

After consolidation, the parts 302 to 305, 307 to 310 and 323 are put into the shrinkable plastics bag 301, and the upper and lower ends of the bag 301 are sealed. The lower insulating plate 323 prevents the tongue 308 from contacting the dolly 302.

This completes the first stage in the manufacture of the cell. The cell differs from a conventional dry cell in that the electrodes and electrolyte are completely enclosed in the shrinkable plastics bag. This basic dry cell is then provided with an outerjacket 313, for example of metal or paper, a top metal cover 314 and metal bottom 315. The upper and lower ends 316 of the jacket 313 are rolled or crimped and pressed inwardly, so that the top metal cover 314 tightly clamps the bag 301 against the top end ofthe carbon rod 303, and the bottom metal plate 315 is pressed upwardly against the underside of the basic dry cell.

The top part 317 of the metal cover 314 is provided with a pointed projection 318 which, when the upper and lower end 316 of the jacket 313 are rolled or crimped and pressed, are pressed downwardly so as to penetrate the plastics bag 301 and the layer 307 qf sealing material to make electrical contact with the carbon rod 303. The metal cover 314 thus provides the positive terminal of the cell.

The metal bottom plate 315 also has one or more projections 319 which, when pressure is applied as described above, penetrate the layer 310 of sealing material and the plastics bag 301 to make electrical contact with the enlarged end 309 of the zinc tongue 308. The metal plate 315 thus provides the negative terminal of the cell.

Whilst the jacket 313 may be made of metal or paper, when the jacket is made of metal, the metal cover 314 and the bottom plate 315 are insulated from the jacket 313 by means of rings 332, made of an insulating material.

Figure 3 B shows the upper portion of a dry cell similar to that of Fig. 3A. However, the single pointed projection 318 is replaced by a plurality of pointed projections which function in the same manner as the single projection of Fig. 3A.

The diameter of the depolarising dolly 302 is larger than that of a conventional battery, and in the cell of Figure 3B, the carbon rod 303 also has a larger diameter so as to reduce the internal resistance of the battery. The diameter of the top part 317 is less than that of the carbon rod 303 so as to fit the appliance for which the battery is intended.

Figures 3C and 3D show a further embodiment of a dry cell similar to that of Fig. 3A.

The cell comprises, in addition to the parts described with reference to Fig. 3A, an inner metal cap 306 which tightly clamps the top end of the carbon rod 303. Thus, it is the metal cap 306 which is coated with the sealing material 307, rather than the carbon rod 303. The sealing material thus assists in inhibiting corrosion of the metal cap 306.

In addition, in the embodiment of Figure 3C, the thickness of the shrinkable plastics bag 301 is increased from 0.06 mm as in the embodiments of Figures 3A and 3B to 0.10 mm or even up to 0.20 mm. Alternatively, a double layer plastics bag may be used. Thus the bag 301 cannot easily be broken by an outside force and can take part in the function of the outer jacket. The bag 301 should protect the basic dry cells after the increase in thickness with the exception of deliberate destruction by knife cutting or piercer pricking. This battery cannot easily be broken even by falling, throwing, collision and dashing because this embodiment has a specially designed zinc tubular electrode with a longitudinal opening. In manufacturing, the longitudinal opening of the zinc electrode is expanded first and members 302, 303 and 304 etc., are introduced. The opening is then restored to its original size, so as to maintain the high hardness of the depolarizing dolly which is pressed by machinery. It is different from the conventional paper lined dry cell having a cup-shaped zinc electrode that requires that the depolarizing dolly must have a lower degree of hardness for inserting the carbon rod. Also the hardness of the depolarizing dolly itself is reduced because of the absorption of the electrolyte in manufacturing or storing of the conventional pastelined dry cell. The two insulating plates 323 are located at the top and bottom ends of the dolly 302. They protect the two ends of the dolly 302 from damage. The insulated plates themselves are made of a hard board.

After the wax is solidified which was absorbed into the insulated plates, the hardness of the insulated plates is increased, forming a single unit with the dolly 302 by the strength of clasping of the bag 301. It can resist outside force and would not be broken so easily.

The pointed projection is one of the preferred features of this invention and is designed to expose the two electrodes of the basic dry cell which is sealed inside the plastics bag for the conduction of the electric current. The pointed projection can be in many forms too numerous to mention. The form of the pointed projection depends on the intended function and the form of the battery.

The embodiment of Fig. 3C has no outer jacket, and differs from that of Fig. 3A in that, in the embodiment of Fig. 3A, it is the pressure of the crimping or.rolling inwardly of the top and bottom ends of the outer jacket which enables the pointed projections to penetrate through the bag 301 for conducting electric current. In Fig. 3C, an eyelet button 326 is used having an upper surface 324 and a skirt 325 facing inwardly and forming a round shaped cramp with the upper surface 324 of the eyelet button 326. At the centre of the eyelet button, there is a hollow 327. When the eyelet button 326 is pressed towards the metal cap 306 by the machinery, one or more pointed projections 318 on cap 306 will penetrate the plastics bag 301 and enter the eyelet button 326 by pressure and along with the inclined surface of the conical hollow 327 then enter the above mentioned round cramp. At that time the machinery is still continuing to press downwardly until the whole pointed projection 318 is sandwiched firmly between the upper surface 324 of the eyelet button and the skirt 325 of the eyelet button. The part of the plastics bag 301 that surrounds the opening which is penetrated by the pointed projection 318 and the sealing material etc. is secured firmly between the eyelet button 326 and the inner metal cap 306. The sealing material sandwiched between fills up all the space at that part. Therefore the function of sealing will be strengthened and leakage will be checked.

The formation of the bottom eyelet button 329 is similar to that of the eyelet button 326, but somewhat larger. The outer edge 330 cannot be the same as 328 which bends downwardly to form a round corner. It can only have a flat shape because the bottom part of the battery is flat. The sign "+" can be pressed or printed at the anode of the battery for distinction of the two electrodes by consumers. The negative pole is however enlarged to assist the distinction.

As shown in Fig. 3C, a space 331 is provided within the plastics bag 301 for liquid storage. The space can be made in various shapes.

The bottom eyelet button 329 presses the pointed projections 334 or the zinc tongue 308 firmly and at the same time together with the enlarged end 309 of the zinc tongue 308 presses the surrounding of the opening where the pointed projections penetrate the plastics bag 301 and the sealing material in order to strengthen the sealing of the portion. It is similar to the top eyelet button 326.

Figure 4 shows an alkaline dry battery in accordance with the invention, containing a single cell.

A shrinkable plastics bag 401 contains an anode tube (positive electrode) 402 which surrounds a depolarizing tube 403 within which is at least one layer of paper tube 404.

A thick layer of alkaline electrolytic paste 405 is contained inside the paper tube 404.

The paste 405 contains zinc dust and mercury. Inwardly of the paste 405 is a tubular cathode (negative electrode) 406 which contains a further quantity of alkaline electrolytic paste 407. The tube 406 is perforated with small holes 408. This enables the electrolytic paste 407 inside the tube 406 to move to 405 to replenish the water in the paste 405 lost during discharging of the cell.

There is a plastics plate 409 at the top of the cell. One of its functions is to keep the cathode tube 406 and anode tube 402 in position. A circular groove 410 in the bottom of the plastics plate 409 accommodates the top end of the cathode tube 406, so that it is maintained in a central position. There is a small circular groove 411 in the outside rim of the plate 409 to accommodate the top end of the anode tube 402, so that it is kept in an appropriate high or low position in the dry cell to avoid the anode tube 402 moving up and down. This also maintains the round shape of the anode tube 402, and strengthens the resistance of the tube 402 and the depolarizing tube 403 to the pressure from outside to avoid being pressed down into a distorted shape or a breakage. In the lower part of the small circular groove 411, there is also a large circular groove 412, which is used to prevent the electrolyte flowing along the inside wall of the top end of the anode tube 402 to the top end of the dry cell. The other functions are to provide electric insulation and to withstand pressure. The top end of the outer metal jacket is mechanically rolled as at 414. The outer rim 416 of the top metal cover 415 is, during this process, urged toward the outer rim of the plastics plate 409 and pointed projections 417 provided on the rim 416 are forced through the plastics bag 401 into electrical contact with a tongue 20 secured to the anode. The tongue is covered with a thick layer of alkaline-proof sealing material 419. It may be noted that the plate 409 serves to protect the depolarizing tube 403 from being damaged during this process.

The pointed projections 417 could, if desired, be formed on the tongue 420 instead of the top metal cover. This arrangement would serve the same penetrating purpose.

There is also a second plastics plate 421 at the bottom of the depolarizing tube 403, and its functions are the same as the plastics plate 409 in the top. It enables the bottom end of the cathode tube 406 (secured to the plate by a rivet 422) to remain in the middle of the plastic plate 421. There is also a small circular groove 423 in the upper part of the outside rim of the plastics plate 421. It is used for accommodating the bottom end of the anode tube 402, so as to avoid the anode tube 402 moving up and down. This also maintains the round shape of the anode tube 402, and strengthens the resistance of the tube 402 and the depolarizing tube 403 to pressure from outside to avoid distortion or breakage.

In the upper part of the small circular groove 423, there is also a large circular groove 424, which is used to avoid electrolyte flowing down along the inside wall of the bottom end of the anode tube 402 to the bottom end of the dry cell. The other functions are to provide insulation and resistance to pressure.

The metal bottom 426, like the top cover 415, has pointed projections 428, so that when the metal bottom and the upper and the lower ends 414 and 425 of the outer metal jacket 413 are rolled and pressed, the projections penetrate the plastics bag and a thick layer of alkaline-proof sealing material 430 to make electrical contact with the rivet 422 and hence the cathode 406.

Alternatively, projections may be provided on the bottom of the rivet 422 which contact the metal bottom 426.

To avoid local short circuits through the contacts of the outer metal jacket, and the top metal cover 415, and the metal bottom 426, each of the inside walls of the top end and the bottom end 414 and 425 of the outer metal jacket 413 has an (additional) insulation ring 431 to separate the top metal cover 415 and the metal bottom 426 to ensure that they cannot make direct contact with the outer metal jacket 413.

In this case, the thickness of the shrinkable plastics bag 401 can also be increased to the extent that can serve as an outer jacket and form the finished product without having to put on another outer jacket. It can also adopt the eyelet buttons at both the top and the bottom parts of the basic dry cell as in Fig.

3B in order to cramp the pointed projections of the top and the bottom parts tightly for conducting of the electric current and forming the two electrodes of the dry cell.

All the pointed projections in all the figures may be made on the opposite component, and penetrate from the opposite direction.

WHAT WE CLAIM IS: 1. A dry battery comprising at least one dry cell whose active components are sealed aginst leakage and held together in compression by a heat shrunk plastics bag completely enclosing them.

2. A battery as claimed in claim 1, wherein connections between terminals of the battery and the electrodes of the or each cell are made by pointed projections penetrating said bag.

3. A battery as claimed in claim 2, wherein projections are provided on at least one of said terminals.

4. A battery as claimed in claim 2 or 3, wherein said projections are provided on at

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which is at least one layer of paper tube 404. A thick layer of alkaline electrolytic paste 405 is contained inside the paper tube 404. The paste 405 contains zinc dust and mercury. Inwardly of the paste 405 is a tubular cathode (negative electrode) 406 which contains a further quantity of alkaline electrolytic paste 407. The tube 406 is perforated with small holes 408. This enables the electrolytic paste 407 inside the tube 406 to move to 405 to replenish the water in the paste 405 lost during discharging of the cell. There is a plastics plate 409 at the top of the cell. One of its functions is to keep the cathode tube 406 and anode tube 402 in position. A circular groove 410 in the bottom of the plastics plate 409 accommodates the top end of the cathode tube 406, so that it is maintained in a central position. There is a small circular groove 411 in the outside rim of the plate 409 to accommodate the top end of the anode tube 402, so that it is kept in an appropriate high or low position in the dry cell to avoid the anode tube 402 moving up and down. This also maintains the round shape of the anode tube 402, and strengthens the resistance of the tube 402 and the depolarizing tube 403 to the pressure from outside to avoid being pressed down into a distorted shape or a breakage. In the lower part of the small circular groove 411, there is also a large circular groove 412, which is used to prevent the electrolyte flowing along the inside wall of the top end of the anode tube 402 to the top end of the dry cell. The other functions are to provide electric insulation and to withstand pressure. The top end of the outer metal jacket is mechanically rolled as at 414. The outer rim 416 of the top metal cover 415 is, during this process, urged toward the outer rim of the plastics plate 409 and pointed projections 417 provided on the rim 416 are forced through the plastics bag 401 into electrical contact with a tongue 20 secured to the anode. The tongue is covered with a thick layer of alkaline-proof sealing material 419. It may be noted that the plate 409 serves to protect the depolarizing tube 403 from being damaged during this process. The pointed projections 417 could, if desired, be formed on the tongue 420 instead of the top metal cover. This arrangement would serve the same penetrating purpose. There is also a second plastics plate 421 at the bottom of the depolarizing tube 403, and its functions are the same as the plastics plate 409 in the top. It enables the bottom end of the cathode tube 406 (secured to the plate by a rivet 422) to remain in the middle of the plastic plate 421. There is also a small circular groove 423 in the upper part of the outside rim of the plastics plate 421. It is used for accommodating the bottom end of the anode tube 402, so as to avoid the anode tube 402 moving up and down. This also maintains the round shape of the anode tube 402, and strengthens the resistance of the tube 402 and the depolarizing tube 403 to pressure from outside to avoid distortion or breakage. In the upper part of the small circular groove 423, there is also a large circular groove 424, which is used to avoid electrolyte flowing down along the inside wall of the bottom end of the anode tube 402 to the bottom end of the dry cell. The other functions are to provide insulation and resistance to pressure. The metal bottom 426, like the top cover 415, has pointed projections 428, so that when the metal bottom and the upper and the lower ends 414 and 425 of the outer metal jacket 413 are rolled and pressed, the projections penetrate the plastics bag and a thick layer of alkaline-proof sealing material 430 to make electrical contact with the rivet 422 and hence the cathode 406. Alternatively, projections may be provided on the bottom of the rivet 422 which contact the metal bottom 426. To avoid local short circuits through the contacts of the outer metal jacket, and the top metal cover 415, and the metal bottom 426, each of the inside walls of the top end and the bottom end 414 and 425 of the outer metal jacket 413 has an (additional) insulation ring 431 to separate the top metal cover 415 and the metal bottom 426 to ensure that they cannot make direct contact with the outer metal jacket 413. In this case, the thickness of the shrinkable plastics bag 401 can also be increased to the extent that can serve as an outer jacket and form the finished product without having to put on another outer jacket. It can also adopt the eyelet buttons at both the top and the bottom parts of the basic dry cell as in Fig. 3B in order to cramp the pointed projections of the top and the bottom parts tightly for conducting of the electric current and forming the two electrodes of the dry cell. All the pointed projections in all the figures may be made on the opposite component, and penetrate from the opposite direction. WHAT WE CLAIM IS:

1. A dry battery comprising at least one dry cell whose active components are sealed aginst leakage and held together in compression by a heat shrunk plastics bag completely enclosing them.

least one of said electrodes.

5. A battery as claimed in any preceding claim, comprising a plurality of cells arranged one above another, each cell being contained within a plastics frame.

6. A battery as claimed in claim 5, wherein each frame contains a metal tray containing the electrolyte.

7. A battery as claimed in claim 6, wherein each frame has a flange around the interior thereof so as to prevent said tray from moving upwardly in the frame.

8. A battery as claimed in claim 6 or 7, wherein an absorbent layer is provided above said electrolyte and above said absorbent layer is provided a depolarising dolly, the depolarising dolly of each cell other than the uppermost making electrical contact with the underside of the metal tray of the cell above, and the depolarising dolly of the uppermost cell making electrical contact with a metal contact plate.

9. A battery as claimed in claim 8, comprising a conductive strip extending from top to bottom of the battery and connected to the negative terminal, at least one pointed projection being provided on said strip or on the lowermost tray, said at least one projection penetrating the tray to make electrical contact between said strip and said lowermost tray.

10. A battery as claimed in claim 8 or 9, comprising at least one pointed projection provided either on a positive terminal or on said contact plate, said at least one pointed projection penetrating the tray to make electrical contact between the positive terminal and said contact plate.

11. A single cell Leclanche battery as claimed in claim 3 or 4, wherein the zinc electrode is in the form of an open-ended tube provided with a tongue, at least one pointed projection being provided either on the negative terminal or at the face end of the tongue, said at least one pointed projection penetrating said bag to make electrical contact between the tongue and the negative terminal.

12. A single cell Leclanche battery as claimed in claim 4 or 11, comprising a metal cap mounted on the carbon electrode, said metal cap having at least one pointed projection, said at least one pointed projection penetrating said bag to make electrical contact with a positive terminal.

13. A battery as claimed in any of claims 4, 11 or 12, wherein either or both terminals are in the form of an eyelet button adapted to receive and bend over the or each pointed projection provided on an electrode.

14. A single cell alkaline dry battery as claimed in claim 3 or 4, wherein at least one pointed projection is provided either at at least one point around the rim of the positive terminal, or at at least one point around the rim of an anode tube surrounding the cell, the projections penetrating the bag to make electrical contact between said anode tube and said positive terminal.

15. A single cell alkaline dry battery as claimed in any of claims 3, 4 or 14, wherein at least one pointed projection is provided either on the negative terminal, or on a rivet in contact with a cathode tube, said at least one pointed projection penetrating the bag to make electrical contact between said rivet and said negative terminal.

16. A dry battery substantially as hereinbefore described with reference to the accompanying drawings.

17. A method of making a dry battery comprising completely enclosing the active components of at least one dry cell within a heat shrinkable plastics bag, and then heatshrinking the bag to seal the components against leakage and hold them together in compression.

18. A method as claimed in claim 17 wherein connections between terminals of the battery and the electrodes of the or each cell are made by pointed projections penetrating the bag.

19. A method as claimed in claim 18, wherein said bag and said at least one dry cell assembly are enclosed in a jacket provided with said terminals and the battery is compressed so as to cause said projections to penetrate said bag.

20. A method as claimed in claim 18, wherein the jacket is fitted to the battery by rolling or crimping and the battery is compressed so as to simultaneously cause said projections to penetrate said bag and to fit said jacket to the battery.

21. A method as claimed in any of claims 17 to 20, wherein the air inside the bag is extracted before or after sealing.

22. A method of making a dry battery substantially as herein described.