GB2045512A - Electric batteries for use with miners cap lamps - Google Patents

Abstract

An electric battery for use with a miner's cap lamp has two or more cells sealed by a common inner lid 6. The battery further has an outer lid 8 extending over the entire area of the inner lid 6, and the two lids together define a space accommodating the terminal connectors 26 and a safety valve 36, 38 and 40 for each cell. <IMAGE>

Description

SPECIFICATION Electric batteries for use with miners cap lamps The present invention relates to electric batteries for use with miners cap lamps.

Such batteries are generally used secured to a miner's belt, and as such they must be able to withstand the arduous treatment which they receive and must be able to work in any orientation. Their electrical connections must be immune to both accidental and deliberate attempts at disconnection or damage and finally they should be as maintenance free as possible.

According to the present invention there is provided an electric battery for use with a miner's cap lamp in which the cells are sealed by a common inner lid, the battery fUrther having a common outer lid extending substantially over the entire area of the inner lid and together with the inner lid defining a space accommodating the terminal connectors and a safety valve for each cell. Therefore, those parts of the battery which are vulnerable to damage are protected by the outer lid which may be removable, but only by means of a special tool.

In a preferred embodiment of the invention the positive and negative plates in each cell are separated by separators of highly absorbent material such as glass paper consisting of microfine glass fibres, the cells being normally sealed so that they can operate at above atmospheric pressure and containing a reduced amount of electrolyte substantially all of which is absorbed and retained by the separator material.

With appropraite battery design and the correct choice of materials and the use of unsaturated and highly absorbent separators under certain conditions, the gas evolved at the positive electrodes can diffuse through the gaseous phase in the separators and react with with the negative electrodes, thereby depressing the potential of the electrodes to a level below the hydrogen evolution potential.

The or each intercell connection is preferably beneath both the inner and outer lids, and the two terminal connectors may be positioned on the same side of the battery container and outside it and accommodated within a space defined by the outer lid.

Further features and details of the invention will be apparent from the following description of one specific construction of lead acid electric battery for use with a miner's cap lamp which is given by way of example only with reference to the accompanying single partly cut-away perspective view. The battery has two cells accommodated in a container 2 made as a single moulding of a polycarbonate plastics material and separated from one another by an integral intercell partition 4. The two cells are sealed by a common inner lid 6 which is connected to the walls of the container 2 and the partition 6 by the method known as "heat sealing" in which the edges to be joined are placed in contact with opposite surfaces of a heated tool which is subsequently withdrawn and the partially melted edges are pressed together.The battery is capped by a further outer lid 8 which is secured to the container and locked in position by means which form no part of the present invention. The container is provided with two integral belt loops on its rear face (not shown) for attaching to a miner's belt, and with a rib or thickened portion 3 at each edge to provide structural strength.

Each cell contains a plurality of positive plates 10 interleaved with a plurality of negative plates 12 separated from one another by separators 14 of microfine glass whose composition and function will be described below.

The positive plates 10 and negative plates 12 are formed from a conventional expanded lead alloy and carry positive and negative active electrode material respectively.

The positive and negative plates are interconnected by a respective positive and negative group bar 16 and 18. integral with the negative group bar in the left hand cell as shown in the Figure is a laterally projecting portion which terminates in a "flag" or upstanding portion 20 which is adjacent to the intercell partition 4 and overlies a hole 22 in the partition.The positive flag in the left hand cell is connected to the similar negative flag in the right hand cell through the hole 22 so as to form an intercell connection by a method known as "extrusion-fusion". This method comprises placing welding jaws against the two opposed flags before the inner lid 6 is placed in position, applying pressure so that the flags distort and meet in the hole 22 and then passing an electric current between the two welding jaws so that the material of the two flags is melted together and seals the hole 22.

The negative group bar in the left hand cell and the positive group bar in the right hand cell are also each provided with a flag 24 overlying a hole in the container 2. Each of the flags 24 is connected by a similar "extru sion4usion" process to a lug 26 outside the wall of the container 2 but within a space defined by the outer lid 8. The lugs 26 are connected to a respective connecting wire of a connecting lead 28 for connecting the battery to a miner's cap lamp.

The connecting lead 28 is provided with a series of circumferential grooves 30 at one end, around which a grommet 32 of elastomeric material is moulded. At its lower end the grommet has a circumferential groove 34, and the grommet is force-fitted into a hole in the external lid 8 until the groove 34 is engaged by the periphery of the hole. The connecting lead is therefore firmly connected to the battery, and a force applied to it will be borne by the lid 8 and not by the connections of the connecting wires to the lugs 26.

Each cell of the battery is normally sealed, that is to say that during normal operation of the battery the cells do not communicate with the atmosphere. However in case a substantial over-pressure should build up in the cells, for instance because the cell is exposed to a very high temperature or over-charged, so that gas is evolved at a faster rate than it can be combined, a relief valve is provided to exhaust the excess gas. Each valve is of the Bunsen type and comprises a passage 36 communicating with the interior of a cell and leading to the space between the interal and external lids 6 and 8. Each passage 36 is within a boss in a respective recess 38 in the internal lid, and the boss is sealingly covered by a resilient cap 40 having a depending skirt around the boss.

The cap 40 normally seals the passage 36, but if an excessive pressure should occur in the battery the skirt of the cap lifts away from the boss to vent the cell. A downwardly extending projection 42 on the outer lid 8 engages each cap 40, thus ensuring that it is not blown off by the gas pressure.

As mentioned above, the separators must be highly absorbent and also hydrophilic, and in the preferred embodiment are of unwoven, short staple fibre glass material. Sheets of such material have an extremely high surface area, and a correspondingly small diameter capable of retaining the battery electrolyte within the separators themselves. The material used preferably has an extremely high surface area per unit weight, and such material has a high heat of wetting, a high retentivity of electrolyte per unit volume of material and is very flexible. The diameter of the fibres in such material may be in the range of 0.2 to 10 microns and the surface area may be from 0.1 to 20 square metres per gramme of material.Such material is not only highly electrolyte-retenti"e, but also promotes the recombination of gases within the cells possibly due to adsorption of the gases on its surface.

When the electrolyte, in this case sulphuric acid, is added to the cell it is added in a very limited quantity, that is to say much less is added than in the case of a conventional fully flooded cell. The electrolyte that is added is substantially all absorbed and retained by the separators and there is substantially no free electrolyte in the cells. This reduced electrolyte condition is important not only because it is desirable to have as little electrolyte as possible in a battery used under mining conditions having regard to safety and spillability but also because this condition is conductive to recombination of the gases within the cell.

Thus, in use, the battery is normally sealed and any gases evolved will be forced to recombine, either with each other in case of hydrogen and oxygen or with a negative plate in the case of oxygen alone, by virtue of the over pressure in the battery and of the conducive effect of the presence of the microfine glass material and the reduced eletrolyte conduction. The battery will therefore generally operate at above atmospheric pressure, and the relief valves only open if the pressure becomes excessive, say 5 to 10 pounds per square inch.

Due to the fact that the cells rarely if ever communicate with the atmosphere, the battery will not need topping up with electrolyte and is therefore maintainance free. Furthermore the battery is unspillable and may be used in any orientation firstly because it is sealed and secondly because there is substantially no free electrolyte in the cells, the electrolyte being retained within the microfine glass separators. The fact that the cells are sealed also means that no spark or explosion can propagate from the atmopshere into the battery or vice versa.

Finally the vents and electrical connections are all beneath the outer lid 8 which is not readily removable and this coupled with the anchoring of the connecting lead 28 renders the battery virtually immune to the arduous conditions to which it may be subjected under mining conditions.

In a modified embodiment the battery container 2 and the lids 6 and 8 are made of polypropylene reinforced by small glass spheres which increase its rigidity, toughness and abrasion resistance.

Claims (13)

1. An electric battery having two or more cells for use with a miners cap lamp in which the cells are sealed by a common inner lid, the battery further having a common outer lid extending substantially over the entire area of the inner lid and together with the inner lid defining a space accommodating the terminal connectors and a safety valve for each cell.

2. A battery as claimed in Claim 1 in which the positive and negative plates in each cell are separated by separators of microfine glass material, the cells being normally sealed so that they can operate at above atmospheric pressure and containing a reduced amount of electrolyte substantially all of which is absorbed and retained by the plates and the separator material.

3. A battery as claimed in Claim 1 or Claim 2 in which the or each intercell connection is beneath both the inner and outer lids.

4. A battery as claimed in any one of the preceding Claims in which the two terminal connectors are on the same side of the battery container and outside it, and are accommodated within a space defined by the outer lid.

5. A battery as claimed in Claim 2 or Claims 3 or 4 when dependent on Claim 2 in which the separator material is a non-woven, short staple fibre glass material.

6. A battery as claimed in Claim 5 in which the fibres have a surface area between 0.1 to 20 square metres per gramme.

7. A battery as claimed in any one of the preceding Claims including a safety valve for each cell adapted to vent the cell at a pressure of more than 5 pounds per square inch.

8. A battery as claimed in any one of the preceding Claims in which the container and the or each intercell partition is formed of polycarbonate material.

9. A battery as claimed in any one of the preceding Claims in which the positive and negative plates comprise a grid of expanded metal carrying active electrode material.

10. A battery as claimed in any one of the preceding Claims in which the or each intercell connection is formed by applying pressure to upstanding flags connected to group bars of opposite polarity in adjacent cells so as to press them into contact through a hole in the intercell partition and passing an electric current between the two flags so as to weld them together.

11. A battery as claimed in any one of the preceding Claims in which each terminal connector is connected to a respective group bar by applying pressure to it, or a member integral with it and to a flag connected to the group bar so as to press them into contact through a hole in the container wall and passing an electric current between them so as to weld them together.

12. A battery as claimed in any one of the preceding Claims in which a connecting lead connected to the terminal connectors passes through a hole in the outer lid and is secured therein by means of a resilient grommet moulded onto the lead.

13. An electric battery or use with a miner's cap lamp substantially as herein described with reference to the accompanying drawing.