GB2322126A - Oxygen candle cover - Google Patents

Abstract

A cover 1 for an alkali metal chlorate candle 2 for producing oxygen is formed from a lightweight moulded material which, in the preferred embodiment, comprises closed cell or partially closed cell silicone foam. The cover has raised areas 3 on its internal surfaces to allow oxygen, produced by the candle 2, to flow across the candle body. The cover reduces heat loss from the candle to the atmosphere or its container.

Description

OXYGEN CANDLE COVER This invention relates primarily to a cover for an alkali metal chlorate candle used to produce oxygen.

To enable oxygen to be released from a candle of alkali metal chlorate (sodium and/or potassium chlorates) it has to be heated. For information, the optimum oxygen release temperature is between 300 and 400 C. It is usual for the temperature to be elevated above this temperature to allow for the loss of heat to the candle container and/or the surrounding atmosphere.

A known method of heating is to mix fine iron powder with the chlorate to act as fuel. The amount of iron added depends on the use of the candle and how it is contained, but is normally about 9% by weight. It is usual to add a "booster mix" and/or a "starter mix" to the candle to ensure a quick start and burn. The booster and starter mix contain a higher percentage of iron than that of the main body. The candle is then mounted in a metal holder with a suitable air gap between the candle and container. A percussion cap or other ignition source is placed in the container.

In use, the iron fuel in the starter or booster is ignited by the percussion cap. As the iron burns, it raises the temperature of the chlorate to produce oxygen.

However, a problem with this system is that the heat loss is so great that the resulting large percentage of iron used to maintain the core temperature renders the unit unstable. This instability can cause the candle to burn erratically and in some cases burn out of control.

It would be desirable to provide a means of limiting the heat loss to enable the percentage of iron to be reduced or even eliminated altogether.

The present invention provides a cover for the candle that greatly reduces the heat loss to the atmosphere or container. The cover only allows the ignition point and gas transfer area (to the delivery system) to be uncovered.

Preferably the cover is made from a lightweight material that can be readily moulded or formed to suit the design of the candle. In a preferred embodiment, the material is a flexible closed cell or partially closed cell silicone foam.

Preferably the cover has periodic raised areas on its internal surfaces to allow the oxygen to flow along and across the candle body.

The cover can be either a stand alone unit or it can form the inner insulation material of a fixed or reusable system.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing which is a longitudinal cross section of candle cover, forming a first embodiment of the present invention, shown in use.

It will be appreciated that alternative designs of candle and cover shape fall within the scope of the present invention.

The drawing shows a cover for an oxygen candle forming a first embodiment of the present invention.

The cover 1 is formed from partially closed cell silicone foam which is chemical resistant, flame retardant, flexible and a very good insulator.

The skilled person will appreciate that it would be possible to use an open or closed cell foam of a lesser specification and coat it with a flame retardant and/or chelEUal.

resistant material.

A chlorate candle 2 is held away from the inner surface of the cover 1, by raised areas 3 thereon, to allow the oxygen to escape from the candle.

The candle cover may be manufactured using a number of methods of which the following are examples: A first method is to mould the candle cover in one piece by forming the foam material within a suitable mould. Ignition points and container location points could be moulded in to form an integral unit.

A second method is to cut the required shape from sheet material and either weld, stitch or glue the pieces together.

A third method is to cut the required shape from sheet and wrap it around the candle and secure it with wire or tape. This method would also allow the cover to be wrapped around the inside of a container without any securing or bonding.

The candle cover I of the first embodiment is used as follows. The chlorate candle 2 is placed inside the candle cover 1. This assembly is then placed in an existing candle holder and oxygen distribution system where it is ignited. The gas produced passes into the existing system in the known manner.

The ability to reduce the radiated and/or conducted heat allows the fuel content of the candle to be reduced and consequently produces a much more stable process.

It will be understood that various modifications may be made to the described embodiment and it is intended to include all such modification and variations as fall within the scope of the present invention.

Claims (8)

CLAIMS :

1. A cover for preventing heat loss from an alkali metal chlorate candle for producing oxygen.

2. A cover as claimed in claim 1, adapted to receive, and cover substantially the whole surface of, a chlorate candle.

3. A cover as claimed in claim 1 or claim 2, wherein the cover is formed from a moulded lightweight material.

4. A cover as claimed in claim 1, 2 or 3, wherein the cover is formed from an insulating material.

5. A cover as claimed in any preceding claim, wherein the cover is formed from an open or closed cell foam.

6. A cover as claimed in claim 5, wherein the foam is silicone foam.

7. A cover as claimed in any preceding claim, comprising raised areas on its internal surfaces to allow the oxygen to flow across the candle body.

8. A cover for an alkali metal chlorate candle for producing oxygen, substantially as hereinbefore described, with reference to the accompanying drawing.