Oxygen candles are well-known. Oxygen candles are devices that produce on demand a supply of oxygen by means of a chemical reaction. (The term “chemical reaction” is used herein to exclude electrolytic decomposition and other methods requiring an external source of energy.) An example of an oxygen candle is disclosed in WO 2009/030921 A2 (Molecular Products Group PLC) published 12 Mar. 2009.
A typical oxygen candle comprises a chemical core of an oxygen-containing substance, for example an alkali metal chlorate or perchlorate, in admixture with a catalyst that facilitates lower temperature decomposition of the chemical to oxygen and residual solids. The catalyst may be manganese dioxide or cobalt dioxide, for example, both of which reduce the temperature at which alkali metal chlorates decompose. The chemical core often also comprises a fuel such as iron.
A known oxygen candle is shown in FIG. 1. The oxygen candle 1 comprises a cylindrical chemical core 2 within an insulated housing 3. A first end of the oxygen candle 1 comprises an ignition apparatus 4, which is used to trigger the production of oxygen by the device. The ignition apparatus 4 may for example be a rotatable body, with a surface facing the chemical core 2 coated with a friction-ignitable substance such as phosphorus. A second end of oxygen candle 1 opposite the first end comprises an oxygen outlet 5. Within the insulated housing 3, between the oxygen outlet 5 and the chemical core 2, there is a filter 6, which contains filtration materials such as soda lime. The filter 6 is a disc-like cylinder a surface of which covers the entire inside surface of the insulated housing 3 of the second end of the oxygen candle 1. The oxygen candle 1 may also comprise a chamber (not shown in FIG. 1) to receive oxygen produced by the chemical core, to cool the oxygen before it is outputted through the oxygen outlet 5.
When a supply of oxygen is required, the ignition apparatus 4 is rotated so that the friction-ignitable substance on its coated surface is forced into contact with the surface of the chemical core 2. This causes an exothermic reaction to be generated, which initiates the chemical reaction that releases the oxygen the chemical core contains. The oxygen is initially released from the end of the chemical core 2 at the first end of the oxygen candle 1, and passes along the sides of the chemical core 2 within the insulated housing 3 along the arrows marked A, towards the oxygen outlet 5 at the opposite end of the oxygen candle 6. Before the oxygen passes out of the oxygen outlet 5 it passes through the filter 6, which removes unwanted reaction products from the oxygen supply, such as carbon dioxide, carbon monoxide and chlorine.
It is a disadvantage of the known oxygen candle 1 that not all unwanted reaction products are removed from the oxygen supply by the filter 6. The present invention seeks to solve or mitigate this problem. Alternatively and/or additionally, the invention seeks to provide an improved chemical core and an improved oxygen generator.