Oxygen generators

Abstract

A chemical core for an oxygen generator. The chemical core is capable on ignition of producing oxygen by chemical reaction. A first end of the chemical core has a smaller cross-sectional area than a second end of the chemical core such that the ratio of the cross-sectional area of the second end to the cross-sectional area of the second end is 0.20:1 or more.

Claims

1. A chemical core for an oxygen generator, the chemical core being capable on ignition of producing oxygen by chemical reaction, the chemical core comprising: a first cylindrical portion; a tapered portion; and a second cylindrical portion of smaller cross-sectional area than the first cylindrical portion, wherein: the first cylindrical portion is positioned at a first end of the chemical core, the second cylindrical portion is positioned at a second end of the chemical core, and the tapered portion is positioned between the first cylindrical portion and the second cylindrical portion, and the first end of the chemical core has a larger cross-sectional area than the second end of the chemical core such that the ratio of the cross-sectional area of the first end to the cross-sectional area of the second end is 1.20:1 or more.

2. A chemical core as claimed in claim 1, comprising metal chlorate or perchlorate.

3. A chemical core as claimed in claim 1, comprising a catalyst and a fuel.

4. An oxygen generator comprising: an insulated housing comprising a first end and a second end opposite the first end; a chemical core as claimed in claim 1 positioned within the insulated housing so that the second end of the chemical core is at the second end of the insulated housing; an ignition apparatus positioned at the first end of the insulated housing, for igniting a first end of the chemical core; an oxygen outlet positioned at the second end of the insulated housing, for outputting oxygen produced by the chemical core; a filter positioned within the second end of the insulated housing between the chemical core and the oxygen outlet, the filter being capable of removing at least one reaction product produced by the chemical reaction of the chemical core.

5. An oxygen generator as claimed in claim 4, wherein the filter is cylindrical.

6. An oxygen generator as claimed in claim 4, wherein the filter extends towards the first end of the insulated housing between the outer surface of the chemical core and the inner surface of the insulated housing.

7. An oxygen generator as claimed in claim 4, further comprising a cooling chamber positioned within the insulated housing having an inlet through which oxygen produced by the chemical core enters into the cooling chamber and an outlet through which cooled oxygen exits to the oxygen outlet.

Description

DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

(2) FIG. 1 is a cross-sectional view of a known oxygen candle;

(3) FIG. 2 is a cross-sectional view of an oxygen candle according to a first embodiment of the invention;

(4) FIG. 3a is a perspective view of the chemical core of the oxygen candle of the first embodiment;

(5) FIG. 3b is a cross-sectional view of the candle core with measurements shown;

(6) FIG. 4 is a graph showing the oxygen output over time of the known oxygen candle and the oxygen candle of the first embodiment;

(7) FIG. 5 is a cross-sectional view of an oxygen candle according to a second embodiment of the invention; and

(8) FIG. 6 is a cross-sectional view of an oxygen candle according to a third embodiment of the invention.

DETAILED DESCRIPTION

(9) An oxygen candle in accordance with a first embodiment of the invention is now described with reference to FIGS. 2 and 3.

(10) Similarly to the known oxygen candle 1 shown in FIG. 1, the oxygen candle 100 of the first embodiment comprises an insulated housing 1 comprising an ignition apparatus 4 at a first end and an oxygen outlet 5 at a second end opposite the first end.

(11) Again similarly to the known oxygen candle 1, the oxygen candle 100 comprises a chemical core 102, which is also shown in FIG. 2. However, while the chemical core 2 of the known oxygen candle 1 is cylindrical in shape, the chemical core 102 of the oxygen candle 1 has a first cylindrical section 101a, a tapered portion 101b, and second cylindrical portion 101c of narrower diameter than the first cylindrical section 101a. (Each of the first cylindrical section 101a, tapered portion 101b, and second cylindrical portion 101c is circular in cross-section.) The first cylindrical section 101a of the chemical core 101 is positioned at the first end of the oxygen candle 100 adjacent to the ignition apparatus 4, and the second cylindrical section 101c of the chemical core 101 is positioned at the second end of the oxygen candle 100 adjacent to the oxygen outlet 5.

(12) As shown in FIG. 3a, the first cylindrical section 101a has a diameter of D.sub.1 and the second cylindrical section 101b has a diameter of D.sub.2. The sections have cross-sectional areas of D.sub.1.sup.2/4 and D.sub.2.sup.2/4 respectively, and the ratio of D.sub.1.sup.2/4 to D.sub.2.sup.2/4 is 1.4 to 1, i.e. D.sub.1.sup.2:D.sub.2.sup.2 is 1.4:1.

(13) FIG. 3b is a cross-sectional view of the chemical core 101, with measurements included. It will be appreciated that in practice, the first cylindrical section 101a and the second cylindrical section 101b will also be slightly tapered, as chemical cores are conventionally manufactured by being pressed within a mould and so a slight taper aids in the release of the chemical core from the mould.

(14) As can be seen from FIG. 3b, the first cylindrical section 101a is of length 50 mm, the tapered section 101b is of length 7 mm, and the second cylindrical section 101c is of length 50 mm. The diameter of the first cylindrical section 101a is 50.6 mm at its widest end, tapering slowly to 49.73 mm at its end adjacent to the tapered section 101b. The tapered section 101b then tapers very quickly to 43 mm at its end adjacent to the second cylindrical section 101c. The second cylindrical section 101c then tapers slowly again to 42.13 mm at its narrowest end. From these measurements it can be calculated that the ratio of the cross-sectional area of the first cylindrical section 101a to the second cylindrical section 101a is at least 1:33 (comparing the narrowest part of the first cylindrical section 101a to the widest part of second cylindrical section 101a), at most 1:44 (comparing the widest part of the first cylindrical section 101a to the narrowest part of second cylindrical section 101a), and is 1:39 taking the midpoint of the sections 101a and 101c. (This compares to a maximum ratio of 1:1.1 for a conventional chemical core that tapers slowly all along its entire length, without any rapidly tapering section.)

(15) Again similarly to the known oxygen candle 1, the oxygen candle 100 comprises a filter 102 at the second end of the oxygen candle 1, between the oxygen outlet 5 and the chemical core 101. However, the filter 102 is cup-shaped, so as well as having a disk-like portion that covers the entire inner surface of the insulated housing 3 of the oxygen candle 100, the filter 102 extends up the gap between the insulated housing 3 and the chemical core 101, so that its inside surface covers the outer surfaces of the second cylindrical portion 101c and tapered portion 101b of the chemical core 101, and its outer surface covers the facing inner surfaces of the insulated housing 3.

(16) As with the known oxygen candle 1, when a supply of oxygen is required from the oxygen candle 100, the ignition apparatus 4 is rotated to initiate the chemical reaction that releases the oxygen from the chemical core. The oxygen is initially released from the end of the chemical core 101 at the first end of the oxygen candle 1, and again passes along the sides of the chemical core 101 within the insulated housing 3 along the arrows marked A, towards the oxygen outlet 5 at the opposite end of the oxygen candle 6. However, in the present embodiment the oxygen passes through the filter 102 in the regions of the tapered portion 101b and second cylindrical portion 101c of the chemical core 101, as well in the region between the end of the chemical core 101 and the oxygen outlet 5. It has been found that this results in much more effective removal of unwanted reaction products from the oxygen supply by the filter 102.

(17) In addition, this configuration has been found to provide an improved oxygen supply. FIG. 4 is a graph showing amount of oxygen L (in litres) output over time t (in minutes) by the known oxygen candle 1 and the oxygen candle 100 of first embodiment.

(18) The output of the known oxygen candle 1 is shown by the line 200. As can be seen, initially at around 2 minutes the amount of oxygen output peaks at around 14 litres, and then drops down to around 7 litres before slowly increasing to a second peak of around 15 litres at around 14 minutes, and then drops sharply to zero at 16 minutes.

(19) The output of the oxygen candle 100 of the first embodiment is shown by the line 201. In this case, initially the oxygen peaks at around 10 litres, and then continues to output oxygen at around that level until around 16 minutes, when it drops down to zero at 18 minutes. Thus, the oxygen candle 100 of the first embodiment provides both a steadier and a longer supply of oxygen.

(20) An oxygen candle in accordance with a second embodiment of the invention is now described with reference to FIG. 5. The oxygen candle 300 of the second embodiment is similar to the oxygen candle 100 of the first embodiment, expect that instead of the filter 102, the oxygen candle 300 comprises the filter 6 of the known oxygen candle 1.

(21) While this is a less advantageous configuration than that of the oxygen candle 100, the reduced diameter of the end of the chemical core 101, and the corresponding larger gap 301 between the chemical core 101 and the inside of the insulated housing 3, can still result in a steadier and a longer supply of oxygen compared to the known oxygen candle 1. In addition, there is a greater area of surface of the filter 6 around the end of the chemical core 101 through which oxygen will enter, which can result in a more effective removal of unwanted reaction products compared to the known oxygen candle 1.

(22) An oxygen candle in accordance with a third embodiment of the invention is now described with reference to FIG. 6. The oxygen candle 400 of the third embodiment is again similar to the oxygen candle 100 of the first embodiment, expect that instead of the chemical core 101 the oxygen candle 400 comprises the cylindrical chemical core 2 of the known oxygen candle 1. The oxygen candle 300 also comprises a cup-shaped filter 401, except that necessarily the gap that the filter 102 extends up into is only the smaller gap between the insulated housing 3 and the cylindrical chemical core 2.

(23) While again this is a less advantageous configuration than that of the oxygen candle 100, the presence of the filter 401 around the sides of the chemical core 2 can still result in a steadier and a longer supply of oxygen, and a more effective removal of unwanted reaction products, compared to the known oxygen candle 1.

(24) Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein.