Pyrogen and canister incorporating pyrogen

The pyrogen of the invention is formed by the compression of ferrosilicon powder and a mixture of ferric oxide powder and another lower order iron oxide powder. This pyrogen overcomes the weaknesses inherent in earlier pyrogens by dispensing with the use of peroxides. The scope of the invention also extends to the canister which holds the pyrogen. The pyrogen, which is positioned inside the canister's combustion chamber in such a way that it comes into contact with the top of said combustion chamber, is supported by a special ceramic thermal insulator which contains an ignition device comprising an ignition agent, which also incorporates an instant high temperature generating ignition material, and a match head chemical which projects out of a hole in the base cover of the canister. The bottom of the canister is covered by a bottom cap which can be freely removed or replaced as required. The canister, which enables the heating or cooking of whatever is placed inside it, is compact, safe and cheap.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a pyrogen, which depends for its heating effect on 
a metal redox reaction, and a self-heating canister which incorporates 
said pyrogen and which is used either to cook or simply to heat up various 
foodstuffs such as grains, noodles and beverages. 
2. Description of the Prior Art 
A substantial number of proposals have already been made in respect of 
pyrogens which make use of the exothermic oxidation of metals (for 
example: Japanese patent publication gazette S27-582, Japanese utility 
model laying open gazette S58-24119, and Japanese patent laying open 
gazette S62-17287, S63-51491, and H1-284582). All these proposals have 
involved the admixture of metal oxides and peroxides to one or more of the 
powders of iron, aluminum and ferrosilicon. 
When a pyrogen which makes use of peroxides in this way burns, however, the 
peroxides not only react with the Si but also break down through a process 
of pyrolysis. This results in the freeing of oxygen gas which in turn 
facilitates the generation of sparks and flames which are sometimes 
emitted from the container thereby creating an obvious hazard. Another 
drawback with this type of pyrogen derives from a tendency to swell 
rapidly following combustion and to assume a sort of spongelike form under 
the influence of the aforementioned free oxygen gas. 
Japanese patent laying open gazette H1-288218, on the other hand, disclosed 
the use of a pyrogen composed of ferrosilicon powder plus one or both of 
the substances Fe.sub.2 O.sub.3 and CuO. Since the pyrogen does not in 
this case contain peroxides, the amount of oxygen gas which is freed is 
considerably reduced but even so, since it is not, in fact, altogether 
eliminated, the aforementioned problem of the swelling and deformation of 
the pyrogen following combustion remains. 
SUMMARY OF THE INVENTION 
In order to solve the problems outlined above, the inventors conducted a 
number of tests and studies as a result of which they perfected the 
pyrogen of the invention which is characterized by the fact that it is an 
oxide which has the potential to remain stable at high temperatures while 
at the same time giving up oxygen to the Si. 
The pyrogen of the invention is formed by the compression of a metal powder 
and a metal oxide powder where said metal powder consists of powdered 
ferrosilicon and said oxide powder consists of a mixture of powdered 
ferric oxide (Fe.sub.2 O.sub.3) and another powdered iron oxide of a lower 
order (Fe.sub.2 O.sub.3 -x where x=0.2 to 1.0). In this pyrogen said 
mixture of ferric oxide powder with a powdered iron oxide of a lower order 
performs the role of oxygen donor, thereby dispensing with the need for a 
peroxide to act as said donor. During combustion, therefore, the pyrogen 
does not produce free oxygen, with the result that the pyrogen itself does 
not swell and the combustion process is able to proceed at a smooth and 
easy pace without the generation of sparks or flames. The invention can 
thus be used either to cook or simply to heat up various foodstuffs, 
thereby making it a perfect portable heat source. 
A self-combusting pyrogen which derives its heat from the exothermic 
oxidation of powdered metal offers the advantage of generating a higher 
level of heat during the course of a reaction than is produced by the more 
conventional lime based pyrogens which make use of the heat which is 
generated by the addition of water of quick lime. For this reason, it has 
proved possible to generate sufficient heat with the pyrogen of the 
invention to produce boiling, a function which has not hitherto been 
achievable using lime based pyrogens. This in turn raised the possibility 
of creating some sort of canister in which to incorporate such a boiling 
function based on the utilization of this type of self-combusting pyrogen. 
However, if this type of canister is to be produced on a commercial basis 
then the complexity of the thermal insulation structure required would be 
likely to necessitate the use of a fairly large canister while the sort of 
ignition device required to generate the high ignition temperature needed 
by the heating agent would almost certainly force up the container's 
production costs and taken together these drawbacks would impair its 
practical value as a disposable canister. 
In order to solve the problems outlined above, the inventors conducted a 
number of tests and studies as a result of which they successfully 
developed the canister of the invention which is characterized by the 
compactness and high heat generation of the pyrogen and its accompanying 
thermal insulator and the rational structure of the related ignition 
device. 
The object of the invention is to provide a cheap, safe canister which 
calls simply for the adjustment of the amount of pyrogen to enable it to 
be used to heat a variety of different foodstuffs ranging from those which 
are sometimes referred to as "fever foods" (hereafter referred to simply 
as "FF") and which require boiling or proper cooking such as grains like 
rice, cereals and beans or noodles such as udon, soba or instant ramen 
through to those which are sometimes referred to as "fever drinks" 
(hereafter referred to simply as "FD") and which only require warming up 
at a single predetermined temperature such as sake, coffee, tea and other 
similar drinks and prepared foods such as western type soups, miso soup 
and rice porridge. 
In order to achieve this object, the canister of the invention has been 
designed such that the lower part of the canister incorporates a 
combustion chamber which in turn houses a pyrogen which comes into direct 
contact with the top of said combustion chamber and which is formed by the 
compression of ferrosilicon powder and a suitable mixture of ferric oxide 
powder and a powdered iron oxide of a lower order. The pyrogen itself is 
in turn supported by a special ceramic thermal insulator with a hole 
through the middle. The hole in the middle of the thermal insulator is 
packed with an ignition device which comprises two distinct layers of 
material, the upper layer consisting of an instant high temperature 
generating ignition material and the lower layer consisting of an ignition 
agent, along with a match head chemical which protrudes from the bottom of 
said ignition device out through a hole in the base cover of the canister. 
The bottom of the canister itself is fitted with a cap which is designed 
such that it can easily be removed or replaced as necessary. The use of a 
solid pyrogen in combination with a thermal insulator made of a special 
highly heat resistant ceramic have together facilitated the creation of a 
more compact, lighter weight canister and this has in turn enabled a 
reduction of approximately 60% in the cubic capacity of the combustion 
chamber compared with that of a more conventional canister. As a result it 
is now possible to heat a given volume of material to a given temperature 
using an aluminum canister which is approximately 25% lighter in weight 
than the sort of conventional canister which would have been necessary to 
heat an identical volume of material to an identical temperature. 
Moreover, whether it is used for FF or for FD purposes, the canister of the 
invention accepts part of the food contents into the space between the 
outer wall of the combustion chamber, and the inner wall of the main body 
of the canister itself, at least for the upper part of the combustion 
chamber, and this serves to increase the overall adiabatic effect in this 
part of the canister. Particularly in cases where the canister is 
structured such that the pyrogen is supported by projections on the upper 
surface of the thermal insulator, an air-filled layer is created in the 
space between the pyrogen and the insulator and this further enhances the 
adiabatic effect while at the same time increasing the safety of the 
canister's design. 
The pyrogen used in the canister of the invention has a high combustion 
temperature (normally about 1,400.degree. C.) and is, therefore, fully 
capable of supporting the sorts of temperatures required for the boiling 
or warming of foodstuffs and it has been possible, as a result, to achieve 
very substantial reductions by comparison with conventional canisters in 
the length of time required from the point of ignition through to the 
point at which the food or drink in the canister is ready for consumption. 
Furthermore, since the aforementioned pyrogen does not change into a 
powdered form following combustion and since it also exhibits only minimal 
cubical expansion, disposal after use is easy. The thermal insulator 
referred to above is itself a specially manufactured compact, light weight 
ceramic with outstanding heat resisting characteristics. This enables 
substantial reductions in the level of external heat emission from the 
canister while at the same time facilitating the achievement of more 
thermally efficient boiling and heating operations. In the case of 
canisters used for the heating of FD, there is a space of constant size 
between the wall of the combustion chamber and the inner wall of the 
canister and this creates an overheat protection effect. Also, in the case 
of canisters used for the heating of FF, which are constructed in such a 
way that the lower part of the thermal insulation comes directly into 
contact with the inner wall of the canister, a similar overheat protection 
effect is nevertheless afforded by the fact that the inner wall of the 
canister in the vicinity of the upper half of said thermal insulation from 
which a significant amount of heat is emitted, is normally in contact with 
some sort of liquid or steam. There is, moreover, a layer of air 
sandwiched between the bottom cap and the base cover of the canister which 
serves to eliminate the risk of overheating or burning of articles close 
to the canister as a result of an abnormal temperature rise in the body of 
the canister itself, even when using a pyrogen with an extremely high 
combustion temperature. 
The ignition device consists of a combination of a low temperature ignition 
agent and an instant high temperature generating ignition material. It is 
thus possible to ignite the pyrogen quickly and easily using a match head 
chemical while at the same time keeping to a minimum the amount of 
canister space required to house the ignition device itself. The canister 
is also fitted with its own water pack in cases where it is to be used for 
the purpose of boiling FF type foods such as rice. Moreover, since the 
pack itself is made of a quick melting material, even if the user forgets 
to empty the contents of the water pack over the rice but still ignites 
the canister, once the water starts to boil the high temperature inside 
the water pack will quickly melt the pack material, thereby releasing the 
water and preventing the canister from boiling dry. 
Since the component parts such as the pyrogen, the thermal insulation 
material and the ignition device, which make up the interior of the 
combustion chamber, have been made more compact than those used in more 
conventional canisters, it is now possible to use a smaller canister than 
would previously have been required to heat up any given amount of food or 
drink. Since the component parts themselves are also cheap, the production 
cost per canister is low and this makes the final product well suited to 
use as a self-heating, throw-away canister. 
The use of a powerful fireproof adhesive to cement the connections between 
the canister parts and the pyrogen and thermal insulation materials, for 
example, also helps keep the cost of production down while at the same 
time increasing the design safety of the finished product by making it 
more difficult to disassemble.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Basically any pyrogen made by compressing ferrosilicon powder and a 
suitable mixture of ferric oxide powder (Fe.sub.2 O.sub.3) and a powdered 
lower order oxide of iron (Fe.sub.2 O.sub.3-x where x=0.2 to 1.0) would 
constitute a valid example of the preferred embodiment. However, if a 
really excellent level of performance is to be obtained, then the metal 
constituents must each conform to their respective specifications as 
detailed below. 
First, the amount of ferrosilicon powder added to the mixture should 
ideally be between 20 and 35 parts by weight. The reason for this is that 
anything less than 20 parts increases the tendency of the mixture to burn 
erratically, thereby impairing the smoothness of the combustion process. 
The addition of more than 35 parts of ferrosilicon, on the other hand, 
tends to reduce the amount of heat generated per unit of weight. The ideal 
average diametric size of the particles of ferrosilicon powder is 20 
microns. The reason for this is that an average particle size of more than 
20 microns tends to make the final mixture more difficult to ignite, 
thereby impairing the overall smoothness of the combustion process. The Si 
content of the ferrosilicon itself should be at least 75%. 
The amount of ferric oxide added to the mixture should ideally be between 
10 and 50 parts by weight. The reason for this is that the addition of 
less than 10 parts by weight may result in an excessive reduction in the 
strength of the pyrogen after compression while the addition of more than 
50 parts may result in an excessive reduction in the effect obtained 
through the addition of iron oxides of a lower order (Fe.sub.2 O.sub.3-x). 
The ideal average diametric particle size of the ferric oxide powder is 10 
microns or less. Impurities in the ferric oxide such as S, Cl and SO.sub.3 
should also ideally be kept to a minimum. 
The lower order iron oxide Fe.sub.2 O.sub.3-x powder referred to above can 
easily be obtained by the partial reduction of ferric oxide (Fe.sub.2 
O.sub.3). It is also possible to use substances obtained through the 
neutralization oxidation of bivalent Fe, for example, or else a fine 
particulate of a naturally occurring low order oxide iron ore. Magnetite, 
which is a triiron tetroxide (Fe.sub.3 O.sub.4) in which the x value of 
Fe.sub.2 O.sub.3-x is approximately 0.33, is particularly suitable for use 
as the principal lower order iron oxide since it is both cheap and easy to 
obtain. Triiron tetroxide also has a number of other outstanding features 
in that it is, for example, even more stable than ferric oxide at high 
temperatures, it does not easily give up oxygen even in response to the 
heat of combustion of Si, it tends to absorb free oxygen released by the 
ferric oxide and it is thus conducive to the suppression of problems such 
as cracking or expansion of the pyrogen following combustion. Moreover, by 
using triiron tetroxide in combination with an Fe.sub.2 O.sub.3 -x in 
which the x value is between 0.2 and 1.0, the combustion process is 
rendered more gentle than that produced by a pyrogen which uses only 
ferric oxide to contribute oxygen to the Si. It is possible, therefore, in 
this sort of case to adjust the speed of the combustion process itself. 
The amount of said lower order iron oxide powder Fe.sub.2 O.sub.3 -x added 
to the mixture should ideally be between 20 and 60 parts by weight. The 
reason for this is that the addition of less than 20 parts by weight would 
tend to lead to a reduction in the effect obtained by adding a lower order 
iron oxide (Fe.sub.2 O.sub.3 -x) to the mixture while the addition of more 
than 60 parts by weight, on the other hand, would tend to reduce the 
amount of heat generated per unit of weight while at the same time leading 
to a reduction in the strength of the mixture after forming. The ideal 
average diametric size of the particles of the lower order iron oxide 
Fe.sub.2 O.sub.3 -x is 10 microns or less. The powdered lower order iron 
oxide Fe.sub.2 O.sub.3 -x should preferably contain only minimal amounts 
of the types of impurities which are likely to become gaseous at high 
temperatures. Although it would be possible to facilitate the adjustment 
of the speed of combustion of the Si and Fe.sub.2 O.sub.3 by incorporating 
into the pyrogen substances such as alumina, silica or powdered rock which 
would not act as oxygen donors, the problem is that even the addition of 
only very small amounts of such substances tends to result in the 
impairment of smooth combustion and may even result in premature 
termination of the combustion process. The addition of such substances 
should, therefore, be avoided wherever possible. 
The aforementioned pyrogen can be compressed into a variety of shapes such 
as pillar or plate shapes as required. Powdered ferrosilicon combined with 
a suitable mixture of powdered ferric oxide and a lower order iron oxide 
powder could also, for example, be compressed without further preparation 
in a metal mold to between 200 and 500 kg/cm.sup.2. A similar mixture 
could, on the other hand, be compressed to just 100 to 300 kg/cm.sup.2 
after the addition of between 1.0% and 3.% of some sort of non-combustible 
ceramic based binder. 
Preferred embodiments No.1 to No.12 of the pyrogen will now be described in 
some detail. 
PREFERRED EMBODIMENT NO.1 
30 parts by weight of a ferrosilicon (Fe: 25%, Si: 75%) particulate with an 
average diametric particle size of 8 microns, 30 parts by weight of an 
Fe.sub.2 O.sub.3 particulate with an average diametric particle size of 2 
microns and 40 parts by weight of a magnetite (mainly Fe.sub.3 O.sub.4, 
x=0.33) particulate were mixed together to form 15 g of powder which was 
then placed inside a metal mold with a diameter of 3 cm and compressed at 
300 kg/cm.sup.2 to form a pyrogen of 1.0 cm in thickness. 
The pyrogen 2 was first placed on top of the thermal insulator 3 shown in 
FIG. 1. Approximately 0.2 g to 0.3 g of a mixture of iron, ferrosilicon, 
copper oxide and barium peroxide powders was then placed more or less in 
the center of said pyrogen 2 to act as an ignition agent 4. 180 ml of 
water 5 at a temperature of 20.degree. C. was then poured into the 
aluminum canister 1 shown in FIG. 1 and then, after igniting the 
aforementioned ignition agent with a match, the pyrogen 2 was immediately 
inserted into the recession in the base of the aluminum canister 1 along 
with the thermal insulator 3. At the end of 5 minutes the temperature of 
the water was measured and was found to have risen to 51.degree. C. It was 
also found that the pyrogen 2 continued to burn gently after it was 
inserted into the bottom of the aluminum canister 1 and that the diametric 
expansion of the pyrogen 2 after combustion was no more than 1.0 mm. 
PREFERRED EMBODIMENTS NO. 2 AND NO. 3 
Apart from altering the Fe.sub.2 O.sub.3 and the Fe.sub.3 O.sub.4 mixture 
ratios, the rise in the temperature of the water was in each case measured 
under exactly the same conditions as those described in connection with 
preferred embodiment No. 1 above. The results of the measurements taken 
are shown in Table 1 below. The combustion of the pyrogens proceeded 
smoothly in each case while the expansion of the pyrogens following 
combustion was again no more than 1.0 mm in either case. 
TABLE 1 
______________________________________ 
Water 
Preferred temperature 
Absolute rise in 
embodiment 
Fe.sub.2 O.sub.3 
Fe.sub.3 O.sub.4 
after 5 temperature 
No. (%) (%) minutes (.degree.C.) 
(.degree.C.) 
______________________________________ 
No. 2 10 60 49 29 
No. 3 50 20 53 33 
______________________________________ 
PREFERRED EMBODIMENTS NO. 4 TO NO. 7 
Apart from altering the Fe.sub.2 O.sub.3 and the Fe.sub.3 O.sub.4 mixture 
ratios, the rise in the temperature of the water was in each case measured 
under exactly the same conditions as those described in connection with 
preferred embodiment No. 1 above. The results of the measurements taken 
are shown in Table 2 below. The degree of diametric expansion measured in 
each of the pyrogens following combustion is also indicated in the table. 
TABLE 2 
______________________________________ 
Absolute 
Preferred Water temp. 
rise in 
Expan- 
embodiment 
Fe.sub.2 O.sub.3 
Fe.sub.3 O.sub.4 
after 5 temp. sion 
No. (%) (%) mins. (.degree.C.) 
(.degree.C.) 
(mm) 
______________________________________ 
No. 4 70 0 54 34 3-5 
No. 5 65 5 54 34 2-3 
No. 6 5 65 44 24 1 max. 
No. 7 0 70 44 24 1 max. 
______________________________________ 
Although the expansion of the pyrogens in each of the preferred embodiments 
No. 6 and No. 7 did not exceed 1.0 mm, a limited amount of cracking was 
found to have occurred in each of the pyrogens following combustion while 
some 3.0 g to 4.0 g of the pyrogens remained uncombusted in both cases. 
PREFERRED EMBODIMENTS NO. 8 TO NO. 10 
Apart from altering the amount of ferrosilicon (Fe: 25%, Si: 75%) added to 
the mixture, the rise in the temperature of the water was in each case 
measured under exactly the same conditions as those described in 
connection with preferred embodiment No. 1 above. The results of the 
measurements taken are shown in Table 3 below. 
TABLE 3 
______________________________________ 
Absolute 
Preferred Water temperature 
rise in 
embodiment 
Ferrosilicon 
after 5 minutes 
temperature 
No. (%) (.degree.C.) (.degree.C.) 
______________________________________ 
No. 8 35 48 28 
No. 9 25 52 32 
No. 10 20 53 33 
______________________________________ 
In the case of preferred embodiment No. 10, combustion proceeded smoothly 
although some 0.5 g of the pyrogen was left uncombusted. Following 
completion of the combustion process, the expansion of the pyrogens was 
found to measure no more than 1.0 mm in each case. 
PREFERRED EMBODIMENTS NO. 11 AND NO. 12 
Apart from altering the amount of ferrosilicon added to the mixture, the 
rise in the temperature of the water was in both cases measured under 
exactly the same conditions as those described in connection with 
preferred embodiment No. 1 above. The results of the measurements taken 
are shown in Table 4 below. Measurements taken on completion of the 
combustion process indicated that the pyrogens had in neither case 
expanded by more than 1.0 mm. 
TABLE 4 
______________________________________ 
Absolute 
Preferred Water temperature 
rise in 
embodiment 
Ferrosilicon 
after 5 minutes 
temperature 
No. (%) (.degree.C.) (.degree.C.) 
______________________________________ 
No. 11 40 42 22 
No. 12 17 40 20 
______________________________________ 
In the case of preferred embodiment No. 12, some 4.5 g of the pyrogen 
remained uncombusted. 
PREFERRED EMBODIMENT NO. 13 
There now follows a description of the preferred embodiment of a canister 
with a built-in pyrogen as referred to above. FIG. 2 shows an example of 
the sort of canister which is designed primarily for use in the heating of 
FF. 11 in the figure represents the main body of a steel or aluminum 
canister, 12 is a pull-top type lid fitted with a ring pull 12a and 13 is 
the base cover of the canister in the middle of which there is a hole 13a. 
The lid 12 of the canister and the base cover 13 are each secured to the 
main body of the canister by means of wrap around jointing. 14 is an inner 
container the bottom half of which is secured by means of an adhesive in 
such a way that its wall comes into direct contact with the inner wall of 
the main body of the canister 11. Said inner container forms the 
combustion chamber 14a. 15 is the pyrogen held in the upper part of said 
combustion chamber 14a and 16 is a special ceramic thermal insulator which 
supports said pyrogen. More or less in the center of said thermal 
insulator 16 there is a hole into which the ignition device is fitted. The 
ignition device itself comprises an ignition tube 17, which extends 
through the hole in the thermal insulator 16 almost up to the bottom of 
the pyrogen 15, an ignition agent 18 which is packed into the inside of 
the ignition tube, an instant high temperature generating ignition 
material 18a, which is laid on top of the ignition agent 18, thereby 
constituting the top layer of the ignition device at the point where it 
meets the under surface of the pyrogen 15, and a match head chemical 18b 
which is fitted in such a way that it projects from the bottom end of said 
ignition tube through the hole 13a in the base cover 13 of the canister. 
19 is a plastic bottom cap, 19a is a plastic top cap and (S) is a thermal 
insulation sheet which may be laid between the thermal insulator and the 
base cover 13 as and when necessary. 
There now follows a description of a typical way in which the FF type 
canister of preferred embodiment No. 13 above might be used. First of all 
60 g of pyrogen in inserted into the combustion chamber 14a. 140 g of 
processed rice (quick boil rice) (R) is then placed in the upper chamber 
of the canister and a 110 ml pack of water (P) is placed on top of the 
rice. The lid 12 is then put on to seal the main canister 11. In order to 
cook the rice, first the top cap 19a must be taken off, then the pull-top 
lid 12 must be released by means of the ring-pull fitting. Next the water 
pack (P) must be taken out of the canister (if the processed rice is also 
enclosed in a pack then this must also, of course, be removed from the 
canister in the same way) and after opening the pack, all the water should 
then be poured over the rice. The top cap 19a must then be replaced on top 
of the canister. 
The next step is to remove the bottom cap 19 and rub the chemical strip 
(not shown in the drawings), which is secured by an adhesive to the 
underside of the bottom cap or similar position, across the match head 
chemical 18b to strike a light. The flame which is generated in this way 
is immediately relayed by way of the ignition agent 18 and the instant 
high temperature generating ignition material 18a to the solid pyrogen 15 
which begins self-combustion in response. The heat generated at this point 
has been measured at 1,400.degree. C. 
From the moment that the pyrogen 15 is ignited in the manner outlined 
above, it will then take approximately 10 minutes to produce perfectly 
cooked and completely scorch free rice. In the case of rice, however, in 
order to ensure that it is cooked to perfection, it is always advisable to 
leave it to steam for a further 5 minutes after the initial cooking has 
been completed. In addition, while the rice is cooking, the steam which is 
generated will be discharged from the canister by way of a gap in the top 
cap 19a while any hot water which might spurt out from the boiling liquid 
will be trapped by said top cap from where it will run down through a gap 
between the main body of the canister and a thermal insulation sheet (not 
shown in the drawings) which is wound around the canister. 
PREFERRED EMBODIMENT NO. 14 
FIG. 3 illustrates the preferred embodiment of an FD type canister. In the 
drawing 101 is the main body of a canister formed by the deep drawing of a 
sheet metal such as aluminum, for example, and 104 is an inner container 
formed by pressing the middle part of the base of the main body of the 
canister 101 inwards in such a way that the wall of said inner container 
104 forms a combustion chamber 104a with a fixed distance between itself 
and the inner wall of the canister. 102 is the pull-top lid of the 
canister complete with ring-pull 102a and is secured to the main body of 
the canister 101 by means of wrap around jointing. 103 is the base cover 
of the canister with a hole 103a at its center. In just the same way as in 
preferred embodiment No. 13 described above, the aforementioned combustion 
chamber 104a contains a pyrogen 105 along with a thick cylindrical thermal 
insulator 106 made of a special ceramic material with an ignition device 
located more or less at its center. Said ignition device comprises an 
ignition tube 107, which extends up through the hole in the thermal 
insulator 106, an ignition agent 108 which is packed into the inside of 
the ignition tube, an instant high temperature generating ignition 
material 108a, which rests on top of the ignition agent 108 and 
constitutes the top layer of the ignition device, and a match head 
chemical 108b which is fitted in such a way that it projects from the 
bottom end of said ignition tube 107 through the hole 103a in the base 
cover 103 of the canister. The ring shaped protuberance 106a on the upper 
surface of the aforementioned thermal insulator 106 constitutes an 
inseparable part of the insulator 106 itself. 
The aforementioned pyrogen 105 is formed by the compression into a solid 
flat shape of ferrosilicon powder and a suitable mixture of ferric oxide 
powder and a powdered iron oxide of a lower order. The special ceramic 
which is used for the aforementioned thermal insulator 106 consists either 
of a substance composed mainly of silicon and baked to give it a 
sponge-like form or else of a suitable mixture of pearlite and clay. 
Furthermore, both the ignition agent 108 and the instant high temperature 
generating ignition material 108a of the aforementioned ignition device 
are each compounds formed by the mixing of fine particulates of metals and 
metal oxides. Ideally, the constituents of the ignition agent 108 should 
be capable of being easily ignited by a match head chemical and also of 
burning fast. In the case of the top layer of instant high temperature 
generating ignition material 108a, on the other hand, the constituents 
should ideally be capable of supporting a combustion temperature in the 
region of 1,000.degree. C. to 1,500.degree. C. 109 is a plastic bottom cap 
and (S) is a thermal insulation sheet which can be laid between the 
thermal insulator and the base cover 103 as and when necessary. 
There now follows a description of a typical way in which the FD type 
canister of preferred embodiment No. 14 above might be used. First of all 
20 g of the pyrogen 105 is inserted into the combustion chamber 104a. 200 
ml of coffee liquid (D) is then placed in the upper chamber of the 
canister 101 and the can sealed. When the time comes to heat up the 
coffee, first the bottom cap is removed and the chemical strip on the side 
of the cap used to ignite the match head chemical. The bottom cap is then 
replaced and within approximately one and a half minutes the coffee liquid 
inside the canister is heated up to a temperature of about 40.degree. C. 
above the ambient temperature. The coffee is now ready to drink. 
Having described the invention in detail and by reference to preferred 
embodiments thereof, it will be apparent that modifications and variations 
are possible without departing from the scope of the invention defined in 
the appended claims.