Chemically heated blanket

The present invention relates to a chemical warmer which comprises an air supply device, a first and a second panel peripherally fastened to each other to form an envelope to contain a chemical thermogenic material. The first panel is configured to include an air-impermeable top layer, an air-permeable middle layer with a plurality of air holes therethrough and an air-permeable inner layer with many micropores therethrough, the top and middle layers being partially welded to each other in such a way that a plurality of air distribution passages and gas exhaust passages are formed for uniformly distributing air inside the panel and extracting exhaust gases/air to a gas exit which is connected to size-adjustable wastegate device. The second panel includes at least an air-impermeable layer. The air supply device is either hand-operated or electronically powered. The present invention further discloses an exothermic material mat which can keep the thermogenic material in place throughout the mat.

The present invention relates to a chemical warmer, and especially to a 
chemically heated blanket. 
A chemical warmer has many known advantages and uses since no flame is 
produced. It is widely used in hospitals, homes and outdoors for applying 
heat to a human body or other objects. Consequently, various types of such 
devices are known in the art. Many improvements have been made in the 
chemical exothermic materials used in the chemical warmers, one useful 
type uses air for activating and maintaining the thermogenic chemical 
reactions in the chemical warmer. In order to introduce air into a 
chemical warmer, the conventional chemical warmers usually utilize an 
air-permeable inner bag which is enclosed in an air-impermeable outer bag, 
or covered by an air-impermeable film or the like. The inner bag may have 
one or more air-permeable layers which are provided with many air holes or 
micropores. Initiation of the heating process occurs when the inner bag is 
exposed to air. Numerous patents have been granted for improvements in 
such chemical warmers such as the following U.S. patents: U.S. Pat. No. 
4,756,299 issued on July 12, 1988 to Car W. Podella, U.S. Pat. No. 
4,268,272 issued on May 19, 1981 to Miyako Taura, U.S. Pat. No. 3,976,049 
issued on Aug. 24, 1976 to Iwao Yamashita et al, and U.S. Pat. No. 
3,301,250 issued on Jan. 31, 1967 to Ernest C. Glasser. 
One of the important factors which affects the thermogenic reaction is the 
amount of air supply per time unit. Due to the structures of the previous 
chemical warmers, the rate of air supply is adjustable only to a very 
imprecise degree. As a result, the heat output from the warmer cannot be 
effectively controlled. In other words, the temperature of the chemical 
warmer is not controllable. Moreover, in most prior art, the air cannot be 
efficiently and uniformly supplied to all parts of the thermogenic 
material, causing hot and cold spots. Furthermore, the thermogenic 
reaction or heating process is not easily stopped when desired as to the 
prior art. Normally, the conventional chemical warmer must be taken away 
from the heated body and put back into an air impermeable bag or resealed 
by a film in order to stop the production of heat. 
Another important factor which affects the uniform heat output throughout 
the warmer or blanket is the manner of containing the exothermic 
materials. In conventional warmers, the powdered exothermic material or 
composition is merely placed loose between two loose covers which form a 
bag or envelope. This structure has been shown by the U.S. Pat. Nos. 
4,268,272, 3,976,049, 4,516,564, 4,756,299. With this configuration, the 
powdered exothermic material tends to gravitate all to one place, like a 
bag of dirt, and cannot be kept in place. Accordingly, the heat cannot be 
evenly distributed throughout the heated area, especially in the case of a 
big warmer, such as a blanket. 
All of these shortcomings associated with the conventional chemical warmers 
limit their applications or areas of use. 
The present invention provides a novel chemical warmer which overcomes the 
limitations and shortcomings of the prior art devices. 
OBJECT OF THE INVENTION 
One object of the present invention is to provide a chemical warmer which 
can control the heat output of the chemical warmer by controlling the 
supply of air. 
Another object of the present invention is to provide a chemical warmer 
that can efficiently and uniformly distribute air to all parts of the 
warmer. 
Still another object of the present invention is to provide a chemical 
warmer in which the production of heat can be easily stopped without 
removing the chemical warmer from the context of its application. 
A further object of the present invention is to provide a chemically heated 
blanket that has the above-mentioned advantages and can be used in 
hospitals, homes, automobiles or outdoors. 
Another object of the present invention is to provide an exothermic 
material mat which can uniformly hold the exothermic material in place and 
is permeable to air. 
These and other important objects of the present invention will be apparent 
from the detailed description provided hereafter. 
SUMMARY OF THE INVENTION 
This invention is an improved chemical warmer or chemically heated blanket 
of the air-activated type, which can supply heat to the human body or 
other objects. The chemically heated blanket comprises an air supply 
device for introducing atmospheric air into the blanket, a gas exhaust 
exit for extracting the exhaustion gases, and first and second panels 
forming an envelope which contains the chemical exothermic material. 
The first panel, functioning as an air distribution and gas exhaust system, 
includes a top layer of air-impermeable material, a middle layer of 
air-permeable material with a plurality of air holes therethrough and an 
inner layer of air-permeable material having many air micropores, the top 
and middle layers being partly welded to each other in such a way that a 
plurality of air passages and gas exhaust passages are formed between them 
for uniformly distributing air from the air supply device to inside the 
panel and transferring exhaust gases to the gas exhaust exit. The second 
panel is provided with at least a layer of air-impermeable material. The 
air supply device which is connected to the air passages by means of an 
air entrance, can be either a hand-operated, an electrically powered type, 
or any other means of introducing air. The gas exhaust exit is provided 
with a wastegate, the size of which is adjustable. 
In another embodiment, the air distribution system and the gas exhaust 
system are separately structured on the first and second panels. 
The present invention further discloses an exothermic material mat which 
can be used in a chemical warmer, including the conventional chemical 
warmers. The exothermic material mat includes an exothermic material 
containing panel which has a plurality of uniformly distributed spaces for 
holding the powdered exothermic material in place so that heat can be 
produced evenly throughout the surface of the chemical warmer. 
Some preferred embodiments and features of the present invention will be 
described hereafter by referring to the attached drawings.

DETAILED DESCRIPTION OF THE INVENTION 
Turning in detail to the drawings, FIGS. 1 and 2 show a preferred 
embodiment of a chemically heated blanket 2 of the present invention which 
has an air supply device 30 and an air distribution and gas exhaust system 
20. 
The thermogenic chemical material used in the present invention can be any 
kind of air-oxidizable thermogenic materials known in the prior art, such 
as the materials described in U.S. Pat. No. 4,093,424. 
The chemically heated blanket 2 includes an envelope 5 which is formed by 
two panels 7 and 8, whereby the exothermic chemical material 6 is 
accommodated therein. The panel 8 is constructed from a layer of 
air-impermeable material. The other panel 7 has a laminated configuration 
which preferably consists of an air-impermeable top layer 12, an 
air-permeable middle layer 13 with a plurality of air holes 40 
therethrough and an air-permeable inner layer 14 having many micropores 
therethrough or made of an air permeable material. As an example, these 
air holes 40 may be 1 mm diameter holes spaced on 1 cm centers, although 
the size and spacing of the holes will depend on the type of thermogenic 
material and the intended conditions of use. The top layer 12 and the 
middle layer 13 are partially united to each other in such a way that a 
plurality of air passages and gas exhaust passages are provided. Since the 
pressure along the passages will decrease progressively, the number of the 
air holes on the middle layer 13 can be arranged to increase progressively 
from the input end to the remote end of the passages so that the air can 
be uniformly distributed. Gas exhaust, as used herein, refers to air 
exiting from the distribution system together with by products (to the 
extent they exist) from the thermogenic chemical reaction. The two panels 
can be made of thermoplastic materials, heat-welded into the desired form 
and then incorporated into the blanket. 
The arrangement of the passages is shown in FIG. 2, and includes a 
plurality of longitudinal air passages 22 and longitudinal gas exhaust 
passages 24, and many transverse sub-passages 23 uniformly arranged 
between the longitudinal air passages 22 and the longitudinal gas exhaust 
passages 24 at equal intervals to each other. (Only a few of the 
transverse sub-passages are schematically shown in FIG. 2.) It should be 
understood that the arrangement of the passages shown in FIG. 2 is only an 
example. Some other arrangements may also be chosen as long as the air 
distribution and gas exhaust system can introduce fresh air and extract 
exhausted gases uniformly across all parts of the blanket. For example, 
the transverse sub-passages may not be necessarily needed. All the 
longitudinal air passages are connected to an air entrance chamber 26 
extending across the head of the blanket like a section of an air mattress 
and acting as a buffer against pulsing of the air supply. The entrance 
chamber 26 can store one or more minutes of air supply and forms the 
initial distribution mechanism, while all the longitudinal gas exhaust 
passages are connected to an outlet chamber 34 extending across the 
opposite head of the blanket with a diameter somewhat smaller than the 
entrance chamber. 
Another example of the arrangement of the air distribution system 20 is 
shown in FIG. 5. The air passages may be structured in a fan-shaped 
channel 31; that is, the diameter of the air passages varies successively 
in cross-section along the channel 31, being small at the input end 32 
(where the pressure is highest) and larger as it gets further from the 
supply. 
As an alternative, the air distribution system can also be formed by using 
a plurality of air-permeable small tubes, such as vinyl tubes, or 
fabricated in such a way that the channel will exist even under no air 
pressure. 
Air is supplied externally through a tube 28 leading to an air entrance 27 
of the air entrance chamber 26. Air supply to the tube 28 is from an air 
supply device 30 which can be a small air compressor or air pump powered 
by line current, batteries or other means. A small compressor may be 
incorporated into the blanket itself, with electric power supplied by 
batteries. Various types of compressors can be used for this purpose, for 
example, the piston type, diaphragm type, gear type or any device that can 
deliver air at a suitable pressure. Air may also be delivered by means of 
a hand-operated air supply device, such as a squeeze bulb, a bellows, an 
accordion device or other similar means. The air pressure is in range of 
about 5 to 15 cm of mercury at a rate of 1 or more liters/minute. But it 
should be understood that the air pressure of the air supply is determined 
depending on the size of the blanket, the type of thermogenic material 
used and the temperature needed. It is calculated that an air flow of 1 
L/min would be sufficient, given standard thermogenics, to produce a heat 
in excess of that given by a standard electrically heated twin-bed blanket 
operated at a moderate rate at temperatures somewhat below room 
temperature. 
In order to avoid overly hot temperatures, particularly while the blanket 
covers an unconscious person, a temperature controlled valve may be 
utilized in the air supply tube (not shown in the drawings). Such a valve 
may be bistable, so that it allows either an unrestricted flow at low 
temperatures or essentially no flow above a certain temperature, or a 
valve with a continuously variable position with respect to temperature. 
In another approach, a temperature-controlled electronically operated air 
pump system may be used, which may include a temperature sensor and a 
control circuit. 
The exhaust gases exit from a gas exit 35 leading from the outlet chamber 
34. There is provided a wastegate device 37 which is connected to the exit 
35 and includes a restricted gate of either fixed or adjustable size for 
the purpose of assuring an optimum pressure in the blanket system. The 
wastegate device can be any suitable valve or the like, including a simple 
cam roller acting in combination with a deformable plastic tube. An 
outflow tube 38 can be provided for leading the exhaust gases away from 
the blanket to diminish the concentration of exhaust gases near the person 
lying on the blanket. 
During the thermogenic operation, air is supplied by means of the air 
supply device 30 into the air entrance chamber 26, then air is delivered 
into a series of air passages 22 under pressure so that a second stage of 
air distribution occurs. Air continues flowing into sub passages 23 in a 
matrix pattern and final air distribution occurs. Passing through the 
holes on the layer 13 of the air distribution system, air reaches the 
final air permeable layer 14 in a uniform manner. Finally, air passes 
through the final layer 14 and activates the thermogenic reaction. Any 
gases produced in the reaction together with excess air will exit through 
the gas exhaust passages 24 under the difference in pressures between the 
gas exhaust system and reaction space. Control of the heat output of the 
blanket is achieved simply by controlling the rate of input airflow. If 
the airflow is stopped completely, the blanket could be shut off by 
terminating the air necessary to react with the thermogenic materials. 
Referring now to FIGS. 3 and 4, there is shown another embodiment of the 
chemically heated blanket which has an air distribution system 18 on one 
panel of the blanket, and a similarly structured gas/air exhaust system 19 
on the other panel. The outlet chamber, in this case, can be at the same 
end as the entrance chamber 26, allowing better access to wastegate 
control. In use, the exhaust surface may be the surface next to the human 
body so as to help distribute heat evenly, diminishing the presence or 
effect of hot spots. In this embodiment, it is necessary that air be able 
to pass through the thermogenic material, which can be configured to make 
this possible. 
In order to obtain a calibrated heat output, particularly when the blanket 
is used in hospitals, an air flowmeter 39 or a pressure gauge may be 
employed on the air input line or on the gas output line. 
FIG. 6A is a cross-sectional view of a thermogenic material mat 50, which 
can keep the thermogenic material in place and be disposed in the 
air-permeable envelope of a chemical warmer. The thermogenic material mat 
50 includes a screen or net 45 with many uniformly distributed small holes 
47 for containing the powdered thermogenic material, two air-permeable 
membranes 48 and 49 having a plurality of uniformly distributed micropores 
therethrough and fastened respectively on the two surfaces of the screen 
45. Such screen 45 can be manufactured by creating appropriately located 
slits 46 in a sheet of plastic foam 45, as shown in FIG. 6B, such as a 
sheet of approximately one-eighth inch thick polyethylene. The sheet is 
then expanded to form a diamond-shaped pattern of holes 47, as shown in 
FIG. 6C. The air-permeable membranes 48 and 49 may be made of a thin 
polyethylene sheet perforated with microscopic holes. During manufacture, 
the membrane is first welded or cemented onto the expanded screen so as to 
form many cells. The welding can be accomplished by placing the screen on 
a flat surface, covering it with the membrane, and pressing a hot, 
teflon-coated roller over it. After the cells are filled with the powdered 
thermogenic material, the second membrane is welded or cemented onto the 
other surface of the screen. The perforation may first be non-permeable 
and perforated after the welding is done. Of course, the portion of the 
process involving the reactive substance must be carried out in the 
absence of air. The screen may also be formed by uniformly punching tiny 
holes in a layer of suitable material, and the air-permeable membrane can 
be an air-permeable and sticky film, such as the product made by 3M called 
micropore tape, which can be simply taped onto the surfaces of the screen. 
Any array of holes of any shape and of a wide range of sizes may 
constitute the cells. The main purpose is to trap the thermogenic material 
uniformly in the screen so that it cannot migrate and can provide a 
uniform heat output throughout the screen. 
FIGS. 7A and 7B show another preferred embodiment of the thermogenic 
material mat 50. The mat 50 is formed by two air-permeable membranes 51 
and 54 which are welded or cemented to each other. In this embodiment, at 
least one of the membranes includes a plurality of uniformly distributed 
and depressed small hollows 52, as shown by FIGS. 7A and 7B. The 
thermogenic material 56 is held in the cells between the two air-permeable 
membranes 51 and 54. 
In the case that both membranes 51 and 54 have hollows as shown in FIG. 7B, 
the hollows on the two membranes match each other so that large cells can 
be provided and easily manufactured. 
In a simplified alternative, an absorbent substrate is adopted, into which 
the thermogenic material can be uniformly distributed. The absorbent 
substance may be absorbent fiber, such as a thin layer of cotton or a 
similar fibrous material, permeated with the active material, or a layer 
of filamentary fine steel wool, the absorbent substrate being anchored by 
the quilting welds passing through it. 
While the preferred application of the present invention has been shown and 
described, it should be apparent to those skilled in the art that many 
more modifications are possible without departing from the invention 
concept herein described. It is intended to cover in the appended claims 
all such modifications as fall within the true spirit and scope of the 
invention.