Note: Descriptions are shown in the official language in which they were submitted.
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A HEAT PACK
The present invention relates to a heat pack and in
particular but not exclusively to a heat pack for
therapeutic use. The pack could, however, be used for the
application of heat in any suitable situation to both live
and inanimate subjects. The pack is also capable of use as
a negative heat pack, ie a cool pack, to abstract heat from
live and inanimate subjects to which it is applied.
A conventional heat pack used for therapeutic use is a
hot water bottle. Whilst modern hot water bottles, which
are made of rubber, are flexible they have the major
disadvantage that they must be filled with hot water, which
is usually at a temperature at or nearing boiling point.
This is dangerous, particularly for children, the elderly,
and persons with impaired movement or vision.
To overcome the aforementioned disadvantage, gel packs
have been developed which can be heated, typically in a
microwave oven, and used therapeutically. However, these
tend to be expensive and hazardous in the case of a leak.
In LJS-4765338 is disclosed a heating or cooling pack
for the entire scalp. The pack has been particularly
developed for use as a cooling pack by patients undergoing
chemotherapy treatment and has not been designed primarily
as a heat pack, unlike the present invention.
In US-54475332 is described a water pillow or "ice
bag" which comprises a closed bag made of a cloth or
nonwoven fabric that has a high water permeability and that
contains a water absorptive high polymer material, i.e. a
gelling material. This pack has again been designed for use
primarily as a cool pack.
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Other conventional heat packs comprise electric
blankets and pads, and devices using exothermic chemical
and physical reactions. These types of apparatus tend to
to be expensive to produce and/or to operate. In addition,
those dependent on exothermic reactions can be unreliable
and may not be sufficiently flexible in their heat-
producing state to be able to mould themselves to a part of
the body to be treated.
Variations on all these products have also been
produced for use on inanimate objects but usually exhibit
the same disadvantages as aforesaid.
The object of the present invention is to provide a
heat pack which overcomes or substantially mitigates the
aforementioned disadvantages and which is inexpensive and
safe to use.
According to the present invention there is provided a
heat pack for being heated to at least 55°C and comprising
a flexible, impervious outer container which is adapted to
be sealed to retain a liquid therein and of maintaining its
sealed integrity when heated to at least 55°C and which
contains a porous, non-rigid filling material and a
predetermined quantity of a preservative at a concentration
that inhibits microbial growth within the liquid-filled
container when sealed, and characterised in that the
filling material comprises at least one of a woven textile
material, a nonwoven fabric, a sponge-like material, and
paper, which filling material absorbs at least its own
weight of said liquid.
For convenience and safety, the liquid used in the
heat pack may be water. It will be appreciated, however,
that the heat pack if not already supplied to the end-user
in a water-filled, sealed condition, can be filled with
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cold water and sealed before being heated. The liquid
within the container is absorbed by the porous filling
material, which in addition to imparting a degree of
rigidity to the heat pack is advantageous from a safety
point of view after the heat pack has been heated should
the outer container be ruptured.
The container may comprise a resealable bag or a
sealed bag with a valve permitting it to be emptied, filled
or topped up with liquid as desired.
It will be appreciated that when the pack is heated
any air trapped inside the pack will expand. In extreme
circumstances this can exacerbate expansion of the pack
causing rupture. Hence, preferably, air is removed from the
outer container prior to it being sealed. Advantageously,
therefore, the valve permits air to be removed from the
container after it has been filled with the liquid.
Alternatively, the container may be permanently
sealedafter the addition of water or other liquid and the
removal of air therefrom, a.nd may be supplied to the end
user ready for use in this condition.
More specifically, therefore, according to the present
invention there is provided a heat pack for being heated to
at least 55°C and comprising a flexible, waterproof outer
container which has been sealed after having had air
removed therefrom to maintain its sealed integrity when
heated to at least 55°C and which contains a porous,
non-rigid filling material, a liquid and a predetermined
quantity of a preservative at a concentration that inhibits
microbial growth within the sealed container, and
characterised in that the filling material comprises at
least one of a woven textile material, a nonwoven fabric, a
sponge-like material, and paper in combination with at
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least the filling material's own weight of liquid which is
absorbed by said filling material.
The air can be removed from the outer container by any
suitable means such as pressing, suction, or vacuum
sealing. Preferably, however, the outer container is vacuum
sealed.
It has been found that in order to ensure that there
is no excessive expansion of the pack during its heating to
temperatures suitable for its appJ.ication to parts of the
human or animal body, the outer container is preferably
exhausted of air down to a pressure equal to 100 millibars
or less.
Removal of air from the outer container also imparts
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degree of rigidity to the pack which will thereby retain
its shape during and after heating. This can be
advantageous if the pack is to be made in a specific shape,
for example for use with a particular area of the body or
in the form of a toy for a child.
Heating of the pack is preferably accomplished using a
microwave oven although other conventional heating methods
could be used and would be required if the container were
to be made of a metallized material. Such an alternative
heating method could comprise immersion of the pack in hot
water for a time sufficient to heat the pack through.
Preferably, therefore, the pack is capable of being
immersed in water which is at or near boiling point.
Another cause of potentially deleterious expansion of
the pack arises if any water contained therein is vaporized
during heating of the pack. Although in most embodiments of
the invention and in most applications it will not be
desirable to heat the pack to temperatures around or in
excess of 100°C, if the pack is heated in a microwave oven
the heating is not uniform so that whilst, for example, the
mean temperature may be only 75°C there may be hot spots
with temperatures in excess of 100°C. The universal gas
equation states that one gram mole of a substance changing
from liquid phase to gas phase will occupy 22.4 litres of
volume at normal temperature and pressure. Hence, 18 g of
water, i.e. 18 ml of water, would occupy 22.4 litres when
boiled and changed into water vapour. Hence, it will be
appreciated that the vaporization of even a small
percentage of the contents of a pack containing 500 g of
water could give rise to a damaging expansion of the
product.
In view of the foregoing, it is advantageous in same
embodiments of the invention for at least a proportion of
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the water, and in some cases all of the water, to be
replaced by a substance capable of being heated by a
microwave oven but with a boiling point significantly
higher than water. Suitable substances for this purpose
5 preferably comprise compounds comprising one or more
hydroxyl _aroups. For example, such substances may comprise
one or more of glycerol, sorbitol or other polyhydric
alcohols; ethylene glycol, propylene glycol or other
glycols; glucose or other sugars; or any of a wide range of
hydroxyl group containing compounds.
It is expected that in cases where a proportion of the
water in the pack is replaced by hydroxl group containing
compounds that at least one part hydroxyl group compound
will be used to four parts water. In one preferred
embodiment the pack comprises at least three parts
hydroxyl group compound to two parts water.
It will be appreciated that the quantity of liquid
Within the pack will determine how quickly it can be heated
for any given heating method. However, too little liquid
within the pack will cause it to heat too rapidly, which
can be dangerous, particularly if the pack is heated by a
microwave oven. However, too much liquid is disadvantageous
as the heating time is inconveniently protracted.
Preferably, therefore, the quantity of liquid the pack
contains is carefully predetermined. Advantageously, the
pack contains a weight of liquid in the range 250 g to 1250
g., Optimally, however, from the point of view of user
safety, convenience, heat content and weight, the pack
contains a weight of liquid in the range 500 g to 1000 g.
Preferably, the container comprises a bag made from a
substantially plastics material. Such a plastics material
may comprise one of a polymer film, polymer laminate, co-
extrusion, metallized plastics film, metallized plastics
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laminate, and an impervious heat-sealable polymeric
nonwoven.
Whilst the heat pack of the invention can be made
inexpensively so that it could be disposed of after a
single use, it is preferably made from materials which
permit it to be heated and cooled, and therefore, used many
times.
Preferably, therefore, the plastics material comprises
at least one of polypropylene, polyethylene, a polyamide,
polyvinyl chloride, an aramid polymer, a polyester. It may
also comprise a combination of these plastics materials
with at least one of a textile material, such as a textile
scrim, a knitted or nonwoven fabric, a metal foil, and a
metallized film, as a laminate.
Such materials are also conducive to the production of
a container in the form of a bag which could be
manufactured by heat sealing or high frequency welding the
edges of sheets of such materials together. Alternatively,
sheets extruded as a lay-flat tube can also be cut and
sealed to form a bag. A resealable container could be
produced similarly but with an opening to which a
conventional water-tight closure means is attached.
The porous textile or paper filling material is
preferably either fibrous or spongy in nature.
Conveniently, such material may comprise scrap, waste or
recycled textile or paper materials such as off-cuts and
edge trim from other processes. In this way, the invention
provides a convenient and beneficial means of using
material which would otherwise comprise a troublesome and
potentially environmentally damaging waste product.
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The filling material may be used in the form of
strips, swatches, rolls, and shreds, or may be specifically
shaped, formed or cut.
Preferably, the filling material can absorb at least
four times its own weight of liquid. In most cases it is
expected that the filling material will be able to absorb
between five and eight times its own weight of liquid and
that it will be this quantity of liquid which will be used
in the heat pack.
Additional filling materials may also be used in
certain embodiments of the invention to produce a heat pack
with certain properties, for example one with a greater or
lesser rigidity or one which will hold its shape after
being moulded following heating. Such additional filling
materials may comprise any of expanded plastics materials,
glass fibres, glass wool, ceramic fibres, and non-absorbent
fabrics.
The fill for the container may also be modified by the
addition of material containing superabsorbent polymers or
other chemical absorbents either in combination with solid
filling material, for example in a laminate form therewith,
or by the direct addition of such chemicals. It may also be
beneficial in some embodiments to add a viscosity modifier,
for example a gum, modified cellulose, bentonite,
hectorite, polyvinyl alcohol, or similar material to any of
these.
Colourings, fragrances, pearlising agents or other
effect chemicals may also be added to the fill as required.
- It is necessary to include in the heat pack a
preservative to inhibit microbial activity such as fungal
and bacterial growth which would detrimentally affect the
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pack once it had been first filled with water. Such growth
would reduce the shelf life of a pack to the extent of
rendering it uncommercialand, once present, may present a
health hazard to the user.
Preferably, the preservative used in the heat pack
comprises at least one of sorbic acid, citric acid,
propionic acid, chlorhexidine, chlorbutol, bronopol,
phenoxyethanoi, phenyl ethyl alcohol, an ester of para
hydroxybenzoic acid, 2.4 dichlorobenzyl alcohol,
polyhexanide, a phenolic compound, and a quaternary
ammonium compound.
Such preservatives are known for their particular
suitability for use in consumer products such as foodstuffs
and cosmetics because they are safe to use and are stable
enabling the resulting product to exhibit a long-term
integrity. However, any suitable preservative could be
used.
It will be appreciated that the concentration of
preservative required and the nature of the preservative
will depend on its own nature, the nature of the filling
material and the container, and on the desired life of the
heat pack itself.
Whilst fabrics and textile materials which have been
pre-treated with biocidal compositions could be used as
filling materials for the pack, the use of such filling
materials would increase the cost of the heat pack and the
invention is not, therefore, limited to their use.
Six examples of heat packs according to the present
invention will now be described.
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Example 1
Outer Container 50 micron polypropylene sheets cut to
size and rotary heat sealed to form a
bag
Fill Thermally banded viscose and cotton
nonwoven fabric, wetted with 500 g
water containing a preservative of 0.2%
methyl para hydroxybenzoate and 0.04%
propyl para hydroxybenzoate.
Example 2
Outer Container A resealable laminate pouch
Fill A cotton fibre, cotton towelling wetted
with water containing a preservative of
500 ppm benzalkonium chloride and 500
ppm polyhexanide.
Example 3
Outer Container A nylon and polythene co-extrusion
pouch capable of retaining 500 ml of
liquid
Fill 100 g of viscose nonwoven fabric wetted
with 200 ml of water and 300 ml of
glycerol containing a preservative of
500 ppm benzalkonium chloride and 500
ppm polyhexanide.
' Example 4
Outer Container A nylon and polythene laminate pouch
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capable of retaining 630 ml of liquid
Fill 120 g of viscose nonwoven fabric wetted
with 630 ml of water containing a
5 preservative of 500 ppm benzalkonium
chloride and 500 ppm polyhexanide.
Example 5
10 Outer Container A high frequency welded polyvinyl
chloride bag.
Fill A wet laid viscose and wood pulp
cellulose nonwoven fabric and airlaid
paper mix wetted with water containing
a preservative of 0.5% chlorbutol and
0.5% phenyl ethyl alcohol.
Example 6
Outer Container A high frequency welded polyvinyl
chloride bag.
Fill A wet laid viscose and wood pulp
cellulose nonwoven fabric wetted with
glycerol containing a preservative of
0.5% chlorbutol and 0.5% phenyl ethyl
alcohol.
Thus the invention provides a heat pack which is
capable of being heated to a temperature of at least 55°C;
which is able to withstand conventional readily available
heating methods, such as the use of microwaves; and which
is relatively inexpensive and safe to use.
The internal structure of the pack may also be
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modified as desired by the addition of physical or chemical
agents to alter its bulk or rheological properties. In
addition, the external appearance, tactile properties, heat
transferance, and function of the pack may be modified by
the use of fixed or loose coverings.
As previously mentioned, it will be appreciated that
in most embodiments detailed above the pack is also capable
of use as a negative heat pack, ie. a cool pack, which can
be used to abstract heat from live and inanimate subjects
to which it is applied. In this case the pack would be
cooled, conveniently by being placed in a refrigerator or
freezer for a predetermined period, before use in the same
manner as the heat pack described heretofore. References
herein, in both the description and the claims to the term
"heat pack" are therefore to be understood in this light.
