Note: Descriptions are shown in the official language in which they were submitted.
WO90/11034 PCT/GB90/00440
2~0~
INSULATING JACKET
- The present invention relates generally to
thermally insulating jackets and is particularly
concerned with jackets in the form of sleeping bags.
However, the invention is also applicable to jackets
used as articles of clothing such as anoraks,
insulated suits and headgear, and even to jackets in
the form of covérings for hot or cold water tanks.
Known thermally insulating jackets comprise an
inner layer and an outer layer between which is
disposed a mass of thermally insulating material. One
problem that arises with such insulating jackets is
that the jackets have to be fabricated in a number of
different sizes so as to fit, in the case of sleeping
bags and clothing, the human being for which they are
designed, and, in the case of water tank coverings,
the particular water tank for which the jacket is
designed.
Furthermore, in the case of sleeping bags, there
must be sufficient room for the person to be able to
m~ve around. A sleeping bag that is too small has the
disadvantage of constricting movement of the person,
and one that is too large has the disadvantage of
allowing convection currents in the space which have
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the effect of increasing body heat loss.
The present applicants have tested a range of
conventional sleeping bags ~nd have measured the
effectLve internal circumference of each bag to be,
when averaged over its }ength, about 42% greater than
the average circumference of a human being of a size
appropriate to the sleeping bag. The effective cross-
sectional area within the sleeping bag, being a
quadratic function of the circumference, is thus about
twice that taken up by the body, resulting in
undesirable convection currents as mentioned above.
It would be possible to mitigate the above
problem by making the bag a tighter fit, but, as
mentioned above, that would make the bag feel
excessively constrictive and also require a greater
variety of bag sizes.
Furthermore, conventional sleeping bags require a
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certain time for the insulating material to return to
its normal thickness after unpacking the sleeping bag
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~ 20 from a compressed state, and, during this time, the
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~ ~insulating effect of the bag is less than its optimum
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value, since less air can be trapped in the compressed
~, insulating material.
It would thereore be desirable to provide a
thermally insulating jac~et ~hich overcomes or at
least mitigates the above-mentioned disadvantages of
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WO90/11034 PCT/GB90/00440
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conventional insulating jackets.
Accordingly, the invention in a first aspect
provides a thermally insulating jacket having an
inner and an outer surface, wherein said inner surface
is elasticated.
Preferably, the outer surface is elasticated to a
lesser degree than the inner surface, or is not
elasticated at all.
Preferably, the arrangement is such that the
elastication of the inner surface tends to cause an
increase in the separation between the inner and outer
surfaces.
The above arrangement has the advantage that the
effective area presented by the inner surface in use
is reduced, as compared with that in the absence of
elastication, possibly to an extent depending on the
size of the person or articles surrounded by the
jacket, thereby reducing the air space in which
convection currents can occur, and this in turn
reduces heat transfer between the person or articles
and the surrounding atmosphere. Also, by not
elasticating the outer surface, or elasticating it to
a lesser degree, the inner surface is enabled to pull
inwards away from the outer layer, thus increasing the
thickness of the jacket in use. This assists the
lofting properties of any insulating material used for
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WO90/l1Q34 PCT~GB90/00440
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the filling. Furthermore, if such a jacket is adapted
to be packed in a compressed state, the elastication
of the inner layer, in conjunction with the outer
layer not being elasticated, causes the inner surface
to pull inwards away from the outer surface, thus
reducing the possibility of cold spots forming where
the layers touch each other and enabling the desired
thickness of the jacket to be attained more rapidly
than in conventional insulating jackets.
- With- prior art bags, with-out elastication, the
filling is relatively thin not only because the inner
and outer layers are not pulled apart by
elastication, but also because the filling has to be
distributed around a large circumference. In a bag
according to the present invention, however, the
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`~ elastication of the inner layer will in practice have
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the effect of pulling the outer layer inwards, albeit
to a lesser extent than the inner layer, so that the
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overall volume occupied by the filling is reduced, or
at least not significantly increased. This has the
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advantage that for a given ~uantity of insulating
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- material the density of the material is not
significantly decreased even though there is an
increase in thickness of the jacket resulting from the
" 25 elastication of the inner layer. Accordingly,
undesirably large air spaces are not created.
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`NO90/11034 PCT/GB90/00440
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Another advantage particularly valuable in
sleeping bags, and to some extent in articles of
- clothing, is that the wearer can have a tightly
fitting garment without feeling constricted, because
only the inner surface is elasticated. I~ will be
appreciated that if the entire jacket were elasticated
throughout its thickness, substantial elastic force
would be necessary to ensure a tight fitting,
resulting in substantial perceived constriction by the
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wearer and reduced insulation resulting from the
constriction of the filling.
A further advantage of particular value in
clothing is that the "bellows effect", whereby a large
percentage of the insulating value can be lost by warm
air being forced from inside loose clothing by body
movement, can be avoided or.substantially reduced.
The inner and outer surfaces would normally be
surfaces of respective inner and outer layers.
Alternatively, the jacket may comprise a single layer
of material which preferably is of a thickness which
is non-resiliently expansible, and in this case the
inner and outer surfaces would be respective surfaces
of the single layer.
In a second aspect, the invention provides a
thermally insulating jacket comprising:
(a) an inner layer and an outer layer;
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WO90/1~34 PCT/GB90/00440
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(b) a plurality of internal walls each attached
at one edge thereof to said inner layer and
at another edge thereof to said outer la~er
so as to define in conjunction with said
inner and outer layers a plurality of boxes;
and
(c) a mass of thermally insulating material
disposed in each of said boxes;
wherein said inner layer is elasticated.
It is appreciated that all threads are elastic to
a small extent. However, the term "elasticated" as
used in the present application is intended to mean
that the resulting linear dimension of the inner
surface or inner layer is caused to be reduced by a
significant extent, and preferably by at least by 10%
s~ from its normal, unelasticated value. Indeed, a
degree of elastication such as to cause a reduction in
linear dimension of in excess of 15% from the normal,
unelasticated value is especially preferred.
The jacket is preferably elongate and the inner
`~ layer preferably elasticated in a transverse direction
and not elasticated along the longitudinal direction.
This arrangement causes the jacket to be wrapped more
efficiently about a person or elongate article.
The means of attachment is preferably not exposed
~; on either the inner layer or ~the outer layer, and this
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W090tllO34 PCTtGB9~tO0440
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is preferably achieved using tuck stitching, wherein
each internal wall is joined to the inner and outer
layers by stitching it to a small raised tuck on the
internal side of each layer. Such an arrangement
renders the stitching not only invisible but also
almost completely protected from abrasion or snagging
from the external side (or "wear" side) of the layers.
The elastication of the inner layer is preferaXly by
means of elasticated thread which constitutes the
- 10 means of attac~ment of the internal walls to the inner
layer. This provides a means of elasticating the
inner layer which is simple to effect in manufacture
and, in the case of an insulating jacket which would
be conventionally manufactured by attaching the
internal walls to the inner layer by means of non-
elasticated thread, this has the advantage that a
jacket according to the second aspect of the present
invention can be manufactured simply by replacing the
non-elasticated thread with elasticated. In such an
arrangement the use of tuck stitching as mentioned
above is even more advantageous, since elasticated
thread is more vulnerable to snagging than ordinary
thread; elasticated thread being generally thicker, it
offers greater friction and is more proud of the
fabric surface. Furthermore, the breaking of
elasticated thread results in greater damage than
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WO90/11034 PCT~GB90/00440
' 20S04~
ordinary thread, since the tension in elasticated
thread will tend to unravel more stitches on breaking
than with ordinary thread.
The outer layer is preferably attached to the
internal walls by means of non-elasticated thread.
Although the invention may of course provide a
jacket made from any suitable thermally insulating
material, whether natural or synthetic, the preferred
material is down or other free-moving insulation,
since this material more rea~ily moves to fill the
spaces within the boxes, thereby minimising relatively
cold (or hot) spots caused by convective heat transfer
through air gaps next to the internal walls. To
achieve the improved ihsulation which results from
lS increasing the separation between the inner and outer
layers, the insulation material preferably has a loft
of at least 300, and preferably at least 500, cubic
inches per ounce, using the standard British fill
power test; this can easily be achieved if down is
` 20 used.
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The thermally insulating jacket may be in the
` form of a sleeping bag, an article of clothing or a
jacket adapted to fit around a water tank.
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~An embodiment of the present invention will now
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be described in detail with reference to the
accompanying drawings, wherein:
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WO90/11034 PCT/GB90/00440
I, j 2 tl S O ~'t 7 ;~
Figure l is a pictorial representation,
partially cut away, of a known sleeping bag;
Figures 2A and 2B are respectively diagrammatic
representations, in transverse cross-section, of a
known sleeping bag and a sleeping bag incorporating
an elasticated thread in accordance with an
embodiment of the present invention;
Figures 3A and 3B are similar to Figures 2A and . .
2B, but show diagrammatically longitudinal cross-
~ lO sections of the bags, and
Figure 4 shows in diagrammatic form the
stitching used to attach the internal walls to the ~.
inner and outer layers of the sleeping bag shown in
. Figures 2B and 3B. ~:
Figure l shows a sleeping bag having an inner
layer l and an outer layer 2 which are joined by
:~ internal baffles or walls 3. The walls shown extend
. longitudinally along the sleeping bag, and
transversely across the bag. The lines 4 indicate
~: 20 stitching joining the walls 3 to the outer layer 2. -
:~ The inner layer l, the outer layer 2 and the internal
;, walls 3 define boxes in which is disposed suitable
~ insulating material such as down or a synthetic
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material.
2S Figures 2A and 3A show diagrammatically the
configurations adopted by the sleeping bag in use. It
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WO90tl1034 PCT/GB90/00440
4~ o
will be noted that there is a large volume 5 of air
between a ~ody 6 in the sleeping bag and the inner
layer l. Figures 2B and 3B are similar views, but
illustrate the configuration of a sleeping bag in
accordance with the present invention, having an
elasticated inner layer 1. It will be noted that
there is a much smaller volume 5 of air between the
body 6 and the inner layer 1, and the thickness of the
sleeping ba~, i.e. the distance between the inner and
o outer layers 1 and 2, has increased substantlaily to
the extent that the walls 3 are fully extended.
As shown in Figure 4, the elastication of the
inner layer l is achieved by incorporating elasticated
thread 7 sewn along the junction of the inner layer 1
and the transversely extending internal walls 3,
thereby attaching the inner layer to the walls. The
elasticated thread 7 would normally be hidden below
the surface of the inner layer 1 so as to prevent it
catching and thereby breaking. This is achieved by
attaching the internal walls 3 to the inner layer 1
using tuck stitching of the elasticated thread, as
shown diagrammatically in Figure 4. The outer layer 2
is attached to the internal walls 3 by means of non-
elasticated thread 8. If desired, tuck stitching
could be used here, also.
The degree of elastication of the inner layer is
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WO90/11034 PCT/GB90/00440
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dependent both on the intrinsic properties of the
elastic thread and also on the tension which is
applied to it when the thread is sewn. The type of
elastic thread in normal use is known as shearing
elastic. The present applicants have found that a
desirable degree of elastication is such as to cause a
reduction in the width of the sleeping bag of about
16% from its normal, "unelasticated" value, and this
causes a corresponding reduction in the excess
circumference referred to above from about 42% to
about 19% without causing any noticeable discomfort to
the person in the sleeping bag. The figure of 19~ is
equivalent to a cross-sectional area of about 40% in
excess of that taken up by the body, compared with the
. 15 100% excess in conventional sleeping bags. The
applicants have also found that the resulting
thickness of the sleeping bag (i.e. the average
separation between the inner and outer walls) is
increased by at least 10%, or preferably by about 15
to 20% as a result of elastication of the inner layer,
giving rise to a significant increase in thermal
insulation.
The st~ength of the elastic used will vary for
different types of sleeping bag. For example, for
larger sleeping bags having a substantial quantity of
insulating material (e.g. down), such as those
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WO90/11034 PCT/GB90/00440
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designed for colder conditions, a stronger elastic
which gathers in the fabric by about 40% before
filling ti.e. causes a 40% reduction in the width of
the bag) is used for two reasons:
(a) in such bags the height of the internal walls
or baffles is greater so as to accommodate a greater
quantity of insulating material, and a greater
strength of elastic is thus required to stretch the
entire height of the walls; and
(b) such bags are larger, so as to allow a
substantial variation in thickness of clothing to be
worn inside the bag, the elastic providing the same
closeness of fit irrespective of this variation, and a
greater strength of elastic is thus required.
For smaller bags having less insulating material
and smaller internal walls, a light elastic providing
approximately a 30~ reduction in bag width before
filling is sufficient for optimum configuration of the
bag.
The preferred elasticated thread is a blend of
rubber and polyester providing an approximate stretch
of 500% before break, i.e. the stretched length is
five times the unstretched length.
Laboratory tests were undertaken at Leeds
University on an elasticated sleeping bag made in
accordance with the above embodiment, having 450g
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WO90/11034 PCT/GB90/00440
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insulating material and designed in the a~sence of
elastication, for use down to -5C. A cold chamber
was used which provided a minimum ambient temperature
of -24C. At this minimum temperature the user in the
sleeping bag did not perceive the temperature to be
uncomfortably low, thus indicating that the
performance of the bag was enhanced considerably by
elastication.
A similar sleeping bag was used at 23000 feet
(7010 metres) on Mount Everest with satisfactory
results. Again this is far beyond the normal
capabilities of a sleeping bag having 450g insulating
material. In such conditions at least twice this
quantity of insulating material would be required.
Similar sleeping bags but filled with 550g
insulating material have also been used in winter in
the mountains of Scotland where the damp cold is
especially penetrating. The degree of insulation
afforded was that to be expected from a normal
sleeping bag having 750 to 850g insulating material.
Comfort was also reported on favourably.
Although some of the above tests were by their
nature subjective, in each case the tests were carried
out and monitored by people independent of the present
applicants.
Although in the preferred embodiment it is the
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WO90/11034 PCT/GB90/00440
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junctions of transversely extending internal walls 3
and the inner layer 1 which are provided with the
elasticated thread, of course it is also or
alternatively possible to provide the junctions of any
longitudinally extending internal walls and the inner
layer with such thread.
In the embodiment described the means of
elastication of the inner layer is by elasticated
thread, but any other suitable means of elastication,
such as for exampie the attachment of elasticated tape
to the inner layer or surface or indeed the inner
layer being fabricated from elasticated material would
- be possible. In addition the inner and outer layers
may be attached to the internal walls by any suitable
means, and the means may be different for the inner
and outer layers. Such means may for example include
adhesives or press-stud fasteners.
In an alternative arrangement, the degree of
elastication of the inner layer can be varied by the
user. Thus, for example, an otherwise conventional
sleeping bag may be provided on its inside with an
elasticated cord which is attached to the inner layer
; by a sheath of material which extends substantially
all the way around the inner circumference of the bag
and extends inwardly away from the inner layer, or
possibly by a plurality of discrete loops of material.
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WO90/110~4 PCT/GB90/00440
. ,.2Q"5~.78
The cord may either be continuous or have ends which
can be fastened together, or held together by a clip.
The user would be able to pull either the ends of the
cord or a portion of the cord so as to tension it to a
desired degree, and would then knot or clip the cord
in order to maintain the tension. Several such cords
could be provided, spaced longitudinally along the
sleeping bag.
The invention has been described above in
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connection with its application to sleeping bags of a
conventional form including boxes defined by
longitudinally and transversely extending inner walls.
It will of course be appreciated that the :invention
can also be applied to other forms of sleeping bags
which omit one or more or all of these inner walls.
Although the present invention has been described
with respect to sleeping bags, it can apply also to
clothing requiring a high level of thermal insulation
and also jackets for insulating either hot or cold
water tanks. The invention can also be applied to
coverings for use in hospitals for treating victims of
hypothermia.
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