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DESCRIPTION
This invention relates to the support of bodies and has particular
reference to a method of lowering unit area pressure between the surface
of an irregularly shaped body and a support or bed therefor.
In particular the invention is concerned with, although not exclusively
restricted to, the comfort of a human body or the like when laying on a
bed or surface. The invention is particularly useful in preventing
decubitus or "bed sores".
The requirement to provide a cushioning action by equalizing pressure over
the surface of an irregularly shaped body is generally well known, and
hitherto the means of providing such support has been by means of water
beds, air beds and the like.
To provide a comfortable bed or surface on which a body can lay or sit, or
to support bodies or limbs in a horizontal, inclined or vertical position,
comfort during rest, work or sleep is probably the main consideration. For
a fit human or animal, comfort in a given supported position is dependent
on reducing the pressure per unit area of body into those portions of the
body and limbs which are more readily able to receive such pressure.
Where, however, a person is disabled, then prolonged confinement in one
position upon a bed results, after a period time, in increasing discomfort
and eventually bed sores when decubitus sets in. If, therefore, a person
is unable to move, or unable to move very much, then various parts of the
body are almost permanently in contact with bedding and sheeting and the
lack of circulation of air to those parts of the body so in contact with
the sheeting and bedding plus the humidity, perspiration and other body
excrements which may be present in the sheeting of bedding, affects those
areas of the skin which rub against the sheetings and this affects the
skin and impairs the blood circulation. Creases in the sheeting and
underclothes and the like will aggravate the condition.
Many systems have been proposed to reduce or prevent decubitus or simply
the discomfort that arises prior to decubitus setting in. None of these
has been proved to be entirely satisfactory.
Rubber rings and water cushions do not help, they simply move the problem
from one part of the body to another due to the tight seal created if a
body rests on either the ring or the water cushion since this prevents the
skin from breathing.
Air beds give reasonably good results, but their cost is high and they are
costly to run and maintain. In consequence, they are used only in the
treatment of very severe burns.
The use of genuine sheepskins has been proposed but they were found to
retain moisture after a relatively short time and they are difficult to
clean and sterilize after cleaning.
Non-woven textile sheet material has been used in different variations, all
of these have been found to retain moisture to a greater or lesser extent
and, of course, they inhibit the free circulation of air in juxtaposition
the skin of the person reclining thereon.
According to one aspect of the present invention there is provided a method
of supporting a body by reducing unit area pressure which method comprises
providing a surface for the support of an irregularly shaped body, said
surface being formed by a cushioning layer having a plurality of shaped
protrusions arranged to contact said body, said cushioning layer being
capable of reversible compression whereby the body is supported so that
air can circulate between the protrusions to contact the body surface, and
the degree of compression is such that the cushioning layer is capable of
yielding further if movement of the body results in the application of a
greater weight to a given area of the surface.
As used herein the term "compressibility" is to be understood to be the
reversible decrease of thickness of the cushioning layer as a percentage
of the thickness of the unloaded cushioning layer. For the purposes of
this specification, "deflection" is to be understood to mean a lateral
movement of tips of the protrusions in response to the application of a
body load thereto.
The compression of the cushioning layer preferably occurs by deflection of
the protrusions rather than a decrease in the length thereof.
According to a different aspect of the present invention there is provided
a cushioning layer for lowering the unit area pressure between a
supporting surface and an irregularly shaped body and comprising:
a flexible base layer; and
a plurality of resilient, shaped protrusions, each upstanding from said
base layer and arranged to contact a surface of said body; wherein said
cushioning layer is capable of resilient compression by way of deflection
of said protrusions thereby to reduce the unit area pressure between the
supporting surface and the body, and to permit air to circulate between
the protrusions and to contact the body surface.
The reversible compressiblity of the cushioning layer is preferably such
that the amount of compression is within the range of 2% to 50% of the
unloaded thickness. It is preferred that the compression is within the
range of 5% to 25% of the original thickness. It is further preferred that
in its loaded state the deflection of each protrusion does not exceed
70.degree. from its unloaded or no load position. It is preferred that the
deflection is under 45.degree. and preferably less than 30.degree. or even
25.degree. in its maximum load condition.
The cushioning layer in accordance with the present invention may be a
unitary construction comprising a sheet-like base having a plurality of
shaped orthogonal protrusions extending upwardly therefrom.
The cushioning layer so constructed is preferably formed from a flexible
material which is typically elastic and resilient like rubber; the
protrusions may be adapted to yield on the application of a load thereto
by deflection of the protrusions laterally in response to the load
applied.
The cushioning layer may alternatively be a textile sheet material provided
with loops; a typical material being a polyester filament of 850 to 900
denier with a 25-30 micron core covered with cotton yarn by, for example,
core spinning.
The protrusions may be substantially regular in cross-section and
preferably have rounded upper surfaces to provide a comfortable contact
with a body with which it is in contact; the protrusions may be arranged
on said base layer to form a regular array.
Provided the protrusions are capable of the deflection referred to above,
the shape of the protrusions may be cylindrical, conal, pyramidal, or
loop-shaped, the physical properties of the material being such that a
body supported on the cushioning layer is always carried by the
protrusions, the protrusions each of which is of sufficient dimension and
substance so that at all times air can circulate between adjacent
protrusions to gain access to the surface of a body supported thereon.
Small movements of the supported body may change the relative loading of
the protrusions on the layer, and thus there may be no distinct pressure
points on the body to which air cannot circulate.
The shape and length of the individual protrusions, and the spacing between
adjacent protrusions may be varied over the surface of the cushioning
layer.
In a further variation of the invention, the base sheet of the cushioning
layer may be provided with a plurality of holes; said holes may be
disposed in a regular array. In some embodiments of the invention, holes
may be provided in the base of the material in some areas of the
cushioning layer but not in others. Further, the size and shape of the
holes may vary over the surface of the cushioning layer.
The protrusions and/or holes of the cushioning layer may be arranged in a
pattern.
The base sheet may also be associated with an absorbent layer which serves
to absorb moisture, perspiration and the like thereby further enhancing
the properties of the support.
Where large areas of cushioning material are required, and/or where the
cushioning layer has to be handled frequently for washing, sterilizing
etc., the cushioning layer, in accordance with the present invention, may
advantageously be assembled from relatively smaller units which are easier
to handle. The smaller units may be assembled to form the required larger
area of cushioning layer by a variety of releasable fastening means such
as zippers, press fasteners, male/female stud/hole systems, meshing studs,
adhesive tape, or "hook and loop" fastening means such as that which is
commercially available under the trade name "VELCRO". Such fastening means
may be formed together with the cushioning layer during e.g. a casting
operation, or it may be inserted into the mould during casting;
alternatively, it may be subsequently applied to the cushioning layer.
The cushioning material, during or after its formation, may be attached to
other sheet materials which, for example, may be capable of being durably
shaped into any desirable shape such as a seat/backrest assembly.
Alternatively, the cushioning material itself may be given a 3-dimensional
shape either during casting, or subsequently by mechanical deformation.
Polymers found to be useful in the manufacture of the cushioning layer, in
accordance with the present invention, and for providing properties
desirable for specific applications of the cushioning layer, include
elastic polymers. Such polymers may be thermoplastic or duroplastic and
they comprise polymers produced by polymerization, polycondensation,
copolymerization, or of polymer blends. The polymeric materials for use in
manufacturing a cushioning layer according to the present invention may
for, certain applications, contain cells filled with air or liquids to an
extent which does not have a deleterious effect on the resilience of the
protrusions of the cushioning layer.
The specific requirements of the end use of the cushioning layer determine
the particular polymeric material to be used.
In the case of decubitus prevention, for example, easy cleaning, resistance
to sterilizing conditions, low aqueous liquid pick up, and resistance to
staining are desirable and, in this case, elastomeric silicone polymers
have been found to be particularly suitable.
The present invention also comprehends beds, couchs, seats, back rests and
the like incorporating the cushioning layer of the present invention.
The following is a description by way of example only and with reference to
the accompanying drawings of methods of carrying the invention into effect
.
In the drawings
FIG. 1 is a perspective view of a typical cushioning layer in accordance
with the present invention.
FIG. 2 is a section on the line II--II of FIG. 1.
FIG. 3 is an enlarged portion of FIG. 2 showing deflection of the
protrusions; and
FIG. 4 is a portion of the underside of the cushioning layer of FIG. 1.
FIGS. 5-8 are portions of the cushioning layer showing the protrusions
having various shapes.
FIG. 9 is a portion of the cushioning layer showing the protrusions varying
in shape, spacing and length.
FIG. 10 is a section on the line X--X of FIG. 9.
FIG. 11 is a section showing the base sheet as an absorbent layer.
FIGS. 12-17 are sections showing various embodiments of fastening means.
FIG. 18 is a section showing the cushioning layer formed from a material
having fluid filled cells.
FIG. 19 is a section showing the cushioning layer with the base sheet
laminated to a layer of moldable material.
The cushioning layer is formed from a flexible resilient plastics material,
typically a silicone rubber of Shore `A` hardness 55, and comprises a base
10 and a plurality of upwardly extending protrusions 11 which extends in
uniform spaced relationship in lines and rows from base 10. Each
protrusion 11 is formed substantially integrally with base 10 and
comprises an upwardly extending cylindrical portion 12 having a
hemispherical upper surface 13, the ratio of the height to diameter of
each protrusion being approximately of the order of 3:1.
The base 10 is provided on its underside 14 with a plurality of recesses 15
each communicating with a through hole 16 which pierces base 10. Each
through hole 16 is adjacent an upstanding protrusion 11, the arrangement
being such that each of four upstanding protrusions are spaced about the
periphery of through hole 16.
The whole product is arranged so that when a load, such as a portion of the
human body, is applied to the cushioning layer, the protrusions flex and
bend as shown in FIG. 3, but the resilience of the protrusions is selected
such that the maximum load applied does not permit complete collapse of
the protrusions, and at all times air will be capable of circulating
between the body surface indicated by line 20 and the base 10 by virtue of
access from the underside via the through holes 16 and through the
spacings between the rows and lines of protrusions 11.
The hemispherical extremity 13 of each protrusion 11 provides a high level
of comfort, while at the same time permits adequate air circulation to
remove water vapor thus reducing the accummulation of perspiration, which
results in the wetting of the skin, sheets or clothing, and reducing the
possibility of the occurence of Decubitus.
A cushioning layer as herein described provides a surface which is capable
of distributing the pressure due to an irregularly shaped load or body
supported thereon which acts on the underlying supporting structure,
thereby to lower the unit area pressure between the body and the support
structure thus providing a generally comfortable support. In use, the
protrusions of the cushioning layer permit free air circulation
therebetween to contact the surface of the body supported and to remove
water vapor, thereby reducing the accumulation of perspiration, which
otherwise may result in the wetting of the skin, sheets or clothing, and
reducing the possibility of decubitus and "bed sores".
Particular applications for a cushioning layer in accordance with the
present invention include seats and back rests for use in vehicles, office
chairs, seats which are used in hot and/or humid environments, and,
generally, seats for use in situations where people have to sit for
prolonged periods of time e.g. aircraft seats. The use of a cushioning
layer as herein described in or on such seats provides more comfort for
bony as well as for obese people by allowing air circulation to remove
humidity and by distributing the weight over a wider surface.
The cushioning layer as herein described may also increase the comfort to a
body lying or sitting on such a layer by stimulating blood circulation in
those parts of the body in contact with the protrusions of the cushioning
layer; this effect may be enhanced when the weight of the body is shifted
slightly from time to time.
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