U.S. patent number 3,678,520 [Application Number 05/097,868] was granted by the patent office on 1972-07-25 for alternating pressure pads for bed patients.
This patent grant is currently assigned to Talley Surgical Instruments Limited. Invention is credited to Ronald James Peter Evans.
United States Patent |
3,678,520 |
Evans |
July 25, 1972 |
ALTERNATING PRESSURE PADS FOR BED PATIENTS
Abstract
An air cell for use in an alternating pressure pad has a tube
with its wall of flexible sheet material and at least the outermost
half of the length of that tube, considered in the direction
outwardly longitudinally from the longitudinal center of the tube,
having its width increasing towards the remote end of the tube, a
preferred form having the tube composed of two similar
frusto-conical portions joined at their smaller ends.
Inventors: |
Evans; Ronald James Peter
(Bushey Heath, EN) |
Assignee: |
Talley Surgical Instruments
Limited (Hertfordshire, EN)
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Family
ID: |
9998094 |
Appl.
No.: |
05/097,868 |
Filed: |
December 14, 1970 |
Foreign Application Priority Data
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Mar 13, 1970 [GB] |
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12,082/70 |
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Current U.S.
Class: |
5/713; 5/932;
297/284.1; 601/24; 297/DIG.3 |
Current CPC
Class: |
A61G
7/05776 (20130101); Y10S 297/03 (20130101); Y10S
5/932 (20130101) |
Current International
Class: |
A61G
7/057 (20060101); A61g 007/10 (); A47c
027/08 () |
Field of
Search: |
;5/91,348 ;297/DIG.3,456
;128/24,33 ;156/156 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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996,959 |
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Dec 1951 |
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FR |
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959,103 |
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May 1964 |
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GB |
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Primary Examiner: Nunberg; Casmir A.
Claims
I claim:
1. An air cell, for use in plural assembly in an alternating
pressure pad, comprising a discrete elongated tube of flexible
sheet material, the wall of said tube being varied, in its
peripheral dimension measured in a plane normal to the median
longitudinal axis of the tube, at points along the length of the
tube such that at least the outermost half of the length of the
tube, considered in the direction outwardly longitudinally from the
longitudinal center of the tube, increases in both width and height
towards the remote end of the tube.
2. An air cell, as claimed in claim 1, wherein the portion of
increasing width and height is frusto-conical.
3. An air cell, as claimed in claim 2, wherein the tube is composed
of two similar frusto-conical portions joined at their smaller
ends.
4. An air cell, as claimed in claim 2, wherein the tube is composed
of an intermediate cylindrical portion, and two similar
frusto-conical portions each joined at its smaller end to a
respective end of the cylindrical portion.
5. An air cell, as claimed in claim 1, connected at one of its ends
to a header tube.
6. For use in an alternating pressure pad, a series of air cells as
claimed in claim 1, disposed in spaced parallel position and each
connected at one end to a common header tube.
7. An alternating pressure pad comprising two series of air cells
as claimed in claim 6 disposed with the cells of the two series
interdigitated.
8. In combination, an alternating pressure pad as claimed in claim
7, and means for supplying air to and exhausting air from the
series of cells, such that the two series of cells are inflated and
deflated alternately.
Description
This invention relates to alternating pressure pads for bed
patients, as used for example for the prevention of bed sores and
other conditions arising from restricted circulation of the blood.
Such pads comprise essentially a number of sets of collapsible air
cells which together provide a surface for supporting the patient,
the arrangement being that from time to time some of the cells are
inflated and others are deflated, with the result that the patient
is supported by pressure exerted at different areas of the body at
different times, and no one area of the body remains permanently
under pressure. A convenient construction already commercially
available in the United Kingdom has the cells in the form of
substantially cylindrical tubes made of flexible plastics material
and each fed with air, and exhausted, through header pipes
connected at one end, the tubes being each positioned loosely
within an open-ended cylindrical pocket of flexible plastics
material serving to retain the assembly of tubes in position.
It has been found that, using cylindrical air tubes, there is a
danger that a patient may simply roll off the pad or mattress
sideways, particularly in the case of subnormal patients.
It has also been found that, as patients vary widely in their width
across the body and also in their weight, it is desirable to
provide such pads or mattresses in which the support given by the
air tubes is provided over a suitable width of the pad, and is also
proportionate to the weight of the patient. Hitherto, this has
necessitated the production of at least two types of pad, i.e. a
pad having a large number of tubes of relatively small diameter,
for use with patients of small size and weight, and a pad having a
lesser number of tubes of greater diameter for use with patients of
greater size and weight.
The object of the present invention is to provide an improvement in
the nature of the air tubes which results in the pad automatically
assuming, under loading, a shape tending to prevent the patient
rolling to either side of the pad, and which permits a single type
of pad to be equally suitable for both small and light patients,
and large and heavy patients.
According to the present invention an air cell for use in an
alternating pressure pad comprises a tube having its wall of
flexible sheet material, at least the outermost half of the length
of said tube, considered in the direction outwardly longitudinally
from the longitudinal center of the tube, having its width
increasing towards the remote end of the tube.
The portion of increasing width may most conveniently be
frusto-conical, and in a preferred construction of the tube it is
composed of two similar frusto-conical portions joined at their
smaller ends. In other form, the tube is composed of an
intermediate portion, which may conveniently be cylindrical, and
two similar frusto-conical portions each joined at its smaller end
to a respective end of the intermediate portion.
Two results are obtained from the construction of the invention.
Firstly, as each tube is wider, i.e. higher, at its ends as
compared with centrally, there is provided a natural rim or barrier
tending to keep the patient on the central area and preventing
rolling off the pad laterally. Moreover, when the weight of the
patient is applied to the pad, the tubes bend under the load until
their lower longitudinal face is presented flat against the
underlying support, whereby the upper longitudinal edge is
presented at a doubly-steep angle and the rim or barrier effect
becomes more pronounced.
Secondly, the assembly of tubes forming the pad are all of the
"narrow center and wide ends" shape, so that when viewed in plan,
the central area of the pad has relatively narrow tubes widely
spaced, whereas the lateral areas of the pad have relatively wider
tubes more narrowly spaced. Accordingly, when a small (narrow
bodied) patient is placed on the pad, the body is supported by
smaller tube portions at wider spacing, which is the desirable
arrangement for a light body. When a heavier (wide bodied) patient
is placed on the pad, the body is then supported largely at the
sides by the wider tube portions of smaller spacing, which is the
desirable arrangement for a heavy body. The width and spacing of
the end portions of the tubes varies progressively towards the
lateral edges, so that there is obtained automatically a
self-proportionating supporting effect, according to the width and
weight of the patient, without requiring any change in the shaping
or degree of inflation of the tubes. As a result, a single
production model of pad can be used for patients of all sizes and
weights.
A further advantage is gained that, as the central portion of the
pad consists of portions of tube which are of smaller diameter and
which are relatively widely spaced, there is considerably less
pressure exerted at the central area, and the spinal cord area of
the patient is accordingly subjected to less upward pressure than
the more lateral portions of the body.
Where the air tubes are each positioned loosely in a tubular
pocket, to retain them in assembly, the further advantage is gained
that each tube, being at some point along each end portion of a
greater diameter than the pocket in which it is positioned,
automatically settles itself symmetrically into the pocket and
remains tightly gripped to prevent any rolling or longitudinal
movement with respect to the pocket.
Whilst the tubes are substantially cylindrical at their center at
the narrowest point, they become gradually more oval in the
direction towards their two ends. For example, in the case of a
practical embodiment in which the center portion is approximately
three inches in circumference, the ends are approximately four
inches high but about seven and one-half inches wide, i.e. somewhat
pillow shaped. This shape is a distinct advantage in the use of the
pad, because it is found that, with patients who are nursed in a
sitting position on such pads, i.e. having separate air tubes
contained in retainer pockets, the tubes may tend to roll under the
patient's body, because of the angle assumed by the body. This
action can be damaging to the patient's skin because it causes the
exertion on the skin of a shearing force due to the weight on the
sacram area. Such shearing force, exerted on the skin, is one of
the major causes of pressure sores. However, the somewhat oval
shape adopted by the tubes described above discourages any tendency
for such rolling to occur in the manner described. Moreover, the
shape adopted by the tube, upon inflation, is substantially
wrinkle-free, so that stress on the material is reduced.
Each cell may be fed with air by connecting it at one end to a
header tube, and in a convenient arrangement a series of the cells
are disposed in spaced parallel position and each connected at one
end to a common header tube. In an alternating pressure pad, two
such series of air cells may be disposed with the cells of the two
series interdigitated, and means may be provided for supplying air
to and exhausting air from the series of cells, such that the two
series of cells are inflated and deflected alternately.
Apparatus for use in making the air cell may comprise two mould
electrodes defining between them a cavity having the shape of the
tube to be formed, means for introducing air between two sheets of
heat-sealable plastics material disposed between said mould
electrodes so as to cause the sheets each to conform to the shape
of a respective mould electrode, means for moving the electrodes
together so as to clamp the two sheets peripherally, and means for
applying R.F. energy to the two mould electrodes so as to seal the
sheets together where they are clamped peripherally. A symmetrical
half portion of the cavity may be included in each of the mould
electrodes, or the entire mould cavity may be included in one mould
electrode whereas the other mould electrode is plane.
A method of making the air cell comprises the steps of disposing
two sheets of heat-sealable plastics material between two mould
electrodes defining between them a cavity having the shape of the
tube to be formed, introducing air between the two sheets so as to
cause them each to conform to the shape of a respective mould
electrode, moving the mould electrodes together so as to clamp the
two sheets peripherally, and applying R.F. energy to the two mould
electrodes so as to seal the sheets together where they are clamped
peripherally.
In order that the nature of the invention may be readily
ascertained, an embodiment of alternating pressure pad
incorporating the improved tube, some constructions of tube, and
apparatus and a method for the manufacture of such tubes, are
hereinafter particularly described with reference to the
accompanying drawings, wherein:
FIG. 1 is a plan view of an embodiment of alternating pressure
pad;
FIGS. 2a and 2b show a first form of tube respectively in unloaded
and loaded condition;
FIG. 3 shows a second form of tube;
FIG. 4 shows in central vertical longitudinal section a form of
mould for making the tube of FIGS. 2a and 2b, the mould being shown
at a first stage of the production;
FIG. 4a is a central vertical transverse section of the mould of
FIG. 4, in a second stage of the production;
FIG. 5 shows, in central vertical longitudinal section, a
modification of the mould of FIG. 4;
FIG. 6 is a plan view of another embodiment of alternating pressure
pad;
FIG. 7 is a partial section taken on the line VII--VII of FIG.
6.
The alternating pressure pad shown in FIG. 1 has two interdigitated
series of tubes 1a, 1a, 1a and 1b, 1b, 1b arranged in parallel
position transversely of the pad, the tubes of each series being
connected together and the two series being alternately inflated
and deflated. The tubes of each series are connected together, all
at the same end, by respective flexible header pipes 2 coupled to a
rotary valve 3 having a connection to a pump 4, and an exhaust 5.
The tubes are arranged each in an individual cylindrical tubular
pocket 6 formed by securing a sheet 7 at intervals to a base sheet
8 of the pad, whereby each tube is held in proper position in
relation to the others. Individual tubes can be disconnected and
changed on site. The entire assembly of tubes, in their pockets, is
covered by a loose top cover 9 which is held in place, at the head
and foot of the pad, by conventional fasteners 10 such as press
studs.
Referring to FIG. 2a, each air tube 1a and 1b is composed of two
similar symmetrical frusto-conical portions 11 connected at their
smaller ends at the longitudinal center point of the tube. By way
of example, for a total tube length end-to-end of about thirty to
thirtysix inches, the smallest diameter would be about three inches
at the center point and about five inches at the extreme ends. As
the tube portions are frusto-conical, the longitudinal seams on
them are linear and accordingly there is no wrinkling of the
material when inflated, and fatiguing of the material is
avoided.
FIG. 2b shows how, when the weight of a patient is applied in the
direction of the arrows, the tube adopts a linear base line and the
upper surface becomes more steeply inclined so as to tend to keep
the patient in a central position.
FIG. 3 shows a tube having two frusto-conical portions 12, and an
intermediate cylindrical portion 13.
The tubes may be made of any convenient flexible sheet material but
preferred materials for the purpose are rubber-coated canvas,
seamed by hand or machine, or plastics material such as
polyvinylchloride, which may be high-frequency welded.
Where welded plastics material is used, the entire tube may be
formed in a single welding operation to form a tear-weld about the
necessary double-conical contour, whereafter the finished tube is
stripped from the surrounding waste. In a preferred method of
forming the tube from plastics material, see FIGS. 4 and 4a, there
is used a welding machine which has a pair of mould-like electrodes
14, 15 which between them define a cavity 16 having the shape of
the eventual tube. Two flat sheets 17, 18 of material are placed
between the mould electrodes 14, 15, and the electrodes are closed
together into the position of FIG. 4, but not sufficiently to grip
the sheets immovably. Air is then blown into the space between the
sheets, in the direction of the arrow in FIG. 4, to cause them to
be inflated to the internal shape of the mould cavity 16. The
electrodes 14, 15 are then brought firmly together, as in FIG. 4a,
to grip the two sheets tightly about the desired contour,
whereafter R.F. energy is applied to the electrodes to form a
heat-seal at 19 about the contour. The material is accordingly
sealed when in its inflated condition, and remains relatively
stress-free. In a modification, seen in FIG. 5, the mould
electrodes 20, 21 are shaped such that the bottom electrode 21 has
a plane face, and the whole of the cavity 22 is contained within
the electrode 20, the bottom sheet 23 of plastics material is
retained flat, and the upper sheet 24 is blown to the shape of the
mould by air introduced in the direction of the arrow, a seal is
formed along the base of the eventual tube as described in relation
to FIG. 4a. A multiple cavity mould-electrode may be used, e.g.
having say four cavities each provided with means for injecting air
between the upper and lower sheets placed between the upper and
lower electrodes.
FIGS. 6 and 7 show another embodiment of alternating pressure pad,
seen in deflated condition. A base sheet 25 has on it two
interdigitated series of tubes 26 each of which is formed by two
similar frusto-conical portions joined at their smaller ends. Each
tube is attached to the base sheet by a fastener 27, to permit easy
replacement.
On top of the two of tubes 26 there are provided three parallel
retainer strips 28 of flexible material which are secured, e.g.
welded, to the base sheet 25 between each neighboring pair of
tubes, so as to form pockets in which the tubes are engaged. At the
ends of the base sheet it has fasteners 29 by means of which a
cover sheet 30 is secured in position.
The two series of tubes 26 are connected by T-junctions 31 to
respective header tubes 32 and 33 which are coupled to a rotary
valve 34 having an inlet 35 from a pump 36, and an exhaust 37.
* * * * *