Wheel chair abstract
A pneumatic device for therapeutic treatment of the skin and skin
pressure areas of immobile patients seated in a chair, or a mobile
wheel chair, which provides for alternating low air loss pressure
sacs that are in contact with the seated patient that includes an
air sac array overlay that is conveniently and quickly mounted to
a bedside chair, or wheel chair, a portable air supply that can
be attached for controlling the individual air sac alternating air
pressures, the portable air supply housing being mounted on the
side arm of a chair, or another location on a wheel chair, and a
separate removable coverlet that is liquid impervious for incontinent
patients while providing for sweat absorption for the patient seated
thereon. The portable air supply can be quickly detached from the
air sac chair overlay for use with a bed mattress air pressure alternating
device. The portable air supply being battery powered when used
on a mobile wheel chair.
Wheel chair claims
What is claimed is:
1. An alternating pressure air sac overlay for therapeutic treatment
of an immobile patient's skin while seated in a wheel chair, comprising:
an array of elongated independently sealed air sacs constructed
of an airtight material, sized in length to fit across a wheel chair,
said individual air sacs being tubular in shape, mounted in a fixed
side-by-side array, the overall longitudinal length of the air sac
array being sized to fit at least on a seat of said wheel chair,
a first group of independent air sacs being separated by a second
group of air sacs in a side-by-side array, so that every other one
of said air sacs in said first group and every other alternating
one of said air sacs is contiguous with said first group to form
said second group of air sacs;
first conduit manifold connected to said first group of air sacs;
second conduit manifold connected to said second group of air sacs;
a battery powered air pump having an inlet and an outlet for providing
pressurized air in fluid communication and connected to said first
conduit manifold and said second conduit manifold;
controllable air inlet valve means connected to said air pump and
said first conduit manifold and said second conduit manifold, whereby
in a first position, said air inlet valve means provides air pressure
only to said first conduit manifold from said air pump, and in a
second position, provides air under pressure only to said second
conduit manifold from said air pump;
means including timing circuits for controlling air in a timed
sequence into said first conduit manifold and said second conduit
manifold from said air pump connected to said air pump;
an electrical battery power supply connected to said air pump,
said electrical battery power supply having means for recharging;
said timing circuits connected to said electrical battery power
supply and said means for controlling air in a timed sequence;
a coverlet comprising a liquid impervious barrier means removably
connectable to said air sac array, covering said air sac array to
provide a protective shield against liquids reaching said air sac
array, said coverlet porous to water vapor molecules, said coverlet
including means for attachment to said wheel chair seat.
2. A device as in claim 1, including a control housing enclosing
said air pump, said controllable air inlet valve means, said battery
power supply, and said means for controlling including said timing
circuits, said control housing being sized for individual lifting
and including fastening means for mounting on said wheel chair.
3. A device as in claim 2, wherein said means for recharging includes
a power cord removably connected to said control housing and connectable
to a standard 110 volt AC house receptacle, wherein said device
recharges and operates from standard 110 volt AC house current.
4. A device as in claim 2, wherein said control housing includes
means, remote from said control housing, for operator control of
5. A device as in claim 1, wherein said electrical battery power
supply is a 12 volt DC battery.
6. A device as in claim 1, wherein said device includes means for
connection to a remote battery power supply.
7. A device as in claim 6, wherein said means for connection includes
a cigarette lighter adapter plug for connection to a car battery
8. A device as in claim 1, wherein said controllable air inlet
valve means include at least one 12 volt DC solenoid.
9. A device as in claim 1, wherein said coverlet means for attachment
includes a sheet of non-skid foam rubber connected to an underside
of said coverlet to keep the coverlet in place on said wheel chair
Wheel chair description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to an alternating low air loss
pressure chair overlay for an immobile bedside patient, or a mobile
patient wheelchair, to prevent treat skin inflammations and decubitus
ulcers while the patient is seated in a bedside, or mobile chair,
and specifically, to an improved alternating air pressure chair
overlay, with coverlet, that prevents skin breakdown and allows
for single patient, bed and chair dual usage with one air pressure
control unit that can be used with an alternating air pressure bed
mattress and with the alternating pressure chair overlay.
2. Description of the Prior Art
The use of air mattresses and in particular, alternating pressure
air mattresses in beds to prevent decubitus ulcers is well known.
U.S. Pat. No. 4,944,060, issued Jul. 31, 1990 to Peery et al., shows
a mattress assembly for the prevention and treatment of decubitus
ulcers. Typically, a plurality of air sacs or cells are individually
filled or emptied at different locations to change the pressure
contact on the immobile patient's skin.
Skin diseases, skin pressure problems, and decubitus ulcers are
caused from lack of movement when skin areas of a person are subjected
to constant pressure for long periods of time. For people who are
basically immobile and are bedridden, decubitus ulcers are a serious
problem. U.S. Pat. No. 5,267,364, issued Dec. 7, 1993 to Volk, shows
a therapeutic mattress that provides a wave-like deformation of
the patient-supporting surfaces in tubular elements along a selected
portion of the length of a mattress to prevent decubitus ulcers.
U.S. Pat. No. 4,953,247, issued Sep. 4, 1990 to Hasty, shows airtight
sacs in a parallel array that supports a patient, in which the air
pressure can be changed in each individual sac as a function of
time. The air sacs are arranged as a support mattress for a patient
in bed. The devices shown in the prior art are shown as support
bed mattresses for patients who are immobile and confined to bed
or bedridden for long periods of time. Oftentimes, it is desirous
to have the patient removed from the bed so that the patient can
sit upright for periods of time, even though the patient is basically
immobile. During periods when the patient is seated in a chair,
it would also be desirous to provide a support system that would
prevent skin problems continuously caused by skin surface pressure
immobility from the support surface. U.S. Pat. No. 4,981,131, issued
Jan. 1, 1991 to Hazard, shows a passive motion back support which
can be attached to a chair for improving the back support for a
None of the devices in the prior art provide for an individualized
skin pressure sensitive support surface for a patient seated in
a chair for long periods of time to prevent decubitus ulcers or
other skin diseases. The present invention overcomes these problems,
while at the same time providing for a chair-mountable air support
device that can utilize a standard air pump and distribution device.
Furthermore, none of the devices provide for portability to allow
use in a mobile wheel chair.
SUMMARY OF THE INVENTION
A pneumatically-adjustable, patient support chair overlay for providing
pneumatic support for a seated person, said overlay being connected
to a chair, or wheel chair, for providing variable pressure pneumatic
support on the chair seat and on the chair back for alleviating
skin disorders of a person seated therein, said overlay comprising
a plurality of parallel, independent elongated tubular air sacs
mounted together side-by-side, said air sac array being sized in
length and width to fit contiguously upon the seat of a chair, or
wheel chair, and upon the inside back of a chair, said overlay including
a first end segment flexible sheet (connected to the air sac array
but having no air sacs) and a plurality of chair mounting straps
connected to selected edges of said air sac array and said flexible
sheet, each of said straps being connectable around parts of a chair
and the chair legs, or wheel chair frame. The overlay also includes
a flexible, protective coverlet having snap fasteners (male and
female connectors) to attach to the top of the air sac array. The
coverlet is sized to fit over the top of said overlay to provide
an impervious liquid barrier to protect against incontinence, but
is vapor permeable (breathable) to prevent moisture buildup between
the patient skin and the fabric. The coverlet structure includes
a moisture absorbent layer to absorb body sweat and moisture. The
coverlet structure is comprised of an absorbent fabric sheet attached
to a liquid proof nylon sheet and a polyurethane barrier.
The overlay air sacs are filled under pressure by an air pump with
pressure and volume control solenoid valves and outlet lines (at
least two) and includes a chair arm mount, such as a U-shaped member,
to allow the air pump to be hung vertically from one of the chair
arms (out of the patient's way).
In the mobile wheel chair embodiment, the controller, pump, and
solenoid valves are enclosed in a larger enclosure that also houses
battery power. The enclosure is provided with a series of hook and
loop fasteners that can be wrapped around any part of the wheel
chair. The enclosure can then be attached to the chair back, the
handles, under the chair, or on a wheel chair platform on larger
models. The overlay cushion of the mobile wheel chair embodiment
can fit the seat only or can fit the seat and back of the wheel
chair, but does not require the "first end segment flexible
sheet without air sacs" that is part of the bedside chair overlay
The air pump and control valves and circulating air supply can
be used interchangeably between the chair overlay and a mattress
system so that the air supply need only be connected to a pair of
flexible input air lines which are connected to the air sacs as
In one embodiment, alternating air sacs in a side-by-side array
are connected together in fluid communication to a first inlet air
supply conduit (manifold) along one side of the length of the chair
overlay connected to the output of the air pump. A second inlet
air supply conduit is connected in fluid communication to the remaining
alternating air sacs not connected to the first air supply conduit.
The air pump has two outlet nozzles that connect to the first and
second inlet air conduits connected to the air sacs. The solenoid
valves direct the air flow from the air pump above atmospheric pressure
either into the first conduit or the second conduit based on an
electric air supply controller. A timer provided in the air supply
control circuitry, which is electrically powered, changes the sequence
of the air control valves after a predetermined amount of time passes,
such as five minutes. Thus, in the first five-minute time period,
the first inlet air supply conduit is supplied with air under pressure
that inflates every other air sac to a predetermined pressure level.
Adjacent air sacs are not inflated.
In the second five minute period, the alternating other air sacs
are filled with air under pressure, while the first filled air sacs
lose their air pressure when the pump flow stops and by the force
of the seated person's weight.
A patient-engaging strap may also be used once the patient is mounted
in the chair for encircling the waist of the patient to aid in or
help prevent the patient from sliding downward in the chair.
The purpose of the coverlet is to provide a hygienically clean
cover that protects the pneumatic air sac array to allow single
patient usage by changing the coverlet and cleaning the coverlet
in case the patient is incontinent. This will prevent damage to
the pneumatic air sac array. The structure of the coverlet includes
a first layer of a nylon material of very minimal thickness attached
to a layer of polyurethane approximately 1 mil. in thickness which
provides a water and liquid proof barrier. Water vapor will pass
through this barrier as backing on the nylon material. An additional
layer of an absorbent Dacron quilting material or other suitable
vapor absorbent backing is sewn around its edges to the nylon, which
is the underside of the coverlet. The Dacron quilting, which is
moisture or sweat absorbent, is thus on the underside of the coverlet
and abuts the top of the air sac array. The nylon and polyurethane
protective barrier is thus on the top side. When a patient sits
on the nylon polyurethane barrier, if the patient is incontinent,
liquid will not pass through the nylon polyurethane barrier. On
the other hand, moisture such as sweat can pass through the nylon
polyurethane as vapor, where it is absorbed into the Dacron quilting
material so that the patient is comfortable and yet the air sac
array is protected, especially from incontinence.
In the operation of the device, the variable air pressure changes
to the air sacs per unit time can be set by control circuitry and
timer circuitry in an air supply control box that is connected electrically
to solenoid-actuated pneumatic valves connected to the air pump
conduits. The control box has a U or L-shaped hanger on the box
housing top that allows the air supply box to be supported from
a chair arm. Each of the air supply first and second air conduits
can be quickly attached or detached from the air supply pump in
the control box, allowing the portable air supply to be connected
to and interchanged with an alternating air pressure bed mattress
so that for cost effectiveness, the same air pressure pump and control
box can be used with either a pneumatic bed or on a pneumatic chair,
depending whether the patient is in the bed or in the chair.
In the mobile wheel chair embodiment, the control box also houses
battery power. The battery can be a 12 volt, 4 amp hour sealed lead
acid type providing approximately 10-15 hours of operation before
recharging is necessary. The pump, control PC board, and solenoids
all run off of 12 VDC instead of standard household current of approximately
110 VAC. The control box, including battery, is a small light weight
unit of approximately 7 pounds and with dimensions of 8".times.31/4".times.51/2".
The control housing in the mobile wheel chair embodiment utilizes
hook and loop fasteners to permit attachment to any part of the
The battery in the mobile wheel chair embodiment recharges in approximately
4 hours using standard 110 VAC household current. An external 110
VAC battery charger cord plugs into a standard wall outlet. If desired,
the mobile wheel chair controller box can operate directly off of
110 VAC household current instead of battery power, using the charger
cord. Alternately, the mobile wheel chair overlay controller can
be plugged into and operated from another 12 VDC system, such as
a car battery, using a cigarette lighter adapter plug.
The mobile wheel chair control box also provides a remote hand
held pendant attachable to any convenient location on the wheel
chair using hook and loop type fasteners. The remote pendant houses
pressure adjustment controls to provide the patient easy access
in turning the unit on or off, selecting between static air pressure
(all air sacs are inflated) or alternating pressure (alternating
inflation and deflation of adjacent rows of air sacs). The remote
pendant also contains a low battery warning light to alert a low
battery power condition. To prevent complete discharging of the
battery, a battery safety cut off is provided.
The coverlet in the mobile wheel chair embodiment is shaped like
a pillow case, having three sides closed. The fourth side is provided
with a series of snaps at its edge to close the coverlet around
the cushion overlay. The bottom of the coverlet has a non-skid sheet
of foam rubber attached to keep the overlay in place on the seat
of the wheel chair.
Accordingly, it is an object of this invention to provide a pneumatic
overlay for a chair that can provide alternating pneumatic pressure
to address problems of skin breakdown and decubitus ulcers for a
It is another object of this invention to provide a variable pneumatic
pressure patient support overlay that can fit over patient bedside
chairs, recliners, stretchers, geriatric chairs, and wheel chairs,
to prevent skin breakdown problems in the patient when seated for
long periods of time.
And yet another object of this invention is to provide an improved
chair for providing alternating air pressure support overlay to
one sitting in the chair, and that also includes a protective cover
for hygiene purposes within a hospital environment, with a detachable
air supply for use with a pneumatic bed mattress.
It is still a further objective of this invention to provide a
portable pneumatic overlay for a wheel chair that can provide alternating
pneumatic pressure to address problems of skin breakdown and decubitus
ulcers for a wheel chair seated patient.
In accordance with these and other objects which will become apparent
hereinafter, the instant invention will now be described with particular
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an exploded perspective view of the present invention.
FIG. 1A is a side elevational view in cross section, partially
cut away, showing a portion of the coverlet.
FIG. 2 shows a cut away side elevational view, partially in cross
section, of the overlay in accordance with the present invention.
FIG. 3 shows a top plan view of the coverlet used in the present
FIG. 4 shows a top plan view of the pneumatic overlay in the present
FIG. 5A shows an exploded perspective view of an alternate embodiment
of the present invention for a mobile wheel chair.
FIG. 5B shows a perspective view of the bottom of the coverlet
of the embodiment of FIG. 5A.
FIG. 5C shows a perspective view of the power cords of the embodiment
of FIG. 5A.
FIG. 6 shows a perspective view of the alternate embodiment shown
in FIG. 5A.
FIG. 7 shows a perspective view of another embodiment of the present
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and in particular FIG. 1, the present
invention is shown generally as a chair overlay 10, comprised of
an alternating air pressure controlled air sac array 12 that can
be removably attached to a conventional chair 14 with a plurality
of straps, a coverlet 18 that can be removably attached over the
top exterior surface of the air sac array 12 as a liquid barrier,
a portable air supply including air flow and pressure control for
providing air pressure, including a pump housed in air control supply
box 16, that includes a hanger 16a which allows the entire device
to be mounted on the arm 20 of chair 14. The air control components
and circuits in supply box 16 are electrically powered, including
the air pump maintained therein, through a cord 44 having an outlet
plug 46 that plugs into a conventional 110-volt electrical system.
Inside the air control supply box 16 is an electrically powered
air pump, an electrical timer that connects to the air pump and
to a pair of solenoid valves that are attached to the outlet side
of the pump and to inlet conduits 36 and 38, each of which are connected
to alternating side-by-side elongated air sacs 12b and 12c which
make up the array. The air supply box 16 includes a controller knob
42 and a power switch 43 which respectively provides for manual
pressure adjustment and turning the device on and off.
The air sac array 12 has numerous elongated individual, and individually
pressurized, air sacs, pressure controllable through two separate
inlet air conduits 36 and 38, which connect alternately to every
other air sac for providing individual air pressure into the air
sacs. The elongated air sacs are formed from a continuous piece
of air impervious material (plastic) that is heat sealed in its
construction that forms a side-by-side array of air sacs that are
independently sealed and function independently as to the containment
of air. The air sacs formed along a single contiguous sheet stretches
from a distance equal to the length of the base seat of the chair
and the length of the inside back of the chair so that when a person
is seated in the chair, their legs, lower torso, and back will press
against the air sac array and will be subjected to the alternating
air pressure in the air sacs as described below.
The back part of the air sac array 12 includes an end panel or
segment 12a that is a sheet that stretches down over the back of
the chair 14 and terminates in a pair of straps 22 that have hook
and pile fasteners 31 connected thereto, which allow the array 12
to be anchored around the legs of the chair 14 to hold the entire
air sac array overlay 12 firmly in place on the chair.
Additional straps 24, 26, 28, and 30 are used to firmly attach
the air sac array 12 to the base legs of the chair. The straps each
contain a fabric fastener such as hook and pile 31, commonly referred
to under the trade name Velcro, to allow each of the straps to be
secured together tightly to prevent movement of the array 12.
The purpose of the invention is for skin treatment and the prevention
of decubitus ulcers, which is provided by alternating areas of force
or pressure on the skin of the user. Specifically, an immobile person
seated in the chair 14 can be stimulated in different skin areas
at different time periods using alternate (spaced apart) air sacs
such as 12c which are fully pressurized while the adjacent air sacs
(on each opposite side) are not pressurized. The unpressurized air
sacs collapse under the weight of the person seated in the chair.
Periodically and in accordance with a predetermined time period
that can be set through the control of the air supply box 16, control
knob 42 can be set for the desired pressure of the inflated set
of air sacs. At the end of the time period, a different solenoid
valve is opened, which allows air under pressure from the air supply
box 16 to fully pressurize the alternate air sacs to a predetermined
pressure. The previously pressurized air sacs, when not being pressurized,
drain air back into their own supply line. By alternating air sacs
and the pressure contained therein, different areas of the body
will be tactilely stimulated with force pushing against the body
area to allow for stimulation of the skin area.
It is important, especially in a hospital environment, and especially
with immobile or geriatric patients, that certain provisions be
made for problems such as incontinency or the like. In particular,
a coverlet 18, shown in FIG. 1, FIG. 1A, and FIG. 3 is provided
that includes snap-fit male and female fasteners 32 that permit
the entire coverlet 18 to fit completely over the exterior top of
air sac array 12 and can be snapped firmly in place. The coverlet
18 includes an impervious liquid barrier made from a nylon sheet
18a and 1 mil. polyurethane sheet 18b to prevent liquids from making
contact with any surfaces of the air sac array. In addition, coverlet
18 includes a moisture absorbing quilted fabric such as Dacron which
may be sewn onto the bottom of the liquid barrier 18b so that sweat
or moisture can be absorbed in sheet 18c to prevent discomfort to
the patient while still not permitting liquid from permeating the
top layers 18a and 18b attached to the fabric layer. Moisture vapor
will pass through sheet 18b but liquid will not.
One important feature of the invention is that the air supply box
16 is portable. The two separate air supply conduits 36 and 38 provide
inlet air under pressure for pressurizing the air sacs and can quickly
be removed from nozzles 35 mounted on the side of box 16. Detachment
allows the air supply box 16 to be transported from the chair 14,
where it is hung from chair arm 20, to bedside so that the same
air supply source can be used for an alternating air pressure bed
mattress that is used on the patient's bed. It is important to note
that the same patient would either be in the patient's bed using
the alternating mattress or the patient would be bedside sitting
in the chair. Since the patient can only be in one or the other
place at a time, it is a definite advantage that the air supply
16 can be easily attached or removed from either the alternating
air supply chair overlay or the bed mattress, resulting in great
cost savings by using only one air supply in both situations.
Each of the air supply conduits 36 and 38 attached along one side
of the air sac array 12 supply inlet air to alternating air sacs
12b or 12c through inlet openings much like a manifold along each
side. Thus, conduit 36 supplies air above atmospheric pressure to
every other air sac through an opening nozzle that is attached to
every other, or alternating, air sacs. Basically, there is one passage
into each air sac from the inlet conduit going in at one end through
an opening with a steady source of air once the air pressure above
atmospheric is introduced into that particular inlet conduit 36
or 38. When the source of air pressure is removed, then residual
air in the air sac will travel back into the inlet conduit by seat
pressure of the patient, reducing the pressure in the particular
A separate strap 28 can be used that fits underneath the chair
and goes around the midsection of a person sitting in the chair
to hold them firmly in the chair to prevent them from sliding or
moving downwardly. The strap 28 also includes Velcro fabric fasteners
31 on each end to allow for maximum adjustability based on the size
of the patient seated in the chair.
Referring now to FIG. 2, inlet air conduits 38 and 36 are shown,
each connected to a different air sac 12b or 12c for providing alternate
air under pressure to alternating air sacs. Air sac 12b includes
an inlet conduit 48 that allows air in inlet conduit 38 to be received
within the air sac 12b. To provide alternate air pressure to alternating
adjacent air sacs 12c, inlet conduit 36 is in fluid communication
with inlet conduits 50, which are sealably attached to one end of
air sacs 12c. Thus, by providing air under pressure into each line
individually at different time, such as air pressure into line 36,
will result in the inflation under pressure of air sacs 12c. Putting
air under pressure into inlet air conduit 38 will result in pressure
being received in air sac 12c. The end of the air sac array conduits
36 and 38 will be sealed as a dead end.
FIG. 3 shows the coverlet 18 that includes a plurality of male
and female fasteners 32 such as snaps, which allow portions of the
coverlet to be snapped together to prevent its removal from, or
slipping on top of, the array 12. Receiving snaps 32 are mounted
on array 12.
FIG. 4 shows the series of straps 22, 24, 26, and 30 which attach
to the chair legs to prevent slippage of the entire overlay 12.
The overall invention offers several advantages, primarily for
preventing or treating skin conditions on immobile patients which
may be subject to severe skin conditions because of the immobility,
even resulting in decubitus ulcers.
The entire device is extremely convenient and can be easily attached
to a bedside chair. With the portable air supply, the air supply
can be plugged into any conventional current outlet and mounted
conveniently on the chair, where it is out of the way of the patient.
The coverlet is put in place which provides for hygienic covering
of the device and prevents liquids from being received directly
on the air sac overlay.
The power supply and the air supply are portable and can be used
in conjunction with either the mattress or the chair, allowing a
single controller and air supply to function for two separate environments,
which is a great cost savings.
Referring now to FIGS. 5A-C and 6, an alternate embodiment of the
present invention, mobile wheel chair overlay 60, which includes
air sac array 61 and coverlet 98, is shown for use in mobile wheel
chair 62. Wheel chair overlay 60 prevents skin breakdown and decubitus
ulcers and covers wheel chair seat 64, as shown in FIG. 6.
Alternately, wheel chair overlay 60 can be configured to cover
seat 64 and wheel chair back 66. Air sac array 61', configured to
cover seat 64 and wheel chair back 66 is shown in FIG. 7.
Mobile wheel chair overlay embodiment 60 operates similarly to
chair overlay 10 already described above, with differences indicated
The controller box 68 houses the air pump, solenoid valves, and
control PC board (not shown), all powered by a 12 volt DC battery
also contained in control box 68. To charge the battery, end 70
of power cord 72, shown in FIG. 5C, is plugged into socket 74 of
control box 68, and end 76 of power cord 72 is plugged into a standard
110 VAC wall receptacle. Recharging the battery takes around 4 hours,
with operation time running approximately 10-15 hours between charges.
Control box 68 can operate directly from 110 VAC current while using
power cord 72. Alternately, control box 68 can be operated from
a separate 12 VDC system, such as a car battery. Cable 78, shown
in FIG. 5C, is connected to socket 74 at end 80 and has a cigarette
plug adapter end 82 for connection to a standard car cigarette lighter
Control box 68 is a small light weight unit weighing approximately
7 pounds including battery and having approximate dimensions of
8".times.31/4.times.51/2". Control box 68 utilizes hook
and loop fasteners 84 to attach to any convenient location of wheel
chair 62, such as below, on the back or on the deck of a large model
wheel chair (not shown).
Remote pendant 86 is connected to control box 68 to provide easy
access to the controls for the wheel chair patient. Remote pendant
86 provides on/off power switch 88, pressure adjustment 90, static/alternating
pressure control 92, and low battery warning light 94. (Static pressure
selection keeps all air sacs inflated and alternating pressure provides
timed, alternating inflation/deflation of adjacent rows of air sacs,
as described herein above). Remote pendant 86 can be attached to
any suitable wheel chair 62 location using hook and loop fasteners
Low battery lamp 94 alerts a user to a low battery condition. To
prevent complete battery discharge, there is a battery safety cut
off that shuts off the device when the battery voltage falls below
a preset minimum level. When the device is shut off, the air sacs
remain inflated so as not to disrupt pressure relief to the patient.
Optionally, control box 68, power cords 72 and 78, and a battery
charger can be placed in a carry case which is hung from the back
of the wheel chair (not shown). Hook and loop fasteners are used
and are sized to allow the carry case to hang low to keep the center
of gravity of the wheel chair low.
Coverlet 98 is constructed similarly to that described herein above
in that it is composed of a nylon material coated with polyurethane
and backed by three layers of quilted batting material and is waterproof
but passes water vapor molecules. The coverlet 98 itself provides
protection against skin breakdown caused by moisture, heat, friction,
and shear. Coverlet 98 is enclosed on three sides, similar to a
pillow case, and slides onto overlay 60 then snapped together at
the open end by snaps 100. The bottom of coverlet 98 has a non-skid
sheet of foam rubber 102, shown in FIG. 5B, attached to it to keep
the wheel chair overlay 60 in place on seat 64.
Construction of air sac array 61 of overlay 60 is similar to air
sac array 12 of overly 10, described herein above, and detailed
as shown and described in the enlarged portion shown in FIG. 2.
The instant invention has been shown and described herein in what
is considered to be the most practical and preferred embodiments.
It is recognized, however, that departures may be made therefrom
within the scope of the invention and that obvious modifications
will occur to a person skilled in the art.