Wheel chair abstract
A pneumatic cushion for a wheel chair and the like is disclosed
which comprises an air plenum box, a plurality of air openings in
the air plenum box, and a plurality of air channels communicating
with an air supply. The air channels communicate with the air openings
to deflate and inflate individual air sacks carried over the air
openings. The air sacks are unattached so that they act individually.
An air distribution manifold includes a rotating blocking member
to periodically block air distribution to the air sacks allowing
them to deflate. The air sacks are constructed from a fabric having
a low air permeability. The blocked air sacks thus allow air to
escape through the sacks for deflation which cools the portion of
the occupant seated on the cushion while allowing temporary pressure
relief during deflation. The air sack inflation system is open so
that, in addition, pressure may be relieved by a backward flow of
air through the system. For this purpose, the blocking member which
selectiely blocks air flow to the air sacks, is in the form of a
one-way valve which blocks air in a first direction, but opens in
a second direction to allow a bleed-off of air from the sacks should
excessive pressures exist in the sacks such as caused by an occupant's
weight shift and the like.
Wheel chair claims
What is claimed is:
1. Apparatus for reducing ischemic injury to a patient which includes
a wheel chair frame and
a pneumatic cushion carried by the frame wherein said pneumatic
air cushion comprises:
an open dynamic air distribution system which periodically reduces
air pressure in selected portions of the cushion wherein said air
distribution system includes:
an air distribution plenum having a plurality of air channels;
an air distribution manifold carried within said plenum for distributing
air to said air channels having an air inlet;
said air distribution manifold extending generally centrally through
said air plenum box with said air channels extending laterally from
said central air distribution manifold;
a plurality of air ports in said air distribution manifold in open
fluid communication with said air channels within said air distribution
plenum;
air blocking means for periodically blocking said air ports in
said manifold to periodically interrupt the distribution of air
in said air channels in accordance with a preselected sequence;
a top member extending over the top of said air distribution plenum
having a plurality of air openings in fluid communication with said
air channels;
a plurality of inflatable air sacks carried by said top member
over said air openings which are inflated and deflated according
to a preselected pattern for reducing ischemic injury to a person
seated on said wheel chair;
a cover extending over said plurality of air sacks which is secured
around the periphery of said air sack; and
a blower for delivering air to said air inlet of said air distribution
manifold.
2. The apparatus of claim 1 wherein said air distribution plenum
includes a plenum box over which said top members extend.
3. The apparatus of claim 2 wherein said air distribution manifold
includes a cylindrical air distribution tube extending centrally
through said air plenum.
4. The apparatus of claim 2 wherein said plenum includes a plurality
of enclosed air compartments formed in said communicating with said
air channels.
5. The apparatus of claim 4 wherein said air compartments are arranged
in an N.times.N matrix where N is the number of compartments in
a row.
6. The apparatus of claim 4 including an air opening over each
said air compartment.
7. The apparatus of claim 6 including sealing means sealing between
said air compartments and said top member.
8. The apparatus of claim 1 wherein said air distribution manifold
includes a cylindrical air distribution tube extending centrally
through said air plenum.
9. The apparatus of claim 8 wherein said air inlet is formed at
a first end of said air distribution manifold tube.
10. The apparatus of claim 9 including a fitting carried by said
air inlet for connection to a blower which delivers air to said
air inlets and air distribution manifold.
11. The apparatus of claim 9 wherein said air inlet includes an
annular disk carried by said manifold tube having a plurality of
circumferentially space holes for the entry of air, and said air
blocking means includes a rotating sequencing member having an end
rotatably received in a center bearing carried by said annular disk.
12. The apparatus of claim 1 wherein said air cells are arranged
in N rows where N is the number of rows, and said air distribution
manifold includes a cylindrical manifold, and said air distribution
ports are spaced equiangularly around said cylindrical manifold.
13. The apparatus of claim 12 wherein said air distribution ports
corresponding to a prescribed row are spaced 72 degrees circumferentially,
and the air distribution ports of sequential rows are spaced a predetermined
length along said air distribution manifold.
14. The apparatus of claim 12 wherein said spacing is 360/N degrees.
15. The apparatus of claim 14 wherein said air blocking means includes
a rotating program member for blocking said air distribution ports
according to said prescribed sequence.
16. The apparatus of claim 15 wherein said rotating program member
includes a rotating shaft and a plurality of wipers carried at programmed
positions on shaft which block air distribution ports.
17. The apparatus of claim 14 wherein said wipers are angularly
spaced from one another and staggered circumferentially on said
shaft corresponding to said equiangular spacing between said air
ports, and said wipers include flexible valve elements which engage
an inside diameter of cylindrical air distribution manifold to block
said air ports and flex away from said air ports to automatically
relieve pressure in a blocked air cell.
18. The apparatus of claim 1 wherein said air sacks are unattached
and are constructed from a material having a low air permeability
which allows slight air escapement from said air sack to relieve
pressure in a generally self-regulating manner and prevent accumulation
of moisture.
19. The apparatus of claim 18 wherein said air sack material is
constructed from a low air permeable fabric through which transmits
a low flow of air to prevent moisture in the buttocks area of person
seated on the wheel chair.
20. The apparatus of claim 1 including a plurality of annular flanges
surrounding said air openings in said top member having an undercut
for receiving a lower edge of said air sacks.
21. The apparatus of claim 20 including elastic retaining means
for securing said lower edge of said air sacks underneath said undercut.
22. The apparatus of claim 1 wherein said air blocking means automatically
includes pressure relief means for automatically unblocking said
air ports in the event a certain pressure is exceeded in said air
sack.
23. The apparatus of claim 22 wherein said pressure relief means
includes a valve means which blocks air through said air ports in
a first direction and vents air through said air ports in a second
opposite direction.
24. The apparatus of claim 1 wherein said air sacks are arranged
in an N.times.N matrix where N is the number of air sacks in a row,
and said matrix or air sacks deflate diagonally from one corner
of said N.times.N matrix to another.
25. A pneumatic cushion for reducing ischemic injury to a person
accommodated on the cushion comprising:
a pneumatic cushion having a plurality of individual inflatable
air sacks;
air supply means for supplying air to inflate said air sacks;
air delivery means for delivering an inward air flow from said
air supply means to air sacks at a system pressure which includes
an air path from said supply means to said air sacks;
self-regulating air flow control means having an open position
for transmitting said inward air flow from said air delivery means
to said air sacks in a first direction for inflating said sacks
in a prescribed sequence, while simultaneously allowing a backward
air flow in a second, opposite direction to prevent excessive pressure
in said air sacks in a self-regulating manner when said air flow
control means is in said open position; and
said air flow control means having a blocked position for preventing
said inward air flow, and said air flow control means being moved
from said blocked position directly by excessive pressure in said
air sack greater than said system pressure for allowing said backward
air flow to prevent excessive pressures in said air sacks in a self-regulating
manner.
26. The apparatus of claim 25 wherein said air sacks are arranged
in rows and said rows are deflated diagonally from one corner of
said rows to another.
27. The apparatus of claim 26 wherein said air sacks are arranged
in an N.times.N matrix where N is the number of air sacks in a row,
and said matrix of air sacks deflate diagonally from one corner
of said N.times.N matrix to another.
28. The apparatus of claim 25 wherein said air sacks are constructed
from a material having low air permeability which retains air during
normal sitting pressures, but allows escapement of air outwardly
in the event of excessive pressures caused by said patient weight
shifts and the like.
29. The apparatus of claim 25 including a cover extending over
said plurality of air sacks which is secured around the periphery
of said air sack constructed from a low air permeable fabric which
allows air to escape from air sacks to escape said cover and dry
moisture in the buttocks area.
30. The apparatus of claim 25 wherein said air flow control means
includes air blocking means which is opened directly by said excessive
pressures to transmit said back air flow when said air flow control
means is in a closed position.
31. Apparatus for reducing ischemic injury to a patient which includes
a wheel chair frame and a pneumatic cushion carried by the frame
wherein said pneumatic air cushion comprises:
an open dynamic air distribution system which periodically reduces
air pressure in selected portions of the cushion wherein said air
distribution system includes;
an air distribution plenum having a plurality of air channels;
an air distribution manifold carried within said plenum for distributing
air to said air channels having an air inlet;
a plurality of air ports in said air distribution manifold in open
fluid communication with said air channels within said air distribution
plenum;
air blocking means for periodically blocking said air ports in
said manifold to periodically interrupt the distribution of air
in said air channels in accordance with a preselected sequence;
a top member extending over the top of said air distribution plenum
having a plurality of air openings in fluid communication with said
air channels;
a plurality of inflatable air sacks carried by said top member
over said air openings which are inflated and deflated according
to a preselected pattern for reducing ischemic injury to a person
seated on said wheel chair;
a cover extending over said plurality of air sacks which is secured
around the periphery of said air sack;
a blower for delivering air to said air inlet of said air distribution
manifold;
said air sacks are arranged in N rows where N is the number of
rows, and said distribution manifold includes a cylindrical manifold,
and said air distribution ports are formed in said cylindrical manifold;
and
said air distribution ports corresponding to a prescribed row are
spaced circumferentially around said manifold, and the air distribution
ports of sequential rows are spaced a predetermined length along
said manifold.
Wheel chair description
BACKGROUND OF THE INVENTION
The invention is directed to a pneumatic wheel chair cushion having
a dynamic pressure relieving system for reducing ischemic injury
to the weight bearing portions of the buttocks of a patient in a
sitting position.
With the increasing number of wheel chair patients, the need for
wheel chair cushions which provide for greater prevention of ischemic
injury are needed. Typically, wheel chair cushions have been provided
in various forms and shapes cut from foam. Other wheel chair cushions
have been provided which include air cushions. U.S. Pat. No. 4,864,671
discloses a controllably inflated wheel chair cushion that includes
a number of independently inflatable rows of cells. The cells are
inflated and deflated according to a sequence selected by the user
to selectively relieve pressure against the buttocks of the patient.
The cells are inflated at a predetermined pressure and may not be
deflated until a valve is opened to exhaust the cell. The cells
are exhausted through a manifold which delivers air between the
cells in order to supply fresh air and reduce the heat from the
cushion. However, the system may not satisfactorily compensate a
patient's weight causing excessive pressure on inflated portions.
U.S. Pat. No. 4,852,195 discloses a similar fluid pressurized cushion
which utilizes air cells arranged in a matrix. The air cells are
inflated and deflated in a sequence to shift body support from one
set of cells to another for promoting blood circulation and comfort.
The cells in each matrix may also be interconnected to shift fluid
pressure as the patient's weight may shift. While the above air
cushions deflate to periodically alleviate pressure against the
occupant's buttocks, the air cells are generally static and closed
by valves and may not suitably allow pressure to be automatically
relieved in instances where the patient's body weight shifts. The
pressurized cushions are alternating, but are static. While the
air cells or cushions are filled and pressurized with air, that
pressure cannot change until the air pressure is released. This
may not be satisfactory for severe cases of amputated wheel chair
patients whose lower stump is very susceptible to acute ischemic
injury and skin decay.
Accordingly, an object of the present invention is to provide an
pneumatic wheel chair cushion having a dynamic air distribution
system which periodically relieves pressure on portions of the occupant's
buttocks.
Another object of the invention is to provide a pneumatic cushion
having a dynamic air distribution system which is self regulating
and adjusts to the shift in weight of the occupant to automatically
relieve pressure and prevent ischemic injury.
Another object of the present invention is to provide a pneumatic
cushion for a wheel chair and the like which utilizes individual
air sacks which are inflated and deflated in a sequence to periodically
reduce pressure against portions of the occupant's buttocks wherein
the air sacks are controlled by a dynamic air pressurization system
which allow a backflow of air to bleed from the air sacks under
excessive pressure to prevent ischemic injury.
Another object of the present invention is to provide a pneumatic
cushion for a wheel chair and the like which uses individual air
sacks arranged in a matrix which can be alternately inflated and
deflated wherein the fabric of the air sacks has a low air permeability
which allows a certain amount of the air to escape to maintain the
cushion dry and also to assist in automatically regulating the air
pressure to shift in occupant's weight.
SUMMARY OF THE INVENTION
The purpose of this invention is to prevent ischemic injury to
the weight bearing portions of the buttocks while in a sitting position.
This object is accomplished by providing an air cushion having a
number of separate unattached air sacks or cells arranged in a matrix.
Reduced air flow and therefore reduced pressure is provided within
the cushion periodically so each air sack on the surface will have
reduced pressure and reduced flow for 12 seconds every minute, for
example, dependent on a clock motor. An air distribution is provided
which at any time, is self-regulating because if pressures increase
when the occupant shifts their weight or the like, the system automatically
buffers the area of exerted weight by a back flow of air to a blower
when the pressure of the occupant exceeds the pressure in that cushion.
The cushion is self-adjusting, and prevents acute trauma to an area.
The air distribution system and cushion allow spontaneous, automatic
adjustment in pressure just from the patient shifting his weight
so that it minimizes the potential for soft tissue injury at any
point in time. There is no closed valve in the system. The system
is a dynamic pressure and flow pressure system. The air system is
continually being charged so that if it is overcome by weight shifts,
the air pressure is bled back.
DESCRIPTION OF THE DRAWINGS
The construction designed to carry out the invention will hereinafter
be described, together with other features thereof.
The invention will be more readily understood from a reading of
the following specification and by reference to the accompanying
drawings forming a part thereof, wherein an example of the invention
is shown and wherein:
FIG. 1 is a perspective view illustrating a pneumatic cushion constructed
according to the invention embodied in a wheel chair;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is an enlarged sectional view of an individual air cell
for a pneumatic cushion according to the invention;
FIG. 4 is a perspective view with parts separated of a pneumatic
cushion according to the invention;
FIG. 5 is a top plan view of individual air sacks according to
the invention illustrating a prescribed inflation/deflation sequence
for relieving ischemic injury to the occupant; and
FIG. 6 is a sectional view taken through an air distribution manifold
according to the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now in more detail to the drawings, a pneumatic cushion
A for reducing ischemic injury to a patient sitting in the wheel
chair and the like is illustrated. As applied to a wheel chair,
a support is provided by a wheel chair frame 10, and pneumatic cushion
A is carried by the frame. Cushion A includes a dynamic, self-regulating
air distribution system which periodically reduces air pressure
in selected portions of the cushion. The air distribution system
includes an air distribution plenum B having a plurality of air
channels C. Plenum B includes a plenum box 12 having a plurality
of air compartments D formed in the box communicating with air channels
C. The air compartments are arranged in an N.times.N matrix where
N is the number of compartments D in a row. In the illustrated embodiment,
there are five rows 14a-14e, each having five air sacks S.
The system includes an air distribution manifold M which extends
centrally through air plenum box 12 with air channels C extending
laterally from central air distribution manifold F. There are four
major air channels 16, 18, 20, 22 extending from the manifold, as
can best be seen in FIG. 2. Air distribution manifold F includes
a cylindrical air distribution tube 24 having an air inlet 26 formed
at a first end of the air distribution manifold which includes an
annular disk 28 with a plurality of circumferentially spaced holes
30 for the entry of air. A center bearing 32 rotatably receives
one end of a rotating program member which has a shaft 34. There
is a fitting 36 carried by the air inlet for connection to a blower
38 for delivering air to the air inlet. An opposite end of shaft
34 is coupled to a clock motor 39 using a set screw 37 by which
shaft 34 is rotated in a programmed manner.
As can best be seen in FIG. 6 and 4, there are a plurality of air
distribution ports P in air distribution manifold F which are in
fluid communication with air channels C in air distribution plenum
B. The air distribution ports include air ports a, b, c, d, e spaced
equiangularly around cylindrical air distribution manifold F. Where
N is the number of rows, the angular spacing "X" of ports
P is 360/N degrees around the circumference of cylindrical manifold
F. In the illustrated embodiment, the five air ports for each row
of air sacks have a 72 degree spacing circumferentially and are
spaced a predetermined length longitudinally along manifold F (FIG.
2).
Air blocking means G is provided for periodically blocking air
distribution ports P in the manifold to periodically interrupt the
distribution of air in air channels C and deflate air sacks S in
accordance with a preselected sequence. The air blocking means includes
rotating program member 34 having rotating one-way valve means 40
with a blocking position in which the valve means is positioned
over an air port P. In this position, valve means blocks air to
deflate air sacks S while, at the same time allowing air to backflow
in the system and vent from the air sack as where excessive pressure
occurs from a person's shifting weight. The valve means includes
flexible wipers carried at programmed positions on shaft 34 which
block air distribution ports P. The wipers are angularly spaced
from one another on said shaft with same spacing as between air
ports, and same longitudinal spacing. Flexible wipers include a
stem 44, and a flapper valve 46 which engages the inside diameter
of cylindrical air distribution manifold F (FIG. 6). As can best
be seen in FIG. 5, air sacks are deflated in diagonal rows from
one corner to an opposite corner. Drive motor 39 carried by a second
end of said air distribution manifold rotatably drives said rotating
program member 34.
A top member 50 extends over the top of said air distribution plenum
B having a plurality of air openings 52 in fluid communication with
air channels C. There is an air opening over each air compartment
D so that there are N.times.N air openings 52. Sealing means 56
in the form of a matrix gasket seals between air compartments D
and top member 50, as can best be seen in FIGS. 4 and 2. Inflatable
air sacks S are carried by top member 50 over air openings 52, and
are deflated as air distribution ports P are periodically blocked
in accordance with the preselected sequence shown in FIG. 5. In
the illustrated embodiment, there are 5 sets of circumferentially
spaced ports spaced along the length of manifold F, as can best
be seen in FIG. 4. The air cells and sacks controlled by ports a-e
are designated in FIG. 5. The air sacks are sequentially inflated
and deflated for reducing ischemic injury to a person seated on
the cushion. Air sacks S are constructed from a material 53 having
a low air permeability to allow slight air escapement from the air
sacks to relieve excessive pressure above and prevent accumulation
of moisture between the cushion and occupant. For this purpose,
it will be seen that the individual air sacks are unattached to
act individually during inflation and deflation for proper support
and relief to prevent ischemic injury. The fabric of the air sacks
and cover is characterized in that the fabric is micro-porous, having
a low transmission of air and water vapor, but which blocks liquid
transmission. Suitable fabrics are constructed from a fine weave
pattern, and either coated, laminated, or impregnated with a material
such as expanded Teflon. Suitable fabrics are sold under the commercial
names of Goretex which is manufactured by the W. L. Gore Company,
Ultrex manufactured by Burlington Industries of Greensboro, N.C.,
and Storm Shed manufactured by Reeves Brothers Manufacturing Company
of Gaffney, S.C.
A plurality of annular flanges 57 surround air openings 52 in top
member 50 having an undercut 58 for receiving a lower edge 60 of
the air sacks. An elastic retaining means 62 secures the lower edge
of the air sacks underneath the undercut. A cover 64 extends over
the plurality of air sacks S which is secured around the periphery
of top member 50. Both air sacks S and cover 64 are preferably constructed
from a low air permeable fabric which allows air to escape from
the air sacks to dry moisture in the buttocks area of the person
seated on the cushion through flow through the cover. It will be
noted that the fabric maintains air for sufficient pressure to support
the person during the inflation/deflation sequences, but bleeds
air to prevent excessive pressure and moisture. The air pressure
in the air sacks automatically adjusts to the shifting of weight
of a patient on the cushion. An open air distribution path extends
from the blower to the air sacks which are not blocked which allows
the backwards flow of air from said air sacks to the blower in the
event of over pressurization of the air sacks due to the weight
of the patient. At the same time, the blocked air ports may be relieved
through the open path by the flapper valves as shown in the direction
of arrow 70, and the air sack fabric, having low air permeability,
retains air during normal sitting pressures, but allows escapement
of air outwardly in the event of excess pressure as shown by arrow
72.
While a preferred embodiment of the invention has been described
using specific terms, such description is for illustrative purposes
only, and it is to be understood that changes and variations may
be made without departing from the spirit or scope of the following
claims. |