U.S. patent application number 13/882625 was filed with the patent office on 2013-08-29 for cushion and self-adjusting valve.
This patent application is currently assigned to ROHO, Inc.. The applicant listed for this patent is Dennis L. Clapper. Invention is credited to Dennis L. Clapper.
Application Number | 20130219626 13/882625 |
Document ID | / |
Family ID | 46025047 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130219626 |
Kind Code |
A1 |
Clapper; Dennis L. |
August 29, 2013 |
CUSHION AND SELF-ADJUSTING VALVE
Abstract
A cushion with a support pad comprising a plurality of
compressible suspension elements with a cover top and bottom joined
together to form an impervious barrier, and a valve in fluid
communication with the plurality of compressible suspension
elements that allows the controlled expulsion of air until a user
positioned on the cushion is optimally immersed in the cushion.
When the user is removed from the cushion, the valve allows ingress
of air into the cushion. In one aspect, the valve comprises an
expansion valve controls air flow out of and into the cushion. In
one aspect, the valve comprises a labyrinth seal that dampens air
flow and pressure spikes. The valve comprises a pressure responsive
compression spring that controls the expulsion of air from the
cushion and, consequently, adjusting the immersion depth of the
seated user.
Inventors: |
Clapper; Dennis L.;
(Swansea, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clapper; Dennis L. |
Swansea |
IL |
US |
|
|
Assignee: |
ROHO, Inc.
Belleville
IL
|
Family ID: |
46025047 |
Appl. No.: |
13/882625 |
Filed: |
October 31, 2011 |
PCT Filed: |
October 31, 2011 |
PCT NO: |
PCT/US11/58582 |
371 Date: |
April 30, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61408774 |
Nov 1, 2010 |
|
|
|
Current U.S.
Class: |
5/655.3 ;
137/493 |
Current CPC
Class: |
A47C 27/081 20130101;
F16K 17/0406 20130101; A47C 27/088 20130101; F16K 17/0413 20130101;
F16K 15/207 20130101; F16K 15/20 20130101; F16K 15/044 20130101;
F16K 17/048 20130101; A47C 7/021 20130101; Y10T 137/7771 20150401;
A47C 27/10 20130101 |
Class at
Publication: |
5/655.3 ;
137/493 |
International
Class: |
A47C 27/10 20060101
A47C027/10 |
Claims
1-18. (canceled)
19. A cushion comprising: a support surface comprising a plurality
of compressible suspension elements, and a valve in fluid
communication with the plurality of compressible suspension
elements having internal labyrinth structures that provide a
controlled expulsion of air from the cushion to dampen air flow
until a user positioned on the cushion is optimally immersed in the
cushion and control pressure spikes caused by movement on the
cushion.
20. The cushion of claim 19 wherein the valve comprises an
expansion valve.
21. The cushion of claim 19 wherein the valve comprises a pressure
responsive compression spring, said compression spring having a
predetermined compression force that controls the expulsion of air
from the cushion corresponding to a desired immersion depth of the
user.
22. The cushion of claim 19 further comprising a cover having a top
and a bottom, the bottom configured complementary to the suspension
elements to control splaying of the suspension elements under
load.
23. The cushion of claim 22 wherein the cover top comprises vacuum
formed polyurethane.
24. The cushion of claim 19 wherein the support surface comprises a
anterior section and a posterior section comprising polyurethane
foam, said posterior section having a greater restoring that the
anterior section.
25. The cushion of claim 24 wherein said anterior section of the
support surface has a cavity formed therein to house the valve.
26. The cushion of claim 19 wherein the compressible suspension
elements are inflatable air cells.
27. The cushion of claim 19 wherein the valve further comprises: a
valve seat, a valve ball positioned adjacent the valve seat, and a
bias spring for biasing the valve ball against the valve seat to
close the valve.
28. The cushion and valve of claim 19 wherein the labyrinth
structures comprise a labyrinth seal that dampens air flow and
pressure spikes at the valve ball.
29. The cushion and valve of claim 19 wherein the valve further
comprises an inflation valve in fluid communication with the
atmosphere to allow expansion of the compressible suspension
elements.
30. A valve for a cushion having compressible suspension elements,
comprising: a valve ball and pressure responsive compression spring
having a predetermined compression force that controls expulsion of
air from the cushion corresponding to a desired immersion depth of
a user, and a labyrinth structure in fluid communication with the
compressible suspension elements and the valve ball that dampens
dynamic air flow and pressure spikes against the valve ball.
31. The valve of claim 30 further comprising inflation valve
structures that allow an ingress of air into the suspension
elements when load is removed from the cushion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 61/408,774, filed Nov. 1, 2010, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The invention relates generally to support surfaces that
facilitate blood flow and prevent tissue breakdown and more
particularly to a cushion that has relatively uniform restoring
forces when deformed under loads from of a user and to a valve that
can be employed with the cushion to vent air when the user is
seated to achieve desired, predetermined immersion into the cushion
to provide optimum seating characteristics including uniform
restoring forces.
[0003] Individuals confined to sitting, for example in a wheelchair
run the risk of tissue breakdown and the development of ischemia
induced sores, which are extremely dangerous and difficult to treat
and cure. For example, when seated much of the individual's weight
concentrates in the region of the ischia, that is, at the bony
prominence of the buttocks, and unless frequent movement occurs,
the flow of blood to the skin tissue in these regions decreases to
the point that the tissue breaks down. When lying down, the hip
region may protrude deeper into the mattress than the adjoining
waist or thigh regions and as a consequence the supporting forces
exerted by the mattress would be greater at the hips than at the
thighs or waist, for example. Any skin area where there is
sustained deformation suffers reduced blood flow and the skin does
not receive sufficient oxygen and nutrients.
[0004] It is desirable to have a support surface that applies
generally uniform supporting forces, for example, a generally
uniform counter force on the tissue of the ischial area of user
positioned on a cushion. When a cushioning structure is deformed
while supporting a person, it is desirable to have a constant
restoring force that exerts equal forces over a broader area of the
body minimizing deformation of the soft tissues and help prevent
skin and tissue breakdown by facilitating blood flow in the
contacted area.
[0005] Cellular cushions generally provide the most uniform
distribution of weight and thus provide the greatest protection
from the occurrence of pressure sores. Inflatable cellular cushions
have an array of closely spaced air cells that project upwardly
from a common base. Within the base the air cells communicate with
each other, and thus, all exist at the same internal pressure.
Hence, each air cell exerts essentially the same restoring force
against the buttocks, irrespective of the extent to which it is
deflected. U.S. Pat. No. 4,541,136 shows a cellular cushion
currently manufactured and sold by assignee, ROHO, Inc. of
Belleville, Illinois, for use on wheelchairs.
[0006] A variation of the cellular cushion provides isolated zones
and also with cells of varying height. By varying the volume of air
between zones, for example, one can accommodate for skeletal
deformities while still maintaining satisfactory protection against
pressure sores. U.S. Pat. No. 4,698,864 shows zoned cellular
cushion with cells of varying height. U.S. Pat. No. 5,163,196 and
U.S. Pat. No. 5,502,855 disclose other zoned cellular cushions
having isolated inflation zones.
[0007] Two types of valves used to maintain air volume in the
inflation zones are shown in U.S. Pat. No. 6,687,936 and U.S. Pat.
No. 6,687,936. These valves, which can be referred to broadly as
slide valves, when employed for example with a zoned cushion having
a plurality of inflation zones, provide an easily manipulated valve
assembly which can be used to allow fluid communication between two
or more zones or can be used to isolate the zones.
[0008] Each valve, in general, includes a casing having an internal
bore and a plurality of openings along the length of the casing
that open into the bore. The openings are connected to the
individual inflation zones via tubing or the like to place the bore
of the casing in communication with the inflation zones. The valve
also includes a movable slide seated snugly within the casing bore.
The slide can be manipulated to align the discrete air chambers
with the casing openings so as to functionally align the slide
openings with the casing openings to allow the inflation zones to
communicate and the air to flow to and from the various inflation
zones through the valve slide bore. The cushion is inflated and the
user positioned on the cushion. Air is released from a fill valve
until the user reaches optimum immersion. The slide is manipulated
to move the slide openings and the casing openings out of
alignment, thereby sealing off the inflation zones and maintaining
the individual inflation zones at optimum internal pressure.
[0009] Zoned cellular cushions with slide valves have become an
industry standard and work exceptionally well for there intended
purposes. As will be understood, users of these cushions and
valves, or their caregivers, require some training and practice at
setting the desired immersion dept and seating position. Although
the needed proficiency in their use is not difficult to obtain,
there are some circumstances in which a user could benefit from a
support surface, such as a cushion or even a mattress or mattress
overlay, that is even simpler or more convenient to use that these
cushion and valve combinations. These circumstances can arise, for
example, where the user is newly disabled and perhaps overwhelmed
by the attendant change in lifestyle. Or, for example, if the user
just does not have the mental acumen to properly use an adjustable
cushion. An example may be a person suffering from dementia or
Alzheimer's.
[0010] It would therefore be advantageous to have a support
surface, such as a cushion or mattress, with a self-adjusting valve
that allows a user rest on the support surface and reach an optimal
immersion level without the manipulation of a valve or the
like.
SUMMARY OF THE INVENTION
[0011] In one aspect, a cushion with a support surface comprising a
plurality of compressible support elements, and a valve in fluid
communication with the plurality of compressible suspension
elements that allows the controlled expulsion of air until a user
positioned on the cushion is optimally immersed in the cushion and
also controls dampens dynamic air flow and pressure spikes
resulting from movement of the seated user.
[0012] In one aspect, a cushion with a support surface comprises a
support pad with a plurality of compressible suspension elements
that when the user gets off of the cushion, the support pad returns
the cushion to the original cushion height and the valve allows
ingress of air into the cushion.
[0013] In one aspect, the valve comprises an expansion valve
design, through multistage pressure reduction, which dampens the
dynamic air flow and pressure spikes that result from movement of
the seated user.
[0014] In one aspect, the valve comprises a labyrinth seal design,
through multistage pressure reduction, which dampens the dynamic
air flow and pressure spikes.
[0015] In one aspect, the valve comprises a pressure responsive
compression spring that controls the expulsion of air from the
cushion and, consequently, controls the immersion depth of the
seated user.
[0016] In one aspect, the cushion comprises a cover bottom under
the support surface; the preferred embodiment of the cover bottom
is a polyurethane film.
[0017] In one aspect, the cushion comprises a cover top over the
support surface; the preferred embodiment of the cover top is a
polyurethane film.
[0018] In an alternative embodiment, the cover top over the support
surface can have fabric bonded to the polyurethane film, providing
a cover top over the support surface that is easily cleaned by
wiping down with a mild cleaning solution.
[0019] In one aspect each suspension element has a displaceable,
load-bearing surface, a first end wall, a second end wall, and an
optional bottom wall. The load bearing surface, end walls and
bottom wall, if present, define an inner chamber. The material
thickness of the load-bearing surface is greater than the material
thickness of the end walls so that the end walls can distend
outwardly when force is applied to said load-bearing surface.
Optionally, a top wall can include a vent opening formed therein of
a predetermined size that allows controlled release of air from
each chamber when force is applied to the load bearing surface to
control collapsing of the cell.
[0020] In one aspect, the support surface of the cushion is
displaceable such that, when deformed, the suspension elements
exert a restoring force that is generally constant irrespective of
the extent of the deflection. The cushion applies distributed
supporting pressure against an irregularly contoured body area,
such as the ischium, supported on the cushion.
[0021] In one aspect of the cushion the array of suspension
elements is arranged in a pattern wherein the longitudinal axis of
each suspension element is positioned at a right angle relationship
to the longitudinal axis of the adjacent suspension elements. The
right angle axis position of the suspension elements improves
stability imparted to the user.
[0022] In one aspect of the cushion the load-bearing surface has a
generally arch-like cross-sectional configuration to facilitate a
controlled buckling function. In other aspects of the invention the
load-bearing surface has a substantially elliptical cross-sectional
configuration or a substantially rectangular cross-sectional
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is an exploded view of one aspect of the cushion;
[0024] FIG. 2 is a front perspective view of the support
surface;
[0025] FIG. 3 is a front plan view of a section of the support
surface illustrating the placement of the self-adjusting valve;
[0026] FIG. 4 is a side elevational view of the self-adjusting
valve;
[0027] FIG. 5 is a bottom plan view of a support surface;
[0028] FIG. 6 is a perspective view of the cover top;
[0029] FIG. 7 is a bottom plan view of the assembled cushion;
[0030] FIG. 8 is a perspective view of an optional top air pad;
[0031] FIG. 9 is a cross sectional view of one embodiment of a
self-adjusting valve, wherein the valve comprises an axial
labyrinth seal design;
[0032] FIG. 10 is a cross-sectional view of another embodiment of a
self-adjusting valve, wherein the valve comprises a radial
labyrinth seal design; and
[0033] FIG. 11 is a cross-sectional view of another embodiment of a
self-adjusting valve, wherein the valve comprises an expansion
valve design.
DETAILED DESCRIPTION
[0034] One aspect of the cushion is indicated generally by numeral
20 in FIG. 1. It will be understood that the term cushion, as used
herein, is intended to include cushions for seating, larger
embodiments often referred to as mattresses or mattress overlays,
pillows or any other such support surfaces for supporting the
anatomy of a user.
[0035] Cushion 20 comprises a support surface 22, a cover bottom 24
a cover top 26 and a valve 28. Referring to FIG. 2, support surface
22 comprises a resilient pad having anterior section 30 and a
posterior section 32. Generally, the anterior and posterior
sections of the support surface are formed from a compressible,
resilient material such as polyurethane foam. In general, posterior
section 32 may be formed from stiffer foam than anterior section 30
such that posterior section 32 will have a greater restoring force
than the anterior section. In most situations, the posterior
section of a cushion supports at least fifty percent (50%) of the
seated user's body weight. A firmer posterior section provides more
support and a feeling of greater stability. The support surface
construction is such that the cushion will not bottom out under a
seated user. It will be understood that support surface 22 can be a
single or unitary piece as well.
[0036] The anterior wall 33 of the support surface defines a cavity
34 for housing valve 28, as will be described below. Both anterior
section 30 and posterior section 32 comprise a plurality of cells
or suspension elements 35 arranged in lateral and transverse rows
across the expanse of the sections, as seen in FIG. 5. It will be
understood that the support surface, whether a single piece or
comprising an anterior or posterior section is made, and functions,
in accordance with the principles disclosed in the assignee's U.S.
Pat. No. 7,424,761 and 7,681,264, both of which are incorporated
herein by reference.
[0037] In one aspect, each suspension element 35 has a
displaceable, load-bearing surface 36, a first end wall 38 and a
second end wall 40. The load bearing surface, end walls define an
inner chamber 42. Chambers 42 can be empty or filled, for example,
with foam or other material to change the support characteristics
of the cushion or the air egress and ingress characteristics of the
cushion. Moreover, chamber 42 can have a thin wall or skin over
them with a small hole in the wall to vary or control the
compression characteristics by controlling the fluid flow from the
chamber under force. In one aspect, the material thickness of the
load-bearing surface 36 is greater than the material thickness of
the end walls so that the end walls can distend outwardly when
force is applied to the load-bearing surface.
[0038] The load bearing surfaces 36 cooperate to form a
displaceable surface that, when deformed, exerts a restoring force
that is generally constant irrespective of the extent of the
deformation. Support pad 22 applies a generally uniform supporting
pressure against an irregularly contoured body supported on the
cushion. In one aspect of the invention the array of suspension
elements is arranged in a pattern wherein the longitudinal axis of
each suspension element is positioned at a right angle relationship
to the longitudinal axis of the adjacent suspension elements. The
right angle axis position of the suspension elements improves
stability imparted to the user.
[0039] In one aspect of the invention the load-bearing surface 36
has a generally arch-like cross-sectional configuration to
facilitate a controlled buckling function. In other aspects of the
invention the load-bearing surface can have a substantially
elliptical cross-sectional configuration or a substantially
rectangular cross-sectional configuration. In another aspect of the
support surface where the arch-like or elliptical suspension
elements 35 have the displaceable load-bearing surface 36 down, a
web-like membrane of compressible resilient material 37 between
suspension elements 35 prevents the suspension elements from
splaying at the user interface of the support surface under the
seated user.
[0040] In the illustrated embodiment there is cover top 26 that
covers the top surface of support pad 22 as well as cavity 34 and
provides openings 43 for valve 28 in fluid communication with the
atmosphere, as seen in FIG. 6. Cover top 26 generally can be a
vacuum formed polyurethane film having a thickness of about 0.020
inches in the exemplary embodiment. In another embodiment, the
cover top can have a fabric bound to the polyurethane film,
providing a cover top over the support surface that is easily
cleaned by wiping down with a mild cleaning solution. In an
alternative embodiment the cover top can have a plurality of small
holes therein, with one hole positioned over each cell chamber 42
or select cell chambers and a top air pad 44 with opening 43, as
seen in FIG. 8, having individual air pads 46 of vacuum formed
plastic can be positioned over the support surface. One aspect of
the top air pad 44 includes the array of individual air cell pads
46 in fluid communication with the support surface to reduce
friction and shear at the user interface of the support surface
under the seated user.
[0041] A cover bottom 24, as seen in FIG. 7, having a configuration
complementary to the suspension elements generally comprises vacuum
formed plastic film, as well, having a thickness of about 0.020
inches in an exemplary embodiment. Cover bottom 24 duplicates the
configuration of the suspension elements 35, as at 47, which seats
the suspension elements. This arrangement reduces the volume of the
cushion and, therefore, reduces the amount of air within cushion
20, making the expulsion of air easier to control. It also
eliminates the user sensation that the cushion feels like a
balloon. This arrangement also prevents or controls splaying of the
suspension elements under load. Cover top 26 and cover bottom 24
can be joined together, either by sonic, RF welding, gluing or
other appropriate means sealing them together around the edges of
the cushion with support pad 22 inside. The cushion then is
impervious to gas or fluids.
[0042] The cushion can have any desired configuration, with the
illustrated embodiment being a rectangle. The dimensions of cushion
20 can vary depending upon the size of the surface on which it will
be used or depending upon the size of the user. A cushion having
dimensions of eighteen (18) inches by eighteen (18) inches is one
representative embodiment. A larger, heavier user would employ a
cushion having greater surface area so as to spread the seated
user's body weight over a larger surface area and thereby
controlling the fluid pressure within the cushion and the restoring
force against the seated user's body. By controlling the surface
area and the spring compression of the valve, as will be explained
below, an optimum pressure of about 40 to about 50 mmHg within the
cushion can be achieved.
[0043] It will be noted that when support pad 22 is compressed by
the weight of a seated user, the inner chambers 42 and the
polyurethane foam itself will expel air. Since the support pad 22
is sealed within the top covering and bottom, air can only escape
through valve 28 and opening 43 to allow the cushion to deform and
the user to be immersed into the cushion. Hence, seating and
positioning characteristics, including immersion, can be controlled
by controlling the egress of air out of valve 28, as will now be
explained.
[0044] Valve 28 is positioned in cavity 34 and is in fluid
communication with the interior of the cushion in any acceptable
manner. For example, valve 28 can be in fluid communication with a
conduit 48 that extends into cavity 34. Alternative, valve 28 can
be in fluid communication with the interior of the cushion though a
hole in the cushion top covering, bottom covering or any other
structure so as to be in fluid communication with the interior of
the cushion. A separate conduit is not required.
[0045] In a preferred embodiment, valve 28 comprises a labyrinth
seal design that dampens dynamic air flow and pressure spikes. In
general, aft pressure from cushion 20 with a seated user causes the
valve ball to close against the spring compression force in the
valve body. The dynamic air pressure resulting from movement of the
seated user is dampened by using of a labyrinth multistage pressure
reduction configuration. Moreover, the compression force of the
spring can be varied to get optimal seating characteristics.
[0046] FIGS. 9 through 11 are cross-sectional schematics of various
configurations of valve 28, referred to as valves 28A, 28B and 28C
in the respective drawings. Referring to FIG. 9, valve 28A has a
casing 49 with an elongated extension 50. Casing 49 can be of any
configuration, however, a cylindrical, circular or disk-like
configuration works well, as seen in FIGS. 3 and 4. Extension 50
can be tubular with an internal bore 52. Circumferential barb 54
functions to secure the extension within conduit 48. Conduit 48 is
in fluid communication with the interior of the cushion and, hence,
bore 52 and valve 28 are in fluid communication with the interior
of the cushion.
[0047] Bore 52 also is in fluid communication with a labyrinth
inside the valve casing. For example, air flow from the interior of
the cushion follows a path shown by arrows A1. At stricture 57 the
fluid flow is constricted; there is a significant pressure drop as
the fluid flow expands into chamber 58; again there is constriction
at stricture 59 and a pressure drop at chamber 60. There is a third
constriction of flow at stricture 62 and a pressure drop at chamber
64. Ultimately, the reduced fluid flow contacts valve ball 66.
Valve ball 66 is biased in a closed position against valve seat 67
by valve spring 68. It will be understood that as long as valve
ball 66 is biased against valve seat 67, no air will escape through
the valve. However, when a predetermined fluid pressure resulting
from the user sitting on cushion 20 is applied against the valve
ball by the air flow, valve ball 66 is urged away from valve seat
67 and air will escape from valve 28 through exhaust port 69.
[0048] Valve spring 68 has preselected compression force depending
upon the surface area of the cushion and the estimated weight of
the user. The valve spring is selected so that sufficient air
escapes the cushion resulting in emersion into the cushion until
the user's anatomy is about one-half (1/2) to (1) inch from the
surface on which the cushion is position, for example, a wheelchair
seat. Also, valve spring 68 is selected so that the fluid pressure
within the cushionis about 40 to about 50 mm Hg, resulting in a
uniform restoring force against the seated user's body.
[0049] Since valve 28 comprises the labyrinth configuration, the
step down in pressure is such that the force required to open the
valve is greatest when the user at first sits on the cushion and
begins to immerse the buttocks and ischial area into the cushion.
This generally constant force on the cushion generates pressure
within the cushion the fluid pressure within the cushion and the
restoring force against the seated user's body allows the valve
spring 68 to overcome the fluid pressure and close the valve,
maintaining the appropriate or desired immersion depth. Once the
user is seated, the pressure reducing labyrinth configuration
within the valve keeps air from leaking under dynamic pressure
changes that may result from user movement. In any event, the valve
spring is such that it will keep the valve closed and not allow the
user to bottom out.
[0050] Valve 28 includes an inflation valve, indicated generally by
reference number 70 which, in a preferred aspect, comprises air
ports 72 in fluid communication with the atmosphere. Inflation
valve 70 includes a flap 74 comprising a somewhat flexible but
durable material such as silicon, Teflon.RTM. or the like, which
seals ports 72 under pressure from within valve 28. However, when
the user is off the cushion, the atmospheric pressure, which then
is generally greater outside the cushion than within, causes air to
flow through ports 72 and into the cushion following a path shown
by arrows A2, aided by mechanical drawing in of air by the foam
within the cushion as a changes from a compressed to non-compressed
state.
[0051] Valve 28B is illustrated in FIG. 10. Valve 28B is
constructed very similarly to valve 28A. Valve 28B includes a
casing 49 with an extension 50 having an internal bore 52 and
circumferential external barb 54. Bore 52 is in fluid communication
with the interior of the cushion and a labyrinth inside the valve
casing. Air flow from the interior of the cushion follows a path
shown by arrows A1. At stricture 57 the fluid flow is constricted
with a pressure drop at the fluid flow expands into chamber 58;
there is constriction at stricture 59 and a pressure drop at
chamber 60. There is a third constriction of flow at stricture 62
and a pressure drop at chamber 64. Valve 28B includes a valve ball
66, valve seat 67, valve spring 68 and exhaust port 69 that that
function in the same manner set out above in regards to valve
28A.
[0052] Valve 28B also includes an inflation valve, indicated
generally by reference number 70 which comprises air ports 72 in
fluid communication with the atmosphere. Inflation valve 70
includes a flap 74, which seals ports 72 under pressure from within
valve 28. Air flows in through ports 72 and into the cushion,
following a path shown by arrows A2, as explained above.
[0053] Valve 28C is illustrated in FIG. 11. Valve 28C is
constructed very similarly to valves 28A and B. Valve 28C includes
a casing 49 with an extension 50 having an internal bore 52 and
external barbs 54. Bore 52 is in fluid communication with the
interior of the cushion and the expansion chambers inside the valve
casing. Air flow from the interior of the cushion follows a path
shown by arrows A1. At orifice 57 the fluid flow is constricted and
a pressure drop as the fluid flow expands into chamber 76; there is
constriction at orifice 77 and a pressure drop at chamber 78. Valve
28C includes a valve ball 66, valve seat 67 and valve spring 68 and
exhaust port 69 that function in the same manner set out above in
regards to valve 28A.
[0054] Valve 28C also includes an inflation valve, indicated
generally by reference number 70 comprises air ports 72 in fluid
communication with the atmosphere. Inflation valve 70 includes a
flap 74 which seals ports 72 under pressure from within valve 28C.
Air flows in through ports 72 and into the cushion following a path
shown by arrows A2, as explained above.
[0055] It will be understood that the valves described can be
employed in cushions or mattresses of designs different from the
cushion illustrated herein. The valve can be constructed so as to
accommodate users of different sizes. The fluid flow
characteristics can be varied by the use of different springs or a
different labyrinth seal clearances or orifices. The valve can be
used in a cushion that provides optimal seating characteristics
without manipulation. The user rests on the cushion and the
self-adjusting valve adjusts so that the cushion has optimum
immersion and restoring force characteristics.
* * * * *