Note: Descriptions are shown in the official language in which they were submitted.
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Background
United States Patent 3,653,083 discloses an inflatable
bed pad with passages which expand and collapse as they are
inflated and deflated. Perforations which are formed in
the top wall of the pad and which communicate with the
passages allow air to escape upwardly through a foam cushion
or sheet extending over the pad. Inflating air is introduced
at one end of each passage by means of an air pressure line
connected to the pad and a valve controls the flow of air
so that one passage is inflated as the other is allowed to
deflate, such deflation occurring because of the upward flow
of air through the perforations of the passage to which the
air supply is temporarilty interrupted. As a result, such
alternating inflation and deflation of the passages produces
a "rippling effect" which stimulates peripheral circulation
and relieves localization of pressure for a patient lying
upon the pad and its foam cushion. Also, because air escapes
from the perforations and passes upwardly through the foam
cushion, a gentle drying effect is produced which prevents
or reduces skin maceration caused by trapped perspiration.
The total effects are an increase in patient comfort and a
substantial elimination in the formation of decubitus ulcers
previously experienced by bedridden patients.
Other U.S. patents reflecting the state of the prior art
are 2,998,817 (an inflatable mattress having two arrangements
of transverse cells, each of the cells being simultaneously
inflated (or deflated) from its opposite ends), 95,848 (an
air bed which, in one embodiment has one or more tubes
supplied with air from one end, closed at the opposite end,
and provided with perforations to discharge air for cooling
and ventilating purposes), 3,486,177 (ventilated cushion),
3,266,064 (ventilated mattress and box spring combination),
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3,394,415 (alternating pressure pad), 3,199,124 (alternating
pressure mattress), 1~772J31O (variable pressure mattress),
2,345,073 (an apparatus including a distribution valve for
controlling the air flow for therapeutic devices), 3,908,642
(a distributor and associated elements for directing
pulsating air into and out of casts), 3,319,730 (inflatable
body support), 3,446,203 (pneumatic cushion), 3,462,778
(inflatable mattress), and 3,467,081 (inflatable mattress).
Summary
One aspect of this invention lies in providing an
inflatable pad system in which the direction of the ripples
or waves is cyclically reversed, thereby tending to produce
a more effective alternation of pressure points, more
complete ventilation, and a more effective massaging action
than prior systems. Aslo, in certain forms of the invention
disclosed herein, greater operating efficiency is achieved
because excess pressurized air is recirculated. Such
automatic recirculation additionally performs a safety
function because it prevents overinflation of the chambers
or passages of the pad.
Positive deflation of each passage, alternately
from opposite ends of that passage, is achieved in one
embodiment of this invention. Thus, in such embodiment
successive deflations as well as successive inflations of
each passage or chamber take place alternatively from opposite
ends of that passage. In all forms, the passages are pro-
vided with perforations in the top wall of the pad which
result in the bleeding or leaking of air towards the patient,
thereby cooling aerating and drying the patient's skin as
well as improving circulation and alternating the points of
pressure. The air discharged from the perforations is directed
through a foam pad or cushion as generally disclosed in
aforementioned U.S. patent 3,653,083.
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In brief, the system includes a pad having a resilient
top wall and a bottom wall joined together to form at least two
separate passages which extend substantially the full length of
the pad and which have interlaced tubular portions extending
transversely of that pad. Each passage is connected at its
opposite ends to a pair of conduits which lead to a suitable
control valve. Therefore, if two such passages are provided,
a total of four conduits would be used to operatively connect
the control valve assembly and the pad. The control valve
10 assembly is also connected to a source of air (or other suitable
fluid) under pressure -- specifically, a compressor or pump --
so that as the valve operates air under pressure is directed
successively into each of the four conduits, thereby inflating
each of the passages from one end and then later from the opposite
end. Deflation of each passage occurs because of the escape of
air through the perforations in the top wall of the pad but, as
already indicated, such deflation may be augmented by positive
evacuation of one passage as another is being inflated. In that r
case, the control valve assembly is modified to utilize each of
20 the conduits at different times as an air evacuation line as well
as an air supply line, the control valve assembly being connected
to the intake of the compressor to accomplish such positive evacuation.
Instead of, or in addition to, positive evacuation,
the control valve assembly may be adapted to recirculate excess
pressurized air, that is, air which is in excess of what is
needed to inflate each of the passages or chambers. In such
modifications or embodiments, the control valve assembly per-
forms a regulator function so that when the inflation pressure
reaches a preselected level the valve assembly will auto-
30 matically divert and recirculate additional air from the
compressor beyond what is required to maintain the air pressure
in the passage at the preselected level. The control valve
assembly may also include flow restricting means for selectively
controlling the flow of air evacuated from the pad and returning
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to the compressor, thereby regulating the extent and rate of
evacuation of each chamber or tube.
In one form the control valve assembly may comprise
a valve body having an inlet for air under pressure and a
plurality of openings for directing air to (and, in some in-
stances, from~ the conduits leading to the inflatable pad;
a rotor for directing the flow of air through the valve body
in accordance with the position of the rotor; and a motor for
turning the rotor relative to the valve body. The valve body
may also be equipped with an outlet for the recirculation of
air back to the compressor and an annular groove which com-
municates with that outlet and which may be placed in comm-
unication with each of the openings leading to the conduits
as the rotor turns. By spring-loading the rotor with a com-
pression spring having selected compression force character-
istics, the rotor may cooperate with the valve body to serve
as a regulator for limiting the pressure to which the passages
of the pad are inflated, the annular groove serving to col-
lect excess air not used by the pad and returning that air to
the compressor.
Other structural features, advantages, and objects
of the invention will become apparent from the specification
and drawings.
Drawings
Figure 1 is a somewhat schematic view of an in-
flatable pad and air control system embodying the present
invention, the system being illustrated with a control valve
in one position of adjustment.
Figure 2 is a schematic view similar to Figure 1 but
showing the control valve in a second position of adjustment.
Figure 3 is an enlarged fragmentary view of the pad
taken along line 3-3 of Figure 1, a foam cushing being
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illustrated in phantom to indicate the full pad-cushion
combination.
Figure 4 is an enlarged view of the valve body
with the rotary valve member depicted in phantom and in
the position shown in Figure 1.
Figure 5 is an enlarged view of the valve body
similar to Figure 4 but showing the valve member in phantom
in the position of Figure 2.
Figure 6 is an exploded perspective view illus-
trating the components of the valve assembly.
Figure 7 is a sectional view taken along line 7-7
of Figure 4 but showing the valve member and associated
elements as well as the valve body.
Figure 8 is a sectional view taken along line 8-8
of Figure 4 but showing the rotary valve member and associated
elements as well as the valve body.
Figure 9 is a sectional view similar to Figure 8
but illustrating in somewhat exaggerated form the axial
displacement of the valve member under increased pressure
conditions.
Figure 10 is a somewhat schematic view of a system
constituting a second embodiment of the invention.
~ Figure 11 is a perspective view of the rotary valve
member used as a component of the control valve assembly
(the remaining components being essentially as depicted in
Figure 6).
Figure 12 is a sectional view showing the control
valve assembly of the second embodiment in a normal
operating condition.
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Figure 13 is a sectional view similar to Figure 12 but
showing an exaggerated form the axial displacement of the rotary
valve member under conditions of increased pressure.
Detailed Description
_
Referring to Figures 1-9, the numeral 10 generally
designates a system or assembly comprising an inflatable pad 11,
conduits 12-15, and a source of pressurized air (or other fluid)
in the form of compressor 17. In the embodiment illustrated, the
compressor is connected to a control valve assembly by means
of a supply conduit 18 and an exhaust conduit 19.
The p~d 11 is generally rectangular in configuration
and, when used as a bed pan, would be dimensioned to be supported
upon a standard bed mattress. The pad may advantageously be
formed of a top wall or sheet 20 formed of a durable and flexible
material and joined to a bottom wall or sheet 21 (which may also
be of flexible material or, if desired, may be relatively rigid)
by heat-sealing, sonic welding, adhesives, or any other suitable
means, along portions 22 to define at least two interlaced ser-
pentine passages 23 and 24 (Figure 3). Natural or synthetic
rubber may be used, as well as any of a variety of durable and
flexible plastics, in fabricating the pad. As shown in Figures
1, 2, and 3, the top wall is provided with perforations 25 for
the escape of air from the passages as will be described hereinafter.
In use, the pad is covered with a porous cushion 26 formed of an
open celled resilient plastic foam or any other suitable material.
Since such a cushion or pad 26, and its use in conjunction with an
inflatable pad, are well known in the art, as fully disclosed in
U.S. patent 3,653,083, the further discussion of such a porous
cushion is believed unnecessary herein.
In the embodiment illustrated, the interlaced passages
23 and 24 extend back and forth throughout substantially the full
width and length of the elongated rectangular pad 11. Each
inflatable passage starts at an opening at one end of the pad and
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terminates at an opening at the pad's opposite end; hence, air
under pressure introduced at one end will produce an inflation
of the passage starting at that end and traveling towards the
opposite end of the pad until the entire passage is inflated. It
is to be noted, however, that although each inflatable passage
terminates adjacent opposite ends of the pad, portions of conduits
12-15 may be enclosed within or built into the pad so that
appropriate connections between the pad and the control valve
assembly need be made only at one end portion of the pad. Further-
more, although the passages are depicted as serpentine, the inter-
laced transverse portions may alternatively be of the general
configuration illustrated in Figures 4-6 of aforementioned U.S.
patent 3,653,083 except that, unlike the patented construction,
each of such passages must effectively terminate at both ends of
the pad.
In Figure 6, the control valve assembly 16 takes the form
of a valve body 27, a rotary valve member 28 a motor 29 secured to
the valve body and equipped with a shaft 30 for supporting and
rotating the rotor, a compression spring 31, and an adjustment knob
32 threadedly carried by the end of drive shaft 30. The valve body
27 is shown as a generally rectangular block having a planar front
face 33 against which the rotary valve member 28 is normally dis-
posed. The block is bored in directions parallel with the face 33
to form inlet and outlet passages or openings 34 and 35, respective-
ly (Figure 7) and also to provide lateral passages 36-39 which com-
municate with conduits 12-15, respectively (Figure 4). Passages or
bores 36-39 extend inwardly and are joined at their respective inner
ends by axial openings 40-43, respectively. Openings 40-43 are
circumferentially and uniformly spaced along an annular portion 44
of the face 33 (Figure 6).
Conduits 12-15 may take the form of flexible tubes or
hoses, or portions of an integrated four-passage tube or hose,
extending between the control valve assembly and the inflatable
pad 11. Similarly, conduits 18 and 19 may take the form of
flexible tubes or hoses, either joined or separate, extending
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.~etween the control valve assembly and the compressor.
Referring to Figure 7, it will be seen that inlet
passage 34 communicates with an annular chamber 45 which
extends about the hub of the drive shaft and which is open
at the face of the valve block within the confines of
annular zone 44. The outer limits of the annular zone are
defined by a groove or channel 46 which communicates with
outlet 35 (Figure 7). Thus, in the operation of the device,
channel 46 communicates with the intake of compressor 17
and is therefore under negative pressure, whereas chamber
45 communicates with the discharge end of the compressor and
is under positive pressure.
The rotary valve member 28 is provided along its
inner face (i.e., the surface facing the valve body) with a
pair of T-shaped recesses 47 and 48. The stem portion 48a
of recess 48 projects radially outwardly and is in constant
communication with channel 46 when the parts are assembled.
The intersecting portion 48b is arcuate and successively
communicates with openings 40-43 of the valve body as the
valve member is rotated.
The stem portion 47a of recess 47 is in continuous
flow communication with chamber 45, whereas the intersecting
arcuate portion 47b also is in successive communication with
openings 40-43 as the rotary valve member is rotated. Thus,
when the valve member is in the position illustrated in
Figures 1, 4, and 8, compressed air discharged from compressor
17 passes into the inlet 34 and chamber 45 of the valve body,
and then into recess 47 of the rotary valve member where it
is distributed to opening 40 and connecting conduit 12
leading to inflatable chamber 23. At the same time, at
the opposite end of the pad 11, inflatable chamber 24 is in
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flow communication with the intake of the compressor 17
through conduit 15, rotor recess 48, and valve outlet
conduit 19. Inflatable chamber or passage 24 is therefore
evacuated from one end of the pad while chamber or passage
23 is inflated from the opposite end. The result is a
clearly noticeable inflation-deflation wave or ripple which
starts at one end of the pad and ends at the opposite end.
Shortly thereafter, when the rotary valve member has advanced
to the position illustrated in Figure 2, the direction of
flow is altered with inflatable chamber 23 being evacuated
and chamber 24 being inflated. As the rotary valve member
advances into its next position, chamber 23 will again be
inflated and chamber 24 will once more be evacuated. It is
to be observed that each of the inflatable chamber is
alternately inflated from its opposite ends. Similarly,
deflation of each chamber occurs alternately from opposite
ends of that chamber. Thus, chamber 23 is first inflated
from one end, then deflated, and then inflated from its
opposite end. The same inflation-deflation pattern occurs
with respect to chamber 24. The result is that an inflation
wave develops at one end of the pad and advances to the
opposite end of the pad, then a second wave again develops
(in the other chamber) starting at the same beginning and
working its way towards the opposite end of the pad. There-
after, the direction of the waves is reversed, an inflation
wave starting at the opposite end of the pad and migrating
to the original end, followed by a second wave originating
at the opposite end (in the other chamber) and advancing
towards the original starting end. The whole cycle is then
repeated. Since the waves propagate in different directions
over a full operating cycle (i.e., for inflations and
for deflations), it is believed that the periodical reversal
of direction of flow contributes significantly in reducing
pressure points and in providing an improved system which
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enhances patient comfort and effectively reduces problems
of decubitus ulcers for bedridden patients. It is also
believed important that the discharge of air through
perforations 25 of the pad, which provides ventilating and
drying air for the patientto offset skin maceration and
increase patient comfort, occurs more uniformly than in
prior systems because of the reversing direction of
inflation and wave propagation.
Referring to Figure 8, channel 46 collects air
returning from the deflation chamber through conduit 15,
passage 39, opening 43, and recess 48 and, as revealed by
Figure 7, the air passing into channel 46 then flows to the
compressor through passage 35 and conduit 19. In some cases,
however, channel 46 may perform an additional function of
collecting excess air and directing such excess air back to
the intake of the compressor. In such a case, the control
valve assembly serves as a regulator to limit the maximum
inflation pressure of the inflatable chambers 23 and 24.
The pressure-limiting operation of the valve assembly is
indicated in Figure 8 and, in particular, in Figure 9.
Referring to Figure 8, which depicts a normal
operating condition, air under pressure enters the chamber
45 in the body of the valve and is directed to the pad
through recess 47, opening 40, passage 36, and conduit 12.
As the chamber 23 or 24 of the pad becomes fully inflated,
a back pressure develops and, if that pressure reaches a
predetermined level while the compressor continues to force
air into the same chamber, the increased pressure within the
valve assembly will cause the rotary valve member to become
displaced axially away from the valve body, thereby allowing
some of the air from the compressor to bypass opening 40 and
enter channel 46 (Figure 9) since the channel serves as an
intake for the compressor, excess air is thereby returned
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directly to the compressor for recirculation. As soon as
the rotary valve member has advanced to the point where
recess 47 no longer overlies opening 40, the compression
spring 31 returns the valve member into surface contact
with the valve body. Adjustment of spring tension to
control -the maximum inflation pressure of the pad may be
achieved by turning the knurled knob 3Z one way or the other
along the threaded end of shaft 30. It will be observed
that the rotary valve member has an axial bore 50 of non-
circular (square) cross section which slidably receives thenon-circular (square) portion 51 of the drive shaft 30.
The valve member is therefore mounted for limited axial
movement while being locked against rotation independently
of the shaft.
In the embodiment of Figures l-9, the valve
assembly also includes flow restrictin~ means in the form
of a needle valve 52 positioned to control flow of air
evacuated from the pad by the compressor. Ideally, the
needle valve 52 is located in the rotor to partially obstruct
the stem portion 48a of recess 48, the valve member being
threadedly mounted and equipped with a slotted and knurled
head portion 52a for selective adjustment of valve
operation. By adjusting the valve member to provide greater
restriction of flow, a smaller proportion of the air supplied
to the compressor 17 is drawn from the inflatable chambers
of the pad and a larger proportion takes the form of room
air drawn through a separate compressor intake 53. As a
result, evacuation of each chamber will occur more slowly.
If the rotor indexes into its next position before evacuation
of a given chamber is completed, then obviously some residual
air will remain in that chamber. The differences in the
heights in the inflated and relaxed chambers may therefore
be controlled to achieve optimum effects.
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While the needle valve member 52 is shown to be
mounted in rotor 28 so that it protrudes into recess 48,
it is believed apparent that the flow restricting means
might be! located elsewhere to achieve similar, although
perhaps less effective, results. Thus, a flow restricting
valve may be located in conduit 19 (Figure 7), just
downstream from the illustrated position, or in compressor
intake 53 since by regulating the proportion of room air
drawn into the compressor through the intake 53 the
proportion of air evacuated from the pad is necessarily
affected. Other valve locations may be selected; however,
the location depicted in the drawings is believed
particularly effective because in that location the flow
restrictor affects only the air withdrawn from the chamber
of the pad undergoing evacuation. The operation of the
negative pressure groove 46 in collecting excess air in the
manner already described is not affected.
In the embodiment of Figures 10-13, the only
structural difference is found in the construction of rotary
valve member 28'. Since the other parts of the system are
the same as in the preceding embodiment, the same numerals
are used.
Rotary valve member 28' is similar to member 28
except that it has only a single T-shaped recess 47. Recess
48 is omitted in valve member 28'. Since there is no
positive evacuation of air from the chamber of the pad
when the valve member is positioned as shown in Figure 12,
deflation of those chambers occurs primarily by reason of
the escape of air through the perforations in the pad's
upper wall.
As in the prior embodiment, the intake of compressor
17 is connected to the valve body by means of conduit 19.
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Although -there is no positive evacuation of the chambers
of the pad when the valve member is seated as shown in
Figure 12, the compressor does draw air from channel 46 in
the valve body, creating a negative pressure in that
channel. Should the inflation pressure in a chamber of
the pad exceed a preselected maximum pressure, causing
axial separation of the rotary valve member 28' from valve
body 27 in the manner previously described, then excess air
is free to pass directly from chamber 45 into channel 46
and be returned to the compressor for recirculation
(Figure 13). When such separation occurs, the channel 46
is also placed in communication with opening 43 and,
consequently, the valve and compressor produce limited
positive evacuation of the relaxed chamber as long as such
separation exists. As before, spring 31 returns the valve
member into its original position (Figure 12) when the excess
pressure condition is relieved.
Spring 31 is disclosed in both forms of the
valve for the purpose of maintaining the valve member and
valve body in sliding engagement with each other and, pre-
ferably, to permit slight axial separation of the parts when
a predetermined back pressure (i.e., the maximum desired
inflation pressure of the chambers of the pad) develops.
It is to be understood, however, that similar results may
be achieved, although perhaps less effectively, even in the
absence of spring 31, as long as air under pressure is cap-
able of leaking outwardly between the opposing faces of the
parts. The channel 46 will perform the function of collect-
ing excess air and returning it to the compressor when
sufficient back pressure develosp so that only a portion
of the air from the inlet chamber 45 enters the selected
openings 40-43, the remaining portion flowing outwardly
between the opposing faces of valve body 27 and valve
member 28 (or 28').
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It is to be understood that in both disclosed
embodiments, the compressor 17 draws only part of its air
requirements from conduit 19. Additional air as needed is
taken directly from the room through an additional compressor
intake 53. Furthermore, it is to be understood that in some
installations the return conduit may be entirely deleted,
thereby eliminating the capability of the system to re-
circulate excess air, evacuated air, or both. In such a
system, however, the valve assembly will nevertheless operate
in conjunction with the pad to cause each inflatable passage
or chamber of that pad to be inflated alternately from its
opposite ends and from opposite ends of the pad as a whole.
While in the foregoing we have disclosed embodi-
ments of the invention in considerable detail for purposes
of illustration, it will be understood by those skilled in
the art that many of these details may be varied without
departing from the spirit and scope of the invention.
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