U.S. patent application number 14/541720 was filed with the patent office on 2015-03-19 for mattress type support device including feed/vent valve.
The applicant listed for this patent is Hill-Rom Industries SA. Invention is credited to Jean-Luc Caminade.
Application Number | 20150074914 14/541720 |
Document ID | / |
Family ID | 38687209 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150074914 |
Kind Code |
A1 |
Caminade; Jean-Luc |
March 19, 2015 |
MATTRESS TYPE SUPPORT DEVICE INCLUDING FEED/VENT VALVE
Abstract
A support device of the mattress type (1), in particular for
supporting the body of an individual, comprises a plurality of n
compartments (2), preferably at least three compartments, more
preferably three to 24 compartments suitable for being inflated
with a fluid, in particular inflated with air, a plurality p of
said compartments, where p is an integer in the range 2 to n, each
having at least one fluid feed and/or vent orifice (4-1, 4-2) for
said compartment and at least one solenoid valve (3-1, 3-2) serving
to control the feed and/or vent of fluid to or from said
compartments, the device being characterized in that said valves
co-operate with or are integrated in said feed and/or vent
orifices, each said valve (3-1, 3-2) being dedicated to filling
and/or venting a single compartment.
Inventors: |
Caminade; Jean-Luc; (St.
Jean de Vedas, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hill-Rom Industries SA |
Montpellier |
|
FR |
|
|
Family ID: |
38687209 |
Appl. No.: |
14/541720 |
Filed: |
November 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12036582 |
Feb 25, 2008 |
|
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14541720 |
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Current U.S.
Class: |
5/713 |
Current CPC
Class: |
F16K 31/0651 20130101;
A47C 27/10 20130101; A47C 27/081 20130101; A61G 7/05776 20130101;
F16K 31/0606 20130101 |
Class at
Publication: |
5/713 |
International
Class: |
A47C 27/10 20060101
A47C027/10; A47C 27/08 20060101 A47C027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2007 |
FR |
0701391 |
Claims
1. A mattress type support device comprising n inflatable
compartments where n is at least two, a plurality p of the
compartments each having at least one combination fluid feed and
vent orifice and a single combination feed and vent valve
associated with the orifice for controlling fluid transfer into and
out of the compartment.
2. The device of claim 1 comprising: a single main feed pipe
extending along a longitudinal side of the mattress type support
device; and a branch pipe extending from each valve to the main
feed pipe, the orifices being disposed on the same longitudinal
side of the mattress type device as the main feed pipe, the main
feed pipe being fed by a fluid injection device common to all the
branch pipes.
3. The device of claim 1 wherein: each valve comprises a first
endpiece connected to its associated orifice, the first endpiece
having a first channel for passing the fluid, and a second endpiece
connected to one end of a branch pipe whose other end is connected
to a main feed pipe, the second endpiece containing a second
channel for passing the fluid.
4. The device of claim 3 wherein each valve comprises an internal
cavity into which both of the first and second channels open out
and a third channel communicating between the internal cavity and
the outside of the valve.
5. The device of claim 4 wherein the third channel opens out
axially inside the internal cavity and transversely through the
outside surface of the valve such that the third channel presents a
bent or L-shape.
6. The device of claim 3 wherein the first and second endpieces of
each valve are disposed symmetrically relative to a main body
defining an outside surface of cylindrical shape, the main body,
the first endpiece and the second endpiece all having a common
longitudinal axis.
7. The device of claim 4 wherein the internal cavity contains a
coil and a magnetic core, the core being movable in a longitudinal
direction of the valve between a first position and a second
position, such that in the first position, the core closes an
internal end of the third channel while leaving open the ends of
the first and second channels that open into the cavity so that
fluid can flow to the compartments by way of the second channel,
the internal cavity, and the first channel, and so that in the
second position the core closes the second channel, while the other
end of the core is separated from the ends of the first and third
channels so that fluid can be vented from the compartment through
the first channel, the internal cavity, and the third channel.
8. The device of claim 7 wherein upon electrical actuation of the
coil the magnetic core overcomes a longitudinally directed spring
force.
9. The device of claim 7 wherein the first position corresponds to
the valve being de-energized and the second position corresponds to
the valve being energized.
10. The device of claim 1 wherein the valves and the pipe reside
inside a protective cover of the device.
11. The device of claim 1, wherein the valves are controlled by an
electronic control unit making it possible to select between
performing: a continuous mode, in which all of the compartments are
inflated; and various alternating pressure modes in which a
fraction only of the compartments in at least one zone of the
mattress are deflated, at least in part, and then reflated, the
compartments for deflating/reflating being spaced apart regularly,
by deflating and reflating in succession each compartment in the
zone going from compartment to neighboring compartment in the
longitudinal direction of the mattress in both the go and the
return directions along the zone.
12. The device of claim 1, wherein the compartments form
sausage-shaped tubes extending transversely relative to the
longitudinal direction of the mattress.
13. The device of claim 3, wherein the valves are solenoid valves
disposed in line, each comprising a main body with an internal
cavity containing a core and an induction coil having the same
longitudinal axis, each of the first and second endpieces being
disposed symmetrically relative to the main body and on the same
longitudinal axis as the main body, and the first and second
endpieces being engaged respectively in bent tubular orifices of
the mattress and bent ends of branch pipes, and are offset from
each other longitudinally in the longitudinal direction of the
mattress so as to enable the valves to be placed in alignment in
the longitudinal direction of the feed pipe and of the
mattress.
14. The device of claim 1 wherein each valve associates with its
fluid transfer orifice by being integrated therein.
15. The device of claim 1 wherein each valve associates with its
fluid transfer orifice without being integrated therein.
16. The device of claim 7 wherein the valve includes grooves around
the core so that air can flow through the internal cavity when the
valve is in the first position.
17. The device of claim 16 wherein the grooves are in an outside
surface of the core.
18. The device of claim 7 wherein a hole passes longitudinally
through the core so that air can flow through the internal cavity
where the valve is in the first position.
19. The device of claim 7 wherein when the valve is in the first
position a fluid injection device maintains a minimum pressure in
the compartments.
20. The device of claim 7 including a fluid injection device
connected to the main feed pipe and wherein when the valve is in
the first position the fluid injection device operates as
appropriate to maintain desired pressure in the compartments.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 12/036,582, filed Feb. 25, 2008, which claims priority, under
35 U.S.C. .sctn.119(a), of French National application Ser. No.
07/01391, filed Feb. 27, 2007, now French Patent No. 2912884,
issued Sep. 28, 2012, both of which are hereby incorporated by
reference herein.
BACKGROUND
[0002] The present disclosure relates to a support device of the
mattress type, in particular for supporting the body of an
individual, the device having a plurality of compartments suitable
for being inflated with a fluid, in particular inflated with
compressed air.
[0003] Some mattresses have compartments in the form of
sausage-shaped tubes, each tube extending transversely relative to
the longitudinal direction of the mattress, and the various tubes
being placed side by side in the longitudinal direction of the
mattress.
[0004] Each compartment generally has a fluid feed orifice and a
fluid vent orifice.
[0005] In order to fill/inflate a compartment, a first solenoid
valve is opened in order to cause the compartment to be fed through
said feed orifice, and then the valve is closed once the required
pressure has been reached, while a second solenoid valve that
serves to vent fluid from said vent orifice is kept closed.
Conversely, in order to empty or deflate the compartment, for the
purpose of adjusting the pressure inside the compartment, said
first valve that controls the feed orifice is kept closed, while
the second valve controlling venting from the vent orifice is
opened.
[0006] Mattresses of this type are used in medical situations,
since they enable fluid distribution within the mattress to be
controlled better. Above all, depending on the number of valves
used, they make it possible to control pressure individually and
thus to fill compartments individually in various zones of the
mattress.
[0007] By way of illustration in FIGS. 1 and 3, there are shown
diagrammatically mattresses each having sixteen compartments
subdivided into three zones: [0008] a first zone for the head and
the shoulders and comprising a single compartment; [0009] a second
zone going from the shoulders to the calves and comprising twelve
compartments; and [0010] a third zone in the vicinity of the heels
and comprising three compartments.
[0011] In theory, and in particular for the purposes of avoiding
bed sores or of alleviating pain located in certain zones where the
body presses against the mattress, good patient comfort is obtained
when the pressure exerted by the various zones of the body on the
mattress (referred to as the "interface pressure") is substantially
identical for all points where the surface of the body is in
contact with the mattress, and when said contact surface of the
body with the mattress is simultaneously of the greatest possible
area, thereby requiring the extent to which the body sinks into the
various compartments to be adapted to match different portions of
the body.
[0012] To do this, it is necessary to distribute pressures inside
the compartments by controlling the extent to which the various
compartments in the longitudinal direction of the mattress are
filled/emptied in compliance with certain pre-established
calculations based on and as a function of measurements made by
sensors in, on, or under the mattress, depending on the type of
sensor used.
[0013] These sensors are known to the person skilled in the art and
they serve to measure pressure inside the compartments or the
extent to which the patient's body has sunk into a given
compartment of the mattress, and they are described for example in
European patent EP 0 676 158 in the name of the Applicant.
[0014] Controlling and regulating the filling/emptying of
compartments using solenoid valves also makes it possible to enable
the mattress to operate in a so-called "alternating pressure" mode
in which a certain number of compartments that are regularly spaced
apart along the length of the mattress are deflated and then
re-inflated, simultaneously for the various compartments concerned.
For example, it is possible to deflate/re-inflate one compartment
in two or one compartment in three, and then to deflate/re-inflate
the compartments adjacent to the compartments that were previously
deflated and then re-inflated.
[0015] Thus, each compartment of the mattress is successively
deflated/re-inflated in turn from compartment to neighboring
compartment, thereby creating a kind of wave that moves in the
longitudinal direction of the mattress in both the go and the
return directions, thereby massaging the patient and encouraging
vascularization of the soft tissue at the interface with the
mattress while re-inflating the compartment, or minimizing the
effects of ischemia, in particular anoxia or hypoxia, while
deflating the compartment.
[0016] At present, the valves in use are designed to be mounted
together in units, in particular pneumatic manifolds, and more
generally in multiple manifolds constituting a manifold unit that
is itself combined, where appropriate, with an electronic control
unit serving to control the feeding and venting of the fluid to or
from the various compartment zones of the mattress and in a manner
that is modulated and controlled. In general, the various feed
valves are fed with fluid from a common feed source, where
appropriate a common pump or compressor, in order to inject air or
compressed gas as appropriate into the compartments.
[0017] Those manifold type units for controlling and distributing
fluid group together the various valves and, by way of example,
they are located at the foot of the bed, so they are necessarily
relatively far away from some of the compartments to which the
valves are connected by feed pipes and by vent pipes.
[0018] In general, each valve serves to feed or vent a plurality of
compartments in order to limit the number of valves.
[0019] Limiting the number of valves also serves to limit the
number of pipes going from the manifold and thus the space occupied
by the pipes. Nevertheless, that requires valves to be used that
are dimensioned so as to be capable of delivering fluid at a rate
that is sufficient for feeding a plurality of compartments.
[0020] By way of illustration, FIG. 1 shows a manifold having three
feed valves on which there are mounted three main feed pipes each
having secondary feed pipes branching therefrom via T-couplings in
order to feed n compartments.
[0021] Symmetrically, n secondary vent pipes connected to the vent
orifices of said compartments are connected via T-couplings to
three main vent pipes, with the main vent pipes serving to convey
fluid to three vent valves mounted on a common manifold.
[0022] More precisely, in FIG. 1, valves V.sub.3 and V.sub.6
together control a single compartment for a head or first zone,
respectively via a first main feed pipe and a first vent pipe.
[0023] Valves V.sub.2 and V.sub.5 serve respectively to feed and
vent twelve compartments of a middle zone extending under the
entire body from the shoulders down to the legs, the twelve
compartments being fed and vented respectively via twelve secondary
feed pipes and secondary vent pipes, themselves connected
respectively to a second main feed pipe and to a second main vent
pipe that are connected to said corresponding valves.
[0024] Finally, the valves V.sub.1 and V.sub.4 control the filling
and emptying of three compartments constituted by a foot zone via a
third main feed pipe and a third main vent pipe, each third main
feed pipe and main vent pipe being connected respectively to three
other secondary feed pipes and to three other secondary vent
pipes.
[0025] FIG. 2 shows a variant of the device for feeding a mattress
having sixteen compartments likewise distributed in three zones,
but capable of operating in an "alternating pressure mode" with it
being possible for one compartment in three to be
deflated/re-inflated in alternation, thus requiring fourteen valves
to be used (seven feed valves and seven vent valves) together with
seven main feed pipes and seven main vent pipes.
[0026] It should be observed that the main feed or vent pipes need
to present a certain amount of rigidity and a section having a
certain diameter in order to enable them to feed a plurality of
secondary pipes, and also to avoid accidental kinking on their
paths between the manifold and the furthest compartment. These
pipes are disposed beside the mattress, generally inside a cover
for protecting the mattress. It will be understood that such a
large number of pipes constitutes a large bulk that is difficult to
put into place and to use. Increasing the number of pipes increases
the risk of kinking. In practice, and in standard manner, the pipes
present circular sections of outside diameter lying in the range 10
millimeters (mm) to 20 mm, and more particularly of about 15 mm,
and an inside diameter lying in the range 5 mm to 15 mm, and more
particularly of about 10 mm.
[0027] Given that each valve must be capable of controlling the
filling or venting of a plurality of compartments over a distance
that is relatively long, said valves must be capable of delivering
fluid at a relatively high rate, which in practice may be as much
as 50 liters per minute (L/min). Such valves thus represent weight,
size, and cost that are relatively great, not to mention the
weight, the size, and the cost of the manifold unit itself. There
is also the sound nuisance due to the valves operating, and large
amounts of energy are consumed both for activating a command and
for maintaining an open or closed command for said valves.
[0028] In all, the various above-mentioned constraints make it very
difficult to implement a fluid feed/vent system of this type for
each compartment without leading to considerable difficulties of
implementation.
SUMMARY
[0029] This disclosure discusses a device for feeding/venting fluid
to or from a plurality of compartments of a mattress, which device
is more compact and less expensive, simpler and easier to
implement, and generally is improved compared with the system
presently in use.
[0030] This disclosure discusses a device for feeding/venting fluid
to or from a plurality of compartments of a mattress that can be
used for controlling and regulating the filling/emptying of fluid
to and from each compartment individually and without involving
excessive difficulty in implementation, as applied to the systems
presently available.
[0031] This disclosure further discusses a device for
feeding/venting fluid to or from a plurality of compartments of a
mattress that can operate in a variety of types of modes that can
be selected as alternatives.
[0032] To do this, the present disclosure discusses a mattress type
support device in particular for supporting the body of an
individual, the device comprising a plurality of n compartments,
preferably at least three compartments, more preferably three to 24
compartments suitable for being inflated by a fluid, in particular
inflated with air, a plurality p of said compartments, where p is
an integer lying in the range 2 to n, each having at least one
fluid feed and/or vent orifice for said compartment and at least
one solenoid valve enabling fluid feed and/or fluid vent to be
controlled for said compartments, the device being characterized in
that each said valve co-operates with or is integrated in one of
said feed and/or vent orifices, each said valve being dedicated to
filling and/or emptying a single compartment, said valve not
co-operating with or not being integrated in a manifold type
unit.
[0033] In a one embodiment of the device disclosed herein, each
compartment has a fluid feed orifice and a fluid vent orifice and
each said compartment in question has or co-operates with two
valves, respectively a feed valve and a vent valve, one serving to
control fluid feed and the other to control fluid vent, said valves
being integrated in or co-operating with said feed and vent
orifices respectively, each said valve being dedicated respectively
to filling or emptying a single compartment.
[0034] This embodiment has two-port valves (referred to as "2/2
valves") to be used and makes it possible to regulate pressure in
compartments fitted with two valves, i.e. one valve at each
orifice, one for feeding and the other for venting the
compartment.
[0035] These two ports comprise:
[0036] for the feed valve: [0037] a first internal channel
communicating with said feed orifice of the compartment; and [0038]
a second internal channel communicating with a feed pipe; and
[0039] for the vent valve: [0040] a first internal channel
communicating with a vent orifice of said compartment; and [0041] a
second internal channel communicating with a vent pipe or opening
out to the atmosphere.
[0042] Nevertheless, in another embodiment, each of said
compartments concerned, i.e. each compartment having or
co-operating with a said valve, has a single orifice co-operating
with a single valve through which said compartment is both fed and
vented. Said valve co-operates with or is integrated in a single
open orifice acting both as a feed orifice and as a vent orifice
depending on whether or not said valve is activated, with the other
orifice, if any, then being closed.
[0043] This other embodiment requires three-port valves to be used
(known as "3/2 valves").
[0044] These three-port valves comprise: [0045] a first internal
channel opening out to a single open orifice for feeding and vent
air to or from the compartment; [0046] a second internal channel
communicating with a pipe for feeding the valve with fluid; and
[0047] a third internal channel opening out to the atmosphere,
enabling fluid to be vented from the compartment.
[0048] However, in some embodiments, such three-port valves make it
possible only to control inflation/deflation of a compartment,
without making it possible to regulate its pressure.
[0049] In any event, given that said 2/2 or 3/2 valves serve to
feed/empty a single compartment only, they may be of a size that is
relatively much smaller than that of the valves conventionally
used, since the prior art valves oftentimes are dedicated to
feeding/venting a plurality of compartments.
[0050] For identical pressure above atmospheric in a compartment,
the required fluid flow rates, and thus the flow sections required
for the valves are much smaller with valves discussed in this
disclosure than they are with valves each dedicated to a plurality
of compartments.
[0051] In addition, for valves that are used and positioned
directly at the orifices of the compartments, the distance between
the feed and vent valves, and thus the head losses between said
feed and vent valves are minimized compared with valves that are
offset to a common remote centralized position, e.g. at the foot of
the bed as in the prior art.
[0052] In all, given that these valves are sometimes required in
practice to regulate pressures in the mattress of only about 10
millibars (mbar) to 100 mbar above atmospheric, the valves
disclosed herein may be configured to deliver fluid at a relatively
low rate (since each feeds only one compartment) and they can
therefore be of size and weight that are smaller than the size and
weight of valves feeding a plurality of compartments, as
conventionally implemented in a manifold unit of the remote type,
e.g. located at the foot of the bed.
[0053] As a result, the solenoid valves also consume less energy
for their control, and in particular they consume only about
one-tenth compared with the solenoid valves that are used
conventionally.
[0054] Finally, valves according to this disclosure serve to
regulate or adapt the inflation of compartments and to make
pressure corrections within compartments with a reaction time that
is much shorter. In practice, the reaction time of the valves
conventionally used in a manifold unit of the type that is offset
to the foot of the bed is about 1 second (s) to 3 s, whereas with
the devices in accordance with this disclosure it is of the order
of 1/2 s to 1 s, or even less.
[0055] In the devices disclosed herein, it is possible to allocate
a pair of two-port valves to each compartment, and to regulate
feeding/venting, in particular inflating/deflating for each
compartment individually, and thus to adapt the configuration of
the inflation of the various compartments of the mattress in a
manner that is more accurate as a function of the morphology of the
patient or in compliance with other criteria, depending on
circumstances.
[0056] Furthermore, as mentioned above, if it is desired merely to
control inflation/deflation of the various compartments concerned,
it is possible to allocate a single three-port valve to each
compartment, each said valve co-operating with a single open
orifice serving to feed and vent fluid to and from the compartment,
with its other orifice, if any, being plugged.
[0057] As explained below, the devices disclosed herein also makes
it possible to provide mattress type support devices with
alternating emptying/filling of the various compartments being
performed in a variety of modes that can be selected by
appropriately programming the control of the valves.
[0058] However, the small size of the valves as dedicated in this
way to each compartment and as located adjacent to the mattress
serves above all to make the valves much easier to put into place
and to use, particularly since it is then possible to use a
simplified network of pipes for transferring fluid in the fluid
feed/vent device, which network is smaller when deployed.
[0059] One advantage of some embodiments of the devices disclosed
herein thus lies in the simplified installation and reduced size of
the device comprising valves and pipes for feeding/venting fluid to
and from said compartments.
[0060] The devices disclosed herein also makes it easy to adapt the
operating features of the mattress on request, merely by adding or
removing valves, thus enabling the functional features of the
mattress to be varied without it being necessary to modify the
pneumatic distribution network, as is necessary in the prior
art.
[0061] In one disclosed embodiment, the device has only one main
feed pipe with a plurality of branch connections for connecting to
a plurality of said valves, each co-operating directly with or
integrated in a corresponding feed orifice selected amongst a
plurality of compartments, and preferably amongst all of the
compartments, said feed orifices being disposed on one longitudinal
side of the mattress type device and said main feed pipe running
along said longitudinal side, said main feed pipe being fed from a
common fluid injection device.
[0062] The phrase "branch connection for connecting" is used herein
to cover, among other things, devices in which the main feed pipe
has branches, e.g. via a plurality of T-couplings, whose other ends
are fitted directly to the coupling endpieces of the valves or else
via short lengths of secondary feed pipes having their ends
connected respectively to the endpieces of the T-couplings located
on the main feed pipe and to the coupling endpieces of the
valves.
[0063] Similarly, the phrase "valve co-operating directly with an
orifice" is used herein to cover, among other things, that an
endpiece of the valve is fitted directly to the orifice, e.g. by
being forced into said orifice.
[0064] According to the devices disclosed herein, the bundle or
network of tubes feeding the various compartments from the various
valves may be replaced, in part, with a bundle or network of
electric wires for electrically powering the solenoid valves, which
network of wires is much more compact.
[0065] Using a single main feed pipe for feeding the various valves
presents a significant advantage in terms of cost and simplicity in
implementing the devices disclosed herein.
[0066] One embodiment of a valve disclosed herein for controlling
feeding and/or venting fluid to or from a compartment may be
capable of conveying fluid at a flow rate that is divided by p
relative to the flow rate of a valve that controls the feeding or
venting of fluid to or from p compartments. In some embodiments,
the valves disclosed herein may be configured to convey fluid flows
in the range 1 L/min to 5 L/min instead of 50 L/min as has been
conventional.
[0067] More particularly, in some embodiments, said valves may
comprise at least: [0068] a first endpiece of circular
cross-section, preferably presenting a serrated outside surface,
said first endpiece being forced into a said feed or vent orifice
that is of resilient tubular shape, and said first endpiece closing
a first cylindrical axial channel for passing said fluid; and
[0069] a second endpiece of circular cross-section, preferably
presenting a serrated outside surface, said second endpiece being
forced into one end of a branch pipe connected to a said main feed
pipe or connected to a vent pipe or open to the atmosphere, and
said second endpiece containing a second cylindrical axial internal
channel for passing said fluid.
[0070] The serrated outside surface provides better retention in
said tubular orifice after being forced into an elastic tubular
orifice.
[0071] Still more particularly, in some embodiments, each of said
feed valves may include a second endpiece of circular
cross-section, preferably presenting a serrated outside surface in
particular, said second endpiece being forced into one end of a
branch pipe connected to said main feed pipe and said second
endpiece containing a second cylindrical axial internal channel for
passing said fluid.
[0072] Still more particularly, in some embodiments, each of said
vent valves may include a second endpiece of circular
cross-section, said second endpiece enabling said fluid to be
vented to the atmosphere.
[0073] Said second endpiece of each of said vent valves, in some
embodiments, is therefore not connected to one end of a vent pipe
or of a branch pipe connected to a main vent pipe, the device of
such embodiments not requiring such a vent pipe to be used.
[0074] As disclosed herein, said valves and said feed pipe are
placed inside a cover for protecting the mattress.
[0075] In some embodiments, said vent valves co-operating with or
integrated in said vent orifices are not connected to a vent pipe,
the fluid being a gas, and in particular air, that is vented to the
atmosphere either freely or, where appropriate, into a said
protective cover.
[0076] In another embodiment, it can be desirable to evacuate the
fluid from the cover by channeling it in a vent pipe going away
from said second endpieces of the vent valves.
[0077] In some embodiments, said valves are controlled by an
electronic control unit making it possible to select between
implementing: [0078] a continuous mode, in which all of the
compartments are inflated; and [0079] various alternating pressure
modes in which a fraction only of the compartments in at least one
zone of the mattress are deflated, at least in part, and then
re-inflated, said compartments for deflating/re-inflating being
spaced apart regularly, preferably comprising one compartment in
two or one compartment in three, more preferably by deflating and
re-inflating in succession each compartment in said zone going from
compartment to neighboring compartment in the longitudinal
direction of said mattress in both the go and the return directions
along said zone.
[0080] In such embodiments, all the compartments may include said
feed valves and/or vent valves, which valves are controlled by an
electronic control unit serving to implement a selected one of
various alternating pressure modes in which a fraction of the
compartments that are regularly spaced apart are deflated, at least
in part, and then re-inflated, with this being done in some
instances to one compartment in two or one compartment in three,
with each of the compartments being deflated/re-inflated from
compartment to neighboring compartment in the longitudinal
direction of said mattress both in the go direction and in the
return direction.
[0081] It will be understood that said valves may be small in size
and of a shape that is suitable for enabling them to be positioned
at the feed and vent orifices of the compartments inside a
protective cover disposed around said mattress and without running
any risk of damaging the mattress or the cover due to their shape,
and without running any risk of hurting or getting in the way of
the patient when the mattress is deflated.
[0082] In some embodiments, each of said valves has two of said
endpieces, namely a first endpiece and a second endpiece disposed
symmetrically relative to a main body defining an outside surface
of preferably rounded shape, said main body being cylindrical in
shape, said main body having the same longitudinal axis as said
first and second endpieces.
[0083] According to this disclosure, the outside diameter of said
cylindrical body may be substantially identical to or a little
greater than that of said feed pipe. Thus, the valve can be placed
in line with the pipe in a compact configuration.
[0084] In some embodiments, said main body has a cylindrical
internal cavity into which both of said first and second internal
channels having the same longitudinal axis open out, said internal
cavity containing a longitudinal magnetic core suitable for being
moved in said axial longitudinal direction of said valve, said
magnetic core moving inside an induction coil extending axially
along the same said longitudinal axis, said core being capable of
moving between firstly an open position in which the core is
separated from the ends of both of said first and second internal
channels on the same longitudinal axis opening out into said
internal cavity so as to allow the fluid to pass through said valve
between the ends of both of said first and second endpieces, and
secondly a closed position in which said core closes the end of one
of said first and second internal channels of the valve where it
opens out into said internal cavity in such a manner as to prevent
the fluid flowing through said valve between the ends of said first
and second endpieces.
[0085] The type of valve disclosed herein is sometimes referred to
as being "compact" and "in line" since its various component
elements are disposed on a common axis that is the same as the
longitudinal axis of the valve.
[0086] Furthermore, the flow of fluid through the valve between its
first and second endpieces, in some embodiments, takes place
axially along the same longitudinal axis as the valve axis, unlike
conventional valves in which the axis of the core and the movement
of the core are generally perpendicular to a fluid flow duct within
the valve.
[0087] In a variant embodiment, in the absence of said core being
electrically activated by said coil, said core is held in its
closed position by a spring acting on the core so as to hold it
against one of the two ends of said channels opening out into said
cavity, and when the core is moved into the open position by
electrically activating the coil, the core is moved so as to act
against the spring and disengage the core from the said end of said
internal channel in such a manner as to be spaced apart from both
ends of said channels opening out into said cavity.
[0088] This variant is generally selected since once the
compartments are appropriately adjusted in pressure, the mattress
is said to be "in equilibrium." It then requires no more than
pressure adjustments to be made from time to time, should the
patient change position. In practice, the valves may not be
operated for 75% of the time or more.
[0089] In another variant, in the absence of said core being
electrically activated by said coil, said core is held in the open
position by a spring acting on the core so as to keep it away from
both of the ends of said first and second channels opening out into
said cavity, and when the core is moved by electrically activating
the coil, the core is moved in such a manner as to be held against
one of the two ends of said first and second channels opening out
into said cavity, thereby closing it.
[0090] In known manner, fluid can flow through said cavity between
said core and said coil via grooves formed in the outside surface
of the core, and/or via a hole passing longitudinally through the
core.
[0091] When said valve is a three-port valve, it further may
include a third internal channel enabling said internal cavity to
be put into communication with the outside (i.e. the atmosphere) in
such a manner that: [0092] in said open position in which the core
is disengaged from the ends of said first and second internal
channels, said third internal channel is closed; and [0093] in said
closed position, said first internal channel communicating with
only one orifice of said compartment is open and said second
internal channel communicating with a said feed pipe is closed, and
said third internal channel is open, enabling the fluid to be
vented from said compartment to the atmosphere.
[0094] By way of illustration, but not limitation, the valves may
present a total length lying in the range 3 centimeters (cm) to 10
cm, preferably in the range 4 cm to 6 cm, and an outside surface of
circular cross-section having a maximum diameter lying in the range
10 mm to 20 mm, said first and second endpieces preferably
presenting a circular cross-section of diameter lying in the range
5 mm to 15 mm, and more preferably having internal channels with a
diameter lying in the range 2 mm to 10 mm, and preferably lying in
the range 4 mm to 7 mm.
[0095] The present disclosure discusses compact solenoid valves
disposed in line, each comprising a said main body with an internal
cavity containing a core and an induction coil having the same
longitudinal axis (X1X'1), each of said first and second endpieces
containing a first or second internal channel and being disposed
symmetrically relative to said main body and on the same
longitudinal axis (X1X'1) as said main body, and said first and
second endpieces are engaged in bent tubular orifices of said
mattress and respectively bent ends of branch pipes, and are offset
longitudinally in the longitudinal direction of the mattress so as
to enable said valves to be placed in alignment in said
longitudinal direction XX' of said feed pipe and of said
mattress.
[0096] In some embodiments, said main body, said first and second
endpieces, and said first and second internal channels are of
circular cross-section.
[0097] In some embodiments, the various solenoid valves are
connected to a control unit making it possible to select a control
mode from a continuous mode and a different mode known as an
alternating pressure mode, thereby making it possible on request to
massage at least a portion of the body of the patient resting on
said mattress.
[0098] It is also possible in this way to cause localized deflation
to take place under a portion only of the body, e.g. under the neck
for a tracheotomy.
[0099] In some embodiments, the electronic control unit for
controlling the solenoid valves is connected to at least one sensor
and said unit includes electronic means suitable for controlling
air feed or air vent to or from said compartments in such a manner
as to maintain a given air pressure within each said compartment,
preferably in such a manner that the pressure applied to the
surface of the mattress by the body of a patient lying thereon is
substantially identical over the entire area of the body that is in
contact with the mattress.
BRIEF DESCRIPTION OF THE DRAWINGS
[0100] Other characteristics and advantages of the devices
according to the present disclosure appear in the light of the
following detailed description:
[0101] FIGS. 1 and 2 are diagrams showing two prior art pneumatic
distribution networks feeding various compartments of a mattress
from a manifold, respectively comprising six solenoid valves (FIG.
1) and fourteen solenoid valves (FIG. 2);
[0102] FIGS. 3A and 3B are diagrams showing the distribution of
solenoid valves in a device according to this disclosure using
two-port valves (FIG. 3A) and three-port valves (FIG. 3B);
[0103] FIG. 4 is a side view of a mattress including a device
according to this disclosure;
[0104] FIG. 5 is a longitudinal section view of a two-port solenoid
valve according to this disclosure;
[0105] FIG. 6 is a longitudinal section view of a three-port
solenoid valve according to this disclosure;
[0106] FIGS. 7A and 7B are views looking along arrows VIIA and VIIB
of FIG. 5; and
[0107] FIG. 8 shows a prior art solenoid valve.
DETAILED DESCRIPTION
[0108] FIG. 1 is a diagram showing a mattress of the prior art
comprising sixteen compartments made up of sausage-shaped tubes
extending transversely to the longitudinal direction (XX') of the
mattress.
[0109] These sixteen compartments are distributed in three zones:
[0110] head zone Z.sub.3: one compartment; [0111] body zone
Z.sub.2: twelve compartments; and [0112] foot zone Z.sub.1: three
compartments.
[0113] FIG. 2 shows a system for feeding/venting air to or from the
various compartments from a manifold unit comprising a feed
manifold M.sub.1 having three solenoid valves V.sub.1, V.sub.2,
V.sub.3 and a vent manifold M.sub.2 comprising three vent solenoid
valves V.sub.4, V.sub.5, V.sub.6.
[0114] This manifold unit is combined with an electronic control
unit (not shown). The feed manifold M.sub.1 is connected to a
single pump/compressor 7.
[0115] Each feed valve V.sub.1 and V.sub.3 is connected to a main
feed pipe t.sub.1 to t.sub.3 feeding one compartment zone (Z.sub.1
to Z.sub.3).
[0116] More precisely, the solenoid valve V.sub.1 feeds the three
compartments of the zone T from the main feed pipe t.sub.1, which
pipe t.sub.1 has two T-couplings each serving to feed a
branch-connected secondary pipe t'.sub.1 for the purpose of
providing a connection via a tubular connection endpiece to a
tubular feed orifice 4-1 of each compartment. The T-coupling
presents tubular endpieces with serrated outside surfaces.
[0117] Symmetrically, from the vent tubular orifices 4-2 of said
compartments, located on the opposite side of the mattress,
secondary vent pipes t'.sub.4 are connected via "serrated" type
tubular endpieces and are in turn connected via T-couplings to a
common main vent pipe t.sub.4 connected to the vent solenoid valve
V.sub.4 of the vent manifold M.sub.2.
[0118] The solenoid valves V.sub.2 and V.sub.5 control respectively
feeding and venting the twelve compartments of the body zone via a
main feed pipe t.sub.2 and a main vent pipe t.sub.5 connected to
the feed and vent solenoid valves V.sub.2 and V.sub.5 respectively
of the manifold unit.
[0119] The feed orifices 4-1 of the twelve compartments of the body
zone are connected to the main feed pipe t.sub.2 via secondary feed
pipes t'.sub.2 connected by T-couplings to the pipe t.sub.2 and via
tubular endpieces (not shown) to tubular feed orifices 4-1.
[0120] Symmetrically, secondary vent pipes t'.sub.5 provide
connection between the tubular vent orifices 4-2 to which they are
connected via tubular endpieces (not shown) at one end, and at
their opposite ends to the main vent pipe t.sub.5 via respective
T-couplings.
[0121] Finally, the feed solenoid valve V.sub.3 and the vent
solenoid valve V.sub.6 serve respectively to control feeding and
venting the single compartment of the head zone via a main feed
pipe t.sub.3 and a main vent pipe t.sub.6 to which they are
respectively connected.
[0122] This pneumatic connection network between the manifolds and
the various compartments of the mattress shown in FIG. 1 operate in
a mode known as "continuous pressure" mode, since all of the
compartments in each zone are fed and/or vented in identical
manner, with the only modulation possible being between the various
zones using the three pairs of feed/vent solenoid valves.
[0123] FIG. 2 shows a mattress of the same type, but connected to
an air feed/vent system that can operate in an "alternating
pressure" mode in which every third compartment can be deflated,
with each successive compartment being successively deflated and
re-inflated.
[0124] This alternating pressure mode requires the control of the
various compartments within each zone to be subdivided into thirds,
where appropriate.
[0125] Thus, in FIG. 2, in order to operate in a one-in-three
alternating pressure mode, it can be seen that it is necessary to
implement the following solenoid valves and pipes: three feed
valves V.sub.1, V.sub.2, V.sub.3 acting via three main feed pipes
t.sub.1, t.sub.2, and t.sub.3 to feed the three feed orifices of
the three compartments of the foot zone. And symmetrically, three
main vent pipes t.sub.8, t.sub.9, and t.sub.10 providing
connections between the vent orifices of the compartments in the
foot zone and three vent valves V.sub.8, V.sub.9, and V.sub.10.
[0126] This installation thus makes it possible to deflate
successively each of the compartments in the foot zone, while the
other two compartments remain inflated.
[0127] Similarly, in order to deflate simultaneously every third
compartment in the body zone, i.e. four regularly spaced-apart
compartments out of the twelve in the body zone, all of the
successive compartments of the body zone being deflated
successively in turn from compartment to neighboring compartment,
it is necessary to make use of three feed valves V.sub.4, V.sub.5,
V.sub.6 acting via three main feed pipes t.sub.4, t.sub.5, and
t.sub.6 respectively to feed four compartments via four secondary
feed pipes all four of which are connected to a common main feed
pipe.
[0128] Thus, each of the main feed pipes t.sub.4, t.sub.4, and
t.sub.6 feeds four branch pipes t'.sub.4, t'.sub.5, and t'.sub.6
respectively.
[0129] Symmetrically, three branch secondary pipes t'.sub.11,
t'.sub.12, and t'.sub.13 are connected to three main vent pipes
t.sub.11, t.sub.12, and t.sub.13, respectively.
[0130] Finally, the feed solenoid valve V.sub.7 and the vent
solenoid valve V.sub.14 respectively control feeding and venting
the head zone, respectively via a main feed pipe t.sub.7 and main
vent pipe t.sub.14.
[0131] The various feed and vent pipes t.sub.1 to t.sub.14 and
t'.sub.2 to t'.sub.13 are sufficiently rigid to avoid kinking,
while being sufficiently flexible to be capable of following paths
that are relatively curved.
[0132] These various pipes have a standard outside diameter of
about 15 mm and an inside diameter of about 10 mm. The various
solenoid valves that need to feed a plurality of compartments and
thus to deliver relatively high fluid flow rates of up to as much
as 50 L/min, are dimensioned accordingly, and they present a total
weight for the manifold unit that may lie in the range 500 grams
(g) (FIG. 1) to more than 1000 g (FIG. 2).
[0133] However, and above all, the multiplicity of feed and vent
pipes represent a large amount of bulk, it being understood that
these pipes need to be inserted within a protective cover
surrounding the mattress.
[0134] FIGS. 3 and 4 are diagrams showing a system for
feeding/venting the various compartments of a mattress in
accordance with this disclosure.
[0135] In FIG. 3, a common air injection device 7 acts via a single
feed main tube 5 (referred to as a "bus") to feed sixteen two-port
feed solenoid valves 3-1 connected directly to each of the sixteen
feed orifices 4-1 of each of the sixteen compartments 2, being
disposed on the same longitudinal side of said mattress. On the
opposite longitudinal side of said mattress, there are disposed
sixteen vent orifices 4-2 which are connected directly to sixteen
two-port vent solenoid valves 3-2 venting air from said
compartments 2 into the atmosphere and not into a vent pipe, as in
the prior art of FIGS. 1 and 2.
[0136] In FIG. 3A, the feed and vent tubular orifices 4-1 and 4-2
together with the feed and vent valves 3-1 and 3-2 are disposed in
a direction that is perpendicular to the longitudinal direction XX'
of the mattress and of the feed pipe 5.
[0137] Nevertheless, in some embodiments, it may be possible to use
feed and vent tubular orifices together with branch pipe ends 6
that are bent through 90.degree. and offset longitudinally in the
direction XX' so as to make it possible to place the two-port
valves 3-1 and 3-2 in alignment in the longitudinal direction XX'
of the feed pipe and of the mattress, in order to further reduce
overall size, as described below for the three-port valves 3-3 of
FIG. 3B.
[0138] FIG. 4 shows a device in accordance with this disclosure
combined with a sensor 18 connected to the general control unit 8
and making it possible also via an electrical connection 19 to
control the pump or compressor 7.
[0139] FIGS. 3 and 4 also show diagrammatically some of the
electric wires 9 for electrically powering the solenoid valves 3-1
and 3-2, which wires are also shown in FIGS. 5 and 7A.
[0140] The feed and vent valves 3-1 and 3-2 present a structure of
the kind shown in FIG. 5.
[0141] The cylindrical main body 10 has an internal cavity 11
containing an induction coil 12 disposed axially relative to the
longitudinal axis X1X'1 of the valve. Inside the internal cavity 11
there is placed a cylindrical longitudinal magnetic core 13
suitable for moving inside the internal cavity 11 in the
longitudinal direction X1X'1 under drive from the coil 12 when it
is activated electrically.
[0142] In FIG. 4, each of the various valves 3-1, 3-2 is connected
via electrical power supply wires 9 to a centralized control unit 8
serving to activate the induction coils 12 electrically and to move
the cores 13, as explained below.
[0143] At each of the longitudinal ends of said cylindrical body
10, the valve 10 has respective first and second endpieces 13-1 and
13-2 of circular cross-section disposed axially and symmetrically
relative to each other.
[0144] These endpieces 13-1 and 13-2 define respective serrated
outside surfaces having serrations 14 of circular cross-section.
These serrations 14 define serrated endpieces suitable for
connecting said endpieces to feed tubular orifices 4-1 or to vent
tubular orifices 4-2, or where appropriate to secondary feed pipes
6.
[0145] Each first endpiece 13-1 has a first axial internal channel
14-1 opening out at one end into the internal cavity 11 and at its
other end into a compartment 2 when said first endpiece 13-1 is
brought into a feed tubular orifice 4-1 or into a vent tubular
orifice 4-2.
[0146] Similarly, each second endpiece 13-2 has a second axial
internal channel 14-2 communicating with the internal cavity 11 and
the free end of the second endpiece 13-2.
[0147] The second endpieces 13-2 are connected to the secondary
feed pipes 6 for the feed valves 3-1 and they open out to the
atmosphere for the vent solenoid valves 3-2.
[0148] The opening and closing operation of said two-port valves
3-1 and 3-2 can be implemented in two modes of operation.
[0149] In FIG. 5, in the absence of said core being electrically
activated by said coil, the core is held in a closed position by a
spring 15 acting on the core 13 so as to hold it against an O-ring
17 at the end of one of said two channels opening out into said
cavity. When the core is moved by electrically activating the coil,
the core is moved so as to compress the spring and disengage the
core from said end of said internal channel so that, possibly in
co-operation with an abutment 16, the core is held apart from the
ends of said channels 14-1 and 14-2 opening out into said cavity,
thereby enabling fluid to flow through said valve from the free
ends of each of the two endpieces 13-1, 13-2. Air can flow through
the cavity 1 around the core 13, possibly along grooves (not shown)
in the outside surface of the core and/or through an axial hole
passing right through the core in the longitudinal direction.
[0150] FIG. 3B shows a variant embodiment of a mattress according
to this disclosure in which some of its compartments are fitted
with respective single three-port solenoid valves.
[0151] Specifically, the compartments of the foot and head zones
Z.sub.1 and Z.sub.3 are inflated in continuous mode from a device 7
that delivers air at a pre-calibrated pressure.
[0152] Only the compartments in the body zone Z.sub.2 are fitted
with respective single three-port valves 3-3 connected directly to
an orifice 4-3 that acts both as a feed and as a vent, with the
outlet orifice 4-4 from each of said compartments being
plugged.
[0153] This FIG. 3B embodiment is particularly useful for providing
a massage mattress in the body zone Z.sub.2 by operating in an
alternating pressure mode of operation, as explained below.
[0154] In FIG. 3B, the three-port valves 3-3 are disposed
longitudinally along a common axis XX' of the mattress and of the
feed pipe 5.
[0155] The feed/vent tubular orifices 4-3 and the branch-pipe ends
6 are bent through 90.degree. and offset longitudinally in the
direction XX' so as to make it possible to place first and second
endpieces of the three-port valves 3-3 in alignment on said
longitudinal direction XX' of the feed pipe and of the mattress so
as to optimize compactness of the installation.
[0156] FIG. 6 shows a three-port solenoid valve with two
longitudinal internal channels, Specifically: [0157] a first
internal channel 14-1 inside a said first endpiece 13-1 fitted
directly to the open tubular orifices 4-3 of said compartments;
[0158] a second internal channel 14-2 within a second endpiece 13-2
forced into the corresponding end of a secondary feed pipe 6; and
[0159] a third internal channel 14-3 communicating between the
inside of the internal cavity and the outside of the valve, opening
out axially on the axis X1X'1 inside the cavity 11 and transversely
through the outside surface of the cylindrical body 10, said third
channel 14-3 thus presenting a bent or L-shape.
[0160] In a normal position, the spring 15 exerts a pressure on the
core 13 so that it moves longitudinally and closes the end of the
third channel 14-3, while leaving open the end of said first
channel 14-1 that opens out into said cavity parallel to the end of
said third channel 14-3. Thus, the fluid can be fed freely to the
compartments 2 by passing via the first and second internal
channels 14-1 and 14-2 and via the internal cavity 11.
[0161] Then, when the three-port solenoid valve 3-3 is activated
electrically, the spring 15 is compressed, the core 13 moving
longitudinally in a reverse direction and closing said second feed
channel 14-2, while the other end of the core is separated from the
ends of the first and second internal channels 14-1, 14-3.
[0162] Thus, the air contained in said compartment can be vented by
passing through the first internal channel 14-1, then the internal
cavity 11, and then be vented to the atmosphere via the third
internal channel 14-3, thereby deflating the compartment.
[0163] In order to illustrate the originality of the in-line
solenoid valves according to this disclosure, FIG. 8 is a view
showing a conventional solenoid valve 3-4 in which the movement of
the core 13a under drive from a coil 12a (not shown) and from a
spring 15a takes place perpendicularly to the direction X1X'1 along
which the fluid flows through said valve between its two
endpieces.
[0164] Because the valves 3-1 to 3-3 of disclosed herein are
incorporated in the tubular orifices 4-1 to 4-3 of the compartments
2, and not offset to a centralized location remote from the tubular
orifices, as in the prior art, each valve serves to control only
one compartment, and head losses between the valve and the
compartment are considerably reduced compared with the prior
art.
[0165] It is recalled that the "gauge" pressures of the flowing air
are about 10 mbar to 100 mbar (above atmospheric pressure), so the
length of the pneumatic connection tubes in the prior art can give
rise to significant head losses.
[0166] This positioning of the valves at the orifices of the
compartments makes it possible to use valves of small dimensions in
which it suffices, in practice, to deliver air at a rate of 1 L/min
to 5 L/min, thereby requiring the use of pressures of 10 mbar to
100 mbar, with the channels 14-1 and 14-2 having inside diameters
lying in the range 5 mm to 8 mm, and more particularly being about
7 mm.
[0167] These compact in-line valves present a fluid flow section
equivalent to that of a duct having a diameter of 2 mm to 3 mm.
[0168] The valves present a total length lying in the range 50 mm
to 70 mm, and more particularly a length of 60 mm for an outside
diameter of the main body lying in the range 15 mm to 20 mm, more
precisely being about 17 mm. Said first and second endpieces
present a maximum diameter of about 11 mm.
[0169] By way of illustration, a valve of the kind described above
presents a weight lying in the range 15 g to 20 g, such that even
when using a larger number of valves (thirty-two valves in FIG. 3
compared with fourteen valves in FIG. 2), the total weight of the
air feed/vent system of some embodiments, such as shown in FIG. 3,
remains much smaller than that of the prior art air feed/vent
system of FIGS. 1 and 2.
[0170] FIGS. 5 to 7 show said first and second endpieces 13-1 and
13-2 having the same outside diameter of about 11 mm to enable them
to be forced into the ends of the pipes 6 and into the tubular
orifices 4-1 of present standard compartments having an inside
diameter of about 10.5 mm so that they become deformed and the
connection is secure. It is desirable to maintain an inside
diameter for the main feed pipe 5 having a value of about 10 mm so
as to enable all of the valves to be fed at the above-specified
flow rate.
[0171] In contrast, it would be possible to provide smaller inside
diameters for the branch secondary pipe 6 and thus for the
T-couplings serving to couple the secondary pipe 6 to the main feed
pipe 5, and also to provide corresponding smaller outside diameters
for the second endpieces 13-2, but for practical reasons it is
preferred to continue using pipes having the common standard
diameter.
[0172] In practice, in some embodiments, the valves replace the
tubular elements connecting between the tubular orifices of the
compartments and the feed or secondary vent pipes.
[0173] The ease with which a feed/vent system according to this
disclosure can be implemented stems from the fact that the control
unit at the foot of the bed 8 is much less bulky, insofar as there
is no longer any need for a manifold unit centralizing the various
valves. In some embodiments, the networks of air feed and vent
pipes between the valves and the various compartments are
eliminated and replaced by a single main feed pipe 5, the network
of feed and vent pipes being replaced by a network of electric
wires 9 serving to deliver electrical power to the various solenoid
valves.
[0174] However this network of electric wires having a diameter
lying in the range 1 mm to 2 mm is much simpler to position around
the mattress and to incorporate, where appropriate, within a
protective cover than is the network of pneumatic feed/vent
pipes.
[0175] One advantage of the feed/vent system of some embodiments is
that it makes a greater degree of modularity possible since each
compartment can be controlled individually and independently of any
of the others.
[0176] Since it is possible to feed/vent air to or from each
compartment individually, it is possible to obtain a configuration
for the mattress that is more exact as a function of the morphology
of the patient.
[0177] Furthermore, the devices according to this disclosure make
it possible to select alternating modes of deflating one
compartment in two or one compartment in three as a function of the
programming of the electronic control unit 8 placed at the foot of
the bed and to which the various solenoid valves are connected.
[0178] Furthermore, since the valves are distributed over the
surface of the mattress, that makes the mattress easier to handle
by nursing staff.
[0179] It is thus easy to add or remove valves to of from the
various compartments and to vary the functions that can be
performed by the mattress on request, whereas such an option is
impossible with the pneumatic networks implemented in the prior
art, for which any changed to the functions of the mattress
requires a complete change to the network of air-distributing
pipes, thus making variations to said functions impractical.
[0180] Finally, the various valves are activated using very low
levels of electric power that do not involve any heating, so they
can operate in contact with the compartments even in the confined
surroundings within the protective cover, providing they are made
of materials that are stainless in a moist atmosphere.
* * * * *