WO2005011555A1

WO2005011555A1 - Inflatable support apparatus

Info

Publication number: WO2005011555A1
Application number: PCT/GB2004/003238
Authority: WO
Inventors: David Lee Sandbach; John Burkitt; Stuart Mark Walkington
Original assignee: Eleksen Limited
Priority date: 2003-07-28
Filing date: 2004-07-28
Publication date: 2005-02-10

Abstract

Inflatable support apparatus for supporting an occupant comprising a plurality of inflatable chambers and sensing means arranged to detect a critical occupant immersion condition. The sensing means comprises a sensor and a yielding force transmitting component. The sensor comprises a first conductive plane, a second conductive plane and separator means between the first and second conductive planes penetrable by at least one of said first and second conductive planes to allow said conductive planes to make contact during a mechanical interaction. The force transmitting component is operatively coupled with the sensor to provide the sensor with modified mechanical interaction triggering. Inflatable support apparatus for supporting an occupant comprising a plurality of inflatable chambers and sensing means, the sensing means comprising a textile sensor.

Description

Inflatable Support Apparatus

Background of the Invention

1. Field of the Invention The present invention relates to inflatable support apparatus, in

particular to inflatable support apparatus comprising a plurality of inflatable

chambers and sensing means arranged to detect a critical occupant

immersion condition.

2. Description of the Related Art

An inflatable support apparatus is designed to uniformly distribute the

weight of an occupant across the contact area between the occupant and the

apparatus. The inflatable support apparatus comprises a plurality of inflatable

chambers, whereby the support surface is provided by upper surfaces of inflated chambers, over which a protective cover may be provided. Such inflatable support apparatus can be found in the form of mattresses and cushions, used to prevent discomfort or injury to an occupant. For example, an inflatable mattress or cushion may be used to prevent the development of skin breakdown or pressure ulcers, to prevent an occupant from resting on a potentially injurious object or to modify the resting position of an occupant. In use, there is an optimum degree of immersion of an occupant into the inflatable support apparatus at which maximum benefit is conferred to 11555

the occupant. Other degrees of immersion within a range of satisfactory degrees of immersion confer less benefit to the occupant. Degrees of immersion outside the range of satisfactory degrees of immersion are potentially detrimental to the occupant, giving rise to a requirement for remedial action. To determine whether an initial degree of occupant immersion is satisfactory, the inflatable support apparatus is fully inflated prior to the user adopting a rest position on the support surface of the apparatus. Once the occupant is positioned, a third party places a guide, for example one finger on top of another, between inflatable chambers. The apparatus is then deflated until the occupant contacts the top of the guide at which instance deflation is stopped and the occupant considered to be immersed in the apparatus to a satisfactory degree. Unfortunately, the occupant may experience distress from such intimate presence of another person during this process. Furthermore, following the setting up process, regular monitoring of the degree of immersion is required. This is also performed using an upstanding guide between the base of the cushion and the occupant, potentially subjecting the occupant to repeated disturbance.

Brief Summary of the Invention According to a first aspect of the invention there is provided inflatable support apparatus for supporting an occupant comprising: a plurality of inflatable chambers, and sensing means arranged to detect a critical occupant immersion condition, said sensing means comprising a sensor and a yielding force transmitting component; said sensor comprising a first conductive plane, a second conductive plane and separator means between said first and second conductive planes penetrable by at least one of said first and second conductive planes to allow said conductive planes to make contact during a mechanical interaction, said force transmitting component operatively coupled with said sensor to provide said sensor with modified mechanical interaction triggering. According to a second aspect of the invention there is provided inflatable support apparatus for supporting an occupant comprising: a plurality of inflatable chambers, and sensing means arranged to detect a critical occupant immersion condition, said sensing means comprising a textile sensor; said textile sensor comprising a first conductive textile layer, a second conductive textile layer, and insulating separator means between said first and second conductive textile layers, penetrable by at least one of said first and second conductive textile layers, to allow said conductive textile layers to make contact during a mechanical interaction. According to a third aspect of the invention there is provided inflatable support apparatus comprising a sensor located within an inflatable chamber. According to a fourth aspect of the invention there is provided an inflatable support apparatus comprising a sensor located externally 11555

between first and second inflatable chambers. According to a fifth aspect of the invention there is provided inflatable support apparatus comprising sensing means configured to raise an alert in response to detecting a critical occupant immersion condition. According to a sixth aspect of the invention there is provided inflatable support apparatus comprising sensing means configured to initiate inflation/deflation of an inflatable chamber in response to detecting a critical occupant immersion condition.

Brief Description of the Several Views of the Drawings Figure 1 shows a typical sitting position; Figures 2A, 2B and 2C each show an occupant sitting on an inflatable cushion; Figures 3A and 3B each show a section view through an inflatable chamber of an inflatable support apparatus including sensing means; Figures 4A and 4B each show a section view through an inflatable chamber of an inflatable support apparatus utilising sensing means comprising a sensor having modified mechanical interaction triggering; Figures 5A and 5B show an inflatable mattress and an internal view of an inflatable chamber of the mattress; Figure 6 shows a conductive strip lattice sensor; Figure 7 shows a conductive strip lattice sensor in use in combination with an inflatable support apparatus having extensible inflatable chambers; Figure 8 shows a force transmitting component in use in combination with the arrangement shown in Figure 7; Figures 9A, 9B and 9C illustrate a sensor and force transmitting component arrangement in use in combination with an inflatable support apparatus having extensible inflatable chambers; Figure 10 shows differently shaped force transmitting components; Figure 11 shows a combined sensor and force transmitting component; Figure 12 shows a sensor and force transmitting component arrangement in use in combination with an inflatable support apparatus having inextensible inflatable chambers; Figure 13 shows a second sensor in use in combination with the arrangement shown in Figure 12. Figure 14 is a schematic of an inflatable support apparatus comprising a plurality of inflatable chambers interconnected into independent groups; Figure 15 shows an occupant adopting a rest position upon inflatable support apparatus comprising sensing means arranged to detect a critical occupant immersion condition.

Written Description of the Best Mode for Carrying Out the Invention

Figure 1

Figure 1 shows a person 101 sitting on a seat 102. Person 101 experiences pressure increases within the body due to the stiffness and hardness of the sitting surface 103 of the seat 102. Whilst adopting the

shown posture, most of the body mass of person 101 is supported by the

ischial tuberosities ("seat bones" under the pelvic bone), located in region 104, thus the greatest pressure experienced is localised in this area.

Person 101 experiences compression of soft tissue in regions where increased pressure is experienced. Soft tissue compression is a significant contributing factor in the development of skin breakdown, and this is exacerbated by the adoption of the same posture over a long period. Hence, if person 101 continues to sit in the shown position for a prolonged period,

although all areas of the body of person 101 supported directly on sitting

surface 103 are vulnerable to the development of skin breakdown, the area

under the ischial tuberosities of person 101, indicated by arrow 105, is identified as being particularly at risk of skin breakdown.

Figures 2A, 2B and 2C Figures 2A, 2B and 2C each show a schematic of person 101 using an inflatable support apparatus, in the form of an inflatable cushion 201, with seat 102. Inflatable cushion 201 comprises a plurality of inflatable chambers, such as inflatable chamber 202, in a matrix arrangement. Inflatable cushion

201 comprises a base element 203 over which is positioned a flexible chamber wall element 204. Chamber wall element 204 provides a matrix of 11555

chamber pockets extending from a substantially planar member of the element, with each chamber pocket opening at the substantially planar member and extending substantially perpendicular to the substantially planar member. Flexible chamber wall element 204 and base element 203 are both fabricated from air impermeable material and are hermetically sealed together around the edges only. This arrangement provides an air impermeable matrix of interconnected inflatable chambers that each comprise a chamber pocket provided by chamber wall element 204 and a

base portion provided by base element 203. The inflatable cushion 201 is provided with a single inflation/deflation tube (not shown) by means of which the inflatable cushion 201 can be inflated and/or deflated. When the cushion 201 is inflated, each inflatable chamber extends substantially perpendicularly to the base element 203. Thus, when the

cushion 201 is inflated and the base element 203 is placed on a substantially horizontal support surface, the inflatable chambers extend substantially upwardly.

The inflatable chambers of cushion 201 are configured to provide an occupant support surface. In use, the occupant support surface supports the areas of the body that would otherwise be supported directly by the surface upon which the inflatable cushion 201 is placed. Inflatable cushion 201 is suitable for use with a wheelchair. In use, an occupant adopts a rest position upon the cushion 201. In adopting the rest 11555

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position, the weight of the occupant is transferred onto the inflatable chambers. The inflatable chambers of cushion 201 are interconnected in an arrangement that allows gas molecules to flow from one chamber to another. This allows variable distribution of air molecules throughout the cushion 201.

With a fixed quantity of gas molecules contained within the cushion 201, the distribution of the molecules throughout the cushion varies according to the posture adopted by the occupant. Where there is no loss of air from the cushion 201, one or more chambers will inflate as another chamber deflates. With this arrangement, the occupant support surface of inflatable cushion

201 simulates a fluid surface, although not continuous, acting to distribute the weight of the occupant as uniformly as achievable over the contact area. The shape of the occupant support surface is dependent upon the extent of inflation of the cushion, and the weight and shape of the occupant. Inflatable cushion 201 is intended to be used whilst inflated to an extent that corresponds to a satisfactory degree of immersion of an occupant within the cushion. At a satisfactory degree of immersion, the distribution of the weight of the occupant across the occupant support surface produces a distribution of pressure that provides a beneficial reduction in the pressures and peak pressure experienced by an occupant. Maximum benefit of the cushion 201 is conferred when the occupant is immersed at an optimum degree of occupant immersion, which provides 11555

the maximum occupant support surface area over which the weight of the occupant is distributed to produce the optimum reduction in the pressures and peak pressure experienced by the occupant. The occupant should be immersed deeply enough to be provided with a large support surface area but no so deeply that there is a risk that weight is not being supported by air within the inflatable support apparatus. The condition in which weight is not being supported by air within the inflatable support apparatus is referred to as "bottoming-out". The optimum degree of immersion is thus found within a range of satisfactory degrees of immersion. The further the degree of occupant immersion moves outside of the range of satisfactory degrees of immersion, the more the corresponding occupant support surface simulates the surface upon which the inflatable cushion 201 is placed.

Figures 2A to 2C shows person 101 sitting on cushion 201 at increasing degrees of occupant immersion. Figure 2A shows person 101 immersed in inflatable cushion 201 at an insufficient degree of occupant immersion. As shown, the cushion 201 is nearly fully inflated, thus person 101 is sitting on near fully inflated inflatable chambers. The inflatable chambers provide an occupant support surface that supports person 101 in an area under the ischial tuberosities only. In Figure 2A, the minimum floatation gap between the base element 203 of the cushion and person 101, which is indicated by arrow 205, is approaching the general height of the cushion 201 when fully inflated. 11555

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In this Figure 2A scenario, the inflatable cushion 201 confers

negligible benefit to person 101. In practice, remedial action is required to

deflate the cushion 201 until a satisfactory degree of occupant immersion for

person 101 is achieved. Figure 2B shows person 101 immersed in inflatable cushion 201 at a

satisfactory degree of occupant immersion. Cushion 201 is less inflated than

in Figure 2A, allowing person 101 to sit deeper into the cushion 201, as

shown. The contours of the occupant support surface complement the body contours of person 101. The inflatable chambers provide an occupant support surface that supports all areas of the body that would otherwise be in contact with the sitting surface 103 of the seat 102. The depth of immersion

of person 101 in cushion 201 is such that upstanding chambers surrounding

person 101 confer side support, for example to inhibit person 101 from moving sideways or falling out of the cushion 201. In Figure 2B, the minimum floatation gap between the base element

203 of the cushion and person 101, which is indicated by arrow 206, is

approximately two thirds of the general height of the inflated cushion 201 when fully inflated. In Figure 2B, person 101 is supported by an occupant support surface having a greater area than that in Figure 2A. The distribution of the weight of person 101 over a greater occupant support surface area produces a more uniform distribution of lower pressures over the contact area between the occupant and the support surface, which reduces occurrences of potentially injurious localised increased pressure regions. In this Figure 2B scenario, the inflatable cushion 201 confers

significant benefit to person 101. Figure 2C shows person 101 immersed in inflatable cushion 201 at a

detrimental degree of occupant immersion. At least one of the inflatable chambers is in the collapsed condition; the extent of deflation of the chamber is such that any support provided by the chamber is provided by compressed structural components of the chamber rather than by the combination of the physical structure of the chamber and the action of gas molecules within the chamber. In this "bottoming-out" condition, the inflatable support apparatus is referred to as having "bottomed-out". In this example, the cushion 201 is nearly fully deflated, thus person

101 is sitting on near fully deflated inflatable chambers. In Figure 2C, the minimum floatation gap between the base element

203 of the cushion and person 101, which is indicated by arrow 207, is approximately the general thickness of the cushion 201 when fully deflated. In effect, the area under the ischial tuberosities of person 101 is now being

supported by the sitting surface 103 of the seat 102. Thus, in this Figure 2C scenario, the inflatable cushion 201 does not confer any benefit to person

101. In practice, remedial action is required to inflate the cushion 201 until a satisfactory degree of occupant immersion for person 101 is achieved. An inflatable support apparatus confers useful benefit to an occupant 11555

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only if the extent of inflation of the cushion corresponds to a satisfactory degree of occupant immersion. The extent of inflation required to achieve the optimum degree of occupant immersion for a particular inflatable support apparatus will vary according to the size and shape of the occupant. Thus, there is an initial procedure to be performed when a new occupant uses an inflatable support apparatus for the first time, to determine that a satisfactory degree of occupant immersion is achieved. Thereafter, a monitoring procedure is to be performed regularly, to determine that a satisfactory degree of occupant immersion is maintained. For example, air may leak from the inflatable support apparatus due to a puncture of an inflation/deflation valve being left open, and the degree of immersion may develop from satisfactory to detrimental. This change may go unnoticed by the occupant, for example because the occupant is unconscious or has suffered permanent nerve damage. It is to be appreciated that there may be little visual difference between a satisfactory degree of immersion and a detrimental degree of immersion.

Figures 3A and 3B Figures 3A and 3B each show a section view through an inflatable chamber, having a similar structure to inflatable chamber 202 of inflatable support apparatus 201, of an inflatable support apparatus including sensing means. The sensing means comprises a sensor comprising a first conductive plane, a second conductive plane and separator means between the first and second conductive planes penetrable by at least one of the conductive planes to allow the conductive planes to make contact during a mechanical interaction. In each of Figures 3A and 3B, the sensor is housed in the shown

inflatable chamber. Figure 3A shows a section through an inflatable chamber 301

comprising a non-conductive rubber base element 302 and a non- conductive rubber chamber wall element 303. The chamber 301 houses a

textile switch 304. Textile switch 304 comprises a first conductive textile

layer 305, a second conductive textile layer 306 and a separating

component 307, fabricated from insulating material, disposed between the

two conductive layers. The construction and operation of textile switch 304 is substantially as described in European patent application no. 01 200 781 Λ currently assigned to the same assignee as the present application, the contents of which are incorporated herein by reference. Textile sensor 304 is located upon the internal surface of base element 302 and is positioned such that an aperture, such as aperture 308, in insulating separating component 307 lies approximately centrally under the closed end of the chamber pocket of chamber wall element 303. In the event that the chamber 301 deflates into the collapsed condition under a component of force acting in the downward direction, indicated by arrow 309, the first conductive textile layer 305 is brought into contact with the second conductive textile layer 306, through aperture 308, at which 011555

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instance the sensor 304 is triggered. Thus, the sensor 304 is arranged to

trigger in the event that the chamber 301 deflates into the collapsed condition beneath an occupant. Figure 3B shows a section through an inflatable chamber 310

comprising a conductive base element 311 and a conductive chamber wall

element 312. The chamber 310 houses an insulating separator sheet 313

defining a matrix of apertures therein. The separator sheet 313 is disposed

between the base element 311 and the chamber wall element 312, and is

positioned such that an aperture, such as aperture 314 lies approximately centrally under the closed end of the chamber pocket of chamber wall element 312. In the event that collapse of the chamber 310 occurs under a component of force acting in the direction indicated by arrow 315, the

conductive rubber chamber wall element 312 will be brought into contact with the conductive rubber base element 311, at which instance the sensor 310 is triggered. According to the arrangement shown in Figure 3B, elements of the sensor utilised to detect collapse of chamber 310 are provided by elements of the chamber 310. Both the base element 311 and the chamber wall element 312 may incorporate conductive elements therein or have conductive elements applied to the internal surface thereof. For example, the elements may be fabricated from conductive rubber or neoprene, or may have a carbon based conductive coating applied thereto or have a conductive textile laminated thereto. Triggering of a sensor may be affected if the sensor or inflatable support apparatus is supported by an uneven surface. Thus, Figure 3B

shows a base element 316 providing an even support surface for the

inflatable chamber 310.

Figures 4A and 4B The sensors in the arrangements shown in Figure 3A and 3B each utilise mechanical interaction triggering. Figure 4A shows an inflatable chamber 401, having a similar

structure to inflatable chamber 301 , of an inflatable support apparatus having sensing means comprising a sensor provided with modified mechanical interaction triggering. Sensor 402 is housed within the chamber

401 and comprises a first conductive layer 403, a second conductive layer 404 and a separating layer 405 penetrable by at least the first conductive layer 403, to allow the conductive layers to make contact during a mechanical interaction. In this example, inflatable chamber 401 is provided with air flow constriction elements, such as air flow constriction element 406. The air flow constriction elements are configured to restrict air flow from an inflatable chamber when an occupant moves rapidly and to allow air to flow from the inflatable chamber when an occupant moves slowly. This feature functions to maintain the occupant in a particular supported posture. A cushion having this feature is available under the trade name Enhancer (RTM) Cushion, available from The ROHO Group, United States. Two constriction elements for inflatable chamber 401 are located

within the chamber 401 and are fabricated from non-conductive material. The air flow constriction elements have been utilised to provide the separator layer 405 of sensor 401. In the shown arrangement, the air flow constriction elements are spaced apart to provide an aperture to allow contact between the conductive layers 403, 404.

The sensing means further comprises a yielding force transmitting component 407. The force transmitting component 407 is operatively

coupled with the sensor 401 to provide the sensor 401 with modified mechanical interaction triggering. In this example, the force transmitting component 407 is located upon the outer surface of the first (upper)

conductive layer 403. The force transmitting component 407 extends

substantially perpendicularly to the first (upper) conductive layer 403, upwardly into the chamber pocket of inflatable chamber 401. The functionality provided by the force transmitting component is illustrated in Figure 4B.

As the chamber 401 begins to deflate under the weight of an occupant, indicated by arrow 408, the yielding force transmitting component 407 is compressed, however, the structural integrity of the force transmitting component 407 is such that it also transmits force to the first conductive layer 403.

As deflation of the chamber 401 continues beyond the limit of the preferred range of degrees of inflation, the force transmitting component 407 forces the first conductive layer 403 into contact with the second

conductive layer 404. Thus, the sensor 402 is triggered as the chamber 401

is deflating towards the collapsed condition. Thus, the modified mechanical interaction triggering provides for detection of an impending requirement for remedial action to be performed. According to the arrangements shown in Figure 3A and Figure 3B, a sensor having mechanical interaction triggering is used with an inflatable support apparatus to detect when a negligible floatation gap between the base of the apparatus and the occupant occurs. According to the arrangement shown in Figures 4A and 4B, a sensor having modified mechanical interaction triggering is used with an inflatable support apparatus to detect an imminent negligible floatation gap between the base of the apparatus and the occupant occurs. Thus, a force transmitting component can be used with a sensor to adjust the magnitude of the floatation gap at which triggering of a sensor will occur. In this way, a sensor and force transmitting component arrangement provides for detection of a critical occupant immersion condition. The term "critical occupant immersion condition" is used to refer to a condition relating to the degree of immersion of an occupant within an inflatable support apparatus that the detection of is of interest to the occupant and/or a third party. The term "critical occupant immersion condition" is intended to include at least the following conditions: the

collapsed condition of a chamber, a condition approaching the collapsed condition of a chamber, a condition indicating a change between

insufficient, satisfactory and detrimental degrees of occupant immersion. Inflatable chamber 401 is part of an inflatable support apparatus for

reducing localised increased pressure areas experienced by an occupant.

Therefore, the force transmitting component is required to yield, to feel soft

and compressible rather than hard, under an occupant, in particular to

avoid causing a localised high pressure area or direct injury to an occupant.

In addition, the force transmitting component is required to be soft enough

so as not to damage the inflatable support apparatus, in particular to avoid causing the inflatable support apparatus to leak. Thus, the soft force

transmitting component is to be arranged in a way that minimises the risk of the component causing any condition that the inflatable support apparatus is being used to prevent. However, the force transmitting component is

utilised to transmit force and is therefore required to provide a relatively firm element on compression. Such a force transmitting component may be fabricated from medium density foam.

Figures 5A and 5B

Figure 5A shows an inflatable support apparatus, in the form of a

mattress 501 comprising a plurality of substantially cylindrical inflatable

chambers, for example chamber 502. Each chamber is an air proof closed environment provided with a unique inflation/deflation tube, for example tube 503 leading into chamber 502. Thus, the construction of mattress 501 allows a chamber to be inflated and deflated independently of the other chambers. Thus, the extent of inflation of each chamber can be set according to which part of an occupant the chamber is providing support.

For example, the midrift and shoulder regions may require more supporting pressure than lighter regions of the body such as the heels or calves. However, such a mattress allows the following mode of operation. Each inflatable chamber can be connected to one of three inflation tubes 504, 505, 506 leading to an air pump 507, to form three groups of

interconnected chambers. According to a time lapse cycle (typically changing every few minutes), each group of chambers is either inflated, deflated or neither inflated or deflated. For example, during one step in such a cycle, the chambers connected to air tube 504 are slowly inflated, the chambers connected to air tube 505 are slowly deflated and the

chambers connected to air tube 506 are left at the same extent of inflation. This mode of operation functions to temporarily relieve the occupant of pressure experienced in different regions along the body, and may be used for example to assist healing of burns. Thus it can be appreciated that the bottoming-out condition is undesirable during cycling. A view inside inflatable chamber 502 is shown in Figure 5B. Located inside chamber 502 is a sensing arrangement 508 comprising a sensor 509 and a force transmitting component 510. Sensor 509 and force transmitting component 510 are both elongate in form and extend along the length of

chamber 502, one on top of the other. The sensing means of inflatable mattress 501 is configured to detect a mechanical interaction and also to provide an indication of the position of a mechanical interaction. The construction and operation of sensor 508 is substantially as described in European application no. 01 200 781.1 , providing X and Y data (relating to the position of a mechanical interaction) and further providing Z data (relating to the extent of a mechanical interaction). The Z data can be used to detect a critical occupant immersion condition and the X and/or Y data used to detect where that condition was detected. In addition, the Z data can be used in pressure profiling and to detect peak pressure. Thus, with the arrangement of independent inflatable chambers of mattress 501, the Z data can be used to identify in which chamber a critical occupant immersion condition is detected and the X and/or Y data used to detect at what point along the chamber this condition was detected. This is useful in applications where a critical occupant immersion condition may relate to an occupant's position or manner of movement. The arrangement can be used to detect the centre of gravity of an occupant and can be used in profiling the pressure across the apparatus. Both of these may be used in posture correction or movement monitoring. For example a detected lack of movement over a period of time may indicate a requirement for the occupant to be turned or repositioned by a third party; for example a nurse, to reduce the risk of the occupant developing a pressure ulcer. A function of an inflatable support apparatus having sensing means is to detect a change in pressure experienced by the occupant, in particular a sudden localised increase in pressure. This condition may occur for example when an occupant is moving from a reclined position to a sitting position. However, in practice, it is found that most transient occurrences of a detrimental occupant immersion condition pose no risk to the occupant. Thus, the data processing means arranged to process data derived from a sensor used with an inflatable support apparatus can be adjusted to ignore momentary triggering of the sensor.

Figure 6 An inflatable support apparatus may be provided with externally located sensing means arranged to detect a critical occupant immersion condition. Thus, an inflatable support apparatus may be provided with retrofit sensing means. The external surface of a member from which inflatable chambers of an inflatable support apparatus extend, for example the external surface of substantially planar member of chamber wall element 204 of cushion 201, may be provided with a sensor. The sensor may provide a single active sensing region or a plurality of active and inactive sensing regions. Figure 6 shows a conductive strip lattice sensor 601 , providing a plurality of active sensing regions, for example active sensing region 602. Conductive strip lattice sensor 601 comprises a plurality of

conductive strips, such as strip 603, laid in a spaced apart substantially parallel arrangement in the X axis direction, and a plurality of conductive strips, such as strip 604, laid in a substantially spaced apart parallel arrangement in the Y axis direction. Separator means are disposed between intersecting strips to provide a sensor having a similar construction to sensor 508 at intersecting regions, for example intersection region 605. In this way active sensing regions are provided at intersections of substantially perpendicular conductive strips. Multiplexing may then be performed as described in European patent application no. 01 200 781 J to detect triggering of an active sensing region or rows and columns may each be connected together to form upper and lower elements of a simple switch. Conductive strip lattice sensor 601 defines aperture regions, such as

region 606, bound by conductive strips, to accommodate an inflatable chamber, for example inflatable chamber 202 of inflatable cushion 201.

Figure 7 A condition giving rise to a problem experienced using an external sensing layer with a type of inflatable support having a plurality of inflatable chambers is illustrated in Figure 7. Inflatable support apparatus 701 is similar in structure to inflatable cushion 201 , having a plurality of interconnected inflatable chambers. External sensing layer 702 comprises a conductive strip lattice sensor, such

as conductive strip lattice sensor 601. Sensing layer 702 is shown fitted around the inflatable chambers of

inflatable support apparatus 701; an active sensing region 703 is now

located between a first inflatable chamber 704 and a neighbouring second

inflatable chamber 705.

The chamber wall element 706 of inflatable support apparatus 701 is fabricated from an extensible material, such as rubber. Under a component of force acting downwards on the inflatable chambers, indicated by arrow

707, each inflatable chamber balloons outwards until contact is made with one or more neighbouring inflatable chambers. Figure 7 shows how

neighbouring inflatable chambers 704, 705 have ballooned out and made contact above active sensing region 703, to the effect that the contacting inflatable chambers 704, 705 now provide support to the other. Under this condition, the ballooned chambers 704, 705 physically mask the active sensing region 703. In response to an increase in the downward component of force indicated by arrow 707 the area of contact between contacting chambers 704, 705 increases, further masking the active sensing region 703. However, triggering of the sensing region may occur following further deflation of the chambers or increased pressure experienced in the sensing region. Thus, in practice, ballooning of inflatable chambers into contact with another can effectively temporarily diminish the capability of an active sensing region to contribute to the detection of a critical occupant immersion condition.

Figure 8 Figure 8 shows the arrangement shown in Figure 7 with the addition of tubular yielding force transmitting components, such as force transmitting component 801. Each tubular force transmitting component is operatively coupled with an active sensing region, for example force transmitting component 801 is laid upon active sensing region 703. The tubular yielding force transmitting components may be fabricated from silicone tube. The tubular yielding force transmitting components function to provide active sensing regions of the sensing layer 702 with modified mechanical interaction triggering. According to this example, the tubular yielding force transmitting components are arranged in substantially parallel lines between rows of inflatable chambers. As neighbouring inflatable chambers 704, 705 balloon towards each other, they balloon around force transmitting component 801. Due to the tubular shape of the force transmitting component 801, the load on the force transmitting component 801 applied by an inflatable chamber is distributed uniformly to the extent that triggering of sensing region 703 is prevented. However, under a point downward component of force applied to the ballooned inflatable chambers 704, 705 indicated by arrow 802, the uniform load distribution experienced by the force transmitting component 801 is overcome and the force transmitting component 801 yields to trigger

the active sensing region 703. Thus, the tubular force transmitting components are configured to distribute any load applied by the inflatable chambers to prevent triggering and to transmit occupant load applied to trigger the sensing means of the inflatable support apparatus. It is found that in seat cushion applications, tubular force transmitting components having a diameter in the range 3-10mm provide satisfactory functionality.

Figures 9A, 9B and 9C Figure 9A shows a section through an inflatable support apparatus

901, similar in structure to inflatable support apparatus 701 , and an external sensing layer 902. External sensing layer 902 comprises a sensor 903, in this example having active and inactive regions, and a force transmitting component 904 operatively coupled with the sensor 903. The sensor 903 and force transmitting component 904 both take an elongate form and are positioned to extend between inflatable chambers. Force transmitting component 904 is profiled along its length to provide block portions, such as block portion 905, and bridging portions, such as bridging portion 906. The block portions are shaped substantially like a cube and the bridging portions are shaped substantially as an arch extending between block portions. Figure 9B is an overhead view of a portion of inflatable support apparatus 901 , illustrating the location of force transmitting component 904 and the location of bridging and block portions relative to inflatable chambers. The strip force transmitting component 904 is located between two parallel rows of regularly spaced apart inflatable chambers, with the chambers in alignment. Moving along the force transmitting component

904, bridging portions are located over regions where two inflatable

chambers appear at either side of the force transmitting component 904

and block portions are located at regions in between. Figure 9C is an overhead view of a portion of inflatable support apparatus 901 showing inflatable chambers 907, 908, 909 and 910.

Bridging portion 906 is located substantially centrally between inflatable chambers 907 and 909. In use, all four inflatable chambers 907, 908, 909, 910 may balloon to make contact to the effect that the chambers are supporting each other in a substantially square formation, as shown in Figure 9C, over block portion 905. It is to be appreciated that the bridging portions yield more readily than the block portions under the same component of downward force. The bridging portions are located where the pressure experienced by the force transmitting component 904 is greater and the block portions where the pressure experienced by the force transmitting component 904 is lower.

Thus, the force transmitting component 904 supports ballooned inflatable chambers away from active regions of the sensor 903 but facilitates

triggering of the sensor 903 in response to a downward component of force applied to the expandable inflatable chambers.

Figure 10 Occupants of different weights and shapes may use an inflatable support apparatus. Since sensors having mechanical interaction triggering have an associated range of pressures that will cause mechanical interaction triggering, a sensor used with an inflatable support apparatus may respond differently with different occupants. Different shapes of force transmitting component may be utilised to modify the mechanical interaction triggering of the sensor. For example, a different shape of force transmitting component may be selected to adjust the exhibited sensitivity of a sensor. Figure 10 shows different force transmitting components, each having a substantially uniform cross sectional shape The cross sectional shape of force transmitting component 1001 is substantially shaped like a semicircle adjoined to a rectangle, the semicircle extending from the centre along a length edge of the rectangle. The component 1001 is configured to be used with the semicircle pointing towards a sensor; the semicircle acts as a force concentrating nodule. In use, the force concentrating nodule provides a local increased pressure adjacent an active region of a sensor. The cross sectional shape of force transmitting component 1002 is

substantially shaped like a "V" shape having a uniform thickness. The component 1002 is configured to be used with the point of the "V" shape pointing away from a sensor, to provide a local decreased pressure adjacent an active region of a sensor. The cross sectional shape of force transmitting component 1003 is substantially shaped like a "U" shape having a semicircle shape within the "U" pointing outwardly, with the ends of the "U" shape joined with the ends of the semicircle. The component 1003 is configured to be used with the semicircle pointing towards a sensor; the semicircle acts as a force concentrating nodule.

Figure 11

Figure 11 shows a combined sensor and force transmitting component 1101 , for use in an external sensing layer application. The component 1101 has a collapsible dome outer structure 1102. Inside the dome is a base layer of high density foam 1103 and a sensor 1104 supported by the base layer 1102. The base layer 1102 functions to provide an even support surface for the sensor 1103. The overhead internal curved section is filled with low density foam 1105. In use, the arch formation of the combined sensor and force transmitting component 1101 is configured to distribute load applied by an inflatable chamber into a uniform load pattern to prevent triggering and is configured to collapse under a downward load to trigger the sensor 1104.

Sensor 1103 may be a membrane sensor, such as a flexi-circuit switch. A membrane sensor having a suitable construction is described in United Kingdom Patent No. 2 365 132 B.

Figure 12 Figure 12 shows two inflatable chambers 1201, 1202 fabricated from inextensible material, such as polyurethane or polyurethane coated textile, between which is located an external sensor arrangement 1203. Inflatable chamber 1201 is shown inflated. Under an occupant load,

the inflatable chamber 1201 is unable to balloon outwardly, but instead the side walls crumple as the chamber collapses downwards. In addition, the chamber is able fall to one side, as indicated by arrow 1204.

Inflatable chamber 1202 is shown only partially inflated. In this condition, under an occupant load, the side walls of the chamber 1202 adopt a concertinaed profile. Thus, inextensible inflatable chambers display a different mode of collapse than extensible inflatable chambers. It is to be appreciated that the location of a sensor arrangement may vary according to the construction and arrangement of inflatable chambers to ensure effective operation. Sensor arrangement 1203 comprises a base support member 1205 that provides an even support surface for a sensor 1206 placed thereon and a force transmitting component 1207 placed on the sensor. By varying the height of the base support member 1205 and/or the force transmitting

component 1207, the mechanical interaction triggering of the sensor can be modified, for example to trigger whilst a chamber is deflating towards the collapsed condition rather than when the collapsed condition occurs.

Figure 13 Figure 13 shows the arrangement shown in Figure 12, with the

addition of a second sensor arrangement 1301 , positioned in the vicinity of

sensor arrangement 1203, between inflatable chambers 1201 and 1202. It

can be seen that the height of the second sensor arrangement 1301 is

greater than that of sensor arrangement 1203. The sensor of the two sensor arrangements 1203, 1301 thus trigger under different occupant immersion conditions. With this arrangement, if fully inflated chambers begin to deflate under an occupant load, the sensor of the second sensor arrangement 1301 will be triggered before that of sensor arrangement

1203. The two sensor arrangements 1203, 1301 may be used in operation where only one or both of the sensors of both arrangements 1203, 1301 are active at a particular moment. Thus, the sensor arrangements 1203, 1301 may be used to provide a dual sensing function or two alternative sensing function. Alternatively, a dual sensing function may be provided by operatively coupling a first force transmitting component and a second force transmitting component to a common sensor. The dual sensing function can be used in an initial procedure to determine that a satisfactory degree of occupant immersion is achieved when a cushion is first used. For example, the sensor arrangements 1203, 1301 may be arranged such that triggering of the second sensor arrangement 1301 indicates that the degree of occupant immersion has entered into a range of satisfactory degrees of occupant immersion, and triggering of the other sensor arrangement 1203 indicates that the degree of occupant immersion has developed into a detrimental degree of occupant immersion. Thus, the sensor arrangements 1203, 1301 can be used to ensure that an occupant is immersed in an inflatable apparatus at a satisfactory degree of occupant immersion, without the requirement for a guide to be used by a third party beneath the occupant. A dual sensing functionality may also be used in a monitoring procedure, to determine that a satisfactory degree of occupant immersion is maintained. For example, one sensor may be arranged to trigger under a critical occupant immersion condition corresponding to an occupant being in a reclined position, and the other sensor may be arranged to trigger under a critical occupant immersion condition corresponding to the occupant being in a sitting position. The two sensor arrangements 1203, 1301 may each be arranged to trigger to detect different critical occupant immersion conditions. For example, one sensor may be arranged to detect an unsatisfactory occupant immersion condition corresponding to an average child using the inflatable support apparatus, and the other sensor may be arranged to detect an

unsatisfactory occupant immersion condition corresponding to an average

male adult using the inflatable support apparatus.

Figure 14

Figure 14 shows a schematic of an inflatable support apparatus

comprising a plurality of inflatable chambers interconnected into independent

groups.

Inflatable support apparatus 1401 comprises four groups of inflatable

chambers 1402, 1403, 1404, 1405, arranged as quadrants of the inflatable

support apparatus. Each group of chambers 1402, 1403, 1404, 1405, is

provided with a chamber inflation/deflation tube 1406, 1407, 1408 and 1409

respectively. In the shown arrangement, each chamber inflation/deflation

tube 1406, 1407, 1408, 1409 is connected to one port of a multiport valve

1410 from which a single apparatus inflation/deflation tube 1411 extends.

The valve 1410 provides a switch between a first condition in which the

groups of chambers 1402, 1403, 1404, 1405 are interconnected to allow

variable distribution of air between the groups of chambers, and a second condition in which the groups of chambers 1402, 1403, 1404, 1405 are isolated from each other to prevent air flowing from one group of chambers to another.

Such an inflatable support apparatus may be used to ensure or correct an asymmetrical occupant posture. During an initial occupant immersion procedure, the valve 1410 is in

the first condition and all of the groups of chambers 1402, 1403, 1404, 1405 are initially in the inflated condition. The occupant to be immersed in the inflatable support apparatus 1401 is then located upon the groups of

chambers 1402, 1403, 1404, 1405 and the desired posture in which the

occupant is to be supported is adopted. With the valve 1410 still switched to the first condition, the groups of chambers are slowly deflated, until the degree of immersion is determined to be satisfactory, at which instance the valve 1410 is switched to the second condition and deflation ceased. Thus, air can flow freely between the groups of chambers during the initial occupant immersion procedure and then once this procedure is complete, the air in each group of chambers is prevented from flowing from the chamber. An inflatable support apparatus having this arrangement is available under the trade name Low Profile Quadtro Select Cushion (TM) from The ROHO Group, United States. Alternatively, during an initial occupant immersion procedure using inflatable support apparatus 1401 , each group of chambers 1402, 1403, 1404, 1405 may be inflated/deflated independently of the others. Inflatable support apparatus 1401 may be fitted with sensing means. The sensing means enables an alternative method of determining a satisfactory degree of immersion of an occupant. According to the method, the sensing means is arranged to a detrimental occupant immersion condition. Initially, the inflatable support apparatus is fully inflated prior to the user adopting a rest position on the support surface of the apparatus. Once the occupant is positioned, the inflatable chambers are allowed to deflate until the sensor is triggered. Thereafter, a predetermined volume of air is pumped into the apparatus to render the degree of immersion into a satisfactory degree of immersion. Alternatively, the inflatable support apparatus may be deflated prior to the user adopting a rest position and the sensor used to prompt a predetermined degree of inflation. The sensing means can be used to determine whether a satisfactory occupant immersion condition is achieved in each quadrant of the apparatus 1401. The sensing means may have mechanical interaction triggering that is modified differently for each quadrant. Internal or external sensing means may be provided. An active sensing region common to a plurality of inflatable chambers may be provided and/or one or more sensing regions unique to each group of chambers 1402, 1403, 1404, 1405. A sensor having a continuous sensing region may be provided. Apertures may be defined in such a continuous area sensor to accommodate inflatable chambers.

Figure 15 As described, an inflatable support apparatus may be provided with sensing means arranged to detect a critical occupant immersion condition. The detection of such a critical condition can be used to prompt remedial action. In an alert mode, for example, on detection of a critical condition, an alert may be raised to prompt the occupant and/or a third party to perform a remedial act in response. Such an alert may be an audio and/or visual alert. In a remedial action mode, for example, on detection of a critical condition, a signal may be sent to a controller unit to initiate inflation or deflation of one or more inflatable chambers. An inflatable chamber may be inflated by means of an air pump or gas canister. Figure 15 shows a convalescing person 1501 on a hospital bed

1502. The hospital bed 1502 is provided with an inflatable support apparatus having a plurality of inflatable chambers interconnected into independent groups. Each group corresponds to a region of the support surface of the bed 1502, for example region 1503. The inflatable support apparatus comprises sensing means arranged to detect a critical occupant immersion condition. The sensing means is configured to send signals to a monitor 1504. In response to detecting a critical occupant immersion condition, the sensing means sends an alert signal to the monitor 1504 to the effect that a visual audio alarm is executed. In addition, the sensing means is configured to send signals to an air pump 1505. In response to detecting a critical occupant immersion condition, the sensing means sends a react signal to the air pump 1505 to the effect that an inflation or deflation operation is executed. For example, in one mode of operation, in the event that the sensing means detects collapse of an inflatable chamber within the group of chambers corresponding to region 1503, an visual audio alert is raised to draw the attention of a hospital carer. In addition, inflation of the group of chambers is automatically initiated and continued until the sensing means no longer detects the critical occupant immersion condition. The utilisation of sensing means as described in combination with an inflatable support apparatus enables a correct degree of occupant immersion to be determined in a way that is not intrusive to the occupant. The sensing means can be effectively utilised in the detection of deflating inflatable chambers, and thus is usable in the prevention of skin breakdown. Portable inflatable support apparatus are known. It is to be appreciated that the flexible sensors described do not add significant additional weight to an inflatable support apparatus, and hence do not diminish the transportability of the apparatus. Furthermore, inflatable support apparatus configured to be folded or rolled are known. Use of flexible sensors as described in combination with such apparatus does not affect this feature and hence does not diminish the storability of the apparatus.

Claims

1. Inflatable support apparatus for supporting an occupant

comprising: a plurality of inflatable chambers, and sensing means arranged to detect a critical occupant immersion condition, said sensing means comprising a sensor and a yielding force transmitting component; said sensor comprising a first conductive plane, a second conductive plane and separator means between said first and second conductive planes penetrable by at least one of said first and second conductive planes to allow said conductive planes to make contact during a mechanical interaction, said force transmitting component operatively coupled with said sensor to provide said sensor with modified mechanical interaction triggering.

2. Inflatable support apparatus as claimed in claim 1 comprising a sensor located within an inflatable chamber.

3. Inflatable support apparatus as claimed in claim 1 comprising a sensor located externally between first and second inflatable chambers.

4. Inflatable support apparatus as claimed in any preceding claim comprising inflatable chambers interconnected to allow variable distribution of gas molecules between the interconnected chambers.

5. Inflatable support apparatus as claimed in claim 4 comprising inflatable chambers interconnected to provide a first group and a second group and said first group is arranged to be inflated/deflated independently of said second group.

6. Inflatable support apparatus as claimed in claim 1 wherein said force transmitting component comprises a force concentrating nodule.

7. Inflatable support apparatus as claimed in claim 1 wherein said force transmitting component is profiled to provide a bridging portion and a block portion.

8. Inflatable support apparatus as claimed in claim 1 wherein said force transmitting component is fabricated from silicone tube or foam.

9. Inflatable support apparatus as claimed in claim 1 wherein said force transmitting component has an upper surface and a lower surface and the area of said upper surface is greater than the area of said lower surface.

10. Inflatable support apparatus as claimed in any preceding claim comprising a first force transmitting component operatively coupled with said sensor to provide first modified mechanical interaction triggering and further comprising a second force transmitting component operatively coupled with said sensor to provide second different modified mechanical interaction triggering.

11. Inflatable support apparatus as claimed in any preceding claim comprising extensible inflatable chambers.

12. Inflatable support apparatus as claimed in any preceding claim wherein said inflatable support apparatus is a mattress or a cushion.

13. Inflatable support apparatus as claimed in any preceding claim wherein said sensor provides an active sensing region and said sensing means is arranged to identify the position of a mechanical interaction within said active sensing region.

14. Inflatable support apparatus as claimed in any preceding claim wherein said sensing means is arranged to identify the extent of a mechanical interaction.

15. Inflatable support apparatus as claimed in any preceding claim wherein said sensor provides a plurality of active and inactive sensing regions.

16. Inflatable support apparatus as claimed in any preceding claim wherein said sensing means is configured to raise an alert in response to detecting a critical occupant immersion condition.

17. Inflatable support apparatus as claimed in any preceding claim wherein said sensing means is configured to initiate inflation/deflation of an inflatable chamber in response to detecting a critical occupant immersion condition.

18. Inflatable support apparatus as claimed in any preceding claim wherein said sensor is a flexible membrane sensor or a textile sensor.

19. Inflatable support apparatus for supporting an occupant comprising: a plurality of inflatable chambers, and sensing means arranged to detect a critical occupant immersion condition, said sensing means comprising a textile sensor; 011555

41 said textile sensor comprising a first conductive textile layer, a second conductive textile layer, and insulating separator means between said first and second conductive textile layers, penetrable by at least one of said first and second conductive textile layers, to allow said conductive textile layers to make contact during a mechanical interaction.

20. Inflatable support apparatus according to claim 1 wherein said textile sensor is located within an inflatable chamber.

21. Inflatable support apparatus for supporting an occupant comprising a plurality of inflatable chambers, and sensing means arranged to detect a critical occupant immersion condition substantially as described herein with reference to and as shown in the accompanying drawings.

22. A method of determining a satisfactory degree of immersion of an occupant in an inflatable support apparatus comprising a plurality of inflatable chambers and sensing means arranged to detect a critical occupant immersion condition, substantially as described herein with reference to the accompanying drawings.