The present invention relates to improvements in fluidized patient supporting systems of the type described in US. Pat. No. 5,008,965.

Patients subject to extensive recuperative periods, must remain in bed for extended periods of time. When such patients lie supinely on a conventional mattress, most of the load is born by protuberances of the posterior surface of the body such as the heels, the buttocks, the scapulae, and the occipital region of the head. The relatively small areas of soft tissue at these points are then subjected to high pressures by being compressed between the skeleton and the supporting surface. When this pressure becomes great enough to cause collapse of small capillaries and veins, pressure sores or decubitus ulcers may result. Burn patients also have problems with rubbing against the surface of an immobile conventional mattress surface that can result in the extraction of a skin graft. In order to overcome these problems, hospital beds have been developed which use fluidized granular material (preferably spherical beads) as a supporting medium in order to uniformly distribute the supporting pressure points along the body surface, thus reducing the pressure at the aforementioned critical areas.

Fluidized bead beds comprise a tank partially filled with a mass of some granular material, the granular material resting on top of a diffuser. A flexible, loose fitting sheet, which is permeable to air but not the granular material, is laid on top of the granular material to form the patient support surface. As gas commonly air, is blown through the diffuser into the granular material fluidizing the material so that a patient laying on top of the covering sheet is buoyantly suspended upon the bed. In this way, the forces imparted to the body are evenly distributed over the body and the chance of decubitus ulcers occurring is greatly lowered. Burn patients lie more comfortably, and the fluidized support medium moves with the body that reduces the likelihood of skin graft extraction. Also, this structure allows body fluids exuded from wounds to flow through the covering and into the granular material away from the patient, quickening the healing process. When the granular material is not being fluidized, the material settles down into a solid structure and contours to the body.

US 4,694,521 discloses a mat having an upper layer of porous elastic material with fine particles mixed therein and a lower layer of porous elastic material. Air is blown through the mat and is discharged through an air permeable sheet covering the upper surface of the upper layer.

Although fluidized bead beds are quite satisfactory in accomplishing the objectives enumerated above, they are not without some disadvantages. Conventional fluidized beds are quite heavy, commonly weighing in excess of 900 Kg (2000 lbs). Also, prior art fluidized beds had rigid diffusers, which were at least uncomfortable, if not dangerous, for the patient using the bed to bottom out on.

Therefore, it is an object of the present invention to provide a fluidized bead bed with a soft surface diffuser.

It is a further object to provide a fluidized bead bed with an inflatable bead diffuser intermediate the bed tub and the fluidizable beads.

It is a yet further object to provide a fluidized bead bed with an inflatable bead diffuser intermediate the bed tub and the fluidizable beads that causes the air used to fluidize these beads to be exhausted through the patient support surface.

It is another of the present invention to provide a fluidized bead bed massing substantially less than 900 Kg. It is a still further object to provide a fluidized bead bed with an inflatable bead diffuser intermediate the bed tub and the fluidizable beds which functions as a soft surface diffuser.

According to a first aspect of the invention, we provide a fluidized bead bed comprising an open tank, an inflatable bead diffuser placed within said tank, said diffuser comprising a non-rigid layer, fluidizable beads placed above said diffuser within said tank, a porous cover sheet secured to said tank so that said beads are intermediate said diffuser and said sheet within said tank and said sheet comprises a patient support surface, and air supply means operatively inflating a plenum within said tank defined beneath said diffuser that allows air to escape therefrom to fluidize said beads, characterized in that the diffuser comprises a plurality of inflatable chambers.

Said bed may comprise monitoring apparatus for monitoring at least one function of the bed.

Said monitoring apparatus may comprise a microprocessor- based system.

Said monitoring apparatus may comprise a temperature probe within said tank.

Said monitoring apparatus may also comprise a transducer to determine how far a patient may be depressed into said bead diffuser.

Said cover sheet may comprise PTFE.

Said beads may be contained in a bead pouch.

The fluidization air may be exhausted through said patient support surface.

Said beads may comprise a soda-lime core encased within a silicon sphere and range from about 50 to about 150 microns in diameter.

Each of said chambers may be adjacent at least one other of said chambers.

Each of the chambers may comprise at least one sidewall which may comprise a baffle.

Said diffuser may be concave in cross sectional shape.

Said air supply means may comprise a variable speed air blower.

Said inflatable air chambers may be inflated to a plurality of pressures.

According to the present invention, a fluidized bead bed is provided an inflatable diffuser intermediate the fluidizable beads and the tank structure. This inflatable diffuser serves to provide a soft surface underneath the beds to prevent a patient who bottoms out through the beads from coming into contact with the bed tub. Further, by raising the level of the beads, the use of an inflatable diffuser acts to reduce the quantity of beads required to be fluidized in order to provide the desired fluidized therapeutic effects commonly provided by a fluidized bed. This allows the air used to fluidize the beads to be exhausted through the patient support surface. Finally, this also results in a significant reduction of the weight of the bed system.

The bed comprises a tube or open tank structure, to side rails may be attached, support means, control means, air supply means, an inflatable diffuser, and contained fluidizable beads comprising a patient support surface. The diffuser is place din the bottom of the tub. Fluidizable beads are placed on top of the diffuser, preferably in a bead pouch. An air permeable cover sheet, fabricated from a material such as high air loss PTFE, is secured to the rim of the tub.

Air is supplied to the inflatable diffuser. This causes the beads to rise within the tank. Air then escapes from the diffuser, in a sufficient quantity to fluidize the beads. The exhaust air from fluidizing the beads then passes through the cover sheet. The exhaust air causes water, or other liquid waste exuded by the patient resting upon the cover sheet to evaporate.

Many other objects will be evident to those of ordinary skill in the art in view of the foregoing and following descriptions, particularly when considered in light of the prior art and in conjunction with the accompanying drawings. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

• FIG. 1 is a perspective view of the fluidized bead bed.
• FIG. 2 is a top view of the tank with the sheets, fluidization material, and inflatable bead diffuser removed.
• FIG. 3 is a sagittal sectional view of the fluidized bead bed of FIG. 1.
• FIG. 4 is a bottom view of the bead diffuser of the fluidized bead bed of FIG. 1.
• FIG. 5 is a cross sectional view of the bead diffuser of the fluidized bead bed of FIG. 1.
• FIG. 6 is a cross sectional view of the air nozzle of the bead diffuser of FIGs. 4 and 5.
• FIG. 7 is a cross sectional view of the air nozzle of FIG. 6 inserted into the fluidization port located on the bottom of the tank.
• FIG. 8 is an exploded view of the air blower assembly of the fluidized bead bed.
• FIG. 9 is a perspective view of the foot pedestal and framed box for housing the air blower assembly.
• FIG. 10 is a cross sectional view of the three piece perimeter bumper for securing the sheets to the tank rim.
• FIG. 11 shows a perspective sectional view of the three piece perimeter bumper and sheets attached to the tank rim.
• FIG. 12 shows a control panel for operating the fluidized bead bed of FIG. 1.
• FIG. 13 shows an alternative embodiment of an inflatable bead diffuser of the fluidized bead bed of FIG. 1.
• FIG. 14 shows an alternative embodiment of an inflatable bead diffuser and bead pouch of the fluidized bead bed of FIG. 1.

As required, preferred embodiments of the present invention are described herein; however, the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms. The figures are not necessarily to scale; some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but as a basis , for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.

FIG. 1 shows a perspective view of a preferred embodiment of the present invention, hereinafter referred to as a fluidized bead bed 100. The fluidized bead bed 100 comprises an open tank structure 101 which is mounted on top of a head pedestal 102 and foot pedestal 103. As shown, the head pedestal 102 and foot pedestal 103 are positioned on top of a platform support surface 104. Side rails 107a-b can be fastened to the side of the tank 101 to provide patient safety. Where side rails 107a-b are used, an adjustable latch assembly 108 is provided to raise or lower the side rails 107a-b when patient or user access is required. A control panel 109 enables the user to control the operation of the bed in a manner described more fully below. It is preferable to provide a hand control 110 (not shown) to enable either the care giver or the patient to control the fluidization of the bead bed 100. As is further disclosed herein, a flow of pressurized air to fluidize a quantity of fluidizable material contained within the tank 101 is provided by an air blower assembly 701 which is preferably housed within the foot pedestal 103 (FIG. 3). A preferred patient support surface is formed by placing a top cover sheet 106 in overlying relation to a top 313 filter sheet (FIG. 3), and attaching the cover sheet 106 to the tank rim 105. A preferred top cover sheet 106 is made of a high air-loss GORE-TEX material which enables the fluidization air to be exhausted through the patient support surface. This preferred embodiment supplies a therapeutically beneficial flow of air against the patient's body which aids in the evaporation and removal of any moisture on the patient's skin.

FIG. 2 is a top view of the bottom surface 203 of the tank 101. The bottom of the tank 101 is constructed with four holes 201a-d which provide ports for establishing an air conduit between the bead diffuser 301 and the air blower assembly 701. Though FIG. 2 illustrates the use of four holes 201a-d in a staggered position on the bottom of the tank 101, it should be evident to someone skilled in the art that different arrangements and numbers of connecting ports may be used without departing from the scope of the i invention. In another preferred embodiment, as shown in FIGs. 2 and 3, a fifth hole 202 is used to provide a communication port between a temperature probe 305 located within the tank 101, and a microprocessor-based system adapted to correspondingly increase or decrease the temperature of the pressurized air flowing through the beads 303. In this way, the temperature of the beads 303 is continuously monitored by the probe 305 which operably signals the heating and cooling system to adjust the air temperature as is necessary to maintain patient comfort. While a temperature probe 305 can be positioned within the air conduit or the air blower assembly, it is preferable to position the temperature probe within the tank 101 to provide a temperature reading which more accurately reflects the temperature of the patient support surface.

Referring to FIGS. 3, 4, and 5 a preferred embodiment of the present invention comprises an inflatable bead diffuser 301 which rest against the bottom surface 203 of the tank 101. In this embodiment, the inflated bead diffuser 301 provides an upper diffuser surface 310 which is elevated relative to the generally horizontal bottom surface 203 of the tank 101. As shown in FIG. 3, a fluidized patient support surface is formed by a quantity of fluidization material 303 supported on top of the normally inflated bead diffuser 301. In this embodiment, the bead diffuser 301 when in an inflated condition increases the height of the fluidized patient support surface relative to the bottom surface 203 of the tank 101. As compared to the prior art, an inflatable bead diffuser 301 therefore provides the means for significantly reducing the quantity of fluidization material 303 required to form a fluidized patient support surface.

In its preferred embodiment, the bead diffuser 301 is initially placed into the tank 101 in a deflated condition, and an air blower assembly 701 provides the necessary flow of air to inflate the bead diffuser 301 and fluidize a quantity of material 303 supported thereon. As illustrated in FIG. 7, the inflatable bead diffuser 301 is assembled with four air nozzles 501a-d specially designed to insert into four fluidization ports 302a-d which are set into four holes 201a-d constructed on the bottom of the tank 101. An air conduit is provided between the bead diffuser 301 and the air blower assembly 701 using flexible air hoses 308a-d attached at a first end to the air blower assembly 701 and a second end to the fluidization ports 302a-d. In this preferred embodiment, a flow of inflation and fluidization air generated by the air blower 701 flows through the air hoses 308a-d to the attached fluidization ports 302a-d and into the bead diffuser 301 through the air nozzles 501a-d releasably inserted into the fluidization ports 302a-d.

As shown in FIG. 6, a preferred air nozzle 501 is integrally attached to the bottom surface 311 of the bead diffuser 301. In a preferred assembly, an air nozzle 501 is coupled to the bottom surface 311 of the bead diffuser 301 by first inserting the air nozzle 501 through the air holes cut into two disk shaped swathes of fabric material 602a-b. The fabric disk 602a-b are preferably constructed of a "REGENCY" fabric, which is a high strength laminated nylon taffeta fabric manufactured in China and distributed in U.S.A. by John C. Tucker Co., Inc. Another fabric disk 604 having a center air hole is then placed on the top surface of the circular head 608 of the air nozzle 501. The top fabric disk 604 is also preferably constructed of REGENCY. Using conventional sewing techniques, the fabric disks 602a-b and 604 are sewn together to securely fasten the circular head 608 of the air nozzle 501 within a three layer fabric disk 605. The air nozzle 501 is then inserted through a hole cut into the bottom surface 311 of the bead diffuser 301. When so positioned, the air nozzle 501 projects out of the bead diffuser 301, and the circular head 608 contained within the three-layer fabric disk 605 rest against the bottom surface 311 of the bead diffuser 301. Once the air nozzle 501 is inserted through the hole in the bottom surface 311, the fabric disk 605 is sewn to the surface 311. A no air-loss disk patch 603 is placed over the top surface of the three-layer fabric disc 605 to eliminate air leaks. The circular patch 603 preferably includes an adhesive surface 607 which adheres the patch 603 to the top surface of the fabric disk 605, and to the bottom surface 311 of the bead diffuser 301. As illustrated in FIG. 6, the perimeter 606 of the circular patch 603 is greater than the perimeter of the fabric disk 605 so that when the patch 603 is adhered to the bottom surface 311 of the bead diffuser 301, the fabric disk 605 is securely fastened between the patch 603 and the bottom surface 311 of the bead diffuser 301. In this manner, the circular patch 603 forms an air-tight seal which prevents any air-loss between the circular head 608 of the air nozzle 501 and the bottom surface 311 of the bead diffuser 301. As illustrated in FIGs. 6 and 7, a relatively gas-tight fit between the air nozzle 501 and the corresponding fluidization port 302 is provided by an "O" ring seal 601 which occupies a groove fabricated into the neck of the air nozzle 501.

In a preferred embodiment, illustrated in FIG. 3, the fluidization material 303 is contained within a bead pouch 307 that is supported on top of the inflatable bead diffuser 301. The bead, pouch 307 is preferably an integral component of the inflatable bead diffuser 301, however, the bead pouch 307 can be separately assembled without departing from the scope of the present invention. The fluidization material preferably consists of medical grade silicone spherical beads 303 of the type commonly employed in air fluidized bead support systems. Such beads 303 generally comprise a soda-lime core encased within a silicone sphere, and range in size from 50 to 150 microns in diameter. As can be appreciated from FIG. 3, the diffuser surface 310 of the inflatable bead diffuser 301 is integral to the bottom bead support surface 309 of the bead pouch 307. The side walls of the bead pouch 307 are formed by attaching one edge of a fabric skirt 304 to the outer perimeter 314 of the top diffuser surface 310 of the bead diffuser 301, and attaching the second edge of the fabric skirt 304 to the tank rim 105. In this manner, the fabric skirt 304 frames the outer perimeter 314 of the top diffuser surface 310 of the bead diffuser 301, and forms the side walls of the pouch 307 for containing the fluidization material therein. The top surface of the bead pouch 307 is formed by placing a bottom filter sheet 306 over the top of the beads 303 contained within the side walls of the fabric skirt 304, and attaching the peripheral edges of the filter sheet 306 to the tank rim 105. A second top filter sheet 313 is then placed over the bottom filter sheet 306, draped over the tank rim 105, and attached along the outer tank wall. In this preferred embodiment, the pressurized air flowing through the inflatable bead diffuser 301 vents through the bottom surface 309 of the bead pouch 307 and fluidizes the quantity of beads 303 contained within the pouch 307. Though the preferred embodiment discloses the use of a single bead pouch 307 to contain the beads 303 therein, it should be evident to those skilled in the art that alternative bead pouch 307 arrangements may be constructed without departing from the scope of the invention. For example, a plurality of adjacently attached bead pouches can be transversely positioned across the top of the bead diffuser 301 to provide a suitable fluidized patient support surface.

In a preferred embodiment, a bead diffuser 301 is constructed of an inflatable material that is distendable upon receiving pressurized air from a pressurized air source. Thus, as can be appreciated from FIG. 3, the flow of pressurized air into the bead diffuser 301 forms a plenum space 315 between the bottom surface 203 of the tank 101, and the quantity of beads 303 supported on top of the bead diffuser 301. As shown, inflation of the plenum space 315 elevates the diffuser surface 310 relative to the bottom surface 203 of the tank 101. As will be evident to those skilled in the art, this embodiment of the presently disclosed fluidized bead bed 100 provides several significant advantages over the prior art. First, elevating the diffuser surface 310 is desirable because it significantly reduces the quantity of beads 303 necessary to form a fluidized patient support surface. This reduction in the quantity of beads 303 substantially decreases the weight of the fluidized bead bed 100 over that of prior fluidization patient support systems. For example, conventional fluidized patient support systems may weigh in excess of 2,000 pounds; however, the presently preferred fluidized bead bed 100 weighs less than 1,000 pounds. Second, the inflatable bead diffuser 301 functions as an air mattress to prevent the undesirable effects associated with what is known in the art as "patient bottoming out." By way of illustration, an occupant of a fluidized support system, for various reasons, may sink through the fluidized beads 303 to the tank bottom 203. This "bottoming out" effect may result in a patient being lacerated by system components located on the bottom of the tank, such as rivets, bolts, and/or systems probes. In the presently disclosed invention, were a patient to sink through the beads 303, the patient would merely come to rest on top of an inflated bead diffuser 301 and not the tank bottom 203. The presently disclosed inflatable bead diffuser 301 therefore provides cushioned support to patients who experience "bottoming out".

FIGS. 4 and 5, illustrate a bottom and cross sectional view of a preferred bead diffuser 301, respectively. Referring to FIG. 4, the outer perimeter of the bead diffuser 301 is specially designed to be substantially similar to the inner perimeter of the tank 101 (FIG. 2). In this manner, the side surfaces 312a-b of a normally inflated bead diffuser 301 fit tightly against the inner wall of the tank 101. This sealed fit prevents any portion of the bead pouch 307 and beads 303 contained therein from sliding down between the inner walls of the tank 101 and the bead diffuser 301. As shown, the bead diffuser 301 forms an inflatable enclosure having a substantially rectangular body with a circular head end 403 and a squared foot end 404. The air nozzles 501a-d are integrally coupled to the bottom surface 311 of the bead diffuser 301 so as to properly align with the air holes 201a-d located on the bottom of the tank 101 (FIG. 2).

As illustrated in FIG. 4, another opening 401 is provided for inserting into the bead diffuser 301 one or more transducers and/or probes for monitoring various bed functions. More particularly, such monitoring apparatus can include a temperature probe 305, a pressure transducer and/or a distance sensing transducer operable to determine how far a patient is depressed into the bead diffuser 301.

FIG. 5 shows a cross sectional view of a preferred bead diffuser 301 in a substantially inflated form. In its preferred embodiment, an inflatable bead diffuser 301 comprises nine inflatable air chambers 502a-i adjacently positioned to at least one other air chamber. Referring to FIG., 4, each inflatable air chamber 502a-i extends longitudinally the entire length of the bead diffuser 301. At least a portion of the upper surface of each inflatable air chamber 502a-i is comprised of a fabric material specially adapted to facilitate the flow of pressurized air out of the inflated bead diffuser 301 at a rate sufficient to fluidize a quantity of fluidization material resting against the upper surface of the bead diffuser 301. In this preferred embodiment, the upper surface of the bead diffuser 301 is therefore operable as a diffuser surface 310. The top diffuser surface 310 of each inflatable air chamber 502a-i is preferably constructed from a high-airloss nylon mesh weave fabric such as that commercially available from W.L. Gore & Associates under the trademark "GORE-TEX." Alternatively, the diffuser surface 310 can be assembled using low-airloss fabric material in which the fabric includes a multiplicity of air apertures that channel the flow of fluidization air out of the bead diffuser 301. Such a diffuser surface 310 can be fabricated by using a standard industrial sewing machine, without spooled thread, to needle the apertures into the low-airloss GORE-TEX fabric material. It should be understood by those skilled in the art, however, that alternative diffuser surfaces and means for fabricating such diffuser surfaces can be used without departing from the scope of the invention.

In a preferred assembly, the bottom surface 311 and side surfaces 312a-b of the bead diffuser 301 are made of a low or no air-loss fabric material. In this manner, the pressurized air within the bead diffuser 301 does not flow out through the bottom surface 311 and side surfaces 312a-b, but is forced upwardly through the diffuser surface 310. A suitable, no air-loss fabric material for assembling the bottom surface 311 and side surfaces 312a-b is a polyurethane-backed nylon fabric material commercially available under the trademark "K-KOTE." Alternatively, a low air-loss GORE-TEX fabric material can be used to construct the side surfaces 312a-b. It should be understood by those skilled in the art, however, that various other no air-loss or low air-loss materials may be used to construct the bottom surface 311 and side surfaces 312a-b of the inflatable bead diffuser 301 without departing from the scope of the invention. In another preferred embodiment, the fabric skirt 304 is assembled using either no air-loss K-KOTE or low air-loss GORE-TEX to prevent fluidization air from escaping between the fabric skirt 304 and the inner wall of the tank 101.

Referring to FIGS. 4 and 5, each inflatable air chamber 502a-i has at least one side wall formed by an air baffle 402a-h, respectively. In this embodiment, the air baffles 402a-h serve primarily to prevent bowing of the inflatable air chambers 502a-i, and to support the upwardly flow of fluidization air through the diffuser surface 310. Each air baffle is preferably made of a low air-loss GORE-TEX fabric material having an upper edge that is attached to at least a portion of the diffuser surface 310, and a lower edge attached to at least a portion of the bottom surface 311 of the bead diffuser 301. In a preferred assembly, each air baffle 402a-h is sewn to the respective surfaces, 310 and 311, using conventional sewing techniques. As disclosed above, it is desirable that the bottom surface 311 and side surfaces 312a-b be substantially air-tight to prevent a reduction in the flow of fluidization pressure through the diffuser surface 311. Therefore, where baffles 402a-h are attached to either the bottom surface 311 and/or side surface 312a-b, it is a preferred that the air baffle be assembled using welding or heat-sealing techniques which form an air-tight seal at the respective site of attachment. It should be understood by those skilled in the art that alternative methods of forming a relatively air-tight seal between the air baffle and the attachment surface can be used without departing from the scope of the invention.

As shown in FIG. 4, the head end 406 and leg end 407 of each air baffle 402a-h is not attached to the head end 403 or leg end 404 of the bead diffuser 301. This preferred assembly provides air passages 405 at the ends of each air baffle 402a-h which allows the fluidization air to flow into each chamber 502a-i. In this way, pressurized air flowing through the air nozzles 501a-d and into the bead diffuser 301 is able to equalize throughout the bead diffuser 301 by flowing through the air passages 405. Air passages (not shown) can also be provided for by placing air openings at various locations along the length of each air baffle 402a-h.

As illustrated in FIG. 5, a preferred bead diffuser 301 is specially designed such that a cross sectional profile of the bead diffuser 301 discloses a concave shaped diffuser surface 310. More specifically, the inflatable chambers 502a-i of the bead diffuser 301 form a trough which extends lengthwise along the upper diffuser surface 310. As shown, the two outer inflatable chambers (502a and 502i) are specially designed to form an upper diffuser surface 310 which is elevated relative to the diffuser surface 310 defined by the three inner inflatable chambers (502d-f). The four inflatable chambers (502b-c and 502g-h) intermediately positioned between the two outer inflatable chambers (502a and 502i) and three inner inflatable chambers (502d-f) form an upper diffuser surface which slopes downwards from the diffuser surface defined by the outer chambers (502a and 502i) to the diffuser surface defined by the inner chambers (502d-f). A preferred assembly for forming a concave shaped bead diffuser 301 includes fabricating air baffles 402a-h with differing heights, whereby the air baffles forming the side walls of the outer inflatable chambers are of a greater height relative to the air baffles forming the side walls of the inner most inflatable chambers. In this way, the greater the height of the baffle relative to the bottom surface 311 of the bead diffuser 301, the greater the height of the diffuser surface 310 relative to the bottom surface 311 of the bead diffuser 301. A concave shaped diffuser surface 310 is highly advantageous in that the quantity of fluidization material required to form a fluidized patient support surface is further reduced as compared to a substantially horizontal diffuser surface. More particularly, the fluidized material situated nearest to the tank wall normally forms the patient support surface for supporting the patient's extremities. As the patient's extremities normally weigh less than the patient's body, less fluidization material is generally required to support the patient's extremities. A preferred bead diffuser 301 comprising upright inflatable chambers (502a and 502i) effectively reduces the quantity of beads 303 needed to form the patient support surface which supports the patient's extremities: Likewise, as compared to the outer chambers (502a and 502i), the inner inflatable chambers 502e-f are specially designed to form a diffuser surface 310 which is more distal to the fluidized patient support surface and is, therefore, able to support the greater quantity of fluidization material generally required for supporting the heavier head, torso, and leg portions of the patient's body. It should be understood by those skilled in the art that a diffuser surface 310 can be variously shaped without departing from the scope of the present invention. For example, the diffuser surface 310 could simply define a horizontal surface.

An exploded view of a preferred air blower assembly 701 for supplying a flow of air through the diffuser surface 310 at a rate sufficient to fluidize the beads 303 supported thereon is illustrated in FIG. 8. In a preferred embodiment, the air blower assembly 701 is housed within a framed box that occupies and is conveniently removed from within the' foot pedestal 103. As shown in FIG. 9, the framed box 705 is set upon a pair of front wheels 702 and rear wheels 703 (not shown) to provide the user with convenient access to the air blower assembly 701. To access the air blower assembly 701 for purposes of repair and general maintenance, the foot end cover 704 of the foot pedestal 103 is removed, and the framed box 705 is simply rolled out of the foot pedestal 103. Once the framed box 705 is removed from within the foot pedestal 103, a hinged top cover 718 is easily lifted to reveal the individual components of the air blower assembly 701. In another preferred embodiment, the side walls and supporting, surfaces of the framed box 705, and the head and foot pedestals (102-103) are fabricated out of a light-weight composite material to further reduce the overall weight of the fluidized bead bed 100.

Referring to FIG. 8, a preferred air blower assembly 701 comprises two electric motor driven air blowers 709a-b which supply a flow of pressurized air sufficient to inflate the bead diffuser 301 and fluidize the fluidization material 303 supported thereon. The air blowers 709a-b are preferrably variable speed type blowers which provide for adjustments in the air flow rate so as to enable the bed user to selectively alter the level of fluidization. In a preferred operation, room air is initially filtered through two air filters 708a-b before entering the air blowers 709a-b through air connection ports 719 (not shown). Pressurized air is channeled out of the air blowers 709a-b through discharge ports 720a-b and into discharge hoses 716a-b which provide an air conduit between the air blowers 709a-b and a heat exchanger 711. To prevent the air blower assembly 701 from becoming overheated during operation, three exhaust fans 717 are provided which function to draw heat away from the air blower assembly 701. A preferred heat exchanger 711 includes a heating element 721 (not shown) which is operable to maintain the temperature of the pressurized air within a preferred range of about 26.7 °C to 37.7 °C (80 to 100 degrees Fahrenheit). A furnace filter 714 is also provided to clean the air used to cool the heat exchanger 711. Pressurized air is discharged from within the heat exchanger 711 into four flexible air hoses 308a-d which provide air conduits between the heat exchanger 711 and the bead diffuser 301. In this manner, pressurized air flows through the flexible air hoses 308a-d and into the bead diffuser 301 which becomes inflated and fluidizes the beads 303 supported thereon. The fluidization air is then exhausted through the bottom 306 and top 313 filter sheets which are permeable to air but not to the beads 303.

In another preferred embodiment, as illustrated in FIG. 8, at least one of the four flexible air hoses 308a-d is in fluid communication with one or more auxiliary air hoses 713a-b via a valve assembly 712. As shown in FIG. 8, air flowing through the air hose 308d can be diverted by the valve assembly 712 and into two auxiliary air hoses 713a-b for the purpose of providing pressurized air to an inflatable patient support system (not shown), or other system requiring pressurized air for proper operation.

A preferred embodiment for attaching the fabric skirt 304, the bottom filter sheet 306 and the top filter sheet 313 to the tank rim 105 are illustrated in FIGs. 10 and 11. Referring to FIG. 11, three strips (1001, 1002, and 1003) of a hook or loop fabric material is attached to the tank rim 105. One such suitable hook and loop fabric is well known in the art, and is commercially available under the trade mark "VELCRO". An opposing hook or loop VELCRO strip for adhering to the strips attached to the tank rim 105 is secured to the perimeter edge of the fabric skirt 304, the bottom filter sheet 306 and the top filter sheet 313. As shown in FIG. 11, the bead pouch 307 is formed within the tank 101 by extending the fabric skirt 304 upward along the inner wall of the tank 101 and attaching the VELCRO strip on the perimeter of the fabric skirt 304 to the first strip 1001 of VELCRO extending about the inner edge of the tank rim 105. The upper surface of the bead pouch 307 is formed by attaching the VELCRO strip on the bottom filter sheet 306 to a second VELCRO strip 1003 positioned about the outer edge of the tank rim 105. As disclosed above, attaching the fabric skirt 304, and the bottom filter sheet 306 to the tank rim 105 forms the preferred bead pouch 307. In this way, the beads 303 are easily removed for the purpose of normal maintenance or replacement by simply removing the bottom filter sheet 306. A top filter sheet 313, as illustrated in FIGS. 3 and 11, is placed in overlying relation to the bottom filter sheet 306. As shown, the perimeter edge of the sheet 313 is stretched over the tank rim 105, and attached to a third VELCRO strip 1002 attached to the outer wall of the tank 101. It should be understood to those skilled in the art that alternative means for attaching the respective sheets 304, 306 and 313 to the tank rim 105 can be used without departing from the scope of the invention.

In a preferred embodiment, as shown in FIGs. 10 and 11, both prevention of patient injury and attachment of the respective sheets 304, 305 and 313 is accomplished using a three piece flexible bumper assembly 904 to overlap the rigid tank rim 105. As shown in FIG. 10, an inner perimeter bumper 901 is placed over the attached sheets (304, 305 and 313), and securely fastened to the inner perimeter of the tank rim 105. A corresponding outer perimeter bumper 902 is fastened to the outer perimeter of the tank rim 105. After the inner and outer perimeter bumpers are secured to the tank rim 105, a middle perimeter bumper 903 is used to demountably engage the inner 901 and outer 902 perimeter bumpers and, thus, secure the bumper assembly 904 to the tank rim 105. Once the flexible bumper assembly 904 is installed, a top cover sheet 106 is fitted over the bumper 904 to form a preferred patient support surface.

FIG. 12 illustrates a control panel 109 which serves as the primary interface for controlling and adjusting the functions of the presently disclosed fluidized bead bed 100. Referring to FIG. 1, the control panel 109 is shown extending from the foot pedestal 102. In a preferred embodiment, the control panel 109 can be stored out of view and in a closed position within the foot pedestal 102. In use, fluidization of the beads 303 is activated or deactivated by switching the ON/OFF switch 1101 to its respective ON or OFF position. The ON light 1105 is illuminated as long as the ON/OFF switch 1101 remains in an ON position. Once the fluidization switch 1101 is turned ON, the air flow adjustment 1102 is used to increase or decrease the flow of fluidization air into the bead diffuser 301 and up through the beads 303 supported thereon. In an alternative embodiment, fluidization may be suspended without deflation of the bead diffuser 301. This embodiment allows the patient to remain accessible on top of the inflated bead diffuser 301 even though fluidization is suspended.

To ensure patient comfort, a temperature adjustment 1103 is provided which enables the care giver or patient to increase or decrease the temperature of the fluidization air flowing through the beads 303 and out the patient support surface. It is preferable that the temperature of the beads 303 be adjustable between the range of 26.7 °C (80 degrees Fahrenheit) at the minimum setting, and 37.7 °C (100 degrees Fahrenheit) at the maximum setting. Illumination of the heat light 1107 or cool light 1106 verifies that the system is either heating or cooling the beads 303 as selected.

In another preferred embodiment, the patient is provided with a hand control 110 to control the bed 100 fluidization functions (not shown). In this preferred embodiment, the main control panel 109 is equipped with a fluidization lock-out switch 1104 to prevent fluidization from being inadvertently activated or deactivated from the hand control 110. The fluidization locked out light 1108 illuminates when this control function is activated.

Though a preferred embodiment of an inflatable bead diffuser 301 is disclosed above, it should be understood by those skilled in the art that alternative inflatable bead diffuser 301 assemblies and configurations may be used with a fluidized bead bed 100 without departing from the scope of the invention. For instance, FIG. 13 shows a substantially inflated bead diffuser 301 comprising three separately inflated chambers (1300a-c) which define a foot section 1301a, a torso section 1301b, and a head section 1301c. In this alternative embodiment, each chamber 1300a-c is in fluid communication with at least one air blower assembly 701 via three flexible air hoses 308a-c, as described above (not shown). More particularly, each chamber 1300a-c is assembled with integral air nozzles 501a-c which insert into fluidization ports 302 located on the bottom of the tank 101. As described above, the fluidization ports 302 are positioned in such a manner as to properly align with the air nozzles 501a-c when the bead diffuser 301 is positioned against the bottom surface 203 of the tank 101. In another embodiment, the rate of air flowing into each chamber 1300a-c can be regulated so as to enable the bed user to adjust the fluidization of the beads 303 immediately above each chamber 1300a-c. This selective fluidization can be accomplished by placing each chamber 1300a-c in fluid communication with distinct variable speed air blowers, or by providing one or more adjustable air valves operable to increase or decrease the flow of air from the air source to each respective chamber 1300a-c. In this manner, fluidization of the beads 303 corresponding to each section 1301a-c of the patient's body can be increased or decreased as is necessary to form an adequate fluidized patient support surface. For example, a patient torso section which may be significantly heavier relative to the head and leg portions of a patient's body can be provided with greater support by merely decreasing the fluidization pressure within the torso section 1301b of the bead diffuser 301. Separate air blowers and/or air valves can be individually actuated from either the control panel 109 or hand control 110 to adjust the fluidization above the respective section 1301a-c.

In another alternative embodiment, the bead diffuser chamber 1300c described above can be raised or lowered to elevate a patient resting on top of the fluidized patient support surface. Referring to FIG. 14, an inflatable air bladder 1401 in a substantially inflated form is shown positioned between the bead diffuser chamber 1300c of the bead diffuser 301, and the bottom surface 203 of the tank 101. Under inflation conditions, an air source provides pressurized air through an air conduit connected to the inflatable air bladder 1401 (not shown). As shown in FIG. 14, the fluidized patient support surface positioned above the head section 1301c is preferably formed using a multiplicity of adjacently attached bead pouches 1402a-d transversely positioned on top of the bead diffuser 301. In this manner, elevation of the head section 1301c of the bead diffuser 301 does not result in the downward displacement of the beads 303, but the beads 303 remain positioned above the head section 1301c within each of the respective bead pouches 1402a-d. A separate bead pouch 307 rest on top of the leg section 1301a and torso section 1302b. It should, however, be understood by those skilled in the art that alternative numbers and/or arrangements of bead pouches can be used to form a fluidized patient support surface without departing from the scope of the invention.

While the description given herein reflects the best mode known to the inventor, those who are reasonably skilled in the art will quickly recognize that many omissions, additions, substitutions, modifications and alternate embodiments may be made of the teachings herein. Recognizing that those of reasonable skill in the art will easily see such alternate embodiments, they have in most cases not been described herein in order to preserve clarity.