Multi-stable Compliant-mechanism Mattress For Bed Sore Prevention Patent Application (2025)

U.S. patent application number 17/585271 was filed with the patent office on 2022-06-09 for multi-stable compliant-mechanism mattress for bed sore prevention. The applicant listed for this patent is THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, Piyush Sheth. Invention is credited to Jonathan Hopkins, Piyush Sheth.

MULTI-STABLE COMPLIANT-MECHANISM MATTRESS FOR BED SOREPREVENTION

Abstract

A pressure sore prevention mattress is provided alternatingpressure points on the body of an occupant that is easilytransformable between two stable configurations. The four-layermattress construction has a top foam pad, a webbing layer, adynamic layer of deformable panels trapezoid-shaped four-barmechanisms that deform to produce an undulating pattern of peaks,and a base. Panel geometry can determine peak height. The mattresshas a spatially hollow geometry that allows natural air convectionthrough the breathable top foam pad to enable drying of moisture aswell as the use of forced air convective drying or cooling. Themattress can be transformed from one configuration to the otherwhile the occupant is on the mattress.

Related U.S. Patent Documents

Claims

1. A mattress apparatus for minimizing pressure ulcers, theapparatus comprising: (a) a foam pad with a top surface and abottom surface; (b) a webbing layer mounted to the bottom surfaceof the foam pad; (c) a dynamic layer of a plurality of planarpanels with a deformable strip coupled to the webbing layer, a baseand two or more legs coupled to the deformable strip and base withresilient hinges; and (d) a foundation layer coupled to the base ofthe panels; (e) wherein the legs and deformable strip of thedynamic layer can move between two stable positions; and (f)wherein movement of the legs and deformable strip in relation tothe base of each panel causes deformations in the deformablestrip.

2. The apparatus of claim 1, wherein the foam pad comprises a foampad with periodically positioned holes through the pad, the holesconfigured for air circulation through the foam pad.

3. The apparatus of claim 1, wherein the foam pad is made of amaterial selected from the group of materials consisting of memoryfoam and foam rubber.

4. The apparatus of claim 1, wherein the webbing layer comprises agrid of orthogonal straps, at least one of said straps configuredfor coupling with a deformable strip of each panel.

5. The apparatus of claim 1: wherein the plurality of panelscomprises a plurality of first panels and a plurality of secondpanels; wherein the first panels configured with an offset that isout of phase from the second panels; and wherein the plurality ofpanels is configured such that the first and second panels arepositioned in a sequentially alternating pattern.

6. The apparatus of claim 1, wherein the deformable strip of saidplanar panels comprises: a top panel layer; a resilient lower panellayer; and a plurality of diamond-shaped flexures disposed betweensaid top panel layer and said lower panel layer.

7. The apparatus of claim 1, wherein the base of said planar panelsfurther comprises: a linear outer edge configured for mounting tosaid foundation layer; an inner edge with triangular shaped rigidbodies spaced regularly along the inner edge of the base member;and pairs of legs flexibly coupled at one end to the inner edge ofthe base member between said triangular shaped rigid bodies withresilient hinges; wherein movement of the legs is limited by saidtriangular shaped rigid bodies.

8. The apparatus of claim 1, wherein the foundation layer isflexible.

9. The apparatus of claim 1, wherein said foundation layercomprises a plurality of rigid horizontal segments.

10. A mattress apparatus, comprising: (a) a support substrate; (b)a plurality of planar panels having an upper member coupled to abase member with a plurality of legs and flexible hinges, said basemember mounted to said support substrate, said panels orientedparallel to each other; (c) a grid of straps joined to said uppermember of said panels; and (d) a top layer coupled to said grid ofstraps; (e) wherein each upper member of said panels moves inrelation to the base member from a first stable position to asecond stable position.

11. The apparatus of claim 10, wherein the support substrate isflexible.

12. The apparatus of claim 11, wherein said support substratecomprises a plurality of rigid horizontal segments flexibly coupledto each other.

13. The apparatus of claim 10, wherein the upper member of saidplanar panels comprises: a top panel layer; a resilient lower panellayer; and a plurality of diamond-shaped flexures disposed betweensaid top panel layer and said lower panel layer.

14. The apparatus of claim 10, wherein the base member of saidplanar panels further comprises: a linear outer edge configured formounting to said support substrate; and an inner edge withtriangular shaped rigid bodies spaced regularly along the inneredge of the base member; and pairs of legs flexibly coupled at oneend to the inner edge of the base member between said triangularshaped rigid bodies with resilient hinges; wherein movement of saidlegs is limited by said triangular shaped rigid bodies.

15. The apparatus of claim 10: wherein the plurality of panelscomprises a plurality of first panels and a plurality of secondpanels; wherein the first panels configured with an offset that isout of phase from the second panels; and wherein the plurality ofpanels is configured such that the first and second panels arepositioned in a sequentially alternating pattern.

16. The apparatus of claim 10, wherein said top layer comprises afoam pad with periodically positioned holes through the pad, theholes configured for air circulation through the top layer.

17. The apparatus of claim 10, wherein said top layer comprises afoam pad made from a material selected from the group of materialsconsisting of memory foam and foam rubber.

18. A multi-stable compliant-mechanism mattress apparatus,comprising: a top layer comprising a foam pad with periodicallypositioned holes through the pad, the holes configured for aircirculation through the top layer; a grid of straps beneath the toplayer the straps configured for air circulation through the toplayer; a plurality of horizontal compliant panels beneath the gridof straps, the grid of straps providing support for the panels, theplurality of panels forming a compliant web; and a supportsubstrate beneath the panels; wherein the compliant web isconfigured to move between first and second stable positions inresponse to application of horizontal force.

19. The apparatus of claim 18: wherein each panel in the pluralityof panels comprises a single planar component; wherein theplurality of panels comprises a plurality of first panels and aplurality of second panels; wherein the first panels are configuredwith an offset that is out of phase from the second panels; andwherein the plurality of panels is configured such that the firstand second panels are positioned in a sequentially alternatingpattern.

20. The apparatus of claim 19: wherein each panel in the pluralityof panels comprises a series of trapezoid-shaped four-barmechanisms; and wherein each bar in the four-bar mechanisms isjoined to the panel by compliant joints that deform under load toproduce an undulating pattern.

21. The apparatus of claim 20, further comprising a plurality ofdiamond-shaped flexures positioned adjacent the four-bar mechanismsand configured for smoothing the undulations.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and is a 35 U.S.C..sctn. 111(a) continuation of, PCT international application numberPCT/US2020/044561 filed on July 31, 2020, incorporated herein byreference in its entirety, which claims priority to, and thebenefit of, U.S. provisional patent application Ser. No. 62/882,283filed on Aug. 2, 2019, incorporated herein by reference in itsentirety. Priority is claimed to each of the foregoingapplications.

[0002] The above-referenced PCT international application waspublished as PCT International Publication No. WO 2021/026013 A1 onFeb. 11, 2021, which publication is incorporated herein byreference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0003] Not Applicable

NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION

[0004] A portion of the material in this patent document is subjectto copyright protection under the copyright laws of the UnitedStates and of other countries. The owner of the copyright rightshas no objection to the facsimile reproduction by anyone of thepatent document or the patent disclosure, as it appears in theUnited States Patent and Trademark Office publicly available fileor records, but otherwise reserves all copyright rights whatsoever.The copyright owner does not hereby waive any of its rights to havethis patent document maintained in secrecy, including withoutlimitation its rights pursuant to 37 C.F.R. .sctn. 1.14.

BACKGROUND

1. Technical Field

[0005] This technology pertains generally to bed mattresses andmedical nursing equipment for people and more particularly topressure alleviating mattresses for bed sore prevention.

2. Background

[0006] A significant concern of medical care providers withpatients who are bedridden for long periods of time is the probableoccurrence of bedsores or skin ulcers in areas of the body that arein constant contact with the mattress. Bed sores are causedprimarily by the occurrence of increased and constant pressure onthe capillaries in the dermis of the skin that results in theprolonged blockage of blood flow. Contact pressures exceeding 32 mmof Hg for longer than two hours can cause pressure sores.

[0007] Bed sores are a complex problem that are influenced by theage, nutrition, hygiene, medical conditions, moisture and prolongedhigher pressure on the contact points of the patient on thesurfaces of the mattress of a bed. Pressure sores typically occurin the bony prominences on the back and hips of patient when theyare laying on the bed. Primary areas of the body that arecandidates for bedsore development include the occipital region,scapula, sacrum. ischium, ankles and heels.

[0008] Immobile, high-risk patients may often develop bed soreswithin 4 to 6 hours if they are not properly and regularlyrepositioned. The current hospital protocol is to turn the patientevery two hours. However, this repositioning requirement not onlydisturbs and awakens sleeping patients, it may also causemaceration due to the shear forces experienced by the often fragileand sensitive skin of the patient. Repositioning can also be aliability for the nurses who have to turn the patient, who may beoverweight and difficult to move.

[0009] Different systems have been developed to prevent bed soresfrom occurring such as the application of pressure on differentareas of the body over time to stimulate blood movement or maintainblood flow. As an alternative to turning the patient every twohours, the most effective bed sore prevention approach to date isthe use of silica-bead air fluidized beds that reduce the pressurepoints on the patient's body. Although effective, air fluidizedbeds are costly and such costs may not be reimbursed by insuranceor government benefits until the patient experiences stage IVbedsores, which is practically the point of no return. Even privatebuyers who can afford the high price of an air fluidized bed mayhave difficulty accommodating a fluidized bed in their home as theyare extremely heavy (>0.5 ton) and difficult to transport andinstall.

[0010] Alternating air pressure cell mattresses are intended tohave similar bed sore prevention outcomes and are less costly.However, use of air pressure mattresses is not currently backed bysufficient evidence of efficacy and durability to deserve a strongrecommendation. They often require noisy pumps that constantlyconsume power and possess numerous valves that are complex andsometimes fragile and often leak after multiple uses.

[0011] Unfortunately, approximately 2.5 million patients areaffected with bed sores every year in the United States. Aboutsixty thousand (60,000) patients die every year as a direct resultof the presence of bed sores. As a consequence, bed sores produce$9.1 to $11,6 billion in treatment costs every year in the U.S.alone. Individual patient care cost is ranging from about $20,900to $151,700. The Centers for Medicare and Medicaid Servicesestimated that in 2007 each pressure sore added $43,180 in costs toa hospital stay. Pressure ulcers in managed care or hospitalizedpatients are one of the most litigated conditions in civil lawsuitsalleging medical malpractice. The average settlement of a pressureulcer lawsuit is in the range of $250,000 with some awards topping$312 million with 87% cases favoring the plaintiffs.

[0012] Accordingly, there is a need for mattress systems that areeffective at limiting the occurrence of pressure ulcers, that aredurable and that are relatively inexpensive to own andmaintain.

BRIEF SUMMARY

[0013] A bi-stable compliant-mechanism mattress is provided thatalternates pressure points on the body of an occupant toeffectively prevent bed sores. In one embodiment, the mattresspassively conforms to the body of the patient in each of its twostable configurations without the need for drawing power orrepositioning the patient. The mattress provides alternatingpressure points as desired depending on which of the two stableconfigurations of the mattress is selected.

[0014] The energy needed to reconfigure the mattress from onestable configuration to the other should be minimal since asubstantial amount of strain energy is stored in the deformedresilient mechanism, which would help counteract the weight of thebody of the patient. In one embodiment, the mattress can bemanually actuated by pulling it from one side to the next with aslittle effort as it would take to open and close a drawer.Alternatively, a single small motor could be automated to shift themattress from one stable configuration to the next every two hoursusing minimal power. Note also that the occupant of the bed moveswith the mattress as it is reconfigured from one stableconfiguration to the next so that the skin of the occupant does notexperience harmful shearing forces as the pressure pointsalternate.

[0015] The mattress will optimally alternate pressure pointssilently without drawing power to prevent bedsores in patients thatweigh up to 600 pounds so that nurses or other caregivers will nothave to physically turn the patient. The mattresses will onlyproduce a quiet clicking noise when shifted from one state to thenext in contrast to the loud squeaking noises and wear caused byfriction generated within the sliding joints of traditional rigidmechanisms that often require lubricants.

[0016] These mattresses also allow air to passively flow throughthe geometry of the mattress to prevent the occupant fromperspiring. The topology of the layers with spatially hollowgeometry allows natural air convection through the breathable topfoam layer to enable drying of any moisture. This geometry alsoallows the use of forced air from a source for convective drying orair flow cooling or heating as desired.

[0017] In one embodiment, the mattresses are designed withhorizontal panels that can be adjusted along their length so thatthe patient's feet and torso can be lowered while their knees andhead are lifted like that of traditional hospital beds withoutmodification to the mattress design.

[0018] According to one aspect of the technology, a dynamic,compliant mechanism based mattress design is provided that canreduce the occurrence of bed sores in the existing immobile andaging population and improve the lives of many patients everyyear.

[0019] According to another aspect of the technology, a low power,functional mattress design is provided that is substantially lowerin cost compared to the cost of silica-bead air fluidized beds.

[0020] Another aspect of the technology is to provide a pressuresore limiting mattress design that is affordable while also beingrobust, lightweight, and transportable.

[0021] Another aspect of the technology is to provide a mattresswith dynamically produced points of contact that can be readilychanged while the bed is occupied eliminating the need for regularposition interventions.

[0022] A further aspect of the technology is to provide a mattresswith undulations with a height that is controllable by the geometryof the elements of the deformable panels.

[0023] Another aspect is to provide a compliant-mechanism platformthat can be adapted for use as wheelchair cushions and also improvethe comfort of airline, car, or truck passengers that have to sitin seats for extended periods of time.

[0024] Further aspects of the technology described herein will bebrought out in the following portions of the specification, whereinthe detailed description is for the purpose of fully disclosingpreferred embodiments of the technology without placing limitationsthereon.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0025] The technology described herein will be more fullyunderstood by reference to the following drawings which are forillustrative purposes only:

[0026] FIG. 1 is a diagram of an expanded view of a mattressstructure with four layers according to one embodiment of thetechnology.

[0027] FIG. 2 is a diagram of an assembled mattress of the fourlayers shown in FIG. 1 with an arrow that indicates the directionof actuation.

[0028] FIG. 3 is a diagram of two different panels that arearranged sequentially, in parallel and out of phase.

[0029] FIG. 4A is a schematic side view of a panel section showingthe trapezoid-shaped four-bars within each panel design shown withdiamond flexures on top and in an unloaded state. The direction ofactuation is also shown.

[0030] FIG. 4B is a schematic side view of a panel section in aloaded state from above showing the four-bar mechanism deforms intoone of its two stable configurations when it is loaded from abovethus producing undulating pressure points.

[0031] FIG. 5 is a side view of a panel section with a top layerwith diamond shaped flexures in an unloaded state.

[0032] FIG. 6 is a side view of a panel section with a top layerwith diamond shaped flexures of FIG. 5 in a loaded state and in afirst configuration.

[0033] FIG. 7 is a side view of a panel section with a top layerwith diamond shaped flexures of FIG. 6 in a loaded statetransitioning to a second configuration.

[0034] FIG. 8 is a perspective view of a sections of panels withalternating panels out of phase coupled to a grid of straps in anunloaded state or an intermediate transition state betweenconfigurations.

[0035] FIG. 9 is a perspective view of the sections of FIG. 8 in aloaded state and in a first configuration producing a first set ofpressure points in the mattress.

[0036] FIG. 10 is a perspective view of the sections of FIG. 9 in aloaded state moved to a second stable configuration producing asecond set of pressure points in the mattress.

DETAILED DESCRIPTION

[0037] Referring more specifically to the drawings, forillustrative purposes, devices, systems and methods for decreasingpressure points and pressure sores in immobile and aging patientsare generally shown. Several embodiments of the technology aredescribed generally in FIG. 1 to FIG. 10 to illustrate thecharacteristics and functionality of the devices, systems,materials and methods. It will be appreciated that the methods mayvary as to the specific steps and sequence and the systems andapparatus may vary as to structural details without departing fromthe basic concepts as disclosed herein. The method steps are merelyexemplary of the order that these steps may occur. The steps mayoccur in any order that is desired, such that it still performs thegoals of the claimed technology.

[0038] Turning now to FIG. 1, an embodiment of affordable,lightweight mattress that utilizes multi-stable compliantmechanisms is used to generally illustrate the bed or cushioningplatform. The bi-stable compliant-mechanism-based mattress 10 is aplatform that periodically shifts pressure points on the body ofthe occupant of the bed or cushion to avoid pressure related sores.The shifting of pressure points by the mattress platform alsoreduces the need for turning hospital patients every two hours andthe associated secondary injuries to patients and staff that canoccur with the frequent repositioning of heavy patients.

[0039] In the expanded embodiment of FIG. 1, thecompliant-mechanism-based mattress 10 comprises four layers. Thetop layer is a rectangular foam pad 12 with periodic holes 14punched through the pad 12. The purpose of the top pad 12 is toprovide a comfortable interface surface for the occupant. The holes14 of pad 12 are there to help circulate air from underneath themattress to passively prevent bed sores by helping to prevent theformation of sweat and to provide openings for the movement of airto and away from the surface of the reclining body of the occupant.Although the pad 12 preferably has holes, the pad may be solid inone embodiment. The foam pad 12 can be made of conventional foamrubber, memory foam or similar material.

[0040] Below the bottom surface of top pad 12 is an open grid ofstraps 16 that allows air to pass through its geometry into theholes 14 of the foam pad 12 of the mattress 10. The straps of thegrid 16 are preferably oriented orthogonally to form a grid withopenings to allow the flow of air through holes 14 of pad 12. Inone embodiment, the intersections of the vertical and horizontalstraps may be joined together. In another embodiment, the verticaland horizontal straps simply overlap.

[0041] The straps of grid 16 also provide lateral support for theelongate horizontal compliant panels below them in the dynamicmechanism layer 18. In one embodiment, corresponding straps of grid16 are oriented and mounted to the top surface of each of theparallel horizontal compliant panels forming the dynamic mechanismlayer 18 of the mattress 10.

[0042] The individual panels forming the dynamic mechanism layer 18are mounted to a foundation layer 20 that supports the wholemattress. The foundation layer 20 may segmented or sectioned acrossthe width as shown in FIG. 1 and FIG. 2 or the foundation 20 may bea solid sheet. The horizontal segments forming of foundation 20,may be held together with straps or flexible hinges so that thefoundation layer 20 is flexible lengthwise but inflexiblewidthwise. In one embodiment, the foundation layer is made from aflexible material that is resilient and can stretch and flex.

[0043] The four layers affixed together forming the mattress 10 areshown in FIG. 2. The arrow that is depicted on the top surface ofthe top pad 12 indicates the side to side direction of actuation ofthe panels of the dynamic mechanism layer 18.

[0044] As shown in detail in FIG. 3 through FIG. 10, the dynamiclayer 18 of the mattress is formed with an array of parallelhorizontal compliant panels that can move between two stablestates. Each panel is preferably planar and mounted on a base edgeto the foundation layer 20. In one preferred embodiment, the panelsare produced from an elongate piece that is cut from a single flatslab using a planar fabrication processes such as waterjet, wireEDM, CNC milling process, etc. Since the panels are two-dimensionalextrusions in this embodiment, the design can be fabricated rapidlywith conventional planar processes and using minimal steps allowinghigh-throughput and low-cost manufacturing. The design is alsoeasily customizable for individual patients without increasing thecost of making each mattress.

[0045] There are two panels 22, 24 illustrated in FIG. 3. Thesepanels are essentially identical to each other, but in differentphases and are configured to be mounted parallel to each other sothat one panel is offset out of phase from the other by a distance,d. The parallel horizontal panels that form the dynamic layer 18are preferably separated from each other with a spacing of the samedistance, d, in one embodiment. It is also preferred that each ofthe panel types are sequentially alternated from one phase to theother along the entire length of the dynamic layer 18 of themattress 10.

[0046] The individual panels 22 have a base with triangle shapedstops 28 along its length with two rigid legs 26 spaced and mountedbetween the triangles with thin compliant and resilient hinges orjoints 30 as seen in the detail of FIG. 3. The hinges 30 allow thelegs 26 to pivot back and forth in the direction of either adjacenttriangular stops 28 within the plane of the panel.

[0047] The top end of each of the legs 26 is mounted to an upperlayer 34 with thin compliant hinges or joints 32. The top hinges 30and the bottom hinges 32 of the legs 26 are also resilient in oneembodiment so that the legs 26 return to a starting position.

[0048] The upper layer 34 of the panel is preferably formed fromtop 42 and bottom 44 flexible strips separated by a layer ofdeformable diamond elements 38. The base of the panel withtriangular shaped stops is mounted to the foundation 20 layer withbolts, glue or other type of fastener. The top strip of the upperlayer 34 with the deformable diamonds 38 of each panel 22, 24 ismounted to the strips of the grid layer 16.

[0049] As seen in the side views of FIG. 4A and FIG. 4B each of thepanels are designed to be a series of trapezoid-shaped four-barmechanisms. The bars forming the mechanism shape are highlighted bysolid lines 40 shown in FIG. 4A and FIG. 4B. The rigid bodies thatconstitute each "bar" that are joined together by thin complianthinges or joints 30, 32. These joints deform when the mattress isloaded thus producing the undulating pattern shown in FIG. 4B. Thepossible horizontal direction of movements of the top surface ofthe panel with respect to the base section as a result of themovement of the legs 26 and hinges 30, 32 is shown in FIG. 4A.

[0050] The layer with diamond shaped flexures 38 of the upper layer34, shown in FIG. 4B on top of the trapezoid-shaped four-barmechanisms, help to smooth out the undulating pattern so that it ismore sinusoidal and gradual than the sharp triangles that thefour-bars would alone produce. These undulations not only occuralong the length of each panel but also occur in two-dimensionsalong the length of the bed when the bed is loaded as shown withvertical arrows in FIG. 4B. This two-dimensional undulationproduced by the panels is enabled because of the two alternatingoffset series of panels as described and shown in FIG. 3.

[0051] The sections of the panels that are shown in FIG. 3 throughFIG. 10 are uniform in size and geometry to illustrate the functionof the panels of the dynamic layer 18. However, the geometry of thepanels and the organization of the panel types in the dynamic layer18 can be selected to control the height and location ofundulations and pattern of pressure points in each configuration.As seen in FIG. 4B, for example, the deformations of the top level34 of the panel form sinusoidal undulations with a height or peakand wavelength that is determined by the geometry of the leg andtriangular stop elements and spacing of elements in each panel. Inone embodiment, the pitch (wavelength of the sine wave i.e., thedistance between two peaks) can vary within the panel.Consequently, it is possible to design the dynamic layer 18 andpanels with a smaller pitch in the middle of the bed in the moresensitive areas like the sacrum (upper hip, buttocks), scapula (thebones in the back under either shoulder), head and the ankles.Smaller pitch will enable finer alternation of pressure points andwill eliminate dead zones (areas where there is no change inpressure) and reduce the unnecessary cost of creating planarfeatures with small pitch in the entire bed.

[0052] The movement of the elements of the panels and the mechanismof deformation into one of its two stable configurations when it isloaded from above producing undulating pressure points on thepatient's body are shown in the side views of FIG. 5, FIG. 6 andFIG. 7 and the perspective views of FIG. 8, FIG. 9 and FIG. 10.

[0053] Referring now to FIG. 5, the resting state of the panels ofthe dynamic layer 18 is depicted in a side view. In this unloadedstate, the legs 26 are not in contact with the triangular stopelements 28 of the base section of the panel 22 and the top layer34 with diamond shaped flexures 38 is approximately horizontal.This configuration in FIG. 5 also illustrates a transition statebetween the two stable positions shown in FIG. 9 and FIG. 10, forexample.

[0054] With the application of a load, as shown in FIG. 4B and FIG.6, the legs 26 move about hinge 30 to engage the triangular stop 28causing the deformation of the lower strip section 44, the flexureof diamond flexures 38 and the deformation top surface strip 42 oftop layer 34. The pair of legs 26 are positioned so that one leg 26can move about the axis of the bottom hinge 30 and engage anadjacent triangular stop 28 while the second leg of the pair oflegs moves in the same direction as the first leg about the axis ofits lower hinge 30 but does not engage a triangular stop 28. Thegeometry of the deformations can also be changed with the angle ofthe triangular stop elements 28 or the selection of the distancesbetween the hinges 30 and the triangular stops 28.

[0055] These deformations result in the creation of a stableundulation 48 in the panels and a pressure point on the load. Theseundulations 48 transfer through the foam pad 12 onto the back ofthe occupant to produce a grid or pattern of stable pressure pointsconfigured by the panel deformations.

[0056] The parallel panels 22 can also be moved to a second stableposition by moving legs 26 of the panel from engaging onetriangular stop 28 to engage an adjacent triangular stop 28 asillustrated in FIG. 7 and FIG. 10. When the panel is moved in oneactuation direction, the left leg 26 will engage a triangular stop28 and when the panel is moved in the opposite direction the rightleg 26 will engage a second triangular stop 28.

[0057] The reconfiguration to the second stable position as shownin FIG. 7 will produce a second grid of undulations 50. Since thelattice of horizontal compliant panels can be reconfigured to twodifferent stable positions, the bed can be actuated back and forthalong the actuation direction, shown in FIG. 2, and the grid ofpressure points can be alternated on any desired timetable. Bypushing or pulling on the mattress along its actuation direction,the mattress can be reconfigured in either of these twoconfigurations with minimal actuation power so the pressure pointson the body of the occupant changes and the occupant is protectedfrom accruing bed sores.

[0058] These undulations not only occur along the length of eachpanel but also occur in two-dimensions along the length of the bedwhen the bed is loaded as shown in FIG. 8, FIG. 9 and FIG. 10. Thistwo-dimensional undulation is enabled because of the twoalternating panel designs shown in FIG. 3. These undulationstransfer through the foam pad onto the back of the recliningoccupant to produce a grid of pressure points that is dynamic.

[0059] Referring now to FIG. 8, a section of the dynamic mechanismlayer 18 with three panels out of phase with the adjacent panel isshown with the grid 16 of straps 52 mounted to the top surface ofthe parallel panels. The section depicted in FIG. 8 is shown in anunloaded state as also illustrated in the cross-sections FIG. 4Aand FIG. 5. In this embodiment, the joints 30, 32 and the flexiblediamonds are compliant and resilient and bring the mattress to aneven planar state. In another embodiment, the hinges 30, 32 at eachend of the legs 26 are flexible but not resilient.

[0060] It can also be seen that there is a lot of open spacebetween the panels for air to pass through the straps and the holesin the foam mattress to passively flow air to and from the body ofthe occupant from below.

[0061] The application of a load on the mattress will cause theformation of undulations 54 from deformations in the top layer ofthe panels with the pivoting movements of the legs 26 asillustrated in FIG. 9. The triangle-shaped rigid bodies in thecenter of each trapezoid in the panels illustrated in FIG. 4B, actas hard-stops so the four bars stop deforming when their legs 26hit the triangular stops 28 and the bed remains in a stableconfiguration. The trapezoid-shaped four-bar mechanisms help tosmooth out the undulating pattern so that it is more sinusoidal andgradual than the sharp triangles that the four-bars would producealone.

[0062] As shown in FIG. 10 the pattern of undulations on themattress can be changed with the actuation of panels from the firstposition illustrated in FIG. 9 to a second position shown in FIG.10 producing new undulations 56. As also shown in FIG. 6 and FIG,7, the legs 26 pivot around hinge 30 in the opposite direction sothat an adjacent leg 26 engages an adjacent triangular stop 28causing a different deformation of the top panel surface and a newundulation or pressure point 56 and overall producing a new patternof pressure points by the mattress.

[0063] A particularly attractive feature of the design is that whenthe patient lays on the bed, the mattress passively deforms to oneof the two configurations shown in FIG. 9 or FIG. 10. Since thecompliant hinges 30, 32 labeled in FIG. 5 remain deformed in thatconfiguration, that strain energy is reclaimed when the caregiverpulls the bed along the actuation direction shown in FIG. 2 andFIG. 4A. Once the caregiver pulls the mattress past thatconfiguration, the mattress will again passively click into itssecond stable configuration. So, because the panels are compliantand resilient, they substantially reduce the force required to liftthe patient and change the bed between its two stable positions asillustrated in FIG. 9 and FIG. 10. Thus, caregivers won't straintheir muscles reconfiguring the bed. If the bed is actuated backand forth every hour or so, the pressure points are guaranteed tochange at all points on the body of the occupant so that theoccupant never develops bed sores.

[0064] One important feature of the mattress is that the patientcan move with the mattress during transition between stable states.As a consequence, there is no relative motion and friction betweenthe occupant and the mattress. There is also no pulling or pushingof any portion of the body of the occupant required eliminating anyshear forces on the skin during transition.

[0065] Although manual actuation of the dynamic panel elements froma first configuration to a second configuration is illustrated, itwill be understood that the configuration changes could beaccomplished mechanically. For example, electric motors orsolenoids could be used to perform the conformational changes. Inone embodiment, a single linear motor could be automated toreconfigure the mattress to each of its two stable positions everyhour or other designated time points. The motor would use minimalpower since most of the energy necessary to lift the patient fromone configuration to the next is passively stored as strain energyin the deformed compliant joints 30, 32 of the legs 26 (FIG. 3).The motor function and timing are programmed with a computerprocessor and programming providing automated control overconfiguration changes so that the occupant will be exposed to a newpattern of undulations and a different set of pressure points atcontrollable intervals.

[0066] The mattress 10 embodiment shown in FIG. 1 has a segmentedfoundation 20 that can flex or bend along the length. The panelsare mounted to the foundation 20 in the same direction ashorizontal segments of the foundation 20 allowing the foundation 20to bend. The segments forming the foundation may be flexiblycoupled or hinged to move in relation to each other in onedirection. In this embodiment, the mattress design with horizontalsegments and panels can be adjusted along their length so that thepatient's feet and torso can be lowered while their knees and headare lifted like traditional hospital beds without modification tothe mattress design. Accordingly, the mattress can be bent atlocations along the length of the patient's body to allow thepatient to sit up in bed and lay down flat like other hospital bedmattresses in use and still allow patient to be exposed to achanging pattern of undulations and set of pressure points.

[0067] From the description herein, it will be appreciated that thepresent disclosure encompasses multiple embodiments which include,but are not limited to, the following:

[0068] 1. A mattress apparatus for minimizing pressure ulcers, theapparatus comprising: (a) a foam pad with a top surface and abottom surface; (b) a webbing layer mounted to the bottom surfaceof the foam pad; (c) a dynamic layer of a plurality of planarpanels with a deformable strip coupled to the webbing layer, a baseand two or more legs coupled to the deformable strip and base withresilient hinges; and (d) a foundation layer coupled to the base ofthe panels; (e) wherein the legs and deformable strip of thedynamic layer can move between two stable positions; and (f)wherein movement of the legs and deformable strip in relation tothe base of each panel causes deformations in the deformablestrip.

[0069] 2. The apparatus of any preceding or following embodiment,wherein the foam pad comprises a foam pad with periodicallypositioned holes through the pad, the holes configured for aircirculation through the foam pad.

[0070] 3. The apparatus of any preceding or following embodiment,wherein the foam pad is made of a material selected from the groupof materials consisting of memory foam and foam rubber.

[0071] 4. The apparatus of any preceding or following embodiment,wherein the webbing layer comprises a grid of orthogonal straps, atleast one of the straps configured for coupling with a deformablestrip of each panel.

[0072] 5. The apparatus of any preceding or following embodiment:wherein the plurality of panels comprises a plurality of firstpanels and a plurality of second panels; wherein the first panelsconfigured with an offset that is out of phase from the secondpanels; and wherein the plurality of panels is configured such thatthe first and second panels are positioned in a sequentiallyalternating pattern.

[0073] 6. The apparatus of any preceding or following embodiment,wherein the deformable strip of the planar panels comprises: a toppanel layer; a resilient lower panel layer; and a plurality ofdiamond-shaped flexures disposed between the top panel layer andthe lower panel layer.

[0074] 7. The apparatus of any preceding or following embodiment,wherein the base of the planar panels further comprises: a linearouter edge configured for mounting to the foundation layer; aninner edge with triangular shaped rigid bodies spaced regularlyalong the inner edge of the base member; and pairs of legs flexiblycoupled at one end to the inner edge of the base member between thetriangular shaped rigid bodies with resilient hinges; whereinmovement of the legs is limited by the triangular shaped rigidbodies.

[0075] 8. The apparatus of any preceding or following embodiment,wherein the foundation layer is flexible.

[0076] 9. The apparatus of any preceding or following embodiment,wherein the foundation layer comprises a plurality of rigidhorizontal segments.

[0077] 10. A mattress apparatus, comprising: (a) a supportsubstrate; (b) a plurality of planar panels having an upper membercoupled to a base member with a plurality of legs and flexiblehinges, the base member mounted to the support substrate, thepanels oriented parallel to each other; (c) a grid of straps joinedto the upper member of the panels; and (d) a top layer coupled tothe grid of straps; (e) wherein each upper member of the panelsmoves in relation to the base member from a first stable positionto a second stable position.

[0078] 11. The apparatus of any preceding or following embodiment,wherein the support substrate is flexible.

[0079] 12. The apparatus of any preceding or following embodiment,wherein the support substrate comprises a plurality of rigidhorizontal segments flexibly coupled to each other.

[0080] 13. The apparatus of any preceding or following embodiment,wherein the upper member of the planar panels comprises: a toppanel layer; a resilient lower panel layer; and a plurality ofdiamond-shaped flexures disposed between the top panel layer andthe lower panel layer.

[0081] 14. The apparatus of any preceding or following embodiment,wherein the base member of the planar panels further comprises: alinear outer edge configured for mounting to the support substrate;and an inner edge with triangular shaped rigid bodies spacedregularly along the inner edge of the base member; and pairs oflegs flexibly coupled at one end to the inner edge of the basemember between the triangular shaped rigid bodies with resilienthinges; wherein movement of the legs is limited by the triangularshaped rigid bodies.

[0082] 15. The apparatus of any preceding or followingembodiment:

[0083] wherein the plurality of panels comprises a plurality offirst panels and a plurality of second panels; wherein the firstpanels configured with an offset that is out of phase from thesecond panels; and wherein the plurality of panels is configuredsuch that the first and second panels are positioned in asequentially alternating pattern.

[0084] 16. The apparatus of any preceding or following embodiment,wherein the top layer comprises a foam pad with periodicallypositioned holes through the pad, the holes configured for aircirculation through the top layer.

[0085] 17. The apparatus of any preceding or following embodiment,wherein the top layer comprises a foam pad made from a materialselected from the group of materials consisting of memory foam andfoam rubber.

[0086] 18. A multi-stable compliant-mechanism mattress apparatus,comprising: a top layer comprising a foam pad with periodicallypositioned holes through the pad, the holes configured for aircirculation through the top layer; a grid of straps beneath the toplayer the straps configured for air circulation through the toplayer; a plurality of horizontal compliant panels beneath the gridof straps, the grid of straps providing support for the panels, theplurality of panels forming a compliant web; and a supportsubstrate beneath the panels; wherein the compliant web isconfigured to move between first and second stable positions inresponse to application of horizontal force.

[0087] 19. The apparatus of any preceding or following embodiment:wherein each panel in the plurality of panels comprises a singleplanar component; wherein the plurality of panels comprises aplurality of first panels and a plurality of second panels; whereinthe first panels are configured with an offset that is out of phasefrom the second panels; and wherein the plurality of panels isconfigured such that the first and second panels are positioned ina sequentially alternating pattern.

[0088] 20. The apparatus of any preceding or followingembodiment:

[0089] wherein each panel in the plurality of panels comprises aseries of trapezoid-shaped four-bar mechanisms; and wherein eachbar in the four-bar mechanisms is joined to the panel by compliantjoints that deform under load to produce an undulating pattern.

[0090] 21. The apparatus of any preceding or following embodiment,further comprising a plurality of diamond-shaped flexurespositioned adjacent the four-bar mechanisms and configured forsmoothing the undulations.

[0091] As used herein, the singular terms "a," "an," and "the" mayinclude plural referents unless the context clearly dictatesotherwise. Reference to an object in the singular is not intendedto mean "one and only one" unless explicitly so stated, but rather"one or more."

[0092] As used herein, the term "set" refers to a collection of oneor more objects. Thus, for example, a set of objects can include asingle object or multiple objects.

[0093] As used herein, the terms "substantially" and "about" areused to describe and account for small variations. When used inconjunction with an event or circumstance, the terms can refer toinstances in which the event or circumstance occurs precisely aswell as instances in which the event or circumstance occurs to aclose approximation. When used in conjunction with a numericalvalue, the terms can refer to a range of variation of less than orequal to .+-.10% of that numerical value, such as less than orequal to .+-.5%, less than or equal to .+-.4%, less than or equalto .+-.3%, less than or equal to .+-.2%, less than or equal to.+-.1%, less than or equal to .+-.0.5%, less than or equal to.+-.0.1%, or less than or equal to .+-.0.05%. For example,"substantially" aligned can refer to a range of angular variationof less than or equal to .+-.10.degree., such as less than or equalto .+-.5.degree., less than or equal to .+-.4.degree., less than orequal to .+-.3.degree., less than or equal to .+-.2.degree., lessthan or equal to .+-.1.degree., less than or equal to.+-.0.5.degree., less than or equal to .+-.0.1.degree., or lessthan or equal to .+-.0.05.degree..

[0094] Additionally, amounts, ratios, and other numerical valuesmay sometimes be presented herein in a range format. It is to beunderstood that such range format is used for convenience andbrevity and should be understood flexibly to include numericalvalues explicitly specified as limits of a range, but also toinclude all individual numerical values or sub-ranges encompassedwithin that range as if each numerical value and sub-range isexplicitly specified. For example, a ratio in the range of about 1to about 200 should be understood to include the explicitly recitedlimits of about 1 and about 200, but also to include individualratios such as about 2, about 3, and about 4, and sub-ranges suchas about 10 to about 50, about 20 to about 100, and so forth.

[0095] Although the description herein contains many details, theseshould not be construed as limiting the scope of the disclosure butas merely providing illustrations of some of the presentlypreferred embodiments. Therefore, it will be appreciated that thescope of the disclosure fully encompasses other embodiments whichmay become obvious to those skilled in the art.

[0096] All structural and functional equivalents to the elements ofthe disclosed embodiments that are known to those of ordinary skillin the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Furthermore, noelement, component, or method step in the present disclosure isintended to be dedicated to the public regardless of whether theelement, component, or method step is explicitly recited in theclaims. No claim element herein is to be construed as a "means plusfunction" element unless the element is expressly recited using thephrase "means for". No claim element herein is to be construed as a"step plus function" element unless the element is expresslyrecited using the phrase "step for".

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