GB2528967A

GB2528967A - Cycloidal vibration support structure, mattress and cushion

Info

Publication number: GB2528967A
Application number: GB1414052.9A
Authority: GB
Inventors: Philip Ellin
Original assignee: Vibrant Medical Ltd
Current assignee: Vibrant Medical Ltd
Priority date: 2014-08-07
Filing date: 2014-08-07
Publication date: 2016-02-10
Also published as: GB201414052D0

Abstract

A support structure for a patient at risk of pressure ulcers comprises a first vibration motor 16 disposed within a housing, a first flexible sheet frame 12 connected to said housing, and a first layer of resiliently deformable plastics material foam 14 bonded to a first surface of said sheet frame 12. The support structure may be used with, or incorporated in, a mattress or cushion on which a patient lies or sits. The mattress or cushion may have pressure relief features such as a castellated surface or a pneumatically operated alternating pressure inflatable cells 42. The sheet frame 12 can be solid or a metal lattice and can have a hinge. The motor 16 may produce cycloidal vibrations and have control means to allow it to operate at specified intervals. A plurality of motors 16 and sheets 12 may be used and may be positioned near high risk areas of a mattress. The device is designed to help prevent pressure ulcers.

Description

Cycloidal Vibration Support Structure, Mattress and Cushion [0001] This invention relates to a cycloidal vibration support structure. Embodiments of the invention relate to a support structure for a patient at risk of pressure ulcers, and a treatment mattress for pressure relief.

BACKGROUND

[0002] Pressure ulcers, also known as decubitus ulcers or bed sores, are caused by continuous pressure at a specific part of the body of an immobile patient.

[0003] Around 412,000 people in the UK are likely to develop a pressure ulcer every year ([1] Bennett et al, 2004), including 4-10% of patients admitted to hospital ([2] RON, 2005).

An estimated 31% of pressure ulcers are severe, category Ill or IV, ulcers ([3] Posnett et al, 2009). Development of a pressure ulcer carries a 2-4 times increased risk of mortality for elderly patients in intensive care ([2] RON, 2005).

[0004] In addition to the significant effects on patient morbidity and mortality, pressure ulcers also cause significant economic costs. Overall in the UK up to £4billion, which is equivalent to 4% of the NHS budget, is spent treating pressure ulcers and their related conditions annually, with costs for the most severe cases ranging from £11,000 to £40,000, depending on the complications.

[0005] Daily costs for a patient with a pressure ulcer are estimated to be between £38 an £196, with nursing and health-care assistant time accounting for almost 90% of this. The costs are correspondingly higher for more severe pressure ulcers, which often affect individuals with pre-existing health problems who usually have more complex requirements. Although the figures above are for the UK, similar problems exist throughout the world.

[0006] Pressure is a major contributor to the development of pressure ulcers. If sufficiently high, pressure may reduce blood flow to tissues, and cause direct damage to cells and tissues. For a healthy individual, the reduction in blood flow causes the individual to change position to relieve the pressure on the affected area, thereby allowing blood to flow again. However, if the pressure is not relieved for some reason, eg the individual is unable to move or has a loss of sensory function, the reduction in blood flow can damage skin and soft tissues. This damage may cause a pressure ulcer. It is known to produce mattresses that at least temporarily reduce the pressure applied to a patient lying on the mattress, either by providing a castellated foam surface that allows the patient to sink into the mattress, thereby increasing the contact area between the patient and the mattress and reducing localised pressure on the patient, or by providing a surface comprising a plurality of inflatable cells that are cyclically inflated and deflated, thereby providing pressure relief to parts of the patient's body that are supported by the deflated cells.

[0007] In addition to pressure, tissue damage may occur when shear forces applied to the skin are increased. For example, shear may be increased when a patient slips down a bed or during repositioning. The friction between the patient and the support surface tends to hold the skin in place while deeper tissues are moved. This is an insipid, rather than a sudden, process, where the skin is gradually stretched and tightened as a patient slips in their position. This can reduce blood flow and damage tissues by crimping or closing blood vessels ([4] International Review, 2010).

(0008] It is known that vibration can assist in preventing the development of such sores.

US-5606754-A suggests a bed which has vibration means to reduce the incidence of bed sores.

(0009] Prior art beds that include vibration means may comprise a robust metal frame to attach the vibration means, for example a vibrating motor, to the bed. Such a metal frame must be suitable for transmitting the vibrations produced by the vibration means to the rest of the bed, and therefore the patient, whilst not being damaged by the vibrations.

(0010] Studies have shown that the non-invasive application of sinusoidal vibration therapy to skin tissue can increase blood flow. The transmission of these vibrations into the tissues generates a range of mechanical forces and stresses on vascular endothelial cells, resulting in a vasodilatory response by enzyme nitric oxide synthase (eNOS), which stimulates production of nitric oxide (NO). Increases in blood flow have been demonstrated in in vivo circulatory models studying the effect of vibration.

(0011] Vascular produced NO by enzyme nitric oxide synthase is an important vasodilator to regulate vascular smooth muscle tone and retain healthy blood flow. NO also has a role in the endocrine and paracrine systems, including inhibition of platelet adhesion and aggregation; suppression of inflammatory mediators; inhibition of smooth muscle proliferation and migration; and promotion of endothelial survival and repair.

BRIEF SUMMARY OF THE DISCLOSURE

(0012] In accordance with the present inventions there is provided a support structure as defined in the claims. A support structure for a patient at risk of pressure ulcers may comprise a first vibration motor disposed within a housing; a first flexible sheet frame connected to said housing; and a first layer of resiliently deformable plastics material foam bonded to a first surface of said sheet frame.

(0013] The support structure may be used with, or incorporated in, a mattress or cushion on which a patient lies or sits (on a bed or chair structure). The mattress or cushion may have pressure relief features such as a castellated surface or a pneumatically operated alternating pressure construction.

[0014] At least part of said housing may be integrally formed with said sheet frame, or wherein at least part of said housing may be formed as a single unitary pad with said sheet frame. The structure may further comprise a second layer of resiliently deformable plastics material foam bonded to a second surface of said sheet frame, said second surface being opposite to said first surface, whereby said sheet frame is sandwiched between said first and second layers of foam.

[0015] The first layer of foam may comprise castellations in a surface thereof, which itself provides pressure relief to a patient lying or sitting directly on the structuyre.

[0016] Said sheet frame may comprises a solid plastics sheet having a thickness between 0.25mm and 2.5mm, or a plastics or metal lattice or mesh having a thickness between 0.25mm and 2.5mm. The sheet frame may incorporate at least one hinge. In that way, a mattress may be capable of adjustment in its disposition from a flat bed to an elevated arrangement to facilitate sitting and or raised legs of a person on the mattress.

[0017] The support structure may comprise a mattress. The vibration motor may be arranged to produce cycloidal vibrations. Control hardware may be provided, in communication with the vibration motor, the control hardware being configurable to initiate and terminate operation of the vibration motor at user selectable time intervals, thereby providing vibration therapy to a patient resting on the support structure.

[0018] In invention provides a mattress comprising a support structure as defined above.

The mattress may comprise a second flexible sheet frame connected to either the first vibration motor or a second vibration motor, in which case there are two of said support structures.

[0019] Conveniently, at least one of said first and second sheet frames are disposed under a portion of a surface of the mattress upon which one of the heels, the sacral area and the shoulders of an average adult patient lying upon the mattress would be likely to rest.

[0020] A pneumatic alternating pressure mattress may be disposed on said support structure, said pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated. Control hardware may be provided in communication with said vibration motor and said pneumatically inflatable cells, said control hardware being configured to provide intermittent pressure relief to a patient lying on the mattress by cyclically inflating and deflating said cells and vibration therapy by periodically activating said vibration motor.

[0021] The control hardware may be configured to initiate vibration therapy in response to the inflation or deflation of one of said groups of cells.

[0022] In one arrangement, the motor of the support structure is disposed outside of a contact area of the mattress. In this event, the mattress can be thinner than would be necessary to avoid an average person contacting (that is, feeling the presence of) the motor through the thickness of the mattress, and whether or not the motor is operating.

[0023] The invention also provides a cushion comprising a support structure as defined above. Likewise, the cushions may further comprise a pneumatic alternating pressure overlay disposed adjacent to said first layer of foam, said pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated. Also like the mattress, the motor of the support structure may be disposed outside of a contact area of the cushion.

The contact area of a cushion or mattress is the area of the top surface of the cushion or mattress that a typical adult will cover when sitting or lying thereon.

[0024] Thus a modular, cycloidal (sinusoidal) vibration motor module, its controls, and flexible sheet frame system to which is bonded a foam or like material layer which can be integrated in either upholstered or moulded surfaces. This structure can be aftached to standard production furniture framework e.g. a bed, chair or couch. In doing so this converts the standard furniture into a product capable of transmitting cycloidal, sinusoidal vibration across its contact surface area. This transforms product into a cycloidal vibration therapy product.

[0025] Cycloidal vibration therapy within the frequency range specified has been shown to stimulate circulation, reduce muscle tension and reduce pain via counter stimulation.

These resulting effects have been shown to treat and or relieve the symptoms of a range of clinical conditions.

[0026] The product may be incorporated inside a seat cushion, back rest and/or a foot stool, or other forms of seating. It may be incorporated inside a bed base or a mattress or a couch.

[0027] A suitable motor and housing construction is disclosed in our co-pending application filed contemporaneously herewith (under the title Cycloidal Vibration Motor Module Construction"). An extract of that application is in the Appendix hereto and is to be

read in conjunction with the present disclosure.

[0028] The invention also provides a treatment mattress to alleviate pressure ulcers comprising a pressure relief mattress and a vibration therapy support structure having a first vibration motor disposed within a housing and a flexible sheet frame connected to said housing and on which said pressure relief mattress is supported.

[0029] The pressure relief mattress may be one comprising a castellated foam structure, or a pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated.

[0030] The vibration therapy support structure may further comprise a layer of resiliently deformable plastics material foam bonded to a first surface of said sheet frame. The sheet frame may have a second surface opposite first surface and said pressure relief mattress is supported on said second surface of said sheet frame. A layer of resiliently deformable plastics material foam may bonded to said second surface of said sheet frame. The layers of foam may have different functions. For example, one layer may be provided to isolate the sheet frame from a support structure such as a bed frame. However, this is not necessary if the bed frame itself has an isolating surface such as an existing mattress.

Also, one layer may be provided to ensure transmission of vibrations from the sheet frame into the pressure relief mattress, thereby avoiding the sheet frame merely slipping under the pressure relief mattress without significant transfer of vibration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is a cross section of a vibrating support structure incorporating a vibration unit according to an embodiment of the present invention; Figure 2 is a cross section of a vibrating mattress incorporating a vibration unit according to an embodiment of the present invention; Figure 3 is a plan view of a vibrating mattress incorporating a vibration unit according to another embodiment of the present invention; Figure 4 is an alternating pressure mattress incorporating a vibration unit according to an embodiment of the present invention; and Figure 5 is a seat cushion incorporating a vibration unit according to an embodiment of the present invention.

Figures Al to A7 are referenced below in the Appendix hereto.

DETAILED DESCRIPTION

[0032] Figure 1 shows a cross section of a vibrating support structure 10 in an embodiment of the present invention. Support structure 10 may be used in the prevention and treatment of pressure ulcers, for example by using the support structure as part of a mattress or a cushion and delivering vibrations to a patient resting on the mattress or cushion.

[0033] Support structure 10 comprises a flexible plastics or metallic sheet frame 12 bonded to a layer of foam 14. Vibration motor 16 is attached to sheet frame 12 via housing 18. In the illustrated embodiment housing 18 includes a plurality of connection lugs 20 (only one being shown), which connection lugs facilitate connection of housing 18 to frame 12 via L shaped connectors 22 and bolts 24. However, the skilled person will understand that any means of connecting housing 18 to frame 12 that results in a sufficiently rigid attachment between the housing and the frame for vibrations to be transmitted from the housing to the frame would be suitable. In some embodiments, the frame 12 and at least part of housing 18 may be integrally formed from two or more pads that are permanently joined together, or formed a single unitary part. Furthermore, a single vibration motor 16 may be attached to more than one sheet frame 12, for example by means of a plurality of L-shaped connectors 22 connected to a single housing 18. Of course, multiple connections are not limited to L-shaped connectors and straight connectors or connectors turned through other than right angles are also feasible.

[0034] Vibration motor 16 may be a conventional AC or DC vibration motor, for example a 12V or 24V DC motor having an eccentric weight disposed on the output shaft thereof.

Rings 26, which may be formed from rubber or another resilient material, are disposed in the gap between the vibration motor 16 and housing 18 to transmit vibrations from the motor to the housing without causing excessive wear to the motor or the housing.

[0035] Foam 14 may be bonded to sheet frame 12 using adhesive or any other suitable bonding technique. Although the embodiment shown in Figure 1 shows foam 14 only bonded to one side of sheet frame 12, in some embodiments a layer of foam 14 is bonded to both sides of sheet frame 12, whereby frame 12 is sandwiched between layers of foam 14.

[0036] Support structure 10 may be utilised as part of a mattress or cushion, with surface 14a of foam 14 providing a surface for a patient to rest upon. Accordingly, the thickness and stiffness of foam 14 must be chosen so that the compression of foam 14 that occurs when an average sized adult patient rests upon foam 14 is not sufficient to cause bottoming out", in which the gap between the upper surface 14a and sheet frame 12 is locally reduced to an extend sufficient to make foam 14 firm and uncomfortable around the locally compressed region. A suitable depth of layer of foam 14 may be between 5 and 30cm, preferably between 10 and 25cm. Furthermore, foam 14 may comprise two or more layers of foam having different stiffnesses and/or thicknesses.

[0037] Surface 14a may comprise castellations to reduce the pressure between the surface and a patient resting on it. Such castellations may comprise a plurality of grooves cut in two mutually perpendicular directions orthogonal to surface 14a, thereby separating surface 14 into a plurality of islands of quadrilateral cross section. Castellations may reduce the pressure between surface 14a and a patient resting upon it by reducing the tension on surface 14a, thereby allowing the patient to sink further into the layer of foam 14 and increasing the contact area between the patient and the mattress. Furthermore, by virtue of the vibration, any tendency of a surface adjacent to the skin of a patient to grip and stretch the skin as a patient slips and gradually changes position is minimised.

Instead, the skin is encouraged to slip, reducing localised shear effects on the patient's body.

[0038] Figure 2 shows a cross section of a mattress 30 having a foot end 32 and a head end 34 according to an embodiment of the present invention. Mattress 30 comprises two flexible sheet frames 12A, 12B bonded to first and second layers of foam 14', 14". Each sheet frame is attached to a vibration motor 16, using attachment means as described in relation to Figure 1. Vibration motors 16 may be disposed within cavities in second layer of foam 14", or they may be disposed outside of the mattress 14". Each vibration motor 16 may be independently controlled, thereby allowing the mattress to selectively provide vibration to the area of the patient's body resting upon the area supported by each of the two sheet frames 12A, 12B. In the embodiment illustrated in Figure 2 the mattress 30 is intended to support a patient lying with their head near to head end 34 and their feet near to foot end 32, so that the area above sheet frame 12A supports the patient's heels and lower leg, and the area above sheet frame 12B supports the sacral area of the patient.

This allows mattress 30 to selectively deliver vibration therapy to the heels and sacral area, without delivering significant vibrations to the rest of the body. It may be especially important to deliver vibrations to the heels and sacral areas, as these areas are critical pressure points at which pressure ulcers most frequently develop. Other embodiments may include additional frames at different locations, for example under the region of the surface on which a patient's shoulders are likely to rest.

[0039] The mattress may be used to deliver local vibration therapy to the heels and sacral areas to treat or prevent pressure ulcers at these locations. Such vibration therapy may, for example, comprise vibration in the frequency range 15-75Hz with amplitude of between 0.1-2mm applied to the target area in individual vibration sessions lasting between 5 minutes and 1 hour, preferably between 20 and 30 minutes. Between 1 and 10 vibration sessions, for example three vibration sessions, may be performed per day. The mattress 30 may further comprise control hardware in communication with vibration motors 16, the control hardware being configured to initiate vibration sessions at predetermined or user selectable times in which the vibration sessions may provide predetermined or user selectable vibrations to a patient for a predetermined or user selectable time period.

[0040] The skilled person will understand that the specification of the vibration motor and control hardware required to produce vibrations of the required frequency will depend upon the specific configuration of the mattress. Selection of a suitable vibration motor is a matter of routine engineering that is within the capability of the skilled person, and is therefore not described in further detail here.

[0041] First and second layers of foam 14', 14" may each comprise several layers of foam of different grades. For example, first layer of foam 14', which may be configured to provide a comfortable surface for a patient to lie on, may comprise a layer of relatively stiff foam bonded to sheet frames 12A,12B and a layer of less stiff foam attached to the relatively stiff layer on a side opposite the side bonded to sheet frames 12A,12B. In this way layer of foam 14' provides a soft upper surface that allows a patient to sink into the mattress 30, thereby increasing the contact area between the patient and the mattress, but the relatively stiff layer of foam prevents bottoming out. For mattresses according to the present invention bottoming out may be considered to occur when the gap between upper surface 14a and sheet frames 12 becomes small enough that the apparent stiffness of the mattress locally approaches that of sheet frame 12. In other embodiments, each of first and second layers of foam 14', 14" comprise a single layer of foam, and the thickness and stiffness of layer of foam 14' are selected to prevent bottoming out. In any event, castellations may be provided in layer of foam 14' to allow the patient to sink further into the mattress 30.

[0042] In the embodiment illustrated in Figure 2 second layer of foam 14" is provided with V shaped cutaways 36, which cutaways allow the mattress 30 to be bent in the region of the cutaways. This allows a suitable bed to bend the mattress, for example to bring a patient lying upon it into a sitting position. Sheet frames 12 may be sufficiently flexible to allow the mattress to be bent into a sitting position, or they may include hinges in the region of the V shaped cutaways 36. A suitable plastics frame may comprise a solid plastics sheet, a plastics lattice or a plastics mesh, having a thickness of between 0.25mm and 2.5mm. Likewise, the sheet frame could be metal, for example, stainless steel between 0.25mm and 1 mm thick, welded or riveted into a lattice frame, and, again, having the option to bend at pivot points.

[0043] Figure 3 shows a plan view of a mattress in another embodiment of the present invention, showing the positions of plastics frames 12 and vibration motors 16 within mattress 30. Similar to the embodiment shown in Figure 2, plastics frames 12A, 12B are located underneath or within portions of the mattress 30 that would be expected to support, respectively, the heels and the sacral area of an average adult patient lying on the mattress. However, in the embodiment shown in Figure 3 both of plastics frames 12A, 12B are split into two separate plastics frames attached to a common vibration motor 16.

This arrangement may allow the motor 16 to be disposed relatively centrally in each of plastics frames 12A, 12B, thereby providing more uniform vibration throughout plastics frames 12A, 12B.

[0044] Figure 4 shows a mattress 50 in a further embodiment of the present invention.

Mattress 50 comprises a pneumatic alternating pressure mattress 38 having a plurality of inflatable cells 42 that are split into at least two different groups, which groups are configured to be cyclically inflated and deflated to provide intermittent pressure relief to a patient lying on top of alternating pressure mattress 38. The manufacture and control of alternating pressure mattresses is well known to those skilled in the art, and it is accordingly not described in detail here.

[0045] Alternating pressure mattress 38 is disposed on top of an underlay comprising a first layer of foam 14', which layer of foam is bonded to plastics frames 12A, 12B that are themselves connected to vibration motors 16. A second layer of foam 14" is also provided to secure the rest of the arrangement and prevent vibrations from vibration motors 16 causing the mattress 40 to wear against a support surface (not shown).

[0046] The arrangement shown in Figure 4 provides a mattress that improves circulation to the skin in patients at risk of pressure ulcers by providing both intermittent pressure relief and vibration therapy. The combination of vibration therapy and intermittent pressure relief may significantly increase blood flow near the skin of a patient, thereby significantly reducing the risk of pressure ulcers, and encouraging healing of any pre-existing pressure ulcers. Indeed, the synergistic effects of intermittent pressure relief and vibration therapy may provide protection against pressure ulcers that is greater than the summative effects of pressure relief alone and vibration therapy alone. The same effect may be experienced with the castellated pressure relief mattress described above.

[0047] It would also be feasible to invert the arrangement of Figure 4 and dispense with the foam layer 14", whereby the alternating pressure mattress 38 is supported directly on the plastics sheets 12A,B, with the foam layer 14' resting on the bed structure (not shown).

(Indeed, this is equivalent simply to dispensing with the layer 14' in Figure 4.) [0048] The thickness of the layer 14" in Figure 4 should be sufficient that the motors 16 do not bottom out on the bed structure and thereby press into the mattress cells 42 and potentially be felt" directly by a patient on the bed.

[0049] When used with a pneumatic alternating pressure mattress system, a support structure in accordance with the present invention may be an additional device that will sit under a standard alternating pressure mattress, between the bed base and the alternating pressure mattress, that is, as an accessory or addition to the alternating pressure mattress. In this event, the foam layer is seated on the bed base to isolate the vibrating frame and motor from the bed base. Alternatively, the structure can be an integrated layer that can form part of an alternating pressure mattress.

[0050] The vibration motor 16 and the valves and compressors (not shown) that control the inflation and deflation of cells 42 may share common control hardware. Furthermore, the timing of the vibration sessions may be determined in dependence on the timing of the inflation and deflation of the cells 42. For example, vibration sessions may be performed immediately after the group of cells that is inflated has been changed, to enhance the effect of pressure relief on blood flow in the region in which pressure relief has been provided.

[0051] Figure 5 shows a cushion 40 in an embodiment of the present invention. Such a cushion may be incorporated into the seat of a wheelchair, or a similar chair in which a patient of limited mobility may be expected to spend extended periods of time. The cushion 40 incorporates a vibration unit comprising a motor 16 connected to a flexible plastics frame 12, to provide vibrations to an occupant sitting on surface 14a through first layer of foam 14'. Cushion 40 may further comprise control hardware in communication with vibration motor 16, so as to provide vibration therapy to treat or prevent pressure ulcers for the patient sitting on cushion 40. The control hardware for cushion 40 may be similar to that described in relation to the mattresses of the present invention.

Furthermore, although this is not shown in Figure 5, the cushion of the present invention may incorporate an alternating pressure overlay similar to alternating pressure mattress 38, thereby enabling a combination of cyclic pressure relief and vibration therapy to be delivered to a patient sitting on the cushion.

[0052] An aspect of the present invention may be that the support structure can be entirely separate from the frame of a bed or chair in which it is disposed. This has several potential effects. The first is that the vibration is essentially isolated from the bed or chair so that its vibrations are not transmitted to the bed or chair. Not only does that mean that energy is not wasted in vibrating such frames, but also disturbance to external environment is minimised. That is, while the vibration is occurring, it is not felt, or is felt to a lesser extent, by others sharing the room with the patient in which the bed or chair is located. This also means that the motor driving the vibrations can be reduced in size without impacting the strength of vibration experienced by the patient.

[0053] Another aspect, which is evident in Figure 5 but which is not limited to cushions or the like and may be applied to bed mattresses also, is that the motor 16 can be disposed with respect to the suiface being lain or sat upon by the person concerned outside the contact area (being that area on which the person tends to lie or sit) so that the possibility of the person detecting the presence of the motor (other than through the vibrations it creates) is excluded, or at least reduced. This means, as regards the embodiments of Figures 2 to 4, that the mattress or cushion need not be so thick or firm that the person lying on the mattress cannot detect the presence of the motor 16 through the softness of the mattress of the mattress above it. This is of course a reasonably necessary requirement of the arrangements of Figures 2 to 4.

[0054] Throughout the description and claims of this specification, the words comprise" and contain" and variations of them mean including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0055] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments.

The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0056] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

REFERENCES

[1] GERRY BENNETT, CAROL DEALEY, JOHN POSNETT; The cost of pressure ulcers in the UK, Age and Ageing 2004; 33: 230-235 [2] The management of pressure ulcers in primary and secondary care: a clinical practice guideline. RCN clinical guideline. September2005 [3] PosnettJ et al., The resource impact of wounds on health-care providers in Europe, a flexible way to prevent pressure ulcers, Wounds UK, Vol 5, No 4, 2009 [4] PRESSURE ULCER PREVENTION pressure, shear, friction and microclimate in context. A consensus document. Wounds International 2010.

APPENDIX

In accordance with the invention claimed in the above-referenced copending patent application (having the title "Cycloidal Vibration Motor Module Construction") there is provided a cycloidal vibration motor module comprising: a motor, having a substantially cylindrical body terminated at each end by an end cap, the end caps each mounting a bearing supporting an armature of the motor on an armature shaft extending through the end caps and having a fan and an eccentric weight mounted at each end of the shaft outside said end caps a pair of clamshell housings mated together; a plurality elastomeric rings around the motor clamped between the motor and clamshell housings; wherein the clamshell housings define a plurality of lugs comprising slots suitable for receipt of an apertured sheet metal connector of a frame and having cross bores through which a fastener is receivable to clamp said metal connector.

[0057] The construction provides an efficient transfer of the imbalance caused by the eccentric weights into the end caps of the motor and thence into the clamshell housings through the elastomeric rings and into a frame connected to the lugs. There is a minimum of energy loss, and yet little opportunity for undesirable noise.

[0058] The lugs may be defined by two lug-halves, one lug-halve being disposed on each clamshell housing and defining the lug when the clamshell housings are mated together. Each lug halve may comprise a plate including said cross bore and fillets between each side edge of said plate and the body of the clamshell. Said plate may be stepped, whereby said slot is formed when the clamshell housings are mated. Optionally, there are four lugs.

[0059] Optionally, the module further comprises a frame attached to at least two of said lugs, where the frame comprises apertured sheet metal connectors, each connector having a bore, and a flexible plastics or metallic sheet to which said connectors are attached. Said connectors may be part of an integral connector unit.

[0060] Said connector may be connected to each of said two axially outwardly directed lugs extending from the substantially circular ends of the cylindrical housing and to one of the radially outwardly directed lugs from the cylindrical surface of the cylindrical housing.

[0061] The integral connector unit is [-shaped in one embodiment, whereby the motor module is substantially outside the plane of the sheet attached to the connector unit [0062] The clamshell housings when mated may define a substantially cylindrical housing. In the case of four lugs, two of the four lugs may be radially outwardly directed from the cylindrical surface of the cylindrical housing and other two lugs may be axially outwardly directed from substantially circular ends of the cylindrical housing.

[0063] Said elastomeric rings may be disposed between said end caps and the clamshell housings. Optionally, one of said end caps and said rings comprise a first circumferential ridge and the other comprises a first circumferential groove to receive the first circumferential groove and retain the ring axially with respect to said body. [ikewise optionally, one of said clamshell housings and said rings comprises a second circumferential ridge and the other comprises a second circumferential groove to receive the second circumferential ridge and retain the ring axially with respect to said clamshell housings. In that way, the rings are securely located between the clamshells and motor and likewise positions the motor securely within the clamshells so that it is spaced therefrom but able to transmit the vibrations smoothly without raftling.

[0064] Said end caps and said clamshell housings may comprise windows to permit flow of air generated by rotation of the fans. The windows in the clamshell housings are optionally disposed in the substantially circular ends of the cylindrical housing.

[0065] The cylindrical body of the motor may be cup-shaped, having a base at one end and an open end at the other, wherein a central boss is formed on the base through which the armature shaft extends and on which a base end cap of the end caps is seated to locate the end cap, and hence the bearing, being a base-end bearing, and armature shaft, radially with respect to motor body.

[0066] A brush end cap of the end caps may be received in the open end of the body and comprise a plurality of collar bosses received in the open end and locating end cap, and hence the bearing, being an open-end bearing, and armature shaft, radially with respect to motor body. There may be two collar bosses, each receiving a brush bearing against a commutator on the armature shaft.

[0067] The brush end cap may have a body side and an outside, wherein each brush comprises an element having a terminal end and an orthogonal leg, and wherein a spring arm mounting a brush body is secured to the element intermediate its terminal end and orthogonal leg, the terminal end being received in a slot through the brush end cap and being electrically connected to a circuit board on the outside of the brush end cap. The terminal end may be apertured and receive a plug fitted in the end of the collar boss and retaining the brush in position.

(0068] Optionally, a U-shaped earth wire has a terminal limb and a contact limb, the terminal limb passing through a hole in the brush end cap and being electrically connected to said circuit board on the outside of the brush end cap, the contact limb being received in an edge slot of the brush end cap and bearing against the motor body to electrically connect the motor body with the circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS (APPENDIX)

(0069] Embodiments of the invention referenced by the present Appendix are further described hereinafter with reference to the accompanying drawings, in which: Figure Al is a perspective exploded view of a motor module according to an embodiment of the present invention; Figures A2a and A2b are respectively a plan view and an end view of an assembled motor module as shown in Figure Al; Figure A3 is a perspective exploded view of the motor of Figure Al; Figure A4 is a side view of the motor; Figure A5 is a section on the line A-A in Figure A2b; Figures A6 (a) to (d) are respectively a perspective view (exploded) perspective view (assembled), end view and side view of a brush end cap of the motor of Figure A3 Figure A7a to A7c are respectively a side section and an end view (in the direction of the Arrow B in Figure A7a) of the brush end cap body of the end cap of Figure A6, and a partly exploded perspective view of the brush assembly of the end cap of Figure A6; and Figures A8a and b show respectively a section and a side view in the direction of the Arrow B in Figure ABa of a module including a frame in one connection arrangement..

DETAILED DESCRIPTION (APPENDIX)

[0070] In the following description, references to Figure numbers are references to the corresponding Figure number preceded by the prefix A in the accompanying drawings.

Likewise, the following reference numerals are with reference to those drawings.

[0071] Figures 1, 2 and 5 (that is, Figures Al, A2 and A5) show a motor module 10 that comprises top and bottom shell housings 12,14 and motor 16. Motor 16 has a substantially cup-shaped metal body 18 to which end caps 20,22 are fixed, one a cup base end cap 20, and the other a brush end cap 22. The end caps support an armature shaft on the ends of which, outside the motor body 18 and end caps 20,22, are mounted fans 24a,b. The fans include a weight 26, integrally formed with blades 28 of the fans, so that the centre of mass of the fans is eccentric with respect to the rotation axis defined by the armature shaft 25. The fans are retained on the shaft 25 by grub screws 30 through the weights, the screws impinging on flats 27 provided on the ends of the shaft 25 which ensure alignment of the weights. The weights may be varied, as also can their effective distances eccentricity with respect to the rotation axis, whereby the degree and strength of vibrations created by the motor can be adjusted as desired. For example, where it is necessary to transmit the vibrations through a relatively great distance or through soft, resilient and/or vibration-damping material, it will be preferred to use heavier weights (eg in the region of 60g) whereas weights in the region of 20g may be used where less vibration is required. Of course, the less vibration that is required, the longer lasting will be the overall construction.

[0072] Around each end cap 20,22 is disposed a circumferential ridge 32 on which is retained a rubber/elastomer ring 34, provided with both a corresponding groove 36 to sit on the ridge 32 and a corresponding circumferential ridge 38 adapted to seat in corresponding grooves 40 formed inside the shell housings 12,14. When the housings are closed and clamped together around the motor 16 using eight set screws 42, the rings 34 are compressed, firmly securing and locating the motor inside the housing.

[0073] When the armature shaft 25 of the motor 16 rotates, the weights 26, being eccentric, cause the motor to vibrate, with a frequency equal to the speed of rotation of the shaft (between about 15 and 75 Hz). These vibrations need to be transmitted effectively to the housing 12,14, but not so as to create noise through direct intermittent contact of the end caps 20,22 and/or body 18 with the housings 12,14. The rings 34 provide this assurance by separating the motor from the housings, but nevertheless inter-connecting them through a resilient mounting that serves to transmit the vibrations of the motor to the housing both without noise and without significant damping of the vibrations.

[0074] Turning to Figures 3, 4 and 5, motor body 18 is a cup-shaped can, open at one end 18, but closed at the other end 1 8b except for a central boss 44 that is located in a corresponding recess 46 in the base end cap 20. The end cap is secured to the can body base 18b by screws 48. The motor is assembled by first securing the base end cap 20 to the can body 18 around the boss 44. Then, a first bearing 54 is pressed into a seat 56 of the base end cap 20. End caps 20,22 are hard plastics material injection moulded components, for example, from nylon or the like. Fans 24a,b each have a spigot 27, which is then pressed into an inner race of the bearing 54.

[0075] A second fan 24a and bearing 54 is then assembled and pressed into similar recess 56' of the brush end cap assembly 22. The motor comprises an armature 50, mounted on the shaft 25. The armature has a commutator 52 and engagement of the armature with the brush end cap 22 involves positioning of motor brushes 70 (described further below) with the commutator 52. The armature shaft 25 is a close sliding fit in the spigot 27 of the fan 24a. It plastics sleeve 29 that abuts the spigot 27, limiting insertion of the shaft 25 in the spigot. The motor armature is then secured axially with respect to the brush end cap 22 by the grub screw 30 in the fan 24a.

[0076] That assembly is then inserted into the open end 1 Ba of the cup body 18, collar bosses 58 being a close sliding fit in the opening, locating the brush end cap 20, and hence the armature centrally with respect to the body 18. At the same time, the other end of the shaft 25 is passed through the boss 44 of the body end 18b and recess 46 of brush end cap 20 and inserted in a close sliding fit through the spigot 27 of the fan 24b, and again secured thereto by grub screw 30 in the fan 24b.

[0077] Permanent magnets are located in the can body 18 and interact with the armature in the usual way of a permanent magnet motor. However, the invention is not predicated on the type of motor employed.

[0078] Turning to Figures 6(a) to (d) and 7a, b and c, brush end cap 22 is itself an assembly comprising the end cap body 22, brushes 70, and suppression and electrical connection board 80.

[0079] As described above, brush end cap 22 comprises central recess 56' to receive bearing 54 that supports the spigot 27 of fan 24a. Externally of the recess 56' are the collar bosses 58, further bosses 58a, and circumferential ridge 32. Windows 90 are disposed between to allow cooling airflow through the motor generated by the fans 24a,b.

(Similar windows are in the base end cap 20, but are not shown or described further.) [0080] Through the collar bosses 58a is formed a slot 72, adapted to receive the terminal 74 of brush 70. Brush 70 is a brass element 75 having a leaf spring arm 76 welded thereto (or otherwise connected for electrical communication therewith). An apertured leg 78 is substantially orthogonally arranged at the end of the element 75, remote from the terminal 74. The slot 72 is open at at least one side to allow egress of the arm 76 when the brush is inserted therethrough. After insertion, a plug 77 is pressed into a hole 79 in the boss 58, through the apertured leg 78, to retain the brush in position.

[0081] The terminals 74 protrude through the other side of the brush end cap 22, as shown in Figure 6(a). Also, a U-shaped earth wire 82 is provided, which has a terminal end 82a and a contact end 82b. The terminal end is inserted through a hole 84 in the end cap (see Figure 7b) whilst the contact end is received in a slot 86 in the edge of the brush end cap 22 so as to hold the earth wire in correct orientation with respect to the end cap and so that the contact end stands slightly proud of the cylindrical surface defined by the collar bosses 58. The end 82a of the earth wire also protrudes through the brush end cap 22 to its other side.

[0082] An arc shaped circuit board 80 is provided with control wires 88 soldered to tracks 90 printed on the board. The board has slots 92 and a hole 94 corresponding with the positions of the terminals 74 and earth wire 82a where they protrude through the end cap and, after positioning the board on them as shown in Figure 6(b), they are soldered to the tracks 90 whereby the board, the earth wire and partially the brushes 70 are secured and complete the end cap assembly. The board also comprises circuit elements 96 that serve to dampen/filter electro-magnetic emissions of the motor 16, generated by interaction between the armature 50 as it rotates and the permanent magnets in the can body 18.

The wires 88 include an earth grounding wire so that the motor cup body 18 is grounded through filter 96, one of tracks 90 and earth wire 82 adapted to contact the can body 18 on assembly of the end cap in the open end 1 8a of the can body. The other two wires provide current that is supplied to the brushes 70. The voltage applied across said other two wires may be any convenient DC voltage (perhaps 12V or 24V) and may be variable to enable variation in the speed of operation of the motor 16.

[0083] Each spring arm 76 of the brushes 70 has a dampening rubber block 83 and a carbon/graphite brush element 85 for engagement with the commutator 52. When terminal 74 is inserted in and through slot 72 in the brush end cap 20, the spring arm 76 is constrained by the slot engaging the sides of the terminal 74 to lie close to the rotational axis 25a of the shaft 25 of the armature 50. When the armature 50 is fitted to the brush end cap 22, the brushes are prized apart to receive the commutator 52 and so that they press against the commutator to make good electrical contact therewith.

[0084] Thus, the order of assembly is as follows: brush end cap 22 is assembled and then fitted on the commutator 52 end of armature and retained in position by engaging the grub screw 30 with the fan 24a; next the base end cap 20 is assembled and screwed to the cup-base end 18b of the can body 18; finally the armature 50 with brush end cap 22 is inserted into cup body 18 with the shaft 25 passing through the fan spigot 27 of the fan 24b and being fixed thereto by its grub screw 30. At the same time, collar boss 58 locate radially the armature and end cap 22 with respect to the body 18, and tabs 18c can both rotationally align the brush end cap 22 with respect to the body, by engagement with a tab 22a on the bosses 58, and optionally be crimped to further secure the body to the brush end cap 22.

[0085] Once the motor 16 is assembled, elastomer rings 34 are attached around ridges 32 on the end caps 20,22 and the motor is inserted in one shell of the shell housings 12,14. The other is clamped around the motor using the screws 42.

[0086] The shell housings 12,14 comprise windows 96 at each end, whereby cooling air can be drawn in and expelled by the fans 24a,b. They also comprise four halves 12a-d, 14a,d of what form lugs 98 of the module 10. The lugs are plates reinforced by fillets 99 and a step in the plates define a slot 101 (see Figure 2b) when the clamshell housings are assembled and clamped together along their joint line. The slot 101 is adapted to receive sheet metal connectors (not shown) of a frame (not shown) to be vibrated by the module 10. Screws pass through holes 103 in the plates of lug-halves 12a-d and screw into threads 105 provided holes in the plates of lug-halves 14a-d, whereby the metal connectors of the frame may be clamped securely. The threads 105 may be provided by brass inserts or the like.

[0087] The module 10 is versatile in that any arrangement of frame can be provided and attached, for example a frame similar to that disclosed in WO/2002/065973 or one comprising a plastics sheet bonded to foam for integration in a mattress or chair cushion,

as disclosed in the main body of this disclosure.

[0088] Cycloidal vibration therapy is a form of sinusoidal vibration in the frequency range of 15 to 75 Hz with an amplitude varying between 0.1 and 2 mm, depending on the orthogonal direction in the X,Y or Z axis. An acceleration rate of between 2 and 40 mS2 RMS is provided, generating between 0.3 and 2G at the surface of the device or frame to which the motor is fixed.

[0089] The motor arrangement, housed in the two piece housing with multiple mounting points allows for mounting to a frame or framework in various configurations at a range of angles. The motor is mechanically clamped in position, and supported by the elastomeric rings. The offset weight is mechanically and/or adhesively secured to the shaft of the DC motor, either at one end or both. If two weights are employed, they are aligned so that they are symmetrical to each other. As shown, the offset weight is cast into the fan arrangement so that it generates the required sinusoidal vibration but also creates air flow to cool the motor. The offset weight on the fan can be varied in size dependant on the weight required, this weight can alter the displacement within the range 0.1 and 2mm at the surface of the device it is mounted within.

[0090] The cycloidal vibration sinusoidal motor 16 is controlled electronically (by means not shown connected to the wires 88) to set and alter: the speed of the motor; the running time of the motor; and a range of oscillation patterns, for example by setting the motor speed to increase and decrease over a set time period.

[0091] The module 10 is connected to a frame by means of a mechanical fix. This may be directly to a frame, or by means of a bracket connecting the module to the frame through any angle up to 90 degrees. Using a bracket allows the motor module to be angled and displaced an appropriate depth or position relative to the frame and its mounting within a product such as a bed or seat cushion.

[0092] The frame may comprise a plastics sheet or mesh bonded between two layers of soft, resilient polyurethane or other plastics foam, to generate a sandwich arrangement.

One layer may form a top layer and become the surface of the product that contacts the human and or animal body. The other layer is supported by the product (bed or seat) and isolates the vibrations from the environment. The softness of the two layers may be different.

[0093] Referring specifically to Figures 8a and b, of a vibrating support structure 100 comprises a flexible plastics or metallic sheet frame 112 bonded to a layer of foam 114.

Vibration module 10 is attached to sheet frame 12 via housing 12,14. Connection lug 12b,14b connects the housing 12,14 to flame 112 via [-shaped connectors 122 and bolts 124. However, the skilled person will understand that any means of connecting housing 12,14 to frame 112 that results in a sufficiently rigid attachment between the housing and the frame for vibrations to be transmitted from the housing to the frame would be suitable.

In some embodiments. Connections are not limited to [-shaped connectors 122 and straight connectors or connectors turned through other than right angles are also feasible.

[0094] In Figure 8b, the [-shaped connector 122 can be seen to have three connection legs or points 128 to the motor module 10 so that a particularly strong and rigid connection between the motor and frame 112 can be achieved.

[0095] A foam layer 114 may be bonded to sheet frame 112 using adhesive or any other suitable bonding technique. Although the embodiment shown in Figure 8a shows foam 114 only bonded to one side of sheet frame 12, in some embodiments a layer of foam 114 is bonded to both sides of sheet frame 12, whereby frame 112 is sandwiched between layers of foam 114. In the arrangement of Figure Sa, the arrangement is such that, then the support structure is itself supported on a frame such as a bed frame or the like, the motor module 10 effectively hangs from the frame 112. This may be because the thickness and stiffness of the foam layer 114 is sufficient to prevent the motor module 10 from contacting a surface on which the support structure is placed when a user is supported by the support structure 100, for example, on a mattress or cushion 130 on the support structure. A suitable depth of layer of foam 114 may be between 5 and 30cm, preferably between 10 and 25cm. Furthermore, foam 114 may comprise two or more layers of foam having different stiffnesses and/or thicknesses. Alternatively, the layer 114 may be much reduced and instead the structure on which the layer 114 is placed has an aperture or space to receive the depending motor module 10.

[0096] In the arrangement shown, the connector 122 is L-shaped and depends from under the sheet frame 112, which substantially forms a T-shape in section. However, the frame 112 need not extend in both directions and instead the motor module could be at one end. Indeed, the sheet 112 could be slipped under a cushion with the motor assembly outside the confines of a chair or bed structure and cushion or mattress supported by the respective chair or bed structure. Likewise the connector 122 need not be L-shaped.

The motor module 10 could be in alignment with the sheet 112, in which event tha mattress or cushion 130 received and the foam 114 beneath would need to be thick and firm to avoid the presence of the motor being felt by a person supported on the cushion or mattress 130, assuming they were above the motor 10. Again, of course, the motor could be positioned outside the contact area.

[0097] In an embodiment the layer of foam 114 may be provided with V-shaped cutaways (not shown), which cutaways allow foam to be bent in the region of the cutaways. This allows a suitable bed to bend the mattress, for example to bring a patient lying upon it into a sifting position. The sheet frames 112 may be sufficiently flexible to be bent itself, or it may include hinges corresponding with the V-shaped cutaways. The frame 112 may comprise a sheet of plastics material of between 0.25mm and 2.5mm thickness.

A suitable plastics frame may comprise a solid plastics sheet, a plastics lattice or a plastics mesh. Alternatively, the sheet frame could be metal, for example, stainless steel between 0.25mm and 1 mm thick, welded or riveted into a lattice frame, and, again, having the option to bend at pivot points.

Claims

CLAIMS1. A support structure for a patient at risk of pressure ulcers comprising: a first vibration motor disposed within a housing; a first flexible sheet frame connected to said housing; and a first layer of resiliently deformable plastics material foam bonded to a first surface of said sheet frame.
2. A support structure as claimed in claim 1 in which at least part of said housing is integrally formed with said sheet frame, or wherein at least part of said housing is formed as a single unitary part with said sheet frame.
3. A support structure as claimed in claim 1 or claim 2, further comprising a second layer of resiliently deformable plastics material foam bonded to a second surface of said sheet frame, said second surface being opposite to said first surface, whereby said sheet frame is sandwiched between said first and second layers of foam.
4. A support structure as claimed in any preceding claim, wherein said first layer of foam comprises castellations in a surface thereof.
5. A support structure as claimed in any preceding claim, wherein said sheet frame comprises a solid plastics sheet having a thickness between 0.25mm and 2.5mm.
6. A support structure as claimed in any preceding claim, wherein said sheet frame comprises a plastics or metal lattice or mesh having a thickness between 0.25mm and 2.5mm.
7. A support structure as claimed in any preceding claim, wherein said sheet frame incorporates at least one hinge.
8. A support structure as claimed in any preceding claim, wherein the support structure comprises a mattress.
9. A support structure as claimed in any preceding claim, wherein the vibration motor is arranged to produce cycloidal vibrations.
10. A support structure as claimed in any preceding claim, further comprising control hardware in communication with the vibration motor, the control hardware being configurable to initiate and terminate operation of the vibration motor at user selectable time intervals, thereby providing vibration therapy to a patient resting on the support structure.
11. A mattress comprising a support structure as claimed in any preceding claim.
12. A mattress as claimed in claim 11, further comprising a second flexible sheet frame connected to either the first vibration motor or a second vibration motor.
13. A mattress as claimed in claim 11 or claim 12, wherein at least one of said first and second sheet frames are disposed under a portion of a surface of the mattress upon which one of the heels, the sacral area and the shoulders of an average adult patient lying upon the maftress would be likely to rest.
14. A mattress as claimed in any of claims 11-13, further comprising a pneumatic alternating pressure mattress disposed on said support structure, said pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated.
15. A mattress as claimed in claim 14, further comprising control hardware in communication with said vibration motor and said pneumatically inflatable cells, said control hardware being configured to provide intermittent pressure relief to a patient lying on the mattress by cyclically inflating and deflating said cells and vibration therapy by periodically activating said vibration motor.
16. A mattress as claimed in claim 15, wherein the control hardware is configured to initiate vibration therapy in response to the inflation or deflation of one of said groups of cells.
17. A mattress as claimed in any of claims 11-16, wherein the motor of the support structure is disposed outside of a contact area of the mattress.
18. A cushion comprising a support structure as claimed in any of claims 1-10.
19. A cushion as claimed in claim 18, further comprising a pneumatic alternating pressure overlay disposed adjacent to said first layer of foam, said pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated.
20. A mattress as claimed in claim 18 or claim 19, wherein the motor of the support structure is disposed outside of a contact area of the cushion.
21. A treatment mattress to alleviate pressure ulcers comprising a pressure relief mattress and a vibration therapy support structure having a first vibration motor disposed within a housing and a flexible sheet frame connected to said housing and on which said pressure relief mattress is supported.
22. A treatment mattress as claimed in claim 21, wherein the pressure relief mattress is one comprising a castellated foam structure.
23. A treatment mattress as claimed in claim 21, wherein the pressure relief mattress is a pneumatic alternating pressure mattress comprising a plurality of inflatable cells divided into at least two groups, which groups are configured to be cyclically inflated and deflated.
24. A treatment mattress as claimed in claim 21, 22 or 23, wherein said vibration therapy support structure further comprises a layer of resiliently deformable plastics material foam bonded to a first surface of said sheet frame.
25. A treatment mattress as claimed in claim 24, wherein said sheet frame has a second surface opposite first surface and said pressure relief mattress is supported on said second surface of said sheet frame.
26. A treatment mattress as claimed in claim 25, wherein a layer of resiliently deformable plastics material foam is bonded to said second surface of said sheet frame.
27. A support structure, mattress or cushion substantially as described herein with reference to the accompanying drawings.