The present invention relates to a pneumatic mattress.

A pneumatic mattress is a mattress having a plurality of pneumatic cells which are so connected that sets of them can be selectively and cyclically pressurised and exhausted - or inflated and deflated - in sequence to support a user, normally a patient liable to suffer or actually suffering from pressure sores. Cycling the mattress simulates movement that a patient would make if fit and healthy so as to avoid supporting his/her weight in the same place all the time. Pneumatic mattress design suffers from a dichotomy that separate independent cells held together only by an outer cover make for simplicity and cheapness, whereas integrally fabricated and smaller cells provide support in such a way that portions of the patient's anatomy are not liable to slip between two pressurised cells when an intervening one is deflated.

Pneumatic mattresses are usually pressurised with air drawn from the ambient atmosphere. However, the term is not intended to preclude use of any other inflation gas.

It is known to provide pneumatic mattresses with upper and lower layers of cells. Often these are pressurised and exhausted in phase, that is the cells above each other being pressurised and exhausted together. Advantages of this are not only that in the event of accidental puncturing of a cell in the upper layer, the corresponding cell in the lower layer can guard against the patient being dropped onto a hard bed base beneath the mattress; but also that two smaller cells on top of each other have less tendency to fill the space left by a deflating neighbouring cell, thus the portion of the patient supported by the neighbouring cell when inflated is more certainly relieved of support by the deflating cell than would be the case if the two superposed cells were a single cell.

It is also known to provide cells as triplets in each layer, with one cell in every three being deflated at any one time. Accidental puncturing is a significant and costly risk. It is liable to result in the entire mattress or at least an entire layer of the mattress being scrap, except in basic designs of mattress employing a single layer of individual cells held together within an outer cover.

The object of the present invention is to provide an improved pneumatic mattress.

According to the invention there is provided a pneumatic mattress comprising:

• a top layer of pneumatic cells and a bottom layer of pneumatic cells,

• the cells in each layer being integrated together in two or more groups of one or more cells and

• the groups of cells in each layer including:

• means disconnectably connecting the groups to each other,

• a cover enclosing the layers,

• a multi-way umbilical hose for selective supply of air to the groups of cells and

• a pneumatic connector for connecting the multi-way umbilical hose to a source of pressure air .

Preferably, the cells of a top layer extend transversely of the length of the mattress.

Conveniently, the groups of cells in the top layer are connected at a knee position, that is to say a nominal position in the mattress at which a user's knee can be expected to be. This arrangement allows the mattress to flex when supported on a bed base having a transverse hinge at the knee position.

Preferably, the connection at the knee position is substantially level with a bottom surface of the top layer, whereby as the two groups of cells are hinged about the connection, a gap opens between the top surfaces of the groups. Such an arrangement is an improvement compared with conventional integration of the entire top layer, which causes the pneumatic inflation of the cells to tend to resist bending of the top layer at the knee hinge.

Whilst it can be envisaged that the top layer could have three groups of cells, it is preferred to maintain the integration of the cells through the hip region, where the patient's body weight is available to deform the mattress to a hinging up of a back region of the bed base. Further, such integration guards against risk of the mattress opening under the weight of the patient.

Whilst the cells in the top layer preferably extend transversely, at least some of those in the bottom layer preferably extend longitudinally of the mattress. This helps with the general structural form of the mattress, in retaining its shape for handling for instance.

In the preferred embodiment, the bottom layer has disconnectable full bed length side/edge aligned cells, disconnectably connectable longitudinal head and leg cells and transverse torso cells.

The disconnectably connected groups and layers conveniently have strips along cells where the cells extend parallel to the zones or tabs at the ends of cells where the cells extend transverse to the connection zones. The strips or tabs are disconnectably connected by connecting means connecting the strips at the apertures.

Complementary pairs of apertures in the strips can be connected by pairs of toggles with an interconnection between the toggles at least within the top layer and between the top layer and the bottom layer. An additional flap can be co-extensive with at least some of the strips and covering the toggles.

In the bottom layer, the disconnectably connecting means comprises strips along cells where the cells extend parallel to the zones or tabs at the ends of cells where the cells extend transverse to the connection zones and pop fasteners connecting the strips. Preferably, within a group of cells the tabs are continuous as strips. Whilst it is envisaged that the cover could be an integral portion of either of the layers, or at least integrally connected to one of the groups of cells in one of the layers, preferably the cover is separable from the cells. Thus it or a damaged part of it, or a damaged group of cells could be replaced alone without the need to replace undamaged parts of the mattress.

In the preferred embodiment, the bottom layer has:

• side cells extending from end to end;

• longitudinal head region cells between the side cells;

• longitudinal lower leg cells between the side cells and

• a removable group of torso and upper leg cells extending laterally.

We have envisaged that it may be advantageous to provide a sheet between the side cells to extend beneath the torso and upper leg cells.

The side cells of the bottom layer can be necked for bending at the knee and hip regions. However, in the preferred embodiment, they are pneumatically divided and provided with common pneumatic pressure.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a hospital bed equipped with a pneumatic mattress of the invention;

Figure 2 is a perspective view of a pneumatic mattress of the invention;

Figure 3 is a transverse cross-sectional view of the mattress;

Figure 4 is a longitudinal cross- sectional view of the mattress;

Figure 5 is an exploded view of the cells of the mattress;

Figure 6 is a partially similar view of the cells partially assembled;

Figure 7 is an assembled view showing the arrangement of the individual cells;

Figure 8 is a similar view of the assembled cells;

Figure 9 is an end view of a representative cell connection within a layer; Figure 10 is a plan view of the cell connection of Figure 9;

Figure 11 is a view similar to Figure 9 of inter-layer cell connection;

Figure 12 is an exploded perspective view of a varied mattress of the invention; and

Figure 13 is a scrap underneath view of the bottom layer of the mattress of Figure 11.

Referring to the drawings, a mattress 1 has a cover 2 enclosing two layers 3,4 of pneumatic cells. The cells are made of impermeable sheet or tube material welded into desired shapes, typically of polyurethane material. The manner in which the cells are made is conventional, known to the skilled reader and will not be described here.

The bottom layer comprises edge cells 31 extending the full length of the mattress. These cells are closed at two positions, a hip position 32 and a knee position 33. Thus these cells have a head and back portion 34, an upper leg portion 35 and a lower leg portion 36. The portions can hinge or pivot with respect to their adjoining portions, without the pneumatic pressure in them tending to keep them rigid. Between the edge cells at the head end of the bed, i.e. between the head portions 34, six short head cells 37 are arranged with their cell length in the direction of the length of the mattress. The head cells are manufactured as a group separate from the edge cells. Similarly six lower leg cells 38 are provided between the lower leg portions 36. The central space in the bottom layer left by cells just described is filled by a group of nine transversely extending cells 39. The groups of cells are held together by toggles described in more detail below.

The upper layer consists of a head back and upper leg group of twelve transverse cells 41 and a second group of seven lower leg cells 42.

The cover is of impermeable material and consists of a lower part 21 having an under-sheet 22, peripheral webs 23, and inwards projecting top lips 24. A sliding clasp fastener strip 25 extends around the edges of the lips. The upper part 26 has an over sheet 27 for filling the opening 28 within the lips and provided with the complementary sliding clasp fastener strip 29. The top sheet extends to the webs 23 and further depending webs 261 extend down the outside the webs 23. The two cell layers 3,4 are contained within the cover and protected by it from any liquid spilled on it. The under-sheet is provided with straps of two types 221,222. The former are loose ended for securing the mattress to a bed frame and the latter are looped to enable the entire mattress to be lifted for patient evacuation.

A multi-way umbilical hose 5 extends from within the cover and for connecting the cells to a pressure air source via a connector 6. The hose includes four pipes, three having cyclically applied pressure and the fourth having constantly applied pressure air. The majority of the cells within the groups are arranged in sets of three, of which two are normally inflated at any one time, with the pipes pneumatically connected to the cells in a known way.

In use, the entire lower layer of the mattress apart from the central cells 39, together with the end three cells of the head portion of the upper layer, are permanently inflated. All the other cells in these sets of three, of the upper layer together with the lower cells at 39, are cyclically inflated and deflated, in a known manner.

Mechanical connection of the groups of cells will now be described. The same connection is used between the side and inner cell groups of the lower layer, wherever separate groups are joined along zones of their connection. It is also used in the top layer, between its two groups along the interconnection zone where the two groups are joined. Accordingly a representative connection only will be described between the cells of the two top groups. Adjoining cells 71,72 are provided with strips 73,74 of material of which the cells are made at a height to allow hinging of the mattress in use. The strips have regularly spaced eyelets 75, provided opposite each other. These are connected by pairs of toggles 76 connected together with a fabric loop 77. One toggle is passed through one eyelet, the other is passed through the opposite one. Thus the adjoining cells are mechanically connected.

Connection of the layers of cells are shown in Figure 11. The ends of the top layer of cells have tabs 83 similar to strips 73, each cell having a tab. The tabs could be separated, but since the cells of the group are formed from sheet material extending from one cell to the next, the tabs are normally connected as a strip. The edge cells of the bottom layer have strips 84. The tabs/strips have eyelet apertures 85 connected together with looped toggles 86. To mitigate against protrusive effects of the toggles, a flap 87 over-lying the tabs/strips 83 is provided.

Turning to Figure 12, the mattress there shown is varied by the head and foot ends of the edge cells 131 being curved in to allow a drip bag post to extend up at the corner of the mattress. The leg end cells 138 of the bottom layer extend towards the head end past the knee connection zone of the top layer of cells, to provide improved support of the region. To allow the cells 138 to hinge at this region, they are provided with necks 101. The edge cells also have divisions 102, comprising a heat seal between the top and bottom layers of the cells, on the same transverse line 103 for the same purpose.

The bottom layer also includes head end longitudinal cells 137 and transverse cells 139. Thus there are three groups of cells 137, 138, 139 and two groups of edge cells 131, all the groups being disconnectably connected to their neighbours.

The top layer consists of two groups of cells, transverse leg cells 142 and transverse head and torso cells 141.

The invention is not intended to be restricted to the details of the above described embodiments. In particular, the number of cells shown in Figures 4 to 7 were those in a prototype. The number shown in Figure 12 represents a production number, but the total number of cells can vary from mattress to mattress. For instance, the torso portion of the top layer can have 12 or 14 cells and the leg portion can have 5 or 6 cells.