Field of the invention

The invention relates to a cushion. The invention also relates to a method for manufacturing such a cushion. The main focus here is a cushion which prevents the occurrence of decubitus in a user, or at least minimizes the chance of it occurring, particularly in the case of a user sitting or lying for a long period in a more or less constant position. The term 'cushion' is used in the context of the present invention in its broadest sense and comprises seat cushions, mattresses and any similar body-supporting elements such as back cushions.

Background of the invention

Decubitus, also referred to as bedsores or pressure sores, is damage to the skin and/or subcutaneous connective tissue due to the degeneration of cells as a result of pressure, whereby blood circulation is wholly or partially obstructed locally, usually in combination with a poor ventilation, moisture regulation and heat regulation. Shear forces which occur also play a part here.

Decubitus generally occurs where the skin lies over a protruding part of a bone: at the coccyx, hips, knees, heels, occiput, shoulder blades, shoulders and elbows. When lying or sitting the skin is squeezed particularly at these positions between the bone and the cushion. If this continues for a longer period, the tissue can even die off (necrosis), after which the dead skin tissue and the underlying connective tissue disappear and an often deep wound results. Decubitus can result in life-threatening complications, particularly when a wound begins to fester and bacteria enter the bloodstream. Decubitus occurs particularly in people who are bedridden and/or incontinent or who sit for long periods in a seat or wheelchair, particularly when the person involved is not able and/or forgets to change position regularly and is not assisted in doing so. Diverse mattresses and seat cushions are known which, according to the producer or supplier, prevent bedsores or pressure sores or reduce the chance thereof or the occurrence thereof. Such a cushion can be filled with air, with gel or with a foam material and is usually provided with a cleanable or washable protective sleeve. Attempts are made here to minimize the pressures occurring by distributing them as uniformly as possible and so preventing pressure points as far as possible. The attempt is usually also made here to minimize the occurring shear forces, and in several cases an effort is also made to achieve an optimum ventilation, moisture regulation and heat regulation. Using known cushions and materials known heretofore it has however not yet been possible to achieve a determined optimum pressure distribution possibly modified to the user involved. The ventilation, moisture regulation and heat regulation are also still far from optimal here. The present invention now provides a solution which does not have these drawbacks, or at least does so to greatly reduced extent.

Summary of the invention

The invention provides a cushion as according to claim 1 and a method for manufacture thereof as according to claim 10. As stated, the term 'cushion' is used in the context of the present invention in its broadest sense and comprises seat cushions, mattresses and any similar body- supporting elements such as back cushions. In the context of the invention 'elasticity' is understood to mean the extent of deformation of a material when an external stress is applied. The deformation need not here be, or need not only be, proportional to the applied external stress. The deformation can also take place wholly or partially only after a period of time, for instance as a result of becoming warmer due to body heat such as in the case of a viscoelastic memory foam. The material will generally, though not necessarily, and possibly only after a period of time, and except for a non- elastic deformation or creep, return to its original shape here once this external stress has been removed.

A determined desirable relation between the indentation value and the location can be achieved by varying the dimensions of the parts and the elasticities. In the context of the invention 'indentation value' is understood to mean the overall deformation/indentation of a piece of material when an external pressure is exerted. One or more boundary planes between the parts can form non-right angles with the layer, which greatly increases the possibilities of arriving at an optimum relation between the indentation value and the location compared to a cushion with boundary planes perpendicular to the layer, wherein the indentation value at the boundary between two parts is always discontinuous.

A cushion according to the invention will mould itself optimally to the contours of the body of a user when the relation between indentation value and the location is such that the pressure distribution between body and cushion is optimal. A determined optimal relation between indentation value and location can be derived by means of an algorithm suitable for the purpose from the forces exerted by a user on the cushion. A set of values, associated with this relation, of dimensions of the parts, elasticities and angles can be determined experimentally and/or by calculation and/or in accordance with a suitable algorithm. A plurality of or a theoretically infinite number of sets can also form part of a determined relation.

The foam material can for instance be a polyurethane foam or a latex foam. The foam material is preferably a polyurethane foam on the basis of a polyol and methane diphenyl diisocyanate, referred to in short as MDI foam. An MDI foam particularly suitable for the given anti-decubitus application is marketed by Draka Interfoam B.V. under the name Pantera® in a series with different specific densities and elasticities / indentation values. Such a foam material is washable, ventilates well and is perceived as very comfortable.

Brief description of the drawings

The invention is elucidated hereinbelow on the basis of non-limitative exemplary embodiments.

Shown more or less schematically in the drawings:

Fig. la is a top view of a mattress according to the invention, and

Fig. lb is a side view thereof; and Fig. 2a is an exploded view of an exemplary embodiment of a seat cushion according to the invention, and

Fig. 2b is a perspective view thereof.

Exemplary embodiments

The mattress (1) shown in figure 1 comprises a flat layer (2) of elastic material assembled from a number of parts (2a-f) with mutually differing elasticities. Such a mattress will generally also comprise a mattress cover (not shown). By means of an algorithm suitable for the purpose a determined optimal relation between indentation value and location is derived from the forces exerted on the mattress (1) by a user. The starting point here is that the mattress (1) moulds itself as well as possible to the contours of the body of the user and the pressure distribution between body and mattress (1) is optimal. A set of associated values of the dimensions of the parts (2a-f) and elasticities is then calculated, although the determining of these values can in principle also take place in partially or wholly experimental manner. In the given example the boundary planes (5) between the parts (2a-f) form right angles with the layer (2), i.e. right angles with a plane parallel to the upper side or underside of the mattress (1). Because of these right angles the indentation value at the boundary between two parts will always be discontinuous, although for a mattress this will generally be less problematic since the optimal relation between indentation value and location can nevertheless be approximated sufficiently closely because the weight of the body of a user is distributed over a relatively large surface area.

The seat cushion (3) according to the invention shown in figure 2 is a seat cushion for use in a wheelchair. Such a cushion will generally also comprise a cover (not shown). The seat cushion (3) again comprises a flat layer (4) of elastic material assembled from a number of parts (4a-e) with mutually differing elasticities. Important are the non-right angles which the boundary planes (6) between the parts (4a-4e) form with the layer (2), i.e. non-right angles with a plane parallel to the upper side or underside of the seat cushion (3). The boundary planes (6) between the parts (4a-e) do not therefore lie here perpendicularly of the upper side or underside of the seat cushion (3). By varying the dimensions of the parts (4a-e), the elasticities and now also the angles, any relation between the indentation value and the location can in principle be realized, and a determined optimum pressure distribution, possibly modified to the user involved, can thus be realized without any discontinuity in the indentation value at the boundary between two parts. It is particularly important for a seat cushion of a wheelchair to approximate the optimum relation between indentation value and location as closely as possible, since a large part of the weight of the body of a user rests on a relatively small surface area. In the given examples (1;3) the elastic material is an MDI foam as marketed by Draka Interfoam B. V. under the name Pantera® in a series with different specific densities and elasticities / indentation values. Such a foam material is washable, ventilates well and is perceived as very comfortable. The parts (2a-f;4a-e) are glued to each other here, in the shown examples with a polyurethane adhesive suitable for the purpose. The parts (2a- f;4a-e) can however consist in principle of other and even mutually differing elastic materials or foam materials.

The mattress and the seat cushion are found to prevent the occurrence of decubitus in a user, or at least to minimize the chance of it occurring. In addition to a very good to optimal pressure distribution, the mattress and the seat cushion have very good properties in respect of ventilation, moisture regulation and heat regulation. This is also brought about by enclosing the foam material with a properly ventilating cover or sleeve. The whole is washable up to 40°C. All these factors make the mattress and the seat cushion very comfortable and practical to use. Anti-decubitus cushions according to the invention are marketed under the name Culsana®.

It will be apparent that the invention is not limited to the shown and described exemplary embodiments, but that diverse variants evident to a skilled person are possible within the scope of the invention.