There is no doubt that wheel-chairs have given mobility to the handicapped and to invalids. Nevertheless, such wheel-chairs suffer from various drawbacks due to the fact that their users can occupy a sitting position only, which position is also generally maintained for relatively long periods of time.
Such a position is unsuitable for providing readaptation to ordinary life and it does not facilitate social contacts. In addition, when a sitting position is maintained for relatively long periods of time, it causes physical deterioration, such as the loss of angular amplitude in the lower limbs, defective blood circulation, slowing down of the digestive and intestinal functions, bone fragility, etc.
To remedy the above drawbacks, proposals have been made for chairs each having a chassis that supports a hinged structure comprising a seat back, a seat, and a footrest. Such a structure is mounted in hinged relationship to the seat on a front horizontal axis, extending perpendicularly to the vertical plane of symmetry of the chassis. The hinged structure can be controlled with full motorization or with motorization for power assistance to cause the seat to pass from a low position to a high position, and vice versa. Such chairs are often referred to as "verticalizing chairs".
Regardless of whether the source of power that controls raising and lowering of the hinged structure or that enables it to be controlled is based on electricity, or on elastic actuators, in particular gas actuators, or is purely manual, chairs of the above type have certainly made it possible to a large extent to solve the drawbacks that stem from using a conventional chair.
That is doubtless why such chairs have been such a success over several years. By way of reference, mention can be made of French patent FR 2 529 456 which specifically relates to a design for such a verticalizing chair.
Although they give satisfaction, it appears that such chairs give rise to objections concerning comfort relating in particular to the nature of the hinged structure for raising and lowering the invalid or handicapped person in a position of maximum safety.
Account needs to be taken of the hinged nature of the structure which is capable of passing from a traditional seated position to an elevated or verticalizing position in which the various segments making up the structure are substantially in alignment one after another, in a pseudo-vertical direction.
To satisfy anatomical requirements in the various positions it can occupy, the hinged structure is made up of a seat element, a back element, and a footrest element which must therefore be capable of occupying a relative position that is generally of the seat type, and also of being placed in line with one another in the verticalization position.
Substantially parallel relative hinge planes are therefore necessarily established which are situated between the seat and the footrest, and between the seat and the back.
Although these various hinged segments do not give rise to major problems of comfort in supporting and holding the body of a handicapped subject or an invalid when they are in the traditional seated position, on passing into the verticalized position these various segments are generally subjected to displacement in which they slide relative to the body of the subject. This relative displacement is not good for maintaining maximum comfort, and in particular it requires appropriate settling back into the chair when in the seated position, so that the subject is again bearing comfortably against the back, against the seat, and against the footrest.
On reflection, it appears that this problem which, even if it is secondary, needs nevertheless to be addressed, stems from the fact that the hinged structures fitted to chairs for verticalizing purposes provide no scope for adjusting the depth of the seat as a function of the morphology of the subject.
Thus, apart from the ideal case where the depth of the seat is right, it can be considered that as a general rule this depth is either too deep or not deep enough to provide the subject with maximum comfort, whether in the sitting position or in the verticalization position.