EP3097898A1 - Hospital chair provided with a system to help patients sit and stand back up - Google Patents

Abstract

Medical armchair (1) comprising: a chassis (2) provided with a base (5), - a seat (14) movable relative to the base (5) and including a half-seat (14A) and a front half-seat (14B) mutually articulated about an axis A, and - a mechanism (33) for articulating the seat (14) can adopt a folded configuration placing the seat (14) in a low position close to the base (5), and an expanded configuration placing the seat ( 14) in a high position spaced from the base (5), this mechanism (33) two superposed deformable quadrilaterals, including a lower quadrilateral which, in the folded configuration, is convex and, in the deployed configuration, is concave.

Description

The invention relates to the field of medical chairs, and more particularly chairs equipped with mobile seats to help people with mobility and / or reduced muscle strength (hereinafter referred to as "patients") to sit down and to get up.

Sitting and standing are complex movements involving the joints of the ankle, knee and hip, calf muscles (anterior tibia), thighs (quadriceps), glutes and back (lumbar) , and further assume a proper functioning of the inner ear, organ of the balance of the human body.

Sitting and standing up, for patients with psychomotor-mismatch or MPRD syndrome (especially elderly or with bone or muscle injuries, or balance disorders), are at high risk of falling and therefore trauma. About this syndrome, cf. especially the article of P.Manckoundia et al "Psychomotor Disadvantage Syndrome", in Geriatrics and Psychology Neuropsychiatry of Aging, Vol.12, March 2014 , and the memoir N. Meesmaecker "State of the art about Psychomotor Disadvantage Syndrome in a Specialized Center for Geriatrics", Rennes Institute of Masso-Physiotherapy Training, 2011 .

In most patients with MPRT, there are postural symptoms called retropulsion (tendency to project backwards during the transition from sitting posture to standing posture) and oppositional hypertonia (reflex muscle tension opposing movement). considered). These symptoms are often accompanied by that of stasobasophobia (phobia of standing, verticality and walking), which leads the patient to fear the action of getting up from the sitting posture.

To sit up and get up, patients can use the arm resting on the armrests that usually equip the medical chairs, but it requires some strength. Patients may also be assisted by carers, but these are then exposed to various musculoskeletal disorders (including low back pain) due to the combination of: discomfort posture, repetition of handling operations; patient weight.

Various chairs and chairs with telescopic seats have been proposed to help patients sit up and get up. There are thus chairs powered by an electric motor driven by a remote control operable by the patient.

This technology, illustrated by the US patent US 7,090,297 (La-Z-Boy ), is not without drawbacks: firstly, to be supplied with electricity, the chair must be connected to the sector and therefore can not be rolling; secondly, because of the power supply, this chair is relatively heavy, which makes it tedious its possible movement (eg from one room to another).

There are also chairs equipped with mechanical spring (spring) or pneumatic (cylinder), which are lighter and do not require any external energy input. This technology is particularly illustrated by the British patent GB 1 406 420 (Warwick ), which describes a medical chair with a movable seat controlled by a spring mechanism. However, it can be shown that this chair lacks ergonomics, because the movement followed by the seat during its articulation is quite different from the movement of the legs of the patient, who therefore risks, by sitting or standing up, losing the balance.

A first objective is therefore to provide a medical chair more secure for patients.

A second goal is to provide a medical chair for patients who have lost the habit of sitting and getting up without help (and especially patients with MPRH) to find this habit.

A third objective is to provide a reliable and relatively lightweight medical chair, allowing easy movement.

• un châssis muni d'une embase,
• une assise mobile par rapport à l'embase et incluant une demi-assise avant et une demi-assise arrière mutuellement articulées autour d'un axe A, et
• un mécanisme d'articulation de l'assise pouvant adopter une configuration repliée plaçant l'assise dans une position basse voisine de l'embase, et une configuration déployée plaçant l'assise dans une position haute écartée de l'embase, ce mécanisme comprenant :
  • o un cadre inférieur monté en rotation par rapport à l'embase autour d'un axe B et par rapport à la demi-assise avant autour d'un axe C situé au voisinage d'un bord avant de celle-ci ;
  • o un cadre supérieur monté en rotation par rapport au cadre inférieur autour d'un axe D situé entre les axes B et C, et par rapport à la demi-assise arrière autour d'un axe E situé au voisinage d'un bord arrière de celle-ci ;
  • o un bras de couplage monté en rotation par rapport à l'embase autour d'un axe F et par rapport à la demi-assise avant autour d'un axe G écarté de l'axe C ;
• un organe de rappel élastique qui sollicite le mécanisme d'articulation vers sa configuration déployée ;

les axes A, B, C, D, E, F et G étant parallèles et définissant, dans un plan qui leur est perpendiculaire :

• les axes B, C, G, F, un quadrilatère inférieur déformable ;
• les axes A, C, D, E, un quadrilatère supérieur déformable ;

les axes A, B, C, D, E, F et G étant positionnés de telle sorte que le quadrilatère inférieur soit convexe dans la configuration repliée, et concave par l'axe G en configuration déployée.For this purpose, there is provided a medical chair comprising:

• a chassis with a base,
• a seat movable relative to the base and including a half-seat before and a half-back seat mutually articulated about an axis A, and
• a hinge mechanism of the seat can adopt a folded configuration placing the seat in a low position close to the base, and an expanded configuration placing the seat in a high position away from the base, this mechanism comprising:
  • a lower frame rotatably mounted relative to the base around an axis B and with respect to the front half-seat around an axis C situated in the vicinity of a front edge thereof;
  • o an upper frame rotatably mounted relative to the lower frame about an axis D located between the axes B and C, and relative to the half-seat back around an axis E located in the vicinity of a rear edge of this one;
  • a coupling arm rotatably mounted relative to the base around an axis F and with respect to the front half-seat about an axis G spaced from the axis C;
• an elastic return member which urges the articulation mechanism towards its deployed configuration;

the axes A, B, C, D, E, F and G being parallel and defining, in a plane perpendicular to them:

• the axes B, C, G, F, a deformable lower quadrilateral;
• the axes A, C, D, E, a deformable upper quadrilateral;

the axes A, B, C, D, E, F and G being positioned such that the lower quadrilateral is convex in the folded configuration, and concave by the axis G in the deployed configuration.

• la somme des entraxes FG et CG est inférieure ou égale à l'entraxe BC ;
• l'angle entre les plans définis respectivement par les axes A et C d'une part et C et G d'autre part est compris entre 70° et 120° ;
• l'angle entre les plans définis respectivement par les axes A et C d'une part et C et G d'autre part est d'environ 90° ;
• l'entraxe DE est supérieur ou égal à l'entraxe AC ;
• l'entraxe CD est inférieur ou égal à l'entraxe BD ;
• l'entraxe AE est supérieur ou égal à l'entraxe CD ;
• l'organe de rappel est un ressort à gaz ;
• le ressort à gaz est du type blocable ;
• le ressort à gaz comprend un corps fixé sur le cadre inférieur, et une tige fixée sur le cadre supérieur.

Various additional features may be provided, alone or in combination:

• the sum of the centers FG and CG is less than or equal to the center distance BC;
• the angle between the planes respectively defined by the axes A and C on the one hand and C and G on the other hand is between 70 ° and 120 °;
• the angle between the planes respectively defined by the axes A and C on the one hand and C and G on the other hand is about 90 °;
• the center distance DE is greater than or equal to the center distance AC;
• the center distance is less than or equal to the center distance BD;
• the center distance AE is greater than or equal to the center distance CD;
• the return member is a gas spring;
• the gas spring is of the lock type;
• the gas spring comprises a body fixed on the lower frame, and a rod fixed on the upper frame.

• la figure 1 est une vue en perspective d'un fauteuil médicalisé, montré seul, dont l'assise est en position basse ;
• la figure 2 est une vue du fauteuil de la figure 1, dans lequel un patient est assis ;
• la figure 3 est une vue en perspective du fauteuil de la figure 1, dont l'assise est en position haute ;
• la figure 4 est une vue du fauteuil de la figure 3, avec un patient en train de se relever du fauteuil ou de s'asseoir dans celui-ci ;
• la figure 5 est une vue de côté de l'assise en position basse et de son mécanisme d'articulation en configuration repliée ;
• la figure 6 est un schéma cinématique illustrant le mécanisme d'articulation dans sa configuration repliée ;
• la figure 7 est une vue de côté de l'assise en position haute et de son mécanisme d'articulation en configuration déployée ;
• la figure 8 est une vue en perspective, par l'arrière, de l'assise en position haute et de son mécanisme d'articulation en configuration déployée ;
• la figure 9 est un schéma cinématique illustrant le mécanisme d'articulation dans sa configuration déployée ;
• la figure 10 est une vue en coupe longitudinale montrant l'assise en position haute et illustrant l'organe de rappel avec, en médaillon, un détail à plus grande échelle centré sur une butée réglable ;
• la figure 11 est un schéma illustrant les différentes positions de l'assise entre sa position basse et sa position haute ;
• la figure 12 est un schéma comparatif illustrant les différentes positions de l'assise du fauteuil du brevet GB 1 406 420 , entre sa position basse et sa position haute.

Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given hereinafter with reference to the accompanying drawings, in which:

• the figure 1 is a perspective view of a medical chair, shown alone, whose seat is in the low position;
• the figure 2 is a view of the armchair of the figure 1 in which a patient sits;
• the figure 3 is a perspective view of the chair from the figure 1 , whose seat is in a high position;
• the figure 4 is a view of the armchair of the figure 3 with a patient getting up from the chair or sitting in it;
• the figure 5 is a side view of the seat in the lower position and its hinge mechanism in folded configuration;
• the figure 6 is a kinematic diagram illustrating the articulation mechanism in its folded configuration;
• the figure 7 is a side view of the seat in the raised position and its articulation mechanism in deployed configuration;
• the figure 8 is a perspective view, from the rear, of the seat in the up position and its articulation mechanism in deployed configuration;
• the figure 9 is a kinematic diagram illustrating the articulation mechanism in its deployed configuration;
• the figure 10 is a longitudinal sectional view showing the seat in the upper position and illustrating the return member with, in medallion, a larger scale detail centered on an adjustable stop;
• the figure 11 is a diagram illustrating the different positions of the seat between its low position and its high position;
• the figure 12 is a comparative diagram illustrating the different positions of the seat of the patent chair GB 1 406 420 , between its low position and its high position.

On the figure 1 is represented a medical chair 1 for elderly people or suffering from bone lesions or musculoskeletal disorders or balance disorders (hereinafter simply referred to as "patients"). This chair 1 is intended not only to enable them to adopt a sitting position, but also to facilitate their movement for caregivers.

The chair 1 comprises a frame 2 formed of tubular metal elements (in particular steel or aluminum alloy). This frame 2 includes a carriage 3 provided with wheels 4 enabling the chair 1 to be moved , a base 5 mounted on the carriage 3, a mast 6 that is adjustably fixed (in particular at an inclination) on the base 5, and, as illustrated, tubes 7 which extend laterally from the base 5 to allow the adjustable mounting of armrests 8. The carriage 3 comprises for example a main beam 9 and a pair of longitudinal members 10 at the ends of which are fixed the wheels 4.

The chair 1 comprises a backrest 11 mounted on the mast 6, and, optionally, a headrest 12 mounted at an upper end of the mast 6, surmounting the backrest 11. Moreover, as in the example illustrated, the chair 1 is preferably equipped with a handlebar 13 formed by a transverse bar fixed to the upper end of the mast 6, to facilitate the movement and operation of the chair 1 by a caregiver. In what follows, the term "back" defines a location on the side of the file 11; the term "before" defines, conversely, an opposite location. The term "bottom" defines a location on the side of the wheels 4; the term "high" defines, conversely, an opposite location. In general, the terms "back", "front", "down" and "up" are used in the context of normal positioning and use of the chair 1, as is customary with the usual in daily life. The same is true of the terms "vertical" and "horizontal", assuming that the chair 1 rests on a horizontal floor.

The chair 1 comprises a seat 14 movable relative to the base 5 between a low position ( figures 1 , 2 , 5 , 6 ) in which the seat 14 extends in the vicinity of the base 5 to allow a patient 15 to be comfortably seated in the chair 1, as illustrated on the figure 2 , and a high position ( figures 3 , 4 , 7, 8 , 9 , 10 ) in which the seat 14 is spaced from the base 5 to help the patient 15 to rise up by pushing behind his thighs or, conversely, to sit by cushioning and accompanying its movement.

The base 5 can be fixed immovably on the carriage 3 , or, as in the example shown, in an adjustable manner at least in height and, optionally, in rotation, by means of a jack 16 provided with a locking mechanism actuable by means of a lever 17 projecting from the patient's reach 15. The base 5 is, in the illustrated example, in the form of a metal part comprising a horizontal plate 18 and lateral flanges 19 folded at right angles to the plate 18 horizontal.

It is preferable that the base 5 (and thus the seat 14 and armrests) is (are) blocked (s) in rotation while the patient 15 sits or stands up, so as to secure it. For this purpose, and as illustrated in particular on the figure 1 at least one of the tubes 7 is provided with a stand 20 which abuts against the cross-member 9.

According to an embodiment illustrated on the Figures 1 to 4 , the chair 1 is equipped with a footrest 21 movable in height between a low position (illustrated in the figures) in which the footrest 21 extends in the vicinity of the ground to allow the patient 15 to take support when seated and up, and a high position in which the footrest 21 is spaced from the ground to keep the feet of the patient away from the ground, which prevents them from rubbing against it during the chair movements 1 . As we see in particular on Figures 1 to 4 , the chair 1 is provided with a mechanism 22 for actuating the footrest 21 , including a lever 23 for foot control and a linkage 24 for coupling the lever 23 to the footrest 21, the tilting of the control lever 23 placing the footrest 21 in its upper position or, conversely, in its low position. Advantageously, the actuating mechanism 22 simultaneously controls the locking of at least two of the wheels 4 (eg the rear wheels) in the lower position of the footrest 21, so as to prevent the chair 1 from escaping when the patient 15 gets up or sits.

The seat 14 is in two parts: it comprises a half-seat 14A front for supporting the thighs of the patient 15 , and a half-seat 14B back to support its pelvis. The half-seats 14A , 14B are mutually articulated about a common axis A, located in the vicinity of a rear edge of the half-seat 14A front and a front edge of the rear half-seat 14B .

As illustrated in the figures, and in particular on the figures 5 and 7 , the front half-seat 14A comprises a metal front plate 25 provided with flanges 26; likewise, the rear half-seat 14B comprises a metal rear plate 27 provided with flanges 28.

The axis A is, in the illustrated example, formed by a pair of bolts 29 through which the plates 25, 27 are rotatably mounted relative to each other.

The seat 14 comprises a flexible cushion 30 having a front portion 30A mounted on the front plate 25 via a front plate 31A slidably mounted thereon, and a rear portion 30B mounted on the rear plate 27 by the intermediate a rear plate 31B slidably mounted thereon and hinged relative to the plate 31A before around a hinge 32.

The cushion 30 is preferably made of a foam, e.g. a viscoelastic foam (commonly referred to as memory foam). The trays 31A, 31B may be made of plastic, wood or, advantageously, a material derived from wood (typically agglomerated, medium, laminate).

The chair 1 further comprises a mechanism 33 for articulating the seat 14, designed to be able to adopt a folded configuration placing the seat 14 in its low position ( Figures 5, 6 μ), and an expanded configuration placing the seat 14 in its upper position ( Figures 7, 8 , 9 ).

This mechanism 33 comprises, in the first place, a lower frame 34 rotatably mounted relative to the base 5 about an axis B and with respect to the half-seat 14A before around an axis C situated in the vicinity of a front edge of it. In the illustrated example, the axis B is formed by a pair of bolts 35 by which the lower frame 34 is rotatably mounted on the flanges 19 of the base 5.

The lower frame 34 could be formed of a pair of parallel rods interconnected by a spacer. In the example illustrated in the figures, and in particular on the figure 8 , the lower frame 34 is, however, in the form of a one-piece metal part comprising a rectangular plate 36 provided with a notch 37 whose function will appear hereinafter), and lateral edges 38 folded at right angles to the plate 36.

According to an embodiment illustrated in the figures, and in particular on the figures 5 , 7 and 8 the axis C is formed by a tube 39 integrated in the lower card (for example being welded to the plate at a front edge thereof) and rotatably mounted between two fixed bearings 40 (e.g. by screwing) to the half-seat 14A before, on both sides laterally thereof.

The mechanism 33 of articulation comprises, secondly, an upper frame 41 rotatably mounted on the one hand with respect to the lower frame 34 about an axis D located between the axes B and C, and on the other hand by relative to the half-seat 14B rear about an axis E located in the vicinity of a rear edge thereof.

The upper frame 41 could be formed of a pair of parallel rods interconnected by a spacer. In the example illustrated in the figures, and in particular on the figure 8 , the upper frame 41 is however in the form of a one-piece metal part comprising a rectangular plate 42 provided with a central slot 43 (whose function will appear hereinafter), and lateral edges 44 folded to the square relative to at plate 42.

In the illustrated example, the axis D is formed by a pair of coaxial bolts 45 by which the upper frame 41 is rotatably mounted on the lateral edges of the lower frame 34 . According to a preferred embodiment, the axis D extends in the plane formed by the axes B and C (in other words, the axes B, C and D are coplanar). The axis E is formed by a pair of coaxial bolts 46 by which the upper frame 41 is rotatably mounted relative to the rear half-seat 14B , and more specifically on lugs 47 formed projecting from the plate 27 back.

The articulation mechanism 33 comprises, thirdly, a coupling arm 48 rotatably mounted on the one hand with respect to the base 5 about an axis F, and on the other hand with respect to the half front seat 14A about an axis G spaced from the axis C and located on the side thereof opposite the front plate 25 .

The coupling arm 48 could be in the form of a single central rod (that is to say extending in a longitudinal plane of symmetry of the chair 1). However, in the illustrated example, the coupling arm 48 comprises a pair of rods 49 arranged laterally. on either side of the base 5, made integral with each other by means of a spacer 50 (here in the form of a transverse bar).

As can be seen in the figures, the axis F of rotation of the coupling arm 48 is offset relative to the axis B of rotation of the lower frame 34 , both forwards and downwards, the arm 48 being itself shifted forward relative to the entire lower frame 34 . The axis F is for example formed by a pair of bolts 51 through which each rod 49 is rotatably mounted relative to a flange 19 of the base 5.

As we see further on figures 5 , 7 and 8 , the arm 48 is rotatably coupled to the half-seat 14A before via a lug 52 projecting from the front plate 25 , which it is secured (eg by welding). According to an embodiment illustrated in these figures, the tab 52 is horn-shaped and the axis G of rotation of the arm 48 relative to the half-seat 14A is attached to one end of the tab opposite to it . In the illustrated example, the axis G is formed by a pair of coaxial bolts 53 .

The axes A, B, C, D, E, F and G are mutually parallel and extend transversely, that is to say perpendicular to a general plane of symmetry of the chair 1 .

• les axes B, C, G, F, un quadrilatère BCGF inférieur déformable ;
• les axes A, C, D, E, un quadrilatère ACDE supérieur déformable.

In this way, the axes A, B, C, D, E, F and G define, in any plane perpendicular to them (and in particular in the general plane of symmetry of the chair 1 ):

• the axes B, C, G, F, a lower deformable BCGF quadrilateral;
• the axes A, C, D, E, a quadrilateral ACDE upper deformable.

Since the tab 52, which carries the axis G, is integral with the front plate 25 , the AC side of the upper quadrilateral ACDE and the CG side of the lower BCGF quadrilateral are rigidly secured. Since, furthermore, the axes B and F are fixed and the axis D is integral with the lower frame 34 (that is to say on the BC side of the lower BCGF quadrilateral), the deformations of the BCGF and ACDE quadrilaterals are linked, each configuration of the lower quadrilateral BCGF corresponding a single configuration of the upper quadrilateral ACDE, and vice versa.

The articulation mechanism 33 is however not free, otherwise gravity would keep it in its folded configuration. The chair 1 comprises a resilient return member 54 which urges the articulation mechanism 33 towards its deployed configuration, so that that in the absence of any resisting force opposing the deformation of the body 54 of return, the deployed configuration is the one occupied by default mechanism 33 articulation.

According to an advantageous embodiment, the return member 54 is interposed between the lower frame 34 and the upper frame 41 which it tends to move away from one another. The return member 54 is for example a gas spring, and in this case comprises a cylinder body 55 which, in the illustrated example, is fixed to the lower frame 34 (and more specifically to a yoke 56 secured to it). ci) being hinged to it, and a rod 57 slidably mounted relative to the body 55 and fixed on the upper frame 41 through the notch 37 and the slot 43, being hinged to the frame higher 41.

As illustrated on the figure 8 the notch 37 and the slot 43 provide an angular clearance for the rod 57 to allow pivoting that accompanies the tilting of the upper frame 41 relative to the lower frame 34 during the deployment (or, conversely, the folding) of the mechanism 33 hinge.

As illustrated on the figure 10 , and more particularly in the detail locket thereof, the articulation mechanism 33 may be provided with an adjustable stop 58 for adjusting the deployed configuration of the mechanism 33 (and thus the high position of the seat 14 ). As in the example shown, this stop 58 may be in the form of a knob screwed into the bar 50 bracing the connecting rods 49 of the coupling arm 48 . The stop 58 has a mushroom grip 59 and a rod 60 at the end of which is mounted a hemispherical shoe 61 . In deployed configuration, the plate 36 of the lower frame 34 abuts against the shoe 61, which blocks in position the articulation mechanism 33 . By screwing (or unscrewing) the rod 60 in the bar 50 by means of the handle 59, the position of the pad 61 is adjusted , which makes it possible to adjust the deployed configuration of the articulation mechanism 33 (and thus the up position from the seat 14) to the morphology (and especially to the size) of the patient 15.

The movable seat 14 (with its articulation mechanism 33) can accompany and assist the actions of the patient 15 of sitting for the standing posture, and conversely to get up from the sitting posture.

We will now describe the movement of the articulation mechanism 33, starting from first posture standing patient 15 and the deployed configuration (adjustable, as we have just seen) of the hinge mechanism 33 (and therefore the high position of the seat). In this configuration, illustrated on the figures 3 and 4 , it is assumed locked the wheels 4 of the chair 1, and lowered the footrest 21.

The patient 15 presents himself back to the chair 1, and, his feet on the footrest 21 lowered, slightly bends the legs. It can use the arms coming to grip the armrests 8 (whose height is preferably adjustable), as illustrated on the figure 4 , which solicits, albeit moderately, the extensor muscles of the elbow (especially the triceps brachii). The back of the thighs (hamstring muscles) coming to rest on the half-seat 14A before, and the pelvis (and glutes) on the back half-seat 14B , the patient 15 can then indulge in sitting in releasing his muscles without fear of shock coccyx, the spring 54 damping its movement.

The spring 54 is, for this purpose, chosen to slow down (and thus dampen, but not annoy) the folding movement of the articulation mechanism 33 , and this for a panel of patients having varied weights between a minimum value ( eg from 35 to 40 kg) and a maximum value (eg of the order of 80 to 90 kg). It is conceivable to choose a gas spring 54 adjustable force to adapt to the weight of the patient 15. Alternatively, it is conceivable to provide several models of chairs 1 each adapted to a limited range of weight and covering a wide range of weight, and that one selects according to the weight of the patient.

Once the patient sits 15 , a carer can unlock the wheels 4 and raise the footrest 21 to freely move the chair 1 (with the patient) by means of the handlebar 13.

Conversely, starting from the sitting posture of the patient 15 and the folded configuration of the articulation mechanism 33 (and assuming the wheels 4 locked and the footrest 21 lowered, figures 1 and 2 ), the patient 15, to initiate the movement of getting up, begins by leaning the bust forward, which moves its center of gravity forward and transfers part of its weight on his feet by reducing the resistance effort opposed to the deployment of the articulation mechanism 33 under the spring return effect 54.

The patient can use his arms by gripping the armrests 8 and leaning against it, which further reduces the weight carried by the seat 14, to the point where the spring 54 can freely stretch by deploying the articulation mechanism 33 , which pushes the patient both upward (by the half-seat 14B rear) and forward (by the half-seat 14A before) and further lighten the weight carried by the seat 14. The patient 15 thus assisted can then easily reach the posture illustrated on the figure 4 where, although his legs are still slightly bent, the effort needs to make the patient 15 to fully extend is modest.

The articulation mechanism 33 is not only designed to provide the patient 15 a thrust force allowing it to rise; it is designed to perform an ergonomic accompaniment movement, that is to say closer to the kinematics of the human body from sitting posture to standing posture, and vice versa.

For this purpose, the axes A, B, C, D, E, F and G are positioned (that is to say that the lower frame 34 , the upper frame 41 , the half-seat 14A before, the half rear seat 14B and coupling arm 48 are sized) such that the lower BCGF quadrilateral is convex in the folded configuration of the mechanism 33, and concave by the axis G in the deployed configuration of the mechanism 33.

Recall that a quadrilateral is said to be convex when its diagonals are included in the perimeter defined by the quadrilateral, and concave when one of the diagonals is located outside this perimeter. In other words, that the lower quadrilateral BCGF is concave by the axis G means that the angle between the segments GF and GC, measured on the inside of the quadrilateral BCGF, is greater than 180 °.

• tant que le quadrilatère inférieur BCGF est convexe, le segment AE (et avec lui la demi-assise 14B arrière) est animé, lors du déploiement ou du repliement du mécanisme 33 d'articulation au cours d'une phase dite translative (notée T sur la figure 11), d'un mouvement essentiellement de translation verticale (flèche F1 sur la figure 6) jusqu'à une configuration intermédiaire dans laquelle les segments GF et GC sont alignés ;
• dès lors que, passée la configuration intermédiaire, le quadrilatère inférieur BCGF devient concave, le segment AE (et avec lui la demi-assise 14B arrière) est animé, lors du déploiement ou du repliement du mécanisme 33 d'articulation au cours d'une phase dite rotative (notée R sur la figure 11), d'un mouvement essentiellement de rotation d'arrière en avant (dans le cas du déploiement, flèche F2 sur la figure 9) ou inversement d'avant en arrière (dans le cas du repliement).

It can be seen that:

• as long as the lower quadrilateral BCGF is convex, the segment AE (and with it the back half-seat 14B ) is animated, during deployment or folding of the articulation mechanism 33 during a so-called translational phase (denoted T on the figure 11 ), with a movement essentially of vertical translation (arrow F1 on the figure 6 ) to an intermediate configuration in which the GF and GC segments are aligned;
• since, after the intermediate configuration, the lower quadrilateral BCGF becomes concave, the segment AE (and with it the back half-seat 14B ) is animated, during deployment or folding of the articulation mechanism 33 during a so-called rotary phase (denoted R on the figure 11 ), essentially turning from back to front (in the case of deployment, arrow F2 on the figure 9 ) or vice versa from front to back (in the case of folding).

The movement of the articulation mechanism 33 (and thus of the seat 14) is therefore subdivided into two phases.

During the translational phase T, the back half-seat 14B accompanies the vertical translational movement of the pelvis (and buttocks) of the patient 15, ie when he initiates the movement of standing up from the sitting posture, or when he finish the movement of sitting down. As for the half-seat 14A before, it is animated by a combined movement of vertical translation and rotation of low angular amplitude which accompanies both the ascent (in the case of the transition to standing posture) or the descent (in the case of transition to sitting posture) of the knee joint and rotation of the thighs around it. In the movement of deployment of the articulation mechanism 33 , the axis C is animated, during the translative T phase, a large amplitude upward movement of rotation, centered on the axis B (arrow F3 on the figure 6 ).

It will be observed that during the translative T phase, the entire seat 14 is translated backwards. This movement reassures (and therefore relaxes muscles) patients with a retropulsion symptom, inclined by reflex to project their body backwards during the transition from sitting posture to standing posture.

During the rotating R phase, the complete seat 14 (half-seat 14A front and back half-seat 14B ) accompanies the rotation movement secured to the pelvis and the thighs of the patient 15 around the knee joint, which remains at substantially constant height. In the movement of deployment of the articulation mechanism 33 , the axis C is animated, during the rotary phase R, with a low amplitude rotational movement downwards, centered on the axis B (arrow F4 on the figure 9 ), which frees the knee joint and allows the patient 15 to complete without hindrance the extension of his legs to get up.

In addition, it will be observed that, during the rotational R phase, the entire seat 14 is translated forward, which, after the translational phase T which accompanies the rearward patient with a retropulsion symptom, propels the latter forward towards the end of the movement and allows him to stand permanently.

1. a) La somme des entraxes FG et CG est inférieure ou égale à l'entraxe BC : $$\mathrm{FG}+\mathrm{CG}\le \mathrm{BC}$$
   
2. b) L'angle, noté α, entre les plans définis respectivement par les axes A et C d'une part et C et G d'autre part, est compris entre 70° et 120° : $$70°\le \mathrm{\alpha }\le 120°$$
   
   (Dans l'exemple illustré, l'angle α est d'environ 90°).
3. c) L'entraxe DE est supérieur ou égal à l'entraxe AC : $$\mathrm{DE}\ge \mathrm{AC}$$
   
4. d) L'entraxe CD est inférieur ou égal à l'entraxe BD : $$\mathrm{CD}\le \mathrm{BD}$$
   
   
   En d'autres termes, le point d'ancrage du cadre 41 supérieur sur le cadre inférieur est plus proche de l'axe C que de l'axe B.
5. e) L'entraxe AE est supérieur ou égal à l'entraxe CD : $$\mathrm{AE}\ge \mathrm{CD}$$
   

To obtain this complex kinematics, at least one of the following conditions a) to e) must be satisfied:

1. a) The sum of the center distances FG and CG is less than or equal to the center distance BC: $$\mathrm{FG}+\mathrm{CG}\le \mathrm{BC}$$
   
2. b) The angle, denoted α, between the planes respectively defined by the axes A and C on the one hand and C and G on the other hand, is between 70 ° and 120 °: $$70°\le \mathrm{\alpha }\le 120°$$
   
   (In the example shown, the angle α is about 90 °).
3. c) The center distance DE is greater than or equal to the center distance AC: $$\mathrm{OF}\ge \mathrm{AC}$$
   
4. d) The distance between centers is less than or equal to the center distance BD: $$\mathrm{CD}\le \mathrm{BD}$$
   
   
   In other words, the anchor point of the upper frame 41 on the lower frame is closer to the axis C than the axis B.
5. e) The center distance AE is greater than or equal to the center distance CD: $$\mathrm{AE}\ge \mathrm{CD}$$
   

Two, three or four conditions a) to e) can be jointly satisfied. In the illustrated example, all conditions a), b), c), d) and e) are jointly satisfied.

As an example, a list of parameters and their corresponding numerical values are provided below, for which the articulation mechanism 33 functions correctly, that is to say that it makes it possible to obtain the translative phase. and the rotating phase, to the benefit of patient safety, and allows for ergonomic seating. In the following table, a succession of two contiguous letters, among the letters A, B, C, D, E, F and G, corresponds to the distance separating the axes defined by their respective letters. So, BC denotes the center distance (i.e. the shortest distance) defined between the B and C axes. parameter value FG 192 mm BC 253 mm CD 65 mm CG 34 mm IT 188 mm AE 160 mm OF 281 mm α 91.8 ° BF _X 64 mm BF _Z 25 mm

BF _X denotes the distance between the vertical planes passing through the axes B and F, and BF _Z the distance between the horizontal planes passing through these same axes.

We drew on the figure 12 , by way of comparison, a scheme similar to that of the figure 11 , to illustrate the different positions of the seat of the patent chair GB 1 406 420 between its extreme positions represented on figures 2 and 3 of this patent. On the diagram of the figure 12 whose orientation is reversed with respect to figures 2 and 3 from this patent, the front of the seat is on the right. It can be seen that the rear portion of the seat is moved essentially vertically and forwardly, without any significant component of rotation, while the front end of the seat is animated by a movement essentially of translation always directed towards the back, including at the end of the movement. Such kinematics do not follow the movement of the human body, and in particular do not provide the patient with the MPRP the forward impulse which, at the end of the movement, is necessary for him to recover.

Conversely, the articulation mechanism 33 of the chair 1 described above allows, thanks to the decomposition of the movement in two phases, namely an essentially translative phase followed (or preceded, depending on whether the patient sits or stands) d a phase essentially rotating, which makes it suitable for the kinematics of the human body. The result is improved safety for the patient 15 suffering from PMWS whose symptoms rétropulsion, of oppositional and stasobasophobie hypertension can thus be effectively combated.

Tests conducted with this chair 1 show that patients who have lost the habit of sitting and getting up without help can find this habit by daily use of the chair.

It is conceivable to go beyond the only assistance to movements consisting of standing up and sitting (for example gradually during a rehabilitation program) by limiting the stroke of the articulation mechanism 33 (and therefore of the seat 14) by means of a locking system of the spring 54.

This locking system acts for example on a shutter valve of a decompression vent of the spring 54, which blocks the rod 57 in position, regardless of this position. The locking system is for example actuated on the handlebar 13 by means of a handle 62 manually operable and connected to the spring 54 by a cable 63, in the manner of a bicycle brake.

The articulation mechanism 33 certainly adds weight to a chair that would be lacking, but this weight can remain contained, insofar as the parts that constitute it are relatively few and light enough. In total, the chair can remain relatively light. In addition, if the axes A, B, C, D, E, F and G are sufficiently greased, the mechanism 33 provides the chair 1 a high reliability, and therefore a long life.

Claims (10)

Medical armchair ( 1 ) comprising: a chassis ( 2 ) provided with a base ( 5 ), - a seat ( 14 ) movable relative to the base ( 5 ) and including a half-seat ( 14A ) and a front half-seat ( 14B ) mutually articulated about an axis A, and - a mechanism ( 33 ) for articulating the seat ( 14 ) can adopt a folded configuration placing the seat ( 14 ) in a low position close to the base ( 5 ), and an expanded configuration placing the seat ( 14 ) in a position at a distance from the base ( 5 ), this mechanism ( 33 ) comprising: a lower frame ( 34 ) rotatably mounted relative to the base ( 5 ) about an axis B and with respect to the front half-seat ( 14A ) about an axis C situated in the vicinity of an edge before it; o an upper frame ( 41 ) rotatably mounted relative to the lower frame ( 34 ) about an axis D located between the axes B and C, and relative to the half-seat ( 14B ) rear about an axis E located near a rear edge thereof; a coupling arm ( 48 ) rotatably mounted relative to the base ( 5 ) about an axis F and with respect to the front half-seat ( 14A ) about an axis G separated from the axis C ; an elastic return member ( 54 ) which biases the articulation mechanism ( 33 ) towards its deployed configuration; the axes A, B, C, D, E, F and G being parallel and defining, in a plane perpendicular to them: the axes B, C, G, F, a deformable lower BCGF quadrilateral; the axes A, C, D, E, an upper deformable quadrilateral ACDE; the axes A, B, C, D, E, F and G being positioned such that the lower BCGF quadrilateral is convex in the folded configuration, and concave by the G axis in the deployed configuration. Armchair ( 1 ) according to claim 1, characterized in that the sum of the centers FG and CG is less than or equal to the center distance BC. Armchair ( 1 ) according to claim 1 or claim 2, characterized in that the angle between the planes respectively defined by the axes A and C on the one hand and C and G on the other hand is between 70 ° and 120 °. Armchair ( 1 ) according to claim 3, characterized in that the angle between the planes respectively defined by the axes A and C on the one hand and C and G on the other hand is about 90 °. Armchair ( 1 ) according to one of the preceding claims, characterized in that the center distance DE is greater than or equal to the center distance AC. Armchair ( 1 ) according to one of the preceding claims, characterized in that the spacing CD is less than or equal to the center distance BD. Armchair ( 1 ) according to one of the preceding claims, characterized in that the center distance AE is greater than or equal to the center distance CD. Armchair ( 1 ) according to one of the preceding claims, characterized in that the member ( 54 ) of return is a gas spring. Armchair ( 1 ) according to claim 8, characterized in that the gas spring ( 54 ) is of the lockable type. Armchair ( 1 ) according to claim 8 or claim 9, characterized in that the gas spring ( 54 ) comprises a body ( 55 ) fixed to the frame ( 34 ) below, and a rod ( 57 ) fixed to the frame ( 41 ) higher.

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