WO2002022067A1

WO2002022067A1 - Dynamic articulated orthopaedic seat-back

Info

Publication number: WO2002022067A1
Application number: PCT/IT2001/000475
Authority: WO
Inventors: Ettore Pennestri'
Original assignee: Itop S.R.L.; Pierro, Marcello, Mario
Priority date: 2000-09-18
Filing date: 2001-09-13
Publication date: 2002-03-21
Also published as: ITRM20000505A1; AU2001295870A1; IT1317909B1; ITRM20000505A0

Abstract

Orthopaedic seat-back (1) for subjects affected by dystonia and the like, apt to accompany, and restrain, the involuntary movements of the subject, having an articulated structure, to make the seat-back assume a plurality of configurations, corresponding to bending and/or torsion stresses exerted by the subject thereon, in which the articulated structure comprises elastic return means (3, 4; 300, 400), arranged at each articulation thereof, to oppose the exerted stress and restore the seat-back to an unrelated resting configuration when the exerted stress is substantially nil.

Description

DYNAMIC ARTICULATED ORTHOPAEDIC SEAT-BACK

DESCRIPTION The present invention relates to a dynamic articulated orthopaedic seat-back, in particular to an orthopaedic seat-back for subjects affected by dystonia and the like. The so-called dystonic subjects are affected by neurological disorders causing involuntary muscle contractions, often in form of violent spasms. The latter mostly reveal themselves as sudden backward bending and/or torsional movements of the torso.

Due to the violence of said involuntary movements, when seated on a orthopaedic chair of traditional type, e.g., a wheelchair, a dystonic subject may violently bump against the seat-back thereof. Due to such bumping, the dystonic subject could self- inflict injuries as well as damage the surrounding environment. In particular, the subject could not only be injured by the impact, but even overturn the chair.

In an attempt to overcome the drawbacks mentioned above, some known wheelchairs have a rotatable connection of the seat-back to the seat-place, so as to allow a relative rotation therebetween when the subject exerts a bending stress onto the seat-back itself. However, this expedient is not decisive, since anyway the chair fails to effectively and safely restrain the subject's movements.

The technical problem underlying the present invention is that of providing an orthopaedic seat-back allowing to overcome the drawbacks hereto mentioned with reference to the known art.

This problem is solved by an orthopaedic seat-back for subjects affected by dystonia and the like, characterised in that it has an articulated structure, to make said seat-back assume a plurality of configurations, corresponding to bending and/or torsional stresses exerted by the subject on the seat-back itself, wherein said articulated structure comprises elastic return means, arranged at each articulation of the structure itself, to oppose the exerted stress and to restore said seat-back in an unrotated resting configuration when the exerted stress is substantially nil.

According to the same inventive concept, the present invention further relates to an orthopaedic chair, characterised in that it comprises an orthopaedic seat-back as defined above.

The present invention provides several relevant advantages.

The main advantage lies in the fact that the seat-back of the invention, by virtue of said articulated structure, can accompany and restrain the involuntary movements of the dystonic subject, changing its configuration according to the stresses applied thereon, i.e., of the movements made by the subject. Thus, the latter does not risk injuries due to bumping on a rigid surface. Moreover, the exerted stresses are absorbed by the seat-back of the invention, hence the chair onto which the latter is mounted will run a lesser risk of overturning.

Other advantages, features, and the operation modes of the present invention will be made apparent in the following detailed description of some embodiments thereof, given by way of example and without limitative purposes. Reference will be made to the figures of the attached drawings, wherein:

Fig. 1 relates to a first embodiment of the orthopaedic seat-back according to the present invention, showing a front perspective view of a seat onto which such seat- back is mounted; Fig. 2 is a rear perspective view of an articulated structure of the seat-back of Fig.

1, in a unrotated resting configuration;

Fig. 3 is an exploded perspective view of a detail of the seat-back of Fig. 1;

Fig. 4 is a front perspective view of a detail of the seat of Fig. 1;

Fig. 5 is a rear perspective view of the detail of Fig. 4; Fig. 6 is a top perspective view of a module of the seat-back of Fig. 1 in an unrotated configuration;

Fig. 7 is a top perspective view of a module of the seat-back of Fig. 1 in a rotated configuration;

Fig. 8 is a rear perspective view of a module of the seat-back of Fig. 1 in a unrotated configuration;

Fig. 9 is a rear perspective view of a module of the seat-back of Fig. 1 in a rotated configuration;

Fig. 10 relates to a second embodiment of the seat-back of the invention, showing a perspective view of a detail thereof; and Fig. 11 relates to a third embodiment of the seat-back of the invention, showing a perspective view of a detail thereof.

With initial reference to Fig. 1, a restraining orthopaedic seat-back for subjects affected by dystonia and the like, apt to be mounted on a chair S, is generally indicated by 1. For the sake of clarity, here the seat-back 1 has been represented without any covering.

According to the invention, the seat-back 1 has an articulated structure, shown in greater detail in Fig. 2. With reference to the latter, to implement such articulated structure, in the present embodiment the seat-back 1 provides a plurality of modules 2 connected one another, each having a bending degree of freedom and a torsional degree of freedom. In particular, each module 2 comprises parts rotatably connected thereamong, to allow a relative bending and/or torsional movement among them when a subject exerts a stress onto the seat-back 1 itself. In the present context, for 'bending movement' is meant a rotation about a substantially horizontal transverse axis of the module, indicated by F in Fig. 2. Therefore, such axis will hereinafter be referred to as bending axis F of the module 2. For 'torsional movement', instead, a rotation about a longitudinal axis of the module, indicated by T in Fig. 2, which will hereinafter be referred to as torsion axis T of the module 2, is meant. This latter axis is substantially vertical and coincident with a general longitudinal axis of the seat-back 1 when the latter lies in an unbent resting configuration.

Always according to the invention, the seat-back 1, at said rotatable connections among parts of a same module 2, provides bending elastic return means 3 and torsion elastic return means 4, to oppose bending and torsional stresses, respectively, and to restore the seat-back 1 in an unrotated resting configuration when the related stress becomes substantially nil. It will be understood that, in the present context, for 'substantially nil' stress a stress of an extent lower than that required to cause an elastic deformation of said return means is meant.

In the embodiment illustrated in Fig. 2, for each module 2 the bending elastic return means 3 comprises two bending springs, also indicated by 3, and the torsion elastic return means 4 two traction-compression springs, also indicated by 4.

The various components of the seat-back 1 hereto introduced will now be detailed with reference to the specific embodiments herein presented.

Initial reference will be made to Figs. 2 and 3 to describe a generic intermediate module 2 of the seat-back 1. This description will be carried out with reference to the aforementioned unrotated resting configuration of the seat-back 1.

Firstly, the module 2 comprises a piece-formed shaped main body 5, having at the top thereof a rotatable connection to a torsion pin 6, to give the module 2 itself said torsional degree of freedom about the torsion axis T. The shaped body 5 further has, at the bottom thereof, a rotatable connection to a bending pin 7, to give the module 2 said bending degree of freedom about the bending axis F.

The shaped body 5 in turn comprises a substantially quadrangular rear plate 51, said traction-compression springs 4 being rearwise blocked thereat. Therefor, such rear plate 51 provides two seats, in form of through holes, located near opposite top vertexes thereof. Each of these seats, hereinafter referred to as first rear plate seats and indicated by 511, receives respective rear holding means 241 of a respective traction-compression spring 4, as it will be detailed later on. Moreover, the rear plate 51 has two second rear plate seats 512, in form of threaded through holes, located near the bottom edge thereof, internally with respect to the first seats 511. Each of such second seats 512 receives a respective torsion stop member 8. In the present embodiment, each of such stop members 8 consists of a screw, and the maximum excursion of the torsional rotation allowed in a certain sense can be adjusted by tightening or loosening such screw, as it will be made apparent in the following. Of course, alternate embodiments could provide a likewise adjustability even in relation to the bending movement.

Moreover, the shaped body 5 comprises a substantially quadrangular base plate

52, adjacent to the rear plate 51 and substantially orthogonal thereto, said bending springs 3 being upperly blocked thereat. Therefor, also the base plate 52 has two seats, indicated by 521, located near the rear edge thereof, apt to receive respective top holding means 231 of a respective spring 3.

The shaped body 5 further comprises a coupling sleeve 53, located above the base plate 52, for the coupling thereof to the torsion pin 6.

Lastly, the shaped body 5 comprises two side flanges 54, located at the bottom of the base plate 52 at opposite side edges thereof and substantially orthogonal to both the base plate 52 itself and the rear plate 51. At the side flanges 54 the coupling between the shaped body 5 and the bending pin 7 is implemented. Therefor, these side flanges 54 have each a side flange seat 541, which rotatably receives the bending pin 7. It will be appreciated that the piece-forming of the shaped main body 5, attained, e.g., from a single aluminium or steel block, renders the manufacture of the module 2 simple and rapid. Of course, alternate embodiments could provide that the main body 5 be made of several components.

The torsion pin 6 is substantially cylindrical, with a widened bottom base 61. To attain an optimal strength, the pin 6 is preferably made of steel.

As mentioned above, the bottom portion of the torsion pin 6 is received within the box 53 of the shaped body 5.

Above this bottom portion, the torsion pin 6 has a first torsion pin seat 62, in form of a through hole, for the connection to a front interface 11 of the module 2, which will be described later on.

Moreover, the pin 6 has two second torsion pin seats 63, always in form of through holes, located above the first torsion pin seat 62 and substantially aligned along the longitudinal axis of the pin itself. Both such second seats 63 are apt to receive a height adjustment member 22, to implement height adjustment means of the module 2, as it will hereinafter be detailed.

The aforementioned rotatable connection between the sleeve 53 and the torsion pin 6 is attained interposing traditional gear members (not shown in the Figures) therebetween. hi the present embodiment, said gear members comprise a sliding bush, inserted onto the torsion pin 6 and interposed between the latter and the internal side wall of the sleeve 53, locked in position by a Sieger ring or an equivalent means. The bush is abutted onto the widened base 61 of the pin 6, to prevent longitudinal translations of the latter within the sleeve 53. The gear members at issue further comprise a sliding thrust block, inserted within the sleeve 53 and located below the widened base 61 of the torsion pin 6.

To allow a low-friction rotation of the torsion pin 6 with respect to the sleeve 53, the bush and the thrust block are made in an anti-friction material, like, e.g., Teflon, nylon and/or the so-called 'delrin'.

Those skilled in the art will understand that alternate embodiments could provide the employ of transmission members other than the ones hereto described, like, e.g., axial and/or radial bearings of traditional type. The bending pin 7, it also preferably made in steel, has two substantially cylindrical end portions 71, the pin being thereat rotatably received into the side flange seats 541 of the main body 5.

Moreover, the bending pin 7 has a squared-section central portion 72, it being thereat made integral to a cylindrical body 9 of the module 2, which will be described later on.

Said rotatable connection between the bending pin 7 and the main body 5 is implemented by interposing between the side flange seats 541 and the pin 7 anti- sliding bushes of traditional type, preferably made in one of the aforementioned antifriction materials. The rotatable connection at issue is completed, externally to the side flanges 54, by aluminium caps 75, made integral to the pin 7 at the transverse end sections thereof by connecting means of traditional type.

Of course, variant embodiments could provide tightening devices of traditional type, like, e.g., washers or nuts, in lieu of said aluminium caps.

The aforementioned cylindrical body 9 has, at an intermediate position along its longitudinal axis, a seat 91 for the bending pin 7, in form of a squared-contour through hole.

The cylindrical body 9 further has a bevelled top end portion. In particular, at the latter the cylindrical body 9 has a substantially horizontal face 93, apt to prevent forward bendings of the main body 5, and a slanting face 94 adjacent thereto, apt to implement an end-of-stroke for the backward bending movement of such body 5. Of course, also the definition of 'horizontal' face refers to the resting unbent configuration of the seat-back 1. In particular, the cylindrical body 9 is arranged, in such resting configuration, substantially axial to the torsion pin 6 and hence to the general longitudinal axis of the seat-back 1.

Preferably, the slanting face 94 forms an angle α equal to about 30 degrees with the substantially horizontal face 93. The cylindrical body 9 is hollow at least at a bottom portion thereof, at which it receives the torsion pin of a bottom module. In order to lock these two components therebetween, the cylindrical body 9 further has, at said hollow bottom portion, a further seat 92, in particular a through hole, to receive said height adjustment member 22. It will be understood that, according to a variant embodiment, the bending pin 7 can be rigidly connected to the side flanges 54 of the main body 5 at the seats 541 thereof, and rotatably received within the cylindrical body 9, with no substantial change in the operation of the structure.

The module 2 further comprises the aforementioned front interface 11, apt to receive the stresses exerted by the subject onto the seat-back 1.

In the present embodiment, the latter consists of several substantially quadrangular plates secured one another.

In particular, this structure comprises a front main plate 111, preferably in aluminium, and a reinforcement plate 112, preferably made of harmonised steel, of a transverse extension smaller than that of the main plate 111 and frontally secured thereto.

The main plate 111 has, at its side portions uncovered by the reinforcement plate 112 and per each side, two plate front seats 110 in form of through holes. Each of such seats allows the connection of the front interface 11 to a respective side band of the seat-back 1, as it will be described later on, with reference to Fig. 4. This connection is implemented by traditional connecting means like screws, bolts or the like.

Of course, a variant embodiment could provide that such reinforcement plate 112 be rearly rather than frontally secured to the main plate 111. The interface 11 has, internally to the plate front seats 110, two interface side seats 114, in form of through holes which interest both the main plate 111 and the reinforcement plate 112. Each of such interface side seats 114 receives respective front holding means 242 of a respective traction-compression spring 4. Hence, each interface side seat 114 corresponds and is axial to a respective first rear plate seat 511.

The interface side seats 114 have, at the level of the reinforcement plate 112, dimensions greater than those strictly required to allow the passage of the front holding devices 242. This allows a limited mobility of the reinforcement plate 112 with respect to the main plate 111, enhancing the capability of the module 2 to adapt its configuration to the stresses exerted by the seated subject onto the seat-back 1. Moreover, the interface 11 has an interface central seat 115, it also in form of a through hole bored through the main plate 111 as well as the reinforcement plate 112. This interface central seat 115 receives a locking member 611 of the interface 11 itself to the torsion pin 6. h the present embodiment, the interface 11 rests onto the base plate 52 of the shaped body 5. h particular, in the resting configuration the it is located substantially parallel to the rear plate 51.

The front interface 11 has plastic feet (not shown in the Figures) to favour a low- friction sliding thereof onto the base plate 52 when the seated subject exerts a torsional stress on the interface itself, as it will hereinafter be illustrated, with reference to the employ modes of the seat-back of the invention. According to a variant embodiment, the interface 11 can be mounted onto the torsion pin 6 so as to have a small slack with respect to the base plate 52, always to allow its rotation with respect to the latter.

In the present embodiment, said blocking member 611 is of traditional type, and consists of a bolt, preferably made of steel. The latter is received in said first torsion pin seat 62, so that the head thereof abuts the outside wall of the torsion pin itself, and be blocked from the opposite side, frontally to the interface 11, by a relative nut. Optionally, onto the member 611, between the main plate 111 and the torsion pin 6, a spacer of traditional type could be inserted.

In the present embodiment, the same blocking member 611 also secures the reinforcement plate 112 to the main plate 111.

The module 2 further comprises an abutment plate 12, substantially centred with respect to the cylindrical body 9 and secured thereon, below the seat 91 of the bending pin 7, by connecting means of traditional type.

The plate 12 has, at the top face thereof, two spring seats 121, each axial to a respective base plate seat 521 and apt to receive in abutment the end coil of a bending spring 3.

The arrangement and the holding modes of the return springs provided in the present embodiment will hereinafter be detailed, with additional reference to Figs. 6 and 8. As mentioned above, each bending spring 3 is held between the base plate 52 of the main body 5 and the plate 12. In particular, the bottom end coil of each spring 3 is blocked within a respective spring seat 121. Top wise, instead, each spring 3 is held by respective top holding means 231. The latter comprises, for each spring 3, a socket-head adjustment dowel, received in a respective seat 521 of the base plate 52. The top coil of each spring 3 abuts the thread of the respective dowel. Therefore, these top holding means 231 allows, by operating said dowel, a simple adjustment of the pre-loading on the spring.

As already mentioned, the traction-compression springs 4 of the module 2 are instead located between the front interface 11 and the rear plate 51 of the shaped body 5. In particular, each spring 4 is held rearwise, at the rear plate 51, by rear holding means 241, and frontwise, at the front plate 111, by front holding means 242. In the present embodiment, the rear holding means 241 comprises a bolt 243, housed in a respective first rear plate seat 511. The means 241 further comprises a plain washer 244, abutted onto the thread of the bolt 243 at the inside face of the rear plate 51, onto which washer 244 the end coil of the spring 4 abuts. The interposition of this plain washer 244 between the bolt 243 and the spring 4 enables the latter to effectively discharge the stress it is subjected to on a wider surface and ensures a better rear holding thereof.

It will be understood that also the rear holding means 241 implements an adjustment means of the pre-loading of the spring 4. In fact, to carry out such adjustment it suffices to operate the bolt 243, and then the washer 244 integral thereto, so as to let the former advance or back with respect to the rear plate 51.

The front holding means 242 relative to each spring 4 further comprises a bolt 245, received in a respective interface side seat 114 and blocked on both faces thereof. In particular, the head of the bolt 245 abuts the outside face of the interface 11, whereas a nut blocks the bolt 245 at the inside face of the interface itself. As for the rear holding means 241, the end coil of each spring 4 abuts a plain washer fixed with the respective bolt 245.

Of course, those skilled in the art will devise several means equivalent to the hereto described ones to hold the return springs. Such means could, e.g., comprise sleeves, screw-associated slotted idle nails, etc.. However, since the blockage modes of a spring on a plate are of traditional type and well-known to those skilled in the art, a further description thereof will be omitted.

The connection modes of adjacent modules of the seat-back 1 will hereinafter be described, always with reference to Fig. 3.

An intermediate module 2 is rigidly connected to the adjacent bottom module at its cylindrical body 9. In particular, as already mentioned above, this cylindrical body

9 is secured to the torsion pin of the bottom module by the said height adjustment member 22, which in the present embodiment is a connecting member of traditional type, in particular a screw. The member 22 is inserted through the seat 92 of the cylindrical body 9 and through one of the second torsion pin seats 63. Which one of the latter is to be engaged depends on the desired height of the bottom module.

Of course, alternate embodiments could provide a different implementation of the hereto described height adjustment means.

The connection of the module 2 to the adjacent top module takes place according to modes in all analogous to the abovedisclosed ones.

Further components of the seat-back 1 of the present embodiment will now be described with reference to Figs. 4 and 5. Firstly, the seat-back 1 also comprises the aforementioned side bands, indicated by 10 in said Figures, apt to envelope the back of the seated subject. These side bands 10 have a curved shape, in order to better receive the subject, and, preferably, a certain degree of plastic deformability, in order to be adapted to the conformation of the subject's back. Moreover, these side bands 10 are preferably made of a material having a certain degree of elasticity, to better assist the subject's movements. By virtue of the connection of the side bands 10 to the interface 11, the stresses exerted by the subject on these side bands are transmitted to the interface 11, and therefrom to the other components of the module 2 and of the seat-back 1.

The seat-back further provides, bottomwise, an elevation structure 15, which in the present embodiment comprises several parallelepiped-shaped members stacked one above the other. This elevation structure 15 allows to secure the seat-back 1 onto the seat-place of a chair so as to position the articulated structure to a determined height with respect to the seat-place, thereby creating an optimal coupling between the spine of the seated subject and the articulated structure itself. In particular, it is advisable that the articulated structure develop starting from the IN or N lumbar vertebra of the subject, i.e. of the first vertebra (starting from the bottom) provided with a certain degree of mobility.

The elevation structure 15 can advantageously be made in an elastic material, so as to have a certain deformability, to even further increase the adjustability of the seat-back 1 to the movements of the seated subject.

Above the elevation structure 15, a base module 20 of the articulated structure is secured.

The base module 20 comprises a fixed basis 16, made integral to the elevation structure 15 by connecting means of conventional type. The fixed base 16 frontally has a profile shaped substantially as a squared "U". In particular, each of the two vertical arms of such "U" consists of a side upright 161 having a substantially triangle-shaped contour. At a bottom portion of each upright 161, a plurality of seats 162, all apt to receive a rod 17, is obtained, to implement means for adjusting the initial slant of the seat- back 1, as it will be detailed hereinafter.

Preferably, the seats 162 are obtained so as to allow a choice among four initial angles equispaced in a range 5÷35 degrees with respect to the vertical.

The uprights 161, above such plurality of seats 162 and near to a top apex thereof, have each a further seat, to implement a rigid connection with a base bending pin 70. It will be understood that such rigid connection, as well as the hereto mentioned ones, can be implemented in several manners, well-known to those skilled in the art. In particular, in case this connection be carried out by traditional connecting means, like screws or bolts, the latter could advantageously be associated with anti- loosening washers, or with deformable rings apt to carry out the same function.

Moreover, the base bending pin 70 is rotatably connected to a shaped base body 50, at side flanges 540 thereof. Such base side flanges 540 differ from those of the aforedescribed intermediate modules 2 in that bottomwise they have an incision 541 promoting the abutment thereof onto the rod 17, frontally thereto, when the seat-back 1 is in a resting configuration. Hence, it will be understood that the angle of the initial slant of the articulated structure can simply be adjusted by selecting the pair of seats 162 of the uprights 161 in which to insert the rod 17. The abutment of the base flanges 540 on such rod 17 further prevents a frontal bending of the seat-back 1 beyond the chosen angle.

Of course, also the base module 20 will have stop means to prevent a rear bending of the module itself in excess of a certain pre-set threshold, hi particular, in the present embodiment such stop means consist of a cylindrical block 90, shown in Fig. 5, located behind the rod 17 and apt to block in abutment a base plate 520 of the base body 50. This cylindrical body 90 is preferably made of a material having damping properties, e.g., a polymeric material.

At the sides of the cylindrical block 90, the base module 20 further comprises elastic base means, in particular bending springs 30, held topwise at the base plate 520 and bottomwise at the basis 16, according to modes analogous to the ones described above with reference to an intermediate module 2. hi the present embodiment, the seat-back 1 also comprises a headrest 18, shown in Fig. 4. The latter is of traditional type, and it is made integral to the torsion pin 6 of the topmost module 2 by a sleeve 19. According to a variant embodiment, within the sleeve a ball joint can be housed, it also of traditional type and well-known to those skilled in the art, to allow any rotation whatsoever to the headrest 18. Always with reference to Fig. 4, the elevation structure 15 of the seat-back 1 is secured onto the seat-place of the chair S, at a seat-place plate 13 secured onto the frame of the chair itself. Preferably, such seat-place plate 13 provides adjusting means 14 to arrange the plate itself in a more or less advanced position onto the chair, according to the user's needs and preferences. In Fig. 4, such adjusting means

14 are depicted in form of bolts apt to be tightened in the desired position within related housing grooves obtained in the seat-place plate 13.

A subject (not shown in the Figures) can sit onto the seat S and rest the torso onto the seat-back 1, so as to have the back enveloped by the side bands 10. Advantageously, the seat S will have anti-turnover means, like, e.g., a front balance weight applied under the seat-place, or stabilising front wheels R, schematically represented in Fig. 1.

It will presently be appreciated that the seat-back of the invention is extremely simple to manufacture, assemble and mount on a chair, allowing, according to the hereto described embodiment, the employ of standard components. Moreover, even the replacement of component parts, and in particular of the return springs, is extremely simple and swift.

It will also be appreciated that the hereto disclosed seat-back provides a wide range of possible adjustment, both in terms of height of the modules and of stiffness of structure, to better adjust to the specific needs of each user. For example, in order to better adjust to the specific properties of the subject's spine, the articulated structure of the invention can provide springs of different rigidity in the various modules of the structure itself.

The employ modes of the seat-back of the invention will hereinafter be described. With initial reference to Fig. 8, the seated subject can exert bending and/or torsional stresses onto the seat-back 1. For simplicity's sake, the case in which such stresses be applied at the level of an intermediate module 2 will be considered.

When the subject exerts a bending stress onto the bands 10 or directly onto the interface 11, this stress is transmitted from the latter to the main body 5 via the torsion pin 6 coupled to the sleeve 53 of the body 5 itself. If the stress suffices to elastically deform the bending springs 3, the main body 5 rotates about the bending pin 7, bending backwards the springs 3, as shown in Fig. 9.

In such rotation, the module 2 also drags therewith all the modules located thereabove, by virtue of the connection of the main body 5 itself to the cylindrical body 9 of the top module implemented by the torsion pin 6. In fact, it has to be pointed out that a top module of the seat-back 1 cannot rotate forward with respect to the bottom adjacent module by virtue of the abutment of the base plate 52 thereof onto the horizontal face 93 of the cylindrical body 9.

The backward rotation of the module 2 is limited by the abutment of the base plate 52 onto the slanting face 94 of the cylindrical body 9. In the present embodiment, the maximum amplitude of the relative rotation between two adjacent modules is of about 30 degrees.

According to a variant embodiment, the end-of-stroke for the backward rotation of the module 2 can directly be attained selecting springs of a predetermined length.

It will be understood at this point that the maximum bending angle with respect to the vertical that a certain module of the seat-back 1 can attain corresponds to the sum of the related bending angles of all the modules located therebelow. In particular, once the stressed module has reached the maximum allowed backward bending, it, if stressed again, induces the adjacent bottom module to rotate backwards, and so on. This increases the absolute bending angle of the module at issue, allowing the seat- back 1 to adjust to the amount of applied stress and, therefore, to the body configuration assumed by the seated subject.

It will be appreciated that the impossibility of forward rotation of the modules prevents a pushing off of the subject from the seat. Such a forward rotation could, e.g., be induced by the elastic return of the bending springs 3.

When the stress applied by the subject is won by the returning force of the involved springs, the seat-back is restored to the initial resting configuration.

With reference now to Fig. 6, when instead the subject exerts a torsional stress onto the bands 10 or directly onto the interface 11, such stress directly induces the interface 11, and therefore the torsion pin 6 fixed thereto, to rotate about the axis T of the latter. Hence, the springs 4 are elastically deformed, as shown in Fig. 7, and in particular one is compressed and the other one stretched.

The adjacent module above the stressed one can be dragged in rotation as well, by virtue of the connection of the torsion pin 6 to the shaped body of the top module, by the cylindrical body of this latter module. The transmission of such rotation movement is mediated by the torsion springs of the top module, which absorb a fraction of the involved energy reducing the range of the transmitted movement.

The torsion rotation of the module 2 may take place both left- and right-wise. The maximum amplitude of such rotation is determined by the abutment of one of the two torsion stop members 8 against the inside face of the interface 11. Upon such abutment, the module 2, if stressed again, induces in rotation also the module bottomwise adjacent thereto, due to the connection of the main body 5 thereof to the cylindrical body 9 by means of the bending pin 7. Hence, also the maximum torsion angle attainable by a certain module of the seat-back 1 corresponds to the sum of the relative torsion angles of all the modules located bottomwise thereto.

It will be understood that for simplicity's sake the cases of torsion and of bending stresses were treated separately, though of course they will typically take place together, without however disproving any of the abovereported considerations. It will now be appreciated that the articulated structure of the invention carries out the double function of supporting the subject when he/she is not experiencing involuntary muscle contractions, and, in presence of such contractions, of restricting without however completely impeding the related movement. Moreover, when the applied stress returns substantially nil, the seat-back restores the subject to a proper erect posture.

Hence, the seat-back of the invention is a 'dynamic' seat-back, i.e., it is mobile and capable of selectively responding to the stresses applied thereon by the seated subject.

In this regard, it has to be pointed out that the bands 10 effectively house and support the subject's torso, favouring an optimal coupling of the latter to the seat- back of the invention, also by virtue of the plastic deformability thereof. The curved shape thereof, associated with the articulated structure of the seat-back itself, implements a so-called 'leaf-shaped' skeleton which reproduces the skeletal structure of the subject's torso, following the spine-ribs association. It will also be appreciated that the headrest 18, by virtue of the rigid connection thereof to the top module of the articulated structure, has the same degrees of freedom of this latter module, and therefore also the subject's head movements are accompanied and restrained by the articulated structure itself. In particular, the headrest 18 can induce a change in the configuration of the entire articulated structure. This is particularly useful, since the cervical vertebrae have a greater mobility with respect to the others, and therefore involuntary spasms at the head level have a high probability of causing injuries to the subject if they are not suitably restrained.

Moreover, it will be understood that the reinforcement plate 112 opposes, by its elastic reaction, the deformation of the interface 11 caused by the stresses exerted by the subject onto the bands 10 and also by the elastic reaction of the abovementioned traction-compression springs 4.

The seat-back of the invention is particularly suitable for dystonic subjects, though of course it can also be employed in all pathologies benefiting from the availability of an elastic, rather than rigid, seat-back. Moreover, the latter can also be advantageously mounted on normal office chairs.

Those skilled in the art will also appreciate that the seat-back of the invention can even be used for rehabilitative purposes, e.g., to allow the subject to train the torso muscles, and/or for educational purposes, to teach a correct posture to the subject.

Though the invention has hereto been disclosed with reference to a preferred embodiment thereof, those skilled in the art will devise several variant for the implementation thereof. For example, the elastic return means could be implemented in several ways, using various differently associated spring systems, or members made in materials having special elastic properties. Likewise, also the end-of-stroke of the bending and torsional movements could be implemented by a number of means alternative to the heretodisclosed ones. In this respect, alternate embodiments of such elastic return means are shown in

Figs. 10 and 11. The seat-backs related thereto will be described with exclusive reference to the members differentiating them from the seat-back of the first embodiment, and analogous components will be indicated by the same reference numbers. Fig. 10 is a bottom perspective view of a part of a module of a second embodiment of the seat-back of the invention. This module, generally indicated by 200, has elastic means to oppose a bending stress, implemented by torsion springs 300 rather than by the bending springs of the first embodiment. These torsion springs 300 are both wound on a bending pin 7 and the ends of each of them are blocked on a base plate 52 of a shaped main body 5 and on a cylindrical body 9, respectively.

Fig. 11 is a perspective view of a part of a module, in this case indicated by 201, of a third embodiment of the seat-back of the invention. In this case, the module 201 has traction-compression springs 400 to oppose torsional stresses, directly anchored to a blocking member 611 of a front plate (not shown in Fig. 11), to a torsion pin 6 and to a cylindrical sleeve 530 of a main body 501. It has to be pointed out that also in this third embodiment the module 201 has torsion stop means comprising a slot 80 of predetermined length, obtained in the sleeve 530.

Further variants could provide that several articulated module-structures of the abovedescribed type be mounted in parallel, to further enhance the adjustability of the structure to the body configurations assumed by the seated subject.

Lastly, it will be understood that the present invention also relates to a simplified embodiment of a seat-back, in which the latter has an individual module provided with a single degree of bending or torsional freedom.

The present invention has hereto been described with reference to preferred embodiments thereof. It is understood that other embodiments thereof afferent to the same inventive concept may exist, all falling within the protective scope of the annexed claims.

Claims

I. An orthopaedic seat-back (1) for subjects affected by dystonia and the like, characterised in that it has an articulated structure, to make said seat-back assume a plurality of configurations, corresponding to bending and or torsional stresses exerted by the subject on the seat-back itself, wherein said articulated structure comprises elastic return means (3, 4; 300, 400), arranged at each articulation of the structure itself, to oppose the exerted stress and to restore said seat-back in an unrotated resting configuration when the exerted stress is substantially nil. 2. The seat-back (1) according to claim 1, wherein said elastic return means comprises at least one spring (3, 4; 300, 400).

3. The seat-back (1) according to the preceding claim, wherein said elastic return means comprises at least one bending spring (3) to oppose a bending stress.

4. The seat-back (1) according to claim 2, wherein said elastic return means comprises at least one torsion spring (300) to oppose a bending stress.

5. The seat-back (1) according to any one of the claims 2 to 4, wherein said elastic return means comprises a pair of traction-compression springs (4; 400) to oppose a torsional stress.

6. The seat-back (1) according to any one of the preceding claims, comprising adjusting means (231, 243) for adjusting the pre-loading of said elastic return means

(3, 4).

7. The seat-back (1) according to any one of the preceding claims, comprising bending stop means (94), for restricting the amplitude of the backward bending motion of said articulated structure caused by a bending stress. 8. The seat-back (1) according to the preceding claim, wherein said bending stop means (94) is apt to prevent, at each articulation, rotations of an amplitude greater than about 30°.

9. The seat-back (1) according to any one of the preceding claims, comprising means (93) for preventing the forward bending of said articulated structure. 10. The seat-back (1) according to any one of the preceding claims, comprising torsion stop means (8; 80), for restricting the amplitude of the torsional movement of said articulated structure caused by a torsional stress.

II. The seat-back (1) according to the preceding claim, wherein said torsion stop means (8) allows an adjustment of the maximum amplitude of the torsional movement.

12. The seat-back (1) according to any one of the preceding claims, comprising side bands (10) apt to envelope the subject's torso, connected to said articulated structure.

13. The seat-back (1) according to the preceding claim, wherein said side bands (10) are plastically deformable.

14. The seat-back (1) according to claim 12 or 13, wherein said side bands (10) are made of an elastic material. 15. The seat-back (1) according to any one of the preceding claims, comprising at least one module (2, 20; 200; 201) having a bending degree of freedom and a torsional degree of freedom.

16. The seat-back (1) according to the preceding claim, wherein said at least one module comprises one main body (5, 50) rotatably connected to further parts (6, 7, 70) of said module (2, 20).

17. The seat-back (1) according to claim 15 or 16, wherein said at least one module (2) provides a front interface (11), apt to receive the stresses exerted by the subject on said seat-back.

18. The seat-back (1) according to any one of the claims 12 to 14 and according to claim 17, wherein said side bands (10) are rigidly connected to said front interface

(11).

19. The seat-back (1) according to claim 17 or 18, wherein said front interface (11) comprises a plurality of plates (111, 112) secured one another.

20. The seat-back (1) according to the preceding claim, wherein said interface (11) comprises a reinforcement plate (112) of harmonised steel.

21. The seat-back (1) according to claim 16 and to any one of claims 17 to 20, wherein said interface (11) is rotatably connected to said main body (5), to allow a relative torsional movement of said interface with respect to said main body.

22. The seat-back (1) according to any one of the claims 15 to 21, wherein said at least one module (2, 20) has height adjustment means (63, 11) thereof.

23. The seat-back (1) according to any one of the preceding claims, comprising a headrest (18) secured topwise of said articulated structure.

24. The seat-back (1) according to any one of the preceding claims, comprising means (161, 17) for adjusting the initial slant of said seat-back with respect to the seat-place of a seat (S).

25. The seat-back (1) according to any one of the preceding claims, comprising an elevation structure (15), apt to be mounted onto the seat-place of a seat (S) to position said articulated structure at a determined height with respect thereto.

26. The seat-back (1) according to the preceding claim, wherein said elevation structure (15) is made of an elastic material.

27. An orthopaedic chair (S), characterised in that it comprises a seat-back (1) according to any one of the preceding claims.

28. The chair (S) according to the preceding claim, comprising a seat-place plate (13) and means (14) for adjusting the position of said plate.

29. The chair (S) according to claim 27 or 28, comprising anti-turnover means (R).