Title: OSCILLATION SYSTEM FOR CHAIRS

Technical field of the invention

The present invention relates to an oscillation system for chairs, in particular of the type in which the magnitude of the reaction of the system itself to a given oscillation is adjustable.

State of art

There are known chairs, in particular for office, which comprise an oscillation system comprising a rigid frame costrained to a floor resting base, a support of the backrest oscillating with respect to the frame and a support of the seat.

In some embodiments, called in the jargon‘with permanent contact’, the support of the seat is fixed (or integral) with respect to the frame and only the support of the backrest oscillates.

In some embodiments, the support of the seat and the the support of the backrest are a single oscillating body (as described for example in WO2016/166728), or two distinct but rigidly constrained bodies that oscillate in unison.

In other embodiments (called in the jargon 'synchronized systems') the support of the seat and the support of the backrest are distinct and separated from each other, and they are both articulated with respect to the frame independently or (as described for example in W02009/153811A1) in a mutually constrained manner, but not rigidly, thanks to an articulation mechanism that connects them. In this way a movement of the one corresponds to a predetermined movement of the other.

When the support of the backrest oscillates due to a user action exerted on the backrest, the oscillation system opposes itself with an elastic reaction which tends to bring the support of the backrest back into the at-rest position (i.e. without actions) and that must be won by the user. This reaction is typically obtained by means of an elastic element, for example at least one spring, interposed between the frame and the support of the backrest and/or of the seat.

There are also known (as described for example in WO2017/064619A1) oscillation systems comprising a user- actuatable adjustment system for adjusting, according to the user preferences, the magnitude of the reaction (called in the jargon 'stifness') that the oscillation system opposes to a given oscillation. For example, the adjustment system can vary the degree of preload (e.g. compression or extension) of the elastic element or the position of at least one anchoring point of the elastic element to the frame and/or to the support of the backrest and/or of the seat. In this way it is possible to adapt the response of the oscillation system to the user preferences. For example, typically a light and/or weak user prefers a softer response of the oscillation system than a heavy and/or strong user.

The adjustment system described in WO2017/064619A1 comprises a movement member on which it is afforded a slot consisting of a discrete series of seats for a pin slidingly movable along the slot. An end of the spring is abutted to the pin, so that when the movement member slides along a guide integral with the support of the backrest, the moving member moves the pin and therefore the end of the spring, thus varying the distance between the pin and the oscillation axis of the support of the backrest. Each seat of the slot is separated from the adjacent seat(s) by a respective relief.

Summary of the invention

The Applicant has found that the known adjustable oscillation systems have some drawbacks and/or can be improved in some aspects.

The Applicant has, for example, found that in WO2017/064619A1 to move the pin from a seat to a contiguous seat along the slot, it is necessary to overcome the aforesaid relief, for example it is necessary to win the elastic reaction force exerted by the wall of the slot opposite to the wall provided with the aforesaid reliefs, said opposite wall being, for example, provided with a series of lightening cavities in order to facilitate its elastic deformation. This entails the application of a physical exertion by the user during the manual adjustment of the stiffness of the oscillation system.

Moreover, if suitable kinematic mechanisms of demoltiplication are introduced in an attempt to reduce the physical exertion exerted by the user in the adjustment, it could occur the disadvantage of a very long adjustment action by the user, for example more than one complete revolution of the control rod, for a given range of the reaction magnitude.

Furthermore, according to the Applicant, the fact of having to overcome a reaction by the adjustment system entails the necessity of a user action capable of exerting sufficient force to overcome this reaction, with consequent difficulty in developing a fully automatic adjustment system, i.e. capable of self-adjusting (for example adjusting the stiffness according to the user weight) without the user action.

An object of the present invention is to provide an oscillation system for chairs comprising an adjustment system capable of varying the magnitude of the reaction that the oscillation system itself opposes to a given oscillation imposed by the user (‘stiffness’), which solves one or more of the aforesaid problems.

An object of the present invention is to provide an oscillation system comprising an adjustment system capable of varying the stiffness of the oscillation system, which at the same time is comfortable and ergonomic, in particular with regard to the manual adjustment of the stiffness.

An object of the present invention is to provide an oscillation system for chairs able to vary the stiffness over a wide range of values, which requires, at the same time, a spatially and/or temporally limited user adjustment action.

An object of the present invention is to provide an oscillation system comprising an adjustment system capable of varying the stiffness of the oscillation system in an automatic way (typically as a function of the user weight), without necessarily requiring a manual action of the user itself.

According to the Applicant, the problem of achieving one or more of these objects is solved by an oscillation system for chairs according to the attached claims and/or having the following features.

According to an aspect the invention relates to an oscillation system for chairs, comprising:

- a frame (e.g. rigid) to be associated with a base of a chair;

- a support, structured to support a backrest and/or a seat, mounted on the frame for oscillating with respect to the frame.

Preferably the oscillation system comprises a first elastic system operatively interposed between said frame and said support, comprising a first elastic element structured to oppose an elastic reaction (tipically increasing) to an (increasing) oscillation of the support with respect to a rest position of the support in absence of oscillation forces. Preferably the oscillation system comprises an adjustment system comprising a guide (afforded within said frame or within said support) and a slider which slidably engages said guide, wherein a first anchoring end of said first elastic element is fixed to said slider and wherein said adjustment system is structured to move said slider (and thus said first anchoring end) along said guide (to vary said elastic reaction opposite to a given oscillation). Preferably the adjustment system comprises a locking system of said slider in said guide comprising respective surfaces of said slider and said guide, said respective surfaces being mutually facing.

Preferably a first surface between said respective surfaces of the slider and of the guide has reliefs and a second surface between said respective surfaces of the slider and of the guide is structured or shaped to physically engage with said first surface.

Preferably said first elastic element, during said oscillation of the support, pushes against each other said first and second surfaces to engage them reciprocally.

Preferably the adjustment system comprises a disengagement system structured to move away one from the other, in the rest position of the support (and for a first section of oscillation), said first and second surfaces to remove said mutual engagement.

According to a further aspect, the present invention relates to a chair comprising the oscillation system according to the present invention.

The expression 'surface (...) has reliefs’ indicates any non-smooth surface, regardless of the height of the reliefs (typically from the order of tens microns to the order of the millimeters) and/or of the distribution of the reliefs heights (which may be a single value or may be any statistical distribution, including the random one) and/or of the spatial distribution of the reliefs (which can be random or ordered, periodic or non-periodic, with respect to one or two dimensions) and/or of the shape of the reliefs (which can be irregular or regular).

The expression‘oscillation’ referred to the support refers to any movement of the support with respect to the rest position, which is for example a pure translation or a pure rotation around an oscillation axis (as descibed in WO2016/166728 and in WO2017/064619A1) or a roto-translation (as described in W02009/153811A1)

The terms vertical, horizontal, upper, lower and similar refer to a condition of normal use of a chair embodying the oscillation system of the present invention.

The terms front and back refer to a normal use of a chair embodying the present invention, in which the legs of the user are located at the front portion of the system.

The expression 'magnitude of the elastic reaction', or briefly 'elastic reaction', refers to a quantity directly or indirectly representative of the value of the torque, with respect to the oscillation axis of the support, applied to the support and generated by the elastic system that reacts to the oscillation. This torque depends on the vector elastic force and on the vector arm of the point of application of the elastic force with respect to the oscillation axis.

According to the Applicant in the adjustment system, comprising a guide and a slider and a locking system comprising respective mutually facing surfaces of the slider and of the guide, the first elastic element, during the oscillation of the support, pushes the respective surfaces against each other to physically engage the reliefs of the first surface with the second surface in order to provide a mechanical engagement between the two surfaces. The mechanical interaction between the first and second surface, thus achieved, prevents the mutual sliding of these surfaces along the tangential direction, thus achieving a locking of the slider along the guide during the oscillation. In this way the user does not experience a variation of the stiffness during the oscillation and/or he does not perceive, during the oscillation, moving members which could give unpleasant feeling.

Moreover, the presence of the disengagement system structured to move away, in the rest position of the support, the surfaces of the slider and of the guide to remove the engagement, allows the slider to move along the guide and then to adjust the stiffness without encountering any resistance at least by the surfaces of the slider and of the guide. In this way, for example in the case of manual adjustment of the stiffness, the user does not perceive any resistance and the operation is particularly ergonomic, even against a short stroke of the control member that adjustes the position of the slider along the guide.

Furthermore, the disengagement system facilitates the realization of an automatic self-adjusting system of the stiffness, i.e. it does not require user action, for example as a function of the user weight only (as better described below). In fact, the adjustment system of the present invention allows the adjustment even against a limited stroke of the movement control members of the movable end of the elastic element and against a limited force applied to the control members.

It is observed that the present solution differs from a comparative solution in which said respective surfaces of the slider and of the guide are made by means of a pad and a disk as in the vehicles braking systems, since in the latter solution both the surfaces are smooth and the locking occurs by friction between the two surfaces, differently from the locking by engagement (or mechanical interlocking) of the present solution.

The present invention in one or more of the aforesaid aspects can have one or more of the following preferred features.

Preferably said first surface is rigid. In this way the reliefs facilitate the desired locking avoiding their deformation or abrasion/wear or possible breakage.

Preferably said second surface has reliefs, more preferably it is rigid. In this way, the physical engagement is achieved by mutual interposition of the reliefs of the two surfaces.

Preferably said second surface is elastically deformable to match the first surface when pushed against the first surface. In this way, the engagement between the two surfaces occurs as a result of the elastic deformation of the second surface which match the reliefs of the first surface, thus achieving a continuum of locking positions along the guide.

Preferably said first surface belongs to the guide and said second surface belongs to the slider. In this way the realization of the first surface is simplified, for example by means of a shaped support (for example made of rigid plastic material), having the reliefs, which can be applied and firmly fixed to the support of the backrest at the guide and which, in general, can differ in the material from the support of the backrest (the latter is usually made of metallic material, typically made of steel). Moreover, in the embodiment in which the second surface is deformable, it is easier to make an elastically deformable slider to which the second surface belongs.

Preferably said reliefs have a height less than or equal to 4 mm, more preferably less than or equal to 3 mm, even more preferably less than or equal to 2 mm. In this way, the excursion required to couple/uncouple the two surfaces by mutual approach/removal remains limited, with consequent structural simplicity and/or overall compactness of the system.

Preferably said reliefs have a height greater than or equal to 10 pm, preferably greater than or equal to 30 pm, even more preferably greater than or equal to 50 pm. In this way, the height of the reliefs facilitates the mechanical interaction between the reliefs themselves to achieve the locking of the respective surfaces and prevent their mutual sliding.

Preferably said reliefs have, along a main development direction of the guide (i.e. the main direction along which the slider slides), a periodic pattern having a period. In this way, it is ensured the possibility of adjusting the locking position of the slider in a discrete succession of regularly spaced positions.

Preferably, said period is greater than or equal to 0.05 mm, more preferably greater than or equal to 0.1 mm, even more preferably greater than or equal to 0.2 mm and/or less than or equal to 5 mm, more preferably less than or equal to 3 mm, even more preferably less than or equal to 2 mm. In this way it is achieved an appropriate discretization of the locking positions between guide and slider.

Preferably each relief has a development along a direction transversal to said main development direction of the guide, more preferably each relief has a constant shape along said development of the relief. In this way it is enhanced the interaction surface between guide and slider.

Preferably said reliefs have a triangular shape on a section orthogonal to said transversal direction, more preferably they have an isosceles trianglular shape, even more preferably an equilateral trianglular shape. In this way it is enhanced the penetration of the first surface into the elastically deformable second surface and, in the embodiment in which also the second surface has reliefs and it is rigid, it is enhanced the mutual interpenetration of the reliefs and the achievement of the locking position, thanks to the invitation function performed by the oblique sides of the triangles. In this way, in addition, flat surfaces are avoided which could result in an incorrect coupling of the first and second surface (for example a square shape would not effectively penetrate the second elastically deformable surface, or could lead to a difficult interlocking between the two surfaces or a rough interlocking, typically a snap interlocking).

Preferably said triangular shape reliefs have an angle at a top vertex of the surface greater than 40° and/or less than 80°. In this way there are avoided, on one hand, too thin triangular profiles (in cases of angles at the vertex less than 40°) that could incur deformation and/or breakege due to the tangential stresses to which they are subjected during operation and, on other hand (angles at the vertex greater than 80°), there are avoided oblique sides with an inclination unfavorable to the correct coupling of the first and of the second surface, with consequent difficult and/or rough interlocking.

Preferably said reliefs are in contiguous succession (e.g. with sawtooth pattern) along said main development direction of the guide. In this way, it is ensured the possibility of locking between the guide and the slider along the whole guide with close locking positions.

Preferably said reliefs have a height greater than or equal to 0.05 mm, more preferably greater than or equal to 0.1 mm, even more preferably greater than or equal to 0.2 mm. In this way, even in the presence of triangular reliefs, it is achieved an adequate resistance to stresses along the sliding direction of the slider along the guide, even in the case of great user actions.

Preferably said reliefs have a height less than or equal to 0.9 mm, more preferably less than or equal to 0.7 mm, even more preferably less than or equal to 0.5 mm. The Applicant has verified that this height is enought to lock the slider, even in presence of triangular shaped reliefs.

Preferably said reliefs have a width at their base greater than or equal to 0.05 mm, more preferably greater than or equal to 0.1 mm, even more preferably greater than or equal to 0.2 mm. In this way the reliefs have a width sufficient to resist, without deforming and/or breaking, to the mechanical stress acting on them during the locking between guide and slider.

Preferably the reliefs of the second surface have at least one, more preferably all, of the features of the reliefs of the first surface. In this way, it is enhanced the physical interference, between the reliefs of the first and the second surfaces, to prevent, during the oscillation, their mutual sliding.

Preferably the reliefs of the second surface are counter-shaped to the reliefs of the first surface. In this way it is maximized the contact area between the two surfaces and therefore the locking effect.

In the embodiment in which the second surface is elastically deformable, said second surface is preferably flat. In this way, it is achieved an appropriate elastic deformation of the second surface to lock the second surface with respect to the first one.

In an embodiment, wherein the second surface is rigid and has reliefs too, said first and second surfaces are rough surfaces, for example with reliefs spatially randomly distributed and/or irregularly shaped, and with heights ranging from one tens of microns up to hundreds of microns. In this way, when the two rough surfaces are kept in thrust against each other during the oscillation, the mechanical interlocking that is created between them prevents their mutual sliding.

Preferably the reliefs of both surfaces are comparable in size and/or spatial distribution. In this way the mechanical interlocking is efficient.

For example, the two rough surfaces are covered (by gluing) with granules of abrasive material (e.g. glass, sand, aluminum oxide, etc.), for example as the surfaces of the abrasive paper, or surperficially treated to make the surface rough.

Preferably said first and second rough surfaces belong to a grain designation class greater than or equal to P12 (coarser grain, having average particles diameter equal to about 1800 microns) and less than or equal to P280 (finer grain, having average particles diameter equal to about 50 microns). The grain designation class is established according to the ISO 6344 standard relating to the abrasive papers and coatings. In this way the reliefs, which constitute the first and second rough surfaces, favor a mutual mechanical interaction between the surfaces and they achieve the mutual locking between the two surfaces.

Preferably the first elastic system comprises a further elastic element, comprising a respective elastic body, distinct from said first elastic element, the further elastic element being preferably deformed (preloaded) in the rest position of the support. In this way the further elastic element exerts a residual elastic force which holds the support in the rest position and which must be won by the user to start the oscillation.

Preferably, said first elastic system comprises at least one elastically deformable body fixed to the slider and, in rest position of the support, in sliding contact with a portion of said guide. In this way the deformable body accompanies the slider in the displacement along the guide, maintaining contact with the guide in each phase of the displacement.

Preferably in the rest position the elastically deformable body is substantially undeformed. In this way, during the adjustment of the stiffness of the system, the deformable body (which remains substantially unloaded by elastic return forces) can slide without developing a friction such as to counteract the adjustment of the system.

Preferably, along a first section of oscillation starting from the rest position of the support, said deformable body is structured to undergo a progressive elastic deformation against said portion of the guide. In this way, the deformable body elastically, and increasingly, opposes itself to the support oscillation along the first section (for example, for a section of oscillation of about 1 °), at which the first elastic element does not exert any opposition to the oscillation due to the disengagement system (and typically the further elastic element exerts a traction). Preferably, the disengagement system is structured to allow a mutual contact between said first and second surface at the end of the first section of oscillation. In this way, at the end of the first section of oscillation, the first elastic element begins to deform and thus to exert a progressive elastic reaction, which is added to the elastic reaction developed by the deformable body (which does not undergo further deformation beyond the first section). In this way, the deformable body prevents for example the occurance of abrupt jumps of elastic reaction, at the end of the first section of oscillation, due to the triggering of the first elastic element, which could instead involve sudden variations of the stiffness of the response of the oscillation system, as well as cause annoyance to the user.

Preferably said elastically deformable body is an elastomeric body (alternatively it can be made of plastic material, or by one or more springs).

Preferably, said support is a support of the backrest.

Preferably, the oscillation system comprises a support of the seat, distinct and separate from the support of the backrest.

Preferably the support of the seat comprises a first support element (e.g. rigid) structured to be coupled (e.g. rigidly) to the seat and coupled to said frame to be able to assume, given an oscillation position of the support of the backrest, a plurality of relative positions with respect to the frame as a function (only) of, and (solely) by effect of, a weight force applied to the first support element, said relative positions having different vertical heights of the first support element with respect to the frame.

Preferably said first elastic element comprises an elastic body (e.g. a spring), a first fastening member and a second fastening member distinct from the first one, wherein two opposite ends of the elastic body are respectively fixed (preferably screwed on respective external threads) to the first and to the second fastening member. Preferably said disegagement system comprises said first and second fastening members.

In an embodiment said disengagement system comprises a stopper integral with the frame (with development parallel to the guide in the rest position) which engages the slider near the rest position to move away the first and second surface.

Preferably a first fastening end of the first elastic element (corresponding to an end of the first fastening member) is fixed (directly or with the interposition of one or more elements which can be rigidly constrained or with one or more degrees of relative freedom, preferably by means of a pivoting hinge) to the frame and a second fastening end of the first elastic element (corresponding to an end of the second fastening member) is fixed (directly or with the interposition of one or more elements that can be rigidly constrained between them or with one or more degrees of relative freedom, preferably by means of a pivoting hinge) to the slider.

Preferably said adjustment system is structured to position said slider (preferably only) as a function of said relative position of the first support element with respect to the frame, with said support of the backrest in a given oscillation position, preferably in said rest position.

Preferably said adjustment system comprises a lever member (preferably rigid) having a fulcrum (e.g. a pin) fixed to said frame and defining a fulcrum axis, the lever member being physically connected to said first support element to be rotated by the first support element during a variation of the relative position, and being physically connected to said slider, so that said rotation of the lever member induces a displacement of the slider.

Preferably, said fulcrum axis does not coincide with an oscillation axis of the support of the backrest.

In this way, the weight force (vertical) applied by the user to the seat is transmitted to the first support element and causes a variation of its vertical position with respect to to the frame (i.e. the first support element is lowered with respect to the frame). In turn, the adjustment system modifies, as a function of the aforesaid relative position, the spatial position of the slider (and therefore of the first anchoring end of the first elastic element), in this way varying the elastic reaction exerted by the first elastic system for a given oscillation of the support of the backrest. For example, the variation of spatial position with respect to the axis of oscillation can induce a variation of the arm (vector) of the elastic reaction force with respect to the oscillation axis, and/or a variation of the degree of the elastic deformation (compression/traction) of the first elastic element for a given oscillation, and/or a variation of the direction of the elastic reaction force of the first elastic element (which causes a variation of the resulting torque and/or a variation of the binding reactions and therefore of the overall elastic reaction exerted). In this way, the elastic reaction complessivly exerted by the oscillation system for a given oscillation is adjusted as a function of the user weight in a completely automatic way, thanks (preferably only) to the functioning of the kinematic mechanisms of the adjustment system, without the necessity of the user action.

Moreover, the distance between the oscillation axis of the support of the backrest and the fulcrum axis makes that, during the self-adjustment and the related physical movement of the slider, it is possible to vary the distance of the first anchoring end of the first elastic element with respect to the oscillation axis of the support, thereby substantially varying the arm of the elastic reaction force with respect to the oscillation axis.

Preferably said adjustment system is structured so that, with said support of the backrest in a given oscillation position, to a relative position of maximum height of the first support element with respect to the frame corresponds a first position of the slider, for which the first elastic element opposes a first elastic reaction to the oscillation of the support of the backrest from the rest position. Preferably in the first position the distance between the first anchoring end and the oscillation axis is minimal. In this way the arm of the elastic force developed by the first elastic element is minimal, as it is the resulting torque.

Preferably said adjustment system is structured so that to a relative position of minimum height of the first support element with respect to the frame corresponds a second position of the slider for which the first elastic element opposes a second elastic reaction to the oscillation of the support of the backrest from the rest position, the second reaction being greater than the first reaction. Preferably, the distance between the first anchoring end and the oscillation axis in the second position is greater than the distance in the first position. In this way the arm of the elastic force developed by the first elastic element is greater, as it is the resulting torque.

In this way, the greater the weight of the user, which pushes down the first support element, the lower is the vertical height of the first element, the greater is the reaction magnitude to a given oscillation.

Preferably in said rest position of the support said first elastic element is in a deformed configuration ('preload'). Preferably in said rest position of the support the first and second fastening members (typically a respective end of the first and second fastening member opposite to the aforesaid respective abutting end and arranged internally of said first elastic element) are in mutual contact and kept in thrust against each other by said first elastic element. In this way said first elastic element, although being in a preloaded state, in the rest position does not exert any elastic force on its fastening ends, thus allowing the displacement of the abutting end of the second fastening member during the adjustment of the stiffness.

Preferably said first and second fastening members are structured to maintain said first and second surfaces, in the rest position of the support (and for the whole first section of oscillation), distant from each other and completely disengaged. In this way, therefore, it is possible to realize said disengagement system of the slider from the guide.

Preferably the adjustment system comprises a second elastic system having a second elastic element operatively interposed between said support and said slider, and structured to oppose a reaction force to a displacement of the slider from the first position. In this way, the second elastic system, once removed the weight force (or with weight force under-threshold), returns and maintains the slider in the first position.

Typically, the second elastic system is structured to maintain said first position of the slider for values of said weight force applied to the first support element less than or equal to a threshold value (for example equal to 40 kg). For example, the second elastic element can be preloaded. In this way the (self)-adjustment system only operates starting from a predetermined minimum user weight, for example set at 40 kg. Preferably the second elastic element is (directly) abutted to said support of the backrest at one side and to said abutting end of the second fastening member at an opposite side.

Preferably said support of the seat comprises a second support element (e.g. rigid) mounted on the frame and connected (preferably in an articulated manner, that is with one or more degrees of relative freedom, as in the 'synchronized' systems) with said support of the backrest for moving following an oscillation of the support of the backrest, wherein said first support element is mounted on said second support element to be able to assume a plurality of relative positions with respect to the second support element corresponding to said plurality of relative positions with respect to the frame. In this way it is realized an oscillation system in which the seat can also oscillate (synchronized).

Preferably said guide, in said rest position of the support of the backrest, has a circular arc development with a center in said fulcrum. In this way the first elastic element does not vary its elastic state (unloaded or preloaded) during the adjustment of the stiffness of the oscillation system.

Preferably said guide is a slot in which slides the slider, said slot being preferably afforded in said support, more preferably in the support of the backrest.

The chair preferably comprises a seat for a user, the seat being (rigidly) coupled to said support (of the seat) and/or a backrest (rigidly) coupled to said support (of the backrest).

Preferably the chair comprises a floor resting base and a stem mounted on the floor resting base, said frame being rigidly mounted at an upper end of said stem.

It is understood that one or more of the features previously described may be present in the oscillation system in double (typically) or multiple copies, for example the oscillation system can have, at least limited to one or more of the aforesaid features, a median plane of symmetry, vertically arranged and crossing a median position of the width of the system itself.

The present invention finds application to oscillation systems with permanent contact, with a single oscillating body, with two distinct but rigidly constrained bodies or, preferably, with synchronized systems.

Brief description of the drawings

The features and the advantages of the present invention will be further clarified by the following detailed description of some embodiments, presented as non-limiting example of the present invention, with reference to the attached figures, in which:

Figures 1 and 2 show, respectively in a configuration of rest and maximum oscillation, a schematic side view of an exemplary oscillation system of the present invention in a configuration of maximum softness, with some parts in transparency or removed;

Figure 3 shows, in a rest configuration, a schematic side view of the oscillation system of Figures 1 and 2 in a configuration of maximum stiffness, with some parts in transparency;

Figure 4 schematically and partially shows an exploded view of the system of Figure 1 ;

Figure 5 schematically shows an exploded view of the adjustment system of the oscillation system of Figure 1 ; Figure 6 schematically shows an exploded view of a portion of the adjustment system of Figure 5; Figures 7 and 8 show, respectively in a rest configuration and at the end of the first section of oscillation, a detail of the adjustment system of Figures 1-6.

Detailed description of some embodiments of the invention

In the figures it is shown an example of an oscillation system 1 for chairs according to the present invention.

The oscillation system 1 for chairs comprises a rigid frame 2 intended to be associated with a base of a chair (not shown, for example by means of a stem, not shown, which engages a suitable seat 2a in the frame) and a support of a backrest 3 mounted on the frame 2 to be able to oscillate around an oscillation axis 4 fixed with respect to the frame and a support of a seat 5 mounted on the frame and distinct from the support of the backrest 3.

The illustrated example shows a "synchronized" oscillation system.

The support of the seat 5 comprises a first support element 6, rigid, structured to be rigidly coupled to the seat (not shown) and a second support element 7, rigid, mounted on the frame 2 and connected in an articulated manner with the support of the backrest 3 in order to roto-translate following the oscillation of the support of the backrest 3. In the shown examples, the second support element 7 and the support of the backrest 3 are connected by a hinge 8 movable with respect to the frame 2. In the example shown in figure 4 the hinge 8 is formed by a rod 18, integral with the two bodies and acting as a pivot of relative rotation between the two bodies.

The second support element 7 is exemplarily directly mounted on the frame 2 by means of a roller 19 which allows the roto-translation of the second support element 7 with respect to the frame 2. In the example, the roller 19 is formed by a pin 9 integral to the frame which engages a slot 10 (in the example straight and horizontal, although it may have any shape and orientation, for example to give a weighing-people effect) afforded in the second support element 7.

Advantageously, the first support element 6 is directly mounted, in an overlying position, on the second support element 7 to assume, given an oscillation position of the support of the backrest 3, a plurality of relative positions having different vertical heights with respect to the second support element 7.

It is observed that in each oscillation position of the support of the backrest, the first element can assume all the possible relative positions. Typically, as in the shown examples, the transition from one relative position to another can take place only in the rest position, i.e. in absence of actions.

In the shown example, for each side of the oscillation system 1 , a front connecting rod 70 and a rear connecting rod 71 provide the articulation between the first 6 and the second 7 support element, the connecting rods being hinged to respective holes and connected to each other by respective rigid rods 12a, 12b, 18 in order to give synchrony to the articulation.

The oscillation system 1 comprises a first elastic system 20 operatively interposed, as shown in the figures, between the frame 2 and the support of the backrest 3, comprising a first elastic element 21 structured to oppose an elastic reaction (typically increasing) to an (increasing) oscillation of the support of the backrest 3 with respect to a rest position of the support in the absence of oscillating forces.

Typically, the first elastic system 20 comprises a further elastic element (not shown), comprising a respective elastic body (not shown), distinct from the first elastic element 21 , the further elastic element being preferably deformed (preloaded) in the rest position of the support 3.

Preferably, the first elastic element 21 comprises an elastic body 24 (e.g. a spring), a first fastening member 25 and a second fastening member 26 distinct from the first one, where the elastic body 24 is fixed (e.g. by screwing on respective external threads) at its opposite ends respectively to the first 25 and the second 26 fastening members.

Preferably, a first anchoring end 22 of the first elastic element 21 (corresponding to an abutting end of the second fastening member 26) is fixed (preferably and exemplary by means of a pivoting hinge) to the frame 2 and a second anchoring end 23 of the first elastic element 21 , opposite to the first one and corresponding to an abutting end of the first fastening member 25, is movably fixed to the support of the backrest 3. Preferably a pin 36 realizes the coupling between the first anchoring end 22 of the first element elastic 21 and a slider 50.

In alternative embodiments, not shown, the first anchoring end 22 can be abutted to the second support element 7 suitably shaped.

The oscillation system 1 comprises an adjustment system 30 comprising a guide 73 and the slider 50 which slidably engages the guide 73. Preferably the guide 73 is a slot 35 afforded in the support of the backrest 3. Preferably the slot 35 has a a circular arc development 39 with center in the hinge point of the second anchoring end 23. Preferably, the oscillation axis 4 lies on an extension of the circular arc.

Preferably the adjustment system 30 comprises a locking system 61 of the slider 50 in the guide 73 comprising respective mutually facing surfaces of the slider 50 and the guide 73.

In the shown example, a first surface 80 of the guide 73 has reliefs and a second surface 81 of the slider 50 has reliefs too, counter-shaped to the reliefs of the first surface 80.

Preferably the reliefs have a sawtooth pattern (as shown in detail in Figures 7-8) along the main development direction 90 of the guide 73 (i.e. the main direction along which the slider slides), comprising a contiguous succession of equilateral triangular reliefs.

Exemplarly the triangular reliefs have a height equal to 0.3 mm, equal to the period of the succession, and an angle at the top vertex equal to 60°. Preferably each relief has a constant cross-sectional development along a direction transversal to the main development direction 90 of the guide 73.

Preferably, the adjustment system 30 comprises a disengagement system 75 structured to disengaged, in the rest position of the support 3, the first 80 and the second 81 surfaces in order to remove the mutual engagement. Preferably, the disengagement system 75 comprises the first 25 and the second fastening member 26. In the shown example, in the rest position of the support of the backrest 3 the first elastic element 21 is in a deformed position ('preload') and the first 25 and the second 26 fastening member (shown in dashed lines in figure 1 ) are in mutual contact and kept in thrust against each other by the first elastic element 21. Furthermore, in the rest position of the support 3 and throughout the whole first section of oscillation, the first 25 and second fastening member 26 are structured (e.g. they are dimensioned in length) to maintain the first 80 and second 81 surfaces distant and disengaged from each other.

In an embodiment (not shown) the disengagement system comprises a stopper integral with the frame (with development parallel to the guide in the rest position) which engages the slider near the rest position to move away the first and second surface.

The adjustment system 30 preferably comprises a lever member 31 , rigid, having a fulcrum 32 (e.g. a pin forming a fulcrum axis 60 of the lever member, parallel to the oscillation axis 4) fixed to the frame 2. In the shown example the lever member 31 is a first-gen lever.

Preferably, the lever member 31 has a first arm 33 having a respective end 91 physically in contact with the first support element 6 to be rotated by the first support element 6 when it is lowered from the maximum vertical height relative position, and a second arm 34 on the opposite side of the first arm 33 with respect to the fulcrum. Preferably, the first elastic element 21 integrally and rigidly makes part of the second arm 34, the first anchoring end 22 of the first elastic element 21 being at the end of the second arm 34 and the second anchoring end 23 of the first elastic element being directly abutted to the frame at the fulcrum 32 (in the example the second anchoring end coincides with the fulcrum 32). In the example shown in the figures, the first elastic element 21 fully realizes the second arm 34 and the first fastening member 25 is integral (preferably in single body) with the first arm 33. Preferably the first arm 33 of the lever member 31 comprises a wheel 37 in contact with the first support element 6 to allow a mutual movement between the first support element 6 and the lever member 31 during the oscillation of the support of the backrest 3 and/or during the variation of the relative position of the first support element 6.

In embodiments not shown, the lever member 31 can be a second or third gen lever.

Preferably, the adjustment system 30 comprises a second elastic system 40 having a second elastic element 41 operatively interposed between the support 3 and the slider 50, and structured to oppose a reaction force to a displacement of the slider 50 from the first position and correspondingly to a sliding of the first support element 6 from the maximum vertical height position. Preferably, the second elastic element 41 is preloaded in the first position. Exemplarly, the second elastic element 41 comprises a torsional spring 72 directly abutted to the support of the backrest 3 at one side and to the first end 22 of the first elastic element 21 at the opposite side (e.g. to the second fastening member 26).

In a possible embodiment not shown, the second elastic system can be displaced (also) at any point of the lever member 31 and/or of the first support element 6.

Preferably, the first elastic system 20 comprises at least one elastically deformable body 82 fixed to the slider 50 and, in rest position of the support 3, in sliding contact with a portion 83 of the guide 73. In the shown example, two elastically deformable bodies 82 are fixed to opposite sides of the slider 50 by means of the pin 36 and of the second fastening member 26.

Exemplarily, each elastically deformable body 82 is a body made of elastomeric material.

In use, in the rest position of the support of the backrest 3 the first support element 6 is maintained in the relative maximum height position (to which corresponds a first position of the slider 50) by the second elastic system 40. In this position the distance d (corresponding to the arm of the elastic force developed by the first elastic element) between the second fastening end 22 and the oscillation axis 4 is minimal, so that the first elastic element 21 opposes a minimal elastic reaction to the oscillation of the support of the backrest 3 from the rest position. Typically, the further elastic element of the first elastic system maintains the oscillation system in preload.

In the case of sitting of a user who weighs less than a threshold weight (e.g. 40 kg), the first support element 6 does not lower due to the preloading of the second elastic element 41 and therefore the whole adjustment system does not operate. In case of oscillation, the oscillation system responds with a minimum reaction torque.

In the rest position, the first 80 and second surfaces 81 are manteined distant and disengaged from each other thanks to the contact between the first 25 and the second fastening members 26 and to the action of the elastic body 24.

In the rest position the elastically deformable bodies 82 are substantially undeformed and in contact with the guide portion 83, exerting a null or negligible elastic reaction force.

At the beginning of oscillation, the second surface 81 remains stationary and the first surface 80 is moved towards the second surface until contacting the second surface at the end of the first section of the oscillation (exemplarily of 1 °). In this position the two surfaces are completely engaged, thus achieving mutual locking.

Along the first section of the oscillation starting from the rest position of the support 3, the deformable bodies 82 undergo a progressive elastic deformation as they are pressed between the portion 83 of the guide and the pin 36 held by the first elastic element (in Figure 8 it is shown the deformable body 82 as deformed at the end of the first section of oscillation). In this way the deformable bodies progressively generate a reaction force to the oscillation, which is additional to that of the further elastic element, and which links the reaction of the system during the first section to the reaction of the system beyond the first section of oscillation (where it is also present the elastic reaction of the preloaded first elastic element). In other words, without the deformable bodies 82, the user could experience a sudden variation of the response of the system at the end of the first section.

At the end of the first section of oscillation, as a result of the contact between the first and second surface, the first 25 and second fastening member 26 separate themselves and during the further oscillation of the support of the backrest 3 the first elastic element 21 keeps in progressively increasing thrust against each other the first 80 and the second 81 surfaces to ensure mutual engagement. During the further oscillation, the deformable bodies 82 maintain the deformation reached at the end of the first section.

In the case of sitting of a user who weighs more than the threshold, the first support element 6, in the rest position, is lowered until the weight is balanced by the second elastic system 40, thanks to the action of the lever member 31 of the adjustment system 30. If the weight force reaches a limit value (e.g. 80 kg), and for all weight force values above this limit value, the first support element 6 reaches the minimum height position, shown in figure 3, at which the slider 50 reaches the stroke end point, wherein the aforesaid distance d is maximum, so that the first elastic element 21 opposes a maximum elastic reaction to the oscillation (not shown) of the support of the backrest 3 from the rest position. To each intermediate position between the minimum and maximum height positions, along a continuum of positions, corresponds one and only one position of the first end 22 of the elastic element, which is intermediate between the first and second position.

During the aforesaid self-adjustment, the disengagement system 75 leaves the first and second surfaces mutually free in order to facilitate movement of the slider 50. It is noted that the presence of the locking system 61 of the slider 50 along the guide 73 can cause, due to the constraints between the various components of the kinematic chain, a slight lifting of the first support element 6 during the oscillation, and/or an elastic deformation of the components of the kinematic chain, such as the lever member 31 (the spring).

In the shown example, the first elastic element 21 works in traction, but in alternative embodiments not shown, it can work in compression.

In the shown and described embodiments the support of the backrest 3 is rigid and rigidly oscillates around the oscillation axis 4.

In alternative embodiments of the present invention, not shown, the support of the backrest is composed of several articulated elements, at least one of which can oscillate around the aforesaid oscillation axis 4. For example, as shown in W02009/153811 (to which reference is made for the constructional details), the support of the backrest comprises a support body intended to be rigidly fixed to the backrest (which in this case can roto-translate rather than simply oscillate around the oscillation axis), and a kinematic linkage to the frame (for example forming an articulated quadrilateral) in which at least one element (e.g. a connecting rod) is directly hinged to the frame in order to oscillate about the oscillation axis. In this case preferably the first elastic system can be abutted to said at least one element.

The present invention also comprises solutions, not shown, wherein the development of the slot is different from the shown circular arc, for example in order to also vary the preload of the first elastic element in the rest position. For example, if the slot 35 is rectilinear instead of with circular arc development, during the adjustment by the adjustment system 30 the degree of deformation of the spring varies.

In an embodiment (not shown), the first and second surface are rough surfaces, for example covered with granules of abrasive material to produce an abrasive surface with grain designation class equal to P80.

In an embodiment not shown, the second surface may be elastically deformable in order to counter-shape to the first surface 80 having reliefs, when pushed against the first surface. For example, the slider may be of elastomeric material, with the second surface being flat.

In a further embodiment not shown, the slider may be a toothed wheel instead of a parallelepiped body as shown. The toothed wheel constantly engages the rack guide (for example totally similar to the shown one). In the rest position of the support of the backrest, the disengagement system (for example, the first and second fastening members) maintains the toothed wheel at a distance from the rack guide such that it is guaranteed the sliding by rolling of the wheel along the guide; thanks to the gear coupling between the two elements. At the beginning of the oscillation, the toothed wheel and the rack guide are approached, thus ensuring mutual locking between the two surfaces thanks to the clamping between the respective teeth, which precludes the fundamental features which allow the movement of the gear (for example the correct distance between toothed wheel and guide).