"DEVICE FOR ADJUSTING THE OSCILLATION OF A CHAIR"

The present invention relates to a device for adjusting the oscillation of a chair, that is, a mechanism interposed between the seat and the support stem of a chair, preferably an office chair, capable of imparting to the seat a certain oscillation movement relative to the stem.

As is known, oscillation devices comprise a main body having a substantially boxlike conformation, engaged on the top of a support stem of the chair.

The box-like body defines a member for housing and supporting articulation means of the seat, which are suitable for permitting the oscillation of the seat.

There are known oscillation devices for chairs which make it possible to produce the oscillation (forward and/or backward) of a chair, where the reaction to the oscillation depends on the weight of the user of the chair (so-called 'self- weighing'), in order to provide adequate comfort to the user and at the same time avoid the danger of tipping over.

However, these devices have numerous drawbacks.

The known devices are structurally complicated and cumbersome. The construction of the known oscillation devices entails long times and high costs of manufacture and assembly, which have an impact on the final cost of the chair. In this context, the technical task at the basis of the present invention is to provide a device for adjusting the oscillation of a chair which overcomes one or more of the above-mentioned drawbacks of the prior art.

In particular, it is an object of the present invention to provide a device for adjusting the oscillation of a chair that is structurally simple, compact and easy and/or inexpensive to make.

A further object of the present invention is to provide an oscillation device for a chair that is capable of effectively improving the stability of the chair and adapts to the user's weight bearing on the seat so as to achieve a comfortable oscillation while avoiding tip-over phenomena.

The stated technical task and specified objects are substantially reached by a device for adjusting the oscillation of a chair, comprising the technical features disclosed in one or more of the claims appended hereto and/or described below. In a first aspect the present invention relates to an oscillation device for a chair comprising a first body engageable on a support stem of the chair and a second body suitable for supporting a seat of the chair and mounted on the first body so as to oscillate about an oscillation axis relative to a resting configuration in which the second body is not subject to external oscillation forces.

The device comprises first elastic means interposed and operatively active between the first body and the second body to react to the oscillation of the second body.

Advantageously, said oscillation axis can be displaced relative to the first elastic means, said displacement causing a change in a distance between the oscillation axis and first elastic means.

Advantageously, the device comprises second elastic means interposed and operatively active between the oscillation axis and the first body to react to said displacement of the oscillation axis relative to the first elastic means.

Advantageously, in this manner the first elastic means will respond variably to the oscillation depending on the position of the oscillation axis relative to the first elastic means.

The displacement is typically generated by a weight force applied to the second body and transmitted to the oscillation axis.

Therefore, the present invention provides a device for adjusting the oscillation of a chair of a "self-weighing" type, i.e. capable of adjusting the response to the oscillation according to the weight of the user seated on the chair, in such a way as to avoid abrupt and violent oscillations that may cause tip-overs or excessively hard responses.

Advantageously, a displacement of the oscillation axis relative to the first elastic means corresponds to a variation in the moment arm of the first elastic means relative to the oscillation axis. In other words, the movement (typically lowering) of the oscillation axis under the user's weight (this movement finding a point of equilibrium between the user's weight and the response of the second elastic means) and the force component of the first elastic means perpendicular to the axis and distant therefrom cooperate with each other to vary the stabilizing effect with variations in the user's weight. For example, the further the oscillation axis is lowered, the more the oscillating arm of the first elastic means will increase relative to the oscillation axis. Changing the position of the oscillation axis of the second body relative to the first elastic means will vary the torque in reaction to the oscillation, and in this manner, advantageously, the reaction torque will be proportional to the weight of whoever is seated.

Overall, the mechanism is structurally very simple, with a reduced number of components, and of reduced dimensions, thus enabling production and/or assembly at modest costs.

Preferably, the oscillation axis is integral with the second body. In this manner, when the user sits down on the seat, applying his or her weight force, the second body will be lowered and the oscillation axis rigidly therewith.

Preferably, the displacement of the oscillation axis relative to the first elastic means has at least a vertical component.

Preferably, the oscillation axis lies below the first elastic means.

Preferably, the device comprises two bars arranged so as to pass through respective slots formed in opposite walls of the first body and translatable within the slots between a position of maximum reciprocal distancing and a position of maximum reciprocal nearing, in which the first elastic means are interposed between the two bars and are configured to react to a change in the distance between the two bars due to the external oscillation forces. Advantageously, the oscillation of the second body is associated with a change in the distance between the two bars which generates a reaction opposing the external oscillation force, the reaction being adjusted based on the user's weight. The arm between the oscillation axis and the bars increases with increases in the weight of the seated user.

Preferably, the device comprises engagement means interposed between the second body and the first body and configured to engage the second body with the bars, in such a way that, following the application of the external oscillation forces, one of the bars is shifted within the respective slots, causing a change in the distance between the two bars.

The engagement means are configured to achieve an engagement between the second body and the bars through contact, so that during the displacement of the oscillation axis the bars can slide or roll along the engagement means. Advantageously, therefore, it is not necessary to provide complicated gear mechanisms or linkages, which considrably simplifies the structure. Preferably, the device comprises a pair of discs respectively rotatably mounted on opposite walls of the first body with a common rotation axis, which is fixed relative to the first body and rigidly interconnected by an eccentric rod relative to the respective rotation axis.

Preferably, eccentrically mounted on the pair of discs there is an oscillation pin defining the oscillation axis in such a way that the oscillation axis is parallel to the rotation axis of the pair of discs so as to define a crank link between the first and the second body.

Advantageously, the oscillation axis can thus translate vertically, carrying out a rotation about the fixed rotation axis of the pair of discs.

Preferably, the second elastic means comprise an elastic element arranged so as to oppose the rotation of the pair of discs.

Preferably, the elastic element is abutted onto the eccentric rod.

In an alternative embodiment, the device comprises an oscillation pin defining the oscillation axis and arranged so as to pass through respective slots extending with at least a vertical component and formed in opposite walls of the first body.

Preferably, the oscillation pin is slidably movable within the slots between a resting position, in which the weight force is zero and the oscillation pin is located in proximity to the upper abutment portions of the respective slots, and a loaded position, in which the weight force is sufficiently different from zero and the oscillation pin is lowered relative to the resting position.

Preferably, the second elastic means comprise an elastic element configured to maintain the oscillation pin pushed towards the resting position.

Advantageously, the elastic element opposes the weight force until reaching a point of equilibrium in which the user is stably seated and the oscillation can take place in safety.

Preferably, the elastic element is a passive element and comprises a spring or a hydraulic or pneumatic piston, or an elastically deformable element.

Preferably, the device (at least in the parts of interest to the present invention) has a plane of symmetry perpendicular to said oscillation axis.

According to a further aspect of the present invention, there is further provided a chair comprising a device for adjusting the oscillation according to the present invention, a stem engaged with the first body and a seat engaged with the second body.

Additional features and advantages of the present invention will become more apparent from the approximate, and hence non-limiting, description of a preferred, but non-exclusive embodiment of a device for adjusting the oscillation of a chair, as illustrated in the accompanying drawings, in which:

- figure 1 is a schematic perspective view of a device for adjusting the oscillation of a chair according to a first embodiment of the present invention;

- figure 2 is a schematic perspective view of a portion of the device of figure 1 , in which the second body is not visible;

- figure 3 is a further schematic perspective view of a portion of the device of figure 1 , in which the first and second bodies are not visible;

- figure 3a is a schematic side view of a detail of figure 3;

- figure 4 is a schematic perspective view of a device for adjusting the oscillation of a chair in a second embodiment of the present invention; and

- figure 5 is a schematic perspective view of a portion of the device of figure 4, in which the second body is not visible.

With reference to the appended figures, 1 denotes in its entirety a device for adjusting the oscillation of a chair, hereinafter simply the device 1 .

The device 1 comprises a first body 2 engageable on a support stem 3 of the chair and a second body 4 suitable for supporting a seat of the chair, not illustrated. The second body 4 is mounted on the first body 2 so as to oscillate about an oscillation axis "X" relative to a resting configuration in which the second body 4 is not subject to external oscillation forces.

The device 1 comprises first elastic means 5 interposed and operatively active between the first body 2 and the second body 4 to react to the oscillation of the second body 4.

Advantageously, the device 1 comprises second elastic means 6 interposted and operatively active between the oscillation axis "X" and the first body 2 to react to a displacement of the oscillation axis "X" relative to the first elastic means 5, so that the first elastic means 5 will respond variably to the oscillation depending on the position of the oscillation axis "X" relative to the first elastic means 5.

The displacement is generated by a weight force applied to the second body 4 and transmitted to the oscillation axis "X".

It may be observed that the first body 2 and the second body 4 could also be inverted, i.e. the first body 2 could be the one associated with the seat and the second body 4 could be the one associated with the support stem 3.

Furthermore, the oscillation can also take place forward or only backward or else both forward and backward relative to the resting configuration.

Preferably, the oscillation axis "X" is integral with the second body 4.

Preferably, the displacement of the oscillation axis "X" relative to the first elastic means 5 has at least a vertical component.

Preferably, the oscillation axis "X" lies below the first elastic means 5.

Preferably, the device 1 comprises two bars 7 arranged so as to pass through respective slots 8 formed in opposite walls 2' of the first body 2 and translatably movable within the slots 8 between a position of maximum reciprocal distancing and a position of maximum reciprocal nearing, in which the first elastic means 5 are interposed between the two bars 7 and are configured to react to a change in the distance between the two bars 7 due to the external oscillation forces.

Preferably, the first elastic means 5 comprise a pair of springs 5a connected to the bars 7.

Preferably, the two bars 7 are parallel and even more preferably they are parallel to the oscillation axis "X".

Preferably, the device 1 comprises engagement means 9 interposed between the second body 4 and the first body 2 and configured to engage the second body 4 with the bars 7, in such a way that following the application of the external oscillation forces, one of the bars 7 is shifted within the respective slots 8, causing a change in the distance between the two bars 7.

The engagement means 9 are configured to achieve an engagement between the second body 4 and the bars 7 through contact, so that during the displacement of the oscillation axis "X" the bars can slide or roll along the engagement means 9. In the first embodiment of figures 1 -3a, the engagement means 9 preferably comprise ribs 9a integral with the second body 4, whereas in the second embodiment of figure 4 the engagement means 9 comprise further slots 9b formed in the second body 4, inside which the bars 7 pass.

Figures 1 -3a illustrate a first embodiment of the device 1 , in which the device 1 preferably comprises a pair of discs 10 respectively rotatably mounted on opposite walls 2' of the first body 2 with a common rotation axis "Y", which is fixed relative to the first body 2 and rigidly interconnected by an eccentric rod 10a, visible in figure 3a, relative to the respective rotation axis "Y".

Eccentrically mounted on the pair of discs pair of discs 10 there is an oscillation pin 1 1 defining the oscillation axis "X" in such a way that the oscillation axis "X" is parallel to the rotation axis "Y" of the pair of discs 10 so as to define a crank link between the first body 2 and the second body 4.

In other words, the oscillation axis "X" in this case can translate with a vertical component, carrying out a rotation about the fixed rotation axis "Y" of the pair of discs 10.

Preferably, the second elastic means 6 comprise an elastic element 6a arranged so as to oppose the rotation of the pair of discs 10.

The rotation axis "Y" of the pair of discs 10 is integral with the first body 2 and the oscillation pin 1 1 is integral with the second body 4; in this manner (the oscillation pin 1 1 being eccentric relative to the rotation axis "Y" of the pair of discs 10), when the first body 2 and the second body 4 are compressed together as a result of the weight force applied, thanks to the present invention a rotation of the pair of discs 10 is obtained, so that the oscillation pin 1 1 is lowered and distanced from the bars 7, thus increasing the arm.

In other words, the pair of discs 10, rigidly linked by the eccentric rod 10a, and the oscillation pin 1 1 make up a crank suspension system.

Preferably, the elastic element 6a is abutted onto the eccentric rod 10a. In an unillustrated embodiment, the elastic element 6a can be a torsion spring applied on the pair of discs 10.

Figures 4 and 5 illustrate a second embodiment of the device 1 , in which the oscillation pin 1 1 defining the oscillation axis "X" is arranged so as to pass through respective slots 12 having at least a vertical component formed in opposite walls 2' of the first body 2. Preferably, the oscillation pin 1 1 is slidably movable within the respective slots 12 between a resting position, in which the weight force is zero and the oscillation pin 1 1 is located in proximity to the upper abutment portions 12b of the respective slots 12, and a loaded position, in which the weight force is sufficiently different from zero and the oscillation pin is lowered relative to the resting position (for example to overcome a preload of the spring) and the oscillation pin 1 1 is lowered relative to the resting position.

In other words, in a loaded configuration the oscillation pin 1 1 is positioned between the upper abutment portions 12b and lower abutment portions 12a opposite the upper abutment portions 12b of the respective slots 12. Preferably, the respective slots 12 are vertical.

Preferably, the second elastic means 6 comprise an elastic element 6a configured to maintain the oscillation pin 1 1 pushed towards the resting position.

Preferably, the elastic element 6a is a passive element and comprises a spring or a hydraulic or pneumatic piston, or an elastically deformable element.

In particular, in the first embodiment illustrated in figures 1 -3a, the elastic element 6a is a spring, whereas in the second embodiment illustrated in figures 4-5, the elastic element 6a is two springs.

Thanks to the device for adjusting the oscillation of a chair 1 of the present invention, it is thus possible to automatically adjust the response and comfort of the oscillation of the seat of a chair based on the user's weight simply by increasing the arm of the reaction torque of the first elastic means 5, which work upon the oscillation of the second body 4.

Advantageously, the oscillation axis of the second body 4 is not rigidly integral with the first body 2, but can also translate vertically thanks to the second elastic means 6, which balance the weight of the seated user, in order to change the reaction arm in the event that the user impresses an external oscillation force.

The present invention achieves the set objectives by providing the user with a device for adjusting oscillation applicable to any chair having a support stem and a seat (to which a backrest can be advantageously applied, rigidly connected to the seat or articulated relative to the seat), thus overcoming the drawbacks of the prior art.