[0001] The present invention relates to a support device of a chair with tilting backrest, and a chair fitted with such device.

[0002] As is known, some chairs, especially office chairs, have a backrest able to tilt backwards in a progressive and controlled manner when the user shifts his/her weight backwards. In some embodiments, the tilting of the backrest is accompanied by a synchronised tilting of the seat of the chair.

[0003] These seats have a tilting support device of the backrest (and sometimes of the seat too) placed between the seat and the support column of the chair. In one embodiment, such device comprises a support plate of the backrest which extends essentially along a horizontal plane, below the seat, when the backrest is in a vertical, erect position. From this plate a support element of the backrest extends rearwards. At the front the plate pivots on a tilting horizontal pivot so as to be able to tilt from a horizontal position and thus enable backward tilting of the backrest. In addition, the plate is provided with at least one lever arm on which an organ contrasting tilting acts. This contrast organ comprises a spring element which, by opposing the force of the user's weight, allows progressive, controlled tilting of the backrest and the return of the same to the vertical position when the user sits up.

[0004] A device for adjusting the force contrasting tilting is ^' associated with the organ contrasting tilting of the plate so that the user can choose, for instance depending on his/her height and weight, the degree of rigidity of the backrest. [0005] In some embodiments, this adjustment of the contrasting force takes place by adjusting the compression of the spring element, for example by means of a conical torque activated by a rotating command lever. This embodiment solution however has the drawback that, given the considerable rigidity of the contrast spring, a high multiplication factor between the turns of the command lever and the turns of the gears acting on the spring axially, is required. In other words, the user must turn the command lever many times before obtaining an appreciable difference in the rigidity of the backrest.

[0006] Other embodiments rather, rely on varying the contrasting force by varying the point of application on the lever arm of the support plate. In fact it is clear that by reducing the length of the arm the force needed to make the backrest tilt is reduced and vice versa. Currently, the variation of the length of the lever arm is achieved by acting directly, for example by means of a command lever, on the point of application of the contrast force. It is easy to imagine in this case too how the force required of the user to modify said position of the point of application is significant, so that once again a high multiplication factor of the rotation of the command lever made by the user is required. It should be noted that the spring of the contrast organ, being usually preloaded, acts on the lever arm with a certain force even when the backrest is in the erect position, making rotation of the command lever laboursome. [0007] In many known embodiments, in addition, the command lever extends horizontally from below the seat at the rear extremity of the elastic element which it acts on, in other words in a significantly rearward position in relation to the chair. If the chair has arms, ^' and considering the fact that for the user to be able to perform such adjustment more easily, he/she must lean forward, away from the backrest, the position of the command lever is quite inconvenient to reach. [0008] The purpose of the present invention is to propose a support device of a chair with a tilting backrest which overcomes the drawbacks mentioned above of the known device s .

[0009] Such purpose ±s achieved by a support device according to claim 1 and by a chair according to claim

14. [0010] The dependent claims describe alternative or preferred embodiment variations of the device according to the invention.

[0011] The characteristics and advantages of the device herein proposed will in any case be evident from the description given below of its preferred embodiments and with reference to the attached figures, wherein:

[0012] Figure 1 is an exploded view of the tilting support device according to the invention;

[0013] Figure 2 shows the device assembled; [0014] Figure 3 shows the support device without the outer casing;

[0015] Figure 4 is a side view of the device, without the outer casing;

[0016] Figures 5 and 5a are schematic side views of the device, in the erect and tilted position, in a first set up of maximum rigidity of the backrest;

[0017] Figures 6 and 6a are schematic side views of the device, in the erect and tilted position, in a second set up of minimum rigidity of the backrest; [0018] Figure 7 is a side view of the device, in one embodiment variation;

[0019] Figures 8 and 8a show a chair fitted with the device according to the invention, in the erect and tilted positions respectively. [0020] In said drawings, reference numeral 1 globally denotes the support device of a chair 3 with tilting backrest 5 according to the invention.

[0021] Hereinafter in the description the terms front and back will be used with reference to the device fitted to the chair, where back means facing the backrest.

[0022] As shown by figures 8 and 8a, the support device 1 is suitable for positioning and attaching below the seat 2 of a chair 3, at the top of a support column 4 of the chair itself. [0023] The device 1 comprises a support organ 10 of the backrest pivoted on a horizontal tilting pivot 14. According to one embodiment illustrated in the drawings, such support organ 10 is in the form of a plate which extends essentially on a horizontal plane ^" when the backrest 5 is in an essentially vertical, erect position

(figure 8) . A support element 12 of the backrest 5 is attached to the support plate 10 extending rearwards to form an ^λΛ L". At the front, the support plate 10 pivots on the horizontal tilting pivot 14. [0024] In addition, the support organ 10 has at least one v lever arm 16, preferably a pair of parallel and distanced arms which, for example, extend forwards and below it, on which an organ 18 contrasting tilting, acts. In other words, in one embodiment the lever arms 16 extend from the point of hinging of the support organ 10 to the horizontal tilting pivot 14 in a tilted direction, facing forwards and downwards. Consequently, the support organ 10 and arms 16 joined to it act as a lever, wherein the support organ acts as the power arm (inasmuch as subject to the force exerted by the user) , while the arms acts as the resistance arm (inasmuch as subject to the contrasting force exerted by the organ 18 contrasting tilting) . [0025] According to one embodiment, the organ 18 contrasting tilting comprises an elastic element 20 acting on the lever arms 16 so as to oppose their rotation upwards following rotation downwards of the support organ 10. [0026] The organ 18 contrasting tilting is lodged in its own box-like body or casing 22, to which it is joined in such a way as to be able to tilt in relation to one of its two extremities, front or back, so that the tilting of the elastic element 20 can be adjusted in relation to the lever arms 16. As will be explained more in detail below, such variation of the tilting of the elastic element 20 corresponds to a variation of the point of application of the force of resistance along the lever arm 16 and/or of the intensity of the component of said force acting on the lever arms. [0027] To perform such variation of the tilting of the contrast organ 18, a , special adjustment device 24 of the contrast force is provided which will be described more in detail below. [0028] [0028] According to a preferred embodiment, the elastic element 20 comprises a spring, for example a helical spring.

[0029] According to a first embodiment, illustrated in figures ■ 1-6, the contrast organ is able to tilt in relation to its front extremity, in other words opposite to the extremity acting on the lever arms 16, so as to modify the point of application of the force exerted by the elastic element on said lever arms. The elastic element therefore has its front extremity 20 ' pivoted on a front tilting pivot 26, joined to the box-like body 22. The back extremity 20" is attached to a back pivot 28 which extends between the lever arms 16 and can move along them. More specifically, the extremities of the back pivot 28 are inserted in respective slotted seats 30, of an elongated shape, made in said arms 16. The elongated shape of the seats accommodating the pivot allow it to move along the lever arms.

[0030] According to one embodiment, the two front 26 and back 28 pivots are supported by a pair of lateral flanges 32 which enclose the elastic element 20, constituting, with said pivots, the support frame. Specifically, the front pivot 26 is joined to the lateral flanges 32 and is attached to the box-like body 22 of the contrast organ, for example by means of a pair of clamps 34 ^" . [0031] The back pivot 28, rather, has its extremities accommodated in respective slotted guide seats 36 made in the lateral flanges 32 and extending parallel to the elastic element 20 so as to enable its compression. [0032] In other words, the elastic element 20 is positioned in its own support frame which defines it laterally, by means of the flanges 32, and at the extremities, by means of the pivots 26, 28. This way when the backrest is in the erect position, that is when the elastic element is not compressed by the rotation of the lever arms, the force which the elastic element in any case exerts by virtue of its pre-loading (which is normally present so as to lend a certain degree of initial rigidity to the backrest) is discharged onto the support frame rather than directly onto the lever arms. In fact, the elastic element acts on the back pivot 28 which in turn hits against the extremities of the slotted seats 36 of the lateral flanges 32. As a result, when the backrest is in an erect position, the back pivot 28 does not act on the lever arms 16. Thanks to this expedient it is easier for the user to adjust the position of the elastic element 20 in relation to the lever arms, in that, with the backrest in the erect position, the elastic element and lever arms hardly interact.

[0033] In one embodiment, the spring 20 engages the front 26 and back 28 pivots by means of respective support blocks 38 having an inner side 38' bearing a support seat of the extremity of the spring 20 and a concave outer side 38", able to support the respective pivot. [0034] Passing now to the adjustment device 24 of the tilting contrast force, which acts on the tilting of the elastic element, in one general embodiment it comprises at least one cam organ 44- acting on the support frame of the elastic element 20 so as to provoke tilting between a lowered position and a raised position; the cam organ 44 can be operated by means of a command lever 46 easily accessible by the user.

[0035] In one embodiment, the cam organ 44 is a rotating organ operatively connected to the command lever 46 by means of a rotation transmission device of said lever defining a transmission ratio between the number of turns of the lever and of the cam organ. [0036] Advantageously, the cam organ 44 is made in a first gearwheel 40, of greater diameter, meshing with at least a second, gearwheel 42, of smaller diameter, joined to the command lever 46. [0037] When the elastic element 20 is in the lowered position, the back, pivot 28 is at the lower extremity of the slotted seats 30 of the lever arms 16, and thus the point of application of the compression force which it generates is near the free extremity of said arms 16, that is, of the extremity opposite the support organ 10. This position corresponds with a lever arm of maximum length. Vice versa, when the elastic element is in a raised position, the back pivot 28 is at the upper extremity of the slotted seats 30 of the lever arms and thus the point of application of the compression force which it generates is closer to the tilting pivot 14 of the support organ 10. This position corresponds to a le ^' ver arm .of minimum length. [0038] Clearly, by means of the command lever, the user may tilt the elastic element into an infinite number of positions between the two limit positions described above .

[0039] According to a preferred embodiment, the diameter of the first gearwheel 40 and the extension of the profile of the cam organ 44 are chosen so that half a turn of said wheel is sufficient to make the elastic element move as ^' far as possible. The diameter of the second gearwheel 42 is about half that of the first wheel, so that a full turn of- the second gearwheel and therefore of the command lever is sufficient to make the elastic element move as far as possible.

[0040] Such embodiment solution offers the best compromise between- the precision of adjustment, speed (the command lever does not need to be turned a great number of times) and force required of the user.

[0041] According to one embodiment, in the larger gearwheel, an eccentric path is made for a pin 48 which extends transversally from one of the lateral flanges 32 of the support frame of the elastic element, in such a way that, following rotation of said wheel, said pin moves from a lowered position near the centre of the wheel to a raised position distant from the centre of the wheel . i [0042] For example, said eccentric path 44 is defined by a groove which extends around the centre of the first

I gearwheel essentially completing an eccentric semi- circumference in relation to the centre of the wheel. [0043] Advantageously, the gearwheel 40 with the eccentric path rotates around a pivot 40' joined to the box-like body 22 of the contrast organ. [0044] In addition, such wheel is positioned essentially halfway across the axial extension of the contrast organ. Advantageously, the smaller gearwheel 42 is positioned in front of the larger wheel, in other words near the front pivot. This way, the command lever too 46, which is coaxial to the second wheel 42, extends in an advanced position in relation to the support device, thus proving easily accessible for the seated user. [0045] In one embodiment variation illustrated in figure 7, the back pivot 28 which the elastic element 20 acts on is attached to the lever arms 16, near the free extremity of these. The front pivot 26 rather, instead of being attached to the box-like body 22 as in the embodiment described above, can be moved in relation to this between a lowered position and a raised position. Correspondingly, the elastic element 20 is able to vary its tilt in relation to the lever arms between a position of maximum contrast force, wherein it is essentially perpendicular to said arms and a position of minimum contrast force, wherein it forms an acute angle with said arms, in such a way that the useful component of the contrast force, directed orthogonally to the arms, is of lesser intensity. [0046] The mechanism for varying the tilting of the contrast organ is the same as that described above.