EP1976414A2

EP1976414A2 - Device for adjusting the tilt of a backrest or seat of a chair

Info

Publication number: EP1976414A2
Application number: EP06831792A
Authority: EP
Inventors: Armando Donati
Original assignee: Donati SpA
Current assignee: Donati SpA
Priority date: 2006-01-23
Filing date: 2006-12-21
Publication date: 2008-10-08
Also published as: WO2007083186A3; WO2007083186A2; US20100219672A1; ITMI20060022U1

Abstract

Device (1) for adjusting the tilt of at least one movable component of a chair, of the type comprising at least one cam (16, 17), constrained in a rotation manner to a bracket (2), and at least one follower (15) constrained in a sliding manner on the profile (23) of said cam, the movable component being integral with the follower and the bracket being fixed with respect to the follower or vice versa. The device furthermore comprises means (13, 18) to constrain the follower to the bracket, the above-mentioned means (13, 18) and the above-mentioned cam (16, 17) being configured so that the constraint reaction of the follower on the cam is substantially always directed towards the centre of instantaneous rotation of the latter.

Description

"DEVICE FOR ADJUSTING THE TILT OF A BACKREST OR SEAT OF A CHAIR"

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FIELD OF THE INVENTION

The present invention concerns α device for adjusting the tilt (i.e. inclination) of a movable component, for example the backrest and/or the seat, of a chair;

Said device, as is known, is particularly suitable for use in chairs in which, for example due to prolonged use thereof, the user requires the most comfortable position possible. In particular, office chairs on which the user is normally sitting for long periods of time must be ergonomic and it must be easy to adjust the position chosen by the user.

PRIOR ART Said chairs are generally provided with at least one movable component, i.e. the backrest and/or the seat and even the armrests and/or footrests, which is constrained, with one or more degrees of freedom, to another movable component or to a chair supporting structure on the ground, for example a base or pedestal. These movable components can, within certain limits, be moved to translate and/or rotate with respect to one another and/or with respect to any fixed components, and can therefore be adjusted by the user, thus obtaining optimal reciprocal arrangements for the comfort of said user. It should be noted that by the term "chair" we mean, here and hereinafter, a generic seating means such as sofas, armchairs or car seats, even though particular reference will be made to office chairs, provided with seat and/or backrest that are movable with respect to the base. It is known that devices exist for adjusting the tilt of a movable component of the chair, and in particular of the backrest and/or seat, comprising a cam, usually constrained in a revolving manner to the base of the chair, and a follower which is integral with or in any case constrained to said movable component. Rotation of the cam, which can be operated by a user by means, for example, of an appropriate control rod, determines the relative movement of the follower on the profile of the cam, with consequent variation in the relative position of the follower with respect to the centre of rotation of the cam, and therefore the translation and/or rotation of the movable component with respect to the chair.

In said known devices, once the position pre-established by the user has been reached, means for fixing the position are operated, for example consisting of a threaded pin and a corresponding housing, which can be engaged between the movable component and the chair and are furthermore configured to lock the above-mentioned movable component in the chosen position. Said fixing means have the purpose of preventing the load exerted by the user on the movable component from inducing undesired movements of the follower with respect to the cam and consequently loss of the optimal position adjusted by the user.

The known devices of the type mentioned above, while allowing considerable freedom in the configuration and reciprocal arrangement of the cam and follower, are complex to produce due to the above-mentioned fixing element, and furthermore do not permit adjustment and fixing of the above-mentioned movable component in one single operation. Furthermore, fixing of the mobile component in said devices can be laborious and inaccurate, due to possible undesired movements of said movable component between the adjustment and fixing operations. The object of the present invention is to remedy the drawbacks of the adjustment devices described above, and in particular of those that make use of devices for adjusting the tilt of the seat or backrest, or other movable component, via the use of cam and follower mechanisms.

A further aim of the present invention is to make possible adjustment of the backrest or seat of the chair once the most comfortable position for the user has been determined, without having to fix the movable component with respect to the chair. SUMMARY OF THE INVENTION

These and further objects are achieved by the device for adjusting the tilt of a movable component of a chair according to the first independent claim and the subsequent dependent claims. The device for adjusting the tilt of at least one movable component of a chair, according to the present invention, comprises at least one cam, constrained in a rotating (i.e. revolving) manner to a bracket and at least one follower, constrained in a sliding manner to the profile of said cam. The movable component of the chair is furthermore integral with the follower, and hence the bracket is fixed with respect to the latter or, vice versa, the movable component is integral with the bracket and therefore the follower is fixed with respect to the latter. The device furthermore comprises means for constraining the follower to the bracket. Furthermore said constraining means and the cam are configured so that the constraint reaction of the follower on the cam is substantially always directed towards the centre of instantaneous rotation (i.e. the swing center) of the latter.

According to the present invention, therefore, the geometric configuration of the cam and the use of appropriate constraints for the follower, suitable for countering the forces acting on the follower with the exception of those forces directed towards the centre of instantaneous rotation of the cam, and which can be obtained, for example, by imposing a certain path on the follower in contact with the cam, prevents the forces exerted by the follower on the cam, and generated by the load exerted by the user on the above-mentioned movable component, generating a non-null moment on said cam which can cause undesired rotation.

Even if said forces, i.e. the constraint reactions, exerted by the follower on the relative cam are not perfectly directed towards the centre of instantaneous rotation of the cam, but only near to the latter, the presence of friction in the contact area between follower and cam and in the constraint between the cam rotation shaft and the relative hub, substantially prevents undesired rotations of said cam. In this way, therefore, the device of the present invention makes the use of auxiliary means for fixing the follower and the corresponding cam in the reciprocal relative position superfluous. According to a preferred embodiment of the present invention, the above-mentioned means for constraining the follower to the bracket comprise a lever hinged to the bracket and preferably integral, at its non-hinged end, with the above-mentioned follower, which can advantageously consist of a driven rod sliding in a guide obtained on the cam and defining the profile of the latter.

The contact point of the driven rod on the cam profile, the profile of the latter and the arrangement of the lever that rotates said driven rod are such that the forces, not countered by other constraints, acting on the driven rod at the contact point on the cam, and therefore transmitted to the latter, are directed orthogonally to the rotation radius of the lever and in the direction of the centre of instantaneous rotation of the cam. In the solution proposed above, the movable component of the chair can be integral with the lever.

According to another embodiment of the present invention, the above-mentioned follower of the adjustment device can be constrained in a sliding manner in a linear guide, integral with said bracket. The function of said guide can be multiple: firstly it can act as a stroke limiter for said follower, for example if the latter is already otherwise constrained to the bracket, secondly it can act as a constraint to counter all the forces acting on the follower not directed towards the centre of instantaneous rotation of the cam, imposing for example a precise path on the follower, in its movement relative to the cam, with respect to the bracket. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the present invention will become clearer from the detailed description of a preferred but not exclusive embodiment of a device for adjusting the backrest or seat of a chair, illustrated with reference to the attached figures, in which: figure 1 is a perspective view of the device according to the invention in a position of minimum tilt of the movable component; figure 2 is a perspective view of the device according to the invention in a position of maximum tilt of the movable component; and figures 3a-3c are lateral views partially in section of the device of figures 1 and 2, showing the reciprocal positions of the follower and cam respectively in the position of minimum tilt, intermediate tilt and maximum tilt of a movable component of the chair.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE

INVENTION

With reference in general to said figures, 1 indicates a device for adjusting the tilt of a movable component of a chair, and in particular W

of the backrest or seat (not illustrated), according to a preferred embodiment of the present invention.

The particular adjustment device 1 herein described comprises a bracket 2 which is fixed, by means of appendixes 7 provided with holes 9 suitable for housing threaded locking means, to a stable component of the chair, for example the base, and bears two parallel cams 16, 17, constrained to said bracket 2 to revolve around a same axis B-B, by means of a rod 14. The axis B-B on the planes on which the two parallel cams 16 and 17 lie respectively determines the centres of instantaneous rotation 14' (see figures 3a-3c) of the latter.

More specifically, the bracket 2 is a structure, preferably metallic, consisting of longitudinal members 4 and transverse plates, or cross members, 5, variously shaped and reciprocally fixed, for example by welding. The bracket 2, at one end, comprises two projecting terminal portions 10, inside which holes 12 are obtained for housing the above- mentioned rod 14 so that it is free to rotate.

As can be seen in the figures, the rod 14 is preferably cylindrical with circular section and is integral, at its ends, with the two parallel cams 16, 17. Said cams 16, 17 can be rotated, by the user, by means of a knob 35, mounted integral and coaxial on said rod 14, and protruding laterally frorp the structure of the chair. Furthermore, the eccentric profile of the two cams 16 and 17, defined, in the particular embodiment of the present invention illustrated here, by two substantially spiral-shaped grooves 23 (of which only the groove of the cam 16 can be seen), is specular with respect to any plane orthogonal to the above-mentioned axis B-B.

The bracket 2 furthermore comprises holes 21 , 22 in which two levers 18 (only one of which can be seen in the figures) are hinged at one of their ends 19; at their other end 20, said levers bear a driven rod 15 which extends between said levers 18. The driven rod 15, integral in a substantially perpendicular manner with said levers 18, is in turn constrained to run along the eccentric profile of the cams 16, 17, due to the engagement of its ends in the grooves 23 defining said profile. The rod 15, in particular, develops along an axis A-A parallel to the axis B-B of rotation of said cams lό, 17 and is furthermore constrained to run inside two elongated slots 13, appropriately arc-shaped, obtained on the two terminal portions 10 of the bracket 2 and defining a linear guide for said rod 15.

The rod 15, due to its constraint with the grooves 23 of the cams 16, 17, constitutes a follower moving on the profile of said cams 16, 17, obliged to follow a well-defined path, moving close to and away from the centres of rotation of the two cams 16, 17, due to the particular modes of constraint with the bracket 2.

Said modes of connection to the bracket 2, obtained by hinging of the lever 18 to the bracket 2 and, in a redundant manner, by sliding of the driven rod 15 in the linear guides 13, oblige the rod 15 to rotate with respect to the axis C-C defined by the centres of rotation 21 , 22 of the levers 18, thus allowing said rod 15 only one degree of freedom with respect to the bracket 2.

It should be noted that the linear guides 13 perform the function of stroke limiter for the rod 15 and therefore of rotation limiter for the two levers 18. It should furthermore be noted that, according to a particular aspect of the present invention, in the tilt adjustment device 1 , the levers 18, and/or the driven rod 15 can be preferably integral with the movable component of the chair to be inclined, for example the backrest or the seat of the chair. The arrangement of the free ends of the driven rod 15 resting on the respective profiles 23 of the cams 16, 17 and the configuration of said profiles 23, as can be seen in particular in figures 3a, 3b and 3c, ensure that the forces exerted by the rod 15 on the respective cams 16 and 17 are always directed towards the relative centres of instantaneous rotation 14' (figures 3a-3c) of the latter, thus preventing the generation of non-null moments on said cams 16, 17, in any relative position assumed by the rod 15 on the profiles 23 of said cams 16, 17. As can be seen in particular from figures 3a-3c, the constraint of the rod 15 to the bracket 2, consisting of the levers 18, substantially prevents forces directed longitudinally to the rotation radius of the lever 18 (and in this case to the lever 18 itself which extends in a straight line), independently of the load acting on the latter, occurring on the rod 15, therefore the forces acting on the rod 15 and transmitted to the relative cams 16, 17 are only orthogonal to the respective rotation radiuses of said levers 18. Furthermore the configuration of the profiles 23 of the cams 16, 17 and the reciprocal arrangement of the rod 15 on the profiles 23 are such that the forces transmitted by the rod 15 to the cams 16, 17 are practically always directed towards the centres of instantaneous rotation 14' of the cams 16, 17.

This implies that no torque is present acting on the cams 16, 17, even if forces (or constraint reactions) are present exerted by the rod (follower) 15 on said cams 16, 17, due to resting of said rod 15 on the profiles 23 of the cams 16, 17, and therefore there can be no undesired rotations of the latter when the position of the follower 15 on the profiles 23 varies.

In fact, any transverse forces with respect to the straight line, which joins on each cam 16, 17 the contact point of the follower 15 on the profile of said cam 16, 17, which could generate a non-null moment on the latter are obstructed and compensated for by the presence of the lever 18 (non-deformable), and in a redundant manner by the constraint reaction exerted by the linear guides 13, while the forces parallel to said straight line, and directed by geometric configuration of the parts towards the centre 14' of the cams 16, 17, are compensated for by the constraint reaction of the support (and possibly by the relative friction) of the end of the rod 15 on the eccentric profile 23 of each cam 16, 17. Furthermore, the engagement of the ends of the driven rod 15, acting as follower, in the grooves 23 means that any, albeit improbable, forces acting on said driven rod 15 in a direction parallel to the above- mentioned straight line defined by the centre of rotation of each cam 16, 17 and by the contact point of each end of the rod 15 with the profile of the relative cam 16, 17, and in the opposite direction with respect to the centre of rotation of the cams 16, 17, are compensated for by the constraint reaction exerted by the upper walls of each groove 23. Therefore, if the movable component of the chair, in the particular embodiment illustrated here integral with the levers 18, were the backrest or seat of the chair, any load exerted by the user would not affect the position reached by the rod 15 on the profile of the cams 16, 17, thus making the presence of auxiliary means to lock the cams 16, 17 and the relative follower 15 in the reciprocal position not necessary.

As already mentioned, in the solution illustrated here, the linear guides, or curved slots, 13 have above all the function of limiting the stroke of the follower 15 and therefore the rotation of the levers 18. In embodiments of the present invention not shown, the device 1 can alternatively comprise any type of constraint of the follower 15 to the bracket 2, also indirect, or obtained by interposition of parts connected in a fixed or movable fashion to the bracket 2, on condition that said constraint allows the follower 15 to translate or rotate with respect to said bracket 2 according to a well-defined path and at the same time guarantees the sliding contact movement of said follower 15 on the profile of the cam or cams 16, 17 so that the constraint reactions (or the forces transmitted) by the follower 15 on said cams 16, 17 are always directed towards the centres of instantaneous rotation of the latter.

For example, the follower 15, variously constrained to the movable component of the chair, could be made to slide in a straight linear guide (not shown) which imposes on said follower 15 one single path passing through the centre of instantaneous rotation 14' of the cam or cams 16, 17, thus allowing the follower 15 to transmit to the cams 16, 17 only forces directed along said path, the force application axes of which therefore pass, without the generation of non-null moments, through the centres of instantaneous rotation of the cams 16, 17. In the particular embodiment of the device according to the present invention described here, the path followed by the driven rod 15 with respect to the bracket 2 is ideally positioned on a plane parallel to the planes on which the cams 16, 17 rotate, thus facilitating translation of the resting point of the rod 15, also preferably cylindrical with circular section, on the profile of each cam 16, 17 with respect to the centre of rotation of the latter.

It should be noted that, alternatively, even if said path of the rod 15 with respect to the bracket 2 were arranged on a plane orthogonal to the plane of rotation of the cams 16, 17, the contact between rod 15 and profile of at least one cam 16, 17, so as to guarantee that the

) forces exerted by the rod 15 on the cam or cams 16, 17 are directed towards the centres of instantaneous rotation of the latter, can be guaranteed nevertheless.

It should be noted that, although an embodiment of the present invention has been described which, advantageously for the resistance and stability of the device 1 , provides for the use of two cams 16, 17 specular and parallel combined with a follower consisting of a rod 15, any other embodiment that provides for the use of at least one cam and a relative follower, constrained, even indirectly, to a supporting bracket as described above, or the cam in rotation and the follower substantially constrained, directly or indirectly, to the bracket, falls within the protection of the present patent. Analogously, the present patent is not limited, as a person skilled in the art will easily realise, to the fact that the bracket 2 is constrained to a fixed component of a chair and the follower 15 is integral with the movable component to be inclined, since each kinematic or structural inversion of the device falls equally within the scope of the protection requested. Again, it should be noted that any constraint, and not only the lever 18 and/or the linear guides 13, suitable for permitting movement of the follower 15 against the eccentric profile of the relative cam 16, 17 only along a well-defined path with respect to the bracket 2, or with only one degree of freedom, and so as to guarantee that the constraint reaction of the follower on the relative cam 16, 17 is directed only towards the centre of instantaneous rotation of the latter, falls within the inventive concept of the present invention. Operation of the device described above is as follows. Starting, for example, from the position of minor tilt of the levers 18 (figures 1 and 3a), and therefore of the backrest or seat of the chair in the particular embodiment described here, shown in figure 1_., the rotation of the knob 36 by the user (clockwise in figure 1 ) determines the integral rotation, around the axis A-A, of the rod 14 in the holes 12 and therefore of the cams 16, 17 with respect to the bracket 2 and with respect to the follower, or driven rod, 15.

Said rotation of the cams 16, 17 thus causes simultaneous movement, to the same extent, of the ends of the driven rod 15 moving away from the centre of rotation of the cams 16, 17 due to the ends of the rod 15 resting within the eccentric profile, in particular spiral-shaped, of the cams 16, 17, defined by the grooves 23. Sliding of the rod 15 along the profile of the cams 16, 17 is furthermore constrained by the presence of the levers 18, and also by the linear guides 13, which determine the only possible rotation of the rod 15 around the hinge axis C-C of said levers 18. Said movement of the driven rod 15, following the spiral profile of the grooves 23, away from the centre of rotation of the cams 16, 17, thus causes rotation of the levers 18 around the relative hinge points 21 , 22 (or around the axis C-C) and therefore the tilt of said levers 18 with respect to the bracket 2. The constraint of the rod 15 in the linear guides, or arc-shaped slots, 13, guarantees the correct movement, within the stroke limits predefined at the design stage, of said rod 15 with respect to the bracket 2. If, as by way of example in the embodiment described here, the movable component of the chair is integral with the levers 18, the tilt of the latter necessarily involves the tilt of said movable component, for example the backrest, with respect to the bracket 2, fixed integrally with the base of the chair. Having reached any tilt required by the user, for example the one illustrated in figure 3b, the stability of the reciprocal position of the follower 15 and the cams 16, 17, as said, is guaranteed by the reciprocal constraints of said follower, or driven rod, 15 with the bracket 2 and with the contact surface of the profile 23 of the cams 16, 17.

In particular, the stability of the relative position of the rod 15 resting on the profile of the cams 16, 17, countering any load present on the movable component constrained to the levers 18, is ensured by the revolving constraint (i.e. the constraint in a rotation manner) provided by said levers 18 and/or by the sliding constraint given to the rod 15 by the slots, or linear guides, 13 obtained on the bracket 2, by the geometric configuration of the parts, and by the contact, with relative friction, of the rod 15 within the profile 23 of the cams 16, 17. Said factors, as has been seen, require the direction of the forces exerted by the rod 15 to pass through the centre of instantaneous rotation 14' of the cams 16, 17, preventing the generation of torques which would induce undesired rotations of said cams 16, 17.

If, from the stable tilt position reached by the user, for example the intermediate position of figure 3b or the position of maximum tilt of the levers 18 shown in figure 2 and in figure 3c, the user wishes to reduce said tilt, rotation of the knob 36 (in this case anti-clockwise) would determine the consequent relative rotation of the cams 16, 17 with respect to the driven rod, or follower, 15, causing the relative movement thereof with respect to the rod 14 and therefore rotation of the levers 18 towards an increasingly small angle of tilt with respect to the bracket 2.

Here again, when the user has obtained the required tilt of the movable component, the stability of said tilt is guaranteed by the above-mentioned method of constraint of the follower 15 to the cams , 17 and to the bracket 2.

Claims

1 . Device (1 ) for adjusting the tilt of at least one movable component of a chair, of the type comprising at least one cam (16, 17), constrained in a rotating manner to a bracket (2), and at least one follower (15) constrained in a sliding manner on the profile (23) of said at least one cam, said movable component being integral with said at least one follower and said bracket being fixed with respect to the follower or, vice versa, said movable component being integral with said bracket and said at least one follower being fixed with respect to the bracket, characterised in that it comprises means (13, 18) for constraining said at least one follower to said bracket, said means (13, 18) and said at least one cam (16,

17) being configured so that the constraint reaction of said at least one follower on said at least one cam is substantially always directed towards the centre of instantaneous rotation of said at least one cam.

2. Device as claimed in claim 1 , characterised in that said means (13,

18) to constrain said at least one follower to said bracket comprise at least one lever (18) hinged to said bracket, said lever being constrained to said follower (15).

3. Device as claimed in claim 2, wherein said follower is a driven rod (15) integral with said lever (18).

4. Device according to claim 2 or 3, wherein said movable component is integral with said lever (18).

5. Device as claimed in any one of the preceding claims, characterised in that said means (13, 18) to constrain said at least one follower to said bracket comprise at least one linear guide (13) within which said follower slides.

6. Adjustment device as claimed in any one of the preceding claims, W

characterised in that said at least one follower (15) is constrained to said bracket, or vice versa, in a sliding and/or rotating manner on a plane parallel to or coinciding with the rotation plane of said at least one cam.

7. Adjustment device according to any one of the preceding claims, characterised in that said at least one follower (15) is furthermore constrained in a sliding manner on the profile of said at least one cam, in a groove (23) which defines said cam profile.

8. Adjustment device as claimed in any one of the preceding claims, characterised in that it comprises two cams (16, 17) on the profile of which (23) at least one follower (15) is constrained in a sliding manner.

9. Adjustment device as claimed in any one of the preceding claims, characterised in that said at least one cam is driven by a rod (14).

10. Adjustment device as claimed in claim 9, characterised in that it comprises a knob (35) integrally constrained to said rod (14).

1 1.Adjustment device as claimed in any one of the preceding claims, characterised in that said movable component is a seat or backrest of a chair.