SYNCHRONIZING MECHANISM FOR A CHAIR

Description

TECHNICAL FIELD

The invention relates to a synchronizing mechanism for a chair, in particular an office chair, according to the preamble of independent claim 1.

Such a mechanism, which makes possible a synchronously adjustable alignment of the backrest and seat, is used in various chairs and armchairs. The corresponding chairs or armchairs should here be designed for ergonomically dynamic sitting and have body-synchronized mobility. The adjustability of the backrest and seat is usually achieved mechanically, but in some cases also by means of motors.

PRIOR ART

From U.S. Pat. No. 7,614,697 A1 a coupling mechanism for a seat and a backrest of a chair is known, which is intended to prevent the seat from tipping over when leaning back. The mechanism includes a pair of opposing front pivot bracket members and a pair of opposing rear pivot bracket members secured to a joining base member on an underside of a seat, each of the front and rear pivot bracket members having a through-hole. The mechanism further comprises a joining member which is fixedly connected to a support tube of the seat, the joining member having two opposing lateral wall sections. Each of the side wall sections has an inclined slot at each of its front and rear sections. The inclined slots are each inclined downwardly toward a rear end, wherein the seat is movably arranged on the joining member, wherein a first pivot shaft is guided through the through-holes of the front pivot tab parts and the front inclined slots of the joining member, and wherein a second pivot shaft is guided through the through-holes of the rear pivot tab parts and the rear inclined slots of the joining member. Each of the side wall portions of the joining member has an adjustment slot between the front and rear inclined slots. The mechanism further comprises a connector connected to the rear side, the connector having a mounting hole in a front section and an inclined slot in a rear section. The inclined slot is inclined upwards towards the rear end. The connecting member and the joining member are connected to each other, wherein a third pivot shaft is guided through the adjusting slots of the joining member and the fastening hole of the joining member, wherein the second pivot shaft is guided through the inclined slot of the connecting member. The connecting member has a pivoting section between the fastening hole and the inclined slot; the connecting element being pivoted to the joining member at its pivoting section. Finally, the mechanism comprises a locating plate and an elasticity adjustment device installed on the locating plate, wherein the locating plate is positioned under the adjustment slots of the joining member and of the connecting member. The elasticity adjustment device comprises a spindle which is fixedly connected to the third pivot shaft which is guided through the adjustment slots in the joining member, and an elastic element arranged around the spindle. The elastic element is designed to change its length when the elasticity adjustment device is rotated.

DE 20 2011 108 433 U1 describes an office chair which comprises a base and an upwardly extending column. A base support is attached to the upper end of the column, with a seat support mounted in the front area of the base support. In the rear area, the seat support and the base support are connected to each other by means of two pivots and a coupling lever. The coupling lever is also positively guided in a bearing point by means of a back rocker arm. The deflection angle of the coupling lever is open towards the back in the upright sitting position and does not go beyond the horizontal axis in the leaning-back sitting position. The bearing point is preferably designed as a sliding pivot joint. The back rocker arm is mounted on the base support via a pivot joint. A spring element rests on the base support and applies a restoring force to the back rocker arm at a pivot. The pivot of the spring element can be changed in relation to the pivot joint via a spiral cam, thus making it possible for the restoring force to be adjusted.

It is an object of the present invention to propose a synchronizing mechanism for a chair, in particular an office chair, which makes possible a safe movement of the chair from a basic position to an end position and back again, without the need for an adjustment of the mechanism depending on the weight of the user.

DISCLOSURE OF THE INVENTION

According to the invention, the object is solved by a synchronizing mechanism for a chair, in particular an office chair, as defined in independent claim 1.

The essence of the invention consists in the following: a synchronizing mechanism for a chair, in particular an office chair, comprising a base part defining an axis of rotation, a backrest support for holding a backrest and a seat support for holding a seat. The backrest support is mounted on the base part so as to be pivotable about a first pivot, wherein the seat support is mounted on the backrest support so as to be pivotable about a second pivot. The first pivot of the backrest support is fixed relative to the base part and the second pivot of the seat support is movable relative to the base part. In a basic position, the second pivot is in a lower basic position and the seat support abuts a support structure, and in an upper end position, the movable second pivot is moved essentially vertically to an upper end position and the seat support is at a distance from the support structure.

The term “synchronizing mechanism” is to be understood in a broader sense in the present case, i.e. when leaning back a combination of seat support and backrest support movement also takes place, but this is combined with a greater freedom of movement when sitting. By flexibly mounting the seat support with the seat plate, the user can control his sitting position solely by means of his lower legs and thighs and, if necessary, by shifting his weight. One can therefore also speak of a (flexible) weight-dependent kinematics concept for a chair, especially an office chair.

In the present case, the term “axis of rotation” also refers to the central axis of the finished chair, which runs through the chair's column and around which the seat routinely can be rotated.

In the present case, the “base part” serves, in particular, as a kind of holder for the backrest support and for the column of the finished chair.

The term “backrest support” refers in the present case to the component on which the backrest of the chair is arranged.

In present case, the “seat support” is the component on which the seat plate is arranged or mounted; in principle, the seat support and the seat plate can also be formed as one piece.

The “fixed first pivot” does not change its position during the various movements or position changes of the synchronizing mechanism, i.e. it always remains in the same place.

The “movable second pivot” on the other hand changes its position during the various movements or position changes of the synchronizing mechanism, i.e. it does not remain in the same place. The movable second pivot may be designed as a pivot of a joint-like connection between the backrest support and the seat support; however, in another embodiment it may also be designed as a notional pivot which lies outside the synchronizing mechanism, in particular, as a pivot relative to a slotted guide of the backrest support in which the seat support is guided.

Furthermore, it is also possible that the fixed first pivot and/or the movable second pivot are not only realized mechanically in the form of a joint or a spindle, but also in the form of deformable structures, such as for example by torsion element arrangements or torsion spring arrangements or the like. It is also conceivable to use plastic-fiberglass material arrangements, which would provide a correspondingly flexible range of motion.

The “basic position” includes the basic state of a corresponding chair in which the movable second pivot is in its lowest position, i.e. in its lower basic position, and in which the seat support with the seat is in a non-tilted state.

The “support structure” holds the seat support or the seat in the basic position, i.e. the support structure can only be overcome by a person shifting his weight forwards on the chair so that the seat support and the seat plate are tilted forwards in the direction of the seat, i.e. away from the backrest. The “support point” is the contact point or the contact surface (i.e. in the case of a sliding block) of the seat support on the support structure in the basic position.

The “end position” of the synchronizing mechanism includes the state in which the second movable pivot and thus also the seat support are in the highest position, i.e. with the greatest distance from the support structure. In this end position, a maximum pivotability of the seat support is guaranteed.

The “essentially vertical” movement of the movable second pivot into the upper end position also includes an upwardly curved movement path, i.e. in particular, a movement path curved forwards from the axis of rotation in the seat direction.

In the present case, an “arrangement at a distance from” the support point can be achieved by lifting or pivoting the seat support upwards or by moving it sideways together with lifting or pivoting the seat support upwards.

Preferably, the second pivot is fixed in relation to the backrest support and can be moved essentially vertically upwards with the backrest support. This has proven to be advantageous with regard to a particularly flexible design of the chair mechanism. Preferably, in a first intermediate position of the synchronizing mechanism, the second pivot is moved from the lower basic position essentially vertically upwards into a first intermediate position and the seat support is arranged to tilt or to be tiltable relative to the support structure (i.e. forwards in the seat direction). By shifting the weight forwards, i.e. away from the backrest, a person can cause the seat support to tilt forwards, while at the same time the second pivot moves slightly upwards and the backrest support assumes a slight backward inclination. This makes it possible to efficiently provide a particularly flexible use of a chair equipped with the synchronizing mechanism according to the invention.

Preferably, in a second intermediate position, the angle or inclination of the seat support and the seat plate can be controlled (solely) by the user's upper and/or lower legs (and not necessarily by the mechanism). It is rather the case that the seat plate adapts to the user through its, albeit limited, pivotability, thereby generating a special seating comfort.

In particular, in the second intermediate position, the second pivot is moved from the lower basic position essentially vertically upwards into a second intermediate position in which the seat support (and the seat plate) is raised to such an extent that it (with its inner surface) is out of contact with the support structure, so that the seat support with the seat plate can be tilted about the second pivot without guidance. The seat support with the seat plate is therefore only connected to the backrest support or the chair mechanism via the second pivot and can be tilted about the same; guide rods or other guide elements are not provided. For this reason, the inclination of the seat support with the seat plate can be controlled (solely and directly) by means of the lower and/or legs of the user and is essentially independent of the position of the backrest. There is no need for forced guidance by the mechanism.

Preferably, however, in the second intermediate position the seat support has not yet reached its maximum pivotability.

Preferably, in the end position of the synchronizing mechanism, the seat support can be pivoted to the maximum extent relative to the backrest support about the second movable pivot. This can further increase the flexibility of use of a chair equipped with the synchronizing mechanism according to the invention.

Finally, the user should be able to perform all possible movements (i.e. tipping forwards, lifting and going into the reclining position) by shifting his weight or using his muscles alone. If the pivots and support structures are appropriately coordinated, the use of springs and/or damping elements can in principle be dispensed with when using the synchronizing mechanism according to the invention. This means that the seat support and seat plate can ideally adapt to the user thanks to the freedom of rotation (albeit limited forwards and backwards), thus generating a specially optimized seating comfort.

In the present context, the term “maximally pivotable” comprises a maximum rotatability, or rotatability and movability of the seat support in the end position, or the highest position of the second pivot, between a first limiting means which limits tilting of the seat support forwards and a second limiting means which limits tilting of the seat support backwards.

In a first embodiment of the invention, the first limiting means is formed by the beveled front end of the backrest support or of the side parts of the backrest support—against which the seat support comes to rest with the inner surface of its upper side when tilted forwards—and the second limiting means is formed by the front lower edge of the backrest support or of the side parts of the backrest support—against which the lower transverse connection of the seat support comes to rest when tilted backwards.

In a second embodiment of the invention, the first limiting means is formed by the front end of the guide slot of the slotted guide of the backrest support or of the side parts of the backrest support—against which the front guide pin of the seat support comes to rest when tilted forwards—and the second limiting means is formed by the rear end of the guide slot of the slotted guide of the backrest support or of the side parts of the backrest support—against which the rear guide pin of the seat support comes to rest when tilted backwards.

In both embodiments of the synchronizing mechanism according to the invention, the seat support or the seat plate assumes a maximum tilt angle perpendicular to the axis of rotation in the backwards tilted end position. This maximum tilt angle is preferably about 5° to about 40°, more preferably about 10° to about 30°, and even more preferably about 15° to about 25°. In these ranges, the weight independence of the mechanism can be used in an optimal way.

Preferably, the base part is designed as a rigid component. This ensures the stability required for the synchronizing mechanism according to the invention.

Preferably, when viewed from the side, the first pivot is arranged behind the axis of rotation in the seat direction and the second pivot is arranged in front of the axis of rotation of the base part in the seat direction. This ensures optimal functionality of the synchronizing mechanism according to the invention.

Preferably, the support structure is arranged in front of the axis of rotation of the base part in the seat direction when viewed from the side. It is designed that way so that the user has to consciously shift his weight in order to be able to tilt the seat support forwards.

Preferably, the movable second pivot is arranged movably between the support structure and the first pivot, when viewed from the side, i.e. on an essentially vertical movement path. Further preferably, the second pivot is arranged to be movable between the support point and the axis of rotation, when viewed from the side, i.e. on an essentially vertical movement path. This measure allows further fine-tuning of the mechanism, allowing the user to change the position of the chair purely based on body movements or muscle power.

Preferably, in the basic position, a support point of the seat support on the support structure is located vertically above the first pivot. This is another measure to fine-tune the individual components to each other.

Preferably, the seat support is designed as a U-shaped profile which, open at the bottom, is arranged on the underside of the seat plate. In this way, a particularly effective articulation of the seat support at the backrest support and, at the same time, an optimal support of the seat support at the support point can be achieved.

Preferably, the support structure comprises a sliding block, which is preferably mounted so as to be rotatable about a third pivot between two tab-like projections of the base part. The sliding block supports the seat support to stabilize the seat and serves as a seat support pivot for the forward tilt according to the first intermediate position.

Preferably, in the basic position and in the first intermediate position, the seat support rests with the inner surface of its upper side on the sliding block (support point).

In another preferred embodiment of the invention, the backrest support has a slotted guide for the seat support. In this case, the second pivot lies outside the mechanism and is therefore also called a notional pivot. In this embodiment, the seat support is not only tilted forwards when moving from the basic position to the first intermediate position, but is also moved laterally forwards at the same time, i.e. it also performs a forward movement; the same applies when the seat support moves from the basic position to the end position. In other words, in this embodiment, the seat support and the backrest support or the backrest of the chair move apart or in virtually opposite directions.

Preferably, in this embodiment, in a second intermediate position, the angle of the seat support and the seat plate can be controlled by the user's lower legs (and not necessarily by the mechanism). It is rather the case that the seat plate adapts to the user through its, albeit limited, pivotability, thereby generating a special seating comfort. In particular, in the second intermediate position, the second pivot is moved from the lower basic position essentially vertically upwards into a second intermediate position in which guide pins operatively connected to the seat support via a slotted guide are raised so far (i.e. together with the seat support and the seat plate) that they are out of contact with the base part, but the seat support has not yet reached its maximum pivotability.

Preferably, when viewed from the side, the slotted guide comprises an upwardly convexly curved guide slot for the seat support, which at least partially extents across an upper edge of the base part. In this way, a guide is created for the seat support or for its guide pins, which project through the guide slot in the slotted guide, with the front guide pin abutting a stop (in the basic position) defined by the upper edge of the base part and the curved guide slot.

Preferably, the fixed first pivot and/or the movable second pivot is/are realized by means of a deformable structure. In particular, a torsion element arrangement, such as a torsion spring arrangement, may be provided. In this way, the movement sequence can be made particularly efficient for the user.

A further aspect of the invention relates to a chair, in particular an office chair, with a synchronizing mechanism of the type described above. With such a chair, the effects and advantages described above in connection with the mechanism according to the invention can be implemented in an efficient manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous embodiments of the invention emerge from the following description of exemplary embodiments of the invention with the aid of the schematic drawing. In particular, the mechanism according to the invention and the chair according to the invention are described in more detail below with reference to the accompanying drawings on the basis of exemplary embodiments. In the drawings:

FIG. 1: shows a perspective view of a first embodiment of a synchronizing mechanism according to the invention;

FIG. 2: shows a side sectional view of the first embodiment of the synchronizing mechanism according to the invention in the basic position with horizontal seat support;

FIG. 3: shows a side sectional view of the first embodiment of the synchronizing mechanism according to the invention in the first intermediate position with the seat support tilted forwards;

FIG. 4: shows a side sectional view of the first embodiment of the synchronizing mechanism according to the invention in a second intermediate position with a raised and essentially horizontal seat support;

FIG. 5: shows a side sectional view of the first embodiment of the synchronizing mechanism according to the invention in an end position with the seat support in the highest position;

FIG. 6: shows a side sectional view of the first embodiment of the synchronizing mechanism according to the invention in the end position with the seat support tilted backwards;

FIG. 7: shows a side sectional view of a second embodiment of the synchronizing mechanism according to the invention in the basic position with the seat support slightly inclined backwards;

FIG. 8: shows a side sectional view of the second embodiment of the synchronizing mechanism according to the invention in the first intermediate position with the seat support tilted forwards;

FIG. 9: shows a side sectional view of the second embodiment of the synchronizing mechanism according to the invention in the second intermediate position with raised seat support;

FIG. 10: shows a side sectional view of the second embodiment of the synchronizing mechanism according to the invention in the end position with the seat support in the highest position; and

FIG. 11: shows a side sectional view of the second embodiment of the synchronizing mechanism according to the invention in the end position with the seat support tilted backwards.

EMBODIMENT(S) OF THE INVENTION

Certain expressions are used in the following description for practical reasons and are not to be understood as limiting. The words “right,” “left,” “bottom” and “top” denote directions in the drawing to which reference is made. The terms “inward,” “outward,” “below,” “above,” “left,” “right” or similar are used to describe the arrangement of designated parts relative to one another, the movement of designated parts relative to one another and the directions toward or away from the geometric center of the invention and designated parts thereof as shown in the drawings. This spatial relative information also comprises different positions and orientations from those shown in the drawings. For example, if a part shown in the drawings is reversed, elements or features that are described as “below” are then “above.” The terminology comprises the words expressly mentioned above, their derivations and words with similar meanings.

In order to avoid repetitions in the drawings and the associated description of the different aspects and embodiments, certain features are to be understood as common for different aspects and embodiments. The omission of an aspect in the description or a drawing does not suggest that this aspect is missing in the associated embodiment. Rather, such omissions are made for the sake of clarity and to avoid repetition. In this context, the following stipulation applies to the entire further description: If reference numerals are contained in a figure for the purpose of graphic unambiguity but are not mentioned in the directly associated descriptive text, reference is made to their explanation in preceding figure descriptions. If reference signs are also mentioned in the text of the description relating directly to a figure that are not included in the corresponding figure, reference is made to the preceding and following figures. Similar reference signs in two or more drawings represent similar or identical elements.

In FIG. 1 a perspective view of a first embodiment of the synchronizing mechanism 1 according to the invention for a chair, in particular an office chair, is illustrated. The synchronizing mechanism 1 comprises a base part 5 with a receptacle 11 for a column of a chair as well as two side parts 5a and 5b. At the rear end of the side parts 5a and 5b, an articulated connection is provided with the side parts 2a and 2b of a backrest support 2, which serves to hold a backrest, wherein the articulated connection comprises the fixed first pivot D1. In the front area of the two side parts 2a and 2b of the backrest support 2, a U-profile-shaped seat support 3 is articulated with its two side parts 3a and 3b, wherein this articulated connection includes the movable second pivot D2. The second pivot D2 is thus fixed relative to the backrest support 2 and can be moved essentially vertically upwards with the backrest support 2. The U-profile-shaped seat support 3 is arranged essentially centrally on the underside of a seat plate 4. With the inner surface of its upper side 7, the U-profile-shaped seat support 3 rests on a sliding block 6, which is rotatably mounted between two tab-like projections 5c and 5d of the base part 5 and which serves as a seat stabilizer and as a seat support pivot, i.e. for tilting the seat support 3 with the seat plate 4 forwards in the seat direction. In the synchronizing mechanism 1 according to the invention, the side parts 3a and 3b of the seat support 3 are arranged on the outside and the two side parts 5a and 5b of the base part 5 are arranged on the inside and the two side parts 2a and 2b of the backrest support 2 are arranged in between. The individual movement sequences of the synchronizing mechanism 1 according to the invention are described in detail below.

FIG. 2 shows a side sectional view of the first embodiment of the synchronizing

mechanism 1 according to the invention in the basic position with horizontal seat support 3 and correspondingly horizontal seat plate 4. The basic position comprises the basic state of a corresponding chair in which the movable second pivot D2 is in its lowest position, i.e. its lower basic position, and the seat support 3 with the seat plate 4 is in a non-tilted, i.e. in this case horizontal, state. The fixed first pivot D1 and the movable second pivot D2 are located approximately at the same height but at different ends of the axis of rotation X, with the fixed first pivot D1 on the rear end being routinely slightly further away from the axis of rotation X than the movable second pivot D2 on the front end. The U-profile-shaped seat support 3 rests with its inner surface 7a on the sliding block 6, with the sliding block 6 being arranged between the two tab-like projections 5c and 5d of the base part 5 so as to be rotatable about the third pivot D3. This support area of the seat support 3 on the sliding block 6 comprises the support point P of the support structure A, which is formed here by the tab-like projections 5c and 5 as well as by the sliding block 6. The user must overcome the support structure A if he wants to get from the basic position of the synchronizing mechanism to a first intermediate position, which is explained below. The support point P (and also the third pivot D3) is routinely located, seen in the vertical direction along the axis of rotation X, above the movable second pivot D2 as well as above the fixed first pivot D1 and in the horizontal direction further away from the axis of rotation X than the movable second pivot D2 as well as further away from the central axis X than the fixed first pivot (on the rear end) in order to ensure optimal functionality of the mechanism. In this position with the backrest support 2 not deflected, a backward tilting of the seat support 3 with the seat plate 4 is prevented by the lower transverse connection 13 of the seat support 3, which here rests on the front lower edge 14 of the backrest support 2 or its side parts.

FIG. 3 now shows a side sectional view of the first embodiment of the synchronizing mechanism 1 according to the invention in a first intermediate position with the seat support 3 tilted forwards and the seat plate 4 tilted forwards. For this movement, a shift of the user's weight on the seat plate 4 is routinely required in order to overcome the support structure A, i.e. to perform a rotation of the seat support 3 about the fixed third pivot D3. During this movement or due to the shift in weight, the movable second pivot D2 is pivoted together with the backrest support 2 essentially vertically upwards, which also leads to a slight backward inclination of the backrest support 2 (and possibly of a corresponding backrest). The forward inclination or forward tipping of the seat support 3 with the seat plate 4 is limited by the front bevel 12 of the backrest support 2.

In FIG. 4 a side sectional view of the first embodiment of the synchronizing mechanism 1 according to the invention in a second intermediate position with a raised and essentially horizontal seat support 3 is illustrated. For this second intermediate position, the user must lean back from the basic position, in which case the backrest support 2 or its front part will be pivoted upwards about the fixed first pivot D1 so far that the movable second pivot D2 moves accordingly further upwards into a second intermediate position. The inner surface 7a of the U-profile-shaped seat support 3 moves correspondingly upwards away from the support structure. Here, the backrest support 2 is with its front lower edge 14 out of contact with the lower transverse connection 13 of the seat support 3, but is not yet in contact with the inner surface 7a of the seat support 3 with its beveled front end 12. The second intermediate position represents a quasi-flexible transition position of the synchronizing mechanism 1 on its way to the end position (highest position of the second pivot D2) according to the following FIG. 5, and possibly back to the basic position according to FIG. 2.

In the second intermediate position according to FIG. 4, the angle of the seat support 3 and the seat plate 4 can be controlled without any guide, i.e. without supporting guide rods or other guide elements, solely and directly by the lower legs of the user and not necessarily by the mechanism. Here, due to its albeit limited pivotability, the seat plate 4 adapts ideally to the user, thereby generating a specially optimized seating comfort.

FIG. 5 shows a side sectional view of the first embodiment of the synchronizing mechanism 1 according to the invention in the end position, in which the seat support 3 with the movable second pivot D2 is in the highest position or the upper end position of the movable second pivot D2. Here, the second pivot is located approximately above the upper edge 10 of the base part 5 or above its side parts. As the user leans back further, the beveled front end 12 of the backrest support 2 will have been pivoted even further upwards about the fixed first pivot D1 compared to the second intermediate position according to FIG. 4, with the beveled end 12 of the backrest support 2 or of its side parts coming into contact with the inner surface 7a of the U-profile-shaped seat support 3 and abutting it. The backrest support 2 is now with its beveled front end 12 in surface contact with the inner surface 7a of the seat support 3, so that the seat support 3 with the seat plate 4 is supported by the beveled front end 12 of the backrest support 12 in an essentially horizontal orientation. In this upper end position of the movable second pivot D2, the seat support 3 can now be rotated about the latter, with the contact with the beveled front end 12 (first limiting means) of the backrest support 2 preventing the seat support 3 with the seat plate 4 from tipping forwards out of the horizontal when leaning back into the end position of the backrest support 2 shown here, which could potentially lead to the user slipping in an undesirable manner on the chair.

On the other hand, however, the user can cause the seat support 3 with the seat plate 4 to tilt backwards from the end position of the synchronizing mechanism 1 according to FIG. 5 by shifting his weight backwards on the seat plate 4, although, as shown in FIG. 6, the backrest support 2 and the movable second pivot D2 no longer change their position. This backward tilting is limited by the front lower edge 14 (second limiting means) of the backrest support 2 or by its side parts against which the seat support 3 comes to rest with its lower transverse connection 13. In other words, in the end position, a maximum pivotability or a maximum rotatability of the seat support about the pivot D2 is provided, namely between the beveled front end 12 of the backrest support 2 as the first limiting means, which limits a tilting of the seat support 3 from the horizontal forwards, and the lower front edge 14 of the backrest support 2 as the second limiting means, which limits a tilting of the seat support backwards (i.e. in that the lower transverse connection 13 of the seat support 3 comes to abutment here). In the final position with the seat support 3 tilted backwards, the seat plate 4 is essentially parallel to the backrest support 2. In the backwards tilted end position, the seat plate 4 assumes a maximum tilt angle α perpendicular to the axis of rotation X, as illustrated in FIG. 6.

In FIG. 7 a side sectional view of the second embodiment of the synchronizing mechanism 1 according to the invention in the basic position is now shown. In the second embodiment of the synchronizing mechanism according to the invention, the side parts of the seat support 3 are also arranged on the outside and the two side parts of the base part 5 are arranged on the inside. The two side parts of the backrest support 2 are arranged in between. In this second embodiment, however, the side parts of the backrest support 2 have a slotted guide 8 which has a guide slot 9 which is convexly curved upwards and in which guide pins 11a, 11b, which movably connect the seat support 3 to the backrest support 2, are guided. The guide slot 8 itself has a corresponding upwardly convex curvature like the guide slot 9. The seat support 3 rests with the inner surface 7a on the upper side of the slotted guide 8 (support point P′ of the support structure A′, which is formed here by the slotted guide 8). At the rear end of the side parts of the base part 5, an articulated connection with the side parts of the backrest support 2 is again provided, which comprises the fixed first pivot D1. The movable second pivot D2′ is designed here as a “notional” pivot, which lies outside the synchronizing mechanism 1, namely as the pivot of the seat support 3, which moves with the backrest support 2 from the basic position essentially vertically upwards, i.e. here also slightly laterally forwards (due to the mobility of the seat support or its guide pins 11a, 11b in the guide slot 9), which results in an upwardly curved movement path of the movable second pivot D2′. The individual movement sequences of the second embodiment of the synchronizing mechanism according to the invention are described in detail below.

In the basic position of this embodiment, the seat support 3 and the seat plate 4 are slightly inclined backwards relative to the axis of rotation X. However, the basic position also includes the basic state of a corresponding chair in which the movable second pivot D2′ is in its lowest position, i.e. its lower basic position, and the seat support 3 with the seat plate 4 is in a non-tilted state, i.e. here slightly tilted backwards. The rear guide pin 11b of the seat support 3 abuts the rear end of the guide slot 9, which initially prevents a further or stronger backward tilt, and the front guide pin 11a abuts the stopping point H in the region of the front end of the base part 5. At the stopping point H, in the basic position, the curvature of the guide slot 9 together with the upper edge 10 of the base part 5 basically prevents a forward/tilting movement of the seat support 3 and the seat plate 4. Here too, a shift in the user's weight on the seat plate 4 is necessary in order to overcome the support structure A′ (and the stopping H) if the user wants to move from the basic position of the synchronizing mechanism 1 to a first intermediate position, which is explained below. The movable second pivot D2′ is located below the fixed first pivot D1. The two pivots D1 and D2′ are located at different ends of the axis of rotation X, with the fixed first pivot D1 on the rear end routinely being somewhat closer to the axis of rotation X than the movable second pivot D2′ on the front end.

FIG. 8 now shows a side sectional view of the second embodiment of the synchronizing mechanism 1 according to the invention in the first intermediate position with the seat support 3 tilted forwards, wherein the seat support and the seat plate 4 move from the slightly backwards inclined position to an essentially horizontal orientation when tilted. As mentioned, this forward/tilting movement requires the user to shift his weight on the seat plate 4 in order to overcome the support point P′ (and the stopping point H). During this weight shift, the movable second pivot D2′ is pivoted together with the backrest support 2 essentially vertically upwards, which correspondingly also leads to a slight backward inclination of the backrest support 2 and to a gradual lifting of the curved guide slot 9 relative to the base part 5. In this way, the front guide pin 11a can move approximately to the front edge 15 of the base part 5 but not beyond that, because further movement is blocked by the curvature of the guide slot 9 in interaction with the base part 5. This blocking at the stopping point H can be removed by a further raising of the seat support 3.

In FIG. 9 a side sectional view of the second embodiment of the synchronizing mechanism 1 according to the invention in a second intermediate position with a raised and essentially horizontal or slightly backwards inclined seat support 3 is illustrated. For this second intermediate position, the user must lean back from the basic position, in which case the backrest support 2 or its front part is pivoted upwards about the fixed first pivot D1 so far that the movable second pivot D2′ moves further upwards into a second intermediate position. In the process, the guide slot 9 with the guide pins 11a and 11b is lifted upwards away from the base part 5 together with the seat support 3 and the seat plate 4 and at the same time the guide pins 11a and 11b of the seat support 3 move laterally a little way forwards in the guide slot 9 of the slotted guide 8, whereby, however, the front guide pin 11a does not yet come to abut the front end 9a of the guide slot 9. The second intermediate position represents a flexible transition position of the synchronizing mechanism 1 on the way to the end position according to the following FIG. 10 (and possibly back to the basic position according to FIG. 7).

In the second intermediate position according to FIG. 9, the angle of the seat support 3 and the seat plate 4 can be controlled by the user's lower legs and not necessarily by the mechanism, in contrast to conventional synchronizing mechanisms. Here, the seat plate 4 adapts to the user through its albeit limited pivotability, thereby generating a special seating comfort.

FIG. 10 shows a side sectional view of the second embodiment of the synchronizing mechanism 1 according to the invention in the end position, in which the seat support 3 with the movable second pivot D2′ is in the highest position or its upper end position, in which the movable second pivot D2′ is located slightly below the front edge 15 of the base part 5 or of its side parts. By leaning back further with a corresponding shift of the user's weight, the front part of the backrest support 2 with the slotted guide 8 has been raised further upwards and tilted backwards compared to the second intermediate position according to FIG. 9. At the same time, the seat support 3 with the seat plate 4 together with the guide pins 11a and 11b has moved laterally forwards, i.e. until the front guide pin 11a abuts the front end 9a of the guide slot 9. The seat support 3 and the seat plate 4 have retained their slight backward inclination in which they are supported here. In this upper end position of the movable second pivot D2′, the seat support 3 can now be freely rotated about it or moved in the guide slot, wherein, however, by the front guide pin 11a abutting the front end 9a (first limiting means) of the guide slot 9, when leaning back into the end position of the back rest 2 shown here, the seat support 3 with the seat plate 4 is prevented from simultaneously tipping further forwards from the horizontal, which could possibly lead to the user slipping off the chair.

In this respect, the user can still cause the seat support 3 with the seat plate 4 to tilt backwards from the end position of the synchronizing mechanism 1 according to FIG. 10 by shifting his weight backwards on the seat plate, wherein, however, as shown in FIG. 11, the backrest support and the movable second pivot D2′ no longer change their position. This backwards tilting is correspondingly limited by the rear end 9b (second limiting means) of the guide slot 9, against which the seat support 3 with the rear guide pin 11b comes to abutment. In other words, in the end position, there is a maximum pivotability or a maximum rotatability or mobility of the seat support 3 around the pivot D2′ between the front end 9a of the guide slot 9 as the first limiting means, which limits tilting forward of the seat support 3 from the slight backwards inclination, and the rear end 9b of the guide slot 9 as the second limiting means, which limits tilting backward of the seat support 3 (i.e. by the rear guide pin 11b of the seat support 3 coming to abutment here). In the backwards tilted end position, the seat plate 4 is essentially parallel to the backrest support 2. In the backwards tilted end position, the seat plate 4 assumes a maximum tilt angle α perpendicular to the axis of rotation X (or a maximum inclination), as illustrated in FIG. 11.

From the above explanations it is clear that by means of the synchronizing mechanism according to the invention, not only according to the first but also according to the second embodiment, the user can carry out a practically fluid adjustment of a corresponding chair solely on the basis of his body posture and/or his muscle strength without the need for further support or return elements. Nevertheless, the use of such elements in connection with the synchronizing mechanism according to the invention is fundamentally possible.

List of Reference Signs

• • 1 synchronizing mechanism
  • 2 backrest support
  • 2a, b side parts
  • 3 seat support
  • 3a, b side parts
  • 4 seat plate
  • 5 base part
  • 5a, b side parts
  • 5c, d tab-like projections
  • 6 sliding block
  • 7 upper side of seat support
  • 7a inner surface of upper side of seat support
  • 8 slotted guide
  • 9 guide slot
  • 9a front end guide slot
  • 9b rear end guide slot
  • 10 upper edge of base part
  • 11a, b guide elements of seat support
  • 11 receptacle for column
  • 12 beveled front end of backrest support
  • 13 lower transverse connection of seat support
  • 14 front lower edge of backrest support
  • 15 front edge of base part
  • A, A′ support structure
  • P, P′ support point
  • D1 fixed first pivot
  • D2, D2′ movable second pivot
  • D3 third pivot (sliding block)
  • H stopping point
  • X axis of rotation
  • α max. tilt angle