Synchronizing mechanism for a chair

Abstract

The invention relates to a synchronizing mechanism (1) for a chair, in particular an office chair, comprising a base part (5) which defines a rotational axis (X), a backrest support (2) for supporting a backrest, and a seat support (3) for supporting a seat. The backrest support (2) is pivotally supported on the base part (5) about a first rotational point (D1), and the seat support (3) is pivotally supported on the backrest support (2) about a second rotational point (D2, D2'). The first rotational point (D1) of the backrest support (2) is fixed relative to the base part (5), and the second rotational point (D2, D2') of the seat support (3) is movable relative to the base part (5). In a basic setting, the second rotational point (D2, D2') is in a lower basic position, and the seat support (3) rests against a support structure (A, A'). In an upper end position, the movable second rotational point (D2, D2') moves substantially vertically into an upper end position, and the seat support (3) is arranged at a distance to the support structure (A, A').

Description

DESCRIPTION title SYNCHRONOUS MECHANISM FOR A CHAIR Technical area

[0001] The invention relates to a synchronous mechanism for a chair, in particular an office chair, according to the preamble of independent claim 1.

[0002] This type of mechanism, which enables synchronous adjustment of the backrest and seat, is used in various chairs and armchairs. These chairs and armchairs are designed for ergonomically dynamic sitting and offer body-synchronized movement. The adjustability of the backrest and seat is usually achieved mechanically, but in some cases also by means of motors. State of the art

[0003] From US 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 reclining. The mechanism comprises a pair of opposed front pivoting bracket parts and a pair of opposed rear pivoting bracket parts, which are attached to a connecting base element on an underside of a seat, wherein each of the front and rear pivoting bracket parts has a through-hole. The mechanism further comprises a connecting element which is fixedly connected to a support tube of the seat, wherein the connecting element has two opposed lateral wall sections. Each of the lateral 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 disposed on the connecting member, wherein a first pivot shaft passes through the through holes of the front. Pivot tab parts and the front inclined slots of the connecting element, 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 connecting element. Each of the side wall portions of the connecting element has an adjustment slot between the front and rear inclined slots. The mechanism further comprises a connecting element connected to the rear side, the connecting element having a mounting hole at a front portion and an inclined slot at a rear portion. The inclined slot is inclined upward toward the rear end.The connecting element and the connecting element are connected to each other, with a third pivot shaft passing through the adjustment slots of the connecting element and the fastening hole of the connecting element, and the second pivot shaft passing through the inclined slot of the connecting element. The connecting element has a pivot portion between the fastening hole and the inclined slot; the connecting element is pivoted toward the connecting element at its pivot portion. Finally, the mechanism comprises a positioning plate and an elasticity adjustment device installed on the positioning plate, the positioning plate being positioned below the adjustment slots of the connecting element and the connecting element.The elasticity adjustment device comprises a spindle fixedly connected to the third pivot shaft, which is guided through the adjustment slots of the connecting element, and an elastic element arranged around the spindle. The elastic element is designed to change its length when the elasticity adjustment device is rotated.

[0004] 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 pivot points and a coupling lever. The coupling lever is also positively guided by means of a backrest swing arm in a bearing point. The deflection angle of the coupling lever is open towards the back in the upright sitting position and does not exceed the horizontal axis in the reclined sitting position. The bearing point is preferably designed as a sliding pivot joint. The backrest swing arm is connected to the base support via a A spring element rests on the base support and applies a restoring force to the backrest at a pivot point. The pivot point of the spring element can be adjusted relative to the pivot joint via a spiral eccentric, thus allowing the restoring force to be adjusted.

[0005] The present invention is based on the object of proposing a synchronous mechanism for a chair, in particular an office chair, which enables 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. Description of the invention

[0006] The object is achieved according to the invention by a synchronous mechanism for a chair, in particular an office chair, as defined in independent claim 1.

[0007] The essence of the invention consists in the following: a synchronous mechanism for a chair, in particular an office chair, comprising a base part defining a rotation axis, a backrest support for holding a backrest, and a seat support for holding a seat. The backrest support is pivotally mounted on the base part about a first pivot point, wherein the seat support is pivotally mounted on the backrest support about a second pivot point. The first pivot point of the backrest support is fixed relative to the base part, and the second pivot point of the seat support is movable relative to the base part. In a basic position, the second pivot point is in a lower basic position, and the seat support rests against a support structure. In an upper end position, the movable second pivot point is moved substantially vertically into an upper end position, and the seat support is spaced from the support structure.

[0008] The term "synchronous mechanism" is to be understood in a broader sense, meaning that while a combination of seat support and backrest support movement also occurs when reclining, this is combined with greater freedom of movement when sitting. Due to the flexible positioning of the seat support with the seat plate, the user can control their sitting position solely by means of their lower legs and thighs, as well as by shifting their weight if necessary. Therefore, one can also speak of a (flexible) weight-dependent kinematics concept for a chair, especially an office chair.

[0009] The term “rotational element” also refers to the central axis of the finished chair, which runs through the chair’s column and around which the seat can be regularly rotated.

[0010] In this case, the “base part” serves in particular as a kind of holder for the backrest support and for the column of the finished chair.

[0011] The term “backrest support” refers to the component on which the backrest of the chair is arranged.

[0012] In this 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 a single piece.

[0013] The “fixed first pivot point” does not change its position during the various movements or position changes of the synchronous mechanism, i.e. it always remains in the same place.

[0014] The "movable second pivot point," on the other hand, changes its position during the various movements or position changes of the synchronous mechanism, i.e., it does not remain in the same location. The movable second pivot point can be designed, for example, as the pivot point of a joint-like connection between the backrest support and the seat support; however, in another embodiment, it can also be designed as a fictitious pivot point located outside the synchronous mechanism, in particular as a pivot point relative to a guide rail of the backrest support, in which the seat support is guided.

[0015] Furthermore, it is also possible for the fixed first pivot point and / or the movable second pivot point to be implemented not only mechanically in the form of a joint or an axis, but also in the form of deformable structures, such as flexural element arrangements or spiral spring arrangements, or the like. Furthermore, the use of plastic-fiberglass material arrangements is also conceivable, which would allow for a correspondingly flexible range of motion.

[0016] The “basic position” comprises the basic state of a corresponding chair in which the movable second pivot point 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.

[0017] The "supporting structure" holds the seat support or seat in its home position. This means that the support structure can only be overcome by a person shifting their weight forward on the chair, causing the seat support and seat plate to tilt forward in the sitting direction, away from the backrest. The "supporting point" is the support point or the support surface (e.g., in the case of a sliding block) of the seat support on the support structure in its home position.

[0018] The "end position" of the synchronous mechanism refers to the state in which the second movable pivot point, and thus also the seat support, are in the highest position, i.e., at the greatest distance from the support structure. In this end position, maximum pivoting of the seat support is guaranteed.

[0019] The “substantially vertical” movement of the movable second pivot point into the upper end position also includes an upwardly curved movement path, ie in particular a movement path curved forwards from the rotation axis in the direction of the seat.

[0020] In the present case, an arrangement “spaced apart” from the contact 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.

[0021] Preferably, the second pivot point is fixed relative to the backrest support and can be moved substantially 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 synchronous mechanism, the second pivot point is moved substantially vertically upwards from the lower basic position into a first intermediate position and the seat support is arranged to tilt relative to the standing structure (ie forwards in the sitting direction) or to be tiltable. By means of a corresponding weight shift forwards, ie Away from the backrest, a person can tilt the seat support forward, with the second pivot point simultaneously moving slightly upward and the backrest support assuming a slight backward tilt. This efficiently provides particularly flexible use of a chair equipped with the synchronous mechanism according to the invention.

[0022] Preferably, in a second intermediate position, the angle and inclination of the seat support and seat plate can be controlled (solely) by the user's upper and / or lower legs (and not necessarily by the mechanism). Rather, the seat plate adapts to the user through its, albeit limited, pivoting capability, thereby generating a special seating comfort.

[0023] In particular, in the second intermediate position the second pivot point is moved essentially vertically upwards from the lower basic position into a second intermediate position in which the seat support (and the seat plate) is raised to such an extent that it is in external contact (with its inner surface) with the standing structure, so that the seat support with the seat plate can be tilted around the second pivot point without any guidance. The seat support with the seat plate is therefore only connected to the backrest support or the chair mechanism via the second pivot point and can be tilted around this; guide rods or other guide elements are not provided. The inclination of the seat support with the seat plate can therefore be controlled (solely and directly) by means of the user's lower legs and / or thighs and is essentially independent of the position of the backrest. There is no need for forced guidance by the mechanism.

[0024] Preferably, however, in the second intermediate position the seat support has not yet reached its maximum pivotability.

[0025] Preferably, in the end position of the synchronous mechanism, the seat support can be pivoted to its maximum relative to the backrest support around the second movable pivot point. This can further increase the flexibility of use of a chair equipped with the synchronous mechanism according to the invention.

[0026] Ultimately, the user should be able to perform all possible movements (i.e. tilting forward, lifting, and lying on his back) by shifting his weight or using his muscles alone. By appropriately coordinating the pivot points and support structures, the inventive synchronous mechanism essentially eliminates the need for springs and / or damping elements. This allows the seat support and seat plate to adapt perfectly to the user thanks to the (albeit limited) freedom of rotation in both directions, thus generating specifically optimized seating comfort.

[0027] In the present context, the term “maximally pivotable” encompasses a maximum rotatability or rotatability and movability of the seat support in the end position, or the highest position of the second pivot point, 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.

[0028] In a first embodiment of the invention, the first limiting means is formed by the bevelled front end of the backrest support or 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 forward - and the second limiting means by the front lower edge of the backrest support or the side parts of the backrest support - against which the lower cross connection of the seat support comes to rest when tilted backward.

[0029] In a second embodiment of the invention, the first limiting means is formed by the front end of the guide slot of the link guide of the backrest support or the side parts of the backrest support - against which the front guide pin of the seat support comes to rest when tilting forwards - and the second limiting means is formed by the rear end of the guide slot of the link guide of the backrest support or the side parts of the backrest support - against which the rear guide pin of the seat support comes to rest when tilting backwards.

[0030] In both embodiments of the synchronous mechanism according to the invention, the seat support or seat plate assumes a maximum tilt angle perpendicular to the rotation axis in the rearward tilted end position. This maximum tilt angle is preferably approximately 5° to approximately 40°, more preferably approximately 10°. up to about 30°, and even more preferably about 15° to about 25°. In these ranges, the weight independence of the mechanism can be optimally utilized.

[0031] Preferably, the base part is designed as a rigid component. This ensures the stability required for the synchronous mechanism according to the invention.

[0032] Preferably, in a side view, the first pivot point is located behind the rotation axis in the seat direction, and the second pivot point is located in front of the rotation axis of the base part in the seat direction. This ensures optimal functionality of the synchronous mechanism according to the invention.

[0033] Preferably, the support structure is positioned in front of the base's rotation axis when viewed from the side in the direction of the seat. This is designed so that the user must consciously shift their weight in order to tilt the seat support forward.

[0034] Preferably, the movable second pivot point is movably arranged between the support structure and the first pivot point in a lateral view, i.e., on a substantially vertical path of movement. Further preferably, the second pivot point is movably arranged between the support point and the rotation axis in a lateral view, i.e., on a substantially vertical path of movement. 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.

[0035] In the initial position, one of the seat support's contact points on the support structure is preferably located vertically above the first pivot point. This also represents a further measure for fine-tuning the individual components.

[0036] Preferably, the seat support is designed as a U-shaped profile, open at the bottom, located on the underside of the seat plate. This allows for a particularly effective attachment of the seat support to the backrest support, while simultaneously ensuring optimal support of the seat support at the point of contact.

[0037] The support structure preferably comprises a sliding block, which is preferably mounted between two tab-like projections of the base part so as to be rotatable about a third pivot point. The sliding block supports the seat support to stabilize the seat and serves as a pivot point for the forward tilt according to the first intermediate position. In this respect, the seat support preferably rests with the inner surface of its upper side on the sliding block (support point) in the home position and in the first intermediate position.

[0038] In another preferred embodiment of the invention, the backrest support has a guide slot for the seat support. In this case, the second pivot point lies outside the mechanism and is therefore also referred to as a fictitious pivot point. In this embodiment, the seat support is not only tilted forward during the movement from the basic position to the first intermediate position, but is also simultaneously moved sideways forward, 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.

[0039] Preferably, in this embodiment, in a second intermediate position the angle of the seat support and the seat plate can be controlled using the user's lower legs (and not necessarily by the mechanism). Rather, the seat plate adapts to the user through its, albeit limited, pivotability, thereby generating a special level of seating comfort. In particular, in the second intermediate position the second pivot point is moved essentially vertically upwards from the lower basic position into a second intermediate position in which guide pins operatively connected to the seat support via a link guide are raised so far (i.e. together with the seat support and the seat plate) that they are in external contact with the base part, but the seat support has not yet reached its maximum pivotability.

[0040] Preferably, in a side view, the guide rail comprises an upwardly convexly curved guide slot for the seat support, which at least partially extends over an upper edge of the base part. In this way, a guide is created for the seat support or for its guide pins, which protrude through the guide slot in the guide rail, wherein the front Guide pin rests on a holding point defined by the upper edge of the base part and the curved guide slot (in the basic position).

[0041] Preferably, the fixed first pivot point and / or the movable second pivot point are implemented by means of a deformable structure. In particular, a bending element arrangement, such as a spiral spring arrangement, can be provided. In this way, the movement sequence can be designed particularly efficiently for the user.

[0042] A further aspect of the invention relates to a chair, in particular an office chair, with a synchronous 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. Short description of the drawings

[0043] Further advantageous embodiments of the invention will become apparent 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 using exemplary embodiments. They show: Fig. 1: a perspective view of a first embodiment of a synchronous mechanism according to the invention; Fig. 2: a side sectional view of the first embodiment of the synchronous mechanism according to the invention in the basic position with horizontal seat support; Fig. 3: a side sectional view of the first embodiment of the synchronous mechanism according to the invention in the first intermediate position with the seat support tilted forward; Fig. 4: a side sectional view of the first embodiment of the synchronous mechanism according to the invention in a second intermediate position with a raised and substantially horizontal seat support; Fig. 5: a side sectional view of the first embodiment of the synchronous mechanism according to the invention in an end position with the seat support in the highest position; Fig. 6: a side sectional view of the first embodiment of the synchronous mechanism according to the invention in the end position with the seat support tilted backwards; Fig. 7: a side sectional view of a second embodiment of the synchronous mechanism according to the invention in the basic position with the seat support slightly tilted backwards; Fig. 8: a side sectional view of the second embodiment of the synchronous mechanism according to the invention in the first intermediate position with the seat support tilted forward; Fig. 9: a side sectional view of the second embodiment of the synchronous mechanism according to the invention in the second intermediate position with raised seat support; Fig. 10: a side sectional view of the second embodiment of the synchronous mechanism according to the invention in the end position with the seat support in the highest position; and Fig. 11: a side sectional view of the second embodiment of the synchronous mechanism according to the invention in the end position with the seat support tilted backwards. Weq(e) for carrying out the invention

[0044] Certain terms are used in the following description for convenience and are not to be construed as limiting. The words "right," "left," "bottom," and "top" indicate directions in the drawing to which reference is made. The terms "inward," "outward," "below," "above," "left," "right," or similar terms are used to describe the relative arrangement of designated parts, the relative movement of designated parts, and the directions toward or away from the geometric center of the invention and of designated parts thereof as illustrated in the figures. These spatial relative terms also include positions and orientations other than those illustrated in the figures. For example, if a part illustrated in the figures is turned over, elements or features described as "below" will then be "above."The terminology includes the words expressly mentioned above, derivatives of the same and words of similar meaning.

[0045] To avoid repetitions in the figures and the associated description of the various aspects and embodiments, certain features should be understood as common to different aspects and embodiments. The omission of an aspect in the description or a figure does not imply that this aspect is missing in the associated embodiment. Rather, such omission can serve to increase clarity and avoid repetitions. In this context, the following stipulation applies to the entire further description: If reference symbols are included in a figure for the purpose of graphic unambiguity but are not mentioned in the immediately associated descriptive text, reference is made to their explanation in preceding figure descriptions.If the descriptive text directly associated with a figure contains reference symbols that are not included in the corresponding figure, reference is made to the preceding and following figures. Similar reference symbols in two or more figures represent similar or identical elements.

[0046] Fig. 1 shows a perspective view of a first embodiment of the synchronous mechanism 1 according to the invention for a chair, in particular an office chair. The synchronous mechanism 1 comprises a base part 5 with a receptacle 11 for a chair column, 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 point D1. In the front region 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 comprises the movable second pivot point D2. The second pivot point D2 is thus fixed relative to the backrest support 2 and can be moved essentially vertically upwards with the backrest support 2.The U-shaped seat support 3 is arranged essentially centrally on the underside of a seat plate 4. The inner surface of its upper side 7 of the U-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 serves as a seat stabilizer and as a seat support pivot point, i.e., for tilting the seat support 3 with the seat plate 4 forward in the seat direction. In the synchronous mechanism 1 according to the invention, the side parts 3a and 3b of the seat support 3 are external. and the two side parts 5a and 5b of the base part 5 are arranged inside, and the two side parts 2a and 2b of the backrest support 2 are arranged between them. The individual movement sequences of the synchronous mechanism 1 according to the invention are described in detail below.

[0047] Fig. 2 shows a side sectional view of the first embodiment of the synchronous 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 point 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. here horizontal, state. The fixed first pivot point D1 and the movable second pivot point D2 are approximately at the same height but on different sides of the rotation axis X, with the fixed first pivot point D1 on the rear side usually being somewhat further away from the rotation axis X than the movable second pivot point D2 on the front side.The U-shaped seat support 3 rests with its inner surface 7a on the sliding block 6, with the sliding block 6 being arranged so as to be rotatable about the third pivot point D3 between the two tab-like projections 5c and 5d of the base part 5. This support area of ​​the seat support 3 on the sliding block 6 encompasses the contact point P of the contact structure A, which is formed here by the tab-like projections 5c and 5d as well as by the sliding block 6. The user must overcome the contact structure A if they wish to move from the basic position of the synchronous mechanism to a first intermediate position, which is explained further below.The contact point P (and also the third pivot point D3) is regularly located, viewed vertically along the rotation axis X, above the movable second pivot point D2 and above the fixed first pivot point D1, and horizontally further away from the rotation axis X than the movable second pivot point D2 and also further away from the central axis X than the fixed first pivot point (on the rear side) 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 cross connection 13 of the seat support 3, which here rests against the front lower edge 14 of the backrest support 2 or its side parts.

[0048] Fig. 3 now shows a side sectional view of the first embodiment of the synchronous 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 in the user's weight on the seat plate 4 is regularly required in order to overcome the standing structure A, i.e. in order to rotate the seat support 3 about the fixed third pivot point D3. During this movement or due to the shift in weight, the movable second pivot point D2 is pivoted essentially vertically upwards together with the backrest support 2, which also leads to a slight backward tilt of the backrest support 2 (and possibly a corresponding backrest). The forward tilt or the forward tipping of the seat support 3 with the seat plate 4 is limited by the front bevel 12 of the backrest support 2.

[0049] Fig. 4 illustrates a side sectional view of the first embodiment of the synchronous mechanism 1 according to the invention in a second intermediate position with a raised and substantially horizontal seat support 3. 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 point D1 until the movable second pivot point D2 moves correspondingly further upwards into a second intermediate position. In doing so, the inner surface 7a of the U-shaped seat support 3 moves correspondingly upwards away from the support structure. Here, the backrest support 2 is in outer contact with the lower cross-connection 13 of the seat support 3 with its front lower edge 14, but its beveled front end 12 is not yet in contact with the inner surface 7a of the seat support 3.The second intermediate position represents a quasi-flexible transition position of the synchronous mechanism 1 on the way to the end position (highest position of the second pivot point D2) according to the following Fig. 5, and if necessary back to the basic position according to Fig. 2.

[0050] In the second intermediate position according to Fig. 4, the seat support 3 and the seat plate 4 can be controlled in angle without any guides, i.e. without supporting guide rods or other guide elements, solely and directly by the user's lower legs and not necessarily by the mechanism. Here, the seat plate 4 adapts itself through its, Although the swiveling is limited, it is ideal for the user, thereby generating a specially optimized seating comfort.

[0051] Fig. 5 shows a side sectional view of the first embodiment of the synchronous mechanism 1 according to the invention in the end position, in which the seat support 3 with the movable second pivot point D2 is in the highest position or the upper end position of the movable second pivot point D2. Here, the second pivot point lies 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 is pivoted even further upwards about the fixed first pivot point D1 compared to the second intermediate position according to Fig. 4, whereby the beveled end 12 of the backrest support 2 or of its side parts comes into contact with the inner surface 7a of the U-profile-shaped seat support 3 and rests against it.The backrest support 2 is now in surface contact with the inner surface 7a of the seat support 3 with its beveled front end 12, so that the seat support 3 with the seat plate 4 is supported by the beveled front end 12 of the backrest support 12 essentially in a horizontal orientation. In this upper end position of the movable second pivot point D2, the seat support 3 can now be rotated about the latter, but the contact with the beveled front end 12 (first limiting means) of the backrest support 2 prevents the seat support 3 with the seat plate 4 from simultaneously tipping forward out of the horizontal when the backrest support 2 is leaned back into the end position shown here, which could potentially lead to the user undesired slipping on the chair.

[0052] On the other hand, the user can, from the end position of the synchronous mechanism 1 according to Fig. 5, but by shifting his weight backwards on the seat plate 4, cause the seat support 3 with the seat plate 4 to tilt backwards, whereby, however, as shown in Fig. 6, the backrest support 2 and the movable second pivot point 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 cross connection 13. In other words, in the end position, a maximum pivotability or maximum rotation of the seat support around the pivot point D2 is provided, namely between the beveled front end 12 of the backrest support 2 as the first limiting means, which limits tilting of the seat support 3 from the horizontal to the front, and the lower front edge 14 of the backrest support 2 as the second limiting means, which limits tilting of the seat support to the rear (i.e., by the lower cross connection 13 of the seat support 3 coming to rest here). In the end position, with the seat support 3 tilted backwards, the seat plate 4 is essentially parallel to the backrest support 2. In the end position tilted backwards, the seat plate 4 accordingly assumes a maximum tilt angle a perpendicular to the rotation axis X, as illustrated in Fig. 6.

[0053] Fig. 7 shows a side sectional view of the second embodiment of the synchronous mechanism 1 according to the invention in the basic position. In the second embodiment of the synchronous mechanism 1 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 between them. In this second embodiment, however, the side parts of the backrest support 2 have a slotted guide 8, which has an upwardly convexly curved guide slot 9, in which guide pins 11a, 11b, which movably connect the seat support 3 to the backrest support 2, are guided. The slotted guide 8 itself has a corresponding upwardly convex curvature, like the guide slot 9.The seat support 3 rests with its inner surface 7a on the upper side of the guide rail 8 (contact point P' of the contact structure A', which here is formed by the guide rail 8). At the rear end of the side parts of the base part 5, there is in turn an articulated connection to the side parts of the backrest support 2, which includes the fixed first pivot point D1. The movable second pivot point D2' is designed here as a "fictitious" pivot point, which lies outside the synchronous mechanism 1 and is specifically the pivot point 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 point D2'.The individual movement sequences of the second embodiment of the synchronous mechanism according to the invention are described in detail below.

[0054] In the basic position, in this embodiment, the seat support 3 and the seat plate 4 are slightly tilted backward relative to the rotation axis X. However, the basic position here also encompasses the basic state of a corresponding chair in which the movable second pivot point 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., slightly tilted backward. The rear guide pin 11b of the seat support 3 rests against the rear end of the guide slot 9, which initially prevents further or greater backward tilting, and the front guide pin 11a rests against the stop point H in the area of ​​the front end of the base part 5. At the stop point H, in the basic position, the curvature of the guide slot 9, together with the upper edge 10 of the base part 5, fundamentally prevents a forward Z-tilting movement of the seat support 3 and the seat plate 4.Here, too, a shift of the user's weight on the seat plate 4 is required to overcome the support structure A' (and the holding point H) if the user wishes to move from the basic position of the synchronous mechanism 1 to a first intermediate position, which is explained further below. The movable second pivot point D2' is located below the fixed first pivot point D1. The two pivot points D1 and D2' are located on different sides of the rotation axis X, with the fixed first pivot point D1 on the rear side usually being somewhat closer to the rotation axis X than the movable second pivot point D2' on the front side.

[0055] Fig. 8 now shows a side sectional view of the second embodiment of the synchronous mechanism 1 according to the invention in the first intermediate position with the seat support 3 tilted forward, wherein the seat support and the seat plate 4 move from a slightly backward tilt to a substantially horizontal orientation upon tilting. As mentioned, this forward Z-tilting movement requires a shift in the user's weight on the seat plate 4 in order to overcome the contact point P' (and the holding point H). During this weight shift, the movable second pivot point D2' is pivoted essentially vertically upwards together with the backrest support 2, which correspondingly also leads to a slight backward tilt 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, because further movement is blocked by the curvature of the guide slot 9 in interaction with the base part 5. This. Blockage at holding point H can be removed by further lifting the seat support 3.

[0056] Fig. 9 illustrates a side sectional view of the second embodiment of the synchronous mechanism 1 according to the invention in a second intermediate position with a raised and substantially horizontal or slightly rearwardly inclined seat support 3. 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 point D1 until the movable second pivot point D2' moves correspondingly further upwards into a second intermediate position.In this case, the guide slot 9 with the guide pins 11a and 11b, together with the seat support 3 and the seat plate 4, is lifted upwards away from the base part 5, and at the same time, the guide pins 11a and 11b of the seat support 3 move laterally a little bit forward in the guide slot 9 of the link guide 8, although the front guide pin 11a does not yet come into contact with the front end 9a of the guide slot 9. The second intermediate position thus 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).

[0057] In the second intermediate position shown in Fig. 9, the angle of the seat support 3 and the seat plate 4 can be controlled by the user's lower legs, unlike conventional synchronous mechanisms, and not necessarily by the mechanism itself. Here, the seat plate 4 adapts to the user through its, albeit limited, pivotability, thus generating a special seating comfort.

[0058] Fig. 10 shows a lateral sectional view of the second embodiment of the synchronous mechanism 1 according to the invention in the end position, in which the seat support 3 with the movable second pivot point D2' is in the highest position or its upper end position, in which the movable second pivot point D2' is located slightly below the front edge 15 of the base part 5 or its side parts. By leaning back further with a corresponding weight shift of the user, the front part of the backrest support 2 with the guide rail 8 is raised further upwards compared to the second intermediate position according to Fig. 9 and tilted backwards. At the same time, the seat support 3 with the seat plate 4 together with the guide pins 11a and 11b has moved sideways forwards, i.e. until the front guide pin 11a rests on 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 point D2', the seat support 3 can now be freely rotated around it or moved in the guide slot, whereby the contact of the front guide pin 11a at the front end 9a (first limiting means) of the guide slot 9 prevents the seat support 3 with the seat plate 4 from tipping further forwards from the horizontal when the backrest support 2 is leaned back into the end position shown here, which could possibly lead to the user slipping off the chair.

[0059] In this respect, the user can still tilt the seat support 3 with the seat plate 4 backwards from the end position of the synchronous mechanism 1 according to Fig. 10 by shifting their weight backwards on the seat plate, whereby, however, as shown in Fig. 11, the backrest support and the movable second pivot point D2' no longer change their position. This backward tilting is correspondingly limited by the rear end 9b (second limiting means) of the guide slot 9, against which the seat support 3 comes to rest with the rear guide pin 11b. In other words, in the end position, maximum pivotability or maximum rotation orMovability of the seat support 3 about the pivot point D2' between the front end 9a of the guide slot 9 as the first limiting means, which limits tilting of the seat support 3 from the slight rearward inclination towards the front, and the rear end 9b of the guide slot 9 as the second limiting means, which limits tilting of the seat support 3 towards the rear (i.e. by the rear guide pin 11b of the seat support 3 coming into contact here). The seat plate 4 is in turn essentially parallel to the backrest support 2 in the rearwardly tilted end position. In the rearwardly tilted end position, the seat plate 4 accordingly assumes a maximum tilt angle a perpendicular to the rotation axis X (or a maximum inclination), as illustrated in Fig. 11.

[0060] From the above explanations it is clear that by means of the synchronous mechanism according to the invention both according to the first and the second In this embodiment, the user can perform a virtually fluid adjustment of a corresponding chair based solely on their posture and / or muscle strength, without the need for additional support or adjustment elements. Nevertheless, the use of such elements in conjunction with the synchronous mechanism according to the invention is fundamentally possible. List of reference symbols: 1 synchronous mechanism 2 backrest supports 2a, b side panels 3 seat supports 3a, b side panels 4 Seat plate 5 Base part 5a, b side panels 5c, d tab-like projections 6 sliding block 7 Top of seat support 7a Inner surface of the top of the seat support 8 Scene guide 9 Guide slot 9a front end guide slot 9b rear end guide slot 10 Top edge of base part 11a, b Guide elements seat support 11 Mounting bracket for column 12 bevelled front end backrest support 13 lower cross connection seat support 14 front lower edge of backrest support 15 Front edge of base part A, A' queue structure P, P' queue point D1 fixed first pivot point D2, D2' movable second pivot point D3 third pivot point (sliding block) H Stop point X rotation axis a max. tilt angle

Claims

CLAIMS Claim 1: Synchronous mechanism (1) for a chair, in particular an office chair, comprising a base part (5) defining a rotation axis (X), a backrest support (2) for holding a backrest and a seat support (3) for holding a seat, wherein the backrest support (2) is mounted on the base part (5) so as to be pivotable about a first pivot point (D1), wherein the seat support (3) is mounted on the backrest support (2) so as to be pivotable about a second pivot point (D2, D2'), wherein the first pivot point (D1) of the backrest support (2) is fixed relative to the base part (5) and the second pivot point (D2, D2') of the seat support (3) is movable relative to the base part (5);wherein in a basic position the second pivot point (D2, D2') is in a lower basic position and the seat support (3) rests against a support structure (A, A'), and wherein in an upper end position the movable second pivot point (D2, D2') is moved substantially vertically into an upper end position and the seat support (3) is spaced from the support structure (A, A'); Claim 2: Synchronous mechanism (1) according to claim 1, wherein the second pivot point (D2, D2') is fixed relative to the backrest support (2) and is movable substantially vertically upwards with the backrest support (2). Claim 3: Synchronous mechanism (1) according to claim 1 or 2, wherein in a first intermediate position the second pivot point (D2, D2') moves from the lower basic position substantially vertically upwards into a first intermediate position and the seat support (3) is arranged to tilt relative to the support structure (A, A'). Claim 4: Synchronous mechanism (1) according to one of the preceding claims, wherein in the end position the seat support (3) is maximally pivotable relative to the backrest support (2) around the second pivot point (D2, D2'). Claim s: Synchronous mechanism (1) according to one of the preceding claims, wherein the base part (5) is designed as a rigid component. Claim s: Synchronous mechanism (1) according to one of the preceding claims, wherein in a lateral view the first pivot point (D1) is arranged behind the rotation axis (X) in the seat direction and the second pivot point (D2, D2') is arranged in front of the rotation axis (X) of the base part (5) in the seat direction. Claim 7: Synchronous mechanism according to one of the preceding claims, wherein the support structure (A, A') is arranged in front of the rotation axis (X) of the base part (5) in a lateral view in the sitting direction. Claim s: Synchronous mechanism (1 ) according to claim 7, wherein the second pivot point (D2, D2') is arranged in lateral view between the support structure (A, A') and the fixed first pivot point (D1 ). Claim 9: Synchronous mechanism (1) according to one of the preceding claims, wherein in the basic position a contact point (P, P') of the seat support (3) on the contact structure (A, A') is located in the vertical direction above the first pivot point (D1). Claim 10: Synchronous mechanism (1) according to one of the preceding claims, wherein the seat support (3) is designed as a U-shaped profile which, open at the bottom, is arranged on the underside of the seat plate (4). Claim 11: Synchronous mechanism (1) according to one of the preceding claims, wherein the contact structure (A, A') comprises a sliding block (6) which preferably rotatable about a third pivot point (D3) between two tab-like projections (5c, 5d) of the base part (5). Claim 12: Synchronous mechanism (1) according to claim 11, wherein in the basic position and in the first intermediate position the seat support (3) rests with the inner surface (7a) of its upper side (7) on the sliding block (6). Claim 13: Synchronous mechanism (1) according to one of claims 1 to 10, wherein the backrest support (2) has a slotted guide (8) for the seat support (3). Claim 14: Synchronous mechanism (1) according to claim 13, wherein in a side view the slotted guide (8) for the seat support (3) comprises an upwardly convexly curved guide slot (9) which extends at least partially over an upper edge (10) of the base part (5). Claim 15: Synchronous mechanism according to one of claims 1 to 9 and 12 to 13, wherein the seat support (3) is configured to execute a lateral forward movement from the basic position into the first intermediate position and from the basic position into the end position. Claim 16: Synchronous mechanism according to one of claims 1 to 12, wherein in a second intermediate position the second pivot point (D2) is moved substantially vertically upwards from the lower basic position into a second intermediate position in which the seat support (3) is raised to such an extent that it is in external contact with the support structure (A), so that the seat support (3) with the seat plate (4) can be tilted around the second pivot point (D2, D2') without guidance. Claim 17: Synchronous mechanism according to claim 15, wherein in the second intermediate position the seat support has not yet reached its maximum pivotability. Claim 18: Synchronous mechanism according to one of claims 1 to 8 and 12 to 16, wherein in a second intermediate position the second pivot point (D2') is pivoted from the lower basic position substantially vertically upwards into a second Intermediate position is moved in which guide pins (11a, 11b) operatively connected to the seat support (3) via a link guide (8) are raised to such an extent that they are in external contact with the base part (5), but the seat support (3) has not yet reached its maximum pivotability. Claim 19: Synchronous mechanism according to one of the preceding claims, wherein the fixed first pivot point and / or the movable second pivot point is / are realized by means of a deformable structure. Claim 20: Chair, in particular office chair, with a synchronous mechanism (1) according to one of the preceding claims.

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