Mechanics for a piece of seating furniture, especially for an office chair

Description

[0001] The invention relates to a mechanism for seating furniture, in particular for an office chair. Furthermore, the invention relates to seating furniture, in particular an office chair, with such a mechanism.

[0002] Synchronous mechanisms are commonly used in office chairs. The term "synchronous mechanism" refers to components within the seat base of an office chair that create a synchronized kinematic system, resulting in a specific relative movement between the seat and backrest. The seat, typically upholstered, is mounted on the seat support. The backrest support, which usually extends backward from the actual synchronous mechanism, carries the backrest of the office chair via an upward-pointing arm. The seat support and backrest support are typically linked by a pivoting mechanism such that a backward swiveling movement of the backrest—such as that caused by the user leaning against it—induces a corresponding movement of the seat.A spring mechanism is used to actuate the seat support against the movement of the backrest support. This mechanism prevents the backrest from tilting backward uncontrollably and ensures that it returns safely to its original position from a tilted position as soon as the user releases their weight. Such a spring mechanism typically consists of a centrally located tension spring. The resistance of the backrest support to the tilting motion can be adjusted or influenced by this mechanism. For this purpose, the spring mechanism usually incorporates adjustment elements. Examples of office chair mechanisms with spring mechanisms where the spring characteristics can be modified using adjustment elements are described in WO2008 / 000295A1 and WO2021 / 156672A1.

[0003] As can be seen directly from this description of how this mechanism works, such mechanisms usually consist of many components and / or are very complex in design and therefore expensive to manufacture.

[0004] An object of the present invention is to provide a piece of seating furniture, in particular an office chair, which has a particularly simple adjustment of the swivel resistance and yet is comparatively simple in construction. This object is achieved by a mechanism according to claim 1 or by a piece of seating furniture according to claim 9. Advantageous embodiments of the invention are specified in the dependent claims. The advantages and embodiments explained below in connection with the mechanism also apply mutatis mutandis to the seating furniture according to the invention and vice versa.

[0005] The invention is based on a conventional mechanism, in particular an office chair mechanism, which comprises a number of mechanical components, namely at least one base support that can be placed on a chair column, a seat support arranged on the base support and movable relative to the base support, and a backrest support coupled to the seat support, wherein pivoting the backrest support backwards causes a subsequent movement of the seat support relative to the base support.

[0006] A key idea of ​​the invention is to use a mechanism to apply pressure to the seat support in the opposite direction to the movement of the backrest support.

[0007] To use a bending spring element that interacts with an additional element to form a resilient composite system, employing adjustment means designed to modify a property of the resilient composite system that influences its stiffness. These properties can be, for example, design features of the composite system, such as its shape, particularly its cross-section. This approach allows for particularly easy adjustment of the pivoting resistance. Simultaneously, it makes it possible to influence the spring behavior of the mechanism with very simple means, thereby reducing the total number of components required compared to conventional mechanisms.

[0008] According to the invention, the position of the additional element relative to the bending spring element of the resilient composite system in the pivoted state of the mechanism depends on the setting of the adjusting means, such that, depending on the setting of the adjusting means along the longitudinal extent of the resilient composite system, the additional element either rests against the bending spring element or is spaced apart from the bending spring element along the longitudinal extent of the resilient composite system. In this way, the thickness (height) of the composite system formed by the spring element and the additional element can be influenced by manipulating the additional element.

[0009] According to one embodiment of the invention, the resilient composite system serves exclusively to actuate the seat support. In particular, the composite system does not actuate any other component of the mechanism besides the seat support. Specifically, neither the bending spring element nor any other element of the composite system is directly and / or immediately connected to the backrest support or interacts directly and / or immediately with the backrest support.

[0010] According to one embodiment of the invention, the bending spring element is designed in the manner of a leaf spring. In particular, the bending spring element is designed as a curved bending spring or a curved flat spring. In particular, the bending spring element has a cross-section that changes along its longitudinal extent.

[0011] According to one embodiment of the invention, the bending spring element is an elastically deformable element integrated in one piece into a mechanical component, in particular the base support, which serves as an energy storage element.

[0012] According to one embodiment of the invention, the bending spring element is the only spring element of the mechanism for acting on the seat support against the movement of the backrest support.

[0013] According to one embodiment of the invention, the additional element is not spring-like or only insignificantly spring-like, and thus contributes nothing or only insignificantly to the spring action of the spring-like composite system.

[0014] According to one embodiment of the invention, the additional element is preferably designed as a tension element in the sense of a tensioning device. In other words, the additional element is subjected to tension by the pivoting movement of the backrest support into the rearward pivoted position, while the bending spring element is subjected to bending.

[0015] According to one embodiment of the invention, the additional element is designed such that when the backrest support is pivoted backwards, no or only an insignificant elongation of the additional element takes place.

[0016] According to one embodiment of the invention, the contact of the additional element with the bending spring element caused by manipulation of the additional element, which influences the effect of the composite system, is understood to mean a contact of the additional element with the bending spring element that occurs at a distance from the spacer element.

[0017] The contact of the additional element with the bending spring element occurs section by section, as defined in claim 1 of the invention. The placement of a spacer element between the additional element and the bending spring element, as described below, wherein the spacer element typically only makes contact with the additional element and the bending spring element at specific points, does not result in section by section of the additional element contacting the bending spring element.

[0018] According to the definition of the invention as in claim 1, in a first setting of the adjusting means, the additional element is at least partially spaced away from the bending spring element along the longitudinal extent of the resilient composite system in the pivoted state of the mechanism, while in a second setting of the adjusting means it bears against the bending spring element with at least a portion along the longitudinal extent of the resilient composite system.

[0019] According to one embodiment of the invention, in a first setting of the adjusting means, the additional element is spaced away from the bending spring element within a functional section along the longitudinal extent of the resilient composite system when the mechanism is pivoted, while in a second setting of the adjusting means it bears against the bending spring element at least with a portion within this functional section along the longitudinal extent of the resilient composite system, wherein the functional section is preferably a rear region of the bending spring element directed towards its fixed end.

[0020] According to one embodiment of the invention, the additional element defines the position of an edge fiber of the resilient composite system. Preferably, the additional element defines the position of the convex edge fiber in the case of the bending spring element being designed as a curved bending spring.

[0021] According to one embodiment of the invention, the additional element to the bending spring spring element is displacement-resistant.

[0022] According to one embodiment of the invention, the additional element extends at least over a part of the length of the bending spring element.

[0023] According to one embodiment of the invention, the additional element extends over essentially the entire length of the bending spring element.

[0024] According to one embodiment of the invention, the additional element is fixed at one end at the connection point of the bending spring element with the seat support.

[0025] According to one embodiment of the invention, there is no force-transmitting connection between the additional element and the bending spring element at this point.

[0026] According to one embodiment of the invention, the additional element is fixed with its other end near the connection point of the bending spring element with the base support.

[0027] According to one embodiment of the invention, the adjusting means are designed to change the cross-section of the resilient composite system, in particular to change the thickness (height) of the resilient composite system, preferably while maintaining the same width.

[0028] According to one embodiment of the invention, the adjusting means are designed to change the distance between the outer fibers of the resilient composite system. The invention thus utilizes the principle that the bending stiffness of the spring system increases with increasing distance between the outer fibers. In other words, the mode of operation of the invention in this embodiment is based on the fact that the distance between the outer fibers of the spring system used to adjust the pivot resistance of the backrest support is variably adjustable, thereby increasing or decreasing the bending stiffness of the resilient composite system with its bending spring element. For this purpose, in accordance with the principles of structural mechanics, the position of the neutral fiber within the resilient composite system is shifted, thus changing the distance between the neutral fiber and the outer fiber.

[0029] According to one embodiment of the invention, the adjusting means are designed in such a way that they allow a load-free and therefore "force-free" adjustment in the unpivoted state of the mechanism, i.e., that they allow a change in a constructive property of the spring-like composite system during a period in which the bending spring element does not act on the seat support against a movement of the backrest support.

[0030] According to one embodiment of the invention, the adjusting means comprise a spacer element arranged between the bending spring element and the additional element, which separates the bending spring element from the additional element at least along a section of the resilient composite system.

[0031] According to one embodiment of the invention, the position of the spacer element along the longitudinal extent of the resilient composite system is changeable, in particular adjustable.

[0032] According to one embodiment of the invention, the position of the spacer element is displaceable along the longitudinal extent of the resilient composite system, in particular by means of an actuating element which is preferably manually operable.

[0033] According to one embodiment of the invention, the spacer element is arranged between the bending spring element and the additional element in such a way that, depending on the selected shape of the spring element, the position of the point where the additional element (preferably section by section) abuts the bending spring element and / or the position of the point up to which the additional element abuts the bending spring element (preferably section by section) can be changed along the longitudinal extent of the resilient composite system by changing the position of the spacer element.

[0034] According to one embodiment of the invention, the bending spring element and / or the additional element and / or the adjusting means can be designed such that a change in the position of the spacer element along the longitudinal extent of the resilient composite system in one direction causes an increase in the stiffness of the resilient composite system, while a change in the position of the spacer element along the longitudinal extent of the resilient composite system in the other, opposite direction causes a decrease in the stiffness of the resilient composite system ("soft" - "hard" or "hard" - "soft").

[0035] According to one embodiment of the invention, shifting the spacer element towards the fixed end of the bending spring element results in an increase in the distance between the outer fibers of the convex outer fiber and thus an increase in the stiffness of the resilient composite system, which in turn results in an increase in the pivoting resistance of the backrest support. Conversely, shifting the spacer element towards the movable end of the bending spring element results in a decrease in the distance between the outer fibers of the convex outer fiber and thus a decrease in the stiffness of the resilient composite system, which in turn results in a decrease in the pivoting resistance of the backrest support.

[0036] According to an alternative embodiment of the invention, the directions of displacement are reversed, such that a displacement of the spacer element towards the movable end of the bending spring element results in an increase in the distance between the outer fibers of the convex outer fiber and thus an increase in the stiffness of the resilient composite system, which results in an increase in the pivoting resistance of the backrest support. Conversely, a displacement of the spacer element towards the fixed end of the bending spring element results in a decrease in the distance between the outer fibers of the convex outer fiber and thus a decrease in the stiffness of the resilient composite system, which results in a decrease in the pivoting resistance of the backrest support.

[0037] According to one embodiment of the invention, the bending spring element and / or the additional element and / or the adjusting means can also be designed such that a change in the position of the spacer element along the longitudinal extent of the resilient composite system in one direction initially causes an increase in the stiffness of the resilient composite system, wherein a continued change in the position of the spacer element along the longitudinal extent of the resilient composite system in this one direction again causes a decrease in the stiffness of the resilient composite system ("soft" - "hard" - "soft"), wherein this scheme is repeated accordingly when the spacer element is moved in the opposite direction of movement.In such a case, it is advantageous if the two "soft" positions, which are preferably the respective end positions of the displacement movement, correspond to different (low) stiffnesses of the composite system.

[0038] Alternatively, the bending spring element and / or the additional element and / or the adjusting means can also be designed such that a change in the position of the spacer element along the longitudinal extent of the resilient composite system in one direction initially causes a decrease in the stiffness of the resilient composite system, whereby a continued change in the position of the spacer element along the longitudinal extent of the resilient composite system in this one direction again causes an increase in the stiffness of the resilient composite system ("hard" - "soft" - "hard"), with this pattern repeating accordingly when the spacer element is moved in the opposite direction. In such a case, it is advantageous if the two "hard" positions, which are preferably the respective end positions of the movement, correspond to different (high) stiffnesses of the composite system.

[0039] The invention allows the spring characteristics of the spring system to be changed particularly easily, namely solely by manipulating or influencing the adjustment means, especially the spacer element. In other words, the entire adjustment of the spring system can be achieved using a single component. It is only necessary to provide suitable means for adjusting the spring system at a single point in the mechanism.

[0040] An embodiment of the invention is explained in more detail below with reference to the drawings. These show: Fig. 1 the mechanism in a "medium" setting in a perspective view, Fig. 2 the unpivoted mechanism in a "soft" setting in a longitudinal section, Fig. 3 the pivoted mechanism in a "soft" setting in a longitudinal section, Fig. 4 the unpivoted mechanism in a "hard" setting in a longitudinal section, Fig. 5 the pivoted mechanism in a "hard" setting in a longitudinal section.

[0041] All figures do not show the invention to scale, only schematically and with its essential components. Identical reference numerals correspond to elements with the same or comparable function.

[0042] "Front" or "frontal" means that a component is located at the front in the longitudinal direction of the seat, or refers to a component extending towards or pointing in the direction of the front edge of the seat, while "rear" or "backal" means that a component is located at the rear in the longitudinal direction of the seat, or refers to a component extending towards or pointing in the direction of the backrest, backrest support, or rear edge of the seat. The terms "top" or "upper" or "higher" and "bottom" or "lower" or "lower" refer to the intended state of use of the office chair or the office chair mechanism.

[0043] The synchronous mechanism 10 has a base support 1 which is placed on the upper end of a chair column (not shown) by means of a conical receptacle 2. Furthermore, the synchronous mechanism 10 comprises a substantially frame-shaped seat support 3 and a fork-shaped backrest support 4 (in plan view), the cheeks 5 of which are arranged on both sides of the base support 1.

[0044] The seat support 3, arranged on the base support 1 and movable relative to the base support 1, is designed to receive or mount a seat, which may be upholstered. Mounting is carried out in the usual manner using fasteners (not shown). A backrest (not shown) is attached to the backrest support 4, which is coupled to the seat support 3. In modern office chairs, the backrest is height-adjustable. The backrest may also be integrally connected to the backrest support 4.

[0045] The entire synchronous mechanism 10 is mirror-symmetrical with respect to its central longitudinal plane, as far as the actual kinematics are concerned. Therefore, in the following description of this and further embodiments of the invention, it must always be assumed that the actual pivoting mechanism consists of paired structural elements on both sides.

[0046] In the non-pivoted basic position of the synchronous mechanism 10, the seat support 3 assumes an essentially horizontal position, as in Fig. 1 , 2 and 4 depicted. The Fig. 3 and 5 The synchronous mechanism 10 is shown in a position of the backrest support 4 that is pivoted maximally backwards.

[0047] The backrest support 4, which pivots in the direction 7, is directly and pivotally connected to the base support 1 via a first pivot joint 21, forming a first transverse axis 11, with its cheek 5 extending towards the front area of ​​the mechanism 10. This transverse axis 11 defines the main pivot axis of the synchronous mechanism 10. Viewed in the longitudinal direction 14 of the seat, the first transverse axis 11 lies behind the conical receptacle 2.

[0048] In the rear region of the mechanism 10, viewed in the longitudinal direction 14 of the seat, the backrest support 4 is connected to the rear region of the seat support 3 via a second pivot joint 22 and an upwardly extending driver 6 of the side panel 5. The first transverse axis 11 is located behind the second transverse axis 12 formed by the second pivot joint 22, viewed in the longitudinal direction 14 of the seat.

[0049] In the front section of the mechanism, the front section of the base support 1 is pivotally connected to the front section of the seat support 3 via a third pivot joint 23, forming a third transverse axis 13. Pivoting the backrest support 4 thus causes the seat support 3 to move relative to the base support 1. The relative movement of the seat support 3 and backrest support 4 is determined primarily by the position of the three transverse axes 11, 12, 13 relative to each other, as well as by the spring system described in more detail below, in particular the deformation of the spring element contained therein.

[0050] The backrest support 4 is connected to the seat support 3 only once, namely via the second transverse axis 12. Furthermore, the base support 1 is connected to the seat support 3 only once, namely via the third transverse axis 13. There is only a single connection between the backrest support 4 and the base support. 1,namely via the first transverse axis 11.

[0051] A spring system in the form of a resilient composite system 30 serves to actuate the seat support 3 against the movement of the backrest support 4. The resilient composite system 30 has a bending spring, hereinafter referred to as a bending spring element 8, which acts between the base support 1 and the seat support 3, i.e., it engages both the base support 1 and the seat support 3. The bending spring element 8 has a fixed end 15 and a movable end 16 such that the fixed end 15 is rigidly connected to the base support 1 and the movable end 16 is connected to the seat support 3 of the mechanism 10 via the pivot joint 23. The spring element 8 can thus be considered a type of bending spring clamped at both ends. The bending spring element 8 serves to actuate the seat support 3 against a movement of the backrest support 4.

[0052] The bending spring element 8, designed as a curved bending spring or curved flat spring, is formed as an integral part of the base support 1. It is an elastically deformable element integrated one-piece into the base support 1 and serves as an energy storage element.

[0053] The bending spring element 8 is the only spring element of the mechanism 10 that serves to actuate the seat support 3 in the opposite direction to the movement of the backrest support 4. The bending spring element 8 is pre-tensioned in the unpivoted starting position of the mechanism 10. The bending spring element 8 is actuated when the backrest support 4 is pivoted by a user of the office chair.

[0054] The bending spring element 8 is preferably designed as a leaf spring, like the deformation element or storage element described in DE 10 2020 110 707 A1 under reference numeral 8 therein, in particular in the manner of a leaf spring with a substantially rectangular cross-sectional profile. In the example shown here, the spring element 8 has a changing cross-section. The bending spring element 8 is integrally formed on the base support 1 and extends forward and upward in the longitudinal direction 14 of the seat, where it is pivotally connected to the seat support 1. The cross-section of the spring element 8 tapers from its fixed end 15 to its movable end 16.

[0055] The mechanism 10 further comprises an additional element 9 that interacts with the bending spring element 8 to form the resilient composite system 30 and is either non-resilient or only slightly resilient. Both the spring element 8 and the additional element 9 have a greater longitudinal than transverse extent. In the example shown, the additional element 9 is plate-shaped and slightly flexible. The additional element 9 essentially spans the entire front-facing outer surface 17 of the spring element 8.

[0056] In the pivoted state of the mechanism 10, the additional element 9 is at least partially, namely with a section 37, spaced from the bending spring element 8 along the longitudinal extent 18 of the bending spring element 8, which simultaneously forms the longitudinal extent of the resilient composite system 30, see Fig. 5 , while in a second setting it at least with the section 37 along the longitudinal extent of the resilient composite system 30 rests on the bending spring spring element 8, see Fig. 3 The additional element 9 thus influences the thickness of the composite system 30. At the same time, the additional element 9 defines the position of an edge fiber of the resilient composite system 30; here, due to the arrangement of the additional element 9 on the forward-facing outer surface 17 of the spring element 8, it defines the position of the convex edge fiber of the curved bending spring element 8. The section 37 of the additional element 9, which is spaced apart from the spring element 8 in one instance and abutting the spring element 8 in another, is located in the rear region 35 of the composite system 30. The rear region 35 has a particularly strong influence on the spring action of the spring element 8 and thus on the function of the resilient composite system 30.

[0057] The additional element 9 is fixed against displacement relative to the bending spring element 8. One end 31 of the additional element 9 is fixed at the connection point of the bending spring element 8 with the seat support 3. For this purpose, the additional element 9 is suspended by an end eye on the pivot axis 13 and, like the spring element 8, is rotatably mounted there relative to the seat support 3. There is no force-transmitting connection between the front end 31 of the additional element 9 and the bending spring element 8. The other end 32 of the additional element 9 is fixed near the connection point of the bending spring element 8 with the base support 1. In particular, the additional element 9 is positively connected to the spring element 8 there, e.g., by screws. Corresponding fasteners 33 are provided in Fig. 1 The connection point of the bending spring element 8 with the seat support 3 forms the load application point of the composite system 30 when the backrest support 4 pivots into the rearward-pivoted position. The additional element 9 thus serves as a tensile force-absorbing component or tensioning element. Due to this load when the backrest support 4 pivots, the function of the additional element 9 can also be described as that of a bottom chord or tension chord.

[0058] The mechanism 10 further comprises adjustment means designed to change a structural property of the resilient composite system 30 that influences its stiffness. In the present example, the adjustment means are designed to change the cross-section of the resilient composite system 30, namely to change the thickness (height) 19 of the resilient composite system 30, see Fig. 3 and 5, while the width of the composite system remains constant at 30.

[0059] For this purpose, the adjusting means comprise a rod-shaped spacer element 20 arranged between the bending spring element 8 on the one hand and the additional element 9 on the other, and separating the bending spring element 8 from the additional element 9 at least along a section of the resilient composite system 30. The spacer element 20, which lies transversely to the longitudinal extent 18 of the spring element 8 and extends over almost the entire width of the spring element 8, rests on the spring element 8 and can therefore also be referred to as a support element. The position of the spacer element 20, which has a trapezoidal cross-section, is variably adjustable along the longitudinal extent 18 of the resilient composite system 30. This adjustment is achieved by a manually operated actuating element in the form of a slider 24, which is directly connected to the spacer element 20.With the aid of this slider 24, the spacer element 20 can be moved along the longitudinal extent 18 of the resilient composite system 30. The slider 24 is located on the outer surface 25 of the additional element 9 and is connected to the spacer element 20 via a connector (not shown) which is guided in a guide slot 26 of the additional element 9 extending in the direction of the longitudinal extent 18. The ends 27, 28 of the guide slot 26 are shown in the figure. Fig. 1 , thereby defining the end positions of the distance element 20 for the mechanics settings "soft" and "hard".

[0060] The spacer element 20 is arranged between the bending spring element 8 and the additional element 9 in such a way that by moving the spacer element 20 the position of the point 29 where the additional element 9 abuts the bending spring element 8 can be changed, see Fig. 3 , along the longitudinal extent 18 of the resilient composite system 30, is variable. In this way, the distance between the outer fibers of the resilient composite system 30 can be specifically varied, namely the distance between the convex outer fiber determined by the additional element 9 and the neutral fiber of the composite system 30. At point 29, this can be a shorter or longer section of the bending spring element 8.

[0061] In the mechanical setting "soft", see Fig. 2 The additional element 9, apart from its two fixed endpoints 31, 32 and the spacer element 20 arranged between the additional element 9 and the spring element 8, is spaced away from the spring element 8 along its entire longitudinal extent. In other words, a gap 34 extends between the two ends 31, 32 of the additional element 9. If the seat support 3 is moved along by the backrest support 4, as is the case when the backrest support 4 pivots rearward in the pivot direction 7, the front end of the base support 1, in the form of the movable end 16 of the spring element 8, moves rearward with the front pivot joint 23, thereby acting upon the composite system 30 with its spring element 8 (see figure). Fig. 3 The spring element 8 bends, causing the additional element 9 to partially, i.e., within a functional section, namely in the rear region 35 of the spring element 8, which is directed towards the fixed end 15, press against the spring element 8 and close the gap 34 there, while the additional element 9 maintains a position spaced apart from the spring element 8 by the gap 34 in the front region of the spring element 8, which is directed towards the movable end 16. The slight stiffening of the composite system 30 resulting from the contact of the additional element 9 against the spring element 8 in the rear region 35 is negligible.

[0062] In the mechanical setting "hard", see Fig. 4 The additional element 9, apart from its two fixed endpoints 31, 32 and the spacer element 20 arranged between the additional element 9 and the spring element 8, is also spaced away from the spring element 8 along its entire longitudinal extent. In other words, as already in the "soft" mechanical setting, the gap 34 extends between the two ends 31, 32 of the additional element 9. However, if the seat support 3 is now moved by the backrest support 4 in the pivot direction 7 and the composite system 30 with its spring element 8 is subjected to force, see Fig. 5 The spring element 8 bends, causing the additional element 9 to again attempt to conform to the spring element 8. However, this is prevented in the rear region 35 of the spring element 8 by the spacer element 20 positioned there. The additional element 9 remains spaced from the spring element 8 in the rear region 35, particularly in the functional section where the gap was previously closed. The gap 34 does not close there; it is kept open by the spacer element 20. Instead, the additional element 9 can conform to the spring element 8 in the front region 36, but this does not significantly affect the stiffness of the spring-loaded composite system 30.

[0063] The displacement of the spacer element 20 towards the fixed end 15 of the spring element 8, as shown in the Fig. 4 und 5 As illustrated, an increase in the distance between the outer fibers of the convex outer fiber in the rear region 35 of the composite system 30 results in an increase in the stiffness of the composite system 30, which in turn results in an increase in the pivoting resistance of the backrest support 4. Conversely, a displacement of the spacer element 20 towards the movable end 15 of the spring element 8, as shown in the Fig. 2 und 3 This illustrates a reduction in the distance between the outer fibers of the convex outer fiber, and thus a reduction in the stiffness of the composite system 30, which results in a reduction in the pivoting resistance of the backrest support 4. Between the two end positions of the spacer element 20, which correspond to the mechanical settings "hard" and "soft", any number of intermediate positions are possible into which the spacer element 20 can be moved.

[0064] By changing the position of the spacer element 20 from the "soft" mechanical setting to the "hard" mechanical setting, the position of point 29 is changed. This point is the point at which, or up to which, the additional element 9 rests against the bending spring element 8 when the backrest support 4 is pivoted backwards. While in the "soft" mechanical setting this point 29 is located in the rear area 35 of the spring element 8, see... Fig. 3 , the position of this point 29 in the mechanical setting "hard" is shifted so far that the additional element 9 no longer makes contact at all in the rear area 35 of the spring element 8.

[0065] The composite system 30 can also be designed differently in other embodiments, in particular such that the directions of displacement are reversed; the "soft" and "hard" positions are then interchanged. The composite system 30 can also be designed such that particularly high stiffness is achieved when the spacer element 20 is arranged in a central region located between the rear region 35 and the front region 36 of the spring element 8, while positioning the spacer element 20 near the ends 15, 16 of the spring element 8 results in particularly low stiffness (not shown).

[0066] The adjustment means are designed such that they allow load-free displacement of the spacer element 20 in the unloaded state, i.e., when the bending spring element 8 does not act on the seat support 3 against a movement of the backrest support 4. In other words, the position of the spacer element 20 can be changed without force in the unpivoted state of the mechanism 10, for presetting the pivoting resistance that will later act when the mechanism 10 is pivoted.

[0067] The described design of the spring system of the mechanism 10 in the form of the resilient composite system 30 is particularly advantageous because no additional installation space is required for spring elements. The entire spring system is completely housed within the installation space already required by the mechanism 10. Since, in particular, no spring elements are arranged in the installation space of the seat support 3, this can be made especially flat, as is often desirable in the open design of the mechanism 10 shown here.

[0068] Physical features of the device can be reformulated and used as process features, and vice versa. Features reformulated in this way are implicitly disclosed. Reference symbol list

[0069] 1 Base support 2 Cone mount 3 Seat support 4 Backrest support 5 Side panel 6 Driver 7 Swivel direction 8 Bending spring spring element 9 Auxiliary element 10 Synchronous mechanism 11 First transverse axis 12 Second transverse axis 13 Third transverse axis 14 Seat longitudinal direction 15 Fixed end of spring element 16 Movable end of spring element 17 Outer side of spring element 18 Longitudinal extent of spring element 19 Thickness of the composite system 20 Spacer element 21 First pivot joint 22 Second pivot joint 23 Third pivot joint 24 Slider 25 Outer side of the auxiliary element 26 Guide slot 27 First end of guide slot 28 Second end of guide slot 29 Contact point 30 Spring composite system 31 First end of auxiliary element 32 Second end of auxiliary element 33 Fastening screw 34 Gap 35 Rear area of ​​the spring element 36 Front area of ​​the spring element 37 Section

Claims

1. Mechanism (10) for a seating furniture item, in particular for an office chair, - with a number of mechanism components, at least comprising: a base carrier (1), a seat carrier (3) arranged on the base carrier (1) and movable relative to the base carrier (1), and a backrest carrier (4) coupled to the seat carrier (3), wherein a pivoting of the backrest carrier (4) causes a movement of the seat carrier (3) relative to the base carrier (1), - with a bending spring spring element (8) for loading the seat carrier (3) against the movement of the backrest carrier (4), - with an additional element (9) cooperating with the bending spring spring element (8) while forming a resilient composite system (30), - and with adjusting means (20, 24) which are designed for changing a property of the resilient composite system (30) that influences the stiffness of the resilient composite system (30), wherein the position of the additional element (9) relative to the bending spring spring element (8) of the resilient composite system (30) in the pivoted state of the mechanism (10) depends on the setting of the adjusting means (20, 24) in such a way that the additional element (9), depending on the setting of the adjusting means (20, 24), bears in sections against the bending spring spring element (8) along the longitudinal extension (18) of the resilient composite system (30) or is spaced in sections from the bending spring spring element (8) along the longitudinal extension (18) of the resilient composite system (30).

2. Mechanism (10) according to claim 1, wherein the bending spring spring element (8) is configured in the manner of a leaf spring.

3. Mechanism (10) according to claim 1 or 2, wherein the bending spring spring element (8) is an elastically deformable element integrated in one piece into a mechanism component, in particular the base carrier (1), which serves as an energy storage member.

4. Mechanism (10) according to one of claims 1 to 3, wherein the additional element (9) is non-resilient or only insignificantly resilient.

5. Mechanism (10) according to one of claims 1 to 4, wherein the additional element (9) defines the position of an edge fiber of the resilient composite system (30).

6. Mechanism (10) according to one of claims 1 to 5, wherein the additional element (9) is fixed against displacement relative to the bending spring spring element (8).

7. Mechanism (10) according to one of claims 1 to 6, wherein the adjusting means (20, 24) are designed for changing an edge fiber spacing of the resilient composite system (30).

8. Mechanism (10) according to one of claims 1 to 7, wherein the adjusting means (20, 24) comprise a spacing element (20) arranged between the bending spring spring element (8) and the additional element (9), which spaces the bending spring spring element (8) and the additional element (9) apart from one another at least along a partial section of the resilient composite system (30), and which is displaceable along the longitudinal extension (18) of the resilient composite system (30).

9. Seating furniture item, in particular office chair, with a mechanism (10) according to one of claims 1 to 8.