Patent Publication Number: US-9839296-B2

Title: Mechanism for an office chair

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a mechanism for an office chair. 
     Synchronous mechanisms and tilt mechanisms are known, among other things, as mechanisms for office chairs. The term synchronous mechanism is to be understood, in this case, as assemblies in the seat substructure of an office chair which provide kinematics coupling together the seat and the backrest and bringing about a certain relative movement with respect to one another. The seat of the office chair, which is generally speaking provided with an upholstered sitting surface, is mounted on the seat support. The backrest support, which commonly extends rearward from the actual synchronous mechanism, supports the backrest of the office chair on an upwardly extending cantilever. The seat support and the backrest support are usually coupled together in an articulated manner in such a manner that when the backrest is pivoted backward—as can be produced, for example, by the user of the chair leaning against the backrest—this causes the rear edge of the seat to be lowered down. As a result, the so-called “shirt riding-up effect” should be prevented and sitting comfort increased. These types of synchronous mechanisms are frequently very costly to construct and are consequently expensive to produce. 
     Tilt mechanisms, in contrast, are comparatively simply constructed assemblies in the seat substructure of chairs where the backrest support is connected in a rigid manner to the seat support, the seat or the frame of the chair. The seat support-backrest support combination created in this manner is pivotable backward by means of the tilt mechanism about a pivot axis which extends transversely with respect to the longitudinal direction of the chair when the user of the chair leans against the backrest. These types of tilt mechanisms are often used in place of synchronous mechanisms in inexpensive visitor or conference chairs in order to provide them with a simple tilt function. On account of their comparatively simple design, tilt mechanisms are clearly more cost-effective to produce in the majority of cases than the synchronous mechanisms previously described. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the invention is to provide an office chair which has a mechanism which is particularly simply designed structurally and is consequently comparatively inexpensive but nevertheless extremely variable. 
     Said object is achieved by a mechanism as claimed or by an office chair as claimed. Advantageous realizations of the invention are provided in the sub-claims. 
     A core idea of the invention is to provide a common pivot axis for the coupling between the seat support and the backrest support of the office chair. 
     Said common pivot axis, in this case, is preferably the only pivot axis common to the seat support and the backrest support, i.e. there is no further pivot axis that connects the seat support and the backrest support together. 
     Said pivot axis is preferably the only pivot axis of the seat support and at the same time the only pivot axis of the backrest support. 
     The common pivot axis is preferably the only pivot axis of said mechanism altogether, in particular the only pivot axis which makes it possible for the mechanism components, such as the seat support or the backrest support, to pivot forward and/or backward in the longitudinal direction of the chair. In other words then, the entire mechanism only comprises one such pivot axis, namely the common pivot axis. 
     As a result of said idea of the common pivot axis, the mechanism is designed in a particularly simple manner and can be produced inexpensively, but at the same is extremely variable, as is shown by the following explanations. 
     The seat support and the backrest support are connected, preferably exclusively, to the base support by means of one or several common pivot bolts, in this case realizing the above-described, preferably only common pivot axis. This means that the at least one common pivot bolt rotatably mounts both the seat support and the backrest support. 
     More precisely, according to the invention, by realizing said common pivot axis the seat support is connected in an articulated manner to the base support by means of at least one pivot bolt and is pivotable relative to the base support. The seat support is preferably connected in an articulated manner to the base support and also to the backrest support exclusively by means of said at least one pivot bolt and is pivotable relative to the base support and relative to the backrest support independently of the backrest support pivoting or being acted upon. 
     According to the invention, over and above this, by realizing said common pivot axis the backrest support is connected in an articulated manner to the base support by means of at the least one pivot bolt and is pivotable relative to the base support. The backrest support is preferably connected in an articulated manner to the base support and also to the seat support exclusively by means said at least one pivot bolt and is pivotable relative to the base support and relative to the seat support independently of the seat support pivoting or being acted upon. 
     Both components of the office chair that can be acted upon with forces when the office chair is in use, namely the seat support and the backrest support, are consequently pivotable individually and independently of one another. Depending on the further special realization of the mechanism, different dependencies between the movements of the seat support and the backrest support can be defined. The common pivot axis, in this case, makes particularly simple handling and adjustment possible. 
     The pivot bolt or bolts used, in this case, always fulfill a dual function. On the one hand, they serve for pivotally mounting the seat support on the base support and, on the other hand, for pivotally mounting the backrest support on the base support. As a result, the pivot bolt serves at the same time for connecting the backrest support and the seat support. The pivot bolt is preferably connected in a rigid manner to the base support and can consequently be seen as part of the base support. A particularly simple structural realization is achieved when simply one single pivot bolt is used which, for example, proceeding from the center of the base support, extends outward on both sides transversely with respect to the longitudinal direction of the chair. 
     In summary, the invention provides a particularly variable office chair mechanism, in particular a tilt or pivot mechanism, which makes it possible for the backrest to pivot individually independently of the degree of pivoting of the sitting surface. At the same time, the simple design of the mechanism described up to now enables the particularly simple use of further components by way of which the movement characteristic of the mechanism is modifiable in a variable manner. In other words, on the basis of one single basic structure, different mechanisms with pivoting characteristics that are clearly different from one another are able to be produced by means of the simplest modifications. 
     In preferred embodiments, the pivoting properties of the individual components are adjustable by means of resilient damping elements. Depending on whether the resilience of said damping elements is chosen to be the same as or different from one another, different pivot characteristics, in particular different pivot resistances and resetting forces for the seat support and the backrest support, are able to be set. At the same time, the different positioning of the damping elements inside the mechanism, more precisely the different positioning of the damping elements between the mechanism components and consequently the choice as to which of said mechanism components serves as the impinging element and which as the abutment, makes it possible to set different movement characteristics. The mechanism according to the invention, in this case, is able to replicate, for example, the movement characteristics of a synchronous mechanism without a costly mechanical structure being necessary for this purpose. 
     In a preferred embodiment of the invention, the mechanism comprises at least one first resilient damping element which is acted upon when the seat support is pivoted. In particular, said first resilient damping element is acted upon by the seat support when the seat support is pivoted forward or backward in the longitudinal direction of the chair. The seat support, which is mounted on the central pivot axis, can consequently be pivoted backward or forward against the resistance of the first resilient damping element for example when the user shifts his weight. 
     If, in this case, as in a particularly preferred embodiment of the invention, the at least one first resilient damping element is arranged between the base support and the seat support, in other words therefore if the base support forms the abutment for the at least one first resilient damping element which is acted upon by the seat support, the damping or the resetting of a pivoting movement of the seat support relative to the base support and also the pivot range of the seat support can be adjusted individually and—depending on the further structural development of the mechanism—independently of an impingement of the backrest support or, however, in dependence on such an impingement of the backrest support, i.e. on the backrest pivoting. 
     In a preferred embodiment of the invention, the mechanism comprises at least one second resilient damping element which is acted upon when the backrest support is pivoted. Said second resilient damping element is acted upon by the backrest support in particular when the backrest support is pivoted in the longitudinal direction of the chair. 
     In a preferred embodiment of the invention according to claim  4 , the mechanism comprises at least one second resilient damping element which is acted upon when the backrest support is pivoted. Said second resilient damping element is acted upon by the backrest support in particular when the backrest support is pivoted in the longitudinal direction of the chair. 
     The arrangement of said second resilient damping element determines then whether it is a mechanism where the seat support and the backrest support are coupled closely together, where a movement of the one component brings about a subsequent movement of the other component, or whether the seat support and the backrest support are more or less completely uncoupled from one another such that there are two pivoting movements which are independent of one another. 
     In a preferred embodiment of the invention, the at least one second resilient damping element is arranged between the backrest support on the one hand and the seat support on the other. In other words, the seat support forms the abutment for the at least one second resilient damping element which is acted upon by the backrest support. 
     In a special embodiment of such a coupled variant, pivoting the seat support, as is preferably effected against the at least one first resilient damping element, results in a subsequent movement of the backrest support, i.e. the backrest support follows the pivoting movement of the seat support without the at least one second resilient damping element needing to be acted upon by the backrest support and the seat support for this purpose. 
     In a special embodiment of such a coupled variant, over and above this, pivoting the backrest support, as is preferably effected against the at least one second resilient damping element, results in a subsequent movement of the seat support, in particular in a subsequent movement of the seat support against the at least one first resilient damping element. In other words, the seat support follows the pivoting movement of the backrest support. In this case, the seat support is entrained by means of the second resilient damping element as the seat support and the backrest support are operatively connected to one another by means of said damping element. 
     In another preferred embodiment of the invention, the at least one second resilient damping element is arranged between the backrest support on the one hand and the base support on the other hand. In other words, the base support forms the abutment for the at least one second resilient damping element which is acted upon by the backrest support. 
     In such an uncoupled variant no subsequent movements, as described above, take place. The seat support and the backrest support are completely decoupled from one another with regard to their pivoting movements. 
     It is advantageous in all the above-described cases when the first resilient damping element comprises a resilience which differs from the resilience of the second resilient damping element. In other words, the resilience of the said damping elements can be predetermined as a result of choosing the damping elements in a suitable manner, in particular by choosing the material in a suitable manner. As a result, the pivot properties of the seat support or of the backrest support are adjustable in a defined manner, on the one hand respectively for the relevant mechanism components per se, and on the other hand matched to one another, for example for providing a movement characteristic which recreates that of a synchronous mechanism. 
     For example, choosing the damping elements in a suitable manner can ensure that the backrest support performs at least the same pivot angle as the seat support. As an alternative to this, for example, the hardness of the damping elements can be adjusted so as to match one another in such a manner that when the user shifts his weight backward the pivot angle of the backrest support is greater than the pivot angle of the seat support. An additional deflection angle of the backrest support is added to the deflection angle of the seat support such that a synchronous effect is experienced. 
     On account of the characteristics of the structural design of the mechanism according to the invention, in particular the common single pivot axis, a multistage locking arrangement for the displacement movements of the seat support and/or the backrest support can be realized with particularly simple means, in particular by way of such produced by a linear displacement movement of a blocking element. For this purpose, the base support, seat support and backrest support preferably comprise openings which are aligned with one another for receiving the blocking element. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The invention is further explained in the figures of the drawing by way of exemplary embodiments, in which figures: 
         FIG. 1  shows an office swivel chair shown in part having a support structure for a sitting surface and a backrest of an office swivel chair; 
         FIG. 2  shows a perspective view of the support structure from  FIG. 1 ; 
         FIG. 3  shows an exploded drawing of the support structure from  FIG. 2 ; 
         FIG. 4  shows a perspective sectional view of the support structure from  FIG. 2  in an upright initial position; 
         FIG. 5  shows a perspective sectional view of the support structure from  FIG. 2  in a pivot position; 
         FIG. 6  shows a further sectional view of the support structure from  FIG. 2 ; and 
         FIG. 7  shows a sectional view of a further embodiment, 
         FIG. 8  shows a perspective sectional view of an “A-type” mechanism, 
         FIG. 9  shows a sectional view of the mechanism from  FIG. 8  in the non-pivoted initial state, 
         FIG. 10  shows a sectional view of the mechanism from  FIG. 8  with the seat support pivoted forward, 
         FIG. 11  shows a sectional view of the mechanism from  FIG. 8  with the seat support pivoted backward, 
         FIG. 12  shows a sectional view of the mechanism from  FIG. 8  with the backrest support pivoted backward, 
         FIG. 13  shows another sectional view of the mechanism from  FIG. 8  looking at a multistage locking arrangement, 
         FIG. 14  shows a perspective sectional view of a “B-type” mechanism from the front, 
         FIG. 15  shows a sectional view, in perspective, of the mechanism from  FIG. 14  from behind, 
         FIG. 16  shows a sectional view of the mechanism from  FIG. 14  in the non-pivoted initial position, 
         FIG. 17  shows a sectional view of the mechanism from  FIG. 14  with the seat support pivoted forward, 
         FIG. 18  shows a sectional view of the mechanism from  FIG. 14  with the seat support pivoted backward, 
         FIG. 19  shows a sectional view of the mechanism from  FIG. 14  with the backrest support pivoted backward, 
         FIG. 20  shows a sectional view of the mechanism from  FIG. 14  with the backrest support pivoted backward and the seat support pivoted forward, 
         FIG. 21  shows a perspective sectional view of a “C-type” mechanism, 
         FIG. 22  shows a sectional view, in perspective, of the mechanism from  FIG. 21  in the non-pivoted initial position, 
         FIG. 23  shows a sectional view of the mechanism from  FIG. 21  with the backrest support pivoted backward, 
         FIG. 24  shows a perspective sectional view of a “D-type” mechanism, 
         FIG. 25  shows a sectional view of the mechanism from  FIG. 24  in the non-pivoted initial position, 
         FIG. 26  shows a sectional view of the mechanism from  FIG. 24  with the backrest support pivoted backward. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     None of the figures show the invention true to scale, in this case they are simply shown schematically and just with their essential components. 
     Identical references in this case correspond to elements with the identical or comparable function. 
     First embodiments of the chair mechanism are explained below by way of  FIGS. 1 to 7 . First of all, said embodiments will be explained in general. In this connection, the mechanism is designated as a “support structure”. 
     The support structure according to the invention for a sitting surface and a backrest of an office swivel chair comprises a sleeve-shaped seat base, a hollow-cylindrical back base, a pivot bolt and a resilient damping element. The seat base has an end face for fastening the sitting surface and an inside lateral surface. The back base is arranged coaxially with respect to the seat base. In addition, a backrest adapter is realized on the back base for fastening the backrest. The pivot bolt comprises a longitudinal axis which extends in the radial direction of the seat base and is mounted in a bearing block of the seat base and in bearing bushes which are realized in the lateral surface of the back base. The resilient damping element is arranged between the end face of the seat base and the end face of the back base at least in the region which is located opposite the backrest adapter when viewed in the radial direction. 
     As a result of the bearing arrangement in the pivot bolt, the seat base and the back base—and consequently the sitting surface and the backrest which are connectable thereto—are pivotable relative to one another. The resilient damping element serves for damping and resetting said pivoting movement into the initial position. All in all, the backrest is consequently able to be pivoted individually independently of the degree of pivoting of the sitting surface. 
     The resilient damping element can be realized as a ring-shaped element and can be realized extensively in the region between the end face of the seat base and the end face of the back base. However, it is enough for the damping element to be realized between the end face of the seat base and the end face of the back base in the region which is located opposite the backrest adapter when seen in the radial direction. A saving in material is possible in this way compared to the realization as a solid ring. Realizing the resilient damping element as a semicircular ring segment has proved to be particularly advantageous. 
     In an advantageous embodiment, the support structure additionally comprises a hollow-cylindrical gas spring base, which is arranged coaxially with respect to the seat base, for receiving a gas spring. The gas spring base, in this connection, is mounted on the inside lateral surface of the seat base with the interposition of a resilient ring element. As a result of the resilient ring element, the seat base—and consequently the sitting surface—is resiliently mounted relative to the gas spring base. The sitting surface can consequently be pivoted/tilted relative to the chair column. In other words, an office swivel chair which has both a pivotable backrest and a pivotable sitting surface is obtained. The pivoting movement of the backrest and of the sitting surface are independent of one another in this connection. 
     By choosing the resilience of the resilient damping element and of the resilient ring element, it is possible to adapt the intensity of the pivoting movement or of the pivoting range of the backrest and/or of the sitting surface. It has proved to be particularly advantageous in this connection to provide the resilient ring element with less resilience than the resilient damping element. The adjusting of the resilience can be effected, for example, by choosing suitable materials for the resilient damping element and the resilient ring element. 
     In an advantageous manner, the pivot bolt is additionally mounted in bearing bushes which are realized in the lateral surface of the gas spring base. As a result, the pivot bolt serves for pivotably mounting both the seat base relative to the back base and the gas spring base relative to the seat base. Consequently, the pivot bolt fulfills a dual function. 
     In an advantageous embodiment, the bearing bushes of the gas spring base, in which the pivot bolt is mounted, are provided with rubber rings. In other words, the pivot bolt is mounted in the bearing bushes of the gas spring base with the rubber rings interposed. As a result of the resilience properties of the rubber rings, the pivot bolt is provided with a resilient (flexible) bearing arrangement. An additional side inclination of the sitting surface can be achieved in this way. 
     In a further advantageous embodiment, a gas spring height adjustment ring is mounted on the pivot bolt. In this way, the pivot bolt serves for adjusting the height of the sitting surface at the same time. The functionality of the pivot bolt is consequently increased further. 
     In a further advantageous embodiment, the support structure additionally comprises a back-locking element, which is arranged between the seat base and the back base and is rotatable in the circumferential direction of the seat base, for locking and unlocking the pivoting movement of the seat base relative to the back base. The relative movement between the seat base and the back base can be suppressed in this manner where necessary by the user of the office swivel chair. In the locked position, the back rest and the sitting surface are pivoted together on the basis of the pivoting movement permitted by the resilient ring element. 
     The office swivel chair according to the invention comprises a pedestal having a gas spring which serves as the chair column, one of the support structures described above, a sitting surface which is connected to the seat base and a backrest which is connected to the backrest adapter. 
     The first embodiments of the invention shown in  FIG. 1 to 7  are described in detail below with reference to said drawings. 
       FIG. 1  shows an office swivel chair  1  with a sitting surface  2  and a backrest  3 . The sitting surface  2  and the backrest  3  are connected together by means of a support structure  4 . More precisely, the sitting surface  2  is fastened on a seat base  6  of the support structure  4 . The backrest  3  is connected to a back base  8  by means of a backrest adapter  7 . 
     In addition, the support structure  4  serves for receiving a top end region of a gas spring  5  (only shown in a reduced form in  FIG. 1 ). The gas spring  5  forms the so-called chair column. The bottom region of the chair column and the pedestal of the office swivel chair  1  are not shown in  FIG. 1 . 
       FIG. 2  to  FIG. 6  show details of the support structure  4 . The seat base  6  is realized in a substantially sleeve-shaped manner. The sitting surface  2  is mounted on the end face  9  of the seat base  6 . The back base  8  is arranged coaxially with respect to the seat base  6 . The back base  8  is formed in a substantially hollow-cylindrical manner, the outside diameter of the lateral surface widening from bottom to top. A bearing bolt  10  extends in the radial direction and is mounted in a bearing block  11  of the seat base  6  and in bearing bushes  12  of the back base  8 . At the same time, the bearing bolt  10  is mounted in bearing bushes  13  of a gas spring base  14 . 
     The gas spring base  14  is arranged inside the seat base  6  and is aligned coaxially with respect to said seat base. The gas spring base  14  is realized in a substantially hollow-cylindrical manner and receives the top end region of the gas spring  5 . A resilient ring element  16  is arranged between the outside lateral surface of the gas spring base  14  and the inside lateral surface  15  of the seat base  6 . Said ring element  16  is mounted in the axial direction between a shoulder  17  on the inside lateral surface  15  of the seat base  6  and a flange  18  which is realized on the end face of the gas spring base  14 . In addition, a gas spring height adjustment ring  19  is mounted on the bearing bolt  10  inside the gas spring base  14 . As a result of rotating the bearing bolt  10 , the height of the gas spring  5  and consequently the height of the sitting surface  2  is adjusted. 
     A resilient damping element  20  is arranged between the end face of the seat base  6  and the end face of the back base  8 . The resilient damping element  20  is realized as a semicircular ring segment and is arranged in the region between the end face of the seat base  6  and the end face of the back base  8  which is located opposite the backrest adapter  7  when seen in the radial direction. The resilient ring element  16  has less resilience than the resilient damping element  20 . 
     A back-locking element  21  is also arranged coaxially with respect to the seat base  6 . The back-locking element  21  is rotatable in the circumferential direction of the seat base  6  and serves for locking and unlocking the pivoting movement of the seat base  6  relative to the back base  8  about the pivot bolt  10 . 
     In the unlocked position of the back-locking element  21 , the seat base  6  is able to pivot relative to the back base  8  around the pivot bolt  10 —and consequently the sitting surface  2  is able to pivot relative to the backrest  3 . At the same time, the seat base  6  is able to pivot relative to the gas spring base  14  around the pivot bolt  10 —and consequently the sitting surface  2  is able to pivot relative to the chair column. In this connection, the relative movement of the seat base  6  with respect to the back base  8  originates from the resilient damping element  20 , whilst the relative movement of the seat base  6  with respect to the gas spring base  14  is made possible by the resilient ring element  16 . 
       FIG. 4  shows the support structure  4  in the initial upright position, whilst  FIG. 5  shows the support structure  4  in a backwardly pivoted position. In the pivot position, the resilient damping element  20  and the resilient ring element  16  are compressed along the region located opposite the backrest adapter  7  when viewed in the radial direction. 
     As a result of the various degrees of resilience of the resilient damping element  20  and of the resilient ring element  16  as well as the various lever arms realized opposite the pivot bolt  10 , the seat base  6  is deflected less strongly out of the initial position than the back base  8 . Consequently, it is possible to pivot the seat base  6  and the back base  8  independently. 
       FIG. 7  shows a further embodiment of a support structure  104 . The support structure  104  differs from the above-described support structure simply in the realization of the gas spring base. The remaining components remain unchanged. 
     The design of the gas spring base  114  used in the support structure  104  corresponds substantially to that of the gas spring base  14  and differs from the gas spring base  14  by rubber rings  22  which are additionally present. Said rubber rings  22  are mounted in the bearing bushes  13  of the gas spring base  114 . The pivot bolt  10  is consequently mounted in the bearing bushes  13  of the gas spring base  114  with the interposition of the rubber rings  22 . As a result of the resilience properties of the rubber rings  22 , the pivot bolt  10  is resiliently mounted inside the gas spring base  114 . This, in turn,—when the user shifts his weight or changes his position—leads to a side of the sitting surface  2  tilting. 
     The invention is consequently focused on a support structure  4 ,  104  for a sitting surface  2  and a backrest  3  of an office swivel chair  1 , comprising: a sleeve-shaped seat base  6  having an end face  9  for fastening the sitting surface  2  and an inside lateral surface  15 ; a hollow-cylindrical back base  8  which is arranged coaxially to the seat base  6  and on which a backrest adapter  7  is realized for fastening the backrest  3 ; a pivot bolt  10  which comprises a longitudinal axis that extends in the radial direction of the seat base  6  and which is mounted in a bearing block  11  of the seat base  6  as well as in bearing bushes  12  realized in the lateral surface of the back base  8 ; and a resilient damping element  20  which is arranged between the end face of the seat base  6  and the end face of the back base  8  at least on the region which is located opposite the backrest adapter  7  when seen in the radial direction. The invention is additionally focused on such a support structure wherein the resilient damping element  20  is realized as a semicircular ring segment. The invention is additionally focused on such a support structure, additionally comprising a hollow-cylindrical gas spring base  14 ,  114 , which is arranged coaxially with respect to the seat base  6 , for receiving a gas spring  5 , the gas spring base  14 ,  114  being mounted on the inside lateral surface  15  of the seat base  6  with interposition of a resilient ring element  16 . The invention is additionally focused on such a support structure wherein the resilient ring segment  16  is mounted in the axial direction between a shoulder  17  of the inside lateral surface  15  of the seat base  6  and a flange  18  which is realized on the end face of the gas spring base  14 ,  114 . The invention is additionally focused on such a support structure wherein the resilient ring element  16  comprises less resilience than resilient damping element  20 . The invention is additionally focused on such a support structure wherein the pivot bolt  10  is additionally mounted in bearing bushes  13  which are realized in the lateral surface of the gas spring base  14 ,  114 . The invention is additionally focused on such a support structure wherein rubber rings  22 , in which the pivot bolt  10  is mounted, are introduced in the bearing bushes  13  of the gas spring base. The invention is additionally focused on such a support structure according to one of the preceding claims, wherein a gas spring height adjustment ring  19  is mounted on the pivot bolt  10 . The invention is additionally focused on such a support structure according to one of the preceding claims additionally comprising a back-locking element  21 , which is arranged between the seat base  6  and the back base  8  and is rotatable in the circumferential direction of the seat base  6 , for locking and unlocking the pivoting movement of the seat base  6  relative to the back base  8  about the pivot bolt  10 . Finally, the invention is also additionally focused on an office swivel chair  1 , comprising: a pedestal having a gas spring  5  which serves as a chair column; a support structure  4 ,  104  according to one of the preceding claims; a sitting surface  2  which is connected to the seat base  6 ; and a backrest  3  which is connected to the backrest adapter  7 . 
     Second embodiments of the chair mechanism are explained below by way of  FIG. 8 to 26 . In this case, four different types of mechanism are described which have been designated with the letters A to D to make differentiation easier. 
       FIG. 8 to 13  show an “A” type mechanism  4 A. 
     The pivoting mechanism comprises a base support  14  which is placed onto the top end of a chair column (not shown) by means of a tapered receiving means. Over and above this, the mechanism comprises a seat support  6  and a backrest support  8 , which is forked when seen in top view and the cheeks  23  of which are arranged on both sides of the base support  14 . The seat support  6  is provided for receiving or mounting an upholstered sitting surface (not shown). An indicated backrest  3 , which is height-adjustable in the case of modern office chairs, is mounted on the backrest support  8 . The backrest  3  can also be integrally connected to the backrest support  8 . 
     The entire “A-type” mechanism  4 A—just as the “B-type”, “C-type” and “D-type” mechanisms described below—is designed in a mirror-symmetrical manner, with reference to a center longitudinal plane, which relates to the actual kinematics. In this respect, the following description always assumes structural elements that are present in pairs on both sides. 
       FIGS. 8 and 9  show the initial position where the backrest support  8  assumes a substantially horizontal position and the seat support  6  has been pivoted neither forward nor backward in the longitudinal direction  24  of the chair. The mechanism  4 A is designed in a comparatively compact manner by the central base support  14  being encompassed at least laterally both by the seat support  6  and the cheeks  23  of the backrest support  8 . 
     By realizing a common pivot axis  25  which extends transversely to the longitudinal direction  24  of the chair, on one hand the seat support  6  is connected in an articulated manner to the base support  14  by means of one single continuous pivot bolt  10  and is pivotable forward and backward in the longitudinal direction  24  of the chair relative to the base support  14  and, on the other hand, the backrest support  8  is connected in an articulated manner to the base support  14  by means of said pivot bolt  10  and is pivotable relative to the base support  14  from its non-pivoted initial state into a pivot state in which it is pivoted down and back. The pivot bolt  10 , in this case, is mounted in bearing bushes  26  or the like, see  FIG. 8 , which are provided for this purpose in the cheeks  23  of the backrest support  8 , in the side walls  28  of the seat support  6  which flank the side walls  27  of the base carrier  14  as well as in the side walls  27  of the base support  14  itself. If a base support  14  without side walls is used, corresponding bearings  26  can also be provided in an upwardly elongated tapered receiving means or in a gas spring base. The common pivot axis  25 , in this case, extends centrally over the tapered receiving means such that the horizontal pivot axis  25  and the vertical center longitudinal axis  29  of the chair column intersect, see  FIGS. 8 and 13 . 
     A front first resilient damping element  16   a , which when the seat support  6  is pivoted forward in the longitudinal direction  24  of the chair is acted upon by the seat support  6 , is provided in front of the tapered receiving means when viewed in the longitudinal direction  24  of the chair. A rear first resilient damping element  16   b , which when the seat support  6  is pivoted backward in the longitudinal direction  24  of the chair is acted upon by the seat support  6 , is provided behind the tapered receiving means when viewed in the longitudinal direction  24  of the chair. 
     Both the front first resilient damping element  16   a  and the rear first resilient damping element  16   b  are arranged between the base support  14  and the seat support  6 . The base support  14  consequently forms the abutment for both damping elements  16   a ,  16   b.    
     The backrest support  8  is connected to the seat support  6  exclusively by means of the pivot bolt  10  and by means of a central second damping element  20  which is arranged behind the tapered receiving means. Said second resilient damping element  20  is acted upon by the backrest support  8  when the backrest support  8  is pivoted back and down in the longitudinal direction  24  of the chair. In order to achieve this, the second damping element  20  is arranged between the backrest support  8  on the one hand and the seat support  6  on the other hand such that the seat support  6  forms the abutment for the second resilient damping element  20  which is acted upon by the backrest support  8 . 
     When the seat support  6  pivots forward in the longitudinal direction  24  of the chair out of the initial state shown in  FIG. 8  and  FIG. 9 , the front first damping element  16   a  is acted upon, see  FIG. 10 . As the backrest support  8  is connected to the seat support  6  by means of the second damping element  20 , the backrest support  8  follows the forward movement of the seat support  6  insofar as the backrest support  8  is not loaded by a user leaning against it and as a result is prevented from a subsequent movement. 
     When the seat support  6  pivots backward in the longitudinal direction  24  of the chair, the rear first damping element  16   b  is acted upon, see  FIG. 11 . As at the same time the seat support  6  supports the second damping element  20 , by means of which the backrest support  8  is connected to the seat support  6 , the tilting of the seat support  6  is followed by corresponding tilting of the backrest support  8  and consequently of the backrest  3 , shown once again in  FIG. 11  for the case where the backrest  3  itself is not acted upon. 
     If, as shown in  FIG. 12 , the backrest  3  is loaded by a chair user leaning against it and consequently the backrest support  8  is acted upon, the backrest support  8  then acts upon the second damping element  20 . As the second damping element  20  is supported by the seat support  6 , the impingement of the second damping element  20  by the backrest support  8  brings about—in dependence on the resilience, more precisely in dependence on the deformation resistance of the second damping element  20  and on the deformation resistance of the rear first damping element  16   b  countering said movement—a more or less strong subsequent movement of the seat support  6  in the same direction, here therefore downward. A typical synchronous movement, that is to say the seat support  6  tilting to the back when the backrest  3  pivots, is consequently achieved without a costly synchronous mechanism being necessary for this purpose. The desired pivoting characteristic of the office chair  1  is able to be adjusted as a result of selecting the material for the damping elements  16 ,  20  in a suitable manner. 
       FIG. 13  shows a further cross section through the mechanism  4 A, from which it can be seen how simply a multi-stage locking arrangement for the pivoting movements of the seat support  6  and/or the backrest support  8  can be realized by means of a linear displacement of a blocking element  30 . The, for example, rod-shaped blocking element  30  can be placed for this purpose selectively into one or several openings  31 ,  32 ,  33  which are aligned with one another and are provided in the base support  14 , the seat support  6  and the backrest support  8  for receiving the blocking element  30 . In the first locking stage shown in  FIG. 13 , where the blocking element  30  is simply inserted in the outer receiving opening  31  of the backrest support  8 , the locking arrangement is released. If the blocking element  30  is pushed further into the mechanism  4 A in the direction of the tapered receiving means such that it is inserted in the next receiving opening  32  of the seat support  6 , the second locking stage is achieved in which movement of the seat support  6  relative to the backrest support  8  is blocked. In this case, the seat support/backrest support combination  6 ,  8  can only still be tilted as one common pivot unit, as a result of which the pivoting principle of a tilt mechanism is realized. In the final third locking stage, which is achieved when the blocking element  30  is also pushed into the next receiving opening  33  of the base support  14  and is inserted within the same, in addition to the blocking action of the second locking stage the seat support/backrest support combination  6 ,  8  is also blocked from pivoting relative to the base support  14 ; this corresponds to a locked tilt mechanism. 
     The multistage locking arrangement, as illustrated in  FIG. 13 , can also be used in the “B-type”, “C-type” and “D-type” mechanisms described below. 
     In contrast to the “A-type” mechanism  4 A shown in  FIG. 8 to 13 , where there is a coupling between the seat support  6  and the backrest support  8  by means of the second damping element  20  which is supported by the seat support  6 , the “B-type” mechanism described below in conjunction with  FIG. 14 to 20  does not comprise any such coupling. 
     In contrast to the “A-type” mechanism, the second resilient damping element  20  is arranged here between the backrest support  8  on the one hand and the base support  14  on the other. In other words, the base support  14  forms the abutment for the second resilient damping element  20  which is acted upon by the backrest support  8  when pivoting. 
       FIGS. 14 and 15  show the sectioned mechanism  4 B from the front and from the rear such that the arrangement of the damping elements  16 ,  20  becomes particularly explicit. In said case, the outside side walls  28  of the seat support  6  encompass the inside central backrest support element  34  of the backrest support  8 , which, in this case, does not comprise any cheeks. The second damping element  20  is situated between said backrest support  8  on the one hand and a base plate  35  of the base support  14  on the other hand, see  FIG. 15 . Provided on both sides between the side walls  28  of the seat support  6 , which for this purpose comprise downwardly pointing, stamp-shaped ends  36 , and the base plate  35  of the seat support  6  are first damping elements  16  which extend continuously from front to back over the entire length of the base support  14 . Both the first damping elements  16  and the second damping elements  20  consequently rest on the same structural element which serves as abutment, the base plate  35  of the base support  14 . The non-pivoted initial state is shown again in  FIG. 16 . 
       FIG. 17  shows that when the seat support  6  pivots forward, when seen in the longitudinal direction  24  of the chair, the front end  37  of the first damping elements  16  is acted upon by the seat support  6 , whilst the seat support  6  lifts from the rear end  38  of the first damping elements  16 , see  FIG. 14 . As there is no coupling to the second damping  20 , the seat support  6  pivoting forward has no effect on the backrest support  8 . The same applies in a corresponding manner to the seat support  6  pivoting backward when seen in the longitudinal direction  24  of the chair, as shown in  FIG. 18 . 
     The backrest support  8  is moved exclusively when the backrest  3  is loaded, that is to say when a user leans against the backrest  3 , see  FIG. 19 . In this case, the second damping element  20  is acted upon by the backrest support  8  and also makes available a corresponding resetting force which—as also in all the other described exemplary embodiments—causes the backrest  3  with the backrest support  8  to pivot back into the initial position when the backrest is no longer loaded by the user  3 . 
     There is no automatic subsequent movement in the case of the “B-type” mechanism such that no synchronous development is replicated either. However, as a result of the damping elements  16 ,  20 , which are arranged separately from one another and are able to be actuated independently, the seat support  6  and the backrest support  8  can also be pivoted independently here, as shown, for example, in  FIG. 20 , where the backrest support  8 , acted upon by a user leaning against it, is pivoted backward and the seat support  6 , correspondingly acted upon by the user of the chair, is pivoted forward. 
       FIG. 21 to 23  show a “C-type” mechanism. In this case, as regards its operation, like the “A-type” mechanism this is a coupled mechanism  4 C where the abutment for the second damping element  20  is formed by the seat support  6 . The “C-type” mechanism differs from the “A-type” mechanism, however, by the form and arrangement of the damping elements  16 ,  20 . 
     Once again, the center of the base support  14  with the tapered receiving means is flanked on both sides initially by the side walls  28  of the seat support  6 , then outwardly by the cheeks  23  of the backrest support  8 . The characteristic is that the damping elements  16 ,  20  are arranged in the interior of the side walls  28  and cheeks  23 . As a result, the installation space required for the mechanism  4 C is clearly reduced and an altogether clearly more compact mechanism  4 C which is particularly flat is produced. 
     In contrast to the “A-type” and “B-type” mechanisms, where cuboid damping elements  16 ,  20  are used, the damping elements  16 ,  20  in this case are realized as blocks which are shaped in the manner of a segment of a ring arch and which, extending over a defined angular portion, encompass the pivot bolt  10  in each case in part. The damping elements  16 ,  20 , in this case, are inserted in suitable receiving chambers inside the side walls  28  or cheeks  23 . 
     Whereas  FIG. 21  is a view from the outside of the mechanism  4 C with the side walls  28  and cheeks  23  which receive the damping elements  16 ,  20 , the section through a side wall  28  of the seat support  6  shown in  FIG. 22  shows the form and arrangement of a front first damping element  16   a  and of a rear first damping element  16   b . Two different materials for the front and rear first damping element  16   a ,  16   b  have been used here as an example in order to clarify that in this way it is possible to set a different pivot resistance for the seat support  6  pivoting forward in the longitudinal direction  24  of the chair than for the seat support  6  pivoting backward in the longitudinal direction  24  of the chair. 
     The two first damping elements  16   a ,  16   b  are separated from one another twice. On the one hand, with the seat support  6  in the non-pivoted initial state, the damping elements  16   a ,  16   b  abut by way of their one end against an entrainment means  39  of the seat support  6 , which extends radially in the direction of the pivot pin  10  in the manner of an overhang from the outside wall of the receiving chamber  40 , and form stop surfaces  41 ,  42 , which extend both forward and backward in the longitudinal direction  24  of the chair, for acting upon the damping elements  16   a ,  16   b . Thus, when the seat support  6  pivots backward in the longitudinal direction  24  of the chair, the front first damping element  16   a  is acted upon by the forwardly pointing stop surface  41  and by the seat support  6  pivoting forward in the longitudinal direction  24  of the chair and the rear first damping element  16   b  is acted upon by the rearwardly pointing stop surface  42 . 
     On the other hand, in the non-pivoted initial state, the damping elements  16   a ,  16   b  abut by way of their oppositely situated other ends against an immovable part of the base support  14 , which serves as abutment  43  and, proceeding from the center of the base support  14 , extending transversely to the longitudinal direction  24  of the chair, projects into the receiving chamber  40  of the first damping elements  16   a ,  16   b . The abutment  43  extends in this case, just as the entrainment means  39 , from the pivot pin  10  to the outside wall of the receiving chamber  40 . In the present example, the abutment  43  is fixedly connected in an integral manner to the pivot pin  10  and corresponds in its form to the entrainment means  39  of the seat support  6 , the pivot pin  10  being fixedly connected, in turn, to the base support  14 . 
     In the example shown here, the front and rear first damping elements  16   a ,  16   b  and the receiving chambers  40  provided for them are the same size. At the same time, the entrainment means  39  and the abutment  43  are precisely opposite one another, the entrainment means  39 , when seen from the pivot pin  10 , pointing downward with the seat support  6  in the non-pivoted initial state, and the abutment  43  pointing upward. In the initial state, therefore, the entrainment means  39  is at a 6 o&#39;clock position, whereas the abutment  43  is arranged in a 12 o&#39;clock position. However, both the size of the damping elements  16   a ,  16   b  and the position of the entrainment means  39  and/or of the abutment  43  can be varied in order to realize certain pivot characteristics. 
     The section through a cheek  23  of the back rest support  8  shown in  FIG. 23  illustrates the form and arrangement of a second damping element  20  of said mechanism  4 C. 
     So that the desired coupling between a movement of the seat support  6  and the backrest support  8  can be achieved once again, a second entrainment means  44  of the seat support  6 , which corresponds in form and realization to the above-described first entrainment means  39 , extends transversely with respect to the longitudinal direction  24  of the chair into the receiving chamber  45  of the second damping element  20  realized in the interior of the cheek  23  of the backrest support  8  and there forms the abutment for the second damping element  20  when the second damping element  20  is acted upon by the backrest support  8 . With the backrest support  8  in the initial state, said abutment  44  is approximately in a 2 o&#39;clock position. The entrainment means  46  of the backrest support  8 , which, in the initial position, is arranged approximately in a 11 o&#39;clock position, once again extends radially as a type of overhang from the outside wall of the receiving chamber  45  in the direction of the pivot pin  10 . It also realizes corresponding stop surfaces both forward and backward in the longitudinal direction  24  of the chair for acting upon the two second damping elements  20   a ,  20   b.    
     In this case, the “rear” second damping element  20   b , which—as can be seen from the arrangement of the entrainment means  46  and the abutment  44 —extends over a clearly larger angular portion than the “front” second damping element  20   a , is inserted in such a manner between the entrainment means  46  and the abutment  44  in the receiving chamber  45  that the backrest support  8  pivoting into the pivoting state, as shown in  FIG. 23 , causes an impingement of the “rear” second damping element  20   b  which consequently determines the pivot resistance of the backrest  8 . At the same time, the “rear” second damping element  20   b  presses by way of its other end against the abutment  44 , which is realized as part of the seat support  6 , such that said pivoting backward of the backrest support  8  causes the seat support  6  to pivot backward as a subsequent movement. 
     The “front” second damping element  20   a  which, with the backrest support  8  in the initial position, abuts against the stop surface of the entrainment means  46  of the backrest support  8 , which points forward in the longitudinal direction  24  of the chair, is acted upon by the abutment  44  formed by the seat support  6  when the seat support  6  pivots backward and causes the backrest support  8  to pivot backward into the same direction as a subsequent movement. Equally, when the seat support  6  pivots forward, the “rear” second damping element  20   b  can be acted upon by the abutment  44  which is formed by the seat support  6 , which causes the backrest support  8  to pivot into the same direction, that is to say forward, as a subsequent movement. 
       FIG. 24 to 27  show a “D-type” mechanism. In this case, as regards its operation, like the “B-type” mechanism this is an uncoupled mechanism  4 D where the abutment for the second damping element  20  is not formed by the seat support  6  but by the base support  14 . Just as in the case of the “C-type” mechanism, however, the damping elements  16 ,  20  in this case are once again arranged around the pivot pin. 
     Whereas  FIG. 24  is a view from the outside of the mechanism  4 D with the side walls  28  and cheeks  23  which receive the damping elements  16 ,  20 , the section through a side wall  28  of the seat support  6  shown in  FIG. 25  shows the form and arrangement of a front first damping element  16   a  and a rear first damping element  16   b . Said design corresponds substantially to the design of a “C-type” mechanism, as shown in  FIG. 22 . 
       FIG. 26  shows a section through a cheek  23  of the backrest support  8 . In contrast to the “C-type” mechanism, there are no components of the seat support  6  which project into the receiving chamber  45  such that, as in the case of the “B-type” mechanism, no subsequent movements are possible due to the lack of a coupling between the seat support  6  and the backrest support  8 . Instead of which, the base support  14  once again forms the abutment  47  for the two second damping elements  20   a ,  20   b , which can be acted upon in a known manner by the entrainment means  46  of the backrest support  8  when the backrest  3  pivots. The abutment  47 , in this case, is realized as a molding of the pivot bolt  10  which points forward and backward in the longitudinal direction  24  of the chair and in the initial state realizes horizontal, upwardly pointing contact surfaces  49  for the second damping elements  20   a ,  20   b . The pivot bolt  10  with its contact surfaces  49 , as in the case of the above-described “C-type” mechanism, is connected in an immobile manner to the base support  14  and can consequently be seen structurally, in any event however functionally, as a component of the base support  14 . 
     In the example shown here, with the backrest support  8  in the initial state, the entrainment means  46  is arranged approximately in a one o&#39;clock position. When the backrest support  8  pivots backward, the entrainment means  46  is moved, for example, into the 12 o&#39;clock position, as shown in  FIG. 26 , and consequently acts upon the “rear” second damping element  20   b  which strikes with its opposite end against the rear contact surface  49  of the abutment  47 . Once again the pivot resistance of the backrest  3  is defined as a result of said “rear” second damping element  20   b . The shorter “front” second damping element  20   a  serves for damping the backrest  3  pivoting forward. 
     As the common pivot axis  25  and the vertical center longitudinal axis  29  of the chair column  5  intersect in the center of the base support  14 , as already described in conjunction with the embodiments described in  FIG. 1 to 7 , also in the case of “A-type” to “D-type” mechanisms, the pivot axis  25 , more precisely the pivot bolt  10 , can serve as a support for a gas spring triggering element, for example in the form of a gas spring height adjustment ring  19 . Said height adjustment ring  19  is realized, for example, in an eccentric manner and is realized for suspending a Bowden cable (not shown) or another pulling means such that when the Bowden cable is pulled, a gas spring pin that is mounted on the top end of the gas spring  5  is depressed and consequently the gas spring  5  is actuated. 
     As a result of a suitable resilient bearing arrangement of the pivot bolt  10  in the base support  14 , for example by means of rubber rings  22  or the like, lateral pivotability of the mechanism  4  can also be realized over and above this in the case of the last described exemplary embodiments. 
     The invention is not restricted to the described exemplary embodiments. Thus, other examples can also realize the inventive core concepts. Thus, for example, the common pivot axis  25  does not necessarily have to be the only pivot axis of the entire mechanism  4 . It is also possible for the mechanism  4  to have further pivot axes so long as at all events the common pivot axis  25  is the only pivot axis that connects the seat support  6  and the backrest support  8  together. The concept of the damping elements  16 ,  20  with different degrees of resilience arranged between individual components of the mechanism  4  can also be transferred to such office chair mechanisms that comprise more than one pivot axis. 
     All the features shown in the description, the following claims and the drawing can be fundamentally inventive both on their own and in arbitrary combinations together. In particular, developments described above in conjunction with a mechanism can also be realized in other mechanisms as a result of corresponding application. 
     LIST OF REFERENCES 
     
         
           1  Office swivel chair, office chair 
           2  Sitting surface 
           3  Backrest 
           4  Support structure, mechanism 
           5  Gas spring, chair column 
           6  Seat base, seat support 
           7  Backrest adapter 
           8  Back base, backrest support 
           9  End face 
           10  Pivot bolt 
           11  Bearing block 
           12  Bearing bush 
           13  Bearing bush 
           14  Gas spring base, base support with tapered receiving means 
           15  Inside lateral surface 
           16  Resilient ring element 
           17  Shoulder 
           18  Flange 
           19  Gas spring height adjustment ring 
           20  Resilient damping element 
           21  Back-locking element 
           22  Rubber ring 
           23  Cheek of the backrest support 
           24  Longitudinal direction of the chair 
           25  Pivot axis 
           26  Bearing bush 
           27  Side wall of the base support 
           28  Side wall of the seat support 
           29  Center longitudinal axis of the chair column 
           30  Blocking element 
           31  Receiving opening 
           32  Receiving opening 
           33  Receiving opening 
           34  Central backrest support element 
           35  Base plate of the base support 
           36  Side wall end 
           37  Front end 
           38  Rear end 
           39  First entrainment means of the seat support 
           40  Receiving chamber of the first damping element 
           41  Front stop surface 
           42  Rear stop surface 
           43  Abutment 
           44  Second entrainment means of the seat support, abutment 
           45  Receiving chamber of the second damping element 
           46  Entrainment means of the backrest support 
           47  Abutment 
           49  Contact face 
           104  Support structure 
           114  Gas spring base