Abstract:
A synchronizing mechanism for a correlated seat/backrest movement of an office chair has a base carrier, which can be placed on a chair column, a seat carrier and a backrest carrier. In order to provide a synchronizing mechanism in which there is no need to adjust a spring force in order to change the “pivoting resistance” of the backrest, the backrest carrier, which can be pivoted about a transverse spindle, is connected on the one hand to the base carrier, via a first link, and on the other hand to the seat carrier, via a second link, such that a pivoting movement of the backrest in the rearward direction induces a raising movement of the rear region of the seat carrier, and that the seat carrier is connected to the base carrier such that a raising movement of the forward region of the seat carrier takes place at the same time. A basic idea of the invention is that the user of the office chair “raises” itself upwards by subjecting the backrest itself to loading.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation, under 35 U.S.C. § 120, of copending international application No. PCT/EP2006/005952, filed Jun. 21, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. DE 10 2005 029 906.7, filed Jun. 26, 2005; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a synchronizing mechanism for a correlated seat/backrest movement of an office chair, having a base carrier, which can be placed on a chair column, a seat carrier and a backrest carrier. 
         [0003]    The term “synchronizing mechanism” is intended to be understood as relating to assemblies in the seat substructure of an office chair which ensure the coupled kinematics which result in a certain movement of the seatrest and backrest relative to one another. The office-chair seat, which is usually provided with an upholstered seat surface, is mounted on the seat carrier. The backrest carrier, which commonly extends rearwards from the actual synchronizing mechanism, bears the backrest of the office chair on an upwardly running extension arm. The seat carrier and backrest carrier are usually coupled in an articulated manner such that a pivoting movement of the backrest in the rearward direction—as may be brought about, for example, by the chair user leaning against the backrest—induces a lowering movement of the rear edge of the seat in the downward direction. 
         [0004]    In order to change the “pivoting resistance” of the backrest, such synchronizing mechanisms usually have a spring arrangement for prestressing the synchronizing mechanism. The level of prestressing here depends, inter alia, on the weight of the user of the chair. 
         [0005]    German published, non-prosecuted patent application (Offenlegungs-schrift) No. 20 26 929 discloses a chair with an automatically adapting backrest, where the rear part of the seat panel rises up when the user leans against the backrest and thus pivots the latter in the rearward direction. This is achieved by a handle-design lever end of the backrest carrier butting constantly against the underside of the seat panel. In the case of the seat panel being lowered, the backrest moves forward. If the user leans against the backrest, the rear part of the seat is raised. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a synchronizing mechanism in which there is no need to adjust a spring force in order to change the “pivoting resistance” of the backrest. 
         [0007]    With this and other objects in view there is provided, in accordance with the invention, a synchronizing mechanism for a correlated seat/backrest movement of a chair, comprising: 
         [0008]    a base carrier configured for placement on a chair support, such as a column; 
         [0009]    a seat carrier having a rear region and a forward region; 
         [0010]    a backrest carrier pivotally mounted about a transverse axis; 
         [0011]    a first link connecting the backrest carrier to the base carrier and a second link connecting the backrest carrier to the seat carrier, such that a pivoting movement of the backrest carrier in a rearward direction induces a raising movement of the rear region of the seat carrier, and wherein the seat carrier is connected to the base carrier such that a raising movement of the forward region of the seat carrier takes place at the same time. 
         [0012]    In other words, the object is achieved in that the backrest carrier, which can be pivoted about a transverse spindle, is connected on the one hand to the base carrier, via a first link, and on the other hand to the seat carrier, via a second link, such that a pivoting movement of the backrest in the rearward direction induces a raising movement of the rear region of the seat carrier. At the same time, the seat carrier is connected to the base carrier such that a raising movement of the forward region of the seat carrier takes place. 
         [0013]    A basic concept of the invention is that the user of the office chair “raises” himself upwards by subjecting the backrest itself to loading. In other words, by pushing back the backrest, upon actuation of the synchronizing mechanism, the user works against his own weight resting on the seat. The desired “pivoting resistance” is thus established in a quasi-automatic manner on account of the weight of the user. There is no need for any prior-art spring-force adjusting means with high-outlay adjusting mechanisms (worm gear mechanisms, gearwheels, threaded rods, etc.). This considerably reduces the production costs of the synchronizing mechanism. At the same time, the fail-safe properties of the mechanism increase. 
         [0014]    Since the seat carrier is raised not just in its rear region, but, at the same time, also in its forward region, the seat is carried along synchronously rearwards and upwards to a defined extent in relation to the backrest. 
         [0015]    It is particularly advantageous if the base carrier is connected to the front end region of the seat carrier via a linear guide. In this case, the seat moves synchronously with the backrest in linear fashion. In addition to guides with rectilinear guideways, other guideways are, of course, also possible. The synchronous movement of the seat carrier can be adapted individually by way of the configuration of the guide and of the position of the guide (for example the angle of inclination of the guide in relation to the horizontal), etc. It is thus, for example, possible for the seat carrier to be moved synchronously with the backrest in absolutely linear fashion without any “tilting” at all. However, “tilting” is also possible by way of a corresponding configuration of the guide. Further variants can be achieved by the connecting point between the base carrier and seat carrier being more or less remote from the front seat edge. 
         [0016]    The lever geometry which is necessary for the “self-adjusting” mechanism of the present invention is achieved by the arrangement and configuration of the two links, it being the case that preferably the first link is provided with a pivot bearing, for producing a pivoting connection to the base carrier, and that the one link end is connected in an articulated manner to the seat carrier and the opposite link end is connected in an articulated manner to the backrest carrier. The movement of the seat carrier and backrest carrier relative to one another is thus defined by the position of the, in total, four hinge pins which run through the ends of the two links. At the same time, the displacement of the seat carrier in relation to the base carrier is defined, on the one hand, by the linear guide in the forward region of the seat carrier and, on the other hand, by the position and functioning of the pivot bearing on the first link. 
         [0017]    It is quite particularly advantageous if the first link and/or the second link are/is covered in the outward direction by a part of the backrest carrier and/or a part of the seat carrier. Such a concealed arrangement “in the interior” of the synchronizing mechanism makes it possible to prevent soiling and damage to the pivoting mechanism. 
         [0018]    In comparison with the solutions which are known from the prior art, the invention presents a pivoting mechanism which is of comparatively straightforward design and considerably reduces the “shirt-pulling effect.” In other words, a particularly high level of comfort is achieved without use having to be made of relatively high-outlay and expensive solutions. 
         [0019]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0020]    Although the invention is illustrated and described herein as embodied in synchronizing mechanism, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0021]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0022]      FIG. 1  is a rear perspective view of a synchronizing mechanism according to the invention; 
           [0023]      FIG. 2  is a side view of the synchronizing mechanism in the basic position; and 
           [0024]      FIG. 3  is a side view of the synchronizing mechanism in a rearwardly pivoted position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    All the figures show the synchronizing mechanism merely schematically with the constituent parts that are primarily important to the invention. 
         [0026]    Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, the synchronizing mechanism has a base carrier  1  which is positioned, by way of a cone mount  2  (i.e., a conical receiver), on the top end of a non-illustrated chair support, such as a column. The synchronizing mechanism also comprises a substantially frame-like seat carrier  3  and a backrest carrier  4 . The backrest carrier  4  is fork-shaped in plan view and its the side pieces  5 ,  6  are arranged on either side of the base carrier  1 . The seat carrier  3  is provided in order for a preferably upholstered seat surface to be accommodated or mounted thereon. The mounting takes place in a conventional manner with the aid of fastening elements. Similarly, a backrest, which is also not illustrated in an effort to maintain a clear and simple disclosure and which in the case of modern office chairs is height-adjustable, is seated on the backrest carrier  4 . The backrest may also be connected integrally to the backrest carrier  4 . 
         [0027]    As can be seen from the figures, the entire synchronizing mechanism is constructed in a mirror-symmetrical manner in relation to the center longitudinal plane M, as far as the actual kinematics are concerned. To this extent, it is always assumed, in the following description, that the structural elements of the actual pivoting mechanism are provided in pairs, on both sides. 
         [0028]      FIGS. 1 and 2  show the basic position, in which the backrest carrier  4  assumes an essentially perpendicular position.  FIG. 3  shows the synchronizing mechanism in a rearwardly pivoted position. In this regard, relative terms such as “rearward” and “forward” relate to a regularly functional position of the chair. 
         [0029]    The backrest carrier  4 , which can be pivoted in the pivoting direction S about a transverse spindle, is connected to the base carrier  1  via a first link  7 . The first link  7  here is provided with a pivot bearing  8 , for producing a pivoting connection to the base carrier  1 . The link  7  is articulated, with the aid of a bearing pin  9 , on a side leg  11  of the base carrier  1 , this side leg extending in the direction of the rear seat edge  10 . The one free end  12  of the first link  7  is connected in an articulated manner, via an articulation  13 , to a side arm  14  of the seat carrier  3 , this side arm extending in the direction of the rear seat edge  10 . The opposite free end  15  of the link  7  is connected in an articulated manner, via an articulation  16 , to a side piece  5 ,  6  of the backrest carrier  4 , this side piece extending in the direction of the front seat edge  17 . The side arm  14  of the seat carrier  3  here runs parallel to the side leg  11  of the base part  1  and to the side piece  5 ,  6  of the backrest carrier  4 . Whereas, however, the side arm  14  and side piece  5 ,  6  are arranged essentially in alignment, the side leg  11  is offset in the direction of the center M of the chair in relation to the side arm  14 . The first link  7  thus runs between the side leg  11  of the base carrier  1 , on the one hand, and the side arm  14  of the seat carrier  3  or the side piece  5 ,  6  of the backrest carrier  4 , on the other hand. 
         [0030]    The first hinge pin  18 , which is defined by the bottom end  15  of the link  7  being articulated on the backrest carrier  4 , is arranged, as seen in the longitudinal direction  19  of the chair, behind the second hinge pin  20 , which is defined by the top end  12  of the link  7  being articulated on the seat carrier  3 . The angle α of the first link  7  in relation to the horizontal in the basic position is approximately 5°. It is also the case that, in a position in which the synchronizing mechanism is pivoted rearwards to the maximum extent, there is no change in this order in which the hinge pins  18 ,  20  are arranged. In the rearwardly pivoted position, as is illustrated in  FIG. 3 , the first link  7  likewise slopes forwards, although in this case it encloses an angle β of approximately 12° with the vertical. In addition, the first hinge pin  18  always runs beneath the second hinge pin  20 , as seen in the vertical direction. 
         [0031]    The pivot bearing  8  is arranged outside the center of the link, that is to say it is offset slightly in the direction of the second hinge pin  20 . The pivot spindle  21 , which runs through the pivot bearing  8 , runs parallel to the two hinge pins  18 ,  20 . In accordance with the course taken by the hinge pin  18 , the two bottom ends  15  of the two first links  7  of the synchronizing mechanism are connected by a retaining spindle  22 , of which the ends, designed as bearing pins, serve for forming the articulations  16 . At the same time, this ensures defined pivoting of the first link  7  and avoids tilting of the link  7 . 
         [0032]    It should be mentioned here once again that two of each of the components of the pivoting mechanism are provided. However, for example  FIG. 1  illustrates only the first link  7  which is arranged on the right-hand side  23  of the seat, while the first link which is present on the left-hand side  24  of the seat is concealed by the side piece  6  of the backrest carrier  4 . 
         [0033]    Furthermore, the backrest carrier  4  is connected to the seat carrier  3  via a second link  25 . The first link  7  is slightly longer than the second link  25 . The length ratio between the (rear) first link  7  and the (front) second link  25  is approximately 1.07:1. The one free end  26  of the second link  25  here is connected in an articulated manner, in turn via an articulation  27 , to the side arm  14  of the seat carrier  3  and the opposite free end  28  of the link  25  is connected in an articulated manner, via an articulation  29 , to the side piece  5 ,  6  of the backrest carrier  4 . The third hinge pin  30 , which is defined by the bottom end  28  of the second link  25  being articulated on the backrest carrier  4 , is arranged, as seen in the longitudinal direction  19  of the chair, behind the fourth hinge pin  31 , which is defined by the top end  26  of the link  25  being articulated on the seat carrier  3 . This means that it is also the case that the second link  25 , in the basic position of the synchronizing mechanism, slopes up from the rear at the bottom to the front at the top, cf.  FIG. 2 . In this case, the angle γ of the second link  25  to the horizontal is approximately 52°. In the rearwardly pivoted position, as is illustrated in  FIG. 3 , the second link  25 , however, slopes rearwards, namely at an angle δ of approximately 24° to the vertical, whereas the first link  7  still slopes forwards. In other words, in this position, the fourth hinge pin  31  has been displaced behind the position of the third hinge pin  30 , that is to say it has been displaced further in the direction of the rear chair edge  10 . 
         [0034]    The vertical arrangement of the hinge pins  30 ,  31  of the second link  25  corresponds, in principle, to the vertical arrangement of the hinge pins  18 ,  20  in the case of the first link  7 . Accordingly, the third hinge pin  30  always runs beneath the fourth hinge pin  31 , as seen in the vertical direction. 
         [0035]    The vertical arrangement of the four hinge pins  18 ,  20 ,  30 ,  31  of the first and second links  7 ,  25  is as follows: the second and fourth hinge pins  20 ,  31  are essentially level both in the basic position and in the pivoted position. The pivot spindle  21  of the first link  7  always runs between the height of the second and fourth hinge pins  20 ,  31  and the height of the first and third hinge pins  18 ,  30 . The first hinge pin  18  is located, in the basic position, between the pivot spindle  21  and the third hinge pin  30  and, in the pivoted position, beneath the fourth hinge pin  31 . 
         [0036]    The pivoting mechanism described ensures that it is possible to pivot the backrest carrier  4  with the backrest in the pivoting direction S about a pivot spindle. At the same time, the pivoting movement S of the backrest in the rearward direction induces a raising movement H 1  of the rear region  32  of the seat carrier  3 , cf.  FIG. 3 . In the case of the backrest being pivoted downwards in the rearward direction, in other words, the seat carrier  3  is displaced rearwards and upwards, while the base carrier  1  remains fixed in position by way of the pivot bearing  8 . 
         [0037]    In the region of the first and second links  7 ,  25 , the side piece  5 ,  6  of the backrest carrier  4  and the side arm  14  of the seat carrier  3  meeting in this region, the bottom edge of the side arm  14 , this edge running from the rear at the top to the front at the bottom, rests on the similarly running top edge  34  of the side piece  5 ,  6  in a defined contact region and thus secures the basic position of the synchronizing mechanism. The slope is followed in the rearward direction by a region in which the essentially vertically running free end  35  of the side arm  14  and the correspondingly formed end surface  36  of the side piece  5 ,  6  are located opposite one another. This arrangement forms a closed covering by means of which the lever structure located behind the same is protected against soiling. A straightforward additional covering, for example in the form of the side pieces  5 ,  6  of the backrest carrier  4  being extended upwards, may additionally make it possible for access through to the pivoting mechanism to be reliably ruled out even in the pivoted state. This allows a high level of safety for handling the office chair. 
         [0038]    At the same time, the seat carrier  3  is connected to the base carrier  1  such that pivoting of the backrest carrier  4  results in a raising movement H 2  of the forward region  37  of the seat carrier  3 . In the exemplary embodiment, the synchronizing mechanism is configured such that the rear region  32  of the seat carrier  3  is raised somewhat more than the forward region  37  of the seat carrier  3  (H 1 &gt;H 2 ), in which case the essentially planar position of the seat carrier  3  in the basic position changes into a slightly forwardly inclined position of the seat carrier  3  in the pivoted position. This avoids the situation where the seat carrier undesirably cuts into, or presses on, the underside of the thighs during pivoting. In the pivoted position, the backrest carrier  4  has been pivoted through a pivoting angle ε of approximately 24° in relation to the base carrier  1 , while the seat carrier  3  is raised more or less parallel. In the exemplary embodiment (H 1 &gt;H 2 ), the rear region  32  of the seat carrier  3  is raised by an angle φ of approximately 2° in relation to the forward region  37  of the seat carrier  3 . 
         [0039]    The base carrier  1  is connected to the seat carrier  3  via a linear guide in the manner of a slot-like guideway  38  arranged in the forward region  37  of the seat carrier  3 . The base carrier  1  has two laterally arranged rockers (not illustrated) running in the direction of the front seat edge  17 . These rockers are connected to one another via a bearing spindle. The bearing spindle is arranged parallel to the hinge pins  18 ,  20 ,  30 ,  31 , the pivot spindle  21  and the retaining spindle  22 . The two ends of the bearing spindle, which are in the form of bearing pins  39 , are each positioned in the guideway  38 , which serves as a linear sliding guide, from the inside. The guideway  38  is formed in a side element  40  of the seat carrier  3 , this side element extending in the direction of the front seat edge  17 . The guideway  38  here slopes from the front at the bottom to the rear at the top and, in the pivoted position, encloses an angle θ of approximately 42° with the horizontal (basic position approximately 40°). In the basic position of the synchronizing mechanism, the ends  39  of the bearing spindle butt against the top stop of the guideway  38 . The bearing spindle is then located approximately level with the second and fourth hinge pins  20 ,  31 . During pivoting, the raising of the seat carrier  3  results in the bearing spindle being displaced in the direction of the opposite, bottom end of the guideway  38 . The bearing spindle is then located approximately level with the pivot spindle  21 . 
         [0040]    This design means that it is not just the rear region  32  of the seat carrier  3  which executes a raising movement H 1  when the backrest is subjected to loading and the backrest carrier  4  executes a pivoting movement downwards and rearwards in the pivoting direction S. The forward region  37  of the seat carrier  3  is also raised linearly in a synchronous manner (raising movement H 2 ). In other words, the front and the rear ends of the seat surface are lifted simultaneously. The entire seat is raised. 
         [0041]    The synchronizing mechanism further comprises a spring element which is arranged essentially horizontally in the seat carrier  3  in the basic position and is in the form of a tension spring  41  which is connected, on the one hand, to the bearing spindle of the base carrier  1  and, on the other hand, to a further transversely located retaining spindle  42  on the seat carrier  3 . The tension spring  41  has its front end fitted on the bearing spindle and its rear end fitted on the retaining spindle  42 . The tension spring is prestressed in the direction of the basic position of the synchronizing mechanism. In the basic position, the retaining spindle  42 , which is arranged between the side legs  11  of the base carrier  1 , is located approximately level with the bearing spindle and the second and fourth hinge pins  20 ,  31 . In the pivoted position, the retaining spindle  42  is carried along rearwards and upwards with the seat carrier  3  and is then likewise located approximately level with the second and fourth hinge pins  20 ,  31 . The spacing between the bearing spindle and retaining spindle  42  increases here and the tension spring  41 , which then slopes up in the rearward direction, is subjected to further stressing. This spring stressing assists the backrest in being returned from the pivoted position into the basic position. Instead of a single tension spring  41  it is also possible, depending on the envisaged loading of the chair, to use a plurality of tension springs in parallel or other spring elements. A mechanism which is not explained specifically, but can be operated with the aid of an actuating lever (not depicted), is provided in order to secure the backrest inclination.