Abstract:
This object is attained in a chair comprising a pedestal; a seat support supported thereon via a chair column, said seat support comprising a front and a rear seat support element being connected with one another via a pivot axis extending substantially horizontally; a seat supported on said seat support elements; a backrest secured on said rear seat support element; a longitudinally adjustable energy storing means for mutually adjusting said backrest and said seat, said energy storing means being joined with said seat support elements at a distance from their pivot axis; a spring abutment being arranged pivotably around said pivot axis for adjustably dampening a pivoting movement of said seat support elements relative to one another; an adjusting element extending substantially tangentially relative to said pivot axis and being pivotable around an adjusting element pivot axis for modifying the bias between said spring abutment and one seat support element; and an actuating twist handle connected with said adjusting element and pivotable around a twist handle pivot axis for manually turning said adjusting element. Said actuating twist handle is connected via a coupling element with said adjusting element for transmitting a turning movement. Said adjusting element pivot axis and said twist handle pivot axis are not flush with one another.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a chair, in particular an office chair.  
           [0003]    2. Background Art  
           [0004]    A chair of the generic type is known from U.S. Pat. No. 5,447,357. It has a seat that is supported on two seat support elements which are pivotable relative to one another. Hard or soft pivotability of the seat support elements relative to one another is determined by a spring abutment, the action of which is modifiable by an adjusting screw. The adjusting screw is extended downwards from the rear seat support element, its outer end being provided with a twist handle. For modification of the action of the spring abutment, a user must get off a chair and operate the twist handle.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to further develop a chair of the generic type in such a way that adjusting the action of the spring abutment is as simple as possible.  
           [0006]    This object is attained in a chair comprising a pedestal; a seat support supported thereon via a chair column, said seat support comprising a front and a rear seat support element being connected with one another via a pivot axis extending substantially horizontally; a seat supported on said seat support elements; a backrest secured on said rear seat support element; a longitudinally adjustable energy storing means for mutually adjusting said backrest and said seat, said energy storing means being joined with said seat support elements at a distance from their pivot axis; a spring abutment being arranged pivotably around said pivot axis for adjustably dampening a pivoting movement of said seat support elements relative to one another; an adjusting element extending substantially tangentially relative to said pivot axis and being pivotable around an adjusting element pivot axis for modifying the bias between said spring abutment and one seat support element; and an actuating twist handle connected with said adjusting element and pivotable around a twist handle pivot axis for manually turning said adjusting element. Said actuating twist handle is connected via a coupling element with said adjusting element for transmitting a turning movement. Said adjusting element pivot axis and said twist handle pivot axis are not flush with one another.  
           [0007]    The gist of the invention resides in that a coupler is provided between the adjusting element and the twist handle, the coupler allowing a turning moment to be transmitted from the twist handle to the adjusting element, there being no need for the axis of rotation of the adjusting element to align with the axis of rotation of the twist handle.  
           [0008]    Additional features and details of the invention will become apparent from the description of an exemplary embodiment taken in conjunction with the drawing.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]    [0009]FIG. 1 is a perspective view of an office chair according to the invention;  
         [0010]    [0010]FIG. 2 is a lateral view of the seat substructure of the office chair according to the invention; and  
         [0011]    [0011]FIG. 3 is a sectional view on the line III-III of FIG. 2. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    An office chair illustrated in FIG. 1 comprises a pedestal  1 , supported via casters  2  on the ground. An adjustable-height chair column  3  which is surrounded by bellows  3   a  is attached to the pedestal  1 . To the upper end of the chair column  3  a seat support  4  is detachably secured, on which an upholstered seat  5  is disposed. A backrest support  6 , which extends substantially upwards and to the upper end of which a backrest  7  is secured, is arranged on the seat support  4 . Height adjustment of the chair column  3  is performed by means of an operating lever  8 . For the purpose of changing the inclination of the backrest  7 , together with the backrest support  6 , while simultaneously changing the inclination of the seat  5 , a further actuating lever  9  is mounted on the seat support  4 . The seat support  4  may be partially or substantially covered optically by a casing  10  arranged on the bottom side of the seat  5 . As can be seen from FIG. 1, the backrest support  6  is coated by bellows  11  for optical reasons.  
         [0013]    The described basic construction of the office chair is generally known. The adjustable-height chair column  3  is known for instance from U.S. Pat. No. 3,711,054 or from U.S. Pat. No. 3,656,593. The construction of the seat support  4 , including the described pivoting possibilities of backrest  7  and seat 5, is known for instance from EP-PS 0 179 185 (corresponding to U.S. Pat. Nos. 4,966,412, 4,662,680 and 4,641,886).  
         [0014]    As can be seen from FIGS. 2 and 3, the seat support  4  is divided. It consists of a front seat support element  12  and a rear seat support element  13 , which have a substantially U-shaped cross section which is open downwards. This results in that they comprise two side walls  14 ,  15  or  16 ,  17 , respectively, which are interconnected by bottoms  18  or  19 , respectively, that faces the seat  5 . The two seat support elements  12 ,  13  are interconnected by a pivot axis  20  that is arranged adjacent to their bottoms  18 ,  19 .  
         [0015]    On the front end of the seat support  4 , a seat holder  21  is arranged to be pivotable about a pivot axis  22 , the seat holder  21  being formed by a profile extending at right angles to the main plane of symmetry of the chair, i.e. at right angles to the plane of the drawing of FIG. 2. On this seat holder  21 , the seat  5  is supported via spacers  23 . The seat  5  is supported on, and secured to, the bottom  19  of the rear seat support element  13  by means of elastic buffers  26 .  
         [0016]    On the rear end of the rear seat support element  13 , i.e. in the region where the backrest support  6  is secured to the rear seat support element  13 , a longitudinally adjustable energy storing device in the form of a longitudinally adjustable gas spring  27  is articulated about a pivot axis  28 , which is parallel to the pivot axes  20  and  22 . The housing  29  of the gas spring  27  faces this pivot axis  28 , a piston rod  30  being extracted from the other end of the gas spring  27 . An actuating pin  31 , by means of which a valve that is located in the gas spring can be actuated for length adjustment, protrudes from the piston rod  30 . By means of a thread the piston rod  30  is connected with an actuating device  32  which includes the actuating lever  9 . This actuating device  32  is supported between the side walls  14 ,  15  of the front seat support element  12  to be pivotable parallel to the pivot axes  20 ,  22 ,  28 . The actuating lever  9  is guided through and out of an oblong hole  33  in the associated side wall  16  of the rear seat support element  13 , this oblong hole  33  being curved in such a manner that its center coincides with the pivot axis  20 . Any length adjustment of the gas spring  27  will result in the front seat support element  12  and the rear seat support element  13  being pivoted relative to each other about the pivot axis  20 , which on the one hand causes the inclination of the seat  5  to be changed and on the other hand the backrest support  6  with the backrest  7  to be pivoted simultaneously. Devices of this type are designated as so-called synchronous mechanisms. If the actuating pin  31  is pushed into the piston rod  30  of the gas spring  27  not just for a short time in order to achieve a change of length of the gas spring  27  and thus a change of the position of the seat  5  and the backrest  7 , but if the actuating pin  31  is pushed into the piston rod  30  for a prolonged time, then the seat  5  together with the backrest  7  can be tilted.  
         [0017]    The construction of the seat support  4  with the seat  5 —as far as it has been described—is known from EP-PS 0 179 185 (corresponding to U.S. Pat. Nos. 4,966,412, 4,662,680 and 4,641,886). The construction and arrangement of the actuating device  32  and of the gas spring  27  are known from EP-OS 0 179 216 (corresponding to U.S. Pat. Nos. 4,966,412, 4,662,680 and 4,641,886).  
         [0018]    A spring abutment  34  of angle-lever-type cross-sectional design is supported to pivot about the pivot axis  20  of the front and rear seat support element  12  or  13 , respectively. An abutment lever  35  extends from the pivot axis  20  backwards, i.e. in the direction towards the backrest support  6 , underneath the bottom  19  of the rear seat support element  13 .  
         [0019]    By means of its external thread  37 , an adjusting screw  36  is arranged in an internal thread  38  on the abutment lever  35  in the vicinity of the free end thereof. The threads  37 ,  38  are not self-locking. The free end of the adjusting screw  36  supports itself on the bottom  19  of the rear seat support element  13 .  
         [0020]    The other abutment lever  39 , which extends approximately vertically of the lever  35  downwards from the pivot axis  20 , bears against a spring  40  formed by a block of elastic material, for example a celled polyurethane elastomer that is commercially available under the designation Vulkocell. The other end of this spring  40  abuts against a stationary, however pivotable abutment  41 , which is formed by a rear wall, located opposite the lever  39 , of the bearing element  46  that is described in detail below. The spring  40  is secured to a pin-like projection  42  of the lever  39  so that it cannot fall out downwardly from the region between the lever  39  and the abutment  41 .  
         [0021]    If—as is shown in FIG. 2—the external thread  37  of the adjusting screw  36  is completely screwed through the internal thread  38  of the spring abutment  34 , the abutment lever  39  is in its position next to the abutment  41 , i.e. the spring  40  is biased most strongly. Once again it is emphasized that the abutment  41  is arranged within the front seat support element  12 .  
         [0022]    If, with the gas spring  27  unlocked, the backrest  6  is pivoted backwards, the portions located below the pivot axis  20  of the front and the rear seat support elements  12  or  13 , respectively, are pivoted towards each other, i.e. the spring  40  is compressed more strongly while this backward pivoting movement of the backrest  7  is progressively damped. This counterforce of the spring  40  thus progressively counteracts the backward pivoting motion of the backrest  7 . When the backrest  7  is relieved, its pivoting forward is assisted by a corresponding release of the spring  40 , this assisting force diminishing while the backrest  7  pivots forward.  
         [0023]    If the adjusting screw  36  is screwed downwardly out of the abutment lever  35  so far that its pilot end  43  is approximately flush with the lever  35 , the spring  40  cannot be effective throughout possible range of pivoting of the front and the rear seat support element  12 ,  13  i.e., it is not compressed between the abutment  41  and the abutment lever  39  while producing a corresponding counterforce.  
         [0024]    In any intermediate positions of the adjusting screw  36 , the spring  40  is engaged in case of correspondingly varying pivoting positions of the rear seat support element  13  in relation to the front seat support element  12 , i.e. in the case of varying backward inclinations of the backrest  7  and thus of the seat  5 . In addition, in these intermediate positions, at first only an edge  44  of the block-like spring  40  rests on the abutment  41 , this contact being steadily increased by any further pivoting motion until it reaches full-face rest on the abutment  41 . This gives also rise to a certain progression in spring action being achieved.  
         [0025]    For the spring abutment  34  to be inherently resistant to bending, the levers  35 ,  39  are reinforced by one or several intermediate webs  24 . In order to prevent the adjusting screw  36  from being inadvertently screwed out of the internal thread  38 , its external thread is slit and pinched in usual manner in the vicinity of its end  43 . In order to permit easy operation of the adjusting screw  36 , it is provided with a twist handle  25  on its end protruding laterally out of the seat support  4 . The adjusting screw  36  is displaced in relation to the gas spring  27 . The gas springs  27  are commercially available and are generally known with regard to construction and mode of operation for instance from DE-PS 18 12 282 (corresponding to U.S. Pat. No. 3,656,593).  
         [0026]    For additional adjustment of inclination of the entire seat  5  by the synchronous mechanism, the front seat support element  12  is articulated to the upper end, forming a bearing cone  45 , of the chair column  3  via a bearing element designated as  46  in its entirety. The bearing element  46  of aluminum diecasting is seated by an internally cone-shaped bearing block  47  on the bearing cone  45  of the chair column  3 . The bearing block  47  is fastened in a longitudinally oriented rectangular tube  48 , which, on its side located downstream of the bearing block  47 , supports an articular axis  49  in the form of a simple screw and nut that is parallel to the pivot axis  20 . The front seat support element  12  is articulated to this articular axis  49 .  
         [0027]    For arrest of the seat  5  in a certain inclined position, the front seat support element  12  is provided with a rack detent arrangement  49   a , which is disposed before the bearing block  47 , acting between the front seat support element  12  and the bearing element  46 . The exact design of the rack detent arrangement  49   a  is described in EP 1 169 947 A1 (corresponding to US 2002/0003367 A1), to the specification of which reference is made. It is also possible to embody the detent arrangement as an arrangement of lamellar packs, as known from U.S. Pat. No. 5,447,357.  
         [0028]    The following is a detailed description of the structure of the spring abutment  34 . The adjusting screw  36  is throughout provided with the external thread  37 . Starting from the bottom  19 , the adjusting screw  36  reaches as far as to where the lower edge  50  of the internal thread  38  extends when the spring abutment  34  is in its outward pivoted position. The external thread  37  may also be slightly longer. The lower end  51  of the adjusting screw  36  is located within the rear seat support element  13 . The adjusting screw  36  takes the function of a regulating element which, as explained above, modifies the pre-load between the spring abutment  34  and the seat support element  12 . The adjusting screw  36  is rotatable about an axis of rotation  52 . The twist handle  25 , which is rotatable about an axis of rotation  53 , is non-rotatably connected to the adjusting screw  36  by way of a spring shaft  54  in the form of a coupler. The spring shaft  54  may be a flexible shaft of the type of a helical spring suitable for torque transmission. It is also conceivable to use two rigid shaft segments that are interconnected by a universal joint in the place of the spring shaft  54 . To this end, the adjusting screw  36  comprises a centric blind hole  55 , which is open downwards and in which an end of the spring shaft  54  is fixed against rotation.  
         [0029]    For the twist handle  25  to be mounted on the seat support element  13 , a rectangular recess  56 , which is open downwards, is provided in the side wall  16 . A bearing sleeve  57  is fixed to the edge of the recess  56  and projects outwards. In the side wall  16  region, the bearing sleeve  57  on the three sides of a rectangular facing the side wall  16  a circumferential groove  58  into which the side wall  16  engages. In this way, the bearing sleeve  57  is fixed along the pivot axis  53 , perpendicularly upward from it and horizontally interlocking. Above the recess  56 , a bore  59  is provided in the side wall  16 . A plate  60  being connected with the bearing sleeve  57  and extending upward from it at the inner side of the side wall  16  comprises a locking heel  61  projecting outward and being in a locking engagement with the bore  59  while also fixing the bearing sleeve  57  relative to the seat support element  13  against a downward pulling force. The bearing sleeve  57  comprises a portion  62  conically tapering from the side wall  15  to the outside and an adjacent annular cylindrical portion  63  having a substantially constant diameter. The twist handle  25  is hollow and closed at its end side by a lid  64  locked thereon. In the side of the twist handle  25  facing the side wall  16 , a projecting pin  65  is provided which comprises at its free end a radially outward projecting locking edge  66 . The pin  65  is turnably positioned in the portion  63  wherein the locking edges  66  come into an interlocking engagement with corresponding projections  67  formed on the inner side of the portion  63  to prevent the twist handle  25  from being pulled off to the outside. In the pin  65 , a pocket bore  68  is provided in which the outer end  69  of the spring shaft  54  is fixed to prevent its rotation. The axis of rotation  53  extends substantially perpendicular to the axis of rotation  52 . However, it is also possible to have the twist handle  25  project laterally from the seat support element  13  at a different angle. In any case, the axis of rotation  53  is not flush with the axis of rotation  52 . In the most simple case, the recess  56  is provided centrally below the adjusting screw  36  so that the spring shaft is deviated by only 90°. Other requirements such as ease of use which specify that the twist handle  25  is to be arranged at another longitudinal position beneath the seat  5  may necessitate an offset of the recess  56  from the adjusting screw  36 . In this case, the flexible spring shaft  54  is able to manage the offset as well as the deviation of the turning movement from the horizontal to the vertical direction. By twisting the twist handle  25 , the adjusting screw  36  is turned so that the position of the spring abutment  34  changes. As described in detail above, this modifies the hardness of a pivoting movement of the backrest  7  relative to the seat  5 .  
         [0030]    The particular advantage of having the twist handle  25  project laterally outward is that the adjustment of the adjusting screw  36  can be performed more comfortably. In particular, such adjustment can be performed when a person is sitting on the chair. This is especially advantageous as the person, while modifying the hardness, is able to carry out pivoting movements with the chair.