Abstract:
An article of furniture for sitting has a seat element, a back, a support frame having a support and a mechanical structure for transmitting a movement, which connects the support in a rear seat region with the seat element, at least one spring element displacing the seat element in an abutment or return position, the spring element being formed as a front mounting for the seat element and supported on the support which is stationary, the spring element in addition to known restoring function also determining a guidance of the seat element in its front region.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to articles of furniture, and in particular to an article of furniture for sitting.  
           [0002]    The German patent document DE 196 07 136 A1 discloses a chair with a so-called synchronizing mechanical system. The synchronizing mechanical system is used for backing in the chair and, in addition to a tilting movement of the back rearwardly, provides the lowering of the seat element in a rear seating region which is close to the back and lifting the seating element in a front seat region which is remove from the back. Therefore the sitting person during backing has the feeling of sliding into the chair and not the filling of sliding from the chair. With a spring element which acts on a suspension arranged in the front seat region on the seat element, the seat element is adjusted in an initial position. Against the force which must hold the seat element in the back in the initial position, the sitting person must apply a force against the back and against the spring element for reaching a back tilting of the chair or a change in angular position of the seat element. A movement of the seat element is possible substantially only by loading or unloading of the back. The front region of the seat element is in a fixed predetermined position when the back is unloaded. The movements of the seat element are provided by levers and/or guides. It is believed to be advisable to further improve the existing chairs.  
         SUMMARY OF THE INVENTION  
         [0003]    Accordingly, it is an object of present invention to provide an article of furniture for sitting which avoids the disadvantages of the prior art.  
           [0004]    More particularly, it is an object of the present invention to provide an article of furniture for sitting which in addition to the comfort provided by the synchronizing mechanical system provides further comfort properties in the region of the seat element and a simplified construction of the synchronizing mechanical system.  
           [0005]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an article of furniture for sitting, comprising a seat element; a back; a support frame having a support and a mechanical means for transmitting a movement, which connects said support in a rear seat region with said seat element; at least one spring element displacing said seat element in an abutment or return position, said spring element being formed as a front mounting means for said seat element and supported on said support which is stationary, said spring element in addition to known restoring function also determining a guidance of said seat element in its front region.  
           [0006]    The article of furniture for sitting in accordance with the present invention has front mounting means for the seat element which is formed as a spring element supported on a stationary support part, wherein the spring element takes over, in addition to the known restoring function, also the guidance of the seat element in its front region. Thereby the components which are required for holding and guiding the spring element as disclosed in the German patent document DE 196 07 136 A1 in the chair with a synchronizing mechanical system are no longer necessary to guide the force of the spring and to control a part of the movement course of the seat element.  
           [0007]    Furthermore such a double function or double functions of the spring increase the comfort or the suitability of the chair for persons with any size and any body weight. This results from the fact that the opening angle between the seat element and the back due to the construction of the inventive spring element is no longer determinable alone by the size of the force against the back and thereby the inclination of the chair. An increase of the opening angle between the seat element and the back which often is desired for heavier persons with a greater body volume can be adjusted now substantially automatically in that the person with a greater body weight and a greater body volume applies a greater force to the spring element and in contrast to the known spring element in the German patent document DE 196 07 136 A1 it has the freedom to deviate in a substantially perpendicular direction. Thereby the seat element is tilted forwardly or sinks in a forward region and obtains independently from the position unloading of the back an increase opening angle between the back and the seat element. In addition to this comfort for the person with a greater body weight and a greater body volume, a further advantage is provided for a person which sits in the front region of the seat element. Such a sitting position is often assumed by persons who operate at a computer. In such a working position it has been found as advantageous when the seat surface is inclined slightly forwardly. This orientation of the seating means is also provided by the additional freedom of the inventive spring element. The person which is loaded in such a seat position of the seat element presses with a small body weight the center of gravity of the body located in this position substantially over the front edge of the seat element the spring element downwardly, so that it adjusts the desired inclination of the seat element forwardly. This position of the seat element facilitates and favors a favorable body hold from the medical point of view, in which the pelvis of the sitting person is tilted forwardly.  
           [0008]    In accordance with another advantageous embodiment of the invention, the spring element is formed as a leaf spring which extends and is bent preferably in a seat direction. A leaf spring, in other words an individual leaf spring or a leaf spring pack satisfies the requirements of the spring element in an ideal fashion, since the bent leaf spring applies passing forces in the both required directions. On the one hand the leaf spring acts upwradly. Thereby the seat element is lifted or held in the front region. On the other hand the leaf spring acts forwardly in seat direction. Thereby the seat element is loaded with a force forwardly and thereby acts for lowering of the rear seat region. Thereby the leaf spring holds the seat element and with it also the back directly or indirectly connected to it, in a front abutment or at a storing position. A backing in the chair leads depending on the shape or bending of the leaf spring, in addition to a sinking of the rear seat region, to a lifting of the front seat region or to a retention of the front seat region at a certain height.  
           [0009]    An adjustability of the spring element allows the maintaining the seat element optimal to the requirements or desires of the sitting person. In particular a small, light person can increase the opening angle between the seat means and the back without tilting back. Simultaneously through the adjustment of the force of the spring element, also the tilting ability or tilting conditions of the chair can be influenced.  
           [0010]    In accordance with another special embodiment of the invention, the spring force of the leaf spring can be varied by displacement of the spring abutment point and/or a change of the distance between the individual spring sheets. These adjustments can be realized by an specially simple and therefore cost-favorable adjusting mechanism.  
           [0011]    Furthermore, it is advantageous when the spring element is formed as helical springs and/or rubber elements, and/or rubber-metallic elements, and/or hydraulic cushions and/or pneumatic cushions, or a combination of these elements. These spring elements provide an adaptation to different requirements and mounting possibilities.  
           [0012]    It is especially advantageous when the invention is utilized in a chair with a back, which is connected through a back support with the means for movement transmission. With this arrangement a chair completely maintain a comfort, which goes beyond the comfort of the chair of the prior art.  
           [0013]    It is further proposed to provide the chair with the inventive comfort function in which the back is directly connected to the seat element. Thereby a mechanically simple and cost-favorable chair is formed with a high comfort. In a transition region from the seat element to the back, of an elastic chair an article of furniture for sitting is formed which despite its simple construction provides the comfort of the above described chairs.  
           [0014]    With the use of a seat element which is composed of a base plate and a support displaceably arranged on it, it is possible to adapt the chair in the sitting region optimally to the required supporting surface for the hip of the person sitting on the chair. Thereby the suitability of the chair for persons of different body sizes and body weights is increased.  
           [0015]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, 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 DRAWINGS  
       [0016]    [0016]FIG. 1 is a side view of office chair in accordance with a first embodiment of the present invention in a forward abutment position;  
         [0017]    [0017]FIG. 2 is a side view of the office chair shown in FIG. 1 in the rear abutment position;  
         [0018]    [0018]FIG. 3 is a plan view of the office chair in accordance with the present invention shown in FIG. 1;  
         [0019]    [0019]FIG. 4 is a side view of an office chair in accordance with a second embodiment of the present invention in a front abutment position;  
         [0020]    [0020]FIG. 5 is a side view of the inventive office chair shown in FIG. 4 in the rear abutment position;  
         [0021]    [0021]FIG. 6 is a plan view of the inventive office chair of the embodiment of FIG. 4;  
         [0022]    [0022]FIG. 7 is a side view of an office chair in accordance with a third embodiment of the present invention, in a front abutment position;  
         [0023]    [0023]FIG. 8 is a side view of the inventive office chair of FIG. 7 in the rear abutment position;  
         [0024]    [0024]FIG. 9 is a plan view of the inventive office chair shown in FIG. 7;  
         [0025]    [0025]FIG. 10 is a side view of an office chair in accordance with a fourth embodiment of the present invention in the front abutment position;  
         [0026]    [0026]FIG. 11 is a side view of the inventive office chair of FIG. 10 in the front abutment position;  
         [0027]    [0027]FIG. 12 is a plan view of the inventive office chair of FIG. 10;  
         [0028]    [0028]FIG. 13 is a side view of an office chair in accordance with a fifth embodiment of the present invention in the front abutment position;  
         [0029]    [0029]FIG. 14 is a side view of the inventive office chair of FIG. 18 in the rear abutment position;  
         [0030]    [0030]FIG. 15 is a plan view of the inventive office chair of FIG. 13;  
         [0031]    [0031]FIG. 16 is a side view of an office chair in accordance with the a sixth embodiment of the present invention in the forward abutment position;  
         [0032]    [0032]FIG. 17 is a side view of the inventive office chair of FIG. 13 and the rear abutment position; and  
         [0033]    [0033]FIG. 18 is a plan view of the inventive office chair of FIG. 16.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    [0034]FIG. 1 shows a side view of an article of furniture for sitting  1  which is formed as an office chair  2 . The office chair  2  substantially has a rotary frame  3  with rollers  4 , which is connected through an axle  5  with a supporting part  6  in a vertically adjustable and rotatable manner. It also has a seat element  7  mounted on the supporting part  6  and a back  9  which is connected with support part  6  through a back support  8 .  
         [0035]    The support part  6  is composed of a rigid support  10  which receives the axle  5 , means  11  for transmission of a movement which are formed as levers  12 , and a front mounting means  14  which is formed as a spring element  15 . The seat element  7  is composed of a support member  16  and a base plate  17 . The support member  16  is displaceable relative to the base plate  17  in a seat direction A between a first position P and a second position P′, and is arrestable. Due to such a displacement, the supporting surface for the hip of a person who sits on the office chair  2  is individually adujustable.  
         [0036]    Forward flange means  19 ,  20  are arranged in a front seat region  18  on the seat element  7  or on the base plate  17 , and rear flange means  22 ,  23 , are arranged in a rear seat region  21  of the same, as shown in FIG. 3. The first flange means  19 ,  20  receive each a spring element  15 , wherein the spring elements  15  are formed as leaf springs  24 ,  25 . The leaf springs  24 ,  25  act as springy jibs, so that the seat element  7  is rotatably hinged on their free ends through the front flange means  19 ,  20 .  
         [0037]    In FIG. 1 the office chair  2  is shown in an upright or front abutment position I, which it assumes in a condition in which it is not loaded with a person or in other words it is unloaded. In this front abutment position I the spring element  15  lifts due to a vertically acting force F z  in the arrow direction Z of the seat element  7  at a height H. Furthermore, a horizontal force F x  of the spring element  15  pulls the seat element  7  in arrow direction x to the position I shown in FIG. 1. The spring force acts through the rear flange means  22 ,  23  also on the lever  12  and the back support  8  which are connected to the support  10  turnably about an axis  26 . Through the lever  12  a circular path K is defined, over which an axle  27  connecting the rear flange means  22 ,  23  with the levers  12  or the back support  8  can move.  
         [0038]    By loading of the office chair  2  with the force F s  by a person sitting on the office chair  2  the seat element  7  turns by the portion of the force F s  acting in the front seating region, substantially against the clockwise direction around the bearing point  27  until the portion of the force F s  is compensated by the force F z  of the spring element  15  acting opposite to it. The portion of the force F s  acting in the rear seat region is taken for the lever  12 , the support part  10 , the axle  5  and the rotary frame or a pulling force by the spring element  12  acts through the lever  12  which is compensated by this force component F s . Therefore depending on the acting forces F s  and F z  an inclined position of the seat element  7  results for example in an inclined position  28  identified with a broken line. Thereby an opening angle a enclosed between the back  9  and the seat element  7  is increased to an opening angle α′. A lowering of the seat element  7  can be performed both by a person which has contact of his back against the back of the chair  9 , which seats exclusively in the front of the seat region  19 . Such a person understandably provides a greater inclined position of the seat surface  7 , when it sits exclusively in the front seat region  18 , since then van a greater part of the body weight acts on the spring element  15 .  
         [0039]    [0039]FIG. 2 shows the office chair  2  of FIG. 1 in a rear abutment position  11 . The office chair  2  in this position is held by a force. F R  originates from the sitting person and acting on the back  9 . The force F R  is compensated by the force F x  of the spring element  15 . Thereby the movement of the back  9  and the seat element  7  is limited by the spring element  15 . Substantially the force F R  is transmitted through the back support  8  and the seat element  7  as a pulling force with a spring element  15 , while the axle  27  assumes the position shown in FIG. 2 by a turning on the circular path K from the position shown in FIG. 1. The force F R  activates thereby, via the synchronous mechanical system, or in other words the special connection of the back  9  and the seat element  7 , in addition to the turning of the back  9  in a clockwise direction, also a movement of the axle  27  in counterclockwise direction over the circular path K which is originated by a rotation of the seat element in a clockwise direction around the axle  27 . Thereby by the synchronous mechanical system a typical sinking of the seat element  7  is produced in the rear seat region  21 , and a lifting of the seat element  7  in the front seat region  18 .  
         [0040]    These movements produced by the synchronous mechanical system are superposed by a further movement which makes possible the unguided spring element. The further movement results in that the sitting person acts with a force F S  on the seat surface  7 , with a part of this force applied in the front seat region  18  compensated by the force F Z  of the spring element  15 . Depending on the magnitudes of the acting forces F Z  and F x  , a changeable opening angle which is changed relative to the opening angle a of FIG. 2 is produced. Thereby the opening angle is not determined by the synchronous mechanical system alone, but substantially is a function of the forces F S  and F z .  
         [0041]    [0041]FIG. 3 shows a plan view of the office chair  2  of FIG. 1, wherein the illustration of the rotary frame and the rollers is dispensed with, however the other components located under the seat element  7  are shown. In the region of the back  9  this illustration is also simplified. The support  10  is U-shaped and receives the spring element  15  at the free legs  29 ,  30 . The back support  8  is arranged in the rear flange means  22 ,  23 , and the lever  20  is formed as a fork  31 .  
         [0042]    FIGS.  4 - 6  show a second embodiment of the office chair  32 . In contrast to the embodiments of FIGS.  1 - 3 , the office chair has means  33  for adjusting the spring force of the spring element  15 . As means  33  for adjusting the spring force, a tensioning device  34  is proposed. The tensioning device  34  has a hand wheel  35  which actuates the not shown tensioning screw for changing the distance between individual spring leaves  36  on the spring element  15 . A smaller distance between the spring leave  36  provides a greater tensioning force of the spring element  15 . Furthermore, the office chair  32  shown in FIGS.  4 - 6  is also different from the office chair of FIGS.  1 - 3  in that, for the springing of a seat element  7  only one spring element  15  is utilized. Thereby a particularly narrow construction of the office chair  32  is possible.  
         [0043]    FIGS.  7 - 9  show a third office chair  37 . In contrast to the office chair  32  shown in FIGS.  4 - 6 , a spring element  15  is formed as a rubber element  38  or a rubber metal  39 . As a rubber metal, a synthetic plastic element, in particular a rubber element provided between two metal plates is utilized. The spring element  15  has spring properties acting in x and z directions. A springing in a transverse direction y is provided by the mechanical connection of a seat element  7  through a lever  12  to a support  10 . When the office chair  37  shown in FIG. 8 is in a rear abutment position II, then the spring element  15  is subjected to a shearing load. Its acts in all positions in which the office chair  37  assumes a position in which a back  9  is inclined relative to the position shown in FIGS. 7.  
         [0044]    FIGS.  10 - 12  show an office chair  40  in accordance with a fourth embodiment of the present invention which is substantially similar to the third office chair of FIGS.  7 - 9 . In this office chair the spring element  15  is formed as a helical spring  41 . As for the operation, here the description of the office chair of FIGS.  7 - 9  is applicable since the helical spring element  41  is comparable with the rubber element  38  or the rubber metal  39 .  
         [0045]    An office chair  42  in accordance with a fifth embodiment of the present invention is shown in FIGS.  13 - 15 . In contrast to the office chair shown in FIGS.  1 - 12 , the office chair  42  has a seat shell  43 . The seat shell  43  is composed of a back  9  which is connected of one piece with a seat element  7 . The seat shell  43  in a transition region  44  is elastic or springy. A partial function of the synchronous mechanical system namely the increase of an opening angle a between the back  9  and the seat  7  is taken in the office chair  42  by the flexible or elastic transition region  44 , which activates a back springing of the back  9  in dependence on the force F R  acting on it and applied by a person sitting on the office chair  42 . Similarly to the office chairs shown in FIGS.  1 - 12  the force F R  , depending on the counter force F X  produced by a spring element  15 , activates sinking of the seat shell  43  in the rear seat region  21  and lifting the seat shell  43  in a front seat region  18 . A weight force F S  applied by a sitting person or its portion acting in the front seat region  18  leads to a lowering of the seat element contrary the clockwise direction. In the office chair  42  it provides driving the back when the opening angle a of the seat shell  43  is not increased by an increasing force F R  acting on the back  9 .  
         [0046]    A sixth office chair  45  is shown in FIGS.  16 - 18 . The office chair  45  has, as the office chair  42  shown in FIGS.  13 - 15 , a seat shell  43  which is composed of a seat element  7  and a back  9  springy connected in a transition region. In contrast to the office chairs shown in FIGS.  1 - 15 , in the office chair  45  the rotatably connected lever which serves as means  11  for transmission of a movement, is replaced by guides  13 . The guides  13  are formed as elongated openings  46  provided in beams  47 . The beams  47  are fixedly connected with a support  10 . Rear flange means  22 ,  23 , which are fixedly connected with the seat shell  43  are supported in a longitudinal openings  46  through a throughgoing axle  27 .  
         [0047]    The invention is not limited to the shown and described embodiments. It includes many further modifications of the invention within the range of the protection rendered by the claims. In particular, it is possible to provide the inventive arrangement of a spring element also on furniture articles for sitting which do not have a rotary frame, but instead have standing legs or standing feet and/or are fixedly mounted.  
         [0048]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
         [0049]    While the invention has been illustrated and described as embodied in sifting article of furniture, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
         [0050]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.