Abstract:
The invention relates to an apparatus for adjusting the arching of a resiliently flexible support element for supporting the pelvic and/or lumbar vertebrae in a back rest of a seat including an arching means. According to the invention, a flexible support element is suspended in a seat by multiple guide rods, and a Bowden cable is connected to the support element in such a manner as to arch the support element when traction is applied thereto. A restoring spring draws the support element from its arched position. An intermediate spring is used in combination with the Bowden cable such that the support element resiliently yields to major pressure. Another spring provides compensating forces to counteract the arching adjustment, thereby substantially reducing the force to be exerted in order to adjust the degree of arching.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. application Ser. No. 10/122,254 filed on Apr. 12, 2002 and expected to be issued as U.S. Pat. No. 6,623,076 on Sep. 23, 2003, which is a continuation of U.S. application Ser. No. 09/300,061 filed on Apr. 27, 1999 and issued on Sep. 10, 2002 as U.S. Pat. No. 6,447,061, which is a continuation of U.S. application Ser. No. 08/564,342 filed Jun. 16, 1994 and issued on Jun. 22, 1999 as U.S. Pat. No. 5,913,569, which claims priority to PCT/EP94/01963 filed Jun. 16, 1994, which claims priority to German Application No. P 43 20 105.9 filed Jun. 17, 1993, and hereby incorporated by reference. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         APPENDIX.  
         [0003]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0004]    1. Field of the Invention  
           [0005]    This invention relates generally to a backrest for a seat and, more particularly, to an adjustment apparatus for a seat support.  
           [0006]    2. Related Art  
           [0007]    An adjustment means is known from U.S. Pat. No. 4,880,271 in which the support element consists of two parallel longitudinal strips firmly interconnected by means of a plurality of transverse strips. Centrally to the longitudinal strips a further sheet metal strip is fixed at its upper end to the uppermost extreme transverse strip of the support element and is also connected to the cams of an excenter device provided at the lower end of the support element, but not to the subsequent transverse strips. The excenter and thus also the cam is adjustable by way of a worm gear by an operating means comprising a handle, in such a manner that the central sheet metal strip, depending en the direction of rotation, brings about an arching or a flattening (detensioning), as the case may be, of the support element such that the adjustment of the desired degree of arching can be brought about. To the rear of the support element at the upper and lower ends thereof a spring is linked up which draws the two ends of the slightly pre-arched support element towards one another, whereby the adjustment in the sense of an increased arching is supported and thereby facilitated. In this context the spring acts permanently onto the support element, even if no adjustment takes place, and is accordingly independent of the operating means.  
           [0008]    In addition, the entire mechanism of the arching means is extremely complicated. Furthermore, which ever degree of arching is set up this is stiff and unyielding, whereby comfort is adversely affected.  
         SUMMARY OF THE INVENTION  
         [0009]    It is in view of the above problems that the present invention was developed, to improve an apparatus of the type referred to above, that in spite of simple construction an easy adjustment of the arching is possible and/or that the tensioning force of any particular set up degree of arching can be adjusted more flexibly, the arched region being moreover able to yield. It is also possible for the adjustment force to be varied by the spring and a certain resiliency of the support element is ensured, i.e., it is not rigid and is able to yield to relatively strong forces whereby the comfort level is increased. In combination with these features or as its own advantage, it is another feature of the disclosed embodiments that the adjustment forces for arching the support element can be compensated for, virtually completely even, by the optional selection of the spring force, so that the adjustment of the degree of arching can proceed virtually without force application.  
           [0010]    Further advantageous embodiments of the invention will be apparent from the further claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    In what follows, the invention will be further explained by way of working examples with reference to schematic drawings. There is shown in:  
         [0012]    [0012]FIGS. 1 a  and  1   b , a back rest comprising a Bowden cable arrangement for adjusting the arching of a support element in plan view and in side elevation;  
         [0013]    [0013]FIGS. 2 a  and  2   b , a back rest including an excenter arrangement for adjusting the arching of a support element in plan view and in side elevation;  
         [0014]    [0014]FIGS. 3 a  and  b , a back rest including traction straps for adjusting the arching in plan view and in side elevation; and  
         [0015]    [0015]FIG. 4, a back rest including Bowden cable arrangements and motors for adjusting the arching and the level of the support element in plan view. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    The back rest illustrated in FIGS.  1  to  4  comprises a frame  1  in which between two transverse struts  2  a guide is fitted composed of two rods  3  parallel to one another for a resiliently flexible support element  4  which is fitted movably up and down thereon.  
         [0017]    The support element  4  in the working example according to FIG. 1 comprises a slightly arched panel  5  in one piece the upper end of which is connected to sliding elements  16  fitted on the rods  3 . The panel  5  comprises an upper panel portion  5   a  for supporting the lumbar vertebrae and a lower portion  5   b  for supporting the pelvis and the pelvic vertebrae. Between the portions  5   a  and  5   b  a linkage member  7  is linked to the rear of the panel  5  and has a free end which is linked to a guide  8  provided on the rods  3 .  
         [0018]    The back rest comprises an apparatus for adjusting the arching as well as a means for level adjustment of the support element  4 .  
         [0019]    The apparatus for level adjustment comprises an axle  9  mounted on either or both sides in the side limbs of the frame  1 , which axle if mounted on one side may in addition be mounted on either or both of the rods  3 . The axle  9  passes on one side out of the frame  1  and is connected at its free end to a hand wheel  10  of an operating mechanism. Within the interspace between the rods  3 , parallel to one another and to the rods  3 , two strips  11 ,  12  are provided, the first strap  11  at one end being fitted to the axle  9  and at its other end to the lower ends of the support element  4 . The second strap  12  is passed around the lower transverse strut  2  of the frame  1  and at one end is fitted to the lower end of the support element  4  and at the other end to the axle  9 . In the position shown in FIG. 1 a  the first strap  11  has been wound virtually completely off the axle  9 , whereas in this position the second strap  12  has been wound by way of several windings onto the axle  9 . The straps  11 ,  12  are so fixed to the axle or so wound thereon that as the axle  9  is turned by means of the hand wheel  10  the one strap  11 ,  12  is wound up and the other strap  12 ,  11  is unwound so that the entire support element  4  can be moved up and down on the rods  3 .  
         [0020]    The apparatus for adjusting the arching of the support element  4  according to FIG. 1 comprises a Bowden cable arrangement  13 . The sheath  14  of the Bowden cable arrangement  13  is at one end fitted centrally to the upper end of the support element  4  and at the other end to a fitting  15  of an operating means  16  fixed coaxially to the axle  9  to the frame  1 . In the fitting  15  a disc-shaped drum  17  is fitted rotatably which by means of a bush on the axis  9  is coupled to a lever  18  outside of the frame  1 . The sheathed cable  19  of the Bowden cable arrangement  13  is fixed at one end to the lower end of the linkage  7  by means of an intermediate helical spring  20 .  
         [0021]    The other end of the sheathed cable  19  extending from the sheath  14  is passed around the revolvable drum  17  its free end being so connected to a second helical spring  21  that the end of the sheathed cable is subjected to tensile force.  
         [0022]    Preferably the sheathed cable  19  passes around the drum  17  in a non-slipping manner, for which purpose the drum comprises at least one rebate for accommodating at least one projection (not illustrated) firmly fitted on the sheathed cable  19 . Preferably the limit of movement of the sheathed cable  19  are also limited between a zero position and the maximum desired degree of arching which can be brought about in optional manner, e.g. by two stop members which may for example coact with the drum  17  or the lever  18  to limit its range of movement (not illustrated). By virtue of the stop members or the limited defined range of movement, overloading or even possible destruction due to an uncontrolled application of forces during adjustment can be obviated.  
         [0023]    In the illustration according to FIG. 1 a , the end of the sheathed cable  19  which has been passed around the drum  17  is held under tension by a compressive helical spring  21  supported from the fixture  15 . It is equally possible to provide a tensile spring fixed to the frame  1 .  
         [0024]    In the embodiment illustrated in FIG. 2, only an apparatus for adjusting the arching is illustrated. In this case the support element  4  is composed of a single panel having a plurality of lateral cuts provided in its lower region which in the lower region outline projections  31 . In the event of arching of the support element  4  these projections  31  emerge from the plane of the support element as apparent from FIG. 2 b  and serve as a support for the pelvic vertebrae.  
         [0025]    In this working example likewise, an axle  9  is provided which in the region between the rods  3  carries a disc  32  which is rigidly connected to the axle  9 . In this working example, the support element  4  at it lower end is linked to the lower transverse struts  2 . To each of the lower edge and the upper edge of the support element, a traction rod  33  and/or  34  respectively is hooked, these being hung from diametrically opposite localities at the edge of the disc  32 . In one of the traction tension rods  33  or  34 , in this case the upper traction rod  34 , a spring  35  is inserted.  
         [0026]    In the region of the frame  1 , a second disc  36  is provided on the axle  9  on which an end of a cable  36  is fitted adapted to be wound up or unwound and the free end of which is fitted to the frame  1  by way of a tensile spring  38 .  
         [0027]    In the embodiment illustrated in FIG. 3, the support element  4  is designed as explained in the description of FIG. 1. In FIG. 3 as well, only one apparatus for adjusting the arching is illustrated. The embodiment according to FIG. 3 is of the same design as that described in the working example of FIG. 2 except that, instead of an excenter arrangement comprising the disc  32  and the traction rods  33 ,  34 , in this case the upper and lower ends of the support elements  4  are interconnected by a strap  40  which passes in a freely movable manner through the axle  9  or alternatively may be connected thereto.  
         [0028]    In the working example illustrated in FIG. 4, in which the springs according to the invention for greater clarity have been omitted, there is provided a Bowden cable arrangement  13  which serves both for level as well as for arching adjustment of the support element  4 , there being provided between the lower end of the support element  4 , in this case taking the form of a metal grid, and the lower transverse strut  2  a restoring spring  41  which draws the support element  4  towards the lower transverse strut  2 . The apparatus for adjusting arching is constructed as described with reference to FIG. 1, except that the sheath  14  of the Bowden cable arrangement  13  is not fixed to the upper end of the support element  4  but to the free end of an extension  42  which is there fitted and that instead of a manual adjustment a gear mechanism  43  with an electric motor  44  is provided. Likewise, a gear mechanism  43  with an electric motor  44  is provided for level adjustment. Preferably, at least all apparatus with manual adjustment are equipped with a free wheel brake  39  (FIGS.  1  to  3 ) which prevent an inadvertent readjusting of the arching and/or level setting, without, however, inhibiting a voluntary adjustment by means of the hand wheel  10  or the lever  18 . Preferably the support element  4  according to FIGS.  1  to  3  is made of plastics which offer the advantage of a simple and inexpensive manufacture combined with low weight even if optionally reinforcements such as ribs or regions of larger cross-section are provided, since these can easily be manufactured in casting procedures or by deforming. Preferably the support elements  4  according to FIGS. 1 and 3 are composed of two parts, the support element  4  proper and the linkage member  7 , in such a manner that they can be assembled without tools, e.g. by insertion of axle stubs into bearings, which permit a predetermined rotation. In the case of the support element  4  according to FIG. 2 these may also be punched out of a plastics sheet.  
         [0029]    The various embodiments as described with reference to FIGS.  1  to  4  may also be employed in optional suitable combinations.  
         [0030]    The apparatus for adjusting arching according to FIG. 1 operates as follows:  
         [0031]    By releasing the lever  18  from its locked position, where the locking device may be of an optional known type, for example a free wheel brake  39 , the drum  17  is turned by a pivotal movement of the lever  18  about the axle  9  causing the latter, depending on the direction of rotation, to wind up or unwind the sheathed cable  19  of the Bowden cable arrangement  13 . Due to the tensile force of the spring  21 , the rotary movement for arching the support element  4  is supported, such that as a result the force required for arching is reduced and arching is facilitated. When making an adjustment with a view to reducing the degree of arching the resiliently flexible support element  4  is detensioned and accordingly thereby counteracts the tensile force of the spring  21  so that in that situation as well an easy adjustment is provided. Due to the spring  20  inserted between the end of the sheathed cable  19  and the suspension point in the lower region of the support element  4  or the linkage member  7  the particular degree of arching which has been set up is no longer rigid as in known constructions but due to the spring  20  the support element can yield resiliently to major pressure and the entire back rest is thereby supplied with softer and more comfortable characteristics. If the increased pressure is reduced, the spring  20  contracts again and the previously set up arching is restored.  
         [0032]    The apparatus illustrated in FIG. 2 for adjusting the arching operates similar to that described with reference to FIG. 1, in this case a rotary movement of the axle  9  being brought about by the hand wheel  10  after the latter has been released from its locked position to bring about a movement of the adjoining ends of the traction rods  33  or  34  in the disc  32  away from or towards one another in respect of their levels whereby the arching or detensioning respectively of the support element  4  takes place. In this working embodiment the spring  38  which is coupled to the cable  37  and the second disc  36  is so employed that it supports the force which has to be exercised onto the hand wheel  10  in order to arch the support element  4 , i.e. so that the force required for adjusting the degree of arching is likewise reduced.  
         [0033]    The working example illustrated in FIG. 3 operates analogously to that illustrated in FIG. 2, the belt  40  in this case, on rotation of the axle  9 , being wound onto the axle  9  in order to achieve arching, here as well due to the spring  38  which is provided the application of force being reduced by the spring action.  
         [0034]    Due to the support or compensation of the forces counteracting the arching adjustment effected by the springs  21  or  38 , as the case may be, the force to be exerted in order to adjust the degree of arching is substantially reduced so that even low powered and therefore small and low noise electric motors can be employed without difficulty, so that the adjustments can also be performed with the aid of motor-driven transmissions. In FIG. 4 electric motors  44  with gear mechanisms  43  are provided both for adjusting the level as well as the degree of arching. The function of these embodiments is analogous to that described with reference to FIG. 1 except that instead of the rotary movement by means of a hand wheel  10  or the lever  18  this takes place by virtue of the electric reversible motors  44 . It is advantageous in all embodiments to limit the respective movements, e.g. by stop formations in order to avoid excessive tensions on the support element  4  which might eventually result in damage or even destruction.  
         [0035]    Therefore, according to the present invention for the lumbar support, an easy adjustment of arching with simple construction is possible and/or that the tensioning force of any particular set up degree of arching can be adjusted more flexibly, the arched region being moreover able to yield. Additionally, the adjustment force can be varied by the spring and a certain resiliency of the support element is ensured, i.e., it is not rigid and is able to yield to relatively strong forces whereby the comfort level is increased. As also disclosed, the adjustment forces for arching the support element can be compensated for, virtually completely even, by the optional selection of the spring force, so that the adjustment of the degree of arching can proceed virtually without force application. Finally, the advantages of the individual features discussed above can also be combined with one another.