Patent Publication Number: US-8991923-B2

Title: Adjusting device for a lumbar support and method of adjusting a lumbar support

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/745,015 filed Jan. 18, 2013, now U.S. Pat. No. 8,544,954 B2, which is a continuation of U.S. patent application Ser. No. 12/946,387 filed Nov. 15, 2010, now U.S. Pat. No. 8,360,523 B2. 
    
    
     The invention relates to an adjusting device for a lumbar support and a method of adjusting a lumbar support. The invention relates in particular to an adjusting device and a method for adjusting a lumbar support that may be provided in a backrest of a vehicle seat, such as an automotive vehicle seat. 
     Lumbar supports are frequently provided in seat backrests in order to provide adequate support in the lumbar vertebral or lordosis region of a person sitting on the seat by forming a suitable support surface. The lumbar support frequently has a support basket or other support member that is attached to a frame arranged in the seat backrest. By means of an adjusting device the curvature or convexity of the support basket may be adjusted. Alternatively or additionally, the position of the support basket along the longitudinal, i.e. height, direction of the backrest may be adjusted. An adjustment of the lumbar support may be effected by means of a manual actuator or by means of a power actuator, which may comprise an electric motor. Lumbar supports may also be implemented as four-way lumbar supports that allow both a curvature and a position of the lumbar support to be adjusted, in order to provide for enhanced comfort. Examples for adjusting devices that provide excellent support to the person sitting on the seat are, for example, known from WO 2005/077705 A1 or from DE 10 2005 027 922 B3. 
     In order to provide enhanced convenience to the user, the lumbar support may be adjusted using a power actuator, which may include an electric motor. In conventional adjusting devices, the power actuator may be coupled to the lumbar support by means of a Bowden cable. The Bowden cable may be coupled to the lumbar support, so as to exert traction onto portions of the lumbar support for adjustment. Electric motors and/or pulleys are required that are dimensioned so as to provide a force or torque that allows a Bowden cable wire to be drawn in or to be played out, even under load conditions. Correspondingly, an installation space required for installing the electric motor or pulley must have a size sufficient for housing such components. The electric motor or pulley may need to be installed spaced from the lumbar support, which may make installation more complex. 
     There is a need in the art for an improved adjusting device for adjusting a lumbar support and an improved method of adjusting a lumbar support. In particular, there is a need in the art for an adjusting device and method in which the installation space may be reduced. There is further a need in the art for an adjusting device and method that allow a lumbar support apparatus having an adjustable lumbar support device to be easily installed in a seat backrest, for example in a vehicle seat backrest. 
     According to the invention, this need is addressed by an adjusting device for a lumbar support and a method of adjusting a lumbar support as defined in the independent claims. Further, a lumbar support apparatus comprising an adjusting device is provided. The dependent claims define preferred or advantageous embodiments. 
     An adjusting device for a lumbar support according to an aspect of the invention comprises a pair of spaced guide members, an adjusting member coupled to the pair of guide members, and a drive mechanism for effecting an adjustment of the lumbar support. The adjusting member is displaceable along the pair of guide members and configured such that the lumbar support is adjusted when the adjusting member is displaced. The drive mechanism comprises a motor, which is provided on the adjusting member so as to be displaceable along the guide members jointly with the adjusting member. 
     In the adjusting device, as the motor is arranged on the adjusting member, it is not necessary to provide a dedicated installation space for installing the motor at a fixed location in a seat. As the motor is provided so as to be displaceable along the guide members jointly with the adjusting member, the motor may move along a portion of the backrest, jointly with the adjusting member, which has to be kept clear of fixed components to allow displacement of the adjusting member. 
     The drive mechanism may comprise a shaft having a structured exterior surface, e.g., a helical thread, and disposed so as to extend parallel to the guide members. The drive mechanism may be configured such that actuation of the motor effects a relative displacement of the adjusting member and the shaft along a longitudinal direction of the shaft. Thereby, a displacement of the adjusting member may be driven by the motor provided on the adjusting member, using a drive mechanism having a simple construction. 
     The drive mechanism may be configured to displace the adjusting member relative to the shaft. Depending on whether the shaft is attached so as to be fixed relative to the guide members, or whether the shaft is attached so as to be fixed relative to another moveable component, a motion of the adjusting member relative to the guide members or to the other moveable component may be attained. 
     The shaft may be flexible. The shaft may in particular be configured such that, when a normal force of about 250 N is exerted onto the lumbar support, as is the case in normal use of the lumbar support, the shaft is still elastically deformed. Thereby, the danger of breakage may be reduced. 
     The shaft may be attached to a mount so that it is pivotable about an axis which is perpendicular to a longitudinal axis of the shaft. Thereby, the risk of breakage of the shaft when a load acts onto the lumbar support may be reduced. 
     The adjusting device may comprise spaced cross members respectively extending in between the pair of guide members. The ends of the shaft may be attached to each one of the cross members. This configuration allows the adjusting member to be displaced along the shaft, while the shaft may be secured, for example, to a wire frame of the adjusting device at both of its ends. When the shaft is flexible, the risk of breakage may be reduced. 
     The drive mechanism may be configured to displace the adjusting member along the guide members. Thereby, the drive mechanism may realize the adjustment of the lumbar support associated with the displacement of the adjusting member. In particular, the drive mechanism may implement a height adjustment of the lumbar support. 
     The drive mechanism may comprise a spindle transmission. A spindle nut of the spindle transmission may be provided on the adjusting member, and the motor may be operatively coupled to the spindle nut. Thereby, a rotary output movement of the motor may be transformed into a displacement along the shaft serving as spindle. The shaft having a structured exterior surface may engage the spindle nut. 
     The drive mechanism may comprise at least one worm transmission, and preferably a two-stage worm transmission, which is coupled between the motor and the spindle transmission. Thereby, a desired speed reduction may be realized, and a motor providing a lower torque may be used. Constraints imposed on the motor may then be relaxed, which facilitates mounting the motor on the adjusting member. 
     The spindle nut of the spindle transmission may be mounted on the adjusting member so as to be pivotable relative to the adjusting member about an axis which is perpendicular to a longitudinal axis of the spindle nut. Thereby, the spindle nut may accommodate a deformation of the spindle which may occur when a normal load is applied onto the lumbar support. 
     At least a portion of the adjusting member may extend in between the pair of guide members, and the motor may be mounted on the portion of the adjusting member in between the pair of guide members. Thereby, the motor may be displaced through a free space in between the two guide members. 
     The adjusting member may have a recess for receiving at least a portion of the motor. Thereby, the combined dimensions of adjusting member and motor may be kept small. 
     The adjusting device may comprise a further adjusting member which is separate from the adjusting member and is displaceable along the pair of guide members. The drive mechanism may be configured so that, upon actuation of the motor, at least one of the adjusting member and the further adjusting member is displaced relative to the guide members. Thereby, a height or a curvature of the lumbar support may be adjusted. 
     The adjusting device may comprise a further drive mechanism comprising a further motor. The further motor may be provided on one of the adjusting member and the further adjusting member. Thereby, the further motor may also be integrated into one of the adjusting member and the further adjusting member, and no dedicated installation space has to be provided outside the adjusting device. 
     The drive mechanism and the further drive mechanism may be configured such that the adjusting member and the further adjusting member are displaced in the same direction along the guide members upon actuation of one of the motor and the further motor, and that the adjusting member and the further adjusting member are displaced relative to each other upon actuation of the other one of the motor and the further motor. Thereby, a four-way actuation allowing both the height and the curvature of the lumbar support to be adjusted may be implemented. 
     The adjusting device may comprise at least one arching member which is respectively coupled to the adjusting member and the further adjusting member. The at least one arching member may be configured to be coupled to the lumbar support such that the curvature of the lumbar support is adjusted when the curvature of the at least one arching member changes. Thereby, the curvature of the lumbar support may be adjusted by changing the curvature of the arching member. Further, the arching member may enhance sitting comfort. 
     The motor may be provided on the adjusting member so that it is located in between ends of the arching member, in a longitudinal direction of the guide members. In particular, the motor may be provided on the adjusting member so that it is located in between the ends of the arching member, in the longitudinal direction of the guide members, for any operation position of the adjusting member and the further adjusting member. 
     According to another aspect of the invention, a lumbar support apparatus is provided. The lumbar support apparatus comprises a lumbar support and the adjusting device for adjusting the lumbar support according to any one aspect or embodiment described herein. 
     This lumbar support apparatus has an improved adjusting device. 
     According to another aspect of the invention, a method of adjusting a lumbar support is provided, in which an adjusting member is displaced along a pair of guide members, to which the adjusting member is coupled, in order to adjust the lumbar support. The lumbar support is adjusted by means of a drive mechanism comprising a motor and a shaft, which may be a spindle. The shaft may be operatively coupled to the motor so that the adjusting member and the shaft are displaced relative to each other along a longitudinal axis of the shaft when the motor is actuated. The motor is provided on the adjusting member so that it is displaced along the guide members jointly with the adjusting member. 
     In the method, as the motor is provided so as to be displaceable along the guide members jointly with the adjusting member, the motor may move along a portion of the backrest, jointly with the adjusting member, which has to be kept clear of fixed components to allow displacement of the adjusting member. No dedicated installation space for installing the motor at a fixed location in a seat has to be provided. 
     According to embodiments of the invention, the method is performed using an adjusting device for adjusting the lumbar support according to any one aspect or embodiment described herein. 
     The devices and methods according to various embodiments may be utilized for adjusting a lumbar support in a seat backrest. In particular, the devices and methods according to the various embodiments may be utilized for adjusting a lumbar support provided in a seat backrest of a vehicle seat, in particular an automotive vehicle seat. 
    
    
     
       Additional features and advantages of the invention will become more readily appreciated from the following detailed description of preferred or advantageous embodiments with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a lumbar support apparatus having an adjusting device according to an embodiment. 
         FIG. 2  is a perspective view of an adjusting device according to an embodiment. 
         FIG. 3  is a detail view showing components of the adjusting device of  FIG. 2  in detail. 
         FIG. 4  is a detail view showing a drive mechanism of an adjusting device according to an embodiment in an assembled state. 
         FIG. 5  is an exploded view of the drive mechanism of  FIG. 4 . 
         FIGS. 6A and 6B  are schematic views for illustrating the operation of the adjusting device according to an embodiment. 
         FIGS. 7A and 7B  are schematic views for further illustration of the operation of the adjusting device according to an embodiment. 
     
    
    
     Exemplary embodiments of the invention will now be described with reference to the drawings. While some embodiments will be described in the context of specific fields of application, such as in the context of automotive vehicle seating, the embodiments are not limited to this field of application. Further, the features of the various embodiments may be combined with each other unless specifically noted otherwise. 
       FIG. 1  is a perspective view of a lumbar support apparatus  1  according to an embodiment. The lumbar support apparatus  1  comprises a lumbar support  2  and an adjusting device  3  for adjusting the lumbar support  2 . The lumbar support  2  may be configured as a so-called support basket having a plurality of resilient fingers for providing support. Other suitable configurations of lumbar support members, such as support plates or similar, may also be used to implement the lumbar support  2 .  FIGS. 2 and 3  show the adjusting device  3  and an adjusting member  14  of the adjusting device in more detail. 
     When the lumbar support apparatus  1  of  FIGS. 1-3  is installed in a backrest of a seat, the adjusting device  3  is operative to displace the lumbar support  2  in a longitudinal direction of a seat backrest. The adjusting device  3  is further operative to adjust a curvature of the lumbar support  2 . To this end, the adjusting device  3  comprises a pair of adjusting members and two drive mechanisms that allow the pair of adjusting members to be displaced along a pair of guide elements, that extend substantially parallel and in a substantially longitudinal direction of the backrest. 
     The adjusting device  3  has a frame which comprises at least two guide members  4  and  5 . Two cross members  6  and  7  extend in between the two guide members  4  and  5 , so that the two guide members  4  and  5  are spaced relative to each other and extend essentially parallel to each other. The guide members  4  and  5  may be formed as guide wires. Extensions  8  and  9  of the frame defined by guide members  4  and  5  and the cross members  6  and  7 , and extensions projecting from the cross member  6  in a width direction of the seat allow the frame defined by the guide members  4  and  5  and the cross members  6  and  7  to be mounted to the frame of a seat backrest. Several of the guide members  4 ,  5  and the cross members  6 ,  7  may be integrally formed. For illustration, the two guide members  4  and  5  and the lower cross member  7  may be formed from a wire which generally has a U-shape. Alternatively, the guide members  4 ,  5  and the cross members  6 ,  7  may be separate members that are attached to each other using suitable mounts. 
     Referring now to  FIG. 2 , the adjusting device  3  will be described in more detail. The adjusting device  3  comprises an adjusting member  14  which is supported on the guide members  4  and  5  such that it can be displaced along the guide members  4  and  5 . The adjusting member  14  extends from one guide member  4  to the other guide member  5 . The adjusting device  3  comprises a further adjusting member  17  which is supported on the guide members  4  and  5  such that it can be displaced along the guide members  4  and  5 . The further adjusting member  17  extends from one guide member  4  to the other guide member  5 . The adjusting member  14  and the further adjusting member  17  may be formed, for example, from plastic. The adjusting member  14  has a portion  15  on which components of a drive mechanism are supported, and a further portion  16  on which ends of arching members  11  and  12  are supported. The portion  15  and the further portion  16  are spaced from each other in a direction parallel to the guide members  4  and  5  at a fixed spacing. The portion  15  and the further portion  16  may be integrally formed, for example as an injection molded plastic member. 
     Two arching members  11  and  12  are respectively coupled to the adjusting member  14  and the further adjusting member  17 . In an embodiment, recesses  18  may be provided on the portion  16  of the adjusting member  14 , in which recesses  18  ends of the arching members  11 ,  12  are received. Another recess  19  may be provided on the further adjusting member  15  in which the other end of the arching members  11 ,  12  is received. The recesses  18  and  19  provided in the adjusting member  14  and the further adjusting member  17 , respectively, are configured such that the ends of the arching members  11  and  12  are securely retained therein even when the adjusting member  14  and the further adjusting member  17  are moved relative to each other, or when a load is applied in a direction perpendicular to the plane defined by the guide members  4  and  5 . The arching members  11  and  12  may respectively be formed of a resilient material. The arching members  11  and  12  may be configured as metal bands formed from a metal sheet. 
     In use of the adjusting device  3 , the lumbar support  2  is coupled to the arching members  11  and  12  such that the curvature of the lumbar support  2  is adjusted when the curvature of the arching members  11  and  12  changes. Further, the lumbar support  2  is coupled to the arching members  11  and  12  such that the lumbar support  2  travels parallel to the guide members, along with the adjusting member  14 , when the adjusting member  14  and the further adjusting member  17  are displaced along the guide members  4  and  5 . 
     The adjusting device  3  comprises at least one drive mechanism configured to displace at least one of the adjusting member  14  or the further adjusting member  17  along the guide members  4  and  5 . The adjusting device  3  of  FIGS. 1-3  comprises a first drive mechanism  30  which is operative to displace the adjusting member  14  relative to a reference frame defined by the guide members  4 ,  5  and cross members  6 ,  7 . Upon actuation of the first drive mechanism  30 , the adjusting member  14  and the further adjusting member  17  are displaced along the guide members  4  and  5  in the same directions, so as to allow a height of the lumbar support  2  to be adjusted. The adjusting device  3  of  FIGS. 1-3  comprises a second drive mechanism  40  which is operative to displace the adjusting member  14  and the further adjusting member  17  relative to each other. Upon actuation of the second drive mechanism  40 , a spacing between the adjusting member  14  and the further adjusting member  17  is adjusted and the curvature of the arching members  11  and  12  is changed, so as to allow a curvature of the lumbar support  2  to be adjusted. 
     The first drive mechanism  30  includes a shaft  32  which has a longitudinal axis extending in general parallel to the guide members  4  and  5 . The shaft  32  is attached at a mount  10  provided on the cross member  7  of the wire frame. The shaft  32  may in particular be attached on the mount  10  so that it is rotationally fixed about its longitudinal axis. Optionally, the shaft  32  may also be attached on the cross member  7 . The first drive mechanism  30  comprises a motor  31 , as can best be seen in  FIG. 3 . The motor  31  is mounted on the adjusting member  14  so that the motor  31  moves along the guide members  4  and  5  and the shaft  32 , jointly with the adjusting member  14 , when the adjusting member  14  is displaced along the guide members  4  and  5  and the shaft  32 . 
     A transmission may be provided to couple an output of the motor  31  to the shaft  32 . The transmission may be configured so as to convert a rotary movement of an output shaft of the motor  31  into a longitudinal movement of the motor  31 , and the adjusting member  14  on which the motor  31  is mounted, along the shaft  32 . The transmission may be implemented as a reduction mechanism which provides a speed reduction. An implementation of the transmission in an adjusting device according to an embodiment will be explained in more detail with reference to  FIGS. 4 and 5 , respectively. 
     As will also be explained in more detail with reference to  FIGS. 4 and 5 , the shaft  32  may have a structured exterior surface that allows the transmission to couple to the shaft  32 . In an embodiment, the shaft  32  may have an external thread and may serve as spindle of a spindle transmission. The external thread of the shaft  32  may be engaged with an internal thread of a spindle nut which is driven by the motor  31  via the transmission coupled in between the spindle nut and the motor  31 . 
     The second drive mechanism  40  comprises a shaft  42  which has a longitudinal axis extending in general parallel to the guide members  4  and  5 . The shaft  42  is attached on the further adjusting member  17 . The shaft  42  may in particular be attached on the further adjusting member  17  so that it is rotationally fixed about its longitudinal axis. The second drive mechanism  40  comprises a motor  41 , as can best be seen in  FIG. 3 . The motor  41  is mounted on the adjusting member  14  so that the motor  41  moves relative to the shaft  42 , jointly with the adjusting member  14 , when the adjusting member  14  and the further adjusting member  17  are displaced relative to each other. 
     A transmission may be provided to couple an output of the motor  41  to the shaft  42 . The transmission may be configured so as to convert a rotary movement of an output shaft of the motor  41  into a longitudinal movement of the motor  41 , and the adjusting member  14  on which the motor  41  is mounted, relative to the shaft  42 . The transmission may be implemented as a reduction mechanism which provides a speed reduction. An implementation of the transmission in an adjusting device according to an embodiment will be explained in more detail with reference to  FIGS. 4 and 5 , respectively. 
     As will also be explained in more detail with reference to  FIGS. 4 and 5 , the shaft  42  may have a structured exterior surface that allows the transmission to couple to the shaft  42 . In an embodiment, the shaft  42  may have an external thread and may serve as spindle of a spindle transmission. The external thread of the shaft  42  may be engaged with an internal thread of a spindle nut which is driven by the motor  41  via the transmission coupled in between the spindle nut and the motor  41 . 
     Referring to  FIG. 3 , a configuration of the adjusting member  14  and the first and second drive mechanisms  30 ,  40  in an adjusting device according to an embodiment will be described in more detail. The adjusting member  14  includes the portion  15  on which the motors  31  and  41  of the first and second drive mechanism  30  and  40 , respectively, are mounted. The adjusting member  14  further includes the portion  16  which has the recesses  18 , in which ends of the arching members  11  and  12  are received. Lateral side sections  21   a ,  21   b  provided on the portion  15  respectively define a recess  22  in which the guide members  4  and  5 , respectively, may be received and retained. Similarly, lateral side sections  23   a ,  23   b  provided on the portion  16  respectively define a recess  24  in which the guide members  4  and  5 , respectively, may be received and retained. The recesses  22  and  24  allow the adjusting member  14  to be retained on the guide members  4  and  5  in a displaceable manner. While not shown in  FIG. 3 , similar lateral side sections may also be provided on the further adjusting member  17 . 
     The portion  15  of the adjusting member  14  has a central portion  25  extending between the guide members. In the central portion  25 , a recess  26  is formed in which at least a portion of the motor  31  of the first drive mechanism  30  may be received. The recess  26  may be dimensioned such that the motor  31  may be fully positioned within the recess  26 . Further, the transmission coupled in between the output shaft of the motor  31  and the shaft  32  of the first drive mechanism may also be positioned within the recess  26 . The motor  31  and other components of the first drive mechanism  30  are mounted on the adjusting member  14  such that a force exerted onto the motor  31  in the axial direction of the shaft  32  also acts on the adjusting member  14 , so as to cause the adjusting member  14  to move relative to the shaft  32 . 
     Similarly, the central portion  25  of the adjusting member  14  has a further recess  27  in which at least a portion of the motor  41  of the second drive mechanism  40  may be received. The further recess  27  may be dimensioned such that the motor  41  may be fully positioned within the further recess  27 . Further, the transmission coupled in between the output shaft of the motor  41  and the shaft  42  of the second drive mechanism may also be positioned within the recess  27 . The motor  41  and other components of the second drive mechanism  40  are mounted on the adjusting member  14  such that a force exerted onto the motor  41  in the axial direction of the shaft  42  also acts on the adjusting member  14 , so as to cause the shaft  42  to move relative to the adjusting member  14 . 
     An end of the shaft  32  of the first drive mechanism  30  may be provided with an attachment member  39  for attaching the end of the shaft  32  to the mount  10 . The attachment member  39  may have an external configuration that allows the shaft  32  to be attached to the mount  10  so that it is rotationally fixed about its longitudinal axis. For illustration, at least one projection  39 ′ may be provided on the attachment member  39  that is received within a corresponding recess in the mount  10 . Similarly, an end of the shaft  42  of the second drive mechanism  40  may be provided with an attachment member  49  for attaching the end of the shaft  42  to the further adjusting member  17 . The attachment member  49  may have an external configuration that allows the shaft  42  to be attached to the further adjusting member  17  so that it is rotationally fixed about its longitudinal axis. For illustration, at least one projection  49 ′ may be provided on the attachment member  49  that is received within a corresponding recess in the further adjusting member  17 . 
     As will be appreciated, as the motors  31  and  41  of the first and second drive mechanisms, respectively, are mounted on the adjusting member  14 , no dedicated installation space has to be provided for the motors  31  and  41  in a space adjacent the adjusting device  2 . Rather, the motors  31  and  41  which are mounted so that they can move jointly with the adjusting member  14  are provided at a location in between the guide members  4  and  5  that has to be kept clear from stationary seat components. 
     As will also be appreciated, when the drive mechanisms  30  and  40  respectively comprise a spindle transmission, a rotary output movement of the motors  31  and  41 , respectively, can be converted into a translatory displacement of the adjusting member  14  and/or of the further adjusting member  17 . The pitch of the external thread provided on the shafts  32  and  42 , respectively, may be selected so as to provide a desired conversion of the rotary output movement of the motors  31  and  41  into a linear displacement relative to the respective shafts  32  and  42 , respectively. 
     Each one of the first and second drive mechanisms  30  and  40  may have further transmission components coupled between the output shaft of the motor and a spindle nut. Configurations of the drive mechanism that may be implemented in an adjusting device according to an embodiment will next be explained in more detail. 
       FIG. 4  is a partially broken away view of a drive mechanism  30 , and  FIG. 5  is an exploded view of the drive mechanism  30 . While reference will be made to drive mechanism  30  in the following description of  FIGS. 4 and 5 , in an embodiment, the second drive mechanism  40  may have a configuration that corresponds to, or is identical to, the configuration of the first drive mechanism  30  explained with reference to  FIGS. 4 and 5 . 
     The drive mechanism  30  generally comprises the motor  31 , the shaft  32  and a transmission coupled in between an output shaft  33  of the motor  31  and the shaft  32 . The motor may be an electric motor. The motor may in particular be a DC motor. The transmission has several reduction stages. In the implementation shown in  FIGS. 4 and 5 , the transmission comprises a two-stage worm transmission, the output of the worm transmission being coupled to a spindle nut  38 . 
     The drive mechanism  30  is configured such that a worm  34  of a first worm transmission is coupled to the output shaft  33  of the motor  31  in a rotationally fixed manner. In an embodiment, the worm  34  may be formed onto the output shaft  33  of the motor. A worm gear  35  engages the worm  34 . A second worm  36  of a second worm transmission is coupled to the worm gear  35  in a rotationally fixed manner. In an embodiment, the second worm  36  and the worm gear  35  may be formed on a common shaft. A second worm gear  37  engages the second worm  36 . It will be appreciated that the worm  34  and worm gear  35  engaged therewith provide a rotation speed reduction, and that the second worm  36  and the second worm gear  37  engaged therewith provide further rotation speed reduction. 
     The second worm gear  37  is coupled to a spindle nut  38  in a rotationally fixed manner. In an embodiment, the second worm gear  37  may be formed onto an outer surface of the spindle nut  38 . A rotary movement of the output shaft  33  of the motor  31  causes the spindle nut  38  to rotate at a reduced speed, the speed reduction being effected by the two-stage worm transmission  34 - 37 . 
     The spindle nut  38  has an internal thread engaging an outer thread of the shaft  32 . Rotation of the spindle nut  38  effects a translatory relative displacement between the spindle nut  38 , as well as the other components of the drive mechanism  30  provided on the adjusting member  14 , and the shaft  32 . 
     As can be seen from  FIG. 5 , the worm  34 , worm gear  35 , second worm  36 , second worm gear  37  and spindle nut  38  are supported in a housing having housing shells  51  and  52 . The housing shells  51  and  52  define recesses in which the worm  34 , worm gear  35 , second worm  36 , second worm gear  37  and spindle nut  38  may be received so as to be rotatable. The housing shells may be attached to one another and to the motor  31  using screws  55 ,  56 . A pin  57  may be inserted into the joined housing shells  51  and  52  along an axial extension of the output shaft  33  of the motor  31 . 
     A connector  54  and associated circuit board  53  may be attached to the motor  31 , so as to allow power to be supplied to the motor  31 . If the connector  54  and circuit board  53 , which defines an arrangement of connection pins, are provided so as to be removably connectable to the motor  31 , the adjusting device  3  may be readily adapted for use with different power supply systems. This may be beneficial when the adjusting device  3  is to be used, for example, in different types of cars using different types of power connectors. 
     It will be appreciated that, for a drive mechanism having at least one worm transmission coupled between the motor and a spindle transmission, a desired speed reduction may be attained in a small installation space. This facilitates the integration of the motor and the at least one worm transmission on the adjusting member  14 . 
     While a configuration for a drive mechanism  30  has been explained with reference to  FIGS. 4 and 5 , the first and/or second drive mechanism  30  and  40 , respectively, may have another configuration in other embodiments. For illustration, while a drive mechanism  30  having a two-stage worm transmission is shown in  FIGS. 4 and 5 , the drive mechanism  30  or the drive mechanism  50  may also have a single-stage worm transmission, or at least three worm transmissions, coupled in between the motor and the spindle nut. In still further embodiments, alternative transmission mechanisms may be utilized to convert the rotary output movement of the motor into a linear movement. 
     Referring again to  FIGS. 2 and 3 , the adjusting device  3  may be configured so as to remain operative even when a force is exerted onto the lumbar support  2  in a direction that is perpendicular to the plane defined by the parallel guide members  4  and  5 . In an embodiment, the adjusting device  3  is configured so as to remain operative even in the misuse case scenario, in which a normal force of 2750 N is applied to the lumbar support for test purposes. Various configurations of the shafts  32  and  42  and/or various configurations of coupling the shafts  32  and  42  to other components of the adjusting device  3  may be utilized to this end. 
     In an embodiment, the shaft  32  may be attached to the mount  10  so that the shaft  32  is pivotable about an axis that extends perpendicularly to a longitudinal axis of the shaft  32 , i.e., perpendicularly to a longitudinal axis of the guide members  4  and  5 . To this end, the attachment member  39  may be provided with pin-shaped projections  39 ′ that extend essentially perpendicular to the longitudinal axis of the shaft  32  and which are received in corresponding recesses in the mount  10 , so as to allow the shaft  32  to pivot about the axis defined by the projections  39 ′. Similarly, the spindle nut  38  through which the shaft  32  extends at the adjusting member  14  may be supported on the adjusting member  14  so that it is pivotable about an axis which is perpendicular to the longitudinal axis of the spindle nut  38 . For a drive mechanism having the configuration of  FIGS. 4 and 5 , this may be attained in that the motor  31  and the transmission componentry mounted thereto in the housing  51 ,  52  is pivotably supported on the adjusting member  14 . As indicated in  FIG. 5 , a projection  58  may be formed on the housing shells  51 ,  52 , which may be received in a recess of the adjusting member  14  so as to allow the housing  51 ,  52  and the spindle nut  38  received therein to be pivoted relative to the adjusting member  14 . When the shaft  32  has a high rigidity, the end of the shaft  32  is preferably not attached to the cross member  6 . When a force is exerted onto the adjusting device  3  in a direction perpendicular to the plane defined by the guide members  4  and  5 , the shaft  32  may pivot at mount  10  and the spindle nut  38  may pivot in the adjusting member  14 . Thereby, transverse loads acting onto the shaft  32  may be reduced. 
     Similarly, the shaft  42  may be attached to the further adjusting member  17  so that the shaft  42  is pivotable about an axis that extends perpendicularly to a longitudinal direction of the shaft  42 , i.e., perpendicularly to a longitudinal axis of the guide members  4  and  5 . Further, a spindle nut of the drive mechanism  40 , through which the shaft  32  extends at the adjusting member  14  may be supported on the adjusting member  14  so that it is pivotable about an axis which is perpendicular to the longitudinal axis of the spindle nut of the second drive mechanism  40 . When a force is exerted onto the adjusting device  3  in a direction perpendicular to the plane defined by the guide members  4  and  5 , the shaft  42  may pivot at its attachment to the further adjusting member  17  and the spindle nut of the second drive mechanism  40  may pivot in the adjusting member  14 . Thereby, transverse loads acting on the shaft  42  may be reduced. 
     Alternatively or additionally, the shaft  32  and/or the shaft  42  may be formed from a flexible material, so as to allow the shaft  32  and/or the shaft  42  to be elastically deformed. In particular, the shaft  32  and/or the shaft  42  may be formed from a material that allows the shaft  32  and/or the shaft  42  to elastically deform in the misuse case scenario, in which a normal force of 2750 N is applied to the lumbar support. 
     For illustration, the shaft  32  and/or the shaft  42  may be a so-called flexible shaft or flex-shaft which is provided with an outer thread. The flexible shaft may have a metal core comprising a plurality of metal wires. The flexible shaft may have an external thread. The flexible shaft may have a metal wire helix on its outer surface for forming the external thread. The flexible shaft may be a flex-shaft which is available, for example, from Otto Suhner AG. 
     In order to be elastically deformable in the misuse case, the shaft  32  and/or the shaft  42  may be a flexible shaft adapted to elastically deform up to a maximum axial load of at least 200 N. In particular, the shaft  32  and/or the shaft  42  may be a flexible shaft adapted to elastically deform up to a maximum axial load of at least 400 N. In particular, the shaft  32  and/or the shaft  42  may be a flexible shaft adapted to elastically deform up to a maximum axial load of at least 500 N. 
     It will be appreciated that, when the shaft  32  or  42  is attached so that it is pivotable about an axis perpendicular to the longitudinal axis of the respective shaft, the risk of the respective shaft being damaged when a force is applied in a direction normal to the plane defined by the guide members is reduced. Additionally or alternatively, when the shaft  32  or  42  is a flexible shaft, the risk of the respective shaft being damaged when a force is applied in a direction normal to the plane defined by the guide members is reduced. Still further, in the latter case, the risk of biting between the internal thread of the spindle nut and the shaft  32  or  42  may be reduced. 
     It will also be appreciated that, if the shaft  32  is a flexible shaft, the shaft may be attached to both cross members  6  and  7 , as the shaft  32  is capable of being elastically deformed for loads that are normally expected to occur. 
     Referring to  FIGS. 6 and 7 , the operation of an adjusting device according to an embodiment will be explained in more detail. The operation illustrated in  FIGS. 6 and 7  may be implemented with the adjusting device according to any one embodiment explained with reference to  FIGS. 1-5  above. 
     With reference to  FIG. 6 , operation of the first drive mechanism  30  will be explained.  FIGS. 6A and 6B  are schematic sectional views showing the adjusting member  14  having portions  15  and  16 , the further adjusting member  17  and the first drive mechanisms  30  of an adjusting device  3 , the section being taken along the lines VI-VI indicated in  FIG. 2 . The adjusting member  14  and the further adjusting member  17  are attached to guide members (not shown in  FIG. 6 ) which generally extend parallel to the shaft  32  of the drive mechanisms  30 , so that the adjusting member  14  and the further adjusting member  17  may be displaced along the guide members. Further, the shaft  42  of the second drive mechanism (not shown in  FIG. 6 ) is mounted to the further adjusting member  17  and engages a transmission, e.g., a spindle nut of the drive mechanism  40 , mounted on the portion  15  of the first adjusting member  14 . The further adjusting member  17  has a through opening that allows the shaft  32  to pass through the further adjusting member  17  and to be freely displaced relative to the further adjusting member  17 . 
       FIG. 6A  shows the adjusting device  3  in an initial state. The shaft  32  has a structured exterior surface which engages a member  38  of a transmission of the first drive mechanism  30 . The member  38  has a structured interior surface which is engageable with the exterior surface of the shaft  32 . The shaft  32  may be a spindle of a spindle transmission. The member  38  may be a spindle nut. When the motor  31  of the first drive mechanism  30 , which is mounted on the adjusting member  14 , is actuated, the member  38  is made to rotate. The engagement between the structured interior surface of the member  38  and the structured exterior surface of the shaft  32  causes the member  38  and the shaft  32  to move relative to each other. 
     The drive mechanism  30  is mounted on the adjusting member  14  such that, when the member  38  of the drive mechanism  30  moves relative to the shaft  32 , the adjusting member  14  is forced to move relative to the shaft  32 . This is indicated by  61  in  FIG. 6B . As an end of the shaft  32  is fixed to the frame defined by the guide member  4  and  5 , the adjusting member  14  is displaced along the guide members  4  and  5  upon actuation of the motor  31 . 
     As the shaft  42  of the second drive mechanism is mounted to the further adjusting member  17  and engages a transmission, e.g., a spindle nut of the drive mechanism  40 , mounted on the portion  15  of the adjusting member  14 , the force acting onto the adjusting member  14  also acts onto the further adjusting member  17  via the shaft  42  of the second drive mechanism  40 . Thereby, the further adjusting member  17  is forced to move in the same direction and by the same amount as the adjusting member  14 , as long as the second drive mechanism is not operated. The corresponding displacement of the further adjusting member  17  is indicated by arrow  62  in  FIG. 6B . 
     By actuation of the motor  31  of the first drive mechanism  30 , a joint displacement of the adjusting member  14  and of the further adjusting member  17  in the same direction along the guide member  4  and  5  may be effected, as indicated by arrows  61  and  62  in  FIG. 6B . 
     It will be appreciated that, in the adjusting device  3 , the shaft  42  of the second drive mechanism  40  is operative to couple the adjusting member  14  and the further adjusting member  17  to each other, which causes the adjusting member  14  and the further adjusting member  17  to be jointly displaced in the same direction when the motor  31  of the first drive mechanism  30  is actuated. Additionally, the shaft  42  also is operative to adjust a curvature of the lumbar support, as will be explained in more detail with reference to  FIG. 7 . 
     With reference to  FIG. 7 , operation of the second drive mechanism  40  will be explained.  FIGS. 7A and 7B  are schematic sectional views showing the adjusting member  14  having portions  15  and  16 , the further adjusting member  17  and the second drive mechanisms  40  of an adjusting device  3 , the section being taken along lines VII-VII indicated in  FIG. 2 . The adjusting member  14  and the further adjusting member  17  are attached to guide members (not shown in  FIG. 6 ) which generally extend parallel to the shaft  42  of the second drive mechanisms  40 , so that the adjusting member  14  and the further adjusting member  17  may be displaced along the guide members. The shaft  42  is engaged with a transmission of the second drive mechanism  40  provided on the portion  15  of the adjusting member. The portion  16  of the adjusting member  14  has a through opening that allows the shaft  42  to pass through the portion  16 . 
       FIG. 7A  shows the adjusting device  3  in an initial state. The shaft  42  has a structured exterior surface which engages a member  48  of a transmission of the second drive mechanism  40 . The member  48  has a structured interior surface which is engageable with the exterior surface of the shaft  42 . The shaft  42  may be a spindle of a spindle transmission. The member  48  may be a spindle nut. When the motor  41  of the second drive mechanism  40 , which is mounted on the adjusting member  14 , is actuated, the member  48  is made to rotate. The engagement between the structured interior surface of the member  48  and the structured exterior surface of the shaft  42  brings about a relative displacement between the shaft  42  and the transmission member  48 . 
     The second drive mechanism  40  is mounted on the adjusting member  14  such that, when the member  48  of the second drive mechanism  40  and the shaft  42  are displaced relative to each other, the shaft  42  is displaced relative to the adjusting member  14 . As an end of the shaft  42  is attached to the further adjusting member  17 , this causes the further adjusting member  17  to be displaced relative to the adjusting member  14 , as indicated by  66  in  FIG. 7B . The resultant change in distance between the further adjusting member  17  and the portion  16  of the adjusting member  14 , on which ends of the arching members  11  and  12  are mounted, adjusts the curvature of the arching members  11  and  12 . 
     By actuation of the motor  41  of the second drive mechanism  40 , the further adjusting member  17  and the adjusting member  14  may be displaced relative to each other, as indicated by arrow  66  in  FIG. 7B . Thereby, the curvature of the lumbar support  2  may be adjusted. 
     While the operation of the first drive mechanism  30  and the second drive mechanism  40  have been separately described with reference to  FIGS. 6 and 7 , respectively, the drive mechanisms  30  and  40  may also be actuated simultaneously. 
     While embodiments of the invention have been described with reference to the drawings, various modifications may be implemented in further embodiments. For illustration, while embodiments in which both motors  31  and  41  are provided on the adjusting member  14  disposed toward the lower end of the seat backrest have been illustrated, the motors  31  and  41  could also be provided in the further adjusting member  17  in other embodiments. In still other embodiments, the motor of a first drive mechanism, which is operative to displace the lumbar support along the longitudinal axis of the backrest, may be provided on one of the adjusting member  14  and the further adjusting member  17 , while the motor of a second drive mechanism, which is operative to adjust a curvature of the lumbar support, may be provided on the other one of the adjusting member  14  and the further adjusting member  17 . 
     In any one of the various embodiments, the motor of a drive mechanism and/or a spindle nut driven by the motor may be arranged in a housing having two housing shells. The two housing shells may be attached to each other by laser welding. The two housing shells may be attached to each other by ultrasonic welding. The portion  15  of the adjusting member on which the motor is provided may act as one of the housing shells. The portion  15  of the adjusting member may have recesses in which the motor(s) and spindle nut(s) are arranged. A cover member may be overlaid on the portion  15  of the adjusting member with the motor(s) and spindle nut(s) received in the recesses. The cover member may be attached to the adjusting member by laser welding and/or ultrasonic welding. 
     While an adjusting device operative to adjust both a height and a curvature of the lumbar support has been described, in other embodiments, the adjusting device is not necessarily implemented as a four-way adjusting device. In an embodiment, the adjusting device may comprise a moveable adjusting member and a drive mechanism having a motor, which is provided on the adjusting member, the adjusting device being configured such that displacement of the adjusting member adjusts a height of the lumbar support along the longitudinal direction of the backrest. In an embodiment, the adjusting device may comprise a moveable adjusting member and a drive mechanism having a motor, which is provided on the adjusting member, the adjusting device being configured such that displacement of the adjusting member adjusts a curvature of the lumbar support. In either case, a shaft having a structured surface may be provided, which engages a transmission coupled between the motor and the shaft. 
     While a drive mechanism has been described in which a two-stage worm transmission is coupled between the rotary output shaft of an electric motor and a spindle transmission, in other embodiments the drive mechanism may comprise only one or at least three worm transmission stages. In other embodiments, another reduction mechanism may be provided. 
     While a drive mechanism has been described in which a spindle transmission is provided for converting a rotary output motion of a motor into a linear displacement relative to a shaft, other drive mechanisms may be in order to effect a height adjustment of the lumbar support and/or a curvature adjustment of the lumbar support. For illustration, a drive mechanism that employs a shaft having a toothed surface may be utilized. 
     While an adjusting member and further adjusting member have been described which respectively are provided with recesses in which a guide wire can be received, other suitable configurations, such as connections employing bolt- or screw-type fasteners that allow the adjusting member and/or the further adjusting member to be displaced along the guide members, may be used for attaching the adjusting member and/or the further adjusting member to guide members in other embodiments. 
     While a lumbar support apparatus having a lumbar support formed as a support basket has been shown in the drawings, the lumbar support may have other suitable configurations in other embodiments. In still other embodiments, the lumbar support may be formed integrally with a backrest upholstery, or with other backrest components. 
     While exemplary embodiments have been described in the context of lumbar support adjustment in the backrest of a vehicle seat, embodiments of the invention are not limited to this particular field of application. Rather, embodiments of the invention may be advantageously employed to adjust lumbar supports in a wide variety of seats.