Lumbar support

1. An adjustable lumbar support for use in the back rest of a seat, wherein the lumbar support includes a flexible band which in use extends longitudinally across the back rest so that opposite ends of the band are adjacent respective opposite sides of the back rest and further includes adjusting means operable to vary the extent to which the flexible band is able to curve rearwardly relative to the seat back rest; wherein the flexible band includes a plurality of elongated members which are spaced along,, and extend transversely with respect to, the longitudinal extent of the band, and a respective resiliently compressible bridging element joining together successive elongated members; wherein each elongated member is sufficiently flexible whereby at least some of the elongated members are adapted to bend resiliently at opposite end portions thereof, and thereby to bend rearwardly to conform substantially to the shape of and provide resilient support for the lumbar region of an occupant of the seat, as the adjusting means is operated to reduce the extent to which the flexible band curves rearwardly; and wherein each bridging element comprises a resilient spring element which has a form of oppositely acting leaf springs with the leaf springs of each pair being joined together at respective ends and each is joined intermediate its ends to a respective one of the respective elongate members joined by the spring element.

2. The lumbar support of claim 1 , wherein each bridging element comprises a resilient spring element, and the bridging elements act to maintain or restore flexible band at a length which maintains or restores the extent of rearward curvature.

3. The lumbar support of claim 1 , wherein the flexible band is formed integrally.

4. The lumbar support of claim 1 , wherein the elongate members are adapted to bend rearwardly, as the adjusting means is operated to reduce the extent to which the flexible band curves rearwardly, in response to pressure applied to the band by the body of an occupant of a seat in which the support is provide.

5. The lumbar support of claim 1 , wherein the flexible band has a thickness of from about 3 to 6 mm.

6. The lumbar support of claim 1 , wherein each elongate member is adapted to bend rearwardly at opposite end portions thereof from a condition in which the front face of the elongate member is substantially planar.

7. The lumbar support of claim 1 , wherein each elongate member comprises a thin plate provided with strengthening ribs.

8. The lumbar support of claim 1 , wherein each elongate member comprises a thin plate of from 0.7 to 1.2 mm thick and which defines a front face of the elongate member, and a plurality of stiffening ribs or fins which extend over a face of the member.

9. The lumbar support of claim 8 , wherein the ribs or fins extend over a major part of the length of the plate.

10. The lumbar support of claim 1 , wherein the adjusting means comprises a Bowden cable system and an actuator device; and wherein the cable system includes a sleeve which extends between the actuator device and one end of the flexible band and a cable which extends from the actuator device, through the sleeve and, form the one end of the flexible band, along the band to the other end thereof, and the actuator device is operable to move the cable longitudinally within the sleeve for varying the extent of rearward curvature of the flexible band.