Adjustable backrest for the seats of vehicles, particularly cars

Claim 1

A backrest for vehicle seats with a support structure for the back of the person occupying the seat wherein said support structure comprises an inverted U-shaped frame member with an upper crossbar and two side arms having spaced apart lower ends, shaft means rotatably mounted between said lower ends, an array of flexible elements extending generally vertically side by side and connected at opposite ends thereof to said crossbar and said shaft means, said flexible elements having a generally S-shaped configuration with a lower forwardly convex curve for supporting the lumbar region of the back and an upper forwardly concave curve for supporting the upper dorsal region. a spacer cross member disposed parallel to said crossbar of said frame and disposed in engagement with said flexible elements adjacent said upper forwardly concave curve, guide bar means secured to said U-shaped frame member between said side arms and extending parallel to said crossbar, tensioning elements connected to said spacer cross member and said shaft means and extending over said guide means to act substantially radially on said upper curve of said flexible elements, and operating means connected to said shaft means for rotating said shaft means to selectively alter the curvature of said lower curve and said upper curve of the flexible elements.