Lumbar support device

Claim 1

A lumbar support device, comprising: a seat back frame having a pair of lateral frame sections; a pair of side brackets each fixedly provided on the respective said lateral frame sections; a pair of arms each pivotally connected to the respective said two side brackets, such that said arms are disposed inwardly of said side brackets and their respective rotation centers are located at their upper end parts relative to the corresponding said two side brackets, so that said two arms are free to rotate about said rotation centers in a fore-and-aft direction with respect to said seat back frame; a lumbar support means extending between said arms, so that said lumbar support means is free to rotate forwardly and backwardly relative to said seat back frame as said arms rotate; a connecting rod extending between said arms; a brake means provided fixedly on one of said two lateral frame sections on said seat back frame, said brake means being adapted for restricting rotation of a drive shaft in order that said drive shaft is only permitted to rotate through operation of an operation spindle; and a link means fixed on said driven shaft of said brake means, said link means being at its free end part in an operative engagement with said lumbar support means, said link means including an engagement pin provided at its end part, wherein said engagement pin is in an slidable engagement with an elongated hole which is formed in one of said arms, whereby rotation of said drive shaft causes a lumbar support action of said lumbar support means via said link means.