Adjustable lumbar support

Claim 1

A lumbar support for a backrest having a lumbar portion designed to be horizontally and vertically aligned with the lumbar region of a user of the backrest, said lumbar support being adjustable according to desired horizontal and vertical adjustment settings and comprising: a. a support plate having front and rear surfaces, at least a portion of said front surface engaging the rear of said lumbar portion of said backrest to define an effective contact region, the horizontal position and vertical alignment of which varies with the vertical inclination and horizontal adjustment of said support plate; b. first bracket means in fixed vertical position relative said backrest, said first bracket means pivotally supporting said support plate to permit changes in the vertical inclination of said support plate; c. a cam member disposed between said support plate and said first bracket means and rotatably fixed to said first bracket means and rotatable in one direction to rotate said support plate to change the vertical inclination of said support plate, said cam member having a series of pawls circumferentially disposed about said cam member; d. a frame supporting said backrest; e. first control means for slidably positioning said support plate by an amount determined by the desired horizontal adjustment setting to align said effective contact region horizontally with the lumbar region of a user, said control means including a first casing fixed to said frame; a first shaft rotatably connected to said first casing; a coupler rotatable with said first shaft and having a cam surface; a torsion spring connected between said support plate and said first casing and slidably contacting said cam surface, wherein rotation of said cam surface varies the tension applied to said support plate by said torsion spring, f. second control means for rotating said cam member by an amount determined by the desired vertical adjustment setting, to align said effective contact region vertically with the lumbar region of a user, said control means including a second casing fixed to said frame, said first and second casings being affixed at substantially opposite sides of said backrest; a second shaft rotatably connected to said second casing; and transmission means for converting rotation of said second shaft into rotation of said cam member, said transmission means including: an adjustment plate integrally attached to said second shaft; a release plate for rotatably positioning said cam member; cable means extending between said adjustment plate and said release plate for rotating said cam member in response to rotation of said adjustment plate in a first direction; and means for biasing said adjustment plate in a direction counter said first direction; and g. means for restricting rotation of said cam member in a direction counter said first direction including an extension pivotally mounted on said support plate and spring means for biasing said extension to engage corresponding ones of said series of pawls.