Abstract: Two spaced wings are mounted on the inner side of a seatback base plate in a manner to pivot about respective axes parallel to the seatback plane. Adjusting levers which move synchronously are connected at respective ends thereof to the wings to transmit the movement of the levers to the wings. An operating device is connected to one of the levers for manually adjusting the lever position.

Abstract: The rear of a seat cushion is adjusted vertically by a bell crank having a pair of opposed ends and an angled portion therebetween. One end of the bellcrank is pivotally coupled to a support of the seat while the other end is coupled to a rotary holding mechanism. The angled portion is pivotally coupled to a rear side of the seat cushion. The rotary holding mechanism is carried by the seat cushion and rotates and maintains the bell crank at the desired position to adjust the seat cushion rear side. The seat cushion is slightly movable horizontally relative to the support during vertical adjustment of the rear side of the seat cushion.

Abstract: A backrest of a seat has therein an adjustable lumbar supporter which comprises a first rod member transversely crossing two side brackets of the backrest to be rotatable about the axis thereof, an arm member secured at one end to the first rod member, a second rod member rotatably supported by the arm member, a lumbar supporter proper fixed to the second rod member, a first control mechanism for forcing the lumbar supporter proper to swing about the axis of the first rod member when operated, and a second control mechanism for forcing the lumbar supporter proper to swing about the axis of the second rod member when operated.

Abstract: Herein disclosed is a seat backrest with an adjustable lumbar supporter which comprises a rod transversely crossing frame members of the seatback to be rotatable about the axis thereof relative to the frame members, an arm member secured to the rod, a support member pivotally connected to the arm member, lumbar pressing means such as spring connected to the support member, first control means for permitting the support member to rotate about its pivoted portion relative to the arm member when operated, and second control means for permitting the arm member and thus the rod to rotate about the axis of the rod relative to the frame members when operated.