Chair with automatically adjustable tilting back

A chair comprising a unitary seat and lower back, an upper back, the seat and lower back and the upper back being contoured longitudinally and transversely to conform generally to the anatomical shapes of the parts of a person sitting in the chair which are supported by the chair, and the lower back and upper back having complementary sockets at each side opening toward each other, a resilient articulating linkage received in each complementary pair of sockets and mounting the upper back on the lower back for articulation between a resiliently restrained relatively upright position and a backward tilted position about a transverse horizontal axis at a height above the seat corresponding to about the middle of the anatomical back of a person sitting in the chair, at least the medial portion of the upper back being located substantially below the axis about which the upper back articulates so that the upper back is vertically coextensive with and supports the major part of the anatomical middle back of a person sitting in the chair from about the waist to about the shoulder blades and the lower medial portion thereof shifts forward when the upper back articulates backward, and each articulating linkage including an upper link and a lower link, means joining the links for articulation about an axis, spring means resiliently urging the links about the axis in a direction toward the relatively upright position of the upper back and stop means for establishing the upright position and the full backward tilted position of the upper back, the links including front walls having complementary rearwardly projecting flanges, and the spring means consisting of compression springs engaged between the surfaces of the flanges remote from each other and spring retainers joined to each other and compressing the springs against the flanges so that the springs urge the flanges toward each other and the links toward the upright position.

A chair comprising a unitary seat and lower back, an upper back, the seat and lower back and the upper back being contoured longitudinally and transversely to conform generally to the anatomical shapes of the parts of a person sitting in the chair which are supported by the chair, and the lower back and upper back having complementary sockets at each side opening toward each other, a resilient articulating linkage received in each complementary pair of sockets and mounting the upper back on the lower back for articulation between a resiliently restrained relatively upright position and a backward tilted position about a transverse horizontal axis at a height above the seat corresponding to about the middle of the anatomical back of a person sitting in the chair, at least the medial portion of the upper back being located substantially below the axis about which the upper back articulates so that the upper back is vertically coextensive with and supports the major part of the anatomical middle back of a person sitting in the chair from about the waist to about the shoulder blades and the lower medial portion thereof shifts forward when the upper back articulates backward, and each articulating linkage including an upper link and a lower link, means joining the links for articulation about an axis, spring means resiliently urging the links about the axis in a direction toward the relatively upright position of the upper back and stop means for establishing the upright position and the full backward tilted position of the upper back, the links including front walls and the spring means consisting of a mousetrap type torsion spring having legs engaging the front walls of the links and mounted on an axle which joins the links, and the links including side walls which partly overlap and the stop means consisting of lugs on the side wall of one link, one of which engages the front wall of the other link to establish the upright position and the other of which engages a rear wall on the other link to establish the full backward tilted position.

A chair comprising a unitary seat and lower back, an upper back, the seat and lower back and the upper back being contoured longitudinally and transversely to conform generally to the anatomical shapes of the parts of a person sitting in the chair which are supported by the chair, and the lower back and upper back having complementary sockets at each side opening toward each other, a resilient articulating linkage received in each complementary pair of sockets and mounting the upper back on the lower back for articulation between a resiliently restrained relatively upright position and a backward tilted position about a transverse horizontal axis at a height above the seat corresponding to about the middle of the anatomical back of a person sitting in the chair, at least the medial portion of the upper back being located substantially below the axis about which the upper back articulates so that the upper back is vertically coextensive with and supports the major part of the anatomical middle back of a person sitting in the chair from about the waist to about the shoulder blades and the lower medial portion thereof shifts forward when the upper back articulates backward, and each articulating linkage including an upper link and a lower link, means joining the links for articulation about an axis, spring means resiliently urging the links about the axis in a direction toward the relatively upright position of the upper back and stop means for establishing the upright position and the full backward tilted position of the upper back, the links including front walls and the spring means being a tension spring connected under tension between the respective front walls, and the links including side walls which partly overlap and the stop means consisting of lugs on the side wall of one link, one of which engages the front wall of the other link to establish the upright position and the other of which engages a rear wall on the other link to establish the full backward tilted position.

A chair comprising a unitary seat and lower back, an upper back, the seat and lower back and the upper back being contoured longitudinally and transversely to conform generally to the anatomical shapes of the parts of a person sitting in the chair which are supported by the chair, and the lower back and upper back having complementary sockets at each side opening toward each other, a resilient articulating linkage received in each complementary pair of sockets and mounting the upper back on the lower back for articulation between a resiliently restrained relatively upright position and a backward tilted position about a transverse horizontal axis at a height above the seat corresponding to about the middle of the anatomical back of a person sitting in the chair, at least the medial portion of the upper back being located substantially below the axis about which the upper back articulates so that the upper back is vertically coextensive with and supports the major part of the anatomical middle back of a person sitting in the chair from about the waist to about the shoulder blades and the lower medial portion thereof shifts forward when the upper back articulates backward, and each articulating linkage including an upper link and a lower link, means joining the links for articulation about an axis, spring means resiliently urging the links about the axis in a direction toward the relatively upright position of the upper back and stop means for establishing the upright position and the full backward tilted position of the upper back, a second seat supported on the seat portion of the unitary seat and lower back for forward and backward movement, means limiting the extent of such movement, a spring urging the second seat to its rearward-most position, coacting guides on the seat portion and the second seat constraining the second seat to move along a longitudinal axis of the seat portion, the guides including transversely spaced-apart flanges on the underside of the second seat and a boss on the upper side of the first seat, the boss being undercut along its lateral edges and the flanges having inturned ribs received in the undercuts to hold the second seat down on the first seat, as well as guide it longitudinally.

A chair comprising a unitary seat and lower back, an upper back, the seat and lower back and the upper back being contoured longitudinally and transversely to conform generally to the anatomical shapes of the parts of a person sitting in the chair which are supported by the chair, and the lower back and upper back having complementary sockets at each side opening toward each other, a resilient articulating linkage received in each complementary pair of sockets and mounting the upper back on the lower back for articulation between a resiliently restrained relatively upright position and a backward tilted position about a transverse horizontal axis at a height above the seat corresponding to about the middle of the anatomical back of a person sitting in the chair, at least the medial portion of the upper back being located substantially below the axis about which the upper back articulates so that the upper back is vertically coextensive with and supports the major part of the anatomical middle back of a person sitting in the chair from about the waist to about the shoulder blades and the lower medial portion thereof shifts forward when the upper back articulates backward, and each articulating linkage including an upper link and a lower link, means joining the links for articulation about an axis, spring means resiliently urging the links about the axis in a direction toward the relatively upright position of the upper back and stop means for establishing the upright position and the full backward tilted position of the upper back, a second seat supported on the seat portion of the unitary seat and lower back for forward and backward movement, means limiting the extent of such movement, a spring urging the second seat to its rearward-most position, coacting guides on the seat portion and second seat constraining the second seat to move along a longitudinal axis of the seat portion, the guides including an upwardly open elongated longitudinal channel on the seat portion, the channel having a lengthwise slot, and an elongated longitudinal rib extending down from the underside of the second seat through the slot in the channel, the rib having along its lower edge a bead which is wider than the slot and holds the second seat down on the first seat.