Chair and components
A chair support shell has an integral back portion, seat portion, and joining portion between the back portion and the seat portion. At least a major portion of the support shell comprises a compliant structure, the compliant structure having a plurality of cells interconnected by a plurality of resilient members. The compliant structure provides compliance in the seat portion, compliance in the back portion, and compliance in the joining portion. The compliant structure enables recline of the back portion relative to the seat portion.
1. A chair comprising a base, a transom supported on the base, a seat portion and a back portion supported on the transom, and a rocking mechanism configured to enable the transom to rock forward and rearward relative to the base; the rocking mechanism comprising:
a concave rock surface provided on the base;
a convex rock surface operatively provided on the transom and arranged to be in rolling contact with the concave rock surface, the convex rock surface having a radius of curvature less than a radius of curvature of the concave rock surface; and
complementary engagement features operatively provided on the transom and on the base;
wherein the engagement features comprise a gear with a plurality of teeth on the transom and a curved array of recesses or teeth or both recesses and teeth on the base, wherein the gear is in rolling contact with the curved array of recesses or teeth or both recesses and teeth on the base, wherein at least one of the teeth of the gear is seated in a complementary recess or between the teeth or both in a complementary recess and between the teeth of the curved array when the transom is in a neutral position, and configured such that rocking the transom forward or rearwards moves the at least one of the teeth away from its seated position.
2. The chair according to claim 1 , wherein the rocking mechanism comprises at least one biasing member acting between the transom and the base to bias the transom to a neutral position, and wherein the transom can be rocked forwards or rearwards or both forwards and rearwards from the neutral position.
3. The chair according to claim 2 , wherein the at least one biasing member comprises a front spring and a rear spring, the springs acting between the transom and the base.
4. The chair according to claim 3 , wherein the front spring is symmetrical with the rear spring(s) about a frontal plane that is coincident with a neutral contact point.
5. The chair according to claim 3 , wherein a spring rate of the front spring is different to a spring rate of the rear spring.
6. The chair according to claim 1 , further comprising a forward or rear stop to limit rock of the transom relative to the base.
7. The chair according to claim 6 , wherein the stop comprises a curved slot provided on the base or the transom, and a pin provided on the other of the base or the transom, the pin being slidable in the slot between a front limit position and a rear limit position.
8. The chair according to claim 1 , wherein the convex rock surface is adjacent the gear and the concave rock surface is adjacent the curved array of recesses or teeth or both recesses and teeth.
9. The chair according to claim 1 , wherein the rocking mechanism comprises two laterally spaced gears and two respective laterally spaced curved arrays of recesses or teeth or both recesses and teeth, the chair comprising two convex rock surfaces and two concave rock surfaces, each concave and convex rock surface being adjacent a respective one of the gears or arrays of recesses or teeth or both recesses and teeth.
10. The chair according to claim 1 , wherein the gear is a spur gear or a partial spur gear.
11. The chair according to claim 10 , wherein the spur gear teeth have varying profiles.
12. The chair according to claim 10 , wherein the convex rock surface has a radius of curvature that is substantially the same as a pitch radius of the spur gear, and the concave rock surface has a radius of curvature that is substantially the same as a pitch radius of the curved array of recesses or teeth or both recesses and teeth.
13. The chair according to claim 12 , wherein the convex rock surface is concentric with the spur gear, and wherein the concave rock surface is concentric with the curved array.
14. The chair according to claim 1 , wherein the convex and concave rock surfaces each have a constant radius of curvature, or wherein the radius of curvature of each of the convex and concave rock surfaces varies along the surface.
15. The chair according to claim 14 , wherein the radius of curvature of each of the convex and concave rock surfaces is smaller at a rear of the surfaces than at a front of the surfaces.
16. The chair according to claim 3 , further comprising a forward or rear stop to limit rock of the transom relative to the base, wherein the transom has a maximum forward rock limit from a neutral position of 8°, and a maximum rearward rock limit from a neutral position of 4°, and wherein rearward rock resistance increases more with tilt or rock angle than forward tilt resistance.
17. The chair according to claim 1 , wherein the seat portion and the back portion are movably mounted on the transom.
18. The chair according to claim 1 , wherein the back portion is reclinable relative to transom and the seat portion.
19. The chair according to claim 1 , wherein the curved array of recesses or teeth or both recesses and teeth is provided by a curved rack that extends through an arc of more than 45 degrees, and wherein an arcuate geared surface of the gear extends through an arc of more than 45 degrees.
20. The chair according to claim 19 , wherein a forward end of the curved rack, a forward end of the arcuate geared surface, a forward end of the concave rock surface, and a forward end of the convex rock surface are oriented at angle(s) of more than 40 degrees above horizontal when the transom is in a neutral position.