Thermoplastic chair flexor
A seating structure employing a thermoplastic flexor defining the flexibility and stiffness of a seatback is provided. The seating structure may comprise a seat portion for supporting a user, a seatback portion for supporting a user, a frame for supporting the seat portion and the seatback portion, one or more base portions extending at an angle from the seatback portion, and one or more thermoplastic flexors affixed to or within the seatback and base portions of the seating structure. The thermoplastic flexor has certain material characteristics which define and limit the deflection and a rebound of the seatback portion relative to the base portion when under load. The seating structure may further comprise one or more anchors securing the seatback portion, base portion, and thermoplastic flexor to the frame. The seat portion, seatback portion, and base portion may comprise a unibody or multipiece chair shell, and the thermoplastic flexor may be completely enveloped within the shell, or partially disposed behind the shell in a nested mechanical relationship.
1. A seating structure comprising:
a. a seat portion for supporting a user,
b. a seatback portion for supporting a user,
c. a frame for supporting the seat portion and the seatback portion,
d. a base portion extending from the seatback portion,
e. a thermoplastic flexor affixed to the seatback and base portions of the seating structure, and wherein the thermoplastic flexor defines and limits a deflection and a rebound of the seatback portion relative to the base portion, wherein the thermoplastic flexor has an upper extension and a lower extension, and wherein the lower extension has a top gap stretching thereacross, and wherein a horizontal rearward force applied to the upper extension of the thermoplastic flexor spreads open the gap thereby causing the lower extension to bottom out on the frame, and
f. an anchor securing the seatback portion, base portion, and thermoplastic flexor to the frame.
2. The seating structure of claim 1 , wherein the thermoplastic flexor is comprised of a material having an ultimate tensile strength ranging from 5-115 MPa.
3. The seating structure of claim 1 , wherein the thermoplastic flexor is comprised of a material having, an elastic modulus characteristic ranging from 587-20700 MPa.
4. The seating structure of claim 1 , wherein the thermoplastic flexor is comprised of a material having a creep modulus ranging from 1800-2500 MPa when a stress is applied for one hour.
5. The seating structure of claim 1 , wherein the thermoplastic flexor is comprised of a material having a yield strain of greater than 5%.
6. The seating structure of claim 1 , wherein the thermoplastic flexor is a curvilinear elbow.
7. The seating structure of claim 1 , wherein the thermoplastic flexor further comprises a bridge connecting two sides of the lower extension separated by the gap.
8. The seating structure of claim 7 , wherein the thermoplastic flexor further comprises a first fulcrum formed at a first interface of the lower extension and the anchor, and a second fulcrum formed at a second interface of the lower extension and the anchor.
9. The seating structure of claim 8 , wherein the first fulcrum is beneath the bridge.
10. The seating structure of claim 9 , wherein the second fulcrum is below a transition region between the lower extension and the waist.
11. The seating structure of claim 8 , wherein the thermoplastic flexor bends around the first fulcrum before the thermoplastic flexor bends around the second fulcrum.
12. The seating structure of claim 7 , wherein a bending moment is applied on the bridge when a horizontal force is exerted on the seatback.
13. The seating structure of claim 7 , wherein the thermoplastic flexor further comprises a fulcrum formed at an interface of the lower extension and the anchor.
14. The seating structure of claim 7 , wherein the thermoplastic flexor further comprises a plurality of fulcrums formed at a plurality of interfaces along the lower extension and the anchor.
15. The seating structure of claim 1 , wherein the seatback portion, base portion, and seat portion comprise a unibody thermoplastic shell.
16. The seating structure of claim 1 , wherein the seatback portion and base portion are together connected to the frame independently from the seat portion.
17. The seating structure of claim 1 , wherein the seatback and base portions are overmolded relative to the thermoplastic flexor.