Seat assembly for an office chair

1. A chair comprising:

a seat/back assembly which includes a cushion assembly for supporting one of a seat and back of a chair occupant, said cushion assembly including a cushion, a cover and an attachment structure for securing said cover in overlying covering relation to said cushion;

said cushion assembly further comprising a horizontally enlarged, inner shell which has a bottom surface and an upper surface which is covered with said cushion, said cushion being resiliently-compressible, and extending outwardly to an outer peripheral shell edge of the inner shell, said cushion being enclosed by said cover which said cover is enlarged widthwise and in the front-to-back direction so as to hang over the sides of the cushion and wrap about the outer peripheral shell edge of the inner shell, wherein a peripheral cover edge of the cover is able to wrap about and extend partially underneath the bottom surface of the inner shell, said inner shell in the edge region of the outer peripheral shell edge including an edgewise-extending securement channel defined by parallel, downwardly-projecting inner and outer channel walls, wherein said inner channel wall includes spaced-apart first teeth for securing said cover;

said cushion assembly further including an outer shell which mounts to the inner shell from the bottom surface thereof and extends along the outer peripheral shell edge, said outer shell including said attachment structure thereon which comprises an upstanding rib that extends edgewise about an outer periphery of the outer shell, a free end of said rib including spaced-apart second teeth so that when said outer shell is fitted onto the inner shell, the peripheral cover edge follows a convoluted path by wrapping about the outer peripheral shell edge of the inner shell and overlapping the bottom surface of the inner shell, and then turning into the securement channel as it wraps over the free end of the rib, and then turns downwardly out of the securement channel and finally extends over and terminates beyond the inner channel wall and the first teeth thereof; and

wherein said cover is pinched at first and second pinch points as said cover passes cross-wise through said convoluted path, wherein said second pinch point is located between the second teeth at the upper end of the rib and the opposing bottom surface of the securement channel, and said first pinch point is located at the first teeth on the inner channel wall which presses the cover against an opposing inside surface of the outer shell.

2. The chair according to claim 1 , wherein said rib is separated edge-wise by the cross-windows to define separated rib sections.

3. The chair according to claim 2 , wherein said separation of the rib sections from each other by the cross-windows allows for outward flexing of the rib sections when the cover is pulled taut on the cushion assembly.

4. The chair according to claim 2 , wherein an interior of the securement channel also includes upstanding cross-ribs which extend between the inner and outer channel walls in crosswise relation and fit into the cross-windows which secures the cover within the cross-windows and defines additional folds along the convoluted path of the cover.

5. The chair according to claim 1 , wherein said first and second teeth are tapered so as to facilitate compression of the cover.

6. The chair according to claim 1 , wherein said rib is formed of aligned rib sections which are separated from each other by cross-windows, said rib sections being edgewise elongate so as to be parallel to the inner and outer channel walls of the inner shell.

7. The chair according to claim 6 , wherein an interior of the securement channel also includes upstanding cross-ribs which extend between the inner and outer channel walls in crosswise relation and fit into the cross-windows which secures the cover within the cross-windows and defines additional folds along the convoluted path of the cover, said cover being pinched at multiple locations along the cross-wise extent of the convoluted path and fixedly secured at the peripheral edge of the cover in compressed, pinched engagement between opposing surfaces of the outer shell and inner shell.

8. A chair comprising:

a seat/back assembly which includes a cushion assembly for supporting one of a seat and back of a chair occupant, said cushion assembly including a cushion, a cover and an attachment structure for securing said cover in overlying covering relation to said cushion;

said cushion assembly further comprising a horizontally enlarged, inner shell which has a bottom surface and an upper surface which is covered with said cushion, said cushion being resiliently-compressible, and extending outwardly to an outer peripheral shell edge of the inner shell, said cushion being enclosed by said cover which said cover is enlarged widthwise and in the front-to-back direction so as to hang over the sides of the cushion and wrap about the outer peripheral shell edge of the inner shell, wherein a peripheral cover edge of the cover is able to wrap about and extend partially underneath the bottom surface of the inner shell, said inner shell in the edge region of the outer peripheral shell edge including an edgewise-extending securement channel defined by parallel, downwardly-projecting inner and outer channel walls;

said cushion assembly further including an outer shell which mounts to the inner shell from the bottom surface thereof and extends along the outer peripheral shell edge, said outer shell including said attachment structure thereon which comprises an upstanding rib that extends edgewise about an outer periphery of the outer shell, the peripheral cover edge follows a convoluted path by wrapping about the outer peripheral shell edge of the inner shell and overlapping the bottom surface of the inner shell, and then turning into the securement channel as it wraps over the free end of the rib, and then turns downwardly out of the securement channel and finally extends over and terminates beyond the inner channel wall and the first teeth thereof, said cover being pinched at multiple locations along the cross-wise extent of the convoluted path and being fixedly secured at the edge of the cover in compressed, pinched engagement between opposing surfaces of the outer shell and inner shell.

9. The chair according to claim 8 , wherein said cover is pinched at first and second pinch points as said cover passes cross-wise through said convoluted path, wherein said second pinch point is located between the upper end of the rib and the opposing bottom surface of the securement channel, and said first pinch point is located at a terminal end of the inner channel wall which presses the cover against an opposing inside surface of the outer shell.

10. The chair according to claim 9 , wherein said free end of said rib includes spaced-apart second teeth to define said second pinch point, and said terminal end of said inner channel wall includes spaced-apart first teeth to define said first pinch point.

11. The chair according to claim 8 , wherein said cushion assembly is supported upon a load-bearing base adapted for support upon a floor.

12. The chair according to claim 11 , wherein said base includes a tilt control mechanism wherein the seat assembly and back assembly are pivotally connected to the tilt control mechanism and rearwardly reclinable in operation.

13. The chair according to claim 8 , wherein said rib is formed of aligned rib sections which are separated from each other by cross-windows, said rib sections being edgewise elongate so as to be parallel to the inner and outer channel walls of the inner shell.

14. The chair according to claim 13 , wherein an interior of the securement channel also includes upstanding cross-ribs which extend between the inner and outer channel walls in crosswise relation and fit into the cross-windows which secures the cover within the cross-windows and defines additional folds along the convoluted path of the cover, said cover being pinched at multiple locations along the cross-wise extent of the convoluted path and fixedly secured at the peripheral edge of the cover in compressed, pinched engagement between opposing surfaces of the outer shell and inner shell.

15. A chair comprising:

a seat/back assembly which includes a cushion assembly for supporting one of a seat and back of a chair occupant, said cushion assembly including a cushion, a cover and an attachment structure for securing said cover in overlying covering relation to said cushion;

said cushion assembly further comprising a horizontally enlarged, inner shell which has a bottom surface and an upper surface which is covered with said cushion, said cushion being resiliently-compressible, and extending outwardly to an outer peripheral shell edge of the inner shell, said cushion being enclosed by said cover which said cover is enlarged widthwise and in the front-to-back direction so as to hang over the sides of the cushion and wrap about the outer peripheral shell edge of the inner shell, wherein a peripheral cover edge of the cover is able to wrap about and extend partially underneath the bottom surface of the inner shell, said inner shell in the edge region of the outer peripheral shell edge including an edgewise-extending securement channel defined by parallel, downwardly-projecting inner and outer channel walls;

said cushion assembly further including an outer shell which mounts to the inner shell from the bottom surface thereof and extends along the outer peripheral shell edge, said outer shell including said attachment structure thereon which comprises an upstanding rib that extends edgewise about an outer periphery of the outer shell, a free end of said rib including spaced-apart second teeth so that when said outer shell is fitted onto the inner shell, the peripheral cover edge follows a convoluted path by wrapping about the outer peripheral shell edge of the inner shell and overlapping the bottom surface of the inner shell, and then turning into the securement channel as it wraps over the free end of the rib, and then turns downwardly out of the securement channel and finally extends over and terminates beyond the inner channel wall and the first teeth thereof, said cover being pinched at multiple locations along the cross-wise extent of the convoluted path and being fixedly secured at the edge of the cover in compressed, pinched engagement between opposing surfaces of the outer shell and inner shell, wherein said cover is pinched at first and second pinch points as said cover passes cross-wise through said convoluted path, wherein said second pinch point is located between the upper end of the rib and the opposing bottom surface of the securement channel, and said first pinch point is located at a terminal end of the inner channel wall which presses the cover against an opposing inside surface of the outer shell; and

said rib being formed of aligned rib sections which are separated from each other by cross-windows, said rib sections being edgewise elongate so as to be parallel to the inner and outer channel walls of the inner shell.

16. The chair according to claim 15 , wherein an interior of the securement channel also includes upstanding cross-ribs which extend between the inner and outer channel walls in crosswise relation and fit into the cross-windows which secures the cover within the cross-windows and defines additional folds along the convoluted path of the cover.

17. The chair according to claim 16 , wherein said cushion assembly is supported upon a load-bearing base adapted for support upon a floor.

18. The chair according to claim 17 , wherein said base includes a tilt control mechanism wherein the chair includes a seat assembly and back assembly which are pivotally connected to the tilt control mechanism and rearwardly reclinable in operation.

19. The chair according to claim 18 , wherein said seat assembly has front and rear seat portions that pivotally connect to the tilt control mechanism supported on the base and wherein the front and rear edge portions of a support plate pivotally connect to the seat or to the tilt control mechanism and the support plate supports said inner shell.