Back shell with selective stiffening

• US 5,487,591 A
• Filed: 05/31/1994
• Issued: 01/30/1996
• Est. Priority Date: 04/10/1986
• Status: Expired due to Fees

• Current Assignee: Steelcase Development Inc.
• Original Assignee: Steelcase Incorporated
• Inventors: Knoblock, Glenn A.
• Primary Examiner(s): Brown, Peter R.
• Application Number:
  US08/252,666
• Time in Patent Office: 609 Days
• Field of Search: 297/303.1, 297/303.3, 297/303.4, 297/452.14, 297/452.15, 297/452.55
• US Class Current: 297/452.14
• CPC Class Codes: A47C 1/03255 with a central column, e.g. rocking office chairs
• CPC Class Codes: A47C 1/03277 with bar or leaf springs
• CPC Class Codes: A47C 3/12 with shell-shape seat and back-rest unit, e.g. having arm rests
• CPC Class Codes: A47C 3/18 Chairs or stools with rotatable seat adjustable in height by rotation A47C3/24
• CPC Class Codes: A47C 3/245 resiliently supported
• CPC Class Codes: Y10S 297/02 Molded

Abstract

A chair includes a base, a seat, a back pivoted to the base and an inner shell construction connecting a cushion assembly to the back. The shell includes a semi-rigid, flexible sheet having a back portion shaped to support a back area of an adult user. The back portion includes a central area and an upper area. A plurality of ribs are formed integrally with the sheet to stiffen the central area of the back portion for lumbar support yet permit the upper portion of the back portion to flex for improved freedom of movement of the upper back area of the user.

Claims

1. A molded seat back, comprising:

a generally planar shell having a forward surface and a rearward surface, said shell having a plurality of ribs disposed on one of the surfaces to control flexure of the shell, said ribs including;

a plurality of angularly related first ribs, at least one of said first ribs being angled different from another of said first ribs to form a generally X-shaped pattern, said first ribs having upper and lower leg portions defined on opposite sides of the point at which said first ribs intersect; and

a plurality of substantially vertical second ribs, said second ribs being laterally spaced apart, at least a portion of at least one of said second ribs being positioned within the space defined between the upper leg portion of one of said first ribs and the lower portion of another, differently angled, first rib, said upper leg portions of said angularly related first ribs defining therebetween an uninterrupted planar portion of said shell.

2. A molded seat back as defined by claim 1 wherein said first ribs are integral with and extend from the rearward surface of said shell.

3. A molded seat back as defined by claim 2 wherein said second ribs extend in generally spaced, parallel relationship on the rearward surface of said shell.

4. A molded seat back as defined by claim 3 wherein said shell includes a marginal edge and said second ribs are spaced rearwardly from said marginal edge.

5. A molded seat back as defined by claim 4 wherein a first pair of said first ribs extend in spaced, parallel relationship.

6. A molded seat back as defined by claim 5 wherein a second pair of said first ribs extend in spaced, parallel relationship and intersect said first pair of said first ribs.

7. A molded seat back as defined in claim 1 wherein said vertical second ribs include upper leg portions located within said pair of opposed spaces defined by said angled first ribs, said upper leg portions of said second ribs having an end section not extending above said first ribs.

8. A molded seat back as defined in claim 1 wherein said vertical second ribs include lower leg portions, at least one of said lower leg portions of said angled first ribs intersecting said lower leg portions of said second vertical ribs in at least one second point and further extending angularly below said at least one second point.

9. A molded seat back as defined in claim 8 including attachment structure formed on the rear surface of the sheet and configured for attachment to a back support, at least one of said lower leg portions of said first and second ribs being interconnected to said attachment structure.

10. A molded seat back as defined in claim 9 wherein said lower leg portions of said first and second ribs interconnect with and form a rigid matrix with said attachment structure.

11. A molded seat back as defined in claim 1 including attachment structure integrally formed on the rear surface of the shell and configured for attachment to a back support.

12. A molded seat back as defined in claim 1 wherein said sheet includes a marginal edge and including a marginal rib extending along but spaced inwardly from said marginal edge.

13. A molded seat back support shell, comprising:

a semi-rigid, substantially planar sheet including generally flat front and rear surfaces;

a plurality of angled, intersecting first ribs forming a generally X-shaped pattern on the rear surface of the sheet, said angled first ribs being selectively positioned to control torsional flexure of said sheet, said first ribs having upper and lower leg portions extending on opposite sides of a point at which said first ribs intersect, said first ribs defining a T-shaped cross section with said planar sheet along intersections formed therewith for stiffening said sheet along the intersections; and

a plurality of substantially vertical second ribs on said rear surface, said second ribs being laterally spaced apart and selectively positioned to rigidify said sheet in a vertical plane for firm support of a user'"'"'s upper back area, at least a portion of at least one of said second ribs being positioned within a pair of opposed spaces defined by said first ribs one either side of the point of intersection of said first ribs;

said upper leg portions of said first ribs defining therebetween an uninterrupted planar portion of said sheet.

14. A molded seat back support shell as defined in claim 13 wherein said vertical second ribs include upper leg portions located within said pair of opposed spaces defined by said angled first ribs, said upper leg portions of said second ribs having an end section not extending above said angled first ribs.

15. A molded seat back support shell as defined in claim 13 wherein said vertical second ribs include lower leg portions, at least one of said lower leg portions of said angled first ribs intersecting said lower leg portions of said second vertical ribs in at least one second point and further extending angularly below said at least one second point.

16. A molded seat back support shell as defined in claim 13 including attachment structure integrally formed on the rear surface of the sheet and configured for attachment to a back support.

17. A molded seat back support shell as defined in claim 13 wherein said sheet includes a marginal edge and including a marginal rib extending along but spaced inwardly from said marginal edge.

18. A molded seat back support shell comprising:

a semi-rigid, substantially planar sheet including generally flat front and rear surfaces;

a plurality of angled, intersecting first ribs forming a generally X-shaped pattern on the rear surface of the sheet, said angled first ribs being selectively positioned to control torsional flexure of said sheet, said first ribs having upper and lower leg portions extending on opposite sides of a point at which said first ribs intersect, said first ribs defining a T-shaped cross section with said planar sheet along intersections formed therewith for stiffening said sheet along the intersections;

a plurality of substantially vertical second ribs on said rear surface, said second ribs being laterally spaced apart and selectively positioned to rigidify said sheet in a vertical plane for firm support of a user'"'"'s upper back area, at least a portion of at least one of said second ribs being positioned within a pair of opposed spaces defined by said first ribs on either side of the point of intersection of said first ribs;

said vertical second ribs including lower leg portions, at least one of said lower leg portions of said angled first ribs intersecting said lower leg portions of said second vertical ribs in at least one second point and further extending angularly below said at least one second point; and

attachment structure formed on the rear surface of the sheet and configured for attachment to a back support, at least one of said lower leg portions of said first and second ribs being interconnected to said attachment structure.

19. A molded seat back support shell as defined in claim 18 wherein said lower leg portions of said first and second ribs interconnect with and form a rigid matrix with said attachment structure.

20. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support;

a cushion assembly shaped to support the back of a user thereon; and

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid, resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair; and

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion in an X-shaped arrangement for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component, said angled ribs defining therebetween an uninterrupted planar portion of said sheet in said upper part of said back portion.

21. A chair as set forth in claim 20 wherein said plurality of angled ribs include first and second angled ribs extending in non-parallel directions which intersect in at least one intermediate point on said back portion, said uninterrupted planar portion being generally above said at least one intermediate point.

22. A chair as set forth in claim 21 wherein said first and second angled ribs include at least two pair of spaced apart, parallel ribs that form an overlapping double X-shaped arrangement of ribs.

23. A chair as set forth in claim 20 wherein said control comprises:

a control housing;

said back support having an upright, said upright being pivoted to said control housing;

a coil spring disposed within said control housing, said spring having first and second ends, said first end engaging said upright;

an adjuster plate having one end pivoted to said control housing, said plate further having another end;

an adjuster nut engaging the another end of said plate, said second end of said spring engaging said adjuster plate; and

an adjuster screw mounted on said housing and engaging said adjuster nut.

24. A chair as set forth in claim 23 wherein said adjuster plate another end has a forked configuration.

25. A chair as set forth in claim 24 wherein said adjuster nut includes an enlarged center section which defines a threaded bore which engages said adjuster screw.

26. A chair as set forth in claim 20 wherein said control comprises:

a control housing;

a pair of coaxially aligned coil springs disposed within said housing;

said back support including at least one back upright pivoted to said control housing about a pivot axis offset forwardly and parallel to the axis of said coil springs, each of said coil springs having an end engaging one end of said at least one back upright;

an adjustment bolt on said housing; and

an adjustment nut having a threaded bore engaging said adjustment bolt and a pair of outwardly extending roller portions positioned to overlie ends of said coil springs whereby rotation of the adjustment bolt moves said adjustment nut and adjust the tension of said springs.

27. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support;

a cushion assembly shaped to support the back of a user thereon; and

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid, resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair; and

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion in an X-shaped arrangement for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component; and

attachment structure integrally formed in a lower part of said back portion, said attachment structure being interconnected to at least one of said vertical ribs and said angled ribs and projecting rearwardly from said rearward surface, said attachment structure being configured to mateably receive and securely attach to said back support.

28. A chair as defined in claim 27 wherein said angled ribs intersect in at least one point and include upper leg portions extending above said at least one point, said upper leg portions defining therebetween an uninterrupted planar portion of said sheet.

29. A chair as defined in claim 27 wherein both of said angled ribs and said vertical ribs include at least one lower leg portion interconnected to said attachment structure.

30. A chair as set forth in claim 27 wherein said angled ribs include at least two pair of spaced apart, parallel ribs that form an overlapping double X-shaped arrangements of ribs.

31. A chair as set forth in claim 27 wherein said control comprises:

a control housing;

said back support having an upright, said upright being pivoted to said control housing;

a coil spring disposed within said control housing, said spring having first and second ends, said first end engaging said upright;

an adjuster plate having a one end pivoted to said control housing, said plate further having another end;

an adjuster nut engaging the another end of said plate, said second end of said spring engaging said adjuster plate; and

an adjuster screw mounted on said housing and engaging said adjuster nut.

32. A chair as set forth in claim 31 wherein said adjuster plate another end has a forked configuration.

33. A chair as set forth in claim 32 wherein said adjuster nut includes an enlarged center section which defines a threaded bore which engages said adjuster screw.

34. A chair as set forth in claim 27 wherein said control comprises:

a control housing;

a pair of coaxially aligned coil springs disposed within said housing;

said back support including at least one back upright pivoted to said control housing about a pivot axis offset forwardly and parallel to the axis of said coil springs, each of said coil springs having an end engaging one end of said at least one back upright;

an adjustment bolt on said housing; and

an adjustment nut having a threaded bore engaging said adjustment bolt and a pair of outwardly extending roller portions positioned to overlie ends of said coil springs whereby rotation of the adjustment bolt moves said adjustment nut and adjust the tension of said springs.

35. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a synchrotilt control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support;

a cushion assembly shaped to support the back of a user thereon; and

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid, resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet having a continuous thickness and extending substantially continuously in a plane so that said sheet exhibits strength in all directions in the plane but is flexible in directions not in said plane, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair;

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component, said angled ribs defining a T-shaped cross section with said planar sheet at an intersection formed therewith for stiffening said sheet along the intersection; and

attachment structure integrally formed on the rear surface of the sheet configured for attachment to a back support, at least one of said vertical ribs and said angled ribs being interconnected to said attachment structure.

36. A chair as defined in claim 35 wherein said vertical ribs include lower leg portions, and said angled ribs include lower leg portions, at least one of said lower leg portions of said angled ribs intersecting said lower leg portions of said vertical ribs in at least one second point and further extending angularly below said at least one second point.

37. A chair as defined in claim 35 wherein said angled ribs include first and second angled ribs extending in non-parallel directions, said first and second angled ribs each including pairs of spaced apart parallel ribs that form an overlapping double X-shaped arrangement of ribs.

38. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a synchrotilt control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support;

a cushion assembly shaped to support the back of a user thereon; and

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid, resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet having a continuous thickness and extending substantially continuously in a plane so that said sheet exhibits strength in all directions in the plane but is flexible in directions not in said plane, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair; and

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component, said angled ribs defining a T-shaped cross section with said planar sheet at an intersection formed therewith for stiffening said sheet along the intersection, said angled ribs including upper leg portions defining therebetween an uninterrupted planar portion of said sheet.

39. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a cushion assembly shaped to support the back of a user thereon; and

a synchrotilt control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support;

said control comprising;

a control housing;

said back support having an upright, said upright being pivoted to said control housing;

a coil spring disposed within said control housing, said spring having first and second ends, said first end engaging said upright;

an adjuster plate having one end pivoted to said control housing, said plate further having another end;

an adjuster nut engaging the another end of said plate, said second end of said spring engaging said adjuster plate; and

an adjuster screw mounted on said housing and engaging said adjuster nut;

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet having a continuous thickness and extending substantially continuously in a plane so that said sheet exhibits strength in all directions in the plane but is flexible in directions not in said plane, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair; and

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component, said angled ribs defining a T-shaped cross section with said planar sheet at an intersection formed therewith for stiffening said sheet along the intersection.

40. A chair comprising:

a base;

a seat supported on said base;

a back support pivotally supported on said base;

a control operatively connecting said base and said back support, and selectively controlling rearward tilting of said back support, said control comprising a control housing, said back support having an upright, said upright being pivoted to said control housing, a coil spring disposed within said control housing, said spring having first and second ends, said first end engaging said upright, an adjuster plate having one end pivoted to said control housing, said plate further having another end, an adjuster nut engaging the another end of said plate, said second end of said spring engaging said adjuster plate, an adjuster screw mounted on said housing and engaging said adjuster nut;

a cushion assembly shaped to support the back of a user thereon; and

a shell construction connecting said cushion assembly with said back support, said shell construction comprising;

a semi-rigid, resiliently flexible sheet having substantially planar forward and rearward surfaces, said sheet including a generally planar back portion shaped to selectively support a back area of an adult user thereon with the cushion assembly being on the forward surface of the shell construction;

a plurality of spaced apart vertical ribs projecting rearwardly from said rearward surface of said sheet and extending across said back portion for selectively reinforcing said sheet, said vertical ribs being selectively positioned at predetermined locations to provide a predetermined amount of forwardly directed support in a vertical plane to the user'"'"'s back area when the user urges his back rearwardly in the chair; and

a plurality of angled ribs interconnected in at least one location with said vertical ribs and projecting rearwardly from said rearward surface of said sheet and further extending diagonally across at least an upper part of said back portion in an X-shaped arrangement for selectively reinforcing said sheet, said angled ribs being selectively positioned at predetermined locations to provide a predetermined amount of torsional support to the user'"'"'s back area when the user moves his upper body in a direction having a torsional component, said angled ribs defining a T-shaped cross section with said planar sheet at intersections formed therewith for stiffening said sheet along the intersections, said angled ribs defining therebetween an uninterrupted planar portion of said sheet in said upper part of said back portion, said plurality of angled ribs including first and second angled ribs extending in non-parallel directions which intersect in at least one intermediate point on said back portion, said uninterrupted planar portion being generally above said at least one intermediate point; and

attachment structure integrally formed in a lower part of said back portion, said attachment structure being interconnected to at least one of said vertical ribs and said angled ribs and projecting rearwardly from said rearward surface, said attachment structure being configured to mateably receive and attach to said back support.