Seat back for an office chair

1 . A seat back for an office chair, comprising:

a structural frame having a pair of spaced apart upright members each having an upper end and a lower end, and an upper cross member connecting the upper ends of the uprights;

a flexible support including a user support surface having an upper edge, a lower edge, and a pair of side edges, the upper edge of the flexible support mounted on the upper cross member of the frame; and

a tensioner connected between the lower edge of the flexible support and the upright members of the frame such that the tensioner stretches the flexible support between the upper and lower edges of the flexible support and maintains the flexible support in tension on the structural frame, wherein the tensioner includes at least one tensioner arm, the at least one tensioner arm having a first end including structure that enables the at least one tensioner arm to pivotally engage with at least one of the upright members at a tensioner mount that is positioned between the upper and lower end of the one of the upright members, the at least one tensioner arm including a second end spaced from the first end and attached to the lower edge of the flexible support, wherein the at least one tensioner arm is pivotable between a first position and an installed position, and wherein the flexible support has a first unstretched length between the upper and lower edges when the at least one tensioner arm is in the first position and a second stretched length that is greater than the first length when the at least one tensioner arm is in the installed position.

2 . The seat back of claim 1 wherein the upright members each include one of the tensioner mounts positioned between the upper and lower end, the tensioner connected between the lower edge of the flexible support and the tensioner mounts.

3 . The seat back of claim 2 wherein the tensioner includes a base and a pair of the tensioner arms extending from the base, the base extending along the lower edge of the flexible support, the arms each extending along one of the side edges.

4 . The seat back of claim 3 wherein each of the tensioner arms includes an end connected to an associated one of the tensioner mounts.

5 . The seat back of claim 4 wherein the upper edge of the flexible support defines a pocket, the pocket extending over at least a portion of the upper cross member of the frame to mount the upper edge of the flexible support to the frame.

6 . A seat back for an office chair, comprising:

a structural frame having an upright member;

an armrest mount formed integrally with the upright member;

an armrest housing vertically adjustably mounted to the armrest mount, the armrest housing having an upper end and a lower end and defining a longitudinal axis extending through the upper and lower ends;

an armrest pad mounted on the upper end;

an activation mechanism within the housing, the activation mechanism including a lock element that is movable between a locked position in which the housing is fixed in position on the armrest mount and an unlocked position in which the housing is vertically adjustable by sliding along the armrest mount; and

an activation portion of the activation mechanism positioned adjacent to the lower end of the housing, the activation portion connected to the lock element such that movement of the activation portion toward the upper end of the housing causes the lock element to move to the unlocked position, wherein the movement of the activation portion and the sliding movement of the armrest housing are aligned along the longitudinal axis.

7 . The seat back of claim 6 wherein the activation portion extends at least partially into the armrest.

8 . The seat back of claim 7 wherein the armrest mount includes a plurality of vertically spaced notches, the lock element positioned in one of the notches when the lock element is in the locked position.

9 . The seat back of claim 8 wherein the armrest mount includes opposing rails and the plurality of vertically spaced notches are defined in one of the opposing rails.

10 . The seat back of claim 8 wherein the armrest mount is molded integrally with the side edge of the backrest.

11 . A seat back for an office chair, comprising:

a structural frame having an upright member;

an armrest mount formed integrally with the upright member;

an armrest housing vertically adjustably mounted to the armrest mount, the armrest housing having an upper end and a lower end;

an armrest pad mounted on the upper end;

an activation mechanism within the housing, the activation mechanism including a lock element that is movable between a locked position in which the housing is fixed in position on the armrest mount and an unlocked position in which the housing is vertically adjustable along the armrest mount; and

an activation portion of the activation mechanism positioned adjacent to the lower end of the housing, the activation portion connected to the lock element such that movement of the activation portion toward the upper end of the housing causes the lock element to move to the unlocked position, wherein the lock element is a pin, and the activation mechanism includes an activation plate that is movable with respect to a retainer plate, wherein the pin extends through an activation slot in the activation plate and a horizontal slot in the retainer plate, the activation slot being angled with respect to the horizontal slot.

12 . The seat back of claim 11 including a tolerance spring within the housing, the tolerance spring interfitted between the housing and at least one of the rails of the armrest mount to bias the housing against the at least one of the rails.

13 . The seat back of claim 12 wherein the lower end of the housing defines an opening, and wherein the activation portion includes a button positioned within the opening, the button connected to the lock element such that pressing the button toward the upper end of the housing moves the lock element to the unlocked position.

14 . The seat back of claim 13 including an activation spring within the housing, the activation spring biasing the button in a direction away from the upper end of the housing.

15 . The seat back of claim 14 wherein the frame includes a pair of the upright members spaced apart from each other, each of the upright members including an upper end and a lower end, the frame including a lower cross member connecting the lower ends of the uprights and an upper cross member connecting the upper ends.

16 . The seat back of claim 15 including a flexible support, the flexible support including a user support surface having an upper edge, a lower edge, and a pair of side edges, the upper edge of the flexible support mounted on the upper cross member of the frame, the seat back including a tensioner connected between the lower edge of the flexible support and the upright members of the frame such that the tensioner stretches the flexible support between the upper and lower edges of the flexible support and maintains the flexible support in tension on the frame.

17 . A method for constructing a seat back, comprising the steps of:

providing a flexible support including a user support surface having an upper edge, a lower edge, and a pair of side edges;

providing a structural frame having a pair of spaced apart upright members each having an upper end and a lower end, a lower cross member connecting the lower ends of the uprights, and an upper cross member connecting the upper ends of the uprights;

providing a tensioner arm having a first and a second end;

attaching the first end of the tensioner arm to the lower edge of the flexible support;

mounting the upper edge of the flexible support to the upper cross member of the structural frame;

engaging the second end of the tensioner arm with one of the upright members of the structural frame; and

pivoting the tensioner arm about the second end of the tensioner arm to draw the first end of the tensioner arm to the structural frame as the tensioner arm acts to stretch the flexible support between the upper and lower edges of the flexible support.

18 . The method of claim 17 including extending a fastener through the structural frame and the tensioner arm to hold the tensioner arm in position with respect to the structural frame.

19 . The method of claim 18 wherein a pair of the tensioner arms are connected to one another by a tensioner base, the tensioner base connected along the lower edge of the flexible support, the tensioner arms each extending along one of the uprights of the structural frame.

20 . The method of claim 19 including an abutment projection provided on at least one of the tensioner arms, the abutment projection extending from the second end of the tensioner arm and abutting the one of the uprights of the structural frame.