Seat back for office chair

Abstract

To provide a seat back for an office chair capable of being efficiently manufactured and assembled.SOLUTION: A seat back for an office chair includes a tensioner for tensioning a flexible support on a structural frame. A tensioner is connected between a lower edge of the flexible support and upright members of the frame so that the tensioner stretches the flexible support between upper and lower edges of the flexible support and maintains the flexible support in tension on the structural frame. Armrests mount may be formed integrally with the upright members of the structural frame, and an armrest housing vertically adjustably mounted to each of the armrest mounts. An activation mechanism is positioned adjacent to a lower end of the armrest housing, and is connected to a lock element so that movement of the activation mechanism toward an upper end of the housing causes the lock element to move to an unlocked position.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention is directed to an office chair, and more particularly to a backrest for an office chair.

Background Art

[0002] In the competitive market of office seating, users are seeking office seating options that provide comfort, functionality, and a high degree of adjustability. However, these chairs must also be cost-effective in terms of purchase and manufacturing. As a result, office chair manufacturers are constantly seeking improved methods of manufacturing office chairs and their components.

[0003] Some office chair manufacturers have increased manufacturing efficiency by reducing or simplifying components such as back supports or mechanisms. For example, some modern office chairs have shifted to a one-piece backrest that is often molded as a single unit to form a plastic shell, thus reducing the number of backrest components from many elements that require assembly to a single element that can be easily attached to the office chair base. Other office chairs have reduced the size of the chair mechanism, typically a series of controls and springs, and the number of spring elements inside the mechanism to simplify the assembly process and reduce weight. Still other office chairs have eliminated features such as some seat adjustments or features such as lumbar support or armrests.

[0004] However, each of the efforts at efficiency noted above has drawbacks, including aesthetic issues, comfort, and a reduction in adjustment features. As a result, manufacturers continue to seek efficiency that can minimize these and other drawbacks.

Summary of the Invention

[0005] The present invention provides a backrest for an office chair that can be efficiently manufactured and assembled. In one embodiment, the backrest includes a structural frame having a pair of spaced-apart upright members each having an upper end portion and a lower end portion, a lower cross member connecting the lower end portions of the upright members, and an upper cross member connecting the upper end portions of the upright members, and a flexible support including a user support surface having an upper edge portion, a lower edge portion, and a pair of side edge portions, the upper edge portion of which is assembled on the upper cross member of the frame.

[0006] The backrest may include a tensioner for applying tension to the flexible support on the structural frame. In one embodiment, the tensioner is connected between the lower edge portion of the flexible support and the upright member of the frame in such a manner as to stretch the flexible support between the upper and lower edge portions thereof and maintain the flexible support in a tensioned state on the structural frame. Each of the upright members may include a tensioner mount between the upper and lower end portions, and the tensioner may be connected between the lower edge portion of the flexible support and the tensioner mount. The tensioner may include a base and a pair of arms extending from the base, the base extending along the lower edge portion of the flexible support and each arm extending along one of the side edge portions of the flexible support. Each tensioner arm may be connected to a corresponding tensioner mount of the tensioner mounts in such a manner as to pivot the tensioner into engagement with the tensioner mount and stretch the flexible support on the structural frame.

[0007] In another embodiment, the backrest includes a mount for the armrest integrally formed with each of the upright members of the structural frame, and an armrest housing assembled in an adjustable manner in a direction perpendicular to each of the mounts for the armrest. The locking mechanism inside the housing may include a locking element movable between a locked position where the housing is fixed at a predetermined position on the armrest mount and an unlocked position where the housing is adjustable in the vertical direction along the armrest mount. An activation mechanism is positioned adjacent to the lower end of the armrest housing and is connected to the locking element such that movement of the activation mechanism towards the upper end of the housing moves the locking element to the unlocked position. In one embodiment, the armrest mount includes a pair of rails, one of which may define a plurality of vertically spaced notches, where the locking element is positioned within one of the notches when it is in the locked position.

[0008] The present invention further includes a method for constructing a backrest. The method includes: 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 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 first and second ends; attaching the first end of the tensioner arm to the lower edge of the flexible support; assembling 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 the upright member 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 towards the structural frame as the tensioner arm acts to extend the flexible support between the upper and lower edges of the flexible support.

[0009] In one embodiment, the method may further include forming the armrest mount integrally with the upright member of the structural frame, and providing a pair of armrest housings each corresponding to one of the armrest mounts. The armrest housing can be mounted slidably with respect to the armrest mount and is selectively adjustable vertically along the armrest mount. The operation of the armrest may include activating an activation mechanism by pressing a button plate on the armrest housing vertically to lock and unlock the adjustability of the armrest.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

DETAILED DESCRIPTION OF THE INVENTION

[0011] A backrest for an office chair according to an embodiment of the present invention is shown in FIG. 1 and is generally designated by the reference numeral 10. The backrest 10 generally includes a structural frame 12, a flexible support material 14 supported on the frame 12, and a pair of armrests 16 directly assembled on the structural frame 12. Although not shown, the backrest 10 is designed to be supported above the ground by a conventional office chair base that may optionally include a height-adjustable pedestal supported on a plurality of legs that may optionally include casters.

[0012] A system for assembling a flexible support material 14 in a tensioned state on a structural frame 12 using a tensioner 18 is shown in FIGS. 1-9. The frame 12 is generally a rigid structural support frame 12 for attachment to a chair base and for supporting the back of a user sitting on a seat that is similarly supported on the chair base adjacent to the backrest 10 in a conventional manner. The frame 12 may be molded from a rigid plastic or may be constructed of another structural material. In one embodiment, the frame 12 is a perimeter frame including a pair of spaced-apart uprights 20 having a lower end 22 and an upper end 24. The uprights 20 may be connected at their upper ends 24 by an upper cross member 26 and at their lower ends 22 by a lower cross member 28. The frame 12 may have a front surface 32 facing the user's direction, a rear surface 34 opposite the front surface, an outer surface 35, and an inner surface 37. As shown, the frame members collectively define a central opening 30. In one embodiment, the frame 12 includes an attachment portion 36 extending from the front surface 32 of the lower cross member 26. While various attachment mechanisms are possible for connecting the backrest 10 to the chair base, the illustrated embodiment shows an attachment portion 36 including a notch 38 for receiving a portion of the chair base and a series of attachment holes 40 for securely fixing the backrest 10 to the chair base. The frame 12 may further include a tensioner mount 41 for engaging the tensioner 18 to enable the flexible support to be stretched over the frame 12, as will be discussed in more detail below. In one embodiment shown in FIG. 6, the frame 12 includes a series of support ribs 43 on the rear surface 34, and the tensioner mount 41 includes a pair of windows 45 formed within the support ribs 43, with one of the windows 45 inside the support ribs 43 being over the first of the uprights 20 and the other window inside the support ribs 43 being over the other of the uprights 20. The windows 45 may each be positioned at the same height on the uprights 20 between the upper end 24 and the lower end 22 of the uprights 20.In one embodiment, window 45 is positioned at approximately the midpoint between the upper end 24 and the lower end 22 of the upright member. In another embodiment, window 45 may be positioned at different heights on upright member 20.

[0013] Flexible support 14 is attached to structural frame 12 and extends across the entire central opening 30 to form a comfortable back support surface for the user. In one embodiment, flexible support 14 is formed from a flexible thermoplastic elastomer and, in a more specific embodiment, is formed from a thermoplastic polyester elastomer made by DuPont (trademark) known as Hytrel (registered trademark). Other flexible materials may also be used, including knit or woven fabrics and elastomeric fabrics. Flexible support 14 may be manufactured in a variety of ways and, in one embodiment, is injection molded as a single unitary part. Referring to FIGS. 1 and 2, flexible support 14 includes a central section 40 having a front user-facing surface 42 and an opposite rear-facing surface 44. As illustrated, central section 40 includes a series of perforations 46 that can add both aesthetic value and comfort to flexible support 14. Flexible support 14 further includes an upper edge 48, a pair of lateral side edges 50, and a bottom edge 52. Edges 48, 50, 52 may be formed with a greater thickness than central section 40 to provide increased strength around the perimeter of flexible support 14. In one embodiment, upper edge 48 is formed to include a pocket 54 that extends from the rear surface 44 of flexible support 14.

[0014] In one embodiment, the flexible support 14 is tension-mounted on the structural frame by the tensioner 18, thereby enabling the flexible support 14 to be efficiently assembled in a tensioned state on the frame 12 using a minimum of fasteners and tools. As will be described in further detail below, the tensioner 18 is attached to the flexible support 14, inserts a portion of the upper cross member 26 of the frame 12 into the pocket 54 on the flexible support 14, engages the tensioner 18 with the frame 12 at the first position shown in FIGS. 4-7, and then pivots to the second installation position on the frame 12 shown in FIGS. 8-9, thereby installing the flexible support 14 on the frame 12, where the tensioner 18 acts to extend the flexible support 14 as it is pivoted from the first position to the installation position. As shown in FIG. 2, the tensioner 18 of the illustrated embodiment is formed from a generally rigid material, such as the same polymer as the frame 12, or a different structural polymer or other material. In one embodiment, the tensioner 18 is a U-shaped member having a base 60 with a first end 62 and a second end 64, and a pair of arms 66 extending from the base 60 at opposing ends 62, 64. The arms 66 may extend parallel or generally parallel to each other, and each may have a base end 68 at the base 60 and a pivoting end 70 distal from the base 60. In the illustrated embodiment, the tensioner base 60 defines a length between the first end 62 and the second end 64 that is approximately the same as the length of the bottom edge 52 of the flexible support 14. The tensioner 18 is attached to the rear surface 44 of the flexible support 14, and in the illustrated embodiment, the tensioner 18 is attached to the rear surface 44 of the bottom edge 52 of the flexible support 14 by conventional attachment methods such as a series of lugs, fasteners, heat stakes, ultrasonic welding, double molding, or other locking features. Although the entire tensioner 18 may be attached to the flexible support 14, in one embodiment, the tensioner arms 66 are not attached to the flexible support 14, and thus the tensioner arms 66 are free to pivot away from the flexible support 14.

[0015] Each tensioner arm 66 includes a structure that enables the arm 66 to pivotally engage with a tensioner mount 41 on the upright member 20. As pointed out above, in the illustrated embodiment, the tensioner mount 41 is a window 45 formed within a support rib 43 of the upright member 20. In one embodiment, each tensioner arm 66 may include a hook 72 extending from a pivotal end 70 of the tensioner arm 66. As shown in FIG. 6, the hook 72 faces the rear surface 34 of the frame 12, and each hook 72 has the ability to fit within one of the windows 45 when the flexible support 14 is attached to the frame 12. In particular, the length of the tensioner arm 66 is predetermined such that when the hook 72 is hooked to the tensioner mount 41 and the arm 66 is positioned in the installed position in contact with the rear surface 34 of the frame 12, a desired amount of tension is provided to the flexible support 14. For example, the length of the tensioner arm 66 is such that when the flexible support 14 is attached to the tensioner 18 and the tensioner is in the installed position on the frame 12 shown in FIG. 8, the distance between the upper edge 48 and the lower edge 52 of the flexible support 14 is stretched. In other words, the flexible support 14 has a first non-extended length between the upper edge 48 and the lower edge 52 when the flexible support 14 is in the first position shown in FIGS. 4 - 7, and a second extended length greater than the first length when the tensioner 18 is attached to the flexible support 14 and the tensioner arm is in contact with the rear surface 34 of the frame 12 and the tensioner 18 is attached to the frame 12 in the installed position.

[0016] In one embodiment, the tensioner arm 66 further includes a structure for fastening the tensioner 18 to the frame 12 when the tensioner 18 is in the installed position. Referring to FIGS. 2-7, the tensioner 18 includes a screw boss 80 on each of the tensioner arms 66. As shown, the screw boss 80 is positioned at approximately the midpoint along the arm 66, although the position on the arm 66 can be varied as desired. Referring to FIG. 8, the frame 12 defines a tensioner hole 82 in each of the uprights 20. Each of the tensioner holes 82 aligns with one of the screw bosses 80 when the tensioner 18 is in the installed position, thus allowing a conventional fastener (not shown) to be inserted through each of the uprights 20 and the tensioner 18 to hold the tensioner 18 in the installed position. In an alternative embodiment, the tensioner 18 and the frame 12 may be provided with features that allow the tensioner 18 to snap-fit with the frame 12 when the tensioner 18 is moved to the installed position.

[0017] The process for attaching the flexible support 14 to the structural frame 12 is shown in FIGS. 2-9. FIG. 2 shows the flexible support 14 before being attached to the tensioner 18 or the frame 12, and the tensioner 18 is shown in an exploded view. In this embodiment, the flexible support 14 and the tensioner 18 are each formed separately as single parts. The flexible support 14 is formed by molding a flexible material such as a thermoplastic elastomer into a desired shape, and the tensioner 18 is formed by molding a rigid plastic into a U-shape. However, in other cases, the flexible material may be considered to be a knitted or woven fabric having elastomeric or other elastic properties. FIG. 3 shows the tensioner 18 attached to the flexible support 14 along the bottom edge 52 of the flexible support 14 with the tensioner base 60 extending along the bottom edge 52 from side edge 50 to side edge 50 of the flexible support 14. As pointed out, the tensioner base 60 may be attached to the bottom edge 52 by conventional methods. With the base 60 attached to the bottom edge 52, the tensioner arms 66 each extend upwardly along one of the side edges 50, and the hooks 72 extend rearwardly from the tensioner arms 66 away from the flexible support 14.

[0018] The assembled flexible support 14 and the tensioner 18 are then attached to the structural frame 12. In one embodiment, this is initiated by inserting a portion of the upper cross member 26 of the frame 12 into the pocket 54 of the flexible support 14, as shown in FIGS. 4-7. At this time, the hook 72 of the tensioner 18 is inserted into the tensioner mounting window 45 on the frame 12 while the tensioner arm 66 extends at a constant angle away from the stud 20, also as shown in FIG. 6. From this position, the tensioner arm 66 is pivoted about the hook 72, moving the base 60 of the tensioner 18 along an arcuate path until the tensioner 18 abuts against the rear surface 34 of the frame 12 and as a result reaches the installed position shown in FIG. 8. In particular, as the tensioner 18 is pivoted to the installed position, the flexible support 14 is extended from a non-extended state to a tensioned extended state by the tensioner 18. The extension occurs primarily in the vertical direction (i.e., the upper edge 48 and the bottom edge 52 are extended away from each other), but may also occur in the lateral direction from side edge 50 to side edge 50 depending on the respective orientation of the tensioner arms 66 in relation to the tensioner base 60. In one embodiment, the extension of the flexible support 14 is enhanced by the concave curvature of the front surface 32 of the structural frame 12 as the flexible support 14 is extended around the curved front surface 32. At the installed position shown in FIG. 8, the screw boss 80 on the tensioner 18 is aligned with the tensioner hole 82 in the frame 12, and a fastener is driven through the hole 82 into the screw boss 80 to hold the tensioner 18 and the flexible support 14 in place.

[0019] Referring to FIGS. 10 to 20, the backrest 10 may further include an armrest system 100 attached to the backrest 10 or integrally formed with the backrest 10. In one embodiment, the armrest system 100 includes an armrest mount 102 integrally formed with the structural frame 12 and an armrest housing 104 adjustably attached to the armrest mount 102. The armrest housing 104 includes an upper end portion 106 and a lower end portion 108, the upper end portion 106 supporting an armrest pad 110, and the lower end portion 108 including an activation mechanism 112 for selectively locking and unlocking the adjustability of the armrest housing 104 on the armrest mount 102.

[0020] Referring to FIGS. 5, 8, and 9, for example, the armrest system 100 includes armrest mounts 102 formed on the outer surface 35 of each upright member 20 of the structural frame 12. These armrest mounts 102 may be in a mirror image relationship with each other, one on the right side of the frame 12 and the other on the left side. In one embodiment, the armrest mounts 102 are integrally molded with the structural frame 12 as a single piece for efficient manufacturing. Each armrest mount 102 includes a first rail member 114 and a second rail member 116 spaced from the first rail member 114. As illustrated, the rail members 114, 116 extend parallel to each other in a vertical direction along the outer surface 35 of each upright member 20. The first rail member 114 includes a base portion 118 and a flange member 120. The base portion 118 extends from the upright member 20 and has an inner wall 122 and an outer wall 124. The inner wall 122 faces the second rail member 116, and the outer wall 124 is on the opposite side of the inner wall 120. In one embodiment, the flange member 120 extends from the outer wall 124 at the distal end of the base portion 118. The second rail member 116 includes a base portion 128, a flange member 130, and a rack 132. The base portion 128 extends from the upright member 120 and includes an inner wall 134 and an outer wall 136. The inner wall 134 faces the inner wall 122 of the first rail member 114. The flange member 130 extends from the outer wall 136 at the distal end of the base portion 128. The rack 132 extends from the inner wall 134 toward the first rail member 114 and includes a series of notches 140 spaced vertically apart.

[0021] Referring to FIG. 12, each armrest housing 104 is assembled in an adjustable manner with respect to one of the armrest mounts 102. Similar to the armrest mounts 102, the armrest housings 104 may be in a mirror image relationship with each other, one on the left side of the frame 12 and the other on the right side. As pointed out, each armrest housing 104 includes a top end 106 and a bottom end 108, and the top end 106 supports the armrest pad 110. In one embodiment, the housing 104 includes an elongated side wall 150 having a C-shaped cross-section. The top end 106 includes a pad support 142 that extends at an angle from the side wall 150 and includes a pair of spaced-apart walls 144 that extend upwardly. A cover 146 fits between the walls 144 on the top end 106 and is attached to the armrest housing 104 via a press-fit pin 148 that extends through portions of the walls 144 and the cover 146. In one embodiment, the cover 146 defines a slot 151 that extends in the front-to-back direction on the cover 146. The armrest pad 110 is attached to the cover 146 in a horizontally adjustable manner via a pair of connectors 152 that extend through the pad 110 and the slot 151. More specifically, the pad 110 includes a plate 154 and a cushion 156. The connector 152 extends through the plate 154 to attach the plate 154 to the cover 146, and the cushion 156 is attached to the plate 154 to form an exposed surface for the user's arm to rest on.

[0022] The C-shaped sidewall 150 defines an elongated opening 160 generally extending from the upper end portion 106 to the lower end portion 108, and a mount insertion opening 162 at the lower end portion 108. When assembled, the elongated opening 160 faces the armrest mount 102, and the armrest housing 104 inserts the first rail member 114 and the second rail member 116 into the mount insertion opening 162, and the first rim 170 of the elongated opening 160 engages with the first rail member 114 and the second rim 172 engages with the second rail member 116 to secure the armrest housing 104 on the rails 114, 116. The armrest housing 104 is attached to the armrest mount 102 by sliding the armrest housing 104 along the first rail member 114 and the second rail member 116.

[0023] Inside the armrest housing 104 is an activation mechanism 200 for selectively locking and unlocking the armrest housing 104 at a desired vertical position along the armrest mount 102. The activation mechanism 200 generally includes an armrest liner 202, an activation plate 204, a retainer plate 206, and a lock pin 208. The armrest liner 202 is positioned within the armrest housing 104 and includes a front surface 212 and lateral side surfaces 214. The armrest liner 202 is positioned in contact with the sidewall 150 of the armrest housing with the front surface 212 facing away from the sidewall 150. In one embodiment, each lateral side surface 214 includes a pair of leaf springs 221 formed with the armrest liner 202. The leaf springs 221 elastically engage the first rail 114 and the second rail 116 respectively when the armrest housing 104 is positioned on the armrest mount 102 to absorb any tolerance between the armrest housing 104 and the armrest mount 102 and make the armrest housing 104 fit snugly on the armrest mount 102.

[0024] The activation plate 204 is slidable vertically within the housing 104 and drives the locking pin 208 between a locked position and an unlocked position. In one embodiment, the activation plate 204 is an elongated plate positioned in contact with the front surface 212 of the armrest liner 202 within the housing 104. The activation plate 204 includes a sidewall 219 having an upper end 220 and a lower end 222, defining a longitudinal length between the upper end 220 and the lower end 222. An angled slot 226 is defined within the sidewall 219, and this angled slot 226 extends at an angle of approximately 45 degrees with respect to the longitudinal length. The angled slot 226 includes an upper end 227 and a lower end 229. In one embodiment, the activation plate 204 similarly defines a pair of vertical slots 228. When positioned within the armrest housing 104, the upper end 220 of the activation plate 204 is positioned near the upper end 106 of the housing 104, and the lower end 222 of the activation plate 204 is positioned near the lower end 108 of the housing 104 adjacent to the mount insertion opening 162. An activation spring 230 is positioned between the upper end 106 of the housing 104 and the upper end 220 of the activation plate 204 within the armrest housing 104. A button plate 205 is attached to the lower end 222 of the activation plate 204 within the mount insertion opening 162.

[0025] The retainer plate 206 is positioned on the activation plate 204 such that an angled slot 204 is sandwiched between the armrest liner 202 and the retainer plate 206. In one embodiment, the retainer plate 206 is fixed in place within the armrest housing 104 such that the activation plate 204 slides in relation to the retainer plate 206. As shown, the retainer plate 206 includes a sidewall 240 having an upper end 242 and a lower end 244. The sidewall 240 defines a horizontal slot 246 generally aligned with the angled slot 226 of the activation plate 204. The sidewall 204 further defines a pair of mounting holes 248 on the retainer plate 206 that align with a screw boss 250 on the housing 104 to enable the retainer plate 206 to be fixedly attached to the housing 104 using a fastener 252 that passes through the vertical slot 228 on the activation plate 204, through the armrest liner 202, and into the screw boss 250. A pair of angled prongs 260 extend from the lower end 244 of the retainer plate 206. The angled prongs 260 enable the slidable insertion of the armrest housing 104 onto the armrest mount 102 and, once fully inserted, engage the rail members 114, 116 of the armrest mount 102 to secure the housing 104 onto the armrest mount 102.

[0026] When the activation mechanism 200 is assembled, the lock pin 208 extends through the angled slot 226 in the activation plate 204 and the horizontal slot 246 in the retainer plate 206. The lock pin 208 may be a bolt or other pin-like member. Referring to FIGS. 19 and 20, the activation mechanism 200 is arranged to move the lock pin 208 between the lock position shown in FIG. 19 and the unlock position shown in FIG. 20. In the lock position, the button plate 205 is released and the button plate 205 extends downwardly beyond the lower end 108 of the armrest housing 104. The activation plate 204 is in the lowered position and is biased in that position by the activation spring 230. The lock pin 208 is driven to the upper end 227 of the angled slot 226 and in this position is moved to engage a selected one of the notches 140 in the armrest mount 102. In the unlock position, the button plate 205 is pressed upwardly in the longitudinal length direction of the activation plate 204 and the activation plate 204 is slid vertically upwardly to compress the spring 230. The path of the horizontal slot 246 in the retainer plate and the angled slot 226 in the activation plate 204 moves the lock pin 208 to the lower end 229 of the angled slot 226 and thus out of engagement with any of the notches 140, allowing the armrest housing 104 to slide freely relative to the armrest mount 102 to the desired vertical position.

[0027] The assembly of the armrest system 100 includes positioning one of the armrest housings 104 vertically above one of the armrest mounts 102, taking care that the appropriate right or left armrest housing 104 is positioned above the corresponding right or left upright member 20 of the structural frame 12. Referring to FIG. 10, the left armrest housing 104 is positioned above the armrest housing 102 on the left upright member 20, the mount insertion opening 162 of the armrest housing 104 is positioned above the rails 114, 116 of the armrest mount 102, and the elongated opening 160 faces the upright member 20. At this time, the armrest housing 104 is slid onto the armrest mount 102 by inserting the rails 114, 116 into the armrest insertion opening 162 and sliding the armrest housing 104 downward onto the armrest mount 102. The angled prong 260 on the retainer plate 206 flexes upon insertion between the rails 114, 116, and the retainer plate 206 is slid between the rails 114, 116 until the prong 260 passes through and slides clear of the rails 114, 116. The button plate 205 may be attached to the activation plate 204 before or after the housing slides onto the rails 114, 116. The leaf spring 221 of the armrest sleeve 202 engages the rails 114, 116 and resiliently absorbs any slack between the armrest housing 104 and the armrest mount 102. With the armrest housing 104 positioned on the armrest mount 102, the armrest system 100 allows adjustment of the height of the armrest housing 104 (and thus the armrest pad 110) depending on whether the user activates or deactivates the activation mechanism 200. As pointed out above, when the button plate 205 of the activation mechanism 200 is deactivated (i.e., not pressed by the user), the lock pin 208 is driven to the upper end 227 of the angled slot 226 and extends into the nearest notch 140 as the armrest housing 104 passes through and is adjusted by the notch 140.Unless the button plate 205 is pressed, the pin 208 is engaged within the notch 140 and the armrest housing 104 cannot move vertically. When the user presses the button plate 205 in the upward direction, the activation plate 204 is slid vertically along the retainer plate 206, and the pin 208 is driven to the lower end 229 of the angled slot 226 to disengage the pin 208 from the notch 140, enabling the vertical movement of the armrest housing 104 along the armrest mount 102 until the button plate 205 is released, and the pin 208 slides back to the upper end of the angled slot 226 and into one of the notches 140.

[0028] Terms indicating directions such as "vertical", "horizontal", "top", "bottom", "upper", "lower", "inner", "inwardly", "outer", and "outwardly" are used to assist in explaining the present invention based on the orientation of the illustrated embodiments. The use of direction-indicating terms should not be construed as limiting the present invention to any specific orientation.

[0029] The above description is of the current embodiments of the present invention. Various modifications and changes can be made without departing from the spirit and broader aspects of the present invention as defined in the appended claims, and these should be interpreted in accordance with the principles of patent law, including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the present invention or as limiting the scope of the claims to the specific elements exemplified or described in connection with these embodiments. For example, without limitation, any individual element of the described invention may be replaced by alternative elements that provide substantially similar functionality or proper operation in another form. This includes, for example, currently known alternative elements such as those currently known to those skilled in the art, and potentially future-developed alternative elements such as those that may be recognized as one alternative at the time of development by those skilled in the art. Further, the disclosed embodiments include a plurality of features that may be considered to simultaneously describe and cooperate to provide a set of advantages. The present invention is not limited to only those embodiments that include all of these features or provide all of the stated advantages, unless otherwise specified within the issued claims. For example, any reference to a claim element in the singular using the articles "a", "an", "the" or "said" should not be construed as limiting that element to the singular.

Claims

1. In a backrest for an office chair: A structural frame having a pair of spaced-apart upright members each having an upper end portion and a lower end portion, a lower cross member connecting the lower end portions of the upright members, and an upper cross member connecting the upper end portions of the upright members; A flexible support including a user support surface having an upper edge portion, a lower edge portion, and a pair of side edge portions, the upper edge portion of which is assembled on the upper cross member of the frame; A tensioner connected between the lower edge portion of the flexible support and the upright member of the frame in such a manner as to stretch the flexible support between the upper and lower edge portions thereof and maintain the flexible support in a tensioned state on the structural frame; A backrest for an office chair, comprising the above.

2. The backrest according to claim 1, wherein each of the upright members includes a tensioner mount positioned between the upper and lower end portions, and the tensioner is connected between the lower edge portion of the flexible support and the tensioner mount.

3. The backrest according to claim 2, wherein the tensioner includes a base and a pair of arms extending from the base, the base extending along the lower edge portion of the flexible support, and each of the arms extending along one of the side edge portions.

4. The backrest according to claim 3, wherein each of the tensioner arms includes one end connected to a corresponding tensioner mount of the tensioner mounts.

5. The backrest according to claim 4, wherein the upper edge portion of the mounting hole of the flexible support defines a pocket, and the pocket extends over at least a part of the upper cross member of the frame to assemble the upper edge portion of the flexible support to the frame.

6. In a backrest for an office type chair: A structural frame having upright members; An armrest mount integrally formed with the upright members; An armrest housing assembled in an adjustable manner in a direction perpendicular to the armrest mount, the armrest housing having an upper end portion and a lower end portion; An armrest pad assembled on the upper end portion; An activation mechanism inside the housing, the activation mechanism including a locking element movable between a locked position where the housing is fixed at a predetermined position on the armrest mount and an unlocked position where the housing is vertically adjustable along the armrest mount; An activation portion of the activation mechanism positioned adjacent to the lower end of the housing, the activation portion being connected to the locking element such that movement of the activation portion toward the upper end of the housing causes the locking element to move to the unlocked position; An office type chair including the above.

7. The backrest according to claim 6, wherein the armrest mount includes opposing rails and the housing is assembled slidably on the rails.

8. The backrest according to claim 7, wherein the armrest mount includes a plurality of vertically spaced notches and the locking element is positioned in one of the notches when it is in the locked position.

9. The backrest according to claim 8, wherein the plurality of vertically spaced notches are defined in one of the opposing rails.

10. The backrest according to claim 8, wherein the armrest mount is integrally formed with a side edge of the backrest.

11. The backrest according to claim 10, wherein the locking element is a pin, the activation mechanism includes an activation plate movable in relation to a retainer plate, the pin extends through an activation slot in the activation plate and a horizontal slot in the retainer plate, and the activation slot is angled in relation to the horizontal slot.

12. The backrest according to claim 11, including a tolerance spring inside the housing, the tolerance spring being fitted 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 lower end portion of the housing defines an opening, the activation portion includes a button positioned inside the opening, the button is connected to the locking element, and by pressing the button toward the upper end portion of the housing, the locking element is moved to the unlocked position. The backrest according to claim 12.

14. The housing includes an activation spring inside, and the activation spring biases the button in a direction away from the upper end portion of the housing. The backrest according to claim 13.

15. The frame includes a pair of upright members spaced apart from each other, each of the upright members includes an upper end portion and a lower end portion, and the frame includes a lower cross member connecting the lower end portions of the upright members and an upper cross member connecting the upper end portions. The backrest according to claim 14.

16. Including a flexible support, the flexible support includes a user support surface having an upper edge portion, a lower edge portion, and a pair of side edge portions, the upper edge portion of the flexible support is assembled on the upper cross member of the frame, and between the upper edge portion and the lower edge portion of the flexible support to stretch the flexible support and maintain the flexible support in a tension state on the frame, including a tensioner connected between the lower edge portion of the flexible support and the upright member of the frame. The backrest according to claim 15.

17. In a method for constructing a backrest: Providing a flexible support including a user support surface having an upper edge portion, a lower edge portion, and a pair of side edge portions; Providing a structural frame having a pair of spaced upright members each having an upper end portion and a lower end portion, a lower cross member connecting the lower end portions of the upright members, and an upper cross member connecting the upper end portions of the upright members; Providing a tensioner arm having first and second end portions; Attaching the first end portion of the tensioner arm to the lower edge portion of the flexible support; Assembling the upper edge portion of the flexible support to the upper cross member of the structural frame; Engaging the second end portion of the tensioner arm with one of the upright members of the structural frame; As the tensioner arm acts to extend the flexible support between the upper and lower edges of the flexible support, pivoting the tensioner arm about the second end of the tensioner arm to draw the first end of the tensioner arm towards the structural frame; A method comprising. **Claim 18** The method according to claim 17, comprising extending a fastener through the structural frame and the tensioner arm to hold the tensioner arm in a predetermined position in relation to the structural frame. **Claim 19** The method according to claim 18, wherein a pair of tensioner arms are connected to each other by a tensioner base, the tensioner base being connected along the lower edge of the flexible support, and each of the tensioner arms extending along one of the uprights of the structural frame. **Claim 20** The method according to claim 19, comprising an abutting projection provided on at least one of the tensioner arms, the abutting projection extending from the second end of the tensioner arm and abutting against one of the uprights of the structural frame.

Images