Abstract:
A compliant back for a seating unit includes a rigid upright defining a track, and a flexible back shell configured to support a seated user&#39;s upper body, including a top pivot pivotally connected to a top section of the back shell and a pivot/slide member slidably connected to the track of the back shell. A biasing device is operably coupled to the pivot/slide member that biases the pivot/slide member toward a position where the flexible back shell protrudes forwardly to a shape chosen to optimally support a seated user.

Description:
BACKGROUND 
     The present invention relates to back constructions for seating units, such as chairs, and more particularly relates to a back construction having a compliant back operably supported by and coupled to a back upright for movement between various flexed positions for optimal ergonomic and aesthetic support. 
     Many modern chairs include a front surface shaped to comfortably support a lumbar region of a seated user&#39;s back, and/or include a lumbar support placed on a front surface of the back support. Sometimes, the lumbar support is made adjustable. However, many of these constructions result in a back construction that is noticeably thick and heavy in appearance, which is undesirable in many chair designs. Further, it is preferable that any mechanisms that provide flexibility and/or adjustability be partially or fully hidden from view, so that they do not detract from the overall appearance of the chair. Still further, it is preferable that any lumbar adjusting mechanism not merely be an extra device with multiple pieces assembled onto a back, but instead that it be well integrated into the back. Also, it is preferable that any back construction, including any adjustable lumbar support positioned thereon/therein, be easy to adjust in shape and also intuitive and/or automatic in its adjustment, as well as use few components. 
     Most chairs are assembled along a production line. It is desirable to provide a back construction that is adjustable in shape but that uses standard components, that uses components easily interchangeable with other components, and that is assembleable using standard assembly techniques, while at the same time maintaining aesthetics and appearance of the chair. 
     Accordingly, an apparatus is desired having the aforementioned advantages and solving the aforementioned disadvantages and problems. 
     SUMMARY OF THE PRESENT INVENTION 
     In one aspect of the present invention, a back construction for a seating unit includes a back frame having a rigid upright having top and bottom connections, and a flexible back shell configured to support a seated user&#39;s upper body, including a pivot pivotally connected to one of the top and bottom connections and a pivot/slide member slidably connected to another of the top and bottom connections. A biasing device is operably coupled to the pivot/slide member that biases the pivot/slide member toward a position where the flexible back shell protrudes forwardly for optimal lumbar support to a seated user. 
     In another aspect of the present invention, a seating unit includes a rigid upright defining a track, and a flexible back shell configured to support a seated user&#39;s upper body, including a top pivot pivotally connected to a top section of the back shell and a pivot/slide member slidably connected to the track of the back shell. A biasing device is operably coupled to the pivot/slide member that biases the pivot/slide member toward a position where the flexible back shell protrudes forwardly to a shape chosen to optimally support a seated user. 
     These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims and appended drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS. 1-3 are front, side, and top views of a back construction including a flexible shell and a removable back covering incorporating an air bladder adjustment mechanism, the adjustment mechanism being inflatable to cause a shape change in a lumbar region of the shell; 
     FIG. 4 is an enlarged side view of a bottom portion of the back shell and bladder in the circled area IV in FIG. 2, the back frame being removed for clarity; 
     FIG. 5 is a front view of a back cover assembly including the adjustable lumbar support mechanism shown in FIG. 1; 
     FIG. 5A is a cross section taken along line IV—IV in FIG. 4, the air bladder being inflated and in an energized state; 
     FIG. 5B is a cross section similar to FIG. 4A, but the air bladder being uninflated and in a relaxed state; 
     FIGS. 5C and 5D are enlargements of the circled areas VC and VD in FIGS. 5A and 5B; 
     FIGS. 6 and 6A are front and side views of a modified back construction including a permanently-attached inflated/energized lumbar adjustment mechanism; 
     FIG. 6B is a side view similar to FIG. 6A, but with the bladder deflated; 
     FIGS. 7-8 are perspective and side views of another modified back construction including a permanently-attached inflated/energized lumbar adjustment mechanism. 
     FIG. 9 is a side view similar to FIG. 8, but with the bladder deflated; 
     FIG. 9A is a fragmentary perspective view of an inside of the rear upright showing details of the slide mechanism in FIGS. 7-9; and 
     FIGS. 10-12 are views of another modified back construction, the views of FIGS. 10-12 being similar to FIGS. 7-9 above. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present illustrated back construction  20  (FIG. 1) is usable in the environment of an office chair having a castored spider-legged base, a seat, and an underseat control for pivoting the back  20  and seat with a synchronous motion upon recline of the back  20 . A more detailed description of one such chair can be found in U.S. Pat. No. 5,975,634, issued Nov. 2, 1999, entitled CHAIR INCLUDING NOVEL BACK CONSTRUCTION, the entire contents of which are incorporated herein by reference. Nonetheless, it should be understood that the present invention is contemplated to be adaptable for any seating unit or other furniture utilizing a flexible support. 
     The illustrated back  20  of FIG. 1 includes an arching back frame  25 , and a sheet-like flexible plastic back shell  26  pivotally attached to the back frame  25  at top and bottom locations  33  and  34  (FIG.  2 ). The general operation and interaction of back shell  26  and back frame  25  are described below in sufficient detail for an understanding of the present invention, but details can be found in U.S. Pat. No. 5,975,634, if the reader desires this information. 
     The back shell  26  (FIG. 1) has a “potato chip” like shape, with its front surface having a horizontal cross section that is forwardly concave, and a vertical cross section that is forwardly convex. The back shell  26  has a flexible lumbar region  27  connecting stiff thoracic and pelvic regions  28  and  29 . The lumbar region  27  includes a pair of vertical edge strips  30  and  31 , and a plurality of horizontally extending strips  32  separated by slots extending between the edge strips  30  and  31  to define a flexible lumbar area. A belt bracket  35  extends along a lower edge of the back shell  26 , and includes forwardly extending flanges  36  that define the bottom pivots  34 . In U.S. Pat. No. 5,975,634, a biasing device is provided on the lower pivot to bias the lumbar region forwardly. In the present construction, a muscle-like air bladder energy mechanism is provided in a cover assembly  37 , as described below, for changing a shape of the lumbar region  27  of the back shell  26 . 
     The cover assembly  37  (FIG. 5) includes a sock-like top section  38  sewn of upholstery or fabric to define a downwardly-facing pocket  38 ′ that fits mateably over a top edge of the back shell  26  (FIG. 1) and onto the thoracic region  28 . A center section  39  of the cover assembly  37  extends downwardly over a center area of the lumbar and pelvic regions  27  and  29 . A stiff strip  40  is sewn along a bottom edge of the center section  39 , and is shaped to fit mateably into a recess  41 ′ (FIG. 4) in a bottom edge of the back shell  26  with a zipper-like motion, where it is frictionally retained. Fasteners can be used for additional retainment, if desired. It is contemplated that other releasable or permanent top and bottom attachment devices can also be used. 
     A constrictable energy mechanism  39 ′ in the form of a pleated bladder is attached to the center section  39  (FIG.  5 ). The energy mechanism  39 ′ extends vertically downwardly onto a front panel of the top section  38 . The energy mechanism  39 ′ comprises a laminate (see FIGS. 5C and 5D) with a non-stretchable first inner layer  41  providing strength and flexibility (such as nylon fiber, woven fabric, or the like), and second and third layers  42  and  43  that are air impermeable (or fluid impermeable) (such as rubber or elastomer), and that define a bladder  45  having horizontal cavities  46  (also called “sub-bladders”) for receiving air (or other fluid). (It is noted that instead of horizontal cavities, the cavities can be round, oval, or other shapes.) As illustrated, a fourth layer  44  similar to layer  41  is provided. It is contemplated that a variety of different materials can be used to form the bladder, and further, that different inflating fluids can be used other than air. 
     In the illustrated arrangement, the first and fourth layers  41  and  44  are the outermost and innermost layers, respectively, and are nylon sheets that allow flexibility but that provide good strength in directions within the sheets. For example, 200 denier nylon woven sheeting will work for this purpose. The second and third layers  42  and  43  are elastomeric film, such as ether-based urethane, having an 85 Durometer. The layers  41 - 44  are bonded together by radio frequency (RF) welding or other bonding technique around their perimeter to define a bladder. The layers  41 - 44  are further bonded together at multiple horizontal pleats  47  (FIG. 6) that extend partially horizontally across the bladder area to subdivide the bladder into multiple discrete horizontally-extending sub-bladders  46  between the pleats. The sub-bladders  46  are connected at edges by air-communicating edge passages  48 . An air line  49  is attached to the bladder  45 , and a hand pump  50  is attached to the air line  49 . The pump  50  can be located at different locations. As illustrated, the pump  50  (FIG. 6A) is located along a side of the seat  23 , but it could also be located under an armrest  51  of the chair, under the seat  23 , on the back  20  such as at a bottom or at a top in a headrest area, on a base of the chair, or at other locations. The air pump  50  includes a flexible bulbous member  51  that can be repeatedly manually squeezed to pump air through the line  49  into the bladder  45 , and further includes a valve  52  that can be opened to release air from the bladder through line  49  to atmosphere. It is contemplated that a powered air pump, such as a battery-powered pump, could be used instead of a manual pump. Further, a flowable fluid other than air could be used, such as a liquid pumped from a container under the seat. 
     When deflated or uninflated (see FIGS.  5 A and  5 C), the illustrated energy mechanism  39  has a thickness of about 5 mm, and the pleats  47  are spaced vertically apart about 15 mm to 20 mm, or more preferably about 19 mm apart. When inflated, each sub-bladder  46  expands from its “linear” shape toward a cylindrical horizontal shape (see FIGS.  5 B and  5 D), such that a gross vertical length of the cover assembly  37  shortens. If the back shell  26  had a flat horizontal cross section, this shortening of the bladder would cause the back shell  26  to bend toward a more planar condition. However, since the edge strips  30  and  31  of the back shell  26  are forward of the sub-bladders  46 , the illustrated back shell  26  actually flexes toward a more curvilinear shape as the sub-bladders  46  are inflated. (Compare FIG. 5A, which has a deep concave shape shown by dimension T 1 , and FIG. 5B, which has a shallower concave shape shown by dimension T 2 .) Notably, the total surface length of the outer and inner layers  41  and  44  always stays the same. As a result, when the bladder  45  is inflated, it reacts much like a human muscle and shortens. For example, the spacing between pleats  47  changes from a dimension “X” of about 19 mm (FIG. 5D) to a vertical spacing of about 13 to 15 mm (dimension “Y”, FIG. 5C) (depending on the amount of air pumped into the bladder  45 ). 
     To operate the present invention, the chair  21  is originally provided with the air bladder  45  not inflated. In this condition, the back shell  26  has a predetermined curved shape, as determined by parameters of the chair  21 . The cover assembly  37  lies generally flat against the back shell  26  and provides a small amount of comfort on a front of the back shell to a seated user. As air is pumped into the bladder  45 , the sub-bladders  46  begin to inflate. This causes the bladder  45  to shorten in a length direction. In turn, the back shell  26  is stressed as the bladder  45  shortens and the edge strips  30  and  31  resist shortening. This causes the back shell  26  to change its shape and flex toward a more curved shape. Also, the air provides some additional cushioned support to a seated user. When air is released from the bladder  45 , the process is reversed, and the back shell  26  moves toward a more linear shape (which is closer to its natural unstressed shape). It is noted that the back shell  26  can be made with enough internal strength to flex toward the relaxed convex shape as shown in FIG.  5 A. Alternatively, a biasing device (such as is illustrated in U.S. Pat. No. 5,975,634, previously incorporated by reference) can be used to assist in biasing the back shell to its forwardly convex shape. It is noted that the illustrated bladder  45  acts both to bias the back shell  26  to a more concave shape, but also combines with the back shell  26  to act like (and produce lumbar support forces similar to) a stiffer back shell ( 26 ) (e.g. a back shell made of stiffer material or made with a thicker dimension). 
     It is noted that the air in bladder  45  provides both an energizing system, and also a cushioning action for supporting a seated user. This multi-functional use has advantages in terms of comfort to a seated user. If the air is heated, the air bladder has further functional benefits. It is noted that a liquid can be used instead of air, if desired. In such case, the liquid could be stored in a reservoir anywhere on the chair, such as under the seat, in an armrest, in the back, or in the base of the chair. 
     By controlling the vertical spacing of the pleats  47 , the operation of flexing the lumbar region  27  is greatly affected. For example, closer vertical spacing of the pleats  47  results in a cover assembly  37  that does not shorten as much as it is filled with air. In turn, closer spacing of the pleats  47  results in a lumbar adjustment mechanism that is not able to make as great of a change to the shape of the lumbar region  27 . Also, the back shell itself can be given different original concave shapes. Thus, the combined system of the back shell and the cover assembly is important to overall operation. It is contemplated that the bladder  45  could also be positioned horizontally, instead of vertically, such that its operation causes a horizontal shape change. Still further, a horizontal bladder and a vertical bladder (and/or an angled bladder) can be overlaid or used together to control the back shape in all directions, or the sub-bladder shapes can be dome-shaped, elongated but nonlinear (e.g. L-shaped or Z-shaped), elongated in multiple directions (e.g. X-shaped or Y-shaped), or any other shape desired. 
     A modified back construction  20 A is shown in FIGS. 6-6B, a second modified back construction  20 B is shown in FIGS. 7-9 on chair  21 B, and a third modified back construction  20 C is shown in FIGS. 10-12. In these embodiments, all similar or identical features and components are identified using the same number as used in back construction  20 , but with the addition of a letter “A”, “B”, or “C”. This is intended to reduce redundant discussion, and not for another purpose. A person of ordinary skill in the art will understand that principles discussed in regard to each embodiment will apply to the other embodiments. 
     The modified back construction  20 A (FIG. 6) includes a back shell  26 A, a bladder  45 A permanently attached to the back shell  26 A, and upholstery (not specifically shown) attached over the bladder  45 A and back shell  26 A to aesthetically cover the same. More specifically, the bladder  45 A includes top and bottom stiff edge sections  54 A and  55 A attached with rivets  56 A and  57 A. The bladder  45 A includes pleats  47 A subdividing it into sub-bladders  46 A. The remaining components and operation are identical to or very similar to the back construction  20 , and thus the details will not be repeated to avoid unnecessary repetition. 
     Another modified back construction  20 B (FIG. 8) is shown as part of a chair  21 B having a castored spider-legged base  22 B, a seat  23 B, the back construction  20 B, and an underseat control  24 B for pivoting the back  20 B and seat  23 B with a synchronous motion upon recline of the back  20 B. In chair  21 B, the back construction  20 B includes a back frame  25 B pivoted to the base  22 B under the seat  23 B at pivot location  24 B′ for reclining movement. A biasing device, such as a torsion spring, is attached at the pivot location  24 B′. A flexible back shell  26 B is pivotally attached to a top of the back frame  25 B, but is slidably supported at its lower edge by a slide member  59 B on a lower portion of the back frame  25 B. When inflated, the bladder  45 B causes the back shell  26 B to flex from its semi-linear shape (FIG. 9) toward a more curved shape (FIG.  8 ), causing the slide member  59 B to slide upwardly along the back frame  25 B. The back frame (or upright)  25 B includes a vertical slot  60 B and a follower  61 B attached to a bottom edge of the back shell  26 B is slidably coupled to the slot  60 B. Top and bottom ends of the slot  60 B limit flexing of the back shell  26 B by engaging the follower  61 B as the back shell  26 B is flexed. A spring  72 B is attached between the follower  61 B and the top pivot connection  73 B on a top of the back frame  25 B. The spring  72 B compliments leaf-spring-like edge strips  30 B and  31 B to cause the back shell  26 B to naturally move toward a curved shape. 
     Back construction  20 B′ (FIG. 9A) replaces the slot  60 B and follower  61 B with a channel/track  63 B′ formed on an inside of the upright back frame  25 B′, and an elongated follower  64 B′ that rides in the channel/track  63 B′. Straps  65 B′ hold the follower  64 B′ in the channel/track  63 B′, and also act as upper and lower limits as the shell-attachment brackets  66 B′ engages them. 
     Back construction  20 C (FIG. 11) is similar to the back construction  20 B (FIG.  8 ), except back construction  20 C has a one-piece member  69 C with a rigid L-shaped back frame  25 C coupled to the back shell  26 C by a living hinge  70 C. Also, a hook  71 C can be provided on the lower leg of the L-shaped back frame  25 C. Optionally, hook  71 C is designed to hookingly engage a flat member, such as a bench or bleacher seat in a football stadium. 
     It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.