US20040140701A1

US20040140701A1 - Backrest for a seating structure with an adjustable sacral support

Info

Publication number: US20040140701A1
Application number: US10/686,554
Authority: US
Inventors: Burkhard Schmitz; Claudia Plikat; Nicolai Neubert; Carola Zwick; Roland Zwick; Chad Aerts; John Aldrich
Original assignee: Herman Miller Inc
Current assignee: MillerKnoll Inc
Priority date: 2002-10-15
Filing date: 2003-10-14
Publication date: 2004-07-22

Abstract

A backrest includes a back member having an upper and lower region and a frame member. A sacral support member has at least one end connected to one of the frame member and the back member and an opposite free end. The sacral support member supports the back member at the lower region thereof. A fulcrum member is moveably disposed between a portion of the sacral support member and one of the frame member and the back member. The fulcrum member is moveable toward and away from the free end of the sacral support member. A method for adjusting a backrest includes engaging a lower region of a back member with a sacral support member having a free end and a cantilevered length, engaging the sacral support member with a fulcrum member, and moving the fulcrum member toward and away from the free end of the sacral support member so as to thereby shorten and length the cantilevered length of the sacral support member.

Description

This application claims the benefit of U.S. Provisional Application Serial No. 60/418,483, filed Oct. 15, 2002, the entire disclosure of which is hereby incorporated herein by reference.[0001]

BACKGROUND

The present invention relates generally to a backrest for a seating structure, and in particular, to a backrest having an adjustable sacral support.

The spine is broken down into four general regions: cervical (neck), thoracic (upper back), lumbar (lower back) and sacral/pelvic (tail bone). In some circumstances, back problems can be experienced at the point were the lumbar spine connects to the sacrum. In particular, sitting up straight can be difficult for the users of many chairs. For example, in many seating devices, a void exists between the backrest of the chair and sacrum of the user. As a result, the user will be placed in a position of poor posture, lack of muscle control and discomfort. Slouching can lead to a number of problems, including increased fatigue and fidgeting due to discomfort. In addition, slouching may also lead to increased pressure on the lumbar discs or muscle spasms. Long-term problems such as lower back pain, sore necks and the like can also occur.

In order to alleviate some of these problems, previous attempts have been made to provide better support for the sacrum. Some of these devices, however, as disclosed for example in U.S. Pat. No. 5,577,811, are not readily adjustable to suit the individual needs of the user. Others, while adjustable, are relatively complex and expensive to manufacture. Accordingly, a need remains for an improved, simple sacral/pelvic support that is readily adjustable.

SUMMARY

The present inventions are defined by the claims, and nothing in this section should be read as a limitation on those claims. Rather, by way of general introduction and briefly stated, various preferred embodiments are described that relate to a seating structure having a backrest with an adjustable sacral support.

In one preferred embodiment, a back member has an upper and lower region and a frame member. A sacral support member has at least one end connected to one of the frame member and the back member and an opposite free end. The sacral support member supports the back member at the lower region thereof. A fulcrum member is moveably disposed between a portion of the sacral support member and one of the frame member and the back member. The fulcrum member is moveable toward and away from the free end of the sacral support member.

In one preferred embodiment, the sacral support has a portion supported by a lumbar support member, which supports the back member above the sacral support.

In another aspect, a method for adjusting a backrest includes engaging a lower region of a back member with a sacral support member having a free end and a cantilevered length, engaging the sacral support member with a fulcrum member, and moving the fulcrum member toward and away from the free end of the sacral support member so as to thereby shorten and length the cantilevered length of the sacral support member.

The various preferred embodiments provide significant advantages over other seating structure having sacral supports. In particular, the sacral support can be easily and quickly adjusted simply by moving the fulcrum member to the desired position. The relatively few and inexpensive parts provide improved support for the user's sacrum in a simple and efficient manner.

The present invention, together with further objects and advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a chair having a backrest. [0011]
FIG. 2 is an exploded perspective view of a backrest assembly. [0012]
FIG. 3 is a side view of a back support member. [0013]
FIG. 4 is a cross-sectional view of the back support member taken along line [0014] 4-4 of FIG. 3.
FIG. 5 is a front view of a back support member. [0015]
FIG. 6 is a cross-sectional view of the back support member taken along line [0016] 6-6 of FIG. 5.
FIG. 7 is a side view of a back support fulcrum member. [0017]
FIG. 8 is a partial top view of the back support fulcrum member shown in FIG. 7. [0018]
FIG. 9 is front view of a back member with a cut-out therein. [0019]
FIG. 10 is a front view of the back member shown in FIG. 9 with a hinge portion overmolded thereon. [0020]
FIG. 11 is a partial cross-sectional view of the back member taken along line [0021] 11-11 of FIG. 10.
FIG. 12 is a rear perspective view of one embodiment of a backrest. [0022]
FIG. 13 is a cross-sectional view of the backrest spine.[0023]

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The terms “longitudinal” and “lateral” as used herein are intended to indicate the direction of the chair from front to back and from side to side, respectively. Similarly, the terms “front”, “side”, “back”, “forwardly”, “rearwardly”, “upwardly” and “downwardly” as used herein are intended to indicate the various directions and portions of the chair as normally understood when viewed from the perspective of a user sitting in the chair. [0024]
Referring to the drawings, FIG. 1 shows one embodiment of a chair having [0025] tilt control housing 10, seat 200, back support 304 and back 302. It should be understood that the term “housing” generally refers to any support member that supports another member, and includes, but is not limited to a structure that provides an enclosure. A pair of armrests 400 extends from, move with and define a portion of the back support 304. Preferably, the back support 304 is pivotally mounted to the control housing 10, and the seat 200 is pivotally mounted to the back support 304 via a pivot axis located on the armrests 400 at the approximate hip joint of the user above the seating surface. The seat 200 is further slideably and pivotally supported by the tilt control housing.
It should be understood that the terms “mounted,” “connected”, “coupled,” “supported by,” and variations thereof, refer to two or more members or components that are joined, engaged or abutted, whether directly or indirectly, for example, by way of another component or member, and further that the two or more members, or intervening member(s) can be joined by being integrally formed, or by way of various fastening devices, including for example and without limitation, mechanical fasteners, adhesives, welding, press fit, bent-over tab members, etc. [0026]
In operation, the [0027] housing 10, seat 200 and back support 304, with the armrests 400, form a three-bar linkage with a slide. It should be understood that the term “slide,” as used herein, refers to two members that translate relative to each other, whether by direct sliding or by rolling. Preferably, the pivot axis formed between the seat 200 and housing 10 is positioned forwardly of the pivot axis formed between the back support 304 and housing 10, which axis is positioned forwardly of the pivot axis formed between the back support 304 and the seat 200, such that the backrest 300 and back support 304 tilt rearwardly at a greater rate and angle than does the seat 200. Preferably, the back tilts relative to the seat at about a preferred 2:1 ratio, such that the shirt-tail pull effect is avoided. Of course, other synchrotilt ratios are contemplated and suitable. In addition, the configuration of the back support, the seat and the various positions of the pivot axes, allow the seat to pivot about the ankles of a user seated in the chair, preferably without the front edge of the seat rising as the user tilts rearwardly. The three-bar linkage provides a simple and compact mechanism that avoids the use of additional links. Additionally, by forming the linkage assembly from the seat, back support and housing, complex and expensive links and load bearing parts are avoided.
Referring to FIG. 1, a [0028] base 26, preferably a five arm base with casters, is mounted to the bottom of a support column 12, which supports the housing, in a conventional manner, although one of skill in the art would understand that other support columns and bases can be used to support the housing, including fixed height support columns and non-rolling bases, including for example a base configured with glides.
Referring to FIGS. 1, 2 and [0029] 12, one embodiment of a backrest 300 includes a backrest frame member, or back support member 304, and a back member 302. The support member 304, otherwise referred to as a frame member, includes a lower support member 308 having a pair of forwardly extending arms 310 that are pivotally connected to the tilt control housing 10.
As shown in FIGS. 2 and 12, a rear portion of the lower support member forms an upwardly extending [0030] arm 322. An upper support member 324, or spine, has a lower end 326 that mates with and is secured to the arm 322 with a pair of fasteners 327. A cover can be disposed over the fasteners to provide a smooth, aesthetic appearance. By making the support member 304 in two- pieces 308, 324 the backrest can be disassembled and the chair can be shipped in a smaller package. In particular, the arm 322 of the lower backrest support preferably does not extend upwardly above the uppermost surface of the armrests, such that the base, seat and armrests can be compressed to a relatively short height. In turn, the backrest 300 can be easily assembled by the end user with a pair of fasteners. Moreover, the backrest can be made offline, if desired. As shown in FIG. 2, the lower end 326 of the spine flares outwardly and defines a pair of opposite landings 328 that mate with the back member 302.
The [0031] spine 324 extends upwardly and has a pair of arms 330 that extend upwardly and outwardly from an upper end thereof. The ends of the arms each have a pad 332 that is secured to the back member 302 with a fastener. In particular, as shown in FIG. 2, a boss 303 extends from the rear of the back member and supports the pad and receives the fastener. A front surface of the spine has a rack, or a plurality of notches formed thereon. In one embodiment, the rack is formed on a lumbar support insert 820, which is secured to the front side of the spine with a plurality of fasteners 822. The lumbar support insert 820 and spine can be made of various materials, such as Capron 8233G-33% Glass Filled Nylon 6, or other materials such as aluminum, steel, fiberglass, composites, plastic, or some other rigid but resilient material.
Referring to FIGS. 2 and 13, in one preferred embodiment, the [0032] spine 324 has a plurality of forwardly extending fins 821, while the lumbar support insert 820 has a plurality of rearwardly extending fins 823 that are shaped to be inserted or nested in the spaces formed between the plurality of fins 821. In this way, the spine and insert are very strong and resistant to bending, yet provide substantially torsional flexibility. In addition, the two pieces can be easily made from molded plastic, with thinner walls and less material. In addition, the insert 820 and spine 824 can be spaced apart along the sides thereof to form a gap.
Referring to FIGS. 2, 9 and [0033] 10, the back member 302 is preferably made of a resilient, compliant material, including various polymeric or plastic materials. For example, in one preferred embodiment, the back member is molded of a polypropylene 76523 Montel Profax material. The back member 302 has a top 336, a bottom 338 and opposite, curvilinear sides 340. The sides 340 preferably have a concave, or hour-glass shape. The top 336 of the back member is preferably curved and has a convex front, body-supporting surface 342 along a peripheral portion thereof.
The back member has a [0034] lumbar region 344, a thoracic region 346 and a lower sacral region 348. The lower region includes a cut-out 350 shaped to be received on the lower end 326 of the spine, with a pair of bosses 352 positioned to mate with holes formed in the landings 328. In one embodiment, the lower region has a sacral regions that is formed by a forwardly extending portion at the center of the lower region. A pair of fasteners secure the bottom of the back member 302 to the landings 328. The back member 302 has a plurality of openings 354 formed therethrough. Preferably, an array of openings in the lumbar region 344 are elongated in the longitudinal direction, which runs between the top and the bottom of the back member. The openings 354 are preferably staggered. For example, in one preferred embodiment, adjacent vertical columns of openings are offset in the vertical direction, such that the openings in adjacent columns are not horizontally aligned.
As with the [0035] lumbar region 344, the thoracic region 346 also includes an array of staggered elongated openings 354. Preferably, the elongated openings formed in the thoracic region are not as elongated, on average, as the openings in the lumbar region. This means, of course, that an occasional opening, or plurality of openings, in the thoracic region can have a greater elongation than an opening or plurality of openings in the lumbar region.
Likewise, the [0036] lower region 348 has an array of staggered elongated openings 354 formed therein, again, with an average elongation less than that of the lumbar region. Referring to FIGS. 2 and 9-10, in one embodiment, the elongated openings 355 in the lower region transition from a longitudinal orientation to a lateral orientation, with the transition being made progressively lower as it moves from a center line outboard, so as to form a generally triangular region of lateral openings. Some of the openings are curved to make the transition.
The elongated openings in the lumbar region and the adjacent transition areas of the thoracic and lower regions are preferably obround [0037] 356. The shapes of the openings then transition from the obround shape to a peanut-shaped opening 358 as the location thereof moves upwardly, and then eventually the peanut-shaped openings are closed at a middle thereof to form substantially circular openings 360 adjacent the top and bottom of the back member. In addition, smaller circular openings 362 are formed along the opposite sides of the back member, including at the lumbar region, and around the entire peripheral portion of the back member. In the embodiment of FIG. 2, the openings in the lower region do not transition to a peanut shape, but rather preferably stay obround, with an outer perimeter of circular openings 362. Of course, it should be understood that the opening could so transition in the lower region, and can remain in a substantially vertical orientation, as shown for example in FIGS. 1 and 12.
The [0038] back member 302, especially in the lumbar region, also preferably has a first thickness along the center line 364 thereof, and a second thickness at the peripheral sides 366 thereof, with the second thickness being greater than the first thickness. For example, in the lumbar region, one preferred first thickness is about 2 mm, and one preferred second thickness is about 3 mm. As shown in FIG. 2, the back member is preferably bowed forwardly at the lumbar region 344. The edge of the back member preferably is formed as a bead. The back member is preferably formed by molding.
Referring to FIGS. [0039] 2-11, a second back support configuration includes a first support member 1300 and a second support member 1302. In one preferred embodiment, the first support member 1300 is formed as a loop having a base 1304, a pair of arms 1306 and a support band 1308 or belt extending between the two arms 1306. The support band has a forwardly facing surface 1310 that engages and supports a rear surface of the back member 302. A downwardly opening recess 1312 or pocket is formed in the middle portion of the belt, as best shown in FIGS. 5 and 6. The recess 1312 forms a guide or track for a portion of the second support member 1302.
As best shown in FIGS. 3 and 4, the [0040] second support member 1302 has a J-shape, with a base arm 1314 connected to a support arm 1316 having an end 1318, which is shaped and configured to be received in the recess 1312 of the second support member. The bottom of the J-shaped support member 1302, or a curved portion 1328 forms a free end of the support member 1302. The end 1318 of the support arm is supported by the lumbar support 1300 as it slides vertically in the recess, so as to allow the first and second support members to function independently. At the same time, the loop supports the support arm 1316 laterally and in the fore/aft direction. Alternatively, the end 1318 of the support arm 1316 can remain unsupported, or it can be fixedly connected to the first support member, or lumbar support, or to the frame.
The [0041] base arm 1314 has an upper end 1320 disposed between the base of the first support member and the lumbar insert member. A fastener secures the first support member 1300 and the second support member 1302 to the insert member 820. The arms 1314, 1316 of the second support member, once installed, function as a cantilevered spring, which is supported at ends 1302 and 1318 and has free end 1328. The base arm 1314 has a plurality of longitudinally extending and rearwardly facing grooves 1322, 1324, which define a plurality of ridges. The base arm 1314 also has a step 1326 formed at the bottom thereof, which is connected to the curved portion 1328 that transitions to the support arm 1316 and provides additional flexibility between the arms 1314 and 1316. In this way, the overall support member 1302, including both arms acting in concert, functions as a cantilevered spring, while the individual arms 1314, 1316 act as individual springs that provide additional independent flexibility.
Referring to FIGS. 2, 7 and [0042] 8, a fulcrum member 1330 is disposed between the insert member 820 and the base arm 1314 of the second support member. The fulcrum member includes a base portion 1344 forming a cavity 1348 that substantially surrounds and conforms to the forward surface of the insert member 820. The base portion includes a plurality of hook members 824 that engage and slide along the sides 826 of the lumbar insert support member 820. Preferably, the hook members extend through the gap 829 formed between the spine and the insert member. In one embodiment, the fulcrum member further includes a detent or latch member that engages the rack to releasably secure the fulcrum member in a plurality of vertical positions. Alternatively, or in combination, the fulcrum includes a guide member 1332 or ridge formed in the cavity 1348 that rides in a groove 1334 formed in the spine insert member. In one embodiment, the fulcrum member includes a pair of handles 1336. The handles extend outwardly and downwardly and include a grippable portion 1338, formed form example as a plurality of annular ridges, on the ends thereof. The front portion of the fulcrum member include a pair of guide members 1340 or tabs that ride in the outer channels 1322 formed in the base support arm. The fulcrum, first support member and second support member are preferably made of one or more types of plastic, such as nylon or glass-filled nylon, but can be made of other materials, such as metal, wood, composites, fiberglass and the like.
It should be understood that in an alternative embodiment, one or all of the sacral support member, the lumbar support member and the fulcrum member can be connected to the back member and engage the frame. [0043]
In operation, the user grips one or both of the fulcrum handles [0044] 1336 and moves the fulcrum in the vertical direction to a desired position. As the fulcrum is lowered, it shortens the cantilevered length of the support member 1302, i.e., the distance between the fulcrum and the bottom curved portion 1328, and the arms 1314, 1316 in particular, and provides a firmer, more rigid support for the lower region 348 of the back member as it engages the rear surface thereof. The user can raise the fulcrum 1330 so as to provide a greater cantilevered length, which in turn provides more flexibility of the support member and a corresponding less rigid support of the back member in the lower region.
Referring to FIGS. [0045] 9-11, the back member 302 can be modified to improve the flexibility of the lower region thereof. In particular, a U-shaped cut-out 1350 can be made in the lower region, for example along one row of openings 354 as they transition from the vertical to the horizontal. In this way, the lower region 348 is provided with a central flap 1352 or support region at the sacral region of the user's back, which is spaced from a firmer lower portion 1356. The back member is then inserted into a mold, wherein a hinge portion 1354 is overmolded on the back member over the cut-out so as to flexibly connect the flap 1352 with the lower portion 1356 of the back member. In one embodiment, the hinge 1354 is formed as a living hinge, with a bellows shape. Of course, it should be understood that the hinge can be in-molded in the original back member, which thereby avoids the cutting and overmolding operations. In addition, it should be understood that the back member can be provided with greater flexibility by providing a thinner material in certain regions, or by providing other hinge type devices, not limited to a living hinge or molded hinges. In this way, the flap portion 1352 of the lower region 348 of the back member being acted upon by the support arm 1316 of the first support member is provided with greater flexibility to move in response to the position of the support member 1302 as the fulcrum member is moved to a desired position. In one embodiment, the hinge is formed from an elastomeric material, such as a thermoplastic elastomer.
The configuration of the [0046] spine 324 and back member 302 provides many advantages. For example, the compliant back member 302, with its larger, or longer, openings in the lumbar region, and its lesser thickness along the center portion, allow that region to be more flexible, such that it can be formed and supported by the lumbar support and/or sacral support. In addition, the entire back is allowed to conform to the back of the user, and in particular at the edge portions thereof, and can flex about the center spine in torsion, which is made more flexible by way of the two-piece construction with nested fins, and also about the bowed lumbar region. In essence, the intelligence of the backrest is shared by the spine 324 and the back member 302. In this way, the backrest provides greater comfort than a backrest formed with a peripheral, and relatively stiff or non-compliant, frame. In addition, by securing the back member 302 to the arms of the spine at a location spaced below the top of the back 336, including at about 14 inches in one embodiment, and preferably between about 2 inches and about 12 inches, and more preferably between about 4 inches and about 8 inches, the top peripheral portion can flex in response to movement from the user's shoulder and neck and further avoids a “hammock” effect between the top and bottom of the backrest.
In addition, the spine member is in essence modular, or provides a mounting configuration, which allows the manufacturer to install various support configurations on the same spine. In this way, for example, different back supports can be configured to mount on the same spine to provide an adjustable lumbar support, or a lumbar support with an adjustable sacral support. Of course, other adjustment configurations would be suitable. [0047]
Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. As such, it is intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it is the appended claims, including all equivalents thereof, which are intended to define the scope of the invention. [0048]

Claims

What is claimed is:

1. An backrest comprising:

a back member having an upper and lower region;

a frame member;

a sacral support member having at least one end connected to one of the frame member and the back member and an opposite free end, wherein said sacral support member supports the back member at said lower region thereof;

a fulcrum member moveably disposed between a portion of said sacral support member and one of said frame member and said back member, wherein said fulcrum member is moveable toward and away from said free end of said sacral support member.

2. The backrest of claim 1 wherein said at least one end of said sacral support member is connected to said frame member and wherein said fulcrum member is moveably disposed between said portion of said sacral support member and said frame member.

3. The backrest of claim 2 wherein said sacral support member comprises a first support member flexibly connected to a second support member at said free end of said sacral support member.

4. The backrest of claim 3 wherein said first support member is fixedly connected to said frame member and wherein said fulcrum member is moveably mounted on said frame member and engages said first support member.

5. The backrest of claim 4 wherein said second support member has an end opposite said free end supported by a lumbar support member.

6. The backrest of claim 5 wherein said end of said second support member is slidably supported by said lumbar support member.

7. The backrest of claim 5 wherein said lumbar support member supports said backrest above said sacral support.

8. The backrest of claim 1 wherein at least a center portion of said lower region of said back member is flexible, wherein said sacral support member supports said back member at said center portion of said lower region.

9. An backrest comprising:

a back member having a lower region and a lumbar region positioned above said lower region;

a frame member;

a lumbar support member connected to said back member and supporting said back member at said lumbar region;

a sacral support member having at least one end connected to the frame member and an opposite free end, wherein said sacral support member supports the back member at said lower region thereof;

a fulcrum member moveably disposed between a portion of said sacral support member and said frame member, wherein said fulcrum member is moveable toward and away from said free end of said sacral support member.

10. The backrest of claim 9 wherein said sacral support member comprises a first support member flexibly connected to a second support member at said free end of said sacral support member, and wherein said first support member is connected to said frame and said second support member is coupled to said lumbar support.

11. The backrest of claim 10 wherein said second support member is slidably supported by said lumbar support member.

12. A method for adjusting a backrest comprising:

engaging a lower region of a back member with a sacral support member having a free end and a cantilevered length;

engaging said sacral support member with a fulcrum member; and

moving said fulcrum member toward and away from said free end of said sacral support member so as to thereby shorten and length said cantilevered length of said sacral support member.

13. The method of claim 12 wherein said sacral support member is connected to a frame member, and wherein said fulcrum member is moveably connected to said frame member.

14. The method of claim 12 wherein said sacral support member comprises a first support member flexibly connected to a second support member at said free end of said sacral support member.

15. The method of claim 14 wherein said first support member comprises an end opposite said free end fixedly connected to said frame and said second support member comprises an end opposite said free end supported by a lumbar support member.

16. The method of claim 15 wherein said end of said second support member is slidably supported by said lumbar support.

17. The method of claim 15 wherein said lumbar support supports said backrest above said sacral support.