WO1998026691A2 - Seat pan, seat assembly made therefrom, and chair made therefrom - Google Patents

Abstract

A seat pan (40) for supporting the cushions (11) of a chair (100), with the seat pan including a recess (43) in which resides a foam insert (51). This recess is positioned so as to be beneath at least a portion of at least one of the coccyx and ischial tuberosities of a seated user. Also disclosed are seat assemblies incorporating the seat pan and seat cushions. Further disclosed are chairs incorporating the seat assemblies.

Description

PATENT SPECIFICATION

TITLE: SEAT PAN, SEAT ASSEMBLY MADE THEREFROM, AND

CHAIR MADE THEREFROM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to apparatus for supporting a body in a sedentary position. In another aspect, the present invention relates to a seat pan, to a cushioned seat which includes the pan and one or more cushioned layers thereon, and to a chair made therefrom. In even another aspect, the present invention relates to a seat pan designed to accomadate a seated users' ischial tuberosities and/or coccyx, to a cushioned seat which includes the pan and one or more cushioned layers thereon, and to a chair made therefrom. In still another aspect, the present invention relates to a seat pan having one or more recessed portions in which reside supportive inserts, to a cushioned seat which includes the pan and one or more cushioned layers thereon, and to a chair made therefrom. 2. Description of the Related Art

There are numerous people who spend large amounts of time in task chairs, office chairs, motor vehicle seats, or even wheelchairs. The continued proliferation of computers in the workplace, home and schools is only increasing the numbers of people who spend extended periods of time in a sedentary position. When working with a computer, it is not uncommon for a person to sit uninterrupted for one to several or more hours . Unfortunately, spending large amounts of time in a sedentary position may lead to anatomical disfunctions of the human anatomy, especially if the chair is poorly designed. It is well established, that the sitting position creates problems of reduced circulatory efficiency due to restrictions in the normal flow of blood to and from the legs. The problems result because, the normal position of the arteries, veins, and nerves are squeezed, pinched, and kinked by the displacement of muscle tissue and fat tissue when a person sits. More specifically, when a person is seated on a cushion, the ischial tuberosities mostly, and the cocyx somewhat, will collectively support as much as 80 percent of the weight of the torso in an area confined to a triagle about five inches on a side with its apex at the rear. Over time, this concentrated weight compresses the seat cushion against the underlying supporting seat structure, causing the seated person to "bottom out" on the structure. Traditionally, the two components of the seat which may be varied are the supporting seat structure or base and the overlying foam. The foam on some chairs is currently utilized in multiple layers of varying densities, with the softer less dense foam oriented closer to the body to provide comfort, and harder more dense foam oriented closer to the seat structure to provide support and hopefully slow the process of "bottoming out". In a chair design, there is a trade-off in the foam densities. Softer foams have a tendency to allow quicker bottoming out on the underlying structure, whereas, denser foams tend to be less comfortable .

There have been many efforts in the prior art to provide suitable apparatus for persons who remain in a sedentary position for long periods of time, of which the following are examples.

U.S. Patent No. 2,150,287, issued March 14, 1939 to Minor, discloses a sponge rubber body of different densities for use with a seat cushion. As disclosed, the chair seat cushion may be formed with depressions and elevated areas in order to provide a shaped surface for the reception of the body of the person sitting upon the cushion.

U.S. Patent No. 3,987,507, issued October 26, 1976 to Hall, discloses a pressure distribution pad assembly for wheelchairs. As disclosed, the assembly is made up of three pads of resilient foam material assembled one on top of the other, the center pad having a greater density than the outer pads. The center pad includes three cut-out openings at locations corresponding to the maxium pressure points exerted by a person sitting on the pads, these openings including a fuller foam of density less than that of the outer pads .

U.S. Patent No. 4,132,228, issued January 2, 1979 to Green, discloses a comfort support seat cushion assembly which is designed to aleviate discomfort of people that are required to sit for long periods of time. This comfort seat provides even pressure distribution on the gluteal region through a cut-out portion that accommodates the ischial tuberosities and a gouged-out area which provides pressure relief for the perineum. A pulsating means can also be provided to administer therapeutic relief to assist in alleviating discomfort for long term sedentary positions .

U.S. Patent No. 4,522,447, issued June 11, 1985 to Snyder et al . , discloses foam seat and back cushions constructed of cellular elastic material which provide more uniform distribution of supportive forces exerted by the cushion over a larger area of the anatomy. The seat cushion is divided into segments having different moduli of elasticity for minimizing squeezing and restriction of arteries and nerves located in the anatomical protions of a person seated on the cushion. The modulus of elasticity of each segment is inversely proportional to the pressure exerted on such segment by the person seated on the cushion.

U.S. Patent No. 4,753,480, issued June 28, 1988 to Morell, discloses a pad assembly for wheelchairs including cover enclosing a bottom pad of resilient foam of high density, and enclosing an upper pad of resilient foam of intermediate density with at least one cut-out portion. Frictionally mounted in the cut-out portion is a filler foam material of low density. U.S. Patent No. 4,755,411, issued July 5, 1988 to Wing et al . , discloses a cushion having flexible outer membrane and multi-density resilient foam member having foam regions of different foam hardness. The foam regions are bonded together along common boundries and are bonded to the membrane at any boundary therewith, such bonding occuring during formation of the foam member and employing the materials of which the foam member is made.

U.S. Patent No. 4,837,881, issued June 13, 1989 to Kondo et al . , discloses a seat cushion with portions having different compression characteristics. As disclosed, the seat cushion includes an upper layer portion, which is made of a low hardness foamed body and forming an entire surface of the seat, and a lower layer portion, which is made of a high hardness foamed body and supporting the upper layer portion. These upper and lower layer portions are made of soft compression polyurethane foamed bodies and are molded together in the same mold to form an integral body with a strong boundary portion along their interface.

U.S. Patent No. 4,912,788, issued April 3, 1990 to Lonardo, discloses a seat pad for invalid patients which includes a base layer of padded material with raised cushion areas and depressed recessed areas. The cushion areas are formed by stuffing compartments formed on the base with a padding material, and correspond to and receive the large muscle masses of the buttocks and thighs so as to distribute the bodyweight over the large muscle masses. The recessed areas are defined by the compartments and correspond to the varying body prominences, so as to receive and suspend the prominences and thereby minimize pressure thereon.

U.S. Patent No. 5,018,790, issued May 28, 1991 to Jay, discloses a customized seat cushion for the human body which includes securable, removable supports used in combination with a shaped tray and a pad containing a fluid filling material.

U.S. Patent No. 5,163,737, issued November 17, 1992 to Navach et al . , discloses a cushion with a contoured base with a layer of resilient cushion foam thereover. The cushion is shaped such that the buttocks of a seated person are clasped positioned rather than supported. Recesses are provided under the ischia, under the trochanters, and beneath the sciatic nerves to limit the local pressure. These recesses may contain air bladders which are inflated by body motion against a back bladder in the cushion, or may contain various bladders sequentially pressurized to shift the bearing areas under the buttocks of the seated user in order to periodically lift the user for stimulating blood circulation. WO 86/07528, published December 31, 1986, discloses a chair seat having a seat cushion with a ventilated central drop-shaped part made of softer material than the seat cushion.

However, in spite of these advancements in the prior art, these is still a need for improvement to the exisiting apparatus for supporting persons in a sedentary position for long periods of time.

There is another need in the art for an improved seat pan. There is even another need in the art for an improved seat assembly.

There is still another need in the art for an improved chair.

These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.

SUMMARY OF THE INVENTION It is an object of the present invention to provide for an improved apparatus for supporting persons in a sedentary position for long periods of time. It is another object of the present invention to provide for an improved seat pan.

It is even another object of the present invention to provide for an improved seat assembly.

It is still another object of the present invention to provide for an improved chair.

These and other objects of the present invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.

According to one embodiment of the present invention there is provided a seat pan, which includes at least one recesses in which resides a foam insert. This recess is positioned so as to be beneath at least one of the ischial tuberosities or coccyx of a seated user.

According to another embodiment of the present invention, there is provided a seat assembly which includes the above described seat pan, and one or more seat cushions supported thereon.

According to even another embodiment of the present invention, there is provided a chair which includes the above described seat assembly.

These and other embodiments of the present invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of one embodiment of a chair 100 of the present invention, showing seat pan structure 40, seat cushion 11, back 15, support pole 18, a plurality of legs 22 each with a caster 23, head rest 25, and arm rests 26 (only one shown) .

FIG. 2 is an illustration of seat pan 40 of the present invention, showing recess 43 designed to be under at least one of the coccyx or ischial tuberosities of a seated user, preferably both.

FIG. 3 is a cross-sectional view of seat pan 40 of FIG. 2, taken at 3-3.

FIG. 4 is an illustration of foam insert 51 which is positioned in recess 43 shown in FIG. 2.

DETTATTiF.n DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown a side view of one embodiment of a chair 100 of the present invention. As shown in FIG. 1, chair 100 includes seat structure 40, seat cushion 11, back 15, support pole 18, a plurality of legs 22 (only two shown) each optionally having a coaster 23, head rest 25, and arm rests 26 (only one shown) .

Chair 100 is supported generally upon one or more legs 22 and support pole 18. Of course, it must be understood that chair 100 may be supported directly upon one or more legs 22 without support pole 18, for example, as three or four legged stools. Alternatively, chair 100 may be supported directly on an anchored support pole 18, for example a bar stool, or supported directly upon a base or framing as with vehicle or equipment seating. The one or more legs 22 may optionally include coasters 23 to allow chair 100 to be easily moved along the floor while the user is seated in chair 100.

As shown in FIG. 1, seat pan 40 is supported by suppport pole 18. As discussed above, seat pan 40 may optionally be supported directly upon one or more legs 22 without support pole 18. To allow a user some adjustment for comfort, optional controls 31 may be provided for adjustment mechanisms to allow the user to adjust the vertical height of seat pan 40 from the floor, the tilt angle of seat pan 40, and/or the rockability of seat pan 40. Seat pan 40 will may be rotatable upon support pole 18 to allow the user to easily turn while seated in chair 100. Referring additionally to FIGs. 2, there is shown an illustration of seat pan 40 of the present invention. Seat pan 40 defines one or more recesses 43 designed to be under at least at portion of at least one of the coccyx or ischial tuberosities of a seated user, preferably under at least the ischial tuberosities of a seated user, most preferably under both the coccyx and ischial tuberosities of a seated user. For the embodiment shown in FIG. 2, section 43A of recess 43 is positioned below the ischial tuberosities of a seated user, and section 43B is positioned below the coccyx of a seated user. While the embodiment of the present invention is shown with one recess 43 having sections 43A and 43B positioned respectively under the coccyx and ischial tuberosities of a seated user, it should be clear that separate recesses for sections 43A and 43B may be utilized.

Seat pan 40 may optionally further define one or more seat anchor bolt recesses 45. A seat anchor bolt is received through opening 45A, with a foam covering placed in recess 45 over the seat anchor bolt head.

Seat pan 40 is a substantially rigid structural member for supporting the weight of a user seated in chair 100. Seat pan 40 may be made of any suitable material. Non- limiting examples of materials suitable for seat pan 40 include metals, thermoplastics, thermosets, elastomers and composites. Preferably, seat pan 40 comprises an acrylonitrile butadiene styrene ("ABS") plastic.

Seat pan 40 may be manufactured by any suitable method known for the type of material utilized. For instance, when plastics are utilized as the material of construction, seat pan 40 may be manufactured using the following non- limiting examples of injection molding, stamp molding, compression molding, extrusion, pultrusion, filament winding and vacuum forming. Residing in recess 43 is an insert 51. Specifically, insert section 51A is generally positioned to receive the weight from the ischial tuberosities and will reside in recess section 43A, and insert section 51B is generally positioned to receive the weight from the coccyx and will reside in recess section 43B.

Insert 51 is of a different, that is, a greater or lesser, density than cushion 11, preferably of lesser density than cushion 11.

Where insert 51 is of lesser density than that of seat cushion 11, as cushion 11 compresses over time, the ischial tuberosities and the coccyx will "dangle" over the lesser dense insert 51, with the broader, gluteal muscle masses dispersing the body's weight and seated pressure over the surface of seat pan 40. Bottoming out of the ischial tuberosities and/or the coccyx on seat pan 40 is thus prevented, resulting in a reduction in overall seated pressure due to the fact that the ischial tuberosities and/or the coccyx are contacting this insert 51.

Thus, insert 51 functions to provide at least enough support of the ischials and/or the coccyx to prevent the buildup of any substantial pressure between the ischial tuberosities and the internal layers of skin (a total lack of support could restrict blood flow) . However, for this embodiment, insert 51 must not provide so much support that would transfer any significant amount of weight and pressure to the ischial tuberosities and/or coccyx. As an alternative embodiment, under some circumstances it might be desirable to utilize an insert 51 of greater density than that of seat cushion 11. In such an instance, as cushion 11 compresses over time, the ischial tuberosities and the coccyx will tend to bear body weight, rather than shift such to the broader, gluteal muscle masses .

Insert 51 is generally made of any suitable elastic material. Non- limiting examples of materials suitable for use as insert 51 include polymeric cellular materials such as foamed plastics including, for example, foamed polyethers, foamed polyurethanes, and further include elastomeric cellular materials such as, for example, various natural and synthetic elastomers including natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, halogen substituted rubbers, and the like.

Recess 43 may be of any shape and size suitable to accommodate at least part of at least one of the coccyx or ischial tuberosities of a seated user, preferably at least the ischial tuberosities, most preferably both. It is also possible to utilize more than one recess 43, one for the ischial tuberosities, and one for the coccyx. The 1st, 50th and 99th percentile center-to-center measurements of the ischial tuberosities for a female are 4.9 inches, 5.5 inches and 5.9 inches, respectively, and for a male are 4.8 inches, 5.2 inches, and 5.6 inches, respectively. Depending upon how much of the population is to be accommodated by the design, whether both the coccyx and ischial tuberosities are to be accomodated, and whether part of or all of the coccyx and ischial tuberosities are to be accomodated, different widths and shapes for recess 43 will be selected. For example, while smaller dimensions will still accomodate a portion of the ischial tuberosities, to accommodate the entire width of the ischial tuberosities of some of the population, the width of recess 43 will need to be at least 4.8 inches. To design for the population at large, it is most preferred that the width of recess 43 be greater than 5.9 inches. The coccyx, being much smaller than the ischial tuberosities will be accommodated by a recess 43 as small as 1 inch across .

The depth of recess 43 will vary depending upon the thickness of cushions 11, and density of foam inserts 51. Recess 43 will generally, have a depth in the range of about 0.1 inches to about 5 inches. Preferably, recess 43 will have a depth in the range of about 0.25 inches to about 3 inches, more preferably in the range of about 0.25 to about 1 inches, and most preferably in the range of about 0.5 to about 0.75 inches.

Seat pan 40 will support one or more seat cushions 11. Optionally, seat pan 40 and the one or more seat cushions 11 may be enclosed in a covering, which covering may be sealed, or may be provided with a zipper, velcro, snap, button or other fastener to allow access to cushions 11 and seat pan 40. With access through the covering, seat cushions 11 and foam inserts residing in recesses 45 may be exchanged or cleaned.

Chair 100 includes back 15 which is connected to support pole 18 by back support bar 12. Back 15 may be contoured to receive the user's back and is suitably padded for comfort. Back 15 may optionally include one or more lumbar supports 37, the pressure of which may be controlled by hand pump 35. Optionally, one of controls 31 may be utilized to adjust the rockability of back 15. Back 15 may optionally be vertically adjustable.

Chair 100 may optionally include headrest 25 connected to back 15 by headrest support bar 28. Headrest 25 is generally contoured to receive a user's head, and suitably padded for comfort. To allow a user some adjustment for comfort, headrest 25 may optionally be vertically adjustable, and may optionally be tiltable on headrest support bar 28.

Chair 100 may optionally include armrests 26 connected to support pole 18 by armrest support bar 21. To allow the user some adjustment for comfort, each armrest 26 may be provided control 21 to allow armrests 26 to be vertically adjusted, tilted, and/or rotated. While the seat pan of the present invention has been described mainly by reference to a contoured seat, it must be understood that the seat pan will find equal applicability to seats of other geometries, including flat seats.

While the seat pan of the present invention has been described mainly by reference to a traditional type of desk chair, it must be understood that the seat pan may be incorporated into any type of chair or seat, including but not limited to, desk chairs, task chairs, stools, theater seats, benches, furniture, vehicle chairs, aircraft chairs, ship and boat chairs, motorcycle seats, mass transit vehicle benches or seats, machinery or equipment chairs, and wheelchairs .

While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those skilled in the art to which this invention pertains.

Claims

I CLAIM :

1. A seat pan for supporting a person in a seated position, the pan comprising: (a) a substantially rigid weight bearing member defining a recess positioned below at least a portion of at least one of the ischial tuberosities and coccyx of the seated person; and (b) an insert residing in the recess.

2. The seat pan of claim 1 wherein the substantially ridid weight bearing member defines a recess positioned below ischial tuberosities and coccyx of the seated person.

3. The seat pan of claim 1 wherein the insert is shaped to substantially fill the recess.

4. The seat pan of claim 3 wherein the insert comprises at least one material selected from the group of materials consisting of polymeric cellular materials and elastomeric cellular materials.

5. The seat pan of claim 4 wherein the polymeric cellular material comprises at least one selected from the group consisting foamed polyethers, foamed polyurethanes, and wherein the elastomeric cellular materials comprise at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers.

6. The seat pan of claim 1 wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.

7. The seat pan of claim 1 wherein the insert is shaped to substantially fill the recess, wherein the insert comprises at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers, and wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.

8. A seat assembly for supporting a person in a seated position, the assembly comprising: (a) a substantially rigid weight bearing member defining a recess positioned below at least a portion of at least one of the ischial tuberosities and coccyx of the seated person; (b) an insert residing in the recess; and (c) a cushion supported by the weight bearing member.

9. The seat assembly of claim 8 wherein the substantially ridid weight bearing member defines a recess positioned below ischial tuberosities and coccyx of the seated person.

10. The seat assembly of claim 8 wherein the insert is shaped to substantially fill the recess.

11. The seat assembly of claim 10 wherein the insert comprises at least one material selected from the group of materials consisting of polymeric cellular materials and elastomeric cellular materials.

12. The seat assembly of claim 11 wherein the polymeric cellular material comprises at least one selected from the group consisting foamed polyethers, foamed polyurethanes, and wherein the elastomeric cellular materials comprise at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers.

13. The seat assembly of claim 8 wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.

14. The seat assembly of claim 8 wherein the insert is shaped to substantially fill the recess, wherein the insert comprises at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers, and wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.

15. A chair in which a person may sit, the chair comprising: (a) a substantially rigid weight bearing member defining a recess positioned below at least a portion of at least one of the ischial tuberosities and coccyx of the seated person; (b) an insert residing in the recess; (c) a cushion resting on the weight bearing member; and (d) a plurality of legs affixed to the weight bearing member.

16. The chair of claim 15 wherein the substantially ridid weight bearing member defines a recess positioned below ischial tuberosities and coccyx of the seated person.

17. The chair of claim 15 wherein the insert is shaped to substantially fill the recess.

18. The chair of claim 17 wherein the insert comprises at least one material selected from the group of materials consisting of polymeric cellular materials and elastomeric cellular materials.

19. The chair of claim 18 wherein the polymeric cellular material comprises at least one selected from the group consisting foamed polyethers, foamed polyurethanes, and wherein the elastomeric cellular materials comprise at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers.

20. The chair of claim 15 wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.

21. The chair of claim 15 wherein the insert is shaped to substantially fill the recess, wherein the insert comprises at least one selected from the group comsisting of natural rubber, polychlorobutadiene, polybutadiene, polyisoprene, styrene-butadiene rubber, butyl rubber, nitrile rubber, ethylene-propylene copolymer, fluorene elastomers, polyacrylates, silicone rubbers, polysulfide rubbers, and halogen substituted rubbers, and wherein the substantially rigid weight bearing member comprises at least one material selacted from the group of materials consisting essentially of metals, thermoplastics, thermosets, elastomers and composites.