Abstract:
The invention provides a chair and mechanism to permit occupant swivelling, bouncing, and tilting. The chair mechanism also provides tilt limitation using a keyhole tilt delimiter. The keyhole orientation follows rotation of the chair. A bearing assembly (preferably using race bearings) facilitates simultaneous swivelling and tilting.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to chairs, and more particularly, to chairs capable of tilting and swivelling.  
         [0003]     2. Description of the Related Art  
         [0004]     An occupant of a chair, such as an office chair, does not remain stationary throughout the course of the day. The occupant is frequently required to change position, whether to move the occupant&#39;s spatial position on the floor, or to rotate to face sideward or rearward, or to reach for an object positioned away from the occupant.  
         [0005]     To an extent, modern desk chairs address these mobility concerns by providing caster wheels on the base (allowing spatial positioning) and by providing a swivel means immediately below the seat part of the chair (allowing the occupant to face in different directions). However, chair designers have had difficulty addressing the reach concern without compromising the comfort or safety of the occupant.  
         [0006]     The ability to move in place while seated is also an ergonomic issue. Certain recent seating improvements have allowed the occupant to tilt in various directions. This moderate degree of mobility is considered important to improve circulation and accommodate the natural “restlessness” of the body, even while seated. Even in stationary chairs, occupants tend to shift their body weight, by leaning from side-to-side and back-and-forth. Stress on the spine and ischia and reduced blood flow to the legs can result if such natural shifting movement is not accommodated in the chair.  
         [0007]     While many chairs provide rearward tilting of the seat pan or seat back (or both) to allow the occupant to partially recline, tilting the entire chair at the base more closely mimics the natural shifting movements of the body, using the ankles as a pivot point. The base tilt also allows the occupant&#39;s feet to stabilize the chair. However, there is a concern that, in rearward or, especially, in rear-sideward tilting, the occupant may lose control, tilting back (and to the side) too far for the occupant to correct, which may result in the occupant either tipping the chair or falling off the seat, which may lead to injury. It would be beneficial to allow base tilting of the chair in circumscribed degrees to reduce the likelihood of rear-sideward spills.  
         [0008]     Such tilting should be accommodated as an additional feature in harmony with other normal functions of a chair, such as swivelling and spring-based “bouncing”.  
       SUMMARY OF THE INVENTION  
       [0009]     According to a first aspect of the invention, a chair is provided comprising a seat, a base and an elongate structure. Preferably, the base has legs that extend to the floor. The base defines a longitudinal axis. Preferably, the elongate structure is connected to the seat at a first end, and to the base, and extends through the base to terminate at a second end. The elongate structure comprises a pillar assembly, an outer cover housing a portion of the pillar assembly, a tilt ring, and a base portion. The pillar assembly is connected to the seat at the first end. The tilt ring preferably engages in part a lower portion of the outer cover. The base portion is preferably connected to the tilt ring and base. The base portion preferably comprises a bearing assembly.  
         [0010]     The chair allows tilting and swivelling movements. To permit tilting, the pillar assembly and outer cover are preferably tiltable in any direction against the tilt ring to tilt the seat. When tilting force is applied to the seat, the seat is moved from an axial orientation with respect to the longitudinal axis of the base. When such tilting force is relieved, the tilt ring returns the pillar assembly and outer cover to axial orientation. To permit swivelling or rotating the seat, the pillar assembly, the outer cover, and the tilt ring are preferably swivellable at the bearing assembly.  
         [0011]     Preferably, the base portion comprises a keyhole delimiter that defines a keyhole. The bottom end of the pillar assembly engages the keyhole, which limits the degrees of tilt permitted. The keyhole may be shaped:  
         [0012]     to permit a greater rearward tilt range than frontward tilt range;  
         [0013]     to permit a greater sideward tilt range than rear-sideward tilt range;  
         [0014]     to permit less rear-sideward tilting than any other direction;  
         [0015]     to encourage rear-sideward tilting toward rearward tilting;  
         [0016]     substantially symmetrically from side-to-side and substantially asymmetrically from back-to-front (meaning that the sides of the keyhole are approximately equidistant from dead-center, whereas the back and front are different distances from dead-center).  
         [0017]     Preferably, the chair further comprises a clocking system. The clocking system allows the swivelling parts, namely the pillar assembly, the outer cover, the tilt ring and the tilt delimiter, to swivel together. This allows the orientation of the keyhole to be maintained in the course of rotating the seat.  
         [0018]     The bearing assembly preferably comprises at least one race bearing, preferably a pair of race bearings. The first race bearing is preferably positioned in an upper portion of the base portion, while the second race bearing is preferably positioned in a lower portion of the base portion. The bearing assembly assists the swivelling of the chair. Preferably, the chair is capable of swivelling in tilted and untilted modes.  
         [0019]     For tilting, the tilt ring preferably comprises a flexible ring capable of elastic displacement when tilting force is applied.  
         [0020]     The chair may also have “spring” or “bounce” movement. The pillar assembly may further comprise a spring system to allow the springing or bouncing movement of the seat. The spring system preferably has starting and ending positions along a second longitudinal axis defined by the pillar assembly and the outer cover of the structure. Preferably, the spring “system” comprises two elements: a cylinder and a spring. The cylinder may be a pneumatic cylinder. The spring may be a coil spring, such as a variable rate coil spring. The spring system is preferably integrated with the pillar assembly, which may be understood as a “spring pillar assembly”.  
         [0021]     As optional features of the chair, the seat may include a back, and the base may include wheels on the legs.  
         [0022]     The foregoing are examples of certain aspects of the present invention. Many other embodiments are also possible and will become apparent to those skilled in the art from a review of the detailed description of certain preferred embodiments of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  shows an exploded view of the mechanism, according to the preferred embodiment.  
         [0024]      FIG. 2  shows an assembled view of the mechanism in  FIG. 1 , with outer cover  6  shown, but with legs  5  truncated.  
         [0025]      FIGS. 3A-3F  show assembly diagrams of the mechanism (in section) in the preferred order of assembly:  
         [0026]      3 A: First stage assembly  
         [0027]      3 B: Second stage assembly  
         [0028]      3 C: Third stage assembly  
         [0029]      3 D: Fourth stage assembly  
         [0030]      3 E: Fifth stage assembly  
         [0031]      3 F: Sixth stage assembly (completed)  
         [0032]      FIG. 4  shows a detailed view of the base  4  and bearing components (in section).  
         [0033]      FIG. 5  shows a sectional view of the mechanism  1  in tilt orientation.  
         [0034]      FIG. 6A  shows a detailed view of area  32  of the cross-section shown in  FIG. 7C .  
         [0035]      FIG. 6B  shows a detailed view of area  30  of the cross-section shown in  FIG. 7B .  
         [0036]      FIG. 6C  shows a detailed view of area  31  of the cross-section shown in  FIG. 7D .  
         [0037]      FIG. 7A  shows a cross-section through line H-H of  FIG. 5 , showing keyhole ring  18 .  
         [0038]      FIG. 7B  shows a cross-section through line G-G of  FIG. 5 , showing coil spring  10  and spring locator  11 .  
         [0039]      FIG. 7C  shows a cross-section through line E-E of  FIG. 5 , showing central post  12  features.  
         [0040]      FIG. 7D  shows a cross-section through line B-B of  FIG. 5 , showing roller  23 ′ and roller holder  24 ′.  
         [0041]      FIG. 8A  shows a front perspective view of the coil spring  10  and base  4  components.  
         [0042]      FIG. 8B  shows a sectional view of the coil spring  10  and base  4  components in  FIG. 8 , also showing roller  23 ′. 
     
    
     DETAILED DESCRIPTION  
       [0043]     The invention provides a tilting and swivelling chair. The mechanism  1  is intended for use in a chair, especially a chair of the type commonly used in offices (having a seat and seat back, the seat being positioned over a column, the column terminating in a branched base with legs). The mechanism  1  is preferably an elongate structure, which takes the place of the seat column. As shown in  FIGS. 1 and 2 , the elongate structure has two ends  2 ,  3 . The first end  2  is connected to the seat, preferably by means of a tapered fit, and the second end  3  extends through the base  4  to terminate slightly above the floor. Advantageously, the legs  5  may include wheels, such as conventional office chair casters (not shown).  
         [0044]     The mechanism  1  allows three basic occupant motions:  
         [0045]     swiveling;  
         [0046]     bouncing (i.e. longitudinal travel); and  
         [0047]     tilting.  
         [0048]     The mechanism  1  is adapted to perform all of the above motions. In addition, the mechanism comprises means for limiting the amount of tilt permitted (independent of swivel). The functional aspects of the mechanism  1  are now described.  
         [0000]     Swivel Motion  
         [0049]     The mechanism  1  allows swivelling with respect to the base  4 . A bearing ring (such as a race bearing) is provided to facilitate the swivelling by reducing friction between swivelling and non-swivelling parts of the mechanism  1 . Preferably, as shown in  FIG. 4 , a pair of bearing rings  16 ,  20  is provided, one each at upper and lower ends of the base  4 .  
         [0050]     The mechanism  1  swivels at the bearing rings  16 ,  20  while the base  4  remains stationary. The mechanism  1  is preferably capable of swivelling in tilted (as shown in  FIG. 5 ) or untilted state (as shown in  FIG. 2 ). The bearing rings  16 ,  20  reduce friction to facilitate smooth rotation of the mechanism about the axis  34  defined by the base  4 .  
         [0051]     The mechanism  1  is preferably constructed so that the swivelling parts turn together (at the same rate of rotation and to the same degree). Rotation is transferred between adjacent parts by means of clocking and locating features. As shown in  FIGS. 5, 6A  and  7 D, a clocking bushing  26  is preferably provided between the pneumatic cylinder  7  and the cylinder extruded tube  8 . The bushing  26  preferably has a tab-in-groove fit with the cylinder extruded tube  8 . The bushing  26  has the function of transferring swivel motion to the bearing rings  16 ,  20 .  
         [0052]     The outer cover  6  preferably rotates with its interior parts, as shown in  FIG. 5 . The cylinder extruded tube  8  threads to a predetermined stop to align the parts to a rubber tilt ring  13 . Furthermore, the tilt ring  13 , bottom post  14  and bearing cup  17  align with the keyhole delimiter ring  18 . As shown in  FIG. 5 , pneumatic cylinder  7  contains a locating feature  35  to align the seat (not shown) attached at the first end  2 .  
         [0000]     Bounce Motion  
         [0053]     In addition to swivel motion, the mechanism  1  preferably allows “bounce” motion along the longitudinal axis  33  defined by the tilting parts of the mechanism  1 . Preferably, two parts supply the bounce action: the cylinder extruded tube  8  and the coil spring  10 . The bounce moves the seat up and down to provide increased comfort and support and aid spinal alignment. The longitudinal axis  33  moves in unison with the axis of the occupant&#39;s spine (i.e. the occupant&#39;s center of gravity moves with the chair). This has the effect of reducing gravitational pressure on the occupant&#39;s spine.  
         [0054]     The cylinder extruded tube  8  preferably moves up and down within the central post  12 , assisted by upper and lower rollers  23 ,  23 ′.  
         [0055]     As shown in  FIG. 5 , the coil spring  10  is preferably acted upon by a spring locator  11 . The coil spring  10  may be a variable rate coil spring that compresses variably with the occupant&#39;s weight (i.e. compression becomes progressively more difficult as load is applied).  
         [0056]     In operation, the pneumatic cylinder  7 , the cylinder extruded tube  8  and the coil spring  10  are activated in series when weight (load) is applied to the seat part (not shown). Downward pressure on the pneumatic cylinder  7  and the cylinder extruded tube  8  causes the spring locator  11  (which is attached to the extruded tube  8  via flange  25 , shown in detail in  FIG. 6B ) to compress the coil spring  10 . Both the cylinder extruded tube  8  and the coil spring  10  act to return the chair seat to preset “normal” height when the seat is not under load. The outer cover  6 , the base  4  and the tilt ring  13  are not affected by the bounce.  
         [0057]     The height of the seat can also be adjusted by extending or compressing the pneumatic cylinder  7  inside the tube  8 . The height of the seat, set by the pneumatic adjustment, does not affect the bounce range of the cylinder extruded tube  8 , which operates independently. A preferred range of bounce travel is approximately 3 inches. Means may optionally be provided to adjust the bounce resistance or to permit a + or − range of travel (not shown).  
         [0000]     Tilting  
         [0058]     As shown in  FIG. 5 , the mechanism  1  (in loaded or unloaded state) allows tilting. At rest, the axis  33  of the tilting parts of the mechanism  1  is substantially co-linear with the axis  34  of the base  4 . When tilt pressure is applied from the seat, certain parts of the mechanism tilt while the base  4  remains stationary. The cylinder  7 , the tube  8 , the coil spring  10 , the outer cover  6 , the central post  12 , and bottom post  14  all tilt together with their internal parts. The lower shoulders of the outer cover  6  (housing the central post  12 , cylinder  7 , tube  8 , and coil spring  10 ) and the attached bottom post  14  bear upon a flexible tilt ring  13 . The flexible ring  13  and bearing cup  17  remain stationary with the base  4 ; however the flexible material of the ring  13  elastically displaces to accommodate the tilting parts.  
         [0059]     The flexible tilt ring  13  has several functions. It cushions and supports the outer cover  6  and bottom post  14  when tilted. The ring  13  provides resistance against tilting, and resistance will increase depending on load. The ring  13  may be made of rubber or synthetic rubber, or similar elastic material, such as silicone. The skilled person will appreciate that the shore hardness of the flexible material used in the ring can be adjusted to modify the resistance. The ring  13  also gently restores the tilting parts of the mechanism  1  back into vertical alignment with the base  4  when the tilt pressure is removed. The ring  13  flexibly bonds the bottom post  14  to the bearing cup  17 .  
         [0000]     Tilt Delimiter  
         [0060]     To control the degree of tilting, a keyhole delimiter ring  18  is preferably provided in the base  4  of the mechanism  1 . As shown in  FIG. 7A , the shape of the interior of the keyhole ring  18  is preferably slightly eccentric. The aperture of the keyhole delimiter ring  18  preferably has a broader “Back” portion and a narrower “Front” portion. (“Front” and “Back” refer to the occupant&#39;s facing direction. Note, however, that the “Back” portion of the aperture governs the occupant&#39;s forward tilt motions, while the narrower “Front” portion of the aperture governs the occupant&#39;s backward tilt motions.) Sloped edges are preferably provided between the front and back portions. The keyhole ring  18  circumscribes where the bottom post  14  (connected with the other tilting parts of the mechanism) may tilt. Front and front-sideward tilt movements are least restricted (to allow reaching motions). Rearward motions are permitted, but rear-sideward motions are nudged into rearward direction to permit relaxation tilt postures, while preventing rear-sideward spills. Preferably, the keyhole delimiter ring permits approximately 7° forward tilt, 10° backward tilt, 7° sideward tilt, and 5° rear-sideward tilt.  
         [0061]     The keyhole delimiter ring  18  preferably moves with the swivelling of the chair, so that the frontward orientation is maintained relative to the occupant in the seat. The function of the keyhole delimiter ring  18  is not affected by downward motion of the cylinder extruded tube  8  and coil spring  10 .  
         [0000]     Construction and Materials  
         [0062]     Looking at  FIGS. 1-4 , the preferred construction of the mechanism  1  will now be described. In particular,  FIGS. 3A-3F  illustrate the assembly of the mechanism, step by step.  
         [0063]     Beginning at  FIG. 3A , the central post  12  is provided, which consists of the main internal support member for the mechanism  1 . The central post  12  is a hollow, tapered body having a wide top section tapering to a narrower mid-section, broadening again at the bottom. The bottom section is preferably provided with a threaded exterior portion adapted for threaded connection to the bottom post  14 , as shown in  FIGS. 3C and 8B . The central post is preferably constructed of cast aluminum.  
         [0064]     As shown in  FIGS. 3A and 8B , the central post  12  houses the lower rollers  23 ′ in roller holders  24 ′. There are preferably 3 rollers arranged as shown in  FIG. 7D . Upper rollers  23  in roller holders  24  are also housed in the central post  12 , as shown in  FIG. 3B . The upper and lower rollers  23 ,  23 ′ are preferably constructed of a roller tube positioned over a dowel pin  28  as shown in  FIG. 6C .  
         [0065]     As shown in  FIG. 5 , the clocking bushing liner  27  is snapped on to the clocking bushing  26  on the pneumatic cylinder  7 . This assembly is next installed in the cylinder extruded tube  8  (sandwiching upper bushing  9 , which is used to guide the cylinder  7  and reduce friction). The flange  25  is slid on the tube  8  and rotated 180° to lock the flange  25  in place. The tube  8  is positioned within the cavity defined in the central post  12  and supported within rollers  23 . The cylinder  7  and tube  8  extend from the top of the mechanism  1  to a point within the base  4 . The spring locators  11  are attached to flange  25 .  
         [0066]     As shown in  FIG. 3C , the central post  12  is threadably connected to a permanently-bonded assembly consisting of the flexible tilt ring  13  and bottom post  14  and bearing cup  17 . As shown in  FIG. 8A , a set screw  29  is screwed to the central post  12  to prevent unthreading of the threaded parts. As shown in  FIG. 3D , the coil spring  10  sits atop the top part of the bottom post  14 .  
         [0067]     As shown in  FIG. 5 , the bearing cups  17 ,  21  sandwich the keyhole delimiter ring  18 . The bearings  16 ,  20  are preloaded due to the height of the keyhole delimiter  18 . This sandwich has the effect of reducing the side-to-side “play”, while maintaining the ability to swivel independently of the base  4 .  
         [0068]     The keyhole ring  18  is preferably constructed of aluminum. The sandwich is preferably held together using socket head cap screws  22  (also shown in  FIGS. 1 and 5 ).  
         [0069]     An outer cover  6  caps the coil spring  10  and central post  12 , as shown in  FIG. 3F . The outer cover  6  is preferably of translucent polypropylene, to allow the coil spring to be visible by the occupant. The cover  6  is preferably attached using molded snap clips.  
         [0070]     The base  4  preferably includes branched legs  5  as shown in  FIG. 1 . Wheels may be provided (not shown).  
         [0071]     The foregoing description illustrates only certain preferred embodiments of the invention. The invention is not limited to the foregoing examples. That is, persons skilled in the art will appreciate and understand that modifications and variations are, or will be, possible to utilize and carry out the teachings of the invention described herein. Accordingly, all suitable modifications, variations and equivalents may be resorted to, and such modifications, variations and equivalents are intended to fall within the scope of the invention as described and within the scope of the claims.