Abstract:
A mechanism is provided for an office chair to adjust the tilt of the seat portion relative to the base of the chair. The mechanism includes an adjustable member tiltably mounted on a base, a compression spring bearing on the adjustable member and connected to the base using a retaining bolt running through the center of the compression spring, and a clutch device fixably attached to the base extending to the adjustable member, which clutch device is capable of holding the adjustable member in a fixed position relative to the base.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an adjustment mechanism for a chair allowing relative displacement of two chair parts. In an exemplary embodiment, the invention provides a seat tilt and locking device.  
       BACKGROUND  
       [0002]     It is typical in office chairs for the seat to tilt rearwardly as an occupant leans back in the seat. To accommodate this motion, known chair control devices allow a seat portion of a chair to tilt in relation to its wheeled support. These chair control devices are provided with an adjustable spring to counteract the rearward force exerted on the chair by the user, which force will ordinarily cause the chair to return to an upright position when unoccupied. This adjustable spring may be pretensioned by a user to a greater or lesser degree to cause the spring to exert a greater or lesser reaction force to the rearward force supplied by the user.  
         [0003]     Sophisticated chair control devices are known which, in addition to having an adjustable spring, incorporate a clutch assembly which allows a user to lock the chair in any reclined or upright position throughout its range of motion. Simpler devices are also known which have a tilt lock mechanism which merely prevents the chair from righting itself when in a reclined position and/or locks the chair in an upright position.  
         [0004]     The more sophisticated chair control devices which incorporate the clutch assembly feature are far more expensive and complicated to manufacture than the simpler tilt lock mechanisms. This is due to certain design considerations, because of which it has been necessary in the past to use an expensive tilt assembly and torsion spring in devices featuring both an adjustable pretensioned spring for counteracting the tilt force exerted by a user and a clutch assembly for locking in a tilt position.  
       SUMMARY OF THE INVENTION  
       [0005]     In an exemplary embodiment, an adjustment mechanism for a chair comprises a base, an adjustable member tiltably mounted on the base and moveable between a first position and a second position, a compression spring bearing on the adjustable member which urges the adjustable member toward the first position when compressed and a clutch attached to the base and the adjustable member capable of engaging to hold the adjustable member in a fixed position relative to the base between or including the first position and the second position.  
         [0006]     In another embodiment, an adjustment mechanism for a chair comprises a base, an adjustable member tiltably mounted on the base and moveable between a first position and a second position, an elastic element bearing on the adjustable member which urges the adjustable member toward the first position when deformed, and a clutch comprising a clutch lever mounted on the base and a clutch assembly attached to the adjustable member. The clutch assembly connects the clutch lever and the adjustable member, and the clutch is capable of engaging to hold the adjustable member in a fixed position relative to the base between or including the first position and the second position.  
         [0007]     In yet another embodiment, an adjustment mechanism for a chair comprises a base comprising a first central plate and a first pair of sidewalls extending substantially perpendicularly downward from the first central plate, the first pair of sidewalls being substantially parallel to one another, an adjustable member tiltably mounted on the base below the first central plate moveable between a first position and a second position, an elastic element provided below the adjustable member and the first central plate of the base which bears on the adjustable member and urges the adjustable member toward the first position when deformed, and a clutch attached to the base and the adjustable member capable of engaging to hold the adjustable member in a fixed position relative to the base between or including the first position and the second position.  
         [0008]     In yet another embodiment, an adjustment mechanism for a chair comprises a base comprising a first central plate and a first pair of sidewalls extending substantially perpendicularly downward from the first central plate, the first pair of sidewalls being substantially parallel to one another, an adjustable member moveable between a first position and a second position which is tiltably mounted on the base, and which comprises a second central plate, a column mount and a second pair of sidewalls extending substantially perpendicularly downward from the second central plate to the column mount, the second pair of sidewalls being substantially parallel to one another, an elastic element bearing on the adjustable member which urges the adjustable member toward the first position when deformed, and a clutch attached to the base and the adjustable member capable of engaging to hold the adjustable member in a fixed position relative to the base between or including the first position and the second position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  shows a conventional tilt mechanism for use with a chair control device;  
         [0010]      FIG. 2  shows another conventional tilt mechanism for use with a chair control device;  
         [0011]      FIG. 3  shows an exemplary embodiment of a tilt mechanism for use the present chair control device;  
         [0012]      FIG. 4  shows perspective view of an exemplary embodiment of a chair control device wherein the tilt mechanism is concealed beneath a shroud;  
         [0013]      FIG. 5  shows another perspective view of the chair control device of  FIG. 4  wherein the shroud has been removed;  
         [0014]      FIG. 6  shows an overhead view of the chair control device of  FIG. 5 ;  
         [0015]      FIG. 7  depicts outlines of an embodiment of the present tilt mechanism in both the reclined and upright positions;  
         [0016]      FIG. 8  shows a side view of an exemplary embodiment of a tilt mechanism;  
         [0017]      FIG. 9  shows an overhead view of the tilt mechanism of  FIG. 8 ;  
         [0018]      FIG. 10A  depicts detail  1  of  FIG. 8 ;  
         [0019]      FIG. 10B  shows an end view of the tilt mechanism of  FIG. 8 ;  
         [0020]      FIG. 11  shows an overhead view of an exemplary embodiment of a base of a chair control device;  
         [0021]      FIG. 12  shows a side view of the base of  FIG. 11 ;  
         [0022]      FIG. 13  shows an end view of the base of  FIG. 11 ;  
         [0023]      FIG. 14A  depicts detail  1  of  FIG. 11 ;  
         [0024]      FIG. 14B  depicts section B-B of  FIG. 11 ;  
         [0025]      FIG. 14C  depicts section A-A of  FIG. 11 ;  
         [0026]      FIG. 15A  shows a top view of one embodiment of a tilt clutch bracket;  
         [0027]      FIG. 15B  shows a side view of the tilt clutch bracket of  FIG. 15A ; and  
         [0028]      FIG. 15C  depicts detail  2  of  FIG. 12 . 
     
    
       [0029]     Before any embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangements of components set forth in the following description, or illustrated in the drawings. The invention is capable of alternative embodiments and of being practiced or being carried out in various ways. Specifically, numerical dimensions, where they appear on the following drawings, represent those of exemplary embodiments only and may be modified by one skilled in the art as conditions warrant. Also, it is to be understood that the terminology used herein is for the purpose of illustrative description and should not be regarded as limiting.  
       DETAILED DESCRIPTION  
       [0030]      FIG. 1  shows a conventional tilt mechanism for use with a chair control device. This device, known in the art as a “tilt lock” device, comprises a tilt mechanism  10  pivotably connected to a base  11 . The underside of the mechanism has a column mount  15  on its underside which may be mounted on the column of the wheeled support of a standard office chair. As the tilt mechanism  10  rotates relative to the base  11 , this causes the wheeled support of the chair to tilt relative to a seat of the chair mounted on the top surface of the base  11 .  
         [0031]     Counteracting the tendency of the tilt mechanism  10  to rotate relative to the base  11  is the compression spring  13  compressed between the underside of the tilt mechanism  10  and a knob  12  secured to the base  11  by the retaining bolt  14 . The knob  12  is adjustably mounted on the retaining bolt  14  so that it may be rotated to add or remove a preloading force to the compression spring  13 . This preloading force causes the tilt mechanism  10  to rotate more or less stiffly relative to the base  11  when subjected to an outside force. Through this mechanism, a user of the chair can adjust the recline resistance of her chair to her personal comfort.  
         [0032]      FIG. 2  shows another conventional tilt mechanism for use with a chair control device. Similarly to the device of  FIG. 1 , a tilt mechanism  20  is provided which rotates relative to the base  21 , and the tilt mechanism  20  is provided with a column mount  25  on its underside. In contrast to the device of  FIG. 1 , in place of a compression spring bearing on the outside of the tilt mechanism  20  a torsion spring  23  is provided within the tilt mechanism  20 , and a knob  22  bears directly on the tilt mechanism  20 . The knob  22  is drawn downwards by a retaining hook  24  which passes through an opening in the tilt mechanism  20  to engage with a torsion spring  23  within. The opposition end of the torsion spring  23  bears on the base  21 , and is provided with a stop  28  for this purpose.  
         [0033]     In the conventional mechanism shown in  FIG. 2 , the compression spring has been replaced by the torsion spring  23  in part to accommodate the addition of the clutch assembly  26 . This assembly connects the base  21  and the tilt mechanism  20  and allows the rotation of one to be halted relative to the other at any position throughout its range. While the clutch assembly provides a useful functionality to the chair control device of  FIG. 2 , it cannot be added to the chair control device shown in  FIG. 1  as is without significantly redesigning the tilt mechanism  11  requiring at the very least that it be made larger overall, significantly so in the area of the added clutch assembly. This larger tilt mechanism  20  cannot easily accommodate a compression spring without impeding its function. Furthermore, if one were to try to add a compression spring to the mechanism shown in  FIG. 2  by placing it between the knob  22  and the tilt mechanism  20 , the knob  22  would extend an unacceptably far distance below the base  21  and interfere with other functions of the chair itself. Thus in the known mechanism of  FIG. 2 , in place of a compression spring a torsion spring  23  is used. Although the redesigned tilt mechanism  20  provides tilt functionality to the chair control device and accommodates the newly added clutch assembly  26 , its complexity makes it difficult to manufacture and thus relatively expensive. Likewise the torsion spring  23  is also more expensive than more common compression springs. As such the chair control device of  FIG. 2 , while providing increased functionality over the chair control device of  FIG. 1 , does so only at an increased cost in materials.  
         [0034]      FIG. 3  shows an exemplary embodiment of a tilt mechanism for use the present chair control device. The device has a tilt mechanism  30  which as in the previous figures rotates relative to the base  31 . However unlike the prior art figures, this embodiment of a tilt mechanism features a clutch assembly  36  together with a compression spring  33 , as well as a relatively simple design for the tilt mechanism  30  comprising a central plate  38 , a column mount  35  and a pair of sidewalls  37  extending from the central plate to the column mount. In one embodiment, the pair of sidewalls  37  are substantially parallel to one another and substantially perpendicular to the central plate  38 . In another embodiment, the pair of sidewalls reinforce and add rigidity to the central plate. In yet another embodiment, an incline  37  may be provided on the central plate  38 , on which incline  37  the compression spring  33  bears.  
         [0035]     Because the tilt mechanism  30  is provided with these sidewalls  37  extending from the central plate  38  away from the base  31  towards the bottom of the device in contrast to the tilt mechanisms of the prior art, the surface of the central plate  38  on which a spring bears can be closer to the base  31  than would otherwise be the case. As such, a compression spring can be used rather than torsion spring of the prior art. To further accommodate this substitution, the clutch assembly  36  and a clutch lever (not shown) can be provided as a unit fixably mounted on the base  31  below which point it pivotably engages the tilt mechanism  30 . A knob  32  is also provided secured to the base  31  by the retaining bolt  34 . The knob  32  is adjustably mounted on the retaining bolt  34  so that it may be rotated to add or remove a preloading force to the compression spring  33 .  
         [0036]      FIG. 4  shows perspective view of an exemplary embodiment of a chair control device wherein the tilt mechanism is concealed beneath a shroud. The device comprises a base  51  and a tilt mechanism (not shown) which may be pivotably connected thereto at the primary pivot point  42 . A shroud  44  attached to the base  51  at least partially covers the tilt mechanism to reduce the risk to a user of a user&#39;s finger being caught between the tilt mechanism and the base  51 . A knob  52  is provided which may be adjusted to add or remove a preloading force to the compression spring  59  mounted beneath the knob  52  on the tilt assembly. In an alternative embodiment, the spring  59  may be any elastic element. The base  51  is provided with tabs  67  through which the device may be attached by bolts or another fastener to the underside of the seat portion of a chair (not shown).  
         [0037]     The tilt mechanism supports the column mount  55  which can be mounted on the column of a standard wheeled support for an office chair (not shown). This column may include a gas cylinder having two-chambers separated by a normally closed valve. A user actuator  62  may be provided tiltably mounted in a housing above the valve opening member, and which may be operated to depress the valve opening member in order to open the cylinder valve to permit height adjustment of the seat.  
         [0038]     Further adjustment devices may be provided as part of the present chair control device including a primary clutch lever  63  attached to the base  51  by a clutch housing  43 . The primary clutch lever  63  is provided to operate a clutch assembly at least partially concealed within the shroud  44 , which assembly comprises at least one clutch plate and a clutch pin  41 . The primary clutch lever  63  may be operated to engage or disengage the clutch assembly to prevent or permit tilt mechanism to move relative to the base  51 . A secondary adjustment assembly  60  may be provided to support element for a chair backrest, the motion of which secondary adjustment assembly  60  may halted by the engagement of a secondary clutch lever  61 . A recline locking lever  65  may be provided mounted on the base  51  having a recline locking stop  66  thereon which may be slid into a blocking position to prevent the tilt assembly from being adjusted to the fully upright position relative to the base  51 .  
         [0039]      FIG. 5  shows another perspective view of the chair control device of  FIG. 4  wherein the shroud has been removed so that the tilt mechanism  50  is visible. As previously mentioned, the tilt mechanism  50  may be pivotably connected to the base  51  at a primary pivot point  42 . Also visible in  FIG. 5  is a spring loaded clutch bracket  64  which the primary clutch lever  63  mounted on the base  51  may be operated to disengage, as well as a clutch assembly  56 .  FIG. 6  shows an overhead view of the chair control device of  FIG. 5  having a clutch spring  68  for spring loading the clutch bracket  64 . The tilt mechanism  50  is shown here having reinforcing ridges  69  thereon to provide additional stiffness.  FIG. 7  depicts an embodiment of the present chair control device wherein an outline of the base  71  is shown in relation to outlines of the tilt mechanism in both the reclined position  70   a  as well as an upright p006Fsition  70   b.    
         [0040]      FIG. 8  shows a side view of an exemplary embodiment of a tilt mechanism  80  provided with a primary pivot point  82  for engaging with a base of a chair control device, column mount flanges  85  for engaging with a column mount, a user actuator  84  to permit height adjustment of the seat and an actuator slot  83  therefore, an incline  86  to provided a bearing surface for a compression spring or other elastic element, and a retaining bolt passage  87  through which a retaining bolt may pass to secure a control knob to the base of a chair control device.  
         [0041]      FIG. 9  shows an overhead view of the tilt mechanism  80  of  FIG. 8  wherein clutch mounts  88  are visible. In one embodiment, the clutch mounts  88  comprise raised tabs which pivotably engage the at least one clutch plate of the clutch assembly of the chair control device. The column mount flanges  85  are also shown having at least one rivet hole  89  to which a plate column mount may be attached to receive the column of a wheeled or other support of a chair. Reinforcing flanges  92  extending downward from the second central plate  90  to reinforce the second central plate  90  are also shown in  FIGS. 8, 9  and  10 B.  
         [0042]      FIG. 10A  depicts detail  1  of  FIG. 8  showing the user actuator  84  to permit height adjustment of the seat and the actuator slot  83  therefore.  FIG. 10B  shows an end view of the tilt mechanism of  FIG. 8  wherein the a tilt mechanism  80  comprises a second central plate  90 , a second pair of sidewalls  91 , and column mount flanges  85  which may be attached to a column mount, in which case a passage is provided through the tilt mechanism  80  defined by the second central plate  90 , the column support and the first pair of sidewalls  91 . In an exemplary embodiment, the second pair of sidewalls  91  extend substantially perpendicular from the central plate  90 , and are substantially parallel to one another.  
         [0043]      FIG. 11  shows an overhead view of an exemplary embodiment of a base  111  for use with a chair control device comprising tabs  117  through which the base  111  may be attached by bolts or other fasteners to the underside of the seat portion of a chair (not shown), a raised portion  115  and retaining bolt socket  116  for securing an end of a retaining bolt, a protrusion  114 , and a neck  113  which narrows to provide an attachment point for a secondary adjustment assembly  60 . In one embodiment, base  111  comprises a base end plate  112  though which a recline locking stop  66  of a recline locking lever  65  passes.  
         [0044]      FIG. 12  shows a side view of the base  111  of  FIG. 11  having a passage  121  for a clutch bracket  64 , a passage  122  for a clutch pin  41 , an actuator slot  118 , a passage  123  for a secondary clutch pin, secondary pivot point  124  for a secondary adjustment assembly  60 , and a primary pivot point  125  for a tilt mechanism  50 .  FIG. 13  shows an end view of the base  111  of  FIG. 11  wherein the base comprises a central plate  131  and a pair of sidewalls  132 . In an exemplary embodiment, the pair of sidewalls  132  extend substantially perpendicularly downward from the central plate  131  and are substantially parallel to one another.  
         [0045]      FIG. 14A  depicts the protrusion  114  highlighted in detail  1  of  FIG. 11 ,  FIG. 14B  depicts the raised portion  115  highlighted in section B-B of  FIG. 11 , and  FIG. 14C  depicts the raised portion  115  and retaining bolt socket  116  highlighted in section A-A of  FIG. 11 .  FIG. 15A  shows a top view of one embodiment of a tilt clutch bracket  154  having a clutch pin passage  151 ,  FIG. 15B  shows a side view of the tilt clutch bracket  154 , and  FIG. 15C  depicts detail  2  of  FIG. 12 .