Abstract:
A chair seat tilt lock mechanism has a detent to latch an actuating lever in a locked and unlocked position. When the lever is moved to a locking position, a spring urges a moveable locking member toward a locking position, however, the moveable locking member only moves to its locking position when the chair is tilted to properly register the moveable locking member with a fixed locking member. When the lever is moved to an unlocking position, another spring urges the moveable locking member to an unlocking position. The moveable locking member may be a slider which slides under a fixed abutment to lock the chair from tilting. Alternatively, the moveable locking member may be a pivoting arm with a series of openings which may receive the forked end of a tongue in a locked position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 08/922,138 and application Ser. No. 09/143,130, both assigned to Northfield Metal Products Ltd. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to chair tilt lock mechanisms and to chairs comprising such lock mechanisms. 
     BACKGROUND OF THE INVENTION 
     It is typical in office chairs for the seat to tilt rearwardly as an occupant leans back in the seat. Other chairs, such as chairs for typing, are designed so that the seat tilts forwardly when an occupant leans forward in a chair. However, sometimes the occupant does not wish the seat to tilt when leaning forwardly or rearwardly. To accommodate such an occupant preference, chairs have been designed with tilt lock mechanisms. 
     U.S. Pat. No. 4,555,085 issued Nov. 26, 1985 to Bauer et al. discloses a chair seat tilt lock mechanism. A horizontal slider slides between a position whereat a bolt extending through the slider blocks the base plate of the seat and, therefore, prevents the seat from tilting and another position whereat the bolt is registered with an opening through the base plate. The slider is moved by an operating arm which is secured to it. 
     The subject invention seeks to provide improved chair seat tilt lock mechanisms. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a chair tilt lock mechanism, comprising: a chair seat post support; a chair seat bracket tiltably mounted to said chair seat post support; a first locking member extending from one of said chair seat post support and said chair seat bracket; a second locking member mounted on another of said chair seat post support and said chair seat bracket and moveable between a locking position whereat said first locking member and said second locking member prevent said chair seat bracket from tilting with respect to said chair seat post support and an unlocking position whereat said first locking member and said second locking member permit said chair seat bracket to tilt with respect to said chair seat post support; an actuator for moving said second locking member; and a detent for latching said actuator. 
     According to another aspect of the present invention, there is provided a chair tilt lock mechanism, comprising: a chair seat post support; a chair seat bracket tiltably mounted to said chair seat post support; a first locking member extending from one of said chair seat post support and said chair seat bracket; a second locking member mounted on another of said chair seat post support and said chair seat bracket and moveable between a locking position whereat said first locking member and said second locking member prevent said chair seat bracket from tilting with respect to said chair seat post support and an unlocking position whereat said first locking member and said second locking member permit said chair seat bracket to tilt with respect to said chair seat post support; an actuator for moving said second locking member, said actuator comprising a locking spring arranged so as to urge said second locking member to said locking position, when compressed. 
     According to a further aspect of the invention, there is provided a chair tilt lock mechanism, comprising: a chair seat post support; a chair seat bracket tiltably mounted to said chair seat post support; a tongue rigidly extending from one of said chair seat post support and said chair seat bracket; an arm having at least one tongue receiving opening mounted on another of said chair seat post support and said chair seat bracket and moveable between a locking position whereat said tongue and said arm prevent said chair seat bracket from tilting with respect to said chair seat post support and an unlocking position whereat said tongue and said arm permit said chair seat bracket to tilt with respect to said chair seat post support; and an actuator for moving said arm comprising a locking spring arranged for urging said arm to said locking position, when compressed. 
     According to a further aspect of the invention, there is provided a chair, comprising: a chair seat post; a chair seat tiltably mounted to said chair seat post; a first locking member extending from one of said chair seat post and said chair seat; a second locking member mounted on another of said chair seat post and said chair seat and moveable between a locking position whereat said first locking member and said second locking member prevent said chair seat from tilting with respect to said chair seat post and an unlocking position whereat said first locking member and said second locking member permit said chair seat to tilt with respect to said chair seat post; an actuator for moving said second locking member; and a detent for latching said actuator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the figures which illustrate example embodiments of the invention, 
     FIG. 1 is a side view of a chair embodying a tilt lock mechanism made in accordance with this invention, 
     FIG. 2 is a perspective view of a tilt lock mechanism made in accordance with one embodiment of this invention shown in an unlocked position, 
     FIG. 3 is a plan view of FIG. 2, 
     FIG. 4 is a cross-sectional view along the lines  4 — 4  of FIG. 3, 
     FIG. 5 is a cross-sectional fragmentary view along the lines  5 — 5  of FIG. 3, 
     FIG. 6 is a cross-sectional view similar to FIG. 4 but with the chair seat bracket in a tilted position, 
     FIG. 7 is a cross-sectional view similar to FIG. 4 but shown with the tilt lock mechanism in a locked position, 
     FIG. 8 is a plan view of the tilt lock mechanism of FIG. 2 but shown in a locked position, 
     FIG. 9 is a plan view of a tilt lock mechanism made in accordance with another embodiment of this invention shown in an unlocked position, 
     FIG. 10 is a perspective view of a tilt lock mechanism made in accordance with a further embodiment of this invention shown in an locked position, 
     FIG. 11 is a plan view of FIG. 10, 
     FIG. 12 is a cross-sectional view along the lines  12 — 12  of FIG. 11, 
     FIG. 13 is a plan view of the tilt lock mechanism shown in FIG. 10 but in an unlocked position, and 
     FIG. 14 is a cross-sectional view along the lines  14 — 14  of FIG. 13; and 
     FIG. 15 is a fragmentary plan view of a tilt lock mechanism made in accordance with a further embodiment of this invention, shown in an unlocked position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to FIG. 1, a chair  10  has a tilt lock mechanism  12  joining the chair seat  14  to the chair seat post  16 . With the chair tilt lock mechanism in an unlocked position, the chair  10  may tilt from a solid line position shown in FIG. 1 to position  10 ′ shown in FIG. 1 in ghost. 
     Referring to FIGS. 2 to  4 , a tilt lock mechanism  12  for the chair comprises a chair seat post support  20  for supporting seat post  16  (FIG. 1) and a chair seat bracket  22  to which the seat of the chair is affixed. The chair seat bracket  22  is pivotally mounted to the chair seat post support  20  by pivot  24  so that distal portion  28  of the chair seat bracket may tilt in direction  30 . A first locking member, namely abutment  32 , rigidly extends from the chair seat post support  20 . A track  34  is mounted to the chair seat bracket  22  and a second locking member, namely slider  36  is slidably received by track  34 . 
     An actuator comprises a lever  38 , a link arm  40 , a locking spring  42  and an unlocking spring  44  (seen in FIGS.  3  and  4 ). The link arm has a finger  46  which pivotably joins the link arm to the lever; the link arm extends through a hole in slider  36  and terminates in an enlarged flange  48 . Flange  48  acts as a backstop for locking spring  42  such that the spring, which surrounds the link arm, is sandwiched between flange  48  and slider  36 . Unlocking spring  44  is sandwiched between a depending leg  35  of track  34  and slider  36  (and preferably both the depending leg and slider have wells which receive the ends of spring  44  to maintain it in position). The lever  38  is pivotally mounted by pivot  50  to the chair seat bracket  22 . A handle  52  is attached to the lever. 
     Referencing FIGS. 3 to  5 , a detent  56  extends from the lever  38  in opposition to a protrusion  58  extending from the chair seat bracket  22 . The detent comprises a spring-loaded lug  60  such that the protrusion must depress the lug for the lug to pass the protrusion. 
     With the lever  38  in the unlocking position shown in FIGS. 2 to  4 , the link arm  40  is in an extended position relaxing spring  42 . In consequence, the slider  36  is urged by unlocking spring  44  to its unlocked position illustrated in these figures whereat the slider is spaced from abutment  32  (an abutment on track  34  may provide a limit stop for slider  36  thereby defining the unlocking position of the slider). In the unlocked position, the chair seat bracket  22  may tilt with respect to the chair post support  20  between the untilted position shown in FIG.  4  and the fully tilted position illustrated in FIG.  6 . 
     When in an untilted or a tilted position, the lever  38  may be pivoted to the locking position shown in FIGS. 7 and 8 by applying sufficient torque to the lever to cause the spring-loaded detent  56  to compress and pass over protrusion  58  on the chair seat bracket. When in the locking position, the link arm  40  is retracted with respect to slider  36  thereby compressing locking spring  42  against the slider so as to urge the slider toward a locking position. The spring constant of locking spring  42  is chosen such that this spring may overcome unlocking spring  44 . However, if the seat bracket  22  is in a tilted position, the slider  36  will stop against the side of abutment  32  where it will remain until the seat bracket  22  is brought to the untilted position. Upon the seat bracket  22  reaching the untilted position, the slider clears the side of the abutment and snaps into registration with the top of the abutment under the urging of locking spring  42 , as illustrated in FIG.  7 . In this position, the distal end  28  of the chair seat bracket is blocked from tilting in direction  30 . 
     Tilt lock mechanism  12  has the advantage that, in view of the detent  56 , the lever is latched in an unlocked or a locked position so that the mechanism is unlikely to be accidentally locked or unlocked. Also an occupant has a positive indication of when the lever has been moved sufficiently to reach its locking/unlocking position. Further, an occupant may move lever  38  to its locking position irrespective of whether the chair tilt locking mechanism is in a position to immediately lock. The occupant may also move the lever to an unlocking position when the tilt lock mechanism is locked even where a temporary tilting torque on the chair seat binds the second locking member (slider  36 ) so as to preclude the second locking member from immediately moving to an unlocking position. 
     A modification to the tilt lock mechanism of FIGS. 1 to  8  is shown in FIG.  9 . Turning to FIG. 9 wherein like parts have been given like reference numerals, link arm  80  comprises a rod  81  which is affixed at one end to slider  36  in any suitable manner. The other end of rod  81  terminates in a tab  82  from which a wire  84  extends. Wire  84 , which is also part of link arm  80 , terminates in bulbous end  86 . A backstop  88  extending from lever  38  has an opening (not shown) through which wire  84  is received. A locking spring  92  is received by wire  84  and sandwiched between the bulbous end  86  of the wire and backstop  88  of lever  38 . An unlocking spring  94  is also received by wire  84  and sandwiched between tab  82  and backstop  88 . 
     In operation, when the lever is moved to the unlocking position shown in FIG. 9, unlocking spring  94  is compressed against backstop  82  and locking spring  92  is relaxed thereby resulting in the link arm  80  urging the slider to move to its unlocking position shown in FIG. 9 whereat the slider is out of registration with the abutment of the chair seat post support. When in the unlocked position of FIG. 9, the lever may be moved to its locked position thereby compressing the locking spring  92  and relaxing the unlocking spring  94  so that the slider  36  is urged by the link arm  80  to a locking position whereat the slider is registered with the abutment. 
     Another tilt lock mechanism made in accordance with this invention is illustrated in FIGS. 10 to  14 . Turning to these figures, wherein like parts have been given like reference numerals, a first locking member is in the nature of a forked tongue  132  rigidly extending from chair post support  20 . A second locking member comprises an arm  136  which is pivotably mounted by pivot  170  to chair seat bracket  22  and has a series of tongue receiving openings  172 . The locking member arm  136  also has an elongate slot  174  which receives a pin  176  that extends from chair seat bracket  20 . The link arm  140  extends through a hole in locking member arm  136  and terminates in an enlarged flange  148 . Flange  148  acts as a backstop for locking spring  142  such that the spring, which surrounds the link arm, is sandwiched between flange  48  and locking member arm  136 . Unlocking spring  144  also surrounds the link arm and is sandwiched between backstop  178  of the link arm and locking member arm  136 . 
     With the lever  38  in the locking position illustrated in FIGS. 10 to  12 , the lever arm  140  is retracted compressing locking spring  142  against locking member arm  136  and relieving unlocking spring  144 . If a pair of tongue receiving openings  172  is aligned with forked tongue  132 , then the locking member arm will pivot to its locking position with the tongue receiving openings receiving the forked end of the forked tongue  172 , as illustrated in FIGS. 10 to  12 . With the locking member arm in its locking position, the tilt lock mechanism is locked. If the lever  38  is in its locking position and no pair of tongue receiving openings  172  is aligned with the forked tongue  136 , then the locking member arm will simply butt up against the forked end of the tongue  172  until a chair occupant varies the tilt of the chair seat sufficiently to align a pair of tongue receiving openings with the tongue, whereupon the locking member arm will pivot to its locking position. 
     An occupant may move lever  38  from its locking position of FIGS. 10 to  12  to its unlocking position illustrated in FIGS. 13 and 14 by applying sufficient torque to the lever to compress detent  56  so that it passes over projection  58 . In such case, unlocking spring  144  is compressed and locking spring  142  is relieved. This urges the locking member arm to pivot to its unlocking position shown in FIGS. 13 and 14 whereat the locking member arm pivots away from tongue  132  until the end of elongate slot  174  abuts pin  176 . With locking member arm  136  in its unlocking position, the tilt lock mechanism is unlocked and an occupant is free to tilt the seat bracket  22  with respect to the post support  20 . 
     From the foregoing, it will be apparent that the occupant may lock in one of several tilt angles with the tilt lock mechanism of FIGS. 10 to  14  by registering different pairs of tongue receiving openings  172  with forked tongue  132 . This tilt lock mechanism also has the advantages related in connection with the tilt lock mechanism of FIGS. 1 to  8 . 
     In another embodiment illustrated in FIG. 15, the first locking member comprises a U-shaped bracket  232  extending from the chair seat post support  20 . The basal wall  233  of this bracket has a number of tongue receiving openings  250 . The second locking member comprises a tongue  252  extending from a slider  236  riding on a track  235  on the chair seat bracket  22 . A pair of support plates  260 ,  262  depend from the chair seat post support  22 , one on either side of the basal wall  233  of the U-shaped bracket  232 . Each of the brackets has one tongue receiving opening  270 ,  272 , respectively. 
     In operation, when the lever (not shown) is moved to an unlocking position, the unlocking spring  44  urges the slider  236  to its unlocking position illustrated in FIG.  15 . In the unlocking position, the tongue  252  extends through tongue receiving opening  270 . 
     A user may move the lever from the unlocking position to a locking position, thereby compressing locking spring  42  which urges slider  236  to move. If a tonque receiving opening  250  of bracket  232  is aligned with the tongue  252 , then the tongue of the slider will slide through this opening and, as well, through tongue receiving opening  272  of support post  262  (which opening is spatially fixed in alignment with the tongue  252 ). With the tongue  252  received through tongue receiving openings  270 ,  272  of support posts  260 ,  262 , respectively, the tongue is firmly supported and even significant forces on bracket  232  will not damage the tongue. Bracket  232  is provided with several tongue receiving openings so that the chair may be locked at different tilt angles. 
     While in the embodiments illustrated, the first locking member extends from the chair post support  20  and the second locking member is carried by the chair seat bracket  22 , this arrangement could equally be reversed in which case, preferably, the lever  38  is also carried by the chair seat post support  20  rather than the chair seat bracket  22 . Similarly, while the detent is shown extending from the lever  38  and the opposing protrusion extending from seat bracket  22 , this too could be reversed so that the detent extended from the seat bracket  22 . 
     While the chair illustrated in FIG. 1 is designed to tilt backwardly from a horizontal position, it could equally be designed to tilt forwardly from a horizontal position. Also, the fork in tongue  132  while preferred, is not necessary. 
     Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.