Abstract:
A chair control mechanism is adapted to decrease a likelihood of the mechanism becoming unintentionally disengaged from a locked position. In particular, a control arm has locked position wherein a seat plate is restricted in movement relative to a main bracket and an unlocked position where the movement relative to said main bracket is allowed. A latch bar is biased against the control arm and the control arm is notched such that axial sliding of the control arm into said unlocked position is possible only after providing a force necessary to disengage said latch bar from said notch.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a chair control mechanism with a latch and a method of retrofitting a chair control mechanism with a latching apparatus. 
     BACKGROUND OF THE INVENTION 
     Chairs may have adjustable parts such as adjustable arm rests, seat and backrest. The angle the seat makes with respect to the floor, for instance, may be adjustable. In some such chairs, a person who wishes to lean back in the chair while maintaining the angle between the seat and backrest may move a control arm axially from a locked position to an unlocked position, to release the seat and backrest to tilt from an upright position. The seated person may subsequently return the seat and backrest to the upright position. In such an instance, to reclaim stability and avoid an unintentional lean, the seated person may move the control arm from the unlocked position to the locked position. 
     Unfortunately, the control arm may tend to creep axially during normal use of the chair such that the control may have a tendency to disengage from its locked position. This unintentional disengagement frees the seat to tilt, presenting a nuisance, or possibly even a dangerous situation to the user. 
     SUMMARY OF THE INVENTION 
     A latch for a chair control mechanism is adapted to decrease a likelihood of the mechanism becoming unintentionally disengaged from a locked position. 
     In accordance with an aspect of the present invention there is provided a chair control mechanism with a latch including an arm mounted in a main bracket for axial sliding between a first position and a second position and a latch bar extending transversely of the arm and biased against the arm to increase the force necessary to axially slide the arm. 
     In accordance with another aspect of the present invention there is provided a method of retrofitting a chair control mechanism with a latching apparatus, where the chair control mechanism includes an arm mounted in a main bracket for axial sliding between a first position and a second position, the method includes biasing a latch bar against the arm, to increase the force necessary to axially slide the arm, where the latch bar extends transversely of the arm. 
     In accordance with another aspect of the present invention there is provided a chair control mechanism with a latch. The chair control mechanism includes an arm mounted in a main bracket for axial sliding between a first position and a second position and a latch bar biased against the arm to increase the force necessary to axially slide the arm. The arm has a restraint adapted to engage the latch bar while the arm is in the first position, such that the axial sliding of the arm into the second position is possible only after providing a force necessary to disengage the latch bar from the restraint. 
     Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the figures which illustrate example embodiments of this invention: 
     FIG. 1 is a schematic side view of a chair embodying the subject invention; 
     FIG. 2 is a schematic underside perspective view of a chair control mechanism having a control arm with a spring latch according to an embodiment of the present invention, where the control arm is in an unlocked position; 
     FIG. 3 is a schematic underside perspective view of the chair control mechanism of FIG. 2 where the control arm is in a locked position; 
     FIG. 4 is a schematic side view of the chair control mechanism of FIG. 2; 
     FIG. 5 is a schematic bottom view of the chair control mechanism of FIG. 2 where the control arm is in the unlocked position; and 
     FIG. 6 is a schematic partial bottom view of the chair control mechanism of FIG. 2 where the control arm is in the locked position. 
    
    
     DETAILED DESCRIPTION 
     Referencing FIG. 1, a chair  10  has a chair control mechanism  12  that is mounted on a spindle base  14  and attached to a seat  16 . 
     Turning to FIG. 2, the chair control mechanism  12  comprises a main bracket  22  and a seat plate  20 . The main bracket  22  is pivotally attached to the seat plate  20  by a pivot pin  24 . The main bracket  22  is mounted to the spindle base  14  of the chair  10 . The seat plate  20  has seat mounting flanges  34  for accommodating bolts  36  to mount the seat  16  to the seat plate  20 . The seat plate  20  also has side walls  21 A,  21 B that support the pivot pin  24 . 
     In a conventional fashion, a tensioned main spring (not shown) within a housing  44  is mounted between the main bracket  22  and the seat plate  20 . The tensioned main spring biases the seat plate  20  to a default (upright) position relative to the main bracket  22 . 
     The main bracket  22  is furnished with corresponding apertures for slidably receiving a control arm  26  therethrough. The control arm  26  when installed in the main bracket  22  is capable of limited axial and rotational movement. The control arm  26  has a jog  48  (FIG. 5) which is positioned over an actuator (not shown) of the gas cylinder (not shown) in the spindle  14  (FIG.  1 ). A paddle  28  is mounted at a free end of the control arm  26 . An enlarged bushing  30  is installed on the control arm  26  proximal to the seat plate side wall  21 A. To accommodate the enlarged bushing  30 , the seat plate side wall  21 A has a wall notch  32 . FIG. 3 illustrates the chair control mechanism of FIG. 2 where the control arm  26  is in a locked position. 
     Referencing FIG. 4 along with FIG. 2, a spring latch  38  is provided between the main bracket  22  and the side wall  21 A. At one end, the spring latch  38  has a hook  50  that hooks onto and bears against the main bracket  22 . From the hook end  50 , the spring latch  38  snakes under the control arm  26  and over the pivot pin  24  to end  52  which bears against the bottom of the seat plate  20 . The spring latch  38  has a configuration such that, when in place, it also bears against the control arm  26 . A spring restraint in the nature of a notch  42  is provided in the control arm  26 . The notch  42  receives the spring latch  38  when the control arm  26  is in its locked position. In other words, the locked position corresponds to a position wherein the enlarged bushing  30  prevents the seat plate  20  from moving relative to the main bracket  22 . 
     FIGS. 5 and 6 illustrate the control arm  26  in an unlocked and locked position, respectively. Turning to FIG. 5, the control arm  26  may be moved in an unlocking direction, U, until a snap ring  46 , provided on one end of the control arm  26 , contacts the side of the main bracket  22 . The control arm  26  is in an unlocked position whenever the enlarged bushing  30  ceases to block the seat plate side wall  21 A. Referencing FIG. 6, the control arm  26  may be moved in a locking direction, L, until snap ring  46  contacts the side wall  21 B of the seat plate  20 . As aforementioned, in the locking position, the spring latch  38 , is engaged by the notch  42  in the control arm  26  (FIG.  2 ). As will be apparent to a person skilled in the art, retainers other than the snap ring  46  may be used for the purpose of limiting the axial sliding of the control arm  26 , such as a cotter pin, a hitch pin, a Woodruff key or a lynch pin. 
     In operation, a user may rotate the control arm  26  to depress the gas cylinder actuator in order to change the height of the chair. When the user of the chair  10  slides the control arm  26  from the unlocked position to the locked position, the spring latch  38  pops into engagement with the arm notch  42 , thus latching the control arm  26  in place in a releasable manner. The spring constant of the spring latch  38  and the depth of the notch  42  are chosen so that the force required from the user of the chair  10  to disengage the spring latch  38  from the arm notch  42  is minimal, yet sufficient to avoid creep of the control arm  26 . 
     Preferably, the arm notch  42  extends through a sufficient arc such that rotational motion of the control arm  26 , while in the locked position, does not disengage the spring latch  38  from the arm notch  42 . 
     Although the spring latch  38 , as illustrated, is a resilient metal wire, it should be apparent that many alternative “latch bars” exist that may fit the criteria that the spring latch meets. Namely, that a given latch bar bears (is biased) against the control arm  26  and releasably engages with the arm notch  42 . For example, the latch bar may comprise two rigid metal rods joined by a medial section of spring steel that biases the rods toward a given orientation. 
     As will be apparent to a person skilled in the art, the arm notch  42  need not be formed through the removal of material from the control arm  26 . Instead, a pair of raised bumps on the control arm  26  would also serve as a notch to releasably engage the spring latch  38 , or other latch bar. Indeed, a single bump, or a shoulder, in the control arm  26  may also serve as a suitable spring restraint. Furthermore, if the spring latch  38  has a sufficiently large spring constant, it may abut the control arm  26  with enough force to avoid control arm creep even absent any spring restraint on the control arm  26 . 
     It will be apparent that the latch bar arrangement has application to a control arm with limited axial freedom but no rotational freedom. 
     Advantageously, the latch bar arrangement may be retrofit to existing chair control mechanisms. Where the existing chair control mechanism has an axially sliding control arm, such as control arm  26  (FIG. 2) a latch bar may be inserted to the position shown in FIG. 2 to increase the force necessary to axially slide the arm. Additionally, optionally, a hack saw or other cutting tool may be used to provide the control arm with a notch  42 . 
     Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.