Patent Publication Number: US-6908158-B2

Title: Lateral motion chair arm mechanism for chair arm

Description:
FIELD OF THE INVENTION 
   The invention relates to a chair arm for an office chair and more particularly, to a chair arm wherein an armrest thereof is adjustable in a longitudinal direction, a lateral direction, and an angular orientation. 
   BACKGROUND OF THE INVENTION 
   Office chairs typically include an armrest supported thereon wherein the armrest has a support post on which the armrest is supported. Often, such armrests are adjustable in various directions to support the arm of the user and accommodate the unique physical characteristics of each chair occupant. 
   Such chair arms include adjustment mechanisms disposed between the support post and the armrest which allow for longitudinal movement in a front to back direction or lateral movement in a side to side direction which is transverse to the longitudinal direction. Also, such armrests have been made angularly adjustable and in some mechanisms, the angular adjustment is provided in combination with longitudinal and lateral adjustment. 
   It is an object of the invention to provide an improved chair arm arrangement which permits longitudinal, lateral and angular displacement of the armrest relative to the support post. 
   The invention relates to an improved armrest wherein the longitudinal, lateral and angular displacement of the armrest is governed by intersecting or overlapping slots on the armrest and support post wherein guide pins are slidably received through each pair of overlapping slots. More particularly, the support post includes a longitudinal slot and a transverse slot which are longitudinally spaced apart generally in the same plane, while the armrest includes a similar but oppositely oriented arrangement of a transverse slot and longitudinal slot. As such, the transverse slot on the armrest is disposed directly above the longitudinal slot on the support post with a guide pin being slidably received therebetween. Similarly, the longitudinal slot on the armrest is oriented vertically above and cooperates with the transverse slot on the support post with an additional guide pin being slidably received therebetween. The cooperating pairs of intersecting slots allow for longitudinal and lateral displacement of the armrest. Additionally, the opposite ends of the armrest are movable in opposite lateral directions to each other to adjust the angular orientation of the armrest relative to the support post. 
   Further, the armrest includes an improved locking arrangement which allows for ready locking and restraint of the armrest in any longitudinal, lateral or angular position and any combination thereof. In this regard, one of the armrests and support posts includes two different patterns of locking formations wherein one pattern of formations are uni-directional and another pattern of formations are bi-directional. First and second locking pins are provided on the other of the armrest and support post with the first locking pin being engageable with the uni-directional formations so as to be restrained only in a lateral or transverse direction and the second locking pin being engageable with the bi-directional formations so as to be restrained in both the longitudinal and transverse directions. 
   While the locking pins are spaced a fixed distance away from each other along the longitudinal axis of the armrest on which they are mounted, the relative distance along the longitudinal axis on the armrest support post varies depending upon the angular orientation of the armrest relative to the post. As such, engagement of the first locking pin with the bi-directional formation, which preferably is a circular opening, restrains one end of the armrest both laterally and longitudinally and defines the longitudinal position of the armrest relative to the support post. The engagement of the second locking pin with the uni-directional formation, which formation preferably is a slot, restrains the armrest transversely and defines the transverse position of the opposite end of the armrest. While the longitudinal position of the second locking pin varies depending upon the angular orientation of the armrest, the second locking pin is not confined in the longitudinal direction of the slot such that the slots accommodate the various angular positions in which the armrest may be oriented while greatly facilitating alignment of the pin with the slots and avoiding misalignment problems. 
   The armrest of the invention therefor provides for improved displacement of the armrest as well as improved locking thereof. Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a left side elevational view of a chair. 
       FIG. 2  is a perspective view of a right side chair arm, the left side chair arm being formed identical to but as a mirror image thereof. 
       FIG. 3  is a perspective view of the left side chair arm. 
       FIG. 4  is an exploded perspective view of the chair arm of  FIG. 3  illustrating a support post, an armrest housing, a cover pad and an actuator arrangement therefor. 
       FIG. 5  is an exploded perspective view of the components of the support post. 
       FIG. 6  is a perspective assembly view of the components of the support post with guide pins disposed in neutral positions. 
       FIG. 7  is a perspective view of the support post of  FIG. 6  with the guide pins illustrated at one end of their range of travel in solid outline and at an opposite end of their range of travel in phantom outline. 
       FIG. 8  is a perspective view of a base housing for the support post. 
       FIG. 9  is a plan view of the base housing. 
       FIG. 10  is a perspective view of the top plate for the support post. 
       FIG. 11  is a plan view of the top plate and base housing with the guide pins illustrated therein and locking pins also illustrated wherein an armrest is illustrated in phantom outline in an initial position. 
       FIG. 12  is a plan view illustrating the guide pins and locking pins with the armrest in a forwardly displaced position. 
       FIG. 13  is a plan view illustrating the guide pins and locking pins with the armrest in a forwardly and angularly inwardly displaced position. 
       FIG. 14  is a plan view illustrating the armrest in a rearwardly displaced position. 
       FIG. 15  is a plan view illustrating the armrest in a rearwardly and angularly inwardly displaced position. 
       FIG. 16  is a plan view illustrating the armrest in a forwardly and angularly outwardly displaced position. 
       FIG. 17  is a perspective view of an armrest housing. 
       FIG. 18  is a plan view of the armrest housing. 
       FIG. 19  is a plan view of the armrest housing with the actuator mounted therein. 
       FIG. 20  is a perspective view of an actuator handle. 
       FIG. 21  is a plan view of the actuator assembly. 
       FIG. 22  is a side cross-sectional view of the actuator assembly as taken along lines  22 — 22  of FIG.  19 . 
       FIG. 23  is a side cross-sectional view of the actuator assembly as taken along lines  23 — 23  of FIG.  19 . 
       FIG. 24  is a side view of a locking pin. 
       FIG. 25  is a side view of a guide pin. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1-3 , a chair  10  is illustrated which includes an inventive chair arm assembly  12  mounted thereto. The chair arm  12  as illustrated in  FIG. 3  includes an armrest unit  15  which is movable longitudinally in a front-to-back direction identified by reference arrow  16  (FIG.  3 ). The armrest  15  further has opposite front and back ends  17  and  18  respectively which are movable independently of each other in opposite lateral directions identified by front and rear reference arrows  19  and  20  ( FIG. 3 ) respectively. 
   More particularly, the chair  10  may be of any conventional construction and typically includes a base  22  which includes radially projecting legs  23  supported on castors  24 . The upper end of the base  22  includes a horizontally enlarged seat assembly  25  wherein the rear end of seat assembly  25  supports an L-shaped upright  26 . The upright  26  has a vertically enlarged back assembly  27  projecting upwardly therefrom in a conventional arrangement. The seat assembly  25  also supports the left and right chair arms  12  as discussed in further detail herein. 
   Referring to  FIGS. 2 and 3 , the chair arms  12  disposed on the opposite sides of the seat assembly  25  are formed substantially identical to each other except that they essentially are formed as mirror images. The following description therefore is applicable to both of the left and right chair arms  12 . 
   More particularly, the chair arm  12  includes an L-shaped mounting bracket  30  which may be a right side version  30 - 1  ( FIG. 2 ) or a left side version  30 - 2  (FIG.  3 ). Each version is formed the same and thus, common reference numerals are used therefor. The bracket  30  includes a horizontal leg  31  which has fastener holes  32  that allow the mounting bracket  30  to be bolted onto the seat assembly  25  laterally adjacent to the seat. The mounting bracket  30  supports a vertical support tube  33  which is formed rigidly at the distal end of the horizontal bracket section  31  and projects vertically. The upper end of the support tube  33  includes an oval opening  34 . 
   The chair arm  12  further includes the armrest  15  which is formed of a post or base section  35  and an armrest assembly  36  which is movably connected to the base section  35 . Generally, the post section  35  includes an oval support tube  37  projecting downwardly therefrom which is slidably received within the tube opening  34  in telescoping relation therewith to permit vertical displacement of the armrest assembly  36  generally in the direction of reference arrow  38  (FIG.  2 ). The entire armrest  15  thereby is vertically displaceable relative to the mounting bracket  30  to accommodate the unique physical characteristics of a chair occupant. The armrest  15  also includes height-adjustment mechanism  39 , diagrammatically illustrated in phantom outline in  FIG. 2 , which adjustment mechanism  39  may have any known construction and operate in a conventional manner to maintain the armrest assembly  36  at a selected elevation relative to the mounting bracket  30 . 
   Referring to  FIG. 4 , the armrest  15  generally includes the aforementioned post section  35  and the armrest assembly  36 . More particularly, the armrest assembly  36  includes an armrest housing  41  which is movably interconnected with the post section  35 . The armrest assembly  36  further includes an actuator mechanism  42  and an arm cap  43  which typically is formed of a soft material and snaps onto the armrest housing  41 . 
   As to the post section  35 , the post section  35  includes a base housing  45  having a top plate  46  in which is formed a longitudinal slot  47  and a transverse slot  48 . The transverse slot  48  is oriented transverse to the longitudinal slot  47  so as to extend in a side-to-side or lateral direction while the longitudinal slot  47  extends in a front-to-back direction. A pair of guide pins  50  and  51  are slidably received through the longitudinal slot  50  and the transverse slot  51  respectively and project upwardly and cooperate with a transverse slot  52  and a longitudinal slot  53  respectively of the armrest housing  41 . The sliding cooperation of the guide pins  50  and  51  within the longitudinal slot and transverse slot  47  and  48  and the transverse and longitudinal slots  52  and  53  thereby govern displacement of the armrest assembly  36  relative to the base section  35 . 
   Generally to secure the armrest assembly  36  in a fixed orientation, the actuator assembly  42  is provided with a pair of locking pins  56  and  57  which project downwardly and are adapted to cooperate with the top plate  46  on the base housing  45 . The top plate  46  includes a first pattern  59  of uni-directional locking formations  60  which cooperate with the rear locking pin  56 , and a second pattern  61  of bi-directional locking formations  62  which cooperate with the front locking pin  57 . The bi-directional locking formations  62  prevent movement of the locking pin  57  longitudinally and transversely to effectively fix the position of the front end  63  of the armrest housing  41  while the uni-directional locking formation  60  fixes the back end  64  of the armrest housing  41  only in the lateral direction while the locking pin  56  remains unconfined in the longitudinal direction. This permits ready engagement of the pins  56  and  57  with the first and second patterns  59  and  61  of the locking formations when the armrest assembly  36  is effectively in an angular orientation or lateral or longitudinal position. The specific cooperation and functional relationship of the above-described parts is described in further detail hereinafter. 
   Referring more particularly to the individual components of the armrest  15 , the base housing  45  ( FIG. 5 ) has a generally rectangular support section  66  which supports the weight of the armrest assembly  36 . The support section  66  is formed of molded plastic material and has appropriate strengthening ribs  67  within the interior thereof. The support section  66  furthermore is molded with a central guide channel  68  which extends from the rearmost end  69  forwardly to approximately three-quarters of the overall length of the support section  66 . The guide channel  68  is formed with upward facing ledges  70  and  71  wherein the ledges  70  and  71  extend from a rear wall  72  of the guide channel  68  to a pair of channel stops  73 . The ledge  71  is formed by spaced apart front and rear sections  71 - 1  and  71 - 2  as seen in  FIGS. 8 and 9 . The longitudinal length extending between the end wall  72  and the channel stop  73  is the length of the guide channel  68  which is adapted to receive the guide pin  50 , wherein the guide pin  50  is vertically supported on and slidable longitudinally along the ledges  70  and  71  between the end wall  72  and the channel stops  73 . 
   The support section  66  further includes a transverse guide channel  75  which extends between opposite side walls  76 . The guide channel  75  also is formed with support ledges  77  and  78  which extend on opposite sides of longitudinal channel  68  and are adapted to vertically support and permit horizontal transverse sliding of the second guide pin  51 . 
   The support section  66  also includes a pair of axle supports  80  and a lever opening  81  which opens downwardly through the bottom wall of the support section  66  near the front end thereof. 
   When the base housing  45  has the post section  37  telescopingly received within the support tube  33  (FIG.  2 ), the support section  66  is effectively non-rotatable about a vertically oriented axis but instead has a fixed orientation relative to the support tube  33 . The support section  66  thereby effectively defines a vertically movable but non-rotatable base for the armrest assembly  36  as described in further detail hereinafter. 
   To permit height adjustment of the support section  66 , an actuator lever  83  is seated in the channel  68  which serves to actuate the height-adjustment mechanism  39  referenced above. The actuator lever  83  includes a horizontal lever section  84  on which a pivot axle  85  is supported wherein the opposite ends of the pivot axle  85  are pivotally received within the axle supports  80 . The front end of the lever  83  includes a manually actuatable handle pad  86  which projects downwardly through the lever opening  81  to permit manual actuation by the chair occupant. The relatively narrow lever section  84  extends rearwardly and is received in the bottom of the longitudinal guide channel  68  wherein an actuator projection  87  acts downwardly through an opening  88  in the support section to effectively operate the height adjustment mechanism  39 . The lever section  84  is disposed vertically below the pin ledges  70  and  71  such that the guide pin  50  is still freely slidable vertically above the lever section  84 . 
   Referring to  FIGS. 5 and 25 , each guide pin  50  or  51  is formed identical to each other and thus, common reference numerals are used herein to identify the individual features of each guide pin  50  or  51 . More particularly, each guide pin  50  or  51  includes a square support block  90  on the lower end thereof which has a width which corresponds to the distance between the support ledges  70 - 71  or  77 - 78 . In other words, the support blocks  90  have a width which is substantially equal to but slightly less than the width of the longitudinal guide channel  68  or the transverse guide channel  75  to permit free sliding of each guide pin  50  or  51  therealong. 
   Referring to  FIG. 9 , the guide pin  50  is shown with its support block slidably supported on the ledges  70  and  71  within the longitudinal guide channel  68 . Additionally, the guide pin  51  is illustrated with its support block  90  supported on the ledges  77  although the support block  90  is able to slide across the open channel section  91  of the channel  68  in which the lever section  84  is received. As such, the guide pin  51  is freely slidable from the ledges  77  to the ledges  78  without interference by the channel section  91 . 
   Referring again to  FIG. 25 , the shaft of each pin  50  or  51  further includes a guide section  92  which has a cylindrical shape and projects vertically from the support block  90 . The guide section  91  terminates at an upper connector section  93  at the upper end thereof which is threaded. During assembly, the guide pins  50  and  51  are first positioned within the respective guide channels  68  and  75  and then the top plate  46  is positioned within the upper end of the support section  66  and affixed in place. More particularly referring to  FIG. 6 , the guide pin  50  projects vertically through the longitudinal guide slot  47  while the guide pin  51  projects vertically through the transverse guide slot  48  of the top plate  46  as seen in FIG.  6 . 
   More particularly, the top plate  46  as seen in  FIG. 10  is formed generally as a flat plate with the slots  47  and  48  formed so as to open vertically through the entire thickness thereof. The longitudinal slot  47  is defined by opposite ends  95  and  96 , while the transverse slot  48  is defined by opposite ends  97  and  98 . The longitudinal slot  47  is oriented transverse to and generally perpendicular to the transverse slot  48  and the front slot end  96  thereof is longitudinally spaced apart from the transverse slot  48 . 
   Additionally, a first pattern  59  of uni-directional locking formations  60  is provided in the region of the longitudinal slot  47 . More particularly, the uni-directional locking formations  60  preferably are formed as spaced apart, longitudinally elongate slots  100  which extend generally parallel to each other and have equal longitudinal lengths. The centermost slot  100 - 1  has a shallow depth near the front end  101  thereof like slots  100  and then opens into the guide slot  47 . As described in further detail herein, these locking slots  100  are adapted to engage the rearmost locking pin  56  and confine this locking pin  56  only in the transverse direction, hence reference to the locking formation  60  is being uni-directional. In other words, the locking pin  56  is unrestrained in the longitudinal direction. 
   As to the second pattern  61  of bi-directional locking formations  62 , these locking formations  62  preferably are formed as circular holes or apertures  102  which are arranged in parallel transverse rows  103  and in longitudinally elongate columns  104 . The holes  102  are arranged in a checkerboard-like grid. These holes  102  are adapted to receive the frontmost locking pin  57  therein and thereby restrain the locking pin  57  both in the transverse and longitudinal directions, hence identification of the holes  102  as bi-directional. 
   Referring to  FIG. 6 , when the top plate  46  is fitted within the support section  66 , the locking holes  102  and locking slots  100  open upwardly while the guide pins  50  and  51  project vertically through the guide slots  47  and  48 . Once assembled, the pins  50  and  51  are freely slidable horizontally along the slots  47  and  48  as illustrated generally in FIG.  7 . 
   For example, the guide pins  50  and  51  are illustrated in an intermediate center position within their respective slots  47  and  48  ( FIG. 6 ) but may be slid to the opposite ends of the slots  47  and  48  (FIG.  7 ). As seen in  FIG. 7 , the pin  50  is located at the rear slot end  95  as illustrated in solid outline but is movable forwardly to the front slot end  96  as illustrated in phantom outline. Similarly, the locking pin  51  is movable transversely or sidewardly to the slot end  97  as illustrated in solid outline but is freely slidable to the opposite slot end  98  as illustrated in phantom outline. 
   More particularly as to the armrest housing  41  (FIGS.  17  and  18 ), this housing  41  has a bottom wall  106  rigidly formed with a peripheral side wall  107  and a peripheral flange  108  extending thereabout. The bottom wall  106  is formed with the transverse slot  52  in the region of the back end  110  of the housing  41  while the longitudinal slot  53  is formed in an intermediate region  111  of the housing  41  disposed forwardly of the back end section  110 . The transverse slot  52  extends sidewardly or transversely between opposite slot ends  112  and  113  while the longitudinal slot  53  extends longitudinally between opposite rear and front ends  114  and  115 . The longitudinal spacing between the slots  52  and  53  is substantially identical to the slots  47  and  48  except that, after assembly, the transverse armrest slot  52  is located vertically above and oriented transverse to the longitudinal base slot  47  associated therewith. Additionally, the longitudinal armrest slot  53  is oriented in transverse relation and preferably perpendicular to the longitudinal base slot  48 . The slots  47  and  52  and the slots  48  and  53  thereby form associated pairs of slots wherein each pair, such as the slots  47  and  52 , are adapted to receive therethrough one of the guide pins, such as the guide pin  50 . Additionally, the remaining pair of slots  53  and  48  align with and are adapted to receive the associated guide pin  51 . The cooperation of these guide slots and guide pins permits the armrest assembly  36  illustrated diagrammatically in  FIGS. 11-16  to move in the transverse, longitudinal and/or angular directions. 
   During assembly, the support section  66  already is assembled together as illustrated in  FIGS. 4 and 6  wherein the pins  50  and  51  project vertically upwardly. Thereafter, the armrest housing  41  is fitted downwardly onto the top plate  46  with the pins  50  and  51  projecting vertically through the slots  52  and  53  as generally illustrated in FIG.  23 . Thereafter, threaded nuts  50 - 1  and  51 - 1  are threaded onto the threaded end sections  93  of the respective pins  50  and  51  to fixedly secure the armrest housing  41  in place while permitting sliding movement of the armrest housing  41  relative to the top plate  46 . 
   Referring to  FIG. 11 , the pin  50  is confined sidewardly in the base guide slot  47  but is slidable longitudinally along the length thereof. Since the pin  50  also is confined in the longitudinal direction in the armrest slot  52  on the armrest assembly  36 , the intersection point of the slots  47  and  52  thereby governs the location of the pin  50  longitudinally within the slot  47  and transversely within the slot  52 . Similarly as to the slots  48  and  53 , the intersection of the base slot  48  and armrest slot  53  defines the position of the pin  51  in the armrest slot  53 . 
   To illustrate the movements of the pins  50  and  51  during movement of the armrest assembly  36 ,  FIGS. 11-16  illustrate various representative positions for the armrest assembly  36  and the resulting positions in which the pins  50  and  51 .  FIG. 11  illustrates the armrest assembly  36  at a neutral position with the guide pins  50  and  51  located at the midpoints of each of the slots  47 ,  48 ,  52  and  53 . 
   As seen in  FIG. 12 , the armrest assembly  36  is moved forwardly to its forwardmost position as diagrammatically illustrated by reference arrow  116 . Forward movement of the armrest housing  36  causes the armrest slot  52  to pull the pin  50  forwardly along the longitudinal base slot  47 . The other pin  51  however is restrained longitudinally in base slot  48  but instead the armrest slot  53  moves relative to the pin  51 . 
   Referring to  FIG. 13 , once the armrest assembly  36  is in the forwardmost position, the front end of the armrest assembly  36  may be swung inwardly as indicated by reference arrow  117  to a new inwardly oriented angular position. As a result of this specific angular repositioning, the armrest slot  52  moves rightwardly along the pin  50  and while pin  51  is pushed rightwardly along the transverse base slot  48  by armrest slot  53 . 
   Alternatively as seen in  FIG. 14 , the armrest assembly  36  may be slid rearwardly such that the guide pin  50  is pushed to the end of the longitudinal base slot  47  by the armrest slot  52  so as to be located at the forwardmost end of the longitudinal armrest slot  53 . The armrest housing  36  also may be swung either angularly inwardly or outwardly as indicated by reference arrow  19  similar to the movement of FIG.  15 . 
   In another example illustrated in  FIG. 15 , the armrest housing  36  may be located somewhere intermediate the forwardmost position of FIG.  12  and the rearmost position of FIG.  14  and when in this intermediate location then displaced angularly. This angular displacement of  FIG. 15  occurs by rotating the back end of the armrest housing  36  inwardly while also rotating the forward end of the armrest housing  36  outwardly. As a result, the pin  50  is located at the outer end of the transverse armrest slot  52  to thereby limit further inward displacement of the armrest housing  36 . However, the front pin  51  is still located between the opposite ends of both slots  48  and  53  such that additional inward or outward angular movement of the front end of the armrest housing  36  is still permitted. 
   Referring to  FIG. 16 , in the same relative angular position of  FIG. 15 , the armrest housing  36  may be slid forwardly without changing the angular orientation thereof. As this occurs, the rear guide pin  50  remains at the outer end of the transverse armrest slot  52 . However, the front guide pin  51  automatically slides inwardly along the slot  48  as the longitudinal armrest slot  53  is displaced forwardly. 
   The armrest housing  36  may be moved through practically any other position beyond those examples illustrated in the prior figures. In particular, the armrest housing  36  may be moved directly sidewardly such as when in the position of  FIG. 11  wherein the pins  50  and  51  slide sidewardly along the transverse slots  52  and  48 . The drawings already depict that the armrest housing  36  may be moved forwardly or rearwardly and may be angularly tilted in any stationary position or may be further moved forwardly or rearwardly even when in an angularly displaced position. The cooperating slots and guide pins thereby provide a highly flexible repositionable armrest housing  36 . 
   In addition to the foregoing flexibility and positioning of the armrest housing  36 , the chair arm  12  further includes the locking arrangement  42  which is readily lockable through any of the numerous angular positions permitted by the foregoing slot and pin arrangement. This locking arrangement  42  includes, as part thereof, the first pattern  59  of uni-directional locking formations  60  and the second pattern  61  of the bi-directional locking formations  62 . 
   The locking arrangement  42  further includes an actuator mechanism  120  to effect engagement and disengagement of the locking pins  56  and  57 . To support the actuator mechanism  120 , the armrest housing  41  includes mounting flanges  121  as seen in  FIG. 17  which project upwardly and support the actuator mechanism  120  within the housing  41 . More particularly, four mounting flanges  121  are provided, two on each opposite side of the longitudinal armrest slot  53 . The mounting flanges  121  are disposed in cantilevered relation on the bottom housing wall  106  and are resiliently deflectable radially inwardly. The upper ends of each flange  121  include an inclined lip  122  that defines a snap-fit connection as described in further detail herein. Further, the bottom wall  106  includes pin holes  124  and  125  which are adapted to receive the locking pins  56  and  57  respectively. The rear pin hole  124  is disposed midway between the transverse slot  52  and the longitudinal slot  53 , while the other front pin hole  125  is spaced forwardly of the front end  115  of the slot  53 . 
   Referring to  FIGS. 19 ,  20  and  22 , the actuator mechanism  120  also includes a rotatable lever  127  which snaps onto the mounting flanges  121  and rotate about a vertical axis. In particular, the lever  127  is formed with an elongate opening  128  in the middle thereof. The opening  128  includes semi-circular wall sections  129  in the center area thereof which effectively define a circular opening  130  through which the mounting flanges  120  are fitted. The cooperating flanges  121  and wall sections  129  are all arcuate so as to permit rotation of the lever  127  in a horizontal plane. The opposite ends of the central open area  128  also include generally trapezoidal extensions  131  defined by radially diverging side walls  132 . These end sections  131  provide clearance space to permit the nuts  50 - 1  to slide longitudinally therealong without interference with the actuator lever  127 . 
   The opposite ends of the lever  127  also include circumferentially arcuate pin slots  135  which are adapted to receive a respective one of the locking pins  56  or  57  vertically therethrough. Additionally, the lever  127  includes upper V-shaped cam notches  136  extending along the opposite sides of the pin slot  135 . Additional pairs of cam notches  137  are formed on the lower side of the actuator. As such, the same actuator lever  127  may be used in either the right chair arm  12  or the left chair arm  12  merely by flipping the lever  127  over. 
   Referring now to FIG.  24  and the locking pins  56  or  57  illustrated therein, these locking pins  56  or  57  are formed identical to each other with a lower locking section  140 , an upper projection  141  and V-shaped radial cam projections  142  which project radially from opposite sides of the pins  56  or  57 . Referring to  FIG. 22 , each of the pins  56  and  57  is slid through a respective one of the pin slots  135 , wherein the radially projecting cam sections  142  seat downwardly within the pair of V-shaped cam notches  136 . The lower pin sections  140  project through the bottom wall  106  of the armrest housing and into selected engagement with one of the holes  102  or the slots  100 . 
   The lever  127  also includes an actuator button  145  which projects outwardly through a square cutout  146  formed through the housing side wall  107 . The button  145  is pressed manually inwards which causes rotation of the lever  127  wherein rotation of the lever  127  causes the pin cams  142  to slide upwardly along the corresponding cam notches  136 . The simultaneous upward movement of the pins  56  and  57  thereby pulls the lower pin section  140  vertically out of the corresponding hole  102  or locking slot  100 . As such, pressing the button  145  inwardly disengages the locking pins  56  and  57  vertically upwardly out of the holes  102  or slots  100 . 
   To generate a restoring force to the pins  56  and  57 , a resilient spring plate  150  is fitted onto the top of the lever  127  in a sandwich-type relationship. The spring plate  150  includes holes  151  and  152  which receive the pins  56  and  57  vertically therethrough. The spring plate  150  has a generally circular opening  153  which is sized slightly larger than the connector flanges  121  so that the spring plate  150  also snaps on top of the upper surface of the actuator lever  127  and is sandwiched between the lip  122  and the lever  127 . Therefore, rotation of the lever  127  lifts the pins  56  and  57  which is permitted because the opposite ends  154  and  155  of the spring plate  150  are able to bend vertically upwardly. However, the spring plate  150  is resilient so as to continuously bias the pins  56  and  57  downwardly. Upon releasing the lever  127 , the cooperating cams  142  and  136  permit the pins  56  and  57  to re-engage with the locking formations  60  or  62 . 
   Referring now to  FIGS. 11-16 , the locking pins  56  and  57  in operation are disposed in a fixed relationship relative to the transverse armrest slot  52  and the longitudinal armrest slot  53  due to the fixed location of the pin holes  124  and  125 . These fixed positions are located so that the locking pin  56  engages one of the slots  100  while the pin  57  engages one of the holes  102  regardless of the angular orientation of the armrest  36 . For example, the bi-directional hole  102  in  FIG. 11  restricts movement of the front end of the armrest housing  36  both laterally and longitudinally. The slots  100 , however, only restrain the locking pin  56  laterally. When the pins  56  and  57  are in their engaged position as generally seen in  FIG. 11 , the armrest housing  36  is unable to move longitudinally, laterally or angularly. 
   After rotation of the lever  127 , the spring plate  150  described above is able to deflect and allow the pins  56  and  57  to be disengaged which allows for free movement of the armrest housing  36  through the various exemplary positions illustrated in  FIGS. 12-16 . However, once the armrest housing  36  is positioned in any desired location such as those illustrated in  FIGS. 12-16 , the lever  127  is released wherein the spring plate  150  causes the pins  56  and  57  to be biased downwardly back into engagement with appropriate slots or openings. 
   In  FIG. 12 , the front pin  57  engages a selected one of holes  102  while the rear pin  56  engages the center slot  100 - 1  near the front portion  101 . In  FIG. 13 , the locking pin  56  is displaced rightwardly to a different slot  100  while the other locking pin  57  moves to another different hole  102 .  FIG. 14  illustrates a different arrangement while  FIG. 15  illustrates the locking pin  56  displaced to one of the leftward slots. If the pins  56  or  57  are slightly misaligned relative to the openings  102  or slots  100 , the armrest housing  36  is still able to displace itself slightly sidewardly so as to effect proper alignment and re-engagement of the locking pins  56  and  57 . 
   With this arrangement, an armrest housing  36  has a high degree of adjustability and the locking mechanism  42  is readily engageable in any of the longitudinally, laterally or angularly displaced positions. 
   Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.