Patent Publication Number: US-6213556-B1

Title: Extendible chair arm

Description:
FIELD OF THE INVENTION 
     The present invention relates to chair arm and more particularly to an extendible arm used in an office chair. 
     BACKGROUND OF THE INVENTION 
     Conventionally, an arm of an office chair is either fixed or adjustable with respect to height. However, there is a gap between either type of above arms. As such, no support provided by such arms for elbow portion as one person uses for example a computer. Such elbow suspension may easily cause fatigue. This is one of the drawbacks of conventional chair arm. 
     An exploded view of a conventional chair arm is shown in FIG. 1 wherein rail member A is open to the top. As such, rear portion of rail member A is open when sliding member B moves forward relative to rail member A. But this is unsatisfactory for the purpose for which the invention is concerned for the following reasons: 
     1. Foreign objects may drop into the open portion of rail member A to clog the sliding member B. Further, it may hurt a child&#39;s fingers if child&#39;s hand is put on that open portion of rail member A. 
     2. Sliding member B is structurally complex. Also, a rubber block B 1  is required to engage with sliding member B. Furthermore, a stopper A 1  is provided in the front portion of rail member A to limit the movement of sliding member B. This results in an increase of manufacturing cost. 
     Thus, it is desirable to provide an improved chair arm in order to overcome the above drawbacks of prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an extendible chair arm which has the feature of rail member being implemented in a closed configuration such that foreign objects may not drop into rail member to clog sliding member as well as prevent sliding member from hurting hand. 
     It is another object of the present invention to provide a simplified extendible chair arm for reducing the manufacturing cost. 
     The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a conventional chair arm; 
     FIG. 2 is an exploded view of a preferred embodiment of extendible chair arm according to the invention; 
     FIG. 3 is a perspective view of assembled chair arm of FIG. 2; 
     FIG. 4 is sectional view of FIG. 3; 
     FIG. 5 is a first environmental view of chair arm of the invention where arm half extended; 
     FIG. 6 is a second environmental view of chair arm of the invention where arm fully extended; and 
     FIG. 7 is an enlarged fragmentary view of the circle area of FIG. 4 to show thumbscrew engaged in the projected aperture of trough. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the figures, particularly to FIGS. 2 to  7 , there is shown an extendible chair arm constructed in accordance with the invention. Arm is supported by an arm stump  1 . Arm comprises a rail member  2 , a sliding member  3 , a first pivot plate  4 , and a second pivot plate  5 . Description of each above component is as below. 
     Rail member  2  is an elongate hollow member open to the front including a lengthwise groove  21 , a horizontal divider  22  on the inside for dividing the interior space into upper and lower portions, a recess  221  in the front end of divider  22 , an elongate trough  23  in the center portion of the bottom surface of rail member  2 , and a generally semicircular projected aperture  231  at the inner end of trough  23  being smaller than width of trough  23  for permitting a thumbscrew  31  to secure therein after moving from trough  23  (see FIG.  7 ). 
     Elongated sliding member  3  is slidably disposed in the lower portion of rail member  2 . Thumbscrew  31  is secured to a hole  34  on the bottom of sliding member  3  after passing trough  23 . As such, sliding member  3  is defined to move a maximum length of trough  23  in rail member  2 . A rubber member  33  is engaged between rail member  2  and sliding member  3  to serve as a cushion to prevent a wobble of sliding member  3 . A bearing  32  is provided on the top front portion of sliding member  3 . The shank of pin  321  is passed through bearing  32  to pivotably secure in hole  41  near one end of first pivot plate  4 . As such, first pivot plate  4  may pivot about pin  321  in  360  degrees. Another hole  42  is provided near the other end of first pivot plate  4 . 
     Second pivot plate  5  is provided below arm pad  6  (FIG. 4) comprising an elongate block  51  projected in the bottom and a short hollow cylindrical member  511  with internal thread provided in the bottom of block  51  wherein screw  43  is screwed through hole  42  of first pivot plate  4  to pivotably secure in member  511  such that second pivot plate  5  may freely pivot about first pivot plate  4 . An assembled arm is shown in FIGS. 3 and 4. As shown in FIG. 4, bearing  32  is horizontally moveable in recess  221 , first pivot plate  4  is disposed in the upper portion of rail member  2 , and block  51  is horizontally moveable in groove  21 . With this, arm pad  6  can move and pivot with respect to the chair (FIGS. 5 and 6) as sliding member  3  moves in cooperation with the rotation of first pivot plate  4  relative to sliding member  3  and second pivot plate  5 . This provides a support is provided for elbow portion as one person uses for example a computer, thereby preventing arm fatigue. Further, no foreign objects may drop into rail member  2  to clog sliding member  3 . Furthermore, it is impossible to hurt fingers when hand is put on arm. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.