Patent Publication Number: US-8109566-B2

Title: Collapsible desk assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a collapsible desk assembly, more particularly, to a collapsible desk assembly adapted to be pivotally assembled to a chair. 
     2. Description of Related Art 
     A conventional collapsible desk assembly commonly known in accordance with the prior art comprises a desk board which is pivotally mounted to one side of an armrest of a chair by a pivotal unit. The desk board is pivotally flipped to a top of the armrest, such that the desk board is flatly placed above the armrest, allowing a user to use the desk board for reading or writing purpose. When not in use, the desk board is reversely flipped to the side of the armrest and is vertically suspended beside the armrest. 
     However, the conventional collapsible desk assembly bears several defects. First of all, the pivotal unit is mounted to the side of the armrest, when not in use, the desk board is reversely flipped to the side of the armrest and is vertically suspended beside the armrest, such that a slit formed between the pivotal unit and the armrest of the chair is emerged. When in sitting position, the user may customarily place his/her arm on the armrest and the slit, or unwarily put his/her fingers into the slit. When the user adjusts sitting position, he/she may unintentionally touch the desk board suspended beside the armrest, causing the pivotal unit to slightly pivotally shift relative to the armrest due to the swing of the desk board. A slight shifting of the pivotal unit will lead to a variation in a size of the slit, and the slit may clamp onto the user&#39;s arm or fingers causing unwanted injuries such as bleeding, or laceration. Therefore, the conventional collapsible desk assembly is unsafe to use. 
     The present invention has arisen to obviate/mitigate the disadvantages of the conventional collapsible desk assembly. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a collapsible desk assembly which comprises a desk board, an elbow joint, a positioning board, and a connecting portion which is adapted to be connected to an armrest of a chair. The desk board is provided for adapting to pivotally connect to the armrest of a chair. A supporting board is mounted to a backside of the desk board. The supporting board has a receiving space defined therein for receiving the elbow joint. The elbow joint includes an upper portion and a lower portion which is pivotally connected to the upper portion. A base is mounted on the upper portion. The base has a trench defined therein. A push block is screwedly received in the trench. A block cover caps the push block. A cover casing completely covers the base. The cover casing has an opening defined therein for partially receiving the block cover. The block cover is abutted against the connecting portion. An position of the block cover with the push block relative to the cover casing is adjustable due to the push block is screwed in/out from the trench. The upper portion is slightly pushed away from the connecting portion, such that the block cover is protruded from the cover casing. An interval between the upper portion and the connecting portion is changed, adjusting a tilting angle of the desk board relative to the connecting portion. The lower portion is threadedly connected to the connecting portion. A securing post is simultaneously passing through the upper portion and the lower portion to be a pivot of the elbow joint. An arc-shaped grooved is defined in the lower portion. The positioning board is connected to the elbow joint. The positioning board is elongated-shaped. The positioning board has a pin disposed on a first side thereof. The pin is inserted into the arc-shaped groove of the lower portion. The pin is able to slide along the arc-shaped groove relative to the positioning board. A pivoting shaft extends from a second side of the positioning board opposite to the first side. The connecting portion has a receiving hole laterally defined therein and extending therethrough for receiving the pivoting shaft. A sleeve is sleeving on the pivoting shaft for assisting the pivoting shaft to pivotally rotate relative to the connecting portion. A bolt is sequentially passing through the receiving hole and the pivoting shaft, and is screwed to the elbow joint. 
     When the elbow joint is pivotally rotated upwardly relative to the connecting portion, the desk board is upwardly lifted with the upper portion. The pin is abutted against a second end of the arc-shaped groove of the lower portion, driving the positioning board to pivotally rotate upwardly. When the desk board is lifted above the connecting portion, the upper portion is pivotally perpendicularly bent relative to the lower portion; such that the desk board is flipped to a top of the connecting portion. When the desk board is descended, the pin is abutted against a first end of the arc-shaped groove, driving the positioning board to pivotally rotate downwardly relative to the connecting portion. The elbow joint and the positioning board are pivotally rotated downwardly relative to the connecting portion. The positioning board blocks the upper portion from pivotally bending relative to the lower portion, such that the upper portion is confined from arbitrarily pivoting relative to the lower portion when the desk board is descended. Therefore, the desk board is stably suspended beside the connecting portion. 
     The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view to show the collapsible desk assembly in accordance with the present invention; 
         FIG. 2  is an exploded perspective view of the elbow joint of the collapsible desk assembly in accordance with the present invention; 
         FIG. 3  is a partially-exploded perspective view of the collapsible desk assembly in accordance with the present invention when assembling with an armrest of a chair; 
         FIG. 4  is an assembled perspective view of the collapsible desk assembly in accordance with the present invention when assembling with the armrest of a chair; 
         FIG. 5  is a plane view of the elbow joint of the collapsible desk assembly in accordance with the present invention, showing a position of the elbow joint relative to the desk board when the desk board is suspended; 
         FIG. 6  and  FIG. 8  are perspective views of the collapsible desk assembly in accordance with the present invention, showing the elbow joint and the desk board in upwardly pivoting positions; 
         FIG. 7  and  FIG. 9  are plane views of the elbow joint of the collapsible desk assembly in accordance with the present invention, showing the positions of the elbow joint relative to the desk board when the desk board and the elbow joint are in upwardly pivoting positions; 
         FIG. 10  is a perspective view of the collapsible desk assembly in accordance with the present invention, showing the desk board is flipped to a top of the connecting portion; 
         FIG. 11  is a plane view of the elbow joint and the desk board of the collapsible desk assembly in accordance with the present invention, showing the upper portion pivotally perpendicularly bent relative to the lower portion; 
         FIG. 12  is a perspective view of the collapsible desk assembly in accordance with the present invention, showing the elbow joint and the desk board in downwardly pivoting position; 
         FIG. 13  is a plane view of the elbow joint of the collapsible desk assembly in accordance with the present invention, showing the position of the elbow joint relative to the desk board when the desk board and the elbow joint are in downwardly pivoting position; and 
         FIG. 14  and  FIG. 15  are operational cross-sectional views of the upper portion of the collapsible desk assembly in accordance with the present invention; respectively showing the push block is screwed in and out from the cover casing. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings and initially to  FIGS. 1 to 3 , a collapsible desk assembly in accordance with the present invention comprises a desk board  1 , an elbow joint  2 , a positioning board  3 , and a connecting portion  4  which is adapted to be connected to an armrest  5  of a chair. The desk board  2  is provided for adapting to pivotally connect to the armrest  5  of the chair. The desk board  1  has a supporting board  10  which is mounted to a backside thereof. The supporting board  10  has a receiving space  101  defined therein for receiving the elbow joint  2 . The elbow joint  2  includes an upper portion  20  and a lower portion  21  which is pivotally connected to the upper portion. The upper portion  20  is mounted to the receiving space  101  of the supporting board  10 . A base  201  is mounted to the upper portion  20 . The base  201  has a trench  2011  defined therein. A push block  202  is screwedly received in the trench  2011 . A block cover  203  caps the push block  202 . A cover casing  204  completely covers the base  201 . The cover casing  204  has an opening  2041  defined therein and corresponding to the block cover  203  for partially receiving the block cover  203 . The block cover  203  is abutted against the connecting portion  4 . A plurality of pivoting lugs  22  extends downwardly from a lower end of the upper portion  20 . The lower portion  21  is threadedly connected to the connecting portion  4 . The lower portion has a plurality of pivoting lugs  22  extending upwardly therefrom. The pivoting lugs  22  of the lower portion  21  are intersectingly engaged with the pivoting lugs  22  of the upper portion  20 . A securing post  23  is simultaneously passing through the pivoting lugs  22  of the upper portion  20  and the lower portion  21  to be a pivot of the elbow joint  2 , such that the upper portion  20  is able to pivotally bend relative to the lower portion  21 . An arc-shaped groove  211  is defined in the lower portion. The positioning board  3  is elongated-shaped and is connected to the elbow joint  2 . The positioning board  3  has a pin  31  disposed on a first side thereof. The pin  31  is inserted into the arc-shaped groove  211  of the lower portion  21  such that the pin  31  is able to slide along the arc-shaped groove  211  relative to the positioning board  3 . A pivoting shaft  32  extends from a second side of the positioning board  3  opposite to the first side. The connecting portion  4  has a receiving hole  40  laterally defined therein and extending therethrough for receiving the pivoting shaft  32 . A sleeve  321  is sleeved on the pivoting shaft  32  for assisting the pivoting shaft  32  to pivotally rotate relative to the connecting portion  4 . A bolt  41  sequentially passes through the receiving hole  40  and the pivoting shaft  32 , and is screwed to the lower portion  21  of the elbow joint  2 , such that the desk board  1  is mounted on an outer side of the armrest  5 . As shown in  FIGS. 4 to 5 , when the desk board  1  is not in use, the desk board  1  is suspended vertically beside the connecting portion  4 , the positioning board  3  is located between the upper portion  20  and the lower portion  21 , and is vertically disposed relative to the connecting portion  4 . The pin  31  is abutted against a first end  2111  of the arc-shaped groove  211 . The positioning board  3  blocks the pivoting lugs  22  of the upper portion  20  and the lower portion  21 , such that the positioning board  3  confines the upper portion  20  from pivotally bending relative to the lower portion  21 , thus the desk board  1  is stably suspended beside the connecting portion  4 . 
     Referring to  FIGS. 6 to 11 , when the desk board  1  is upwardly lifted, the elbow joint  2  is pivotally rotated upwardly relative to the connecting portion  4 . The pin  31  is slid from the first end  2111  of the arc-shaped groove  211  to a second end  2112  of the arc-shaped groove  211 , and is abutted against the second end  2112  of the groove (as shown in  FIGS. 6 to 7 ). Referring to  FIGS. 8 to 11 , as the elbow joint  2  continues to pivotally rotate upwardly, the pin  31  which is abutted against the second end  2112  of the arc-shaped groove  211  drives the positioning board  3  to pivotally upwardly rotate relative to the connecting portion  4 . When the desk board  1  is lifted above the connecting portion  4 , the upper portion  20  is pivotally perpendicularly bent relative to the lower portion  21 , such that the desk board  1  is flipped to a top of the connecting portion  4 , and is flatly placed above the connecting portion  4 . Thus allows a user to use a front side of the desk board  1  for reading or writing purpose. When the desk board  1  is flipped to the top of the connecting portion  4 , the positioning board  3  is located beside the lower portion  21  and is horizontally disposed relative to the connecting portion  4  and the lower portion  21  (as shown in  FIG. 11 ), such that the upper portion  20  is freely pivotally bend relative to the lower portion. 
     Referring to  FIGS. 12-13 , when the desk board  1  is descended, the elbow joint  2  is pivotally rotated downwardly relative to the connecting portion  4 . The pin  31  is then slid from the second end  2112  to the first end  2111  of the arc-shaped groove  211  of the lower portion  21 . As the elbow joint  2  continues to pivotally rotate downwardly, the pin  31  which is abutted against the first end  2111  of the arc-shaped groove  211  drives the positioning board  3  to pivotally downwardly rotate relative to the connecting portion  4 . The positioning board  3  is located between the upper portion  20  and the lower portion  21  and is vertically disposed relative to the connecting portion  4 . The positioning board  3  blocks the pivoting lugs  22  of the upper portion  20  and the lower portion  21  and confined the upper portion  20  from pivotally bending relative to the lower portion  21 , such that the desk board  1  is stably suspended when not in use (as referring back to  FIGS. 4 to 5 ). 
     Referring to  FIGS. 14-15 , the push block  202  is screwed to the trench  2011  of the base  201  of the upper portion  20 . A position of the block cover  203  with the push block  202  relative to the cover casing  204  is adjustable due to the push block  202  is screwed in/out from the trench  2011 . As shown in  FIG. 15 , when the push block  202  is adjustably screwed toward the opening  2041  of the cover casing  204 , the upper portion  20  is slightly pushed away from the connecting portion  4 , such that the block cover  203  is protruded from the opening  2041  of the cover casing  204 . An interval between the upper portion  20  and the connecting portion  4  is changed. Therefore, a tilting angle of the desk board  1  relative to the connecting portion is adjusted. A pivotal bending angle of the upper portion  20  relative to the lower portion  21  is also changed due to the change in the interval between the connecting portion  4  and the upper portion  20 , such that the user is able to freely adjust the tilting angle of the desk board  1  by screwing in/out the push block  202  from the trench to fit his/her sitting postures, reading and/or writing habits. 
     Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.