Patent ID: 8109566

Claim:
A collapsible desk assembly comprising: a desk board, the desk board provided for adapting to pivotally connect to an armrest of a chair; an elbow joint mounted to a backside of the desk board, the elbow joint having an arc-shaped groove defined therein, the elbow joint pivotally perpendicularly bent; a positioning board connected to the elbow joint, the positioning board having a pin disposed on a first side thereof, the pin inserted into the arc-shaped groove such that the pin is able to slide along the arc-shaped groove relative to the positioning board, a pivoting shaft extending from a second side of the positioning board opposite to the first side; and a connecting portion adapted to be connected to the armrest, the connecting portion having a receiving hole laterally defined therein and extending therethrough for receiving the pivoting shaft, a bolt sequentially passing through the receiving hole and the pivoting shaft, and screwed into the elbow joint; the elbow joint including an upper portion and a lower portion pivotally connected to the upper portion; the upper portion mounted to the backside of the desk board, the lower portion threadedly connected to the connecting portion; a securing post simultaneously passing through the upper portion and the lower portion to be a pivot of the elbow joint; the arc-shaped grooved positioned in the lower portion; wherein when the desk board is pivotally lifted, the pin abutted against a second end of the arc-shaped groove, driving the positioning board to pivotally rotate upwardly; when the desk board descended, the pin abutted against a first end of the arc-shaped groove, driving the positioning board to pivotally rotate downwardly relative to the connecting portion, the positioning board blocking the elbow joint from pivotally bending relative to the connecting portion, such that the desk board is stably suspended beside the connecting portion; furthermore when the elbow joint is pivotally rotated upwardly relative to the connecting portion, the desk board is upwardly lifted with the upper portion, 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 elbow joint and the positioning board is pivotally rotated downwardly relative to the connecting portion, the positioning board blocking 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.