Automatically lockable pivoting mechanism and sliding mechanism, and frame and table having same

1. A pivoting mechanism comprising:

a first coupling piece configured to be fixed at a proximal end of a first bar, wherein the first coupling piece comprises a first slot elongated in a first direction;

a second coupling piece configured to be fixed at a proximal end of a second bar, wherein the second coupling piece comprises a second slot, wherein the second slot has a closed bottom and an open top, and wherein the second slot has a length in the first direction that is shorter than the first slot of the first coupling piece in the first direction;

a third coupling piece comprising a third slot having a closed bottom and a closed top, wherein the third slot is elongated in the first direction;

a first rod disposed, cross-sectional-wise, in the third slot of the third coupling piece and movable along the third slot of the third coupling piece, wherein the first and second coupling pieces are pivotally coupled with each other by the first rod; and

a second rod integrally formed or coupled with a top portion of the third coupling piece, the second rod disposed, cross-sectional-wise, in the first slot of the first coupling piece and movable along the first slot of the first coupling piece;

wherein when the first and second coupling pieces are aligned with each other and the open top of the second slot of the second coupling piece faces downwardly, the third coupling piece together with the second rod moves by gravity to a first position where the second rod is disposed outside of the second slot of the second coupling piece, thereby allowing the first and second coupling pieces to rotate with respect to each other around the first rod; and

wherein when the first and second coupling pieces are aligned with each other and the open top of the second slot of the second coupling piece faces upwardly, the third coupling piece together with the second rod moves by gravity to a second position where the second rod is disposed in the second slot of the second coupling piece, thereby restricting the first and second coupling pieces from rotating with respect to each other around the first rod.

2. The pivoting mechanism of claim 1 , wherein the first rod is disposed adjacent to the bottom of the third slot of the third coupling piece at the first position, and adjacent to the top of the third slot of the third coupling piece at the second position.

3. The pivoting mechanism of claim 1 , wherein each of the first and second coupling pieces comprises a horizontal piece, a first lug at a first side of the horizontal piece and a second lug at a second side of the horizontal piece, wherein

the first and second lugs are substantially parallel to each other; and

each of the first and second lugs is formed with a corresponding first or second slot.

4. The pivoting mechanism of claim 3 , wherein at least a portion of the third coupling piece is disposed between the first and second lugs of the first coupling piece, and at least a portion of the first and second lugs of the first coupling piece is disposed between the first and second lugs of the second coupling piece.

5. The pivoting mechanism of claim 1 , wherein the first and second coupling pieces are pivotally coupled with each other by the first rod through a first hole formed at the first coupling piece and a second hole formed at the second coupling piece, and wherein the second rod is coupled with the third coupling piece by passing through a third hole formed at the third coupling piece.

6. The pivoting mechanism of claim 1 , wherein when the first and second coupling pieces are aligned with each other, the first slot of the first coupling piece and the third slot of the third coupling piece are aligned with each other in the first direction.

7. A frame comprising:

a first longitudinal bar disposed at a first side of the frame; and

a second longitudinal bar disposed at a second side of the frame and substantially parallel to the first longitudinal bar;

wherein each of the first and second longitudinal bars comprises a first bar and a second bar pivotally coupled with each other at their proximal ends by the pivoting mechanism of claim 1 .

8. The frame of claim 7 , further comprising:

a first lateral bar disposed at a third side of the frame and having a first end pivotally coupled with the first longitudinal bar and a second end pivotally coupled with the second longitudinal bar;

a second lateral bar disposed at a fourth side of the frame and having a first end pivotally coupled with the first longitudinal bar and a second end pivotally coupled with the second longitudinal bar;

a plurality of legs, each having an end fixedly coupled with the first or second lateral bar;

a plurality of sliding mechanisms, each comprising a sleeve slidably coupled with the first or second longitudinal bar and selectively movable along a length direction of the first or second longitudinal bar; and

a plurality of oblique bars, each having a first end and a second end, wherein the first end is pivotally coupled with a corresponding leg in the plurality of legs, and the second end is pivotally coupled with the sleeve of a corresponding sliding mechanism in the plurality of assemblies.

9. The frame of claim 8 , wherein for each of the first and second longitudinal bars, the frame further comprises:

a first coupler disposed adjacent to a distal end of the first bar; and

a second coupler disposed adjacent to a distal end of the second bar;

wherein when the first and second bars are folded onto each other, the first and second couplers are engaged with each other, thereby preventing the first and second bars from accidental unfolding.