Patent ID: 8256630

Claim:
A frame structure, comprising: two spaced apart side frames; a foldable frame, which is operatively provided only at a rear of said side frames to fold between an unfolded position and a folded position, comprising: a transmission link, which is an elongated member, rigidly supported between said side frames; a sliding joint slidably coupling with said transmission link; and two folding arms movably coupling said transmission link to said side frames respectively, wherein each of said folding arms has an upper end pivotally coupling with said sliding joint and a lower end pivotally coupling with said respective side frame, wherein when said foldable frame is folded at said unfolded position, said sliding joint is upwardly slid to an upper end of said transmission link so as to move said side frames away from each other, and when said foldable frame is folded at said folded position, said sliding joint is downwardly slid away from said upper end of said transmission link so as to move said side frames towards each other for folding said side frames side-by-side; a retention stopper provided at said upper end of said transmission link to bias against said sliding joint when said sliding joint is slid at said upper end of said transmission link at said unfolded position so as to prevent any further upward sliding movement of said sliding joint; and a locking means for releasably locking said foldable frame at said unfolded position, wherein said locking means comprises a first locker provided at said retention stopper provided at said upper end of said transmission link and a second locker provided at said sliding joint to releasably engage with said first locker, so as to lock up sliding joint at said upper end of said transmission link when said foldable frame is folded at said unfolded position; wherein said transmission link, said sliding joint, and said folding arms of said foldable frame are embedded between said side frames in a hidden manner when said foldable frame is folded at said folded position.