Collapsible seat assembly and a stroller with the same

A stroller comprising a frame which is operable between folded and unfolded states and which includes a handle assembly, a front leg assembly, a rear leg assembly and a fold joint assembly, said handle assembly having a handle pivot portion pivotably mounted on said fold joint assembly to be turned to the folded state,

• said stroller further comprising a collapsible seat assembly which includes
• a joint member;
• a backrest support member having a backrest pivot portion which is pivotably mounted on said joint member;
• a leg support member having a leg pivot portion which is pivotably mounted on said joint member such that said collapsible seat assembly is operable between a folded position, where said backrest support member is proximate to said leg support member, and an unfolded position, where said backrest support member is distal from said leg support member;
• and
• a locking mechanism disposed between said backrest pivot portion and said leg pivot portion, and operable between a locking position, where said backrest pivot portion is retained relative to said leg pivot portion so as to hold said collapsible seat assembly in the unfolded position, and an unlocking position, where said backrest pivot portion is turnable relative to said leg pivot portion so as to permit movement of said collapsible seat assembly to the unfolded position, said locking mechanism being actuated to move from the locking position to the unlocking position by the operation of said frame of said stroller from the unfolded state to the folded state, said locking mechanism including a first locking member which is slidable relative to said joint member and which is disposed to retainingly engage both said backrest pivot portion and said leg pivot portion in the locking position, and to be disengaged from one of said backrest pivot portion and said leg pivot portion in the unlocking position, said locking mechanism further including a second locking member which is disposed to be slidable relative to said backrest pivot portion,
• said joint member being removably mounted on said fold joint assembly, said frame further including a pressing member which is disposed to be slidable relative to said fold joint assembly and which has at least one pressing portion projecting from said fold joint assembly and disposed to be moved when said handle assembly is turned relative to said fold joint assembly, said locking mechanism having at least one pressed portion which projects from said joint member and which engages said pressing portion to be pressed by said pressing portion so as to disengage said locking mechanism from one of said backrest pivot portion and said leg pivot portion in the unlocking position.