upward the two driving parts 146 can be respectively driven to displace in the mount structures 144 in opposite directions d 1 and d 2 toward the center of the seat frame 113 as a result the spring 152 can be compressed and the two latch assemblies 130 can be driven to displace along the transversal support tube 128 in opposite directions toward the center of the seat frame 113 the latches 134 can thereby compress the spring 132 in the transversal support tube 128 and disengage from the front tube segment 110 to allow rotation of the rear tube segment 112 about the pivot axis y relative to the front tube segment 110 to the collapsed state fig1 through 15 are schematic views illustrating intermediate stages in collapsing the support frame 102 provided with the seat 104 facing forward when the actuator 162 is pulled upward the latches 134 can be driven to disengage from the front tube segment 110 while the actuator 162 is pulled upward the support frame 102 can also be raised above the ground and then self collapse owing to the action of its own weight as a result the front tube segment 110 and the front legs 106 can rotate in the direction r 1 whereas the rear tube segment 112 the rear legs 108 and the seat 104 can rotate in the direction r 2 opposite to r 1 accordingly the front and rear legs 106 and 108 the front and rear tube segments 110 and 112 and the seat.