Patent ID: 8109564

Claim:
A seat self-lifting device for a portable chair, mounted between a seat frame and a front leg of the portable chair, the seat self-lifting device comprising: a rotary axle having two opposite portions that are a first portion and a second portion, the first portion of the rotary axle being shaped in a non-circular cylinder, laterally passing through the front leg and connected with a connecting plate mounted on the seat frame to move therewith, the second portion of the rotary axle being shaped in a cylinder and exposed on the front leg; a fixing rod perpendicularly mounted to the front leg and disposed proximate to the second portion of the rotary axle; and a spiral spring having a first end connected with the second portion of the rotary axle and a second end wrapped around the fixing rod, the spiral spring being rotatable and twistable along an axial direction of the rotary axle, wherein when a user sits on the seat, the rotary axle rotates with the connecting plate and twists the spiral spring to be deformed and accumulate a resilient force, and when the user leaves the seat, the resilient force is released and the release of the resilient force causes the rotary axle to rotate along a reverse direction to flip the seat to a collapsed state.