Seat angle adjustment device for liftable seatpost

A seat angle adjustment device for a liftable seatpost, comprising:

• a seat tube including a top end provided with two through holes and a convex curved surface located between the through holes;
• a clamping component including a lower clamp and an upper clamp, the lower clamp having two lower clamping grooves and a concave curved surface located between the lower clamping grooves and abutted against the convex curved surface of the seat tube, the upper clamp having two upper clamping grooves corresponding to the lower clamping grooves of the lower clamp, so that two saddle rail clamping grooves are formed between the upper clamping grooves of the upper clamp and the lower clamping grooves of the lower clamp, the saddle rail clamping grooves each having a position lower than a vertex of the convex curved surface of the seat tube;
• and
• a fixing component having two nuts and two bolts screwed to the nuts, one of the nuts and the bolts being disposed to the upper clamp, and the other of the nuts and the bolts being disposed to the through holes of the seat tube;
• wherein the lower clamp has a first top wall provided with the concave curved surface, and two opposite first lateral walls extending downwards from the first top wall to cover the convex curved surface of the seat tube and provided with the lower clamping grooves;
• wherein the upper clamp has a second top wall located above the first top wall, and two opposite second lateral walls extending downwards from the second top wall to cover the first lateral walls and provided with the upper clamping grooves.