The toilet seat, what is the principle of slow falling?

The principle of slow-down toilet lid bai is made by adding slow-duration damping grease between the shaft and the shaft sleeve, and combining the forward and backward cards. When the lid is opened, the shaft and the shaft sleeve are stuck together and rotate at the same time, the damping grease does not work. , So it opens normally; when it is dropped, the shaft and the shaft sleeve are not stuck together, and the outer sleeve and the shaft sleeve base are stuck in the reverse direction, and the damping grease works, forming a slow drop.