| 摘要 |
An improved multi-stage door closer for automatically closing a door after the door is opened, is disclosed. It contains a cylinder having three sections each with a different diameter, with the middle section having the largest diameter. A pair of speed adjusting mechanisms are provided which are sleeved about a piston rod placed inside the cylinder. Each of the speed adjusting mechanism contains a rotatable piston head, which will rotate with the cylinder, and a fixed piston head, which will not rotate with the cylinder. In a preferred embodiment, the rotatable piston head contains a radially extending groove in communication with an axially extending graded groove, and the fixed piston head contains a spiraled or serpentined O-ring that cuts across the axially extending graded groove. When the rotatable piston head is rotated relative to the fixed piston head, it changes the portions of the axially extending graded groove blocked by the serpentined O-ring, so as to control the flow rate at which the compressed fluid can flow through the axially extending graded groove, and thus the door closing speed is adjusted according.
|
