| 摘要 |
The apparatus comprises a number of blades 1 mounted on a common driveshaft 2 and a drive system for moving the blades between a first position where they are substantially retracted in a housing and a second position where they protrude from the housing, with a clutch mechanism 8 is provided such that if a vehicle passes the protruding blades in one direction the blades are freely pushed by the vehicle towards the retracted position and the drive means is operated but the clutch prevents movement of the blades towards the protruding position until the force exerted by the vehicle ceases, whereupon the blades may be returned by the drive system to the protruding position. The apparatus preferably has a motor 7 that drives the blades towards the protruded position via a transmission line and one or more switches may be located so that the motor is operated once the blades are moved from the fully protruding position and stopped when in the fully protruding position. The clutch preferably comprises two clutch plates forced together under spring tension, which may be variable. Also claimed is a drive mechanism for a vehicle arresting device and a method of operating a vehicle arresting device. |
