Speed responsive device characterised by constant radius and oscillating movement of the pawl

摘要

A speed responsive engagement device for use in fall arrest apparatus is disclosed. The device comprises a ratchet wheel (23) arranged for rotation about a first axis and having a plurality or outwardly projecting spaced apart teeth (24). Each part of adjacent teeth (24) is separated by a circumferential surface (29) with a constant radius. The device also comprises a pawl (25) which is arranged for pivotal movement about a second axis between a first unengaged position and a second engaged position in which the pawl (25) engages one of the teeth (24) and contacts a circumferential surface (29). A resilient means (27) such as spring are arranged which biases the pivoted pawl (25) towards the unengaged position. The rotation of ratchet wheel (23) in one direction will cause the pawl (25) to move towards the engaged position. As the pawl (25) is biased towards the unengaged position, oscillating movement of the pawl (25) occurs. At a particular frequency of oscillation, the movement of the pawl (25) increases such that it engages with the teeth of the ratchet wheel (23), stopping its rotation.