Pneumatic feed safety apparatus with re-setting control

摘要

A re-settable apparatus for producing a signal for triggering off a safety measure on an installation with at least a pneumatic feed in response to a drop in the pneumatic feed pressure comprises a body providing an internal chamber connected by a first duct to a first orifice for connection thereof to the pneumatic feed, by a second duct to at least one member for outputting a signal for control of the triggering effect, and by a third duct to an exhaust orifice. The first duct opens into the chamber through a first seat and the third duct opens into the chamber through a second seat of larger diameter than the first seat. A valve member is mounted in the chamber movably between a first position in which it is applied against the first seat and a second position in which it is applied against the second seat, while a resilient return member between the body and the valve member urges the valve member towards its first position with a force of given intensity. A voluntary re-setting control arrangement comprises a thrust member disposed in opposite relationship to the resilient return member with respect to the valve member between the latter and an actuating member which is accessible from the exterior of the body, the thrust member being displaceable in the body with a movement of an amplitude which is at least equal to the value of the displacement of the valve member when it moves from one of the seats to the other.