ATTUATORE PNEUMATICO ATTO A COMANDARE LO SPOSTAMENTO DI UN ORGANO MOBILE IN PARTICOLARE DI UN ASTA PER L AZIONAMENTO DELLA FARFALLA DI UN CARBURATORE

A membrane 22 when subject to manifold vacuum in a chamber 21, e.g. when an engine coolant temperature responsive valve (4 Fig 1) is open at low temperatures, abuts an adjustable screw 24 through its centre element 23,44. A valve 37 in the element 23 is opened by the vacuum which is transmitted to a chamber 27 and a membrane 28 connected to a throttle valve opening rod 7 is moved to a position determined by the element 23 to provide a rod stroke C1. When vacuum is applied directly to the chamber 27, e.g. when the coolant temperature valve (4, Fig 1) is closed and an electrically operated valve (6) is opened, the membrane 22 is moved until its support plates 33 abut the actuator body 17 at 25 and the rod stroke is reduced to a lower valve (C2, Fig 4).