DISPOSITIF DISTRIBUTEUR POUR LA COMMANDE DU MOUVEMENT ALTERNATIF D'UN PISTON MOTEUR DANS UN SYSTEME DE COMMANDE PNEUMATIQUE

摘要

A control device for controlling a pneumatic piston and cylinder type actuator in conjunction with a 2-position 3-port valve comprises a differential piston mounted in a stepped cylinder bore for sliding movement into one or the other of two end positions according to whether compressed air is admitted under the control of the valve to the smaller diameter end of the bore or to both the smaller and larger diameter ends of the bore. Two ports opening respectively to the smaller and larger parts of the bore are controlled by the differential piston and each acts as a combined flow-and-return passage for pressure fluid for one end of the motor cylinder. A by-pass passage having both ends opening to the larger diameter portion of the bore permits air exhausting from the motor into this portion of the bore, during part of the travel of the differential piston, to by-pass the larger diameter part of the piston and to exhaust to atmosphere via an exhaust port which is in permanently open communication with a part of the bore between the larger and smaller diameter ends of the piston.