DISPOSITIF HYDRAULIQUE POUR COMMANDER UNE COMMUNICATION

DISPOSITIF HYDRAULIQUE POUR COMMANDER UNE COMMUNICATION.DISPOSITIF HYDRAULIQUE QUI COMPREND UNE VALVE PILOTE ET UNE VALVE DE COMMUTATION CARACTERISE EN CE QU'UN ORGANE DE COMMANDE 25 DE LA VALVE PILOTE 9 EST CONSTITUE PAR UN TIROIR ETAGE, TANDIS QUE LA FACE FRONTALE DU PISTON DE COMMANDE 19 EST CHARGEE PAR LA PRESSION REGNANT DANS LE RESERVOIR D'ALIMENTATION DANS LA REGION CENTRALE DU TIROIR ETANT PREVUS DEUX PISTONS 27, 28 DONT LES DIAMETRES CORRESPONDENT RESPECTIVEMENT A CEUX DES PISTONS DES EXTREMITES ADJACENTES, SUR LES DEUX COTES MUTUELLEMENT OPPOSES DES DEUX PISTONS DE COMMANDE 27, 28 SONT PREVUS DES BORDS DE COMMANDE 38, 39 QUI COOPERENT AVEC LES BORDS DE COMMANDE 40, 41 DE L'ENVELOPPE 23 DANS LAQUELLE EST LOGE LEDIT TIROIR. Change over valve for monitoring a connection between a pressure- medium source, an accumulator and a reservoir has a reversing valve (7, Fig. 1, not shown) which is controllable by a pilot valve 9, the valve member 25 of the pilot valve 9 is constructed as a stepped piston, to which the pressure in the accumulator (5) is applied at 42 and to which the pressure in the reservoir connection is applied at 45 and in the central zone of the valve member are arranged two additional control pistons sections 27,28, on which are provided control edges 38,39 which co-operate with control edges 40,41 of a valve housing 23 to control a connection between the source at 44 and the control side of the reversing valve (7) connected at 43. When the accumulator pressure is high the piston is moved to full flow from 44 to 43 and connect 43 to tank via bores 36 and 35.