Actuator for gear shifting mechanisms for motor vehicles

An actuator for a gear shifting mechanism of a motor vehicle, said actuator comprising:

• a housing with pressure chambers;
• each one of said pressure chambers having a connector for supplying a pressure medium into said pressure chambers;
• a control member positioned in said housing so as to be axially displaceable in said housing by said pressure medium into at least three switching positions;
• a first auxiliary piston and a second auxiliary piston supported on said control member and displaceable relative to said control member by said pressure medium;
• said first auxiliary piston having a first end distant from said second auxiliary piston, said first end of said first auxiliary piston having a first abutment;
• said second auxiliary piston having a first end distant from said first auxiliary piston, said first end of said second auxiliary piston having a first abutment;
• said first auxiliary piston delimiting at least partially a first one of said pressure chambers and said second auxiliary piston delimiting at least partially a second one of said second pressure chambers;
• said first ends of said first and second auxiliary pistons surrounding said control member at a spacing defining a first and a second annular gap;
• said housing having at least one counter abutment for each one of said auxiliary pistons;
• said first auxiliary piston having at least one second abutment;
• said second auxiliary piston having at least one second abutment;
• said control member having a first annular shoulder and a second annular shoulder, wherein said at least one second abutment of said first and second auxiliary pistons are located in a path of movement of said first and second annular shoulders of said control member;
• said first annular shoulder communicating via said first annular gap with said first pressure chamber and said second annular shoulder communicating via said second annular gap with said second pressure chamber so that said first and second annular shoulders are loadable by said pressure medium for moving said control member;
• each one of said connectors having a valve controlling flow of the hydraulic medium into said pressure chambers;
• an annular chamber defined between said first and second auxiliary pistons, wherein said annular chamber in any position of said control member is under atmospheric pressure.