PNEUMATIC SERVO DRIVE Russian patent published in 1995 - IPC

FIELD: brake system boosters. SUBSTANCE: servo drive has housing 10 accommodating piston (22, 14, 102) formed by tubular rear part 22 with skirt 14 resting on tubular rear part. By means of turning diaphragm 12, it separates servo drive front chamber 16 constantly connected with vacuum source from servo drive rear chamber 18 selectively connected either with front chamber 16, or with atmosphere through air valve (136, 138, 140) set into action by control rod 34 which presses plunger 32 against one of surfaces of reaction disk 58 rigidly coupled with pushing rod 56. Pull-back spring 150 of control rod 34 is arranged between skirt 14 of piston and plunger 32. Air valve (136, 138, 140) has shutoff member 138 engaging, by its active part reinforced by circular insert 118, with valve first seat 136 formed on plunger 32 and with valve second seat 140 formed on piston. Shutoff member 138 is formed by flexible tubular diaphragm 114 whose active part 138 is arranged between its ends 112 and 116. According to offered invention, shutoff member 138 has holes 120 providing communication of front chamber 16 and rear chamber 18 of servo drive. EFFECT: enhanced reliability of operation. 8 cl, 2 dwg