PNEUMATIC SERVO DRIVE Russian patent published in 1995 - IPC

FIELD: automotive vehicles; brake system booster pneumatic servo drive. SUBSTANCE: servo drive has housing 10 accommodating piston (22, 14, 102( which forms rear tubular part 22 with skirt 14. By means of turnable diaphragm 12, piston separates front chamber 16 of servo drive connected with vacuum source and rear chamber 18 selectively connected either front chamber 16, or with atmosphere through air valve (136, 138, 140) set into operation by control rod 34 which presses plunger 32 to one of flats of reaction disk 58 rigidly coupled with pushing rod 56. Air valve (136,138,140) has shutoff member 138 reinforced by insert 118 and engaging through active part with first seat 136 of valve formed of plunger 32 and with second seat 140 of valve formed on piston. Shutoff member 138 is formed by flexible tubular diaphragm 114. Active part of shutoff member is arranged between two ends 112, 116 of flexible tubular diaphragm 114, and thrust member 152 defines simultaneously initial position of piston (22, 14, 102) and initial position of plunger 32. According to offered invention, piston (22, 14, 102) of servo drive has, additionally, intermediate partition 102 of piston which separates, together with piston skirt 14, circular space 123. According to invention valve first seat 126, valve second seat 140 and valve plate 138 are arranged in circular space 123. Valve second seat 140 is formed on piston skirt of servo drive. EFFECT: enhanced reliability of operation. 8 cl, 2 dwg