Abstract: The setting of the dead travel of a servo-motor for assistance during braking is carried out in the factory during its assembly. For this purpose, a subassembly (68) comprising the piston (20), the operating pushrod (30) and its plunger (28), the valve head (34), the springs (38, 40) and the fixed (44) and tilting (50) keys, is placed in a setting sleeve (70). A load (F1) is exerted on the front face of the piston (20) sufficient to maintain a bearing surface (20b) permanently against a reference surface (70a) formed on the sleeve, and the pushrod (30) is freed from the action of the spring (40) by means of a fork (70a) formed on the sleeve, and the pushrod (30) is freed from the action of the spring (40) by means of a fork (72), after having pushed the plunger (28) up against the valve head (34) by applying a load (F3), the movement (.DELTA.) made by the mobile key (50) is measured between the reference surface (170a) and a shoulder formed on the plunger (28).

Abstract: A stationary stop member (44) and a tilting stop member (50) limiting the stroke of the plunger (28) inside the piston (20) of a brake booster are held in place in the piston, independently of one another, by a retaining ring (46). To this end, a first end (46a) of the retaining ring is bent back against a finger (44b) formed on the stationary stop member, while the second end (46b) of the retaining ring is bent back in an axial groove (54b) formed in a stop (54) fastened to a tongue (50b) formed on the tilting stop member.

Abstract: The return spring (16) for the actuating rod (14) of the servomotor bears against a tubular stop member (18) which is slidably mounted on the rod (14) and which comes to bear, in the rest position of the servomotor, against a reference stop (22), a ring (21) being firmly fixed to the rod (14) when contacting, in an inactive condition of the servomotor, against the tubular stop member (18) after having exerted a pull on the rod (14) bringing the valve seat (12) formed by the valve plunger (13) into full contact with the valve member (10) of the distribution valve means (6) of the servomotor.

Abstract: The assembly nut (5) is prescrewed onto the bolt (4) fixed to the booster (1), the nut and its bolt being introduced through a first end zone of enlarged cross-section (9) of an orifice in the wall (3), after which the booster is moved relative to the wall (3), in order to bring the body of the bolt (4) into a second end zone (10) of the orifice of a cross-section corresponding to that of the bolt, the nut (5) then being screwed home against the wall in the assembly position thus obtained. Advantageously, the wall (3) has a projecting part (11) adjacent to the orifice between the first (9) and second (10) end zones of the latter, so that, by putting itself in the path of the nut (5), it opposes a tendency for the unit to come apart.

Abstract: The assembly nut (6) is prescrewed onto the bolt (5) so as to be up against a tubular spacer (15); the bolt, together with its nut and its spacer, is introduced through a first end zone of enlarged cross-section of an elongate orifice made in the fixed wall (4), after which the booster is moved relative to the wall in order to bring the spacer (15) into a second end zone of the orifice in the wall, of a cross-section corresponding to that of the spacer, and then a plate (18) likewise having an elongate orifice with two end zones of different cross-sections is interposed between the wall (4) and the nut (6), the plate being moved in order to place the spacer (15) in the end zone of corresponding cross-section (22) of the orifice in the plate, this movement producing, between the wall (8) and the nut (6), a wedge effect attributable to an edge of variable thickness (24) of the orifice in the plate (18).

Abstract: The movable wall structure (4, 5) dividing the housing (1) of the booster on the inside possesses a metal plate (4) having a central annular part (6), to which are fixed a stepped tubular insert (9) protecting the reaction disk (25) and a rear tubular element (8), in which is mounted a plastic body part (7) forming communication ducts (16, 23) for the distributor valve mechanism of the booster.

Abstract: The valve member (5) of the distribution valve mechanism of the booster comprises an active part (19), cooperating selectively with the valve seats (18; 17) in the hub (8) of the piston (2) and on the valve plunger (13), and an axial undulated tubular part (24) mounted, by its rear end, on an internal end (26) of a valve-member support (27) forming bearing zones (282; 281) for a spring (31) causing the return movement of the input rod (14) and for a spring (30) biasing the valve member and mounted, by its external periphery (29), in the tubular hub (8).

Abstract: The booster comprises a positioning member (24) for placing the distribution valve mechanism (12, 13, 14) in a specific rest position in the rest position of the booster, the positioning member (24) being coupled to one end (28) of a retractable elastic member of low elasticity (29), advantageously a spiral spring, which is deformable between a relaxed configuration and, in the rest position of the booster, a retractable configuration, in which the end (28) is located in a fixed reference position relative to the housing (1) of the booster, determining the rest position of the positioning member (24).

Abstract: The booster comprises a first member (23) positioning the plunger (14) and fastened in the valve body (8) and interacting with a the first zone of a shoulder (21) of the plunger to position the latter in a specific position of maximum retraction relative to the valve body (8), and a second member (29, 31) positioning the plunger and mounted pivotally in the valve body and having a ramp surface (34) formed in a first portion (29) interacting with a second zone of the first shoulder (21) to position the plunger in a specific position of rest relative to the valve body (8) under the control of a second outer portion (31) interacting with a stationary element connected to the housing (9).

Abstract: The stop key (20) of the valve plunger (4) is made of metal wire and comprises a central portion having two lateral mounting strand parts (23) housed in grooves facing each other (13) in the radial opening (11) for mounting the key in the hub (1) of the servomotor, the two lateral parts (23) being joined by a central strand part in the shape of a V or a Y (24) and extending outward by parts forming arms (22) cooperating in elastic engagement with the outside periphery of the hub (1).

Abstract: Two pressure disks (13, 19) are arranged in tandem between the valve plunger (9) and the rear end (21) of the booster output rod (22), a stepped middle member (23), having a front portion with a reduced diameter (24) sliding inside an annular spacer member (17), being arranged between the two pressure disks and cooperating with the latter.

Abstract: The servomotor, of the type incorporating an abutment component (7, 70) which is mounted on the input rod (6) and which cooperates in bearing, in the rest position of the servomotor, against a stop structure (9, 12) which is firmly fixed to the casing, incorporates in the stop structure an electrical contact mechanism (13, 15) which is capable of being actuated by the abutment component (7, 70) and which advantageously incorporates and actuating portion (17) which is interposed between the abutment component (7, 70) and an internal bearing surface (20) of an end collar portion (12) of the stop structure which carries the fixed electrical contacts (13).

Abstract: The device incorporates a tubular bearing component (20) having an end portion inserted into the bottom (11) of the piston (1) and a portion projecting into the cavity (9) of the piston, the uni-directional clutch-spring (14) for the tapped sleeve (12) engaged on the threaded rod (8) for the handbrake being mounted on this projecting portion of the bearing component and incorporating an end arm (15) joined to the sleeve (12).