Abstract: A pneumatic brake-booster having a casing with a piston located therein consisting of a hub and a skirt to define a front chamber and a rear chamber. The front chamber is connected permanently to a vacuum source and the rear chamber is connected selectively through a bore in the hub to one of the front chamber and atmosphere by a control valve. The control valve is actuated by a control rod capable of pressing through a front face of a plunger on a back face of a reaction disk fastened securely to a thrust rod. A return spring for the control rod is located between the piston and the plunger. The control valve includes a shutter valve which interacts with a first circular valve seat formed on the plunger and a second circular valve seat formed on the piston. The shutter valve is characterized by a flexible membrane having a first bead fixed in a leaktight manner to a peripheral edge of the hub and a second bead connected in a leaktight manner to an internal peripheral edge of a rigid tubular component.

Abstract: A guide rod extends longitudinally through the power piston of a vacuum power booster providing lateral support thereto and tying the master cylinder housing to a bracket on the rear of the power booster housing. A guide rod provides a means of positively laterally supporting the power piston, control valve and push rods of the power booster thereby providing the ability to reduce the relative supportive strength of the housing, housing divider and piston bearings.

Abstract: A brake booster, specifically, an improvement of a valve mechanism for booster is disclosed. According to the invention, the rear side of a curved portion of a valve element is surrounded by a retainer to be interrupted from the atmosphere. This prevents the atmospheric pressure from acting upon the curved portion of the valve element owing to the presence of the retainer.

Abstract: This device comprises in a manner known per se a valve (7) cooperating with two valve seats (10b, 16a) to control the operation of the booster.The second seat (16a) is formed on a sliding sleeve (16) in such a manner as to accelerate the admission of air and to shorten the response time of the booster.

Abstract: A pneumatic booster having a casing (16) formed from a cylinder (32) and a cover (34). The casing (16) is divided into two chambers (18,20) by a movable wall (10). The movable wall. (20) has a plate (12) and a flexible membrane (14). A bead (30) on the outer peripheral edge of flexible membrane (14) is fixed to the casing (16). The flexible membrane (14) forms a fold in a space located between the peripheral edge of the plate (12) and the casing (16). The plate (12) is secured to a hub structure which houses a valve member for operating the pneumatic booster. The plate (12) which is substantially parallel to the end cover has an extension (40) that extends in a forward direction substantially concentric to the cylinder (32). The extension (40) has front part (46) and a rear part (44) with a radial shoulder (42) on the front part.

Abstract: A control valve for controlling the pressurisation of a power chamber of the booster comprises a spool working in a bore in a boost piston. The spool carries longitudinal spaced radial seals, a first one of the seals being disposed so as to prevent fluid from a radial high pressure supply port entering the power chamber through the spool at least when the booster is in an inoperative position. Movement of the spool in a forward operating direction, in response to an input force, causes the first one of the seals to uncover the port so that fluid can enter the power chamber through the spool. The other seal is adapted to uncover a radial return port connected to a reservoir when the input force is released.

Abstract: A pneumatic booster has a valve member arranged to operate stably even under a large differential pressure. The inside of a housing is divided into a constant-pressure chamber and a variable-pressure chamber by a diaphragm. A plunger and a valve member are disposed in a valve body supported by the diaphragm such that the plunger and the valve member are slidable relative to each other. The valve member is formed from a rigid reinforcing member and an elastic member bonded to the reinforcing member. The plunger is movable in association with an input shaft. The movement of the plunger is transmitted to the valve member through a valve spring, causing the valve member to separate from a seat portion provided on the plunger.

Abstract: To optimize the ratio of forces which are caused during operation of a vacuum brake power booster, in particular the response force and the resetting force, according to the present invention, means are provided which permit applying the pneumatic pressure, which prevails in the ventilatable working chamber, to the side of the valve member of a control valve remote from the sealing seats of the control valve, the control valve controlling the pneumatic pressure differential between a vacuum and the atmospheric pressure.

Abstract: An actuator which causes an input shaft to move forward is disposed within the inner periphery of a valve body at its rear end. When a brake booster is inoperative, an atmospheric pressure is introduced into a pressure chamber of the actuator, but when a flow path switching valve is operated to introduce a negative pressure into the pressure chamber as required, a pressure differential is developed across a piston of the actuator, thus driving the piston forward. This allows the input shaft to be driven forward, whereby the brake booster can be operated without depressing a brake pedal. Since the atmosphere is introduced into the pressure chamber of the actuator when the brake booster is inoperative, a fracture or disengagement of a conduit which is connected to the pressure chamber cannot develop a pressure differential across the piston of the actuator, thus preventing the actuator from operating.

Abstract: In a booster shell reinforcing structure in a vacuum booster which makes a booster shell rigid enough to withstand the load applied thereto during operation and reduces the weight thereof, a reinforcement member includes an outer peripheral portion corresponding to a coupling angular portion between the flat portion and the tapered portion in a front shell half of the booster shell, being laid on an inner surface of the flat portion. The reinforcement member has a plurality of cuts formed in the outer peripheral portion at predetermined angular intervals so that each of the cuts is opened outside the reinforcement member and closed with inner edges of the cuts in the radial direction of the booster shell, and a plurality of main reinforcing portions which are located between the cuts.

Abstract: A muffler for booster, as may be used in a brake of an automobile or the like, is provided for reducing the generation of sounds during the suction stroke when a pressure fluid is introduced into a variable pressure chamber. An uneven surface is defined on the internal surface of a tubular portion of a shell in a region which is located opposite to an opening of a variable pressure passage when the booster is inoperative. With this construction, as the atmosphere is introduced into the variable pressure chamber through the opening of the variable pressure passage, the impingement of the atmosphere against the uneven surface is effective to reduce the generation of sounds during the suction stroke. This occurs without using any sound absorbing material, and hence does not degrade the response of the booster.

Abstract: A pneumatic brake booster having a piston which slides in a casing with a portion that extends outside of the casing. A tubular protective bellows has a first end connected to the casing and a second end that engages an input rod through which an operational signal is communicated to a valve retained the valve. The bellows is made of a porous and deformable material such that air communicated to the valve in response an input force applied to the control rod is directly passes through the porous bellows. The porous bellows has a pore size such that any contamination in the air is removed or filtered before being presented to the valve.

Abstract: The present invention provides a booster of the gaseous pressure type.

Abstract: The valve portion of pressure control valve tends to be unstable because when the valve is opened, the valve opening pressure intensifies. To prevent this, the valve portion of the pressure control valve is in the form of a puppet valve so that the valve body of the valve portion receives the pressure of a dynamic pressure source in the valve-opening direction and receives the pressure of an fluid pressure introducing chamber in the valve-closing direction. With this arrangement, when the valve opens and the dynamic pressure source pressure drops, the valve-closing force increases, so that the pressure control valve shows a stronger tendency to close. This prevents the freefall of the pressure source pressure, so that the behavior of the valve portion stabilizes. Thus, it is possible to prevent vibrations and abnormal noise.

Abstract: First seat S.sub.1 and second seat S.sub.2 on valve element 18 are axially separated to provide a tubular connection 18a therebetween. Support member 42 is fitted into the tubular connection 18a, and carries a sound extinguishing member 41 in the form of a cylindrical metallic filter on its inner peripheral surface. Upon actuation of the booster, pressure fluid from pressure passage 23 flows into variable pressure chambers B, D after passing through the second seat S.sub.2 which is then broken, and then through the inside of the sound extinguishing member 41. The pressure fluid, which passed through the second seat S.sub.2, flows inside the sound extinguishing member 41, whereby its flow direction is rectified, and is prevented from assuming a vortical turbulent flow. This reduces the generation of sounds during the suction stroke without degrading the response of the booster.

Abstract: To infinitely variably adjust the distance between a reaction disc and an interacting second part of a bipartite valve piston in a completely assembled vacuum brake power booster, which is already mounted to the automotive vehicle, a tubular sleeve is provided, arranged coaxially to a piston rod that actuates the valve piston, and is in engagement with a first part of the valve piston, connected with the second part by a threaded union, to apply a torque to the first piston part. For this purpose, the sleeve has at its end projecting from the control housing with an extension permitting rotation of the sleeve.

Abstract: In a tandem type vacuum booster a coupling cylinder extending from the inner peripheral edge of a front booster piston is coupled to a piston boss with bolts, and the inner peripheral bead of the front diaphragm is held inserted between the front booster piston and the piston boss in which the coupling cylinder is increased in rigidity so that seal members are prevented from being adversely affected in seal characteristic by the deformation of the coupling cylinder, a reinforcing cylinder of synthetic resin which has an inward flange at the front end is fitted in the coupling cylinder extending from the inner peripheral edge of a front booster piston, and the reinforcing cylinder is held on the bottom plate of the coupling cylinder by the elastic force of a return coil spring applied to the inward flange. It is unnecessary to provide a particular mounting member for the reinforcing cylinder.

Abstract: In a booster housing (10) two chambers (12, 14) separated from each other by a movable wall (16) are connectable to each other by a control valve (20) having a valve body (22) axially movable in common with the wall (16), said valve body having a first valve seat (24), a sealing element (60) axially movable in said valve body and pretensioned in the direction of said first valve seat and a valve barrel (30). The valve barrel (30) has a second valve seat (32) and is pretensioned in the direction of the sealing element (60), is couplingly connected for movement by means of a piston (42) movable by an actuator element (44) in the direction away from the sealing element (60) and is movable by means of a solenoid (40) also independently of the piston (42).

Abstract: This device, which is intended for vehicles equipped with a brake system comprising a pneumatic brake booster (1) and a master cylinder (2), enables the braked vehicle to be held back on an upslope. It comprises an inclinometric valve (12) which under certain conditions prevents the booster (1) from returning to its position of rest.

Abstract: A vehicle comprises an engine compartment and a passenger space which are separated by an apron (76), and a pneumatic brake booster comprises a casing (10) formed of a front shell (10a) and a back shell (10b) inside which is located a piston (20) including a back tubular part (22) and supporting a skirt (14) which, with the aid of an unrolling membrane (12), defines a first chamber (16), or front chamber, connected permanently to a source of partial vacuum and a second chamber (18), or back chamber, connected selectively to the front chamber (16) or to atmosphere by a valve mechanism (40) actuated by a control rod (34), the casing (10) of the booster comprising a mechanism (74) for securing the booster to the apron (76) of the vehicle.

Abstract: A brake servo booster capable of operating in a traction control mode has a housing (100) containing a diaphragm assembly (500) which divides the housing into two chambers A and B. Supply of air to the diaphragm assembly is controlled by a valve mechanism which includes a reciprocable valve member (7) operatively connected to a force input member (5) actuated by a driver-operated control. The force input member includes two parts (11,12) connected respectively to the valve element and driver-operated control. The arrangement is such that operating force applied to the control is transmitted through both of the first and second input member parts (11,12) whilst a traction control operative mode is permitted by the second part (11) moving relative to the first part (12).

Abstract: This brake-booster device comprises a pneumatic brake-booster (1) associated with a master cylinder (2). The booster comprises a movable pneumatic piston (5) bearing a valve (7) and functions according to a hydraulic reaction principle, the hydraulic piston (11) of the master cylinder comprising in fact a hollow movable cylinder (13) receiving a boost force, and a secondary hydraulic piston receiving an input force, these two forces constituting the total actuation force. A helical spring (22), exerting an adjustable resilient force, is disposed between the secondary hydraulic piston and the movable cylinder so as to permit the adjustment of the non-zero minimal value of the actuation force.

Abstract: In a booster housing (10) two chambers (12, 14) separated from each other by a movable wall (16) are connectable to each other by a control valve (20) having a valve body (22) axially movable in common with the wall (16), said valve body having a first valve seat (24), a sealing element (60) axially movable in said valve body and pretensioned in the direction of said first valve seat and a valve barrel (30). The valve barrel (30) has a second valve seat (32) and is pretensioned in the direction of the sealing element (60), is couplingly connected for movement by means of a piston (42) movable by an actuator element (44) in the direction away from the sealing element (60) and is movable by means of a solenoid (40) also independently of the piston (42).

Abstract: Two chambers (12, 14) in a booster casing (10) are separated by a movable wall (16) which is connected to a valve housing (22). The housing contains a movable sealing member (60) with which a first valve seat (24), formed in the valve housing (22), and a second valve seat (32), formed on a movable valve closing member (30), are associated. The valve closing member (30) is guided for axial displacement on a piston (42) and designed as the armature of an electromagnet (40) which is arranged inside the valve housing (22) in such a way that, when energized, it moves the valve closing member (30) away from the sealing member (60) against the resistance of a valve spring (38). The piston (42) is guided for axial displacement in the valve housing (22) and serves to transmit actuating forces from an actuator member (44) to an output member (50).

Abstract: A brake actuation apparatus includes a pneumatic booster and a master cylinder. A control rod in the booster responds to an input force for actuating a valve in the brake booster to develop an actuation force which is applied to a main hydraulic piston located in the master cylinder to pressurize fluid and effect a brake application. The main hydraulic piston includes a cylinder member with a bore therein for retaining a secondary hydraulic piston connected to the control rod. The cylinder member has at least one opening whereby pressurized fluid is communicated between the master cylinder and bore as function of a flow-rate reducer located in the one opening. The communication of fluid between the master cylinder and bore is always from the higher fluid pressure toward the lower fluid pressure.

Abstract: A pneumatic booster comprises a piston dividing a housing into front and rear chambers, the front chamber being is constant communication with a vacuum source, the rear chamber being selectively supplied with an atmospheric pressure source or a compressed air source, wherein a valve body of the piston includes a bore having a retainer mounted within, and an input rod movable within the retainer and having a compressed air passage extending therein, the bore of the valve body also having a first rear control valve and a second front control valve, such that movement of the input rod opens the first rear control valve to allow atmospheric air into the booster chamber and a further movement of the input rod opens the second front control valve to allow compressed air into the booster chamber, resulting in an increased output force of the booster.

Abstract: The invention relates to a removable thrust rod in a brake-booster of the partial vacuum type. The thrust rod (24) is attached securely to a skirt-shaped component (42) which surrounds the reaction disk (30) and to a component (44). A detachable component (50) comprises clipping fingers (54) which interact with the periphery of the component (44) and an annular part (52) which is flattened onto the piston (18) of the booster by a return spring (34).

Abstract: A push rod button is made by stamping thin strip stock to form a multiple piece article having interfitted complementary parts, thereby producing a unitary integrated composite which is strong enough to withstand the forces generated in the power train of an automotive braking system.

Abstract: A fluid-operated brake actuator having a check valve in the spring chamber to equalize the pressure on opposite sides of an operating movable diaphragm. The brake actuator comprises a service brake housing divided into first and second service chambers by a diaphragm or piston, and a spring brake housing arranged in tandem with and attached to the service brake housing, also divided into a first and second spring chambers by a diaphragm or piston. The check valve connecting the first and second spring chambers blocks flow between the first and second chambers when the second spring brake chamber is pressurized and opens up flow between the two chambers when the second spring chamber is depressurized.

Abstract: A vacuum brake power booster for automotive vehicles having control valve which is operable, irrespective of an actuating rod displacing a valve piston (9), by an electromagnet which actuates a third sealing seat thereby ventilating the working chamber. To minimize the independent actuating force generated by the electromagnet the electromagnet, of the present invention, is rigidly connected to the valve piston, and is arranged to be slidable in the control housing so that the third sealing seat is synchronously movable with the valve piston.

Abstract: The invention relates to a rigid mounting for a brake unit with pneumatic booster (2) the walls of which can be lightened. The booster comprises an internal reinforcement (9) in the shape of a hat with a rim, the bottom (9a) of which is attached to the master cylinder (1) and the rim (9b) of which applies the booster against the perimeter of an aperture (5a) of the apron (5) of the vehicle.

Abstract: In order to be able to adjust the distance between a reaction disc and a second part of a a two-part valve piston interacting with the former in a completely assembled vacuum brake power booster, a tubular sleeve is provided according to the invention which is disposed coaxially with a piston rod actuating the valve piston, which is axially slidable and which is engageable with a first part of said valve piston being coupled to the second part by means of a threaded union in order to apply a torque to the first piston part.

Abstract: An improvement of the inner periphery of a power piston which is connected to a valve body of a booster is disclosed. The inner periphery of the power piston comprises a radial portion which is disposed in abutment against an end face of a step formed on the valve body, an annular groove located radially outward of the radial portion, and a step formed at the boundary between the radial portion and the annular groove. The provision of the annular groove and the step assures sufficient strength around the inner periphery of the power piston without requiring an increased wall thickness of the power piston.

Abstract: The present invention relates to an assembly comrising a bulkhead (10) separating an engine compartment from a passenger compartment of a vehicle and a pneumatic booster (12) assisting the braking of the vehicle and comprising essentially a tube into which an operating rod (16) actuated by a brake pedal situated in the passenger compartment penetrates and a closed casing defining the pneumatic chambers of the booster disposed in the engine compartment. According to the invention the tube (14) is fastened to a collar (18) which has a diameter substantially smaller than that of the opening; the collar (18) is shaped in such a way as to have, at least in part, an end wall (20) parallel to the bulkhead; the collar (18) has a peripheral groove housing a ring (22); the ring (22) has, at least in part, an elastic edge (24) projecting outwards.

Abstract: The invention relates to a motor vehicle pneumatic brake booster, comprising a casing (10) inside which a piston (20) formed from a rear tubular part (22) supporting a skirt (14) defines, with the aid of an unrolling membrane (12), a front chamber (16), permanently connected to a vacuum source and a back chamber (18) alternately connected to the front chamber (16) or to the atmosphere via a valve (40) actuated by a control rod (34) capable of bearing, by a plunger (32), on one of the faces of a reaction disk (58) securely fastened to a thrust rod (56), the valve comprising a valve element interacting via an active part (40) with a first valve seat (32a) formed on the plunger (32) and a second valve seat (20a) formed on the piston (20), the valve element (40) normally being stressed forward by an elastic element (44).

Abstract: An improvement of a variable pressure passage formed in a valve body of a booster to provide a communication between a valve mechanism and a variable pressure chamber is disclosed. The variable pressure passage comprises a pair of radial bores formed in the valve body and a plurality of axial grooves which provide a communication between the radial bores. This secures a sufficient channel area for the variable pressure passage, which then includes a plurality of flow paths. Accordingly, sound which is produced upon actuation of the booster as the atmosphere flows through the variable pressure passage can be reduced without degrading the response of the booster upon actuation.

Abstract: In a vacuum booster in which a holding tube is fitted in a cylindrical valve case, and the base end portion of a valve member is fitted in an annular holding groove formed in the outer surface of the front end portion of the holding tube in such a manner as to be sealingly engaged with the inner surface of the cylindrical valve case, the inner surface of the cylindrical valve case is gradually larger in diameter towards the open rear end thereof, while the outer surface of the holding tube is tapered towards the rear end thereof, and guiding grooves and arcuate engaging grooves are formed in the inner surface of the cylindrical valve case in such a manner that each guiding groove is axially extended a predetermined distance from the open end of the cylindrical valve case, and each engaging groove is extended circumferentially of the cylindrical valve case, while guiding pawls and engaging pawls are formed on the outer surface of the holding tube in such a manner that the guiding pawls are slidably engaged wit

Abstract: The invention relates to a pneumatic brake-booster comprising a casing (10) inside which is a piston formed of a back tubular part (22) supporting a skirt (14) and which, with the aid of an unrolling membrane (12), defines a front chamber (16) connected permanently to a source of partial vacuum and a back chamber (18) connected selectively to the front chamber (16) or to the atmosphere via a valve (40) actuated by a control rod (34) capable of bearing, through the intermediary of the front face of a plunger (32), on a first face of a reaction disk (58) securely attached through a second face to a thrust rod (56). According to the invention, the piston (20) bears against the reaction disk (58) through a resilient annular front face (68, 68').

Abstract: A brake pressure booster for a vehicle brake system comprises a vacuum booster which includes two chambers, the low pressure chamber (16) of which is evacuated during actuation in a brake pressure boosting fashion, while a pressure higher than that in the low pressure chamber is adjustable in the high pressure chamber (14) by means of a control valve (28), the higher pressure exceeding the external atmospheric pressure. That is accomplished by a mechanical regulating valve (12) connected upstream of the control valve (28). Upon connection of a pressure source (18) to the high pressure chamber (14), a valve seat controlling access from the pressure source (18) to the valve opens before another valve seat closes that controls the connection between an inlet (24) into the valve and the high pressure chamber (14).

Abstract: An improvement of a recess formed in one end of an output shaft of a brake booster is disclosed. At its one end, the rear extremity of the output shaft is formed with a flange-like stop, which is formed of an annular sheet material. The engagement of the stop with the retainer is effective to prevent said one end of the output shaft from being disengaged from an annular projection on a valve body. This allows the diameter of a reaction disc to be increased without requiring an increase in the diameter of the valve body. Accordingly, a brake feeling can be adjusted over an increased extent than before by increasing the diameter of the reaction disc.

Abstract: The present invention refers to a control valve provided with a valve closure member (5) for closing and opening a valve opening. The valve closure member (5) has attached thereto a piston (11), which is arranged such that it is movable within a housing (13), said piston (11) being adapted to be acted upon by the force of a spring (spring 27) in one direction and by a fluid pressure in the opposite direction. A property characterizing the present invention is that the length of the path of movement of the piston (11) can be adjusted with the aid of a positioning means (29, 73). In accordance with a preferred embodiment, the positioning means (29) consists of a rod (31), which is adapted to be axially moved in the direction of movement of the piston (11).

Abstract: A valve mechanism for a brake or clutch booster, and more particularly, an improvement of a valve element used therein is disclosed. The valve element includes a seat which is located at the front end, a connection located at the rear end and connected to the inner periphery of a valve body, and a curved portion which is axially collapsible and interconnecting between the seat and the connection. An annular groove is formed in the inner peripheral surface of the connection at its front end. With this arrangement, the provision of the annular groove is effective to prevent any reduction in the flexibility of the curved portion if the diameter of the seat of the valve element is increased in order to increase the flow rate of the atmosphere into the booster. Thus, if the diameter of the seat 10a of the valve element 10 is increased, there is no need to increase the diameter of the connection 10b of the valve element 10.

Abstract: A fluid-operated brake actuator having a hollow actuator rod between a spring chamber of a spring brake housing and a spring chamber of a service brake housing incorporates a valve within the actuator rod. The valve isolates the two spring chambers from each other in normal operation and releases a vacuum in the spring brake housing spring chamber when the spring brake is activated. A separate one-way check valve mounted in a well of the spring brake housing permits fluid to exhaust from the spring chamber to atmosphere and prevents contaminants in the atmosphere from entering the spring chamber.

Abstract: The invention relates to a pneumatic brake-booster comprising a casing (10) inside which is a piston formed by a hub (20) and by a skirt (14) and which, with the aid of an unrolling membrane (12), defines a front chamber (16) permanently connected to a partial vacuum source and a back chamber (18) connected selectively to the front chamber (16) when a first valve passage (56, 58) is opened or to the atmosphere when a second valve passage (76, 78) is opened, the first and second valve passages (56, 58; 76, 78) being formed by first valve means (58, 78) co-operating with second valve means (56, 76), and being actuated by a control rod (35) capable of bearing, through the intermediary of a plunger (32), against one of the faces of a reaction disk (42) securely attached to a push rod (44).According to the invention, the first valve means (58, 78) are formed on the hub (20) of the piston.

Abstract: A brake pressure control device for a road vehicle with a hydraulic brake system has a pneumatic braking force amplifier which is provided with a switch-over device which switches ever the braking force amplifier to operation with increased amplification factor when the speed with which the driver actuates the brake pedal exceeds a threshold value .phi..sub.s. In the axial force transmission train leading from the brake pedal via a reaction piston of the control part, via a reaction element and via the actuating piston of the braking force amplifier to the main cylinder. A rigid force transmission element is in mechanical parallel connection to a flexible transmission element and associated with which there is a position engaged in the force transmission train as the basic position for the judicious braking operation, and an actuation device, which responds when the threshold value .phi..sub.s of the pedal actuation speed is exceeded and then disengages the distance piece from its supporting position.

Abstract: A tandem brake booster ( 12 ) having a flow path ( 145 ) between a control valve (118) and a solenoid valve (180) connected to a source of vacuum and the surrounding environment. The flow path (145) is created by first (140) and second (150) telescoping sleeves that are resiliently urged into sealing engagement with a front shell (58) and hub member (92) by a return spring (164).

Abstract: A valve mechanism for brake booster, in particular, of a brake booster which is provided with a mechanism for reducing a lost stroke, includes a first valve seat on which a plurality of tabs are formed, with communication areas being defined by spaces left between adjacent tabs. When the brake booster is inoperative, if the first valve seat moves close to the valve element such that the latter may be seated upon the first valve seat, the tabs abut against the valve element to assure a reliable communication between the inside and the outside of the first valve seat by means of the communication areas. When the booster is inoperative, the tabs are embedded in the valve element to block or interrupt the communication through the first valve seat. In the conventional practice, the design has been to minimize the lost stroke to the extent that the valve element cannot be seated upon the first valve seat when the booster is inoperative.

Abstract: A hydraulic booster for a vehicle and more particularly an improved hydraulic booster with improved brake-relieving action, among other improvements.

Abstract: A brake-pressure control device for a road vehicle with a hydraulic brake system has a pneumatic brake booster provided with a change-over device which changes over the brake booster to a mode with an increased boost factor when the speed with which the driver actuates the brake pedal exceeds a threshold value. A reaction piston of the axial force-transmission train, leading from the brake pedal via the reaction piston, a flexible reaction element and the driving piston of the brake booster to the master cylinder, is constructed in two parts. One of the two part-pistons engages axially on the reaction element and the other of the part-pistons acts as a valve element of the inlet valve and via which the driving chamber of the brake booster can be exposed to the ambient pressure. The two part-pistons have complementary threads which engage one another.

Abstract: A spring brake actuator, formed by a housing having an elastomeric diaphragm dividing the interior into two chambers, comprises a pressure plate adjacent the diaphragm in one of the chambers with a large force compression spring between the pressure plate and the housing. A hollow actuator rod is mounted within the chamber for reciprocal movement with the diaphragm and the pressure plate and receives a permanently installed caging tool extending through a housing aperture, a pressure plate aperture and into the hollow actuator rod. The pressure plate includes a bearing in the pressure plate aperture to facilitate reciprocal movement of the pressure plate over the caging tool.