Abstract: The invention relates to a spring brake cylinder with an emergency release device, comprising the following: a housing in which a spring-loaded piston can be moved axially with a piston rod, at least one spring-loaded spring, wherein the emergency release device comprises an actuation device, an emergency release mechanism to interrupt the power transmission between the spring-loaded piston and the piston rod and a holding device for holding the emergency release device in a transmission condition.

Abstract: A spring brake actuator comprises a housing including a first housing portion and a second housing portion. A spring disposed in the housing exerts a biasing force tending to separate the first housing portion from the second housing portion. A band clamp connects the first housing portion with the second housing portion. The band clamp comprises at least one band segment engaging the first and second housing portions, at least one fastener securing the band segment in a tamper-resistant manner, and a cover at least partially enclosing the fastener in a tamper-resistant manner.

Abstract: A service brake actuator (10) having a unitary pushrod assembly (42) in combination with a bushing (62) having a separable portion that permits the assembly of the service brake actuator without the need for the clevis (48) to be removably mounted to the pushrod.

Abstract: Disclosed is a diaphragm-based spring brake actuator assembly which allows for the delivery of more force to the push rod without increasing the size of the actuator unit. The invention allows for the use of a stronger heavy main compression spring in the emergency brake chamber to provide greater emergency or parking brake force to the push rod. The invention also allows the service brake chamber to operate more efficiently when braking pressure is introduced. These functions are accomplished through modifications in the design of the actuators which allow for the deployment of a larger pressure plate inside either the emergency housing or the service brake housing, or both, allowing delivery of more force to the push rod of the actuator; and are made possible in actuator units having the same dimensional profile as existing weaker units.

Abstract: A spring brake actuator has a sealed spring chamber with a hot set large force compression spring. An alternative embodiment has the hot set spring guided by the actuator rod.

Abstract: A sealed air-operated brake actuator comprising a brake actuator divided into a spring chamber and a pressure chamber. An extra-large force compression spring is contained in the spring chamber. The spring chamber is fluidly exhausted through a one-way valve located in the end of an actuator rod extending out of the brake actuator. The large force compression spring overcomes any vacuum or pressure that might form within the spring chamber upon the release of the parking brake and the one-way valve relieves any pressure buildup in the spring chamber upon the release of the parking brake.

Abstract: A spring brake actuator having a flange case and a head is provided. The flange case and the head each have a radially outwardly extending annular flange having a plurality of radially spaced apart axial holes passing therethrough which correspond to and align with each other. A diaphragm is clamped in a fluid tight manner between the annular flange of the head and the annular flange of the flange case. A plurality of disassembleable fastening members pass through the holes in the annular flange of the head and the holes in the annular flange of the flange case in order to undetachably secure the head on the flange case.

Abstract: Disclosed is an easily removable and replaceable filter cap for attachment the caging tool opening in the top of the upper housing of an emergency brake actuator. The cap includes a plurality of ventilation holes and a membrane preferably made of oilophobic and hydrophobic material which allows air to pass into and out of the emergency brake housing, while keeping foreign material out. The present invention may be easily adapted for use on any of a large number of existing emergency brake housing assemblies at minimal cost. When the filter cap of the present invention is installed, breather openings in the housing are plugged so that all air is filtered through the membrane in the cap. In an emergency or service situation, the cap may be easily removed to allow a caging tool to be inserted into the upper housing to release the emergency spring brake. After removal, the cap may be reused or replaced.

Abstract: The brake actuator assembly of this invention significantly reduces accumulation of road debris, reduces the weight of the push rod and yoke assembly and friction between the mating parts. The brake actuator includes a housing defining a chamber having an opening through the end wall, a push rod and yoke assembly reciprocally mounted within the housing chamber and a shield located within the housing closely receiving the exterior surface of the push rod and yoke assembly which has a smooth substantially continuous external surface. In the preferred embodiment, the yoke is secured to the push rod within the housing chamber, surrounding the push rod having an elliptical exterior surface which sheds accumulation of road debris.

Abstract: An improved brake actuator and method of assembling a cup-shaped housing on a housing member of a brake actuator, wherein the housing member has an open end, an annular radially projecting rib adjacent to and surrounding the open end and a plurality of spaced channel-shaped transverse depressions in the radial rib extending toward the open end of the flange case, a cup-shaped metal cover including a tubular open end having an inside diameter initially less than the outside diameter of the annular radial rib of the housing member, wherein the tubular end portion of the cover is pressed telescopically over the radial rib of the housing member, thereby simultaneously deforming the tubular end portion of the cover into the channel-shaped depressions in the rib of the housing member and stretched over the radial rib, thereby preventing rotation of the cover relative to the housing member.

Abstract: A spring brake actuator (10), with a first spring brake chamber (76) filled with compressed air and a second spring brake chamber (78) housing a large-force compression spring (82), includes an elastomeric diaphragm (74) having a centrally-disposed aperture (90) separating the first and second spring brake chambers (76 and 78). The elastomeric diaphragm (74) is compressed at a peripheral edge (138) between housing sections (66, 68) and at a collar (140), which is adjacent the centrally-disposed aperture (90), between a ring-shaped retainer (142) and at least one of an actuator rod, a pressure plate (92), and an annular recess (144) in a pressure plate (92). In one embodiment, the retainer (142) includes an annular channel (154) having an inner rim (150), an outer rim (152), and a base (156). Evenly-spaced flanges (146) radiate axially from, and are separated by slots (148) on, the inner rim (150).

Abstract: A spring brake actuator being divided into a first spring brake chamber and a second spring brake chamber by a diaphragm extending across the actuator. A pressure plate is provided in the first spring brake chamber and rests on the diaphragm. A power spring is positioned between the spring brake chamber housing and the pressure plate to urge the pressure plate toward the bottom of the actuator housing. Pressurized air is supplied to the second spring brake chamber to hold the power spring in a compressed state. A normally closed one-way check valve extends through the pressure plate and the diaphragm to provide for temporary fluid communication between the first spring brake chamber and the second spring brake chamber upon the exhausting of pressurized air from the second spring brake chamber to thereby prevent the creation of a vacuum in the first spring brake chamber that might retard the application rate of the spring brake actuator.

Abstract: A method and device for automatically adjusting the lightening of a working unit (U) of a machine by use of a hydraulic ram (57) associated with a hydropneumatic accumulator (67). Use is made of a second hydraulic ram (58) of which the piston (53), which can move as far as a predetermined position (PP) in the cylinder (C2) and which is detached from the rod (46) of the first hydraulic ram (57), acts directly or indirectly on the latter rod via the oil (O) contained in the first hydraulic ram (57). The working unit (U) is raised and lowered by the second hydraulic ram (58). When raising the working unit (U), the volume of oil in the first hydraulic ram (57) is increased or decreased in such a way that the working unit (U) is always at a predetermined height (HP) at the end of raising travel.

Abstract: An improved spring brake actuator includes an improved valve housing which incorporates pressure test points into the air supply, and further incorporates an anti-compounding valve. By incorporating the anti-compounding valve and test points directly into the valve manifold, the inventive spring brake actuator reduces the number of separate parts. The anti-compounding valve is operable to insure that there will be no compounding of the braking force.

Abstract: A pneumatic booster for use in association with heavy duty truck brakes including an emergency mechanism whereby the brakes are automatically applied in the event of a pneumatic system failure. An intermediate housing portion of the booster, typically provided as a heavy and complicated casting, is provided as a composite stamping comprising front and rear stampings held together by a series of clinch joints.

Abstract: A pneumatic drive unit is provided for partially opening a vehicle body part such as a trunk lid. The pneumatic drive unit includes a working chamber which in use applies pressure to move a control member which engages a contact surface of the vehicle body part. A vent channel is provided which selectively connects the working chamber with the atmosphere as a function of the position of a movable closing element of the drive unit element and contact of the control member with the vehicle body part such that when the body part is closed after a partial opening, the drive unit is ready for another control operation.

Abstract: A spring brake actuator (10), with a large-force compression spring (72) in a spring chamber (101) of the housing, has vent openings (102) in the housing communicating with the spring chamber (101). A gas permeable filter element (104) covers the vent openings (102), and a filter frame assembly (106) is disposed over the filter element. The filter frame assembly (106) defines tortuous air passages from the filter element (104) to atmosphere so that air entering the spring chamber from atmosphere will be substantially free of contaminants.

Abstract: A spring brake actuator (14) includes a housing having first (51) and second (52) housing sections defining a housing interior (53). A support plate (70) is movable between retracted and extended positions relative to the housing and a spring (72) is disposed between the second housing section and a first surface of the support plate for biasing the support plate to the extended position. An actuator rod (60) is operably connected to the support plate (70) at a first end for reciprocal movement with the support plate. Another end of the actuator rod extends through an aperture (64) in the first housing section (51). A flexible diaphragm (358) abuts a second surface of the support plate opposite the first surface and divides the interior of the housing into a first chamber and a second chamber. A surface of the diaphragm is exposed to fluid pressure to thereby force the support plate (70) to the retracted position against the bias of the spring (72).

Abstract: A fluid-operated brake actuator having a housing with one or more vent openings in communication with an interior chamber is provided with a filter assembly mounted to the housing over the vent openings.

Abstract: Brake actuator housings (120) are provided with mounting studs (105, 125) which are spaced from each other a standard predetermined distance so that smaller brake actuators can be mounted to a bracket (5) on a vehicle by way of the same apertures (108) as larger brake actuators.

Abstract: A spring brake actuator (10), with a large-force compression spring (82) in a second spring chamber (78) of the housing, has vent openings (100) in the housing communicating with the second spring chamber (78). A filter assembly (134) covers the vent openings (100). Weep holes (62), (104), (102), and (100) in a sleeve (50) of an push rod (18), in a spring brake actuator rod (84), and in a spring brake housing portion (68) together permit fluid compressed in a first service brake chamber (30) to flow through a conduit define by these weep holes out of the brake actuator (10) wherein it is filtered by the filter assembly (134).

Abstract: A hydraulic servo device for an automatic transmission is presented with a reduced axial length as a result of the manner in which oil pressure is fed into the cylinder. The hydraulic servo device includes a cylinder, a piston position to slide within the cylinder, a rod connected to the piston, and a cover member for closing the open end of the cylinder. The cover member, in association with the cylinder and the piston, defines an oil chamber in the cylinder. An oil passage for feeding an oil pressure to the oil chamber is formed by an opening in the cover member.

Abstract: A hydraulic servo-mechanism for an automatic transmission, including a hydraulic servo for applying a band brake to engage a band to a drum. The hydraulic servo includes a rod which is selectively positionable to an apply position for applying the band brake, a standby position in which the rod is retracted by a predetermined extent in a release direction from the apply position, and a retracted position in which the rod is further retracted in the release direction from the standby position to release the band brake.

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 check valve being double redundant and tamper resistant and comprising a tubular body having a first one-way valve disposed and one end of the tubular body and a second one-way valve disposed at an opposite end of the tubular body. A support plate is mounted to the tubular body to support the second valve and prevents the easy removal of the check valve from the brake actuator.

Abstract: A pneumatic spring brake for an automotive vehicle has a housing formed of a spring chamber head and an adapter head, and has a spring brake diaphragm, a power spring, and a spring plate. The spring chamber head is a generally bowl-shaped structure having an end wall and a surrounding, generally frustoconical side wall. The surrounding side wall of the spring chamber head is formed with a plurality of vent or breather openings therein. According to the improvement of the invention, the spring brake diaphragm is configured so as to cover and seal all of the breather openings when the power spring is compressed in its caged position. Preferably, a guide mechanism is employed to ensure that the power spring remains in coaxial alignment with the service brake push rod, and to prevent any misalignment of the spring brake diaphragm from occurring within the confines of the spring chamber head and adapter head.

Abstract: A sealed bushing assembly adapted to permit a push rod to pass through an adapter isolating a pressurized chamber, formed by attaching a sleeve to said adapter, inserting a bushing, and crimping the end of said sleeve opposite said adapter to restrain said bushing.

Abstract: A two-ply pressure plate (36) for use in an air brake system (10) for a vehicle, such as a bus, truck or the like, is shown. The two-ply pressure plate (36) includes a diaphragm plate (92) which abuts a diaphragm (32) of an air brake system (10) and a support plate (98) which abuts the rear surface of the diaphragm plate (92). A control rod (18) is welded to the support plate (98) and diaphragm plate (92). Some form of mechanical or metallurgical interconnection between the support plate (98) and diaphragm plate (92) is formed in between the mounting point of the rod (18) and the outer perimeter of the smaller of the two plates.

Abstract: A double diaphragm spring brake actuator comprising both a spring brake actuator and a service brake actuator separated by a universal adapter pressure cap, which allows the service brake actuator to be used as a stand-alone unit, or coupled to a spring brake actuator.

Abstract: An improved mounting bolt for attaching brake actuators to the frame of a vehicle includes a head having outermost portions which contact the service chamber housing, and inner portions which are spaced from the housing. The bolt spreads the force from carrying the brake actuator over a greater area on the service chamber housing and away from the bolt hole. The bolt preferably has a generally rectangular head.

Abstract: Brake actuators are provided with self-centering diaphragms. In one embodiment, the diaphragm is provided with a centering bead radially outwardly of a sealing bead. The centering bead ensures the diaphragm is properly centered prior to the brake actuator housings being secured together. In a second embodiment, the self-centering structure includes structure fit into mating structure in one of the brake actuator housings to ensure the diaphragm is properly centered. The self-centering structure ensures the brake actuator diaphragms are properly centered before connection of the two brake actuator housings. This invention is particularly useful in the type of brake actuator housings having deformed housing portions.

Abstract: A connector for a spring brake actuator comprises a threaded bolt having at least one flat portion on an outer surface thereof, a nut having a threaded central aperture threaded onto the bolt, and an embossment on the nut, extending inwardly of the central aperture to frictionally engage the flat portion of the bolt, so that the embossment prevents rotation of the nut with respect to the bolt. A method for fixedly attaching a nut onto a bolt comprises forming a flat portion on an outer surface of the bolt, threading the nut onto the bolt in alignment with the flat portion, and pressing inwardly of the nut with a punching tool to cause a portion of the material of the nut to extend inwardly of the central aperture forming an embossment in engagement with the flat portion on the bolt to hold the nut rigid with respect to the bolt.

Abstract: A brake actuator (10) for a vehicle comprises a service brake housing (14), a tandem spring brake housing (16) and a diaphragm (52), dividing the interior thereof into a first spring chamber (62) and a second spring chamber (63). In one embodiment, the first spring chamber (62) is completely sealed from the environment, being open only through a hollow actuator rod (56) connected to the diaphragm (52) and extending from the first spring brake chamber (62) into the service brake housing (14). A control valve (300) in the actuator rod (56) controls flow through the actuator rod (56) and is closed when the actuator rod (56) is retracted and also when the actuator rod (56) is extended to apply the brakes. The control valve (300) is open only as the diaphragm (52) and actuator rod (56) are moving.

Abstract: Measuring the force of a spring (28) in a spring brake actuator (10) comprising a housing (14) having an end wall (46), a spring plate (30) within the housing (14), the spring (28) being disposed between the spring plate (30) and the housing end wall (46) and a caging bolt (34) extending from the spring plate (30) through the housing end wall (46) and having a nut (44) thereon with a gauge between the caging bolt nut (44) and the housing (14). The gauge comprises a pressure-responsive element which detects the compressive force between the nut (44) and the housing (14) and generates a signal responsive thereto. An indicator (86) is coupled to the pressure-responsive element and visually displays the force on the spring (28) as a function of the compressive force signal. An embodiment of the gauge (50) comprises a body (52) having a bore (58), a piston (64) received within the bore (58) defining a chamber (74) between the piston (64) and the body (52) and a fluid (72) in the chamber (74).

Abstract: The fluid-operated brake actuating mechanism comprises a casing having a partition wall to divide the casing into upper and lower coaxial chambers. First and second fluid-tight diaphragms are mounted in the upper and lower chambers, respectively. First and second ports enable injection of a pressurized fluid in the cavities delimited in the upper chamber between the first diaphragm and the partition wall and in the lower chamber between the second diaphragm and the partition wall. A coaxial power spring is mounted into an enclosure formed in the upper chamber at the upper end of the casing for limiting axial extension of the power spring upon opening of the casing to access the upper chamber. The upper chamber can therefore be accessed easily and safely upon maintenance of the brake actuating mechanism.

Abstract: A hydraulic system for accommodating fluid pressure variations is provided. The system includes a housing for an actuating piston with the housing having a first end with a hydraulic fluid port and a second end. The actuating piston includes a body portion, having a face, and a rod portion. A first resilient member is confined between the actuating piston and the second end of the housing. A second resilient member is confined between the body portion and the face of the actuating piston. The face of the actuating piston is preferably a pressure accommodating piston which moves relative to the body portion of the actuating piston. Preferably, the second resilient member has a tension force greater than the tension force of the first resilient member. As the actuating piston moves against the bias of the first resilient member toward the second end of the housing in response to hydraulic fluid entering the housing through the fluid port, the movement of the actuating piston is limited by a stop.

Abstract: A motor or pump includes a stator and a rotor supported for rotation with respect to the stator by a bearing arrangement. The rotor has a cylinder block thereon having radial cylinder bores equipped with radially reciprocable pistons. Rollers on the pistons abut a cam ring fixed to the stator so that the pistons to reciprocate radially to displace fluid when the rotor turns relative to the stator. The stator includes a control device fixed thereon having a pair of fluid passages therein. One side of the control device constitutes a distribution face with outlets therein connecting the fluid passages to the cylinder bores as the rotor rotates. A counterpart fastens to the rotor adjacent the opposite side of the control device so as to define an annular chamber therebetween. A shuttle valve operatively interposed between the passages and chamber ensures that the chamber remains in connection with the passage having the higher pressure.

Abstract: Pressure medium pliers for clamping rings, comprising a pressure medium connection and a pressure medium valve connected thereto, at least one piston controlled by the pressure medium valve, a traverse member drivable by the piston and pivoted pliers members at the inner lever ends of which the traverse member engages for pivoting them, the pressure medium valve having a valve pin which is shiftable in traverse direction of the movement of the piston and operatable by a release trigger, the valve pin blocking the connection of the piston with the pressure medium connection and connecting it with a lower pressure level in a rest position and blocking the connection of the piston with the lower pressure level and connecting it with the pressure medium connection in a working position being reachable by operation of the release trigger, a switching bar which is held in a slideway movable in the direction of the piston and which is mechanically biased by a spring towards the valve pin, the switching bar having a

Abstract: A small envelope is achieved for an inelastically deformed connection between a spring cover and a central housing in a spring brake actuator. The connection is deformed radially inwardly and then extends radially outwardly from the radially inwardly extending portion. This eliminates the radially outwardly extending portion and flanges as are typically utilized in the prior art. Thus, a much smaller envelope is provided. In preferred embodiments of this invention, a seal groove is positioned axially adjacent a securement groove in the central housing. A seal is positioned in the seal groove to ensure an air-tight seal. In addition, a unique diaphragm guiding structure is incorporated into one embodiment of this invention.

Abstract: An improved brake actuator is fully sealed against ingress of liquid or other contaminants. Separate breather tubes selectively communicate each of the pressure ports to the non-pressurized sides of the service and spring chambers. The separate breather tubes provide clean air into the non-pressurized chambers. Relief valves are positioned in each of the breather tubes. The pressurized ports may be reconfigured into two configurations such that the source of pressurized air may be connected to either of two orientations. In addition, a seal closely receives the push rod such that the non-pressurized chamber of the service side is fully sealed against ingress of liquids.

Abstract: A spring break actuator (10) with a cast aluminum adapter (74) partially defining tandem spring brake and service brake portions has several corrosion fuses on the adapter. Each corrosion fuse is defined by a recessed or thinned area which does not compromise the structural integrity of the adapter.

Abstract: A nut and bolt assembler comprises a threaded bolt (78a) having a proximal end (140) with a knurled outer surface (142). A nut (144) is press fit onto the bolt knurled proximal end (190) to prevent rotation of the nut (144) with respect to the bolt (78a). Preferably, the knurled outer surface preferably comprises axial splines (142). The connection is most useful on the proximal end of a caging bolt (78a) in a spring brake actuator (10) having a hollow actuator rod (60) into which a head (86) at a distal end of the caging bolt (78a) is positioned with the proximal end (140) of the caging bolt (78a) extending out of the brake actuator through a threaded aperture (77) in an end portion of a brake actuator housing (52). A washer (148) can be provided between the nut (144) and the brake actuator housing (52) to prevent foreign material from entering the break actuator housing (52) through the threaded aperture (77).

Abstract: An air-operated combination diaphragm spring brake has a service chamber in tandem with a spring chamber. The service chamber being separated into an upper and lower section by a first elastomeric diaphragm. The spring chamber is separated into upper and lower sections by a second elastomeric diaphragm. A lever type stroke indicator is positioned within either or both the lower sections of the service chamber and the spring chamber.The stroke indicator in the service chamber pivots about a pin when contacted by a plate associated with the service push rod when the brakes are applied, resulting in a portion of the stroke indicator to extend beyond the periphery of the service chamber housing and provide a visual indication of the need to inspect the brake system.

Abstract: A bearing (104) is mounted to the caging bolt head (86) within a hollow actuator rod (60) of a spring brake actuator (14). The bearing (104) is self-lubricated to guide movement of the actuator rod during application and release of the spring brake and to minimize friction.

Abstract: In a method of forming tamper-resistant brake actuators, the ports for connecting air pressure sources to apertures within the central housing of the brake actuator are bolted to the central housing after the brake housing members have been inelastically deformed together. In this way, the deformation tools utilized to deform the housing members will not contact the air pressure ports. In the past, brake actuators have required spacing the deformation tools from the ports to avoid damaging the ports. This has required that the central housing be undesirably long. With the inventive method, the deformation is performed prior to attachment of the ports. Thus, the axial length of the central housing may be greatly reduced over the prior art. Once the deformation is completed, the ports are then bolted to the central housing. In this way, the length of the central housing and the amount of material required by the central housing are greatly reduced.

Abstract: A brake release tool incorporates a two-part structure wherein a portion accessible from outside the brake actuator does not move axially away from the brake actuator during caging. In this way, less room is necessary outwardly of the brake actuator housing than has been required in the prior art. An operator turns an outer bolt, which turns a threaded inner nut. The threaded inner nut moves axially to contact a piston, and moves the piston to cage the power spring. The bolt need not move axially outwardly, although in one embodiment it may move slightly axially inwardly as the spring is caged to provide a visual indication that the spring is not uncaged.

Abstract: A unique indicator system is incorporated into a release tool for a spring brake actuator. The indicator provides an indication of when the release tool has is fully released. The release tool is preferably of the type wherein a threaded member does not extend outwardly of the actuator during caging of the power spring. The inventive indicator is biased outwardly of the actuator when the release bolt has even partially caged the power spring. It is only when release bolt is fully released that the indicator is pulled inwardly. Thus, an observer has a visual indication of when the power spring caging mechanism has been fully released.

Abstract: A spring brake actuator includes a unique release bolt having two distinct threaded portions. A first-threaded portion is received in a threaded insert in the brake actuator outer housing. The second-threaded portion has its threads extending in an opposed direction to the first-threaded portion and is threadably received within a nut caging member. The nut is received in a bore in the push rod and constrained against rotation relative to the push rod. The nut moves axially within the push rod. The second-threaded portion rotates with the entire release bolt. When the release bolt is rotated, the first-threaded portion moves outwardly of the threaded insert, and the nut moves with the release bolt. At the same time, the second-threaded portion is rotating within the nut, and the nut moves axially relative to the second-threaded portion. The nut is moving axially due to two actions of the release bolt.

Abstract: A long-stroke fail-safe spring brake assembly for heavy duty vehicles comprises aligned first and second cups secured adjacent one another to form a housing for a compressed power spring which biases a spring piston, a hollow tubular push rod having one end open and sealingly secured, preferably by press fitting, to the spring piston and the other end closed and extending sealingly through the second cup for reciprocal control of a brake actuator by the power spring, an annular-shaped flexible diaphragm having an outer periphery radially-sealingly secured adjacent between the cups and an inner periphery sealingly secured adjacent the outer periphery of the spring piston, the intermediate portion of the diaphragm being disposed radially-outwardly of the spring piston. The spring piston is disposed to compress the compressed spring still further toward the first cup under the influence of a compressed fluid medium, the push rod, and the spring piston being sealingly secured to each other.

Abstract: An improved spring brake actuator includes a dome extending into the service chamber from the center housing. The spring chamber push rod is formed with a plate having a cross-section corresponding to the dome. The service chamber diaphragm as well as the service chamber piston are also formed with surfaces that correspond to the shape of the dome. The surfaces "stack up" to ensure alignment between the spring chamber push rod and the service chamber push rod. The use of the dome also provides additional stroke to the spring chamber push rod without requiring additional axial length for the overall brake actuator.

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.