WO1999038744A1

WO1999038744A1 - Submersible brake actuator

Info

Publication number: WO1999038744A1
Application number: PCT/US1999/002221
Authority: WO
Inventors: John P. Bowyer
Original assignee: Neway Anchorlok International, Inc.
Priority date: 1998-02-03
Filing date: 1999-02-02
Publication date: 1999-08-05

Abstract

An air-actuated brake actuator (10) for a vehicle comprising a housing having first and second end walls (21, 22) defining a housing interior whereby the first end wall (21) has an aperture therethrough. A movable member (32) is disposed within the housing and divides the interior thereof into a first chamber (27) and a second chamber (31). An actuator rod (18) is operably connected to the movable member (32) for reciprocating movement relative to the housing, and has an end (20) extending through the aperture (34) for operative connection to a brake. The first chamber (27) has a first port and the second chamber (31) has a second port, and a control valve (102) is in fluid communication between the first and second ports and a pneumatic source (114) of pressurized air to control the flow of air between the pneumatic source (114), the first and second chambers (27 and 30) and the atmosphere as the brake actuator (10) is actuated. The housing interior of the brake actuator (10) is thereby effectively sealed against the introduction of contaminating fluids from the atmosphere.

Description

-1- SUBMERSIBLE BRAKE ACTUATOR

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims the benefit of U.S. Patent Application Serial No. 60/073,538, filed February 3, 1998 BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to air-operated diaphragm brakes for vehicles and particularly to brake actuator assemblies which can be submerged without damage or corrosion to the interior thereof.

Description of Prior Art

An air brake system for a vehicle such as a bus, truck or the like typically includes a brake shoe and drum assembly which is actuated by means of an actuator assembly operated by the selective application of compressed air. Conventional air brake actuators have both a service brake actuator for actuating the brakes under normal driving conditions by the application of compressed air and a spring-type emergency brake actuator which causes actuation of the brakes when air pressure has been released. The emergency brake actuator includes a strong compression spring which forces application of the brake when air is released. This is often referred to as the spring brake.

Typically, the spring brake actuator is disposed in tandem with the service brake actuator. When full pressure is applied to the spring brake actuator, pressurized air acting against a diaphragm compresses the compression spring. A spring brake actuator rod is either held in a retracted position by a relatively small return spring or affixed to the diaphragm and held with it by air pressure, thus not affecting the operation of the brake. When the brake is to be applied during normal driving operation, pressurized air is supplied to a pressure chamber in the service brake actuator and acts against a diaphragm. Resulting movement of the service brake diaphragm urges a service brake push rod on the non-pressure side of the diaphragm to be extended from brake actuator and causes the brakes to be applied with an application force which is proportional to the air pressure applied to the service brake -2- actuator. In the event of a loss of air pressure or an intentional exhaustion of air from the spring brake actuator, the brake will be mechanically activated by the force of the compression spring acting on the spring brake actuator rod which in turn acts upon the service brake push rod to apply the brakes. Thus, the spring brake portion serves both as a parking brake and an emergency brake.

The non-pressurized chamber on the service side of the service brake diaphragm is typically vented to the outside atmosphere to allow air to be exhausted from that portion of the housing when the diaphragm is actuated by introduction of pressurized air to the opposite side of the service brake diaphragm. As the brakes are applied, the service brake diaphragm moves in a direction that expels air out of the non-pressure chamber and through the vented openings in the service chamber. When the pressurized air is released, the service brake return spring returns the diaphragm to its unexpanded position. This movement tends to create a vacuum in the non-pressure chamber that draws air into the chamber from the atmosphere. Since the service chamber is vented to the outside atmosphere under the truck chassis, the outside air drawn into the service chamber is often accompanied by moisture and corrosive substances, such as road salt. Because the return spring wears as it cycles and its bare metal becomes exposed as a result, the return spring can corrode due to contaminants in the air. Also, because the service brake return spring must exert substantial force in order to return the service diaphragm to its unexpanded position, the service brake return spring can be subjected to large stresses when it cycles. The spring life is inversely proportional to the amount of corrosion and stress it experiences. In sealed housings, the spring cannot be removed from the housing without permanently deforming the housing. In other housings, the actuator must be replaced by a new actuator and the old actuator sent to a rebuilder. In any case, the actuator is not serviceable by the truck operator. Often the entire brake actuating unit must be replaced when the service chamber needs repair.

In addition to air and moisture being drawn into the service chamber during normal use, liquids can also enter through the vents if the vehicle is parked in an area with standing water having a depth sufficient to submerge the brake actuator. -3- Substantial damage can be caused to the brake actuator if standing water is allowed to enter into the vents.

SUMMARY OF THE INVENTION The invention relates to an air-actuated brake actuator for a vehicle comprising a housing having first and second end walls defining a housing interior. The first end wall has an aperture therethrough. A movable member is disposed within the housing and divides the interior thereof into a first chamber and a second chamber. An actuator rod is operably connected to the movable member for reciprocating movement relative to the housing and has an end extending through the aperture for operative connection to a brake.

In one aspect, the first chamber has a first port and the second chamber has a second port, and a control valve is in fluid communication between the first and second ports and a pneumatic source of pressurized air to control the flow of air between the pneumatic source, the first and second chambers and the atmosphere as the brake actuator is actuated. The housing interior of the brake actuator is thereby effectively sealed against the introduction of contaminating fluids from the atmosphere.

The control valve preferably comprises a first valve fluidly interconnected to a second valve. The first valve is also preferably fluidly connected to the first chamber, and the second valve is fluidly connected to the second chamber.

The first valve can have a supply port, the second valve can have a supply port, and both supply ports are preferably fluidly interconnected to the pneumatic source. The first valve can have a discharge port fluidly interconnected to the first chamber, and the second valve can have a discharge port fluidly interconnected to the second chamber. The first valve can have an exhaust port, and the second valve can have a control port fluidly interconnected to the first valve exhaust port. The second valve can have an exhaust port fluidly interconnected with one of atmosphere and a return conduit to the pneumatic source. .4. The first valve is preferably movable between a first position wherein the first valve discharge port is fluidly interconnected to the first valve supply port and a second position wherein the first valve discharge port is fluidly interconnected to the first valve exhaust port. The second valve is preferably movable between a first position wherein the second valve discharge port is fluidly interconnected to the second valve control port and a second position wherein the second valve discharge port is fluidly interconnected to the second valve exhaust port.

The first valve can be moved to the first position when the source of pressurized air is actuated whereby the pressurized air is supplied to the first chamber and the diaphragm is moved to an actuated position. The second valve is preferably moved to the second valve first position as the first valve is moved to the first valve first position whereby air exiting the second chamber is released through the second valve into the exhaust port. The first valve is preferably moved to the second position when the source of pressurized air is deactivated whereby the pressurized air is released from the first chamber through the first valve exhaust port and the diaphragm is moved to a non-operative position. The second valve is preferably moved to the second valve second position as the first valve is moved to the first valve second position whereby air enters the second chamber through the second valve control port and second valve discharge port. In another aspect, the invention relates to a brake actuator wherein the control valve comprises a first valve having a supply port fluidly interconnected to the pneumatic source, a discharge port fluidly interconnected to the first chamber, and an exhaust port fluidly interconnected to the second chamber. The control valve can further comprise a second valve fluidly interconnected to one of the atmosphere and the pneumatic source. The second valve can be fluidly interconnected to the second chamber. The second valve is preferably a one-way check valve adapted to exhaust air from the second chamber when the pressure therein reaches a predetermined value and thereby prevents return flow of air into the second chamber regardless of the internal pressure in the second chamber. The second valve is preferably sealingly mounted within the housing. -5- The first valve is preferably movable between a first position wherein the discharge port is fluidly interconnected to the supply port and a second position wherein the discharge port is interconnected to the exhaust port. The first valve can be moved to the first position upon actuation of the source of pressurized air whereby the pressurized air is supplied to the first chamber through the discharge port whereby sufficient compressed air is supplied to the first chamber to move the diaphragm .and, in turn, the actuator rod to an actuated position while, simultaneously, air in the second chamber is exhausted through the second valve.

The first valve can be moved to the second position when the source of pressurized air is de-activated whereby pressurized air in the first chamber is passed to the second chamber through the first valve exhaust port as the diaphragm returns to an unactuated position. Excess air in the second chamber as a result of the movement of the first valve to the second position above a predetermined value can be released through the second valve. The second valve is preferably sealingly mounted within the housing. The first valve can be a quick release valve. The second valve can be a pilot valve. The movable member can be a diaphragm. The movable member can be a piston. The control valve can be remote from brake actuator housing. The control valve is preferably elevated with respect to the brake actuator housing whereby the control valve is not submerged if the housing is lowered into standing water. The brake actuator can be any type of brake actuator such as a service brake actuator, spring brake actuator or a tandem service and spring brake actuator.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to the drawings in which:

FIG. 1 is a cross-sectional view of an air-actuated brake actuator having an air control valve assembly shown schematically according to the invention;

FIG. 2 is a schematic view of the control valve assembly of FIG. 1 shown during a period when pressurized air is supplied to the brake actuator of FIG. 1 ; FIG. 3 is a schematic view of the control valve assembly of FIG. 1 during a period where air is exhausted from the brake actuator; -6- FIG. 4 is a fragmentary, cross-sectional view of an air-actuated brake actuator having a second embodiment of the control valve assembly according to the invention;

FIG. 5 is a cross-sectional view of an example of a quick-release valve used in the control valve assembly shown in FIGS. 1-4; and

FIG. 6 is an example of a quick-release valve used in the control valve assembly of FIGS. 1-4.

DETAILED DESCRIPTION FIG. 1 shows a cross-sectional view of an example of an air-operated brake actuating unit 10 having a general configuration well known in the art. The actuating unit 10 comprises a service brake portion 12 mounted in tandem to a spring brake or emergency brake portion 14. A service brake push rod 18 extends from the service brake 12 and has an end 20 adapted to operably connect to a conventional brake shoe and drum (not shown in the drawing) in a conventional fashion. Reciprocating motion of the push rod 18 causes the brake to be alternately applied and released.

The service brake 12 comprises a pair of facing cup-shaped housing sections 21 and 22, each having an outwardly directed flange edge 25. The housing sections 21, 22 are clamped together at their flange edges by means of a clamp 26 to form a second service brake chamber 30. An elastomeric diaphragm 32 is suspended within the second chamber 31 and is compressed at the peripheral edge thereof between flange edges 25 of the housing sections 21, 22. A first service brake chamber 27 is defined between the housing section 22 and the elastomeric diaphragm 32. The service brake push rod 18 extends through a central opening 34 in housing section 21 and into the service brake chamber 30 where it terminates in a pressure plate 36. The portion of the service brake chamber 30 on the push rod side of the diaphragm 32 is generally non-pressurized and is characterized with the numeral 31. A return spring 40 extends between the pressure plate 36 and the interior surface of the housing section 21. A push rod guide 42 mounted to housing section 21 defines the central opening 34 and has a spring seat 48 which receives one end of the compression spring 40 to retain it in position around the opening 34. The spring 40 thus tends to urge the -7- pressure plate 36 .and the service brake push rod 18 to a fully retracted position shown in FIG. 1. The first service brake chamber 27 is pneumatically sealed with respect to the atmosphere, and the entire service chamber 30 may be so sealed such as by the provision of a seal around the rod 18 in the opening 34. To operate the service brake, compressed air is introduced into the first chamber 27 to force the diaphragm 32 and the pressure plate 36 against the force of the spring 40 to actuate the push rod 18. Mounting studs 46 .are provided to mount the brake actuating unit 10 onto a vehicle.

The spring brake 14 comprises a pair of facing cup-shaped housing sections 51 , 52 joined at their edges to form an inner chamber 53. Typically, housing sections 22, 51 are formed of an integral cast piece. Housing section 51 is provided with an outwardly directed circumferential flange edge 54. The housing sections 51 and 52 are typically clamped together by a peripheral curved edge 56 on housing section 52 engaging edge 54 on housing section 51. An elastomeric diaphragm 58 is suspended within the inner chamber 53 and is compressed at its peripheral edge between the edges 54, 56 of the housing sections 51, 52. The portion of the inner chamber 53 between the diaphragm 58 and the housing section 51 forms an air chamber 99 filled with compressed air typically supplied through an inlet port 59 in housing section 51 when the emergency brake is in its normal, released position. The portion of inner chamber 53 between the diaphragm 58 and housing section 52 defines a compression spring chamber 101, containing a large-force spring brake compression spring 72.

An actuator rod 60, aligned with the push rod 18, has a distal end extending through a central opening 64 in an end wall of housing section 51. The distal end of actuator rod 60 terminates in a reaction plate 62 disposed in an annular seat 63 in an end wall of housing section 22. The opening 64 is provided with a bearing 66 having at least one annular recess which accommodates at least one O-ring seal 68. The bearing 66 defines a bearing surface for actuator rod 60, and the O-ring 68 seals the pressure chamber in the service brake 12 from the air chamber 99 in the spring brake 14. The proximal end of the actuator rod 60 extends through a centrally disposed aperture 81 in the diaphragm 58 and terminates in a pressure plate 70 which engages the spring brake compression spring 72. The pressure plate 70 comprises a -8- substantially flat portion 73 engaging one end of the spring 72 and a tubular portion

74 extending generally axially along the axis of the spring 72. The tubular portion 74 is press-fit onto an end portion of the actuator rod 60 such that the pressure plate 70 and the actuator rod 60 form an integral unit. An annular recess 76 in an end wall of the housing section 52 serves as a seat for the spring 72 and also provides rigidity to the end wall against the force of the spring 72.

During normal operation of the brake actuator 10, the actuator rod 60 is in the fully retracted position, as depicted in FIG. 1 , by means of compressed air which is maintained in the air chamber 99. When the compressed air is exhausted, the compression spring 72 forces the pressure plate 70 and the rod 60, integrally attached to the pressure plate, in the direction of the brake push rod 18 of the service brake 12. The force of the spring 72, when released, causes the actuator rod 60 to be extended through the central opening 64 which, in turn, causes the reaction plate 62 to apply a force to the diaphragm 32 and the pressure plate 36 of the service brake 12. This action causes the service brake push rod 18 to be actuated and the brake to be applied. When the emergency brake is to be released, compressed air is once again introduced into the air chamber 99. The force of the compressed air against the diaphragm 58 urges the pressure plate 70, the rod 60, and the spring 72 toward the retracted position depicted in FIG. 1. It will be understood that the spring brake 14 is preferably provided with a valve system or other fluid passageway to accommodate the flow of air between the chambers 99 and 101 of the spring brake 14 as the spring brake is actuated and released. The interconnection of the chambers 99 and 101 prevents a vacuum from forming in either of the chambers 99 and 101 and prevents excessive retardation during movement of the diaphragm 58, while maintaining the chambers 99, 101 fully sealed from atmosphere.

The actuator rod 60 preferably is a hollow tube or rod provided with a central bore 61 to accommodate a brake release caging rod or tool 78. The distal end is closed by the reaction plate 62, but the proximal end is open, and an aperture is provided in the pressure plate 70 to permit the caging rod 78 to extend therethrough. The caging rod 78 is used to manually release the spring brake or to ensure that the -9- compression spring 72 will remain compressed (or caged) when maintenance functions .are performed on the brake assembly. The caging rod 78 preferably is a bolt or the like threaded into a fixed threaded opening such as the threaded collar 77 affixed by welding to the end wall of housing section 52. A hex-head nut 79 is fixedly attached to the caging rod 78 to facilitate threading the bolt into and out of the chamber 14 by a common wrench or the like. The end of the caging rod 78 within the actuator rod 60 has an enlarged head or plate 86.

An inwardly directed annular shoulder 80 in the tubule section 74 provides positive engagement with the actuator rod 60 when the rod is actuated and further serves as an engagement surface for the caging rod head 86 against which the caging rod head 86 will bear when the caging rod 78 is withdrawn. Upon withdrawal, the caging rod 78 retains the compression spring 72 in its compressed or caged state. Otherwise, the caging rod 78 extends into the central bore 61 of actuator rod 60 by a sufficient distance to allow the actuator rod 60 to extend its full length of travel without engagement between the shoulder 80 and the caging rod head 86.

FIG. 1 also shows the brake actuator 10 provided with a control valve assembly 100 mounted thereto which is adapted to supply compressed air to the first chamber 27 between the housing section 22 and the diaphragm 32, transfer air between the first chamber 27 and the second chamber 31 , and exhaust air from the second chamber 31 to the atmosphere. It will be understood that the control valve assembly 100 can be provided within a housing shown in phantom lines in FIG. 1 by reference numeral 102 that can be integrally formed with the brake actuator 10 or provided as separate housing remote from the brake actuator 10.

The control valve assembly 100 further comprises a first valve 104 and a second valve 106. The first and second valves 104 and 106 are provided with supply ports 108 and 110, respectively, which are fluidly interconnected with a common supply conduit 112 which, in turn, is fluidly interconnected with a conventional air compressor or pressure reservoir 114 typically provided on commercial vehicles.

The first valve or quick-release valve 104 has one or more discharge ports 116 fluidly interconnected with the first chamber 27 of the brake actuator 10 located between the housing section 22 and the diaphragm 32. The first valve 104 also -10- preferably has an exhaust port 118 which is in fluid communication with the second valve 106.

The second valve or pilot valve 106 is provided with a discharge port 120 fluidly interconnected with the second chamber 31 of the brake actuator 10. The second valve 106 also preferably has an exhaust port 122 which is fluidly interconnected with the atmosphere. Alternatively, the exhaust port 122 can be fluidly interconnected with a compressed air storage facility provided on the vehicle. The second valve also receives control pressure via a supply conduit 110 connected to the pressure source 114. Preferably, the first valve 104 comprises a quick-release valve such as the first and second examples of quick-release valves shown in FIGS. 5 and 6, respectively. It will be understood that the examples of the quick-release valves shown in FIGS. 5-6 are designated with reference numerals common to those shown in FIG. 1 for describing the first valve 104. The example valve 104 shown in FIG. 5 has a housing 124 which defines an internal chamber 126 therein. A diaphragm 128 is biased by a spring 130 against a supply port seat 129 adjacent the supply port 108. When compressed air is supplied through the supply port 108 as when the service brake is engaged, pressurized air enters the port 108 and urges the diaphragm 128 against an exhaust port seat 131 which seals the exhaust port 118. At the same time, pressurized air forces the edges 133 of the diaphragm 128 against the bias of the spring 130 which allows the air to flow through the discharge port or ports 116 and into the first chamber 27 of the brake actuator 10.

When air pressure at the discharge port 116 (beneath the edges 133 of the diaphragm 128) equals the pressure at the supply port 108 (above the edges 133 of the diaphragm 128), the spring 130 urges the outer edge 133 of the diaphragm 128 to seat against the housing 124 closing the supply port 108. The exhaust port 118 remains sealed by a center portion of the diaphragm 128 as the brake remains engaged. When the compressed air application is released as when the brake is released, the air pressure in the supply line 112 is released back through the brake valve exhaust in conventional manner. The air pressure beneath the diaphragm 128 at the discharge port 116 forces the diaphragm 128 to rise, opening the exhaust port 118 and allowing -11- air within the chamber 27 to exhaust back through to discharge port 116 into the chamber 126 and through the exhaust port 118.

FIG. 6 shows a second embodiment of the first valve 104 wherein a single flexible diaphragm 132 mounted over a protruding valve seat 134 replaces the diaphragm 128 biased by the spring 130 therein. The operation of the valve shown in

FIG. 6 is the same as that shown in FIG. 5.

Although a quick-release valve is shown in the drawings as a preferred embodiment of the first valve 104, other types of valves, such as check valves, pilot valves, ball valves, etc. can be used without departing from the scope of this invention.

The second valve 106 is preferably a pilot valve having a control port 110, exhaust port 122 and the discharge port 120 and is adapted to receive the exhaust port

118 of the first valve 104. It will be understood that valves of other types can be employed without departing from the scope of this invention. It will further be understood that both chambers 27 and 31 , located on either side of the diaphragm 32 of the service brake 12, may be sealed so that the only passages for ingress and egress of air from the chambers 27 and 31 are through the discharge ports 116 and 120 of the first and second valves 104 and 106, respectively.

FIG. 2 shows the flow path of air when the supply line 112 is pressurized as when the brake is to be engaged. The compressed air flows into the first valve 104 through the supply port 108 which opens the first valve 104 to supply the compressed air to the discharge port 116 and into the first chamber 27 in the direction designated by arrow A. The diaphragm 32 is thereby operated to move the actuator rod 18 to the actuated position. The exhaust port 118 of the first valve 104 is maintained in a closed position.

Simultaneously, compressed air also flows through the control port 110 into the second valve 106. The supply of compressed air to the control port 110 operates to open a fluid passage between the discharge port 120 and the exhaust port 122.

Thus, as air is supplied to the first chamber 27 to move the diaphragm 32 toward the actuated position, air within second chamber 31 on the opposite side of the diaphragm -12- 32 is exhausted to the atmosphere through the discharge port 120 and the exhaust port

122 in the direction designated by arrow B.

FIG. 3 shows the air flow path when pressure in the line 112 is released as when the brake is released. The first valve 104 is thereby biased into a closed position as described above so that a flow passage is opened between the discharge port 116 and the exhaust port 118 of the first valve 104. Simultaneously, the release of pressure at the control port 110 establishes a passageway between the exhaust port 118 of the first valve 104 and the discharge port 120 of the second valve 106.

Thus, when the brake is released, pressurized air is exhausted from the first chamber 27 through the discharge port 116, allowing the diaphragm 32 to return to the rest position under the bias of the return spring 40. The air flows through the discharge port 116, to the exhaust port 118 of the first valve 104 in the direction shown by arrow C, into the second valve 106 and into the second chamber 31 through the discharge port 120 of the second valve 106 in the direction shown by arrow D in FIG. 3.

In any event, the air flowing through the first and second valves 104 and 106 into and out of the service brake 12 is entirely self-contained and does not permit outside contaminants to enter the brake actuator 10. Further, if the vehicle is parked within an area having standing water of sufficient depth to submerge the brake actuator 10, the one-way positioning of the valves 104 and 106 in connection with the fluidly-sealed environment for the compressed air entering and exiting the brake actuator 10 cooperate to prevent the standing water from entering the chambers 27 and 30 of the service brake 12.

FIG. 4 shows an alternative embodiment of an control valve assembly 140 according to the invention. The control valve assembly 140 comprises a housing 142 having a valve 144 located therein. The valve 144, of a similar configuration as the first or second valves 104 and 106, has a supply port 146 interconnected to a compressor or reservoir 114 by a supply conduit 148, a discharge port 150 fluidly interconnected to the first chamber 27 of the service brake 12, and an exhaust port 152 fluidly interconnected with the second chamber 31 of the service brake 12. In addition, a second valve 154 is sealingly mounted within a sidewall of one of the -13- housing sections 21, 22 which define the service brake 12. Preferably, the second valve 154 is a one-way valve, such as a check valve, to exhaust air from the chamber

31 when it reaches a predetermined pressure value and prevent return flow regardless of the internal pressure in the chamber 31. The embodiment of the control valve assembly 140 operates similarly to the control valve assembly 100 shown in FIGS. 1-3. As compressed air is supplied to the first valve 144 from the supply conduit 148 and the supply port 146, the exhaust port

152 is closed, which directs the compressed air entering into the first valve 144 through the discharge port 150 and into the chamber 27 behind the diaphragm 32. Sufficient compressed air is supplied to the chamber 27 to move the diaphragm 32 and, in turn, the actuator rod 18 to the actuated position. Simultaneously, ambient air in the service brake chamber is exhausted through the second valve 154.

When the brake 10 is to be deactivated, air is released from the supply line 148 by conventional means, which seals the supply port 146 and opens a path from the discharge port 150 to the exhaust port 152. Thus, compressed air within the chamber 27 is thereby released from the service brake 12 through the discharge port 150, the first valve 144, and the exhaust port 152 to enter the service brake chamber 30 as the diaphragm 32 returns to its unactuated position. Any excess air pressure is exhausted through the second valve 154 in the service brake 12. Thus, as in the previous embodiment, a sealed environment for the brake actuator 10 is created which prevents the entry of contaminants and permits the brake actuator 10 to be submerged within water without allowing the water to enter within the chambers 27 and 31 thereof.

It will be appreciated that a similar structure can be applied with similar results to the spring brake housing 14 in lieu of, or in addition to, any valve system which interconnects the chambers 99 and 101 of the spring brake 14.

Although the features of this invention are shown in connection with a diaphragm-type brake actuator, this invention can also be employed with a rolling lobe-type actuator, a piston-type brake actuator or any other type of brake actuator which is known in the art. -14- The invention encompasses other variations and modifications not illustrated in the drawings, but clearly evident to one skilled in the art. It will be understood that other variations and modifications of the foregoing embodiments may be devised by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

-15- CLAIMSWhat is claimed is:

1. In an air-actuated brake actuator (10) for a vehicle comprising: a housing having first and second end walls (21,22) defining a housing interior, the first end wall (21) having an aperture (34) therethrough; a movable member (32) disposed within the housing and dividing the interior thereof into a first chamber (27) and a second chamber (31); an actuator rod (18) operably connected to the movable member (32) for reciprocating movement relative to the housing, and having an end (20) extending through the aperture (34) for operative connection to a brake; the improvement wherein: the first chamber (27) has a first port and the second chamber (31) has a second port; and a control valve (102), (142) is in fluid communication between the first and second ports and a pneumatic source (114) of pressurized air to control the flow of air between the pneumatic source (114), the first and second chambers (27, 31) and the atmosphere as the brake actuator (10) is actuated whereby the housing interior of the brake actuator (10) is effectively sealed against the introduction of contaminating fluids from the atmosphere.

2. The brake actuator (10) of claim 1 wherein control valve comprises a first valve (104),(144) fluidly interconnected to a second valve (106), (154).

3. The brake actuator ( 10) of claim 2 wherein the first valve ( 104), (144) is fluidly connected to the first chamber (27) , and the second valve (106), (154) is fluidly connected to the second chamber (31).

4. The brake actuator (10) of claim 2 or 3 wherein: the first valve (104) has a supply port (108); the second valve (106) has a supply port (110), and -16- both supply ports (108,110) are fluidly interconnected to the pneumatic source (114) .

5. The brake actuator (10) of claim 2, 3, or 4 wherein:

(a) the first valve (104) has a discharge port (116) fluidly interconnected to the first chamber (27) ; and

(b) the second valve (106) has a discharge port (120)fluidly interconnected to the second chamber (31).

6. The brake actuator (10) of claim 2, 3 ,4 or 5 wherein:

(a) the first valve (104) has an exhaust port (118); and

(b) the second valve (106) has a control port (118) fluidly interconnected to the first valve (104) exhaust port (118).

7. The brake actuator (10) of any of claims 2, 3, 4, 5 or 6 wherein the second valve (106) has an exhaust port (122) fluidly interconnected with one of atmosphere and a return conduit to the pneumatic source (114).

8. The brake actuator (10) of claims 5, 6 or 7 wherein the first valve (104) is movable between a first position wherein the first valve (104) discharge port (116)is fluidly interconnected to the first valve (104) supply port (108) and a second position wherein the first valve (104) discharge port (116)is fluidly interconnected to the first valve ( 104) exhaust port (118).

9. The brake actuator (10) of claim 7 or 8 wherein the second valve (106) is movable between a first position wherein the second valve (106) discharge port (120)is fluidly interconnected to the second valve (106) control port (118) and a second position wherein the second valve (106) discharge port (120) is fluidly interconnected to the second valve ( 106) exhaust port ( 122).

10. The brake actuator (10) of claim 8 or 9 wherein the first valve (104) is moved to the first position when the source (114) of pressurized air is actuated whereby the pressurized air is supplied to the first chamber (27) and the movable member (32) is moved to an actuated position. -17-

11. The brake actuator ( 10) of claim 9 or 10 wherein the second valve (106) is moved to the second valve (106) first position as the first valve (104) is moved to the first valve (104) first position whereby air exiting the second chamber

(31) is released through the second valve (106) into the exhaust port (122).

12. The brake actuator (10) of any of claims 8 through 11 wherein the first valve (104) is moved to the second position when the source (114) of pressurized air is deactivated whereby the pressurized air is released from the first chamber (27) through the first valve (104) exhaust port (118) and the movable member (32) is moved to a non-operative position.

13. The brake actuator ( 10) of any of claims 9 through 12 wherein the second valve (106) is moved to the second valve (106) second position as the first valve (104) is moved to the first valve (104) second position whereby air enters the second chamber (31) through the second valve (106) control port (118) and second valve (106) discharge port.

14. The brake actuator ( 10) of claim 2 wherein the first valve ( 104), (144) is movable between a first position wherein the first valve (104), (144) fluidly interconnects the pneumatic source (114) to the first chamber (27) and a second position wherein the first valve (104), (144) exhausts air from the first chamber (27) .

15. The brake actuator ( 10) of claim 14 wherein the first valve (104), (144) is moved to the first position when the pneumatic source (114) is actuated whereby pressurized air is supplied to the first chamber (27) and the movable member

(32) is moved to an actuated position.

16. The brake actuator of claim 14 or 15 wherein the first valve (104), (144) is moved to the second position when the pneumatic source (114) is deactivated whereby the pressurized air is released from the first chamber (27) through the first valve (104) and the movable member (32) is moved to a non- operative position. -18-

17. The brake actuator (10) of claim 2, 14, 15, or 16 wherein the second valve (106) is movable between a first position wherein the second valve (106) fluidly interconnects the second chamber (31) to the first chamber (27) and a second position wherein the second valve (106) exhausts air from the second chamber (31).

18. The brake actuator ( 10) of claim 17 wherein the second valve (106) is moved to the second valve (106) first position as the pneumatic source (114) is actuated whereby air exiting the second chamber (31) is released through the second valve (106).

19. The brake actuator (10) of claim 17 or 18 wherein the second valve (106) is moved to the second valve (106) second position as the first valve (104) is deactivated whereby air is directed into the second chamber (31).

20. The brake actuator (10) of claim 1 wherein control valve (102) comprises a first valve (104), (144) having:

(a) a supply port (108), (146) fluidly interconnected to the pneumatic source (114) ; (b) a discharge port (116), ( 150) fluidly interconnected to the first chamber (27) ; and

(c) an exhaust port (118), (152) fluidly interconnected to the second chamber (31).

21. The brake actuator ( 10) of claim 1 or 20 wherein the control valve (102) further comprises a second valve (106), (154) fluidly interconnected to one of the atmosphere and the pneumatic source (114).

22. The brake actuator (10) of claim 27 wherein the second valve (106), (154) is fluidly interconnected to the second chamber (31).

23. The brake actuator ( 10) of claim 21 wherein the second valve (106), (154) is a one-way check valve adapted to exhaust air from the second chamber (31) when the pressure therein reaches a predetermined value and thereby prevents -19- rerurn flow of air into the second chamber (31) regardless of the internal pressure in the second chamber (31).

24. The brake actuator ( 10) of claims 21 , 22 or 23 wherein the second valve (106), (154) is sealingly mounted within the housing.

25. The brake actuator ( 10) of any of claims 20 through 24 wherein the first valve (104), (144) is movable between a first position wherein the discharge port (116), (150) is fluidly interconnected to the supply port (108), (146) and a second position wherein the discharge port (116), (150) is interconnected to the exhaust port (118), (152).

26. The brake actuator (10) of claim 35 wherein the first valve (104), (144) is moved to the first position upon actuation of the source (114) of pressurized air whereby the pressurized air is supplied to the first chamber (27) through the discharge port (116), (150) whereby sufficient compressed air is supplied to the first chamber (27) to move the movable member (32) and, in turn, the actuator rod to an actuated position while, simultaneously, air in the second chamber (31) is exhausted through the second valve (106), (154).

27. The brake actuator ( 10) of claims 25 or 26 wherein the first valve (104), (144) is moved to the second position when the source of pressurized air is de-activated whereby pressurized air in the first chamber (27) is passed to the second chamber (31 ) through the first valve ( 104), ( 144) exhaust port ( 118), ( 152) as the movable member (32) returns to an unactuated position.

28. The brake actuator ( 10) of any of claims 25 through 27 wherein excess air in the second chamber (31) as a result of the movement of the first valve (104), (144) to the second position above a predetermined value is released through the second valve (106), (154).

29. The brake actuator ( 10) of any of claims 21 through 28 wherein the second valve (106), (154) is sealingly mounted within the housing. -20-

30. The brake actuator (10) of any of claims wherein the first valve

(104), (144) is a quick release valve.

31. The brake actuator ( 10) of any of claims wherein in the second valve (106), (154) is a pilot valve.

32. The brake actuator ( 10) of any of the claims herein wherein the movable member (32) is a diaphragm.

33. The brake actuator ( 10) of any of the claims herein wherein the movable member (32) is a piston.

34. The brake actuator (10) of any of the claims herein wherein the control valve (102) is remote from the brake actuator housing.

35. The brake actuator (10) of any of the claims herein wherein the control valve (102) is elevated with respect to the brake actuator housing whereby the control valve (102) is not submerged if the housing is lowered into standing water.

36. The brake actuator ( 10) of any of the claims herein wherein brake actuator (10) is a service brake actuator.

37. The brake actuator (10) of any of the claims herein wherein brake actuator (10) is a spring brake actuator.

38. The brake actuator (10) of any of the claims herein wherein brake actuator (10) is a tandem service and spring brake actuator.