CA1057797A - Brake system - Google Patents
Brake systemInfo
- Publication number
- CA1057797A CA1057797A CA309,630A CA309630A CA1057797A CA 1057797 A CA1057797 A CA 1057797A CA 309630 A CA309630 A CA 309630A CA 1057797 A CA1057797 A CA 1057797A
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- fluid
- brake
- valve
- air
- conduit
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Abstract
BRAKE SYSTEM
Abstract A brake system for stopping rotation of a pair of inde-pendently rotatable elements of a vehicle including a valve arrangement for controlling the application of a fluid applied brake and a spring applied, fluid released brake individually associated with the rotatable elements by simultaneously increasing fluid pressure to the fluid applied brake and decreasing fluid pressure to the spring applied, fluid released brake for stopping rotation of both rotatable elements.
Abstract A brake system for stopping rotation of a pair of inde-pendently rotatable elements of a vehicle including a valve arrangement for controlling the application of a fluid applied brake and a spring applied, fluid released brake individually associated with the rotatable elements by simultaneously increasing fluid pressure to the fluid applied brake and decreasing fluid pressure to the spring applied, fluid released brake for stopping rotation of both rotatable elements.
Description
~os77st7 This application is divided out of copending Canadian application No. 225,012 filed April 18, 1975.
A common form of vehicle service brake systems employs a master cylinder which may be operated to transmit a fluid pressure to individual brakes at each of the vehicle wheels for the purpose of applying the brakes.
~leavy trucks, earthmoving vehicles and the like often have a pneumatic circuit for actuating the master cylinder or cylinders in response to manipulation of an operator's brake control. It is customary to supplement the service brake system with an emergency brake system which may be independent of or an integral part of the service brake system.
In many cases, the emergency brake is of the spring applied fluid released type for braking the rear wheels only. Such emergency brakes are generally automatically applied by the actuating springs upon loss of fluid pressure in the service brakes. While this is fundamentally a valuable safety measure it can also complicate the operator's task. If conditions permit, the operator would generally prefer to bring the vehicle to a more controlled emergency stop by modulated controllable braking rather than by suddenly having the brakes locked on and out of manual control. Furthermore, under certain conditions, it is desirable to be able simultaneously to actuate the emergency brake on the rear wheels along with the front service brakes for additional braking power. However, this has not heretofore been possible since the front brakes are applied by an increase in fluid pressure and the rear brakes are only applied by a loss of fluid pressure.
It is also desirable to be able to tow the vehicle without the brakes applied and it is the particular object of the invention of this divisional application to provide for that desirability.
A common form of vehicle service brake systems employs a master cylinder which may be operated to transmit a fluid pressure to individual brakes at each of the vehicle wheels for the purpose of applying the brakes.
~leavy trucks, earthmoving vehicles and the like often have a pneumatic circuit for actuating the master cylinder or cylinders in response to manipulation of an operator's brake control. It is customary to supplement the service brake system with an emergency brake system which may be independent of or an integral part of the service brake system.
In many cases, the emergency brake is of the spring applied fluid released type for braking the rear wheels only. Such emergency brakes are generally automatically applied by the actuating springs upon loss of fluid pressure in the service brakes. While this is fundamentally a valuable safety measure it can also complicate the operator's task. If conditions permit, the operator would generally prefer to bring the vehicle to a more controlled emergency stop by modulated controllable braking rather than by suddenly having the brakes locked on and out of manual control. Furthermore, under certain conditions, it is desirable to be able simultaneously to actuate the emergency brake on the rear wheels along with the front service brakes for additional braking power. However, this has not heretofore been possible since the front brakes are applied by an increase in fluid pressure and the rear brakes are only applied by a loss of fluid pressure.
It is also desirable to be able to tow the vehicle without the brakes applied and it is the particular object of the invention of this divisional application to provide for that desirability.
- 2 -. ~ ~ ", 1(~5~7~7 According to the invention there is provided a brake system for a vehicle comprising a first source of pressurized fluid; a spring applied fluid released brake which is automatically applied in the absence of actuating fluid thereto, a fluid conduit connecting said first source of pressurized fluid to said springapplied fluid released brake; valve means disposed in said fluid conduit and having a position for directing pressurized fluid to said spring applied fluid released brake releasing said spring applied fluid released brake, said valve means being selectively positionable to block fluid flow to said spring applied fluid released brake; a second source of pressurized fluid; a fluid applied brake; conduit means connecting said second source of pressurized fluid to said fluid applied brake; valve means disposed in said conduit means for controlling flow of pressurized fluid therethrough and selectively positionable to direct pressurized fluid through said conduit means to apply said fluid applied brake; and a towing valve disposed in said conduit means having a first position for communicating said pressurized fluid from said second source of pressurized fluid to said fluid applied brake and selectively positionable to connect said conduit means to said fluid conduit for communicating said pressurized fluid from said second source of pressurized fluid to said spring applied fluid released brake for releasing said spring applied fluid released brake to permit the vehicle to be towed in the absence of pressurized fluid from said first source of pressurized fluid.
~s~ ,"
1~57797 Brief Description of the Drawing The sole figure is a schematic drawing of a brake system embodying the principles of the present invention.
Description of the Preferred Embodiment Referring more particularly to the drawing, a brake system embodying the principles of the present invention is generally in-dicated by the reference numeral 10 in association with a pair of front wheels 11 of a vehicle, not shown, and a pair of rotatable shafts 12 each of which is operatively associated with a rear wheel, not shown, for such a vehicle. A pair of fluid applied front brake mechanisms 13 are individually operatively associated with the front wheels 11 for stopping rotation thereof in the usual manner. A pair of rear brake mechanisms 14 are individually associated with the rotatable shafts 12 for stopping rotation thereof when the brakes are applied.
Each of the rear brake mechanisms 14 includes a nonrotatable housing 16 having an end wall 17. A first annular piston 18 is dis-posed within the housing and adapted to clamp a plurality of alter-nately interleaved stationary and rotatable discs 19 against the end wall 17 for stopping rotation of the shaft 12. An actuating chamber 21 is formed between the first piston and the housing and is adapted to receive pressurized fluid to move the piston toward the end wall as will hereinafter be described. A second annular piston 22 is disposed within the housing and is resiliently urged into abutting engagement with the first piston by a plurality of springs 23 such that the discs are clamped against the end wall. An actuating chamber 24 is formed by the second piston and the housing and is adapted to receive fluid to move the second piston against the bias of the springs for freeing the first piston, which is retracted by return springs, not shown.
~577~7 Actuation of the front and rear brake mechanisms 13 and 14 is controlled through a control system 26 having a service brake cir-cuit 27, a retarder circuit 28, and an emergency brake and parking circuit 29. An air tank 32 is common to both the service brake cir-cuit and the retarder circuit and stores pressurized fluid directed thereto through a check valve 33 from a compressor, not shown. The service brake circuit includes a first air actuated relay valve 34 disposed within a line 36 connecting the air tank with a master cylin-der 37 and is normally resiliently positioned for blocking air flow through the line. A second air actuated relay valve 38 is disposed withln a line 39 co~necting the air tank with a double check valve 42 and is normally resiliently positioned for blocking air flow through the line. A manually controllable service brake valve 43 is disposed within a line 44 connecting the air tank with one end of the first relay valve 34 and is normally resiliently positioned for blocking flow of actuating air to the first relay valve. A branch line 45 connects the line 44 between valves 43 and 34 with one end of the second relay valve 38. A manually actuatable on-off valve 46 is disposed within the line 45 for controlling flow of actuating air to the second relay valve.
The master cylinder 37 is of the usual type having an air chamber 50 connected to the line 36 and a fluid chamber 51 separated from the air chamber by a stepped actuator piston 52. A conduit 53 connects the fluid chamber with a double check valve 54 which in turn is connected by a conduit 56 to the actuating chambers 21 of the rear brake mechanisms 14. The fluid chamber is also connected to a makeup tank 57 through a check valve 58.
A line 59 connects the check valve 42 with an air chamber 61 of a master cylinder 62. A fluid chamber 63 of the master cylinder is separated from the air chamber by a stepped piston 64 and is connected 1~)577~7 to the front brake mechanisms 13 through a conduit 66. A fluid makeup tank 67 is connected to the fluid chamber through a check valve 68.
The retarder circuit 28 includes an air actuated relay valve 69 disposed within a line 70 eonnecting the air tank 32 with an air chamber 71 of a master cylinder 72. A manually positionable control valve 73 is disposed within a line 74 connecting the air tank with one end of the relay valve 69. A fluid chamber 76 is separated from the air chamber by a stepped piston 77 and is connected to the double check valve 54 by a conduit 78 which has a two-position manual towing valve 79 disposed therein. The towing valve is normally suitably retained in the position shown to permit fluid flow through the conduit 78 to the double check valve.
The emergency and parking brake circuit 29 includes an air actuated modulating valve 82 disposed within a conduit 83 connecting a pump 84 with the aetuating chambers 24 of the brake mechanisms 14.
The modulating valve is normally resiliently positioned to communicate the actuating chambers with a tank 85. A check valve 86 is disposed within the conduit 83 between the pump and the modulating valve. A
normally closed pressure switch 87 is in communication with the con-duit 83 and controls an electrical circuit to a warning light 88. Amanual emergency valve 89 and a parking valve 91 are disposed in series within a line 92 which is connected to and transmits actuating air from an air tank 93 to one end of the modulating valve 82. The air tank receives pressurized air from the compressor, not shown, through a check valve 94. An air actuated inversion valve 96 is disposed within a line 97 connecting the air tank 93 with the double check valve 42 and is normally resiliently positioned to permit air flow there-through. A line 98 is connected to the line 92 between the manual emergency valve and the parking brake valve and communicates actuating air from the manual emergency valve to one end of the inversion valve.
1~5'7'7~';'' The relay valves 34, 38 and 69, the inversion valve 96, the service brake valve 43, the retarder valve 73, and the emergency brake valve 89 are of the type wherein air flow therethrough is selectively modulatable. Likewise, the modulating valve 82 is constructed for modulating fluid flow therethrough.
Operation ~ hile the operation of the present invention is believed clearly apparent from the foregoing description, further amplifica-tion will subsequently be made in the following brief summary of such operation. The air compressor and the pump 84 are driven by the vehicle engine in the usual manner such that the air tanks 32 and 93 are pressurized by the air compressor automatically after the engine is started and fluid from the pump is directed to the modulating valve 82. The valves 89 and 91 are normally in the position shown so that pressurized air is transmitted through line 92 to shift the modulating valve to a position for communicating the pump 84 with the chambers 24 of the brake mechanisms 14 through the conduit 83. The fluid in these chambers moves the second pistons 22 against the bias of the springs 23 and frees the first piston 18 for normal service brake operations.
Manually positioning the on-off valve 46 permits the operator to choose between service braking with the rear brake mechanisms 14 only or the combination of both front and rear brake mechanisms 13 and 14. With the valve 46 in the position shown, cnly the brake mechanisms 14 are employed for normal service braking which is init-iated by manually positioning the service brake valve 43 for directing pressurized air to the end of the first relay valve 34. The first relay valve is in turn shifted to establish communieation through line 36 to the air chamber 50 of the master cylinder 37. The pressurized air in the air chamber acts against the piston 52 which pressurizes the fluid in the fluid chamber 51 and directs such fluid through l~S77~'7 conduit 53, check valve 54 and conduit 56 to the chambers 21 of the rear brake mechanisms for moving the first pistons 18 toward the end walls 17 of the housings 16. The first pistons clamp the discs 19 against the end walls stopping rotation of the shafts 12 and thus the rear wheels. Releasing the service brake valve results in the air chamber 50 being vented to the atmosphere and releases the rear brake mechanisms.
Manually shifting the on-off valve 46 to establish communi-cation through the line 45 results in the simultaneous shifting of both the first and second relay valves 34 and 38, respectively, when the service brake valve 43 is manually shifted. Shifting valve 34 causes the rear brake mechanisms 14 to be applied as previously described while shifting the relay valve 38 directs pressurized air through line 39, double check valve 42, and line 59 to the air chamber 61 of the master cylinder 62. This pressurizes the fluid in the fluid chamber 63 with the fluid being directed to the front brake mechanisms 13 thereby stopping rotation of the wheels 11. Thus, with the on-off valve shifted both brake mechanisms 13 and 14 are applied simultan-eously.
Considering now the retarding mode of braking, the control valve 73 is manually shifted to direct pressurized air to the end of the relay valve 69 which in turn is shifted to communicate pressurized air to the air chamber 71 of the master cylinder 72. The control valve 73 is preferably frictionally retarded or detented so that it can be positioned in predetermined increments for precisely controlling the air flow directed to the relay valve and thus to the master cylinder. The air pressure in the air chamber results in pressuri-zation of the fluid in the fluid chamber 76 with the fluid being directed through the conduit 78, the normally open towing valve 79, the 30 double check valve 54, conduit 56 and into the actuating chambers 21 1~57~7 of the rear brake mechanisms 14. The fluid in the actuating chambers moves the first pistons 18 against the discs 19 an amount proportional to the air pressure in the air chamber 71 of the master cylinder.
Thus the rear brake mechanisms are applied for the purpose of con-trolling vehicle speed while traveling down a slope. Returning the control valve 73 to the position shown releases the brake mechanisms to permit rotation of the shafts 12.
The manually controlled emergency braking mode of operation is initiated by manually shifting the manual emergency valve 89 simul-taneously to block flow of pressurized actuating air through lines92 and 98 permitting the modulating valve 82 and the inversion valve 96 to be resiliently shifted toward their normal position. Shifting the modulating valve toward its normal position results in blocking fluid flow from the pump 84 while modulating the exhausting of fluid from the chambers 24 of the brake mechanisms 14. This permits the , H~Lb& 23 to move the second pistons 22 against the first pistons 18 which clamp the discs 19 against the end plates 17 for stopping rotation of the shafts 12. The shifting of the inversion valve 96 toward its normal position by reducing actuating air pressure thereto results in pressurized air being modulatably directed through line 97, the double check valve 42, line 59, and into the air chamber 61 of the master cylinder 62. This causes pressurized fluid to be directed through the conduit 66 to apply the front brake mechan-isms 13 for stopping rotation of the front wheels 11. Thus, both brake mechanisms 13 and 14 are applied simultaneously through the shifting of the manual emergency valve 89.
The rear brake mechanisms 14 may be used as a parking brake by manually shifting the parking brake valve 91. This vents the con-duit 92 permitting the modulation valve 82 to shift to a position blocking fluid flow from the pump 84 while exhausting the actuating l(~S77~7 chambers 24 through the conduit 83. This causes the springs 23 to move the second pistons 22 against the first pistons 18 which in turn clamp the discs 19 against the end plates 17 for preventing rotation of the shafts 12.
Although the brake system 10 is arranged to minimize the probability of the rear brake mechanisms 14 being suddenly applied and out of control of the operator, the rear brake mechanisms are auto-matically applied under certain conditions for safety reasons. For example, a loss of pressurized fluid from conduit 83 results in auto-matic application of the rear brake mechanisms. Likewise, a suddenloss of air pressure in the conduit 92 permits the modulating valve 82 to shift to block fluid flow from the pump while exhausting the fluid from chambers 24 and conduit 83 permitting the springs 23 to apply the rear brake mechanisms.
The towing valve 79 is included to provide an alternate source of pressurized fluid for releasing the rear brake mechanisms 14 when fluid pressure is not available from the pump 84 such as when the engine is inoperative. Of course, the towing mode of operation is dependent upon having pressurized air in the air tanks 32 and 93.
In some cases sufficient air pressure may remain in the air tanks for the towing operations while in other cases it may be necessary to connect the air tanks to the air system of the towing vehicle. With air pressure in tank 93, the modulating valve 82 is shifted to permit fluid flow through conduit 83. The towing mode is initiated by shifting the towing valve 79 to connect the conduit 78 to the conduit 83. The control valve 73 of the retarder circuit 28 is then manually shifted to direct actuating air to shift the relay valve 69 which in turn causes pressurized air to be directed to the air chamber 71. This results in pressurized fluid from the fluid chamber 76 being directed through conduit 78, towing valve 79, conduit 83 and into the chambers 24. The 1()577~
pressurized fluid in tbe chambers moves the second pistons against the bias of the springs 23 to release the clamping force on the discs 19.
While the vehicle is being towed, both brake mechanisms 13 and 14 can be applied to stop the vehicle by actuation of the valve 89 as pre-viously described.
In view of the foregoing it is readily apparent that the structure of the present invention provides an improved brake system which provides for the simultaneous application of a fluid applied brake and a spring applied fluid released brake by the manual manipu-lation of a single control valve. This is accomplished by providingan air actuated modulating valve for controlling fluid flow to the spring applied fluid released brake and an air actuated inversion valve for controlling fluid flow to the fluid applied brake. Reducing the flow of actuation air to the modulating valve causes it to shift toward a position for blocking fluid flow therethrough for-s ~ ~ the spring applied~released brake while reducing the flow of actuating air to the inversion valve causes it to shift toward a position for directing pressurized fluid to apply the fluid applied brake. Thus, by controlling the flow of actuating air to the modulating and in-version valves by a single control valve, both brakes are actuatedsimultaneously. Also, the spring applied fluid released brake is always available for automatic emergency braking when fluid pressure is lost from the system. Furthermore, the spring applied fluid re-leased brake may be independent of or an integral part of a service brake mechanism with the spring applied fluid release brake providing an emergency brake system to supplement the service brake system.
While the invention has been described and shown with par-ticular reference to the preferred embodiment, it will be apparent that variations might be possible that would fall within the scope of the present invention which is not intended to be limited except as defined in the following claims.
~s~ ,"
1~57797 Brief Description of the Drawing The sole figure is a schematic drawing of a brake system embodying the principles of the present invention.
Description of the Preferred Embodiment Referring more particularly to the drawing, a brake system embodying the principles of the present invention is generally in-dicated by the reference numeral 10 in association with a pair of front wheels 11 of a vehicle, not shown, and a pair of rotatable shafts 12 each of which is operatively associated with a rear wheel, not shown, for such a vehicle. A pair of fluid applied front brake mechanisms 13 are individually operatively associated with the front wheels 11 for stopping rotation thereof in the usual manner. A pair of rear brake mechanisms 14 are individually associated with the rotatable shafts 12 for stopping rotation thereof when the brakes are applied.
Each of the rear brake mechanisms 14 includes a nonrotatable housing 16 having an end wall 17. A first annular piston 18 is dis-posed within the housing and adapted to clamp a plurality of alter-nately interleaved stationary and rotatable discs 19 against the end wall 17 for stopping rotation of the shaft 12. An actuating chamber 21 is formed between the first piston and the housing and is adapted to receive pressurized fluid to move the piston toward the end wall as will hereinafter be described. A second annular piston 22 is disposed within the housing and is resiliently urged into abutting engagement with the first piston by a plurality of springs 23 such that the discs are clamped against the end wall. An actuating chamber 24 is formed by the second piston and the housing and is adapted to receive fluid to move the second piston against the bias of the springs for freeing the first piston, which is retracted by return springs, not shown.
~577~7 Actuation of the front and rear brake mechanisms 13 and 14 is controlled through a control system 26 having a service brake cir-cuit 27, a retarder circuit 28, and an emergency brake and parking circuit 29. An air tank 32 is common to both the service brake cir-cuit and the retarder circuit and stores pressurized fluid directed thereto through a check valve 33 from a compressor, not shown. The service brake circuit includes a first air actuated relay valve 34 disposed within a line 36 connecting the air tank with a master cylin-der 37 and is normally resiliently positioned for blocking air flow through the line. A second air actuated relay valve 38 is disposed withln a line 39 co~necting the air tank with a double check valve 42 and is normally resiliently positioned for blocking air flow through the line. A manually controllable service brake valve 43 is disposed within a line 44 connecting the air tank with one end of the first relay valve 34 and is normally resiliently positioned for blocking flow of actuating air to the first relay valve. A branch line 45 connects the line 44 between valves 43 and 34 with one end of the second relay valve 38. A manually actuatable on-off valve 46 is disposed within the line 45 for controlling flow of actuating air to the second relay valve.
The master cylinder 37 is of the usual type having an air chamber 50 connected to the line 36 and a fluid chamber 51 separated from the air chamber by a stepped actuator piston 52. A conduit 53 connects the fluid chamber with a double check valve 54 which in turn is connected by a conduit 56 to the actuating chambers 21 of the rear brake mechanisms 14. The fluid chamber is also connected to a makeup tank 57 through a check valve 58.
A line 59 connects the check valve 42 with an air chamber 61 of a master cylinder 62. A fluid chamber 63 of the master cylinder is separated from the air chamber by a stepped piston 64 and is connected 1~)577~7 to the front brake mechanisms 13 through a conduit 66. A fluid makeup tank 67 is connected to the fluid chamber through a check valve 68.
The retarder circuit 28 includes an air actuated relay valve 69 disposed within a line 70 eonnecting the air tank 32 with an air chamber 71 of a master cylinder 72. A manually positionable control valve 73 is disposed within a line 74 connecting the air tank with one end of the relay valve 69. A fluid chamber 76 is separated from the air chamber by a stepped piston 77 and is connected to the double check valve 54 by a conduit 78 which has a two-position manual towing valve 79 disposed therein. The towing valve is normally suitably retained in the position shown to permit fluid flow through the conduit 78 to the double check valve.
The emergency and parking brake circuit 29 includes an air actuated modulating valve 82 disposed within a conduit 83 connecting a pump 84 with the aetuating chambers 24 of the brake mechanisms 14.
The modulating valve is normally resiliently positioned to communicate the actuating chambers with a tank 85. A check valve 86 is disposed within the conduit 83 between the pump and the modulating valve. A
normally closed pressure switch 87 is in communication with the con-duit 83 and controls an electrical circuit to a warning light 88. Amanual emergency valve 89 and a parking valve 91 are disposed in series within a line 92 which is connected to and transmits actuating air from an air tank 93 to one end of the modulating valve 82. The air tank receives pressurized air from the compressor, not shown, through a check valve 94. An air actuated inversion valve 96 is disposed within a line 97 connecting the air tank 93 with the double check valve 42 and is normally resiliently positioned to permit air flow there-through. A line 98 is connected to the line 92 between the manual emergency valve and the parking brake valve and communicates actuating air from the manual emergency valve to one end of the inversion valve.
1~5'7'7~';'' The relay valves 34, 38 and 69, the inversion valve 96, the service brake valve 43, the retarder valve 73, and the emergency brake valve 89 are of the type wherein air flow therethrough is selectively modulatable. Likewise, the modulating valve 82 is constructed for modulating fluid flow therethrough.
Operation ~ hile the operation of the present invention is believed clearly apparent from the foregoing description, further amplifica-tion will subsequently be made in the following brief summary of such operation. The air compressor and the pump 84 are driven by the vehicle engine in the usual manner such that the air tanks 32 and 93 are pressurized by the air compressor automatically after the engine is started and fluid from the pump is directed to the modulating valve 82. The valves 89 and 91 are normally in the position shown so that pressurized air is transmitted through line 92 to shift the modulating valve to a position for communicating the pump 84 with the chambers 24 of the brake mechanisms 14 through the conduit 83. The fluid in these chambers moves the second pistons 22 against the bias of the springs 23 and frees the first piston 18 for normal service brake operations.
Manually positioning the on-off valve 46 permits the operator to choose between service braking with the rear brake mechanisms 14 only or the combination of both front and rear brake mechanisms 13 and 14. With the valve 46 in the position shown, cnly the brake mechanisms 14 are employed for normal service braking which is init-iated by manually positioning the service brake valve 43 for directing pressurized air to the end of the first relay valve 34. The first relay valve is in turn shifted to establish communieation through line 36 to the air chamber 50 of the master cylinder 37. The pressurized air in the air chamber acts against the piston 52 which pressurizes the fluid in the fluid chamber 51 and directs such fluid through l~S77~'7 conduit 53, check valve 54 and conduit 56 to the chambers 21 of the rear brake mechanisms for moving the first pistons 18 toward the end walls 17 of the housings 16. The first pistons clamp the discs 19 against the end walls stopping rotation of the shafts 12 and thus the rear wheels. Releasing the service brake valve results in the air chamber 50 being vented to the atmosphere and releases the rear brake mechanisms.
Manually shifting the on-off valve 46 to establish communi-cation through the line 45 results in the simultaneous shifting of both the first and second relay valves 34 and 38, respectively, when the service brake valve 43 is manually shifted. Shifting valve 34 causes the rear brake mechanisms 14 to be applied as previously described while shifting the relay valve 38 directs pressurized air through line 39, double check valve 42, and line 59 to the air chamber 61 of the master cylinder 62. This pressurizes the fluid in the fluid chamber 63 with the fluid being directed to the front brake mechanisms 13 thereby stopping rotation of the wheels 11. Thus, with the on-off valve shifted both brake mechanisms 13 and 14 are applied simultan-eously.
Considering now the retarding mode of braking, the control valve 73 is manually shifted to direct pressurized air to the end of the relay valve 69 which in turn is shifted to communicate pressurized air to the air chamber 71 of the master cylinder 72. The control valve 73 is preferably frictionally retarded or detented so that it can be positioned in predetermined increments for precisely controlling the air flow directed to the relay valve and thus to the master cylinder. The air pressure in the air chamber results in pressuri-zation of the fluid in the fluid chamber 76 with the fluid being directed through the conduit 78, the normally open towing valve 79, the 30 double check valve 54, conduit 56 and into the actuating chambers 21 1~57~7 of the rear brake mechanisms 14. The fluid in the actuating chambers moves the first pistons 18 against the discs 19 an amount proportional to the air pressure in the air chamber 71 of the master cylinder.
Thus the rear brake mechanisms are applied for the purpose of con-trolling vehicle speed while traveling down a slope. Returning the control valve 73 to the position shown releases the brake mechanisms to permit rotation of the shafts 12.
The manually controlled emergency braking mode of operation is initiated by manually shifting the manual emergency valve 89 simul-taneously to block flow of pressurized actuating air through lines92 and 98 permitting the modulating valve 82 and the inversion valve 96 to be resiliently shifted toward their normal position. Shifting the modulating valve toward its normal position results in blocking fluid flow from the pump 84 while modulating the exhausting of fluid from the chambers 24 of the brake mechanisms 14. This permits the , H~Lb& 23 to move the second pistons 22 against the first pistons 18 which clamp the discs 19 against the end plates 17 for stopping rotation of the shafts 12. The shifting of the inversion valve 96 toward its normal position by reducing actuating air pressure thereto results in pressurized air being modulatably directed through line 97, the double check valve 42, line 59, and into the air chamber 61 of the master cylinder 62. This causes pressurized fluid to be directed through the conduit 66 to apply the front brake mechan-isms 13 for stopping rotation of the front wheels 11. Thus, both brake mechanisms 13 and 14 are applied simultaneously through the shifting of the manual emergency valve 89.
The rear brake mechanisms 14 may be used as a parking brake by manually shifting the parking brake valve 91. This vents the con-duit 92 permitting the modulation valve 82 to shift to a position blocking fluid flow from the pump 84 while exhausting the actuating l(~S77~7 chambers 24 through the conduit 83. This causes the springs 23 to move the second pistons 22 against the first pistons 18 which in turn clamp the discs 19 against the end plates 17 for preventing rotation of the shafts 12.
Although the brake system 10 is arranged to minimize the probability of the rear brake mechanisms 14 being suddenly applied and out of control of the operator, the rear brake mechanisms are auto-matically applied under certain conditions for safety reasons. For example, a loss of pressurized fluid from conduit 83 results in auto-matic application of the rear brake mechanisms. Likewise, a suddenloss of air pressure in the conduit 92 permits the modulating valve 82 to shift to block fluid flow from the pump while exhausting the fluid from chambers 24 and conduit 83 permitting the springs 23 to apply the rear brake mechanisms.
The towing valve 79 is included to provide an alternate source of pressurized fluid for releasing the rear brake mechanisms 14 when fluid pressure is not available from the pump 84 such as when the engine is inoperative. Of course, the towing mode of operation is dependent upon having pressurized air in the air tanks 32 and 93.
In some cases sufficient air pressure may remain in the air tanks for the towing operations while in other cases it may be necessary to connect the air tanks to the air system of the towing vehicle. With air pressure in tank 93, the modulating valve 82 is shifted to permit fluid flow through conduit 83. The towing mode is initiated by shifting the towing valve 79 to connect the conduit 78 to the conduit 83. The control valve 73 of the retarder circuit 28 is then manually shifted to direct actuating air to shift the relay valve 69 which in turn causes pressurized air to be directed to the air chamber 71. This results in pressurized fluid from the fluid chamber 76 being directed through conduit 78, towing valve 79, conduit 83 and into the chambers 24. The 1()577~
pressurized fluid in tbe chambers moves the second pistons against the bias of the springs 23 to release the clamping force on the discs 19.
While the vehicle is being towed, both brake mechanisms 13 and 14 can be applied to stop the vehicle by actuation of the valve 89 as pre-viously described.
In view of the foregoing it is readily apparent that the structure of the present invention provides an improved brake system which provides for the simultaneous application of a fluid applied brake and a spring applied fluid released brake by the manual manipu-lation of a single control valve. This is accomplished by providingan air actuated modulating valve for controlling fluid flow to the spring applied fluid released brake and an air actuated inversion valve for controlling fluid flow to the fluid applied brake. Reducing the flow of actuation air to the modulating valve causes it to shift toward a position for blocking fluid flow therethrough for-s ~ ~ the spring applied~released brake while reducing the flow of actuating air to the inversion valve causes it to shift toward a position for directing pressurized fluid to apply the fluid applied brake. Thus, by controlling the flow of actuating air to the modulating and in-version valves by a single control valve, both brakes are actuatedsimultaneously. Also, the spring applied fluid released brake is always available for automatic emergency braking when fluid pressure is lost from the system. Furthermore, the spring applied fluid re-leased brake may be independent of or an integral part of a service brake mechanism with the spring applied fluid release brake providing an emergency brake system to supplement the service brake system.
While the invention has been described and shown with par-ticular reference to the preferred embodiment, it will be apparent that variations might be possible that would fall within the scope of the present invention which is not intended to be limited except as defined in the following claims.
Claims (4)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A brake system for a vehicle comprising a first source of pressurized fluid; a spring applied fluid released brake which is auto-matically applied in the absence of actuating fluid thereto, a fluid conduit connecting said first source of pressurized fluid to said spring applied fluid released brake; valve means disposed in said fluid conduit and having a position for directing pressurized fluid to said spring applied fluid released brake releasing said spring applied fluid released brake, said valve means being selectively positionable to block fluid flow to said spring applied fluid released brake; a second source of pressurized fluid; a fluid applied brake;
conduit means connecting said second source of pressurized fluid to said fluid applied brake; valve means disposed in said conduit means for controlling flow of pressurized fluid therethrough and selectively positionable to direct pressurized fluid through said conduit means to apply said fluid applied brake; and a towing valve disposed in said conduit means having a first position for communicating said pressurized fluid from said second source of pressurized fluid to said fluid applied brake and selectively positionable to connect said conduit means to said fluid conduit for communicating said pressurized fluid from said second source of pressurized fluid to said spring applied fluid released brake for releasing said spring applied fluid released brake to permit the vehicle to be towed in the absence of pressurized fluid from said first source of pressurized fluid.
conduit means connecting said second source of pressurized fluid to said fluid applied brake; valve means disposed in said conduit means for controlling flow of pressurized fluid therethrough and selectively positionable to direct pressurized fluid through said conduit means to apply said fluid applied brake; and a towing valve disposed in said conduit means having a first position for communicating said pressurized fluid from said second source of pressurized fluid to said fluid applied brake and selectively positionable to connect said conduit means to said fluid conduit for communicating said pressurized fluid from said second source of pressurized fluid to said spring applied fluid released brake for releasing said spring applied fluid released brake to permit the vehicle to be towed in the absence of pressurized fluid from said first source of pressurized fluid.
2. The brake system of claim 1 wherein said first source of pressurized fluid is a hydraulic pump.
3. The brake system of claim 2 wherein said second source of pressurized fluid includes a tank of compressed air and a master
3. The brake system of claim 2 wherein said second source of pressurized fluid includes a tank of compressed air and a master
Claim 3 - continued cylinder having a fluid chamber and actuator means for generating fluid pressure in said fluid chamber in response to pressurized air directed to said master cylinder, said conduit means include a fluid conduit connecting said fluid chamber with said fluid applied brake, and an air conduit connecting said tank of compressed air with said master cylinder, said valve means being disposed in said air conduit with said towing valve being disposed in said fluid conduit.
4. The brake system of claim 3 wherein said valve means includes an air actuated relay valve disposed within said air conduit, an air line connected to said tank of compressed air for delivering actuating air to said relay valve, and a manual control valve dis-posed in said air line selectively positionable for controlling flow of pressurized air through said line for actuating said relay valve.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA309,630A CA1057797A (en) | 1974-11-11 | 1978-08-18 | Brake system |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US522393A US3917037A (en) | 1974-11-11 | 1974-11-11 | Brake system |
| CA225,012A CA1044281A (en) | 1974-11-11 | 1975-04-18 | Brake system |
| CA309,630A CA1057797A (en) | 1974-11-11 | 1978-08-18 | Brake system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057797A true CA1057797A (en) | 1979-07-03 |
Family
ID=27163915
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA309,630A Expired CA1057797A (en) | 1974-11-11 | 1978-08-18 | Brake system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1057797A (en) |
-
1978
- 1978-08-18 CA CA309,630A patent/CA1057797A/en not_active Expired
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