Systems and methods for trailer brake control valves

Abstract

A valve assembly is provided herein. The valve assembly includes a service brake supply line to connect a service brake supply port to a first pump, a brake release valve to connect to a parking brake release line, and a safety valve connected to a supply port of the brake release valve. The safety valve is configured to connect the supply port to a second pump in a first position and to connect the supply port to a tank in a second position. The safety valve comprises an operator to place the safety valve in the second position responsive to a pressure reduction at the service brake supply port.

Description

SYSTEMS AND METHODS FOR TRAILER BRAKE CONTROL VALVESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 558,072, filed February 26, 2024, which is hereby incorporated by reference in its entirety.BACKGROUND

[0002] Off-highway vehicles, such as construction equipment or agricultural tractors, often tow trailers equipped with both service brakes for normal operation and parking brakes for stationary security. These trailers typically utilize a SAHR (Spring Actuated Hydraulically Released) brake system, where springs apply the brakes by default, and hydraulic pressure is used to release them for movement.

[0003] Off-highway vehicles towing trailers typically have two distinct hydraulic brake connections to the trailer. The first connection supplies pressurized fluid from the towing vehicle's hydraulic system to operate the trailer's service brakes. The second connection provides a pressure signal to release the trailer's SAHR parking brake. A trailer brake control valve is typically capable of disabling the pressure signal to the SAHR parking brake if the first connection fails due to rupture, excessive leakage, or disconnection.SUMMARY

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] Some exemplary embodiments are related to a valve assembly. The valve assembly includes a service brake supply line to connect a service brake control line to a first pump, a brake release valve to connect to a parking brake release line, and a safety valve connected to a supply port of the brake release valve. The safety valve is to connect the supply port to a second pump in a first position and to connect the supply port to a tank in a second position. The safety valve comprises an operator to place the safety valve in the second position responsive to a pressure reduction on the service brake supply line.

[0006] Other exemplary embodiments are related to a valve assembly. The valve assembly includes a service brake supply line configured to connect a service brake control line to a first pump, a brake release valve configured to connect to a parking brake release line, and a safety valve connected to a supply port of the brake release valve. The safety valve is configured to connect the supply port to a second pump in a first position, and connect the supply port to a tank in a second position. The valve assembly further includes a sense orifice disposed in the service brake supply line, a first sense pilot line connected to the service brake supply line upstream of the sense orifice, a second sense pilot line connected to the service brake supply line downstream of the sense orifice, and an operator configured to place the safety valve in the second position responsive to a pressure differential between the first sense pilot line and the second sense pilot line.

[0007] Still further exemplary embodiments are related to a method of operating a valve assembly connected to a vehicle. The method includes controlling a service brake supply line to connect a service brake control line to a first pump, controlling a brake release valve connected to a parking brake release line, and operating a safety valve connected to a supply port of the brake release valve responsive to a pressure reduction on the service brake supply line to connect the supply port to a tank in a second position.

[0008] The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.BRIEF DESCRIPTION OF FIGURES

[0009] Non-limiting and non-exhaustive examples are described with reference to the following figures.

[0010] FIG. 1 illustrates a schematic diagram of an example brake control valve in accordance with some aspects of the described technology.

[0011] FIG. 2 illustrates a schematic diagram of an example brake control valve in accordance with some aspects of the described technology.

[0012] FIG. 3 illustrates a schematic diagram of an example brake control valve in accordance with some aspects of the described technology.

[0013] FIG. 4 illustrates a schematic diagram of an example brake control valve in accordance with some aspects of the described technology.

[0014] FIG. 5 illustrates a schematic diagram of an example brake control valve in accordance with some aspects of the described technology.DETAILED DESCRIPTION

[0015] The following description sets forth exemplary aspects of the present disclosure. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure. Rather, the description also encompasses combinations and modifications to those exemplary aspects described herein.

[0016] The technology described below may provide trailer brake control valves. Some such valves comprise two hydraulic brake connections between the towing vehicle and the trailer. A primary connection may deliver pressure from a primary pump to a service brake during normal operation. A secondary connection may deliver pressure from a secondary pump to maintain parking brakes in a released state. A feature of this system may include a pressure sensing safety valve configuration. This configuration may enable the trailer brake control valve to disable the pressure signal to the secondary connection in the event of a failure in the primary connection, such as a rupture, excessive leakage, or disconnection. By implementing this dual-connection system with a safety valve, the technology may enhance brake system reliability and vehicle safety in towing scenarios. In some cases, the safety valve may monitor pressure differentials across a sense orifice to detect failures in the service brake line and respond accordingly.

[0017] The control valves illustrated below represent possible implementations and may be realized through any logically equivalent fluidic circuit. It should be understood that these control valves are not necessarily contained within a common manifold and may instead be implemented as any system of coupled valves that achieves the described functionality. Additionally, while described with respect to hydraulic valves, thetechnology may be implemented via any fluidic power system, including pneumatic as well as hydraulic circuits. Further, while various valves may be described with respect to discrete positions, some examples may include variable position valves. Thus, unless indicated otherwise, description of a valve being in a first position or a second position should be understood as including the valve being in an intermediate position between the first and second (e.g., to provide variable flow / pressure). Moreover, the described valve assemblies may include various supportive components, such as dampening orifices, check valves, or the like; explicit inclusion of such supportive components in some places does not imply their exclusion in others.

[0018] An example brake control valve 100 for controlling service and parking brakes of a towed device is illustrated in FIG. 1. While some examples may be described with respect to off-highway vehicles, brake control valve 100 may be used in any dual line hydraulic braking system. The brake control valve 100 may include various input and output ports to connect to a vehicle's hydraulic braking system. For example, the brake control valve 100 may include a brake signal input port 103 to receive a pressure signal from a human-mechanical braking interface (such as a foot pedal 101 ), a first pressure supply port 105 to connect to a first pump 102, a second pump input port 140 to connect to a second pump 141 , a tank port 146 to connect to a tank 147 (e.g., a hydraulic reservoir), a service brake output port 153 for a service brake 157, and a parking brake release port 154 for a parking brake 158. In some examples, brake control valve 100 may include further ports, such as a load sense port 104 connected to a pilot line 131 connected to a service brake supply line 136, an excess flow port 120, or a secondary output port 155. While not illustrated, valve 100 may include various electrical connections to connect to operators 128, 149, as discussed below.

[0019] In some implementations, the service brake 157 is hydraulically actuated and parking brakes 158 are spring actuated and hydraulically released (SAHR). In some such examples, the first pump 102 provides pressure to actuate the service brake 157 while the second pump 141 provides pressure to release the parking brakes 158. In these examples, loss of pressure at port 153 releases the service brake 157 while loss of pressure at parking brake release port 154 causes the parking brakes 158 to engage. In some implementations, the first pump 102 may operate at a higher pressure rangecompared to a second pump 141. For example, the first pump 102 may operate at pressures ranging from 120 to 200 bar, while the second pump 141 may operate at pressures ranging from 20 to 40 bar. The brake control valve 100 may be configured to disable the pressure signal (e.g., to release pressure supplied via port 156) to the parking brake 158 in a pressure loss event to the service brake 157.

[0020] The brake control valve 100 may include a priority valve 109 to provide a prioritized pressure for service brake output port 153. In the illustrated example, the prioritized output port of the priority valve 109 may be connected to a supply port of the brake pressure regulating valve 129. As an example, the priority valve 109 may connect to the first pump 102 via the supply port 105. In the illustrated, example, priority valve 109 may comprise a three-position spring return valve. A pilot 107 may be connected to a supply line 106 of the priority valve 109 to actuate the valve from its first position 110 to its third position 112 based on system pressure. In some examples, the pilot 107 may include a dampening orifice 115 to stabilize the operation of the priority valve from transient pressure fluctuations (e.g., pressure ripples) at the supply port 105.

[0021] The priority valve 109 may be biased by a return spring to the first position 110 when no pilot pressure is applied. In position three 112, excess flow from the first pump 102 may be directed through an excess flow port 120. The valve 109 is closed in the first position 110 while positions 111 or 112 provide direct flow between the first pump 102 and a brake pressure regulating valve 129. In the second position 111 , excess flow port 120 is closed so that all flow is directed to the pressure regulating valve 129. In the third position, the excess flow port 120 is open (e.g., to provide flow for secondary hydraulic systems).

[0022] In some examples, a second pilot 131 may be coupled to valve 109 to bias the valve 109 towards the first position 110. In this configuration, pressure on the service brake supply line 136 (e.g., when the service brake 157 is engaged) increases the biasing force on the priority valve 109 and further prioritizes the service brake supply line 136 (e.g., by increasing the pressure on pilot 107 necessary to actuate the valve 109). In some cases, pilot 131 may be shared by a load sense port 104.

[0023] The illustrated control valve 100 may include a brake signal input port 103 to receive a pressure signal to actuate the service brake 157. For example, a pedal pressure line 108 may extend from the brake signal input port 103 to control the pressure regulating valve 129. Of course, a pedal is simply an example of a human mechanical interface, alternative brake control mechanisms may include a hand lever connected to a hydraulic master cylinder or other suitable human-mechanical brake interfaces. In the illustrated example, the brakes may be further controllable via an electronic valve 119, as discussed below. Here, a shuttle valve 114 may comprise a first input port connected to pressure line 108 and a second input port connected via line 118 to electronic valve 119. The shuttle valve 114 may include an output port connected to a pilot line 113. Thus, the shuttle valve 114 may pressurize the pilot line 113 based on input from the pedal pressure line 108 or a valve line 118. In this example, the output pilot line 113 may actuate a pilot operator 124 of the pressure regulating valve 129 to control pressurization of service brake supply line 136.

[0024] The brake pressure regulating valve 129 may control service brake pressure by connecting the service brake supply line 136 to the first pump 102 in a first position 125 and the tank 147 in a second position 126. A first pilot operator 124 may be actuated by the pilot 113 as discussed above, moving the valve into the first position 125. The brake pressure regulating valve 129 may be actuated into the second position 126 by two additive operators: a line pressure operator 116 connected to a tank line 132, and a pilot operator 127 connected to a pilot line 131. In this example, the pilot line 131 may be connected to the service brake supply line 136, so that the pressure on line 136 actuates the valve 129 and releases the service brake 157 (e.g., when pressure on pilot 113 is reduced by easing on the pedal 101 , etc.). The line pressure operator 116 may be connected to a tank line 132 to bias the valve 129 to the second position 126.

[0025] The control valve 100 may include an electronic pressure regulating valve (EPRV) 119 connected to the pilot 113 to actuate the pressure regulating valve 129. For example, an output line 118 of the EPRV 119 may be connected to a second input port of the shuttle valve 114. In this example, the EPRV 119 may comprise a variable force solenoid operator 128, which may be connected to a controller, such as a vehicle brake controller, transmission, etc. The EPRV 119 may have a supply port connected to thesecond pump port 140 via a second pump supply line 139 and a tank port connected to the tank line 132 and the tank port 146. Accordingly, in this example, the second pump 141 is used to actuate the valve 129 via pilot 113. Various alternative examples are illustrated below with respect to FIGS. 2-5. In further examples, the EPRV 119 may be connected to the first pump supply line 106 or the prioritized output line of the priority valve 109.

[0026] The EPRV 119 may have a first position 121 where the second pump 141 is connected to the line 118 and a second, return position 122 where the line 118 is connected to the tank 147. Responsive to an energizing current, the solenoid operator 128 may bias the EPRV 119 to the first position 121. Removal of the current may cause the EPRV 119 to return to position 122 (e.g., via the action of a return spring). The EPRV 119 may include features to regulate pressure proportionally to current applied to the operator 128. For example, a pilot 123 may be connected from the output line 118 to the EPRV 119 to bias the EPRV 119 to the second position 122. The pilot 123 may provide feedback based on pressure in the output line 118. Applying current to solenoid operator 128 generates a bias force tending to push EPRV 119 to position 121 (e.g., where the second pump supply line 139 is connected to the output line 118). As pressure in the line 118 increases, the pilot 123 biases the EPRV 119 toward the second position 122 (e.g., where the line 118 is connected to the tank line 132). In this way, for any current applied to the solenoid operator 128, the EPRV 119 will find a position between the first position 121 and second position 122 where the bias force due to pressure in pilot 123 is balanced by the force applied by solenoid operator 128. In some examples, the EPRV 119 may include a second pilot 133 connected to the tank line 132 to bias the EPRV 119 towards the second position. In these examples, the second pilot 133 may provide a reference pressure based on the pressure regulated in the output line 118 as it affects the pressure on the tank line 132.

[0027] As discussed above, the parking brake release port 154 is connected to the second pump input port 140 to provide hydraulic release pressure to the parking brakes 158. Some implementations may include a second output port 155 connected to the port 154. For example, the second output port 155 may comprise a gauge port that may be connected to a pressure gauge to monitor the pressure at the port 154.

[0028] In some examples, a release valve 150 is connected between the second pump port 140 and the parking brake release port 154 to control the delivery of pressure to the parking brake release line 156. For example, the release valve 150 may be an electro-hydraulic (EH) valve and may comprise a solenoid 149. As an example, the release valve 150 may comprise a bi-positional valve having a first position 151 and a second, return position 152. In this example, the release valve 150 may connect its supply port to its output port when in the first position 151 and may connect its tank port to its output port when in the second position 152. In some examples, the release valve 150 may be an on / off valve configured to be fully in either position 151 or position 152 with only transient intermediate positioning. In some cases, the release valve 150 may comprise components to support the bistable operation, such as a pair of pilots 144a and 114b coupled to its tank port to balance the valve based on tank line 132 pressure, so that the release valve 150 is balanced such that the actuation force of the solenoid 149 is opposed by the spring load of the release valve 150’s return spring, and is independent of pressure in the line connected to the safety valve 138 or the parking brake release line 156.

[0029] The example control valve 100 is configured to release pressure at the parking brake release port 154 responsive to a pressure loss event at the service brake output port 153. In this example, a safety valve 138 is connected to the tank line 132 and second pump pressure line 139 upstream of the release valve 150. Here, the safety valve 138 connects the supply port of the release valve 150 to the tank line 132 responsive to the pressure loss event. In particular, the safety valve 138 may comprise pilot operated safety valve 138 comprising a valve arrangement with a first position 134 and a second position 135. In the first position, the supply port of the safety valve 138 connects the second pump line 139 to the supply port of the release valve 150. In the second position 135, the tank port of the safety valve 138 connects the tank line 132 to the supply port of the release valve 150.

[0030] In the illustrated example, the safety valve 138 is operated by a first sense pilot 142 and a second sense pilot 148. Here, the service brake supply line 136 comprises a sense orifice 145 upstream of the service brake output port 153. The first sense pilot 142 is connected upstream of the sense orifice 145 and the second sense pilot 148 isconnected downstream of the sense orifice 145 (between the sense orifice 145 and the service brake output port 153). As illustrated, a return spring biases the safety valve 138 towards the first position 134. During operation, normal operational pressure at the service brake output port 153 provides sufficient pressure downstream of the sense orifice 145 for the second pilot 148 to overcome the actuation force of the upstream pilot 142 (when added to the safety valve 138’s return force). However, a pressure loss event on service brake output port 153 (e.g., from a burst hose, disconnect between the towing vehicle and trailer, etc.) may result in excessive flow and a larger pressure differential across sense orifice 145. In this state, the higher pressure upstream of the sense orifice 145 may result in pilot 142 overcoming the return force and actuation force of pilot 148, actuating the safety valve 138 into the second position 135.

[0031] As described above, the control valve 100 may include various supportive components. For instance, the control valve 100 may include a check valve 130 for the second pump supply line 139 upstream of the safety valve 138. The check valve may prevent pressure at the parking brake release port 154 from back flowing to the second pump supply line 139 (e.g., in the event of a transient pressure loss) and inadvertently releasing the pressure in the parking brake release port 154. For instance, such a transient may occur if the second pump 141 is supplying other circuits, momentarily causing pressure in the second pump port 140 to drop. As another example, the control valve 100 may include a dampening orifice 137 disposed within the second sense pilot 148. The dampening orifice 137 may dampen motion of the safety valve 138 to stabilize its operation against pressure fluctuations (e.g. pressure ripples) at the service brake output port 153.

[0032] During normal operation (when the pilot operated safety valve 138 is in the first position 134), placing the release valve 150 into the first position 151 may connect the second pump 141 to the parking brake release line 156, thereby releasing the brake 158. Placing the release valve 150 into the second position 152 may connect the parking brake release line 156 to the tank 147, allowing the spring to engage the parking brake 158.

[0033] When the pilot operated safety valve 138 is in second position 135, the supply port of release valve 150 is connected to the tank 147. Therefore, the parking brakerelease line 156 is connected to the tank 147 independently of the position of the release valve 150. In this state, when in first position 151 , the parking brake release line 156 may be connected to the tank 147 via the pilot operated safety valve 138 (in second position 135). When in position 152, the parking brake release line 156 may be connected to the tank 147 via the release valve 150 as in the normal operational state. Thus, in this example, a pressure loss event on the service brake supply line 136 may result in the parking brake 158 being connected to the tank 147 independently of the energization state of the solenoid 149. In this state, the pressure in parking brake release line 156 is thereby released to engage the parking brakes 158 in the event of a loss of pressure in service brake output port 153.

[0034] FIG. 2 illustrates another example brake control valve 200 for controlling service and parking brakes of a towed device. Various illustrated aspects of the example control valve 200 may be similar to aspects of the control valve 100 of FIG. 1. Unless indicated otherwise to the contrary, such aspects should be understood to be implemented and / or operated in a similar manner.

[0035] The example brake control valve 200 may include various ports to connect to a vehicle's hydraulic braking system. For example, valve 200 may include a port 203 to receive a pressure signal from a human-mechanical braking interface (such as a foot pedal 201 ), a first supply port 205 to connect to a first pump 202, a second supply port 238 to connect to a second pump 239, a tank port 244 to connect to a tank 245, and a pair of output ports 251 , 252 for the service brake 255 and parking brakes 256. In some examples, brake control valve 200 may include further ports, such as a load sense port 204 for a service brake line 230 or a secondary brake release port 253.

[0036] The first pump supply port 205 may connect to a supply line 207 leading to a priority valve 208 and a brake pressure regulating valve 213. The illustrated configuration of the priority valve 208 represents an alternative arrangement compared to the priority valve 109 illustrated in FIG. 1. Here, the priority valve 208 comprises a bi-positional priority valve comprising a first, return position 218 and a second position 220. In the first position 218, the priority valve 208 restricts the flow to the excess flow port 219, so that the flow to the brake pressure regulating valve 213 is prioritized. A pilot line 206 mayextend from the supply line 207 and operate the priority valve 208 after an orifice 21 OAs described with respect to FIG. 1 and pilot 131 , the priority valve 208 may be operated by a pilot 224 connected to the service brake supply line 230. For instance, pilot 224 may be a pilot connected to the load sense port 204. During operation, the priority valve 208 may actuate such that the pressure in pilot 206 remains greater than the pressure in pilot 224.

[0037] The illustrated example 200 may include a brake pressure regulating valve 213, which may operate generally as described with respect to the brake pressure regulating valve 129 of FIG. 1. In its first position 216, the valve facilitates the flow of pressurized fluid to the service brake, while the second position 212 enables pressure release. For example, the brake pressure regulating valve 213 may be operated based on operator pressure signals provided via input port 203 as well as based on pressure from pump 239 based on electrical actuation signals provided via a variable solenoid operator 229. Compared to the example control valve 100, the control valve 200 may include dual operators 217, 227 to actuate the pressure regulating valve. In this example, a pedal pilot operator 217 is connected to the pressure signal input port 203 via a pilot line 209, ensuring actuation based on driver input. Additionally, a second pilot operator 227 is connected to an electronic valve, such as an EPRV 223.

[0038] The electronic pressure regulating valve (EPRV) 223 may operate as described with respect to the EPRV 119 of FIG. 1. The EPRV 223 may have a first position 222 and a second, return position 221. Responsive to a signal to a variable solenoid operator 229, the EPRV 223 may be placed into the first position 222, connecting a pilot line 225 to the second pump 239 via a second pump supply line 237. The second pump 239 may thereby be connected to the pilot operator 227 to operate the brake pressure regulating valve 213. The EPRV 223 may be controlled by current supplied by a controller in the towing vehicle. This arrangement allows the service brake pressure regulator to regulate pressure based on operator input and / or pressure supplied by the EPRV 223. In some examples, the EPRV 223 may include pilots 232b and 232a, which may function as described with respect to pilots 123 and 133 of FIG. 1 , respectively.

[0039] The brake control valve 200 may include a parking brake release valve 247 and a safety valve 235. In some examples, the parking brake release valve 247 and a safety valve 235 may be implemented as described with respect to the parking brake release valve 150 and the safety valve 138 of FIG. 1 . Briefly, a pilot operated safety valve 235 may include a valve arrangement with positions 234 and 233. In normal operation, the pilot operated safety valve 235 may be in position 234 and may connect the second pump 239 to a supply port of the release valve 247 via a check valve 231 . A sense orifice 242 may be disposed in a service brake line 230, upstream of a service brake output port 251 . A first sense pilot line 240 and a second sense pilot line 249 may be connected to a service brake line 230 upstream and downstream of the sense orifice 242, respectively. Responsive to a pressure drop across the orifice 242, the pilot operated safety valve 235 may be placed into the second position 233, which may connect the supply port of the release valve 247 to a tank 245 via a tank line 228. In some cases, the second sense pilot 249 may include a dampening orifice 236, as described with respect to the dampening orifice 137 of FIG. 1.

[0040] The release valve 247 may be actuated by a solenoid operator 246. When the pilot operated safety valve 235 is in the second position 233, the supply port of the release valve 247 is connected to the tank 245. In this configuration, regardless of the position of the release valve 247, the parking brake release line 254 remains connected to the tank 245. Specifically, when the release valve 247 is in the first position 248, the parking brake release line 254 is connected to the tank 245 via the pilot operated safety valve 235 in its second position 233. Similarly, when the release valve 247 is in the second position 250, the parking brake release line 254 is directly connected to the tank 245 through the release valve 247 itself.

[0041] FIG. 3 illustrates another example brake control valve 300 for controlling service and parking brakes of a towed device. Various illustrated aspects of the example control valve 300 may be similar to aspects of the control valves 100 of FIG. 1 and 200 of FIG. 2. Unless indicated otherwise to the contrary, such aspects should be understood to be implemented and / or operated in a similar manner.

[0042] The example brake control valve 300 may include various ports to connect to a vehicle's hydraulic braking system. For example, valve 300 may include a port 303 to receive a pressure signal from a human-mechanical braking interface (such as a foot pedal 301 ), a first supply port 305 to connect to a first pump 302, a second supply port 329 to connect to a second pump 330, a tank port 334 to connect to a tank 335, and a pair of brake output ports 343, 344 for service brake 347 and parking brakes 348. In some examples, brake control valve 300 may include further ports, such as a load sense port 304 for a service brake supply line 323 or a secondary port 345.

[0043] The illustrated example may include a priority valve 306. In this example, the priority valve 306 be implemented as described with respect to the priority valve 208 of FIG. 2. For example, the priority valve 306 may actuate between positions 307 and 308 based on the action of pilots 311 and 313 as described with respect to positions 218 and 220 and pilots 224, 206, respectively.

[0044] The example brake control valve 300 may further comprise a pressure regulating valve 315, which may be implemented as described with respect to the pressure regulating valves 129 FIG. 1 . In a first position 316, the valve may facilitate the flow of pressurized fluid to a service brake supply line 323, while a second position 317 may enable pressure release to a tank line 324. The pressure regulating valve 315 may include operators 314, 322 to return the valve 315 to position 317 as described with respect to the operators 116, 127 of FIG. 1. A pedal pilot 312 may be connected to the foot pedal 301 and a pilot operator 320 as described with respect to pilot 209 and operator 217 of FIG. 2. Compared to the examples of FIGS. 1 and 2, the brake control valve 300 may lack an EPRV.

[0045] During normal operation, a second pump 330 supply line 319 is connected to the supply port of a brake release valve 340, as described with respect to the second pump 141 , second pump supply line 139, and the brake release valve 150 of FIG. 1.

[0046] The brake control valve 300 may further include a safety valve 331 that is actuated by a pair of sense pilots 332, 338. In normal operation, the safety valve 331 may be in a first position 326 and may connect the second pump 330 to a supply port of the release valve 340. Responsive to a pressure drop across a sense orifice 333, the safetyvalve 331 may be placed into the second position 327, which may connect the supply port of the release valve 340 to a tank 335. For example, the safety valve 331 may be implemented as described with respect to the safety valve 138 of FIG. 1 .

[0047] The release valve 340 may be actuated by a solenoid operator 339. In normal operation (when the safety valve 331 is in the first position 326), placing the release valve 340 into a first position 341 may connect the second pump 330 to a parking brake release line 346. In normal operation, placing the release valve 340 into a second position 342 may connect the parking brake release line 346 to the tank 335, releasing a spring actuator of the parking brake 348. Responsive to a pressure drop, when safety valve 331 is in second position 327, the supply port of the release valve 340 is connected to the tank 335 via tank line 324. Accordingly, in this state, the parking brake release line 346 is connected to tank 335 in both positions 341 , 342.

[0048] FIG. 4 illustrates another example brake control valve 400 for controlling service and parking brakes of a towed device. Various illustrated aspects of the example control valve 400 may be similar to aspects of the control valves 100 of FIG. 1 , 200 of FIG. 2, and 300 of FIG. 3. Unless indicated otherwise to the contrary, such aspects should be understood to be implemented and / or operated in a similar manner.

[0049] The brake control valve 400 may include various ports to connect to a vehicle's hydraulic braking system. For example, valve 400 may include a first supply port 403 to connect to a first pump 401 , a second supply port 433 to connect to a second pump 434, a tank port 441 to connect to a tank 442, and a pair of brake output ports 447, 448 for a service brake 451 and a parking brake 452. In some examples, brake control valve 400 may include further ports, such as a load sense port 402 or a secondary supply line output port 449.

[0050] The first pump 401 may connect to a first pump supply line 405 feeding into a priority valve 404 and a brake pressure regulating valve 410. In this example, the priority valve 404 may be implemented as described with respect to the priority valve 208 of FIG. 2. For example, the priority valve 404 may actuate between positions 414 and 415 based on the action of pilots 422 and 408 as described with respect to positions 218 and 220 and pilots 224, 206, respectively.

[0051] The example brake control valve 400 may further comprise a brake pressure regulating valve 410, which may be implemented as described with respect to the pressure regulating valves 129 FIG. 1 . Compared to the examples of FIGS. 1 and 2, the brake control valve 400 may lack a brake pedal. In this example, the brake control valve 400 comprises an EPRV 416 coupled to a pilot 413 and a pilot operator 412 to actuate the brake pressure regulating valve 410 from position 421 to position 420. For example, the EPRV 416 may be implemented as described with respect to the EPRV 119 of FIG. 1 . Briefly, the EPRV416 may be controlled by a variable solenoid operator 424 to actuate the EPRV 416 between a first position 417 and a second position 418.

[0052] In the illustrated example, the brake control valve 400 may include a parking brake release valve 444 and a safety valve 431 , which may be implemented as described with respect to the parking brake release valve 150 and the safety valve 138 of FIG. 1. Briefly, in its return position 428, safety valve 431 may connect second pump supply line 430 to the supply port of the release valve 444. The safety valve 431 may actuate based on the action of a first and second sense pilot 436 and 440 connected to the service brake supply line 435 upstream and downstream of a sense orifice 437. In position 429, the supply port of the release valve 444 is connected to a tank line 425 and the tank port 441 . Accordingly, when safety valve 431 is in second position 429, parking brake release line 450 is connected to tank 442 independent of the actuation state of the solenoid operator 443. The release valve 444 may include a first position 445 and a second, return position 446. In normal operation (e.g., when safety valve 431 is in first position 428), the release valve 444's supply port is connected to second pump 434 via the second pump supply line 430. In this state, when the release valve 444 enters its first position 445, pump 434 pressurizes parking brake release line 450, preventing spring actuation of parking brakes 452. In reduced pressure operation (e.g., when safety valve 431 is in second position 429), the release valve 444's supply port is connected to tank line 425. In both states, when the solenoid operator 443 is deenergized, the release valve 444 returns to second position 446 and the parking brake release line 450 is depressurized.

[0053] In contrast to the configurations shown in FIGS. 1-3, the brake control valve 400 in FIG. 4 may lack a foot pedal or other human-mechanical braking interface. Instead, the brake pressure regulating valve 410 may be operated by pressure from the secondpump 434 via the EPRV 416. This configuration may represent an example of an autonomous vehicle without a brake pedal, where braking control may be performed via the variable solenoid operator 424. Alternatively, FIG. 4 may also represent an example of a brake-by-wire vehicle, with the brake pedal not pictured. In this scenario, the brake pedal may be electrically connected to the EPRV operator 424, allowing for electronic control of the braking system.

[0054] FIG. 5 illustrates another example brake control valve 500 for controlling service and parking brakes of a towed device. Various illustrated aspects of the example control valve 400 may be similar to aspects of the control valves 100 of FIG. 1 , 200 of FIG. 2, and 300 of FIG. 3. Unless indicated otherwise to the contrary, such aspects should be understood to be implemented and / or operated in a similar manner.

[0055] The brake control valve 500 may include various ports to connect to a vehicle's hydraulic braking system. For example, valve 500 may include a port 503 to receive a pressure signal from a human-mechanical braking interface (such as a foot pedal 501 ), a first supply port 505 to connect to a first pump 502, a second supply port 530 to connect to a second pump 531 , a tank port 543 to connect to a tank 544, and a pair of brake supply ports 550, 551 for a service brake 554 and a parking brake 555. In some examples, brake control valve 500 may include further ports, such as a load sense port 504 connected to a pilot line 511 connected to a service brake supply line 528, an excess flow port 519 connected to a priority valve 508, or a secondary supply line output port 552.

[0056] The first pump 502 may connect to a first pump supply line 506 leading to a priority valve 508 and a brake pressure valve 516. In this example, the priority valve 508 be implemented as described with respect to the priority valve 208 of FIG. 2. For example, the priority valve 208 may actuate between positions 509 and 510 based on the action of pilots 527 and 513 as described with respect to positions 218 and 220 and pilots 224, 206, respectively.

[0057] The example brake control valve 500 may further comprise a brake pressure regulating valve 516. In a first position 517, the valve may facilitate the flow of pressurized fluid to a service brake supply line 528, engaging service brake 554. A second position 518 may enable pressure release to a tank line 514, releasing service brake 554. Thebrake pressure valve 516 may be actuated to first position 517 based on the action of a pilot operator 525 and may be returned to second position 518 based on the action of a pressure line operator 515 (connected to tank line 514) and / or a pilot operator 526 connected to pilot 527.

[0058] The brake pressure regulating valve 516 may be actuated by a pilot operator 525 connected to a pilot line 520 leading from an EPRV 521 . Compared to the EPRV 119 of FIG. 1 , the EPRV 521 may boost a pressure signal received via foot pedal pressure line 507. The EPRV 521 may have a first position 522 and a second, return position 523. In the second position 523, foot pedal pressure line 507 is connected to pilot line 520. Pressing the brake pedal increases pressure on foot pedal pressure line 507, which actuates pilot operator 525 to bias brake pressure regulating valve 516 towards the first position 517. Further, the EPRV 521 may comprise a variable solenoid operator 529. Energizing the solenoid operator 529 moves the EPRV 521 towards position 522 and connects the second pump supply line 536 to the pilot 520. This increases the flow / pressure at the pilot 520, boosting the pressure signal provided by the foot pedal 501.

[0059] In the illustrated example, the brake control valve 500 may include a parking brake release valve 546 and a safety valve 538, which may be implemented as described with respect to the parking brake release valve 150 and the safety valve 138 of FIG. 1. Briefly, in its return position 535, the safety valve 538 may connect the second pump supply line 536 to the supply port of the release valve 546. The safety valve 538 may actuate based on the action of a first and second sense pilot 539 and 549, which may be connected to the service brake supply line 528 upstream and downstream of a sense orifice 542.

[0060] The release valve 546 may include a first position 547 and a second, return position 548. When the solenoid operator 545 is energized, the release valve 546 is placed into first position 547 and connects its supply port to the parking brake release line 553. When the solenoid operator 545 is deenergized, the release valve 546 is returned (e.g., by a return spring) to position 548. In normal operation (e.g., when safety valve 538 is in first position 534), the release valve 546's supply port is connected to the second pump531 via the second pump supply line 536. In this state, when the release valve 546 enters its first position 547, pump 531 pressurizes parking brake release line 553, preventing spring actuation of parking brakes 555. In reduced pressure operation (e.g., when safety valve 538 is in second position 535), the release valve 546's supply port is connected to tank line 514. In both states, when the solenoid operator 545 is deenergized, the release valve 546 returns to second position 548 and the parking brake release line 553 is depressurized.

[0061] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims:

Claims

CLAIMS1 . A valve assembly, comprising: a service brake supply port to connect a service brake to a first pump; a brake release valve to connect to a parking brake release line; and a safety valve connected to a supply port of the brake release valve, wherein the safety valve is to connect the supply port to a second pump in a first position and to connect the supply port to a tank port in a second position and wherein the safety valve is to place the safety valve in the second position responsive to a pressure reduction at the service brake supply port.

2. The valve assembly of claim 1 , further comprising: a service brake supply line connected to the service brake supply port and comprising a sense orifice; a first sense pilot line connected to the service brake supply line upstream of the sense orifice; and a second sense pilot line connected to the service brake supply line downstream of the sense orifice, wherein the safety valve is operated by a pressure differential between the first sense pilot line and the second sense pilot line.

3. The valve assembly of claim 2, further comprising a brake pressure regulating valve connected to the service brake supply line.

4. The valve assembly of claim 3, further comprising: a pressure regulating valve to connect to the second pump; a brake control input; and a shuttle valve having an output connected to an operator of the brake pressure regulating valve and inputs connected to the pressure regulating valve and the brake control input.

5. The valve assembly of claim 3, further comprising: a pressure regulating valve to connect to the second pump; and a brake control input, wherein the brake pressure regulating valve comprises a first pilot operator connected to the brake control input and a second pilot operator connected to the pressure regulating valve.

6. The valve assembly of claim 3, further comprising: a brake control input, wherein the brake pressure regulating valve comprises a pilot operator connected to the brake control input.

7. The valve assembly of claim 3, further comprising: a pressure regulating valve to connect to the second pump, wherein the brake pressure regulating valve comprises a pilot operator connected to the pressure regulating valve.

8. The valve assembly of claim 3, further comprising: a pressure regulating valve to connect to the second pump and to a brake control input, wherein the brake pressure regulating valve comprises a pilot operator connected to the pressure regulating valve.

9. A valve assembly, comprising: a service brake supply port to connect to a service brake; a service brake supply line to connect the service brake supply port to a first pump; a brake release valve configured to connect to a parking brake release line; a safety valve connected to a supply port of the brake release valve, wherein the safety valve is configured to: connect the supply port to a second pump in a first position, and connect the supply port to a tank in a second position; a sense orifice disposed in the service brake supply line; a first sense pilot line connected to the service brake supply line upstream of the sense orifice; a second sense pilot line connected to the service brake supply line downstream of the sense orifice; and an operator configured to place the safety valve in the second position responsive to a pressure differential between the first sense pilot line and the second sense pilot line.

10. The valve assembly of claim 9, further comprising a brake pressure regulating valve connected to the service brake supply line, wherein the brake pressure regulating valve has a first position that connects the first pump to the service brake supply line and a second position that connects the service brake supply line to the tank.11 . The valve assembly of claim 10, further comprising: a pressure regulating valve connected to the second pump; a brake control input; and a shuttle valve having an output connected to a pilot operator of the brake pressure regulating valve and inputs connected to an output of the pressure regulating valve and the brake control input.

12. The valve assembly of claim 10, further comprising: a pressure regulating valve connected to the second pump; and a brake control input; and wherein the brake pressure regulating valve comprises a first pilot operator connected to the brake control input and a second pilot operator connected to an output of the pressure regulating valve, and wherein the first and second pilot operators are configured to additively control the position of the brake pressure regulating valve.

13. The valve assembly of claim 10, further comprising: a brake control input connected to a pilot operator of the brake pressure regulating valve; and wherein the pilot operator is configured to move the brake pressure regulating valve to the first position based on a pressure signal received via the brake control input.

14. The valve assembly of claim 10, further comprising: a pressure reducing valve connected to the second pump and to a pilot operator of the brake pressure regulating valve; and wherein the pilot operator is configured to move the brake pressure regulating valve to the first position.

15. The valve assembly of claim 10, further comprising: an electronic pressure regulating valve (EPRV) having a first position and a second position; wherein in the first position, the EPRV is configured to connect a second pump supply line to a pilot line; and wherein in the second position, the EPRV is configured to connect a brake control input to the pilot line; wherein the EPRV is operated by a variable solenoid operator; and wherein the pilot line is connected to a pilot operator of the brake pressure regulating valve.

16. A method of operating a valve assembly connected to a vehicle, the method comprising: controlling a service brake supply line to connect a service brake supply port to a first pump; controlling a brake release valve to connect a parking brake release port to a second pump; and operating a safety valve connected to a supply port of the brake release valve responsive to a pressure reduction on the service brake control line to connect the supply port to a tank port in a second position.

17. The method of claim 16, wherein the service brake supply line comprises a sense orifice, the method further comprising: operating the safety valve based on a pressure differential between a first sense pilot line and a second sense pilot line; wherein the first sense pilot line is connected to the service brake supply line upstream of the sense orifice; and wherein the second sense pilot line is connected to the service brake supply line downstream of the sense orifice.

18. The method of claim 16, further comprising operating a brake pressure regulating valve connected to the service brake supply line.

19. The method of claim 18, further comprising: controlling a pressure regulating valve connected to the first pump; receiving a brake control input; and operating a shuttle valve having an output connected to an operator of the brake pressure regulating valve and inputs connected to the pressure regulating valve and the brake control input.

20. The method of claim 18, further comprising: controlling a pressure regulating valve connected to the second pump; and receiving a brake control input; wherein operating the brake pressure regulating valve comprises controlling a first pilot operator connected to the brake control input and a second pilot operator connected to the pressure regulating valve.21 . The method of claim 18, further comprising: receiving a brake control input; and wherein operating the brake pressure regulating valve comprises controlling a pilot operator connected to the brake control input.

22. The method of claim 18, further comprising: controlling a pressure regulating valve connected to the second pump; and wherein operating the brake pressure regulating valve comprises controlling a pilot operator connected to the pressure regulating valve.

23. The method of claim 18, further comprising: controlling a pressure regulating valve connected to the second pump; receiving a brake control input; and wherein operating the brake pressure regulating valve comprises controlling a pilot operator connected to the pressure regulating valve.

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