Abstract: A control valve for a fluid pressure braking system includes a housing which receives a pair of identical plungers and corresponding springs acting on the plunger which activate automatically at different trip pressures. The differential trip pressures are attained by providing different valve seating areas on the housing and spring cavities of different depths.

Abstract: A brake slip control system for trailers equipped with overrun brakes is disclosed, in order to make the brake device independent of the towing vehicle, the pressure fluid source is arranged at the trailer.

Abstract: A antilock brake system utilizes a microprocessor controller to monitor the rate of speed decay of a braked wheel of a vehicle and to cause release of braking force under incipient wheel lock-up conditions. The microprocessor receives a single digital wheel speed input signal and processes the latter in accordance with a program whereby a reference signal is generated and is periodically compared with the wheel speed signal to determine if a lock-up condition is in progress. The microprocessor compares the speed signal with the reference signal at frequent sampling intervals and when the wheel speed decreases at a rate exceeding a desired value, the reference signal is varied by the microprocessor to decrease at a predetermined first rate of decrement until the wheel speed signal and the reference signal correspond to each other, indicating that the wheel speed is dropping at a rate in excess of a desired rate of speed decay.

Abstract: A tractor-(28) trailer (30) vehicle (24) brake system control for distributing the brake effort to obtain inter-tractor-trailer proportional braking (H.sub.1 /V.sub.1 =H.sub.2 /V.sub.2) by use of sensors (170, 172) mounted to the trailer only is provided. The control system senses (80) acceleration (a) and the ratio of vertical to horizontal forces (H.sub.F /V.sub.F) at the fifth wheel (34) by sensors (170, 172) mounted to the tractor (28) only and modulates the brakes to cause the ratio H.sub.F /V.sub.F to equal acceleration.

Abstract: A tractor (28)-semi-trailer (30) brake system control for distributing brake effort to obtain inter-tractor-trailer balanced and proportional braking (H.sub.1 /V.sub.1 =H.sub.2 /V.sub.2), depending upon the magnitude of operator demand for braking effort, is provided. The control utilizes sensors (80, 170, 172) provided on only the tractor.

Abstract: A tractor (28) semi-trailer (30) brake system control for distributing brake effort to obtain inter-tractor-trailer balanced and proportional braking, depending upon the magnitude of operator demand for braking effort, is provided. The control utilizes sensors (80, 170, 172) provided solely on the tractor.

Abstract: An anti-jackknifing valve is designed for use with tractor trailers and is operably inserted in the hydraulic fluid brake line of such vehicles. The valve prevents jackknifing of a trailer during brake applications by initially actuating the brakes on the trailer. The valve arrangement directs hydraulic brake fluid to the trailer brakes first, and a continuing movement of the valve piston then permits hydraulic brake fluid to be delivered to the tractor brakes to thus substantially eliminate the risk of jackknifing.

Abstract: A brake pressure control valve for regulating the braking pressure in the trailer brake system of a tractor-trailer vehicle, so as to develop the trailer brake pressure to a preset level ahead of the braking pressure in the tractor brake system during a pilot phase of brake operation. The preset level of this advance trailer brake pressure can be selected by an adjustable member that forms a part of the auxiliary valving that controls the point at which the pilot phase of operation is terminated. A limit stop is cooperatively arranged with this adjustable member in order to provide a means for limiting the point beyond which the auxiliary valving is activated, to thereby prevent the advance trailer brake pressure from exceeding a specified safe maximum value.

Abstract: An apparatus is disclosed for the control of brake pressure in a trailer pulled by a tractor. The apparatus includes a two-circuit controllable relay valve as the trailer control valve. The first circuit is controlled by the brake valve of the tractor with the pressure from the brake apparatus of such tractor. The second circuit can be optionally-connected to a distribution valve with a pressure medium source with a specified pressure or with atmosphere. Activation of the distribution valve is controlled so that the distribution valve connects the second circuit with the pressure medium source before or at the beginning of the activation of the first circuit. With this apparatus, the brake pressure can be increased in the brake apparatus of the trailer prior to increase of the brake pressure in the brake apparatus of the tractor. The level of brake pressure increased first in the brake unit of the trailer can be regulated by a set screw acting on the trailer control valve.

Abstract: A vehicle braking control system is provided for sensing (76) the magnitude of the vehicle operator's demand for braking effort and for distributing the braking effort between the individually controllable vehicle (22) brake sites to achieve balanced braking (12) if relatively low braking effort demand (0% to A%) is sensed and to achieve proportional braking (14) if relatively high braking effort demand (B% to 100%) is sensed.

Abstract: A fluid pressure braking system includes pressure sensors in each of the supply and service reservoirs and in the supply line to the trailer. The system includes an air compressor which is loaded and unloaded in response to variations in the pressure level in the supply reservoir by actuation of a solenoid valve by an electronic control module which is responsive to the pressure sensors. The system includes spring brakes which are controlled by the control module through actuation of solenoid valves. The control module is similarly responsive to supply line pressure and the pressure level in the supply line to control a solenoid valve which controls communication through the supply line.

Abstract: A proportioning control valve for a fluid pressure braking system for a tractor-trailer combination vehicle permits unproportioned communication of control pressure when the tractor is pulling a trailer but proportions communication of control pressure when the tractor is operated without a trailer to establish a proportionally lower pressure level at the outlet of the valve. When the pressure level at the control port exceeds a predetermined level established by a spring, the control valve proportions at a rate which increases the pressure level at the outlet at a rate greater than the rate of increase of control pressure until the unproportioned pressure level is attained.

Abstract: An improved remote braking system (10, 100) is provided which allows simultaneous actuation of the braking system of a motor home (12) and an automobile (14) towed behind the motor home. An advantage of the present invention is the incorporation of the system within the self-contained hydraulic brake system of the automobile, which permits the braking system of the automobile to be operated in the normal manner. The system includes an actuator (26, 102) which is secured between the vacuum booster (18) and the master cylinder (20) of the automobile. Within the actuator is a piston (38, 114) which separates the interior of the actuator into two chambers. A pressure differential is created between the chambers when the brakes of the motor home are applied to generate a force on the piston (38, 114), to apply the brakes of the towed automobile as well. The system is operable with either air brakes or hydraulic brakes in the motor home.

Abstract: An electronically controlled fluid pressure braking system for a heavy duty vehicle includes an operator controlled mechanism which generates independent brake pressure command signals, each of which are transmitted to separate auxiliary controllers. Each of the controllers transmits its command signal to the other auxiliary controllers and also to a master control unit. The master control unit sorts between the command signals and generates a preliminary brake pressure request signal which is transmitted back to each of the auxiliary controllers. Each of the auxiliary controllers then examines the brake pressure request signal received from the master controller and actuates the corresponding vehicle brakes if the pressure request signal is within normal limits. If the signal is not within normal limits, each of the auxiliary controllers is capable of generating a brake pressure request signal independently of the master control unit.

Abstract: An anti-skid brake control system for a vehicle having a first and a second set of wheels with each wheel being provided with a brake and a brake actuator. The first set of wheels tend to lock at a lower braking pressure than the second set of wheels. Wheel speed sensors are fitted to the first set of wheels. The system includes a first and a second regulator for separately regulating the braking pressure acting on the brake actuators of the first and second set of wheels respectively. The first and second regulator co-operate to control the braking pressure acting on the first and second sets of wheels by equalizing the braking pressure.

Abstract: A failsafing device is proposed for an anti-skid system of a tractor-trailer combination. If the trailer anti-skid system fails at the rear axle, instead of shutting off the entire anti-skid system of the trailer, the anti-skid control at the front axle of the trailer is maintained.

Abstract: An integrated pressure exhaust valve and pneumatic coupling is used on a truck trailer for bringing air brake pressure from a tractor to the truck trailer. A gladhand coupling moiety is used for quick connection with an identical coupling moiety on the air pressure hose from the tractor. A check valve mechanism is incorporated in the body of the trailer coupling moiety for permitting air flow to the brakes when pressure from the tractor is greater than pressure in the trailer brake lines, and for permitting air flow from the brake lines to the atmosphere when pressure from the tractor is decreased. The integrated pressure exhaust valve and pneumatic coupling moiety can be mounted on the front of the trailer where it is found that pressure exhaust valve placement is most effective.

Abstract: A proportioning control valve for a fluid pressure braking system for a tractor-trailer combination vehicle permits unproportioned communication of control pressure when the tractor is pulling a trailer but proportions communication of control pressure when the tractor is operated without a trailer to establish a proportonally lower pressure level at the outlet of the valve. The control valve, when operating in the proportioning mode, is also responsive to pressure in the brake reservoir. When pressure in the reservoir drops below a predetermined level, the control valve proportions at a rate which increases the pressure level at the outlet at a rate greater than the rate of increase of control pressure until the unproportioned pressure level is attained.

Abstract: An electric brake control circuit is responsive to an activation signal and a vehicle deceleration signal for generating a brake control signal representing a predetermined amount of braking. A comparator compares the voltage level of the brake control signal with the voltage level of a sawtooth waveform to produce a pluse width modulated signal having a duty cycle corresponding to the predetermined amount of braking. This pulse width modulated signal is supplied to an output driver for generating a brake driving signal to energize the brakes. The activation signal is generated at the voltage level of the vehicle power supply when the driver actuates the vehicle stop light switch. The circuit is responsive to the activation signal for disabling the output driver when the voltage level of the activation signal is below a predetermined level. The circuit also senses the current load on the brake driving signal to protect the output driver in the event of a full or partial short circuit condition.

Abstract: A fluid pressure control portion for a fluid brake motor is inserted in a fluid pressure control passage between a triple valve and a brake motor for a particular car truck. This portion comprises a proportioning valve connected to an inshot valve through a pipe bracket to proportionally reduce brake pressure on a particular brake motor, after inshot at the same pressure as other brake motors of the same vehicle to adjust braking in accordance with lighter loading of end trucks for articulated freight cars.

Abstract: A spring-loaded parking-brake and service-brake system for trailers of motor-vehicle combinations is provided which increases safety. The system does this by allowing the service brake of the trailer to respond at the same time as the service brake of the towing motor vehicle, and the spring-loaded parking brake of the trailer to respond at the same time as the parking brake of the motor vehicle. To guarantee safe parking and maneuvering of the uncoupled trailer, the control system of the spring-loaded trailer parking brake is electrical, and furthermore the service brake is also controlled by an additional electrical signal. For this purpose two electrical coupling parts, a pneumatic control-line coupling and a pneumatic supply coupling are attached to the trailer.

Abstract: A multiple-circuit pressure-medium braking system for vehicle and trailer combinations that increases safety by allowing the front-wheel brake, the rear-wheel brake and the trailer brake to respond simultaneously. The system comprises electrical control circuits and pressure medium circuits which are controlled by the electrical control circuits. Each pressure-medium circuit has its own electrical circuit assigned to it. The trailer brake valve is controlled by an electrical signal from an one of the electrical control circuits. This is in addition to the direct pneumatic control of the trailer brake valve by the trailer control valve, and allows for the simultaneous braking of the trailer and the vehicle.

Abstract: A fluid pressure responsive brake system for the trailer of a vehicle. The brake system includes a trailer supply circuit, which can be connected with the supply circuit of the tractor and which can be connected with an electrical trailer brake circuit, which is connected with the brake system emitting electrical brake signals and the electrical feed of the tractor. There is an electro-fluidic switching apparatus with an OR circuit, by means of which and in connection with an electronic control unit of the trailer, the brakes of the trailer are set if the trailer brake system is separated from the supply circuit of the tractor and/or from the electrical brake signals or the power supply of the tractor.

Abstract: A dual circuit brake valve includes a relay piston (50) having primary (82) and secondary (84) areas which are normally communicated to the pressure level at the primary outlet or delivery port (18). The relay piston (50) responds to a pressure differential across the relay piston to control communication to the secondary outlet or delivery port (22). A control mechanism (92) is responsive to a control signal to vent the secondary area (84) to thereby establish a differential area across the relay piston (50), so that the relay piston (50) will establish a pressure level at the secondary outlet or delivery port (22) which is a predetermined fraction of the pressure level at the primary outlet or delivery port (18).

Abstract: A vehicle brake system for an arrangement having a prime mover and at least one tandem trailer. The system includes a respective sub-system for the prime mover and each tandem trailer and each sub-system has a plurality of spring brakes which are held out of a park mode by pressurized air in a hold-back chamber and are caused to operate in a normal manner by pressurized air supplied to a service chamber. Each sub-system includes a service relay valve which is operable to connect pressurized air with the service chambers of the respective spring brakes and the prime mover sub-system includes a control relay valve which is operable to cause operation of the service relay valves of that sub-system and the adjacent tandem trailer sub-system. If there are two or more tandem trailers, each tandem trailer sub-system apart from the last includes a control relay valve and each succeeding control relay valve is operated as a consequence of operation of the control relay valve of the respective preceding sub-system.

Abstract: In a fluid-pressure operated anti-skid braking system operation of a brake-applying relay valve is controlled by control pressure in an application chamber. A memory chamber is charged on initial brake application with pressure from supply passage connected to a brake actuator through one-way valve and an orifice permits pressure in the memory chamber to decay when the pressure in the supply passage reduces. This reduces the effective volume of air required for initial operation of the relay valve thereby increasing its response time. Re-application of the brake following a skid is controlled by closure of a latch valve which permits only a restricted flow of control pressure into the application chamber.

Abstract: Hydraulic brake system between two vehicles provides for simultaneously braking both vehicles with equal intensity. An auxiliary master cylinder in the towing vehicle controls, through fluid pressure, four auxiliary brake cylinders, the middle two being part of a removable unit. The fourth auxiliary cylinder exerts fluid pressure during a towing mode, on the conventional brake system of the towed vehicle through a valve that shuts down the pressure exerted by the towed vehicle's master cylinder during the towing mode.

Abstract: A dual-circuit pressure medium brake system is equipped with relay valves disposed ahead of the brake cylinders. Each brake circuit is equipped with a control also acting in the other circuit and overlapping each other, and a primary brake circuit is designed in such a way that it contains all control elements necessary for optimal brake pressure adaptation, while a secondary brake circuit is merely an auxiliary brake circuit without control elements. In this manner each brake pressure metering can be simultaneously adjusted. During the loss of the primary brake circuit, the secondary brake circuit guarantees a minimal brake pressure. Such a pressure medium brake system is preferably used in air brake systems of motor vehicles.

Abstract: A fluid pressure braking system for a tractor-trailer vehicle in which the braking system of the tractor is connected to the braking system of the trailer through trailer control and trailer supply lines includes a relay valve which controls communication between service reservoirs on the tractor and the trailer control line in response to operation of the vehicle brake valve. Use of the relay valve to control the communication to the trailer control line permits greater volumes of air to be supplied to the trailer control line, thereby appreciably reducing transmission times of brake application signals.

Abstract: A tractor-trailer braking system with a control valve for the trailer which is controllable by at least two service brake circuits of the tractor. One circuit of this multi-circuit control has an electrical control in the form of magnetic valves, or the like, in order to speed up the control process. The system may be combined with a load-dependent switching element and/or with an anti-skid protection-dependent switching element.

Abstract: An improved disc brake system of the general type including a brake frame having a pair of spaced apart rails, a pair of brake linings slidably carried on the brake frame rails, a circular rotor rotatably carried on the wheel assembly of a vehicle and having smooth planar inboard and outboard contact faces, a caliper assembly slidably mounted on the rails of the brake frame, and, a brake pedal operatively associated with the caliper assembly, the caliper assembly having a piston which when actuated by depressing the brake pedal first forces one brake lining against the inboard contact face of the rotor and then causes the caliper assembly to slide along the brake frame rails to force the other brake lining against the outboard contact face of the rotor. The improved disc brake system minimizes the amount of heat generated when the brake linings frictionally contact the rotor and markedly increases the operational life of the rotor and brake linings.

Abstract: An air brake control system for use in truck trailers having at each axle compressed-air brakes including spring brakes and service brakes, and each trailer being coupled to receive compressed air through an emergency (supply) gladhand and to receive service brake signals through a service (control) gladhand, the invention comprising an integrated brake valve system for each axle of each trailer, including a common valve housing; a spring brake valve cluster having a non-return check valve connected to receive and pass air pressure from the emergency gladhand and to deliver it directly to the spring brakes and an air pressure responsive shuttle operative to open the check valve whenever the emergency line pressure falls below a predetermined spring brake isolation pressure above which the spring brake holding pressure is not affected by fluctuations of the emergency gladhand pressure; and including an air tank supply valve cluster connected between the emergency gladhand and the tank and operative to sense pr

Abstract: An air brake system for a truck in which various control valves controlling air supply to air sub-systems, parking and trailer brakes, and various brake system condition signal generators are mounted on a common manifold positioned remotely from the truck engine compartment and instrument panel, removing them from the instrument panel area and improving the plumbing arrangements for installation, diagnostics and servicing while clearing instrument panel space for other controls and devices which need the benign environment such as that in the truck cab provided for the truck driver. The system components may be used as needed for a straight truck or one composed of a tractor and trailer combination, or on a truck tractor adapted to tow a trailer.

Abstract: A brake system for combinations of vehicles in which a truck tractor and/or trailer (semi-trailer) is or are equipped with a supplementary electrical brake system. By the particular embodiment of the brake system, it is possible to couple a truck tractor, with or without an electrical brake system, to a trailer, with or without an electrical brake system, without infringing safety regulations.

Abstract: A fluid power circuit providing a selective operation of a trailer brake system, coupleable with a tractor brake system, comprises a pilot operated valve located between tractor and trailer brake system. The pilot operated valve can be put in a fluid flow passing mode from its fluid blocking mode by simultaneous engagement of two tractor brakes. An independent engagement of either of the tractor brakes, which is necessary for sharp turns in the field operation, does not actuate the trailer brake system.

Abstract: A proportioning relay valve (10) includes a housing (12) receiving a relay piston (28) which controls communication between supply (14), exhaust (18) and delivery or outlet (16) ports. Control pressure is communicated to the relay piston (28) through a proportioning piston (58). The proportioning piston (58) is controlled by the pressure level at the actuating pressure port (22) to proportion communication to the relay piston (28) when the pressure level at actuating pressure port (22) is low and to permit unproportioned communication to the relay piston (28) when the pressure at actuating pressure port (22) is high. A bypass passage (80) and relief valve (86) also control the proportioning piston (58) so that unproportioned communication to relay piston (28) is permitted regardless of the pressure level at the actuating pressure port (22) when pressure at the control port (20) exceeds a predetermined value.

Abstract: A brake system for vehicles with trailers and having a compressed-air, dual-line brake system, in which a pressure sensor is associated with the trailer brake valve, with which sensor an electronic switching system disposed on the trailer can be triggered. A following pressure control valve is either switched parallel to a brake line leading from the trailer brake valve to the brake cylinders or, given dual-circuit triggering, of itself takes on the function of supplying the brake cylinders.

Abstract: A compressed air brake system including a low pressure control circuit and a high pressure operating circuit. The control circuit is interfaced by a plurality of relay valves with the operating circuit for the direct actuation of the wheel brake cylinders with high pressure. The dual pressure arrangement results in a significant reduction in consumption of air while retaining the advantages which are common to a high pressure system.

Abstract: A dual circuit brake valve for an articulated vehicle is responsive to a pressure signal provided by the system tractor protection valve to provide a full brake application in both the primary and secondary braking circuits actuating the front and rear wheel brakes of the vehicle respectively when the portions of the articulated vehicle are connected for movement together. A proportioning piston is responsive to the pressure signal to proportion braking pressure in the secondary when the towing portion of the vehicle is operated in the "bobtail" mode without the towed portion of the vehicle. The brake valve includes mechanism for mechanically actuating the secondary circuit valve to provide a full brake application under emergency conditions during operation of the vehicle in the bobtail mode.

Abstract: The force applied to brake a towed vehicle (18) is varied in response to the load of the vehicle (18). A signal generating device (38) generates a first signal when the load weighs more than a selected value and a second signal when the load weighs less than such value. Pressure reducing circuitry (46) reduces the pressure supplied in opposition to the biasing of the towed vehicle brake valve (34) when the second signal is generated and does not reduce such pressure when the first signal is generated. A manual override (52) serves for manually overriding the pressure reducer (44) when the signal generating device (38) generates the second signal. This supplies substantially unreduced pressure in opposition to the biasing of the towed vehicle brake valve (34). In this manner, towed vehicles (18) are prevented from being overbraked when empty. The operator may override the system as necessary, e.g., when both vehicles are empty.

Abstract: A brake activation system for reducing the time between the brake application of tractors and trailers utilizes a speed differential between the electrical and air signals. The application of the tractor brake actuates simultaneously a stop light circuit and the air brake systems. The electrical signals from this energized stop light circuit actuates solenoid valve which releases the air from the trailer reservoir being subsequently reduced to a predetermined low pressure level. This low pressure air reaches the trailer wheel brake chambers prior to the arrival of the brake air with high pressure overriding the low pressure air route and completing the trailer brake application.

Abstract: A pair of tandem master cylinders have primary pressure spaces connected to the brakes on one pair of wheels on opposite sides of the vehicle, and an actuator for the brakes on a trailer is supplied with fluid under pressure from pipe-lines connected to each of the four pressure spaces and under the control of first and second disabler valves. Each disabler valve has a pair of inlet ports, each connected either to respective primary pressure spaces or respective secondary pressure spaces, and an outlet port connected to the actuator. When one master cylinder is operated on its own both disabler valves are closed to prevent the actuator from being operated. Failure of one pressure space, when both master cylinders are operated simultaneously, causes the corresponding disabler valve to close but the actuator can still be operated from the operative pressure spaces, through the other disabler valve.

Abstract: According to the invention, the braking system includes two tandem master cylinders (100, 200), the first (100) having a first pressure chamber (110) connected to the left brake (132) of the tractor and a second pressure chamber (112) connected to the trailer brakes (300), and the second having a first pressure chamber (210) connected to the right brake (232) of the tractor and a second pressure chamber (212) likewise connected to the trailer brakes (300). The invention may be utilized with certain vehicles, in particular agriculture tractors.

Abstract: An improved trailer braking system for a tractor-trailer configuration is of the type which includes a primary air reservoir on the tractor which supplies an auxiliary air reservoir on the trailer. A pedal brake actuator on the tractor selectively provides control air from the primary air reservoir on the tractor to a relay valve on the trailer which control air causes air from the auxiliary air reservoir to be directed to the brakes on the trailer. The improvement includes a secondary source of control air on the trailer in the form of a control air reservoir having a volume significantly smaller than the volume of the auxiliary air reservoir. The control air reservoir is supplied control air through a first line from the auxiliary air reservoir. A second line from the control air reservoir goes to the relay valve and includes a check valve therein to only allow the control air to be capable of passing from the control air reservoir to the relay valve.

Abstract: The invention relates to an improvement in a valve for a tractor air brake system for changing the pressure delivered to air brakes on a tractor rear axle during "bob tail" operation and particularly to a valve wherein the ratio is changed by communication of control pressure to a second control surface in accordance with the presence of trailer emergency pressure. The improved ratio control valve enables fluid pressure communication to both control surfaces of the ratio valve until a predetermined input pressure is reached so that the "crack-open" input pressure for both the "trailer-connected" and the "bob tail" modes of operation will be the same. Further in accordance with the invention, a blend-back valve is provided which is biased by the available fluid pressure in the tractor reservoir tank so that the maximum available tractor reservoir pressure may always be applied to the tractor rear axle brakes even when the trailer is operating in the "bob tail" mode.

Abstract: A tractor air brake system including front wheel brake actuators, rear wheel brake actuators, and control valve structure for controlling the service air pressure delivered to the front wheel brake actuators. When a tractor is equipped with this brake system, the control valve structure operates to vary the service air pressure delivered to the front wheel brake actuators relative to that delivered to the rear wheel brake actuators in order to minimize tractor front wheel lock and loss of steering control when operating a tractor-trailer combination and to provide safe stopping when operating the tractor only.

Abstract: A valve for a tractor air brake system for changing the pressure delivered to air brakes on the rear axle depending on whether the trailor is attached or whether the tractor is operating in the "bob tail" mode. According to the invention, a rear axle ratio control valve provides an automatic selection of input to output ratio in accordance with the presence or absence of trailor emergency pressure. In the ratio control valve, service brake control pressure always acts against a first effective area of a piston for providing a first ratio of input to output. A second effective area of the piston receives pressure with the presence of the trailer emergency so that the ratio of pressure delivered from the valve will be changed. Further in accordance with the invention, a blend-back valve operates at a higher, predetermined pressure range, even when the pressure communication is closed by the absence of the emergency pressure to enable the valve to deliver the maximum pressure at high input pressure.

Abstract: A braking system for towed vehicles is disclosed which provides for controlled application of hydraulic brakes in a towed vehicle in response to the application of the brakes by the driver of the towing vehicle. An electromagnetic variable valve means provides the responsive braking pressure in a towed vehicle by employing an electric current signal from the towing vehicle to create an electromagnetic force which is balanced against the hydraulic pressure present in the towed vehicle's brakelines.

Abstract: A braking system for automatically braking a towed vehicle coupled to a towing vehicle having an electrical brake control circuit and a vacuum line wherein the towed vehicle is provided with a normally closed solenoid valve for connecting both a vacuum reservoir in the towed vehicle and the vacuum line in the towing vehicle with a vacuum responsive bellows operatively connected to the brake pedal in the towed vehicle with the solenoid operated valve electrically connected through a normally open breakaway switch to the battery whereby the operation of the braking system on the towing vehicle is accompanied by an actuation of the solenoid operated valve and the application of a vacuum to the bellows for concomitant operation of the brake pedal on the towed vehicle and upon a decoupling of the towed and towing vehicles, a similar actuation of the solenoid operated valve when the breakaway switch closes to apply vacuum to the bellows for actuation of the brake pedal to brake the decoupled towed vehicle.

Abstract: A multi-axle vehicle brake system includes an air receiving portion, a valve portion, an air storage portion and a brake portion. The air receiving portion receives air from a supply source. The valve portion is connected to the air receiving portion. The storage portion includes a plurality of storage reservoirs connected for receiving air from and communicating air to the valve portion. The brake portion includes service and parking brake actuating chambers mounted on each end of each axle. Certain ones of the service brake actuating chambers are connected for receiving air from one of the storage reservoirs. Others of the service brake actuating chambers are connected for receiving air from another of the storage reservoirs. Each of the parking brake actuating chambers are connected for receiving air from either of the storage reservoirs. .Iadd.