Brake system with at least one brake circuit

A brake system with at least one brake circuit comprises a mechanical brake-pressure control device and an electrical brake-pressure control device. The brake system is constructed without additional expenditure and by use of a mechanical brake-pressure control device and by an electrical control valve device. The system is constructed such that the brake-pressure modulator (8) of the electrical brake-pressure control device (6, 8, 11, 19) can also be controlled by pressure. The brake-pressure modulator (8) meters the brake pressure, both on the strength of the supplied electrical signal as well as according to the value level of the fed-in redundant brake pressure. The control electronics (11, 19) of the electrical brake-pressure control device (6, 8, 11, 19) is constructed such that it sets the strength of the electrical signal to a value required for covering and for meeting the respective brake-pressure demand request. The invention structure can be employed preferably in connection with road vehicles and motor vehicles.

BACKGROUND OF THE INVENTION 
1. Field Of the Invention 
The invention relates to a brake system with at least one brake circuit, 
actuated by a feeding of a brake pressure, with a mechanical 
brake-pressure control device and an electrical brake-pressure control 
device. 
2. Brief Description of the Background of the Invention Including Prior Art 
Such a brake system is actuated predominantly by the electrical 
brake-pressure control device. In case of a fault in the electrical 
brake-pressure control device, the brake system remains functioning based 
on the redundant brake-pressure transmitted by the mechanical 
brake-pressure control device. 
Such a brake system is known from the German Patent Document herein 
incorporated by reference DE-OS-3,501,179-Al. The brake-pressure modulator 
of this brake system is formed as a blockin device with respect to the 
redundant brake pressure. For this purpose, the brake-pressure modulator 
of the German Printed Patent Document, herein incorporated by reference, 
DE-OS-3,501,179-Al is structured such that, upon actuation of the brake 
system in the sense of an increasing or level-maintaining brake pressure, 
its passage is blocked for the redundant brake pressure and, upon 
actuation in the sense of a falling brake pressure, its passage is open. 
Thereby, the desired brake-pressure drop is made possible by means of the 
mechanical brake-pressure control device. 
If the known brake system is to comprise one or several elements, which 
require a particularly quick brake-pressure drop, then the brake system 
has to contain an electrically controlled valve device, as taught for 
example in FIG. 2 of the German Printed Patent Publication, herein 
incorporated by reference DE-OS-3,501,179-Al. This electrically controlled 
valve device assures the required quick brake-pressure drop during 
operation of this element or these elements, respectively. Such elements 
are, for example, an anti-skid protection system and a superposed 
electrical or hydraulic long-time brake, conventionally designated as 
retarder. 
The German Printed Patent Document DE 3,212,930 to Werner Stumpe, herein 
incorporated by reference, teaches a multi-circuit braking system. A 
pressure control valve is employed which, on the one hand, assures that 
the control circuits are always in use and that the pressures furnished to 
the brake cylinder compensate in each case. 
The German Printed Patent Document DE 2,218,315 to Joseph R. Morse et al., 
herein incorporated by reference, teaches a braking system for a vehicle. 
A control unit is furnished by an electronic signal processing unit which 
delivers electrical output signals, and is connected to a braking valve or 
to brake cylinders and coordinated to pressure indicators. This electronic 
signal processing unit compares the signal corresponding to the momentary 
pressure values present in the brake control valve and in the brake 
cylinders. 
The German Printed Patent Document 1,555,556 to Heinz Nicolay et al., 
herein incorporated by reference, teaches a pressure operated braking 
system for vehicles, as well as a relay valve and a solenoid valve for the 
switching on of a retarder. A relay valve is constructively combined with 
a solenoid valve such that the double valve body of the relay valve can 
also be actuated by a piston subjectable to a pressure controlled by the 
relay valve. 
The German Printed Patent Document DE 3,703,639 to Werner Stumpe, herein 
incorporated by reference, teaches an electro-pneumatic braking system for 
tractors. An emergency brake release device is furnished, which can be 
activated in case of an intereruption of a brake line by electrical and/or 
pneumatic signals generated by an activation of a brake-Pedal 
The German Printed Patent Document DE 3,240,276 to Ewald Hubl et al., 
herein incorporated by reference, teaches a pressure control valve for a 
braking system. The reference employs a solenoid valve disposed at least 
indirectly analog relative to the brake cylinders for controlling the 
brake pressure, where the solenoid valve is continuously adjustable 
depending on the current fed to the solenoid valve. 
The German Printed Patent Document DE 3,205,228 to Egbert Muller et al., 
herein incorporated by reference, teaches a multi-circuit braking system 
based on a pressurized medium. The pressure control valve of the reference 
is controlled from several circuits and includes electrical switches for 
at least one control circuit. 
The German Printed Patent Document DE 3,416,338 to Gerhard Fauck et al., 
herein incorporated by reference, teaches an apparatus for the adaptation 
of the distribution of the brake force. A delay valve allows the pressure 
to pass with a value level reduced by the opening pressure in case of a 
further increasing pressure, once the opening pressure has been reached. 
The German Printed Patent Document DE 3,239,970 to Ingolf Grauel et al., 
herein incorporated by reference, teaches a braking system for a vehicle 
train. The brake value sensor is formed for controlling both, 
electrically-actuated and pressure-actuated braking circuits. One of the 
pressure-activated circuits for controlling the trailed control valves is 
a pure control circuit. 
The German Printed Patent Document DE 2,939,907 to Erich Reinecke, herein 
incorporated by reference, teaches a dual-circuit braking system. An 
adapter valve is employed between the control connection for the 
subjection of the second part face and the conduit carrying the pressure 
for the rear-axle brake circuit. 
The WABCO pocket book addition, published in 1987 illustrates on page 241 a 
load/empty valve. 
SUMMARY OF THE INVENTION 
1. Purposes of the Invention 
It is an object of the invention to provide a brake system which operates 
safely and performs reliably the braking function. 
It is another object of the invention to prepare a brake system of the kind 
set forth above for the application of elements which require a 
particularly quick pressure drop. 
It is another object of the invention to provide a brake system which is 
based on a base-level brake component and a subsidiary quick-reaction 
component. 
It is yet another object of the invention to provide an automatic brake 
system which assures that at least one component of the brake system will 
continue to act with a braking force in case one of the two devices should 
fail to operate properly. 
These and other objects and advantages of the present invention will become 
evident from the description which follows. 
2. Brief Description of the Invention 
The present invention provides for a brake system with at least one brake 
circuit actuated by a feeding-in of a brake pressure as well as with a 
mechanical brake-pressure control device furnishing a redundant brake 
pressure and with an electrical brake-pressure control device. Said 
electrical brake-pressure control device comprises at least one 
brake-pressure modulator, actuated by a magnet and coordinated to the 
brake circuit, and an electronic control device, controlling the 
brake-pressure modulator. The brake-pressure modulator is connected at a 
first inlet port with a pressure supply. A second inlet port of the 
brake-pressure modulator is connected with the mechanical brake-pressure 
control device. The outlet port of the brake-pressure modulator, 
delivering the brake pressure, is connected with the brake circuit. The 
brake-pressure modulator is of a construction also employing pressure 
control, which meters the brake pressure both according to the fed-in 
magnet current strength as well as according to the value level of the 
redundant brake pressure. The electronic control device is constructed 
such that it sets the magnet current strength to a value required for 
covering the momentary brake-pressure demand request. 
The electronic control device can deliver a warning signal if the magnet 
current strength goes beyond and leaves a prespecified set-point region. 
The brake-pressure modulator can comprise a dual-circuit relay valve device 
and a magnet-actuated valve device, connected at the inlet port of the 
magnet actuated valve device to the first inlet port and delivering a 
pressure, dependent on the fed-in magnet current strength. The 
dual-circuit relay valve device is connected at its first control device 
to the outlet port of the magnet-actuated valve device, and at its second 
control device to the second inlet port, and at its outlet port to the 
outlet port, and at its supply connection with the first inlet port. 
The mechanical brake-pressure control device can exhibit a retention 
device. This retention device retains the redundant brake pressure up to a 
prespecified retaining pressure. The retaining pressure can be a function 
of the brake pressure delivered by the brake-pressure modulator. 
The electrical brake-pressure control device can include a load dependent 
brake pressure controller. In this case, the retaining pressure can at 
most be equal to the brake pressure delivered from the brake-pressure 
modulator in case of an empty vehicle. 
The retention device can be furnished by an overflow valve or by a 
load/empty valve. 
At least in a partial brake-value region the brake-pressure demand request 
can be larger than the redundant brake pressure. 
At least one relay valve can be contained in the brake circuit. The brake 
pressure, delivered by the brake-pressure modulator, is can be as a 
control pressure to the control device of the relay valve. The relay valve 
can simultaneously be employed as a magnet-controlled control valve of an 
anti-skid protection system. 
The brake system can include a pressure-controlled trailer control valve 
and an additional brake-pressure modulator of the kind specified can be 
present. One pressure control device of the trailer control valve can be 
connected with the outlet port of the additional brake-pressure modulator. 
In accordance with the invention, the magnet current strength is adjusted 
such that the brake-pressure component, originating from the magnet 
actuations amounts exactly to the difference between the brake-pressure 
demand request entered and the brake-pressure components derived from the 
redundant brake pressure. 
In order to monitor the redundant brake pressure, test routines are 
furnished in the known brake system in which the brake-pressure modulator 
is automatically actuated in the sense of a falling brake pressure upon 
actuation of the brake system. During the test routines, the redundant 
brake pressure can therefore be transferred as a brake pressure to the 
output of the brake-pressure modulator. A pressure sensor of the 
electronic control device, serving for a monitoring of the brake pressure, 
then indicates at which height level the redundant brake pressure is 
present and available. 
In contrast, the invention can be further developed with simple means such 
that the invention device allows a continuous monitoring of the redundant 
brake pressure upon brake actuation. 
The invention can be performed in connection with any suitable transferring 
pressure agents. The invention can be performed cost-advantageously by 
employing substantially commercially available apparatus and equipment. 
For example, in one embodiment, the pressure-control valve, described in 
the German Printed Patent Document DE-OS-3,038,797-Al, is employed as a 
brake-pressure modulator. In another embodiment, the brake-pressure 
modulator can, for example, be produced of a commercially-available 
proportional solenoid valve and a commercially available increasing 
dual-circuit relay valve device. 
The novel features which are considered as characteristic for the invention 
are set forth in the appended claims. The invention itself, however, both 
as to its construction and its method of operation, together with 
additional objects and advantages thereof, will be best understood from 
the following description of specific embodiments when read in connection 
with the accompanying drawings.

DESCRIPTION OF INVENTION AND PREFERRED EMBODIMENT 
FIG. 1 as drawn schematically with solid lines illustrates a base 
configuration of a brake system of a motor vehicle including a brake 
circuit actuated by feeding in of brake pressure, including an actuator 1, 
as well as with a mechanical brake-pressure control device 5 and an 
electrical brake-pressure control device 6, 8, 11, 19. Air serves as a 
pressure medium. The following statements hold also for brake systems 
employing different pressure media in view of a corresponding adaptation. 
The mechanical brake-pressure control device comprises a pressure part 5 of 
a brake-value furnishing unit 7. The electrical brake-pressure control 
device 6, 8, 11, 19 comprises an electrical part 6 of the brake-value 
furnishing unit 7, an electronic control device 11, 19, where the 
electronic control device 11, 19 includes a control circuit 11 and a 
brake-pressure sensor 19, and a brake-pressure modulator 8. 
The recited components of the brake system are of conventional construction 
with the exception of the control device 11. 
The brake-pressure modulator 8 is connected at an inlet port 3 to a 
pressure supply 4, and at an outlet port 17 with the actuator 1. The 
brake-pressure modulator 8 is magnet actuated and pressure actuated. The 
brake-pressure modulator 8 includes a control device for a pressure 
actuation. This control device is connected via a second inlet port 9 with 
the outlet port of the pressure part 5 of the brake-value furnishing unit 
7. Consequently, the control device of the brake pressure modulator 8 is 
subjected to the redundant brake pressure. The brake-pressure modulator 8 
includes an actuating magnet or a solenoid, not designated in detail, for 
magnet actuation. Upon actuation by one or by both actuation devices, the 
brake pressure modulator 8 connects the actuator 1 with the pressure 
supply 4, until a brake pressure has built up in the actuator. The height 
level of this built-up brake-pressure depends both on the fed-in magnet 
current as well as on the height level of the redundant brake pressure. 
The brake pressure delivered by the brake-pressure modulator 8 is thus 
comprised of a brake-pressure component derived from the redundant brake 
pressure and on a brake-pressure component derived from the magnet 
actuation. Depending on the embodiment and structure of the control device 
of the brake-pressure modulator 8, furnished for the pressure actuation, 
the brake-pressure component value derived from the redundant brake 
pressure can be equal or higher or lower as compared to the redundant 
brake pressure value. 
The pressure-control valve described in the German Printed Patent document 
DE-OS-3,038,797-Al can be employed as a brake-pressure modulator 8. This 
pressure-control valve is pressure actuated by connection of its venting 
connection to the outlet of the mechanical pressure part 5 of the 
brake-value furnishing unit 7 in the sense of the present invention. This 
brake-pressure modulator 8 determines the brake pressure by adding the 
brake-pressure components derived from its individual actuation devices. 
However, any other suitable kind of brake-pressure determination can be 
employed. 
The pressure sensor 19 monitors the brake pressure at the outlet port 17 of 
the brake-pressure modulator 8 where the brake pressure is delivered to 
the actuator 1. The pressure sensor 19 delivers a corresponding actual 
brake-pressure signal to the control circuit 11. 
The brake-value furnishing unit 7 delivers an electrical signal at its 
electrical part 6 upon actuation by the driver and depending on the 
actuation force or on the actuation path. In the following, this signal is 
called the actuation signal. Simultaneously,, the brake-value furnishing 
unit 7 transmits at its pressure part 5 from the pressure supply 4 the 
redundant brake pressure which depends also on the recited actuation 
parameters. The brake-pressure control device, represented by the pressure 
part 5, is called "mechanical" because this brake-pressure control device 
transforms the actuation parameters fed to the brake-value furnishing unit 
7 into the redundant brake pressure in a conventional way and by 
mechanical means. 
The control circuit 11 receives the actuation signal from the electrical 
part 6 of the brake-value furnishing unit 7 and the brake-pressure signal 
of the pressure sensor 19 and furnishes the magnet current required for 
actuation of the brake-pressure modulator 8 to the actuating magnet of the 
brake-pressure modulator 8. In the base embodiment, the control circuit 11 
evaluates the actuation signal as a brake-pressure demand request signal. 
The control circuit 11 compares this brake-pressure demand request signal 
to the actual brake-pressure signal and, in case of a deviation, 
determines and adjusts the magnet current strength to a value suitable for 
elimination of the deviation, i.e. to a value as necessary for satisfying 
the momentary brake-pressure demand request. In other words, the control 
circuit 11 sets the magnet current strength such that the brake-pressure 
component, derived from the magnet actuation, just corresponds to the 
difference between the brake-pressure demand request and the 
brake-pressure component derived from the redundant brake pressure. 
The electrical brake-pressure control device 6, 8, 11, 19 and/or the 
mechanical brake-pressure control device 5 can be constructed such that at 
least in the partial brake-value region, the brake-pressure demand request 
is higher than the redundant brake pressure such that a brake-pressure 
component, derived from the magnet actuation, always occurs at least in 
the partial brake-value region. In this case, upon a full brake pressure 
demand request, the brake-value furnishing unit 7 requires a substantially 
increased actuation force or a substantially increased actuation path for 
transmitting the full supply pressure as redundant brake pressure. 
In addition, a set-point region for the mutual coordination of the magnet 
current strength and of the brake pressure for the proper functioning of 
the pressure part 5 and of the pressure actuation of the brake-pressure 
modulator 8 can be stored in the control circuit 11. The control circuit 
11, in this case, can also be constructed such that it determines, under 
use of the actual brake-pressure signal, the position of the magnet 
current strength relative to the set-point region and delivers a warning 
signal if the magnet current strength leaves the set-point region. Due to 
this construction the electronic control device 11, 19 can serve 
simultaneously for monitoring the redundant brake pressure, and thus for 
monitoring the pressure part 5 and the control device for pressure 
actuation of the brake-pressure modulator 8 with respect to functioning 
and integrity of its operation. A magnet current strength outside the 
set-point region indicates too-high a brake-pressure or too-low a 
brake-pressure component, as derived from the redundant brake pressure. 
Interferences and/or failures of the pressure part 5 and/or of the 
pressure actuation of the brake-pressure modulator 8 and/or of the 
coordinated pressure-medium conduits are thereby indicated. 
FIG. 1 illustrates in dotted lines additionally further embodiments of the 
invention going beyond the previously described base structure and beyond 
the precedingly described additional feature. 
An additional actuator 21 indicates that the brake circuit can also be 
furnished with several actuators. The additional actuators can be 
connected to the brake-pressure modulator 8 of the base construction as 
illustrated. Alternatively, each individual actuator can be provided with 
its own brake-pressure modulator or several combined actuators can be 
provided with their own brake-pressure modulator. 
It is indicated by automatic control valves 2 or 20, respectively, of an 
anti-skid protection system, not illustrated in detail, that the invention 
brake system can also be furnished with an anti-skid protection system. In 
this case, the brake pressures in the actuator 1 or actuators 1 or 21, 
respectively, and at the outlet port 17 of the brake-pressure modulator 8 
can be different. The electronic control device of the anti-skid 
protection system can be combined fully or in part with the control 
circuit 11. 
The anti-skid protection valves 2 or 20, respectively, are furnished with 
their own venting device based on a conventional construction. The 
anti-skid protection valves 2 or 20, respectively, are disposed, as 
illustrated, between the outlet port 17 of the brake-pressure modulator 8 
and the actuator or actuators 1, 21, respectively. Therefore, the 
anti-skid protection valves 2 or 20, respectively, permit, if necessary, a 
very quick brake-pressure drop in the actuator or actuators 1, 21, 
respectively on the shortest path and thus without further devices. 
At least one further signal sensor is indicated by the reference numeral 
10. During the determination of the brake-pressure demand request, the 
control circuit 11 evaluates, in addition to the actuation signal of the 
electrical part 6 of the brake-value furnishing unit 7, the signal of said 
signal sensor 10. Such a signal sensor can be furnished, for example, by 
one or several load sensors, if the electrical brake-pressure control 
device, designated in this case with the reference numerals 6, 8, 10, 11, 
19, comprises a load dependent brake pressure controller. In each case, 
one or several retarder sensors, draw-bar force sensors, brake-torque 
sensors, brake-temperature sensors and similar sensors can be considered 
as additional or alternative signal sensors. According to this further 
embodiment, it can occur that the brake-pressure component, derived from 
the redundant brake pressure, exceeds already the brake-pressure demand 
request. A regulation and adaptation is possible based on the arrangement 
of a retention device, indicated by the reference numeral 18, in the 
mechanical brake-pressure control device, in this case designated with the 
reference numerals 5, 18. This retention device 18 limits the redundant 
brake pressure up to a predetermined limiting retention pressure. 
The retention pressure can be a fixed pressure value or can be variable 
depending on the requirements of the specific use or application. A fixed 
pressure value results during employment of a conventional overflow valve 
as a retention device. A variable retention pressure can, for example, be 
achieved by employing a retention device according to the principles of 
the regulating valves according to the WABCO Printed Publications 975,001, 
Edition March 1977, or 975,002, Edition August 1973. Another possibility 
by way of example to provide a variable retention pressure, is furnished 
by the embodiment of a retention device according to the principle of the 
load/empty valve, illustrated in WABCO Printed Publication 473,300, 
Edition January 1974. As illustrated, the brake pressure could in this 
case be fed to the control input of the load/empty valve. If the 
electrical brake-pressure control device comprises a load dependent brake 
pressure controller, this embodiment can be particularly adapted to this 
load dependent brake pressure controller by disposing and constructing the 
load/empty valve such that the retention pressure is at most equal to the 
brake pressure delivered from the brake-pressure modulator 8 in case of an 
empty vehicle. 
The total brake-pressure region can be subdivided by the retention device 
into a partial region with wear-optimized braking and into a second 
partial region where a good use of the available brake potential is more 
important. In the first partial region, the redundant brake pressure is 
lower, and in the second partial region, the redundant brake pressure is 
higher than the retention pressure. 
According to a further embodiment, the preceding exemplified embodiment 
incorporates a device for co-control of a trailer brake system. This 
co-control of a trailer brake system comprises a supply line 12 with a 
supply coupling 13 as well as an electrical and a pressure-actuated 
control device. The electrical control device comprises a control 
connection terminal 14 and the control circuit 11. For this purpose, that 
control circuit 11 is constructed such that it transforms the actuation 
signal, received from the electrical part 6 of the brake-value furnishing 
unit 7, and possibly a part or all of the signal sensors 10, into a 
trailer brake signal. The pressure-actuated control device comprises a 
trailer control valve 16 and an additional brake-pressure modulator. The 
trailer control valve 16 corresponds to the conventional pressure-actuated 
constructions. It is connected on the supply side to the supply line 12 
and delivers upon actuation a trailer brake control pressure to a trailer 
brake line with a brake coupling 15. The additional brake-pressure 
modulator corresponds in principle to the above-described brake-pressure 
modulator 8. However, the additional brake-pressure modulator is 
incorporated in part differently relative to the brake-pressure modulator 
8. The additional brake-pressure modulator is connected at its first inlet 
port 3 with the supply line 12 and at its outlet port 17 with a 
pressure-control device of the trailer control valve 16. The output port 
17 of the additional brake-pressure modulator 8 can also be directly 
connected with the trailer-brake line, according to an embodiment not 
illustrated here. The magnet actuation of this brake-pressure modulator 8 
is also supplied with magnet current by the correspondingly constructed 
control circuit 11. 
FIG. 2 illustrates in part a further embodiment of the exemplified 
embodiment of FIG. 1. The further embodiment comprises that the brake 
circuit includes a relay valve 25. The relay valve 25 is predisposed 
and/or shunted in a conventional manner relative to the actuator 1 or to 
the actuators 1, 21, respectively. The control device of the relay valve 
25 receives the brake pressure, delivered by the brake-pressure modulator 
8, as control pressure. 
The brake-pressure sensor 19 is illustrated at the outlet port of the 
brake-pressure modulator 8. However, the brake-pressure sensor 19 can also 
be disposed at the outlet port of the relay valve 25. 
Otherwise, the statements made relative to FIG. 1 hold in an identical or 
corresponding way for this embodiment precedingly described. 
FIG. 3 schematically illustrates, in full lines, the base construction of a 
brake system of a trailer. 
The mechanical brake-pressure control device 33, 34 comprises in this case 
a relay emergency valve 33 and an automatic load-sensing valve 34. The 
trailer brake valve 33 and the automatic load-sensing valve 34 are of 
conventional construction and are disposed in a conventional manner. 
Consequently, the relay emergency valve 33 serves simultaneously for 
transferring the pressure medium fed via a supply coupling 36 from the 
motor vehicle to the pressure supply 4. The relay emergency valve 33 is 
controlled via a brake coupling 35 and a control line, in which control 
line also the automatic load sensing valve 34 is disposed. 
Depending on the individual application, the automatic load-sensing valve 
34 can also be eliminated and dispensed with. 
The electrical brake-pressure control device 30, 8, 31, 19 comprises an 
electrical control connection 30, of the electronic control device 31, 19. 
The electronic control device 31, 19 includes a control circuit 31, a 
pressure sensor 19, and a brake-pressure modulator. The brake-pressure 
modulator, designated again with the reference numeral 8, and the 
brake-pressure sensor, designated again with the reference numeral 19, 
correspond in their individual construction in principle to the 
components, designated with the same reference numerals, of the preceding 
exemplified embodiment. Of course, the connections of these components in 
the present embodiment do not necessarily correspond to those of the 
preceding embodiment. 
The control connection 30 receives the trailer brake signal generated in 
the motor vehicle and delivers and feeds this trailer brake signal to the 
control circuit 31. One inlet port 3 of the brake-pressure modulator 8 is 
connected with the pressure supply 4 and a second inlet port 9 of the 
brake-pressure modulator 8 is connected with the outlet port of the relay 
emergency valve 33. The brake-pressure modulator is connected at its 
outlet port 17 with the pressure control device of a relay valve 32. The 
relay valve 32 includes in addition a magnet actuation and thereby 
simultaneously represents a magnet-controlled anti-skid protection valve 
of an anti-skid protection system. Such a anti-skid protection valve, also 
designated as anti-skid relay valve, is described for example in the 
German Printed Patent Document DE-OS 3,730,779-Al. 
The illustrations and explanations given with respect to the mode of 
operation of the prior embodiment according to FIG. 2 hold identically or 
correspondingly for this further embodiment according to FIG. 3. In this 
latter, the trailer brake signal is to be considered equivalent to the 
actuation signal of the electrical part 6 of the brake-value furnishing 
unit 7. 
A person of ordinary skill in the art will recognize that this embodiment 
can be derived in the region of the anti-skid relay valve 32 from the base 
construction and the further embodiments constructions of FIG. 1 and FIG. 
2 and that, on the other hand, the latter embodiments can be further 
developed based on the construction of this exemplified embodiment 
according to FIG. 3. 
FIG. 4 illustrates the exemplified embodiment according to FIG. 1 with a 
further different structure feature of the brake-pressure modulator. 
The brake-pressure modulator, designated in this case in general with 41, 
comprises a dual-circuit relay valve device 44 and a magnet-actuated valve 
device 40. The dual-circuit relay valve device 44 is of a commercial 
construction of the additive increasing type. In this case, "additive 
increasing" means that, there is delivered at the outlet port of the dual 
circuit relay valve device 44 a higher pressure than upon pressure 
application at only one of its control devices, upon a simultaneous 
pressure application at the two of the dual circuit relay valve device 44. 
The valve device 40 is formed in a conventional manner such that it 
functionally controls a pressure dependent on the fed-in magnet current 
strength. As such a valve device, there can for example be employed a 
commercially available proportional solenoid valve. The drawn lines 
surrounding the two recited valve devices 40 and 44 indicate that said 
valve devices are constructed as a single component for the formation of 
the brake-pressure modulator 41. The valve devices 40 and 44 can of course 
perform the function of the brake-pressure modulator 41 alternatively as 
correspondingly individual devices connected to each other in a 
corresponding way on-the pressure side. 
The first inlet port 3, the second inlet port 9, and the outlet port 17 of 
the brake-pressure modulator 41 are represented as connection points of 
the corresponding pressure-means conduits at the recited drawn lines. In 
case of a separate disposition of the valve device 40 and of the 
dual-circuit relay valve device 44, the inlet ports 3 and 9 as well as the 
outlet port 17 can coincide with the connections of the valve device 40 or 
of the dual-circuit relay valve device 44, respectively. 
The valve device 40 is connected at its pressure medium inlet with the 
first inlet port 3. The dual-circuit relay valve device 44 is connected at 
its supply connection also with the first inlet port 3, at its first 
control device 42 with the outlet port of the valve device 40, at its 
second control device 43 with the second inlet port 9, and at its outlet 
port with the outlet port 17. 
The actuator magnet of the valve device 40 represents the magnet actuation 
of the brake-pressure modulator 41. 
Based on the connections of the control devices 42 and 43 of the relay 
valve device 44 to the valve device 40 or via the second inlet port 9, 
respectively, with the mechanical brake-pressure control device 5 or, 
respectively, 5, 18, the dual-circuit relay valve device 44 is controlled 
both by the pressure transmitted from the valve device 40 as well as by 
the pressure delivered from the mechanical brake-pressure control device 5 
or, respectively, 5, 18, Since the pressure delivered by the valve device 
40 depends on the current strength fed to the actuator magnet, the control 
of the dual-circuit relay valve device 44 at the control device 42 is 
dependent on this magnet current strength. 
Because of the "additive increasing" type of construction of the 
dual-circuit relay valve device 44, the valve device 40 and the 
dual-circuit relay valve device 44 produce in connection with each other 
the same functions as are brought by the brake-pressure modulator 8 of the 
exemplified embodiment of FIG. 1. 
The brake-pressure modulator 8 can also be replaced in the precedingly 
recited arrangements and in general, possibly by use of simple adaptation 
measures by the brake-pressure modulator 41, in a way not illustrated in 
detail. 
Furthermore a statement made in connection with one embodiment also holds 
for the other embodiments in an identical or corresponding way. 
A person of ordinary skill in the art will recognize that the scope of 
protection of the invention is not exhausted by the preceding embodiments 
but comprises all embodiments which have the features recited in the 
patent claims. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of brake 
systems differing from the types described above. 
While the invention has been illustrated and described as embodied in the 
context of a brake system with at least one brake circuit, it is not 
intended to be limited to the details shown, since various modifications 
and structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.