Abstract:
A braking device for braking a moving mass includes a movably guided coupling member for pressing a brake lining against a braking surface, a brake cylinder, filled with a hydraulic liquid, a brake piston which is movable inside the brake cylinder and which is connected to the coupling member. At least one hydraulic line can be connected to the brake cylinder. The device ensures the moving masses to be reliably decelerated. For that purpose, a fluidic-mechanical safety brake device is used to connect the brake cylinder to the one or more hydraulic lines.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a device for decelerating a moving mass, comprising a movably guided coupling element for pressing a brake lining against a braking surface, a brake cylinder which is filled with hydraulic fluid, a brake piston which can move in the brake cylinder and is connected to the coupling element, and at least one hydraulic line which can be connected to the brake cylinder. 
     Such a device is already known from DE 34 41 128 A1. The device disclosed in said document has a brake actuator which comprises a brake cylinder which is filled with hydraulic fluid, wherein a moving part which projects into the cylinder is provided with a brake applying means for pressing a brake lining against a brake disk is provided. The brake actuator is part of a brake caliper which is guided in a movable fashion on a pitch circle. A cylinder bore is provided as a supporting cylinder, tangentially with respect to the pitch circle, wherein a supporting piston, which is supported on a chassis of a mass to be decelerated, projects into the supporting cylinder. If the hydraulic pressure in the brake cylinder is increased, the brake linings are pressed against a brake disk which rotates in the direction of travel. Frictional locking occurs and therefore the brake caliper moves tangentially with respect to the direction of rotation of the brake disk, wherein the supporting piston which is supported on the chassis and projects into the supporting cylinder is moved deeper into the supporting cylinder. The supporting cylinder is filled with a hydraulic fluid whose pressure is increased. The supporting cylinder is connected to the brake cylinder via a hydraulic line, with the result that power boosting occurs. 
     GB 1,019,982 describes a device comprising a spreading element which is arranged inside a brake disk and is provided as a brake applying means for pressing a brake lining against a brake disk. In this context, the spreading element is pivotably mounted. Owing to the deceleration force occurring in the case of braking, the brake disk is pivoted as a function of the direction of rotation. In this context, the spreading element and therefore the brake lining are connected via hydraulic lines to a pressure transducer which is attached to the frame of the mass to be decelerated and has a supporting cylinder and a supporting piston which projects into the supporting cylinder. As a result of the pivoting of the spreading element, the supporting piston is pushed into the supporting cylinder, which causes pressure to be applied to the hydraulic fluid of the supporting cylinder. The supporting cylinder is connected to a further spreading element via hydraulic lines. 
     DE 43 04 905 A1 describes a self-energizing brake which is based on purely mechanical principles. 
     DE 15 30 869 describes a hydraulic brake system with a brake actuator which is connected to a brake lining via a brake applying means. Furthermore, an additional pressure transducer in the form of a cylinder bore is provided, wherein the cylinder bore is filled with a hydraulic fluid, and after the frictional locking between the brake disk and the brake lining the hydraulic fluid is compressed by a plunger. This compression amplifies the braking force in the brake actuator, with the result that brake boosting occurs. 
     The device of the generic type has the disadvantage that in the event of a fault it is not possible to carry out safety braking. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is therefore to ensure safe braking of the moving masses in the event of a fault. 
     The invention achieves this object by fluid-mechanical safety braking means for connecting the brake cylinder to the hydraulic line or lines. 
     According to the invention, safety braking is carried out in the event of a fault. In order to be able to reliably bring the mass to a standstill even when electronic components fail, the safety braking means are not implemented as electronic components. Instead, a fluid-mechanically regulated safety braking operation with fluid-mechanical safety braking means is provided. The safety braking means are in other words fluid-mechanical regulatable safety braking means which can be used to permit safety braking even when the entire electronic system fails. The invention therefore makes available a hydraulic-mechanical brake device which is particularly fail-safe. Within the scope of the invention, for example a hydraulic line is provided which has a raised hydraulic pressure compared to the atmospheric pressure or to which pressure is applied for the purpose of braking. 
     However, at least two hydraulic lines with different hydraulic pressures are advantageously provided. The provision of at least two or more hydraulic lines is advantageous when regulating means are used for setting the braking operation as a function of predefined set point values. 
     According to one expedient development, the safety braking means comprise a brake valve which can be triggered mechanically in the hydraulic lines for setting the hydraulic pressure in the brake cylinder, a mechanical set point value transmitter which is configured to apply a set point force, dependent on a set point value, to the brake valve, and a hydraulic actual value transmitter which communicates via a hydraulic regulating line with the hydraulic line or lines or the brake cylinder, and is configured to apply an actual force to the brake valve, which actual force is dependent on the pressure in the hydraulic regulating line, wherein the set point force counteracts the actual force. According to this advantageous development, a brake valve is provided which has, for example, a sliding element. The brake valve is connected on the inlet side to, for example, two hydraulic lines which have different hydraulic pressures. On the outlet side, the brake valve is connected to the brake cylinder. Depending on the position of the sliding element, a pressure or differential pressure can be generated in the brake cylinder and is used to determine the pressing force of the brake lining against the braking surface such as, for example, a rotatable brake disk. According to this advantageous development of the invention, the position of the sliding element corresponds to the difference between the set point force and the actual force. The two forces act, for example, on the sliding element from different sides. If the set point force is greater than the actual force which is derived, for example, from the hydraulic pressure in the brake cylinder, the sliding element is slid into a position with which the hydraulic pressure in the brake cylinder is increased. Increasing the hydraulic pressure causes the actual force to be increased. This brings about sliding of the sliding element in the opposite direction to the set point force, with the result that the hydraulic force in the brake cylinder is reduced. This process is repeated until the difference between the set point force and the actual force is minimized. In other words, regulated safety braking is made available by fluid-mechanical safety braking means. The safety braking means according to the invention are based on pneumatic, hydraulic or other mechanical forces which can be generated in a failsafe fashion. 
     The brake lining is expediently supported via connecting means with a pressure transducer which is attached to a frame of the mass to be decelerated and has a supporting cylinder which is filled with hydraulic fluid and a supporting piston which projects into the supporting cylinder, wherein the supporting cylinder communicates with the brake cylinder via the hydraulic line. According to this expedient development, a self-energizing hydraulic brake is made available which has a safety function. The self-energization is based on the fact that the brake lining is supported on a hydraulic or pneumatic pressure transducer. In the case of braking, the brake lining engages with the braking surface, and owing to the frictional locking it is accelerated tangentially with respect to the direction of rotation of the braking surface. The resulting force is applied via the connecting means to the pressure transducer whose supporting piston applies pressure to the hydraulic fluid, in which case the pressure is also increased in the brake cylinder via the hydraulic lines. However, this causes the brake lining to be pressed with greater force against the braking surface, and therefore brings about brake boosting. The surfaces of the supporting cylinder and brake actuator are advantageously selected in such a way that the pressure which is brought about in the supporting cylinder when braking occurs is higher than the pressure which is necessary for braking. 
     The hydraulic regulating line expediently communicates with the supporting cylinder. According to this advantageous development, the actual force for regulating the safety braking is based on the hydraulic pressure in the supporting cylinder. Said actual force therefore corresponds precisely to the deceleration force in the brake radius, that is to say the force with which the braking lining is supported on the pressure transducer. The deceleration force therefore makes available a particularly precise regulating variable since the deceleration force is causally linked to the slowing down of the moving mass. 
     According to one preferred exemplary embodiment, the supporting cylinder is divided into a supporting chamber and a supporting return chamber by the supporting piston, wherein the supporting chamber and the supporting return chamber communicate with a high pressure line or low pressure line via nonreturn valves. According to this advantageous development, the rotational direction of the braking surface is irrelevant for the self-energization. Self-energization of the braking is possible both for forward travel and reverse travel. 
     According to a development which is expedient in this regard, compression springs are provided in the supporting chamber and in the supporting return chamber, wherein a pressure transducer return valve is provided for equalizing the pressure between the supporting chamber and the supporting return chamber, and wherein a control unit initiates the pressure equalization by means of the pressure transducer return valve and the compression springs. The pressure transducer return valve can connect the two chambers of the pressure transducer to one another given corresponding activation by the control unit. Pressure equalization therefore occurs between the two chambers. The compression springs which are arranged in the chambers subsequently cause the supporting piston or the supporting cylinder to slide into the home position. This avoids braking being initiated if the supporting piston is already just before the location at which it strikes against a boundary of the supporting cylinder. 
     The hydraulic regulating line is expediently connected to the outlet of a valve which communicates on the inlet side with the supporting chamber or with the supporting return chamber as a function of the relatively high pressure. According to this advantageous development, the safety braking means are adapted to a two-chamber supporting system. The two-chamber supporting system permits self-energization both for forward travel and reverse travel. This is advantageous in particular in vehicles. 
     According to one expedient development, the set point value transmitter has an adjusting screw which interacts with an adjusting spring. The adjusting spring is, for example, a compression spring. This is compressed by rotating the adjusting screw with the result that the compressive force of the adjusting spring which acts on the brake valve is increased. Rotating the adjusting screw in the other direction reduces the spring force and therefore the set point force which is applied to the brake valve. 
     The set point value transmitter advantageously has a fluidic or mechanical converter which generates a set point force which is dependent on the mass to be decelerated. According to this advantageous development, the converter continuously measures, for example, the weight of the mass to be decelerated. A corresponding set point force is generated by the converter as a function of the measured weight, with the result that safety braking which is determined by the mass to be decelerated is carried out. Of course, it is also possible within the scope of the invention for both a converter and an adjusting screw to be provided, in which case the converter acts directly or via the adjusting screw. 
     The actual value transmitter advantageously has a pressure cylinder with a sliding element. For example, a hydraulic pressure which causes the sliding element to slide is generated in the actual value transmitter, in which case the sliding of the sliding element causes, for example, a compression spring to be compressed, with the result that a spring force, which counteracts the applied set point force, can be generated from the hydraulic pressure in the actual value transmitter. The hydraulic pressure can be generated basically in any desired way within the scope of the invention. For example, in one differing variant of the invention the sliding element is connected to the brake lining via a suitable lever mechanism. In other words, the brake lining is supported on the pressure cylinder via fluidic or mechanical means. 
     An electric regulating device is expediently provided, wherein the safety braking means is configured to initiate a regulated braking operation if the electric regulating device fails. The electric regulating device is configured to regulate the deceleration of the mass in the normal operating mode. In this context, the electric regulating device allows for the safety braking means, specifically for example to the extent that the electric regulating device calculates a predetermined set point force taking into account the mechanical set point force which has already been predefined by the safety braking means, with the result that the set point force which is predefined by means of the electric regulating device corresponds, for example, to the difference between a desired set point force and the mechanical set point force. However, if the electric regulating device fails, the safety braking means intervene and carry out a safety braking operation as a function of the mechanical set point force. 
     According to one expedient development, an electric regulating device acts on the brake valve by means of an actuating element. The brake valve is therefore accessed by means of an actuating element, for example a component which acts on a sliding element of the brake valve. The actuating element is, for example, a component which operates electrodynamically and which applies a force to the sliding element of the brake valve as a function of a current. In contrast to this, the actuating element is configured to rotate an adjusting screw. 
     According to one expedient development, the coupling element is connected to the brake lining via a lever mechanism. The coupling element is, for example, a push rod which acts on the brake lining via levers and linkages and which is arranged spatially remote from the brake cylinder. However, such lever mechanisms are known to a person skilled in the art so that more details will not be given on them at this point. 
     According to one advantageous development, the brake actuator comprises a brake cylinder which is filled with hydraulic fluid and a brake piston which can move relative to one another. However, in contrast to this customary configuration of the brake actuator, other brake actuators which are known as such to a person skilled in the art can also be used within the scope of the invention. 
     The brake piston is expediently permanently connected to the coupling element. 
     According to one preferred embodiment of the invention, the brake cylinder is divided into a braking chamber and a braking return chamber by means of the brake piston. The brake cylinder is, in other words, configured as a double-acting cylinder. The braking force which is set is therefore substantially dependent on the pressure difference between the braking chamber and the braking return chamber. 
     According to a further advantageous refinement of the invention, the coupling element comprises a brake rod which extends through the braking return chamber. According to this advantageous development of the invention, when there is a pressure equilibrium between the braking chamber and braking return chamber a relatively large force is generated in the braking chamber owing to the relatively large surface of the brake piston in the braking chamber, with the result that when there is a pressure equilibrium the brake piston is slid out of its center position. This is advantageous, for example, in order to initiate safety braking when there is a loss of pressure. There may also be the effect of a pre-stressing spring. 
     The brake actuator advantageously comprises a brake cylinder and a brake piston which divides the brake cylinder into a braking chamber and into a braking return chamber, wherein the braking chamber and the braking return chamber can be connected, by means of a brake valve, both to a fluidic high pressure circuit and to a fluidic low pressure circuit. 
     According to a further advantageous development of the invention, a pre-stressing spring for pressing the brake lining against the braking surface is provided. Within the scope of the invention the pre-stressing spring is basically arranged in any desired way. If pressure is not present in the hydraulic lines, the brake lining continues to be pressed against the braking surface by the force of the pre-stressing spring. 
     A high pressure vessel, which is part of a high pressure circuit, and a low pressure vessel, which is part of a low pressure circuit, are advantageously provided for making available hydraulic fluid, wherein the high pressure circuit and the low pressure circuit are connected to the brake valve. The brake valve is expediently provided for generating any desired pressures in the brake actuator, wherein the pressures which can be generated are in the range of the pressure difference between the high pressure circuit and the low pressure circuit. 
     According to one development which is expedient in this regard, each high pressure vessel and each low pressure vessel is respectively equipped with a nonreturn valve and a restrictor. If the pressure in the high pressure vessel or the pressure in the low pressure vessel exceeds the pressure in the high pressure circuit or in the low pressure circuit respectively, further hydraulic fluid is fed from the respective pressure vessel into the hydraulic circuit via the restrictor, with the result that there is always a sufficient quantity of hydraulic fluid available. 
     The brake lining is expediently connected to the supporting cylinder via the connecting means, the supporting piston being attached to the frame. This variant of the invention permits particularly compact manufacture of the device according to the invention since all the cylinders and lines which are filled with hydraulic fluid can, for example, be combined to form one component. In particular, common manufacture of these components is made possible. The supporting piston, or the supporting rod which extends out of the supporting cylinder from the supporting piston, merely has to be attached by its free end, facing away from the supporting piston, to the frame of the mass to be decelerated. 
     According to an embodiment of the invention which differs from this, the brake lining is connected to the supporting piston via the connecting means, wherein the supporting cylinder is attached to the frame. 
    
    
     
       Further expedient embodiments and advantages of the invention are the subject-matter of the following description of exemplary embodiments of the invention with reference to the figures in the drawing, in which identical reference symbols refer to identically acting components, and of which figures 
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIGS. 1A-1C  show an exemplary embodiment of the device according to the invention, the safety braking means of which device are not illustrated figuratively, and 
         FIGS. 2A-2C  show the device according to  FIGS. 1A-1C  when the electronic regulating unit fails. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIGS. 1A-1C  show a first exemplary embodiment of the device  1  according to the invention in a schematic illustration, with the safety braking means not being illustrated figuratively. The device  1  according to the invention comprises a high pressure circuit  2  and a low pressure circuit  3 , which each communicate with a high pressure vessel  4  or with a low pressure vessel  5 . The high pressure vessel  4  and the low pressure vessel  5  are each equipped with a combination of a restrictor and nonreturn valve  6 , via which nonreturn valve  6  the latter is connected to the respective hydraulic line  2 ,  3 . If the pressure in the respectively assigned hydraulic line  2 ,  3  is lower than in the high pressure vessel  4  or the low pressure vessel  5 , hydraulic fluid exits the respective pressure vessel  4 ,  5  and is made available to the system. A lack of hydraulic fluid is counteracted in this way. The high pressure circuit  2  and the low pressure circuit  3  are connected via an analog slider control valve  7  as a brake valve to a brake actuator  8  which has a brake cylinder  9 . The brake cylinder  9  is divided by a brake piston  10  into a braking chamber  11  and a braking return chamber  12 . A coupling rod  13   a  extends as a coupling element from the pressure piston  10  to a brake lining  14 , which is provided for pressing against a brake disk  15  as a braking surface. The coupling element  13   a  is connected to the brake lining  14  via a lever mechanism  13   b .  FIGS. 1A-1C  show the brake disk  15  and the brake lining  14  both in a plan view and in a side view. 
     In the illustration shown in  FIGS. 1A-1C , it is possible to see that the brake lining  14  is connected via supporting means  16   a , such as for example a simple rod or any desired other lever mechanism, to the supporting piston  17  of a pressure transducer  18 . The pressure transducer  18  has a supporting cylinder  19 , in addition to the supporting piston  17 . The supporting piston  17  divides the supporting cylinder  19  into a supporting chamber  20  and into a supporting return chamber  21 . Compression springs  22  are respectively arranged in the supporting chamber  20  and in the supporting return chamber  21 . The supporting cylinder  19  is attached to a frame  52 . 
     The brake lining  14  is mounted so as to be movable tangentially with respect to the direction of rotation of the rotary disk  15 , and is therefore supported on the pressure transducer which is attached to a bogie of a rail vehicle. 
     The supporting chamber  20  and the supporting return chamber  21  are each connected via expedient hydraulic lines  23  or  24  to the high pressure circuit  2  or the low pressure circuit  3 . In this context, the hydraulic lines  23 ,  24  communicate with nonreturn valves  25  to  28 . The nonreturn valves  25 ,  26  which are arranged in the hydraulic line  24  of the supporting return chamber  21  are oriented in opposite directions to one another. If the pressure in the supporting return chamber  21  is higher than in the low pressure circuit  3 , the nonreturn valve  25  closes the connection between the hydraulic line  24  and the low pressure circuit  3 . If, on the other hand, the pressure in the supporting return chamber  21  is higher than that in the high pressure circuit  2 , the nonreturn valve  26  opens with the result that fluid, for example a suitable hydraulic fluid, is forced out of the supporting return chamber  21  and is fed into the high pressure vessel  4 . If, in contrast, the pressure in the supporting return chamber  21  is lower than in the low pressure circuit  3 , the valve  25  opens, permitting hydraulic fluid to flow out of the low pressure vessel  5  into the supporting return chamber  21 . The same applies to the interaction of the supporting chamber  20  and the nonreturn valves  27 ,  28  via the hydraulic line  23 . 
       FIGS. 1A and 1C  also show a pressure transducer return valve  29  which communicates with the supporting chamber  20  or the supporting return chamber  21  via hydraulic lines  30  and  31 . The pressure transducer return valve  29  has a sliding element  32  which, when activated, brings about the pressure equalization between the supporting chamber  20  and the supporting return chamber  21 . If a pressure equalization occurs, the pressure springs  22  slide the supporting piston  17  back into the central position shown in  FIGS. 1A and 1C . This avoids the supporting piston  17  being slid against a boundary wall of the supporting cylinder  19 , therefore interrupting the brake boosting. An expedient pressure equalization control unit  33  serves to activate the pressure transducer return valve  29 . The activation is in turn carried out, for example, by means of electrodynamic forces. 
     The pressure equalization control unit  33  also acts on a regulating valve  34  which can be released and which permits the pressure from the high pressure circuit  2  to be let out, for example for maintenance purposes. 
     The hydraulic lines  23  and  24  are each provided with calibrated pressure/voltage converters (not illustrated figuratively). Each pressure/voltage converter makes available, at its output, a voltage which is proportional to the pressure in the supporting chamber  20  and/or in the supporting return chamber  21 . 
     The output of each pressure/voltage converter is connected to the input of a difference generator  35 . The difference generator  35  is connected at the output end to an absolute value generator  36  which calculates the absolute value |Δp| from the pressure difference Δp made available by the difference generator  35 . The absolute value of the pressure difference |Δp| is finally applied to the input of a comparator  37 . A set point pressure difference Δp setp  is applied as set point value to the second input of the comparator  37 , said set point pressure difference Δp setp  being calculated on the basis of a set point force F setp  and as a function of a predefined area factor  38 . The set point force F setp  is input by a user of the device by means of an expedient control unit  39 . The comparator  37  generates, at its output, a difference value ΔF which is applied to the input of a control unit  40 , which subsequently slides a sliding element  41  of the brake valve  7  in such a way that the difference value ΔF is minimized. The brake valve  7  is, for example, a proportional valve. 
     A pre-stressing spring  45  is used to press the brake lining  14  against the brake disk  15 . The pre-stressing spring  45  presses the brake lining against the brake disk if a pressing-on force cannot be generated hydraulically. 
     The method of operation of the device  1  according to the invention is as follows: in order to apply a braking process a set point force F setp  is requested using the regulating means  42 . The regulating means  42  comprise the control unit  39 , the measuring sensors (not illustrated figuratively), the difference generator  35 , the absolute value generator  36 , the area factor generator  38 , the comparator  37 , the regulating unit  40  and the brake valve  7 . The pressure difference Δp between the supporting chamber  20  and the supporting return chamber  21  is equal to zero at the start of the braking operation, with the result that a large difference value ΔF is generated by the comparator  37 . The regulating unit  40  subsequently slides the sliding element  41  to the left, with the result that a large pressure difference is generated between the braking chamber  11  and the braking return chamber  12 . In this context, the pressure in the braking chamber  11  is higher than in the braking return chamber  12 . The brake piston  10  is slid and as a result a pressing-on force F N  is applied to the brake disk  5  in the direction indicated by the arrows. The frictional locking between the brake lining and the brake disk  5  causes a frictional force to be generated which is directed tangentially with respect to the direction of rotation of the brake disk  5  or, in other words, a deceleration force F act  is generated. The deceleration force F act  is applied to the supporting piston  17  via the connecting means  16   b , that is to say the lever mechanism, owing to the movable mounting of the brake lining  14 . When the brake disk  15  rotates, the supporting piston  17  is slid to the right in the clockwise direction out of the position shown in  FIGS. 1A and 1C . The pressure of the hydraulic fluid is therefore increased in the supporting chamber  20  compared to the pressure of the hydraulic fluid in the supporting return chamber  21 . The pressures are respectively sensed by the pressure/voltage converter and are applied to the input of the difference generator  35 . This gives rise to a pressure difference Δp at the output of the difference generator  35 , and therefore to a corresponding absolute value |Δp| at the output of the absolute value generator  36 . The difference value ΔF becomes smaller, and in the further course of the regulating process the regulating unit  40  ensures here that the difference value ΔF is ultimately minimized. In other words, the invention brings about self-energization and simultaneous regulation of the braking force. 
       FIGS. 2A-2C  show the exemplary embodiment according to  FIGS. 1A-1C , but here the electronic components of the electric control device  42  have been omitted for reasons of clarity. It is apparent that the regulation of the brake valve  7  is now carried out by the fluid-mechanical safety means  43 . The latter comprise a load correction means  44 , which is indicated schematically. The load correction means  44  comprises a load signal transmitter which, as a function of the weight of the mass to be decelerated, adjusts an adjusting screw  46  in such a way that the spring force of a compression spring  47  applies the necessary set point force to the sliding element  41  of the brake valve  7 . In contrast to this, the load correction means can also act directly on the sliding element. The set point force is counteracted by an actual force, with the actual force being generated by an actual force signal transmitter (not illustrated figuratively). The actual force signal transmitter comprises a pressure cylinder (not illustrated) which comprises a sliding element  41  and applies an actual force to the sliding element  41 . The actual force is opposed to the set point force. The pneumatic pressure in the pressure cylinder of the actual value signal transmitter corresponds either to the pressure of the supporting chamber  20  or of the supporting return chamber  21 , depending on which of said chambers has the higher hydraulic pressure. A double nonreturn valve  49 , whose two inlets are connected to the supporting chamber  20  or to the supporting return chamber  21 , is used for this. A hydraulic regulating line  50  connects the outlet of the double nonreturn valve  49  to the pressure cylinder of the actual value signal transmitter. 
     The safety braking means  43  comprise the load correction means  44 , the adjusting screw  46 , the compression spring  47 , the brake valve  7  with sliding element  41  and the actual value signal transmitter (not illustrated figuratively). 
     If the electronic components of the electric regulating unit  42  fail, the safety braking means  43  therefore initiate a regulated safety braking operation. The braking force is predefined by the set point force here. At the start of the braking operation, the pressure in the supporting chamber  20  or in the supporting return chamber  21  is equalized and is so low that the actual force which is generated by means of the actual value signal transmitter is lower than the set point force which is set by the set point value transmitter, that is to say by the adjusting screw  46  with the compression spring  47 . Accordingly, the sliding element  41  is moved to the left in the illustration according to  FIGS. 2A and 2C . This means that a large pressure difference is generated in the brake cylinder  9 , and the brake lining  14  is pressed with a high normal force F N  against the brake disk  15 . The brake disk  15  moves in the clockwise direction, with the result that pressure is built up in the supporting return chamber  21 . The increased pressure in the supporting return chamber  21  causes the pressure in the pressure cylinder (not illustrated figuratively) of the actual value signal transmitter also to be increased. This brings about an increase in the actual force which causes the sliding element  41  in  FIGS. 2A and 2C  to be slid to the right, with the result that the pressure difference in the chambers of the brake cylinder  9  is reduced. The normal force F N  is attenuated. This is continued until the supporting force of the brake lining  14  at the pressure transducer  18  corresponds to the set point force which has been set.