Brake cylinder with integrated wear adjusting device for rail vehicles

A brake caliper for a disk brake or to a disk brake with a brake caliper for rail vehicles. A brake caliper has caliper arms at which at the ends brake shoes are mounted and which are pivotally driven against each other by a brake cylinder. The brake caliper or disk brake has the advantage that the brake cylinder and the wear adjusting device are contained in a common housing and that the wear adjusting device acts along the same linear axis of movement as the force which is generated between two carriers which are pivotally connected to the caliper arms and drive the same for pivoting in order to subject the brake shoes to tension against each other.

PRIORITY CLAIM AND REFERENCE TO RELATED APPLICATION

The application claims priority under 35 U.S.C. § 119 and all applicable statutes and treaties from DE 10 2015 218815.9, filed on 29, Sep. 2015, and from DE 10 2015 219 058.7, filed on 1 Oct. 2015.

FIELD

Fields of the invention including braking devices and rail vehicles. The invention concerns brake calipers for disk brakes and disk brakes with a brake caliper for rail vehicles.

BACKGROUND

DE 195 09 540 C1 describes a brake caliper for a disk brake the caliper arms of which are pivoted against each other by a rotary arm eccentrically supported approximately centrally at one of the caliper arms wherein the rotary arm is rotated by a brake cylinder. A wear adjusting device with a spindle is arranged between the ends of the caliper arms opposite to the brake shoes mounted at the ends of the caliper arms wherein the spindle is moved out by rotating the spindle nut by a control rod which extends along a caliper arm and which is driven by a lever arm arranged at the rotary arm.

DE 43 30 440 A1 describes a brake caliper for a disk brake, the caliper arms of which are approximately centrally engaged by an arrangement of a force reservoir which is pivoted by an adjustment device and acts onto a rocker through a control curve so that the caliper arms and the brake shoes mounted at one end are pivoted towards one another. A wear adjusting device is arranged at the caliper end opposite to the brake shoes and has a gear box and a motor operator.

The above-cited prior art has the disadvantage that a wear adjusting device is arranged at one end of the caliper arms opposite to the brake shoes while the caliper arms are approximately centrally engaged by the force generating means of the brake caliper.

EP 2 154 391 B1 describes a force generating means of a brake caliper with a brake cylinder acting onto a wedge which is guided between two rollers in order to displace the same along a linear axis of movement against each other wherein the rollers act onto carriers located in the linear axis of movement and pivotally connected to the ends of the arms of a brake caliper. The one roller acts upon a spindle located in the linear axis of movement and having a spindle nut which, dependent on the movement of the spindle against a housing, is rotated by a spring compressed by this movement and defines a wear adjusting device.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a brake caliper for a disk brake or to a disk brake with a brake caliper for rail vehicles. A brake caliper has caliper arms at which at the ends brake shoes are mounted and which are pivotally driven against each other by a brake cylinder. The brake caliper or disk brake has the advantage that the brake cylinder and the wear adjusting device are contained in a common housing and that the wear adjusting device acts along the same linear axis of movement as the force which is generated between two carriers which are pivotally connected to the caliper arms and drive the same for pivoting in order to subject the brake shoes to tension against each other.

Embodiments of the invention provide an alternative brake caliper for a disk brake, especially a brake caliper with an alternative wear adjusting device which preferably is arranged in a common housing with a brake cylinder and especially has a force generating means with a wear adjusting device in a housing. Further preferred, the brake caliper is to allow a direct measurement of the force acting on the caliper arms which is generated by pressure acting onto the brake cylinder.

A preferred embodiment is a brake comprising two caliper arms at the end of which brake shoes are arranged each, and between which a force generating device is pivotally mounted by means of a first carrier and a second carrier spaced therefrom, characterized in that the first and the second carriers are arranged on a common linear axis of movement and the first carrier has a stud disposed along the linear axis of movement and guided longitudinally displaceably and torque-proof in a guidance arranged at the first end of a housing, and the second carrier is disposed at the opposite second end of the housing, wherein a first end of a spindle is rotatably supported at the stud, the spindle is guided in a spindle nut coaxially with respect to the stud in the housing, the spindle nut being guided in the housing torque-proof and displaceably parallel to the linear axis of movement and being driven along the linear axis of movement by a piston arranged in the housing and loadable with pressure, with a controlled motor arranged in the housing which motor is arranged to rotate the spindle against the housing.

LIST OF REFERENCE NUMBERS

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides advantages, especially with a brake or brake caliper which has respective brake shoes at the ends of its two caliper arms. A force generating device is arranged between the caliper arms at the ends of the caliper arms opposite to the brake shoes, and a connection is arranged between the ends of the caliper arms, for instance approximately centrally, around which the caliper arms are pivotable.

The force generating device is articulated at the caliper arms with a first carrier arranged at the first end of the housing and with a second carrier arranged at the opposite second end of the housing. The first and second carriers are arranged on a common linear axis of movement along which the carriers are moved away from one another by the force of a piston. The first carrier has a stud which is guided longitudinally displaceably and torque-proof or rotationally fixed, respectively, in a guidance of a housing. The second carrier is fixed at the housing. The first end of a spindle is rotationally supported at the stud of the first carrier. The axis of the spindle is located coaxially to the linear axis of movement and coaxially to the longitudinal axis of the stud. The spindle is guided in a spindle nut which is guided in the housing in a torque-proof or rotationally fixed manner and parallelly displaceably with respect to the linear axis of movement in the housing. The spindle nut is displaceably driven in parallel to the linear axis of movement by a piston so that the spindle nut and with the same the spindle is displaceable along the linear axis of movement by the piston and with the spindle the stud of the first carrier is displaceable in its guidance.

Generally, the cylinder in which the piston is guided can be loaded by the pressure of the brake, for instance, by the pressure of the service brake.

The force generating device is preferably characterized by the feature that in the housing a sensor is arranged which is designed to take up the path and/or the position of the spindle along the linear axis of movement in the condition in which the brake shoes are spaced from one another, in which the brake linings lie against a brake disc. Generally, the force generating device is characterized by a motor driving the spindle to rotate, which is e.g. an electric motor, a pneumatic or a hydraulic motor, is arranged in the housing. The motor forms the drive for the spindle. The motor can be an electric, hydraulic or pneumatic rotary drive or linear drive. A hydraulic motor can e.g. be a hydraulic cylinder or a hydraulic linear motor or rotary motor, a pneumatic motor can e.g. be a pneumatic cylinder or a pneumatic linear motor or rotary motor.

In the following, an electric motor is mentioned as a representative of a motor. The electric motor is preferably controlled in dependence on a signal of the sensor for the position and/or for the path of the spindle in the housing. By the rotation of the spindle by the electric motor the spindle and thus the stud of the first carrier is displaced along the linear axis of movement relative to the spindle nut. The displaceability of the spindle nut and with the same of the spindle and of the stud of the first carrier along the linear axis of movement by the piston is not changed by the rotation of the spindle. So, the rotation of the spindle acts for the adjustment of the distance between the first carrier and the second carrier for the wear adjustment, wherein the piston displaces the spindle nut in order to form a service brake. Preferably, the electric motor is controlled to rotate the spindle only in a condition in which the piston forming the service brake is not loaded by pressure. The electric motor is preferably controlled in dependence on the signal of the sensor and together with the spindle forms a wear adjusting device. Since the wear adjusting device is arranged within the housing and is integrated into the drive means between the carriers, the force generating device according to the invention has the advantage that no slack adjuster is present outside of the housing which, for instance, engages the caliper arms with a spacing from the force generating device.

Preferably, the electric motor is controlled in dependence on the signal of the sensor in a manner that it rotates the spindle only when a predetermined path of the spindle nut in the housing is exceeded, and is especially set up for rotating the spindle nut for an amount which causes a displacement of the spindle nut for the amount that exceeds the predetermined path. Additionally or alternatively the electric motor is preferably controlled to move the spindle into a position along the linear axis of movement in which the carriers are moved away from one another only for a predetermined maximum path by the pressure loading of the piston, for instance, until the carriers have moved the caliper arms of the brake so far until the brake shoes have a distance from one another in which the brake linings have a predetermined distance from the brake disc.

The electric motor is for instance stationarily fixed in the housing, especially arranged with its shaft stud, optionally by means of a gear box, coaxially with regard to the axis of the spindle and rotationally fixedly connected to the same. Preferably, the electric motor is located at the second end within the housing. For the purposes of the invention the electric motor can have or contain a gear box driving the shaft stud, for instance. Preferably, the electric motor is a step motor. Preferably, the electric motor is controlled to rotate the spindle only in a case in which the piston is not loaded with pressure, for instance in the released condition of the brake.

The spindle is connected to the electric motor in a longitudinally displaceable manner in order to admit a longitudinal displacement of the spindle upon a movement of the spindle nut along the linear axis of movement which is driven by the piston. For this, the shaft stud of the electric motor is coaxially and longitudinally displaceably arranged with respect to the spindle directly or by means of a gear box and, for instance, by means of engagement means displaceable along the axis of the spindle is rotationally fixedly connected to the spindle, especially at the second end of the spindle which is located opposite to its first end and to the stud of the first carrier. Such an engagement means can, for instance, consist of a longitudinal slot in one of spindle and shaft stud and a peg guided in the longitudinal slot in the other member of spindle and shaft stud. The shaft stud can be arranged coaxially within or outside the spindle. Preferably, the shaft stud of the electric motor is longitudinally displaceably and torque-proofly guided in a coaxial bore of the spindle at the second end thereof, for instance by means of two pegs of the shaft stud which are displaceably guided in longitudinal slots of the spindle.

Preferably, the sensor by means of a data line is connected to an electronic microcontroller which is designed to control the electric motor in response to a signal of the distance sensor.

In a variant the sensor is a distance sensor which is designed to detect the path and/or the position of the spindle nut along the linear axis of movement, especially the path of the spindle nut along which the same is moved upon loading of the piston with pressure and/or the position of the spindle nut which the same takes upon loading of the piston with pressure. Since the spindle is engaged with the spindle nut the path and respectively the position of the spindle nut upon loading of the piston with pressure is the same as the path and the position of the spindle, respectively, when the electric motor stands still and the spindle is not rotated, respectively. Preferably, the distance sensor is a contact-free sensor.

In another variant the sensor is a force sensor which is designed to detect the force between the first end of the spindle and the stud of the first carrier. Here it is preferred that a microcontroller controlling the electric motor is designed to control the electric motor for the rotation of the spindle in the absence of pressure onto the piston until the force sensor detects a steeply increasing force acting from the spindle onto the stud as a signal for a distance of the brake shoes in which brake linings mounted thereon lie against a brake disc, and the microcontroller is designed to control the electric motor subsequently for the rotation of the spindle in the opposite direction for a predetermined amount. In this variant the brake is designed for the wear adjustment by the feature that in the condition, in which the piston does not load the spindle nut, the electric motor rotates the spindle until the force sensor shows the position of the brake linings lying against a brake disk by the force between the spindle and the stud of the first carrier steeply increasing. In this position of the spindle the brake linings lie against the brake disc. Therefore, the microcontroller is designed to control the electric motor for the rotation of the spindle in the opposite direction so that, without pressure loading of the piston, the spindle is located in a position along the linear axis of movement in which it does not apply a force between the carriers and the brake linings lie in a distance from the brake disc. The rotation of the spindle in the opposite direction results in a movement of the spindle in the direction towards the second end of the housing. The rotation of the spindle in the opposite direction occurs especially for a predetermined amount so that the spindle brings together the caliper arms and therefore also the brake linings into a predetermined distance with respect to one another. So, the rotation of the spindle in the opposite direction can occur until, for instance, the brake linings take in a predetermined distance with respect to one another, respectively, in which they take a predetermined distance from the brake disk.

The condition in which the piston does not load the spindle nut especially is a condition in which the cylinder in which the piston is guided is not loaded with pressure and the piston is not loaded by a second piston by means of an extension, either, which second piston, for instance, is loaded against the piston by means of a second pressure spring in the absence of operating pressure.

Preferably, a pressure spring is disposed between the first end of the housing and the spindle nut which loads the spindle nut away from the first end and in the direction towards the second end of the housing. Such a pressure spring defines a readjusting spring for the spindle nut which acts against the displacement caused by the piston. This pressure spring can be also designated as readjusting spring for the spindle and/or as readjusting spring for the service brake.

Optionally, especially in the second variant, a force sensor is arranged between the stud of the first carrier and the spindle to measure the force with which the spindle loads the stud. The force sensor can be disposed in a gap between the spindle and the stud of the first carrier wherein the gap or the force sensor, resp., is arranged to detect the force along the linear axis of movement. Therein, the spindle, especially its first end, can be supported at the stud coaxially, rotationally and displaceably along the linear axis of movement. Preferably, the housing at its first end has a common guidance for the stud and the spindle. Optionally, the stud and the spindle have the same outer diameter within a common guidance.

Further optionally, a pressure sensor can be arranged in the cylinder in which the piston is guided in order to detect the pressure acting onto the piston. Preferably, the pressure sensor and the force sensor are connected to an electronic microcontroller which is designed to compare the measuring signal of the force sensor with the measuring signal of the pressure sensor and which is preferably further designed to indicate deviations of the ratio between the measuring signal of the force sensor and the measuring signal of the pressure sensor from a predetermined amount or amount range. In this embodiment the brake is designed to indicate a malfunction, for instance a force which is too small for the pressure applied inside the cylinder.

Further optionally, the microcontroller can be designed to determine the path along which the spindle was moved by rotation by the electric motor in the direction towards the first end and preferably to indicate the arrival over a predetermined path for which the spindle was moved by rotation in the spindle nut. In this embodiment, the brake is designed to indicate the attainment of a predetermined wear of the brake shoes or the brake linings mounted thereon, resp. Therein, preferably, the microcontroller is designed to add up the respective paths along which the spindle is moved in the direction towards the first end of the housing by rotation by means of the electric motor and optionally to indicate, to transmit and/or to compare the same with a predetermined amount, wherein the predetermined amount corresponds to an allowable wear of the brake linings. Preferably, the respective paths along which the spindle is moved in the direction towards the first end of the housing by rotation by means of the electric motor are determined by the distance sensor.

Further optionally, the microcontroller can be designed to determine the path of the spindle nut along which the same moves in the direction towards the first end of the housing at brake pressure applied and to transmit this path, wherein this path can be indicated as a measure for the wear of the brake disk when new brake linings having a certain thickness are mounted. For this, the path of the spindle nut can be determined by the sensor which, in a variant, is a distance sensor detecting the path of the spindle nut in the housing. Alternatively, the sensor can be formed by a force sensor arranged between the spindle and the stud of the first carrier, as described here, wherein the microcontroller is designed to detect the rotations transmitted by the electric motor onto the spindle and to calculate the path from these along which the spindle is moved along the linear axis of movement until the force sensor indicates the engagement of the brake linings with the brake disk by a steeply increasing force.

Preferably, the microcontroller is designed to be connected to the brake system of a rail vehicle, for instance by means of an electronic system, in order to transmit data. For this, the microcontroller can have an electronic system, for instance, which forms a bus system which can be cable-less or cable-bound.

The force generating device can have a manual control system by which the electric motor is moved for the rotation of the spindle into its position near the second end of the housing in order to open the brake caliper in this position and to exchange the brake linings. Additionally, the force generating device can include a manual control system by which the electric motor is controlled for the rotation of the spindle in order to move the same into a position in which the brake linings have a predetermined distance with respect to one another or to a brake disk arranged between these. In this embodiment the force generating device allows a motoric movement of the brake caliper into an opened position and preferably a motoric movement of the brake caliper into a position of the brake linings in a desired distance with respect to one another or to a brake disc, resp.

In a first embodiment, the piston, which is generally also designated as a brake piston and is loadable with pressure in a controlled manner in order to form a service brake, can act upon a wedge which acts between the second end of the spindle or between the spindle nut on the one side and the second end of the housing on the other side, respectively, so that the spindle or the spindle nut, resp., is displaced along the linear axis of movement from the second end of the housing to the first end of the housing. Preferably, the spindle nut has a first press roller the rotary axis of which being arranged perpendicularly to the spindle axis or to the linear axis of movement, and a second press roller is mounted at the housing and has a rotary axis which is arranged parallel to the rotary axis of the first press roller, wherein the wedge is guided between the first and the second press rollers. Preferably, the press rollers each have two respective partial press rollers which are arranged on both sides of the spindle.

Preferably, in a first embodiment, a pressure spring is disposed at the piston which acts against the pressure acting upon the piston. This pressure spring can correspondingly be designated a readjustment spring for the service brake. Preferably, in this embodiment the pressure spring is mounted between a spring abutment stationarily mounted at the housing and the piston, especially perpendicularly to the spindle axis. The spring abutment for the pressure spring can be arranged adjacent to the spindle nut and, for instance, can form a part of the guidance for the spindle nut in the housing. Optionally, the guidance for the spindle nut is arranged between a wall of the housing and the spring abutment or is formed by a wall of the housing and the spring abutment.

In a second embodiment the piston is arranged at the spindle nut and can be connected to the spindle nut in a fixed manner or be formed with the spindle nut in a one-piece manner. Accordingly, the distance sensor can be designed to measure the path of the piston relative to the housing. The piston is guided in a cylinder which is arranged in parallel to the linear axis of movement, for instance, coaxially to the spindle axis or to the linear axis of movement, respectively. The cylinder is arranged in a first portion of the housing and is designed to act load the piston in the direction towards the first end of the housing upon loading with pressure. The cylinder can be formed in a one-piece manner in the housing. In this embodiment an optional pressure spring disposed between the first end of the housing and the piston acts both as a readjustment spring for the spindle nut and as a readjustment spring for the piston. This piston acts as service brake since upon the loading with pressure it loads the spindle nut and thus the spindle in the direction towards the first end of the housing.

Preferably, in the embodiments of the invention a second piston in a second cylinder is arranged in the housing coaxially to the piston. Generally, the second piston has an extension which, in a position that the second piston takes without the application of pressure, lies against the first piston, which is also designated as a brake piston. The second cylinder is designed to load the second piston with pressure which loads the second piston in the direction towards the second end of the housing so that upon loading with pressure, the second piston is moved away from the first piston and does not apply any force upon the first piston or brake piston, resp. A pressure spring is arranged between the second piston and the second end of the housing which pressure spring loads the second piston in the direction towards the first piston so that the extension of the second piston is loaded against the first piston. Therefore, the second piston acts as a locking brake which without pressure present by the pressure spring loading the second piston in the direction towards the first piston, loads the spindle nut towards the first end of the housing. Generally, the second piston can be loaded with pressure on its piston surface facing the brake piston and is loaded in the direction towards the brake piston by the second pressure spring, wherein the second piston has an extension which in the condition without pressure loading loads the brake piston by the second pressure spring. In the first embodiment the arrangement consisting of brake piston and second piston is disposed at the wedge in order to load the same in the direction to the intermediate space between the press rollers. In the second embodiment the brake piston and the second piston are preferably arranged coaxially with regard to the linear axis of movement or coaxially with regard to the spindle axis, resp., wherein the brake piston is fixed at the spindle nut.

Generally, the brake piston and the second piston can be arranged along a common axis of movement. In the second embodiment the second piston is preferably arranged displaceably on the spindle, and further preferred, both pistons or cylinders, resp., are arranged coaxially with regard to the linear axis of movement or to the spindle axis, resp.

Preferably, the extension of the second piston is tubularly formed and arranged coaxially to the spindle axis. Optionally, the two walls on the head-sides of both cylinders extend approximately radially with regard to the spindle axis or radially with regard to the linear axis of movement, resp. This embodiment is shown in the figures with respect to the second embodiment according to which the second piston is moreover arranged coaxially with regard to the spindle axis or to the linear axis of movement, resp.

Preferred embodiments of the invention will now be discussed with respect to the drawings. The drawings may include schematic representations, which will be understood by artisans in view of the general knowledge in the art and the description that follows. Features may be exaggerated in the drawings for emphasis, and features may not be to scale.

In the figures identical reference numbers designate functionally identical elements. The arms of the brake caliper are not shown. The figures show the sensor both in the first variant as distance sensor21between spindle nut19and housing4and in the second variant as force sensor13between the first carrier1and the spindle12. The first carrier1and the second carrier2which are arranged on a common linear axis3of movement at the housing4are provided for the articulation to a respective caliper arm of a brake.

The second carrier2is arranged at the second end6of the housing4which is located opposite to its first end5. Accordingly, the force generated by the force generating device loading the first carrier1in a direction away from the second carrier2, for the spreading of two caliper arms, can be pivotally mounted at their ends, wherein at their opposite ends brake shoes are mounted and which between their ends are pivotally connected to each other.

The first carrier1is disposed at the first end5of the housing4and has a stud7guided in a guidance8which extends along the linear axis of movement3at the first end5of the housing4. The stud7is guided in a torque-proof manner along the linear axis of movement3within the guidance8, for instance by a longitudinal groove9in the stud7into which a pin10fixed at the first end5displaceably engages, for instance in the guidance8.

The first end11of the spindle12is rotationally supported at the stud7, for instance, the stud7is disposed in a coaxial dead hole of the spindle12. Since the stud7is guided in the guidance8at the first end5of the housing in a longitudinally displaceably manner secured against rotation, the spindle12can rotate relative to the stud7.

According to a preferred embodiment a force sensor13is arranged between the spindle12and the stud6of the first carrier1in order to measure the force with which the spindle12is loaded against the stud7.

Preferably, the guidance8is rotationally symmetrical to the linear axis of movement3, for instance a bore at the first end5of the housing4, and the first end11of the spindle12is guided rotationally and longitudinally displaceably in the guidance8.

The second end14of the spindle12opposite to the first end11is connected longitudinally displaceably and rotationally fixed to the shaft stud15of an electric motor16which is fixed at the second end6of the housing4. In the embodiment shown in the figures the shaft stud15is arranged coaxially in a dead hole at the second end of the spindle12in a longitudinally displaceable manner along the linear axis3of movement which is generally preferably identical with the spindle axis. The shaft stud15has pegs17which are guided in longitudinal slots18arranged along the spindle12. In this manner the electric motor16can rotate the spindle12by means of its shaft stud15while the spindle12rotates in the spindle nut19guided torque-proof and displaceably at the housing and moves along the linear axis3of movement. A pressure spring20is arranged between the spindle nut19and the first end5of the housing4which loads the spindle nut19in the direction towards the second end6of the housing4.

According to the first variant a distance sensor21is arranged in the housing4as sensor which is designed to measure the path of the spindle nut19along the linear axis of movement3. The distance sensor21is connected to a microcontroller22which, for instance, is an electronic calculator, for transmitting a signal for the movement or position of the spindle nut19, resp., in the housing4. As shown in the figures, the distance sensor21can be arranged between the housing4and the side of the piston23facing away from the cylinder28.

The microcontroller22is connected to the electric motor16for transmitting a control signal, wherein the microcontroller22is designed to generate the control signal in dependence on the signal of the distance sensor21. Especially, the microcontroller22is designed to compare signals for the movement or position of the spindle nut19in the housing4transmitted by the distance sensor21with a predetermined amount for the movement or position, resp., of the spindle nut19and to control the electric motor16dependent on this comparison. Therein, the microcontroller22can be designed to control the electric motor16in such a manner that the same rotates the spindle12until the spindle12has been moved with respect to the spindle nut19for the amount which results from this comparison.

Accordingly, the force generating device contains a wear adjusting device formed with or consisting of the spindle12the first end11of which being rotationally supported at the stud7of the first carrier1, the spindle nut12guided displaceably along the linear axis of movement3and rotationally fixed within the housing4, the distance sensor21as a sensor determining the path of the spindle nut19with respect to the housing4, and the electric motor16controlled in dependence on a signal of the distance sensor21, which electric motor16is stationarily disposed in the housing4and the shaft stud15thereof is connected to the second end14of the spindle12coaxially, longitudinally displaceably and rotationally fixed. As alternative to the sensor formed as distance sensor21, the sensor can be formed by a force sensor13arranged between the spindle12and the stud7, wherein the electric motor16is controlled by a microcontroller22to rotate the spindle12until the force sensor13receives a steeply increasing force as signal.

The longitudinal slots18at the second end14of the spindle12move along the pegs17upon the displacement of the spindle12in the direction towards the first end5of the housing4. The pegs17allow a rotation of the spindle12by the shaft stud15of the electric motor16.

The second variant of the sensor is represented by the force sensor13which receives the force between the first end11of the spindle12and the stud7of the first carrier1. In a condition of the brake in which the piston23is not loaded with pressure acting against the spindle nut the microcontroller22is designed to control the electric motor16for the rotation of the spindle12until the force sensor13receives a force acting from the spindle12upon the stud7. This condition of the brake is, for instance, a condition of the absence of pressure upon the piston23in the cylinder28and of the absence of pressure by a second cylinder30which, by means of an extension32, acts upon the piston23which, for instance, is driven by a second pressure spring31. Preferably, the force is a force which steeply increases during the rotation of the spindle and thus indicates the engagement of brake linings mounted on the brake shoes with a brake disk and, for instance, is not caused by frictional forces within the brake. Therein, the microcontroller22is designed, at the signal of the force sensor13for a steeply increasing force between the spindle12and the stud7of the first carrier1, to stop and to subsequently control the electric motor16for the rotation of the spindle12in the opposite direction for a predetermined amount in order to space the brake linings apart from the brake disk16. The predetermined amount for the distance is the one for which the brake shoes or brake linings are moved against each other and against the brake disk by the action of the brake piston23.

FIGS. 1 to 4show the drive of the spindle nut19and of the spindle12connected to the spindle nut19, resp., in the first embodiment of the force generating device according to the invention. Therein,FIGS. 1 and 2show the piston23which is also designated as brake piston and which is connected to a wedge24guided between a first press roller25preferably formed by two partial rollers25a,25barranged laterally from the spindle12at the spindle nut19, as shown, on the one side and a second press roller26stationarily disposed at the housing on the other side. Preferably, the second press roller26is formed by two partial rollers26a,26b, as shown. The rotary axes of the first press roller25and of the second press rollers, resp. their first partial rollers25a,25bor of the second partial rollers26a,26bare arranged perpendicularly to the linear axis of movement3and to the spindle axis, resp. The first press roller25is mounted at the spindle nut19so that the movement of the wedge24between the first press roller25and the second stationary press roller26results in a displacement of the spindle nut19and of the spindle12which is in engagement with the spindle nut19.

FIGS. 1 and 2show the piston23in the position not loaded by pressure in which the wedge24adjusts a small distance between the first press roller25and the second press roller26. In the embodiment shown here the wedge24is guided perpendicularly against the linear axis of movement3or spindle axis, resp., correspondingly, the central axis of the piston23and of the cylinder28guiding the same, is arranged perpendicularly to the linear axis of movement3or to the spindle axis, resp. The pressure spring27arranged between the spring abutment37fixed at the housing4and the piston23loads the piston23into its position not loaded by pressure in the cylinder28so that the pressure spring27can be also designated a readjustment spring for the brake piston23. In the first embodiment the guidance for the spindle nut19is optionally formed by the wall of the housing4and the parallel spring abutment37.

FIGS. 3 and 4show the piston23in its position loaded by pressure in the cylinder28in which the wedge24moves the first press roller25in the direction towards the first end5of the housing4, wherein the pressure spring20is compressed between the spindle nut19and the first end5of the housing4. The spindle nut19moves the spindle12in the direction towards the first end5of the housing4so that the first carrier1by its stud7is moved away from the second carrier2.

Optionally, a switch35is mounted at the housing which is designed for the manual control of the electric motor16in order to move the spindle12by the same.

By means of the example of the second embodimentFIG. 5shows the drive of the spindle nut19or the drive of the spindle12connected to the spindle nut19of the force generating device according to the invention in a preferred embodiment which, in addition to the brake piston23in a cylinder28, contains a second piston29guided in a cylinder30in the housing4. The second piston29is arranged coaxially with respect to the linear axis of movement3or to the spindle axis, resp., and is loaded by a second pressure spring31in the direction towards the braking piston23, while the second cylinder31is arranged to move the second piston29upon loading with pressure away from the braking piston23and against the second pressure spring31. The second piston29has a tubular extension32which is loaded by the second pressure spring31against the first piston in a position of the second piston29without loading of the second cylinder31with pressure. In this position the second piston29through its extension32loads the brake piston23and the spindle nut29connected to it and thus the spindle12in the direction towards the first end5of the housing4, so that without loading of its second cylinder with pressure the second piston29acts as locking brake.

In the embodiment shown inFIG. 5the extension32of the second piston29is formed tubularly coaxially around the spindle12. The cylinder28in which the brake piston23and the spindle nut19connected therewith are guided, and the second cylinder30are arranged coaxially with respect to the linear axis of movement3or the spindle axis, resp., wherein a wall33arranged between these cylinders separates the cylinders and optionally forms the respective cylinder head. The spindle nut19can be rotationally fixed and displaceable with respect to the housing4, for instance, by a linear guidance36in the form of a pin which is guided in a bore fixed at the housing4.

In every embodiment shown a pressure sensor34is arranged in the cylinder28, in which the brake piston23is guided or is loaded with pressure in order to drive the spindle nut19in the direction towards the first end5of the housing4.

Generally, the second carrier2can be connected to the second end6of the housing4in a fixed manner.