Patent Description:
Combined pneumatic service brake and spring brake cylinders with a service brake function and a parking brake function are usually arranged on rear axles of commercial vehicles and usually have two compressed air ports. One compressed air port controls the parking brake function and is under a parking brake release pressure for compressing an accumulator spring of the spring brake cylinder when the commercial vehicles are in a driving state. The other compressed air port controls the service brake function and is vented in the driving condition to brake the commercial vehicle via the service brake. The service brake function is controlled by means of a usually in the form of a diaphragm cylinder. If the commercial vehicle is to be parked, the spring brake cylinder is released and the parking brake is applied via the spring tension of the accumulator spring.

A combined service brake cylinder and spring brake cylinder is known, for example, from <CIT>. There, the spring brake cylinder and the service brake cylinder are arranged coaxially one behind the other and connected to each other by an intermediate flange. However, such an arrangement requires a relatively long installation space within the wheel arches of the commercial vehicles, which can cause space problems.

In order to solve this problem, a combined service brake cylinder and spring brake cylinder is proposed in <CIT>, in which the service brake cylinder and the spring brake cylinder are placed laterally next to one another, the accumulator spring being arranged there around the service brake cylinder. In this case, the service brake piston is guided within the spring brake piston and axially thereon, which has a radially inwardly extending circumferential edge which abuts against an end-face annular surface of the service brake piston in order to drive the service brake piston together with the service brake piston rod into the applied position when the parking brake is applied. However, this arrangement has some disadvantages. Firstly, the radially inwardly extending peripheral edge of the spring brake piston is loaded by the service brake pressure in the service brake chamber, so that during service braking a force is generated at the spring brake piston directed against the spring brake release pressure in the spring brake chamber, which loads the spring brake piston in the application direction of the parking brake. Secondly, the effective area of the spring brake piston on which the parking brake release pressure can act to hold the parking brake released is relatively small, resulting in a high required parking brake release pressure or a low spring stiffness of the accumulator spring, but with disadvantages in terms of compressed air consumption or parking brake force.

<CIT> discloses a brake cylinder according to the preamble of claim <NUM>. There, to cause air brake action and spring brake action through the same piston rod, a service brake piston and a spring brake piston are provided, where the piston rod is attached to the service brake piston which extends through the spring brake piston. When the spring brake is activated, a spring chamber where an accumulator spring is accommodated is connected with a return spring chamber where a return spring for the service brake piston is accommodated. This connection can cause an unwanted flow of dirt and/or air from one chamber to the other. Thus, the parking and service brake functions are affected by each other.

It is the object of the present invention to provide a short design combined service brake and spring brake cylinder having a low compressed air consumption and parking and service brake functions which are unaffected by each other. Likewise, to provide a pneumatic or electro-pneumatic vehicle brake having at least one such combined service brake and spring brake cylinder.

This object is solved with the features of claims <NUM> and <NUM>. Advantageous further embodiments are the subject of the subclaims.

The invention is based on a combined service brake and spring brake cylinder for operating a service brake and a parking brake, comprising:.

That the service brake cylinder, when viewed radially, is disposed within the spring brake cylinder may mean that the service brake cylinder, when viewed radially, is disposed completely within and enclosed by the wall of the spring brake cylinder. Further, it may mean that the service brake cylinder, when viewed axially, is disposed partially or completely within the spring brake cylinder. "Radial" and "axial" refer in particular to a common longitudinal axis of the combined service brake cylinder and spring brake cylinder, wherein the service brake cylinder and the spring brake cylinder are arranged in particular coaxially.

Furthermore, a spring brake cylinder housing of the spring brake cylinder may comprise a closed housing of the spring brake cylinder, in which the service brake cylinder is then completely accommodated, for example.

"Directly guided" should mean here, for example, that a radially outer circumferential surface of the service brake piston is guided on the radially inner circumferential surface of the service brake cylinder. In this case, a sealing element is preferably arranged therebetween, which, in addition to a sealing function, then also performs a guiding function for the service brake piston.

Alternatively, a diaphragm cooperating with the service brake piston may be provided, in which case the service brake piston forms a pressure plate, for example a central pressure plate, on which the diaphragm acts. The diaphragm may, for example, be secured to or in a joint of the service brake cylinder and the spring brake cylinder. Conceivably, a radially outer edge of the diaphragm may be clamped between the service brake cylinder and the spring brake cylinder.

With such an arrangement, the combined service brake and spring brake cylinder is short on the one hand, because the service brake cylinder is arranged radially and particularly also axially and particularly completely inside the spring brake cylinder.

On the other hand, the disadvantages of the prior art described above with regard to an influence of the spring brake piston by the service brake pressure present in the service brake chamber are thereby avoided, because the service brake piston is guided directly on a radially inner circumferential surface of the service brake cylinder in a displaceable manner or because a diaphragm cooperating with the service brake piston is attached to the service brake cylinder and/or to the spring brake cylinder.

Last but not least, the spring brake piston can then also have a larger effective area in relation to the parking brake pressure, so that the pressure level of the parking brake release pressure and thus also the energy consumption can be reduced. The parking brake release pressure is the pressure at which the parking brake releases against the action of the at least one accumulator spring.

Also, the service brake cylinder may include an edge or a rim that is internally attached to the spring brake cylinder.

According to the invention,
g) a breathing device is provided comprising at least:.

For example, the second flow connection may comprise a through opening in the cylindrical wall or in the bottom of the service brake cylinder.

For example, the third flow connection may comprise a through opening in a wall or a cover of the spring brake cylinder. Also, the third flow connection may comprise a filter and/or a valve that prevents dirt and moisture from entering the spring brake cylinder from the outside.

For example, the breathing valve may include a valve seat and a valve body biased away from the valve seat by spring means to the breathing valve open position, the valve body being urged against the valve seat by service braking pressure against the action of the spring means to move the breathing valve from the open position to the closed position.

The operation of the breathing device may then be described by way of example as follows:
For example, when the service brake chamber is pressurized, the breathing valve assumes the closed position so that no compressed air can pass from the service brake chamber into the return spring chamber. On the other hand, the moving service brake piston reduces the volume of the return spring chamber, thereby creating a first air flow which then passes through the second flow connection and the third flow connection to enter the atmosphere. Then, no excess pressure in the return spring chamber can impede the movement of the service brake piston in the service brake application direction.

On the other hand, when the spring brake chamber is pressurized to release the parking brake, the volume of the spring chamber is reduced, thereby creating a second air flow which can then pass through the third flow connection to enter the atmosphere. Then, no excess pressure in the spring chamber can impede the movement of the spring brake piston in the parking brake release direction.

Preferably, the service brake piston may be connected to a service brake piston rod which actuates the service brake when the service brake chamber is pressurized by the service brake pressure and which releases the service brake when the service brake chamber is vented. In particular, the service brake piston rod can be formed by a cylindrical or rod-shaped body, to the end of which the service brake piston projecting radially outwards from this end is then attached.

Also, the spring brake piston may include a central opening having a bearing through which the spring brake piston is axially guided on the service brake piston rod and/or through which the service brake piston rod and the spring brake piston are axially movable relative to each other.

According to a further embodiment, the service brake piston rod may have, in particular at its radially outer periphery, a radial protrusion which forms an axial stop for the spring brake piston.

The radial protrusion can then be arranged on the service brake piston rod in such a way that.

A particularly large effective area of the spring brake piston with respect to the parking brake release pressure results if the spring brake piston, viewed radially, extends from the central opening beyond a radially outer circumferential surface of the service brake cylinder to the radially inner circumferential surface of the spring brake cylinder. The effective surface of the spring brake piston on which the parking brake release pressure acts is then located, for example, on the side of the spring brake piston facing the spring brake chamber.

The invention also relates to a pneumatic or electro-pneumatic vehicle brake comprising at least one combined service brake and spring brake cylinder described above.

A preferred embodiment of the invention is shown below in the drawing and will be explained in more detail in the following description. The drawing shows.

A combined pneumatic service brake and spring brake cylinder <NUM> having a service function and a parking brake function as described hereinafter is usually arranged on a wheel of a rear axle of commercial vehicles and usually has two compressed air ports <NUM>, <NUM>. A first compressed air port <NUM> controls the parking brake function and, in the driving state of commercial vehicles, is under a parking brake release pressure for compressing an accumulator spring <NUM> of a spring brake cylinder <NUM>. A second compressed air port <NUM> controls the service brake function and, particularly in the driving state, can be pressurized to brake the commercial vehicle via the service brake. In this case, the service brake function is carried out by means of a service brake cylinder <NUM> designed as a diaphragm cylinder or brake piston cylinder. If the commercial vehicle is to be parked, the spring brake cylinder <NUM> is vented and the parking brake is applied via the spring tension of the accumulator spring <NUM>.

In an electro-pneumatic brake system, for example, the pressure for the two compressed air ports <NUM>, <NUM> is generated by a solenoid valve device not shown here, which is supplied with compressed air under supply pressure from at least one compressed air supply. For coordinated control or regulation of the service brake pressure or parking brake pressure introduced into the two compressed air ports <NUM>, <NUM>, the solenoid valve device is controlled by an electronic control system.

<FIG> shows a perspective view of a preferred embodiment of a combined service brake and spring brake cylinder <NUM> of an electro-pneumatic brake system of a commercial vehicle according to the invention, looking at one end face from which a first actuating element <NUM>, for example for a disc brake, can be seen. <FIG> represents a perspective view of the combined service brake and spring brake cylinder <NUM> of <FIG>, looking at the other end face from which a second actuating element <NUM> of an emergency release device <NUM> protrudes.

As shown in <FIG>, which is a cross-sectional view of the service brake and spring brake cylinder <NUM> of <FIG> in a situation in which the parking brake and the service brake are released, in particular during a driving condition of the commercial vehicle, the combined service brake and spring brake cylinder <NUM> comprises the spring brake cylinder <NUM>, a spring brake piston <NUM> axially slidably guided therein, and the accumulator spring <NUM> loading the spring brake piston <NUM> in an applied position of the parking brake.

The spring brake cylinder <NUM> comprises a substantially cylindrical spring brake cylinder housing <NUM> with here, for example, two covers <NUM>, <NUM> attached to the end faces, wherein the first actuating element <NUM> for the disc brake projects from a central through-opening of a first cover <NUM> and the second actuating element <NUM> of the emergency release device <NUM> projects from a central through-opening of a second cover <NUM>. Alternatively, the spring brake cylinder housing <NUM> could also be pot-shaped and then have, for example, only one cover. Generally, the spring brake cylinder housing <NUM> forms a closed housing of the spring brake cylinder <NUM>, in which the service brake cylinder <NUM> is completely excluded here, for example.

The spring brake piston <NUM> is axially displaceably guided on a radially inner circumferential surface of the spring brake cylinder <NUM> or of the spring brake cylinder housing <NUM>, wherein a first movement seal <NUM> is arranged between a radially outer edge of the spring brake piston <NUM> and the radially inner circumferential surface of the spring brake cylinder <NUM> or of the spring brake cylinder housing <NUM>, a first movement seal <NUM> is arranged which is connected here to the radially outer edge of the spring brake piston <NUM> and which, in addition to a sealing function, also performs a guide function for the spring brake piston <NUM>.

With its one side facing away from the accumulator spring <NUM>, the spring brake piston <NUM> delimits a spring brake chamber <NUM> which can be pressurized and vented by a parking brake pressure via the first compressed air connection <NUM>. The accumulator spring <NUM> is then supported with its one end on the other side of the spring brake piston <NUM>, the other end of which is supported on the spring brake cylinder housing <NUM>. The first air pressure port <NUM> is formed, for example, in the first cover <NUM>. However, it could also be formed in a bottom of the spring brake cylinder or the spring brake cylinder housing <NUM> of the spring brake cylinder <NUM> if the spring brake cylinder housing <NUM> is pot-shaped, for example.

The accumulator spring <NUM> is then accommodated in a spring chamber <NUM> which is formed here as an annular chamber and is radially outer with respect to the service brake cylinder <NUM>, and which is limited or bounded radially inwardly by a radially outer circumferential surface of a service brake cylinder housing <NUM> of the service brake cylinder <NUM> and radially outwardly by the radially inner circumferential surface of the spring brake cylinder housing <NUM>. Axially, the spring chamber <NUM> is limited or bounded by the spring brake piston <NUM> and the spring brake cylinder housing <NUM>.

The service brake cylinder <NUM> or the service brake cylinder housing <NUM> directly guides an axially displaceable service brake piston <NUM>, the service brake cylinder <NUM> and the service brake piston <NUM> delimiting a service brake chamber <NUM> which can be pressurized and vented with a service brake pressure via the second compressed air port <NUM>.

The service brake cylinder <NUM> or the service brake cylinder housing <NUM> of the service brake cylinder <NUM> is arranged radially and here, for example, also axially, preferably completely within the spring brake cylinder <NUM> or within the spring brake cylinder housing <NUM> of the spring brake cylinder <NUM>. Further, the service brake piston <NUM> is axially slidably guided directly on the radially inner peripheral surface of the service brake cylinder <NUM> or the service brake cylinder housing <NUM>. This direct guidance includes that a second movement seal <NUM> is arranged therebetween, which here is connected to the radially outer edge of the service brake piston <NUM> in addition to a sealing function also performs a guiding function for the service brake piston <NUM>.

According to a further embodiment not shown here, a diaphragm cooperating with the service brake piston <NUM> may, for example, be attached with its radially outer edge to the service brake cylinder <NUM> and/or to the spring brake cylinder <NUM>. The service brake cylinder <NUM> is then a so-called diaphragm cylinder. In this case, the service brake piston <NUM>, which is then smaller in its radial extension, forms a pressure plate, for example a central pressure plate, on which the diaphragm acts, is connected with or on which the diaphragm is supported. The diaphragm may, for example, be secured to or in a joint between the service brake cylinder <NUM> and the spring brake cylinder <NUM>. It is conceivable, for example, that a radially outer edge of the diaphragm is clamped between the service brake cylinder <NUM> and the spring brake cylinder <NUM>. With reference to <FIG>, the radially outer edge of the diaphragm may be clamped between the second cover <NUM> of the spring brake cylinder <NUM> and an edge <NUM> of the service brake cylinder <NUM>, which is preferably pot-shaped, as in this case.

In both embodiments, the service brake piston <NUM> is connected to a service brake piston rod <NUM>, which is made hollow here, for example, to receive the emergency release device <NUM> in its interior. The service brake piston rod <NUM> then actuates the service brake via the second actuating element <NUM> when the service brake chamber <NUM> is pressurized with a service brake application pressure, and which releases the service brake when the service brake chamber <NUM> is vented. The end of the service brake piston rod <NUM> facing the service brake chamber <NUM> can then project radially outwardly away from the service brake piston rod <NUM> in a mushroom-like manner.

The second compressed air port <NUM>, which is formed for example in the second cover <NUM>, is then used for pressuring/venting the service brake chamber <NUM>. As indicated above, the emergency release device <NUM> for manual emergency release of the combined service brake and spring brake cylinder <NUM>, which is not described in detail here, may be accommodated or integrated in the service brake piston rod <NUM>. By turning the second actuating element <NUM> projecting from the combined service brake and spring brake cylinder <NUM>, the service brake piston rod <NUM> can then be screwed into the release position of the parking brake or the service brake. Such manual emergency release is necessary in particular if no more parking brake release pressure can be generated in the spring brake chamber <NUM>, for example, due to an electrical defect in the solenoid valve device or in its control system or also in the event of a power failure.

The service brake cylinder <NUM> or the service brake cylinder housing <NUM> is here, for example, of pot-shaped design and has a cylindrical wall <NUM> extending in parallel into the spring brake cylinder <NUM> or into the spring brake cylinder housing <NUM>, and a bottom <NUM>. The bottom <NUM> is provided, for example, with a central opening through which the service brake piston rod <NUM> then projects into the spring brake cylinder <NUM> or into the spring brake chamber <NUM>. Furthermore, the service brake piston rod <NUM> penetrates the spring brake chamber <NUM> centrally and then receives the first actuating element <NUM> for the disc brake in a recess at its end facing the disc brake and projecting out of the spring brake cylinder housing <NUM> through the through-opening.

A return spring chamber <NUM> is formed here between the service brake piston <NUM> and the bottom <NUM> of the service brake cylinder <NUM>, with a return spring <NUM> which loads the service brake piston <NUM> into the service brake release position. Also, the return spring chamber <NUM> is penetrated axially and centrally by the service brake piston rod <NUM>.

As explained above, the here for example pot-shaped service brake cylinder <NUM> has the free edge <NUM> which is preferably fixed to the spring brake cylinder <NUM> on the inside, in particular in the region of the fixing of the end-face second cover <NUM> to the spring brake cylinder <NUM>, whereby this second cover <NUM> also delimits or closes the service brake chamber <NUM>. Then, the service brake chamber <NUM> which can be ventilated and exhausted is delimited by the cylindrical wall <NUM> of the service brake cylinder housing <NUM>, the second cover <NUM> of the spring brake cylinder <NUM> and the service brake piston <NUM> or, alternatively, by the above-mentioned diaphragm in the case a the above-mentioned diaphragm cylinder used as the service brake cylinder <NUM>.

As preferably shown in <FIG>, in the parking brake release position, i.e. when the spring brake chamber <NUM> is pressurized, the spring brake piston <NUM> contacts the bottom <NUM> of the service brake cylinder <NUM> from the outside with respect to the service brake cylinder <NUM> with its side facing away from the spring brake chamber <NUM>. This contact is caused by the parking brake release pressure acting on the spring brake piston <NUM>.

For example, the spring brake piston <NUM> includes a central opening having a bearing <NUM> through which the spring brake piston <NUM> is axially guided on the service brake piston rod <NUM>. The bearing <NUM> therefore allows the service brake piston rod <NUM> and the spring brake piston <NUM> to move axially relative to each other. The bearing <NUM> is designed, for example, as a sealing bearing.

The spring brake piston <NUM> then extends, viewed radially, from the bearing <NUM> or from the central opening of the spring brake piston <NUM> beyond a radially outer circumferential surface of the service brake cylinder <NUM> or of the service brake cylinder housing <NUM> to the radially inner circumferential surface of the spring brake cylinder <NUM> or of the spring brake cylinder housing <NUM>. The effective surface of the spring brake piston <NUM> on which the parking brake pressure or the parking brake release pressure acts is located on the side of the spring brake piston <NUM> facing the spring brake chamber <NUM> and then also extends from the bearing <NUM> or from the central opening of the spring brake piston <NUM> to the radially inner circumferential surface of the spring brake cylinder <NUM> or of the spring brake cylinder housing <NUM>. The effective surface of the spring brake piston <NUM> on which the parking brake pressure or the parking brake release pressure acts is located on the side of the spring brake piston <NUM> facing the spring brake chamber <NUM>. The effective surface of the spring brake piston <NUM> also extends from the bearing <NUM> or from the central opening of the spring brake piston <NUM> beyond the radially outer circumferential surface of the service brake cylinder <NUM> or of the service brake cylinder housing <NUM> to the radially inner circumferential surface of the spring brake cylinder <NUM> or of the spring brake cylinder housing <NUM>.

As also shown in <FIG>, the service brake piston rod <NUM> has, in particular at its radially outer periphery, a radial protrusion <NUM> which forms an axial stop for the bearing <NUM> or for the central opening of the spring brake piston <NUM>. This radial protrusion <NUM> is arranged on the service brake piston rod <NUM>, for example, in such a way that the spring brake piston <NUM> brings the service brake piston rod <NUM> into the spring brake application position by abutting against the radial protrusion <NUM> when the spring brake chamber <NUM> is vented to apply the parking brake, as shown in <FIG>. It is immaterial whether the service brake chamber <NUM> is additionally pressurized to bring the service brake piston rod <NUM> into the applied position of the service brake, because the service brake piston rod <NUM> has already moved into the applied position as a result of the release of the accumulator spring <NUM>. However, in order not to overload the disc brake mechanism, parallel application of the parking brake and the service brake may be undesirable.

On the other hand, the radial protrusion <NUM> of the service brake piston rod <NUM> comes out of contact or engagement with the spring brake piston <NUM> when the service brake piston rod <NUM> is brought into the applied position of the service brake by pressurizing the service brake chamber <NUM>, when at the same time the spring brake chamber <NUM> continues to be pressurized the parking brake is thereby released. This condition is shown in <FIG>.

Further, by abutting against the radial protrusion <NUM>, the spring brake piston <NUM>, together with the service brake piston <NUM>, can move the service brake piston rod <NUM> to the spring brake application position and the service brake application position when the spring brake chamber <NUM> is vented and when the service brake chamber <NUM> is pressurized, as can be readily imagined with reference to <FIG>. Therefore, the service brake piston rod <NUM> connected to the service brake piston <NUM> and acting axially on the first disc brake actuating member <NUM> actuates both the service brake and the parking brake respectively by applying the disc brake.

Particularly preferably, a breathing device is also provided, which comprises, for example, a breathing valve <NUM> which is arranged here, for example, in a through-opening of the service brake piston <NUM> and is controlled by the service brake pressure in the service brake chamber <NUM>.

As can be seen from <FIG>, the breathing valve <NUM> may comprise, for example, a valve seat <NUM> formed in a valve body <NUM> and a valve body <NUM> biased by a spring <NUM> away from the valve seat <NUM> into the open position of the breathing valve <NUM>, the valve body <NUM> being urged against the valve seat <NUM> by the service brake pressure acting on it against the force of the spring <NUM> to move the breathing valve <NUM> from the spring biased open position to the closed position. <FIG> then shows the open position and <FIG> the closed position of the breathing valve <NUM>.

When the service brake chamber <NUM> is vented, the breathing valve <NUM> can then assume the open position in which a first flow connection <NUM> through the through opening between the service brake chamber <NUM> and the return spring chamber <NUM> is open due to the bias of the spring <NUM>. When the service brake chamber <NUM> is pressurized, the breathing valve <NUM> is then moved from the open position to the closed position in which the first flow connection <NUM> through the through opening is blocked because the flow caused by the service brake pressure first passes through a radially outer gap <NUM> between the valve body <NUM> and the valve base body <NUM>, and then also passes through the through opening in the service brake piston. However, after some time, i.e. in a transition phase, the pressure exerted on the valve body <NUM> becomes so great that a sealing portion <NUM> of the valve body <NUM> comes into contact with the valve seat <NUM>, thereby closing the first flow connection <NUM> or the through-opening. This prevents compressed air from then still flowing from the service brake chamber <NUM> into the return spring chamber <NUM>.

Furthermore, an in particular always open second flow connection <NUM> between the return spring chamber <NUM> and the spring chamber <NUM>, as well as an in particular always open third flow connection <NUM> between the spring chamber <NUM> and the atmosphere can be components of the breathing device.

For example, the second flow connection <NUM> may comprise a through opening in the cylindrical wall <NUM> or in the bottom <NUM> of the service brake cylinder <NUM> or the service brake cylinder housing <NUM>. Furthermore, the third flow connection <NUM> indicated in <FIG> may comprise a through opening in the spring brake cylinder housing <NUM>, in particular a through opening on the front side. Consequently, the second flow connection <NUM> and the third flow connection <NUM> open into the spring chamber <NUM> here and also communicate with each other through the spring chamber <NUM>.

Also, the third flow connection <NUM> may comprise a filter and/or a valve, for example in a cap, to prevent dirt and moisture from entering the spring brake cylinder <NUM> from the outside.

The operation of the breathing device may then be described by way of example as follows:
For example, as described above, when the service brake chamber <NUM> is pressurized, the breathing valve <NUM> assumes the closed position so that no compressed air can pass from the service brake chamber <NUM> into the return spring chamber <NUM>. On the other hand, the volume of the return spring chamber <NUM> is reduced by the shifting or moving service brake piston <NUM>, thereby creating a first air flow which then passes the second flow connection <NUM> and the third flow connection <NUM> to enter the atmosphere. Then, no excess pressure in the return spring chamber <NUM> can impede the movement of the service brake piston <NUM> in the service brake application direction.

On the other hand, when the spring brake chamber <NUM> is pressurized to release the spring brake, the volume of the spring chamber <NUM> is reduced, thereby creating a second air flow which can then pass through the third flow connection <NUM> to enter the atmosphere. Then, no excess pressure in the spring chamber <NUM> can impede the movement of the spring brake piston <NUM> in the parking brake release direction.

Claim 1:
Combined service brake and spring brake cylinder (<NUM>) for operating a service brake and a parking brake, comprising:
a) a spring brake cylinder (<NUM>), a spring brake piston (<NUM>) and at least one accumulator spring (<NUM>) loading the spring brake piston (<NUM>) in a direction of application of the parking brake, wherein the spring brake piston (<NUM>) is displaceably guided on a radially inner circumferential surface of the spring brake cylinder (<NUM>), and the spring brake piston (<NUM>) and the spring brake cylinder (<NUM>) delimit a spring brake chamber (<NUM>) which can be ventilated by a parking brake pressure,
b) a service brake cylinder (<NUM>) and a service brake piston (<NUM>), the service brake cylinder (<NUM>) and the service brake piston (<NUM>) delimiting a service brake chamber (<NUM>) which can be pressurized with a service brake pressure and vented, wherein
c) the service brake cylinder (<NUM>), viewed radially, is arranged inside the spring brake cylinder (<NUM>), and
d) wherein the service brake piston (<NUM>) is displaceably guided directly on a radially inner circumferential surface of the service brake cylinder (<NUM>), or
e) wherein a diaphragm cooperating with the service brake piston (<NUM>) is attached to the service brake cylinder (<NUM>) and/or to the spring brake cylinder (<NUM>), and wherein
f) between a radially outer circumferential surface of the service brake cylinder (<NUM>) and the spring brake cylinder (<NUM>) a spring chamber (<NUM>) is formed as an annular chamber in which the at least one accumulator spring (<NUM>) is arranged, characterized in that
g) a breathing device is provided comprising at least:
g1) a breathing valve (<NUM>) which is arranged in a through-opening of the service brake piston (<NUM>) and is controlled by the service brake pressure in the service brake chamber (<NUM>) in such a way that it assumes an open position when the service brake chamber (<NUM>) is vented, in which a first flow connection (<NUM>) between the service brake chamber (<NUM>) and a return spring chamber (<NUM>) is open, and it is brought from the open position into a closed position, in which the first flow connection (<NUM>) is blocked, when the service brake chamber (<NUM>) is pressurized,
g2) a second flow connection (<NUM>)-between the return spring chamber (<NUM>) and the spring chamber (<NUM>),
g3) a third flow connection (<NUM>) between the spring chamber (<NUM>) and the atmosphere.