Pneumatic spring brake cylinder with central venting device

Abstract

The invention proceeds from a pneumatic spring brake cylinder (3) with a spring brake cylinder housing (13) and a piston (19) which is axially actuable by an accumulator spring (20) within the spring brake cylinder housing (13), is delimited on one side by a pressure chamber (24) and on the opposite side by the spring chamber (26) receiving the accumulator spring (20), and is connected to a piston rod (23), and with a venting device (4) which comprises at least one venting valve (41), wherein the venting valve (41) is designed and configured to establish a flow connection between the pressure chamber (24) and the spring chamber (26) or to shut off this flow connection depending on the pressure (p12) which prevails in the pressure chamber (24), wherein at least the piston (19) and the piston rod (23) are arranged coaxially with respect to a centre axis (18) of the spring brake cylinder housing (13). It is provided according to the invention that the venting valve (41) is supported coaxially in relation to the centre axis (18) by the piston rod (23) and / or by the piston (19).

Description

[0001] DESCRIPTION

[0002] Air-operated spring brake cylinder with central breathing device

[0003] The present invention relates to a compressed air-operated spring brake cylinder according to the preamble of claim 1, a combined service brake and spring brake cylinder according to claim 14 and a compressed air-operated braking device of a commercial vehicle according to claim 15.

[0004] Breathing devices in spring brake cylinders serve to create a connection between the spring chamber of the spring brake cylinder and its pressure chamber when the piston of the spring brake cylinder is moved for braking while the pressure chamber is vented by the accumulator spring. The resulting increase in volume in the spring chamber creates a vacuum, which is dissipated by the breathing device, i.e. this ventilates the spring chamber while the piston of the spring brake cylinder is moved, thereby bringing about the desired pressure equalization. If the brake is released again by ventilating the pressure chamber of the spring brake cylinder, the breathing device blocks the aforementioned connection, whereby the air compressed in the spring chamber when the piston is moved can be blown off via a pressure relief device.The same applies to breathing devices for combination cylinders consisting of a service brake cylinder and a spring brake cylinder, in which case the spring brake cylinder has such a breathing device. A spring brake cylinder of this type is disclosed in DE 29 43 763 A.

[0005] In the case of such a spring brake cylinder, which in a frequent application forms a component of a compressed air-operated spring brake of a commercial vehicle, it is desirable that it be as small as possible due to the limited installation space in the wheel house.

[0006] The object of the present invention is to provide a spring-loaded brake cylinder with a more compact design. Furthermore, a combination cylinder with such a spring-loaded brake cylinder is to be provided.

[0007] This object is achieved by the features of claims 1, 14 and 15. Advantageous further developments are the subject of the subclaims. Disclosure of the invention

[0008] The invention is based on a compressed air-operated spring brake cylinder with a spring brake cylinder housing and a piston which can be actuated axially by a storage spring within the spring brake cylinder housing, which piston is delimited on one side by a pressure chamber and on the opposite side by the spring chamber accommodating the storage spring and which is connected to a piston rod, as well as with a breathing device comprising at least one breathing valve, wherein the breathing valve is designed and configured to create a flow connection between the pressure chamber and the spring chamber or to block this flow connection depending on the pressure prevailing in the pressure chamber, wherein at least the piston and the piston rod are arranged coaxially to a central axis of the spring brake cylinder housing.

[0009] In the spring-loaded brake cylinder of DE 29 43 763 A mentioned above, the breather valve is located off-center, i.e., decentrally in the piston, which necessitates a relatively long design. Furthermore, due to the radial extension of the breather valve in the piston, it is virtually impossible to design the piston as a diaphragm piston.

[0010] To solve this problem, the invention provides that the breathing valve is supported by the piston rod and / or the piston coaxially with respect to the central axis, i.e., it is arranged or formed centrally in or on the piston rod and / or centrally in or on the piston. Consequently, the components of the breathing valve can be partially or completely integrated into the piston rod or the piston, or the piston rod and / or the piston itself can form at least a portion of a component(s) of the breathing valve.

[0011] These measures, in particular, allow the piston to be shorter, resulting in a shorter design for the spring brake cylinder. Furthermore, the central positioning of the breather valve also makes it possible for the piston to be designed as a diaphragm piston, comprising a diaphragm held at the edge of the spring brake cylinder housing and a central diaphragm pressure plate against which the diaphragm is supported. This in turn advantageously results in a short design for the spring brake cylinder. Furthermore, the breather valve of the breather device is preferably arranged entirely within the spring brake cylinder housing, protecting the breather valve from external influences and completely unaffected by splash water and contamination.

[0012] In the spring brake cylinder, the breather valve can have an open position in which the breather valve connects the pressure chamber and the spring chamber, as well as a closed position in which the breather valve separates the pressure chamber and the spring chamber from each other.

[0013] In the spring-loaded brake cylinder, the breather valve can also have a valve body, arranged in particular coaxially with respect to the central axis, which is biased into the open position of the breather valve by spring means, in particular by a compression spring. The valve body is acted upon, in particular, by the pressure prevailing in the pressure chamber, which forces it into the closed position, and, in the axially opposite direction, by the spring forces of the spring means, which force it into the closed position.

[0014] According to a further embodiment of the spring brake cylinder, the valve body can be axially guided in a guide section of a bore in the piston rod and / or piston. In particular, the bore can be arranged coaxially to the central axis and open into the spring chamber on one side and the pressure chamber on the other.

[0015] Furthermore, the or a valve body can be pressed sealingly against a shoulder of the bore in the closed position, such that the valve body blocks the connection between the spring chamber and the pressure chamber when sealingly resting against the shoulder of the bore, and which in the open position is lifted from the shoulder of the bore in such a way that the connection between the spring chamber and the pressure chamber opens.

[0016] The shoulder of the bore and / or the valve body may also be provided with a valve seat.

[0017] The valve body can also be axially guided with a circumferential gap in the guide section of the bore such that, in the open position, the circumferential gap forms part or a section of the flow connection between the spring chamber and the pressure chamber. Consequently, fluid can flow around the valve body in the circumferential gap, with the clear circumferential gap forming a section or part of the flow connection. Particularly preferably, the valve body is designed in a stepped manner, with the guide section of the bore being designed in a stepped manner complementary to the valve body. This provides the possibility of axially abutting the valve body against a step in the bore.

[0018] According to a further development, one end of the piston rod can be accommodated in a central stepped bore of the piston. The end of the piston rod can then form a stop for the valve body. Furthermore, a chamber can be formed between the end of the piston rod and the bottom of the stepped bore, in which the valve body is housed. This allows for simple assembly of the valve body, as it only requires inserting the valve body into the stepped bore of the piston, and then inserting the end of the piston rod into the stepped bore.

[0019] The bore can also comprise a first bore section within the piston rod, which opens into the pressure chamber, and a second bore section within the piston, which opens into the spring chamber. The first bore section can comprise an axial section and a transverse section attached to the axial section, which is arranged transversely to the axial section and opens into the pressure chamber.

[0020] The valve body can in particular consist of a plastic body which is in particular at least partially silicone-coated.

[0021] As already explained above, in the spring brake cylinder, the piston is preferably designed as a diaphragm piston and comprises a diaphragm held on the edge of the spring brake cylinder housing and a central diaphragm pressure plate on which the diaphragm is supported.

[0022] In a combined service brake and spring brake cylinder, the edge of the diaphragm is preferably clamped in a joint between the spring brake cylinder housing and an intermediate flange which is arranged in the axial direction, i.e. viewed in the direction of the center axis of the spring brake cylinder, between the spring brake cylinder and the service brake cylinder.

[0023] In the spring-loaded brake cylinder, the breathing device preferably further comprises a pressure relief device which is designed and configured to direct compressed air from the spring chamber into the atmosphere when the volume of the spring chamber decreases as a result of a movement of the piston. The pressure relief device therefore provides a constant or temporary flow connection between the spring chamber and the atmosphere. The pressure relief device can also perform a filtering function to prevent moisture, dirt, or particles from penetrating the spring chamber from the outside. The filtering function can be performed, for example, by a valve which opens only to the atmosphere and is actuated into its open position, in particular by the pressure in the spring chamber, and which is preloaded, for example, into the closed position by spring means.Also conceivable are at least one through-hole covered by a filter element or a labyrinth guide for the air escaping from the spring chamber. Combinations of these measures are also conceivable and planned.

[0024] In particular, the pressure relief device can be designed as an insert that is accommodated in a through-hole in the base of the spring brake cylinder housing coaxially with respect to the central axis. This insert can then have at least one through-hole described above, with and without a filter element, the valve described above, and / or the labyrinth guide described above.

[0025] The invention also provides a combined service brake and spring brake cylinder comprising a spring brake cylinder described above and a compressed air-operated braking device of a commercial vehicle comprising a spring brake cylinder described above or the combined service brake and spring brake cylinder.

[0026] Advantageous developments of the invention emerge from the patent claims, the description, and the drawings. The advantages of features and combinations of several features mentioned in the introduction to the description are merely examples and can be effective alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention. Further features can be found in the drawings—in particular the illustrated geometries and the relative dimensions of several components to one another, as well as their relative arrangement and operative connection. The combination of features of different embodiments of the invention or of features of different patent claims is also possible, deviating from the selected references of the patent claims, and is hereby suggested. This also applies to features that are illustrated in separate drawings or mentioned in their description.These features can also be combined with features of different patent claims. Likewise, features listed in the patent claims can be omitted for further embodiments of the invention.

[0027] drawing

[0028] A preferred embodiment of the invention is shown in the drawing and explained in more detail in the following description. In the drawing,

[0029] Fig. 1 is a longitudinal sectional view of a combined service brake and spring brake cylinder with a spring brake cylinder with a breathing device according to a preferred embodiment, wherein a pressure chamber of the spring brake cylinder is vented, the spring brake cylinder is consequently in an applied state and a breathing valve of the breathing device is in the open position;

[0030] Fig. 2 is an enlarged longitudinal sectional view of the breathing valve of Fig. 1 in the open position;

[0031] Fig. 3 is a longitudinal sectional view of the combined service brake and spring brake cylinder of Fig. 1 in a situation in which the pressure chamber of the spring brake cylinder is ventilated in order to transfer the spring brake cylinder from the applied state of Fig. 1 to the released state of Fig. 5 and in which the breathing valve is still in the open position and, on the other hand, air is forced from the spring chamber into the atmosphere by means of a pressure relief device of the breathing device;

[0032] Fig. 4 is an enlarged longitudinal sectional view of the breathing valve of Fig. 1 , which has assumed the closed position after the pressure chamber has been completely vented;

[0033] Fig. 5 is an enlarged longitudinal section of the combined service brake and spring brake cylinder of Fig. 1 in the situation in which the pressure chamber is fully ventilated, the spring brake cylinder is fully released and the venting valve is in the closed position;

[0034] Fig. 6 is an enlarged longitudinal section of the combined service brake and spring brake cylinder of Fig. 1 in a situation in which the spring brake cylinder is brought from the released state of Fig. 5 back into the applied state of Fig. 1 by venting the pressure chamber, whereby the breather valve moves into the open position and air is forced from the pressure chamber into the spring chamber through the now opening breather valve (pressure equalization).

[0035] Description of the embodiment

[0036] Fig. 1 shows a longitudinal sectional view of a combined service brake and spring brake cylinder, hereinafter referred to as combination cylinder 1, with a service brake cylinder 2 and a spring brake cylinder 3 with a breathing device 4 according to a preferred embodiment.

[0037] The service brake cylinder 2 and the spring brake cylinder 3 are separated from one another by an intermediate flange 5. An edge 6 of a service brake cylinder housing 7 of the service brake cylinder 2 can be connected to a first edge 8 of the intermediate flange 5 by a first connection 9, here for example a clamp, and an edge 10 of a spring brake cylinder housing 13 of the spring brake cylinder 3 can be connected to a second edge 14 of the intermediate flange 5, pointing away from the first edge 8, by a second connection 15, here for example by a flange or a bayonet lock. The spring brake cylinder housing 13 and the service brake cylinder housing 7 are each pot-shaped, for example, and each have a base 16, 17.Consequently, the service brake cylinder 2, the intermediate flange 5 and the spring brake cylinder 3 are arranged serially one behind the other in the direction of a central axis 18 of the combination cylinder 1 or the spring brake cylinder 3.

[0038] A first piston is slidably arranged within a spring brake cylinder housing 13, with a storage spring 20 resting on one side of the first piston 19. The storage spring 20 is supported on its opposite side on the bottom 16 of the spring brake cylinder housing 13. The first piston 19 is here, for example, a diaphragm piston comprising a first diaphragm 21, which is clamped with its radially outer edge between the edge 10 of the spring brake cylinder housing 13 and the second edge 14 of the intermediate flange 5, and a central first diaphragm pressure plate 22, against which the first diaphragm 21 is supported. The first diaphragm pressure plate 22 is connected to a first piston rod 23 in a manner explained further below.

[0039] The first piston 19 defines, with one side, a first pressure chamber 24 of the spring brake cylinder 3, which can be vented and vented by means of a valve device (not shown here), and which is also defined by the intermediate flange 5. Furthermore, the first piston 19 defines, with its other side, a spring chamber 26, which is additionally defined by the spring brake cylinder housing 13 and accommodates the accumulator spring 20.

[0040] For venting and venting the first pressure chamber 24, a first inlet 27 opens into it, through which a pressure medium, in particular compressed air at a pressure p12, is introduced in order to displace the first piston 19 while compressing the accumulator spring 20. During this displacement of the first piston 19, the air located within the spring chamber 26 accommodating the accumulator spring 20 would be compressed without the breathing device 4, which will be described in detail later. As a result, the spring brake cylinder 3 is released, i.e., transferred from an applied state to a released state, wherein the released state corresponds to a released spring brake and the applied state to an applied spring brake in a known manner.

[0041] If, however, the first pressure chamber 24 of the spring brake cylinder 3 is vented by actuating a valve device connected to the first inlet 27 for the purpose of applying the spring brake cylinder 3, the accumulator spring 20 can displace the first piston 19 in the opposite direction. This displacement of the first piston 19 causes the air located within the spring chamber 26 accommodating the accumulator spring 20 to expand. Without the breathing device 4, a vacuum would be created there, which would suck moisture and dirt from the atmosphere into the spring chamber 26.

[0042] At least the spring brake cylinder housing 13, the first piston 19, the first piston rod 23, the accumulator spring 20, and the breathing device 4 are arranged coaxially with the central axis 18 of the spring brake cylinder 3 or the combination cylinder 1. The service brake cylinder 2 is also arranged coaxially with this axis.

[0043] The first diaphragm plate 22 of the first piston 19 is connected to the first piston rod 23, for example, in that one end 28 of the first piston rod 23 is received in a stepped bore 29 of the first diaphragm plate 22 and fixed there, here for example by a threaded connection.

[0044] With its other end, the first piston rod 23 extends through a through-opening 30 of the intermediate flange 5 into the area of ​​a second pressure chamber 31 of the service brake cylinder 2. A seal 32 inserted in the through-opening 30 of the intermediate flange 5 seals off the outer diameter of the first piston rod 23 during its axial movements. The first piston rod 23 carries a pressure piece 33 at its other end, which extends into the area of ​​the second pressure chamber 31 of the service brake cylinder 2. A second inlet 34 opens into the second pressure chamber 31 of the service brake cylinder 2, through which pressure medium, such as compressed air, is admitted to actuate the service brake and discharged to release the service brake.

[0045] This compressed air acts on a second piston 35 inserted within the service brake cylinder housing 7, here also designed in the form of a diaphragm piston, which has a second diaphragm 36, which here, for example, is clamped with its radially outer edge between the edge 6 of the service brake cylinder housing 7 and the first edge 8 of the intermediate flange 5.

[0046] The second diaphragm 36 acts on a second diaphragm pressure plate 37 in the form of a piston rod head, which is connected to a second piston rod 38, which extends through a return spring chamber 40 of the service brake cylinder 2, which receives a return spring 39, and is connected (in a manner not shown) to a brake actuation mechanism outside the combination cylinder 1. This can be, for example, the actuation parts of a disc brake of a commercial vehicle. If the service brake is actuated by introducing compressed air into the second inlet 34, the compressed air displaces the second diaphragm 36 together with the second diaphragm pressure plate 37 and the second piston rod 38 in such a way that the brake actuation mechanism interacting with the second piston rod 38 is actuated and the service brake is applied.During this normal service braking, the spring brake can remain in its released state, in which the accumulator spring 20 is compressed by maintaining the pressure p12 in the first pressure chamber 24 of the spring brake cylinder 3.

[0047] The spring-loaded brake can be used, for example, as an auxiliary brake if the service brake fails, or as a parking brake. In this case, it acts as a parking brake when the vehicle is parked.

[0048] The breathing device 4, explained in detail below, is described with reference to a combination cylinder 1 of the aforementioned design. The breathing device 4 is naturally also suitable for spring-loaded brake cylinders 3, which operate either in a pulling or pushing manner without a front-mounted service brake cylinder 2. Such spring-loaded brake cylinders 3 are intended for both rail and road vehicles. They can, of course, also be used as actuating cylinders for other purposes.

[0049] Here, for example, in or on the first piston 19 and in or on the first piston rod

[0050] 23, a breathing valve 41 of the breathing device 4 is formed, held or arranged, which is used to bring about a pressure equalization within the spring chamber 26 when the pressure p12 for the purpose of the above-described application of the spring brake within the first pressure chamber

[0051] 24 is reduced. If the first piston 19 moves from bottom to top in Fig. 6 during this pressure reduction, the volume of the spring chamber 26 increases accordingly.

[0052] Conversely, when the pressure p12 is built up within the first pressure chamber 24 for the purpose of releasing the spring brake as described above, the first piston 19 moves from top to bottom in Fig. 1 during this pressure build-up, whereby the volume of the spring chamber 26 decreases accordingly.

[0053] The breathing device 4 is then designed and provided so that pressure equalization can be brought about during the movement of the first piston 19 within the spring chamber 26, which increases or decreases in volume. For this purpose, the breathing valve 41 of the breathing device 4 is designed and configured to create a flow connection between the first pressure chamber 24 and the spring chamber 26 or to block this flow connection depending on the pressure p12 prevailing in the first pressure chamber 24. For this purpose, the breathing valve 41 has an open position in which the breathing valve 41 connects the first pressure chamber 24 and the spring chamber 26 to one another, and a closed position in which it separates the first pressure chamber 24 from the spring chamber 26.

[0054] Furthermore, the breathing valve 41 has a valve body 42, which is arranged in particular coaxially with respect to the central axis 18 and is preloaded into the open position of the breathing valve 41 by spring means 43, here in particular by a compression spring. The pressure p12 prevailing in the first pressure chamber 24, which urges the valve body into the closed position, acts on the valve body 42 by means described later, on the one hand, and urges the valve body into the closed position, and on the other hand, in the axially opposite direction, the spring forces of the spring means 43, by which the valve body is urged into the closed position. The valve body 42 here consists in particular of a plastic body, which is at least partially silicone-coated, in particular on its end face.

[0055] The valve body 42 is axially guided in a guide section 44 of a bore 45, which extends, for example, through the end 28 of the first piston rod 23 and, for example, completely through the first diaphragm pressure plate 22 of the first piston 19, in particular also through its stepped bore 29. This bore 45 is arranged coaxially with respect to the central axis 18 and opens, on the one hand, into the spring chamber 26 and, on the other hand, into the first pressure chamber 24.

[0056] The valve body 42 of the breathing valve 41 interacts with a shoulder 46 of the bore 45, this shoulder 46 being formed here in particular in the stepped bore 29 of the first diaphragm pressure plate 22. In the closed position of the breathing valve 41, the valve body 42 is then pressed sealingly against the shoulder 46 of the bore 45, such that the valve body 42, when sealingly abutting the shoulder 46, blocks the connection between the spring chamber 26 and the first pressure chamber 24, as shown in Fig. 4, which shows the closed position of the breathing valve 41.

[0057] In the open position of the breathing valve 41, however, the valve body 42 is lifted off the shoulder 46 of the bore 45, such that the connection between the spring chamber 26 and the first pressure chamber 24 opens. The valve body 42 is axially guided by a circumferential gap 47 in the guide section 44 of the bore 45, in particular the stepped bore 29, such that the circumferential gap 47 forms a part or section of the flow connection between the spring chamber 26 and the first pressure chamber 24 in the open position of the breathing valve 41. Consequently, in the open position, compressed air can flow around the valve body 42 in the circumferential gap 47, with the clear circumferential gap 47 then forming a section or part of the flow connection, as shown in Fig. 2, which shows the open position of the breathing valve 41.

[0058] The valve body 42 is particularly preferably designed in a stepped manner, wherein the bore 45 in the region of the guide section 44 is designed in a stepped manner complementary to the valve body 42. This creates an axial stop of the valve body 42 at a step of the bore 45. Since the end 28 of the first piston rod 23 is preferably received in the stepped bore 29 of the first piston 19 or, in this case, by its first diaphragm pressure plate 22, an end face of the end 28 of the first piston rod 23 can form the axial stop for the valve body 42 when the breathing valve 41 is in the open position, wherein the valve body 42 is then urged against this end 28 by the spring means 43.Furthermore, a chamber 48 is formed between the end 28 of the first piston rod 23 and a bottom of the stepped bore 29, on which the shoulder 46 of the bore 45 is formed, and the radially inner diameter of the stepped bore 29, in which chamber the valve body 42 is guided axially.

[0059] The bore 45 here, for example, has a first bore section 45a within the first piston rod 23, which opens into the first pressure chamber 24, and a second bore section 45b within the first diaphragm pressure plate 22, which opens into the spring chamber 26. As can be seen particularly clearly in Fig. 5, the first bore section 45a can have an axial section opening into the breathing valve 41 and a transverse section attached to the axial section, which is arranged transversely to the axial section and opens into the first pressure chamber 24.

[0060] Via the first bore section 45a of the bore 45, a first end face 49 of the valve body 42 is therefore loaded by the pressure p12 in the first pressure chamber 24 and via the second bore section 45b of the bore 45, a second end face 50 of the valve body 42 is loaded with the pressure in the spring chamber 26 (Fig. 2). Furthermore, the second end face 50 of the valve body 42 is loaded by the spring force of the spring means 43 into the open position of the breathing valve 41.

[0061] The breathing device 4 preferably further comprises a pressure relief device 51, which is designed and configured to direct compressed air from the spring chamber 26 into the atmosphere when the volume of the spring chamber 26 decreases as a result of a movement of the first piston 19. The pressure relief device 51 therefore provides a constant or temporary flow connection between the spring chamber and the atmosphere.

[0062] Here, the pressure relief device 51 is designed in particular as an insert 52, which is accommodated in a central through-bore in the base 16 of the spring brake cylinder housing 13 coaxially with respect to the central axis 18. This insert 52 can then, for example, have a valve, a through-hole with or without a filter element, and / or a labyrinth guide for the compressed air.

[0063] The breathing device works as follows:

[0064] The initial state of the spring brake cylinder 3 is intended to be the applied state of Fig. 1, in which the first pressure chamber 24 of the spring brake cylinder 3 is vented. The low pressure p12 in the first pressure chamber 24 is then present at the first end face 49 of the valve body 42, whereby a relatively low pressure force acts on the valve body 42. In contrast, the opposing pressure force exerted by the spring means 43 on the second end face 50 is greater, so that the valve body 42 is lifted off the shoulder 46 of the second bore section 45b of the bore 45 and the vent valve 41 is thus in its open position, which is shown in Fig. 2.The arrows 54 shown there symbolize the air flow through the first bore section 45a in the first piston rod 23, through the circumferential gap 47 around the valve body 42 and through the second bore section 45b in the first diaphragm pressure plate 22, whereby a flow connection is present between the first pressure chamber 24 and the spring chamber 26.

[0065] Fig. 3 now shows the situation in which the first pressure chamber 24 of the spring brake cylinder 3 is ventilated in order to transfer the spring brake cylinder 3 from the applied state of Fig. 1 to the released state of Fig. 5 and in which the breathing valve 41 is still in the open position. As shown by the arrows 55 in Fig. 3 symbolizing the air flow that then occurs, compressed air flows from the first pressure chamber 24 into the spring chamber 26. On the other hand, the volume of the spring chamber 26 is reduced by the movement of the first piston 19 (from top to bottom in Fig. 3). Compression of the air in the spring chamber 26, which would counteract the movement of the first piston 19, is prevented by the fact that air from the spring chamber 26 is forced into the atmosphere by means of the pressure relief device 51 of the breathing device 4.

[0066] If, after some time, the pressure p12 in the first pressure chamber 24 has increased to such an extent that the resulting pressure force on the first end face 49 of the valve body 42 is greater than the spring force of the spring means 43 and the pressure force on the second end face 50 resulting from the pressure in the spring chamber 26, the valve body 42 is pressed against the shoulder 46 of the second bore section 45b, thus closing the bore 45, which also blocks the flow connection between the first pressure chamber 24 and the spring chamber 26. The breathing valve 41 is then in the closed position shown in Fig. 4.

[0067] Fig. 5 then shows the resulting situation in which the first pressure chamber 24 is completely ventilated, the breathing valve 41 is in the closed position and the spring brake cylinder 3 is completely released.

[0068] If the pressure p12 within the first pressure chamber 24 is now reduced for the purpose of braking the spring brake cylinder 3, the first piston 19 moves from bottom to top in Fig. 6. During this movement, the volume of the spring chamber 26 increases, so that the pressure in the spring chamber 26, which initially exists as atmospheric pressure, decreases.

[0069] The decreasing pressure p12 in the first pressure chamber 24 and the negative pressure prevailing in the spring chamber 26 when the volume thereof increases are initially able, acting in the same direction, to hold the valve body 42 in sealing contact with the shoulder 46 of the second bore section 45b, whereby the connection between the spring chamber 26 and the first pressure chamber 24 is still prevented. However, if the pressure p12 in the first pressure chamber 24 is further reduced, the force of the spring means 43 begins to predominate, i.e. the spring means 43 press the valve body 42 against the effect of the negative pressure in the spring chamber 26 and against the effect of the residual pressure in the first pressure chamber 24 in such a way that the valve body 42 is released from the shoulder 46 and the breathing valve 41 is thereby moved into its open position shown in Fig. 2.

[0070] The compressed air in the decreasing-volume first pressure chamber 24 can then pass through the open vent valve 41 into the increasing-volume spring chamber 26, as shown by the arrows 56 in Fig. 6, thus achieving the desired pressure equalization between the first pressure chamber 24 and the spring chamber 26. The opening of the valve body 42 can be determined by appropriately dimensioning the area ratios of the first and second end faces 49, 50 and by a suitable selection of the spring means 43. In any case, with a sufficient pressure increase in the first pressure chamber 24, it is ensured that the vent valve 41 between the spring chamber 26 and the first pressure chamber 24 moves into the closed position.

[0071] The aforementioned pressure relief device 51 is preferably designed such that it prevents outside air and any dirt or particles contained therein from entering the spring chamber 26 when the above-described volume increase of the spring chamber 26 occurs during the application of the spring brake cylinder. In the opposite direction, however, i.e. when the volume of the spring chamber 26 decreases, the pressure relief device 51 is permeable such that air located in the spring chamber 26 is blown off into the atmosphere through the pressure relief device 51 when the first piston 19 is displaced downwards according to Fig. 3 for the purpose of releasing the spring brake upon venting the first pressure chamber 24 and the accumulator spring 20 is tensioned.

[0072] LIST OF REFERENCE SYMBOLS

[0073] 1 combination cylinder

[0074] 2 service brake cylinders

[0075] 3 spring brake cylinders

[0076] 4 Breathing device

[0077] 5 Intermediate flange

[0078] 6 Edge

[0079] 7 Service brake cylinder housing

[0080] 8 first edge

[0081] 9 first connection

[0082] 10 Rand

[0083] 13 Spring brake cylinder housing

[0084] 14 second edge

[0085] 15 second connection

[0086] 16 Floor

[0087] 17 Floor

[0088] 18 Central axis

[0089] 19 first piston

[0090] 20 storage springs

[0091] 21 first membrane

[0092] 22 first membrane pressure plate

[0093] 23 first piston rod

[0094] 24 first pressure chamber

[0095] 26 spring chamber

[0096] 27 first entry

[0097] 28 End

[0098] 29 stepped bore

[0099] 30 passage opening

[0100] 31 second pressure chamber

[0101] 32 Seal

[0102] 33 Pressure piece

[0103] 34 second inlet 35 second piston

[0104] 36 second membrane

[0105] 37 second diaphragm pressure plate

[0106] 38 second piston rod

[0107] 39 Return spring

[0108] 40 Return spring chamber

[0109] 41 Breathing valve

[0110] 42 valve body

[0111] 43 spring means

[0112] 44 Guide Section

[0113] 45 bore

[0114] 45a first drilling section

[0115] 45b second drilling section

[0116] 46 shoulder

[0117] 47 circumferential gap

[0118] 48 Chamber

[0119] 49 first frontal surface

[0120] 50 second frontal surface

[0121] 51 Pressure relief device

[0122] 52 deployment

[0123] 53 passage opening

[0124] 54 arrows

[0125] 55 arrows

[0126] 56 arrows p12 pressure in the first pressure chamber

Claims

PATENT CLAIMS 1. A compressed air-operated spring brake cylinder (3) with a spring brake cylinder housing (13) and a piston (19) which can be axially actuated by a storage spring (20) within the spring brake cylinder housing (13), which piston is delimited on one side by a pressure chamber (24) and on the opposite side by the spring chamber (26) accommodating the storage spring (20), and which is connected to a piston rod (23), as well as with a breathing device (4) comprising at least one breathing valve (41), wherein the breathing valve (41) is designed and configured to create a flow connection between the pressure chamber (24) and the spring chamber (26) or to block this flow connection depending on the pressure (p12) prevailing in the pressure chamber (24), wherein at least the piston (19) and the piston rod (23) are arranged coaxially to a central axis (18) of the spring brake cylinder housing (13), characterized in thatthat the breathing valve (41) is carried by the piston rod (23) and / or by the piston (19) coaxially with respect to the central axis (18).

2. Spring brake cylinder according to claim 1, characterized in that the breathing valve (41) has an open position in which the breathing valve (41) connects the pressure chamber (24) and the spring chamber (26) to one another, and a closed position in which the breathing valve (41) separates the pressure chamber (24) and the spring chamber (26) from one another.

3. Spring brake cylinder according to claim 2, characterized in that the breathing valve (41) has a valve body (42) which is prestressed into the open position by spring means (43).

4. Spring brake cylinder according to claim 3, characterized in that the valve body (42) is axially guided in a guide section (44) of a bore (45, 45a, 45b) of the piston rod (23) and / or the piston (19), which a) in the closed position can be pressed sealingly against a shoulder (46) of the bore (45, 45a, 45b) in such a way that the valve body (42) blocks the connection between the spring chamber (26) and the pressure chamber (24) when in sealing contact with the shoulder (46) of the bore (45, 45a, 45b), and which b) in the open position is lifted off the shoulder (46) of the bore (45, 45a, 45b) in such a way that the connection between the spring chamber (26) and the pressure chamber (24) opens, wherein c) the bore (45, 45a, 45b) is arranged coaxially to the central axis (18) and opens on the one hand into the spring chamber (26) and on the other hand into the pressure chamber (24).

5. Spring brake cylinder according to claim 4, characterized in that the valve body (42) is axially guided with a circumferential gap (47) in the guide section (44) of the bore (45, 45a, 45b) in such a way that the circumferential gap (47) forms part of the flow connection between the spring chamber (26) and the pressure chamber (24) in the open position.

6. Spring brake cylinder according to one of claims 4 to 5, characterized in that the valve body (42) is stepped and the guide section (44) of the bore (45, 45a, 45b) is stepped complementary to the valve body (42).

7. Spring brake cylinder according to claim 6, characterized in that one end (28) of the piston rod (23) is received in a central stepped bore (29) of the piston (19) and between the end (28) of the piston rod (23) and a bottom of the stepped bore (29) a chamber (48) is formed, in which the valve body (42) is guided axially.

8. Spring brake cylinder according to one of claims 4 to 7, characterized in that the bore (45, 45a, 45b) has: a) a first bore section (45a) within the piston rod (23), which opens into the pressure chamber (24), and b) a second bore section (24b) within the piston (19), which opens into the spring chamber (26).

9. Spring brake cylinder according to claim 8, characterized in that the first bore section (45a) has an axial section and a Section has a transverse section which is arranged transversely to the axial section and opens into the pressure chamber (24).

10. Spring brake cylinder according to one of the preceding claims, characterized in that the valve body (42) consists of a plastic body which is in particular at least partially silicone-coated.

11. Spring brake cylinder according to one of the preceding claims, characterized in that the piston (19) is designed as a diaphragm piston and comprises a diaphragm (21) held on the edge of the spring brake cylinder housing (13) and a central diaphragm pressure plate (22) on which the diaphragm (21) is supported.

12. Spring brake cylinder according to one of the preceding claims, characterized in that the breathing device (4) further comprises a pressure relief device (51) which is designed and arranged to direct compressed air from the spring chamber (26) into the atmosphere when the volume of the spring chamber (26) is reduced as a result of a movement of the piston (19).

13. Spring brake cylinder according to claim 12, characterized in that the pressure relief device (51) has an insert (52) which is received in a central through-opening (53) in the base (17) of the spring brake cylinder housing (13) coaxially with respect to the central axis (18).

14. Combined service brake and spring brake cylinder (1) comprising a spring brake cylinder (3) according to one of the preceding claims.

15. Compressed air-operated braking device of a commercial vehicle, comprising at least one spring-loaded brake cylinder (3) according to one of claims 1 to 13 or a combined service brake and spring-loaded brake cylinder (1) according to claim 14.

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