WO2026008145A1

WO2026008145A1 - Pneumatic double check valve and electro-pneumatic brake pressure modulator comprising such pneumatic double check valve

Info

Publication number: WO2026008145A1
Application number: PCT/EP2024/068895
Authority: WO
Inventors: Michal KALISZUK; Pawel Swiatek; Thooyavan JANAKIRAMAN; Sankarapandiyan Subramanian
Original assignee: ZF CV Systems Global GmbH
Current assignee: ZF CV Systems Global GmbH
Priority date: 2024-07-04
Filing date: 2024-07-04
Publication date: 2026-01-08
Anticipated expiration: 2027-01-04

Abstract

A pneumatic double check valve comprising a valve body having a longitudinal axis, a cavity, a first inlet opening, a second inlet opening and an outlet opening, the cavity being in fluid communication with the first inlet opening, the second inlet opening and the outlet opening. A sleeve is placed inside the cavity of the valve body and a shuttle is movable therein, when loaded with pneumatic-induced pressures greater than the shuttle crack off pressure, between first and second positions spaced therefrom, so that to alternatively close and open the first and the second inlet openings, respectively. The sleeve comprises annular lip seals having a crack off pressure that is greater than the shuttle crack off pressure. The pneumatic double check valve is designed to avoid shuttle swimming failure, improve response time behaviour and facilitate port interchangeability.

Description

Pneumatic double check valve and electro-pneumatic brake pressure modulator comprising such pneumatic double check valve

The present invention relates to a pneumatic double check valve, to an electro-pneumatic brake pressure modulator comprising such a pneumatic double check valve, to a brake system comprising such an electro-pneumatic brake pressure modulator, and to a vehicle, in particular a passenger car or commercial vehicle, comprising such a brake system.

In general, pneumatic double check valves (also known as pneumatic DCVs) may come in different kinds. For instance, they may be of the kind labelled “Select High DCV”, i.e. pneumatic DCVs that only allow a high pressure to the delivery connections. In other known kinds, pneumatic double check valves of the “Select High DCV” are also frequently equipped with a preloaded spring acting on the guide piece. Also other known kinds are “Select low DCV”, i.e. pneumatic DCVs that only allows a low pressure to the delivery connections.

Double check valves are widely used in pneumatic circuits to prevent backflow or to provide backup connections. Pneumatic double check valves usually comprise two inlets or inlet openings as control ports and one outlet or outlet opening. They are often used in pneumatic brake circuits of passenger or commercial vehicles for various control purposes, e.g. for connection and separation of multiple air circuits with compressed air reservoirs. Pneumatic DCVs are often used inparking brake systems, service brakes, secondary consumers, clutches and transmissions, etc. Select high DCVs are used in anti-compounding relay valves of air brake systems, or in quadruple system protect valves used to prevent back flow of compressed air into upstream. Select high DCVs are also used in back up supply circuits of axle modulators in air brake systems.

A pneumatic double check valve can usually close one or the other of the two inlet openings by way of a spring or pressure force acting in the closing direction, and be opened in the other direction by an airflow, such as compressed air, which overcomes the closing force at one or both inlets. Closing usually takes place e.g. in that a guide piece is arranged in a respective blocking position in which the guide piece closes one of the inlets.

Known pneumatic double check valves generally comprise a preferably cylindrical guide piece that is inserted so as to be longitudinally movable within the cylindrical bore of the valve body or within an additional support sleeve member bore inserted within the cylindrical bore of the valve body. The guide piece end faces can form two check valves in series acting opposite one another. Also known are pneumatic double check valves where two separate guide pieces are arranged in the same valve body's cylindrical bore or cylindrical sleeve bore.

The pneumatic double check valves according to the prior art work as a function of a pneumatic force and require an air flow and associated pressurized air-induced pressure in order to set, maintain and/or change the state of the pneumatic double check valve in well-defined fashion. Pneumatic DCVs may be used in both pneumatic control applications and pneumatic supply applications. In pneumatic control applications, air pressure is instantly applied with a high apply rate (i.e. pressure gradients such as >25 bar/s). In such cases, the guide piece (also known as shuttle) instantly reacts and closes the opposite side. However, in pneumatic supply application, air pressure may be applied at a very slow rate (i.e. ~0.1 bar/s). In such cases, the shuttle may not react properly and sometimes close the DCV side which is opposite to the intended side. This often results in the shuttle swimming in-between the two supply connections. In the field of pneumatic DCVs, such a failure is called “shuttle swimming failure” and may result in damaging all connected pneumatic circuits in the system.

To avoid shuttle swimming, prior art solutions are known, that include providing shuttles having very tight radial and axial sealings. Such designs however suffer the issue of different pressures required to switch the shuttle, depending whether air is trapped between the axial and radial sealings, which is undesired in a vehicle braking scenario. Another known issue of the solutions with very tight radial and axial sealings, lies in the poor response time of the pneumatic DCV. The issues of the different pressures required to switch the shuttle, together with the issue of poor response time, make such DCVs unattractive in the context of pneumatic applications. Other issues of prior art pneumartic DCVs, both in the case of pneumatic control applications and pneumatic supply applications, reside in the difficulty to achieve the desired response behavior in devices with complex parts and/or multiple components. Similarly, port interchangeability is generally not possible with exiting pneumatic DCVs, especially with those equipped with a spring, due to the fact of their non-sym metrical air flow design.

An object of the present invention is therefore to eliminate or at least minimize the issue of pneumatic DCV shuttle swimming failure.

Another object of the present invention is to provide a pneumatic DCV for an inlet section of an electro-pneumatic brake pressure modulator that can effectively be used and perform well in both pneumatic control applications and pneumatic supply applications. For the purpose of the present invention, the inlet section of the electro-pneumatic brake pressure modulator can be referred to as a section where inlet or supply ports of the electro-pneumatic brake pressure modulator meet. In the case of the present invention, since the electro-pneumatic brake pressure modulator takes advantage of two supply ports to enable redundancy in supply, the region where said two supply ports meet may be considered as the inlet section for the sake of understanding.

Another object of the present invention is to provide a pneumatic DCV that does not suffer the issue of different pressures required to switch the shuttle, depending whether air is trapped between the axial and radial sealings. A further object of the present invention is to provide a pneumatic DCV having a fast response time. Another object of the present invention is to provide a pneumatic DCV that exhibit a predictable response behavior in devices with complex parts and/or multiple components. A further object of the present invention is to provide a pneumatic DCV enabling a good port interchangeability. Another object of the present invention is to provide an electro-pneumatic brake pressure modulator comprising such a pneumatic double check valve, a brake system comprising such an electro-pneumatic brake pressure modulator, and a vehicle, in particular a passenger car or commercial vehicle, comprising such a brake system.

These and other objects are achieved by a pneumatic double check valve for the inlet section of the electro-pneumatic brake pressure modulator comprising a valve body having a longitudinal axis, a first inlet opening, a second inlet opening and an outlet opening. The pneumatic double check valve of the invention also comprises a sleeve having a longitudinal axis parallel with the longitudinal axis of the valve body. The sleeve has an internal surface and an external surface and it is placed in a cavity of the valve body. Such a cavity of the valve body preferably has a cylindrical shape and it is in fluid communication with the first inlet opening, the second inlet opening and the outlet opening. A guide piece or shuttle, preferably having an elongate, cylindrical shape, is movably arranged in the sleeve along its longitudinal axis when loaded with a pneumatic-induced pressure greater than a guide piece crack off pressure, the guide piece being movable between a first blocking position and a second blocking position spaced therefrom. The guide piece preferably comprises at least one radial seal extending towards and contacting the internal surface of the sleeve. The guide piece comprises at least an axial seal portion extending along the longitudinal axis of the sleeve. In the pneumatic double check valve of the invention, the first inlet opening is closed by the guide piece when the guide piece is in the first blocking position and the second inlet opening is closed by the guide piece when the guide piece is in the second blocking position. When the guide piece is in the first blocking position, the second inlet opening is opened and in fluid communication with the outlet opening, and when the guide piece is in the second blocking position, the first inlet opening is opened and in fluid communication with the outlet opening. Thus, the technical advantage of the present invention is to provide the pneumatic double check that is configured to be used at the inlet section for the electro-pneumatic brake pressure modulator without any additional support element such as a spring used to support the guide piece in providing resistance to the pressure received at any of the inlet openings. This enables a substantial flexibility during the usage of the electro-pneumatic brake pressure modulator as it provides port interchangeability independent of the magnitude of the pressure received at either of the inlet openings. Furthermore, it is also not easy to recognize any malfunction associated with elements such as spring when they are, in particular, used in association with the inlet section of the electro-pneumatic brake pressure modulator.

In the pneumatic double check valve of a preferred embodiment of the present invention, the sleeve comprises at least one further radial seal provided on the external surface of the sleeve and extending towards an internal surface of the cavity of the valve body, the at least one further radial seal exhibiting a further radial seal crack off pressure that is greater than the guide piece crack off pressure. For instance, by providing two different magnitudes of the seal crack off pressure associated with the pneumatic double check valve, it is ensured that firstly at least the guide piece is moved either to the first or to the second blocking position when there is even a small pressure difference with the pressure received at each of the inlet openings of the pneumatic double check valve. Secondly, it is ensured that the pressure equalization occurs at the area or space above the guide piece due to the opening of the at least one further radial seal at the further radial seal crack off pressure. By this way, the orientation of the guide piece at the first or second blocking position is ensured without usage of additional elements such as springs with different characteristics.

In an alternative embodiment, the at least one further radial seal is provided directly on the valve cavity surface of the valve cavity rather than on the sleeve.

The term crack off pressure generally refers to the pressure force is required to move a part. For instance, the crack off pressure of the shuttle means the pressure required to move the shuttle from its position. Or else, the crack off pressure of a lip seal means the pressure required to move its dynamic lip side. Crack off forces vary and depend on the component friction force against its movement.

In an embodiment, the at least one further radial seal is a lip seal, preferably an annular lip seal.

In a preferred embodiment, the at least one radial seal of the guide piece is an O-ring, preferably the at least one radial seal comprises two O-rings.

In an embodiment, the at least one further radial seal comprises a static side and a dynamic side, the static side being located in proximity to the external surface of the sleeve and the dynamic side being located in proximity to the surface of the cavity of the valve body.

In an embodiment, the dynamic side of the at least one further radial seal contacts the internal surface of the cavity of the valve body.

In an embodiment, the sleeve comprises at least one annular protrusion extending from its external surface towards the surface of the cavity of the valve body. A space is therefore defined, that is located between the at least one annular protrusion, the external surface of the sleeve, the surface of the cavity of the valve body and the at least one axial seal portion of the guide piece.

In an embodiment, the dynamic side of the at least one further radial seal is adapted to crack off when the pneumatic-induced pressure is greater than the at least one further radial seal crack off pressure, allowing air into the space between the at least one annular protrusion, the external surface of the sleeve, the surface of the cavity of the valve body and the at least one axial seal portion of the guide piece.

According to an embodiment, the sleeve has a first axial end and a second axial end, the first axial end and the second axial end having a plurality of cutouts configured to allow flow of air.

According to a preferred embodiment, the at least one further radial seal comprises a first further radial seal placed in proximity to the first axial end and a second further radial seal placed in proximity to the second axial end.

According to an aspect, both the first further radial seal and the second further radial seal are lip seals. Preferably, both the first further radial seal and the second further radial seal are annular lip seals.

In an embodiment, the at least one annular protrusion comprises a first annular protrusion and a second annular protrusion, the first annular protrusion and the second annular protrusion being placed in proximity to and encompassing the first further radial seal. The first annular protrusion is located in a proximal position with respect to the first axial end and the second annular protrusion is located in a distal position with respect to the first axial end. The at least one annular protrusion also comprises a third annular protrusion and a fourth annular protrusion, the third annular protrusion and the fourth annular protrusion being placed in proximity to and encompassing the second further radial seal. The third annular protrusion is located in a proximal position with respect to the second axial end and the fourth annular protrusion is located in a distal position with respect to the second axial end. In other words, according to the embodiment described above, the first annular protrusion and the second annular protrusion define a first annular channel encompassing the first further radial seal, whereas the third annular protrusion and the fourth annular protrusion define a second annular channel encompassing the second further radial seal.

According to a further embodiment, the sleeve comprises at least an opening located in correspondence with the outlet opening of the valve body.

In a preferred embodiment the sleeve comprises a plurality of openings located in correspondence with the outlet opening of the valve body. According to an aspect, the plurality of openings located in correspondence with the outlet opening of the valve body, are designed in a way to ensure either of the radial seals of the guide piece, or shuttle, to always stay in contact with the internal surface of the sleeve, even during shuttle movement.

According to a preferred aspect, each opening of the above mentioned plurality of openings of the sleeve has equal dimensions with respect to the other openings. According to an aspect, each opening of the above mentioned plurality of openings of the sleeve is designed in a way to facilitate maximum flow of air towards delivery openings.

In an embodiment, the axial seal portion of the guide piece has a sealing edge, preferably of annular or circular shape, the diameter of which is smaller than the outer diameter of the guide piece.

In an embodiment, the valve body comprises an adaptor placed at either the first inlet opening and/or the second inlet opening.

The objects of the present invention are also achieved by an electro-pneumatic brake pressure modulator, for instance an axle modulator, comprising an electro-pneumatic pressure control circuit. In general, an axle modulator is an electro-pneumatic pressure control circuit (channel) to control brake pressure of the front and/or the rear axle(s) of a vehicle.

The electro-pneumatic pressure control circuit of the invention is a combination of a relay valve portion (or optionally merely referred to as “relay valve”), an inlet solenoid valve, an outlet solenoid valve, a backup solenoid valve. The relay valve portion com- prises a pneumatic supply port system with a double check valve according to the invention, a delivery port system and a backup pneumatic port. The supply double check valve is adapted to connect a first and a second supply port of the relay valve portion and vice versa, mainly to provide a backup supply connection to the relay valve portion.

Also, the electro-pneumatic pressure control unit is provided with a pressure sensor that monitors the delivery brake pressure of the relay valve in a closed loop manner.

The objects of the present invention are also achieved by a brake system comprising an electro-pneumatic brake pressure modulator as described above, the brake system being adapted to control the brake pressure at an axle of a vehicle. According to one aspect, the axle of the vehicle is a front axle. According to another aspect, the axle of the vehicle is a rear axle. According to a further aspect, the brake system is adapted to control the brake pressure at both the front and the rear axles of a vehicle. The objects of the present inventions are also achieved by a vehicle, in particular a passenger car or commercial vehicle, comprising a brake system as described above.

The objects of the present invention are also achieved by an industrial pneumatic system comprising the double check valve of the invention, for instance other automobile pneumatic systems comprising such a double check valve, e.g. an air suspension system in a vehicle, a door control system, and others.

For a more complete understanding of the invention, the invention will now be described in detail with reference to the accompanying drawings. The detailed description will illustrate and describe what is considered as a preferred embodiment of the invention. It should of course be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention may not be limited to the exact form and detail shown and described herein, nor to anything less than the whole of the invention disclosed herein and as claimed hereinafter. Further, the features described in the description, the drawings and the claims disclosing the invention may be essential for the invention considered alone or in combination. In particular, any reference signs in the claims shall not be construed as limiting the scope of the invention. The wording “comprising” does not exclude other elements or steps. The word “a” or “an” does not exclude the plurality. The wording “a number of” items comprising also the number 1 , i.e. a single item, and further numbers like 2, 3, 4 and so forth. In the accompanying drawings:

Figure 1 shows a cutout view of a pneumatic double check valve according to the invention, in a first operative configuration;

Figure 2 shows a shows a cutout view of a pneumatic double check valve according to the invention, in a second operative configuration;

Figure 3 shows, in an enlarged view, a detail from Figure 2 when the pneumatic double check valve is in the second operative configuration;

Figure 4 shows, in perspective view, a detail of a component of a pneumatic double check valve according to the invention;

Figure 5 shows a detail of another component of a pneumatic double check valve according to the invention; and

Figure 6 shows a schematic diagram of an electro-pneumatic brake pressure modulator according to the invention.

With reference to Fig. 1 , the pneumatic double check valve 1 comprises a valve body 2 having a longitudinal axis L, a first inlet opening 3, a second inlet opening 4 and an outlet opening 5.

The valve body 2 has a cylindrical cavity 7 within which a sleeve 6 is placed. The sleeve 6 has an elongate, cylindrical shape and a longitudinal axis M that is parallel to, or coincident with, the longitudinal axis L of the valve body 2. The sleeve 6 has an internal surface 61 and an external surface 62.

The cavity 7 of the valve body 2 is in fluid communication with the first inlet opening 3, the second inlet opening 4 and the outlet opening 5, and so is the sleeve 6, which sleeve 6 has a plurality of openings 60 located in correspondence with the outlet opening 5 of the valve body 2. A first air filter 210 is place in proximity of the first inlet opening 3 and a second air filter 220 is placed in proximity with the second inlet opening 4. An adaptor 20 is placed in correspondence with the second inlet opening 4.

The shuttle or guide piece 8 is movably arranged inside the sleeve 6 along the longitudinal axis M when loaded with a pneumatic-induced pressure greater than the guide piece crack off pressure. The guide piece 8 is movable between a first blocking position, where the first inlet opening 3 is closed and the second inlet opening 4 is open and in fluid communication with the outlet opening 5 (as shown in Fig. 1 ) and a second blocking position spaced therefrom, where the second inlet opening 4 is closed and the first inlet opening 3 is open and in fluid communication with the outlet opening 5 (as shown in Fig. 2).

The guide piece 8 shown in Fig. 1 and Fig. 2 comprises two radial seals 81 , in the form of O-rings, extending towards and contacting the internal surface 61 of the sleeve 6, and at least an axial seal portion 82 extending along the longitudinal axis M.

The axial seal portion 82 may be provided as a separate component that is mounted on the main body of the guide piece 8 or else directly moulded with the guide piece 8.

The axial seal 82 is shaped as two interconnected, substantially identical cup-like parts, linked together via an interconnecting portion that is extending along the longitudinal axis M. The material used to form the axial seal 82 is generally different from the material used to form the main body of the guide piece 8. Preferably, the material used to form the axial seal 8 is softer than the material used to form the main body of the guide piece and may exhibit fluid-tight properties. Preferably, the main body of the guide piece 8 is made with a stiffer material than that of the axial seal portion 82.

The sleeve 6, in accordance with a preferred embodiment, comprises at least one further radial seal 9 provided on the external surface 62 of the sleeve 6 and extending towards the surface 71 of the cavity 7 of the valve body 2, the at least one further radial seal 9 being provided in the form of two annular lip seals 901 , 902 each of which has a crack off pressure greater than the crack off pressure of the guide piece 8. With reference to Fig. 5, the at least one further radial seal 9, or annular lip seal, comprises a static side 91 and a dynamic side 92. The static side 91 is placed into contact with the external surface 62 of the sleeve 6 whereas the dynamic side 92 departs from the static side 91 and extends towards the internal surface 71 of the cavity 7 of the valve body 2. The sleeve 6 has a first axial end 64 facing the first inlet opening 3 and a second axial end 65 facing the second inlet opening 4. The first annular lip seal 901 is placed in proximity with the first axial end 64 of the sleeve 6, and the second annular lip seal 902 is placed in proximity with the second axial 65 of the sleeve 6. The first annular lip seal 901 exhibits a dynamic side that is slanted towards the first inlet opening 3, whereas the second annular lip seal 902 exhibits a dynamic side that is slanted towards the second inlet opening 4. The dynamic side 92 and the static side 91 of both the first and the second annular lip seals are joined together via a connecting portion 93 shaped as a U-groove that is facing the first inlet opening 3 and the second inlet opening 4, respectively.

In general, the guide piece crack off pressure may be defined as a function of the weight of the guide piece, or shuttle, and the internal friction acting between the guide piece 8 and the internal surface 61 of the sleeve 6. The lip seals 901 , 902 crack off pressure may instead be defined as a function of the elastic force of the dynamic side of the annular lip seals 901 , 902 and the internal friction between the portion of the dynamic side of the annular lip seal which is in contact with the internal surface 71 of the cavity 7 of the valve body 7, and said internal surface 71 .

With reference to Fig. 2, the first annular lip seal 901 is encompassed between first and second annular protrusions 601 , 602 of the sleeve, the first annular protrusion 601 being proximal to the first axial end 64 of the sleeve 6 and the second annular protrusion 602 being distal to the first axial end 64 of the sleeve 6.

With reference to Fig. 1 , the second annular lip seal 902 is encompassed between third and fourth annular protrusions 603, 604, the third annular protrusion 603 being proximal to the second axial end 65 of the sleeve 6 and the fourth annular protrusion 604 being distal to the second axial end 65 of the sleeve 6.

Fig. 3 represents an enlarged view of the pneumatic double check valve 1 according to the invention, in a second operative configuration, where the shuttle closes the second inlet opening 4. In such a configuration, the first inlet opening 3 is in fluid communication with the outlet opening 5 and a pneumatic-induced pressure is provided at the first inlet opening 3. To reach this configuration, sufficient pressure had to be applied to the guide piece 8 so that to move it and close the second inlet opening 4. In this configuration, the sealing edge 820 of the axial seal portion 82 of the shuttle 8 contacts the surface of the adapter 20 and properly seal the second inlet opening 4. The sealing edge 820 of the axial seal portion 82, which has an annular shape, features a diameter that is smaller than the outer diameter of the guide piece 8. If sufficient pressure is applied, the lip seal 9 also cracks off and allows air into a space 10 located between the annular protrusion

63, the external surface of the sleeve 62, the surface 71 of the cavity 7 of the valve body 2 and the at least one axial seal portion 82 of the guide piece 8. This ensures that the pressure acting on both sides of the shuttle 8 will be always equal, in order to enhance the stability of the sealing and avoid the issue of different pressures required to switch the shuttle.

As shown in Fig. 4, in order to further improve sealing stability, both axial ends 64, 65 of the sleeve may be provided with cutouts 66 designed to allow airflow through axial ends

64, 65 and facilitate the filling of the space 10 behind the annular lip seals. In other words, the annular lip seal works as a one-way valve and the opening of the dynamic side of the annular lip seal takes places only after sufficient pressure (i.e. crack off pressure) is reached. The closing of the second inlet opening 4 is therefore carried out in two sequential steps, a first step wherein sufficient pressure is provided to crack off the guide piece 8 and properly seal the second inlet opening 4 through contacting the sealing edge 820 of the axial seal portion 82 with the adapter 20, and a second step where an higher pressure is provided, i.e. a pressure sufficient to crack off the annular lip seal 9, so that to allow pressurized air to fill the space 10 via cutouts 66 of the sleeve 6 and ensure an excellent sealing stability.

What discussed above, mutatis mutandis, also happens when the pneumatic double check valve 1 of the invention is in its first configuration, namely, when the guide piece 8 closes the first inlet opening 3 and the second inlet opening 4 is in fluid communication with the outlet opening 5. In this case, if no adapter 20 is present in proximity to the first inlet opening 3, as is the case shown in Fig. 1 , then the sealing edge 820 of the axial seal portion 82 of the guide piece 8 directly contacts the surface 71 of the cavity 7 of the valve body 2. The crack off pressure of the shuttle 8 is preferably designed to be approximately comprised between 0.4 and 1 .0 bar, preferably between 0.5 and 0.8 bar, even more preferably to be approximately equal to 0.6 bar.

The crack off pressure of the annular lip seals is preferably designed to be higher than 1 .5 bar, preferably higher than 1 .7 bar, even more preferably to be approximately equal to 1.9 bar.

In the pneumatic double check valve 1 of the invention, shuttle swimming failure is avoided even if air pressure is applied at a very slow rate, i.e. at a gradient less than 0.1 bar/s, preferably less than 0.06 bar/s, even more preferably swimming failure does not happen for any pressure higher than 0.03 bar/s.

With reference to Fig. 6, the pneumatic double check valve 1 of the invention can be incorporated in an electro-pneumatic brake pressure modulator 100, for instance an axle modulator, at e.g., an inlet section IS as indicated in Fig. 6, to control the brake pressure at at least one brake actuator (not showing in the figures) or at an axle of a vehicle, for instance at a front axle, a rear axle or both.

In general, an axle modulator comprises an electro-pneumatic pressure control circuit 101 to control brake pressure of the front and/or the rear axle(s) of a vehicle.

The electro-pneumatic pressure control circuit 101 comprises a relay valve portion 105, an inlet solenoid valve 103, an outlet solenoid valve 104, and a backup solenoid valve 102. The relay valve portion 105 comprises a pneumatic supply port system a first supply port 111 and a second supply port 112 connected to a double check valve 1 according to the invention. In accordance with an embodiment, the section of relay valve portion 105 where first and second supply ports 111 and 112 meet is generally referred to as inlet section IS, as can also be derived from Fig. 6. It should be noted that either of the supply ports 111 and 112 can lead to either of the openings 3 and 4 of valve 1 as shown in Figs. 1 and 2. Thus, the orientation of the supply ports 111 and 112 is independent of orientation of openings 3 and 4 shown in Figs. 1 and 2. The pressure received at the supply ports 111 and 112 lead to any of first and second inlet openings 1 and 2. The relay valve portion 105 also comprises a delivery port system comprising a first delivery port 221 and a second delivery port 222 and a backup pneumatic port 400. The double check valve 1 is adapted to connect to the first and to the second supply port 111 , 112 of the relay valve portion 105 and vice versa, mainly to provide a backup supply connection to the relay valve. In other words, should the pressure supply at one of the first and second supply ports 111 and 112 fail, the other port will still be able to provide back-up supply pressure to the electro-pneumatic brake pressure modulator 100.

Also, the electro-pneumatic pressure control circuit 101 is provided with a pressure sensor P that monitors the delivery brake pressure of the relay valve 105 in a closed loop manner.

In the event of vehicle braking, when in electronic braking mode, the electro-pneumatic pressure control circuit 101 facilitates the delivery of the required brake pressure. In this case, pneumatic control pressure, the one received via the backup pneumatic port 400 from a brake signal transmitter (not shown in the figures, which is, for example, a foot brake valve controlled by the driver) is selectively blocked by the backup solenoid valve 102 in the electro-pneumatic pressure control circuit. The brake signal transmitter is configured to send the brake pressure demand as commanded by the driver by depressing a brake pedal. One such brake signal transmitter is disclosed, for instance, in the patent publication WO2023186313A1.

In the event of vehicle braking, when in redundancy mode (which is what happens when the electro-pneumatic pressure control circuit fails or is deactivated), the pneumatic back-up pressure via the backup pneumatic port 400 generated by the brake signal transmitter shall control the internal relay valve portion 105, when, for instance, the back-up solenoid valve 102 is in an open position to allow the flow of the pneumatic back-up pressure and is adapted to deliver the required brake pressure. List of reference signs (Part of the description)

1 pneumatic double check valve

2 valve body

20 adaptor

210 first air filter

220 second air filter

3 first inlet opening

4 second inlet opening

5 outlet opening

6 sleeve

10 space located between the at least one annular protrusion, the external sur- face of the sleeve, the surface of the cavity of the valve body and the at least one axial seal portion of the guide piece

60 opening

61 internal surface of the sleeve

62 external surface of the sleeve

63 annular protrusion of the sleeve

64 first axial end of the sleeve

65 second axial end of the sleeve

66 cutouts

601 first annular protrusion

602 second annular protrusion

603 third annular protrusion

604 fourth annular protrusion

7 cavity of the valve body

71 surface of the cavity

8 guide piece or shuttle

81 radial seal of the guide piece

82 axial seal of the guide piece

820 sealing edge of the axial seal of the guide piece

9 further radial seal

91 static side of the further radial seal

92 dynamic side of the further radial seal

93 connecting portion shaped as an U-groove 901 first further radial seal

902 second further radial seal

100 electro-pneumatic brake pressure modulator

101 pressure control circuit

102 backup solenoid valve

103 inlet solenoid valve

104 outlet solenoid valve

105 relay valve portion

111 first supply port

112 second supply port

221 first delivery port

222 second delivery port

400 backup pneumatic port

IS inlet section of electro-pneumatic brake pressure modulator 100

L longitudinal axis of the valve body

M longitudinal axis of the sleeve

P pressure sensor

Claims

1 . A pneumatic double check valve (1 ) for an inlet section (IS) of an electro-pneumatic brake pressure modulator (100), comprising a valve body (2) having a longitudinal axis (L), a first inlet opening (3), a second inlet opening (4) and an outlet opening (5); a sleeve (6) having a longitudinal axis (M) parallel with the longitudinal axis (L) of the valve body (2), the sleeve (6) having an internal surface (61 ) and an external surface (62); wherein the sleeve (6) is placed in a cavity (7) of the valve body (2), the cavity (7) being in fluid communication with the first inlet opening (3), the second inlet opening (4) and the outlet opening (5); a guide piece (8) movably arranged in the sleeve (6) along the longitudinal axis (M) when loaded with a pneumatic-induced pressure greater than a guide piece crack off pressure, the guide piece (8) being movable between a first blocking position and a second blocking position spaced therefrom, the guide piece (8) comprising at least an axial seal portion (82) extending along the longitudinal axis (M); wherein the first inlet opening (3) is closed by the guide piece (8) when the guide piece (8) is in the first blocking position and the second inlet opening (4) is closed by the guide piece (8) when the guide piece (8) is in the second blocking position; wherein when the guide piece (8) is in the first blocking position the second inlet opening (4) is opened and in fluid communication with the outlet opening (5), and wherein when the guide piece (8) is in the second blocking position the first inlet opening (3) is opened and in fluid communication with the outlet opening (5).

2. The pneumatic double check valve (1 ) of claim 1 , wherein the sleeve (6) comprises at least one further radial seal (9) provided on the external surface (62) of the sleeve (6) and extending towards a surface (71 ) of the cavity (7) of the valve body (2), and in that the at least one further radial seal (9) exhibits a further radial seal crack off pressure that is greater than the guide piece crack off pressure.

3. The pneumatic double check valve (1 ) of claim 1 , wherein the at least one further radial seal (9) comprises a static side (91 ) and a dynamic side (92), the static side (91 ) being located in proximity to the external surface (62) of the sleeve (6) and the dynamic side (92) being located in proximity to the surface (71 ) of the cavity (7) of the valve body (2).

4. The pneumatic double check valve (1 ) of claims 1 or 2 or 3, wherein the sleeve (6) comprises at least one annular protrusion (63) extending from the external surface (62) of the sleeve (6) towards the surface (71 ) of the cavity (7) of the valve body (2), the at least one annular protrusion (63) defining a space (10) between the at least one annular protrusion (63), the external surface of the sleeve (62), the surface (71 ) of the cavity (7) of the valve body (2) and the at least one axial seal portion (82) of the guide piece (8).

5. The pneumatic double check valve (1 ) of claims 3 or 4, wherein the dynamic side (92) of the at least one further radial seal (9) is adapted to crack off when the pneumatic-induced pressure is greater than the at least one further radial seal (9) crack off pressure, allowing air into the space (10) between the at least one annular protrusion (63), the external surface (62) of the sleeve (6), the surface (71 ) of the cavity (7) of the valve body (2) and the at least one axial seal portion (82) of the guide piece (8).

6. The pneumatic double check valve (1 ) of any of the preceding claims, wherein the sleeve (6) has a first axial end (64) and a second axial end (65), the first axial end (64) and the second axial end (65) having a plurality of cutouts (66) configured to allow delivery of airflow.

7. The pneumatic double check valve (1 ) of claim 6, wherein the at least one further radial seal (9) comprises a first further radial seal (901 ) placed in proximity to the first axial end (64) and a second further radial seal (902) placed in proximity to the second axial end (65).

8. The pneumatic double check valve (1 ) of claim 7, wherein the at least one annular protrusion (63) comprises a first annular protrusion (601 ) and a second annular protrusion (602), the first annular protrusion (601 ) and the second annular protrusion (602) being placed in proximity to and encompassing the first further radial seal (901 ), the first annular protrusion (601 ) being located in a proximal position with respect to the first axial end (64) and the second annular protrusion

(602) being located in a distal position with respect to the first axial end (64), and wherein the at least one annular protrusion (63) comprises a third annular protrusion (603) and a fourth annular protrusion (604), the third annular protrusion

(603) and the fourth annular protrusion (604) being placed in proximity to and encompassing the second further radial seal (902), the third annular protrusion (603) being located in a proximal position with respect to the second axial end (65) and the fourth annular protrusion (604) being located in a distal position with respect to the second axial end (65).

9. The pneumatic double check valve (1 ) of any of the preceding claims, wherein the sleeve (6) has at least an opening (60) located in correspondence with the outlet opening (5) of the valve body (2).

10. The pneumatic double check valve (1 ) of any of the preceding claims, wherein the axial seal portion (82) of the guide piece (8) has a sealing edge (820), the sealing edge (820) having a diameter that is smaller than a diameter of the guide piece (8).

11 . The pneumatic double check valve (1 ) of any of the preceding claims, wherein the valve body (2) comprises an adaptor (20) placed at either the first inlet opening (3) and/or the second inlet opening (4).

12. The pneumatic double check valve (1 ) of any of the preceding claims, wherein the at least one further radial seal (9) is a lip seal.

13. The pneumatic double check valve (1 ) of any of the preceding claims, wherein the guide piece (8) comprises at least one radial seal (81 ) extending towards and contacting the internal surface (61 ) of the sleeve (6), the at least one radial seal (81 ) of the guide piece (8) preferably being an O-ring.

14. An electro-pneumatic brake pressure modulator (100) comprising an electro-pneumatic pressure control circuit (101 ) comprising a relay valve portion (105), an inlet solenoid valve (103), an outlet solenoid valve (104) and a backup solenoid valve (102), and having a pressure sensor (P) adapted to control pressure in a closed loop manner, wherein the relay valve portion (105) comprises a pneumatic double check valve (1 ) according to any one of claims 1 to 13, the pneumatic double check valve (1 ) being operatively connected to the pressure control circuit (101 ) and adapted to connect a first supply port (111 ) and a second supply port (112) to supply pressure to the control circuit (101 ).

15. A brake system comprising an electro-pneumatic brake pressure modulator (100) according to claim 14, the brake system being adapted to control the brake pressure at an axle of a vehicle.