Patent Description:
Such kind of brake pressure modulator comprises.

More particularly, the present invention relates to the brake pressure modulator operable by a pneumatic force that operates as, for example, a multi-relay valve for wheel end actuators associated with a pneumatic brake system.

For instance, the brake pressure modulator of the present invention can be a pneumatic brake pressure modulator (PCV unit section, pressure control valve unit section) that is provided at either a front and/or auxiliary axle of the vehicle (AVP, axle valve package) or associated with applying control pressure for the trailer brake system.

Electronic brake systems allow precisely controllable and rapid braking of a vehicle. In this context, the output signal of a brake signal transmitter, which depends on a deceleration demand of the driver, is passed to a control unit. In the control unit, the output signal of the brake signal transmitter can be modified additionally by driving safety systems, such as an antilock system, a traction control system or a system for electronic stability control. From this, the control unit produces control signals, which are passed to "brake pressure modulators", which control the supply of a pressure medium, generally compressed air in the case of utility vehicles, to the individual braking devices or brake cylinders in a manner specific to the wheel or axle-wise by means of electromagnetically actuable valve arrangements.

In the event that said control unit fails, e.g. because the power supply thereof is interrupted, the electronic brake system generally has a redundant device associated with the service brake or the pressure control system in order to be able to bring the vehicle safely to a halt, even in this operating situation, by brake actuation. More particularly, the redundant device comprises a modulator (PCV, pressure control valve) operable merely by a pneumatic force; this is without the need and/or independent of an electronic control.

However, the use of spatially and structurally separate brake pressure modulators for the individual pressure control circuits gives rise to a relatively large installation space requirement and manufacturing expense for air brake systems of the type described on light to medium-weight utility vehicles. Given this background <CIT> discloses a dual-circuit brake pressure modulator for an electronic brake system of a vehicle.

Brake pressure modulators for controlling the pressurized airflow to the brake actuators associated with either a front axle or to the brake actuators associated with the trailer have been known in the art.

For instance, <CIT> further discloses a conventional brake pressure modulator provided for the purpose of the controlling the flow of the pressurized flowed to the brake actuators. This conventional brake pressure modulators discloses use of a number of <NUM>/<NUM> solenoid control valves to manage the supply of the pressurized air from a brake signal transmitter to open or close one or more relay valves.

<CIT> relates to an electropneumatic brake system for motor vehicles, in which a pedal-operated braking power generator is provided which acts electrically upon an electronic control unit and feeds pneumatically into a pressure modulator which includes a proportional valve device and a reversing valve device. The pressure modulator is also controlled by desired electric value signals of the electronic control unit and is used for activating a valve device which modulates pressure mediums for the brake operation of the brake system. When the electric control fails, the pressure modulator operates redundantly. <CIT> discloses an electronically controlled pneumatic (ECP) brake system which is retrofitted to or a modification of an existing relayed or non-relayed brake setup. The modification involves installing a primary and a secondary relay control valve and, respectively on a pneumatic relay control line, connecting a supplementary reservoir and a two-way valve. The two-way valve or double check valve is located between a dummy reservoir and a relay valve and also connects the supplementary reservoir to the relay valve through the primary solenoid valve. <CIT> discloses an electronic-pneumatic braking system for a vehicle, for example for a heavy goods vehicle or an articulated truck, includes a TCS/ESC modulator, enabling control functions for a traction control system (TCS) and a vehicle stability control system. The TCS/ESC modulator includes a pneumatic relay valve, a solenoid valve and a changeover valve device.

A conventional brake pressure modulator <NUM> is also shown in <FIG> of the present application. This figure has also been clearly demarcated as 'prior art' in the drawings accompanying the present application. While the general functioning of brake pressure modulator <NUM> will be derivable to the person skilled in the art of the vehicle brake systems and from the above cited <CIT>, it is nevertheless shortly (to the extent necessary) explained herewith.

As can be derived from <FIG>, in order for service brake pressure inlet <NUM> to be connected with service brake pressure outlet <NUM> for pressure from reservoir II, a relay valve <NUM> should to be activated. In accordance with the conventional brake pressure modulator <NUM>, a pneumatic pressure is applied for actuating relay valve <NUM> in order to selectively enable or disable such a connection between inlet <NUM> and outlet <NUM>. This control pressure is derived from control pressure inlet <NUM> receiving pressurized fluid from a reservoir via brake signal transmitter (BST). As can also be derived from <FIG>, the activation of relay valve <NUM> is however dependent on receiving the control pressure supply from e.g., a first valve unit <NUM> and/or a second valve unit <NUM>. Based on the activation states of first and second valve units <NUM> and <NUM>, the pressurized air is supplied to relay valve <NUM>.

It is noted that there are also default positions for first and second valve units <NUM> and <NUM> in which the pressurized air is supplied to relay valve <NUM> almost one of the two valve units <NUM> and <NUM> as safety precaution. In other words, should the electronic control of valve units <NUM> and <NUM> not work, they retain default positions, which will still enable the pressurized air supply for actuating relay valve <NUM>. The default positions of each of <NUM>/<NUM> solenoid valves provided in first and second valve units <NUM> and <NUM> will guarantee that the required connection between inlet <NUM> an outlet <NUM> is established so that during emergency brake application scenarios, when the driver presses the brake pedal (not shown in <FIG>), the control pressure is still supplied to relay valve <NUM> to be activated. Such solutions may be referred to as safety braking solutions and may for instance be sometimes stipulated by regulations.

For instance, UN-ECE Reg. No. <NUM>, in the paragraph <NUM>. provides one such requirement for trailer brakes in the situations, for instance, when an electric line is found to be defective.

It follows from the above that valve units <NUM> and <NUM> however can only be electronically actuated. Therefore, if valve units <NUM> and <NUM> require changing of positions from a 'default' position, solenoids of the respective valve units are indispensable. Furthermore, this requires additional wiring and related provisions within conventional brake pressure modulator <NUM>. Needless to say, this has direct effect on the cost of the product due to additional manufacturing and constructional costs that using electronically controlled solenoids entail, but at the same time complying with the safety requirements of the regulations.

<FIG> shows a cross-sectional view of the conventional brake pressure modulator <NUM> where the location of valves 406c, 404a and 404b is shown with valve units <NUM> and <NUM> as described before. Furthermore, inlets <NUM>, <NUM>, of modulator can also be located. However, what is most important is location of valve 406c. Valve 406c hereinafter is also referred to as an electronically actuable pressure control valve.

As can be noticed, three electronically actuable valves 404a, 404b and 406c are placed in parallel positions within a modulator housing <NUM> of brake pressure modulator <NUM>. As mentioned above, providing spatial allocation for three valves 404a, 404b and 406c arranged in parallel to each other and each of them being solenoid actuated may not be cost-effective.

It follows from the above, one of the cost effective solutions is, for instance, to use a mechanically operable valve instead of solenoid valves, which can be found in e.g., the German application <CIT> filed also by the Applicant of the present application. However, one of the challenges is the implementation of such an idea is the design constraints involved within the brake modulator when the mechanically operable valve is utilized and at the same time to achieve same function of the electronically operated valves. It is one of the objectives to reduce to the costs on wiring and other details of the brake pressure modulators such as conventional brake pressure modulator <NUM>, but at the same time providing the same functionality as the electronically operated valves and complying with the spatial constraints within the brake pressure modulators.

It follows from the above section that the cost effective solution is not only in replacing e.g., the existing solenoid valve with a mechanical valve, but obtaining the same functionality using said mechanical valve taking the spatial constraints within the brake pressure modulators into account.

The major object of the invention is to provide a preferred brake pressure modulator wherein said mechanically operable valve is established and integrated in the brake pressure modulator in an advantageous way observing the above conditions.

This objective is achieved through the invention as claimed in independent claim <NUM>.

In accordance with an embodiment of the present invention, a brake pressure modulator is provided, wherein said modulator comprises a relay valve for controlling a supply of pressurized air from a primary source (II) to at least one brake actuator,.

Furthermore, according to the invention the second valve unit is a mechanically operable valve in form of a pneumatically controlled valve having a valve casing, the valve casing comprising:.

the valve chamber is free of a spring and the coil chamber is free of a coil or the like solenoid, such that the spool is actuable pneumatically only, in particular wherein the spool is subject to a pneumatic force only due to pneumatic pressure in the valve chamber.

In essence, according to the inventive concept the pneumatically controlled valve uses the same components of the existing solenoid valve, but without the spring and electrical coil that is used to excite the spool and/or assist in retaining said spool in the excited position.

One of the technical advantages of providing the mechanically operable valve for the second valve unit is, unlike the second valve unit of conventional brake modulators with electronically controlled solenoid valve, space for wirings and other hardware requirements associated with the solenoid valve are done away with. This has a direct effect on the cost of the product as well as makes the brake pressure modulator more self-reliant and not always dependent on electronic control. In this certain way, the redundant functioning (or functioning of the brake modulator without electronic control) is boosted at the same time satisfying the safety requirements of the pneumatic braking system. The pneumatically controlled valve enables a simple mechanism in which selective transmission of the brake pressure is taken care of as only one of pressure lines can be connected to the relay valve for its actuation and as a result, same control achieved due to the usage of solenoid valves is achieved using the pneumatically controlled valve.

The pneumatically controlled valve can be established as an "only" mechanically operable valve, this is more precisely "only" a mechanically-pneumatically operable valve. This means the mechanically-pneumatically operable valve switches without electrical or electro-magnetic aid.

Apart from this, the mechanically-pneumatically operable valve can be established generally in any form advantageous way to be integrated in the brake pressure and configured to switch between a first and a second state when receiving a first and/or second switch-control pressure derived from the primary and/or secondary control pressure.

The invention also leads to a pneumatic brake system of claim19 and a vehicle of claim <NUM> comprising the pneumatic brake system.

The pneumatic brake system comprises:
the brake pressure modulator according to the invention or a development thereof;.

These and further developed configurations of the invention are further outlined in the dependent claims. The dependent claims provide further embodiments and associated technical advantages. Thereby, the mentioned advantages of the proposed concept are even more improved. For each feature of the dependent claims, it is claimed independent protection independent from all other features of this disclosure.

In a preferred development the valve chamber provides a spool chamber and a spring chamber, wherein the valve chamber provides an empty and/or hollow spring chamber, in particular wherein a spring space of the valve chamber is free of a spring.

In a preferred development, the coil chamber is empty and/or hollow, in particular wherein the coil chamber provides a coil space, which is free of a coil or the like solenoid.

In a preferred development the pneumatically controlled valve is configured to switch between a first and a second state.

In an exemplifying preferred first variant, which is described with preferred developments the mechanically-pneumatically operable valve switches when, receiving a first and/or second switch-control pressure against a spring force. In an exemplifying preferred second variant, which is described with preferred developments, the mechanically-pneumatically operable valve switches when receiving a first and/or second switch-control pressure against each other, thus in particular configured to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively.

In a preferred development the pressurized guiding sleeve is configured to guide the pressure pickup piston or the like spool in a first position corresponding to the first state and in a second position corresponding to the second state, in particular wherein the first and second position of the spool are selected from positions on the valve seat and the spool stop respectively.

In a preferred development, the valve chamber extends between a valve seat on a valve body and a spool stop on a first pressure-guiding casing path.

Furthermore, according to a first variant of development the pneumatically controlled valve is a double check valve, in particular wherein the double check valve is configured to switch between a first and a second state when receiving the primary and/or secondary control pressure. The double sided check valve is configured to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively.

Furthermore, according to a second variant of development the second valve unit is a pneumatically controlled <NUM>/<NUM>-directional valve that is configured to switch between a first and a second state when receiving a first and/or second switch-control pressure derived from the primary and/or secondary control pressure. More particularly the pneumatically controlled valve, in particular a <NUM>/<NUM>-directional valve, is configured to switch from the second to the first state when receiving the first switch-control pressure derived from the primary control pressure such that the primary control pressure is transmitted to the relay valve. More particularly the pneumatically controlled valve, in particular a <NUM>/<NUM>-directional valve, is configured to switch from the second to the first state when receiving the first switch-control pressure derived from the primary control pressure such that the primary control pressure is transmitted to the relay valve.

In a particular preferred development, the pneumatically controlled <NUM>/<NUM>-directional valve in the second state is adapted to transmit the secondary control pressure to the relay valve and in the first state is adapted to transmit the primary control pressure to the relay valve. These two states have been shown to be particular advantageous to be established in the pneumatically controlled <NUM>-port/<NUM>-way-directional valve.

Thus, in a further particular preferred development the pneumatically controlled valve, in particular a double check valve or a <NUM>/<NUM>-directional valve, is configured to switch from the second to the first state when receiving the first switch-control pressure derived from the primary control pressure such that the primary control pressure is transmitted to the relay valve. In particular, the pneumatically controlled <NUM>/<NUM>-directional valve here is according to the above-mentioned first variant and switches a control pressure against a switch-control pressure.

In a particular preferred development, the variants of a double check valve and a <NUM>/<NUM>-directional valve can be combined, in particular preferably with omitting the need for a valve spring.

Preferably therein the pneumatically controlled valve, in particular a double check valve or a <NUM>/<NUM>-directional valve, is configured so as to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively. In particular, the pneumatically controlled valve here is according to the above-mentioned second variant and switches upon load by a first and a second switch-control pressure against each other. A respective piston loaded by a first switch-control pressure against a load of a second switch-control pressure of the piston is provided in the pneumatically controlled valve.

In accordance with the same development as above, in which the brake pressure modulator is described, the pneumatically controlled valve, in particular a double check valve or a <NUM>/<NUM>-directional valve, includes a spool with two opposing sides, wherein a first one among the two opposite sides receives the pressurized air from the primary source (II) and a second one among the two opposite sides receives the pressurized air from the secondary source (BST). The resulting configuration as provided in this development enables a mechanism that can translate the selective application through simple hardware means i.e., the spool configuration. The linear translation of the spool enables which supply of the pressurized air i.e., whether from the secondary source or from the primary source be given priority, based on the respective magnitude of the pressure.

In accordance with one or more of the above developments, in which the brake pressure modulator is described, the pneumatically controlled valve, in particular a double check valve or a <NUM>/<NUM>-directional valve, includes a casing which covers the spool, wherein the spool is configured to linearly translate within the casing, and wherein the direction of movement of the spool within the casing is directly dependent on a difference in the magnitude of the pressure received from primary source (II) and the secondary source (BST). It is one of the most advantageous developments of the present invention where the mechanically operable spool valve enables the Boolean operation of supplying the connection with a higher pressure air supply. The surface interaction between the spool and the casing enables realizing the simple mechanism of three ports, two position configuration direction control valve with minimal number of components.

In the same or different development, in which the brake pressure modulator of the present invention is described, the first valve sub-unit is provided which includes two solenoid controlled <NUM>/<NUM> direction control valves and wherein, based on an actuation state of each of the two direction control valves, the brake pressure modulator is configured to perform one of the following functions:.

In a development, in which the brake pressure modulator is described, the relay valve, the first valve sub-unit, and the second valve unit are encompassed within a single cast body of the brake pressure modulator. For an ease of manufacture, all the components are incorporated in a single cast unit. For instance, aluminum or cast iron could be used make the cast body of the brake pressure modulator.

The brake pressure modulator of any one of the above developments, wherein the brake pressure modulator is for controlling supply of the pressurized air to the brake actuators associated with a front axle of a vehicle.

The brake pressure modulator of any one of the above-discussed developments, wherein the brake pressure modulator is for controlling coupling head control pressure provided to the brake system of a vehicle trailer.

In an development, a pneumatic brake system is disclosed which system comprises the brake pressure modulator one or more of the above discussed developments, a centralized pressure modulator connected to the brake pressure modulator, and a centralized electronic control unit mounted on the central axle control valve wherein the centralized electronic control unit transmits control signals to at least the first valve sub-unit. In another development, a vehicle comprising the pneumatic brake system is disclosed.

For a more complete understanding of the invention, the invention will now be described in detail with reference to the accompanying drawing. 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 scope of the invention as claimed. It is 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 drawing 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 wording "a" or "an" does not exclude a plurality. The wording, "a number of" items, comprises also the number one, i.e. a single item, and further numbers like two, three, four and so forth.

Further details and advantages of different components are explained in the detailed description provided below. The labeling of the elements of different drawings is not to be construed as limiting. The scope of the present invention is defined by one or more claims listed under 'claims' section.

For identical or equivalent items or items of identical or equivalent function in the following, the some reference marks are used. For corresponding features, thus it is referred to the above description.

<FIG> illustrates a pneumatic brake system <NUM> of a vehicle (not labeled) in accordance with an embodiment of the present invention. Alternatively, the vehicle (not labeled) includes pneumatic brake system <NUM>.

Pneumatic brake system <NUM> in general includes a centralized (brake) pressure modulator <NUM>, which is configured, inter alia, to receive a brake control input in the form of control pressure from a brake signal transmitter (labeled as 'BST' in <FIG>) and in a preferred embodiment, to receive electronic signals from Electronic Stability Controller Module (ESCM) 102a connected to it via e.g. CAN (Controller Area Network) bus. In a further preferred embodiment, centralized pressure modulator <NUM> is also connected to a Power Line Carrier (PLC) <NUM> that is connected, for example, to a trailer (not shown in <FIG>). It is noted that the driver of the vehicle actuates a brake pedal or BST to supply brake pressure to wheel end actuators 112a, 112b, 112c, 112d associated with different wheels (not shown in the figure).

In modern pneumatic brake systems such as the one shown in <FIG>, the BST simply transmits an electronic signal using a stroke sensor (not shown in <FIG>) to read a control output from a brake pedal (not shown in <FIG>) to a central brake pressure modulator unit provided in combination with centralized pressure modulator <NUM>. Said stroke sensor (not shown in <FIG>) is configured to read or determine the movement of a plunger as a result of the driver applying pressure on the brake pedal.

On receiving the control inputs from the BST, centralized pressure modulator <NUM> transmits control pressure to the brake pressure modulators, in particular to the ones located at front axle 'FA' as well as to the brake pressure modulator assigned for trailer brakes. In <FIG>, the brake pressure modulator assigned for the front axle brakes is labeled as "<NUM>" and the brake pressure modulator assigned for the trailer brakes is labeled as "<NUM>". From the respective brake pressure modulators, the control pressure is transferred to respective wheel end actuators 112a, 112b, 112c and 112d through which the vehicle brakes are applied.

Furthermore, there different accumulators or reservoirs displayed in <FIG> are for supplying pressurized air to different receivers present within pneumatic brake system <NUM>. For instance, reservoir 'I' is configured to supply pressurized air to wheel end actuators 112c and 112d present at the rear axle of the vehicle whereas reservoir 'III' is predominantly for applying parking brakes and supplying pressurized air to trailer brake pressure modulator <NUM>. Reservoir 'II' is for supplying pressurized air to front axle brake control modulator <NUM>.

Pneumatic brake system <NUM> of the present embodiment also additionally discloses wheel speed sensors WSS1, WSS2, WSS3 and WSS4 located at each of the wheels to determine their rotational speeds, a CAN network unit <NUM> (refers to a networking unit operating via CAN protocol), an on-board battery <NUM>, and a steering angle sensor <NUM>. The functioning of these components is not part of the present invention and therefore, no further explanation is provided in this regard.

Additionally, pneumatic brake system <NUM> includes also park brake control unit denoted as -PB - in <FIG>. For instance, PB is connected to brake pressure modulator <NUM>, which in accordance with an embodiment used for modulating parking brakes, and which is also associated with the spring brakes (or e.g., the actuators 112c and 112d) of a rear axle, (denoted as -'RA' - in <FIG>).

Further details of brake pressure modulators <NUM> and/or <NUM> of the present invention are provided in the forthcoming sections. To the extent the subject-matter of the present invention relates to the brake pressure modulator <NUM> associated with front axle FA of the vehicle, the underlying features of the claimed invention and the technical teaching associated with the brake pressure modulators provided at other parts of pneumatic brake system <NUM>, including centralized pressure modulator <NUM>, trailer brake pressure modulator <NUM> and exceptionally, rear axle pressure modulator or relay valve <NUM>.

<FIG>, <FIG>, <FIG> and <FIG> each respectively in a scheme of circuit diagram illustrate a brake pressure modulator <NUM>, 110a, 100b, 100c in accordance with an embodiment of the present invention, which each can be provided as a brake pressure modulator <NUM>, <NUM> -in particular the front axle brake control modulator <NUM> and/or a trailer brakes pressure modulator <NUM>-- shown in <FIG>.

As shown in each of <FIG>, <FIG>, <FIG> and <FIG> the brake pressure modulator <NUM>, 110a, 100b, 110c comprises a relay valve <NUM> for controlling a supply of pressurized air from a primary source (II) to at least one brake actuator of 112a, 112b (see <FIG>). For instance, actuation of relay valve <NUM> enables connection between supply lines <NUM> and <NUM>. Supply line <NUM>. <NUM> is connected to reservoir 'II' (see <FIG>) whereas supply line <NUM> leads to Anti-lock Braking System valves ABS-<NUM> and ABS-<NUM> (see <FIG>) and consequently, to wheel end actuators 112a and 112b.

However, in order to open and/or close relay valve <NUM>, typically, a control pressure is required.

As can be derived identical from each of <FIG>, <FIG>, <FIG> and <FIG> this control pressure is received from a second valve unit <NUM>. The second valve unit <NUM>, in accordance with the present embodiments of <FIG>, <FIG>, <FIG> and <FIG>, is a mechanically operable valve in form of a pneumatically controlled valve, also referred to with reference mark <NUM> for the second valve unit.

In turn, the second valve unit <NUM> receives control pressure inputs from either of control input lines <NUM> and <NUM>. In an exemplary embodiment, control input line <NUM>, for instance, is connected to a first valve sub-unit <NUM> whereas control input line <NUM> is connected to BST (see <FIG>).

The second valve unit <NUM> is a mechanically operable valve, which will now be described below with regard to <FIG> in detail as a functioning like a pneumatically controlled double check valve 206D of the second valve unit <NUM>. The description also holds for <FIG>, <FIG> and <FIG> in principle; details and differences follow with explicit reference to <FIG>, <FIG> and <FIG>.

In accordance with the present embodiment --exemplary with regard to <FIG>-- first valve sub-unit <NUM> is configured to be electronically actuated, wherein first valve sub-unit <NUM> is configured to receive a primary control pressure Pc1 from the primary source such as reservoir 'II' intended for opening relay valve <NUM>. For instance, see e.g. reference sign <NUM> where connection to reservoir II is shown to bifurcate, wherein one leads to supply line <NUM> and another leads to port <NUM> of a first solenoid controlled <NUM>/<NUM> direction control valve <NUM> of first valve sub-unit <NUM>.

Further, in accordance with the same embodiment, the second valve unit <NUM> is a mechanically operable valve. It is configured to at least receive a secondary control pressure Pc2 from a secondary source ( such as 'BST' of <FIG>) and at least part of the primary control pressure Pc1 from the primary source (such as reservoir 'II' of <FIG>) and to transmit either the primary control pressure Pc1 or the secondary control pressure Pc2 to the relay valve <NUM>. This is in particular for activation of the relay valve <NUM> to e.g., open, and wherein, when the secondary control pressure is transmitted to the relay valve <NUM>, the primary control pressure from the primary source (such as reservoir 'II' of <FIG>) is disconnected and/or when the primary control pressure is transmitted to the relay valve <NUM>, the secondary control pressure from the secondary source (BST) is disconnected.

In accordance with this preferred embodiment, it should be noted that the second valve unit <NUM> receives at least part of the primary control pressure Pc1 from the primary source via the first valve sub-unit <NUM>.

In accordance with the present embodiment, the first valve sub-unit <NUM> includes two solenoid controlled <NUM>/<NUM> direction control valves <NUM>, <NUM> and wherein, based on an actuation state of each of the two direction control valves <NUM> and <NUM>, brake pressure modulator 110a is configured to perform one of the following functions:.

The prime preferred embodiment of <FIG> provides a mechanically operable valve, which is functioning like and -in this embodiment-- is formed as a pneumatically controlled double check valve 206D; the structure is advantageously integrated in the brake pressure modulator as will be further elucidated with regard to <FIG>.

The mechanically operable valve according to another first, second and third embodiment of the second valve unit <NUM> will be described below with regard to <FIG>, <FIG> and <FIG> in detail. Namely in these further embodiments the mechanically operable valve is a pneumatically controlled <NUM>/<NUM>-directional valve that is configured to switch between a first and a second state when receiving a first and/or second switch-control pressure P1, P2 derived from the above mentioned primary and/or secondary control pressure Pc1, Pc2; at least the embodiment of <FIG> is operated in a preferred nearest analogy to the prime preferred embodiment of a pneumatically controlled double check valve 206D in <FIG>.

In <FIG>, <FIG> and <FIG> respectively each embodiment features a pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C and in the second state (shown in the figures <FIG>, <FIG> and <FIG>) it is adapted to transmit the secondary control pressure Pc2 to the relay valve <NUM> and in the first state it is adapted to transmit the primary control pressure Pc1 to the relay valve <NUM>. These two states have been shown to be particular advantageous to be established in the pneumatically controlled <NUM>-port/<NUM>-way-directional valve 206A, 206B, 206C.

Like the double check valve 206D in <FIG>, as described above, the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C is established as an "only" mechanically operable valve; this is more precisely "only" a mechanically-pneumatically operable valve. This means the mechanically-pneumatically operable valve switches without electrical or electro-magnetic aid. In these embodiments of <FIG>, <FIG>, <FIG> the mechanically-pneumatically operable valve is established in form of the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C configured to switch between a first and a second state when receiving a first and/or second switch-control pressure P1, P2 derived from the primary and/or secondary control pressure and/or above mentioned primary and/or secondary control pressure Pc1, Pc2 - the choice of control is different in each of the embodiments shown in <FIG>, Fl. This being said, at least the embodiment of the pneumatically controlled <NUM>/<NUM>-directional valve 206C of <FIG> is operated in nearest analogy to the prime embodiment of a pneumatically controlled double check valve 206D. The "only" mechanically operable valve replaces an electro-magnetic actuable pneumatic valve of the valve unit with electronically actuable valve <NUM> shown in <FIG> and <FIG>.

The mechanically operable valve -in particular the double check valve 206D in <FIG> or the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C-- is advantageously integrated in the brake pressure modulator <NUM>, <NUM> as will be further elucidated with regard to <FIG>.

In an exemplifying preferred first variant, which is described with the embodiments of <FIG> and <FIG> the mechanically-pneumatically operable valve in form of the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B switches when receiving a first and/or second switch-control pressure P1, P2 against a primary and/or secondary control pressure Pc1, Pc2. This means the mechanically-pneumatically operable valve switches without the aid of a solenoid.

In the first preferred embodiment of <FIG> the pneumatically controlled <NUM>/<NUM>-directional valve 206A is configured to switch from the second state "<NUM>" to the first state "<NUM>" when receiving the first switch-control pressure P1 in switch-control line <NUM> derived from the primary control pressure Pc1 such that the primary control pressure Pc1 from control input line <NUM> is transmitted to the relay valve <NUM> via control output line <NUM>. In particular, the pneumatically controlled <NUM>/<NUM>-directional valve here is according to the above-mentioned first variant and switches against a secondary control pressure Pc2. A respective piston <NUM> loaded by a first switch-control pressure P1 against a secondary control pressure Pc2 load of the piston <NUM> is provided in the pneumatically controlled <NUM>/<NUM>-directional valve. The piston is pressure loaded with first switch-control pressure P1 via a respective pressure port <NUM>.

In the second preferred embodiment of <FIG> the pneumatically controlled <NUM>/<NUM>-directional valve 206B is configured to switch from the first state "<NUM>" to the second state "<NUM>" when receiving the second switch-control pressure P2 in switch-control line <NUM> derived from the secondary control pressure Pc2 such that the secondary control pressure Pc2 from control input line <NUM> is transmitted to the relay valve <NUM> via control output line <NUM>. In particular, the pneumatically controlled <NUM>/<NUM>-directional valve here is according to the above-mentioned first variant and switches against a primary control pressure Pc1. A respective piston <NUM> loaded by second switch-control pressure P2 against a primary control pressure Pc1 load of the piston <NUM> is provided in the pneumatically controlled <NUM>/<NUM>-directional valve. The piston is pressure loaded with second switch-control pressure P2 via a respective pressure port <NUM>.

In an exemplifying third preferred embodiment of a second variant, which is described with the embodiment of <FIG>, the mechanically-pneumatically operable valve 206C--without a spring-- switches when receiving a first and/or second switch-control pressure P1, P2 against each other. Thus in particular it is configured to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively. This means also this mechanically-pneumatically operable valve switches without the aid of a solenoid. The piston "<NUM>. 6A to <NUM>. B" is pressure loaded via respective pressure ports <NUM>. 7A and <NUM>. 7B with first and second switch-control pressure P1, P2.

Thus, in a particular preferred embodiment-- so to say both variations of <FIG> and <FIG> can be combined, in particular preferably with omitting the need for a valve spring. Preferably therein, the pneumatically controlled <NUM>/<NUM>-directional valve 206C is configured so as to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively. In particular, the pneumatically controlled <NUM>/<NUM>-directional valve here is according to the above-mentioned second variant and switches upon load by a first and a second switch-control pressure P1, P2 against each other. A respective piston loaded by a first switch-control pressure against a load of a second switch-control pressure of the piston is provided in the pneumatically controlled <NUM>/<NUM>-directional valve.

In accordance with the same embodiment as above, in which the brake pressure modulator is described, the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or a double check valve 206D includes a spool with two opposing sides, wherein a first one among the two opposite sides receives the pressurized air from the primary source (II) and a second one among the two opposite sides receives the pressurized air from the secondary source (BST). The resulting configuration as provided in this embodiment enables a mechanism that can translate the selective application through simple hardware means i.e., the spool configuration. The linear translation of the spool enables which supply of the pressurized air i.e., whether from the secondary source or from the primary source be given priority, based on the respective magnitude of the pressure.

In accordance with one or more of the above embodiments, in which the brake pressure modulator is described, the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206b, 206C or double check valve 206Dincludes a casing which covers the spool, wherein the spool is configured to linearly translate within the casing, and wherein the direction of movement of the spool within the casing is directly dependent on a difference in the magnitude of the pressure received from primary source (II) and the secondary source (BST). It is one of the most advantageous embodiment of the present invention where the mechanically operable spool valve enables the Boolean operation of supplying the connection with a higher pressure air supply. The surface interaction between the spool and the casing enables realizing the simple mechanism of three ports, to position configuration direction control valve with minimal number of components.

An additional function of releasing the primary control pressure towards second valve unit <NUM> with the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206D is also provided, which will be explained below. The functions listed above will be explained in detail as follows.

For instance, when first solenoid controlled <NUM>/<NUM> direction control valve <NUM> is in an open state, supply of at least part of the primary control pressure form the primary source such as reservoir II is allowed. When said valve <NUM> is in closed state, the supply of the primary control pressure from the primary source (II) to relay valve <NUM> is either disabled or blocked. In the same example, when valve <NUM> is in the open state, the primary control pressure exits valve <NUM> at port <NUM>.

It follows from the above, when second controlled <NUM>/<NUM> direction control valve <NUM> is in an open state, the primary control pressure is exhausted at port <NUM>. However, when second solenoid controlled <NUM>/<NUM> direction control valve <NUM> is closed, the primary control pressure from valve <NUM> is directed to port <NUM> of second valve unit <NUM>. In accordance with this embodiment, valve <NUM> includes first and second connection ports <NUM> and <NUM> where first connection port <NUM> is configured to act as inlet port for valve <NUM> and second connection port <NUM> is configured to act as outlet port for valve <NUM>.

Further, in the present embodiment of brake pressure modulator 110a, 110b, 110c the second valve unit <NUM> is a pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206D that is configured to switch between a first and a second state when receiving a first and/or second switch-control pressure derived from the primary and/or secondary control pressure. The pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206D in the second state is adapted to transmit the secondary control pressure to the relay valve <NUM> and in the first state is adapted to transmit the primary control pressure to the relay valve <NUM>.

In embodiments of a first variant as shown in <FIG> and <FIG> the pneumatically controlled <NUM>/<NUM>-directional valve 206A is configured to switch from the second to the first state "<NUM>" to "<NUM>" when receiving the first switch-control pressure derived from the primary control pressure such that the primary control pressure is transmitted to the relay valve <NUM>, and/or the pneumatically controlled <NUM>/<NUM>-directional valve 206B is configured to switch from the first to the second state when receiving the second switch-control pressure derived from the secondary control pressure such that the secondary control pressure is transmitted to the relay valve <NUM>.

In embodiments of a second variant as shown in <FIG> the pneumatically controlled <NUM>/<NUM>-directional valve 206C is configured to selectively transmit the pressure of a higher magnitude among the primary and secondary control pressures received from the primary source (II) and the secondary source (BST), respectively.

For instance, more details on the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206Dand its functioning are explained in conjunction with <FIG> below.

The primary technical advantage of the presence of the mechanically operable valve in form of the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206D is to, for instance, prevent additional wiring elements and associated space constraints by simply providing a mechanical solution that is workable in all pressure differential conditions. For instance, a minor difference in pressure magnitude between the pressurized air received from e.g., ports <NUM> and <NUM> makes a spool to move. This opens the possibility of the pressure with higher magnitude to be supplied for actuating relay valve <NUM> and making it to open connection between lines <NUM> and <NUM>. For a manufacturer, such as the Applicant, considering the number of products manufactured, this results in also considerable cost savings.

Still further, as mentioned before, in brake pressure modulator 110c of the present embodiment of the pneumatically controlled <NUM>/<NUM>-directional valve 206C or double check valve 206D includes the spool <NUM> , in particular, with two opposing sides, wherein a first one among the two opposite sides receives the pressurized air from the primary source (II) e.g., via port <NUM> and a second one among the two opposite sides receives the pressurized air from the secondary source (BST) e.g., via port <NUM>.

In accordance with one of the advantageous embodiments of the present application, in particular the pneumatically controlled <NUM>/<NUM>-directional valve 206C or double check valve 206Dincludes a valve casing <NUM> which covers the spool <NUM>, wherein the spool <NUM> is configured to linearly translate within the casing and wherein the direction of movement of the spool within the casing is directly depended on a difference in the magnitude of the pressure received from primary source (II) and the secondary source (BST). Further details on the type of functioning of the pneumatically controlled <NUM>/<NUM>-directional valve 206C or double check valve 206D and its technical characteristics are explained in reference to <FIG> below.

Finally, a pressure sensor <NUM> is provided in supply pressure line <NUM> connecting relay valve <NUM> and port <NUM>, which connects to actuators 112a and 112b. This pressure sensor <NUM> sends readings to centralized brake pressure modulator <NUM>, for instance, to determine the presence of flow of pressurized air in line <NUM> and or the magnitude of the pressure.

In an exemplary embodiment, it should be noted that valves <NUM>, <NUM> are electronically actuable based on the pressure modulating signals received from centralized pressure modulator <NUM>. For instance, electronically controlled braking processes such as Electronic Braking System, anti-roll braking methods, anti-skid braking methods, anti-jack-knifing methods are implemented through the controlled logic stored in centralized pressure modulator <NUM>, which naturally may include an electronic processing unit of suitable caliber.

More particularly, as as has been indicated with <FIG>, <FIG>, <FIG> the mechanical pneumatic pressure control valve is formed as a <NUM>/<NUM>-switch valve 206A, 206B, 206C or a double check valve 206D as will be described further below, respectively and has been indicated in <FIG>, <FIG>, <FIG> already, namely as a <NUM>/<NUM>-mechanical pneumatic switch valve 206A, 206B, 206C or a double check valve 206D with a pressure pickup piston or the like spool <NUM> as is shown in <FIG>, view (C).

This is indicated by the pressure pickup casing part <NUM> for receiving the pickup pressure to the pressure pickup piston or the like spool, which is more generally the pressure pickup piston or the like spool <NUM> as shown in view (C) of <FIG> - the pressure pickup piston or the like spool <NUM> corresponds to piston <NUM>, <NUM>. 6A, <NUM>,6B as outlined above. This is, the pneumatically controlled valve 206D, 206A, 206B, 206C is configured to switch between a first and a second state.

<FIG> schematically shows an embodiment to illustrate the principle of the invention as compared to the embodiment of <FIG> view (C); the inventive principle can be drawn from a comparison of three views (A), (B) and (C) of <FIG> thereof.

Therein in view (A), a picture of a pressure control valve unit section (PCV-unit section) is shown; in the instant case, the PCV-unit section is provided as an axle valve package AVP. The PCV-unit section is shown with comprising an exhaust valve EV and a supply valve SV and position for a back-up valve BUV. The back-up valve BUV deliberately is missing therein in a free space, which has been chosen for illustrations reasons.

To be inserted in said free space a back-up valve BUV is provided as a pressure control valve PCV' as commonly known and shown in view (B) of <FIG> or in the present case --according to an embodiment of the instant invention-- as a pressure control valve PCV as shown in view (C) of <FIG>.

Therein --in view (B) of <FIG>--, a further control valve is shown as a magneto-pneumatic valve. In contradistinction in view (C), the pressure control valve is shown according to the concept of the invention as a mechanical pneumatic valve; namely as a mechanically and pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C with a pressure pickup piston or the like spool <NUM> as described above.

In the instant case, the PCV-Unit section is formed as an axle PCV valve unit section APCV and the backup valve BUV is formed as an axle valve of the axle valve package respectively - this is, the backup valve is formed as an axle valve whereas the pressure control valve unit section is formed as an axle valve package AVP. Still further, the embodiment shown herein with regard to an axle valve package are also suitable to be applied to a trailer valve package TVP that follows the same principle corresponding to the following embodiments. Hereinafter, it is referred to the backup valve BUV as a pressure control valve, axle pressure control valve respectively (PCV).

As shown in view (B) of <FIG>, at first, a usual pressure control valve PCV', as for instance shown with <FIG> as an electro pneumatic <NUM>/<NUM>-valve, is shown. The pressure control valve PCV' has a commonly known valve casing <NUM> with a first pressure-guiding casing part <NUM> and a second pressure-guiding casing <NUM> and possibly an pressure pickup casing part <NUM> in case of the PCV according to the invention to the valve casing <NUM>. Further, between the first pressurized part <NUM> and <NUM>, the pressurized guiding sleeve <NUM> holds therein a valve body <NUM> with valve seat, a pressure pickup piston or the like spool <NUM> for interaction to close and open respectively the first and second pressurized path <NUM>, <NUM>, in particular the respective first and second pressurized port <NUM>, <NUM> in the first and second pressure-guiding casing part <NUM>, <NUM> to selectively guide, pressurized air through the valve body <NUM>.

As clearly visible, in view (B) of <FIG>, the pressure control valve PCV' is in the form of a magneto-pneumatic switch valve, wherein the solenoid piston interacts upon force applied by a solenoid <NUM> to the pressure pickup piston or the like spool <NUM> against the force of a spring <NUM> provided in the above-mentioned first pressure-guiding casing part <NUM>. In addition, the coil casing <NUM> of the valve casing <NUM> is shown to cover and hold the solenoid <NUM>.

Guiding from view (B) to view (C) of <FIG> the comparison indicates the main differentiating feature in the pressure control valve PCV of the invention as regards the structural assembly thereof.

The gist of the invention starts from the fact that while a mechanical pneumatic pressure control valve PCV has advantages in operation, still nevertheless, packaging thereof in an axle or trailer valve package is also efficient for low weight and package volume of a pressure control valve PCV is to be reduced.

According to the gist of the invention, the inventive pressure control valve PCV, as shown in the preferred embodiments of <FIG>, <FIG> and <FIG> here in <FIG> view (C), for a PCV unit section as shown in view (A) of <FIG> is free of the solenoid <NUM> and also free of the spring <NUM> - this is, in contradistinction to the electropneumatic pressure control valve PCV'; the pressure control valve according to the invention PCV is structured as a mechanical pneumatic pressure control valve without spring and without solenoid <NUM>, <NUM>.

More clearly, it is seen therefrom in view (B) of <FIG> that the second valve unit <NUM> is a mechanically operable valve, in form of a pneumatically controlled valve 206D, 206A, 206B, 206C, and has a valve casing <NUM>. The valve casing <NUM> comprises:.

Therein the valve chamber <NUM> is free of a spring <NUM> and the coil chamber <NUM> is free of a coil or the like solenoid <NUM>, such that the spool <NUM> is actuable pneumatically only, in particular wherein the spool <NUM> is subject to a pneumatic force only due to pneumatic pressure in the valve chamber <NUM>.

<FIG> shows, in detail, an axle pressure control valve APCV as a particular embodiment of the pressure control valve PCV of the invention as shown in view (C) of <FIG>. The axle pressure control valve APCV is shown as part of an APCV valve unit section in a cross-sectional view with the APCV to form the backup valve, respectively the pressure control valve, a supply valve SV and an exhaust valve EV.

The supply valve SV and the exhaust valve EV are generally of a known kind with pressure path connected in the APC valve unit section wherein the pressure path <NUM> is directed to the first pressure path <NUM>, in particular port, and a second pressure path <NUM>, in particular port, as indicated above and further, the pressure pickup path <NUM>, in particular port, as has been shown with view (C) of <FIG>.

Whereas the solenoids 311SV, 311EV of the supply valve SV and the exhaust valve EV and also the solenoid <NUM> of the pressure control valve PCV, more specifically axle pressure control valve APCV are indicated with similar reference marks, and also the pressure pickup piston or the like spools, still nevertheless, it is to be recognized that the pressure pickup piston or the like spools 320SV, 320EV are activated under force of a respective solenoid 311EV, 311SV respectively and spring 321EV, 321SV respectively against a valve seat on the valve body 310SV, 310EV respectively- however, a solenoid and possibly also spring as indicated with <NUM>, <NUM> in view (B) of <FIG> -this is spring 321PCV, and solenoid 311PCV for the pressure control valve PCV-- is missing in the pressure control valve as part of the APCV.

Still nevertheless, the APCV is well suitable to be assembled in the axle valve package as shown in <FIG>; this is more particularly, it has been shown that by forming the APCV as a pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or double check valve 206D --that is configured to switch between a first and a second state when receiving a first and/or second switch-control pressure Pc1, Pc2 derived from the primary and/or secondary control pressure P1, P2 as described above or directly the primary and/or secondary control pressure P1, P2 as described above with a pressure pickup piston or the like spool <NUM>-- said APCV, according to the concept of the invention, can use the same package structure as a magneto-pneumatic APCV with a magneto-pneumatic pressure control valve PCV' (as shown in view (B) of <FIG>).

Thus, although a mechanically operable valve for use as a pressure control valve PCV in principle can be construed in other form, still nevertheless, the form of the instantly invented <NUM>/<NUM>-mechanical pneumatic switch valve with a pressure pickup piston or the like spool <NUM> is particularly useful, as the packaging structure as such is preserved, which has various advantages with consistency and conformity of existing products and assembly thereof.

<FIG> shows the backup valve BUV, respectively pressure control valve PCV, namely, in particular in this case the axle pressure control valve APCV as part of the APCV valve unit section in a three-dimensional cutout sectional view, wherein the pressure ports <NUM> respectively <NUM> from pilot valves and <NUM>, respectively <NUM> from control port BST are shown in addition to the control port <NUM> to connect to the relay control room in the main body sleeve of the pressure control valve PCV.

Clearly, it is seen --from <FIG> in common with <FIG> (C) and <FIG>-- that the valve chamber <NUM> provides a spool chamber 305V and a spring chamber <NUM>, wherein the valve chamber <NUM> provides an empty and/or hollow spring chamber <NUM>, in particular wherein a spring space 305SR of the valve chamber <NUM> is free of a spring <NUM>. In addition, the coil chamber <NUM> is empty and/or hollow, in particular wherein the coil chamber <NUM> provides a coil space 306C, which is free of a coil or the like solenoid <NUM> (thus indicated in fading dashed lines; which means that the coil space 306C has no solenoid <NUM>).

The valve chamber <NUM> extends between a valve seat <NUM> on a valve body <NUM> as described before and a spool stop <NUM> on a first pressure-guiding casing part <NUM>. The brake pressure modulator <NUM>,<NUM> thus provides for a first pressure-guiding casing part <NUM>, which has a first pressurized path <NUM> and a pressure pickup path <NUM>, and the valve body <NUM> is resided in a second pressure-guiding casing part <NUM> providing a second pressurized path <NUM>. Therein the spool <NUM> includes a rubber base at at least one side of the spool, and the valve body <NUM> features a sealing ring.

The principle, as elucidated above, will be shown in a more technical view of the axle valve package AVP in a cross-sectional view as shown in <FIG> as follows. <FIG> illustrates a cross-sectional view of brake pressure modulator <NUM> in accordance with an embodiment of the present invention. As can be noticed in <FIG> a brake pressure modulator <NUM> of the present invention is shown to include the pneumatically controlled <NUM>/<NUM>-directional valve 206A, 206B, 206C or a double check valve 206D in exact the same position as electro- magnetic actuable valve <NUM> provided in conventional brake pressure modulator <NUM> of <FIG>, without effecting further detailed changes within a housing <NUM> of brake pressure modulator <NUM>.

In the same embodiment, it is also clear that the spatial arrangement of each of two solenoid controlled <NUM>/<NUM> direction control valves <NUM>, <NUM> within brake pressure modulator <NUM> or <NUM> is same as the spatial requirement of double sided check valve <NUM>.

It constitutes one of the technical advantages of the present invention that the (only) pneumatically controlled valve --this is a <NUM>/<NUM>-directional valve 206A, 206B, 206C or a double sided check valve 206D as such as described above-- of the present invention and also solenoid operated valve <NUM> of a conventional brake modulator <NUM>, even though provided in exactly same spatial constraints, they act in a similar manner in allowing both pneumatic control from BST as well as electric control provided by first valve sub-unit <NUM>.

Claim 1:
A brake pressure modulator (<NUM>, 110a, 110b, 110c, <NUM>), comprising:
- a relay valve (<NUM>) for controlling a supply of pressurized air from a primary source (II) to at least one brake actuator (112a, 112b);
- a first valve sub-unit (<NUM>) configured to be electronically actuated, wherein the first valve sub-unit (<NUM>) is configured to receive a primary control pressure from the primary source (II) intended for opening the relay valve (<NUM>); and
- a second valve unit (<NUM>) configured to at least receive a secondary control pressure from a secondary source ("BST") and at least part of the primary control pressure from the primary source (II) and to transmit either the primary control pressure or the secondary control pressure to the relay valve (<NUM>), wherein, when the secondary control pressure is transmitted to the relay valve (<NUM>), the primary control pressure from the primary source (II) is disconnected, and/or when the primary control pressure is transmitted to the relay valve (<NUM>), the secondary control pressure from the secondary source (BST) is disconnected, wherein the second valve unit (<NUM>) is a mechanically operable valve, in form of a pneumatically controlled valve (206D, 206A, 206B, 206C) having a valve casing (<NUM>), characterized in that, the valve casing (<NUM>) comprises
- a pressurized guiding sleeve (<NUM>) providing a valve chamber (<NUM>) configured to axially guide a pressure pickup piston or the like spool (<NUM>) adapted for pneumatic actuation thereof, in particular adapted for mere pneumatic actuation thereof, and
- a coil casing (<NUM>) configured to provide a coil chamber (<NUM>) peripheral next to the pressurized guiding sleeve (<NUM>), wherein the valve chamber (<NUM>) is free of a spring (<NUM> ) and the coil chamber (<NUM>) is free of a coil or the like solenoid (<NUM> ), such that the spool (<NUM>) is actuable pneumatically only, in particular wherein the spool (<NUM>) is subject to a pneumatic force only due to pneumatic pressure in the valve chamber (<NUM>).