Shuttle valve with pneumatic priority position

Abstract

The invention relates to a shuttle valve (1) for a pneumatic system, comprising: a valve housing (2) having a primary compressed air inlet (11), a secondary compressed air inlet (12) and a compressed air outlet (8); and a valve body (6) which is movably arranged in the valve housing (2) and which can be moved between a first end position (EL1), in which the main compressed air inlet (11) is connected to the compressed air outlet (8), and a second end position (EL2), in which the secondary compressed air inlet (12) is connected to the compressed air outlet (8). According to the invention, an overflow chamber (22) is provided in the valve housing (2), which overflow chamber is connected to an auxiliary control surface (16) of the valve body (6), the overflow chamber (22) being pressure-free at least in a first end position (EL1) and being pressurized in at least one further position of the valve body (6) in order to temporarily provide an auxiliary force acting on the valve body (6).

Description

Technical Field

[0001] The present invention relates to a shuttle valve for a pneumatic system. The shuttle valve comprises a valve housing and a valve body movably arranged in the valve housing. The valve housing has a primary compressed air inlet, a secondary compressed air inlet, and a compressed air outlet. The valve body is movable between a first end position, in which the primary compressed air inlet is connected to the compressed air outlet, and a second end position, in which the secondary compressed air inlet is connected to the compressed air outlet. The present invention also relates to a pneumatic braking device, a commercial vehicle, and the use of the shuttle valve. Background Art

[0002] A shuttle valve, also known as a double check valve (DCV) or a reversing valve, is used to alternately connect two ports to a third port—in particular, to connect two inlets to one outlet. These double check valves or shuttle valves are typically designed so that the higher pressure applied to the first and second, or primary and secondary, compressed air ports is connected to the compressed air outlet. The switching point of such a shuttle valve lies roughly within the range where the pressures applied to the primary and secondary compressed air ports are approximately the same. Instabilities can occur precisely within this range because, at the same pressure, the position of the valve body can be undefined. This can also result in slow movement of the valve body. In the worst case, this can also lead to prolonged intermediate positions of the valve body, in which the compressed air outlet is typically closed. This means that when the valve body position is switched, the compressed air outlet can experience a long closing time, which is generally undesirable.

[0003] In other embodiments, longer phases may occur in which two compressed air inlets and one compressed air outlet are connected to one another, so that an undesired connection may exist between the two sources of the compressed air inlets, which leads to pressure compensation between these sources.

[0004] Furthermore, some shuttle valves are known that have a preferred position. This results in the valve element being preloaded into one of two end positions by means of a spring. A disadvantage is that the pressure at one of the two compressed air inlets must always overcome the force of the spring in order to assume the other position. Another disadvantage is that such spring-loaded shuttle valves can easily become stuck.

[0005] A shuttle valve of the type mentioned at the outset is known from KR 101 234 623 B1. Summary of the Invention

[0006] The object of the present invention is to specify a shuttle valve which preferably has a pneumatically predefined priority position, has a switching point which is not at the same pressure at the primary and secondary compressed air inlet, and which is preferably simple and reliable.

[0007] The invention achieves this object in a shuttle valve of the type mentioned at the outset by means of an overflow chamber in the valve housing, which is connected to an auxiliary control surface of the valve body, wherein the overflow chamber is pressure-free in at least a first end position and is pressurized in at least one other position of the valve body in order to temporarily provide an auxiliary force on the valve body.

[0008] The present invention is based on the recognition that, by means of an auxiliary control surface on the valve body that is only temporarily and preferably only in specific positions of the valve body in the valve housing, an auxiliary force can be applied to the valve body in precisely these positions in order to move the valve body into the desired position. According to the present invention, the overflow chamber is pressureless in specific positions, so that no pressure acts on the auxiliary control surface, and is pressure-loaded in specific positions, so that in these specific positions the auxiliary control surface is pressure-loaded and provides an auxiliary force. The overflow chamber can have an overflow chamber inlet, which is arranged between the primary or secondary compressed air inlet and the compressed air outlet. The overflow chamber inlet can preferably be blocked and released by the valve body so that it can be pressure-loaded or not pressure-loaded, depending on the position of the valve body.

[0009] In this way, instabilities can be prevented and the valve body can be loaded and brought into a specific position in a targeted manner by applying an auxiliary force in a specific position. This allows for a rapid switchover between the first and second end positions with a short closing time and a short or eliminated oscillation time. Furthermore, the switching point of the shuttle valve can be shifted in this way from equal pressure at the primary and secondary compressed air inlets toward a higher pressure difference, which is required to move the valve body from one end position to the other.

[0010] Such shuttle valves are particularly suitable for connecting the primary and secondary circuits of pneumatic brake systems to brake pressure modulators, such as front-axle modulators, rear-axle modulators, or trailer control valves. The primary circuit can be, for example, a primary circuit, and the secondary circuit can be, for example, an auxiliary circuit. Auxiliary circuits can be used, for example, in redundancy or fallback configurations of brake systems and generally need to be isolated. For such redundancy, the shuttle valves described herein allow for rapid switching at a specific pressure difference between the primary and secondary compressed air inlets with a very short blocking period.

[0011] In a preferred embodiment, the valve body further comprises a primary control surface and a secondary control surface, wherein the primary control surface is connected to the primary compressed air inlet and the secondary control surface is connected to the secondary compressed air inlet. If the pressure applied to the primary compressed air inlet results in a greater force acting on the valve body than the pressure applied to the secondary compressed air inlet, the valve body is thereby moved to the first end position. Conversely, provision can be made for the valve body to move to the second end position when the force acting on the piston due to the pressure applied to the secondary compressed air inlet is greater than the force acting on the valve body due to the pressure applied to the primary compressed air inlet.

[0012] Particularly preferably, the primary control surface is larger than the secondary control surface, preferably at least 5% larger. Further preferably, the primary control surface is 10%, 15%, 20%, 25%, 30%, 35%, 40% larger than the secondary control surface.

[0013] It should be understood that this aspect of the invention can also be disclosed and claimed independently of the solution mentioned at the outset. In this regard, the object mentioned at the outset is also achieved by a shuttle valve for a pneumatic system, comprising a valve housing and a valve body movably arranged in the valve housing, the valve housing having a primary compressed air inlet, a secondary compressed air inlet, and a compressed air outlet, the valve body being movable between a first end position, in which the primary compressed air inlet is connected to the compressed air outlet, and a second end position, in which the secondary compressed air inlet is connected to the compressed air outlet, the valve body comprising a primary control surface and a secondary control surface, the primary control surface being connected to the primary compressed air inlet and the secondary control surface being connected to the secondary compressed air inlet, and the primary control surface being larger than the secondary control surface.

[0014] Preferably, the primary and secondary control surfaces are formed at two opposite end sides of the valve body, preferably parallel to each other. Preferably, the valve body is essentially rotationally symmetrical and has, for example, a cylindrical base body, so that the primary and secondary control surfaces in this case form the axial end sides of the essentially cylindrical base body.

[0015] In a preferred refinement, the overflow chamber is pressurized in the second end position. In the second end position, the secondary compressed air inlet is connected to the compressed air outlet, and the main compressed air inlet is closed. Because the primary control surface is preferably larger than the secondary control surface, the secondary control surface can be pressurized in the second end position by pressurizing the overflow chamber in the second end position. Consequently, in the second end position, an auxiliary force acts on the valve body in the direction of the second end position and holds the valve body in the second end position, despite the fact that the primary control surface is larger than the secondary control surface. This ensures that the valve body is switched to the first end position only when the pressure applied to the primary compressed air inlet is at least as great as the pressure applied to the secondary compressed air inlet.

[0016] In the first end position, the overflow chamber is preferably pressure-free, so that the valve body is held in the first end position even when the pressures at the primary and secondary compressed air inlets are equally high due to the larger primary control surface.

[0017] Preferably, the overflow chamber is connected to the secondary compressed air inlet in at least one further position of the valve body. Preferably, the overflow chamber is also connected to the secondary compressed air inlet in the second end position. That is, in the overflow chamber, in at least one further position of the valve body and / or in the second end position, the pressure prevailing at the secondary compressed air inlet and thus the same pressure acting on the secondary control surface prevails.

[0018] Advantageously, the valve body can be configured to assume a closed position, in which the primary compressed air inlet, the secondary compressed air inlet, and the compressed air outlet are closed, preventing overflow from the primary compressed air inlet to the secondary compressed air inlet and vice versa. This allows for a clear separation of the primary and secondary compressed air inlets, so that the shuttle valve can also be used for circuit separation and in circuit separation arrangements for pneumatic brake systems. However, other embodiments are also possible, in which no absolute closed position is provided and one or more of the three connections are not completely closed in intermediate positions of the valve body, and / or in which overflow from the primary compressed air inlet to the secondary compressed air inlet and vice versa is explicitly permitted.

[0019] In cases where a dedicated closed position is provided that can also be used for circuit separation, the auxiliary control surface is preferably active only between the closed position and the second end position. This ensures that the valve body is brought into the closed position when moving out of the first end position and then quickly brought from the closed position into the second end position. Preferably, the auxiliary control surface becomes effective as soon as the valve body is in the closed position, shortly after the valve body is in the closed position, or shortly before the valve body is in the closed position. Therefore, when entering the closed position, an auxiliary force becomes effective, and the valve body is accelerated due to the suddenly effective auxiliary force and quickly brought into the second end position. This allows the closed position to be maintained for as short a time as possible, and thus the pressure drop at the compressed air output can also be maintained for a short time. This can improve the availability of a brake system in which the shuttle valve according to the present invention is used.

[0020] In a preferred refinement, the shuttle valve has a leakage hole that connects the overflow chamber to the external environment. If the shuttle valve is arranged at or in the brake module, the leakage hole preferably connects the overflow chamber to a bleed portion, preferably a bleed portion of the brake module. The leakage hole serves to bleed the overflow chamber when the valve body moves into the first end position, thereby enabling the valve body to be fully moved into the first end position. The leakage hole preferably comprises a throttle element.

[0021] In a preferred refinement, the valve body has at least one first radial seal for radially sealing the valve body relative to the valve housing. Preferably, the valve body has at least one second radial seal for radially sealing the valve body relative to the valve housing. Preferably, the valve body is formed substantially rotationally symmetrically, with the valve body having a section with a larger diameter forming the primary control surface and a section with a smaller diameter forming the secondary control surface. Preferably, at least one radial seal is provided in both the section with the larger diameter and the section with the smaller diameter. The radial seal may comprise a sealing ring. A shoulder between the area with the smaller diameter and the area with the larger diameter may form the secondary control surface.

[0022] Preferably, a guide element is also provided for at least sectionally guiding the valve body between the first and second end positions. The guide element can, for example, be a cage in which the valve body can move back and forth between the end positions, wherein the cage has radial openings at least in sections to allow for pressure-loaded overflow chambers. The guide element can also be a grid, a mesh, or the like that radially guides the valve body. Further alternatives are a slide in the valve housing with a pin engaging in the valve block, or vice versa, with a pin located on the valve housing and engaging in a slide on the valve body, as well as axially arranged projections, rods, or tabs that engage in corresponding guide elements.

[0023] According to a preferred refinement, the pressure difference between the primary compressed air inlet and the secondary compressed air inlet, which is used to cause the valve body to switch from the first end position to the second end position, is in the range of 1.5 bar to 5 bar, preferably 2 bar to 4 bar, and more preferably 2.5 bar to 4 bar. A particularly preferred range may be 3.5 bar, for example. Typical operating pressures in pneumatic brake systems are between 10.5 bar and 12.5 bar, so a difference of 3.5 bar represents approximately 25% to 35% of the operating pressure. This prevents the shuttle valve from switching due to small pressure fluctuations, for example, in the range of 5% to 10%.

[0024] In a second aspect, the aforementioned object is achieved by a pneumatic brake system having a pneumatic brake module and a shuttle valve according to one of the aforementioned preferred embodiments of the shuttle valve according to the first aspect of the invention. The pneumatic brake module has at least one pneumatic supply or control connection and at least one pneumatic working connection for providing brake pressure, wherein the compressed air output of the shuttle valve is connected to the supply or control connection of the pneumatic brake module. The pneumatic brake module can be, for example, a front axle modulator, a rear axle modulator, an additional axle modulator, a parking brake modulator, or a trailer control module, which provides brake pressure for an axle or trailer at a working connection. These brake modules in pneumatic brake systems are typically supplied at the supply connection via a first and a second circuit to increase redundancy and, therefore, residual availability.

[0025] For further advantages and embodiments of the shuttle valve, reference can be made to the above description.

[0026] In a third aspect, the present invention achieves the aforementioned object by means of a commercial vehicle having a pneumatic brake system and a pneumatic brake device according to the aforementioned preferred embodiment of the brake device of the second aspect of the invention. It should be understood that the pneumatic brake device of the second aspect of the invention and the commercial vehicle of the third aspect of the invention have identical and similar sub-aspects, as set forth in particular in the dependent claims. Reference is hereby made in its entirety to the above description.

[0027] Furthermore, in a fourth aspect, the present invention achieves the aforementioned object by using a shuttle valve according to one of the aforementioned preferred embodiments of the shuttle valve according to the first aspect of the invention to connect a primary compressed air circuit and a secondary compressed air circuit to a pneumatic brake module. The primary compressed air circuit is preferably a primary circuit, and the secondary compressed air circuit is preferably a secondary circuit. The primary circuit is preferably assigned to an operating level of the brake system, while the secondary circuit is assigned to a redundancy level of the brake system.

[0028] Embodiments of the present invention will now be described with reference to the accompanying drawings. These figures do not necessarily show the embodiments to scale; rather, when used for illustrative purposes, they are presented in a schematic and / or slightly distorted form. Reference is made to the relevant prior art to supplement the teachings directly apparent from the drawings. It should be noted that various modifications and changes may be made to the form and details of the embodiments without departing from the general concept of the present invention. The features disclosed in the description, drawings, and claims of the present invention, whether alone or in any combination, are essential for the development of the present invention. Furthermore, all combinations of at least two of the features disclosed in the description, drawings, and / or claims fall within the scope of the present invention. The general concept of the present invention is not limited to the exact form or details of the preferred embodiments shown and described below, or to subject matter that is restricted compared to the subject matter claimed in the claims. Within the given design scope, values within the limits are disclosed as limit values and may be used and claimed as such. For simplicity, identical or similar parts or parts with identical or similar functions will be referred to using the same reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages, features and details of the invention will be found in the following description of preferred embodiments and with the aid of the accompanying drawings, in which:

[0030] Figure 1 Shows a cross section of a shuttle valve according to the present invention;

[0031] Figure 2 Shows the Figure 1 a cross-section of a shuttle valve having a valve body in a first end position;

[0032] Figure 3 Shows the Figure 1 a shuttle valve having a valve body in a closed position;

[0033] Figure 4 Shows the Figure 1 a shuttle valve having a valve body in an intermediate position between a second end position and a closed position;

[0034] Figure 5 Shows the Figure 1 a shuttle valve having a valve body in a second end position;

[0035] Figure 6 Shows the Figure 1 a shuttle valve having a valve body in an intermediate position between a closed position and a first end position;

[0036] Figure 7shows a time-pressure graph for a shuttle valve; and

[0037] Figure 8 A commercial vehicle is shown with a pneumatic brake system and a shuttle valve. DETAILED DESCRIPTION

[0038] For use in pneumatic systems, such as pneumatic brake devices 100 (see Figure 8 ) has a valve housing 2, which is essentially rotationally symmetrical here and, therefore, only the upper part with respect to the center axis A is shown in the figures. However, it should be understood that the valve housing and, therefore, the shuttle valve 1 do not necessarily have to be rotationally symmetrical and can, for example, also have a rectangular or polygonal cross section.

[0039] A valve chamber 4 is formed in the valve housing 2, and a valve body 6 is movably arranged in the valve chamber. Specifically, the valve housing 6 can be moved in the valve chamber. Figure 1 The first end position EL1 and Figure 5 Between the first and second end positions EL1 , EL2 , the valve body can assume a plurality of further positions, as will be explained in more detail below.

[0040] The valve housing 2 has three connections: a compressed air outlet 8, a main compressed air inlet 11, and a secondary compressed air inlet 12. The shuttle valve 1 serves to alternately connect the main compressed air inlet 11 or the secondary compressed air inlet 12 to the compressed air outlet 8. The compressed air outlet 8 can be connected, for example, to a pneumatic consumer, and the main and secondary compressed air inlets 11, 12 can be connected to different pressure sources, as will be explained in more detail later. In the first end position EL1 of the valve body 6, the secondary compressed air inlet 12 is closed, while the main compressed air inlet 11 is connected to the compressed air outlet 8. This means that the main pressure p11 provided at the main compressed air inlet 11 is connected to the compressed air outlet 8.

[0041] The valve body 6 can be constructed rotationally symmetrically and in this case in a stepped manner. This means that the valve body 6 has a portion with a larger diameter and a portion with a smaller diameter, such as in particular Figure 1As can be seen in the figure, the valve body 6 has a main control surface 13 on the larger diameter portion of the valve body 6 and a secondary control surface 14 on the smaller diameter portion. The main and secondary control surfaces 13, 14 are arranged on opposite end faces of the valve body 6. In the embodiment shown here, the main control surface 13 is larger than the secondary control surface 14. The ratio of the main control surface 13 to the secondary control surface 14 is preferably in the range of 2:1 to 1.5:1, but can also be 1.1:1. The valve body 6 has a step 15 on its circumference, which defines a secondary control surface 16. The step 15 is designed as a radial shoulder in the valve body 6, but can also be formed in other ways. The secondary control surface 16 is preferably arranged parallel to the main and secondary control surfaces 13, 14 and preferably oriented in the same direction as the secondary control surface 14. A first seal 18 is arranged on the larger diameter portion of the valve body 6, and a second seal 20 is arranged on the smaller diameter portion. In the exemplary embodiment shown here, the first and second sealing elements 18, 20 are each designed as sealing rings, which are seated in corresponding circumferential grooves on the valve body 6. The first and second sealing rings 18, 20 rest against corresponding sealing surfaces of the valve housing 2 and thus seal the valve body 6 from the valve housing 2. Due to the radially acting first and second sealing elements 18, 20, the primary and secondary control surfaces 13, 14 also have defined dimensions in the end positions, so that a respectively defined force acts on the valve body 6 even in the end positions.

[0042] Furthermore, an overflow chamber 22 is provided in the valve housing 2. The overflow chamber 22 serves to pressurize the auxiliary control surface 16 in a specific position of the valve body 6 and is pressure-free in other specific positions of the valve body 6 and thus does not pressurize the auxiliary control surface 16. In this way, in a specific position of the valve body 6, an additional force is exerted in the direction of the second end position EL2, which can partially or completely compensate for the different dimensions of the primary and secondary control surfaces 13, 14.

[0043] Overflow chamber 22 Figure 1 In the illustrated embodiment, the connection to the external environment and preferably to a vent 26 is via a leakage hole 24. The overflow chamber 22 can be kept pressure-free by the leakage hole 24 under certain conditions. The leakage hole 24 is designed so that a high pressure gradient can be maintained and, in particular, the connection to the external environment can be throttled. The leakage hole 24 serves, in particular, to allow residual venting of the overflow chamber 22.

[0044] exist Figures 2 to 6 In FIG. 5 , different positions of the valve body 6 are now described depending on the pressure conditions between the main pressure p11 and the secondary pressure p12. Figure 2 , the pressure p11 is higher than the pressure p12 and is, for example, in the range of 10.5 bar to 12.5 bar, while the secondary pressure p12 is, for example, approximately 8.5 bar. The valve body 6 is in the first end position EL1 and is also Figure 1As shown, the main compressed air inlet 11 is connected to the compressed air outlet 8. In this respect, the main pressure p11 is also available at the compressed air outlet 8. The valve body 6 is in the first end position EL1 not only due to the higher main pressure, but also because the main control surface 13 has a larger effective area than the secondary control surface 14. The overflow chamber 22 is pressureless because it is not connected to the main compressed air inlet 11, the secondary compressed air inlet 12, or the compressed air outlet 8, but is connected to the environment only via the leakage hole 24.

[0045] If the main pressure p11 continues to drop under any circumstances, the valve body 6 will initially maintain this position (first end position EL1). This is because, due to the larger main control surface 13, even when the pressures between the main pressure p11 and the secondary pressure p12 are equal, the force in the first end position EL1 is still greater than the force in the second end position EL2. In the embodiment shown here, the position between the main control surface 13 and the secondary control surface 14 is selected so that the valve body 6 only begins to move from the first end position EL1 in the direction of the second end position EL2 when the main pressure p11 drops to a range of approximately 4 bar to 6 bar. This is caused by the Figures 2 to 3 The transition of Figure 3 The shorter arrows acting on the main control surface 13 indicate that the main pressure p11 is decreasing, while the secondary pressure p12 remains constant, for example, at 8.5 bar.

[0046] The valve body 6 is therefore referred to as Figures 1 to 8 Moves from right to left and initially into the closed position SL (at Figure 3 ), but the valve body is unstable in the closed position. In the closed position SL ( Figure 3 ), all interfaces are blocked and pressure can neither be supplied from the main compressed air inlet 11 to the compressed air outlet 8, nor can pressure be connected from the secondary compressed air inlet 12 to the compressed air outlet 8, and overflow from the main compressed air inlet 11 to the secondary compressed air inlet 12 or vice versa is not allowed. This is achieved by selecting the axial distance between the first and second seals 18, 20 so that in the closed position, the second seal 20 is still in contact with the sealing surface of the valve housing 2 corresponding thereto and the first seal 18 is already in contact with the corresponding sealing surface of the housing 2, which is arranged between the main compressed air inlet 11 and the compressed air outlet 8. It should be understood that the closed position SL is not an important feature of the present invention, but may be advantageous when circuit separation between the circuits connected to the main and secondary compressed air inlets 11, 12 is to be achieved. In other embodiments, the axial distance between the first and second seals 18, 20 can be selected differently, so that, for example, in Figure 3The intermediate position shown allows air to flow between the various connections.

[0047] If the pressure conditions between the primary and secondary pressures p11, p12 do not change or do not change significantly, the valve body 6 first moves further to the left, so that the second seal 20 is released from the corresponding radial sealing surface on the valve housing 2 and the pressure is allowed to overflow from the secondary compressed air inlet 12 first into the overflow chamber 22. The compressed air can then flow from the overflow chamber to the compressed air outlet 8, thus ultimately connecting the secondary compressed air inlet 12 to the compressed air outlet 8 (see FIG. Figure 4 ).

[0048] In order to stabilize the valve body 6 radially in the valve housing 2 in this position, a guide 28 is provided in the embodiment shown here, which can be designed, for example, as a cage, a grid, etc. The guide 28 can also be provided as a slide in the housing or by an axial projection on the valve body 6 that can be moved in a corresponding clamping portion.

[0049] Since the overflow chamber 22 is now loaded with the secondary pressure p12, the auxiliary control surface 16 is also loaded with the secondary pressure p12, which is indicated by the arrows of equal length on the auxiliary control surface 16 and the secondary control surface 14. In other words, starting from this position of the valve body 6, the auxiliary force acts on the valve body 6 in the direction of the second end position EL2, which is indicated by the dashed arrow below the valve body 6. The valve body 6 is thus accelerated out of this position and towards the end position EL2. This is particularly advantageous in order to maintain the closed position SL (see FIG. 1 ) as short as possible. Figure 3 ) and the cross section between the second seal 20 and the valve housing 2 is increased as quickly as possible, so as to achieve the fastest possible pressure supply of the secondary pressure p12 at the compressed air output 8. Based on this force situation, the valve body 6 then continues (see Figure 5 ) moves to the second end position EL2, in which the main compressed air inlet 11 is completely closed and the secondary compressed air inlet 12 is completely open and connected to the compressed air outlet 8. The overflow chamber 22 is pressure-loaded and serves for the overflow of the secondary pressure p12 to the compressed air outlet 8. In this positioning of the valve body 6, the connection of the overflow chamber 22 to the external environment via the leakage hole 24 is not hindered, because the leakage hole 24 is throttled and there is only a small and negligible pressure loss in this respect. Due to the pressurized auxiliary control surface 16, a stable position is also achieved in this position and the valve body 6 does not immediately move out of its position in the event of a brief pressure fluctuation of the main pressure p11. In particular, the valve body 6 moves out of the second end position EL2 only when the main pressure p11 becomes greater than the secondary pressure p12. This is Figure 6When the primary pressure p11 exceeds the secondary pressure p12, the valve body 6 moves from the second end position EL2 to the right in the direction of the first end position EL1. Once the second seal 20 contacts the radial sealing surface of the housing 2 again, the overflow chamber 22 is first disconnected from the secondary compressed air inlet 12. In this position (not shown), the overflow chamber can still be connected to the compressed air outlet 8. In this position, the valve body 6 is more stable than in the first position. Figure 6 . However, when the consumer is connected to the compressed air outlet 8, the overflow chamber 22 is already as nearly pressure-free as possible in this position. Therefore, the auxiliary control surface 16 is no longer loaded with the secondary pressure p12, and the auxiliary force acting on the valve body in the direction of the second end position EL2 is lost. If the valve body 6 now moves further to the right in the direction of the first end position, especially because the main control surface 13 is larger than the secondary control surface 14 and the auxiliary control surface 16 is already as nearly ineffective as possible in this position, the valve body 6 enters the Figure 6 In the intermediate position shown, the compressed air outlet 8 is completely connected to the main compressed air inlet 11 and the main pressure p11 is provided to the compressed air outlet 8. In this position, the overflow chamber 22 is not connected to any connection and is only connected to the external environment via the leakage hole 24. Figure 6 It can be seen that the valve body 6 is not yet completely in the first end position. If the valve body 6 continues to move into the first end position EL1, the overflow chamber 22 will become further reduced. In this situation, the leakage hole 24 is used to minimize overpressure in the overflow chamber or to vent it, so as to prevent undesirable forces on the auxiliary control surface in this position.

[0050] As can be seen from the foregoing description, the overflow chamber 22, particularly in conjunction with the auxiliary control surface 16, can, under certain circumstances, exert an additional force on the valve body 6, initially into the second end position and then also into the first end position during the return movement, i.e., when the auxiliary control surface 16 becomes inactive. The valve body 6 is thus accelerated from the intermediate position into the end positions EL1 and EL2, thereby occupying the closed or intermediate position with a reduced cross section and a shortened time. Furthermore, the design according to the present invention creates a hysteresis between the primary and secondary pressures p11 and p12, depending on the direction of movement of the valve body 6. The valve body 6 only moves out of the first end position EL1 when the primary pressure p11 is lower than the secondary pressure p12 by a specific pressure predetermined by the ratio of the primary and secondary control surfaces 13 and 14. In order for the valve body 6 to move back from the second end position EL2 to the first end position EL1, at least an equalization between the primary and secondary pressures p11 and p12 must be established.

[0051] This pressure and motion situation Figure 7 This is shown with the help of a diagram.

[0052] The pressure is plotted on the left ordinate and the travel is plotted on the right ordinate. The travel is shown between the first end position EL1 and the second end position EL2 and involves the valve body 6, which is shown by a dense dashed line. The other line is the pressure line, which is shown in FIG. Figure 7 The main pressure p11, the secondary pressure p12, the pressure p8 at the compressed air outlet 8 and the pressure p22 in the overflow chamber 22 are shown horizontally in FIG. The time is shown on the abscissa and follows Figures 2 to 6 First, from time point t0 (not shown) to time point t1, Figure 2 The pressure situation shown is that the valve body 6 is in the first end position EL2 and a main pressure p11 is present at the compressed air outlet 8. The secondary pressure p12 is lower than the main pressure p11.

[0053] At time t1, the main pressure p11 drops and the pressure p8 at the compressed air outlet also drops. When at time t2 the main pressure p11 is significantly lower than the secondary pressure p12, i.e. lower by the absolute value of the hysteresis HY, the valve body 6 starts to move, as indicated by the dense dashed line. Then, at the corresponding pressure Figure 4 At the time point t3 of the positioning, the overflow chamber 22 is loaded with pressure, i.e. with the secondary pressure p12, which is indicated by the dotted line of the pressure change curve of the overflow chamber 22, and the pressure rises to the level of the secondary pressure p12, for example. At this point in time, the auxiliary control surface 16 is also loaded with pressure, thereby accelerating the movement of the valve body, which is indicated by the now steeper movement curve of the valve body 6. The pressure at the compressed air output end 8 also begins to rise again at the same time; the reason for the larger pressure drop at the secondary compressed air input end 12 is the complete connection of the secondary compressed air input end 12 to the compressed air output end 8. The valve body 6 reaches the second end position EL2 and does not move further. The pressure p8 at the compressed air output end 8 rises to the level of the secondary pressure p12. The system is at a standstill again. This positioning corresponds to Figure 5 .

[0054] Then, the main pressure p11 starts to rise again (time t5) and reaches the level of the secondary pressure p12 at time t6, so that the valve body 6 starts to move from the second end position in the direction of the first end position. Figure 6At time t7, the overflow chamber 22 becomes pressure-free again, as evidenced by the pressure drop in pressure p22. The movement of the valve body 6 accelerates again because no supporting force is acting in the direction of the second end position EL2, as indicated by the steeper curve of the valve body 6's travel. Finally, the valve body 6 reaches the first end position EL1, where ambient pressure prevails in the overflow chamber 22, the main pressure p11 has returned to its initial level, and consequently, the pressure p8 at the compressed air outlet 8 has also returned to its initial level. This state is achieved at t8.

[0055] Figure 8 A commercial vehicle 200 is now shown with a pneumatic brake system 202, although many parts of the pneumatic brake system are omitted for clarity. Figure 8 are omitted. Arranged at the front axle VA are first and second brake actuators 204a, 204b, which receive the front axle brake pressure pBVA from a front axle modulator 206. The front axle modulator 206 forms a pneumatic brake module 207. The front axle modulator 206 has a pneumatic supply or control interface 208; the first and second brake actuators 204a, 204b are connected to pneumatic working interfaces 210a, 210b.

[0056] Supply or control interface 208 in Figure 8 In the illustrated embodiment, a shuttle valve 1 is connected, which is constructed in the manner described above. Specifically, the compressed air output 8 of the shuttle valve 1 is connected to the supply or control interface 208. The primary compressed air input 11 is connected to a primary compressed air circuit 211, which is shown here merely as a compressed air reservoir, for example, and the secondary compressed air input 12 is connected to a secondary compressed air circuit 212, which is also shown merely as an example as a compressed air reservoir. The primary compressed air circuit 211 can, for example, be the primary circuit or operating level of the pneumatic brake system 202, while the secondary compressed air circuit 212 is a secondary or redundant circuit in the fallback level of the pneumatic brake system 202.

[0057] The front axle modulator 206 also has a bleed 214 to which the leakage bore 24 can be connected.

[0058] It should be understood that the embodiments / examples shown herein are merely exemplary and that other, particularly structural, designs can also be implemented without altering the functionality of the shuttle valve described herein. The valve housing 2 can be constructed in one piece or in multiple pieces. For example, to accommodate the valve body 6 and for assembly reasons, a cage can be provided within the cylindrical valve housing 2, which cage defines the overflow chamber 2 and also forms a guide. The valve housing can also be constructed in multiple pieces overall, separated in the axial and / or radial directions. The valve body 6 itself can also be constructed in one piece or in multiple pieces.

[0059] List of reference numerals (part of the description)

[0060] 1 shuttle valve

[0061] 2 valve housing

[0062] 4 valve chambers

[0063] 6 valve body

[0064] 8 Compressed air output

[0065] 11 Main compressed air input

[0066] 12 pairs of compressed air input ports

[0067] 13 Main Control Surface

[0068] 14 control surfaces

[0069] 15 steps

[0070] 16 auxiliary control surfaces

[0071] 18 first seal

[0072] 20 Second seal

[0073] 22 Overflow chamber

[0074] 24 leakage holes

[0075] 26 Deflating section

[0076] 28 guides

[0077] 100 pneumatic brake device

[0078] 200 commercial vehicles

[0079] 202 pneumatic braking system

[0080] 204a, 204b first and second brake actuators

[0081] 206 front axle modulator

[0082] 207 pneumatic brake module

[0083] 208 supply or control interface

[0084] 210a, 210b working interface

[0085] 211 main compressed air circuit

[0086] 212 compressed air circuits

[0087] 214 venting unit

[0088] A center axis

[0089] EL1 first end position

[0090] EL2 second end position

[0091] HY hysteresis

[0092] p11 main pressure

[0093] p12 secondary pressure

[0094] p8 Pressure at the compressed air output

[0095] p22 pressure in the overflow chamber

[0096] pBVA front axle brake pressure

[0097] SL closed position

[0098] VA front axle

Claims

1. A shuttle valve (1) for a pneumatic system, the shuttle valve comprising: a valve housing (2) having a primary compressed air inlet (11), a secondary compressed air inlet (12) and a compressed air outlet (8), and A valve body (6) is movably arranged in the valve housing (2), the valve body being movable between a first end position (EL1) and a second end position (EL2), wherein in the first end position the main compressed air inlet (11) is connected to the compressed air outlet (8), and in the second end position the secondary compressed air inlet (12) is connected to the compressed air outlet (8), It is characterized by An overflow chamber (22) is provided in the valve housing (2), the overflow chamber being connected to the auxiliary control surface (16) of the valve body (6), wherein the overflow chamber (22) is pressure-free at least in the first end position (EL1) and is pressurized in at least one other position of the valve body (6) to temporarily provide an auxiliary force acting on the valve body (6).

2. The shuttle valve according to claim 1, wherein: The valve body (6) further comprises a main control surface (13) and a secondary control surface (14), wherein the main control surface (13) is connected to the main compressed air inlet (11) and the secondary control surface (14) is connected to the secondary compressed air inlet (12).

3. The shuttle valve according to claim 2, wherein: The primary control surface (13) is larger than the secondary control surface (14), preferably at least 5% larger.

4. A shuttle valve according to any one of the preceding claims, wherein: The overflow chamber (22) is pressurized in the second end position (EL2).

5. A shuttle valve according to any one of the preceding claims, wherein: The overflow chamber (22) is connected to the secondary compressed air inlet (12) in at least one other location of the valve body (6).

6. A shuttle valve according to any one of the preceding claims, wherein: The valve body (6) can assume a closed position (SL), in which the main compressed air inlet (11), the secondary compressed air inlet (12) and the compressed air outlet (8) are closed and overflow from the main compressed air inlet (11) to the secondary compressed air inlet (12) and vice versa is prevented.

7. The shuttle valve according to claim 6, wherein: The auxiliary control surface (16) is only active between the closed position (SL) and the second end position (EL2).

8. A shuttle valve according to any one of the preceding claims, wherein: The overflow chamber (22) is connected to the external environment via a leakage hole (24) for degassing the overflow chamber (22).

9. A shuttle valve according to any one of the preceding claims, wherein: The overflow chamber (22) and the auxiliary control surface (16) are configured so that when the valve body (6) moves from the first end position (EL1) to the second end position (EL2), the valve body (6) is accelerated when the auxiliary control surface (16) becomes effective.

10. A shuttle valve according to any one of the preceding claims, wherein: The valve body (6) has at least one first radial seal (18) for radially sealing the valve body (6) relative to the valve housing (2).

11. The shuttle valve according to claim 1, comprising a guide element (28) for guiding the valve body (6) at least sectionally between the first end position (EL1) and the second end position (EL2).

12. A shuttle valve according to any one of the preceding claims, wherein: A pressure difference between the primary compressed air inlet (11) and the secondary compressed air inlet (12) for causing the valve body (6) to switch from the first end position (EL1) to the second end position (EL2) is in the range of 1.5 bar to 5 bar.

13. A pneumatic braking device (100) comprising a pneumatic braking module (207) and a shuttle valve (1) according to any one of the preceding claims, the pneumatic braking module having at least one pneumatic supply or control connection (208) and at least one pneumatic working connection (210a, 210b) for providing a brake pressure (pBVA), wherein: The compressed air outlet (8) of the shuttle valve (1) is connected to the supply or control interface (208) of the pneumatic brake module (207).

14. A commercial vehicle (200) comprising a pneumatic brake system (202) and a pneumatic brake device (100) according to claim 13.

15. Use of the shuttle valve (1) according to any one of claims 1 to 12 for connecting a primary compressed air circuit (211) and a secondary compressed air circuit (212) to a pneumatic brake module (207).

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