Railway damper valve assembly, and railway damper comprising such a railway damper valve assembly

Abstract

The present invention relates to a railway damper valve assembly (10, 10′, 10″) comprising—a valve body (11) with a primary chamber (12) for connecting to a hydraulic flow passage (13);—a sleeve (20) slidably arranged on an outer circumference of the valve body (11) and delimiting the primary chamber (12);—a spring (15) configured to bias the sleeve (20) towards a meeting surface (16) on a stop (17) to reach a closed position, said closed position being a position where the primary chamber (12) is outwardly sealed for preventing a flow of hydraulic fluid from the primary chamber (12) out of the valve assembly (10, 10′, 10″) between the meeting surface (16) and the sleeve (20); wherein the valve assembly (10, 10′, 10″) is pressure-balanced by the spring (15) such that a predetermined opening pressure of hydraulic fluid in the primary chamber (12) causes the sleeve (20) to move away from the meeting surface (16), thereby enabling a flow of hydraulic fluid from the primary chamber (12) in a radial direction (R) out of the valve assembly (10, 10′, 10″). The invention also relates to a railway damper (100) comprising such a railway damper valve assembly (10, 10′, 10″).

Description

TECHNICAL FIELD

[0001] The present invention relates to a railway damper valve assembly that is pressure-balanced and configured to open at a predetermined opening pressure to enable a flow of hydraulic fluid through the valve assembly.BACKGROUND

[0002] Railway dampers are typically used to absorb energy that occur during operation of a railway vehicle. The generated forces would otherwise cause increased wear and tear to the railway vehicle itself or its components, or would in the event of large forces cause damage to both the railway vehicle and any persons or cargo transported therein.

[0003] The main operating principle for hydraulic or gas-hydraulic dampers is to absorb the energy of an impact by pushing a piston into a working chamber filled with hydraulic fluid and to allow a restricted flow of the hydraulic fluid into an overflow chamber. This is typically achieved by at least one flow passage through the piston head, and there is also a return flow passage to allow hydraulic fluid to flow back into the working chamber when the piston is retracted to its neutral position.

[0004] When absorbing energy from a high impact velocity (such as a sudden braking of the railway vehicle or a crash), it is advantageous to provide multiple flow passages to allow a larger flow of hydraulic fluid in a short time. Pressure-balanced valves may be provided in the flow passages to allow the flow only when pressure in the working chamber is above a given threshold, and by using different opening pressures for the valves it is possible to design the damper so that some flow passages are active at lower pressures whereas others open only at high pressure.

[0005] Known dampers with such valve assemblies are disclosed by EP2925588 (Voith) and by EP2065287 (Leben).

[0006] One limitation with such dampers could be that they have difficulty handling high impact velocities applied at very short time periods, such as those associated with a crash. Instead of managing the impact as intended, the crash may cause the damper to generate too high forces. Apart from breaking the damper itself, this also has very serious consequences for the railway vehicle since the damper fails to perform in the crash management system as intended, causing damage to other components and often resulting in serious injury or death for any passengers and destruction to any cargo as well as to the railway vehicle itself.

[0007] There is therefore a need for improvements within this area, and in particular for providing a railway damper valve assembly for a railway damper that is able to absorb energy at high velocities to avoid breakage when handling crash forces.SUMMARY

[0008] The object of the present invention is to eliminate or at least to minimize the problems discussed above. This is achieved by a railway damper valve assembly and a railway damper according to the appended independent claims.

[0009] The railway damper valve assembly according to the invention comprises a valve body with a primary chamber for connecting to a hydraulic flow passage; a sleeve slidably arranged on an outer circumference of the valve body and delimiting the primary chamber; and a spring configured to bias the sleeve towards a meeting surface on a stop to reach a closed position, said closed position being a position where the primary chamber is outwardly sealed for preventing a flow of hydraulic fluid from the chamber out of the valve assembly between the meeting surface and the sleeve. Also, the valve assembly is pressure-balanced by the spring such that a predetermined opening pressure of hydraulic fluid in the primary chamber causes the sleeve to move away from the meeting surface, thereby enabling a flow of hydraulic fluid from the primary chamber in a radial direction out of the valve assembly.

[0010] Thereby, a reliable and highly efficient valve assembly is achieved that is configured to open at a desired pressure and to allow a high flow of hydraulic fluid in a very short time from opening. This is due to the primary chamber being delimited by the sleeve so that movement of the sleeve enables the radial flow outwards from the valve assembly; thereby, the area of the opening is rendered very large so that a large flow is enabled. This in turn renders the response time of the valve assembly very small so that a maximum flow is achieved shortly after the sleeve starts its movement away from the meeting surface. One particular advantage of the present invention is also that the valve assembly is able to handle very high flows without generating a high response force, but that an intended maximum force (also known as a blow off force or force at a blow off level) is maintained for a large part of the stroke of the piston in a damper where the valve assembly is mounted. Thus, the present invention discloses a valve assembly with a significantly higher flow capacity than known prior art valve assemblies.

[0011] By the present invention, a weaker spring, and thereby a more cost-effective solution, can be used even where the pressure is high, and this renders the valve assembly as a whole more cost effective.

[0012] In some embodiments, the primary chamber extends along a portion of the inner circumference of the sleeve, preferably at least 90°, more preferably at least 180° and even more preferably at least 270°. By thus providing the opening between the sleeve and the meeting surface with a large area, a large flow of hydraulic fluid is enabled.

[0013] Suitably, the primary chamber extends around the entire inner circumference of the sleeve. Thereby, the hydraulic fluid is able to flow outwards along the entire circumference of the sleeve, i.e. 360°. This ensures a very high flow of hydraulic fluid immediately after opening the valve assembly, since the opening area is rendered very large.

[0014] The sleeve may comprise an actuation surface forming a part of an interior wall of the primary chamber, said actuation surface facing at least partly in a direction towards the meeting surface such that a pressure against the actuation surface acts against the bias of the spring. Thereby, a force against the actuation surface will act against the bias of the spring and move the sleeve to open the valve assembly.

[0015] Suitably, the sleeve comprises a contact surface configured to contact the meeting surface in the closed position and the contact surface extends around the circumference of the valve body. Thereby, the opening between the sleeve and the valve body has a very large area that enables a high flow of hydraulic fluid for only a small movement of the sleeve. This is highly advantageous in reducing the response time when the valve assembly is mounted in a damper.

[0016] In some embodiments, the valve assembly also comprises a secondary chamber connected to the hydraulic flow passage and comprising at least one outward opening for allowing a flow of hydraulic fluid through the secondary chamber and out of the valve assembly; a biased closure for closing a passage between the secondary chamber and the hydraulic flow passage, said biased closure being configured to open at a biased closure pressure threshold that is lower than the predetermined opening pressure and allow a flow of hydraulic fluid into the secondary chamber; and a throttle configured to limit the flow of hydraulic fluid from the hydraulic flow passage through the secondary chamber and out of the valve assembly. Thereby, the spring may be dimensioned to provide a weaker bias while still being able to absorb large forces in the damper where the valve assembly is arranged.

[0017] The throttle may be arranged in the at least one outward opening and the secondary chamber may be in unrestricted flow connection with the primary chamber when the biased closure is open. Thereby, a force peak is created at opening of the valve assembly, causing an impact to other components in the railway coupler or railway vehicle. This in turn activates deformation tubes provided as part of the crash management system. It is also advantageous that the pressure area is constant during opening of the valve assembly, and that the blow off level is even at different velocities.

[0018] In other embodiments, the throttle is arranged between the hydraulic flow passage and the secondary chamber, and the valve assembly further comprises a tertiary chamber arranged between the throttle and the biased closure. Thereby, the valve assembly generates a slightly lower initial force and this in turn causes a gradual increase to the blow off level. Also, as the pressure decreases the biased closure is closed and this in turn increases pressure in the primary chamber. One particular advantage is that the generated force is held at a maximum level while absorbing a maximum of energy and preventing force increases above the maximum level to avoid damage to other components of the railway vehicle.

[0019] Suitably, the secondary chamber is connected to the hydraulic flow passage through the primary chamber. Thereby, a compact design of the valve assembly is achieved.

[0020] Also, the biased closure may comprise a closure spring connected to the valve body and a closure element that is urged by the closure spring towards a closed position where the closure element blocks the passage between the secondary chamber and the hydraulic flow passage. Thereby, an efficient closing of the secondary chamber is achieved.

[0021] The present invention also relates to a railway damper for shock absorption. The railway damper comprises:

[0022] a cylindrical housing wherein a hollow piston is received axially movable, the housing having a first end and a second end,

[0023] a hydraulic working chamber of variable volume in the housing,

[0024] a hydraulic overflow chamber of variable volume in the piston,

[0025] a spring means confined in a chamber of variable volume in the piston,

[0026] a piston head on an inner end of the hollow piston, the piston head separating the hydraulic working chamber in the housing from the hydraulic overflow chamber in the piston,

[0027] a first pressure-balanced valve in the primary flow passage, the first pressure-balanced valve being configured to open at a first pressure,

[0028] at least one secondary flow passage between the working chamber and the overflow chamber through the piston head, wherein the at least one secondary flow passage is arranged with a second pressure-balanced valve that is configured to open at a second pressure, said second pressure being higher than the first pressure,

[0029] at least one return flow passage between the overflow chamber and the working chamber through the piston head,

[0030] wherein at least one of the first pressure-balanced valve and the second pressure-balanced valve is a railway damper valve assembly according to the invention.

[0031] Thereby, a highly efficient and reliable railway damper is achieved and the risk of failure or breakage when the damper is subjected to large forces such as a crash is minimized.

[0032] Suitably, the first pressure-balanced valve is a railway damper valve assembly according to the invention and wherein the valve body forms part of an elongated housing that extends into the overflow chamber and is configured to house the primary flow passage. Thereby, the valve assembly of the invention can be used as the first pressure-balanced valve in the railway damper.

[0033] Also, the at least one second pressure-balanced valve may be a railway damper valve assembly according to the invention. The valve body then extends into the overflow chamber from the piston head, the primary chamber of the valve body being connected to or integrated with the secondary flow passage. Thereby, the valve assembly of the invention can be used as the second pressure-balanced valve in the railway damper.

[0034] Many additional benefits and advantages of the present invention will be readily understood by the skilled person in view of the detailed description below.DRAWINGS

[0035] The invention will now be described in more detail with reference to the appended drawings, wherein

[0036] FIG. 1 discloses a cross-sectional view of a railway damper according to a first embodiment of the invention with valve assemblies according to the invention in both positions in a closed state;

[0037] FIG. 2 discloses a cross-sectional view of the railway damper of FIG. 1 with both valve assemblies in an open state;

[0038] FIG. 3a discloses the valve assembly according to the first embodiment of the invention in the closed state;

[0039] FIG. 3b discloses the valve assembly of FIG. 3a in the open state;

[0040] FIG. 4a discloses a diagram of force related to stroke in railway dampers according to the prior art;

[0041] FIG. 4b discloses a diagram of force related to stroke in the railway damper according to the invention;

[0042] FIG. 5 discloses a cross-sectional view of a single acting railway damper with one valve assembly according to the invention in the closed state;

[0043] FIG. 6 discloses a cross-sectional view of a double-acting railway damper with one valve assembly according to the invention in the open state;

[0044] FIG. 7 discloses a cross-sectional view of a valve assembly according to a second embodiment of the invention in the closed state in a railway damper according to the invention;

[0045] FIG. 8 discloses a cross-sectional view of the valve assembly of FIG. 7 in the open state;

[0046] FIG. 9a discloses the valve assembly according to the second embodiment in the closed state;

[0047] FIG. 9b discloses the valve assembly of FIG. 9a in the open state;

[0048] FIG. 10 discloses a cross-sectional view of a valve assembly according to a third embodiment of the invention in the closed state in a railway damper according to the invention;

[0049] FIG. 11 discloses a cross-sectional view of the valve assembly of FIG. 7 in the open state;

[0050] FIG. 12a discloses the valve assembly according to the third embodiment in the closed state; and

[0051] FIG. 12b discloses the valve assembly of FIG. 9a in the open state.

[0052] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Any reference number appearing in multiple drawings refers to the same object or feature throughout the drawings, unless otherwise indicated.DETAILED DESCRIPTION

[0053] A railway damper 100 according to a first embodiment of the invention will now be described, followed by a description of three main embodiments of a railway damper valve assembly 10, 10′, 10″ arranged in the railway damper 100. It is to be noted that although the railway damper 100 in the first embodiment will be described as a double-acting gas-hydraulic damper, the invention also encompasses other kinds of railway dampers such as single-acting dampers or hydraulic dampers without spring means such as gas. Thus, the railway damper 100 according to the invention can be any type of railway damper suitable for shock absorption as long as it includes at least one valve assembly 10, 10′, 10″ according to any embodiment disclosed herein. The railway damper 100 may also include any kind of hydraulic damping or buffering component suitable for use in a railway vehicle, as long as it includes at least one valve assembly 10, 10′, 10″ according to the invention.

[0054] It is in particular to be noted that what is said herein of one embodiment of the valve assembly 10, 10′, 10″ or the railway damper 100 may freely be applied to any other embodiment of the valve assembly 10, 10′, 10″ or the railway damper 100 disclosed herein. Thus, features from one embodiment may freely be introduced into or combined with any other embodiment, unless such a combination is expressly stated as unsuitable. When describing various embodiments, the focus of this text will be on features where they differ from each other, and it is to be assumed that any feature not stated as different to any other embodiment may be similar or identical.

[0055] When using the term “substantially equal” this is to be understood as equal within manufacturing tolerances or not differing from each other more than 10 %. Also, when the pressure inside different chambers is given as substantially equal, this means that the chambers are connected to each other such that a flow of hydraulic fluid may pass unrestricted from one to the other.

[0056] FIG. 1 discloses the railway damper 100 in a neutral position, the railway damper 100 having a cylindrical housing 110 with a first end 111 and a second end 112, and also having a hollow piston 120 that is axially movable in the cylindrical housing 110. The railway damper 100 also comprises a hydraulic working chamber 130 in the housing 110 and a hydraulic overflow chamber 140 in the piston 120. Inside the piston 120 is also a spring means 150 in the form of a gas volume in a gas chamber 151 separated from the overflow chamber 140 by a partitioning wall 152 that is sliding freely inside the hollow piston 120. The volume of the working chamber 130, overflow chamber 140 and the gas chamber 151 varies during use in order to absorb forces acting on the damper 100, as is well known within the art.

[0057] The railway damper 100 also comprises a piston head 121 on an inner end 122 of the hollow piston 120 between the working chamber 130 and the overflow chamber 140, and through the piston head 121 are provided a primary flow passage 123 and at least one but preferably a plurality of secondary flow passages 124 that are configured to allow a flow of hydraulic fluid from the working chamber 130 and into the overflow chamber 140 when allowed by a first pressure-balanced valve 1 arranged in an elongated housing 125 that extends from the piston head 121 into the overflow chamber 140 and at least one second pressure-balanced valve arranged in the piston head 121, respectively, as will be explained in detail below. In FIG. 1, all the valves are closed. The first pressure-balanced valve 1 and the second pressure-balanced valve 2 are in this embodiment railway damper valve assemblies 10 according to the first embodiment of the invention (described in detail below with reference to FIG. 3a-3b).

[0058] Optionally, the railway damper 100 may also comprise a metering pin 160 that is connected to the first end 111 of the housing 110 and that protrudes into the primary flow passage 123 through the piston head 121. The metering pin 160 forms a flow restriction by blocking part of the primary flow passage 123 and is tapered so that the flow restriction it creates varies with the position of the piston 120 relative to the housing 110. It is to be noted that the metering pin 160 is not a necessary feature for the railway damper 100 and that although some embodiments do include it, it is omitted from other embodiments.

[0059] At least one return flow passage 170 is also provided through the piston head 121 to allow a return flow of hydraulic fluid into the working chamber 130 as the piston 120 returns to the neutral position after the damper 100 has been compressed (see below).

[0060] The valves are pressure-balanced by springs (see below) and the springs are selected so that the first pressure-balanced valve 1 in the primary flow passage 123 is configured to open at a first pressure and the at least one second pressure-balanced valve 2 in the at least one secondary flow passage 124 is configured to open at a second pressure that is higher than the first pressure. In some embodiments, a second pressure-balanced valve 2 is provided for each of the secondary flow passages 124, but in other embodiments one second pressure-balanced valve 2 may be connected to a plurality of the secondary flow passages 124 or to all of them.

[0061] The railway damper 100 is mounted in a railway vehicle, and suitably in a coupler for a railway vehicle, when in use. This means that the first end 111 of the damper 100 is mounted on or connected to one part of the coupler or railway vehicle and the piston 120 on another part. When a force is applied to the piston 120 or to the housing 110, the piston 120 is pushed towards the first end 111 of the housing 110 so that hydraulic fluid in the working chamber 130 is compressed. This causes pressure in the working chamber 130 to rise, and when the pressure reaches a first pressure the first pressure-balanced valve 1 opens and allows the hydraulic fluid to flow into the overflow chamber 140. As the piston 120 is pushed further towards the first end 111, the pressure in the working chamber 130 increases further, and if it reaches a second pressure the at least one second pressure-balanced valve 2 also opens to allow a larger flow of hydraulic fluid to flow into the overflow chamber. In situations where the velocity of the piston 120 is low, the pressure in the working chamber 130 may not be sufficient to open the second pressure-balanced valve 2 and the railway damper 100 is able to reach an end of its stroke without opening the second pressure-balanced valve 2. This may be the case for any or all embodiments of the present invention.

[0062] FIG. 2 shows the damper 100 in the open state, i.e. with both the first pressure-balanced valve 1 and the second pressure-balanced valve 2 open. However, it is to be noted that FIG. 2 does not show the piston 120 pushed into the housing 110, so the situation disclosed by FIG. 2 is one where a very large force such as a crash is applied to the damper 100 and causes all the valves to open due to the very high pressure. Since the operation of hydraulic dampers and of gas-hydraulic dampers is well known within the art, this will not be described further herein. Thus, FIG. 2 serves mainly to illustrate the open state of the first pressure-balanced valve 1 and the at least one second pressure-balanced valve 2.

[0063] FIG. 3a discloses the railway damper valve assembly 10 according to a first embodiment with a valve body 11 that comprises a primary chamber 12 that is connected to a hydraulic flow passage 13. In the first embodiment, the primary chamber 12 is connected to the hydraulic flow passage 13 by openings 19 but in other embodiments the primary chamber 12 can instead form part of the hydraulic flow passage 13 or be connected thereto via another chamber or passage. The valve assembly 10 also comprises a sleeve 20 that is slidably arranged on an outer circumference of the valve body 11 and that delimits the primary chamber 12. In the first embodiment, the primary chamber 12 extends along the entire inner circumference of the sleeve 20, i.e. it forms a volume delimited by an inner wall of the valve body 11 and an outer wall of the sleeve 20, where the outer wall is at a distance from the inner wall in a radial direction R, said radial direction R being a direction from a center of the valve body 11 towards the sleeve 20. In other embodiments, the primary chamber 12 instead extends along a portion of the inner circumference of the sleeve, preferably at least 90°, more preferably at least 180° and even more preferably at least 270°. The primary chamber 12 may also be partitioned into primary chamber sections that are each connected to the hydraulic flow passage 13 directly or via another chamber or passage.

[0064] The valve assembly 10 further comprises a spring 15 that is configured to bias the sleeve 20 towards a meeting surface 16 on a stop 17 of the valve body 11 to reach a closed position. Suitably, the spring 15 is held between the sleeve and a spring stop 18 connected to or integrated with the valve body 11 so that the spring 15 urges the sleeve 20 towards the stop 17. In the first embodiment, the spring 15 is suitably at least one disc spring, preferably a stack of disc springs, that are held between the spring stop 18 and the sleeve 20. In other embodiments other types of springs can also be used as long as they are able to bias the sleeve 20 towards the stop 17. The closed position of the sleeve 20 is a position where the primary chamber 12 is outwardly sealed so that hydraulic fluid is not able to flow out of the valve assembly 10 between the sleeve and the meeting surface 16.

[0065] Suitably, the sleeve 20 is also provided with at least one seal 14 such as an O-ring that prevents hydraulic fluid from escaping between the sleeve 20 and the valve body 11.

[0066] Furthermore, the sleeve 20 comprises an actuation surface 21 that forms part of an interior wall of the primary chamber 12, said interior wall being a wall that is formed by or connected to the sleeve 20. The actuation surface 21 faces at least partly in a direction towards the meeting surface 16. This means that the actuation surface 21 is angled or curved so that a normal to any point of the actuation surface has at least one component in the direction towards the meeting surface 16. This is a direction that is also the direction of movement of the sleeve 20, and suitably a direction that is perpendicular to the radial direction R. In this embodiment, the actuation surface 21 is also a planar surface but in other embodiments any other shape may be used as long as it is facing at least partly in the direction towards the meeting surface 16. Also, in some embodiments the actuation surface 21 may be parallel to the meeting surface 16 or may comprise more than one surface distributed in the primary chamber 12 on walls that are formed by the sleeve 20. When in use, hydraulic fluid inside the primary chamber 12 exerts a pressure on the actuation surface 21 and due to the orientation of the actuation surface 21, this pressure acts against the bias of the spring 15 and causes the sleeve 20 to move when the pressure is larger than the bias.

[0067] The sleeve 20 further comprises a contact surface 22 that contacts the meeting surface 16 in the closed position. In the first embodiment, the contact surface 22 forms a ring on an edge of the sleeve 20 and thus extends around the entire circumference of the sleeve 20, i.e. also around the entire circumference of the valve body 11. This means that a movement of the sleeve 20 away from the meeting surface 16 causes an opening to form around the entire circumference of the sleeve 20.

[0068] Operation of the valve assembly 10 will now be described with reference to FIG. 3a (closed position) and FIG. 3b (open position).

[0069] When arranged in a railway damper 100, the hydraulic flow passage 13 is connected to or forms part of the primary flow passage 123 or one of the at least one secondary flow passage 124. Thus, the working chamber 130 is in fluid connection with the hydraulic flow passage 13 and hydraulic fluid is also able to fill the primary chamber 12 through the openings 19. When the piston head 121 is pushed towards the first end 111 of the housing 110, the pressure in the working chamber 130 increases and so does the pressure in the hydraulic flow passage 13 and in the primary chamber 12. As long as the pressure is below a pressure required to act against the bias of the spring 15 and move the sleeve 20 away from the meeting surface 16, the valve assembly 10 remains closed. When the pressure reaches a predetermined opening pressure, the force on the sleeve from the hydraulic fluid inside the primary chamber is sufficient to move the sleeve 20 and this causes the valve assembly 10 to open and allow a flow of hydraulic fluid between the sleeve and the meeting surface 16 radially outwards from the primary chamber 12 into the overflow chamber 140 of the damper 100. The predetermined opening pressure is selected by choosing the spring 15 and mounting it to act with a suitable bias on the sleeve 20 as explained above. Thus, moving the sleeve 20 against the bias of the spring 15 enables the flow of hydraulic fluid out of the valve assembly 10.

[0070] When the valve assembly 10 opens, the area of the opening between the sleeve 20 and the meeting surface 16 is very large and this in turn enables a very large flow of hydraulic fluid as compared with known prior art valves. Due to the large flow, the valve assembly 10 is very quick in responding to the increased pressure and therefore enables a damping of large forces that are applied suddenly, such as crash forces.

[0071] Immediately after the valve assembly 10 starts to open, the pressure in the primary chamber 12 is reduced due to the release of hydraulic fluid out of the valve assembly 10. This may cause the valve assembly 10 to close if the pressure in the primary chamber 12 sinks below the predetermined opening pressure, or at least to hold the sleeve 20 at a small distance from the meeting surface 16 so that a controlled flow of hydraulic fluid flows through the valve assembly 10. As the pressure increases further, the sleeve 20 is moved toward an end position shown in FIG. 3b where the spring 15 is fully compressed and no further movement of the sleeve 20 in the opening direction is possible.

[0072] It is important to note that the valve assembly 10 in some embodiments may be arranged similar to FIG. 3a-3b with the sleeve biased towards an upper end of the valve body 11, but in other embodiments the sleeve 20 may instead be biased in the opposite direction and strive towards a meeting surface that is at a distance from the upper end (with the upper end being the end that is oriented upwards in FIG. 3a-3b). The features and the operation of the valve assembly 10 is substantially the same regardless of such a modification.

[0073] FIG. 4a shows the relationship between a generated force and a stroke for known prior art dampers. Thus, when a force acts on the damper, the piston must move part of its available stroke before any significant absorption of the force can take place. More particularly, when a large force is applied quickly (as in the uppermost curve), there is a significant delay in the response of the damper and the maximum force is very large, thereby causing possible damage to other components of the railway vehicle that are not able to withstand large forces.

[0074] FIG. 4b shows the same relationship for the railway damper 100 according to the present invention. Due to the design of the valve assembly 10 that enables a very large flow when the valve assembly 10 starts to open, the maximum force absorption takes place quickly and conveniently. The maximum level of generated force in the valve assemblies can be referred to as a blowoff level and is substantially flat, i.e. when reaching the maximum force this level is maintained as the stroke progresses and does not decrease shortly after the maximum as is the case with the prior art dampers (see FIG. 4a). This renders the present invention highly efficient at absorbing large forces quickly and therefore significantly reduces the risk of malfunction or breakage in the event of a crash. This in turn ensures that the railway damper 100 is able to perform its intended function in the crash management system of the railway vehicle, thereby preventing malfunction due to overload of the other components of the crash management system and minimizing damage or injury to cargo or passengers.

[0075] FIG. 5 discloses a railway damper 100′ according to a second embodiment of the invention where the railway damper 100′ is single acting and so does not dampen the movement of the piston 120 back to the neutral position. The components of the railway damper 100′ are substantially the same as those of the first embodiment disclosed above, apart from the railway damper 100′ being single acting whereas the previously described railway damper 100 is double-acting, i.e. dampens the movement of the piston 120 both in the compression and extension direction. Similar or identical components are denoted by the same reference numerals in all embodiments where they are disclosed.

[0076] The railway damper 100′ according to the second embodiment has a valve assembly 10 according to the first embodiment of FIG. 3a-3b arranged as the first pressure-balanced valve 1. However, the second pressure-balanced valve 2 is another type of valve (here a washer valve, but any kind of pressure-balanced valve would be suitable).

[0077] When in use, the valve assembly 10 arranged as the first pressure-balanced valve 1 operates as disclosed above and opens at the first pressure that is the predetermined opening pressure. When the pressure in the working chamber 130 is increased to the second pressure, the at least one second pressure-balanced valve 2 opens and allows hydraulic fluid to enter the overflow chamber 140. Thus, the valve assembly 10 according to the present invention operates as disclosed herein and can act alongside valves of other kinds to achieve the benefits disclosed herein.

[0078] FIG. 6 discloses a railway damper that lacks the first pressure-balanced valve altogether but where a valve assembly 10 according to the invention is arranged as the second pressure-balanced valve. This railway damper serves to illustrate that the valve assembly 10 of the present invention can be arranged also in dampers of other kinds than those railway dampers that fall under the independent claim directed to the damper.

[0079] It is in particular to be noted that the valve assembly 10 shown in FIG. 6 is arranged in reverse compared to that of FIG. 3a-3b, i.e. that the sleeve 20 is biased away from the upper end of the valve body 11.

[0080] The first embodiment of the valve assembly 10 has the advantage of being cost efficient and easy to manufacture, while still having a significantly higher flow capacity than known prior art solutions. It is particularly advantageous that the flow from the valve assembly 10 into the overflow chamber 40 takes place in the radial direction around the valve body 11, since this ensures a very large area of the opening between the sleeve 20 and the stop 17 and thereby a very large flow of hydraulic fluid.

[0081] FIG. 7-8 disclose a double-acting damper 100 that differs from that shown in FIG. 1 by using valve assemblies 10, 10′ according to two different embodiments of the present invention. Thus, the valve assembly 10 arranged as the first pressure-balanced valve 1 is according to the first embodiment as disclosed above, whereas the valve assembly 10 arranged as the second pressure-balanced valve 2 is according to a second embodiment. In FIG. 7, the damper 100 is shown with both valve assemblies 10, 10′ in the closed state, and in FIG. 8 they are shown with both valve assemblies 10, 10′ in the open state.

[0082] The valve assembly 10′ according to the second embodiment will now be described in detail with reference to FIG. 9a-9b. FIG. 9a discloses the valve assembly 10′ in the closed state, whereas FIG. 9b discloses a state where the valve assembly 10′ has started to open. FIG. 9b shows only the right-hand side of FIG. 9a to focus on the operational principle, but it is to be noted that a movement of the sleeve 20 will take place symmetrically on the valve assembly 10′.

[0083] The valve assembly 10′ comprises the valve body 11 with the hydraulic flow passage 13 that in this embodiment is connected to or integrated with the secondary flow passage 124 of the damper 100. Of course, the valve assembly 10′ according to the second embodiment can also be arranged as the first pressure-balanced valve 1.

[0084] The primary chamber 12 is located between the valve body 11 and the sleeve 20 and preferably extends around the entire inner circumference of the sleeve 20 as described above for the first embodiment. The sleeve 20 is also biased by the spring 15 towards the meeting surface 16 on the stop 17 of the valve body 11. The valve body 11 itself may be integrated with the piston head 121 of the damper 100 or may be a separate component that is mounted on or connected to the piston head 121.

[0085] The second embodiment of the valve assembly 10′ differs from the first embodiment in comprising a secondary chamber 30 delimited by the valve body 11 and the sleeve 20. The secondary chamber 30 is connected to the hydraulic flow passage 13 and comprises at least one outward opening 31 that allows a flow of hydraulic fluid through the secondary chamber 30 and out of the valve assembly 10, i.e. into the overflow chamber 140 of the damper 100. The secondary chamber 30 is in this embodiment connected to the hydraulic flow passage 13 by a passage 32 such as a channel from the primary flow passage 12 to form a connection to the to the hydraulic flow passage 13 through the primary chamber 12, but in other embodiments the secondary chamber 30 may be connected in another way not including the primary chamber 12.

[0086] Furthermore, the valve assembly 10′ comprises a biased closure 40 closing the passage 32 to prevent the flow of hydraulic fluid into the secondary chamber 30 when the pressure in the hydraulic flow passage 13 is lower than a biased closure pressure. The biased closure 40 comprises a closure element 41 that is biased by a closure spring 42 towards a closed position where the closure element 41 blocks the passage 32 between the secondary chamber 30 and the hydraulic flow passage 13. The closure spring 42 is connected to a closure spring stop 43 that is connected to or integrated with the valve body 11. The closure element 41 is preferably spherical or at least rounded at the end that faces the passage 32, which gives the advantage that the area of the closure element 41 on which the hydraulic fluid acts is small so that a low bias of the closure spring 42 can be used. This in turn renders the components more cost effective while at the same time enabling a reliable and stable operation. Compared to the spring 15, the closure spring 42 acts on the closure element 41 with a lower force and the pressure inside the primary chamber 12 is able to act against the bias of the closure spring 42 to open the biased closure 40 at a lower pressure than that required to act against the bias of the spring 15 to move the sleeve 20 and open the valve assembly 10′.

[0087] The valve assembly 10′ also comprises a throttle 50 that is configured to limit the flow of hydraulic fluid from the hydraulic flow passage 13 through the secondary chamber 30 and out of the valve assembly 10′. In the second embodiment, the throttle 50 is located at the at least one outward opening 31 from the secondary chamber 30 out of the valve assembly 10′, and the throttle 50 may be a restriction in the outward opening 31 or may alternatively be a blocking object that serves to decrease the outward opening 31 to provide a suitable throttle for the hydraulic fluid.

[0088] The operation of the valve assembly 10′ according to the second embodiment will now be described with reference to FIG. 9a-9b.

[0089] Similar to the first embodiment disclosed above, the hydraulic flow passage 13 is in fluid connection with the working chamber 130 so that a change to the pressure in the working chamber 130 causes a corresponding change to the pressure inside the hydraulic flow passage 13. When the pressure increases, the biased closure is opened and allows hydraulic fluid to flow into the secondary chamber 30 and out of the valve assembly 10′ through the throttle 50. The secondary chamber 30 is in unrestricted flow connection with the primary chamber 12. This means that the pressure inside the primary chamber 12 is substantially equal to a sum of the pressure inside the secondary chamber 30 and a pressure fall at the biased closure when the biased closure is open.

[0090] Due to the throttle 50, an increased pressure in the working chamber 130 then causes an elevated pressure in the secondary chamber 30, resulting in a force on the activation surface both in the primary chamber 12 and in the secondary chamber 30. This force acts against the bias of the spring 15 and causes movement of the sleeve 20 to open the primary chamber 12 when the pressure reaches the predetermined opening pressure. The hydraulic fluid is then allowed to flow out of the primary chamber 12 into the overflow chamber 140 and achieves the benefits disclosed above for the first embodiment.

[0091] The main advantage of the second embodiment is that a spring 15 with a low bias can be used even when a very high blow off level is used. This in turn enables very high blow off levels without requiring costly springs or springs that need to be custom made to be able to withstand the high forces involved. Another advantage is that the delay in filling the secondary chamber gives a small pressure spike before opening of the valve assembly 10′, and this pressure spike is transferred to other parts of the railway vehicle and causes activation of e.g. deformation tubes provided as part of the crash management system. Thus, the design of the second embodiment ensures that activation of the available deformation tubes takes place as desired.

[0092] FIG. 10-11 disclose a railway damper 100 that comprises a valve assembly 10 according to the first embodiment and a valve assembly 10″ according to a third embodiment of the invention. In all other respects, the railway damper 100 is similar or identical to the railway damper 100 as described above.

[0093] FIG. 12a-12b show the valve assembly 10″ of the third embodiment that is similar to the second embodiment since it includes the secondary chamber 30 with the at least one outward opening 31 and with the biased closure 40 for closing the passage 32 between the secondary chamber and the hydraulic flow passage 13. The third embodiment differs from the second embodiment by the throttle 50 being provided as a throttle passage 51 between the secondary chamber 30 and the primary chamber 12. Thus, the secondary chamber 30 is in this embodiment not in unrestricted flow connection with the primary chamber 12. There is a tertiary chamber 52 between the throttle passage 51 and the secondary chamber 30.

[0094] When in operation, the hydraulic flow passage 13 is connected to the working chamber 130 as described above, and an increased pressure results in the pressure also increasing in the primary chamber 12 and in the passage 32 until the biased closure pressure is reached and the biased closure 40 is opened. Hydraulic fluid is then free to flow out of the valve assembly 10″ and causes pressure to fall in the secondary chamber 30 and the tertiary chamber 52 but not in the primary chamber 12 due to the throttle 50. This in turn enables the pressure in the primary chamber 12 to act on the activation surface 21 and act against the bias of the spring 15 to lift the sleeve 20 so that the valve assembly 10″ opens.

[0095] The third embodiment has the same advantages as the second embodiment regarding the use of a weaker and more cost effective spring 15, but rather than causing a pressure spike the delay to fill the secondary chamber 30 of the third embodiment causes a lower opening force and ensures that a maximum force above the blow off level is avoided. This in turn safeguards other components of the railway vehicle so that damage to them is minimized.

[0096] In both the second and the third embodiments, the throttle 50 is formed in the sleeve 20 and this enables a heightened pressure at the throttle 50 to act on the sleeve 20 and lift the sleeve 20 to open the valve assembly 10′, 10″.

[0097] It is to be noted that where the damper 100 comprises more than one secondary flow passage 124, all embodiments of the valve assembly 10, 10′, 10″ may comprise a plurality of hydraulic flow passages 13 that can each be connected to or integrated with one secondary flow passage 124.

[0098] It is to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

Claims

1. A railway damper valve assembly (10, 10′, 10″) for a damper or buffer, the railway damper valve assembly comprising yp2 a valve body (11) with a primary chamber (12) for connecting to a hydraulic flow passage (13);a sleeve (20) slidably arranged on an outer circumference of the valve body (11) and delimiting the primary chamber (12); anda spring (15) configured to bias the sleeve (20) towards a meeting surface (16) on a stop (17) to reach a closed position, said closed position being a position where the primary chamber (12) is outwardly sealed for preventing a flow of hydraulic fluid from the primary chamber (12) out of the valve assembly (10, 10′, 10″) between the meeting surface (16) and the sleeve (20);wherein the valve assembly (10, 10′, 10″) is pressure-balanced by the spring (15) such that a predetermined opening pressure of hydraulic fluid in the primary chamber (12) causes the sleeve (20) to move away from the meeting surface (16), thereby enabling a flow of hydraulic fluid from the primary chamber (12) in a radial direction (R) out of the valve assembly (10, 10′, 10″).

2. The railway damper valve (10, 10′, 10″) assembly according to claim 1, wherein the primary chamber (12) extends along a portion of the inner circumference of the sleeve (20), preferably at least 90°, more preferably at least 180° and even more preferably at least 270°.

3. The railway damper valve assembly according to claim 2, wherein the primary chamber (12) extends around the entire inner circumference of the sleeve (20).

4. The railway damper valve assembly (10, 10′, 10″) according to claim 1, wherein the sleeve (20) comprises an actuation surface (21) forming part of an interior wall of the primary chamber (12), said actuation surface (21) facing at least partly in a direction towards the meeting surface (16) such that a pressure against the actuation surface (21) acts against the bias of the spring (15).

5. The railway damper valve assembly (10, 10′, 10″) according to claim 1, wherein the sleeve (20) comprises a contact surface (22) configured to contact the meeting surface (16) in the closed position, and wherein the contact surface (22) extends around the circumference of the valve body (11).

6. The railway damper valve assembly (10′, 10″) according to claim 1, further comprising:a secondary chamber (30) connected to the hydraulic flow passage (13) and comprising at least one outward opening (31) for allowing a flow of hydraulic fluid through the secondary chamber (30) and out of the valve assembly (10′, 10″);a biased closure (40) for closing a passage (32) between the secondary chamber (30) and the hydraulic flow passage (13), said biased closure (40) being configured to open at a biased closure pressure threshold that is lower than the predetermined opening pressure and allow a flow of hydraulic fluid into the secondary chamber (30); anda throttle (50) configured to limit the flow of hydraulic fluid from the hydraulic flow passage (13) through the secondary chamber (30) and out of the valve assembly (10′, 10″).

7. The railway damper valve assembly (10′) according to claim 6, wherein the throttle (50) is arranged in the at least one outward opening (31) and wherein the secondary chamber (30) is in unrestricted flow connection with the primary chamber (12) when the biased closure is open.

8. The railway damper valve assembly (10″) according to claim 6, wherein the throttle (50) is arranged between the hydraulic flow passage (13) and the secondary chamber (40), and further comprising a tertiary chamber (52) arranged between the throttle (50) and the biased closure (40).

9. The railway damper valve assembly (10′, 10″) according to claim 6 wherein the secondary chamber (30) is connected to the hydraulic flow passage (13) through the primary chamber (12).

10. The railway damper valve assembly (10′, 10″) according to claim 6, wherein the biased closure (40) comprises a closure spring (42) connected to the valve body (11) and a closure element (41) that is urged by the closure spring (42) towards a closed position where the closure element (41) blocks the passage (32) between the secondary chamber (30) and the hydraulic flow passage (13).

11. A railway damper (100) for shock absorption, the railway damper comprising:a cylindrical housing (110) wherein a hollow piston (120) is received axially movable, the housing (110) having a first end (111) and a second end (112),a hydraulic working chamber (130) of variable volume in the housing (110),a hydraulic overflow chamber (140) of variable volume in the piston (120),a piston head (121) on an inner end (122) of the hollow piston (120), the piston head (121) separating the hydraulic working chamber (130) in the housing (110) from the hydraulic overflow chamber (140) in the piston (120),a first pressure-balanced valve (1) in a primary flow passage (123) between the working chamber (130) and the overflow chamber (140) through the piston head (121), the first pressure-balanced valve (1) being configured to open at a first pressure,at least one secondary flow passage (124) between the working chamber (130) and the overflow chamber (140) through the piston head (121), wherein the at least one secondary flow passage (124) is arranged with a second pressure-balanced valve (2) that is configured to open at a second pressure, said second pressure being higher than the first pressure, andat least one return flow passage (170) between the overflow chamber (140) and the working chamber (130) through the piston head (121),wherein at least one of the first pressure-balanced valve (1) and the second pressure-balanced valve (2) is a railway damper valve assembly (10, 10′, 10″) according to claim 1.

12. The railway damper according to claim 11, wherein the first pressure-balanced valve (1) is a railway damper valve assembly (10, 10′, 10″) and wherein the valve body (11) forms part of an elongated housing (125) that extends into the overflow chamber (141) and is configured to house the primary flow passage (123).

13. The railway damper according to claim 11, wherein the at least one second pressure-balanced valve (2) is a railway damper valve assembly (10, 10′, 10″) and wherein the valve body (11) extends into the overflow chamber (140) from the piston head (121), the primary chamber (12) of the valve body (11) being connected to or integrated with the secondary flow passage (124).

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