Foot brake valve
By introducing an adjustable sealing element and a metal skeleton plastic combination structure into the foot brake valve, the problem of needing to manufacture foot brake valves with different cylinder diameters and functions using separate molds has been solved, resulting in cost reduction and simplified assembly.
Patent Information
- Application Number
- CN202520095291.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-15
- Publication Date
- 2026-01-20
- Estimated Expiration
- 2035-01-15
AI Technical Summary
Existing foot brake valves require different molds to be manufactured due to differences in cylinder diameter and function, resulting in high production costs and a large number of parts.
A foot brake valve is designed by setting movable upper and middle pistons in the valve body and using adjustable sealing elements and inclined transition parts to realize the common mold manufacturing of foot brake valves with different cylinder diameters and functions. The upper outer piston structure combining metal skeleton and plastic parts reduces the difficulty of materials and assembly.
By using a shared mold for foot brake valve parts with different cylinder diameters and functions, production costs have been reduced and the assembly process has been simplified.
Smart Images
Figure CN223814360U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to the technical field of vehicle braking. More particularly, the present disclosure relates to a foot brake valve. BACKGROUND
[0002] Braking, also known as braking, refers to the action of slowing down or stopping a vehicle or other means of transport in operation. During braking, a foot brake valve is usually used to control braking.
[0003] In order to meet different use requirements, there are various foot brake valves with different cylinder diameters (such as 52mm or 47mm cylinder diameter, etc.) or with different functions (such as with pressure limiting function or without pressure limiting function). At present, different cylinder diameters or foot brake valves with different functions need to use different molds to manufacture parts of different sizes, and in some cases, the number of parts included in these foot brake valves is large, resulting in high production cost of these foot brake valves. Therefore, it is desirable to improve the existing foot brake valve to reduce its production cost or achieve other additional advantages. CONTENT OF THE UTILITY MODEL
[0004] The present disclosure provides a foot brake valve. The foot brake valve comprises a valve body, a push element, an upper piston capable of moving downward under the drive of the push element, and a first valve capable of opening under the drive of the upper piston, wherein the valve body comprises a first circumferential portion having a first inner diameter and a second circumferential portion having a second inner diameter and located below the first circumferential portion, wherein the first inner diameter is greater than the second inner diameter; wherein the upper piston comprises an upper outer piston and an upper inner piston disposed below the upper outer piston, the upper outer piston comprises a top wall and a first circumferential wall extending downward from the top wall, the upper inner piston comprises a bottom wall and a second circumferential wall extending upward from the bottom wall, wherein at least a portion of the upper inner piston is disposed in the second circumferential portion of the valve body and is capable of moving up and down therein, and the first circumferential wall of the upper outer piston is disposed between and capable of moving up and down between the first circumferential portion of the valve body and the second circumferential wall of the upper inner piston; and wherein the foot brake valve further comprises: a first sealing element disposed at the bottom of the first circumferential wall of the upper outer piston and between the first circumferential portion of the valve body and the second circumferential wall of the upper inner piston, so that the foot brake valve has a first cylinder diameter; or a second sealing element disposed between the second circumferential portion of the valve body and the second circumferential wall of the upper inner piston, so that the foot brake valve has a second cylinder diameter different from the first cylinder diameter.
[0005] According to some embodiments of the present disclosure, the first sealing element is configured as an annular sealing ring in the shape of an inverted "Y" in cross-section, comprising a first branch extending vertically and a second branch and a third branch extending obliquely downward and to both sides from the first branch.
[0006] According to some embodiments of the present disclosure, the first branch of the first sealing element comprises an annular protrusion extending radially inward, and a bottom portion of the first circumferential wall of the upper outer piston comprises an annular groove for receiving the annular protrusion, so as to be able to fix the first sealing element at the bottom of the first circumferential wall of the upper outer piston.
[0007] According to some embodiments of the present disclosure, the second sealing element is configured as an "O" ring.
[0008] According to some embodiments of the present disclosure, an outer periphery of the upper inner piston is provided with an annular groove for accommodating the "O" ring.
[0009] According to some embodiments of the present disclosure, the upper outer piston comprises a first metal skeleton portion and a second plastic portion, and the second plastic portion is over-molded with the first metal skeleton portion.
[0010] According to some embodiments of the present disclosure, the first metal skeleton portion forms part of a top wall of the upper outer piston, and the second plastic portion forms the rest of the top wall of the upper outer piston and a first circumferential wall of the upper outer piston.
[0011] According to some embodiments of the present disclosure, the valve body has an inclined transition between the first circumferential portion and the second circumferential portion.
[0012] According to some embodiments of the present disclosure, an outer diameter of the top wall of the upper outer piston is greater than an outer diameter of the first circumferential wall of the upper outer piston, and the valve body further comprises a third circumferential portion having a third inner diameter above the first circumferential portion, the third inner diameter being greater than the first inner diameter, wherein the top wall of the upper outer piston is disposed within and movable up and down within the third circumferential portion of the valve body.
[0013] According to some embodiments of the present disclosure, the valve body has a step portion between the third circumferential portion and the first circumferential portion, and in the initial state, a first top wall portion of the top wall of the upper outer piston facing the step portion is at a first distance from the step portion, and a second top wall portion of the top wall of the upper outer piston facing the second circumferential wall of the upper inner piston is at a second distance from a top end of the second circumferential wall.
[0014] According to some embodiments of the present disclosure, the first distance and the second distance are set such that the second top wall portion of the upper outer piston cannot contact the top end of the second circumferential wall of the upper inner piston during downward movement, thereby causing the foot brake valve to have a pressure limiting function.
[0015] According to some embodiments of the present disclosure, the first distance is 9.5 mm and the second distance is 9 mm.
[0016] According to some embodiments of the present disclosure, the first distance and the second distance are set such that the second top wall portion of the upper outer piston can contact the top end of the second circumferential wall of the upper inner piston during downward movement, thereby causing the foot brake valve to not have a pressure limiting function.
[0017] According to some embodiments of the present disclosure, the first distance is 11.5 mm and the second distance is 8 mm.
[0018] According to some embodiments of the present disclosure, the valve body further comprises a middle piston located below the first valve and capable of moving downward, and a second valve capable of being opened under the driving of the middle piston.
[0019] According to some embodiments of the present disclosure, the first cylinder diameter is 52 mm and the second cylinder diameter is 47 mm.
[0020] It is to be noted that aspects of the present disclosure described for one embodiment can be incorporated into other different embodiments, although not specifically described for the other different embodiments. In other words, all embodiments and / or features of any embodiment can be combined in any manner and / or combination, as long as they are not mutually contradictory. BRIEF DESCRIPTION OF DRAWINGS
[0021] Aspects of the present disclosure will become better understood upon reading the following detailed description in conjunction with the drawings in which:
[0022] Figure 1 is a cross-sectional view of a foot brake valve having a 52 mm cylinder diameter according to one embodiment of the present disclosure;
[0023] Figure 2 is a cross-sectional view of a foot brake valve having a 47 mm cylinder diameter according to one embodiment of the present disclosure;
[0024] Figure 3 is a cross-sectional view of a ring-shaped sealing ring having an inverted "Y" shape in cross-section according to one embodiment of the present disclosure;
[0025] Figure 4 is a perspective view of a first metal skeleton portion of an upper outer piston of a foot brake valve according to one embodiment of the present disclosure;
[0026] Figure 5 is a cross-sectional view of an upper outer piston of a foot brake valve according to one embodiment of the present disclosure.
[0027] It should be understood that like reference numerals in all figures represent like elements. In the figures, the dimensions of certain features can be exaggerated for clarity. DETAILED DESCRIPTION
[0028] The present disclosure will be described with reference to the accompanying drawings, which show several embodiments of the present disclosure. It is understood that the present disclosure can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; in fact, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the present disclosure to those skilled in the art. It should also be understood that the embodiments disclosed herein can be combined in a variety of ways, thus providing more additional embodiments.
[0029] It is to be understood that the phraseology and terminology used herein is for the purpose of description and not of limitation. All technical and scientific terms used herein are to be interpreted according to their ordinary meaning to one skilled in the art unless otherwise defined. For the sake of clarity and / or conciseness, well-known functions or constructions can not be described in detail.
[0030] As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used in the specification and the appended claims, the term "or" as used in the "and / or" include any and all combinations of one or more of the associated listed items.
[0031] In the specification, when an element is referred to as being "on," "attached to," "connected to," "coupled to," or "contacting" another element, it can be directly on, attached to, connected to, coupled to, or contacting the other element or one or more intervening elements can also be present.
[0032] In the specification, the terms "first," "second," "third," etc. are used only to facilitate the description and are not intended to limit. Any technical features denoted by "first," "second," "third," etc. are interchangeable.
[0033] In the description, spatially relative terms, such as "upper," "lower," "front," "back," "top," "bottom," and the like, can be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device is inverted from the orientation depicted in the figures, elements described as being on the bottom of other features would then be oriented upward and elements described as on the top of other features would then be oriented downward. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors will be interpreted accordingly.
[0034] Referring to Figure 1 , a foot brake valve 1 having a first bore φ1 is shown according to one embodiment of the present disclosure. The foot brake valve 1 can include a valve body 10. The valve body 10 can be configured substantially cylindrical to house internal components. To facilitate assembly of the foot brake valve 1, in some embodiments, the valve body 10 can include an upper valve body 11 and a lower valve body 12 that are fixedly coupled to each other.
[0035] The valve body 10 of the foot brake valve 1 can be provided with, in order from top to bottom, a push element 20 (e.g., a push rod or a push column), an upper piston 30 that is movable downward under the drive of the push element 20, and a first valve 40 that is openable under the drive of the upper piston. In Figure 1 the illustrated embodiment, the valve body 10 can also be provided with a middle piston 50 that is movable downward, and a second valve 60 that is openable under the drive of the middle piston 50. However, the present disclosure is not limited thereto. In some cases, the foot brake valve can not include the middle piston 50 and the second valve 60.
[0036] In Figure 1 the illustrated embodiment, the upper piston 30 includes an upper outer piston 31 and an upper inner piston 32 disposed below the upper outer piston 31. The push element 20 is configured to abut and push the upper outer piston 31. A first spring 71 can be disposed between the push element 20 and the upper inner piston 32, which is compressible under the drive of the push element 20 to transmit a pushing force to the upper inner piston 32, and extendable after the pushing force is released to reset the push element 20. A second spring 72 can also be disposed between the upper outer piston 31 and the upper inner piston 32, which is compressible under the drive of the upper outer piston 31 to transmit a pushing force to the upper inner piston 32, and extendable after the pushing force is released to reset the upper outer piston 31. Similarly, a third spring 73 can also be disposed at the bottom of the upper inner piston 32 to facilitate the reset of the upper inner piston 32.
[0037] When assembled into the foot brake valve 1, a first gas chamber A is formed between the first portion of the valve body 10 and the upper inner piston 32, a second gas chamber B is formed between the second portion of the valve body 10 and the first valve 40, a first communication port C is provided between the first gas chamber A and the second gas chamber B, and the opening and closing of the first communication port C is controlled by the first valve 40. A third gas chamber D is formed between the third portion of the valve body 10 and the middle piston 50 (more specifically, the lower portion of the middle piston 50), a fourth gas chamber E is formed between the fourth portion of the valve body 10 and the second valve 60, a second communication port F is provided between the third gas chamber D and the fourth gas chamber E, and the opening and closing of the second communication port F is controlled by the second valve 60. In some embodiments, a fifth gas chamber G is also formed between the fifth portion of the valve body 10 and the middle piston 50 (more specifically, the upper portion of the middle piston 50). The first gas chamber A can be configured to be in fluid communication with the fifth gas chamber G.
[0038] The foot brake valve 1 can also include a first gas inlet, a first gas outlet, a second gas inlet, and a second gas outlet (not shown in the figures). The first gas inlet can be in fluid communication with the second gas chamber B, the first gas outlet can be in fluid communication with the first gas chamber A, the second gas inlet can be in fluid communication with the fourth gas chamber E, and the second gas outlet can be in fluid communication with the third gas chamber D.
[0039] When the brake is depressed, an external force is applied to the push element 20. The push element 20 drives the upper outer piston 31 and the upper inner piston 32 to move downward. The downward movement of the upper inner piston 32 causes the first valve 40 to open. At this time, compressed gas can enter the second gas chamber B via the first gas inlet and enter the first gas chamber A via the first communication port C. Part of the compressed gas entering the first gas chamber A is output from the first gas outlet (e.g., to the rear axle of the vehicle for braking), and another part can enter the fifth gas chamber G. The compressed gas entering the fifth gas chamber G acts on the middle piston 50, causing the middle piston 50 to move downward, thereby causing the second valve 60 to open. At this time, compressed gas can enter the fourth gas chamber E via the second gas inlet and enter the third gas chamber D via the second communication port F. The compressed gas entering the third gas chamber D is output from the second gas outlet (e.g., to the front axle of the vehicle for braking).
[0040] With continued reference to Figure 1 , the valve body 10 (more specifically, the upper valve body 11) can include a first circumferential portion 111 having a first inner diameter and a second circumferential portion 112 having a second inner diameter and located below the first circumferential portion 111, the first inner diameter being larger than the second inner diameter. An inclined transition portion 114 can be provided between the first circumferential portion 111 and the second circumferential portion 112. However, the present disclosure is not limited thereto. In other embodiments, no inclined transition portion can be provided between the first circumferential portion 111 and the second circumferential portion 112 (e.g., as shown in FIG. 2).Figure 2 As shown.
[0041] The upper outer piston 31 can include a top wall 311 and a first circumferential wall 312 extending downward from the top wall. The upper inner piston 32 can include a bottom wall 321 and a second circumferential wall 322 extending upward from the bottom wall. At least a portion of the upper inner piston 32, such as the bottom wall 321 or even a portion of the second circumferential wall 322, can be disposed within and movable up and down within the second circumferential portion 112 of the valve body 10. The first circumferential wall 312 of the upper outer piston 31 can be disposed between and movable up and down between the first circumferential portion 111 of the valve body 10 and the second circumferential wall 322 of the upper inner piston 32, as shown. Figure 1 As shown.
[0042] The foot brake valve 1 can further include a sealing element 80 (which can also be referred to as a "first sealing element"). The sealing element 80 can be disposed at the bottom of the first circumferential wall 312 of the upper outer piston 31 and between the first circumferential portion 111 of the valve body 10 and the second circumferential wall 322 of the upper inner piston 32 to provide the foot brake valve 1 with a first bore diameter φ1. As shown, Figure 1 As shown, the first bore diameter φ1 substantially corresponds to the inner diameter of the first circumferential portion 111 of the valve body 10. In Figure 1 In the embodiment shown, the first bore diameter φ1 can be 52 millimeters. However, the present disclosure is not limited thereto. The first bore diameter φ1 can be any other suitable size.
[0043] Referring to Figure 3 In some embodiments, the sealing element 80 can be configured as an annular sealing ring having an inverted "Y" shape in cross-section. The sealing element 80 can include a first branch 81 extending vertically and a second branch 82 and a third branch 83 extending obliquely downward and to both sides from the first branch 81. The first branch 81 of the sealing element 80 can include an annular protrusion 84 extending radially inward. Correspondingly, the bottom portion of the first circumferential wall 312 of the upper outer piston 31 can include an annular groove 313 (see Figure 5 ) for receiving the annular protrusion 84 to enable the sealing element 80 to be secured to the bottom of the first circumferential wall 312 of the upper outer piston 31. In other embodiments, the sealing element 80 can have other different configurations or can be secured to the bottom of the first circumferential wall 312 of the upper outer piston 31 in other different ways.
[0044] Figure 2 A foot brake valve 1' having a second bore diameter φ2 different from the first bore diameter φ1 is shown. The foot brake valve 1' is similar to the foot brake valve 1 except that the foot brake valve 1' has the second bore diameter φ2 instead of the first bore diameter φ1. The foot brake valve 1' can be used in place of the foot brake valve 1 in the vehicle 100. Figure 1The shown foot brake valve 1 has substantially the same structure. The difference between the foot brake valve 1 and the foot brake valve 1’ is that the foot brake valve 1’ includes a sealing element 80’ (which can also be referred to as a “second sealing element”). The sealing element 80’ can be arranged between the second circumferential portion 112 of the valve body 10 and the second circumferential wall 322 of the upper inner piston 32, so that the foot brake valve 1’ has a second cylinder diameter φ2 different from the first cylinder diameter φ1. As shown, the second cylinder diameter φ2 substantially corresponds to the inner diameter of the second circumferential portion 112 of the valve body 10. As shown, the second cylinder diameter φ2 substantially corresponds to the inner diameter of the second circumferential portion 112 of the valve body 10. As shown, the second cylinder diameter φ2 substantially corresponds to the inner diameter of the second circumferential portion 112 of the valve body 10. Figure 2 In the shown embodiment, the second cylinder diameter φ2 can be 47 millimeters. However, the present disclosure is not limited thereto. The second cylinder diameter φ2 can be any other suitable size. Figure 2 In the shown embodiment, the second cylinder diameter φ2 can be 47 millimeters. However, the present disclosure is not limited thereto. The second cylinder diameter φ2 can be any other suitable size.
[0045] In some embodiments, the sealing element 80’ can be configured as an “O”-ring. In order to better position the “O”-ring, the outer circumference of the upper inner piston 32 can be provided with an annular groove 323 for accommodating the “O”-ring. In other embodiments, the sealing element 80’ can have other different configurations, or can be positioned in other different ways.
[0046] By comparing the foot brake valve 1 of Figure 1 and the foot brake valve 1’ of Figure 2 , it can be seen that, in addition to the sealing element 80 and the sealing element 80’, the foot brake valve 1 of Figure 1 and the foot brake valve 1’ of Figure 2 contain substantially the same structure and size of parts (in particular, the valve body, the upper outer piston and the upper inner piston). The foot brake valves with different cylinder diameters in the prior art contain different structure and size of parts and thus need to be respectively manufactured by using different molds, which is different from the design of the present disclosure, which means that the parts of the foot brake valves with different cylinder diameters can be substantially manufactured by using the same mold (for example, the parts can be manufactured into standard parts by using the same mold, or the standard parts can be used after a small amount of machining), so that the manufacturing cost can be greatly reduced.
[0047] With reference to Figure 4 and Figure 5 , in some embodiments, the upper outer piston 31 can be further designed to include a first metal skeleton portion 31-1 and a second plastic portion 31-2. The second plastic portion 31-2 and the first metal skeleton portion 31-1 can be over-molded together to form the upper outer piston 31. For example, in the manufacturing process, the first metal skeleton portion 31-1 can be first machined (for example, punched) from a metal material, and then the second plastic portion 31-2 can be over-molded on the first metal skeleton portion 31-1 from a plastic material to mold the second plastic portion 31-2 around the first metal skeleton portion 31-1, thereby forming the upper outer piston 31. As shown, the second plastic portion 31-2 can be arranged between the first metal skeleton portion 31-1 and the upper outer piston 31. Figure 5As shown, the first metal skeleton portion 31-1 can form a portion of the top wall 311 of the upper outer piston 31 for enhancing the strength of the upper outer piston 31, and the second plastic portion 31-2 can form the rest of the top wall 311 of the upper outer piston 31 and the first circumferential wall 312 of the upper outer piston 31. Compared with the prior art upper outer piston which is made of metal as a whole, the upper outer piston 31 of the present disclosure reduces the material cost due to the use of plastic material. In addition, when using the upper outer piston which is made of metal as a whole, at least two plastic guide rings are usually needed to be used in order to reduce the friction between the upper outer piston and the valve body, which not only increases the number and cost of the parts used, but also increases the difficulty of assembly. When using the upper outer piston 31 of the present disclosure which comprises the first metal skeleton portion 31-1 and the second plastic portion 31-2, there is no need to use additional plastic guide rings (because the outer circumference of the upper outer piston 31 is made of plastic material as a whole), which not only reduces the number and cost of the parts used, but also reduces the difficulty of assembly.
[0048] Returning to Figures 1 to 2 In some embodiments, the outer diameter of the top wall 311 of the upper outer piston 31 can be greater than the outer diameter of the first circumferential wall 312 of the upper outer piston 31. In this embodiment, the valve body 10 can further comprise a third circumferential portion 113 having a third inner diameter which is greater than the first inner diameter and located above the first circumferential portion 111. A step portion 115 is formed between the third circumferential portion 113 and the first circumferential portion 111. The top wall 311 of the upper outer piston 31 can be disposed within and moveable up and down within the third circumferential portion 113 of the valve body 10. The movement of the upper outer piston 31 within the third circumferential portion 113 can be blocked by the step portion 115 between the third circumferential portion 113 and the first circumferential portion 111 of the valve body 10.
[0049] In the initial state, the first top wall portion 314 of the top wall 311 of the upper outer piston 31 facing the step portion 115 can be apart from the step portion 115 by a first distance H1, and the second top wall portion 315 of the top wall 311 of the upper outer piston 31 facing the top end of the second circumferential wall 322 of the upper inner piston 32 can be apart from the top end of the second circumferential wall 322 by a second distance H2. In some embodiments, the second top wall portion 315 of the upper outer piston 31 can be made to contact or not contact the top end of the second circumferential wall 322 of the upper inner piston 32 during the downward movement by selecting the sizes of the first distance H1 and the second distance H2, thereby making the foot brake valve 1 and 1' have or not have a limited pressure function as needed. In one embodiment, the first distance H1 is designed to be 9.5 millimeters, and the second distance H2 is designed to be 9 millimeters. Since the upper inner piston 32 also moves downward by a certain distance (e.g., 1.5 millimeters) when the upper outer piston 31 moves downward, the second top wall portion 315 of the upper outer piston 31 cannot always contact the top end of the second circumferential wall 322 of the upper inner piston 32 during the downward movement, thereby making the foot brake valve 1 and 1' have a limited pressure function. In another embodiment, the first distance H1 is designed to be 11.5 millimeters, and the second distance H2 is designed to be 8 millimeters. Since the first distance H1 is significantly greater than the second distance H2, the second top wall portion 315 of the upper outer piston 31 can contact the top end of the second circumferential wall 322 of the upper inner piston 32 during the downward movement, thereby making the foot brake valve 1 and 1' not have a limited pressure function. In other embodiments, the first distance H1 and the second distance H2 can have other appropriate size combinations.
[0050] The sizes of the first distance H1 and the second distance H2 can be changed by appropriately machining the valve body manufactured by the same valve body mold, the upper outer piston manufactured by the same upper outer piston mold, and / or the upper inner piston manufactured by the same upper inner piston mold, respectively, thereby not needing to use different sizes of molds for each part when manufacturing a plurality of foot brake valves having different first distances H1 and different second distances H2, and thus reducing manufacturing costs.
[0051] The exemplary embodiments according to the present disclosure are described above with reference to the accompanying drawings. However, it will be understood by those skilled in the art that various changes and modifications can be made to the exemplary embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. All changes and modifications are intended to be included within the scope of the present disclosure as defined by the claims. The present disclosure is defined by the appended claims, and equivalents thereof, are also intended to be encompassed by the claims.
Claims
1. A foot brake valve, characterized in that, The foot brake valve includes a valve body, within which are disposed a push element, an upper piston capable of moving downward under the drive of the push element, and a first valve capable of opening under the drive of the upper piston. The valve body includes a first circumferential portion having a first inner diameter and a second circumferential portion having a second inner diameter and located below the first circumferential portion, wherein the first inner diameter is larger than the second inner diameter; The upper piston includes an upper outer piston and an upper inner piston disposed below the upper outer piston. The upper outer piston includes a top wall and a first circumferential wall extending downward from the top wall. The upper inner piston includes a bottom wall and a second circumferential wall extending upward from the bottom wall. At least a portion of the upper inner piston is disposed within a second circumferential portion of the valve body and is capable of moving up and down within the second circumferential portion. The first circumferential wall of the upper outer piston is disposed between the first circumferential portion of the valve body and the second circumferential wall of the upper inner piston and is capable of moving up and down therebetween. The foot brake valve further includes: a first sealing element disposed at the bottom of the first circumferential wall of the upper outer piston and located between the first circumferential portion of the valve body and the second circumferential wall of the upper inner piston, so that the foot brake valve has a first cylinder diameter; or a second sealing element disposed between the second circumferential portion of the valve body and the second circumferential wall of the upper inner piston, so that the foot brake valve has a second cylinder diameter different from the first cylinder diameter.
2. The foot brake valve according to claim 1, characterized in that, The first sealing element is configured as an annular sealing ring with an inverted "Y" shaped cross-section, including a vertically extending first branch and a second and third branch extending downward from the first branch and inclined to both sides.
3. The foot brake valve according to claim 2, characterized in that, The first branch of the first sealing element includes a radially inwardly extending annular protrusion, and the bottom portion of the first circumferential wall of the upper outer piston includes an annular groove for receiving the annular protrusion, so as to fix the first sealing element to the bottom of the first circumferential wall of the upper outer piston.
4. The foot brake valve according to claim 1, characterized in that, The second sealing element is configured as an "O"-shaped seal.
5. The foot brake valve according to claim 4, characterized in that, The outer periphery of the upper inner piston is provided with an annular groove for accommodating the "O"-shaped sealing ring.
6. The foot brake valve according to claim 1, characterized in that, The upper outer piston includes a first metal skeleton portion and a second plastic portion, wherein the second plastic portion is molded together with the first metal skeleton portion.
7. The foot brake valve according to claim 6, characterized in that, The first metal skeleton portion forms part of the top wall of the upper outer piston, while the second plastic portion forms the remainder of the top wall of the upper outer piston and the first circumferential wall of the upper outer piston.
8. The foot brake valve according to claim 1, characterized in that, The valve body has an inclined transition section between the first circumferential portion and the second circumferential portion.
9. The foot brake valve according to claim 1, characterized in that, The outer diameter of the top wall of the upper outer piston is larger than the outer diameter of the first circumferential wall of the upper outer piston. The valve body also includes a third circumferential portion having a third inner diameter and located above the first circumferential portion. The third inner diameter is larger than the first inner diameter. The top wall of the upper outer piston is disposed within the third circumferential portion of the valve body and is capable of moving up and down within the third circumferential portion of the valve body.
10. The foot brake valve according to claim 9, characterized in that, The valve body has a stepped portion between the third circumferential portion and the first circumferential portion. In the initial state, the first top wall portion of the top wall of the upper outer piston facing the stepped portion is a first distance away from the stepped portion, while the second top wall portion of the top wall of the upper outer piston facing the upper inner piston is a second distance away from the top of the second circumferential wall.
11. The foot brake valve according to claim 10, characterized in that, The first distance and the second distance are set such that the second top wall portion of the upper outer piston cannot contact the top of the second circumferential wall of the upper inner piston during downward movement, thereby enabling the foot brake valve to have a pressure limiting function.
12. The foot brake valve according to claim 11, characterized in that, The first distance is 9.5 mm, and the second distance is 9 mm.
13. The foot brake valve according to claim 10, characterized in that, The first distance and the second distance are set such that the second top wall portion of the upper outer piston can contact the top of the second circumferential wall of the upper inner piston during downward movement, thereby eliminating the pressure limiting function of the foot brake valve.
14. The foot brake valve according to claim 13, characterized in that, The first distance is 11.5 mm, and the second distance is 8 mm.
15. The foot brake valve according to claim 1, characterized in that, The valve body is also provided with a middle piston located below the first valve and capable of moving downwards, and a second valve that can be opened under the drive of the middle piston.
16. The foot brake valve according to any one of claims 1 to 15, characterized in that, The first cylinder has a diameter of 52 mm, while the second cylinder has a diameter of 47 mm.