JPH0240535B2 - FUKUSHIKIBUREEKIBEN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dual brake valve used in an air brake device for a vehicle, etc., and in particular, it is composed of an upper body, an intermediate body, and a lower body, and at least a first input port and an output port are connected to the intermediate body. a valve body having a second input port and an output port in the lower body; a lid member fixed to the lower body; and a plunger provided in the upper body so as to be slidable in the axial direction of the valve body. and;
a first piston that is slidably and tightly fitted in the first cylinder hole of the intermediate body in the axial direction of the valve body and driven by the plunger; a first cylindrical valve member that controls communication with the output port; a first cylindrical valve member that is tightly fitted into the second cylinder hole of the intermediate member so as to be slidable in the axial direction of the valve body; a second piston having a cylindrical portion slidably and tightly fitted into the center hole of the cylindrical valve member; built in the lower body and controlling communication between the second input port and the output port; a second cylindrical valve member; a first preload spring biasing the second piston toward the second cylindrical valve member; and a first preload spring configured to move in the axial direction of the valve body together with the first piston. a connecting rod inserted into the center hole of the cylindrical portion of the second piston; and a connecting rod having a spring force greater than that of the first preload spring;
The second piston is biased in a direction opposite to the first preload spring until the second piston moves a predetermined distance toward the cylindrical valve member; A second preload spring disposed to release the dual brake valve.

In this type of compound brake valve, conventionally, an annular stopper part projecting inward in the radial direction is integrally formed at the upper end part of the cylindrical part of the second piston, and the upper end part that comes into contact with this stopper part The second preload spring is stretched between the spring receiver and the lower spring receiver fixed to the lower end of the connecting rod, and the second piston normally holds the upper spring receiver and the stopper. The biasing force of the second preload spring is applied through the spring.

Alternatively, the stopper part of the second piston is engaged with the increased diameter part formed integrally with the lower end of the connecting rod, and the first piston is inserted upwardly into the upper end of the connecting rod extending into the plunger. A second preload spring is stretched between the fixed spring receiver and the push plate that abuts the plunger.

However, in any of the above configurations, a considerable number of man-hours are required to assemble and disassemble the second preload spring and other members. For example, when replacing the first cylindrical valve member described above, first the lower body must be removed from the intermediate body by loosening the mounting bolts, and then the second piston must be removed from the intermediate body. The connecting rod must be removed from the intermediate body first. To do this, for example, a screwdriver is engaged in a groove formed at the lower end of the connecting rod, and a nut screwed onto the upper end of the connecting rod is fixed by some means (one worker can do this with the other hand). (difficult), the screwdriver must be rotated. Although the first cylindrical valve member is then removed, the same effort as described above is required to install a new first cylindrical valve member. Moreover, when the connecting rod is removed, the second preload spring is also removed or left free, so that when the connecting rod is installed, the second preload spring is preloaded correctly, i.e. compressed correctly. must be set to obtain the state. For example, if the second preload spring is set in an inclined position, the operation of the brake valve will become unstable or the desired effect will not be obtained.

The present invention has been made in view of the above points, and an object of the present invention is to provide a dual brake valve whose components are easier to assemble and disassemble than the conventional brake valve. This object according to the invention consists of an upper body, an intermediate body and a lower body,
a valve body having at least a first input port and an output port in the intermediate body, and a second input port and an output port in the lower body; a lid member fixed to the lower body;
a plunger provided on the upper body so as to be slidable in the axial direction of the valve body; a plunger tightly fitted in the first cylinder hole of the intermediate body so as to be slidable in the axial direction of the valve body; and driven by the plunger; a first piston built in the intermediate body and controlling communication between the first input port and the output port; a first piston installed in the second cylinder hole of the intermediate body; a second piston that is slidably and tightly fitted in the axial direction of the valve body, and has a cylindrical portion in the center thereof that is slidably and tightly fitted into the center hole of the first cylindrical valve member; the lower body; a second cylindrical valve member incorporated in the second cylindrical valve member for controlling communication between the second input port and the output port; a second cylindrical valve member for biasing the second piston toward the second cylindrical valve member; a preload spring; a connecting rod provided to move in the axial direction of the valve body together with the first piston and inserted into a center hole of the cylindrical portion of the second piston;
a spring force greater than the first preload spring to move the second piston in a direction opposite to the first preload spring until the connecting rod moves a predetermined distance toward the second cylindrical valve member. and a second preload spring disposed so as to bias the second piston from the biasing force when the second piston moves beyond the predetermined distance. A stopper part is integrally provided on the inner wall of the second piston, and the stopper part regulates the upper position, and is capable of coming into contact with the lower end of the connecting rod, and vertically within the center hole of the cylindrical part of the second piston. The second preload spring is inserted into the center hole of the second cylindrical valve member and stretched between a movably provided spring receiving member and a lid member fixed to the lower body. This is achieved by a dual brake valve, which is characterized by:

Hereinafter, a dual brake valve according to an embodiment of the present invention will be explained with reference to the drawings.

In FIG. 1, the dual brake valve is indicated as a whole by 1, and its valve body 2 consists of an upper body 4, a lower body 5, and an intermediate body 6, each having a hole 3 for attachment to a toeboard at one end. 4 and the intermediate body 6 are fixed by bolts 101, and the intermediate body 6 and the lower body 5
As shown in the figure, it is fixed via a seal ring with a bolt (not shown). The opening of the lower body 5 is covered by a lid member 77.

A plunger support hole 7 is formed approximately in the center of the upper body 4, into which a bush 9 made of oil-impregnated sintered metal is press-fitted and fixed. A substantially cup-shaped plunger 10 is slidably fitted into the hole 8 of the bush 9. The stopper 11 fixed to the top of the plunger 10 by a method such as welding is
Brake pedal 1 whose upper surface is covered with a rubber plate 12
3 and is in contact with the circumferential surface of a roller 15 which is pivotally supported by a shaft 14. The brake pedal 13 is attached to the upper body 4
It is swingably attached to the upper body 4 by a rotating shaft 17 which is supported via a bearing 16 at the upper body 4 . Bolt 18 is an adjustment bolt for adjusting the non-operating position of brake pedal 13, and 19 is a fixing nut.

The plunger boot 20 has a small hole 20a, the upper end of which fits into the upper outer periphery of the plunger 10, and the lower end thereof into an annular groove 21 formed by the outer periphery of the upper body 4 and the bush 9. do,
It is installed.

A piston 25 having a seal member 24 attached to its outer periphery is slidably fitted into the upper cylinder hole 23 of the intermediate body 6, and a first control pressure chamber 27 communicating with the first output port 26 is provided below the piston 25. is formed. 1st
An operating device of one system is connected to the output port 26 of the output port 26 via a pipe (not shown). piston 25
A rubber spring 30 constituting a reaction spring is interposed between the upper surface and a push plate 29 that is slidably guided by the shaft portion 28 of the piston 25 and abuts the lower end of the plunger 10 on the upper surface. are doing.

Further, a first input port 35 is formed in the intermediate body 6 at the same level as and opposite to the first output port 26 described above, and these first output ports are arranged to define a first control pressure chamber 27 within the hole 23. A first partition wall 6 a is formed integrally with the intermediate body 6 at a position between the intermediate body 26 and the first input port 35 . The first partition wall 6a has a valve hole 32, and a cylindrical valve member 34 covered with a rubber member 33 forming a seat surface on the upper surface is disposed inside the valve hole 32. A first input chamber 36 communicating with the first input port 35 is formed therein. A compressed air source is connected to the first input port 35 via a pipe (not shown).

The above-mentioned valve member 34 is urged upward by a valve spring 37, and is pushed through the rubber sheet surface 33 into an inner air supply valve seat 39 formed at the upper end of the valve hole 32 of the first partition wall 6a. In the normal state, it is in contact with the side protrusion as shown in the figure. Further, a flange 38 serving as an exhaust valve seat is provided at the lower end of the piston 25 to the valve member 3.
It is formed so that it can be seated on the seat surface 33 of No. 4.
The valve member 34, the exhaust valve seat 38, and the air supply valve seat 39 constitute a first supply/discharge valve 40.

The lower end of the valve hole 32 of the first partition wall 6a and the valve member 3
Seal rings 41 and 42 are provided between the outer circumferential surface of
, and an annular member 44 which is prevented from coming off by a retaining ring 43 via a seal ring presser plate 46 is disposed. The first input chamber 36 is airtightly partitioned from the lower cylinder hole 49 of the intermediate body 6 by the annular member 44 .

A relay piston 47 is fitted with a seal ring and slidably inserted into the lower cylinder hole 49 of the intermediate body 6, and a relay chamber 45 is provided above the relay piston 47, and integrally with the lower body 5 below the relay piston 47. Second partition wall 5a formed
A second control pressure chamber 51 is formed by this. The relay chamber 45 connects to the first control pressure chamber 27 through a through hole 48 formed at the lower end of the first partition wall 6a.
is connected to. A second output port 50 is also formed in the lower body 5, with which the second control pressure chamber 51 communicates. The second output port 50 is connected to the operating equipment of the other system via piping (not shown).

The relay piston 47 has a cylindrical portion 53 in its center.
The cylindrical portion 53 is fitted with a seal ring and is slidably fitted into the hole 52 of the valve member 34. Further, an exhaust passage 54 is formed inside this, and this exhaust passage 54 is connected to the first control pressure chamber through a groove-shaped opening 55 formed on the upper end side of the cylindrical portion 53. It communicates with 27. A connecting rod 56 is inserted into the cylindrical portion 53 from above, and this rod 56 connects to the piston 25.
It is threaded into a through screw hole formed in a shaft-like part 28 of the plunger 10 and extends upward, and its upper end protrudes into the space 22 in the plunger 10 and is connected to the piston via a contact member 59 by a nut 58. Cylindrical portion 53 of relay piston 47 fixed to 25
A stopper member 61, a plan view of which is shown in FIG. This stopper member 61 consists of a cylindrical portion 61a and four arm portions 61b extending radially from the cylindrical portion 61a, and these arm portions 61b are fixed to the inner wall of the cylindrical portion 53 of the relay piston 47. The lower end of the connecting rod 56 is slidably inserted into the center hole 61c of the cylindrical portion 61a. A spring receiving member 60, the plan view of which is shown in FIG. A preload spring 57 is inserted through a center hole of a second cylindrical valve member 64, which will be described later, and stretched between the member 77 and a spring receiving portion 77a formed integrally with the bottom wall portion of the member 77. Under normal conditions as shown,
The spring receiving member 60 is urged upward by the preload spring 57 and is in contact with the stopper member 61 . Also, the lower end of the connecting rod 56 is connected to the spring receiving member 6.
It is in contact with the center part 60b of 0. Or it may be slightly away from this.

Therefore, the relay piston 47 is urged upward by the preload spring 57 via the spring receiving member 60 and the stopper member 61. On the other hand,
A differential pressure eliminating spring 62 is stretched in a compressed state between the relay piston 47 and the first partition wall 6a, and urges the relay piston 47 downward. However, since the spring force is greater in the preload spring 57 described above, under normal conditions the relay piston 47 is in the position shown. Regarding the action and effect of the differential pressure canceling spring 62, for example, see
Although it is described in detail in No. 27870, briefly stated here, it is caused by the sliding resistance that occurs when the relay piston 47 moves downward and the valve closing force of the second supply/discharge valve 71 described below. It functions to greatly reduce the differential pressure between the first output port 26 and the second output port 50.

Further, a second input port 66 is formed in the lower body 5 at the same level as and opposite to the second output port 50 described above, and the second input port 66 is connected to the output port 50 to define a second control pressure chamber 51 within the hole 49. A second partition 5a is integrally formed with the lower body 5 at a position between the opening 66 and the opening 66. This second partition wall portion 5a also has a valve hole 63, and this valve hole 63
A cylindrical valve member 64 covered with a rubber member 68 forming a seat surface on the upper surface is disposed inside the valve member 64, and a second input chamber 67 communicating with a second input port 66 is formed around the valve member 64. . A compressed air source is connected to the second input port 66 via a pipe (not shown).

The valve member 64 is urged upward by a valve spring 65, and an inward protrusion serving as an air supply valve seat 70 formed at the upper end of the valve hole 63 of the second partition portion 5a is inserted through the rubber sheet surface 68. In the normal state, they are in contact as shown in the figure. Further, a flange 69 serving as an exhaust valve seat is provided at the lower end of the relay piston 47 for the valve member 6.
It is formed so that it can be seated on the seat surface 68 of No. 4.
The valve member 64, the exhaust valve seat 69, and the air supply valve seat 70 constitute a second supply/discharge valve 71.

The lower end of the valve hole 63 of the second partition portion 5a and the valve member 6
Similarly to the first supply/discharge valve 40, seal rings 72 and 73 are installed between the seal rings 72 and 73, and an annular ring which is prevented from coming off by the flange portion 72 of the lid member 77 via the seal ring presser plate 74. A member 76 is placed.
The second input chamber 67 is airtightly partitioned from the atmosphere by the annular member 76 . Like the valve member 34 of the first supply/discharge valve 40, this valve member 64 is also slidably and airtightly guided in the center hole of the annular member 76. Further, the center hole of the valve member 64 forms an exhaust passage 205, and this passage 205 is connected to the exhaust passage 54 in the relay piston 47 and the notch 60 of the spring receiving member 60.
It communicates with the second control pressure chamber 51 at all times via a, and in the normal state shown in the figure.

A lid member 7 integrally fixed to the lower end of the lower body 5
7 is fitted with a rubber dust cover 78, whose flat plate portion 79 normally comes into elastic contact with the lower surface of the lid member 77 as shown in the figure, thereby establishing communication between the exhaust passage 205 and the atmosphere. However,
When compressed air is discharged from the first and second control pressure chambers 27 and 51 to the exhaust passage 205, the flat plate portion 79 is deformed by the pressure, and the compressed air is discharged from the lid member 77.
is discharged to the outside through the through hole 80.

Note that in the above configuration, the relay piston 47
The distance α from the exhaust valve seat 69 formed at the lower end of the cylindrical portion 53 to the seat surface 68 of the second valve member 64
and an exhaust valve seat 3 formed at the lower end of the piston 25.
8 to the seat surface 33 of the first valve member 34 and the distance β from the upper end of the cylindrical portion 53 of the relay piston 47 to the piston 2 to which this upper end portion is slidably fitted.
Between the distance γ to the upper surface S of the recess No. 5, α<
There is a relationship of β<γ.

Although the embodiment of the present invention is configured as described above,
This effect will be explained below.

When the brake is not applied, the parts of the brake valve 1 are in the positions shown, and the first supply and discharge valve 4
The valve member 34 of No. 0 is seated on the air supply valve seat 39 and is spaced from the exhaust valve seat 38. Therefore, the first control pressure chamber 27 is isolated from the first input chamber 36, communicates with the exhaust passage 54, and is at atmospheric pressure. On the other hand, the second
The valve member 64 of the supply/discharge valve 71 is also seated on the intake valve seat 70 and is spaced from the exhaust valve seat 69. Therefore, the second control pressure chamber 51 is also cut off from the second input chamber 67 and communicated with the exhaust passage 205 to be at atmospheric pressure.

Now, to apply the brakes, brake pedal 1
3, the brake pedal 13 swings around the rotating shaft 17, and the plunger 10 is pushed down by the roller 15. As a result, the piston 25
is moved downward via the push plate 29 and the rubber spring 30 against the spring 31. At the same time, the connecting rod 56 also moves downward, and its lower end pushes against the center portion 60b of the spring receiving member 60. As a result, the spring receiving member 60 tries to separate from the stopper member 61, but at the same time, the relay piston 47 is released from the biasing force of the preload spring 57, and moves downward under the biasing force of the differential pressure canceling spring 62. do. Therefore, the spring receiving member 60 does not separate from the stopper member 61, and the relay piston 47 moves downward together with the piston 25.
The lower end of the exhaust valve seat 69 comes into contact with the seat surface 68 of the second valve member 64 . Since the connecting rod 56 continues to move downward and presses down the spring receiving member 60 against the spring force of the preload spring 57, the spring force of the differential pressure canceling spring 62 acts exclusively on the relay piston 47. The relay piston 47 is the valve member 6
4, but cannot overcome the sum of the valve spring 65 that urges the valve member 64 upward and the compressed air pressure from the second input port 66, and does not open the valve member 64. .

Further, the piston 25 moves downward, and the piston 2
An exhaust valve seat 38 formed at the lower end of the exhaust valve seat 38 is seated on the first valve member 34 to connect the first control pressure chamber 27 to the exhaust passage 5.
4, the valve member 34 is removed from the air supply valve seat 39. As a result, the compressed air in the first input chamber 36 flows into the first control pressure chamber 27 .
From here, the compressed air is supplied to one of the operating devices through the first output port 26 and flows into the relay chamber 45 through the through hole 48. This compressed air acts on the relay piston 47 to open the valve member 64 of the second supply/discharge valve 71. That is, after the exhaust valve chamber 69 formed at the lower end of the relay piston 47 seats on the seat surface 68 of the valve member 64 and blocks the second control pressure chamber 51 from the exhaust passages 54 and 205, the piston 25 described above The additional downward movement causes the air supply valve seat 70 to separate from the seat surface 68 of the valve member 64, thereby communicating the second control pressure chamber 51 with the second input chamber 67. This allows the second input port 6
Compressed air is supplied from 6 to the other operating device through a second output port 50.

Then, when the pressure in the first control pressure chamber 27 rises to a value corresponding to the pushing force applied to the plunger 10 from the brake pedal 13, the piston 25 moves slightly upward, and the valve member 34 moves to the air supply valve seat. 3
9, the pressure in the first control pressure chamber 27 is maintained at a predetermined value. At the same time, the second control pressure chamber 5
1 rises to the pressure in the relay chamber 45, the valve member 64 in the second air supply/discharge valve 71 also closes to the air supply valve seat 7.
0, the pressure in the second control pressure chamber 51 is also maintained at a predetermined value.

To release the brake, press the brake pedal 13.
When the pedal force applied to the piston 25 is removed, the piston 25 moves upward due to the pressure in the first control pressure chamber 27 and the spring force of the spring 31, and the exhaust valve seat 38 is separated from the seat surface 33 of the valve member 34. , first control pressure chamber 27
communicates with exhaust passages 54 and 205. At the same time, the relay piston 47 also moves to the second control pressure chamber 51.
The exhaust valve seat 69 is moved upward by the pressure inside the relay piston 47 and the spring force of the spring 57 transmitted through the stopper member 61 fixed to the cylindrical portion 53 of the relay piston 47 and the spring bearing member 60 that comes into contact with the stopper member 61 . is separated from the seat surface 68 of the valve member 64, and the second control pressure chamber 51 communicates with the exhaust passage 205. In this way, the compressed air in each control pressure chamber 27, 51 is transferred to the exhaust passage 5.
4, 205 to the flat plate part 7 of the dust cover 78
9 is deformed and discharged from the through hole 80 to the outside.

Although the embodiment of the present invention operates as described above, the ease of assembling and disassembling each component of this dual brake valve 1 will now be explained.

Each component can be removed directly from the valve body 2, which consists of an upper body 4, a lower body 5, and an intermediate body 6, or can be easily removed after removing the upper body 4 or the lower body 5 from the intermediate body 6. For example, the first cylindrical valve member 3
4, the relay piston 47 can be easily removed from the intermediate body 6 by pulling the relay piston 47 downward after removing the lower body 5 from the intermediate body 6. At this time, the spring receiving member 60 and the spring 57 are also pulled out. After that, if the retaining ring 43 is removed and the annular member 44 is pulled out, the valve member 34 is also removed from the intermediate body 6. After setting the new valve member together with the annular member 44, the replacement work is completed by fixing it with the retaining ring 43 and performing the work in the reverse order of removal.

However, in the conventional dual brake valve, the connecting rod 5
6 was locked at the top of the cylindrical part 53 of the relay piston 47 (on the other hand, in this embodiment, as shown in the figure, such a locking part was not installed at the top of the cylindrical part 53). However, before pulling out the relay piston 47 from the intermediate body 6, it was necessary to release the locking state between the connecting rod and the relay piston 47. Such work was very troublesome, but in this embodiment, the lower end of the connecting rod 56 is slidably inserted into the center hole 61c of the stopper member 61 fixed to the inner wall of the cylindrical portion 53 of the relay piston 47. As described above, the relay piston 47 can be easily removed. The first valve member 34 can therefore be easily removed.
Also, when incorporating the first valve member 34,
Conventionally, the process involved putting the connecting rod and relay piston in a locked state and then inserting the relay piston into the intermediate body 6, or inserting the relay piston into the intermediate body 6 and then obtaining a locked state with the connecting rod. I had to do it. Therefore, the number of man-hours required for replacing the first valve member 34 is greatly reduced by this embodiment.

The above description has been about the work of replacing the first valve member 34, but it is clear that the number of man-hours required for replacing, disassembling, or assembling parts related to the connecting rod or the relay piston is also reduced compared to the conventional method. For example, a spring corresponding to the preload spring 57 that biases the relay piston 47 upward has conventionally been wrapped around a connecting rod and received by a spring receiving member, but it is also difficult to remove and disassemble this spring. It is much easier than before. That is, by simply removing the lid member 77 from the lower body 5, the preload spring 57 can be easily removed downward. However, in conventional dual brake valves, this spring must be removed and installed in conjunction with the connecting rod, which is very cumbersome. In particular, when the spring is assembled with other products, it is necessary to set the spring in the correct setting, which is also troublesome. However, in this embodiment, the spring receiving member 60 is brought into contact with the stopper member 61 from below (when the valve body 2 is turned upside down and assembled, the stopper member 61
1 from above), and the spring 57 is brought into contact with the second valve member 6 from above.
4 and then fixing the lid member 77 to the lower body 5, it is very easy to set and assemble.

The embodiments of the present invention have been described above, but of course the present invention is not limited thereto, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, the stopper member 61 was fixed to the inner wall of the cylindrical portion 53 of the relay piston 47, but this may be omitted. In this case,
A step may be formed on the inner wall, and the spring receiving member 60 may be brought into contact with this step. In this embodiment, the center hole 61c of the stopper member 61 is connected to the connecting rod 56.
Although the lower end of the guide acts as a guide, this is not necessarily necessary.

As described above, the dual brake valve of the present invention has a stopper part integrally provided on the inner wall of the cylindrical part of the second piston, and the upper position is regulated by the stopper part so that it can come into contact with the lower end of the connecting rod. and a spring receiving member provided vertically movably within the center hole of the cylindrical portion of the second piston, and a lid member fixed to the lower body, which is inserted into the center hole of the second cylindrical valve member. Since the second preload spring was tensioned,
Assembling and disassembling each component is easier than before, and the number of work steps can be greatly reduced.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a dual brake valve according to an embodiment of the present invention, FIG. 2 is a plan view of the stopper member in FIG. 1, and FIG. 3 is a plan view of the spring receiving member in FIG. 1. In the figure, 1...double brake valve, 2...valve body, 4...upper body, 5...lower body, 6...intermediate body, 1
0...Plunger, 23...Upper cylinder hole, 25...
Piston, 26...first output port, 34...first cylindrical valve member, 35...first input port, 39...air supply valve seat, 47
...Relay piston, 50...Second output port, 52...
Hole, 53...Cylindrical part, 56...Connection rod, 57...Spring, 60...Spring receiving member, 61...Stopper member, 62...Differential pressure eliminating spring, 64...Second cylindrical valve member, 66...Second input Mouth, 70...Air supply valve seat, 77...
Lid member, 205...exhaust passage.

Claims (1)

[Claims] 1 A valve body consisting of an upper body, an intermediate body, and a lower body, and having at least a first input port and an output port in the intermediate body, and a second input port and an output port in the lower body; fixed to the lower body; a plunger provided on the upper body so as to be slidable in the axial direction of the valve body; a plunger tightly fitted in the first cylinder hole of the intermediate body so as to be slidable in the axial direction of the valve body; a first piston driven by the plunger; a first cylindrical valve member built in the intermediate body and controlling communication between the first input port and the output port; A second cylinder portion that is slidably and tightly fitted in the second cylinder hole in the axial direction of the valve body, and has a cylindrical portion that is slidably and tightly fitted in the center hole of the first cylindrical valve member. a piston; a second cylindrical valve member that is built into the lower body and controls communication between the second input port and the output port; a first preload spring that biases the piston; a communication rod provided to move in the axial direction of the valve body together with the first piston and inserted into a center hole of the cylindrical portion of the second piston; a first preload spring having a spring force greater than the first preload spring to move the second piston in a direction opposite to the first preload spring until the connecting rod moves a predetermined distance toward the second cylindrical valve member; a second preload spring disposed to bias the second piston, but to release the biasing force when the second piston moves beyond the predetermined distance;
In the dual brake valve, a stopper part is integrally provided on the inner wall of the cylindrical part of the second piston, and the stopper part restricts the upper position of the second piston so as to be able to come into contact with the lower end part of the connecting rod. A spring receiving member provided vertically movably within the center hole of the cylindrical portion of the second piston and a lid member fixed to the lower body are provided in the center hole of the second cylindrical valve member. A dual brake valve, characterized in that the second preload spring is tensioned by being inserted therethrough.