JP3303451B2 - Bottom valve for tank truck, bottom valve device for tank truck, and valve device for tank truck - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom valve, a bottom valve device, and a valve device mounted on a tank truck.

[0002]

2. Description of the Related Art A tank lorry is provided with a plurality of tank chambers separated by partition walls for transporting a plurality of types of oil, and a bottom valve is provided for each tank chamber. In addition, when unloading oil from the tank chamber or loading oil into the tank chamber via the bottom valve, the air introduction valve should be at the top of each tank chamber so that the tank chamber will not deviate from the atmospheric pressure and work will not be hindered. The tank chamber is maintained at atmospheric pressure.

In conventional tank trucks, when unloading or loading oil from a tank chamber via a bottom valve, an operator goes up to the top of the tank and operates a handle at the top of the tank to open the bottom valve. At the same time, the air introduction valve is open.

[0004]

It is cumbersome and dangerous for an operator to climb to the top of the tank and operate the bottom valve.

It is an object of the present invention to provide a tank lorry bottom valve which can be operated by a worker when unloading oil from a tank chamber or loading oil into the tank chamber without having to go up to the top of the tank. It is to be. An object of the invention of claim 2 is that when oil is loaded into a tank chamber via a tank lorry bottom valve, even if oil comes to each tank lorry bottom valve via a common pipe, the oil is related to the oil. The purpose of this is to prevent the tank lorry bottom valve in the tank chamber from opening due to hydraulic pressure from the piping side. It is an object of the present invention to prevent a water hammer from being transmitted to a discharge valve or the like on a pipe side when a bottom valve starts to be opened for unloading oil from a tank truck. An object of the invention of claim 4 is to further improve the achievement of the object of the invention of claim 2. A fifth object of the present invention is to simplify the holding structure of the packing on the valve body side which comes into contact with the valve seat in the bottom valve for a tank lorry according to the third invention. The object of the invention of claim 6 is:
It is to prevent moisture generated by adiabatic expansion of pressurized air from accumulating in the air chamber. It is an object of the invention of claim 7 to provide a tank lorry vehicle bottom valve device in which the tank lorry vehicle bottom valve of claims 1 to 6 is appropriately controlled. It is an object of the invention of claim 8 to provide a valve device for a tank lorry vehicle in which an air introduction valve in an upper part of a tank chamber can be controlled together by operating a bottom valve for the tank lorry vehicle.

[0006]

The present invention will be described with reference to the drawings corresponding to the embodiments. The tank lorry bottom valve (20) of the first aspect has the following components (a) to (f). (A) A suction / discharge port (30) formed at the bottom of the tank chamber (16)
(B) a cylinder member (44) which is closed and open at the top and bottom, respectively; (c) a cylinder member (44) having a through hole (56) penetrating vertically. A valve body (34) fixed to the lower end and capable of being seated from above on the valve seat (32). (D) A hollow shaft fixed in the axial direction and penetrating through the valve body (34) relatively slidably. 50) (e) A piston (48) which is slidable on the inner peripheral side of the cylinder member (44), defines an air chamber (52) on the upper side, and is fixed to the upper end of the hollow shaft (50). An urging member (58) for urging the valve body (34) downward.

In the tank lorry bottom valve (20) of the second aspect, the valve element (34) has a pressure action area from the inside of the cylinder member (44) smaller than a pressure action area from the suction / discharge port (30) side. It is getting bigger. The cross-sectional area of the through-hole (56) is set to be about 30% or more of the cross-sectional area on the inner peripheral side of the cylinder member (44).

In the bottom valve (20) for a tank lorry according to the third aspect, when the valve body (34) is seated on the valve seat (32), the gap (41) is formed between the peripheral portion and the suction / discharge port (30). Is formed integrally on the lower surface side of the valve element (34).

[0009] In the tank lorry bottom valve (20) of the fourth aspect, the hanging member (38) of the third aspect is an annular member (38). The annular member (38) has a tapered inner periphery (39) whose diameter gradually increases downward.

In the bottom valve (20) for a tank truck, the packing (36) is applied to the contact portion of the valve body (34) with the valve seat (32), and the valve is lowered by the hanging member (38). Fastened to the body (34).

In the bottom valve (20) for a tank truck, the communication passage (60) extends obliquely downward from the upper surface of the piston (48) to reach the inside of the hollow shaft (50).

According to a seventh aspect of the present invention, there is provided a tank lorry bottom valve device having the following components (a) and (b). (A) a bottom valve (20) according to claims 1 to 6 (b) a pneumatic circuit (64) for controlling the supply of pressurized air to the lower end of the hollow shaft (50) of the bottom valve (20)

The bottom valve device for a tank lorry according to claim 8 has the following components (a) to (c). (A) the bottom valve (20) according to any one of claims 1 to 6; (b) an air introduction valve (22) provided above the tank chamber (16) of the bottom valve (20); Connected to the cylinder member (44) of the bottom valve (20), and at the upper position of the cylinder member (44), push up the valve body (80, 94) of the air introduction valve (22) to forcibly activate the air introduction valve (22). Open bar operating member (24)

[0014]

In the tank lorry bottom valve (20) of the first aspect, the oil (18) in the tank chamber (16) is unloaded and the tank chamber (1) is unloaded.
6) When the oil (18) is loaded into the air chamber (52), the pressure in the air chamber (52) is increased by the supply of air pressure through the hollow shaft (50). Since the piston (48) is fixed via the hollow shaft (50), the cylinder member (44) and the valve body (34) are moved by the piston (48) and the hollow shaft, respectively, due to the high pressure of the air chamber (52). (50), and ascends integrally, the valve body (34) separates from the valve seat (32),
The suction port (30) is opened.

When the bottom valve (20) for the tank truck is closed, the air chamber (52) is supplied by supplying air pressure through the hollow shaft (50).
Is set to low pressure. Since the piston (48) is fixed via the hollow shaft (50) and the urging member (58) urges the cylinder member (44) downward, the cylinder member (44) and the valve body (34) Is
The piston (48) and the hollow shaft (50) slide relative to each other,
As a result, the valve body (34) is seated on the valve seat (32), and the suction / discharge port (30) is closed. Note that the cross-sectional area of the through hole (56) is approximately 30 to the cross-sectional area on the inner peripheral side of the cylinder member (44).
The percentages above are based on experiments. That is, in the experiment, if it is set to 30% or more, the oil (18)
Is squeezed by the through hole (56) after reaching the lower surface side of the valve body (34), and is delayed from being introduced to the upper surface side of the valve body (34). It was surely prevented from rising by the force from the side.

In the tank lorry bottom valve (20) of the second aspect, the oil (18) is loaded when the bottom valve (20) is opened when the bottom valve (20) is opened.
When the oil (18) reaches the lower surface side of (4), the oil (18) passes through the through hole (5) of the valve body (34).
Through 6), it enters the cylinder member (44) between the upper surface side of the valve element (34) and the lower surface side of the piston (48). The valve element (34) has a suction / discharge port (3
0), the force acting downward on the valve body (34) is greater than the upward biasing force on the reached oil (18), and the valve body (34) The seating position for the seat (32) is maintained. When the air chamber (52) is switched to the high pressure, the cylinder member (44) receives an upward force from the pressure of the air chamber (52) and rises, and the valve body (34) separates from the valve seat (32). And
Oil (18) on the lower surface side of the valve element (34) is introduced into the tank chamber (16).

In the tank lorry bottom valve (20) of the third aspect, the valve body is used to unload the oil (18) in the tank chamber (16).
(34) rises integrally with the cylinder member (44), and the valve seat (3
When separating from 2), at the initial stage of separation, the hanging member (38)
Are still located inside the suction / discharge port (30). As a result, the oil (18) in the tank chamber (16)
Small gap (41) between suction port (30) and hanging member (38)
After the hanging member (38) comes out of the suction / discharge port (30), the hanging member (38) is drawn out via the widely opened suction / discharge port (30).

In the bottom valve (20) for a tank truck, the oil (1) reaching the lower surface of the valve body (34) for loading.
8) passes through the tapered inner periphery (39) of the annular member (38) and proceeds to the through hole (56).

In the bottom valve (20) for a tank lorry according to a fifth aspect, the packing (36) is fixed to the lower surface side of the valve body (34) via the hanging member (38), and the packing (36) is closed. Valve seat (32) at sitting
Adhere to

According to the tank lorry bottom valve (20) of the present invention, the water collected on the upper surface side of the piston (48) in the air chamber (52) is:
According to gravity, it descends obliquely through the communication passage (60) and the hollow shaft
(50) and descends in the hollow shaft (50).

In the bottom valve device for a tank truck, the pneumatic circuit (64) controls the supply of pressurized air to the lower end of the hollow shaft (50) of the bottom valve (20). When the pneumatic circuit (64) is supplying pressurized air to the lower end of the hollow shaft (50), the pressurized air is introduced into the air chamber (52) via the hollow shaft (50), and the air chamber (52) Becomes high pressure, and the bottom valve (20) opens.

In the tank lorry valve device according to claim 8,
When the bottom valve (20) is open, the pressure in the air chamber (52) is high, and the cylinder member (44) rises. The rod-shaped operation member (24) pushes up (80, 90) of the air introduction valve (22) at the upper part of the tank chamber (16) with the rise of the cylinder member (44), whereby the air introduction valve
(22) is forcibly opened. As a result, the tank room (16)
The inside communicates with the atmospheric pressure space through the air introduction valve (22) and is maintained at the atmospheric pressure.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 3 is a side view of the tank truck 10. The tank truck 10 includes a tank 12, and the inside of the tank 12 is partitioned into a plurality of tank chambers 16 in the front-rear direction by a partition wall 14, so that different types of oil 18 can be stored in the respective tank chambers 16.
Each tank chamber 16 is equipped with a bottom valve 20 and an air introduction valve 22 at the bottom and the top, respectively.
Extending between.

FIG. 1 is a detailed view of the bottom valve 20 and the pneumatic circuit 64. The bent pipe 28 is disposed below the tank chamber 16, and has an upwardly upper end fixed to the bottom wall 26 of the tank chamber 16 and a lower end horizontally oriented. An unloading pipe (not shown) common to each tank chamber 16 extends in the front-rear direction of the tank truck 10 below the tank 12 and is connected to the lateral lower end of each bottom valve 20. The suction / discharge port 30 is defined inside the upper end of the bent pipe 28, and connects the inside of the tank chamber 16 and the inside of the bent pipe 28 to each other. The valve seat 32 is formed on the upper surface of the peripheral portion of the suction / discharge port 30 as an annular ridge along the peripheral portion. Valve body 34
The annular packing 36 is fitted into the annular groove on the lower surface side, and the annular packing 36 is brought into close contact with the valve seat 32 to be seated. The annular member 38 is applied to the lower surface of the valve body 34, and the bolt 40 is inserted through the valve body 34 and the annular member 38 from the upper surface side of the valve body 34,
The nut 42 is screwed from below the 38, and the annular member 38 is
Fix to 34. The annular member 38 has a tapered inner periphery 39 whose diameter gradually increases downward. The outer diameter of the annular member 38 is slightly smaller than the diameter of the suction / discharge port 30. When the valve body 34 is seated on the valve seat 32, the annular gap 41 is formed between the peripheral surface of the suction / discharge port 30 and the annular member.
It is formed between the outer circumference of 38.

The cylinder member 44 has a structure that closes and opens at upper and lower ends, and is screwed to the inner peripheral side of the upper end of the valve body 34 at the lower end. Annular packing 46
Is pressed between the lower end of the cylinder member 44 and the valve body 34 in the vertical direction, and seals the joint between the cylinder member 44 and the valve body 34. The piston 48 is disposed in the cylinder member 44 so as to relatively slide vertically on the inner circumference of the cylinder member 44. The hollow shaft 50 has a lower end fixed to a lower portion of the bent tube 28, protrudes below the bent tube 28, and extends upward into the cylinder member 44. The hollow shaft 50 is slidable up and down relative to the valve body 34 at a penetrating portion of the valve body 34, and a piston 48 is fixed at an upper end portion. The piston 48 divides the inside of the cylinder member 44 into an upper air chamber 52 and a lower liquid chamber 54, and a through hole 56 is formed in the valve body 34 to move the liquid chamber 54 to the lower surface side of the valve body 34. They are communicating. The pressure acting area where the liquid pressure in the liquid chamber 54 acts on the upper surface of the valve body 34 is larger than the pressure acting area where the hydraulic pressure of the suction / discharge port 30 acts on the lower surface of the valve body 34. And cylinder members 44
Is set. The communication hole 60 extends obliquely downward radially inward from the recess on the upper surface side of the piston 48,
Inside.

The compression coil spring 58 has a piston
It is contracted between the lower surface of 48 and the upper surface of the valve element 34 to urge the valve element 34 downward. The filter 62 has a cylindrical shape whose upper end is closed, covers and covers the bottom valve 20 from above, and has a lower end peripheral edge fixed to the bottom wall 26. The total cross-sectional area of through hole 56 is valve seat 32
Is set to 30% or more of the cross-sectional area on the inner peripheral side of. Operation stick
24 has its lower end screwed to the upper wall of the cylinder member 44, extends through the upper wall of the filter 62, and extends upward.

The pneumatic circuit 64 includes a pressurized air source 66 and a hollow shaft
A switching valve 68 for selectively connecting the lower end of the valve 50 to a pressurized air source 66 or an air space. The switching valve 68 is disposed on the tank truck 10 at a height that can be operated by the operator from the ground.

FIG. 2 is a detailed structural view of the air introduction valve 22. The housing 70 has a lower end fixed to the upper wall 72 of the tank chamber 16, protrudes upward from the upper wall 72, and has an opening 74 on a side portion. The air inlet 76 is formed in the housing 70 with the center line extending vertically. The valve seat 78 is an air inlet
It is formed on the upper surface side of the peripheral edge of the air inlet 76 and extends along the peripheral edge of the air inlet 76. The valve element 80 can be moved vertically by the guidance of the cylindrical wall portion 82, and the notch window 84 is
The hole is drilled at a position on the opening 74 side of the opening 82 so that the opening 74 and the air inlet 76 communicate with each other at the raised position of the valve body 80. The compression coil spring 86 is contracted between the lower surface of the upper wall portion of the housing 70 and the valve element 80 to urge the valve element 80 downward. A plurality of through holes 88 are drilled through the valve body 80
Is inserted into the boss 92 of the valve body 80 so as to be relatively slidable in the vertical direction. The disc-shaped valve element 94 is disposed coaxially with the valve element 80, and is closely attached to the lower surface of the valve element 80 at the periphery. The compression coil spring 96 urges the shaft 90 upward.

The operating rod 24 has a housing 70 at its upper end.
A boss 100 at the lower end of the boss 100 is slidably penetrated, and has a flange 98 above the boss 100. The through-hole 102 is formed on the outside of the boss 100 in the radial direction, and allows the upper and lower portions to communicate with each other.

The safety valve function of the air introduction valve 22 will be described. When the pressure inside the tank chamber 16 becomes significantly higher than the atmospheric pressure, the valve body 80 receives a large force from the tank chamber 16 side, rises against the compression coil spring 86, and separates from the valve seat 78. Thereby, the inside of the tank chamber 16 has a through hole 102, an air inlet 76,
The high pressure in the tank chamber 16 is released by communicating with the atmosphere through the notch window 84 and the opening 74.

On the other hand, when the pressure in the tank chamber 16 becomes significantly lower than the atmospheric pressure, the valve body 94 is sucked by the negative pressure on the tank chamber 16 side and descends against the compression coil spring 96, and the valve body 94 is lowered. 80
Away from the lower surface of the. As a result, the inside of the tank chamber 16 communicates with the atmosphere through the through hole 102, the through hole 88, the upper end opening of the cylindrical wall portion 82, and the opening 74, and the atmospheric pressure is introduced into the tank chamber 16.

The opening and closing operation of the bottom valve 20 will be described. Normally, the switching valve 68 connects the lower end of the hollow shaft 50 to the atmospheric pressure space. Thus, the atmospheric pressure is supplied from the air space opening port of the switching valve 68 to the air chamber 52 via the hollow shaft 50. As a result of the inside of the air chamber 52 being at atmospheric pressure, the valve element 34 is pressed downward by the compression coil spring 58 and is held in a state in which the annular packing 36 is in close contact with the valve seat 32. Thereby, the bottom valve 20 is closed.

When the oil 18 is loaded into the tank chamber 16,
Oil 18 flows into each bent pipe 28 from a common unloading pipe. When the bottom valve 20 is closed, the oil 18 that has reached the lower surface of the valve body 34 is
The liquid chamber 54 passes through the tapered inner periphery 39 of the annular member 38 and the through hole 56.
Introduced into. Since the cross-sectional area of the liquid chamber 54 is slightly larger than the cross-sectional area of the suction / discharge port 30, the pressure acting area of the annular packing 36 on the liquid chamber 54 side is larger than the pressure acting area on the suction / discharge port 30 side. Oil for loading, 18
A large force is exerted downward from above to maintain the seated position on the valve seat 32. The total cross-sectional area of the through hole 56 is the liquid chamber 54
30% or more of the cross-sectional area of
This is based on the result of an experiment in which it was confirmed that the valve body 34 was quickly introduced into the liquid chamber 54 in spite of the restriction in the above to prevent the valve body 34 from separating from the valve seat 32. As a result, the bent pipe 28
Tank chamber 16 bottom valve unrelated to the loading oil 18 that has reached
20 holds closed.

The oil 18 in the tank chamber 16 is unloaded or the tank chamber 16 is unloaded.
When the oil 18 is loaded, the switching valve 68 is manually switched to connect the lower end of the hollow shaft 50 to the pressurized air source 66. The pressurized air from the pressurized air source 66 is introduced into the air chamber 52 via the hollow shaft 50, and the air chamber 52 becomes high pressure. Since the piston 48 is vertically fixed to the curved pipe 28 via the hollow shaft 50, the cylinder member 44 rises as a result of the high pressure in the air chamber 52, and the valve body 34 is moved to the valve seat 32.
Depart from. At the initial stage of the separation, the annular member 38 is still inside the suction / discharge port 30 and the inside of the tank chamber 16 and the inside of the bent pipe 28 only communicate with each other via the annular gap 41,
When unloading the oil 18 from the tank chamber 16, the oil 18 in the tank chamber 16 is led out at a small flow rate through the annular gap 41, and the large water hammer is transmitted to the discharge valve at the lower end of the unloading pipe. Is suppressed. The cylinder member 44 gradually rises,
When the upper position (the position indicated by the two-dot chain line in FIG. 1) is reached, the annular member
38 comes out of the suction / discharge port 30, the suction / discharge port 30 is widely opened, and the inside of the tank chamber 16 and the inside of the bent pipe 28 communicate with each other through the widely opened suction / discharge port 30.

On the other hand, as the cylinder member 44 rises, the operating rod 24 is pushed up, and the operating rod 24 is
Is brought into contact with the lower surface of the valve element 94 (the position indicated by the two-dot chain line in FIG. 2).
The valve body 94 and the valve body 80 are raised. This allows the tank chamber
The inside of the tank chamber 16 is maintained at the atmospheric pressure by communicating with the outside atmospheric pressure space through the through hole 102, the air inlet 76, the notch window 84, and the opening 74.

When the pressurized air enters the air chamber 52 from the upper end of the hollow shaft 50, moisture in the pressurized air condenses due to adiabatic expansion and accumulates on the upper surface of the air chamber 52. The accumulated water enters the hollow shaft 50 through the communication hole 60 by gravity, descends the hollow shaft 50, and is discharged to the outside.

[0037]

According to the first aspect of the present invention, since the opening and closing of the valve body can be switched by switching the pressure in the air chamber, when the oil is unloaded from the tank chamber or loaded into the tank chamber, the operator can move the upper part of the tank. The opening and closing operation of the bottom valve can be performed without the trouble of ascent.

According to the second aspect of the invention, the oil that reaches the lower surface side of the valve body for loading is introduced into the upper surface side of the valve body through the through hole of the valve body. Since a large force is received from the oil on the upper surface side and the oil is urged downward, it is possible to reliably prevent the bottom valve in the tank chamber irrelevant to the oil from being opened carelessly.

According to the third aspect of the present invention, when the bottom valve starts to open at the time of unloading, the oil flows out through a small gap between the suction / discharge port and the hanging member. Water hammer can be prevented from being transmitted.

According to the fourth aspect of the present invention, the oil that reaches the lower surface of the valve body during loading flows toward the through hole through the tapered inner periphery of the annular member. The introduction of oil is facilitated, and erroneous opening of the bottom valve can be reliably prevented. Further, since the annular member also serves to suppress water hammer, it contributes to reducing the number of parts.

According to the fifth aspect of the present invention, since the valve seat is fixed to the valve body by the hanging member, it is possible to simplify the structure by omitting an additional component for holding the valve seat.

According to the sixth aspect of the present invention, the water generated in the air chamber due to the adiabatic expansion of the pressurized air flows out to the hollow shaft through the communication passage. Can be prevented.

According to the seventh aspect of the present invention, the pneumatic circuit is connected to the lower end of the hollow shaft of the bottom valve to control the supply of pressurized air to the air chamber of the bottom valve so that the bottom valve can be properly operated. Opening and closing can be controlled.

According to the eighth aspect of the present invention, the rod-shaped operating member is displaced with the rise of the cylinder member to forcibly open the air introduction valve in the upper part of the tank chamber. The operation can be performed together with the operation of the bottom valve.

[Brief description of the drawings]

FIG. 1 is a detailed view of a bottom valve and a pneumatic circuit.

FIG. 2 is a detailed structural view of an air introduction valve.

FIG. 3 is a side view of the tank truck.

[Explanation of symbols]

 Reference Signs List 16 tank chamber 18 oil 20 bottom valve (bottom valve for tank truck) 22 air introduction valve 24 operation rod (rod-shaped operation member) 30 suction / discharge port 32 valve seat 34, 80, 94 valve body 36 annular packing (packing) 38 annular member (ring) Hanging member) 39 tapered inner periphery 41 annular gap (gap) 44 cylinder member 48 piston 50 hollow shaft 52 air chamber 56 through hole 58 compression coil spring (biasing member) 60 communication hole (communication passage) 64 pneumatic circuit

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masahiro Ikeda 5-5-5 Shirokane, Minato-ku, Tokyo Inside Keiwa Kogyo Co., Ltd. (56) References JP-A-2-93734 (JP, A) JP-A Hei 2-85196 (JP, A) Japanese Utility Model 62-12554 (JP, U) Japanese Utility Model 3-123180 (JP, U) Japanese Utility Model 3-2984 (JP, U) Japanese Utility Model 56-168430 (JP, U) , U) (58) Field surveyed (Int.Cl. ⁷ , DB name) B60P 3/22-3/24

Claims (8)

(57) [Claims] (A) a valve seat (32) provided at an upper peripheral portion of a suction / discharge port (30) formed at the bottom of a tank chamber (16);
(B) a cylinder member (44) which is closed and open at the top and bottom, respectively, and (c) a through-hole (56) penetrating vertically.
A valve body (34) fixed to the lower end of the cylinder member (44) and capable of being seated on the valve seat (32) from above,
(D) a hollow shaft (50) fixed in the axial direction and penetrating the valve body (34) relatively slidably, and (e) the cylinder member (4).
4) a piston that is slidable on the inner peripheral side, defines an air chamber (52) on the upper side, and is fixed to the upper end of the hollow shaft (50).
(48) and (f) a biasing member for biasing the valve body (34) downward.
(58) A bottom valve for a tank lorry vehicle, comprising: 2. The valve body (34) is connected to the cylinder member (44).
The pressure acting area from the inner side is larger than the pressure acting area from the suction / discharge port (30) side, and the cross-sectional area of the through hole (56) is approximately 30 times the cross-sectional area of the inner peripheral side of the cylinder member (44).
%. The bottom valve for a tank lorry vehicle according to claim 1, wherein When the valve body (34) is seated on the valve seat (32), a hanging member (38) forming a gap (41) between a peripheral portion and the suction / discharge port (30) is provided. 3. The bottom valve for a tank lorry vehicle according to claim 1, wherein said bottom valve is integrally provided on a lower surface side of said valve body. 4. The hanging member (38) is an annular member (38), and the annular member (38) has a tapered inner periphery (39) whose diameter gradually increases downward. The bottom valve for a tank lorry vehicle according to claim 3, wherein 5. A packing (36) is applied to a contact portion of the valve body (34) with the valve seat (32), and is fixed to the valve body (34) by the hanging member (38). The bottom valve for a tank lorry according to claim 3, wherein the bottom valve is provided. 6. The communication path according to claim 1, wherein the communication path extends obliquely downward from the upper surface of the piston and reaches the hollow shaft. Bottom valve for tank lorry described. 7. (a) The bottom valve (20) according to any one of claims 1 to 6, and (b) pressurized air to the lower end of the hollow shaft (50) of the bottom valve (20). A bottom valve device for a tank truck including a pneumatic circuit (64) for controlling supply. 8. An air introduction valve provided at (a) the bottom valve (20) according to any one of claims 1 to 6, and (b) an upper part of the tank chamber (16) of the bottom valve (20). (22) and (c) connected to the cylinder member (44) of the bottom valve (20) at the lower end side, and the valve body (80, 80) of the air introduction valve (22) at an upper position of the cylinder member (44). And a rod-shaped operating member (24) forcibly opening the air introduction valve (22) by pushing up the air introduction valve (94).