JP2003240141A - Back-flow preventing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backfire preventing device which prevents the backfire phenomenon at the maximum. <P>SOLUTION: This back-flow preventing device comprises a gas injection member 4 comprising a gas introduction hole 3 for introducing a supply gas to a valve housing, and a valve seat 17, a valve guide member 8, and a valve operating member 12 comprising a valve 11 and being slid on the basis of pressure difference between the gas introduction hole 3 and the valve guide member 8. Gas holes 7, 10 are fitted to each other when the valve operating member 12 is moved to a stroke front end to communicate the valve housing 2 and the valve guide member 8, and when the valve operating member 12 is moved toward the stroke rear end, the gas holes 7, 10 are shifted from each other before the valve seat 17 is closed by the valve 11, and the gas holes 7, 10 are respectively closed by peripheral faces of the mating gas holes 10, 7 to cut the communication of the valve housing 2 and the valve guide member 8, whereby the primary cut-off by shifting the gas holes 7, 10, and the secondary cut-off by closing the valve seat 17 and the gas introduction hole 3 by the valve 11, are performed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing the reverse flow of a fluid, which is installed at a location where the relationship of the pressure difference is reversed and a reverse flow of the fluid may occur, and a gas cutting machine and a gas using the same. The present invention relates to a pipe coupling device. More specifically, the present invention is a device or pipe, etc., which is required to prevent backflow of fluid, in particular, a gas cutter, a gas cylinder, various gas appliances such as a gas range, and a gas for supplying a combustible gas to these various gas appliances. A backflow prevention device that can be used by being applied or attached to a place where it is necessary to prevent backflow of flammable gas in a coupler of a supply pipe, that is, a place where backfire prevention is required, and gas cutting using this Machine and gas pipe coupling device.

[0002]

2. Description of the Related Art A general flashback prevention device for a gas appliance is a filter-shaped valve actuating pipe having a large number of gas supply holes penetrating the outer periphery of a main body thereof. When the gas is supplied, the valve actuating pipe moves forward by the supply pressure to open the gas supply passage, and the gas can be supplied through the gas supply hole of the valve actuating pipe. At the time of reverse flow, the valve actuating pipe moves rearward to shut off the gas supply passage to prevent the flashback phenomenon in which the ignition source flows into the low-pressure gas supply pipe.

[0003]

However, in the conventional flashback preventive device as described above, due to the abnormal pressure of the gas, the instantaneous speed of the valve actuating pipe moved rearward is relatively high and the collision at the time of shutting off. There is a problem in that the gas supply hole cannot be completely shut off because it can bounce off due to the repulsion of the gas.

Therefore, there is a problem in that a fire that could not be extinguished completely by momentary interruption flows in through the gas supply path and a backfire occurs, resulting in damage to human life or damage to equipment.

An object of the present invention is to provide a flashback prevention device which can prevent the flashback phenomenon that occurs to the maximum extent.

[0006]

In order to achieve the above object, a backflow prevention device according to the invention of claim 1 is a gas having a valve accommodating chamber, a gas introducing hole for introducing a supply gas into the chamber, and a valve seat. An injection member, a valve guide member having openings at both ends which are fitted into the gas outlet of the gas injection member and accommodated in the valve accommodating chamber, and a valve accommodating chamber of the valve guide member slidably externally inserted into the valve accommodating chamber. A valve operating member that closes an opening to be opened and that closes a valve seat, and has a valve operating member that slides due to a pressure difference between the gas introducing hole and the valve guiding member; At least one gas hole is formed in each of the peripheral walls, and when the valve operating member moves to the front end of the stroke, the gas holes are aligned with each other to communicate the valve accommodating chamber and the valve guiding member with each other. When the operating member moves toward the rear end of the stroke, the gas holes are displaced from each other before the valve seat is closed by the valve element, and the gas holes on the other side are closed by the peripheral surfaces of the valve housing chamber and the valve guide member. I am preparing for the position where communication with is closed.

Therefore, when the gas is normally supplied, the valve operating member is moved to the front end of the stroke along the valve guiding member by the gas supply pressure so that the gas holes of the valve operating member and the valve guiding member are aligned with each other. The supply gas can be supplied by passing through the valve guide member. On the other hand, in the case of gas reverse flow in which the relationship of the pressure difference is reversed, while the valve operating member is moved to the valve seat side along the valve guide member due to the pressure difference, the gas reversely flows due to the position shift of the gas holes. After shutting off, the valve seat of the gas injection member is further blocked by the valve element at the tip of the valve operating member to secondarily block the backflow. That is, at the time of reverse gas flow, the valve operating member moves rearward along the valve guiding member,
The gas holes of the valve guiding member and the valve operating member are displaced. Then, first, the backflow of gas is temporarily blocked by closing the gas hole, and then the valve element at the tip of the valve operation member closes the valve seat of the gas injection member by the movement of the valve operation member. It is a mechanism to secondarily block the reverse flow of gas to the valve, and the valve operating member pushed by the pressure of the backward flowing gas bounces off the valve seat surface by the repulsive force when it collides with the valve seat of the gas inflow member. However, since the outlet of the valve guide member itself is covered with the valve operating member and the gas holes are also closed by the peripheral surface of the valve operating member, the backflow gas does not leak into the gas injection member. Further, the valve actuating member that has rebounded due to the pressure of the backflow gas is pressed against the valve seat side of the gas injecting member at the time of collision, and the valve seat at the tip closes the valve seat. As a result, backflow gas leakage due to the collision between the valve operating member and the gas injection member is completely blocked.

Here, the gas injection member of the flashback preventive device comprises a tube having a valve accommodating chamber and a gas introducing hole having a smaller diameter than that and forming a valve seat at a boundary portion with the valve accommodating chamber.
The valve guide member is a pipe which is housed in the valve housing chamber and whose outer end is fitted to the opening of the valve housing chamber and fixed to the gas injection member. Further, the valve operating member slides on the valve guiding member. It is preferable to be configured by a pipe that is freely inserted and has a lid-like valve element that closes an opening of the valve guiding member inside the valve housing chamber and a valve element that closes a gas introduction hole of the gas injection member.

According to a third aspect of the present invention, in the backflow prevention device according to the first or second aspect, the valve actuating member is an annular member fitted to the gas injection member on the outer side of the gas hole without a gap. A guide part is provided.
In this case, the valve operating member can be slid without rattling while the guide portion seals between the valve operating member and the gas injection member and between the valve operating member and the valve guiding member.

The invention according to claim 4 is the backflow prevention device according to any one of claims 1 to 3, wherein the valve guide member and the valve operating member are made of stainless steel, and the gas injection member is made of brass. I am trying to configure it. In this case, even if the interruption occurs continuously for a short time, the stainless steel valve guide member and valve actuating member on the flashback occurrence side are more resistant to heat and stronger than brass, and therefore melt. Less likely to be lost or damaged.
Moreover, since the gas injection member is made of brass, it is possible to use welding for joining with the gas supply pipe, which is generally made of brass. When stainless steel is used for the gas injection member, brazing with silver braze must be used to join the gas supply pipe, which is generally made of brass. There is a risk of melting the brazing filler metal / silver brazing filler metal that joins the gas supply pipe on the supply source side and causing a joint failure.

Further, in a gas cutting machine according to a fifth aspect of the present invention, the backflow prevention device according to any one of the first to fourth aspects is incorporated in the upstream side of the gas flow path in the immediate vicinity of the torch head. There is. In this case, the backflow of the fluid, that is, the flashback can be stopped in the torch head to prevent the flashback from occurring in the gas pipe of the gas cutter, and there is no risk of explosion in the gas supply pipe or the like. Therefore, since the gas pipe does not require strength, a light and inexpensive material (generally, such a material has low rigidity) can be used for these, and the cutting torch can be made lightweight.

Further, the backflow prevention device of the present invention may be incorporated in the gas cutter itself, but in some cases, it may be incorporated in an independent coupler for connecting the gas pipes, or both ends of the gas injection member. It is also possible to provide a screw for connection and a connecting means to itself and use it as a coupling.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described below in detail based on the embodiments shown in the drawings.

FIG. 1 is an exploded perspective view showing an embodiment in which the backflow prevention device according to the present invention is used as a flashback prevention device. The flashback preventive device 27 is fitted with the gas injection member 4 including the valve housing chamber 2 and the valve housing chamber 2 of the gas injection member 4, and forms the outlet of the gas injection member 4.
And a valve actuating member 12 that is housed between them and moves by the pressure difference generated between the inlet side and the outlet side of the device to shut off / open the flow path. Here, the valve body 1 is constituted by the valve guide member 8 and the valve actuating member 12 slidably fitted to the outside thereof. And the valve operating member 1
2 is housed in the valve accommodating chamber 2 of the gas injecting member while being fitted in the valve guiding member 8.
Is fixed to the opening 21 of the gas injection member 4 so as to be slidable along the valve guide member 8 in the gas injection member 4.

The gas injection member 4 comprises a valve accommodating chamber 2, a gas introducing hole 3 for introducing a supply gas into the valve accommodating chamber 2, and a valve seat 17. For example, the gas injection member 4 forms a circular valve accommodating chamber 2 for accommodating the valve body 1 on one side, and has a smaller diameter than the valve accommodating chamber 2 on the opposite side and a valve seat 17 at a boundary portion with the valve accommodating chamber 2. It is composed of a circular tube provided with a gas introduction hole 3 that forms The gas introduction hole 3 is
The valve housing chamber 2 and the outside of the gas injection member 4 are communicated with each other,
Gas can be injected into the valve accommodating chamber 2.
The end portion 25 provided with the gas introduction hole 3 has a smaller diameter than the portion in which the valve accommodating chamber 2 is formed, and a counterpart member to which the gas injection member 4 is attached, for example, the gas supply pipe 13
Care has been taken to facilitate the joining between and. Positioning with the mating partner is achieved by the stepped portion formed by the existence of the small-diameter end portion 25.

The valve guide member 8 is formed of a cylinder having openings at both ends. The end portion of the valve guide member 8 is fitted into the opening portion 21 while being housed in the valve housing chamber 2 of the gas injection member 4, and the outlet serving as a flashback prevention device is provided. Constitute. That is, the valve guide member 8 is fixed to the opening 21 of the valve housing chamber 2 of the gas injection member 4 to partially form the valve housing chamber 2 as a double cylinder, and the opening 20 is formed on the back side of the valve housing chamber 2. It is provided so as to function as a spool and to form a spool valve with the valve operating member 12. For example, the valve guide member 8 may include the inner peripheral surface of the valve housing chamber 2 and the opening 2 on one side.
1. A joint step 5 and a support step 6 which are fitted in the concave portion 26 of the No. 1 and join the valve guide tube 8 and the gas injection member 4 are formed,
When the valve guide member 8 is cantilevered by the gas injection member 4 only by the joint step 5 and the support step 6 when inserted into the valve housing chamber 2, The valve actuating member 12 is slidably accommodated therein and forms a flow path 24 through which gas flows.

The valve operating member 12 is the valve guiding member 8
Is slidably inserted into the inner flow path 2 of the valve guiding member 8.
A valve element 11 that closes the opening 20 on the back side of the valve 2 and closes the valve seat 17 is provided, and slides due to the pressure difference between the gas introduction hole 3 and the valve guide member 8. The valve actuating member 12 has a gas introducing hole 3 which is located on the inner side of the valve accommodating chamber 2.
A lid-shaped valve element 19 that closes the opening 20 of the valve guide member 8 and a valve element 11 that closes the gas introduction hole 3 (valve seat 17) are provided at the end on the side, and the valve element is provided outside the gas holes 10 in the peripheral wall portion. Part,
An annular guide portion 9 is preferably provided at the end of the valve storage chamber 2 on the side of the opening 21. The valve actuating member 12 is preferably constructed of a bottomed circular tube. That is, FIG.
As shown in FIG. 5, the lid-shaped valve element 19 is formed by the bottom portion of the bottomed cylinder, and the spherical valve element 11 is formed by pressing the ball into the recess 18 on the opposite surface. Also,
The annular guide portion 9 is formed by making the end portion of the valve operating member 12 larger in diameter and thicker than the other portions. That is, the valve actuating member 12 is provided so as to form a gap / flow passage 24 through which the fluid flows between the valve operating member 12 and the gas injecting member 4 in the region excluding the guide portion 9. The ball forming the valve element 11 of the valve actuating member 12 is not particularly limited by the material or the like, but in the present embodiment, a ball made of stainless steel is used. Then, the balls made of stainless steel are integrated by being press-fitted into the recesses 18 or by silver brazing or the like. Of course, the valve element 11 may be integrally formed of the same material as the valve actuating member 12, that is, stainless steel, by die-cast molding, shaving, or the like. The valve seat 17 at the edge of the conical shape or the opening of the gas introduction hole 3
It may have a planar shape that covers the.

At least one gas hole 7, 10 is provided in each of the peripheral walls of the valve guiding member 8 and the valve operating member 12.
Is provided and constitutes a spool valve. The pair of gas holes 7 and 10 coincide with each other when the valve actuating member 12 moves to the front end of the stroke so that the valve accommodating chamber 2 and the valve guiding member 8 communicate with each other and the valve actuating member 12 moves toward the rear end of the stroke. When moving toward each other, the gas holes 7 and 10 are displaced from each other before the valve seat 17 is closed by the valve element 11, and the gas holes 7 or 10 on the other side are closed by their peripheral surfaces to guide the valve housing chamber 2 and the valve. It is provided so as to form a positional relationship that closes communication with the inside of the member 8. Here, the gas holes 7,
It suffices that at least one valve guide member 10 and at least one valve guide member 12 are provided in each of the valve guide members 8 and 12, but it is preferable to arrange a plurality of them 10 in the circumferential direction. For example, FIG. 1 shows a case where four gas holes 7 and 10 are arranged at intervals of 90 degrees in the circumferential direction, but the invention is not particularly limited to this and one gas hole is provided. It is also preferable to reduce the opening area of the holes 7 and 10 and increase the number. For example, although not shown, eight holes having a symmetrical arrangement that is easy to process may be used. In these cases, even if the valve guide member and the valve actuating member are installed while being displaced in the circumferential direction, the gas holes 7 and 10 overlap at least partially, or one of the gas holes 7 and 10 overlaps, The internal flow path 22 of the valve guide member 8 and the flow path 24 of the valve accommodating chamber 2 are surely communicated with each other, and the gas introduced into the flow path 24 from the gas introduction hole 3 passes through the internal flow path 22 and the outlet 23. Can be discharged from. Of course, even if the number of gas holes 7 and 10 is not increased, if the valve operating member 12 is slidable with respect to the valve guiding member 8 but cannot rotate, for example, in the sliding direction. If a combination of extending irregularities and a combination of grooves and protrusions are provided between the two, the positional deviation of the gas holes 7 and 10 will not be a problem.

In the present embodiment, the gas injection member 4, the valve guide member 8 and the valve actuating member 12 are all circular pipes. In this case, the gas injecting member 4, the valve guiding member 8 and the valve operating member 12 can be easily manufactured only by cutting or boring, and they can be assembled simply by concentrically incorporating them. Of course, the cross-sectional shape of the gas injection member 4, the valve guiding member 8, and the valve operating member 12 is not limited to the above-mentioned circular tube shape, and may be formed in a rectangular shape, a triangular shape, or a polygonal shape of pentagon or more depending on the case. May be done. In this case, since the valve guiding member 8 and the valve operating member 12 do not shift in the circumferential direction after being assembled,
Even one gas hole 7, 10 can be surely overlapped, and the flow of gas can be blocked / opened. In some cases, only the gas injection member 4 is a tube having a circular cross section, and the valve guide member 8 and the valve actuating member 12 are formed in a rectangular shape, a triangular shape, or a polygonal shape of pentagon or more, and rotation is generated between them. May be prevented to prevent the gas holes from being displaced.

The material of the valve guide member 8, the valve actuating member 12, and the gas injection member 4 is not limited to a particular material, and may be appropriately selected as needed. For example, if all the components are made of brass, the processing becomes easy and the cost can be reduced. However, when it is assumed that there is a possibility of continuous interruption due to flashback in a short time, the valve guide member 8 and the valve operating member 12 are made of stainless steel, and the gas injection pipe 4 is made of brass. It is preferable. In this case, the valve guide member 8 and the valve operating member 12 made of stainless steel on the flashback occurrence side are more resistant to heat and stronger than brass, and therefore are less likely to be melted or damaged, and gas Since the injection member 4 is made of brass, the injection member 4 can be joined to the gas supply pipe 13 generally made of brass by welding, and the joint failure between the gas injection member 4 and the gas supply pipe 13 can be prevented.

Flashback prevention device 27 constructed as described above
According to this, at the time of gas supply, the valve operating member 12 is pushed by the supply pressure of the gas flowing in from the gas introduction hole 3 and moves forward along the valve guiding member 8 until it comes into contact with the supporting step 6. The valve actuating member 12 is constantly held in the state of being pressed against the support stage 6 because the gas supply pressure is constantly applied to the valve element 11. Then, the gas flows into the internal flow path 22 of the guide pipe 8 through the matching gas holes 7 and 10 and is discharged from the outlet 23 (see FIG. 2).

On the other hand, when a gas backflow occurs due to some cause such as clogging of the crater 16 at the gas supply destination,
The lid-like valve element 1 of the valve operating member 12 controls the pressure of the gas flowing back.
9 receives and slides the valve operating member 12 on the valve guiding member 8 toward the rear (gas introducing hole 3) (see FIG. 3). At this time, the gas holes 7 and 10 of the valve guide member 8 and the valve actuating member 12 which form the spool valve are displaced, so that the gas holes 7 and 10 are first closed by the peripheral wall surfaces of the mating member and the gas is temporarily changed. The reverse flow is blocked, and then the valve seat 17 at the edge of the gas introduction hole 3 is closed by the spherical valve element 11 at the tip of the valve operating member 12 to secondarily block the reverse flow of gas. As a result, the reverse flow of gas due to the primary cutoff is prevented even if the gas introduction hole 3 is not completely blocked by the valve actuating member 12 bouncing due to the collision repulsive force at the time of cutoff, so that the flashback phenomenon is maximized. Can be prevented as much as possible.

The flashback prevention device of the present invention having the above-described structure prevents the flashback of not only the gas cutting machine but also various gas combustion equipment such as a gas cylinder and a gas range and couplers of various gas combustion equipment. It can be applied to any place where is required, built in, or configured as an independent part and mounted on various gas combustion equipment for use. In addition, the present apparatus can also be configured as an independent coupler that connects the gas pipes with each other by providing connecting screws and connecting means at both ends of the gas injection pipe 4. Alternatively, it can be housed in a casing having a connecting function and used as a coupling.

(Embodiment 1) FIG. 4 shows a flashback prevention device 2 of the present invention.
An example of a gas cutting machine incorporating No. 7 is shown. In this gas cutting machine, a flashback preventive device 27 is mounted in the vicinity of the torch head 14 at the tip of the heating gas supply pipe 13. The flashback prevention device 27 has a recess 28 at the end of the gas supply pipe 13 connected to the torch head 14, and a large-diameter portion of the gas injection pipe 4 that forms the valve housing chamber 2 is fitted into the recess 28. . Then, the end of the gas supply pipe 13 and the end of the gas injection member 4 are aligned and joined with silver brazing. Then, the heating gas (usually a premixed gas of acetylene gas and oxygen) supplied through the gas supply pipe 13 is supplied to the mixing chamber 15 of the torch head 14 via the flashback prevention device 27. still,
Reference numeral 13 in the drawings is a heating gas supply pipe, 14 is a cutting machine torch head, 15 is a mixing chamber of the cutting machine torch head 14, 16 is a crater, and 39 is an oxygen supply pipe.

According to this gas cutter, if a heating valve is introduced into the gas supply pipe 13 by opening a control valve (not shown) for performing the cutting work, the gas flows in the gas supply pipe 13. The flashback prevention device 27 installed at the tip of the gas supply pipe 13 pushes the valve element 11 of the valve actuating member 12 blocking the gas introduction hole 3 from the gas introduction hole 3 to pass through the gas holes 7 and 10. It flows into the internal flow path 22 of the valve guiding member 8 and is smoothly supplied to the mixing chamber 15 of the torch head 14.

When the crater 16 is clogged during the gas cutting operation and the high pressure gas in the mixing chamber 15 flows back into the heating gas supply pipe 13, the high pressure gas is introduced into the valve guiding member. 8 against the gas supply pressure applied from the gas introduction hole 3 side to the valve operating member 1
While pushing back (retracting) 2, the primary cutoff due to the displacement of the gas holes 7 and 10 of the spool valve, and the valve element 1 at its tip
With the secondary shutoff that closes the valve seat 17 and the gas inflow passage 3 with 1,
Backflow gas is completely prevented from flowing back into the gas supply pipe 13. At this time, since the valve actuating member 12 rebounds due to the collision, even if the gas introducing hole 3 cannot be completely blocked by rebounding, the backflow is blocked by the temporarily closed gas holes 10 and 7. It can prevent flashback to the maximum. Moreover, since the flashback preventive device is installed at the position farthest from the body part of the worker, it is possible to prevent the human life hazard and the equipment damage caused by the flashback during the work. Furthermore, since the gas can be shut off near the crater of the torch, there is no effect of flashback on the upstream side of that, so a material with low strength can be used for the gas supply pipe 13 and the like, and the overall torch can be made lighter. it can. Moreover, if the flashback prevention device of the present invention is provided with the discharge device, the flashback can be discharged to the outside of the gas pipe when the flashback occurs, and the efficiency of use of the flashback prevention device can be further enhanced.

(Embodiment 2) FIG. 5 shows another embodiment of the gas cutting machine 30 incorporating the flashback prevention device 27 according to the present invention. This gas cutting machine 30 is provided with a flashback prevention device 27 in the heating gas supply pipe 13 in the immediate vicinity of the torch head 14 of the cutting torch, and the ignition crater 3 is provided slightly upstream thereof.
It is equipped with 1. The ignition device includes a crater 31 that forms an ignition flame 32, an electrode 33 that causes a spark / discharge in the crater 31, and a piezoelectric device 34 that applies a sufficient voltage between the electrode 33 and the crater 31. , A pipe 35 for supplying to the crater 31 an ignition fuel gas (premixed gas) in an amount capable of forming a flame of a scale that completely covers the crater 16 of the torch head 14, and the electrode 33 and the piezoelectric device 34 are electrically connected. And an electric wire 36. The ignition device uses, for example, a piezoelectric element, but is not particularly limited thereto. In the case of the present embodiment, the piezoelectric element 34 is built in the grip 38 of the gas cutting machine 30, and the piezoelectric element 34 is struck by pushing down the ignition push button 37 to cause discharge ignition between the crater 31 and the electrode 33. It is a thing. Also, crater 3
The ignition flame 32 formed by No. 1 is of a scale that completely covers the crater 16 of the torch head 14, thereby ensuring complete ignition.

According to this gas cutter 30, the flashback prevention device 27 installed in the gas supply pipe 13 in the immediate vicinity of the head torch 14 stops the flashback in the head torch 14 and reverses it in the gas supply officer 13. Gas supply pipe 1 to prevent fire
The strength required for 3 is smaller. In addition, the pipe 35 for supplying the fuel gas for ignition (premixed gas) and the electric wire 36 for discharge can be passed through the gas supply pipe 13.
Therefore, the gas cutting machine can use a light and inexpensive material (generally, such a material has low rigidity) since there is no risk of explosion in the gas supply pipe, etc. Since only two pipes, the supply pipe 27 and the heating gas supply pipe 13, can be used, the overall weight can be reduced.

The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, the flashback prevention device of the present invention can be applied to a combustion device other than a gas cutting machine, such as a gas torch, a gas range, or a premix burner. In this case, when a flashback occurs, the fuel supply can be cut off instantly, so accidents such as burner damage can be prevented, and it is also possible to use fuel with a high burning rate, that is, fuel that easily causes a flashback. Becomes In addition, a coupler (Couple) for the gas supply pipe that connects the gas cylinder to various gas appliances such as a gas stove
It is also possible to incorporate it in r) and apply it as a flashback prevention device. Further, it can be applied to prevent backflow of non-combustible gas. In this case, it is not necessary to use metal as the valve element 11, and for example, balls made of an elastomer material such as synthetic rubber can be used. preferable. In this case, the impact at the time of collision can be mitigated, the generation of noise can be reduced, and the sealing performance can be improved.

Further, in the present embodiment, one spool valve is constituted by one valve guiding member 8 and the valve operating member 12, but the present invention is not limited to this, and the valve guiding member 8 may be used in some cases. The valve operating member 12 outside the member 8 is provided with another valve operating member as a valve guiding member, and further another valve operating member is provided with this valve operating member as a valve guiding member to provide double or triple It is also possible to arrange two or more spool valves in the valve accommodating chamber 2 by arranging the spool valves. In this case,
Higher barrier property is obtained. The outermost valve actuating member, that is, the valve actuating member at the final stage, has a lid-like valve element 1 that completely closes the opening at the tip of the valve actuating member inside thereof.
9 is provided, and a spherical valve element 11 is provided on the opposite side. The valve actuating member inside the final stage valve actuating member has a tip surface so that a part of the pressure when the fluid flows backward acts directly on the lid-like valve element 19 of the final stage valve actuating member. A partial opening is provided, and the area of the closed portion around the opening is larger, smaller, or substantially the same as the area of the opening. Therefore, when backflow pressure is applied to the internal flow passage 22 of the innermost valve guiding member 8, the valve operating member 12 on the inner side slides toward the valve seat 17 of the gas injection pipe 4, and the spool valves are sequentially moved. Constituent gas holes 7,1
The valve seat 17 can be closed by the valve 11 while the 0s are closed together.

[0030]

As is apparent from the above description, according to the flashback prevention device of the present invention, the valve actuating member collides with the gas injection member at high speed due to the primary shutoff and the secondary shutoff. However, the backflow gas leakage is completely shut off. Therefore, it is possible to prevent a backfire phenomenon that occurs because the gas introduction hole cannot be completely blocked, and to prevent accidents and disasters such as equipment damage to the maximum extent.

According to the second aspect of the present invention, the gas injection member, the valve guide member and the valve actuating member can be easily manufactured only by cutting or boring, and they are simply concentrically assembled. Since it can be assembled into a unit, the manufacturing cost can be reduced.

According to the third aspect of the invention, the guide portion rattles the valve operating member while sealing the valve operating member and the gas injection member and the valve operating member and the valve guiding member, respectively. Since it can be slid without using it, the operation is smooth and there is little gas leakage due to delayed response.

Further, according to the invention as set forth in claim 4, the valve guide member and the valve actuating member made of stainless steel on the side where the flashback occurs are different from brass even if the interruption occurs continuously in a short time. Since it is strong against heat and has high strength, it is less likely to be melted or damaged. Moreover, since the gas injection member is made of brass, it is possible to use welding for joining with the gas supply pipe, which is generally made of brass, and it is possible to reduce the occurrence of joint failure and to strengthen the joint.

Further, according to the gas cutting machine of the fifth aspect of the present invention, the backflow of the fluid, that is, the flashback is stopped in the torch head to prevent the flashback from occurring in the gas supply pipe of the gas cutting machine. There is no risk of explosion in the supply pipe. Therefore, since the gas pipe does not require strength, a light and inexpensive material (generally, such a material has low rigidity) can be used for these, and the cutting torch can be made lightweight. Moreover, since the flashback prevention device is installed at the position farthest from the operator's body, it is possible to minimize the effects of accidents due to equipment damage due to flashback during gas cutting work. Can be suppressed to

Further, according to the gas pipe coupling device of the sixth aspect of the present invention, the backflow of gas can be instantaneously completely shut off when a flashback occurs, so that the safety can be enhanced.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a flashback prevention device of the present invention.

FIG. 2 is a vertical cross-sectional view showing a state of the flashback prevention device of FIG. 1 during gas supply.

FIG. 3 is a vertical cross-sectional view showing a state of the flashback preventive apparatus of FIG. 1 during reverse gas flow.

FIG. 4 is a view showing an example in which the flashback prevention device of the present invention is incorporated into a gas cutter, and is a partial cross-sectional view showing only the vicinity of the cutting torch.

FIG. 5 is a schematic view showing an example of implementation of a gas cutting machine in which the flashback prevention device of the present invention is incorporated.

[Explanation of symbols]

2 valve housing 3 gas introduction holes 4 gas injection pipe 7,10 gas holes 8 Valve guide member 9 Guide part Eleven 12 Valve operating member 13 Heating gas supply pipe 14 Cutting machine head

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Claims (6)

[Claims] 1. A valve accommodating chamber, a gas injection member having a gas introduction hole for introducing a supply gas into the chamber, and a valve seat, and a gas outlet of the gas injecting member fitted into the valve accommodating chamber. The gas guide includes a valve guide member having openings at both ends, and a valve element that is slidably inserted into the valve guide member to close an opening of the valve guide member that opens to the valve accommodating chamber and closes the valve seat. A valve operating member that slides due to a pressure difference between the inside of the introduction hole and the inside of the valve guiding member, and at least one gas hole is provided in each of the peripheral walls of the valve guiding member and the valve operating member;
When the valve operating member moves to the front end of the stroke, the gas holes are aligned with each other to communicate the valve storage chamber and the valve guiding member, and when the valve operating member moves toward the rear end of the stroke, Before the valve seat is closed with the valve element, the gas holes are displaced from each other so that the gas holes on the other side are closed by the peripheral surfaces of the other side to close the communication between the valve accommodating chamber and the valve guiding member. A backflow prevention device characterized in that 2. The gas injecting member is composed of a tube having a valve accommodating chamber and a gas introducing hole having a diameter smaller than that of the valve accommodating chamber and forming a valve seat at a boundary portion between the valve accommodating chamber and the valve inducing member. The valve actuating member slides on the valve guiding member, and is housed in the valve accommodating chamber and has an outer end fitted to the opening of the valve accommodating chamber and fixed to the gas injection member. It is characterized by comprising a pipe which is freely inserted and which has a lid-like valve element that closes an opening of the valve guiding member inside the valve housing chamber and a valve element that closes the gas introducing hole of the gas injection member. The backflow prevention device according to claim 1. 3. The valve actuating pipe is provided with an annular guide portion, which is fitted to the gas injection pipe without a gap, on the outer side of the gas hole. Backflow prevention device. 4. The backflow prevention device according to claim 1, wherein the valve guide pipe and the valve actuation pipe are made of stainless steel, and the gas injection pipe is made of brass. 5. A gas cutting machine, characterized in that the backflow prevention device according to any one of claims 1 to 4 is built in on the upstream side of a gas supply pipe in the immediate vicinity of a torch. 6. A gas pipe coupling device comprising the backflow prevention device according to any one of claims 1 to 4.