JPH0493506A - Blow pipe for flame cutting - Google Patents

Abstract

PURPOSE:To prevent backfire from occurring when the tip nozzle is pressed against a steel plate, etc., by providing one or a plurality of throttling mechanisms at a specified position in a fuel gas channel. CONSTITUTION:An acetylene channel is formed of an acetylene hose tip 11 that is connected to an acetylene hose connected to an acetylene supply device and fixed to the rear main body 3 by a cap nut 12, fuel valve 10, inner pipe 5 soldered to the rear main body 3 and front main body 6, and member that reaches the space 30 in front of a mixer nozzle 23 via a fuel channel 28 that is pierced through the front main body 6. In the hose coupling section 18 of the fuel valve 10 an orifice and filter 16 made of a sintered alloy as the throttling mechanism are fixed by an orifice screw. When the tip nozzle 41 is pressed against a steel plate as it is ignited, the gas pressure in the tip nozzle is raised by the throttling mechanism provided in the fuel gas channel, and the speed of the mixture gas jetted out from the tip nozzle becomes thereby faster, and it is faster than the combustion speed of the mixture ture gas at the tip nozzle and no backfire occurs.

Description

Detailed Description of the Invention "Industrial Field of Application" The present invention relates to a blowpipe for fusing that has a flashback prevention mechanism installed in a soft pipe, and in particular, to This invention relates to welded blowpipe or cut soft pipe equipped with a mechanism to prevent backfire that occurs when

“Prior Art” Conventionally, various measures have been taken to prevent backfire in blowpipe used for welding and cutting metals using a premixed gas of oxygen/fuel gas, but even now, backfire often occurs. Accidents caused by fire have been reported.

In order to eliminate this drawback, various proposals have been made to install devices for preventing flashback in the flow path between the blowpipe and the fuel gas supply source.

For example, the Industrial Safety and Health Regulations stipulate water seal safety devices, which supply acetylene through a check valve located below the water surface, so even if there is a backfire, the combustion waves will be dissipated by the water surface. It is configured to be blocked.

Also, Special Publication No. 33-7983 and Special Publication No. 34-722
In No. 6, the check valve is closed by the compression wave running in front of the combustion wave caused by the flashback, while the substance of the combustion wave reaches the check valve via a detour. To provide a dry safety device which prevents backfire by eliminating the time delay until the valve closes due to inertia by using the detour.

Furthermore, 15O5175 stipulates a flashback preventer as an accessory to a blowpipe for blowing. This type of flashback preventer is miniaturized so that it can be connected between the blowpipe and the acetylene hose, and is configured to prevent flashback by cooling and extinguishing combustion waves using a built-in sintered metal. There is.

``Technical Problems to be Solved by the Invention'' However, in the water-sealing safety device in the prior art, it is difficult to prepare each acetylene container because ice is used, and it is difficult to prepare it for each acetylene container. It is simply installed at the toe and connected to the blowpipe via a rubber hose.

Furthermore, dry safety equipment has a complicated structure, requires periodic maintenance and inspection, and is large and expensive as a whole, so it is only installed in an acetylene container.

The flashback preventer specified in 15O5175 is small and can be attached to a hand-held blowpipe because it does not give a sense of weight, but it is not necessary due to its complicated structure. Maintenance inspections are essential;
Furthermore, it has not seen widespread use, perhaps because the expected effects have not been evaluated in comparison to the price.

In view of the shortcomings of the prior art, the present invention avoids a complicated structure by substantially employing no mechanical moving parts, and is particularly designed to be compact and lightweight so that it can be incorporated into a hand-held soft tube, and to accurately and reliably operate the system. It is an object of the present invention to provide a blowpipe for blowing which is equipped with a backfire prevention mechanism for blowing sound, which does not deteriorate in accuracy over time and does not require maintenance inspection.

"Technical Means for Solving the Problems" The present invention provides a fuel gas passage at a predetermined location so that when the tip of the crater is brought as close as possible to the workpiece, the pressure of the mixed gas in the crater increases. Alternatively, the present invention proposes a blowpipe for fusing, which is characterized by being provided with a plurality of ridge mechanisms.

More specifically, (a) since the blowpipe for fusing is a blowpipe having a mixing part for mixing oxygen and fuel gas, the throttle mechanism is provided in the fuel gas passage located close to the mixing part; Since the blowpipe has a fuel valve that controls the opening and closing of the fuel gas supplied to the oxygen/fuel gas mixing section, the throttle mechanism is provided upstream of the valve body of the fuel valve. Furthermore, c) a blowpipe for melt cutting is proposed, characterized in that the throttle mechanism is provided inside the hose port attached to the inlet side of the fuel valve.

Note that the blowpipe for fusing is not limited to a soft pipe for welding and a blowpipe for cutting, but also includes a hand-held blowpipe such as a heating blowpipe, a scarfing soft pipe, a gouging soft pipe, and a blowpipe mounted on a machine.

Further, in the embodiments described later, an oxygen/acetylene flame is used as the premix length, but the fuel gas of the present invention is not limited to acetylene, and for example, LP gas, ethylene, hydrogen, etc. may be used.

"Operation" According to this technical means, when the crater is pressed against the iron plate with the ignition still lit, the gas pressure inside the crater increases due to the throttle mechanism provided in the fuel gas passage, and the mixed gas flows out from the crater. The speed of ejection becomes faster than the combustion speed of the mixed gas at the crater, and flashback does not occur. Following the route, the flame blows out at point d along the way, making it possible to prevent backfire.7 In addition, if the orifice is equipped with a throttle mechanism in a hose joint, etc., there will be no deterioration over time, and it will last for a long time. This allows the flashback prevention effect to be maintained.

Another point that may require maintenance is the clogging of one orifice with dust, which can be easily eliminated by installing a filter.

rEmbodiment J Hereinafter, embodiments of the present invention will be described in detail by way of example based on the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. Not too much.

FIG. 1 is a sectional view of a hand-held blowpipe to which the present invention is applied, and in the same figure, l is an oxygen hose port connected to an oxygen hose (not shown), which is fixed to the rear body 3 of the blowpipe by a cap nut 2. be done. The oxygen passage passes through an internal pipe 4 that is brazed to the rear body 3 and the front body 6 to prevent leakage, and an oxygen passage 27 drilled in the front body 6, and then the needle valve rod 22 connects to the back of the mixer nozzle 23. It is formed by a member corresponding to the space 29 in contact with the space 29.

On the other hand, the acetylene passage is connected to an acetylene hose (not shown) connected to an acetylene supply device, and is fixed to the rear main body 3 with a cap nut 2.
The space 3 in front of the mixer nozzle 23 passes through the internal vibe 5 which is brazed to the rear body 3 and front body 6 to prevent leakage, and the fuel passage 28 drilled in the front body 6.
It is formed by members scattered at 0.

In addition, 7 is brazed to the rear main body 3 and the front main body 6,
It is a grip pipe that the worker holds the blowpipe.

Furthermore, the mixed gas passage has a throat 31 cut inside.
and an enlarged part 32, a mixing pipe 24 screwed onto the front main body 6 with a cap nut 25, a mixed gas pipe 26 whose other end is brazed to the crater compound to prevent leakage, and a crater 41 via the crater stand 40. It is formed by members corresponding to the boat 42 of.

According to this mechanism, the supply pressures of oxygen and acetylene are adjusted to about 3 to 6 kgf/cm2 (hereinafter referred to as absolute pressure) and 1.3 to 1.6 kgf/cm2, respectively.
When the fuel is supplied to the blowpipe via a rubber hose, the fuel valve 10 and the mixer valve 20 are opened as appropriate, and the fuel is ignited at the tip of the nozzle 41, an oxygen/acetylene premixed flame is formed at the nozzle 41.

The fuel valve lO and the mixer valve 20 are each operated by a knob 1.
3 or the knob 21, the valve stem 14 or the needle valve stem 22 spirally moves, and the respective gas flow rates (mixing ratios) can be adjusted.

In gas welding of steel, it is said that a flow rate ratio of about 1.1:l between oxygen and acetylene is appropriate, and the same flow rate ratio is also applied to gas cutting. Depending on the size of the diameter, 0.1 to 1
The diameter is about m”/h.

Furthermore, in FIG. 1(B), the hose joint part 1 of the fuel valve IO
An example is shown in which an orifice 15 as a throttle mechanism, which is a feature of the present invention, and a filter 16 made of a sintered alloy are fixed inside the housing 8 by an orifice screw 17.

In addition, in FIG. 1(C), as another embodiment of the throttle mechanism which is a feature of the present invention, the throttle mechanism is press-fitted with an orifice 15a (orifice diameter of about 1 mm) cut on the side connecting to the joint part 18 of the fuel valve. The hose port 11 (inner diameter 5 to 6 strokes) is shown equipped with a filter 16.

Furthermore, in FIG. 1(A), the inner diameter of the fuel passage Z8 drilled in the front body 6 may be made as thin as necessary to form the throttling mechanism.

Next, the operation of this embodiment will be explained with reference to FIG. 2.

Fig. 2 is a concept showing the form of the premix length formed in the boat when the horizontal axis is the volume ratio % of the oxygen/acetylene premix gas and the vertical axis is the flow velocity of the premix gas in the boat 42. It is a diagram. Moreover, the pressure of the premixed gas inside the crater at which the flow velocity is obtained is also plotted on the vertical axis, and the path is indicated by a broken line in the figure.

In FIG. 2, in the area marked ■, the proportion of acetylene is higher than that of oxygen, so a flame containing soot is formed on the boat. The region (■) is the premixed length region where welding and cutting work is performed, the region (T) is the region where no flame is formed, and at the boundary between the mouth and the region M, the flame often blows or the flame floats up from the boat. can be seen. Region (2) is the flashback region in question, and it can be seen that flashback occurs when the flow velocity of the premixed gas is low. It is expected that the speed will be highest when the S combination ratio is a chemically equivalent mixing ratio (acetylene: oxygen = 1: 2.5 = 28.6: 71.4), but in reality the concentration of acetylene is somewhat excessive. The point (acetylene: oxygen = 35
: Reaches maximum speed at 65).

The fact that the flashback region (■) is in a region where the flow velocity of the mixed gas is low and the flow velocity increases greatly in a composition where the combustion reaction of the mixed gas is fast is due to the flow velocity of the mixed gas in the boat and the combustion speed of the mixed gas at that mixing ratio. If we understand that backfire occurs when the speed of the former outweighs the speed of the former, this is a natural conclusion.

In order to understand the flashback region (■), let's look at an example in which the fuel valve IO and mixer valve 20 are operated simultaneously and closed while keeping the mixture ratio constant. In Fig. 2, if the position of the premix head being worked on was point A, under the above conditions, the flow velocity would decrease vertically from point A, and at point b the flame would reach the flashback region ■. It penetrates inside the sound and backfires.

There are two types of flashback phenomena: a flashback occurs with a crackling sound, and then combustion continues inside the mixed gas pipe 26 from the enlarged part 32 of the mixing pipe 24 to the slow h31 (sustained flashback). In other cases, the backfire simply makes a crackling sound, but it does not continue to burn inside the mixed gas pipe (backfire in the narrow sense).The mechanisms of backfire in the narrow sense and sustained flashback are unknown. Therefore, the two are not shown separately in Figure 2, but it is certain that sustained flashback is included in the flashback region (■).

As a second example, let us consider a case in which the nozzle 41 of a blowpipe of the prior art which is not provided with the throttle mechanism of the present invention is pressed against an iron plate while the blowpipe is lit.

Since the mixer valve 20 remains open, oxygen is ejected a.
Continue to do so. As mentioned above, the supply pressure of oxygen and acetylene is 3 to 6 kgf/c+n2.1.3 to 1.6 kg, respectively.
f/cm2, so as long as the ratio between the pressure of the oxygen ejected from the mixer nozzle 23 and the pressure of the atmosphere of the ejected light is 1°89, the ejected velocity of oxygen is the speed of sound at that temperature. However, the oxygen ejected from the mixer nozzle 23 flows into the fuel passage 2 in a larger amount than that which flows into the mixed gas pipe 26.
8, through the internal pipe 5, fuel valve lO, hose port 11,
Continue to flow backwards into the acetylene hose until the pressure on both sides is equal. In other words, for a short period of time until the boat 42 is completely blocked, the pressure inside the mixed gas pipe hardly changes from the initial water column of several 10 mm, and the oxygen concentration increases without increasing the pressure inside the crater. Move in direction Xτ,
On the way, it backfires at point C (see Figure 2).

As a final example, let us consider a case in which the blowpipe for melt cutting equipped with the throttling mechanism of the present invention is pressed against a steel plate with the nozzle 41 kept ignited.

The pressure inside the mixed gas pipe is reduced from the initial water column of 10 mm (oxygen supply pressure) because the throttle mechanism prevents backflow.
/1.89. During a short period of time until the boat 42 is completely closed, the pressure inside the crater increases linearly along the line X in FIG. In response to the rising pressure, the speed of the mixed gas discharged from the boat 42 also increases, and the oxygen concentration also rises, following the r line in Figure 2, causing the boat 42 to become blocked. , it reaches point D where the flow velocity becomes zero. On the way, the flame passes through the blow line at point d and is extinguished.

In this way, by providing the throttle mechanism, the path in Figure 2 transitions in a direction away from the flashback area ■.
It is possible to provide a blowpipe that is safer than a blowpipe for fusing without equipment.

Note that the throttle mechanism is located in the space 30 at the front of the mixer nozzle 23.
It is expected that the closer it is to , the steeper the pressure in the mixed gas pipe 26 (flow velocity in the boat) will rise. Therefore, if the fuel passage 28 itself is used as a throttling mechanism, a favorable effect can be obtained (see FIG. 1).

However, the hole diameter of the fuel passage 28 is determined at the design and manufacturing stage, and a crater larger than the expected boat diameter cannot be used. From this point of view, it is a preferable solution to provide a throttling mechanism in the hose port 11 or in the joint part 18 of the fuel valve IO. In particular, if the hose port is provided with a throttle mechanism, even when changing ports with greatly different diameters on the boat 42, the hose ports 11 with various orifices 15a corresponding to the respective flow rates can be used. You can choose from and respond accordingly.

Returning now to FIG. 2, let's consider the ideal form of the throttling mechanism with reference to the path T taken by the pre-mixing head of the present invention to extinguish the fire when the boat is blocked.

The throttle mechanism must at least satisfy the maximum flow rate according to the diameter of the crater.

Furthermore, even without undue restrictions, the gradient of increase in the flow velocity (pressure in the mixed gas pipe 26) in the boat when the boat 42 is closed is at least equal to the gradient of the tangent at the five points in the flashback region (2). If they are equal, I am satisfied.

In other words, the mixing ratio of the premix length used in the blowpipe for blowing is approximately 1.
:1, and in Figure 2, the flame working point A is on the clove line and its upward extension, and the curvature is an upwardly convex curve from the 5 points of the backfire area ■ to the top. , if the above slope condition is satisfied, the path of the mixed flame will not pass through the flashback region (2), but will be blown out at point d on the way to extinguish the flame. In other words, it is possible to provide a soft pipe that does not cause backfire.

Note that 15O5172 stipulates a method for testing the flashback resistance of soft pipes by a method of pressing the tip of the soft pipe. That is, four grooves are dug on the surface of a copper plate, and a lit tinder is pressed and slid over the grooves. In one test, it will be completely blocked 5 times and partially blocked 4 times when passing through the 4 grooves, and this test will be performed 5 times in a row in 1 minute, that is, the crater will be blocked for 1 minute. 5X5=2
The 0 pass/fail criterion of 5 complete occlusions and 5×4 = 20 partial occlusions states that this test must not result in sustained flashback. However, the flame conditions are
Based on the flow rate specified by the supplier.

The following table shows the results of a test conducted on two arbitrarily selected similar nozzles by replacing the hose port 11 with an orifice with a diameter of 1°0 mm with a normal hose port.

However, in the table, "oxygen" means "acetylene", "ace" means acetylene, and "pressure" means gauge pressure.

Although there are only a few cases, orifices have been found to be effective in preventing (sustained) backfire.

``Effects'' As described above, according to the present invention, since the throttle mechanism is provided inside the soft pipe or at the hose mouth attached to the soft pipe, the nozzle can be pressed against an iron plate etc. without any special preparation as a device. It is possible to provide a soft pipe that can prevent backfire when the pipe is exposed to water.

By using an orifice as the throttle mechanism, it is possible to provide a soft pipe that prevents backfire without degrading accuracy over time.

Furthermore, with multiple cut soft pipes mounted on a machine, even if the iron plate being cut has irregularities due to thermal distortion, etc., there is no need to worry about backfires caused by the crater hitting the iron plate. A soft tube may be provided.

It has various effects such as

[Brief explanation of the drawing]

1(A), 1(B), and 1(C) are front views showing the structure of the present invention, FIG. 1(A) is a sectional view showing the overall structure, and FIG.
) (C) is a cross-sectional view of the main parts showing the inside of the fuel valve joint and hose port according to this embodiment, and FIG. FIG. 3 is a diagram showing the state of the flame and the effect of the present invention when the flow velocity of the mixed gas in the boat of the crater (and the pressure of the mixed gas inside the crater) is measured. Patent applicant: Tanaka Seisakusho Co., Ltd.

Claims (1)

[Claims] 1) One or more throttling mechanisms are provided at predetermined locations in the fuel gas passage so that the gas pressure within the crater increases when the tip of the crater is brought as close as possible to the workpiece. 2) A blowpipe for fusing, characterized in that the blowpipe for fusing has a mixing part for mixing oxygen and fuel gas, characterized in that a throttle mechanism is provided in the fuel gas passage located close to the mixing part. 3) A blowpipe for melt cutting having a fuel valve that controls opening and closing of fuel gas supplied to an oxygen/fuel gas mixing section, characterized in that a throttle mechanism is provided on the upstream side of the valve body of the fuel valve. 4) A blowpipe for fusing that has a fuel valve that controls the opening and closing of the fuel gas supplied to the oxygen/fuel gas mixing section, characterized in that a throttle mechanism is provided inside the hose port attached to the inlet side of the fuel valve. Blowpipe for fusing