US2164295A - Prevention of explosions and backfire in torches - Google Patents

Description

burner.

,cumulation of such deposits seriously restricts Patented June 27, 1939 rREvEN'rroN 0F PATENI OFFICE 2,164,295 EXPLOSIONS AND BACK- FIRE IN TORCHES Chester Mott, Evanston,

Cylinder Gas Company tion of Delaware IlL, assignor to National Chicago, 111., a corpora- Application July 1, 1938, Serial No. 216,881

4 Claims.

This invention relates to gas burners for heating purposes and of that type in which the acetylene or other combustible or fuel gas, and the oxygen or other combustion supporting gases are delivered under pressure to a mixing chamher and from which the mixed gases flow to the An apparatus to which my invention is particularly applicable is a type of torch delivering a sheet-like flame for the surface hardening of metals. Such an apparatus is usually provided with control valves which may be separately adjusted to regulate the relative quantities of the two gases flowing to the mixing chamber. In addition thereto, it is desirable to provide valve mechanism whereby the flow of both gases may be shut ofi instantly to extinguish the flame. As the gases in the mixing chamber and between it and the burner outlet include both the fuel gas and the oxygen, there is always the liability of an explosion or a burning in the apparatus with the resulting partial decomposition of the .acetylene and the formation of carbon deposits in the ports, the passages of the mixing chamber, and the passage leading to the burner outlet. Ac-

the flow of the gases and in some cases the carbon which has been raised to a high temperature by the explosion is caused to ignite. Such phenomenon commonly known as a back fire is objectionable for many other reasons Well known in the art. The restriction of the orifices in a flame-" hardening burner is a serious matter because in flamehardening, it is most essential that very definite quantities .of gas be passed in performing accurate. work, as otherwise, the depth of hardness or the degree of hardness may be seriously affected. Restriction of the passages by carbon deposits built up through a succession of explosions within the device makes the passages or ducts smaller and reduces the flow of the gas. Furthermore, the carbon may become very firmly embedded in the walls of the passages and therefore, difficult to remove. The passages of a flamehardening burner are ordinarily very small and any reduction in size has a very undesirable effect.

The main object of my invention is to insure against an explosion or burning of the residual mixed gases in the mixing chamber and passages when the supply of gases is shut 01?, and to thereby prevent the accumulation of carbon deposits obstructing such passages.

I accomplish this object by providing simple, easily operated and efiicient means whereby the pressure of the oxygen between the shut off mechanism and the burner outlet is reduced far more rapidly than the pressure of the acetylene so that the mixed gases will contain such an excess of acetylene or such insufficient amount of oxygen that burning, explosion, or backfiring is "5 effectively prevente In carrying out my inventionI provide means for releasing the pressure on the oxygen at the delivery side of the shut off valves at the instant that said valves close and at a point closely ad- '1 jacent to the shut off valves so that the portion of the oxygen under pressure between the shut off valves and the burner may escape without flowing to and through the mixing chamber. By the sudden release of pressure on the oxygen line 1 the mixed gas that is entrapped in the chamber between the mixer and the burner outlet is suddenly robbed of its oxygen pressure so that the mixed gases instantly become extremely rich in acetylene and poor in oxygen. Thus, the gases-20 entrapped between the mixer and the burner are not liable to explode upon the simultaneous shutting off of the gases. Furthermore, the steel or other metal being treated is notsubjected to any cutting effect. In flame-hardening the steel is at ;25 or higher than the kindling temperature and the instantaneous shutting ofi of the oxygen and the robbing of the acetylene of its oxygen supply insures against any continued supply of oxygen to the hot metal to oxidize or kindle the latter.

I do not wish to be limited to any specific construction of valve mechanism but prefer two separate valves, one for the oxygen and the other for the acetylene. These are connected so as to be operated simultaneously, easily and quickly. The oxygen valve is so constructed that it opens the oxygen pipe on the discharge side directly to the atmosphere the instant the flow from the intake side stops, whereas the acetylene valve acts merely as a shut off without opening any port to 40 V the atmosphere.

In the accompanying drawings I have illustrated anapparatus embodying my invention and adapted for use in carrying out my improved method, the valves illustrated being of the type above referred to.

in these drawings:

Figure 1 is a somewhat diagrammatic showing of a. flame-hardening burner with attached piping and valves including shut off valves for carrying out my invention;

- Figure 2 is a side elevation showing the oxygen valve;

Figure 3 is a view taken at right angles to m Figure 2, forinstance, on the line 3-3 ure 1;

Figure 4 is a central longitudinal through the acetylene valve;

Figure 5 is a central longitudinal section through the oxygen valve, the valves in Figures 4 and 5 being indicated in dotted lines in open position;

Figure 6 is a longitudinal section through another form of valve mechanism;

Figure 7 is a section on the line of Figure 6, showing the oxygen valve open;

Figure 8 is a section similar to Figure '7 but showing the oxygen valve closed;

Figure 9 is a section on the line 9-9 of Figure 6 showing the acetylene valve openxand Figure 10 is a section similar to Figure 9 but showing the acetylene valve closed.

My invention may be applied to a type of construction in which there are employed oxygen and acetylene supply pipes l and H with the usual type of adjusting valves l2 and I3 and connected by hose or flexible conduits l4 and to a handle l6 including a mixing chamber, and from which the mixed gases are delivered through a torch tip ll having a plate l8 with passages therethrough for forming the sheet-like flame. Such a torch tip may be similar to that disclosed in co-pending application, Serial No. 200,646 filed April 7, 1938.

The supply pipes l0 and II, or in some cases the conduits H and I5, are provided with the shut off valves constructed to carry out my invention. Simple forms of valves are shown in Figures 4 and 5. The acetylene pipe is shown as provided with a transverse partition wall IS with annular series of ports 20 and 2| through the peripheral wall and upon opposite sides of the partition. Encircling the pipe is a sleeve 22 having a chamber 23 which, when the valve is moved from the position shown in solid lines in Figure 4 to the position shown in dotted lines, will register with both series of ports 20 and 2| so that the acetylene may flow through the ports 20, the chamber 23, and the ports 2| to the burner. The sleeve may be easily moved axially along the pipe and leakage of acetylene to the atmosphere may be prevented by suitable gaskets 24 and 25 at opposite ends of the chamber and pressed against the ends as well as against the surface of the pipe ID by a coil spring 25. In order to prevent the uncovering of the ports 2| when the valve is in closed position the valve sleeve may have an auxiliary chamber 21 containing a gasket or packing 28 and a spring abutting a flange 29 and said gasket or packing. Thus, when the valve is moved to the position shown in solid lines so that the ports 20 register with the chamber 23 between the packings 24 and 25, the ports 2| will register with the chamber 21 between the packings 25 and 28.

The oxygen valve shown in Figure 5 may be similar in most respects to the acetylene valve shown in Figure 4 except that the auxiliary chamber 21 and packing 28 are omitted. In the construction shown in Figure 5 the pipe I I has a partition |9a and the valve sleeve 22a has a chamber 23a with gaskets 24a and 25a at opposite ends and pressed apart by the coil spring 28a. As the parts 21 and 28 are omitted from the oxygen valve, it will be apparent that when the valve is moved to open position as shown in dotted lines, there may be a free flow of oxygen through the ports 20a, chamber 23a and ports 2|a, but when moved to the position shown in solid lines there of Fig section is no outlet from the chamber 23a. and the oxygen in the pipe H at the discharge side may freely escape through the ports 2|a directly to the atmosphere.

The two valves are mounted closely adjacent to each other and are interconnected so that they may be simultaneously moved to open or shut off position. Merely as an example of such inter connection, each of the valve sleeves 22 and 22a is provided with an annular groove 39 on the periphery and intermediate of the ends, and a lever 30 pivoted on a pin 3| in a bracket 32 has connecting parts engaging in these grooves so that as the lever is moved the valves are moved axially, simultaneously, and to the same extent. Although the lever 30 may be so mounted and pivoted in such position that it may have parts directly engaging in said grooves, I have shown a mechanism which permits the independent movement of the two valves in case that should be desirable under any circumstances. This interconnecting means includes a pair of levers 33 pivoted on pins 34 in the bracket 32. The central lever 30 has two pairs of arms 35, 36, one pair on each side and engaging opposite sides of the levers 33. Thus, by moving the lever 30 in either direction the two levers 33 are simultaneously moved about their own pivots and in the same direction. By means of an adjusting screw 31 for each pair of layers the initial setting of either lever 33 may be adjusted in respect to the other so that the two valves will shut off the oxygen and acetylene simultaneously or may shut off the oxygen slightly in advance of the shutting off of the acetylene. In any event the adjustment should be such that when the oxygen and acetylene are both shut ofl the ports 2|a of the oxygen pipe will be open to the atmosphere.

When the torch is in normal operation with the valves 22 and 22a permitting free flow of the gases to the mixing chamber and thence to the burner, both the oxygen and the acetylene will be under pressure in the passages connecting the valves to the burner and in the desired proportion for forming the combustible or explosive mixture in the mixing chamber. Normally the flame cannot recede from the burner outlet to the mixing chamber due to the velocity of flow of the gases and the small size of the passages of the burner. When the flow of both gases is shut off by the valves 22 and 22a, and if the oxygen ports Zla were not open, there would be a continued flow of gas from the burner until the pressure between the valves and the burner had dropped to that of the atmosphere. As the pressure drops and the velocity reduces, the flame might travel back from the burner outlet to the mixing chamber and burn or explode therein and form the undesirable carbon deposits. By opening the oxygen ports 2|a in accordance with my invention and at the instant the flow of the two gases is shut off at the shut off valves, the oxygen in the pipe I and the hose l5 at the delivery side can escape more rapidly through the ports I la than through the mixing chamber and burner outlet and therefore, the pressure in this section of the oxygen conduit will drop to atmospheric pressure almost instantly, but the acetyl -rie pressure drops only by the escape of excess acetylene through the mixing chamber and the burner. Therefore, due to the fact that the oxygen pressure is reduced from the rear end while the acetylene pressure can drop only by escape from the burner, there will automatically result a mixture in the mixing chamber and from it to the burner outlet which is far richer in acetylene than the normal mixture, and due to the insutliciency of the oxygen, this mixture is not explosive'and the flame cannot recede from the burner outlet to the mixing chamber to cause any backfire, explosion, or carbon deposit. Upon opening the shut off valves for the simultaneous delivery of oxygen and acetylene to the mixing chamber and the relighting of the gas at the burner outlet, it will be noted that there is no liability of backfiring or explosion because there was an excess of acetylene in the mixing chamber and the first gas which escapes from the burner outlet and which is lighted will be primarily acetylene and the gas mixture will not reach explosive propor-.

tions until the mixture rich in acetylene has been swept out and by which time the pressure and velocity has been built up to the point where the flame will not flash back through the passages to the mixing chamber.

The valve mechanism shown is simple, inexpensive to manufacture, and easy to operate, but it will be obvious that other types of valve mechanism might be employed which would operate to open the oxygen pipe at the discharge side and at a point close to the shut oif valve when the flow of both gases is instantly shut off. As previously noted the separate valve levers 33 and other parts may be omitted and the lever 30 so mounted as to directly connect with both valve sleeves. Likewise, means other than a lever may be employed for effecting the simultaneous operation of the two valve sleeves.

In Figures 6 to lu'inclusive another form of valve mechanism is shown. The oxygen pipe II and the acetylene pipe III are provided with a common valve plug 40 which has a main passage 4| in the acetylene pipe and a. separate mainpassage 42 in the oxygen pipe. The portion of the valve plug in the oxygen pipe has an auxiliary passage 43 and the valve casing has an outlet port 44 to the atmosphere. When the valve is in the position illustrated in Figures 6, 7, and 9, the oxygen and acetylene may flow freely to the torch and the passage 43 will be out of registry with the outlet port 44. By rotating the valve clockwise through the pasage 43 will be brought into registry with the oxygen passage on the delivery side of the valve and the main passage 42 will be brought into registry with the outlet port 44 so that the oxygen pressure in the pipe H on the delivery side may escape as indicated by the arrows in Figure 8.

In these figures the valve mechanism is shown somewhat diagrammatically, as obviously in commercial practice a suitable valve casing separate from the conduits would be provided, and the valve plug might be made of two separate sections, one for the oxygen and the other for the acetylene, and connected so that the two sections will rotate simultaneously.

Various other types of valve mechanism may be employed for carrying out my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. 'The combination with a fuel gas burner of conduits for the delivery of fuel gas and combustion supporting gas, a mixing chamber receiving gas from both conduits and delivering the mixture to the burner, and shut off valve mechanism in said conduits, the combustion supporting gas conduit having a port to the atmosphere at a point adjacent to and on the delivery side of the point of shut oil", and means operable to simultaneously stop the flow of gases through both conduits and open said port.

2. The combination with a flame-hardening burner, of an oxygen supply pipe, an acetylene supply pipe, a pair of quick operating valves in said pipes for controlling flow of gas there through, the oxygen supply pipe having ports at the delivery side of the oxygen valve and connecting the oxygen pipe between the burner and the valve to the atmosphere when the supply of oxygen is shut off.

3. The combination with an oxy-acetylene burner of an oxygen supply pipe, an acetylene supply pipe, separate valves in said pipes, the acetylene valve being adapted to permit or prevent the fiow of acetylene to the burner and the oxygen valve being adapted to permit or prevent the flow of oxygen to the burner and to permit escape of oxygen from the delivery :side ofthe valve when the supply is shut off, and means for operating said valves simultaneously.

4. The combination with a flame-hardening burner of an oxygen supply pipe, an acetylene supply pipe, a pair of valves in said pipes for permitting or preventing flow to the burner, and means for operating said valves simultaneously to shut off supply through both pipes and substantially simultaneously open the oxygen pipe at the discharge side to permit escape of oxygen between said valve and the burner.

CHESTER MOTT.

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