US2681701A - Electrical igniter - Google Patents

Description

June 1954 M. SCHLUMBERGER ELECTRICAL IGNITER Filed NOV. 19, 1949 ENTOR. MBERGER lNV SCHLU MAR iar/1, 23 S I.

7'02 f izmw. H IS ATTORNEYS.

CEL

Patented June 22, 1954 UNITED STATES OFFICE ELECTRICAL IGNITER France Application November 19, 1949, Serial No. 128,323

Claims priority, application France February 19, 1949 8 Claims.

This invention relates to devices for setting off explosive charges. lore specifically, it has to do with new and improved electrical igniters which are particularly well adapted for firin explosive charges in bore hole equipment or the like, although they are not limited to such uses.

The several types of electrical igniters employed heretofore for setting ofi explosive charges in bore hole equipment such as formation sample takers, gun pcrforators or the like have not been particularly satisfactory. Filament type igniters, for example, are usually placed in the corresponding explosive chambers and connected in the firlllg circuit before the explosive charges are put in place. This has proved to be a tedious and time consuming operation that cannot readily be accomplished in the field. Further, the delicate igniter filaments may be damaged or broken in loading or in handling prior to use so that improper operation may result. Also, the presence of the igniters in the loaded piece of equipment increases the likelihood of a dangerous premature explosion.

In an effort to overcome the above-noted disadvantages, it has been proposed to make either the charge or a detonator disposed in proximity thereto out of explosive material containin conductive particles, and to connect thedetonator or charge to the firing circuit after completion of the loading operation by means of a needle inserted thereinto through a port in the bore hole equipment; Such charges, however, are non-standard and diiiicult to manufacture in large quantities and are, therefore, expensive. Further, the igniter resistance is not constant as required for proper operation of the-better igniter networks.

One object of the invention, accordingly, is to provide new and improved electrical igniters for setting off explosive charges in bore hole equipment or the like that can be put in place after the explosive charges have been loaded into the equipment.

Another object of the invention is to provide new and improved electrical igniters of the above character that can be readily assembled in thebore hole equipment, even under field conditions.

A further object of the invention is to provide new and improved electrical igniters of the above character which include in a unitary assembly all of the elements necessary for proper ignition of an explosive charge.

Still another object of the invention is to pro vide a new and improved electrical igniter of the above character havinga given resistance which remains constant even after the igniter has-been inserted in an explosive charge.

In accordance with the invention, electrical igniter means is provided which comprises an sniter element either partly or wholly enclosed in an envelope of suiiicient strength to enable it to be forced into an explosive charge without damage to the igniter element. Preferably, the envelope is made of electrically conducting material to which one end of the igniter element is connected, its other end being connected to a conductor extending through the envelope andinsulated therefrom. The envelope may be inserted into an explosive charge in bore hole apparatus through a port therein, suitable packing material being employed to insure watertightness.

The invention may be better understood from the followin detailed description of several representative embodiments thereof, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a view in longitudinal section of electrically operated igniter means constructed according to the invention;

Fig. 2 is a view in transverse section of gun perforator apparatus equipped with electricaligniter means of the type shown in Fig. 1; and

Figs. 3 and 4 illustrate two other modified forms of electrical igniters constructed according to the invention, respectively.

In the exemplary embodiment shown in Fig. l, the igniter comprises a thin hollow tube l0, preferably made of strong conductive material such as aluminum, for example. The tube H] is provided with a sharp pointed tip H at one end thereof and a laterally extending flange i2 at its other end. The tube NJ is preferably cut slantwise at the tip I i to enable it to be forced through sturdy materials with ease. Mounted in the tube H} and insulated therefrom by suitable insulating material M is a conductor I3. A filament wire l5, preferably of known resistance, is connected between the tip it of the tube l6 and the conductor i3. By passin electric current of proper intensity between the conductor is and the tube :8, the filament it can be heated sufiiciently to ignite an explosive charge in the immediate vicinity thereof, as is well known in the art.

The igniter may be adapted to be mountedin an adapter it having external threads l'i' and a laterally extending flange la. The adapter It also has a bore !9 of sufficient diameter to accommodate the tube Hi, which communicates with a bore 2 0" of larger diameter, a shoulder 2| being formed therebetween. The tube i is adapted to be inserted through the bores 25 and I9 until the flange i2 is seated on the shoulder 2|, The tube IQ should preferably be crimped in several places to insure good elec trical contact with the adapter 16. A washer 22 of nonconductive material such as rubber, for example, may be inserted around the conductor i3 and tightly fitted into the bore 28 in the head of the adapter 26. The conductor l3 may be further covered with insulating material 23, if necessary.

By way of example, a transverse section of a gun perforator equipped with an electric igniter according to the invention is shown in Fig. 2. For a more detailed description of the perforator, reference is made to the applicants copending application Serial No. 128,386, filed November 19, 1949, for Electrical Firing System for Explosively Operated Bore Hole Tools.

Referring now to Fig. 2, the perforator comprises a long cylindrical housing 2 which is preferably fashioned from steel, containing a threaded cavity 25 into which a gun barrel 26 is adapted to be fitted. The gun barrel 25 has a gun bore 2? therein and its rear portion 28 cooperates with a cavity 29 in the housing 2 to form a chamber 33. The chamber 36 is adapted to receive an explosive charge 3;! encased in a plastic container 32. The gun bore 2'!" is adapted to receive a bullet assembly Formed in the housing 24 is a laterally extending bore 34 into which is threaded an adapter i6, gasket means 35 being inserted under the flange 3 to insure a watertight joint. Electrical energy is adapted to be supplied to the igniter by an insulated conductor 35 mounted in a groove 3? formed in the outer wall of the housing 25.

The perforator is loaded by removing the gun barrel 2B, inserting an explosive charge 3! into the chamber SE3, and replacing the gun barrel 2%. An igniter assembly of the type shown in Fig. 1 is then inserted through the bores 28 and is in the adapter it until the pointed tip it of the tube lEi pierces the explosive charge con-- tainer 3-2 and the igniting filament lies well within the explosive charge 3!. The washer 22 is forced tightly into the bore 23 in the adapter 26. The end 3% of the conductor 13 is preferably pointed and inserted through the insulation on the conductor 36 to bring it into electrical contact with the conductor 35. Since the source connectable to the conductor 36 has a grounded terminal, the conductive housing E i also being grounded, it will be understood that a firing circuit to the filament i5 is now prepared. The bullet assembly 33 may now be inserted in the gun bore 2'? whereupon the entire device is ready to be lowered into a bore hole.

The washer 22 in the adapter 16 and the gasket 35 prevent the bore hole fluid from enter-- ing the chamber 3i! through the port 35. A gasket 39 between the gun barrel 26 and the housing 2 5, and a stopper it which forms part of the bullet assembly 33 prevent fiuid from entering the chamber 38 through the main gun opening.

When the housing 2% has been lowered to the proper level in a bore hole (not shown), a current source is applied between the conductor 35 and ground. This causes the igniter filament I5 to heat up sufiiciently to set off the explosive charge 3], thereby discharging the projectile ll in the bullet assembly 33 at a high velocity from the gun bore 27.

It is assumed, of course, that part of the explosive charge 3! was forced up into the tube it! around the filament I? when the tube H] was forced into the charge 3!, so that heating of the filament l5 resulted in ignition of the charge 3|. It may be desirable, however, to coat the igniter filament i5 with a varnishor other suitable material containing particles of finely divided explosive material which will ignite when the wire 15 is heated, thus insuring more uniform and effective ignition of the charge.

If the container 32 is very thick or if the charge 3| is firmly packed, it may be desirable to employ the embodiment shown in Fig. 3, which offers more protection for the igniting filament 55. In Fig. 3, the hollow, conductive tube It) has a broad, sharp tip 42 fashioned thereon, which prevents any external pressure from being exerted on the filament 15 as the tube N3 is forced into an explosive charge. The tube It may be provided with small ridges 43 or the like to insure good electrical contact with the adapter 56. Also, an opening 64 may be formed in the tube iii to provide communication between the explosive charge and the filament l5, so that when the latter becomes heated sufficiently, the charge will be set off.

Where the explosive charge is firmly packed, the tip Q2 of the tube It may leave a hollow therein as it is forced into the charge, so that the igniter 55 may not come into contact with the charge at all. For this reason, it is preferred, in the embodiment of Fig. 3, to pack a suitable explosive material 45 around the filament 15 before the tube it is forced into the charge. Thus, when filament it? becomes heated, the material 5 will be ignited and will in turn set off the explosive charge, regardless of how firmly the latter may be packed.

in the embodiment shown in Fig. 4, the filament i5 is wholly enclosed by a tube 56 and is surrounded by explosive material 41. Thus, when the tube it is inserted in an explosive charge and current is passed through the igniter IS, the explosive material 4'! will be ignited, destroying the tube 36 and setting oif the main explosive charge. It will be observed that the filament wire 15 in Fig. 4 is well protected from exterior forces which might tend to break it. If desired, particles of conductive material which becomes heated when current is passed therethrough may be incorporated in the explosive material 4'! in Fig. 4. In such case, the filament l5 can be eliminated since the passage of current from the conductcr It to the tube 36 ignites the charge 41 which, in turn, sets oif the main explosive charge in which the tube 4% has been placed.

From the foregoing, it will be understood that the invention provides novel and highly efiective electrical igniters for setting off explosive charges in bore hole equipment, for example. By virtue of the construction outlined above, the igniters may be put in place after the explosive charges have been loaded into the equipment. Further, this can be done easily even under field conditions without damaging the igniters in any way.

It will be understood that the several illustrative embodiments disclosed herein are susceptible of numerous modifications in form and detail within the scope of the invention. The embodiments described and shown in the drawings, therefore, are not to be regarded as limiting the scope of the following claims.

I claim:

1. Electrical igniter apparatus comprising a relatively rigid housing having a pointed end, electrical igniter means or the like disposed wholly within the housing and adapted to be protected thereby, means forming an opening in said housing providing communication between said igniter means and the exterior of said housing, and electrical connections to said igniter means.

Electrical igniter apparatus comprising a relatively rigid, conducting housing having a pointed end, an electrical conductor in said housing and insulated therefrom, electrical igniter means or the like in the housing and adapted to be protected thereby, said igniter means having one terminal connected to said housing and an other terminal connected to said conductor, and explosive material in said housing and adapted to be ignited by said igniting means.

3. Electrical igniter apparatus comprising a hollow conducting tube adapted to be inserted in an explosive charge or the like and having a pointed end, an electrical conductor in said tube and insulated therefrom, electrical igniter means in said tube having one terminal connected to said tube and another terminal connected to said conductor, and means forming an aperture in said tube providing communication between said igniter means and the exterior of said tube.

4. Electrical igniter apparatus comprising a hollow conducting tube cut slantwise at one end to form a sharp point enabling said tube to be inserted into an explosive charge, an electrical conductor in said tube and insulated therefrom, and an igniting filament in said tube having one terminal connected to the tube near said one end and another terminal connected to said conductor.

5. Electrical igniter apparatus comprising a hollow conducting tube having a sharply pointed portion at one end thereof, an electrical conductor in said tube and insulated therefrom, an igniting filament in said tube having one terminal connected to the tube and another terminal connected to said conductor, means forming an opening in the side of said tube to provide communication between said igniting means and the exterior of the tube, and a body of explosive material in said tube and adapted to be ignited by said igniting means.

6. In bore hole apparatus comprising a body adapted to be lowered into a bore hole and having an explosive charge therein, the combination of means forming a bore in said body extending from said charge to the outer wall of the body, a hollow tubular housing mounted in said bore, said tubular housing having a tip portion the cross sectional area of which is forwardly diminishing to a point to facilitate insertion into said charge, electrical igniter means confined wholly within said housing in the portion thereof penetrating the charge, and an electrical connection extending from said igniter means to the outside of said body.

7. In bore hole apparatus comprising a body adapted to be lowered into a bore hole and having an explosive charge therein, the combination of means forming a bore in said body extending from said charge to the outer wall of the body, a hollow conducting tube mounted in said bore and having a shaped end for facilitating insertion into said charge, an electrical conductor in said tube and insulated therefrom, electrical igniter means in said tube in the portion thereof penetrating the charge, said igniter means having one terminal connected to said conductor and another terminal connected to the tube, and means forming an aperture in said tube providing communication between said igniter means and the explosive charge.

8. In bore hole apparatus comprising a body adapted to be lowered into a bore hole and having an explosive charge therein, the combination of means forming a bore in said body extending from said charge to the outer wall of the body, a hollow tubular adapter secured in said bore, gasket means providing a watertight joint between said adapter and the bore, a hollow, conducting tube snugly fitted in said adapter and having a pointed end penetrating said explosive charge, packing means providing a watertight joint between the adapter and said tube, an insulated conductor in said tube and extending to the outside of the body, electrical igniter means in said tube in the portion thereof penetrating the charge, said igniter means having one terminal connected to said conductor and another terminal connected to the tube, and means forming an aperture providing communication between said igniting means and the explosive charge.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 319,629 Russell June 9, 1885 389,448 Day Sept. 11, 1888 2,155,322 McCullough Apr. 18, 1939 2,216,145 Turecheck Oct. 1, 1940 2,216,151 Barnum Oct. 1, 1940 2,296,971 Zschokke Sept. 29, 1942 2,452,892 Appleton et al Nov. 2, 1948 FOREIGN PATENTS Number Country Date 502,474 France Feb. 23, 1920

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