US3019732A

US3019732A - Electrical primers

Info

Publication number: US3019732A
Application number: US768634A
Authority: US
Inventors: Kaspaul Alfred
Original assignee: Brevets Aero Mecaniques SA
Current assignee: Brevets Aero Mecaniques SA
Priority date: 1957-10-29
Filing date: 1958-10-21
Publication date: 1962-02-06
Anticipated expiration: 1979-02-06
Also published as: FR1213110A; CH355379A; GB862987A; DE1115629B; LU35542A1

Description

Feb. 6, 1962 A. KASPAUL 3,019,732

ELECTRICAL PRIMERS Filed Oct. 21, 1958 Patented Feb 6, 1&652

The present invention relates to electrical primers and it is more especially, but not exclusively, concerned with primers for setting oii a propelling charge or bursting charge.

The chief object of this invention is to provide a primer device of this le'nd which is better adapted to meet the requirements of practice than those used up to the present time and, in particular, which is easier to be checked up and less sensitive to stray currents.

A primer device according to this invention includes a sensitive charge and two electrodes adapted to be connected with the two terminals respectively of a source of electric voltage and it is characterized by the fact of interposing, between these electrodes and in contact with said charge, a body or" a semi-conductor material, said body being so chosen and dimensioned that the flow of current therethrough produces therein a spark capable of igniting said charge.

The term semi-conductor material is used in the present application to designate a solid body having a crystallized structure, which is an insulator at temperatures close to the absolute zero but which, at higher temperatures, either has an electronic conductivity that can be easily detected or acquires such a conductivity under the effect of a disturbance of its ideal crystallized structure, or again can be made conductive, for instance when it is subjected to an external influence.

These semi-conductor materials are characterized in that at least within some ranges of temperature their resistance decreases when the temperature rises, in opposition to what takes place in the case of metallic conductors.

Preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawing, given merely by way of example and in which:

FIGS. 1 and 2 of this drawing show, in axial section, two electric primer devices made according to diiierent embodiments of the present invention.

The primer device shown by the drawing includes a source of electric voltage in the form of a condenser 1 adapted to be charged in advance.

The primer device, according to the invention, essentially includes two metal electrodes 2 and 3 adapted to be connected respectively to the two terminals of condenser 1 and, interposed between these electrodes, an element t of a semi-conductor material chosen and dimensioned in such manner that the flow of electric current from said condenser l and through said electrodes 2 and 3 produces in element 4 a spark capable of setting off a sensitive charge 5 placed in contact with said element 4.

Advantageously, according to this invention, the semiconductor is either a metalloid or an anhydride of a metalloid having a relatively low melting point and preferably a boiling point such that it can be evaporated under vacuum. For instance, this element consists of selenium (Se), germanium (Ge), vanadium pentoxide (V or silicon monoxide (SiO).

Other bodies may be used, for instance:

Silicon (Si) Silicon bioxide-or silica-($0 Silicon sesquioxide (SiO-SiO 2 Calcium silicate (CaO-SiO Cerium bioxide (CeO Cadmium sulphide (CdS) Cadmium selenide (CdSe) Antimony sesquisulphide (Sb S' Aluminum antimony (Al-Sb) Gallium antimony (Ga-Sb) Uranium bioxide (U0 Cadmium oxisulphide (CdS-CdO) Cadmium oxiselenide (CdSe-CdO) Advantageously, the semi-conductor material is in the form of a thin film or layer 4 at least a small area of which (for instance averaging a fraction of a square millimeter) has one of its faces in contact with one electrode, the other of saidfaces being in contact with the other electrode. The thickness of the layer of semiconductor material thus inserted between the electrodes will be determined experimentally in every case so as to obtain the desired result. In the particular case where the voltage supplied by the source is close to volts (capacity averaging 2 at), satisfactory results have been obtained with a thickness averaging 1 micron.

The film 4- of semi-conductor material is advantageously deposited by the known method of evaporation under a high vacuum which makes it possible to obtain a layer of accurate and regular thickness owing to the measurement of the amount of material to be evaporated and to the control of the time of action of the jets of vapour during the evaporation of the semi-conductor material.

According to one advantageous embodiment of the invention, one of the electrodes (2) is in the form of an axial rod the upper end of which has a very small area (for instance less than 0.2 mm. This electrode is supported by an insulating filler 6 (for instance of a ceramic material or a synthetic resin) suitably chosen so that layer 4 can be deposited in good condition upon its fiat upper surface which is at the same level as the top end of electrode 2. This insulating material is packed in a cylindrical sleeve 3 made of a conductor material which constitutes the second electrode. This sleeve 3 is disposed coaxially with electrode 2. In the particular case above referred to, the inner diameter of sleeve 3 was 8 mm.

Of course, means must be provided for feeding current from sleeve 3 to the portion of the upper surface of film 4 located opposite the portion of the under surface of said film 4 that is in contact with the top end of electrode 2. Such means must be such that the heat of the spark produced in film 4 between these two surface portions s transmitted directly to the primary charge 5 which Is supposed to b disposed above film t.

in the construction of FIG. 1, the whole upper surface of film 4 is covered by a thin conductor layer 7 in electric contact at least over a portion of its edges with the inner surface of sleeve 3, this layer 7 being advantagesously deposited by evaporation under a high vacuum, as above described with reference to film 4.

Advantageously, layer 7 is made of a suitable metal capable of being evaporated in a vacuum, preferably at a temperature higher than that of the semiconductor material that has been previously disposed on the insulator 6. Indium is a particularly advantageous metal to constitute layer 7, due to its relatively low melting point (156 C.) and to its high boiling point (above 1,400 C.). Furthermore, it can easily be eva-orated under a vacuum. This metal has, with respect to atmospheric agents, qualities of stability comparable to that of silver, the melting point of which is six times higher. Furthermore, indium is a ductile metal. it deposits, by evaporation, in a granular form but very adhesive to film 4.

Anyway, it is advantageous to provide, above layer 7, a ring 8 made of a conductive material which is forced into sleeve 3. This ring, which is tightly applied against layer 7, ensures a good electric contact between sleeve 3 and layer 7. The inside of said ring may constitute a housing for the primary charge which is suitably compressed.

it will be readily understood that with such an arrangement, a small central portion of film 4 is inserted between the two electrodes and the spark will thus be produced in this portion of filn1'4, which spark will pass through layer "7, if the thickness thereof is suitably chosen, and will set oil charge 5.

For practical purposes, the thickness of layer 7 may be very small. It will be chosen sufficient to permit the passage therethrough of the "current which is to produce the ignition spark in the semi-conductor material. A layer of indium having a thickness ranging from V2 micron to 1 micron gave good results. i

According to the embodiment of FIG. 2, sleeve 3 carries a finger 9 of a conductor material extending radially and the end of which is in contact with the portion of film 4 located above the upper end of electrode 2. Charge 5 is then compressed directly above film 4 and finger 9.

It Will be understood that in this case the spark that is n electrodes to complete a circuit between the two electrodes to allow an electric charge of said predetermined potential to penetrate therethrough and ignite said sensitive primary charge and to dissipate an electric charge of less than said predetermined potential.

2. An electric primer device adapted to be fired by a flow of electrical current from a source of electrical voltage comprising in combination a sensitive primary charge, two electrodes, one of said two electrodes comprising the outer metal surface of the primer device and parallel to the second of said two electrodes, said second electrode being located axially of said first electrode, a plastic insulating material disposed around said second electrode,

both electrodes adapted to be connected to a voltage source, a semi-conductive material, said material being selected from the group consisting of Se, Ge, V 0 SiO,

electric charge of sufiicient potential can penetrate the r semi-conductive material and base material and ignite produced in film '4, between the end of finger 9 and the axial electrode 2, can directly set off the primary charge 5.

The primer device above described is very simple to manufacture and it gives very constant results due, in particular, to the possibilities given by the semi-conductor materials of accurately adjusting the sensitiveness thereof.

Furthermore, such primer devices have an electrical resistance that can be easily measured, which is interesting for checking up purposes. Such a checking up can be effected by passing through the device a current under a voltage lower than the limit voltage which would produce the electric spark.

By way of example, it will be indicated that this limit voltage is only volts in the case of an indium layer 1 micron thick and of a layer of SiO-Si0 0.5 micron thick.

As a matter of fact, the initial electrical resistance of the primer device, before the explosive charge is in place, is generally high. But after said charge has been placed and compressed on film 4, the electrical resistance is greatly reduced and becomes easy to measure.

Finally, such primer devices are very little sensitive to stray currents due to static or friction electricity, which currents can be discharged by passing, without producing a spark, through the semi-conductor material.

The manufacture of such primer devices is easy, their mechanical rigidity is satisfactory and there is no difficulty in complying with the tolerances during their manufacture. e

In a general manner, while'I have, in the above description, disclosed what I deem to be practical and elficient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the'arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. An electric primer adapted to be fired by a flow of electrical current from a source of electrical voltage which comprises in combination, a sensitive primary charge adapted to be exploded by an electrical discharge of predetermined high potential, two electrodes disposed adjacent to said sensitive charge, both electrodes adapted to be connected with a source of electrical energy, a semiconductive material, said material being selected from the group consisting of Se, Ge, V 0 SiO, Si, SiO SiO-SiO CaO-SiO CeO CdS, CdSe, Sb S Al-Sb, Ga-Sb, U0 CdS-CdO, CdSe-CdO, said semi-conductive material abutting said sensitive charge and electrically coupled with said said sensitive charged primary.

3. An electrical primer device adapted to be fired by a flow of electric current from a source of electrical voltage comprising in combination a sensitive primary charge, two electrodes, said electrodes adapted to be connected to a voltage source, the first said electrode forming the outer casing of the primer device, a semi-conductor layer, said material being selected from the group consisting of Se, Ge, V 0 SiO, Si, SiO SiO-SiO CaO-SiO Ce0 CdS, CdSe,' Sb S Al-Sb, Ga-Sb, U0 CdS-CdO, CdSe-CdO, a conductive material supporting said semi-conductor layer, the combination of said semi-conductor and conductive material being attached to the periphery of said first electrode casing and located such that an electric charge of sufficient potential from the second of said two electrodes can penetrate the semi-conductive material and base material and ignite said sensitive charged primary.

4. An electrical primer device adapted to be fired by the flow of electric current from a source of electrical voltage comprising in combination a sensitive primary charge, two electrodes, said electrodes adapted to be attached to an electric voltage of predetermined potential, one of said electrodes forming the outer casing of the primer device, a semi-conductor material, said material being selected from the group consisting of Se, Ge, V 0 SiO, Si, SiO SiO-SiO CaO-SiO 0e0 CdS, CdSe, 812 8 Al-Sb, Ga-Sb, U0 CdS-CdO, CdSe-CdO, said material being attached to said first electrode and located such that an electric charge of sufiicient potential from the second of said two electrodes can penetrate the semiconductive material to ignite said sensitive charged primary, an annular conductance ring, said ring encasing said primary charge and maintaining positive electrical contact between said first electrode and said semi-conductive material.

References Cited in the file of this patent UNITED STATES PATENTS 319,627 Russell June 9, 1885 319,628 Russell June 9, 1885 2,021,661 Kisfaludy Nov. 19, 1935 2,676,117 Colbert Apr. 20, 1954 2,696,191 Sheehan Dec. 7, 1954 2,708,877 Smits May 24, 1955 2,754,757 MacLeod July 17, 1956 2,762,302 MacLeod Sept. 11, 1956 FOREIGN PATENTS 982,837 France Jan. 31, 1951

Claims

1. AN ELECTRIC PRIMER ADAPTED TO BE FIRED BY A FLOW OF ELECTRICAL CURRENT FROM A SOURCE OF ELECTRICAL VOLTAGE WHICH COMPRISES IN COMBINATION, A SENSITIVE PRIMARY CHARGE ADAPTED TO BE EXPLODED BY AN ELECTRICAL DISCHARGE OF PREDETERMINED HIGH POTENTIAL, TWO ELECTRODES DISPOSED ADJACENT TO SAID SENSITIVE CHARGE, BOTH ELECTRODES ADAPTED TO BE CONNECTED WITH A SOURCE OF ELECTRIAL ENERGY, A SEMICONDUCTIVE MATERIAL, SAID MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF SE, GE, V2O5, SIO, SI, SIO2, SIO-SIO2, CAO-SIO2, CEO2, CDS, CDSE, SB2S3, AL-SB, GA-SB, UO2, CDS-CDO, CDSE-CDO, SAID SEMI-CONDUCTIVE MATERIAL ABUTTING SAID SENSITIVE CHARGE AND ELECTRICALLY COUPLED WITH SAID ELECTRODES TO COMPLETE A CIRCUIT BETWEEN THE TWO ELECTRODES TO ALLOW AN ELECTRIC CHARGE OF SAID PREDETERMINED POTENTIAL TO PENETRATE THERETHROUGH AND IGNITE SAID SENSITIVE PRIMARY CHARGE AND TO DISSIPATE AN ELECTRIC CHARGE OF LESS THAN SAID PREDETERMINED POTENTIAL.