Electric Detonator Element

Abstract

An electric detonator element in which an incandescent bridge, intended to set off a charge, is formed on one side of a non-conductive carrier which is inserted into a conductive housing and rests on its side opposite the bridge, against a center pole electrically connected with the housing by way of the bridge. The present invention relates to an electric detonator element with an electrically conductive housing and a pole piece arranged therein and accessible from the outside, which pole piece is connected with the housing in an electrically conductive manner by way of an incandescent or heater bridge, as well as with an ignitable charge accommodated in the housing and being in operative connection with the incandescent or heater bridge. In such detonator elements, it is necessary to so construct the electrically conductive connection between the outer pole and the center pole that, on the one hand, the manufacturing expenditures thereof are as low as possible with a view toward a series or mass production and, on the other hand, it is nevertheless assured that the resistance of the electric circuit exhibits only as minor deviations as possible. It is known in the prior art to construct the incandescent or glow bridge as an extremely thin and very short metallic wire which is connected with the housing or the pole piece, respectively, by soldering or welding. However, this procedure entails the disadvantage that the manufacturing expense is relatively high since the dimensions of the individual components are very small, and accordingly a large amount of skill and patience is required to carry out completely satisfactorily and flawlessly the welded or soldered connections of the incandescent or heater bridge with the poles. The present invention is based on the aim to simplify the manufacture of the electrical connection between the housing and the pole piece, constructed as a glow or incandescent bridge, and thus simultaneously to make the same also more reliable. The underlying problem is solved, in accordance with the present invention, in that the glow or incandescent bridge is formed on the side opposite the pole, of an electrically non-conductive carrier element abutting at the pole piece and together with the same held in the housing by form-locking and/or frictional contact. Such a construction makes it possible to apply the glow or incandescent bridge, independently of the housing and of the pole piece, onto an element which, as compared to the incandescent bridge, is relatively large and correspondingly more easy to handle whereby this element, like the pole piece, can then be inserted simply into the housing and, with a corresponding shape of the housing, can be maintained in secure contact connection with the housing as well as with the pole piece so that the electrically conductive connection between the housing and the pole piece can be established by way of the glow or incandescent bridge by simple contact connections, and accordingly the otherwise required, time-consuming welding or soldering operations, which frequently are carried out not completely satisfactorily, may be completely dispensed with. In this connection, the housing can be formed, for example, as a sleeve open at both ends which, after insertion of the pole piece and of the carrier element, is together, crimped or flanged over at the ends in such a manner that the individual parts are pressed against one another to a sufficiently great extent. The construction of the contact connection between the pole piece and one end of the glow or incandescent bridge thereby becomes particularly simple and reliable if, according to an appropriate refinement of the present invention, one end of the glow or incandescent bridge is extended possibly with an increasing cross section, to the side of the carrier element facing the pole piece. Of course, one must make sure that this end of the glow or incandescent bridge extended to the pole piece, does not come into electrically conductive contact with the housing, since otherwise the flow or incandescent bridge would be connected at both ends with the housing, i.e., would be short-circuited. This prerequisite can be advantageously met according to a further proposal of the present invention by providing the carrier element, made from an electrically non-conductive material, with a bore disposed, for example, in the center thereof, through which an end of the glow or incandescent bridge is then extended to the side of the carrier element facing the pole piece. Another improvement of the contact connection between the ends of the glow or incandescent bridge and the outer pole or center pole, respectively, can be achieved in accordance with another proposal of the present invention by enlarging the surface area of the glow or incandescent bridge at the ends. The same effect is also obtained if the housing, on the end facing the glow or incandescent bridge, is formed with a shoulder or offset, instead of being simply pressed or flanged over against the glow or incandescent bridge, against which the carrier element can rest in flush contact with one end of the glow or incandescent bridge. In this connection, it has been found to be advantageous for manufacturing reasons to make this shoulder or offset in the shape of a sleeve of an electrically conductive material, which contains at least a portion of the ignitable charge, is inserted into the housing, and is electrically conductively connected with this housing by form-locking and/or frictional contact. The glow or incandescent bridge itself can be formed in a conventional manner, for example, as an extremely thin metallic wire which is held on the carrier element, for instance, by means of an adhesive or bonding material. However, an essentially more economical and yet more reliable manufacture of the glow or incandescent bridge and the application thereof to the carrier element is possible if according to a further suggestion of the present invention, the glow or incandescent bridge is applied to the carrier element in accordance with the conventional methods for the manufacture of printed electric circuits. This can be done, for example, by applying a metallic foil, possible with the aid of an adhesive, onto a carrier material with the use of pressure and heat. Examples for the metallic foil material are, depending on the requirements to be met by the glow or incandescent bridge, for example, copper, silver, gold, nickel, chrome nickel, or also Constantan (an alloy consisting of about 60 percent copper and of about 40 percent nickel), whereas for the carrier material can be used, for example, a molded laminated plastic which consists of cellulose paper, cotton fabric, glass fiber fabric, synthetic fiber fabric, or the like impregnated with a synthetic resin on the basis of phenol, epoxy, or an unsaturated polyester of any known type. Thereafter, the metallic foil is masked with an etch-resistant coating such as varnish or lacquer corresponding to the intended construction of the glow or incandescent bridge, thereupon the metallic foil is removed in the unmasked areas by means of an etching acid, and finally the etch-resistant varnish or lacquer is removed, so that there remains on the molded laminated plastic only a metallic foil pattern corresponding to the desired configuration of the glow or incandescent bridge. Instead of applying first a metallic foil onto the molded laminated plastic from which the desired shape of the glow or incandescent bridge is then etched out, this glow or incandescent bridge could also be applied directly in the desired configuration to the carrier element by chemical and/or galvanic process, for example according to the "Noviganth" process of Schering A.G., Berlin, or the "Nibodur" process of Farbenfabriken Bayer A.G., Leverkusen. Aside from the fact that these known processes for the manufacture of printed electric circuits enable the simultaneous manufacture of a very large number of glow or incandescent bridges, these processes entail the additional advantage that the shape of the glow or incandescent bridge and of the ends thereof formed as contact surfaces can be adapted to the respective requirements in a particularly simple manner, i.e., the glow or incandescent bridge can be constructed, for example, rectilinearly or spirally shaped and the contact surfaces can be constructed, for example, approximately in the shape of a circular disk, of a ring or also of an annular segment.

Description

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, one embodiment in accordance with the present invention, and wherein

FIG. 1 is a plan view on the carrier element in accordance with the present invention and having a glow or incandescent bridge with an enlarged surface area at the ends thereof;

FIG. 2 is a cross sectional view of the carrier element, taken along line A--A of FIG. 1; and

FIG. 3 is a longitudinal axial cross sectional view through an electric detonator of center pole construction with a carrier element inserted therein according to the present invention.

Referring now to the drawing, wherein like reference numerals are used throughout the various view to designate like parts, the circular-disk-shaped carrier element 1 illustrated in FIGS. 1 and 2 is provided on the topside with a radially extending metallic web of a small thickness and width, forming the glow or incandescent bridge 2, which is enlarged at the outer end thereof into an annular contact surface 3 and whose inner end is extended through a central bore 4 to the circular-disk-shaped contact surface 5 formed on the bottomside of the carrier element 1. The connection between the inwardly disposed end of the heater or incandescent bridge 2 and the lower contact surface 5 can thereby be either so constructed that the entire cross section of the bore 4 is filled out, in that for example, a solid rivet is inserted into the bore 4, or -- as indicated in dashed lines--in that this connection is limited only to a thin layer along the wall of the bore, which can, for example, be applied simultaneously with the other metallic surfaces by galvanic means.

In the electric detonator illustrated in FIG. 3, the carrier element 1 is inserted with the lower contact surface 5 abutting against pole piece 6 serving as center pole, into a cylindrical housing 7 forming the outer pole whereby the pole piece 6 is supported against the bottom 9 of the housing by way of a cup-shaped electrical insulation 8 and is accessible from the outside by way of central apertures 10, 11 formed in this housing bottom 9 as well as in the insulation 8. A metallic cylindrical sleeve 12 is placed over the carrier element 1, the sleeve, on the one hand, is in electrically conductive connection with the contact surface 3 of the carrier element 1 and, on the other hand, with the housing 7, and is formed, on the end opposite the carrier element 1, with an external annular chamfer 13 against which is pressed the housing after the insertion of the sleeve 12. The ignitable composition or charge 14 is arranged in the sleeve 12 which for the purpose of a completely satisfactory and flawless ignition, should touch the heater or incandescent bridge 2 to the greatest extent possible. This is applicable, in particular, when the conditions are such that the glow or incandescent bridge 2, is brought only to incandescence, but not to an explosive vaporization as a result of the electrical voltage applied to the pole piece 6 and to the housing 7.

While we have shown and described only one embodiment in accordance with the present invention, it is understood that the same is susceptible of numerous changes and modifications as known to a person skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are within the scope of those skilled in the art.

Claims

We claim:

1. An electric detonator element having an electrically conductive housing with a pole piece arranged therein so as to be accessible from the outside, which pole piece is electrically connected with the housing by way of incandescent bridge means, and an ignitable charge accommodated in the housing in operative contact with the bridge means, characterized in that the bridge means is formed on one uniformly planar side of an electrically nonconductive carrier means facing opposite the pole piece, the other side of said carrier means resting against the pole piece and together with said pole piece being retained in the housing, one end of said bridge means being extended to said other side of said carrier means through a bore formed in the carrier means and the other end of said bridge means being connected to an annular conductive member surrounding said bridge means and electrically contacting said housing, said bridge means and said annular conductive member being contiguous plated layers of substantially the same thickness.

2. An electric detonator element according to claim 1 characterized in that said carrier means, together with said pole piece, is retained in said housing by form-locking means.

3. An electric detonator element according to claim 1, characterized in that said carrier means, together with said pole piece, is retained in said housing by frictional contact means.

4. An electric detonator element according to claim 1, characterized in that a shoulder is formed in the housing on the side of said carrier means opposite said pole piece by a sleeve means of an electrically conductive material containing at least a portion of the ignitable charge, said sleeve means being inserted into the housing and being connected with the housing in an electrically conductive manner.

5. An electric detonator element according to claim 4, characterized in that the bridge means is applied to the carrier means in the manner of a printed electric circuit.

6. An electric detonator element according to claim 1, characterized in that the bridge means is applied to the carrier means in the manner of a printed electric circuit.

7. In an electric detonator having a conductive housing, a pole piece insulatedly positioned within said housing so as to protrude from one end thereof, a generally annular conductive sleeve positioned in the other end of said housing in conductive contact therewith and an ignitable charge disposed within said annular sleeve, the improvement comprising incandescent bridge means connecting said pole piece to said conductive sleeve including an electrically non-conductive carrier having a hole therethrough, first and second concentric conductive rings on one surface of said carrier, said first ring surrounding said hole and being in contact with said ignitable charge, said second ring following the periphery of said carrier and contacting said sleeve, a conductive bridge formed on said one surface of said carrier and interconnecting said first and second rings while contacting said ignitable charge, a conductive disc formed on the other side of said carrier surrounding said hole and contacting said pole piece, and conductive means interconnecting said first ring with said conductive disc through said hole, said first and second rings and said conductive disc being plated layers disposed on said carrier.