Main charge holder for electro-explosive devices (EEDs)
The header of an EED is redesigned to increase stiction forces to better hold the main charge throughout deflagration. The header includes a main charge holder, integrally formed or as a discrete component, that has internal structure that is press fit to a complementary outer surface of the main charge. The contact area between the internal structure and the main charge being greater than the contact area between a cylinder that circumscribes the internal structure (the uniform cylindrical shape of a typical EED contact area of π*D*L) to increase stiction forces between the main charge holder and the main charge. For a given diameter and length, the inclusion of the internal structure will reduce the mass of the main charge.
1 . An electro-explosive device (EED), comprising:
a metal header having a cylindrical cavity, said metal header having an external thread;
a plurality of wires extending through a preform at one end of the header;
at least one bridgewire operatively coupled to the plurality of wires at a closed end of the cylindrical cavity;
an insulating ignition charge holder positioned at the closed end of the cylindrical cavity;
an ignition charge loaded and compacted into the ignition charge holder;
a main charge holder positioned on top of the ignition charge holder;
a main charge loaded and compacted into the main charge holder; and
a closure disk that seals the main charge within the header;
wherein the main charge holder includes an internal structure press fit to the main charge;
wherein the internal structure has a contact area with the main charge greater than π*D*L where D is the diameter of a circle than circumscribes the internal structure and L is the length of the main charge holder to increase stiction forces between the main charge holder and the main charge to enhance retention of the main charge during deflagration of the main charge.
2 . The EED of claim 1 , wherein the contact area is at least 5% greater than π*D*L.
3 . The EED of claim 1 , wherein the contact area is at least 50% greater than π*D*L.
4 . The EED of claim 3 , wherein the mass of the main charge is at most 20% less than the volume π*D 2 /4*L.
5 . The EED of claim 3 , wherein the mass of the main charge is at most 10% less than the volume π*D 2 /4*L.
6 . The EED of claim 1 , wherein the internal structure extends the entire length L of the main charge holder.
7 . The EED of claim 1 , wherein the internal structure stops short of the length L of the main charge holder so that the main charge is a contiguous piece opposite the closure disk.
8 . The EED of claim 1 , wherein the main charge is a contiguous piece.
9 . The EED of claim 8 , wherein the contiguous piece is an N-pointed star in which the N points of the star lie on the circumscribed circle, where N is an integer of at least 3.
10 . The EED of claim 8 , wherein the contiguous piece includes N evenly-spaced spokes that extend radially from a point on the circumscribed circle through the center of the circle to another point on the circumscribed circle opposite the point, wherein N is at least 2.
11 . The EED of claim 8 , wherein the contiguous piece includes N evenly-spaced spokes that extend radially from a point on the circumscribed circle towards the center of the circle but stopping short of the circle, wherein N is at least 4.
12 . The EED of claim 1 , wherein the main charge is segmented.
13 . The EED of claim 12 , wherein the internal structure includes N evenly-spaced spokes that extend radially from a point on the circumscribed circle through the center of the circle to another point on the circumscribed circle opposite the point, wherein N is at least 2.
14 . The EED of claim 2 , wherein the internal structure includes N evenly-spaced spokes that extend radially from a point on the circumscribed circle towards the center of the circle but stopping short of the circle, wherein N is at least 4, wherein the internal structure further includes an inner ring center about the center of the circle and supported by the N evenly-spaced spokes.
15 . A main charge holder for use with an electro-explosive device (EED) having a metal header with a cylindrical cavity having a length L and a diameter D1, said main charge holder comprising:
a sleeve having a cylindrical outer diameter D1 and length L and a cylindrical inner diameter D2; and
an internal structure integrally formed and supported on the cylindrical inner diameter D2 configured to accept a main charge;
wherein the internal structure has a contact area with the main charge greater than π*D2*L to increase stiction forces between the main charge holder and the main charge to enhance retention of the main charge during deflagration of the main charge.
16 . The EED of claim 15 , wherein the contact area is at least 5% greater than π*D2*L.
17 . The EED of claim 15 , wherein the contact area is at least 50% greater than π*D2*L.
18 . The EED of claim 17 , wherein the mass of the main charge is at most 20% less than the volume π*D2 2 /4*L.
19 . The EED of claim 15 , wherein the internal structure extends the entire length L of the main charge holder.
20 . The EED of claim 15 , wherein the internal structure stops short of the length L of the main charge holder so that the main charge is a contiguous piece opposite the closure disk.