Radial-linear shaped charge pipe cutter
A radial-linear shaped charge pipe cutter is constructed with the booster explosive packed intimately into a booster aperture that is bored axially through the charge upper end plate. The cutter explosive is initiated at the interface between the upper margin of the cutter explosive and the contiguous inside surface of the upper end plate. This interface is within a critical initiation distance from the half charge juncture plane. In one embodiment, a half charge liner is configured as the assembly of two, coaxial, frusto-cones with the smaller cone diverging from the half charge juncture plane at a smaller angle than the outer cone. In another embodiment, the liner thickness increases from the juncture plane out to the liner perimeter.
1. A shaped charge tubing cutter comprising:
a first explosive unit and a second explosive unit that are substantially matched, the first unit and the second unit each being a single unitary part extending substantially about an axis of revolution,
the first unit comprising an first explosive material that is formed intimately against a first metallic liner, said first metallic liner being configured substantially about the axis of revolution substantially to the shape of a conical frustum between a normally truncated apex and a normally truncated base, said first explosive material being between said first liner and a first metallic end plate having a perimeter about said axis of revolution that substantially corresponds to a perimeter of said truncated base,
the second unit comprising an first explosive material that is formed intimately against a second metallic liner, said second metallic liner being configured substantially about the axis of revolution substantially to the shape of a conical frustum between a normally truncated apex and a normally truncated base, said first explosive material being between said second liner and a second metallic end plate having a perimeter about said axis of revolution that substantially corresponds to a perimeter of said truncated base;
said first unit and said second unit are joined coaxially with one another at each said respective truncated apex, a first explosive material interface being between the explosive of the first unit and the first explosive of the second unit, and being along a substantially common juncture plane between the first unit and the second unit,
an aperture perforates the first end plate along said axis of revolution between said outside and inside surfaces of said first end plate, said inside surface of said first end plate being contiguous with said first explosive material of said first unit, a first column of second explosive material fills said aperture between said outside and inside surfaces of the first end plate,
an aperture perforates the second end plate along said axis of revolution between said outside and inside surface of said second end plate, said inside surface of said second end plate being contiguous with said first explosive material of said second unit, a second column of second explosive material fills said aperture between said outside and inside surfaces of the second end plate,
wherein said first column of second explosive material and said second column of second explosive material are separate from one another and each terminate proximate of each respective said inside surface of each respective; and
the explosive of the first unit against a first metallic liner and the explosive of the second unit against the second metallic liner extend between and separate the first column of explosive from the second column of explosive.
2. A shaped charge tubing cutter as described by claim 1 wherein the termination of at least one of said explosive material columns is displaced from said juncture plane by a critical initiation distance.
3. A shaped charge tubing cutter as described by claim 2 wherein said critical initiation distance is about 0.050″ to about 0.100″.
4. A shaped charge tubing cutter as described by claim 1 wherein said end plate apertures are tapered to a diminishing cross-sectional area from said outside surface to said inside surface.
5. A shaped charge tubing cutter as described by claim 4 wherein said end plate apertures are tapered at an approximately 10° included angle.