Importance

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Abstract

A large-diameter, cylinder-shuttle airgun for seismic uses has a cylinder shuttle configured as a hollow, elongated cylinder body of revolution with an inwardly-facing cylinder guide surface and having two outwardly-extending, axially-spaced annular flanges. These two annular flanges are an operating flange at an upper end of the body of revolution and a firing flange at an intermediate region thereof. A cylinder skirt extends down below the firing flange, and the cylinder shuttle has an overall axial length L. The firing flange has a perimeter of outside diameter OD, and the ratio of L to OD is at least about 1 to 1. A cylinder housing of the airgun has a main inner cylinder structure encircled by the cylinder shuttle. This main inner cylinder structure may have an axial passageway of sufficient diameter for passing at least one compressed air hose and at least one multi-conductor electric cable axially therethrough. The housing provides an annular operating chamber for receiving the operating flange therein and has an annular firing chamber with removable interchangeable annular chamber walls for changing volume of the annular firing chamber. The skirt on the cylinder shuttle extends down into the firing chamber. The housing defines an annular discharge port positioned intermediate the operating and firing chambers and extending 360.degree. around the axis of the housing. By employing a firing flange of large OD, a Torus bubble is produced of large 'C' radius in relation to its axis of revolution which provides enhanced peak pressure output and improved PBR compared with a standard airgun.

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First Claim