Pipeline pig

A pipeline pig adapted to be propelled through an oil and gas pipeline by fluid pressure injected into the pipeline comprising:

• an elongated flexible member having a front end and a rear end,
• a plurality of spaced annular flexible rings circumscribing said member at positions spaced inward from said front and rear ends and extending radially outward from said member for contracting the inside wall of a pipeline, all of said plurality of annular rings have substantially the same diameter,
• said pig, including said elongated member and said annular rings, being formed of non-metallic flexible material capable of bending or flexing and resuming its original shape,
• said elongated member having an elongated central aperture open at its rear end and extending from its rear end forward to a point beyond its midpoint and near the front end thereof for receiving fluid pressure to facilitate movement of the pig through a pipeline,
• said front end being defined by a forward projecting wall means which extends forward of the forwardmost annular ring and is smaller in cross section than the cross section of said forwardmost annular ring,
• said central aperture having its sidewall closed to the passage of fluid therethrough along its length from the rear end of said member to a point near the front end thereof,
• a rear annular ring which extends outward from said rear end and which defines the entrance to said central aperture,
• said rear annular ring having substantially the same diameter as the diameter of said plurality of annular rings,
• said rear annular ring being formed of non-metallic flexible material capable of bending or flexing and resuming its original shape,
• said annular rings and the outer wall structure of said elongated member being formed of foam-like material,
• said central aperture being formed by a non-porous liner around which the foam-like material is bonded.

A pipeline pig adapted to be propelled through an oil and gas pipeline by fluid pressure injected into the pipeline comprising:

• an elongated flexible member having a front end and a rear end,
• a plurality of spaced annular flexible rings circumscribing said member at positions spaced inward from said front and rear ends and extending radially outward from said member for contacting the inside wall of a pipeline,
• said front end of said pig being defined by a forward projecting wall means which extends forward of the forwardmost annular ring and is smaller in cross section than the cross section of said forwardmost annular ring,
• said member having an elongated central aperture open at its rear end and extending from its rear end forward to a point beyond its midpoint and near the front end thereof for receiving fluid pressure to facilitate movement of the pig through a pipeline,
• a rear annular ring extending outward and rearward from said rear end and which defines the entrance to said aperture,
• all of said annular rings having substantially the same diameter,
• the angle formed between the front wall of each of said annular rings and the portion of the axis of said elongated member ahead of each of said front walls being not less than about 90.degree.,
• the angle formed between the rear wall of each of said annular rings ahead of said rear annular ring and the portion of said axis behind each of said rear walls being not less than 90.degree.,
• each of said annular rings ahead of said rear annular ring having a curved outer surface between its front and rear walls,
• said annular rings and the outer wall structure of said elongated member being formed of foam-like material,
• said aperture being formed by a non-porous liner having closed sidewalls and a closed front end around which said foam-like material is bonded,
• said foam-like material and non-porous liner being capable of bending or flexing and resuming their original shape.