Unitary pig for use in a pipeline

An improved pig for use in a pipe line comprising:

• an elongated cylindrical body having a forward end portion and a rearward end portion, at least a major portion of the body having an axial opening therein;
• at least one forward cup extending from said body forward end portion, the cup extending rearwardly and outwardly to a peripheral pipe engaging surface;
• at least one rearward cup extending from said body rearward end portion, the cup extending rearwardly and outwardly to a peripheral pipe engaging surface, the body and said cups being integrally formed of non-metallic material, and wherein said rearward cup has an opening therethrough providing a fluid passageway whereby pressure across said rearward cup is equalized, and an insert of stiff material received in said axial opening serving to increase the rigidity of said body.

An improved pipeline pig according to clam 18 wherein each said cup has a forward exterior and a rearward interior conical configuration, and wherein the thickness of the cups as measured perpendicular the interior surface is greater in the outer portions than adjacent the body, and wherein the outer peripheral surface of each cup is tapered to a relatively thin circumferential pipe engaging surface.