Patent ID: 7614109

Claim:
A pig towing device adapted for moving through a conduit having bends and open T intersections, the device comprising: at least a front leading cup and a rear trailing cup adapted to seal with the conduit for propelling the device through the conduit, the leading cup and the trailing cup being spaced apart a predetermined distance whereby at least one of the leading and trailing cups is adapted to maintain the seal with the conduit as the pig towing device negotiates past the open T intersections, and a flexible body interconnecting the front leading cup and the rear trailing cup, the flexible body being urged normally into a straight position extending along a central axis thereof to maintain the front leading cup and the rear trailing cup spaced apart by the predetermined distance, and the flexible body having predetermined limited flexibility permitting it to bend relative to the central axis as the pig towing device negotiates through the bends in the conduit, wherein the flexible body has a first tension means, a flexible compression sleeve means, and a second tension means, the first tension means is connected with both the front leading cup and the rear trailing cup for transferring drag forces from the front leading cup to the rear trailing cup, the flexible compression sleeve means surrounds the first tension means and is sandwiched between the front leading cup and the rear trailing cup for transferring compression forces from the rear trailing cup to the front leading cup, and the second tension means is operably connected with one of the first tension means and the flexible compression sleeve means to provide a predetermined tension load that normally urges the flexible body into its straight position extending along the central axis and limits bending of the flexible body relative to the central axis, wherein the rear trailing cup has a first central aperture, the first tension means has a threaded end portion, and the second tension means comprising a compression spring surrounding the threaded end portion that extends through the first central aperture and a nut like connector secured to the threaded end portion for engagement with the compression spring, the nut being rotated about the threaded end portion to compress the compression spring against the rear trailing cup thereby providing the predetermined tension load to the first tension means, and wherein the flexible compression sleeve means comprises a plurality of compressible metallic disk elements stacked adjacent to each other, each of the compressible metallic disk elements having a central opening through which the first tension means extends whereby relative movement between the compressible metallic disk elements allows the flexible body to bend relative to the central axis.