Patent ID: 6857329

Claim:
A caliper pig for detecting an obstruction in a pipeline, comprising: (a) an elongated body including a front end and a rear end; (b) a front carrying guide ring at the front end and a rear carrying guide ring at the rear end, the carrying guide rings being adapted for supporting the body in a coaxial sliding engagement with an interior surface of the pipeline and driving the body through the pipeline, the front end first, using the flow of fluid in the pipeline; (c) a transfer mechanism comprising a converting member movably secured to and coaxial with the body, and an electrical signal producing device actuated by movements of the converting member; and (d) a generally disc-shaped, resiliently flexible detector movable along and coaxial with the body and having an outer diameter smaller than the inside diameter of the pipeline to define therewith a generally annular void having a predetermined radial clearance, the detector being connected to the transfer mechanism such that contact by the detector with an obstruction larger than the radial clearance causes the converting member to move.