Variable length pipe

Claim 1

A VARIABLE LENGTH DRILLING PIPE COMPRISING, IN COMBINATION: A FIRST PIPE SECTION TERMINATING IN ONE END IN A THREADED COUPLING AND INCLUDING A REDUCED DIAMETER PORTION EXTENDING TO ITS OTHER END; A SLEEVE SECURED AT ONE END TO SAID FIRST PIPE SECTION AND SURROUNDING SAID REDUCED DIAMETER PORTION TO DEFINE BETWEEN ITS INNER WALL AND THE EXTERIOR WALL OF SAID REDUCED DIAMETER PORTION AN ANNULAR CHAMBER; A SECOND PIPE SECTION HAVING A LESSER REDUCED DIAMETER PORTION EXTENDING TO ONE END AND RECEIVABLE WITHIN SAID ANNULAR CHAMBER TO TELESCOPE OVER SAID FIRSTMENTIONED REDUCED DIAMETER PORTION, AND TERMINATING AT ITS OTHER END IN A THREADED COUPLING; AN INLET CHECK VALVE MEANS MOUNTED TO SAID FIRST PIPE SECTION TO CONNECT THE INTERIOR OF SAID FIRST PIPE SECTION TO SAID ANNULAR CHAMBER; AN OUTLET CHECK VALVE MEANS MOUNTED TO SAID SLEEVE TO CONNECT SAID ANNULAR CHAMBER TO THE EXTERIOR OF SAID SLEEVE, AND SEALING MEANS BETWEEN SAID SECOND PIPE SECTION AND SAID SLEEVE AND BETWEEN SAID PIPE SECTION AND SAID FIRST MENTIONED REDUCED DIAMETER PORTION, TO SEAL SAID ANNULAR CHAMBER WHEREBY FLUID INTRODUCED UNDER PRESSURE TO SAID ANNULAR CHAMBER THROUGH SAID INLET CHECK VALVE HYDRAULICALLY EXTENDS SAID SECOND PIPE SECTION FROM SAID FIRST PIPE SECTION TO INCREASE THE OVERALL LENGTH OF SAID SECTIONS.