Bladder mandrel for hydraulic expansions of tubes and sleeves

Abstract

A bladder mandrel utilizing a sleeve of Pellethane.RTM. to effect tube expansions is disclosed herein. The sleeve which forms the bladder of the mandrel terminates in sealing beads which include fluid-capturing recesses. When the beads of the sleeve are secured within grooves provided in the mandrel body, pressurized fluid flowing through the fluid port of the mandrel enters the fluid-capturing recesses of the beads and sealingly engages these beads within their respective grooves. The sleeve consequently fills with the pressurized fluid, and effects the desired tube expansion. The walls of the sleeve are thinnest at their center portion, and become progressively thicker toward the sealing beads. The use of a Pellethane.RTM. sleeve having a centrally disposed thin-walled section results in a bladder mandrel having a relatively small outer diameter, which in turn allows it to be inserted within a tube without the need for lubricants. Additionally, the invention inclues a pair of grooved joints for conveniently detaching the sealing beads of the sleeve from the body of the mandrel when replacement of the sleeve is necessary.