Patent ID: 8011885
Filing Date: 2011-09-06
Classification: F01D,F05D,F16J,Y10T

Abstract:
1. A method for sealing a shaft of a turbocharger to a housing in which it is mounted for rotation about an axis so as to restrict gas flow across the sealing from a relatively high pressure area to a relatively low pressure area within the turbocharger, the method comprising the steps of arranging a plurality of axially spaced seals in sealing engagement with said housing so as to provide a restriction to gas flow and such that they project into recesses provided in the shaft by recess walls with axial and radial clearance to allow passage of gas across the seals from the high pressure to the low pressure area, the seals comprising a downstream seal that is closest to the low pressure area and an upstream seal, each seal being movable axially relative to its respective recess between a first position in which there is an axial clearance between said wall of the recess and the respective seal so as to allow gas to flow in the clearance past the seal from the high pressure area to the low pressure area and a second position in which the seal sealingly engages said wall so as to close said axial clearance, and allowing gas to leak through at least one leak flow passage associated with the downstream seal so as to permit gas to leak past the downstream seal in a direction towards the low pressure area when the seal is in said second position thereby maintaining a gas flow across the seals that is sufficient to ensure there is a pressure drop across the upstream seal, wherein the leak flow passage is provided by a slot in the downstream seal, the leak flow passage in the downstream seal being larger than that in any upstream seal.