Patent ID: 8770319

Claim:
An apparatus comprising: a variable-diameter drill rod comprising: a first portion having a first, larger inner diameter; and a second portion having a second, smaller inner diameter; and a first seal disposed within the variable-diameter drill rod, the first seal comprising: a central core; and a lip spaced apart from the central core, the lip comprising: a projection configured to form a seal with the larger and smaller inner diameters of the variable-diameter drill rod, wherein the projection of the first seal is configured to, when forming a seal with the larger inner diameter of the variable-diameter drill rod, be disposed in an expanded configuration in which the projection is radially-extended and axially-retracted; wherein the projection of the first seal is configured to, when forming a seal with the smaller inner diameter of the variable-diameter drill rod, be disposed in a compressed configuration in which the projection is radially-retracted and axially-extended; and wherein the first seal further comprises means for biasing the projection from the compressed configuration towards the expanded configuration.