Pressure compensator for rotary earth boring tool

Claim 1

A pressure compensator for being removably installed in the bit body of a rotary earth boring tool, said compensator comprising: an upper capsule half having a first hemispherical cavity and a step in the edge thereof around the periphery thereof; a lower capsule half having a second hemispherical cavity and a step in the edge thereof around the periphery thereof; said first and second capsule halves having the peripheries abutting each other to form a substantial spherical space with a circumferential groove defined by said steps around the joint between said capsule halves; and a diaphragm member of distendable material and having a periphery and a reinforcing ring of hard material embedded in the distendable material and extending around said periphery, said ring embedded in said distendable material being positioned in said groove with the edges facing the respective capsule halves being snugly engaged with the steps, and said diaphragm extending across said spherical space and dividing said space into two portions.