Patent ID: 8231179

Claim:
A mining machine cutting structure including a support member, an elongated cutting head assembly mounted at the forward end of said support member for powered rotation about a longitudinal axis, said cutting head assembly comprising: a centrally located main cutting head portion, and at least one drum extension portion located at an end of said cutting head assembly axially outward of said main cutting head portion, said drum extension portion being capable of moving in an axial direction along said longitudinal axis from a retracted position to an extended position with respect to said main cutting head portion, said drum extension portion having an axial inner end adjacent the main cutting head portion and an axial outer end, and said drum extension portion including: an inner end structure attached to said main cutting head portion, an outer cylinder attached to said inner end structure, an inner cylinder attached to said inner end structure and having an outer surface, said inner cylinder being coaxial with and received within but spaced apart from said outer cylinder, an extendable cylinder having an inner annular enlarged end, a portion of said extendable cylinder being received between said inner cylinder and said outer cylinder for a sliding movement of the extendable cylinder between the inner cylinder and the outer cylinder, a first space being defined between the inner end structure and the enlarged end of the extendable cylinder, and an end cap positioned at an outer end of the inner cylinder, the end cap having a flange that receives coaxially within it the outer end of the inner cylinder, the extendable cylinder enlarged end being received between the end cap flange and the outer cylinder, and a second space being defined between said inner cylinder and said extendable cylinder and between said extendable cylinder enlarged end and said end cap flange, so that when fluid enters said first space and leaves said second space, said extendable cylinder moves to said extended position, and so that when hydraulic fluid enters said second space and leaves said first space, said extendable cylinder moves to said retracted position.