Patent ID: 6918636

Claim:
A pick assembly for mounting on a rotatable drum, said drum having a longitudinal axis of rotation, said pick assembly comprising a pick holder and a pick having a longitudinal axis, said pick having: a non rotating cutting head having a straight cutting edge which delimits substantially planar front and trailing faces of said head; a securing end engaged within said pick holder to secure said pick relative to said drum so that in use, rotation of said drum drives said cutting edge forward in a generally circular path and so that said pick is prevented from moving substantially relative to said drum; and a shank extending along said longitudinal axis between said cutting head and said securing end, said pick assembly being oriented such that said trailing face is inclined at an acute back clearance angle of about 7 to 15 degrees to a cutting plane, which is defined by a tangent to said circular path at said cutting edge, said front face is inclined at an acute front rake angle of about 10 to 45 degrees to an axis perpendicular to said cutting plane such that said front and trailing faces define an acute angle at said cutting edge, and said cutting edge is maintained in a fixed orientation relative to said drum and substantially parallel to said longitudinal axis; and characterised in that both said front and trailing faces converge outwardly with respect to said drum toward said longitudinal axis of extension and wherein said pick and said pick holder are adapted so that said longitudinal axis is inclined by an acute angle extending rearwardly to said cutting plane.