Plate mill for pebbles, gravel or like materials

Claim 1

In a plate mill for gravel or like materials, of the type comprising: a support structure, a first crusher plate mounted on said support structure for rotation about an axis perpendicular to said plate, a second crusher plate carried on said support structure facing said first plate, a shaft carried by said support structure so as to be rotatable about its longitudinal axis and angularly adjustable in relation to the axis of rotation of said first plate, said shaft carrying said second plate at one end thereof for rotation about the axis of said shaft perpendicular to said plate, and means for driving one of said two plates to rotate, the improvement wherein there is provided: a cylinder carried by said support structure coaxial with said first plate and surrounding a portion of said shaft at the upper end thereof, an inner sleeve fixed to said support structure at one end of said cylinder, said inner sleeve defining, with said cylinder, an annular chamber coaxial with said cylinder, said annular chamber being closed by said support structure at the end remote from said second plate, a piston assembly with an annular cross-section rotatably and axially slidable within said cylinder and extending into said annular chamber, a first member of said piston assembly having means defining a part-spherical socket in the end thereof nearest said second plate, said part-spherical socket having means defining a central opening therein larger than the diameter of said shaft, said shaft extending through said opening, an enlarged, part-spherical head on the end of said shaft, said part-spherical head being engaged in said part-spherical socket, means defining an annular groove extending around said part-spherical head coaxially with respect to the axis of said shaft, means defining a first lubricant conduit in said annular piston said first lubricant conduit communicating at one end thereof with said annular chamber, and at the other end thereof with said annular groove in said part-spherical head of said shaft, a lubricant reservoir, means defining a second lubricant conduit in said shaft, said second lubricant conduit communicating at one end thereof with said annular groove in said part-spherical head of said shaft, and at the other end with said lubricant reservoir, and means for pressurising said lubricant in said reservoir whereby to urge said piston assembly, carrying said second plate, towards said first plate whereby to position said two plates a selected distance apart.