Apparatus for grinding plane, annular surfaces, especially on faying rings in gate valves

Apparatus, for grinding plane annular surfaces, comprising:

• (i) a support
• (ii) means for mounting the support opposite to the annular surface with the support being rotatable about an axis which is substantially in alignment with the axis of the annular surface,
• (iii) a plurality of grinding heads carried in freely rotatable manner by said support, said grinding head being rotatable about a respective axis of rotation which is parallel to the axis of rotation of the support, the respective axes pf rotation of the grinding heads being all disposed on a pitch circle concentric with the axis of rotation of the support, the radius of the pitch circle being different from the main radius of the annular surface whereby each grinding head as a result of grinding engagement with the annular surface performs a planatary rotation as the support is rotated, wherein the means for mounting the support comprises:
• (a) a multi-part hub having an integral part-spherical bearing surface, said support being mounted on said hub with the axis of rotation of the support coincident with the center of said bearing surface,
• (b) a driving shaft having a part-spherical head on which said multi-part hub is engaged by its part-spherical bearing surface, said part-spherical head having in it a diametral opening which increases in cross-section from the center of the head to the periphery of the head, and
• (c) an entraining member disposed in said diametral opening and extending radially therefrom at each end to engage into said multi-part hub, whereby the axis of rotation of said multi-part hub may vary, with respect to the axis of rotation of said part-spherical head to the extent permitted by movement of the entraining member within said diametral opening.