Abstract: A chipper roller for a two-stage grinding machine has removable circular knives spaced axially and circumferentially in an array following a helical path of two turns about the surface of the roller. Each knife is in the form of a disc with a central aperture for accepting a fastening element and with a cutting edge on one side adjacent its periphery and an annular groove on the same side adjacent said edge creating a rake which cooperates with the walls of the groove to produce curls from chunks of material. The knives are fastened to the roller in recesses with only a minor portion of the knife projecting above the surface of the roller. Upon dulling of the exposed edge the knife can be rotated to bring a sharp section of the cutting edge into operation.

Abstract: Various embodiments of a proportioning valve are described and shown for location at the discharge ends of a pair of conduits wherein the movable valve member cooperates with the open ends of said conduits. The valve member can be planar or with a dihedral surface and mounted for rotation alternately into obturating relation with one or the other of said conduit open ends which may be square with the conduit axis or cut obliquely. Additionally, the conduit ends may be straight or bent so as to position their mouths either horizontally, vertically or in an oblique plane. Some of the valve members are mounted centrally while others are mounted adjacent an edge, some are mounted for movement about a vertical axis, others about a horizontal axis. An example is given of a use for the valves in combination with a vacuum loader although the valves can be used effectively for controlling discharge of fluent solid material from two sources into any space either under vacuum or positive pressure feed.