ROTOR FOR IMPACT CRUSHER

An impact crusher is disclosed having a rotor with four hammers equally spaced around the periphery thereof. Two of the hammers, diametrically opposite each other, are each fitted in slots and have a leading hammer face of conventional radial length while the other two hammers are substantially shorter. The shorter hammers each comprise an integral formation with a spiral body extension that projects progressively farther radially outward beginning at the leading peripheral edge of one slot and reaching maximum outward projection at the back wall of the other slot. The two shorter hammers each have a leading surface having a flat portion substantially perpendicular to the periphery of the spiral body extension from which the flat portion projects, and terminates with a radially outer edge which traces a common circle with outermost edges of the two longer hammers. Each of such short hammers strikes, deflects and throws pieces of rock of a size which in the absence of such short hammers can slide along the periphery of the rotor from the trailing side of one long hammer to the leading hammer face of the other long hammer, and which if permitted to occur can result in the crusher discharging such pieces which may sometimes be more than three times the size the crusher is set to produce.