Patent GB-725513-A (GB)
Title: Improvements in continuous or semi-continuous open-circuit ball-mills and the like
IPC: B02C17/06
Filed: 1953-08-17
Abstract: 725,513. Ball &c. mills. HIND, S. R. Aug. 17, 1953, No. 22573/53. Class 59. A continuous or semi-continuous, open-circuit wet-grinding or mixing mill wherein the charge is ground or mixed by loose balls, pebbles, cylinders, rods, &c., in a vessel of cylindrical or other symmetrical or approximately symmetrical shape which is rotated about an horizontal or slightly inclined axis, comprises one or more partitions f to divide the vessel into at least two chambers and formed with apertures m connecting the chambers so that the mill may be fed at the first chamber and discharged at the last, the total effective area of the apertures in any of the partitions not exceeding 3 per cent of the internal crosssection area of the vessel adjacent the partition. The vessel, which may be of conical form, is supported as by trunnions or rollers and driven through belt gearing, gear-wheels or the rollers. The feed and discharge openings h need not be on the axis of the vessel. Valve plates n may be provided to control the size of the apertures which may accommodate replaceable liners to vary their effective size and centre location. The vessel and the partitions may be lined with chert or porcelain k or the partitions may be formed of rubber, with or without reinforcement, or other hard-wearing material which may be used alone or on a backing plate and is not an objectional impurity in the ground state or can readily be removed from the finished product. The area of the apertures in a partition need not exceed 1 per cent of the area of the partition if the apertures are intended to pass only the material under treatment, most of the grinding bodies being too large to pass. The apertures may each be such as to harbour temporarily one or more of the grinding bodies, thus obstructing most of the area of the passages, or non-circular pebbles may produce the same effect in circular apertures. The apertures may also be graded so that successive partitions pass grinding bodies of progressively smaller size. In this case, the content of grinding bodies may be introduced intermittently or continuously into the first chamber. If the apertures do not allow passage of the grinding bodies, the mill is stopped periodically and an access door j for each chamber removed to allow the content of gridning bodies to be checked and replacements made. Before starting the mill, each of the chambers is charged separately through its door j with liquid, grinding bodies and the material to be processed, the latter having been reduced in a batch mill to the correct consistency for the particular chamber charged. Alternatively, when valves n are provided to temporarily close the apertures m, the last chamber may be charged first, with material which has not been prepared in a batch mill, and the mill operated for a time; the next chamber to the last one is then charged and followed by a further operation of the mill, and so on until all the chambers are charged with material of the correct consistency. The charge may be mixed with water or mixtures of other liquids with or without water.