Show J CUSHING CRASHING MACHINERY FOR GOLD MILLING PROCESS ploce SS sj dy chas char H fulton E M of south school of miner a l ii 11 ll 1 i i ISO wool imm HE E coarse crushing of ores preparatory C to amalgamating stamp milling or cy abiding or chlorination is done by one of two types of crushers either the jaw crusher or the gyratory crusher both of these types of machines are so well known that no description of them is necessary and only the principles of their working and application will be discussed jaw crushers many manufacturers dadufa make jaw crushers all of which are alike in principle but differ in detail of construction jaw crushers are divided into two classes classe s 3 1 the blake type and 2 the dodge e type the first of ase these has the power applied at the bottom the movable jaw being hinged at the top and the greatest motion at the discharge opening or near it thus aiding in the discharge of the crushed material and also exerting the most powerful crushing effect on the largest piece of ore the dod dodge 9 e type of jaw crusher is different in that the swinging jaw is hung at or near the discharge opening the power being applied at the top this fact makes the discharge opening more nearly constant the discharge of broken ore not being aided by much movement at the point of discharge also the least power is applied to the largest ore pieces the blake type of crusher has a greater capacity size for size than the dodge type the size of the crushers being designated by the dimensions of the mouth or receiving openings it is a well established fact that in in crushing to a given size of ore the dodge produces more fines than the blake which may or may not be desirable according to what the further treatment of the ore is in concentrator mills this is usually an able property on account of its greater capacity for a given size of machine the blake type of jaw crusher is much more I 1 numerous in mills than the dodge although I 1 the dodge finds its application under special 1 conditions such as when the coarse crushing is done in two stages in which case it is used as the secondary crusher the capacity of crushers is best stated in cubic feet per unit of time as to state it in tons leads to error for the specific gravity of the ore to be crushed affects the tonnage crushed the blake crusher ordinarily is made with a mouth opening up to inches which last is a special size As regards the capacity of the blake type of jaw crusher that depends anthe nature of the ore whether the ore be brittle and easily fractured like quartz or tough and resistant or clayey or soft like some rome other ores also when the capacity is stated as aa tons on the specific gravity of the ore it also depends of course on the size to which the ore is broken A few figures from practice will illustrate the capacity aft tons size of character of ore per per crusher crushed down to hour hour I 1 inches quartz ore cr cripple creek down to li 1 inch 25 siliceous ore quartzite inches black hills hills down to 94 3 30 10 inch inches siliceous limestone black hills down to 1 inch 13 the capacity of the dodge type is from 25 to 30 per cent less than the same size of blake the power required for jaw crushers varies according to the nature of the ore but may be stated generally as 11 HP per cubic yard crushed per hour GYRATORY CRUSHERS the introduction of the gyratory type of crusher has become very general in the last few years especially in its application as a rough crusher to large gold mills in the united states and south africa as well as other countries it is so well known that a description is not necessary the size of gyratory crushers are designated by letters or figures and also by mouth opening which is an annular space this space in the older form ot oi cru crusher s h e r was divided into three segments by a ahr three armed spider the length and width of each space measured in a straight line at the shortest distance determining the size of rock the crusher takes in the newer form the three armed spider is replaced by a two armed one giving two openings in place of three enabling somewhat larger pieces of ore to be fed to the crusher gyratory crushers have replaced the jaw crushers in many large gold stamp mills but have not as yet found much application in coarse concentrating mills the last fact is probably lar largely gely due to conserva cism although the blake crusher makes a rather smaller percentage of fines than the gyratory which is an advantage in coarse concentration of brittle minerals the gyratory crusher also possesses the advantage of running with but very little vibration as compared to the jaw crushers enabling r the crusher to be installed without danger a at t the top of the mill buildings or close to gallows frames the modern tendency however is to place the coarse crusher at the mine rather than at the mill if this be possible for small capacities say up to 75 tons the small sized k gyratory crushers possess no advantage over the blake type of crusher in fact are rather at a disadvantage in that they choke up more easily if the ore be clayey or in the least wet for large capacities above tons the gyra tories seem to possess distinct advantages in substituting one large gyratory crusher running without vibration in pa place ace of the greater number of blakes a considerable sid erable saving in labor at least is made with probably some saving of power |