Concentrating-Machinery has been wonderfully improved during the past few years both in technical efficiency and in economy of power; and, in the writer’s opinion, the prosperity which the mining industry has of late enjoyed is due in large part to this improvement. Many properties are yielding handsome profits at the present time which were considered, a few years ago, too low in grade of ore to be profitably operated; and I think that fully half of these once worthless properties owe their successful development to recent improvements in concentrating-machinery.
The present paper calls attention to a jig and an ore-classifier of new design, invented by Mr. John Klein, and already used in the lead-region of SE. Missouri, and in the Philipsburg district of Montana. Having built a number of these machines, and seen them in successful operation, I am able to speak with confidence concerning them.
The general form of the Klein jig, as shown in Figs. 1 and 2, closely resembles that of a Hartz jig, being of the same inverted- pyramid type. It has, however, three main advantages over the Hartz jig of the old style: it requires less power; it has greater capacity; and, above all, it effects a cleaner separation. In a Hartz jig, every plunger is individually operated by an eccentric; in a Klein jig, any number of plungers may be operated by one eccentric, whereby the horsepower required for a given number of jigs is materially reduced. Fig. 2 illustrates the method employed to effect this result by means of the eccentric, a, and the rocker, b, which operates the plungers, c, c’.
The use of compressed air plays a very important part in the operation of a Klein jig. The main advantages derived therefrom are (1) an increased, and (2) a cleaner product as compared with that of a machine in which water alone is the concentrating-agency. In Fig. 1 the space (f) acts as an air-receiver. An air-pipe (f—f, etc.), leading from this receiver, is run directly under the ore-caps below n and n’. The whistle-valves, s s’, on this pipe, operated through x and y—y by an arm from the rocker-shaft, regulate the admission of air. With every stroke of the plunger a puff of air is forced up through the ore-cap, effecting a clean and regular output of concentrates through the gates, n and n’. The usual pressure in the receiver varies from 25 to 35 lbs.
The eccentric can be regulated so as to give a throw of from 0 to 3 in., according to the class of ore to be treated. In SE. Missouri, where only galena-ore is concentrated, strokes of 0.625, 0.875 and 1.25 in. respectively, are employed for material of 4, 7 and 12 mm. grain; the number of strokes per minute averaging about 150.
At a plant in SE. Missouri, 27 of these jigs, of 4 compartments each, are treating from 450 to 500 tons of lead-ore every 24 hours. A test run of several weeks’ duration was made on a lot of 2.5 per cent, lead-ore which had been thrown aside before the machines were installed; and the net returns showed 1 that an extraction of 90 per cent, of the metal had been obtained, at a commercial profit.
Figs. 3, 4 and 5 show respectively the side and front elevations, and the plan, of the Klein classifier. The housing of this machine is made entirely of iron, cast in one piece. This construction prevents leaks, and secures, what is almost impossible with a wooden housing, that the pipe-fittings (of which there are a considerable number) will remain permanently in position.
Compressed air plays an important part in the operation of this machine, as in that of the jig. The working-parts of the classifier are as follows: In Fig 3, the 1.25-in. pipes B, B, connected with the 2-in. pipe S, bring the main supply of water used in classifying the ore from a tank, elevated 15 ft. above the classifier. As the ore, mixed with water, comes from the trommels, it passes into the receiving chamber R, Figs. 4 and 5. As this chamber fills, the material flows over into the compartment M, Fig. 4, in which the classification takes place. In this compartment there are a series of air-inlets, both on the sides and bottom. The six circles marked D in Fig. 5 are the air-inlets on the bottom, each of which is regulated by a globe-valve. On the sides, air is inserted through the hoods H, H, Figs. 4 and 5, with sprays of perforated copper (also regulated by globe-valves), which blow directly against the water coming from pipes B, B, thereby causing a continuous agitation of the ore.
This use of air in combination with water is certainly a new departure in ore-classification; but it is, in my opinion, destined to become, in this branch of ore-dressing, as common as the use of water itself. Every bubble of air, as it comes from the bottom of the classifier, carries to the top a certain amount of fine material, which is washed into the outlet S’, Figs. 3, 4 and 5, while the larger particles, not thus acted upon, are left on the bottom, to find their way through the outlets O, O, Fig. 3. I have found that the air-pressure required for the jigs will also answer very well for the classifier.
When these machines have once been installed, their maintenance is an easy matter. They can be regulated with such delicacy that ores particularly rebellious to machines of this class may be successfully treated. The expense of repairs is reduced to a minimum by the simplicity of their structure; and, above all, they are easily tended.
Since the limits of this paper will not permit a thorough discussion of all details, U. S. Patents Nos. 674,169 and 674,269 may be consulted for a more complete description of these machines.