December 22, 1916. THE COLLIERY GUARDIAN. 1229 excellent results, on account of the uniformity of the product, which is of the texture of coarse sand and contains very little dust. Special types of edge runners are also used for crushing both pitch and coal. The track is surrounded by an annular sieve, and the material is alternately led on to the sieve and underneath the runners by suitably-disposed scrapers. They are better than centrifugal mills for crushing hard material, but less suitable for dealing with material of medium hard- ness. The finely-divided coal and pitch are passed on to their respective hoppers by means of conveyors and elevators. Mixing Appliances The coal and pitch have to be mixed in definite proportions that depend upon the nature of the coal and other circumstances; at the same time, the mixing appliances must permit of the ratio between coal and binding material being altered at will. In one method of effecting this slowly-revolving tables (10 revolutions per minute) are placed below the mouths of the storage- hoppers, which are fitted with sliding rings capable of being brought nearer to or removed away from the tables. The width of the annular openings determines the rate at which the material falls onto the tables, and the material issuing through the annular opening is led by means of a scraper into a common worm-conveyor, which also acts as a mixer. Another but less suitable method is to use an appliance known as the “ supply shoe.” Liquid pitch is often blown into the coal by means of a steam jet. In any case, the proper proportions of small coal and pitch is allowed to fall into a worm-conveyor, which must be of such a length as to ensure adequate mixing. The mixture is conveyed to the drying plant, unless the coal has been dried separately. Since, however, the mixture must be heated for the purpose of pressing, it appears to be of distinct advantage to effect the drying after mixing, so as to carry out the drying and the greater part of the heating in one operation. Drying appliances are of two types—namely, (1) steam-heated drying tables, and (2) fire-heated drums. Steam-heated Drying Tables.—The table drier consists of a vertical series of hollow iron tables, through which steam is circulated. Wet coal is allowed to fall regularly from a hopper on to the centre of the upper- table, and by means of revolving arms, to which inclined shovels are attached, the material is gradually worked to the edge of the table and caused to fall on to the outer edge of the table below. The shovels are inclined on this table, in order that the coal may be moved towards the centre of the table, where it is caused to fall on to the centre of the third table. This operation continues in similar cycles until the dry and hot material is discharged from the bottom. Sieves are placed between two of the lower tables for the removal of foreign materials so as to protect the press. Flame-heated Drying Drums.—One of the latest drum driers of the Zeitzer Eisengiesserei consists of a fixed outer drum and a revolving inner drum, provided with suitable shovels outside and a spiral conveyor inside. The wet coal and hot gases are admitted at one end of the outer drum, and the hot gases travel along the annulus to the other end of the drum, where they are deflected into the inner tube, through which they pass to the chimney. The coal is carried by the shovels to the far end of the outer drum, and then discharged into the inner tube, through which it is caused to pass by means of the worm. As compared with the drum driers, table driers are about twice as expensive in capital cost, and, in addition, for equal size and weight, the output from a drum drier is considerably greater than that from a table drier. The steam-heated driers, however, are free from dangers arising from explosions and fires : the coal is less likely to be overheated; the heat can be better regulated,' resulting in a more regular product; the running and repair costs are much lower; and, in addition, little labour is required in their working. From the drier the dried mixture is discharged into another worm conveyor, and is led away to the steam kneader, where the process of heating and mixing is completed. The steam kneader is usually _ directly connected with the briquette press. It consists of a sheet-iron cylinder open at the top and closed at the bottom. A central vertical shaft carries knife-arms arranged spirally for forcing the material introduced at the top downwards the one or several discharge openings at the bottom corresponding to the number of presses served. Steam jets protrude through the cylinder walls, and blow highly superheated steam directly into the mixture. The material is discharged from the bottom of the kneader at a temperature of about 90 degs. Cent, in the form of a thick pulpy plastic mixture, and is then introduced directly into the mould of the press. Briquette Presses. In the earlier briquette presses it was customary to apply the pressure on one face of the briquette only. The resulting bricks were not eminently satisfactory, because of consequent variations in density throughout the mass. Experiments made in France indicated that of the work expended in pressing in a single-sided press, only 30 per cent, was usefully employed, the remainder being expended in overcoming friction. The modern tendency in the design of presses is towards the produc- tion of machines in which pressure is applied to two sides, usually the top and bottom of the briquette, and it is very gratifying to note that British designers have played no small part in the development of the briquette press. The Couffinhal Press.—The first press to apply the two-sided pressure principle was designed by the French engineer Couffinhal close on 40 years ago- In this press, which was taken up by a number of German firms, and is probably the most widely-used press throughout the world, the hot coal-pitch mixture is conveyed from the kneader into the distributor which overhangs the mould table, the moulds being filled by means of arms revolving at the bottom of the distributor. The table is horizontal, and is provided on the outside with projecting pins in number equal to the number of moulds. These engage with a helical groove cut in the leading roll, and this causes the table to be set round on its foundation-plate once every cycle. The mould table revolves between two levers, the lower one of which is hung from a dashpot at one end, while the other end forms the fulcrum of the system. This lever carries the lower stamp which projects through the foundation- plate so as just to miss the lower face of the mould table. The upper lever carries the upper stamp and also the mould stripper. It is attached at one end to the lower lever and at the other end to two connecting- rods attached to flywheels that revolve in opposite directions When a mould filled with material passes between the stamps, the connecting-rods pull the upper lever down round the far end as axis until the face of the upper stamp comes into contact with the material in the mould. The axis of rotation then changes to the pivot of the upper stamp, when the lower stamp is raised and the two stamps enter the mould and com- press the material from above and below. A further revolution of the flywheels raises the upper lever, and the stamps are withdrawn from the mould, The briquette remains in the mould for half a revolution of the table, when it comes under the influence of the stripper, which pushes the briquette on to a belt-conveyor below. Delta metal has been found to be the best material for the renewable linings of the mould. Revolver Presses.—These are so called because the mould tables revolve in a vertical plane, the stamps working hori- zontally. They were first introduced over 20 years ago by Robert Middleton, of the Sheepscar Foundry, Leeds, but were improved by Messrs. Yeadon and Company, and are now generally known as the Yeadon press. In this type of machine the material is introduced into the mould by means of a single stamp, and the final compression is effected after the mould table has made a quarter revolution, and after a further quarter revolution stripping is effected. The latest type of this press makes 25 briquettes or sets of briquettes per minute. Toggle-joint Presses.—The toggle joint was first applied in the old Middleton press, but its application to double presses was taken up by the Maschinenbau Aktiengesellschaft Tigler, and the principle has also been applied by Messrs. Sutcliffe, Speakman and Company. In the toggle-joint press the mould table is fixed; the material to be compressed is first intro- duced into a charging box, which at the proper moment is pushed over the mould proper; the material is then charged into the mould, after which the charging box is removed and the compression allowed to take place. The upper and lower stamps are connected by strong tie-rods in such a way that when the toggle joint is straightened out tjie upper stamp is pushed downwards and the lowei- stamp lifted. After compression, the briquette is lifted out of the mould by a secondary movement of the lower stamp. It is not easy to glean any very - definite information with regard to the relative merits of the Couffinhal, the revolver and toggle-joint presses. The toggle-joint presses are the most costly, and the consensus of opinion appears to be that the running and repair costs are greater than in the case of the other two types. Nevertheless, they are capable of much greater outputs, and are eminently adapted to the production of very large briquettes. The Couffinhal type is undoubtedly the simplest, and shows the lowest repair costs. It has the distinct advantage that the briquettes are com- paratively cool when they are pushed out of the moulds; they are also stronger, and the liability of producing damaged briquettes is considerably lessened. Toggle- joint presses, however, are still in theii- infancy; excellent results have nevertheless been obtained with them, and the accessibility of the parts and the large outputs are certainly desirable features. Rope Presses.—In this press a quantity of material sufficient to make one briquette is allowed to fall in front of a stamp, by means of which it is pushed into a long channel open at both ends. Owing to friction between the materials and the walls considerable pressures are set up, and the material issues in the form of a rope, which is cut up by suitable knives. The Bouriez press, of this class, is used to a considerable extent in Belgium. Roller Presses.—These are used for the production of egg-shaped briquettes. They consist of two horizontal rollers revolving in opposite directions so as to touch each other. Semi-ellipsoidal cavities are cut in each roll in such a way that they register when these particular parts of the circumference of the rolls come into contact. The soft mass is fed between the two rolls, fills the cavities, and becomes compressed into briquettes. These presses find a fair amount of application in North America. From these descriptions it will have been gathered that a briquette factory is so designed and equipped as to require very little labour. A typical plant is that of the Kbnigsgrube briquette works in Upper Silesia, which is equipped with three Tigler toggle-joint presses for an output of 400 tons of briquettes per nine-hour day. The cost of the equipment (including buildings) was about £1,700. At the anthracite and coke- briquette factory of the United Gas Improvement Company of Philadelphia, anthracite culm and coke- breeze are briquetted with 5 to 7 per cent, of pitch in Belgian roll presses. The briquettes are consumed in the firm’s own gas-producers. It does not seem to be of much use at the present time to go into the question of costs of production, because reference could only be made to the conditions which existed prior to the war, and such data will be of very little use when applied to the constantly-changing conditions of to-day. It will be sufficient to say that the capital outlay and the costs of production are low enough to be of no concern when it becomes a question of effecting economies in our stock of fuel. UNDERGROUND MINE AMBULANCE.* The transporting of persons injured in mines from the working face to the outside, especially when the distance to be travelled is great, has long been a serious problem. At No. 7 mine of the Union Pacific Coal Company, Rock Springs, Wyoming, the mine foreman, John Maxwell, and the assistant mine foreman, Charles Gregory, have successfully solved this problem by designing a mine ambulance, the construction details of which are quite original. The ambulance is roomy enough to accommodate the B I* Electrically-heated Mine Ambulance. patient and an attendant without inconvenience. It is electrically lighted and heated, and is equipped with a cot suspended from springs to obviate any jarring. On either side are receptacles for first-aid supplies, hot water bottles, blankets, etc. It was formerly a custom at this mine when men were injured to place them on a stretcher, and transport them in a mine car to the surface. As the distance to be travelled was often from three to four miles, the injured men frequently became chilled and suffered from shock, no matter how well they were protected by blankets. As they travelled this distance against the intake air current, which moves at a high velocity, and is, especi- ally in the winter time, of a very low temperature, they often suffered severely, and their recovery was materially retarded. * Coal Age. THE MINERS’ FEDERATION. A meeting of the executive was held on Wednesday at the Imperial Hotel, London, Mr. R. Smillie, president, in the chair. After discussing the question of the proposed State control of mines and passing the resolution mentioned elsewhere, the meeting considered the report of the sub-committee appointed some time ago to deal with the question of craft unions existing about mines, with a view to securing their amalgama- tion or federation with the Miners’ Federation. It is suggested that these unions, which include the colliery enginemen, should continue their separate organisa- tions, but should become affiliated branches of the Federation, with representation on the executive, in the same way as the various miners.’ associations. It was agreed that the proposals submitted by the sub-com- mittee should be forwarded to the various unions with which negotiations have been in progress. The question of naval and military pensions for youths disabled in the war and the separation allowances to the dependants of young persons was under con- sideration, and the following resolution was carried :— In the opinion of the executive the present method of augmenting the allotment made by apprentices and other young persons who have joined the Army and Navy is absolutely unjust, and we call upon the Government to make provision for an increase in the payment to the home immediately upon a soldier arriving at the age when he would have been earning full or increased wages had he been in his ordinary employment. In view of the real urgency of this question we request the Labour Party to seek an interview with the Minister of War and the Pensions Minister with a view of having the present anomaly removed. Hull Coal Exports. — The. official return of the exports of coal from Hull to foreign countries for the week ending Tuesday, December 12, is as follows :—Amsterdam, 198 tons; Caen, 319; Christiansund, 247; Christiania, 1,125; Dieppe, 2,063; Fecamp, 670; Harlingen, 600; Havre, 1,258; Rouen, 9,028; Rotterdam, 1,355; Treport, 866—total, 17,729 tons. Corresponding period December 1915—total, 31,117 tons. Corresponding period December 1914—total, 34,946 tons. These figures do not include bunker coal, shipments for the British Admiralty, nor the Allies’ Governments.