July 24, 1914. THE COLLIERY GUARDIAN. 197 from the tank. In either case, the height available must be about 2| times the height of the switch when it is closed up. The Ellison switches are fitted with two screws with crank handles, as shown in figs. 7 and 8. One man can lower the tank quite conveniently : it is in use by the Staveley Coal and Iron Company Limited. Time Lags. A “ time lag ” is a device for extending and control- ling the time taken by a circuit breaker or a relay to come into operation. When applied to a motor starter, it is usually set so that the motor can give a 25 per cent, continuous overload in half-an-hour. At the same time, it will not operate at great loads for sharp peaks, such as frequently occur on motor circuits. The ideal requirements of a time lag are as follows :—(a) It should prevent movement until the required time has elapsed, and should not retard movement until it has commenced. When movement does commence, it should be swift. (5) It should give long lags for moderate overloads, and allow quick action when there is an excessive one. (c) It should be adjustable, so that any desired retardation can be obtained to meet conditions of service, (d) It should have a correct inversed time element, that is to say, the time by which the circuit breaker tripping gear is delayed should diminish as the overload, (e) It should be so simple that under no conceivable condi- tions can the device prevent the breaker from opening if an overload has been on long enough to become dangerous. (/) It should be independent of variations in 33* Fig. 8.—Ellison Oil-break Triple-pole Switch, fitted with Connection-box, Screw - lowering Gear for Tank, Ammeter and Volt-meter. Fig. 9.—Statter Time-lag. CONICAL SUCKER SURFACES GROUND TOGETHER \ SCREW FOR TIME - ADJUSTMENT temperature. (g) It should be independent of atmo- spheric conditions : thus in power houses which have gas engines, and in mines where the atmosphere is gassy or dusty, the essential parts of the gear should be efficiently enclosed. Time lags may be operated or controlled by an oil dash pot; a damping fan; a “ thermal ” device (due to Barton), depending on the heating of two bent strips which expand unequally; a rotation inductive device constructed on the principle of the alternating current meter, etc. The Statter time lag depends on the action of suckers, which adhere one to the other when in contact, but cease to adhere at all if separated by no in. The latest form (shown in fig. 9) consists of two cones, with a valve in the top cone to allow of the escape of air. Fig. 10 gives the curves obtained with various settings. The Ellison adjustable time lag is of the dash pot type, and works with oil or glycerine. As seen in fig. 11, it consists of a cylinder and piston, the latter being covered with the liquid. When in its normal position, the rod attached to the piston carries at its upper end an iron core acted on by a solenoid. The piston is turned slightly taper, and the cylinders bored to fit, the object of this being to permit adjustment of the retard- ation by varying the clearance. The time occupied in raising the piston is determined by the rate of flow of the oil from the top to the under side of the piston. It is obvious that if the opening round the piston is increased, the rate of flow will increase, and the time required to pull up the piston be reduced. By means of the screw A, and a series of holes, the cylinder can be given 11 different retardations between three seconds and five minutes. An increase of temperature tends to reduce retardation. Inter-Locks. Inter-locks are desirable in places where a gassy or inflammable atmosphere may so obtain that it is impos- sible for the switch to give open sparking; also to protect those who have to inspect or repair the switchgear. Inter-locks are usually provided between the main switch, the isolating links, and the oil tank; and also the door enclosing the gear. Sometimes several of these are substituted by gear of the withdrawal type, as in the case of that made by Messrs. Reyrolle and Company. Messrs. Allen, West and Company’s motor starter has an inter-lock on the oil tank, so arranged that when the tank is lowered it actuates the no-volt release. By a mechanical inter-lock the opening of the main switch also withdraws a rod on the tank. The Electrical Apparatus Company has an ingenious float device, which renders it impossible to close or open the switch unless there is sufficient oil to cover the con- tacts. It will be remembered that after a certain col- liery disaster in Lancashire, it was suggested that the level of the oil in one of the switches had fallen below the switch contacts. 15] io 80 100 300 500 700 900 1100 1300 1500 Percenfa.§e Overload IQ go Amperes Applied 30 ! 4jQ I 5.0 I 6.0 t 7< Current Setting 5 Amps Time Setting Not, 13 Secs at SO % O/Load “ No2,6 It 1! No5,l-8 11 !» Fig. 10.—Curves of Statter Time-lag. Fig. 11.— Ellison Adjustable Time-lag. Motor Fig. 12.—Connections for Star-delta Starter. When large induction motors are used underground, it is important to inter-lock the stator switch to the rotor switch. As a matter of fact, this is very rarely done, because the two switches are generally some dis- tance apart, and so it cannot be conveniently done in a mechanical way. Messrs. Reyrolle and Company have overcome the difficulty by means of an electrical inter- lock, and thus the switches may be at any'distance apart. Star-Delta Starter. For squirrel cage motors, the star-delta starter is very useful. The connections are shown in fig. 12, and it will be seen that the effect is equivalent to switching the motor on to a reduced voltage at starting up, which, of course, reduces the rush of current. The requirements of such a starter are as follow :—The starting lever can only be placed in the reversing position after having first been in the starting position. It must be in the starting position for a certain length of time, so as to allow the motor to get up speed. The change from the starting to the reversing position must be done briskly, so that the motor cannot slow down. The starting lever must not stay in the starting position. Messrs. Switchgear and Cowans Limited have brought out a star-delta starter, which carries out all the above operations automatically. The apparatus is combined with a Statter time lag, and a magnetic device, so that the change over takes place at the correct moment. Controllers. The correct, design of contact fingers is important; many are too flimsy, and liable to lose their spring uses, so that they get out of line. If adjusted by twisting there is liability of further burning. The limiting width for a single controller finger is about 1 in., and such a finger will safely carry 130 amperes. For larger cur- rents than 130 amperes, it is best to use two or more fingers in parallel. The British Westinghouse controller finger is clamped to a square shaft insulated with mica. It has a swan-necked spring of phosphor-bronze, which gives a firm even pressure between the finger tips and drum contacts throughout the life of the finger. The drop or lift of the finger may be adjusted by hand, without the use of tools. A flexible copper shunt takes the current from the terminal block, and so prevents overheating of the bronze spring. The Electric Ordnance and Accessories finger consists of a brass carrier pressed from heavy gauge sheet brass, and is so designed that, although its weight is small, it has considerable strength in the direction of stress. It is fixed to the terminal block by a pivot pin. The ter- minal block of cast brass is clamped to the finger bar and insulated therefrom by mica. Tension is applied- by a spiral spring fitted between the terminal block and the carrier. The adjustment of this finger is regulated by a steel rod passing through the centre of the tension spring, this rod being screwed for the reception of a square nut, one side of which engages with a projection on the terminal block, thus preventing turning, unless the finger be first lifted by hand. The finger used by the Electrical Apparatus Company is on the lines of a carbon brush holder. For mining work, headroom is a consideration, and therefore the drum is placed hori- zontally. In a controller made by the British Westing- house Company, which works in this position, the drum is attached to the hinged cover. In the Allen-West controller, the drum is carried on a separate frame, which reduces the labour involved in opening up the controller. It does not in any way interfere with the connections, since these are of the laminated strip type, and so arranged that their bend- ing portion is in the same plane as the bearing point of the auxiliary frame. The spindles of controller barrels are frequently made with the contact rings clamped on to mica insulation on a square section. As the contact rings have to be turned up when mounted on the insulated square spindle a strain is put upon the insulation. If they should work loose and require tightening up again, they may become eccentric. On account of this Mr. Ellison was led to design a method of threading the contact rings on a round section spindle, and to employ a separate round section driving rod to drive the rings. Both the spindle and the driving rod are insulated with mica tubes. New Industrial Disease.— The Home Secretary has issued an Order, dated July 1, 1914, extending the provisions of section 8 of the Workmen’s Compensation Act, 1906 (6 Edw. 7, c. 58), By it, so much of the Order made on July 30,1913> under sub-section (6) of the said section, as applies to “ epitheliomatous cancer or ulceration of the skin or of the corneal surface of the eye, due to pitch, tar, or tarry com- pounds,” is revoked, except as regards cases arising before the date of the new Order, and a new description is added. The following is the Schedule to the Order:— Description of disease or injury. Epitheliomatous cancer or ulcera- tion of the skin or of the corneal surface of the eye, due to tar, pitch, bitumen, mineral oil or paraffin, or any compound, pro- duct or residue of any of these substances. Description of process. Handling or use of tar, pitch, bitumen, mineral oil or paraffin, or any compound, product or residue of any of these sub- stances. American Peat Society.—The 8th annual meeting of the American Peat Society is to be held at the rooms of the Commercial Club, Duluth, Minnesota, on August 20, 21, and 22, 1914. This meeting promises to be a most important one in the history of the society, as well as in the movement already begun by State and National Governments to reclaim the swamp lands of the couAtry. The interest in this meeting is shown by the number and variety of papers already promised. It is expected, from enquiries from Europe, that representatives of the Governments of some of the more important peat using countries abroad will be present at the meeting and take part in the proceedings. Timely papers from European investigators and practical peat producers are already promised. Amongst the papers on the preliminary programme are the following :—“ Pro- blems to be Solved in Developing a Dewaterer for Peat,” by G. Herbert Condict; “ Latest Development in the Peat Gas Producer,” by F. B. Haanel, of the Canadian Depart- ment of Mines; “ The Possibilities of Peat in the Beneficia- tion and Smelting of Iron Ores,” by Prof. Peter Christiansen, of the University of Minnesota; ‘‘Converting Peat into Fuel,” by Prof. Charles A. Davis, of the U.S. Bureau of Mines; ‘‘The Peat Industry in Ireland,” by Thomas Tomlinson; “ The Use of Peat in the North-West Provinces of Russia,” by Engineer K. v. Lubkowski, of Warsaw; ‘‘Peat Briquetting,” by Dr. J. Me William; “ Briquettes from Peat and Petroleum,” by Robert Blei, of Sacramento, California; ‘‘Practical Demonstration of Her- bein’s Patent, by a Small Working Model of the Herbein Briquetting Machine,” by C. A. Squire, of Cleveland, Ohio; “ How to Prepare a Peat Bog for Fuel Making,” by Gustave Carlson, of Farnham, Ont.; “ Application of Machinery on Peat Deposits,” by L. A. Krupp, of Findlay, Ohio; ‘‘ Economic Aspect of Peat in America,” by John N. Hoff, of New York; ‘‘Comparative Costs of Driving Peat Fer- tiliser with Fuel Oil and Coal,” by John Wiedmer, of St. Louis, Mo.; “ The Peat Industry of Russia,” by Gr. Lisitzin, of Riga. An exhibition of peat, peat products, and any- thing pertaining to peat development has been arranged under the auspices of the Duluth Committee of Arrange- ments.