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July, 1949

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Unit Lighting Fittings. — By arranging these five simple unit fittings and the four accessories in the desired combination it is claimed to be possible to meet all underground lighting requirements — both in the roadways or at the coal face. Another interesting feature is the provision whereby it is possible for the number of fittings to be increased as required without re-making any joint. Similarly, in retreating work, lighting fittings may be taken down and transferred to other districts without re-making joints. This facility is available as a result of incorporating a self-aligning plug and socket in the design.

The bulkhead lighting fitting is used as a wall-fixing light where space and minimum projection are important. In order to withstand rough usage, the globe is made of toughened glass which also has a smooth exterior surface so as to avoid the accumulation of dirt and dust. The interior surface of the globe includes serrations to give a particular form of light distribution. When the globe is fitted to the unit in the "road" position, the polar distribution of the light takes the form of two parallel beams along the roadway; but when fitted in the "flat" position, which is 90 degrees rotation from the "road" position, the serrations on the inner surface of the globe glass disperse the light in the form of a fan around the lighting fitting, making the light emission merely local and thereby better suited for use in haulage houses, switch houses or loading points. This lighting unit will take up to a 100 watt lamp and may be plugged directly into any standard socket flange or switch fuse, or junction box unit.

The pendant fitting is designed to fulfil needs where sufficient roof height is available. It incorporates the same type of glass globe as is used on the bulkhead lighting fittings, and may also be plugged directly into a standard socket.

The junction box is arranged with four socket ways for entry and exit and a top cover which is held in position by four shrouded bolts. The interior of the junction box contains permanent busbar connections to each way and, if preferred, the box may be filled with compound without impairing flexibility of use. By using this junction box, any combination up to and including three lights and an incoming cable may be arranged at the one box.

The switch unit is approximately 4 in. square by 4 in. deep, and has three standard socket flanges and one extension flange. A fifteen-ampere, double-pole, double-break switch with quick make and break action is fitted in the interior. The switch handle is incorporated in the top cover and is so arranged as to be dirt proof, and incapable of being accidentally knocked on or off by a fall of material from the roof.

The fuse unit is contained in a case 4 in. square by 4 in. deep, which has three standard socket flanges and one extension flange. The case contains two 15-ampere renewable fuses.

Victor 150-cycle Coal Drill. — The efficiency of high-frequency drilling has now been well established. To provide the necessary high-frequency current, a frequency changer is incorporated in the gate end box, which steps up the frequency of the supply from 50 to 150 cycles, so allowing the use, in the drill, of a motor which develops a synchronous speed of 9,000 r.p.m. This, in combination with epicyclic gearing and light-weight alloys, enables a machine of exceedingly high power-weight ratio to be produced. The switch mechanism is of the butt and brush double-break type, and the cable connection is of the reversible plug type.

50-cycle Direct-switching Drill. — This has been designed for use where the Regulations do not require remote control. It weighs 37 lb., runs at 580 r.p.m., and may be used to drill coal or stone. When used as a stone drill, the machine is fitted with lugs for the force-feed mechanism. The switch is of the three-pole, trigger-operated, quick-make-and-break type, and is accessible by a separate cover so that unit replacement is simplified.

Slow-speed, Heavy-duty Stone Drill. — Designed for use where there is a possibility of silicosis and associated troubles, this design is common to 50-cycle and 150-cycle operation. The rod speed is approximately 120 r.p.m., and the gear - box assembly may be taken away as a separate unit, so assisting proper maintenance. The water feed attachment shown in the illustration takes hollow section drill rods, and so enables a water feed to be given directly to the cutting edges of the bit

Mining Air Drill. — This machine incorporates many of the features of the more familiar electric drills, but is driven by a rotary vane power unit. These drills, whether for stone or coal, are designed for a full load speed of 450 r.p.m. at 60 lb. per sq. in. gauge pressure. Speed regulation, where necessary, is accomplished by a replaceable static volume control. When required to work as a stone drill in hard formations, a force feed mechanism is used, but for the softer stones and for coal, the machine may be hand held.

Drill Rods. — Drilling auxiliaries marketed by this firm include diamond drill rods, turbine drill rods, hollow-section drill rods, advance bore rods, large diameter rods, and tipped drill bits. Hollow-section rods are, of course, designed to permit a water feed direct to the cutting edges of the drilling bit, and are used where dust suppression is of primary importance. The advance bore rods may be in either solid or hollow section, and are used in exploratory work. They are made up from a combination of three types, the bit rod, the machine rod, and the extension rod. Large diameter rods enable holes up to 3 in. diameter to be drilled in coal with a hand-held machine.

Drill Gate-end Box. — This unit will control two 50-cycle drills of either the pilot-circuit controlled or direct-switching type. It is of the transformer type and will give a l25-volt, 50-cycle supply from any incoming 50 cycle circuit up to 650 volts. Although the overall height is only 19 in., overload and no volt protection, leakage protection and visual trip indication are provided.

Midget Gate-end Box. — This is designed to control one drill only, and is equipped with overload and earth-leakage protection. The dimensions of the box component are 18 in. by 14 in. by 13½ in., the overall length including the incoming trifurcating box is 29 in., and the weight is 125 lb. If desired the unit can be supplied for mounting directly to the side of a coalcutter, in which case the trifurcating box is replaced by a 100-ampere socket.

Midget Transformer Control Unit. — This has the same dimension as the midget gate end box, is designed to give 125-volts, 50-cycle supply from an incoming 50-cycle circuit up to 625 volts, and may be used to control a small portable pump or fan up to 2 h.p.

Drawings and Photographs accompanying the article