Modern Gasworks Practice

288 MODERN GASWORKS PRACTICE the distributing valve of a small actuating ram, the stroke of which reverses the Controlling valve and opens the exhaust port to the pusher cylinder, thus with ch-a. wing the telescopic rams. This tappet is engaged by the ram-head at a predetermined point on. the outer stroke. In practice it is found that the outward discharging stroke takes about 10 seconds to be completed, whilst the return stroke ic accom-plished in 8 seconds. The chief merit of this type of pusher lies in the faet tliat there are only four giands to pack, whilst only one of them has to withstand the severe effeets of entering the retort. The wear and tear is, in faet, almost inconsiderable, a pusher chain lasting for about twelve months before it has finally to be discarded. The De Brouwer Stoking Machine The first charging machine involving the projector principle was introduced by the late M. De Brouwer, gas engineer at Bruges. The outstanding advantage of this machine compared with otters in use at the time was its ability to charge a full-sized retort from one side only, thus avoiding the necessity of installing machines on both sides of the bench. The whole apparatus is extremely simple, and consists of carrying a large grooved pulley, three band pulleys for guiding a broad for coal. The principle Telescopic Shoot Tand isli Grooved Pulley 1 metre diam. Electric Motor Power to start Machine 10-15 amps at 220 volts. a steel frame Fig. 205.—Line Diagram showing Principle of De Brouwer Projector. band, a driving motor, and a telescopic feeding shoot of operation will be readily understood by reference to the line diagram (Fig. 205). The three band pulleys are arranged on the inside of the broad endless coal belt, and are so placed that this belt is made to take about a quarter turn round the large grooved pulley. The coal band bears on the two flat flanges of the pulley and causes the pulley to revolve at the same speed as the belt. The band is driven by ordinary belt drive on to the front band pulley from an ordinary shunt wound variable speed electric motor of 4 to 6 b.li.p., having a speed variation of from 750 to 1,500 revolutions per minute. Equally good results, however, may be obtained with compressed air motors or rope drives. The ordinary type of machine as now in general use is illustrated in Fig. 206. From this it will be seen that at the upper portion of the travelling framework there is a small hopper or measuring chamber into which the coal is fed from contimious hoppers erected in the retort house. A telescopic shoot leads from the measuring chamber to the groove of the large pulley, thus the delivery tundish for coal automatically adjusts itself as the machine is raised or lowered to the various tiers of retorts. The operation of charging is as foliows :—Assuming that the overhead hopper