THE MECHANICAL HANDLING OF MATERIALS 303
and similar objections. Coal is received on the drag-bars, and the charger-discharger travels forward with. the “ shot ” of coal (automatically closing on its way the cut-off at' shoot bottom) until the required position is reached at fur ther end of retort, when the mechanism being reversed causes the grid of drag-bars, before any backward movement is commenced, to lift vertically through the coal to the top of the retort, in which. position it travels during the return stroke. This movement (1) frees the drag-bars from the coal; (2) loosens the coal as the bars pass vertically through, it, while the drag-bars finally level the charge in the retort, the heiglit to which they are raised being capable of adjustment. This provision, togetlier with. one for adjusting cut-ofi at the shoot bottom, enables the charge of coal to be regulated as desirecL The charger-discharger is then hronght back to the loading position, and a slight forward movement drops the drag-bars to level of retort bottom ready for the second instalment of coal, which, adinitted through the cut-off door, is carried forward like the first one. Three such operations suffice for a 20-feet retort. For discliarging coke. a foot-lever is depressed, and the drag-bars in their raised position are drawn back clear of the top of the push-plate by a short backward movement of the push-chain. In this way a fixed ram for discharging is formed. The operation of the machine will best be understood by reference to the diagrams given in Fig. 220.
Fig. 221.—The Nebbiebb Coke Discharger fob Stop-ended Retorts.
The Nerkiére Coke Discharger
An interesting example of a drawing machine designed for the extraction of coke from stop-ended retorts on small works is the Nerriére discharger. The appara-tus has mainly been employed in France, and consists essentially of two jointed portions carried upon a horizontal piece, and terminated by two Steel hooks which