The Mechanical Handling and Storing of Material

COAL TIPS OR HOISTS 535 unloaded. This does not cause any waste of power, as the water only circulates between pump and tank. When the truck is ready to be tipped the water from the pump is forced into the hydraulic cylinder by turning a lever which controls a valve, when the ram slowly lifts the back portion of the truck off the line, whilst the front wheels rest against stop- blocks. The coal begins to discharge from the removal of the tail-board till the truck has been lifted to an angle of 45°. To lower the truck on to the line the water is allowed to escape from the cylinder into the tank out of which the pump is fed. This can be done slowly by carefully opening the valve. Coal Tip of Pohlig.—A powerful platform tip is that built by Pohlig, of Cologne, shown in Fig. 750. The platform is pivoted at its fore end, and is raised above the level of the ground by hydraulic force applied to its centre. The truck, of course, moves Fig. 750. Coal Tip as built by Pohlig. with the platform until it is tilted at an angle of 45°, at which angle the rest of the material is discharged into the hopper or other receptacle on a level with the line. 1 o minimise the expenditure of power, the weight of the platform is balanced by counter- weights. In other respects this platform is designed exactly on the plan of the cradle used in the other automatic tipping devices built by the same firm, which are described elsewhere. To prevent a sudden drop of the heavy platform and its truck, which might happen if some portion of the gear were accidentally to give way, this tip is provided with a safety brake which holds the truck and platform so that in case of breakage it cannot move either up or down any faster than at its normal speed. Tips in Factory Yards.—For use in factory yards the tips previously described have the inherent disadvantage that, unless the railway siding is raised on some structure above the ground level, it is difficult to dispose of the material unloaded by them, as