Page:Popular Science Monthly Volume 90.djvu/753

 A Mine-Car Which Unloads Itself

Start the mechanism, and the car will be loaded, driven to its destination, emptied and returned in one minute

��ANEW drop-bottom mining car is being used in the larger mines of the country. It operates automatically. It is loaded by automatic chutes; it is driven in trains by an electric motor and it is even dumped by me- chanical trippers. The car is of larger capacity than previous types, although the distance from its top to the rails is only a little over two feet.

The bottom of each

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��The three sections which comprise the bottom of the automatic dumping car

��.TRIGGER STRIKES LATCrt IN FIRST TRAP DOOR OF LOADED CAR

���INCLINED TIMBER KNUCKLE CLOSES DOOR

���ALL THREE DOORS AU END DOOR

�TOMATlCALLY LOCKED BY CLOSING OF REAR

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� ��CAR EMPTY AND LOCKED-

���A car loaded with coal passes over a projection above the tracks. A trigger is operated and the three sections at the bottom of the car open one after the other. The car then moves over a sloping beam and the sections slide up this and are closed and latched once more

��car is divided into three sections. As a train of cars loaded with coal passes over a storage pit, a rail projecting upwards from the track operates a trigger at the rear of each car. The trigger moves sideways and releases the bottom section of the car next to it. The weight of the coal in this section immediately forces the section open. Just as soon as this happens, the middle section is also released. When this middle section has swung open, the construction of the bottom of the car is such as to release the re- maining section also.

Thus, in a very few seconds all the sections will have swung open and all the coal will have been dumped. The car then travels onward to another mechanism. This automatically closes the bottom sections of the car. It consists merely of a sloping beam against which the opened sections slide as the car moves along. The sections slide to the top of the beam one after the other. They are thus raised up past their catches and successively closed.

The cars are drawn from the mine by a small electric locomotive. In some mines, however, neither motor nor mule is required to draw the loaded cars to the storage pits. Instead the roadway of the cars is made sloping. The weight of the loaded cars is suffi- cient in these cases to furnish the drawing power. In the run back to the mine the locomotive is, of course, used. The cars are empty on this return trip, so that little electric power is needed.

The cars are of all-steel construction and will last for many years. Besides their simplicity of operation, they can haul the coal far more quickly than can other types. From fifteen to twenty two-and-a-half-ton cars are operated in one minute without requiring the slightest attention after being started.

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