Unloader

unloader [¦ən′lōd·ər]

(mechanical engineering)

A power device for removing bulk materials from railway freight cars or highway trucks; in the case of railway cars, the car structure may aid the unloader; a transitional device between interplant transportation means and intraplant handling equipment.

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unloader

A control mechanism for an electric-motor-driven compressor; controls the pressure head of the compressor; permits the motor to be started at low starting torque by removing the load during this initial period of operation.

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Unloader 

(unloading machine), a machine used to unload bulk goods into spoil banks, bins, or conveyors. Unloaders include dumpers, scoopers, and vibrators, as well as pneumatic and plow unloaders.

Car dumpers and dump trucks are two types of dumpers. Plow unloaders push loads from railroad flatcars to the bunkers beneath them by means of plows, which move back and forth.

Scoopers are used to unload open cars and consist of a combination of either scoop elevators or flight conveyors and a stacker belt conveyor, which are mounted on a self-propelled chassis or gantry; the open car being unloaded is set beneath the chassis or gantry.

The basic element of vibrators is a vibration table, which communicates oscillations to the load. The load pours through the hatches of a car under the impulse of vibration. Loosening clamps are secured on vibration tables to free frozen loads.