334

MODERN STEAM PRACTICE.

steadily in position whilst passing over the carrying rollers at thehighest rate of speed. Comparing the amount of power requiredto convey a stream of grain at the rate of 50 tons per hour througha distance of 100 feet, by means of the common screw in stationarycasing, the tubulär screw with revolving casing, and the travellingband 18 inches wide, the following are the results:—

With the common screw..,...18*38 horse-power.

,, tubulär screw..25*00 ,,

,, 18-inch travelling band. 1*02 ,,

This shows the great superiority of the band over the screws ineconomy of power.

For the purpose of passing the grain off at any point on eitherside of the main travelling bands, several contrivances with air-blast and brushes driven from the band itself were tried, but withindifferent success; both methods were objectionable on account ofraising dust, and the friction of the brushes proved injurious to theband in course of time. The idea then occurred of diverting thestream of grain by means of an upward deflection of the carryingband, which would throw it clear from the band into the air for ashort distance, and in falling it would be caught and led off by aspout to either side as required. This plan proved successful, andhas been extensively adopted in connection with the use of theendless travelling bands for carrying grain. The throwing-offapparatus is shown in Fig. 212. It consists of a couple of wrought-iron rollers B B, centred in gun-metal bearings in a rocking frame C,which is hung in a movable carriage D running upon the timbers Eof the wooden framing that Supports the travelling band 11 . Thecarriage is moved to any position along the length of the bandwhere the grain is required to be discharged, and is then securedby the wedges F F and the clamping screw G. The rocking frame Cis rotated in either direction by means of the screw and wormwheel H, so as to bring the pair of rollers B B into action at theproper position for throwing the grain off in the direction in whichthe band I is running; and the rollers are turned back into thehorizontal position so as to be clear of the band when the carriage Dis required to be moved to another position. A curved spout K isattached to the carriage D for catching the stream of grain in itsfall, and leading it off on either side of the band I. No difficultyis experienced in keeping the grain on the band; but it is foundnecessary to let it fall upon the band from a feeding hopper through