The Mechanical Handling and Storing of Material

74 THE MECHANICAL HANDLING OF MATERIAL This type of conveyor is also used in the United States for handling salt from grainers. The trough is there made of hard maple wood, and the base sometimes lined with crude j-in. plate glass. The reciprocating motion is slow, and obtained either by a connecting rod and crank similar to those already described, or by an hydraulic cylinder. The stroke is 5 ft. and the feathering blades 24 by 6 by | in., placed 3 ft. pitch and heavily galvanised. These conveyors are frequently 200 ft. long, and it is believed that when the base is lined with glass they may safely be made 300 ft. long. Such conveyois have been at work for four years handling the salt from sixteen grainers, each 176 ft. long by 13 ft. wide. There is a further type of conveyor which, though differing from the foregoing, ought to be dealt with under the same heading. It is built on the Commichau principle, in which case the trough oscillates as well as the plates. This con- veyor is illustrated in Figs. 99 and 100, which show it in its extreme forward and its extreme backward position. The upper drawing shows the trough on the point of starting the forward movement, pushing the material forward by means of plates attached to the longitudinal rod. The lower illustration gives the conveyor ready for its backward movement, the plates having been turned upward through a turning motion of 180 of the spindle instead of being hinged as in the former case. It is only in short conveyors that the trough receives a backward and forward motion. In the case of greater lengths the spindle with its plates performs the back- ward and forward as well as the turning motion, while the trough remains stationary. Conveyors of this type are said to have been built for considerable lengths, but thgj appear to be more generally used for short lengths. It is said that a trough 12 in. wide will convey 50 tons of coal per hour. It is claimed for this appliance that it is more suitable than worm conveyors for handling material of a sticky nature. Figs. 99 and 100. Push-Plate Conveyor on the Commichau Principle.