The Mechanical Handling and Storing of Material

204 THE MECHANICAL HANDLING 0E MATERIAL revolving disc and into the shoot. The capacity is fixed by the speed of the plate and the location of the adjustable gate. Fig. 276 illustrates the apron-conveyor feeder used for handling material of all sizes. The conveyor may be of any of the various types of apron flights, depending upon the nature of the material to be handled. The chain should be provided with rollers or wheels travelling on track to prevent the apron from sagging. The capacity is fixed by the speed of the apron and the position of the adjustable gate. The disadvantage of this type is the inherent disadvantage of the apron conveyor. Should the flights become bent or buckled, the material leaks through or catches between them. It has an advantage over other feeders in that it may be used to carry the material a greater distance. A rubber or canvas belt may be used in place of the apron, in which case the Fig. 275. Revolving-Plate Feeder. belt is supported by idlers placed close together. I he swinging-plate feeder, shown in Fig. 277, is used for handling coal and such material of all sizes. It consists of two castings pivoted at their tops and swung alternately so as to move the material forward on the bottom plate. The plates are moved by connecting rods from a crank or eccentric through a rocker shaft. The capacity is fixed by the length and number of the strokes, but as it is limited to the amount of material displaced by the plates, a wide range is not possible. The disadvantages are the lack of adjustability and the tendency of the material to pack. It will also be noted that the feeder is not self-cleaning, so that the bottom plate always contains material which is very liable to freeze in the winter.1 The plunger feeder, illus- trated in Fig. 278, is similar in Fig. 276. Apron-Conveyor Feeder. operation to the swinging-plate feeder in pushing the material along the bottom plate. 1 he plunger may be built either in one or two parts, moving ahead alternately and driven through a rocker shaft, as in the case of the one previously described. The capacity is fixed by the number and length of the strokes and the location of the adjust- ing gate. 1 his type has the same disadvantages as the swinging-plate feeder, the most serious being that it is not self-cleaning. Fig. 279 shows the reciprocating-plate feeder, consisting of a plate mounted on four wheels forming the bottom of the hopper. When the plate is moved forward, it carries the material with it, and when it is moved back the plate is withdrawn from under the 1 This defect does not obtain in the English climate.