The Mechanical Handling and Storing of Material

CHAPTER XV MISCELLANEOUS CONVEYORS, MOSTLY FOR SPECIAL PURPOSES AND NOT CLASSIFIABLE UNDER ANY OF THE PREVIOUS CHAPTERS Roller Conveyors, Live Rollers, or Roller Trains.—These differ from roller runways in the important detail that the rollers are mechanically driven, and the revolutions of the rollers carry the material forward, either on the level or on an upward or downward gradient, whereas in the roller runway (see page 197) the object to be transported travels by its own gravity over a series of rolls down an incline, the load revolving the rollers as it passes over them. Roller ways without driving power can be, and indeed are, used on the level or incline in connection with rolling mills where red-hot girders newly rolled are pushed over such roller ways, but in these cases the rolling mill furnishes the driving power and conveys it to the small rollers by the object itself, the rollers merely reducing friction or resistance which would otherwise be offered to the progress of the rolled bar, girder or rail. Power driven roller conveyors are used in plate glass factories, in rolling mills for handling ingots, and in engineering works, to take away the products of cutting shears, saws, or other machine tools ; carrying away objects in course of manufacture which are too heavy or bulky to be easily removed, and which, if not continuously cleared away, would encumber the machine tools producing them. The upward gradient for these roller conveyors is limited by the amount of friction between the rollers and the material. The original type of such roller conveyors is exceedingly simple in principle, but not in construction. The rollers are placed fairly close together and each is driven by a pair of bevel wheels from a small shaft which runs alongside at right angles to the roller spindles and forms a portion of the conveyor. The rollers, of course, all revolve in the same direction and must therefore not touch each other. The difficulty in the construction is principally due to the close proximity of the parts to each other, and as the driving wheels should be smaller in diameter than the rollers, in order that they should not project above them and thereby obstruct the passage of the material conveyed, or be exposed to damage, the rollers must either be larger than would otherwise be necessary, or the wheels must be very small. The “Thomas” Roller Conveyor.—-A great improvement in this type of conveyor has been made by the Belgian engineer, A. Thomas, who has overcome the difficulties above referred to as will be seen from the conveyor illustrated in Fig. 245. Here the rollers are all loose, /.<?., they do not run on axles or bearings, but revolve on rotating rings, every fifth or sixth pair of rings being driven by a pair of mitre wheels; the rings with their driving spindle being on a lower level than the rollers, give ample space for fair sized mitre wheels without their projecting above the carrying plane, level with the top surface of the rollers. The upper of the two cross sections (see Fig. 245) shows one of the driven pair of rings, while the other cross section shows a pair of the loose rings, unconnected with driving power. The working of the conveyor depends on the driving 182