Fig. 49.—Beating Engine with Four Beater Rolls.
The Hollander.—This beating engine in its simplest form consists of an oval shaped trough, divided into two channels by a “midfeather,” which does not, however, reach completely from one end to the other.
In one of the channels the bed of the trough slopes up slightly to the place where the “bedplate” is fixed. The bedplate consists of a number of stout metal bars or knives firmly fastened into an iron frame, which lies across this channel. The beater roll, a heavy cast-iron roll provided with projecting knives or blades arranged in clumps of three around the circumference, and supported on bearings at each side of the engine, revolves above the bedplate with the knives adjusted to any required distance from it, the raising or lowering of the beater roll for this purpose being effected by the use of adjustable bearings.
The bed of the trough behind the beater roll rises sharply up from the bedplate and then falls away suddenly, as shown in the diagram, forming the “backfall.”
When the engine is in operation the mixture of water and pulp is drawn between the knives and circulated round the trough. The material is disintegrated into fibres of the required condition, discharged over the backfall, and kept in a state of continual circulation, and the beating maintained until the stuff has been sufficiently treated.
The dimensions of the engine vary according to the capacity, which is usually expressed in terms of the amount of dry pulp the beater will hold, and the following figures may be taken as giving the average sizes:—
| — | 2 cwt. Engine. | 5 cwt. Engine. |
| Length | 11 ft. 0 in. | 16 ft. 0 in. |
| Width | 5 ft. 6 in. | 8 ft. 0 in. |
| Depth (average) | 2 ft. 3 in. | 2 ft. 9 in. |
| Diameter of roll | 3 ft. 6 in. | 3 ft. 6 in. |
Sundry modifications in the form and arrangement of the beater have been tried from time to time. In 1869 Granville patented the substitution of a second beater roll in place of the stationary bedplate for the purpose of hastening the operation. Repeated attempts have been made to construct a beating engine with two or more rolls, but it is evident that such a device could hardly succeed, since it would be impossible to ensure proper adjustment of the rolls, and in that case one roll might be doing all the work.
The first machine of this type was patented in 1872 by Salt. Similar beaters were devised by Forbes in 1880, Macfarlane in 1886, Pickles in 1894, who proposed to use three rolls, and Partington in 1901. Hoffman describes a beating engine which was working in America containing four rolls, as shown in the diagram.