By advancing the dog along the stud and setting up the small hand-wheel tight against it, any desired position of the curved arm can be maintained. Rota ting the curved arm, the dog remaining fixed, alters the justment of the rolls, but they can be restored to their previous adjustment by bringing the curved arm back to the dog. Generally about Fin. is the maxi mum spread of rolls required. The wooden housing is parted horizontally at the roll cen ters, the top being lifted bodily so that the rolls can be easily removed when necessary.
In the top is placed the feed-device. This consists essentially of two gates, extending across the top part of the housing. and swung on axes at their upper edge, and connected by levers and links, so that motion of one implies that of the other. The upper gate forms one side of a V-shaped hopper, into which the material falls. The lower edge of the other gate ap proaches a feed-roll located as shown by the extended bearings near the bottom of feed hoppering. Fastened to the shaft on which this gate swings is the arm carrying the counter weight.
When no material is in the hopper, this lower gate is swung against the feed-roll, but as material enters in the upper gate it accumulates in the hopper formed by this gate and the stationary cant-board at center of the housing, until the weight is sufficient to overcome the effect of the counter-weight, when this upper gate swings down, allow ing the material to pass to the space below it, where it meets the lower swinging gate, and passes between its lower edge and the feed-roll to the grinding-rolls beneath. The secondary hopper is provided so that material coming into it from the first hop per will have a chance to distribute itself over the entire length of the feed-roll. The greater the quantity of material press ing against the upper gate, the greater the opening at the feed-roll, and consequently the greater the quantity passing to the grinding rolls. The desired quantity of feed can be obtained by adjusting the counter-weight on its arm. The lower part of the housing contains the brushes for cleaning the rolls, and the door in front permits access to materials passing from the rolls. The feed-rolls are driven by a single belt ;missing from the neck of one slow roll over each pulley on the feed-rolls, and the tightener-pulley shown at top of the housing.
The following table gives the dimensions, capacity, etc., of mills using a belt-drive on the slow roll : Several makes of roller-mills are made with box-frame construction, and with rolls mounted in swinging arms. The Gray mill is the pioneer in this form of construction. In this mill
the vertical adjustment of the rolls is obtained by an eccentric bash fitting over the stud, on which the swinging arms are suspended. Notion to the rolls is obtained by the use of one belt, a counter-shaft and pul lers running in boxes hung to the frame acting to Ininsinit motion from the main belt to the slow rolls, a pulley on one end of the counter being the tight ener pulley for the main belt, while the pulley on the other end of the counter serves to carry the slow-roll belt.
Fig. 7 shows a method for driving both fast and slow rolls in a Stevens double mill which has proved satisfac tory, The large pulley on the beneath the floor drives the fast rolls, the small pulley the slow ones. The means for tightening the belts are read ily seen. In some short systems of mill ing only two or three breaks are made, and in such cases the machines shown in Fig. 8 can he used especially where economy of room is necessary. The ma chine drown has two pairs of corru gated rolls and two reciprocating sieves. The grain passes through the first or upper pair of rolls and on to the first or upper sieve. A separation of the prod uct is here made. flour and middlings passing through the sieve and away from the machine; the large unreduced por tion passes over the tail of the sieve on to the second pair of rolls, and from there on to the second sieve, when a second separation is made. The sieves have traveling brushes beneath them, thereby enabling the meshes to be kept clean. The machine is driven by a sin gle belt, and adapted to mills of 75 to 150 bbls. capacity, the power required being-from 3i horse-power with 9 X 14 in. rolls to 6 horse-power with '9 X 30 in. rolls.
In Fig. 9 is shown a type of roller mill used in grinding corn, as made by the Nordyko & Marmon Co., of Indian apolis, Ind. Three pairs of rolls are used, disposed so as to break the grain successively. The first pair are ad justed solely by the hand-wheels shown, while the middle and lower pairs are spread or thrown together by a single lever. The. fast roll of each pair is driven belt from the main shaft. The slow rolls are driven by gears. The machine is built very rigid in order to meet the hard usag,e found in this class of wurk. In a mill using rolls 9 X 2-1 in. the capacity is stated to be 65 to 100 hush. per Mum and the power required 12 to 20 men The upper pul ley runs 400. the middle 445. and the hover 500 revolut bins per min. The pulleys are 20. IS. and 16 in. diameter and Hi in. rime for upper, middle, and lower drives respectively.