692,518. Roller mills. TURNER, Ltd.. E. R. & F. Jan. 22. 1952 [Jan. 31. 1951; Nov. 16, 1951], Nos. 2471/51 and 26990/51. Class 59 A roller mill is provided with a hydraulic system arranged to separate the grinding rollers and to bring them together, a control device responsive to the feed of material to the grinding rollers, and electrical means responsive to the control device for automatically operating the hydraulic system. The control device is in the form of a spring-influenced plate 1 pivotally mounted on a shaft 2 carrying a cam 4 which is engaged by a roller 5 carried on an end of a push rod 6 the other end of which carries a strip 7 provided with contacts 8, 9 engageable with contacts 10, 11 respectively. The contacts 8 and 10 are in a circuit to a red lamp R, and the contacts 9 and 11 in a circuit to a green lamp G and a solenoid 13. The latter is connected to the stem 15 of a control valve 16, Fig. 4, which is fed with oil under pressure from a sump 21 via a pump 22 and a port 23. When the stem is in its lower position, the oil is returned to the sump by means of exhaust ports 24, 25, and when the stem is in its upper position, corresponding to energization of the solenoid, the oil passes through an exit port 28 through a pipe 29 to a pivoted hydraulic ram cylinder 30. The upper end of the ramrod 35 of this cylinder is pivotally connected to a link 36 which is rigidly connected to a crank shaft 37 formed with a crank pin 38 to which is pivotally connected a bearing 39 having screwed therein one end of a screw-threaded rod 40. The other end of the rod 40 extends into a housing 41 and engages with a gearing 42 adapted to be turned by a handle 43 to rotate the rod and adjust the distance between the housing 41 and bearing 39. A bottom bearing 44 supporting an end of the movable grinding roller, whose axle is shown at 45, is pivoted at 46. The other end of the bearing 44 is slidably mounted on a rod 47, which is screwed into the housing 41, and is pressed against the housing 41 by means of a spring 48. The axle of the fixed grinding roller is shown at 49. 'One, 54, Fig. 4, of the feed rollers is driven from the other feed. roller 53 which is driven from the movable grinding roller by means of a chain 52 and sprocket wheels, and in this drive is a clutch which may be engaged or disengaged by means of a clutch rod 55 which is pivotally connected to one end of a bar 56 the other end of which is pivotally connected to an arm 57 of the link 36. In operation, when the normal feed of material is passed down on the feed duct, the plate 1 is forced to the "on" position causing the shaft 2, and hence the cam 4, to be rotated. The rod 6 is forced to the left, thereby breaking contacts 8 and 10 and making contacts 9 and 11. The red lamp R is thus de-energized and the green lamp G and the solenoid 13 energized. Energization of the solenoid raises the stem 15 of the valve 16 causing oil to pass to the ram cylinder 30, and the ram rod 35 to rotate the crank shaft 37 in a clockwise direction. Rotation of the crank shaft will cause the crank pin 38 to move upwardly in a clockwise direction pulling the rod 40 upwardly and causing the bottom bearing 44 to pivot clockwise about the pivot 46. This will cause the axle 45 to come nearer the axle 49 and the grinding rollers to come to a predetermined setting. Clockwise rotation of the crank shaft will also move the bar 56 to the right, thereby causing the clutch rod 55 to engage the clutch and the feed rollers to be driven. When the flow of feed material ceases or falls to a very low value, the plate 1 reverts to the "off" position, the contacts 9 and 11 are broken and the contacts 8 and 10 made thus de-energizing the solenoid and forcing the stem 15 downwardly by its spring 14. The oil pressure in the ram cylinder 30 will be relieved and the ram rod will be forced downwardly under spring action thereby rotating the crank shaft in an anti-clockwise direction, separating the grinding rollers and disengaging the clutch to the feed rollers. In a modification, Fig. 6 (not shown). the shaft 2 is freely mounted in a cylindrical cavity formed in the side of the cam 4 and is provided with spigots which project into radial slots in the cam, the shaft being free to rotate without any effect on the cam until the spigots contact either side of the slots. In a further modification, Figs. 1 and 2 of the second Provisional Specification (not shown), hydraulic rams act directly on the bearings of the movable grinding roller, and the clutch to the feed rollers is operable by a hydraulic ram.