GB853465A - A control device for grinding rolls of the automatically engaging and disengaging type, particularly in mills - Google Patents

Abstract

853,465. Roller mills. BASS, E. July 16, 1958 [July 22, 1957], No. 22782/58 Class 59 [Also in Group XXIX] In roll grinding mills, particularly flour mills, the rolls are moved into engagement with each other by hydraulic pressure supplied by a continuously running pump, on the closing of a by-pass control valve controlled by a device sensitive to the weight of feed material in the feed hopper of the mill, and the engaging movement causes a second by-pass valve to open and unload the pump again on completion of this movement. The rolls are held in the engaged position by a latch which is released by the weight sensitive device on emptying of the hopper to allow the rolls to return to the disengaged position under gravity. Another latch and a rod system operatively associated with the engaging movement act on the second by-pass valve to release it for opening on engagement of the rolls and to return this valve to a closed and latched position on disengagement of the rolls. The movable grinding roll 31, Fig. 1, of a flour mill is carried on a lever 29 pivoted at 28 and is movable into engagement with the fixed roll 32 by a hydraulic device "A" which comprises a servo piston 12, Fig. 3, supplied by a pump 9 continuously with liquid which normally traverses the piston and passes freely back to a sump through a pipe 14, a piston control valve 8 in its open position, and pipes 15, 16. Control valve 8 is moved to the closed position as shown, in response to the weight of grist in a feed hopper 1 acting on a pivoted flap 2 to depress it against the resistance of a weighted arm 3 and lift the control valve to a closed position through a rod 4 and lever 7. Indefinite or incomplete closing of this control valve, which might occur owing to insufficient grist in the hopper, is avoided by a free force piston 17 below the valve, which piston, as soon as the valve has only partially closed and some pressure has built up in pipe 14, forces the valve to the fully closed position. Hydraulic pressure is thus applied beneath the servo piston 12 which, through a lever 20, pull rod 21, eccentric shaft 22, rod 25, and spring box 27, raises the lever 29 to engage the rolls. A lever 33 on the eccentric shaft 22 simultaneously through a push rod 34 pushes forward a lever 36 having a detent to engage a pivoted latch 51 and hold the rolls in the engaged position. Towards the end of this engaging movement, a push rod 42 connected to lever 36 acts through a bell crank 43, a pull rod 44 and a further pull rod 47, Fig. 3, to release a second latch 41 from beneath a weight loaded by-pass valve 39 which drops, assisted by the thydraulic pressure, to the open position as shown and unloads the pump again through a pipe 40 and pipe 16. On emptying of the feed hopper, the weighted. arm 3 descends and releases the latch 51. from lever 36 to allow the roll 31 to return under gravity to its disengaged position. Arm 3 in descending returns the control valve 8 to its open position, whilst the descent of the roll lever 29 simultaneously allows a spring-loaded rod, system 49, 52 (Fig. 3) to rise and return the by-pass valve 39 to its closed position and re-engages the second latch 41 beneath this valve. In a modification (Fig. 4, not shown), the second latch 41 is actuated hydraulically in phase with the control valve 8. The rolls may in emergency be engaged directly by applying manual effort to the lever 36.