GB930797A - Hydraulic control of feed rolls of roller mills - Google Patents

Abstract

930,797. Roller mills. MIAG MUEHLENBAU UND INDUSTRIE G.m.b.H. Sept. 19, 1960 [Sept. 19, 1959], No. 32077/60. Class 59. [Also in Group XXIX] The regulation of the feed rolls in a roller mill is effected by hydraulic gear constituted by a pump 1, the displacement of which is variable by swinging the pump housing against a spring loading, and a motor 2, the gear, which also regulates a servo-mechanism, having its power device 5 connected to grinding rolls, being under the control of a spring-loaded material supply feeler 81 through an amplifier 6. In the idling position the parts are in the positions shown, the amplifier 6 having adjusted the pump 1 for minimum displacement whilst the motor 2 and power device 5 are inoperative. Upon supplying material to be ground to the mill, the feeler 81 is depressed so causing pin 8 to close the central bore 61<SP>1</SP> of the amplifier piston 61, whereupon fluid supplied to a chamber 62 above the piston 61 by the pump 1 increases in pressure and causes leftward movement of a spring-loaded valve-member 91<SP>1</SP>, whereby ports 95<SP>1</SP>, 9511 are interconnected so opening pipe 15 to exhaust. Pressure fluid from the pump 1 is fed to a chamber 53 of the power device 5 through a pipe 41, a bore and a radial port 97 in the valve member 91<SP>1</SP>, and a pipe 42; resulting leftward movement of the spring-loaded power device piston 51 brings the movable grinding roll towards the operative position, and uncovers a port whereby pressure fluid is supplied to the feed roll motor 2, which latter rotates before the piston 51 has completely aligned the movable grinding roll. Concomitantly, the exhaust path from the other side of the piston 51 through the pipe 15 is closed so that the remainder of the exhausting fluid is directed through an adjustable check valve 13 to retard the last part of the piston movement. Any variation in the supply of material to be ground repositions the feeler 81 and the pin 8, the piston 61 following up the pin 8 and effecting adjustment of the pump output. Upon cessation of the supply of material the parts return to the positions shown under the action of the varying loading springs, the feed being terminated only when the movable grinding roll has been partly removed from its operational position. The spring loading of the piston 51 may be replaced by fluid loading. If for any reason the pump fails, the motor 2 stops at once, since the supply thereto is cut off; however, the pressure in chamber 62 is maintained by the pin 8, but since the pressure supply to the bore of the valve member 91<SP>1</SP> is also cut off, an auxiliary piston 90 therein can move under the loading against a stop 98 and exhaust the pressure in chamber 62 via a passage 99 in member 91<SP>1</SP>, whereupon the loading on the latter moves the member 91<SP>1</SP> to the inoperative position shown; the piston 51 is also forced to return to its rightward position. The piston 90 need not be used in which case the valve port 91<SP>11</SP> is formed as a leaky piston.