Patent GB-245850-A (GB)
Title: Improvements relating to pulverising mills
IPC: B02C25/00
Filed: 1924-10-16
Abstract: 245,850. Imray, O. Y., (Raymond Bros. Impact Pulverizer Co.). Oct. 16, 1924. Roller-and-ring mills; feeding-devices for granular and like material.-An electrically-driven pulverizing mill is provided with feeding- mechanism which by electric means is rendered inoperative or diminishes the feed when the overload on the mill has attained a certain predetermined magnitude and resumes its normal feeding operation when the overload has been reduced to normal. The mechanism for regulating the material fed to the mill is responsive to changes in the motor current caused by variations in the load on the mill. The regulating-device may be pneumatically operated, and the pneumatic operation electrically controlled. The feeder of a mill may comprise a pair of members that can be disengaged from each other, such as a pawl-andratchet mechanism, and the feed-regulator constructed so as to lift the pawl from engagement with its ratchet when the mill is overloaded and to allow the pawl to engage with the ratchet when, through cessation or diminution of feed, the load thereon has been reduced to the extent desired. The pawl is moved into and out of engagement with its ratchet by a quick and practically an instantaneous action, and a lag is provided in the mechanism so that it will respond only to load changes of a certain magnitude. In the mill shown, Fig. 1, the material is pulverized between a stationary ring 10 and revolving rollers 11 and the pulverized material is withdrawn by a fan E connected to the pipe D. The pocket-feeder 12 receives a step-by-step rotation from a ratchet 13 and pawl 15. Fig. 4, pivoted at 16 to a carrier 17 which is rocked on the shaft 14 by a pitman 18 operated by a crank 21 on a shaft 22 driven by a belt 23. The pawl 15 is raised from the ratchet by means of a pneumatic device F evacuated when the overload on the mill has attained the degree at which the feedregulator is set to operate. The device F consists of a casing 31 secured to a flange 33 on the carrier 17 and of a flexible diaphragm 34 secured to the casing rim 35, a coiled spring 38 being interposed between the bottom of the casing and a plate 39 on the diaphragm. A lip 40 on the pawl 15 is engaged by a finger 41 carried by a bell-crank 42 which is pivoted at 43 to a bracket 44 on the casing 31 and at 45 to the plate 39. The finger 41 is carried on a slide 46 which extends into a recess 47 in the upper end of the bellcrank so that by retracting the slide the feedregulator may be rendered inoperative. A tube 48 connects the device F with a controller G which responds to changes in intensity of the current passing through the motor B and is connected by a pipe 49 to the discharge pipe D of the mill. Fig. 2 shows the construction of the controller G. An electromagnet, preferably a solenoid coil 53, is supported on the top of a casing 51 by an arm 52 which is secured to the casing by a bushing 54 through which projects a sleeve 55 extending through the coil 53 and adapted to receive the solenoid core 56. A valve 58 secured to the core 56 seats on the upper extension 60 of an adjustable tube 61 which screws into the bottom 62 of the casing, and a rod 65 extends through the tube 61 and valve 58 into the core 56 and carries nuts 69, 70 by means of which the lift of the valve 58 can be varied. A flexible diaphragm 73<1> is clamped at its edge between casing members 72, 73 carried on the side of the casing 51, and a ring 74 screwed on to the member 73 holds in place a number of air-filters 75. A valve 78 secured to the diaphragm 73<1> bears in one position against a seat 79 on a web 80 of the member 73 and in another position against a seat 81 secured to a web 83 on the member 73. When the mill is feeding, the device F is open to atmosphere through tube 48, chamber 196, and chamber 86. When the mill is overloaded, the solenoid 56 is attracted by the coil 53 which is arranged in circuit with the leads 100, 101 of the motor B and the valve 58 is raised so that air from the port 85 passes into the chamber 89 on the inner side of the diaphragm 73<1> which is thereby deflected outwardly and the valve 78 moved from the seat 79 to the seat 81. With the valve 58 closed, the chamber 89 is subject to the vacuum through the port 93, space 92, and pipe 49. With the valve 58 open, the exhaust of air from the chamber 89 continues, but as the opening 93 is small the pressure in chamber 89 increases to a point but little below atmospheric. The suction from the mill continues to be exerted against the other side of the diaphragm 73<1>, the chamber 91 being in communication with space 92 and pipe 49 through the relatively large opening 94. With the valve 78 on its seat 81, the chamber 96 is closed to the chamber 86 and open to the chamber 91 which is subject to the mill vacuum, so that the device F is exhausted and the bell-crank 42 rocked to disengage the pawl 15 from its ratchet 13, thereby stopping the feed, or, if a second pawl 29 engaging a second ratchet 30 with smaller teeth than the ratchet 13 is provided, diminishing the feed. Figs. 5 and 7 show a modified form of controller responsive to the changes in the intensity of the motor current. The solenoid coil 104 is arranged in a casing 105 secured to the under side of the casing 102, and a member 110 set into the back of the casing 102 has ports 111, 112 connected to the pipe 49 and tube 48 respectively. A sliding valve casing 114 adjustable by means of a screwed rod 117 bears against the inner face 113 of the member 110. The rod 107 screwed into the solenoid core 106 carries a valve 136, 137 co-operating with seats 132, 135 in the casing 114, the lower valve 137 being adjustable on the rod 107. With abnormal load on the mill, the solenoid 104 will raise the core 106 and valve structure, thereby closing the port 134 so that the device F is shut off from the atmosphere and opening the port 131 so that the device F will be exhausted, the air passing through port 112, chamber 128, port 131, chamber 126, and port 111.