Patent GB-521959-A (GB)
Title: Means for distributing comminuted material flowing in a duct in desired proportions
IPC: F26B17/10
Filed: 1938-11-29
Abstract: 521,959. Mills and apparatus. GROVES, W. W. (Combustion Engineering Co., Inc.). Nov. 29, 1938. No. 34727. [Class 59] [Also in Groups XIII, XXX and XXXVII] A method of distributing comminuted material in desired proportions to a number of different ducts, the material flowing through a conduit or carried in suspension in a gas flowing through a duct, comprises valve means arranged to open in succession each of the ducts to the conduit so as to receive material therefrom while closing the remaining ducts and maintaining the various ducts open to the conduit for time periods the relative lengths of which are determined in dependence on the proportion of the material to be received by each duct. The method is applied in a drying system in which comminuted material is dried and part is discharged while the remainder is mixed in the supply of raw wet material. As shown in Fig. 1 for supplying a ball or impact mill 23 with wet material such as grain, sewage sludge &c. together with a proportion of dried material, the apparatus comprises a hopper 1 for wet material and a feed screw 3 which discharges the material through a pipe 9 to mixing blades 11 where it mixes with dry material fed through a duct 15 from a separator 31. The mixed material falls into a drying chamber 19, fed with hot gases from a furnace 21, and is led to the mill 23. Ground material from the mill is exhausted by a fan 29 and is discharged into the separator 31, the moist gases leaving the separator through pipe 33. The separated material in the mill is partly returned through the duct 15 for mixing with the uncrushed wet material, and partly discharged through a duct 37 by means of a continuously - operating flap - valve 39 operated mechanically; or by a solenoid 49, the proportion of discharged material to refed material being controlled by the length of time one or the other duct is closed. A mechanical device for operating the flap is shown in Fig. 5, a constants speed motor 133 drives a cam 139 through 'gears 135, 137, the cam actuating a spring-controlled pushrod 141 provided with spring-controlled adjustable stops 143, 145 which contact alternately with an arm 127 on the: pivotal shaft 41a of the flap-valve 39a. The shaft 41a is also provided with an arm 125 connected by a spring 129 to the conduit whereby the valve is rapidly closed when the arm passes over the dead centre. By altering the position on the rod of the stop 143 or 145 the length of time during which the flap closes a conduit may be varied. The solenoid 49 is energized through a circuit shown in Fig. 4. In this circuit a time-swtich A, shown in Fig. 2, is driven by a constant speed motor, the shaft 93 of which drives a connecting rod 97 non- electrically connected to a block 99 slidable on insulated rods 89 to move an electric contact 101 thereon away from a similar contact 105 on insulated rods 87. The contact 105 is adjusted in position along the rod by a cam 107 which is insulated from the contact by material 113, the position of the cam being indicated by a pointer 121 and disc 119. The rods 87, 89 are provided with terminals 109; 111 which in Fig. 4 are shown connected in circuit with a solenoid 65 operating a relay switch 59 and a secondary coil 67 which derives a low potential current from a primary winding 69. When the switch 57 in the main leads 53, 55 is closed current flows through the primary coils 69 and 77 and starts up the motor 91 of the timing switch A. The primary coil 69 induces current in the secondary coil 67 during the interval the switch A is closed thus energizing the coil ,65 to close the switch 59. Two leads 61, 63 to the solenoid 49 actuating the flap 39 are thus supplied with current from the mains 53, 55 to energize the solenoid to move the flap 39 into the right-hand position shown in Fig. 1. When timing switch A is opened the coil 65 becomes de-energized, the switch 59 opens, the leads 61, 63 no longer supply current to the coil 49 and the spring 51 moves the flap 39 into its left-hand position. Lamps 73, 75 indiccate when the coils 65, 49 are energized and furnish visible signals of the time between the two positions of the flap and indicate the proportional division of the material. U.S.A. Specificaton 2,023,247 is referred to.