Patent GB-509694-A (GB)
Title: Improvements connected with the regulation of the density of pulps, sludges or fluids
IPC: B03B13/00
Filed: 1937-10-18
Abstract: 509,694. Automatic control systems ; specific-gravity estimating - apparatus ; weighing-apparatus. FIFER, A. J. J. Oct. 18, 1937, Nos. 28362/37 and 4721/38. [Class 38 (iv)] [Also in Groups XVIII and XX] Concentration.-The specific gravity of pulps, sludges, slurries, or fluids is regulated by varying the flow of the lighter or heavier constituent to the main pulp circuit in accordance with the movement of a weighing apparatus arranged periodically to weigh a representative sample of the pulp and to operate means for indicating the specific gravity of the pulp. A test tank 7 is filled with pulp at intervals under control of a time switch 169 which first closes contacts 167 to effect closure of valve 19. When the tank is filled, 16, 17 are operated under control of float 27 to divert the stream of pulp. The tank 7 is carried on a balanced beam 32 normally held by clamps 38 which are opened under control of the time switch 169 when the tank is full. If the specific gravity of the pulp is incorrect the beam 32 tilts and operates a graphic recorder 171, a mechanical indicator 177 and moves a frame 88 carrying a contact making arm 95. The recorder 171 indicates throughout the daily working period the changes from normal of either the light or heavy constituents of the pulp or of its specific gravity. The contact arm makes contact with one or more members of one of two sets of contact members 96, 98, 100, 102 or 97, 99, 101, 103 depending on the amount and direction of its movement. When the clamps 38 have almost reached their maximum opening the time switch 169 opens switch 162 and closes switch 163 and switch 185. The arm 95 is then closing circuit through the members in contact therewith to selected relays of one of the relay sets 106-109 or 110-113. An indicator lamp corresponding to the specific gravity of the pulp in tank 7 is then lit and an appropriate solenoid in one of the groups 152-155, 156-159 is energized to control devices 4, 65 to vary the amount of lighter or heavier constituent fed to the pulp tank 1. This solenoid may control the devices 4, 65 through tap changing arrangements controlling the torque motors operating these devices. The mechanical indicator 177 is' clamped at its operated position by coil 181 on closure of switch 185. In an alternative arrangement, the control may be effected by an induction coil secured to the end of the beam 32 and arranged, on movement of 32 to move past and induce current in a series of coils arranged in an arc, such current being used to control the constituents supplied to tank 1 through tapchanging devices and torque motors. In an arrangement described with reference to the drawing accompanying the first Provisional Specification (not shown), a contact member carried on the beam is arranged to co-operate with contacts arranged adjacent thereto, to indicate the specific gravity by illumination of appropriate lamps and control the amount of water to the pulp mixing tank. The time between tests may be halved by using two tanks carried by separate balance beams and filled alternately. For pulp of high viscosity, a tank having a narrow neck is used. Various arrangements for ensuring the correctness of level of the pulp in the tank, e.g. scraping devices for removing excess pulp and devices for vibrating the tank may be employed. A continuous stream of pulp may run through the testing tank when no test is taking place or a pulp stream may be diverted to the tank only when it is desired to fill it. The second Provisional Specification describes an arrangement for controlling the specific gravity of sludge in an ore mill by control of the amount of dry solids fed to the mixing chamber.