Patent GB-670896-A (GB)
Title: Improvements in or relating to the blending of dry powdered or other finely divided dry materials
IPC: B01F3/18
Filed: 1950-01-12
Abstract: 670,896. Charging and discharging storage bins; trimming and spreading apparatus; conveyers. URBAN, V., and PRETORIA PORTLAND CEMENT CO., Ltd. Jan. 12. 1950. [Jan. 13, 1949] No. 791/50. Classes 78 (i) and 78 (iv). [Also in Group II] Powdered or granular materials to be mixed, e.g. during the manufacture of cement, are superimposed in evenly spread layers in a bin and are then caused to flow, mixing, down a progressive free face approximating the natural plane of repose, for discharge from the base of the bin. Materials are laid in evenly spread layers in a bin 1 (Fig. 1) by a belt 6 and tripper 7 for removal by an oscillating screen 2 which directs the material so blended to screw conveyers 5 (see also Fig. 2) in tunnels beneath the bin. The screen is gradually moved along the bin during unloading and with it move endless chains or cables 35 carrying a belt 23 closing the discharge openings of the troughs 4 which feed the screw conveyers 5. When the bin has been emptied the oscillating screen and belt 23 are returned to the starting position bv a drive at a higher speed. The screen is carried by links 12 from a steel structure 9 supported by rollers 10 running on rails 11a fixed to the side walls of the bin. As shown in Fig. 2, it is in three parts, which are oscillated by pairs of eccentrics 13 set 120 degrees out of phase on a pair of shafts 14 mounted on the frame 9 and driven through a reduction gear 16 from an electric motor. Each part of the screen is shaped at 3a to enter the corresponding trough 4 and consists of wire mesh carried on a frame. Aluminium baffle plates 18 (Fig. 1) fixed to the structure 9 or carried by the frames of the screens prevent material flowing through the screen when stationary: material lodged between the screens and the baffles during loading is released to flow through a gate 38 before unloading is started by moving the screens backward slightly. The wire mesh screens may be replaced by perforated plates or by a system of slats . similar to a venetian blind : the slats may have a feathering action as they rise and may be wide enough to present a closed baffle when feathered. The baffle plate 18 may be replaced by a light canvas-covered frame or frames and these may be removed during discharge; alternatively, temporary closures similar to roller or slatted blinds may be used. The screens, etc. are preferably inclined slightly less steeply than the natural angle of repose of the material, the end wall of the bin being inclined at the same angle : the inclination of the screens may, however, be adjustable. The use of two bins as shown in Fig. 2, provides a continuous action, one being loaded as the other is discharged. Other means, such as a pneumatic conveyer or a bucket elevator and screw conveyer may be arranged for laying the material in layer in the bin and the belts 23 for closing the troughs 4 may be replaced by a construction which relies on the material arching in the troughs until disturbed by the screen. Where belts are used they may be relieved of some of the weight of the material by inverted V-section girders secured centrally in the troughs 4.