GB907136A - System controlling the preparation of mixtures of bulk materials - Google Patents

Abstract

907,136. Weighing apparatus. PARKER Ltd., FREDERICK. Jan. 12, 1960 [Oct. 22, 1958], No. 33812/58. Class 143. [Also in Group II] A system for controlling the preparation of mixtures of bulk materials from ingredients in separate containers comprises air-operated means by which measured quantities of the separate ingredients are discharged into a common mixer in a sequence automatically controlled by a timing device. The invention is described with reference to the preparation of an asphalt mix from four sizes of granite A, B, C, D, a filler component such as cement E and a liquid bitumen product F. These components are measured out in automatic feed weighers having, in the case of the solid components, a hopper 2 (Fig. 1 ) closed by an air-pressure operated door 6, and, in the case of the liquid component, a tiltable bucket 5 fed from a pipe. The hoppers and bucket constitute the separate containers from which the mixer 8 is fed and the quantities fed are controlled by weigh-heads 3 of the type described in Specification 907,134. The control system (Fig. 2) is operated automatically by air pressure from a line 11 which, by a switch valve 17, is connected to lines 18 and 29. Line 18 operates a further switch valve 26 by which the storage bin or supply conduit 20 of each component is opened to be subsequently automatically reclosed under the control of the respective weigh-heads 3, this part of the system being as described in Specification 907,135 In the case of ingredient E the air pressure which opens its feed gate also operates a vibrator 49 to assist the feed. When the ingredients have been thus weighed out an operator switches on an electric motor (not shown) to rotate a camshaft 41 whose cams 37 to 40 open valves 43 to 46, respectively, to control the discharge sequence by air from line 29. Cam 37 momentarily opens its valve to provide a pressure pulse by which the condition of a two-way valve 51 is changed to admit air from a constantly live line 10 to a valve 55 which operates the clutch of the belt elevator 9 by which the granites A to D are conveyed to the mixer. The same air pressure through line 53 is fed by an adjustable restrictor 56 to a cylinder 57 which, when sufficient pressure has built up therein, opens a valve 59 to supply pressure to the opening means of the hoppers of ingredients A to D. The hopper doors are opened in pairs, A and B by a valve 63 and C and D by a valve 64. In order that the two pairs may open at different times the delay device comprising the parts 56, 57, 59 may be duplicated, one controlling each valve 63, 64 and made to operate in sequence by appropriate adjustment of the restrictors 56. Visible indicators 73 show the condition of the hopper doors which are closed automatically when a cam 74 carried by the elevator which operates a valve 76 by which the valve 51 is restored to its original condition. Cams 38 and 39 respectively control the discharge from the bitumen bucket and hopper E by the opening of valves 80 and 91 which are subsequently reclosed by delay devices 88 and 94. When all the ingredients have been mixed cam 40 admits pressure to a line 97 from which a valve 98 is operated to open the discharge doors of the mixer which are closed when the pressure in line 97 is cut off. The required opening time is determined by the shaft of cam 40 which, unlike cams 37 to 39, is of the " dwell " type. The operating doors when open operate an indicator 104 and also a batch counter 107. Independent control of each of the operations performed in the above automatic sequence may be obtained if required by the reversal of switch valve 17 so as to energize line 19 and de-energize lines 18 and 29. Line 19, through manually-operated valves 112, 115, 116 and 119 to 122 may then be connected at will to the feeding means of any of the hoppers, or the bitumen bucket and to any of the corresponding discharge controlling means. Specification 856,091 also is referred to.