Patent GB-1408370-A (GB)
Title: Flow controllers for flowable substances and apparatus and  installations incorporating such controllers
IPC: G05D7/03
Filed: 1973-08-06
Abstract: 1408370 Weighing BUEHLER AG Gebr 6 Aug 1973 [23 Aug 1972 27 April 1973] 37274/73 Heading G1W [Also in Division G3]  A flow controller, e.g. for grain or liquids entering a storage container, comprises, Figs. 1 to 3, a downwardly convergent duct 13 which directs the flow medium past a rotary valve-member 132 on to an impact plate 14 secured to the end of a counterweighted beam 6 pivoted at 7, the opposite end of beam 6 controlling compressed air leak-off. from a nozzle 9 so as to set up a variable control pressure in line 11 connected to a diaphragm type servomotor 12 actuating valve-member 132 to maintain the mass flow of the medium constant at a pre-set value. The pre-setting means comprises an auxiliary beam 1 pivoted at 8 and bearing on beam 6 via a member 4 which can be adjusted in the longitudinal direction by a guide screw 5 carried by and below auxiliary beam 1. The latter also carries a weight 2 slidable along a percentage scale 3 representative of the desired mass flow of the medium. The control pressure line 11 includes a valve 15 which in an emergency blocks the line and vents servomotor 12 to atmosphere so that spring 122 moves valve-member 132 into the closed position. Impact plate 14 is of stainless steel coated with P.T.F.E. to reduce friction. In a modification Fig. 4 (not shown) adjustable weight 2 is assisted or replaced by the action of a pre-set air-pressure (S) on a diaphragm device (20) bearing on a lever (22) attached to auxiliary beam 1. In a further modification Fig. 5 (not shown) adjustable weight 2 is replaced by a diaphragm device (200) subject to the action of a pre-set airpressure (S) and movable by an electric motor (19) along a guide bar (17) so as to vary the point at which the device bears on auxiliary beam 1. A battery of flow controllers, each as in the Fig. 4 arrangement, may be provided to control the flow of individual components to a mixing apparatus. In this arrangement the loading pressure (S) to each diaphragm device (20) is supplied via a line 29 from a respective control device 40 in a central control station LS, Fig. 6. Each of the devices 40 is connected to a common control device 40. The former and latter respectively pre-set the desired individual and total mass flows. Each control device 40 comprises a pivoted beam 28 controlling compressed air leak-off from a nozzle 24 so as to set up the variable loading pressure (S) in a line 26 communicating with a diaphragm device 27 acting on the beam 28 and with diaphragm device (20) acting on auxiliary beam 1. A further lever 30 bears on beam 28 under the action of diaphragm device 33 and is pivotably mounted on a plate 31 which can be moved longitudinally of beam 28 by a guide screw 34 engaging nut 35 on the plate. The latter carries a pointer 32 co-operating with a percentage scale 38 representative of the desired mass flow of the individual component. Diaphragm device 33 is connected via lines 29', 26' to diaphragm device 27'and leak-off nozzle 25' of the common control device 40'. The latter is constructed in similar manner to control device 40 except for the provision of springs 33', 33". Percentage scale 38' is representative of desired total mass flow. Lines 29", 29''' connect with the respective diaphragm devices 27 associated with the respective control devices 40 of the other flow components.