GB1325859A - Mass measuring system - Google Patents

Abstract

1325859 Screw conveyers MERRICK SCALE MFG CO 23 July 1971 34818/71 Heading B8A [Also in Division G1] Apparatus for determining the rate of delivery of fluent material by a screw conveyer comprises means for measuring the resonant frequency of the conveyer system, representing the mass of material in the conveyer, and multiplying this value by the rotational speed of the screw conveyer. Material is fed from a hopper 10 (Fig. 2) via a screw conveyer 14 on a hollow shaft 15 to a drum 17 mounted on a hollow shaft 18 rotatably supported in a housing 19 attached by plates 20, 21 to two pins 22 (Fig. 3). A motor 26 drives the shaft 15 through gear-wheel 32, and shaft 18 through gear-wheel 31, flexible shaft 34 and collar 35. The material is fed from screw 14 to the closed upper end of drum 17 and out from the open lower end to a shoot 38. A motor 46 drives an eccentric 44 through a flexible shaft 47, producing a rocking motion of a frame 39, which is transmitted by a pivoted arm 41 to produce oscillation of the drum 17 about pins 22. The phase of the rotation of motor 46 is sensed by an inductive pick-off 50, and that of the vibration of frame 39 and drum 17 by inductive pick-off 481. When the vibration frequency is the resonant frequency of the drum the phase difference is 90 degrees, and this con - dition is obtained by a phase comparator 54 (Fig. 1) which compares the pick-off signals and supplies a voltage to a controller 48 energizing motor 46 to maintain this relationship. Motor 46 also drives a disc 56 via chain 70 and lead screw 67, which rides on a cone 55 driven by a constant speed motor 60, whereby the axial position of the disc along the surface of the cone is indicative of the speed of motor 46. The linear position of the disc 56 is translated via crank mechanism 75, 76 into angular position of a wheel 83, coupled to the slider of a potentiometer 86 fed by a tachogenerator 90 driven by the screw conveyer motor 26, whereby the voltage at the potentiometer slider is proportional to load X speed, i.e. rate of delivery of material from the conveyer in, e.g. pounds per minute.