GB1161542A - Conveyor System - Google Patents

Abstract

1,161,542. Drives for belt conveyers. HEWITT-ROBINS INTERNATIONAL S.A. 17 May, 1967, No. 22866/67. Heading B8A. [Also in Division H2] The torque/speed characteristics of head and tail drives, including electric motors, for a conveyer belt are so selected that the drives apply differential torques to the belt, which torques act in opposition or in the same direction, depending whether the action of gravity on the load on the conveyer is or is not acting to increase the speed of the conveyer, so as substantially to compensate for unequal tension forces introduced by the weight and distribution of the load on the conveyer. In one example, a head motor 21 is provided with a control 34 and an eddy current coupling 22 between the motor and the belt drive is adjustable. A motor 29 with a control 30 drives the tail end of the conveyer and brakes 25, 31 are provided. With a 100 H.P. 3% slip characteristic tail drive motor, a 50 H.P. 8% slip head drive motor and a load A as shown in Fig. 1, an average estimated belt tension of 6000 pounds and a horse-power of-50 is required. The latter results from 25 H.P. drive applied by the head motor and a resistance of-75 H.P. applied by the tail motor and is shown graphically in Fig. 4. The effect is to resist the tendency of the descending load A to cause loss of belt tension. With an increased descending load, Fig. 2 (not shown), the belt speed rises but is stabilized and the tension maintained due to an increase in the resistance to -109 H.P. by the tail motor. With the load entirely on an uphill slope, Fig. 3 (not shown), a total positive application of 84 H.P. is necessary at a reduced speed (see Fig. 4). A counterweight 2 provides adjustment for changed belt lengths due to stretch or contraction. In a further construction, Fig. 5, a master counterweight system 52 is supplemented by a slave system 54 which during starting, provides tension at the tail 53. The differential drive may be obtained by using different gear ratios for the two drives in Fig. 1. Alternatively different pulley diameters and connections having different slippage characteristics can change the ratios between the drives.