Patent GB-450753-A (GB)
Title: An improved method of automatic tension control in belt and rope drives
IPC: F16H7/14
Filed: 1934-11-19
Abstract: 450,753. Tensioning belts. SWIFT, H. W., 2, Ellenthorpe Road, The Glen, Shipley, Yorkshire. Nov. 19, 1934, No. 33180. [Class 80 (i)] [See also Group XXXV] In an automatic tension control for belt and rope drives of the type in which the drive is effected through a pulley mounted on a unit in which the torque is wholly or mainly transferred through a usually stationary part mounted in such a way that it is capable of rotating to some extent about a substantially horizontal axis parallel and eccentric to the axis of the pulley, the usually stationary part of the driving or driven unit is mounted in such a way that it is capable of a substantial angular displacement about a real or virtual axis parallel to the axis of the pulley and eccentric to it by an amount not exceeding the radius of the pulley and chosen according to the permissible ratio between the tensions in the tight and slack sides of the belt or rope as hereinafter described, the weight of the unit being so disposed or modified, when a real axis is employed, that it produces initial tension in the belt or rope. The Specification contains an explanation of the principles underlying the invention. As applied to an electric motor with a substantially horizontal drive with the tight side of the belt above, the motor 1 is carried in a rectangular frame 2 having one longitudinal member carried pivotally, in brackets 3 secured to the feet of the motor, the other longitudinal member being held adjustably by set-screws 4 in brackets 5 fixed to the motor casing. The two end members of the frame carry pins 6 above the pulley axis 7, these pins being supported in pedestals 8 bolted to and adjustable horizontally on slide rails 9. The eccentricity of the pivot is determined jointly by the position of the pins 6 and the adjustment of the pedestals. Rotation of the frame is limited by stops 10, 101 on the pedestals. In another construction Fig. 5 (not shown), the motor is at the lower end of a vertical belt and its casing is pivoted at an eccentricity approximately equal to the radius of the pulley and which is adjustable. The effective weight of the motor is adjustably taken by a spring. In another construction, Fig. 6, the drive is horizontal with the tight side below. A pair of similar toothed wheels 21, less in diameter than the motor pulley 23, are secured, one to each end plate of the motor 22, concentric with its shaft and mesh with a pair of racks 24 which carry the weight of the motor. Each rack forms part of a frame 25 on the under side of whose upper member is a rack 26 parallel to the supporting racks 24. An idle wheel 27 engages each wheel 21 and the rack 26, the dimensions &c. being such that slight play exists between racks 26 and idlers 27, the latter being located axially by shrouds on the outer faces. Each frame 25 is bolted on an adjustable pedestal 28. The instantaneous pivotal axis of the motor is, in this case, the line joining the points of contact between wheels 21 and racks 24, and, under the transmitted torque, the motor casing tends to roll back along the racks 24 to tighten the belt. The wheels 27 serve merely to keep the wheels 21 gearing with the racks 24, but if the drive were such that the tight side is above, then the frames 25 with wheels and motor could be inverted. In a still further construction, Fig. 7 (not shown), the motor is at the upper end of a vertical belt and is suspended by a pair of adjustable links inclined to one another to determine an instantaneous pivotal axis. Specification 442,904 is referred to.