| 摘要 |
550,087. Chain-tensioning devices. RENOLD & COVENTRY CHAIN CO., Ltd., and COULSON, R. Sept. 2, 1941, No. 11232. [Class 80 (i)] Relates to automatic chain tensioning devices in which the chain passes over a sprocket rotatable on a hub eccentrically mounted on a spindle, the hub being urged in a direction to tighten the belt by a spring, reverse movement being prevented by a ratchet and pawl device. According to the invention, a frictional damper opposes rotation of the hub, the damping effect being increased when the hub moves in a direction to relieve tension in the chain. The sprocket 16 is freely mounted on a hub 12 eccentrically mounted on a fixed spindle 10, a spindle 24 in the hub carrying a pawl 22 adapted to engage teeth on a ratchet 18 on a mounting 20 carrying the spindle. The pin 24 serves as an anchorage for a coil spring 26, the other end of which is attached to the spindle. Between one end of the hub and the spring is arranged a multi-plate brake, alternate plates 28 of which engage the pin 24, the others having a projection engaging a recess 32 in the spindle. The outermost plate 33 is held on the spindle by a U-shaped washer 34 engaging a groove 36 and lying in a depression in the plate 33. The plates are pressed together by two springs 40. To obtain the braking movement, the ratchet 18 is mounted on its support with slight relative rotary movement and is formed with three conical recesses engaging the conical ends of pegs 42 secured to the mount 20, these ends acting as cams. When, therefore, the ratchet tends to move backwards under the action of the pawl 22, the ratchet and hub are moved axially to the left to press the plates 28, 30 together. A forced oil-feed for lubrication may be provided through a bore 37 in the spindle 10 and radial passage 41 leading to the chain wheel. The oil also lubricates the eccentric hub and passes to the brake plates. The pawl has a tail-piece which projects, under the action of a spring, beyond the surface of the hub 12 so that if the chain wheel is displaced laterally its bore may be utilized to hold the pawl clear of the ratchet teeth and thus facilitate assembly.
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