Patent GB-712752-A (GB)
Title: Improvements in idler rollers for conveyor belts
Inventor: WALKER DANIEL NORMAN
IPC: B65G39/02
Filed: 1951-02-27
Abstract: 712,752. Endless belt conveyers. NATIONAL COAL BOARD. May 27, 1952 [Feb. 27, 1951; June 11, 1951], Nos. 4769/51 and 13807/51. Class 78 (1) In an idler roller for a conveyer belt in which the roller is rotatably mounted on a stationary spindle, the roller and the spindle or a stationary frame supporting the spindle are provided with stops which cannot normally engage each other but which on the occurrence of friction between the roller and material adjacent to it or of friction between the roller and its spindle due to failure of the bearings or to the infiltration of dust into the bearings substantially exceeding that existing in normal operation, come into engagement so that the roller is prevented from rotating. Figs. 1, 2, 7 show the application to an idler roller supported on a stationary spindle 10 having flat end portions engaging in slots 36 in frame portions 35. The roller is provided at each end with a bearing comprising two semi-circular collets 4, 5 'each provided with a rectangular-recess which together form a rectangular slot 9 in which engages the portion 11 of the shaft having a square cross section. Each portion 11 is formed with recesses 13 in each of which a ball is held by a spring 23 housed in a recess in one of the collets 4, 5. Rigid with the collets is the inner race of a ball bearing, the outer race of which is rigid with an annual member 17 rigid with the roller. When increased internal or external friction occurs, this.tends to resist rotation of the roller and cause belt drag whereby sideways movement of the roller is effected and the balls 22 are forced from the recesses 13. The roller thus becomes eccentrically mounted on the spindle, whereby stops 18, 19 on the spindle abut against stops 20, 21 on the roller and further rotation of the roller is prevented. In a modification, Fig. 9, the spindle part 11 is normally held centrally within the slot 9 by two springs 38, but when increased belt drag takes place, the roller moves on its spindle in the direction of movement of the belt and the stops 18, 19 engage the stops 20, 21. In a further modification, Figs. 10, 11, spring-loaded balls 26 seated in recesses 25 in the square or rectangular section ends of the spindle, normally hold each spindle end central within a slot 28 in a frame 27. Excessive friction causes the roller and its spindle to move sideways in the direction of motion of the belt whereby stops 29 on the roller abut against stops 30 on the frame 27. In another arrangement, Fig. 12, a plate 40, keyed to the spindle 10 is normally pressed by a spring 42 against a pin 43 of fusible material of comparatively low melt-' ing point. Any abnormal rise in temperature due to friction causes the pin to melt whereby the plate 40 is pushed along the spindle so that its ends engage stops 44 on the roller. In a further construction, the roller is mounted on its spindle by means including a member of fusible material of comparatively low melting point, so that upon the occurrence of excessive friction the resulting rise in temperature causes the member to melt and the roller to become eccentric relative to its spindle and the stops provided on the roller abut stops on the spindle. In any of the above arrangements, the stops on the spindle and roller may form parts of an electric circuit which in normal operation is not closed, but becomes closed when the stops contact one another, this circuit then being operative to actuate a warning device and/or to switch-off the conveyer motor.