Patent GB-682070-A (GB)
Title: Control mechanism for motor-driven conveyor belts
IPC: B65G43/04
Filed: 1949-04-20
Abstract: 682,070. Engine stop-gear. FRONHOFF, J., and GRIMBERG, H. April 20, 1949, No. 10440/49. Class 122(iv) [Also in Group XXX] Control means actuated by slip between a conveyer belt and its driving means actuates an indicator for total slip, a signal device when the total slip is a predetermined length short of a predetermined total length, and finally stops the drive motor, e.g. a fluid pressure motor, upon the slip reaching said predetermined total length. The driving shaft of the conveyer belt (not shown) rotates a shaft 11, Fig. 3, through a pulley 12, whilst an idler roller over which the belt passes rotates a shaft 16, in alignment with shaft 11, through a pulley 17. The speeds of rotation of shafts 11 and 16 are arranged to be equal when there is no slip of the belt on its driving drum. When slip occurs the one or ones of four planet gears 6 which are in the upper half cycle of revolution about the shafts 11 and 16 are rotated by the relative rotation of a sun wheel 15 on shaft 16 and a carrier bracket 8 for the planet gears mounted on shaft 11. During the lower half cycle of each planet gear a fixed cam 53 engages a roller 52 on the planet gear shaft 7 and pushes shaft 7 radially outwards in a slot in bracket 8 against the action of a spring 49, out of engagement with the sun wheel. While the planet gear is thus freed, opposed spiral springs 54, 55 bring it to a neutral position, whereby a pair ot arms 22 formed integrally with the planet gear are set perpendicular to the radial direction. Upon each planet wheel engaging the sun wheel at the beginning of its upper half cycle it is rotated by slip between the belt and its drive to cause one arm 22 to be moved into a substantially radial position as it reaches the top of the cycle, at which point a roller 21 on the arm engages a lever 23, Fig. 2, pivoted at 24 to a casing 9, which lever has a spring pressed pawl 26 adapted to operate a ratchet wheel 28, so that the ratchet wheel is moved one step. Lever 23 is spring-returned, and a hump 45 on pawl 26 engages during the return motion a peg 46 to withdraw the pawl from the orbit of the ratchet teeth, so that the latter can be moved by a hand wheel (not shown). A shaft 27 supports ratchet wheel 28 and also two cams 29 and 31, one in front and one behind, Fig. 2. In operation of the control means, the ratchet wheel is set back by the hand wheel a predetermined number of teeth from the position in which a depression 37 in the front cam 29 receives a roller 38 on the end of a lever 33 pivoted at 32. As the total slip in lengths of one metre or more builds up towards the predetermined total length the ratchet wheel is stepped forwards by the pawl 26 whereby before depression 37 is in position to receive roller 38, a second roller on a lever similar to lever 33 and behind the ratchet wheel falls into a long recess 39 in the cam 31. this being arranged to operate a signal device, and upon roller 38 falling into depression 37 in the cam 29, lever 33 operates a switch 35 to close a valve in a fluid supply line and thereby stop the drive motor. Any slip of the belt in lengths of less than one metre does not actuate the ratchet wheel since the arms 22 of the operative planet wheel 6 are not deflected sufficiently for one of them to engage lever 23.