HOIST HAVING YIELDING MEANS FOR LOAD LIMITING

1380604 Slip clutches; clutch brake combinations EATON CORP 12 April 1972 [12 April 1971] 16872/72 Headings F2C and F2L [Also in Division B8] A load limiting device between the drum drive shaft 10 and a chain drive wheel 11 of a hoist, comprises a hub portion 13 of the drive wheel operatively connected to the drive shaft 10, a driving portion 14 mounted for rotation on said hub portion, a series of asymmetrical detent recesses 24 formed in the driving portion 14 for engagement with spring biased detents 17 mounted in openings 16 in the hub portion 13 to normally form a driving connection between the two portions, the detents yielding and moving into successive recesses to enable the driving portion 14 to rotate on the hub portion 13 when subjected to more than a pre-determined torque in the load lifting direction. The detents 17 comprising either rollers or balls normally seat in the bottom portion 25 of adjacently disposed recesses 24, but upon excessive torque due to lifting too high a load, the detents roll along relatively gradual inclines 26 of the recesses and out into the next recess providing a slipping action. During lowering of a load the detents engage the other relatively steep sides of the recesses which offer far greater resistance to any slipping action, so that the drum shaft 10 can be forced in the load lowering direction against any brake binding of the hoist brake mechanism. The hub portion 13 is screwed on to the shaft 10 and moves up to compress friction discs on to a ratchet disc and a further hub rotatable with the shaft, when the drive wheel 11 is rotated in the load lifting direction, the ratchet preventing reverse rotation of the shaft unless disconnected therefrom by unscrewing motion of the hub portion 13.