Patent ID: 8221247

Claim:
A transmission device, comprising: a first transmission mechanism comprising a sleeve-shaped first rotatable member, a first transmission member having a plurality of first permanent magnets fixed to the first rotatable member for rotating together with the first rotatable member, and a plurality of ridge-shaped spacing portions disposed on an inner surface of the first rotatable member to space the plurality of first permanent magnets; a second transmission mechanism comprising a second rotatable member and a second transmission member fixed to the second rotatable member for rotating together with the second rotatable member, the second transmission member received in the first transmission member and having a plurality of second permanent magnets corresponding to the plurality of first permanent magnets for being magnetically connected with the first transmission member, when an actual load applied to the first transmission mechanism is less than a predetermined value of the first transmission mechanism, the first transmission member rotates together with the second transmission member by a magnetic force generated therebetween, which in turn makes the first transmission mechanism rotate with the second transmission mechanism together.