Patent ID: 8251826

Claim:
A transmission device, comprising: a first transmission mechanism comprising a first rotating portion and an engaging portion fixed on the first rotating portion; and a second transmission mechanism comprising a second rotating portion with substantially a round flat shape and at least one overload protection subassembly, the second rotating portion defining a receiving hole in the middle thereof to receive the engaging portion, and a cavity communicating with the receiving hole, the at least one overload protection subassembly comprising: a transmission member pivotally positioned at an external side of the engaging portion and in the cavity of the second rotating portion, one end of the transmission member engaging with the engaging portion to rotate with the first rotating portion; and two flexible members resisting against an opposite end of the transmission member in opposite rotating directions of the transmission member to make the transmission member locate at a non-rotatable position with respect to the first rotating portion; wherein the transmission member is elongated-shaped, a positioning hole is defined in the middle of the transmission member, a fixing hole is defined in the second rotating portion corresponding to the positioning hole, a fixing member passes through the fixing hole and inserts into the positioning hole for pivotally positioning the transmission member in the cavity of the second rotating portion.