Chain transmission device

The utility model relates to a range-extending transmission device, in particular to a chain transmission device. The chain transmission device is characterized in that the chain transmission device comprises a linear supporting frame, a linear machining part in the shape of chain wheel teeth is fixed to the linear supporting frame and is integrally connected with an L-type piece, a chain supporting plate is fixed to a right supporting plate on the linear supporting frame through a cushion block, an idle wheel fixing plate is connected to the chain supporting plate through a cushion block, an idle wheel is fixed to the idle wheel fixing plate, a force-bearing plate is connected between a left supporting plate and the right supporting plate of the linear supporting frame, and an air cylinder is connected with an air cylinder floating connector and is then fixed to the force-bearing plate. The range-extending transmission device is compact in structure, light in weight, stable and reliable in operation and capable of achieving the range extending function.