Abstract: A gear-skipping prevention mechanism including a first gear, a second gear, and a positioning member is provided. The first gear is sleeved on an axle. The second gear meshes with the first gear and has a first guiding groove. The positioning member includes at least one body and at least one engaging portion. Each of the at least one body has a sleeving hole. The sleeving hole is sleeved on the axle, and each of the at least one engaging portion is slidably disposed in the first guiding groove to limit a relative position between the first gear and the second gear.

Abstract: A gear-skipping prevention mechanism including a first gear, a second gear, and a positioning member is provided. The first gear is sleeved on an axle. The second gear meshes with the first gear and has a first guiding groove. The positioning member includes at least one body and at least one engaging portion. Each of the at least one body has a sleeving hole. The sleeving hole is sleeved on the axle, and each of the at least one engaging portion is slidably disposed in the first guiding groove to limit a relative position between the first gear and the second gear.

Abstract: A projection device comprises a plurality of elements, a base seat and an outer cover. The elements are used for respectively executing specific functions to cause the projection device to operate. The base seat comprises a first side surface and a second side surface, an element fixing structure is disposed on the first side surface and used for fixing the elements, and a first fixing device is disposed on the second side surface. The outer cover comprises a third side surface and a fourth side surface, the third side surface is used for forming an outlook surface and a second fixing device is disposed on the fourth side surface. The elements are installed on the element fixing structure, the first fixing device and the second fixing device are combined together when the projection device is assembled.