Apparatus with automatic belt tensioning

An apparatus with automatic belt tensioning comprising:

• a casing;
• a winding seat pivotally contained in the casing and including a winding portion and a first gear, the winding portion being disposed on one side of the first gear;
• a belt windable around the winding portion, one end of the belt being fixed at the winding portion and the other end passing through the casing;
• a first elastic element contained in the casing and connected with the winding portion, the first elastic element releasing elastic potential energy to rotate the winding portion to allow the belt to be wound around the winding portion;
• a rotation preventing element rotatably contained in the casing and including a bearing shaft and a protrusion, the belt being disposed across the bearing shaft from the winding portion and the protrusion being capable of retaining the first gear;
• and
• a second elastic element contained in the casing, one end of the second elastic element abutting on the rotation preventing element, and the second elastic element releasing elastic potential energy to push the protrusion of the rotation preventing element towards the first gear;
• wherein when the belt is pulled to be away from the casing, the belt drives the winding portion to rotate and drives the rotation preventing element to rotate to allow the protrusion to be separated from the first gear, thus allowing the first elastic element and the second elastic element to store the elastic potential energy, respectively.