| 摘要 |
PURPOSE:To automatically provide a spring material with a tensile strength to cope with its stretch to improve its durability and to prevent positional deviation of carriers by providing a pressure plate which has two legs that are abuttingly provided on exterior surfaces of the frames that are facing each other and deflected towards inside, and a pressing portion which is located in the middle of the legs and pushes supporting members towards outside of the frames. CONSTITUTION:Since a left supporting member 2 is pushed towards left side by a pressure plate 5, a belt 6 is kept in tension. If the belt 6 stretches during prolonged use, the pressure plate 5 moves correspondingly to the stretching to gradually move the supporting member 2 towards left, and the belt 6 is automatically provided with an appropriate tensile strength. No excessive tensile strength is given to the belt 6, and its life is extended. After the belt is provided with the tensile strength, the leg 3 does not open towards because of its elasticity and interlinking with a protrusion, and the supporting member 2 is kept under a static condition. Therefore, regardless of a difference in a moving direction of the carrier, either forward or backward, a stretching or a shrinking of the belt 6 is prevented, and the positional deviation of the carrier 8 is also prevented. |
