| 摘要 |
PROBLEM TO BE SOLVED: To provide a sewing machine which can improve the durability of a double-toothed belt for linking an upper shaft and a lower shaft together and can suppress the tooth skip and the fluttering of the double-toothed belt while saving space.SOLUTION: In a double-toothed belt 99, internal teeth 99A mesh with an upper shaft pulley 75, a left pulley 71 and a right pulley 72, and external teeth 99B mesh with a lower shaft pulley 85 and an intermediate pulley 73. The top edge of tooth parts 71A of the left pulley 71 is located above the bottom edge of tooth parts 85A of the lower shaft pulley 85. Thus, the number of teeth meshing with each other is increased in the meshing of the tooth parts 85A with the external teeth 99B of the double-toothed belt 99. Load applied to each tooth forming the external teeth 99B is reduced, so that the durability of the double-toothed belt 99 is improved. The intermediate pulley 73 meshes with the double-toothed belt 99, so that a straight part shorter than a virtual straight line 77 is formed on each of the upstream side and the downstream side in the travel direction of the double-toothed belt 99 with respect to the intermediate pulley 73. As a result, the double-toothed belt 99 is hardly fluttered while traveling.SELECTED DRAWING: Figure 6 |
