is provided in each of the fixing portions 24b the protruding portion 28 is formed to protrude in the direction of the wall thickness of the drum casing wall 12 and engages with the corresponding step 12a in the drum casing wall 12 consequently when the steps 12a are engaged with the protruding portions 28 the wire guide 20 will not move in the circumference direction as a result dislodging of the wire guide 20 can be prevented moreover as shown in fig3 since the engaged surfaces form an angle greater than a semicircle the wire guide 20 is most difficult to dislodge also by providing the reinforcing portion 26d each protruding portion 28 is rendered difficult to be deformed and strong engaging can be realized the wire guide 20 further comprises guide portions 22 since the guide portions 22 differ in shape from the wire guide portions 116a shown in the prior art example of fig8 and 9 but have the same function a detailed description is omitted below fig7 shows a modified wire guide in fig7 an endless wire 30 passes through a tube 32 an insert portion 34 to be guided by the guide portion 40 is provided at the end of the tube 32 to be more precise the insert portion.