To smoothly rotate a control lever without a deformation even when the left-right sizes of the control lever are increased for improving workability.

A handle frame 6 with an inserting port 10 communicated with an opening section 4 is installed on the rear of a front plate 3a. Both-side end sections of a rotating shaft 16 for the control lever 15 made slightly shorter than the breadth of the inserting port 10 of the handle frame 6 are supported rotatably by the front of a rear plate 3b so that the lower end section of the control lever 15 is suspended into the inserting port 10. A plurality of control members (guide pieces) 11 controlling the front and upward movement of the upper end section of the control lever 15 are mounted in the horizontal direction at the upper end section of the handle frame 6.