| 摘要 |
PURPOSE:To eliminate the need of both a cam and a cam shaft by forming an operating lever as to have an elongated part and having said part directly press a primary shoe and, to reduce a ratio between the lever composites of the operating lever by locating the turning center of the operating lever in a position outside of a drum. CONSTITUTION:A hole 9 in which an operating force transmitting means, such as a wire and a pulling rod is to be fixed is formed on one end part of an operating lever 8. The operating lever 8 has an elongaged part, which bypasses a drum 5 and further goes inside it. Said part is partially bent in the vertical direction at the end thereof, forming a contacting part 10 which is to press a primary shoe 1. When the operating lever 8 is turned in the arrowed direction A, the contacting part 10 which is integrated with the operating lever 8 presses the primary shoe 1. The primary shoe 1 will then be widened against a tensile spring 11 to make contact with the internal face of the drum 5. |
