A flexible line trimmer for cutting vegetation having a rotary drive for swinging a nylon line. A housing with an actuator button on its bottom is connected to the rotary drive. A spool for the line is located in the housing. An actuator mechanism is connected between the button and the spool for feeding...http://www.google.com.tw/patents/US4236309?utm_source=gb-gplus-share專利 US4236309 - Flexible line trimmer with line feeding apparatus
