APPARATUS FOR CONTROLLING THE OPERATION OF ELECTRIC MOTORS IN SEWING MACHINES

摘要

The electric motor and the needle locating device of a sewing machine are adjusted by a pivotable treadle controlling a radiation directing member which is located in the path of radiation issuing from one end of one or more first optical fibers the other end or ends of which receive radiation from a suitable source, and the member controls the amount of radiation entering the adjacent end or ends of one or more second optical fibers which convey the radiation to an optical detector. The latter selects the speed of the motor in dependency on the amount of radiation which is transmitted into the second optical fiber or fibers and selects the position of the needle when the motor is off. The radiation directing member can constitute a glass plate which is rotatable or performs translatory movements between the first and second optical fibers and includes portions of different radiation transmissivity or reflectivity.