Importance

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Abstract

A monitoring device for monitoring a low thread supply in a sewing machine comprises a light emitter and light receiver positioned on opposite ends of a rotary hook in the sewing machine. The sewing machine is equipped with the rotary hook, a bobbin case, a bobbin in the bobbin case for carrying the thread and a drive shaft for rotating the rotary hook or which rotates as a function of rotation of the rotary hook. A pulse transmitter is connected to the drive shaft which supplies pulses to a control circuit connected to the light emitter. The control circuit, responsive to the pulses, activates the light emitter only during intervals at which apertures in the rotary hook, the case and the bobbin are aligned. Light passing through the aligned apertures indicates whether there is a low supply of thread on the bobbin.

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First Claim