Automatic thread tension control device of sewing machine
AssigneeJanome Sewing Machine Co., Ltd.
InventorYoshiaki Tonomura
Life of this patent
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Abstract
An electronic thread tension control device whereby electrical signals indicating the fabric thickness, the amount of fabric being fed, the needle's amplitude and the size of the thread to be used are transmitted to the control circuitry thereby producing the appropriate output signal that will adjust the tensioning means accordingly.
Claims6
A thread tension control device for a sewing machine of the type having a pressor bar with a pressor foot, a spool for supplying an upper thread, a feed dog for feeding a fabric to be sewn and a thread tension device including a pair of thread tension discs, comprising means for measuring the amount of thread actually drawn out from the spool during operation;
- means for changing the measured amount of thread into a first electrical signal operatively connected to said means for measuring the amount of thread;
- means for measuring the thickness of a fabric to be sewn;
- means for changing the measured thickness into a second electrical signal operatively connected to said means for measuring the thickness of a fabric;
- means for measuring a fabric feeding amount;
- means for changing the measured fabric feeding amount into a third electrical signal operatively connected to said means for measuring a fabric feeding amount;
- means for measuring the thickness of thread to be used;
- means for changing the measured thickness of the thread into a fourth electrical signal operatively connected to said means for measuring the thickness of thread;
- means for receiving the second, third and fourth electrical signals and changing the same into a value identifying the desired amount of thread drawn out from the spool on the stitching conditions;
- comparator means for comparing said value identifying the desired amount of thread with said first signal identifying the actual amount of thread drawn out from the spool, to produce a difference value;
- and means for adjusting the thread tension device operatively connected to said tension discs and to said comparator means and operative for adjusting the position of said tension discs in response to said difference value.
Dependencies are inferred from the claim text.