Sewing – Elements – Starting or stopping
Patent
1991-01-09
1993-04-06
Nerbun, Peter
Sewing
Elements
Starting or stopping
D05B 6936
Patent
active
051993651
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention pertains to a thread monitor for monitoring the thread on a stitch-forming machines wherein the thread may always be fed to a sorted stitch-forming element from an endless thread reserve.
BACKGROUND OF THE INVENTION
In sewing machines, the needle thread is monitored, in general, between the endless thread reserve and the needle. The looper thread is monitored between the endless thread reserve and the shuttle in the case of multiple-thread chain stitch sewing machines, and between the shuttle and the stitch formation site in the case of double lockstitch sewing machines. After a thread disturbance appears, the thread monitor sends a signal eliciting a response from the machine.
For example, a thread monitor for monitoring the needle thread is disclosed in West German Utility Patent No. 69,13,073. To achieve this, a disk, which is set into rotation by the needle thread being pulled off from the thread reserve and is interrupted by radially extending slots in its edge zone, is monitored by a sensor device. As soon as one of the slots is flush with the sensor device, an impulse is sent to an electronic switch of a control circuit. When the disk stops after breaking of the needle thread and no more impulses are sent to the electronic switch, the sewing machine is stopped.
A thread monitor, whose sensor device, which serves to monitor the needle thread, is held on a holder fastened on the head of the sewing machine, is disclosed in U.S. Pat. No. 4,754,722.
The needle thread is led through the monitoring zone of the sensor device to the needle. As a consequence of the upward and downward movements of the needle bar during sewing, the needle thread is swung out of its middle position alternatingly in opposite directions, so that it performs an oscillating motion at right angles to the direction of thread pull and it traverses the monitored zone of the sensor device once per stitch, oscillating to and fro. Disappearance of this thread movement is indicated as a disturbance.
SUMMARY AND OBJECTS OF THE INVENTION
The basic object of the invention is to design a thread monitor for a stitch-forming machine such that it monitors the thread along its path at a plurality of points, and in the case of a thread disturbance, it controls the machine such that a switching process corresponding to the site of disturbance is induced on the machine, depending on the site of disturbance.
According to the invention, a thread monitoring arrangement for monitoring the thread on stitch-forming machines, wherein the thread may always be fed over a tensioning device to the associated stitch-forming element from an endless thread reserve.
According to the invention, a thread monitoring arrangement for monitoring the thread on stitch-forming machines, wherein the thread can always be fed over a tensioning device to the associated stitch-forming element from an endless thread reserve is provided including a thread monitor having first sensor units positioned between the thread reserve and the respective associated tensioning device. Second sensor units are provided positioned between each of the tensioning devices and the respective stitch-forming element associated therewith. Upon a thread disturbance occurrence, the sensor units send signals that can be evaluated differently to induce different switching processes. This function is provided by monitoring means for evaluating signals from each of the sensor units differently and issuing a switching signal depending upon the signal received.
For example, on multiple-thread chain stitch sewing machines, the needle thread and the looper thread are monitored by the first sensor unit immediately after being pulled off from the endless thread reserve. Due to this measure, early detection of the thread end is possible, because a relatively long thread remnant remains between the sensor unit and the tensioning device associated with the thread. Thus, after indication of the thread end or a thread break, it is still possible to finish the seam in
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patent: 4192243 (1980-03-01), Blessing et al.
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patent: 4284020 (1981-08-01), Conner, Jr. et al.
patent: 4426948 (1984-01-01), Olasz et al.
patent: 4429651 (1984-02-01), Tajima
patent: 4602582 (1986-07-01), Rawson
patent: 5018465 (1991-05-01), Hager et al.
Nerbun Peter
Pfaff Industriemaschinen GmbH
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