Sewing – Elements – Thread sensing
Patent
1983-02-07
1986-02-11
Nerbun, Peter
Sewing
Elements
Thread sensing
112273, 250561, 242 37R, D05B 6936, D05B 4500, G01N 2130
Patent
active
045692980
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for supplying a signal pre-warning the operator of a sewing machine of the fact that the thread on a bobbin is about to run out.
Arrangements for immediate detection of the thread content of a bobbin are known in which several principles based on several kinds of signals have been used. Mechanical devices, such as lever arms, sensing the thread content and putting a sound source into action when a predetermined minimum is reached have, however, the drawback of poor accuracy and of making the change of the bobbin difficult. By the introduction of an optic detection by means of a photoelectric cell, mechanical components can be omitted, but the accuracy is still bad. Therefore, it is considered necessary to develop this system by making use of distinct points of measuring etc. whereby the accuracy is improved.
In the present invention a signal arrangement is provided with a light source and a light sensor directed to a reflecting surface on the bobbin body which reflects the light when the bobbin is nearly empty. A reflection is then received by the sensor which applies a signal to an electronic unit from which a warning signal is passed to the operator. At this moment there is still thread on the bobbin but if the sewing proceeds so that the thread goes out pulses of reflected light will occur in a predetermined order in dependence on the positions of the source and the sensor, respectively. These pulses release another signal from the electronic unit by which (for example) the sewing is stopped.
The advantage of such an arrangement is achieved therein that the sewing can proceed until the thread has in practice run out. Moreover, the drawbacks of mechanical detection arrangements as mentioned in the foregoing are eliminated.
An example of an embodiment of the invention will be described in the following with reference to the accompanying drawing, which shows in
FIG. 1 a vertical projection of a shuttle mechanism of a sewing machine, in
FIG. 2 the same mechanism in a cross section at the arrows II--II of FIG. 1, in
FIG. 3 an exploded sketch of the shuttle mechanism, in
FIG. 4 the same projection as in FIG. 1 but with the bobbin in another position and in
FIG. 5 a block diagram of a decoder.
The Figures show the whole shuttle mechanism including the signal arrangement according to the invention. The mechanism comprises a loop taker 10 on a carrier 11 having a horizontally journalled shaft 12 so that a bobbin case 13 is inserted into the loop taker from the side and is retained there by a releasable latch 14 engaged in an annular groove 15 on a bobbin shaft 16. The bobbin case can be released from the shaft and removed by rotating the latch about a pin 17. Arranged in the bobbin case is an exit 18 for thread from a bobbin 19 located in the case. At the exit a leaf spring 20 projects under which the thread is pressed against the surface of the case and is thus tensioned. The bobbin is inserted in the case in such a manner that it rotates in the direction of the arrow 21 when the thread is pulled out therefrom. In its wall the case has an opening 22 extending about half the way around the periphery of the case so that the bobbin is visible through the opening. The entire mechanism is assembled under a loop taker cover 23 which by means of screws is secured to a bearing bracket in the sewing machine body.
The design of the signal arrangement of this embodiment is shown in FIGS. 1, 3 and 4. In a plan perpendicular to the bobbin shaft 16 electronic components are inserted, each one into its hole in the loop taker cover 23 and directed to the bobbin shaft. One component is a lamp (LED or the like) 24, the light beam of which is shown by arrows 25 in FIGS. 1 and 4. The beam passes through the opening 22 and a fissure 26 in the loop taker towards the central portion 27 of the bobbin 19. This portion has a plurality of plane surfaces of a reflecting material which reflects the light along the arrows 28 through the fissure and the opening against someone of the other comp
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patent: 4212257 (1980-07-01), Herron et al.
patent: 4216733 (1980-08-01), Kornatowski
patent: 4237807 (1980-12-01), Meier
patent: 4331090 (1982-05-01), Hanyu et al.
Lindh Per A. L.
Skogward Kenneth O. E.
Husqvarna Aktiebolag
Miller Alfred E.
Nerbun Peter
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