JPS6151916B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bobbin thread breakage detection device for a sewing machine that can sufficiently follow high-speed rotation of the sewing machine.

Conventionally, bobbin thread breakage detection devices for sewing machines have, for example, provided a lever that intermittently comes into contact with the bobbin thread, which repeatedly tightens and loosens as the thread take-up moves up and down, and detects the amount of movement of the lever when there is no bobbin thread. There is a method of detecting bobbin thread breakage, no bobbin thread on the bobbin, or poor bobbin thread condition by turning on a limit switch or proximity switch due to an increase in If the biasing force of the spring is weakened, the swinging of the lever will not be able to follow the rotation of the sewing machine, and even if the biasing force of the spring is strengthened, the sewing machine will not rotate at high speed. The drawback was that if you let it move, it would become impossible to follow.

On the other hand, as a method for detecting bobbin thread breakage without contacting the bobbin thread, there is a method that uses a photoelectric element to detect the horizontal runout of the bobbin thread in the direction perpendicular to the center of the needle hole due to the rotation of the outer hook. There was a drawback that the bobbin thread detection function of the photoelectric element was lost due to fluff of the bobbin thread floating around.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bobbin thread breakage detection device for a sewing machine that can detect bobbin thread breakage by lightly contacting the fin of the outer hook and displacing the bobbin thread in a direction perpendicular to the center of the needle hole when the outer hook rotates. The object of the present invention is to eliminate the above-mentioned conventional drawbacks.

Next, the configuration of a first embodiment of the present invention will be explained with reference to FIGS. 1 to 4.

On the back surface of the throat plate 1, a piezoelectric element 6, in this case lead zirconate titanate, is disposed, which contacts the fin 3 of the outer hook 2 and displaces the lower thread 5 in a direction perpendicular to the center of the needle hole 4 when the outer hook rotates twice. Two bimorph type piezoelectric elements 6, each having a silver electrode 8 vacuum-deposited on a ceramic 7 made of (Ztp), are connected in parallel (see Fig. 4) and mounted via a soft rubber 9 and a bracket 10. , when the outer hook 2 rotates in this installed state, the bobbin thread 5
moves laterally on the groove 12 of the inner hook 11 between the bottom surface of the groove 12 and the thread shedding surface of the fin 3 as shown in FIG. It is displaced from L3. the result,
Every time the outer hook 2 rotates once, the lower thread 5 pulled out from the thread guide 14 of the bobbin 13 is displaced as shown by the two-dot chain line in FIG. 3, and during this displacement, the lower thread 5 comes into contact with the piezoelectric element 6. do. Next, FIG. 4 is an electrical circuit diagram of this embodiment, and shows SW1 to SW3.
is a switch, R1 to R4 are resistors, C1 to C3 are capacitors, D1 and D2 are diodes, TR1 is a transistor, RY1 and RY2 are relays, RY1a is a normally open contact of relay RY1, and IC1 is when both inputs are "H" This is a Motorola MC-14093B gate-controlled Schmitt-trigger unstable multivibrator that generates a constant frequency output.

Next, the operation of this embodiment will be explained with reference to the electric circuit shown in FIG.

First, with switch SW1 turned on, switch SW2 is turned on, and relay RY2 for starting the sewing machine is turned on.
When turned on, the sewing machine is operated, the take-up lever moves up and down, and the outer hook 2 rotates. As a result, the bobbin thread 5 is moved by the fin 3 of the outer hook 2 in a direction perpendicular to the center of the needle hole 4 (CL in Fig. 3). Each time it is moved, it contacts the piezoelectric element 6, and each time it makes contact, the piezoelectric element 6 generates an output corresponding to the contact, and during this output period, the IC
2 inputs of circuit IC1 become "H" and IC circuit IC1
A constant frequency output is generated.

Therefore, when the sewing machine starts operating, the IC circuit IC
1 generates a pulse-like output with a constant frequency corresponding to the intermittent contact of the bobbin thread 5 with the piezoelectric element 6, and the diode D1, capacitor C2, and
Transistor by input via resistor R4
TR1 turns on and its contacts along with relay RY1
As a result of turning on RY1a, the sewing machine continues to operate even if switch SW2 is turned off when this contact RY1a is on.

If the bobbin thread 5 breaks while operating in this manner, the IC circuit IC due to the non-contact of the bobbin thread 5
1's output "L" turns off transistor TR1, and relay RY1 and relay contact RY
Operation of the sewing machine is immediately stopped by turning off relay RY2 by turning off relay 1a.

Next, FIG. 5 shows a second embodiment of the present invention, in which
In this case, when the balance moves up and down once for every 22 rotations of the outer hook, a limit switch is activated via a cam on the main shaft of the hook shaft, which rotates once for every 2 rotations of the hook shaft.
Activate LS1 and turn off limit switch LS1 when only the bobbin thread 5 comes into contact with piezoelectric element 6, so that "H" is input to one input terminal of AND circuit AND1 via resistors R5 and R6. Except for the timing, the configuration, operation, and effects are almost the same as in the first embodiment.

Next, FIG. 6 shows a third embodiment of the present invention, in which
In this case, in place of the IC circuit IC1 of the first embodiment, an IC circuit using a motorola MC-1590G AGC wideband amplifier with terminals as a voltage comparator.
The configuration, operation, and effects are almost the same as in the first embodiment except that IC2 is used.

Next, FIG. 7 shows a fourth embodiment of the present invention, in which
In this case, for the third embodiment, the AND circuit
AND1, resistor R5, R6, limit switch LS
The configuration, operation, and effects are almost the same as in the second embodiment except that a timing circuit consisting of 1 is added.

Next, the effects of the present invention will be explained.

The present invention provides a lower thread that contacts the fin of the outer hook and is displaced in a direction perpendicular to the center of the needle hole when the outer hook rotates, and a space between the throat plate release surface and the outer periphery of the outer hook so that intermittent contact is possible in response to the displacement of the lower thread. A piezoelectric element is fixedly attached, and when the piezoelectric element makes intermittent contact with the bobbin thread, the sewing machine continues to operate when the piezoelectric element generates an output, and the bobbin thread breaks and the bobbin thread makes intermittent contact with the piezoelectric element. A bobbin thread breakage detection device for a sewing machine includes an electric circuit that stops operation of the sewing machine when an output corresponding to the output is not generated.

As a result, the present invention has the effect of being able to detect bobbin thread breakage without damaging the bobbin thread, and by sufficiently following the high-speed rotation of the sewing machine.

The piezoelectric elements 6 in this embodiment can be connected in any combination such as two piezoelectric elements 6 connected in parallel as shown in FIG. 4, one piezoelectric element shown in FIGS. 5 to 7, or a plurality of piezoelectric elements connected in series. The bobbin thread breakage detection relay RY1 can be turned off when the bobbin thread breaks or turned on when the bobbin thread breaks, and in addition to the circuits shown in the drawings, any element and any contact or non-contact circuit may be used. I can do it.

[Brief explanation of the drawing]

1 is a front view of the first embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a cutaway side view thereof, FIG. 4 is an electric circuit diagram thereof, and FIG. 5 is a second embodiment of the present invention. FIG. 6 is an electrical circuit diagram of the third embodiment of the present invention, and FIG. 7 is an electrical circuit diagram of the fourth embodiment of the present invention. 1...throat plate, 2...outer hook, 3...fin, 4...needle hole, 5
...Bobbin thread, 6...Piezoelectric element.

Claims (1)

[Claims] 1. A lower thread that contacts the fin of the outer hook and is displaced in a direction perpendicular to the center of the needle hole when the outer hook rotates, and a fixed connection between the back surface of the throat plate and the outer periphery of the outer hook so that intermittent contact can be made in response to the displacement of the lower thread. The attached piezoelectric element and the sewing machine are made to continue operating when an output is generated from the piezoelectric element when the bobbin thread comes into intermittent contact with the piezoelectric element, and the bobbin thread breaks and the bobbin thread is intermittently contacted from the piezoelectric element. A bobbin thread breakage detection device for a sewing machine, comprising: an electric circuit that stops operation of the sewing machine when no output is generated.