JP2960777B2 - Method and apparatus for photoelectrically detecting edges of a sewn product - Google Patents

Description

The present invention relates to a method and an apparatus for detecting an edge of a sewn product by a photoelectric sensor provided in a sewing machine according to the preamble of claim 1 or 6.

2. Description of the Related Art There is known an edge sensor which is photoelectrically activated to detect an edge of a sewing product just before a stitch forming position of a sewing machine when the sewing product is transported. Its general working principle is:
The fact that the optical properties of the upper sewn product are different from the optical properties of the lower sewn product, and thus the optical characteristics at the detection position change dramatically when the edge of the upper sewn product appears at the detection position in the sewing process. It is to utilize. In order to automatically detect the edge of the sewn object, the area immediately before the stitch forming position is illuminated, and the output of the light receiver directed to this detection position is monitored, so that a jump indicating the appearance of the edge of the sewn object is performed. Change is detected. This detection is performed in various ways, at least in comparison with some reference value. This reference value is fixedly set in advance during a special adjustment phase (DE-A 36).
06208) or can be obtained by averaging previous output signals (DE 32 24 314),
Either based on the output of the second light receiver directed to the position immediately before the detection position (DE 3323214).

The sewing material whose edges are to be detected can have properties such that very little or little light reaches the light receiver. In the case of such a "dark" material, the output signal of the light receiver may be too weak to reliably detect an edge even when the illumination intensity and the measured amplification value are set to the maximum. The edge detector described in the above publication is useless especially when the conveyed sewing material is made of a non-translucent material such as leather. In this case, the light receiver does not generate an output signal for deriving a reference value for edge detection before an edge appears. Also, the output signal of the light receiver cannot be brought to a measurement range optimal for edge detection. A similar problem is
Occurs when the sewn article is a single layer or multiple layers and at least one of the layers is made of, for example, leather or felt. When such a sewn article acts as an underlay for sewing another sewn article thereon, neither the leading edge nor the trailing edge of the other sewn article can be detected. This is because there is no light change in the light receiver at the edge of such a sewing product.

It is an object of the present invention to provide a method and an apparatus for photoelectrically detecting the edge of a sewn object, which are more reliable than the conventional methods and apparatuses of this kind due to the nature of the sewn object at the detection position. An object of the present invention is to provide a method and an apparatus as described above, wherein the method and apparatus have less inhibition. This object is achieved according to the invention by the features of claim 1 or claim 6.

The invention takes advantage of the fact that different types of sewing products have different optical properties. In addition, the realization that one extreme of these properties does not necessarily have to appear simultaneously with the extreme of the other, and that different types of sewn materials with similar optical properties may have different optical properties. The realization that they can be very different in that respect is exploited. According to the present invention, by selecting or switching between the result of the reflected light measurement (epi-light measurement) and the result of the transmitted light measurement, a property that gives a more suitable discrimination criterion among the two optical properties for edge detection. Can be referred to.
Two optical properties are light reflectivity and light transmission.

It is known from DE 3514459 to perform epi-illumination and transmitted illumination in order to detect a target edge. In the case of this known example, the transmitted illumination image and the epi-illumination image are superimposed using an optical system, and an intensity distribution is obtained in the combined image. This intensity distribution is symmetric with respect to the edge position. The reason why such an intensity distribution is derived is to correct an error caused by constantly moving the edge image in the direction of a brighter image with respect to the original edge when forming a high-contrast edge. However, the premise is that the intensity distribution in the epi-illumination image is exactly complementary to the intensity distribution in the transmitted illumination image. However, this is only the case when the object has a reflective property and the underlay has a transmissive property. Therefore, this edge detection method is limited to a few special cases.

The difference between the method known from the above publication and the present invention is that, in the present invention, an edge detection signal is generated when the intensity measurement value changes drastically, as in the case of the last published publication. Another problem is that it is not generated at a position of a symmetrical intensity distribution. Also, in the present invention, transmitted light and reflected light are measured separately, and only one of these measurements is evaluated to generate an edge detection signal, whereas in known methods, the transmitted light is reflected. Is to evaluate the total intensity of the superimposed light of the reflected light.

In the method according to the invention, the decision whether to use the transmitted light measurement or the reflected light measurement is made so that which measurement value can be better discriminated when the edge of the sewing object to be detected appears at the detection position. It depends on what makes you leap. In most cases, this decision can be made without difficulty. An advantageous choice is to select a measurement scheme in which the measured values show a greater amplitude when the edges of the sewing product have not yet appeared. As a result, the detection method can be automated, and more precisely, can be already automated during the pre-adjustment process. Here, the pre-adjustment is an adjustment for increasing the illumination intensity or the amplification value of the measurement signal from a low value for setting the measurement range so that the measurement signal reaches a desired measurement range. This adjustment, and thus the determination of the measuring method to be selected, can be made anew after the edge of the sewing is detected in order to provide optimal conditions for the reliable detection of the edge of the next sewing. .

The above-described and other advantageous configurations of the method or device according to the invention are described in the dependent claims.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a front view of a sewing machine provided with a sewing product scanning device, FIG. 2 is a side view of the sewing machine also showing the basic configuration of an interrupter combining a transmitted light photo interrupter and a reflected light interrupter, The figure is a block diagram of the circuit of the device according to the present invention.

FIG. 1 shows a sewing machine 1 having a stand, an upper arm, a head, and a cloth supporting plate 1a. Cloth carrying plate
1a is fixed to a part of the table plate 2a of the sewing machine base 2, and is driven via a V-belt 4 by a sewing motor 3 fixed below the table plate 2a.

The head of the sewing machine 1 has a usual presser bar 5 (FIG. 2). The presser foot 5 carries a presser foot 6. The cloth presser foot 6 is placed on a sewing object to be sewn, and is arranged behind a needle bar 7 driven by the sewing motor 3. The needle bar 7 carries a needle 8. The needle 8 penetrates the puncture hole 9a of the needle plate 9 arranged in the cloth holding plate 1a and cooperates with a thread catcher (not shown) driven in synchronization with the needle bar 7 in a known manner. .

As shown in FIG. 2, a photo interrupter is disposed on the front surface of the sewing machine 1 in front of the working range of the needle bar 7. The photointerrupter has a light source configured as a light emitting diode 13, a first optical sensor configured as a photodiode 14, and a second optical sensor configured as a phototransistor 14a. The light emitting diode 13 and the phototransistor 14a are provided in the reflection scanner 10 fixed to the head of the sewing machine 1 in front of the stitch forming position. In this case, the light emitting diode 13 and the phototransistor 14a are in close contact
, But are shielded from each other to prevent direct light incidence. Glass fiber optics or reflective couplers can be used instead of a reflective scanner. The interval between the reflection scanner 10 and the needle plate 9 is selected to be an interval at which the sewing products N1 and N2 can pass well, for example, approximately 5 mm.

On the other hand, the photodiode 14 is housed in a part 9 b of the needle plate 9.

The sewing object whose edge is scanned passes between the light emitting diode 13 and the photodiode 14 during the sewing process. The sewn product in the illustrated embodiment consists of two sewn products, an upper sew product N1 and a lower sew product N2 to be sewn together.

The photodiode 14 captures, among the light emitted from the light emitting diode 13, the light that has passed through the sewn items N1 and N2, and generates a voltage corresponding to the output of the measurement amplifier 15. The light emitting diode 13 is modulated by the oscillator 11 having a predetermined frequency via the drive amplifier 12 and the output signal of the measuring amplifier 15 is passed through the bandpass filter 16 which is tuned to the above frequency. It is provided to a synchronous rectifier 17 which is synchronized with the frequency. The delay element 18 provided between the oscillator 11 and the synchronous rectifier 17 provides a synchronous rectifier
It is used to correct the operating time so that The light modulation and the subsequent synchronous rectification are performed in order to suppress disturbance, and it is not necessary to provide an extra optical system. A low-pass filter 19 provided after this smoothes the rectified measured voltage.
The smoothed measurement voltage is sent to an analog / digital converter 21 via a changeover switch 20 (the function of which will be described later) to form a measurement signal U as a continuous digital scan value.

The digitized measurement signal U is sent to the input of the processing device 40. The processing device 40 can be configured as, for example, a microcontroller. This processing device 40 provides the measurement signal U
Is monitored, and when there is a sudden change in the measurement signal U indicating the appearance of the edge W of the sewing product, the edge detection signal K is output from the output side. The processing method used for this is arbitrary and therefore will not be described in detail here. An example of the prior art is as described above. However, if the jump of the measurement signal U is made sufficiently noticeable when the edge W of the sewn article appears, it can be distinguished from the fluctuation of other measurement signals. It is advantageous.

Phototransistor Phototransistor 14a
Are arranged to receive a component of light emitted from the light source 13 and reflected by the upper sewn product N1. Similarly, the measurement amplifier 15a is located behind the phototransistor 14a.
, A band-pass filter 16a, a synchronous rectifier 17a, and a low-pass filter 19a. The functions of these elements are the same as those of the elements 15, 16, 17, and 19 behind the output of the photodiode. If the sewing N2 is made of a light-impermeable material, for example leather, so that the photodiode 14 does not receive light either before or after the edge W of the sewing,
The signal corresponding to the light transmitted from the low-pass filter 19a and reflected by the upper sewn product N1 has a greater edge W of the sewn product N1 than the "transmitted light signal" sent from the low-pass filter 19. It may be preferable for detection. Even when the light transmittance of the sewn product N2 is low or does not transmit at all, there is a problem in edge detection by the light transmission measurement method at least when detecting edges. Therefore, in such a case, it is necessary to switch to the reflected light measurement method.

The criterion for switching is determined by comparing the amplitudes of the transmitted light signal and the reflected light signal. The amplitude comparator 30 used for this receives the output signals of the two low-pass filters 19 and 19a and is activated before the appearance of the edge W of the sewn product, and its output is sent to the output side which sends the measurement signal with a larger amplitude. Set the changeover switch 20 each time. When the operator is instructed which measurement signal is stronger, or has enough experience to determine which measurement method should be given priority in consideration of the nature of the sewing product to be processed. , It is of course possible to switch manually.

The selection of the measurement method (transmitted light measurement method or reflected light measurement method) can also be performed in connection with the setting of the measurement range. In setting the measurement range, the irradiation intensity at the detection position and / or
Alternatively, the amplification of the measurement signal in the preparation adjustment process is adjusted. For this purpose, the drive amplifier 12 and / or the measurement amplifier
Advantageously, the amplification factor of 15,15a is adjustable. This is shown in FIG. 3 by the control input S _{T of the} amplifier.
And it was suggested by S _M. Control signal S _T for the above amplifier
And _SM are sent from an adjustment device that receives the measurement signal U as an actual value and receives a value in the desired measurement range as a target value. Advantageously, the corresponding adjustment mechanism is realized using special software of the processing device 40. Control signal S _T and S _M is in digital form, it can be sent to the corresponding digital regulator of the driving amplifier 12 or the measuring amplifier 15, 15a.

To set the measurement range, first select the switch
20 can be set to any one of the two measurement paths 14-19 and 14a-19a. For example, transmitted light measurement path 14-19
(The illustrated position of the changeover switch 20). The drive amplifier 12 and the measurement amplifier 15 are initially set to the minimum amplification value and then adjust the drive amplifier 12 high until the measurement signal U is in the desired measurement range. If the desired measurement range is not reached even when the amplification value of the drive amplifier 12 is adjusted to the maximum, the amplification value of the measurement amplifier 15 is adjusted to a higher value to reach the desired measurement range. This is all processing equipment
This can be done automatically using 40.

For example, if it is clear that the desired measurement range is not reached by the transmitted light measurement path, the same procedure can be performed using the other measurement path by switching the changeover switch 20. This switching can also be performed automatically. Both measurement paths can also be tested independently of each other in order to select a measurement path that reaches the desired measurement range earlier (ie with a smaller amplification value). The use of the amplitude comparator 30 performs this test automatically, in which case the amplitude comparator 30 always sets the changeover switch 20 to a measurement path that produces a stronger output signal.

Various modifications are of course possible in addition to the above-described embodiment. For example, instead of providing two separate measurement channels 15-19 and 15a-19a behind the optical sensor 14 or 14a, a common measurement channel can be used. The input of this common measurement channel is
And 14a. In this case, not only one of the measurement paths shown in FIG. 3 but also the amplitude comparator 30 and the changeover switch 20 need not be provided. Nevertheless, in order to enable a comparison of the amplitudes of the two measuring methods, a measuring value memory can be provided in the processing device 40, possibly with a display device. Both measurement schemes are tested sequentially in time or almost in parallel by a time multiplex scheme.

Instead of combining transmitted and reflected light interrupters, two separate photo interrupters, each with its own light source, can be used. These interrupters are advantageously arranged side-by-side with respect to the direction of the relative movement of the object and can be operated at different modulated light frequencies if desired. In principle, two light transmitters can be provided on opposite sides of the object, and a common light receiver can be provided. The light receiver receives light transmitted from one light source and transmitted, and receives light reflected and emitted from the other light source. In this case, to separately measure the transmitted light and the reflected light, one of the two light transmitters is turned on and the other light transmitter is turned off.

Continuation of front page (56) References JP-A-61-109596 (JP, A) JP-A-61-165679 (JP, A) JP-A-61-199896 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) D05B 69/00 D05B 35/10

Claims (16)

(57) [Claims] 1. A method for detecting at least one edge of a sewing product by a photoelectric sensor provided on the sewing machine so as to be located immediately before a stitch forming position of the sewing machine, the illumination sensor illuminating the sewing product via a light source. In the above method, the intensity of light emitted from an object is measured, and a signal for detecting an edge of the object is generated when the intensity measurement value changes drastically. Separately performing a first measurement step of measuring the intensity of the light component and a second measurement step of measuring the intensity of the light component transmitted through the sewn object; When appearing, of the first measurement process and the second measurement process, a measurement process whose measured value shows a larger leap is selected to generate an edge detection signal of a sewing product. how to 2. The method according to claim 1, further comprising the step of selecting a measuring process whose measured value has a larger amplitude when an edge of the sewn object does not appear in order to generate an edge detection signal of the sewn object. 2. The method according to 1. 3. A preparatory adjustment is made to increase at least one of the illumination intensity and the measured amplification value from a low value until a measured value in at least one of the two measuring processes reaches within a predetermined measuring range; 2. The sewing process according to claim 1, wherein a measurement process is selected such that the measured value reaches the measurement range when the illumination intensity or the measured amplification value is the lowest, and an edge detection signal of the sewing product is generated. Method. 4. A pre-adjustment process in which, when the measured value does not reach a predetermined measurement range when the illumination intensity is at a maximum, the measurement amplification value is increased until the measurement signal reaches the measurement range. The method according to claim 3, wherein 5. The method according to claim 3, wherein a new preparation adjustment is performed after the generation of the signal for detecting the edge of the sewing product. 6. The sensor has a photointerrupter,
An illumination device for illuminating the sewn object in front of the stitch forming position, the photointerrupter measuring an intensity of light emitted from the illumination position and generating a measurement signal as a function of the intensity; Receiving the measurement signal,
6. The method according to claim 1, further comprising a processing device for generating a signal for detecting an edge of the sewing product when the measurement signal changes drastically. Device for measuring separately the light component reflected at the illuminating position and the light component transmitted at the illuminating position and separately generating a corresponding measuring signal (14a −19a and 14−19), and select the measurement signal that shows a larger leap among the two measurement signals used for processing to generate a signal for detecting the edge of the sewing product. Selection device for (20,30)
A sewing machine characterized in that a sewing machine is provided. 7. The light measuring device (14a-19a and 14-19) has a display device for displaying the amplitude of both measurement signals, and the selecting device (20, 30) is adapted to select one of the two measurement signals. The sewing machine according to claim 6, further comprising a manually operable changeover switch (20) for selecting a sewing machine. 8. The selection device (20, 30) has an amplitude comparator (30), which compares the two measurement signals with each other and outputs the stronger measurement signal in each case. 7. The sewing machine according to claim 6, wherein the sewing machine is selected for processing. 9. The light measuring device (14a-19a, 14-19) has two light receivers, and the first light receiver (14a-19a) mainly receives only light components reflected at the illumination position. And the second light receiver (14
-19), mainly receiving only the light component transmitted through the illumination position, and each of the two light receivers emits a measurement signal corresponding to the intensity of the received light. The sewing machine according to any one of the above. 10. The illumination device (11-13) having a light transmitter with only one light source (13);
10. The sewing machine according to claim 9, wherein a-19a, 14-19) are responsive to a component of light energy emitted from the light source. 11. A light transmitter (11-13) sends modulated light of a predetermined frequency, and both light receivers (14a-19a, 14-19) transmit band-pass filters (16a, 16) tuned to the frequency of the modulated light. ) And a synchronous rectifier (17a, 17) connected thereto and having a low-pass filter (19a, 19).
The sewing machine described in 1. above. 12. The sewing machine according to claim 10, wherein at least one adjusting element (12, 15a, 15) for adjusting the measuring range of the light measuring device is provided. 13. An adjustable amplifier (1) as an adjusting element.
13. The sewing machine according to claim 12, wherein 2) is provided in a drive circuit of the light transmitter (11-13). 14. An adjustable amplifier (15) as an adjusting element.
14. The sewing machine according to claim 12, wherein (a, 15) is provided in the light receiver (14a-19a, 14-19). 15. A processing device (4) in which each of the adjusting elements (12, 14a, 15) is selectively switchable and configured as an adjusting circuit.
0), wherein the processing device (40) receives the respective measurement signal as an adjustment amount and receives a value within the measurement range as a target value.
A sewing machine according to any one of 12 to 14. 16. A light source (13) and a first light receiver (14a-19a).
That the optical sensor (14a) of the second optical receiver (14-19) is a component of the reflection scanner (10).
The sewing machine according to claim 10, characterized in that 4) is provided for receiving a component of light emitted from the light source (13) of the reflection scanner (10), which is transmitted at the illumination position.