CN107099951A - A kind of sewing machine and its bouncing pilotage detection means and detection method - Google Patents

Abstract

The invention discloses a skipped stitch detection method for a sewing machine, which includes: obtaining the time length occupied by the upper thread in the feeding process within a preset time period; judging whether the ratio of the time length to the preset time period is within If it is within the preset duty ratio range; if not, go to the next step; prompt the operator for sewing abnormality. The invention also discloses a skipping stitch detection device for a sewing machine. The invention also discloses a sewing machine comprising the skipping stitch detection device. The skipped stitch detection method described above can know in time whether a skipped stitch occurs during the sewing process.

Description

A sewing machine and its skipped stitch detection device and detection method

technical field

The invention relates to the technical field of sewing machines, in particular to a stitch skip detection method for sewing machines. The present invention also relates to a skipped stitch detection device for a sewing machine; moreover, the present invention also relates to a sewing machine with the skipped stitch detection device.

Background technique

As we all know, during the use of the sewing machine, sometimes the needle passes through the sewing material, but the bottom thread and the upper thread cannot continuously form stitches, which is called skipped stitches. During the sewing process, once skipped stitches occur, empty stitches will be left, which will affect the appearance of the stitches. Especially in the high-end sewing process of automotive supplies and leather, once skipped stitches occur, the finished product must be treated as a defective product.

In fact, when airbag manufacturers in Asia and the United States produce airbags, most of them use polyamide thread for sewing. Due to the safety of the airbag, the sewing process must be strictly controlled, and the principle of zero defect must be adhered to. Threads and empty needles will be scrapped directly. According to statistics, skipped stitches and broken threads are the most frequent occurrences in the sewing process. For the sake of safety, the sewing machine must be able to give timely alarms for skipped stitches and broken threads to ensure that the airbags leave the factory with zero defects.

Contents of the invention

The object of the present invention is to provide a skipped stitch detection method for a sewing machine, which can know in time whether a skipped stitch occurs during the sewing process. Another object of the present invention is to provide a skipped stitch detection device for a sewing machine. Another object of the present invention is to provide a sewing machine with the device for detecting skipped stitches.

To achieve the above object, the present invention provides a method for detecting skipped stitches of a sewing machine, comprising:

Obtain the duration occupied by the upper thread during the feeding process within the preset time period;

Judging whether the ratio of the duration to the preset time period is within a preset duty cycle range; if not, go to the next step;

Notify the operator of sewing abnormality.

Preferably, the judging whether the ratio of the duration to the preset time period is within the preset duty cycle range; if not, before proceeding to the next step, it also includes:

Obtain the theoretical time taken by the upper thread during the feeding process during normal sewing;

calculating a theoretical duty ratio of the ratio of the theoretical duration to the preset time period;

The duty ratio range is determined according to the theoretical duty ratio.

Preferably, the judging whether the ratio of the duration to the preset time period is within a preset duty cycle range; if not, the next step further includes:

Judging whether the duration is zero, if yes, proceed to step S010; if not, proceed to step S02;

S010, giving a disconnection prompt to the operator;

S02. Judging whether to change the needle distance within the current preset time period; if not, proceed to step S020;

S020. Prompt the operator for jumper wires.

Preferably, in the step S02, if yes, step S03 is also performed;

S03. Compensate the duration according to the changed needle distance, and judge whether the ratio of the compensated duration to the preset time period is within the duty ratio range; if not, execute the Step S020.

Preferably, the preset time period is specifically the time required for the main shaft to rotate one revolution.

The present invention also provides a skipped stitch detection device for a sewing machine, comprising:

Piezoelectric sensor: used to obtain the length of time occupied by the upper thread during the feeding process within the preset time period;

Controller: for judging whether the ratio of the duration to the preset time period is within a preset duty ratio range;

Alarm: used to prompt the operator that the sewing is abnormal when the ratio of the duration to the preset time period is not within the preset duty cycle range.

Preferably, the alarm is specifically a disconnection alarm that prompts the operator for disconnection when the duration is zero, and when the ratio of the duration to the preset time period is not within a preset occupancy A wire jumper alarm that reminds the operator of the wire jumper when it is within the range of the empty ratio and the duration is not zero.

Preferably, it also includes:

Memory: used to obtain the theoretical time taken by the upper thread during the feeding process during normal sewing;

A duty ratio range determination unit: used to calculate a theoretical duty ratio of a ratio between the theoretical duration and the preset time period, and determine the duty ratio range according to the theoretical duty ratio.

Preferably, the piezoelectric sensor is arranged around the thread tensioner stud.

The present invention also provides a sewing machine, comprising the device for detecting skipped stitches described in any one of the above items.

With respect to the above-mentioned background technology, the skipped stitch detection method for sewing machines provided by the present invention mainly includes: obtaining the duration occupied by the upper thread in the feeding process within the preset time period; judging the duration and the preset time Whether the segment ratio is within the preset duty ratio range; if not, the operator will be prompted for sewing abnormalities. So set, by judging the length of time occupied by the upper thread in the feeding process within the preset time period, it is known whether the needle skipping or thread breakage occurs, and the ratio of the time length to the preset time period is not in the preset duty When the ratio is within the range, the operator will be prompted for sewing abnormalities; in this way, the operator can be informed of the occurrence of abnormal phenomena in the sewing process in time, so that they can take appropriate follow-up operations.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings on the premise of not paying creative efforts.

Fig. 1 is a schematic diagram of thread usage of skipped stitches in the sewing process;

Figure 2 is a schematic diagram of the change of the thread feeding amount after the needle skipping phenomenon occurs;

Fig. 3 is a flow chart of a skipped stitch detection method for a sewing machine provided by an embodiment of the present invention;

FIG. 4 is a program flow chart of a skipped stitch detection method for a sewing machine provided by an embodiment of the present invention;

Fig. 5 is a structural block diagram of a skipped stitch detection device for a sewing machine provided by an embodiment of the present invention;

Fig. 6 is a cross-sectional view of the tensioner equipped with piezoelectric sensors.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Please refer to Fig. 1 to Fig. 6, Fig. 1 is a schematic diagram of thread used in skipped stitches in the sewing process; Fig. 2 is a schematic diagram of the change of thread feeding amount after skipped stitches occur; Fig. 3 is a sewing machine provided by an embodiment of the present invention The flow chart of the skipped stitch detection method; Fig. 4 is the program flow chart of the skipped stitch detection method for the sewing machine provided by the embodiment of the present invention; Fig. 5 is the skipped stitch detection device for the sewing machine provided by the embodiment of the present invention The block diagram of the structure; Figure 6 is a cross-sectional view of the clamp equipped with piezoelectric sensors.

A kind of stitch skip detection method for sewing machine provided by the present invention, as shown in accompanying drawing 3, mainly comprises:

S100. Obtain the duration of the feeding process of the upper thread within the preset time period;

S200. Determine whether the ratio of the duration to the preset time period is within a preset duty ratio range; if not, proceed to the next step;

S300. Prompting the operator of a sewing abnormality.

Before introducing the stitch skip detection method of the present invention, parameters such as the amount of thread used and the thread feeding time of the sewing machine during normal operation can be studied, as shown in accompanying drawings 1 and 2 of the specification.

As shown in Figure 1 of the manual, the amount of thread used for normal sewing is:

L=P+2(h+c)

And the amount of thread used for stitch skipping: L=P

Among them: P - the amount of thread used for each stitch

h - the thickness of the upper fabric

c—hinge length of upper thread;

It can be seen from the above equation that the difference between normal sewing and skipped stitches is 2(δ+t). Therefore, in the sewing process, if skipped stitches occur, it will inevitably cause thread feeding in the next spindle cycle after skipped stitches. The quantity changes, and the specific change is reflected in the lag of the wire feeding time. The present invention detects the skipped stitches of the sewing machine by detecting this change.

It should be noted that the thread feeding here is the thread feeding process of the upper thread feeding frame through the thread gripper, rather than the thread feeding process of the stitch formation process by the take-up and release action of the thread take-up lever. , the former is the input line quantity from the outside, and the latter is the consumption of the internal line quantity. Therefore, the amount of wire feeding involved in the present invention is mainly the change of the external input wire amount, and the consumption of the internal wire amount is reflected in the change of the length of the slack part, which is difficult to detect, while the change of the external wire feeding amount is relatively easy accomplish. Because the sewing thread is input from the thread stand, it needs to pass through the thread gripper. It is advisable to use the thread gripper as the dividing line. The clamping function of the thread clamp keeps the sewing thread in a tensioned state. During the sewing process, the internal circuit needs thread volume, and the external circuit will replenish it in time to eliminate the sewing state. The sewing machine that works stably will consume the thread volume of the internal circuit. It is also regular, and the specific consumption has been given by the aforementioned formula, so the supply of external lines to the line is also regular. If there is an abnormal jumping needle, the change of the wire consumption of the internal line will lead to a corresponding change in the amount of external wire transmission. In the sewing process, the thread feeding is not carried out in the whole cycle, but only in a certain period of time. The upper stop position of the needle is the start of a spindle cycle, that is, the change of the needle position corresponds to different In the working state, for different sewing machines, the time starting point of thread feeding is also different, and for different stitch lengths and fabrics, the amount of thread used is also different.

When the sewing machine breaks, the sewing thread loses its tension, and the consumption of the thread amount does not occur, and there is no thread delivery at this time, so the present invention can also judge the situation of the thread breakage.

As shown in Figure 2 of the manual, the delay of the wire feeding time δ _t can be used to indicate the reduction of the wire feeding amount, and T is the time for one rotation of the main shaft; the detection circuit compares the wire feeding time of the preceding and following cycles by monitoring the rising edge time of the level The delay δ _t is used to judge whether needle jumping occurs. Of course, the falling edge time of the level can also be monitored, and the length of the cycle occupied by the wire feeding time can also be obtained.

In the present invention, step S100 is to obtain the duration of the upper thread during the feeding process within the preset time period; and the duration of the upper thread during the feeding process can be known through the piezoelectric sensor, and the piezoelectric sensor can be set to On the thread clamp; as shown in accompanying drawing 6 of the manual; the piezoelectric sensor 101 is sleeved on the thread clamp stud 3, the thread clamp stud 3 is arranged on the lower clamp plate 2, and the sewing thread 1 (that is, the surface thread) is wound around the piezoelectric sensor 101, the specific setting method of the thread gripper can refer to the prior art, and the present invention only adds the piezoelectric sensor 101 to know the duration of the upper thread during the feeding process; in addition In addition, the preset time period may be the time required for the main shaft to rotate one revolution.

In step S200, it is judged whether the ratio of the duration to the preset time period is within the preset duty ratio range; if not, proceed to the next step; Next, the thread feeding time in a cycle T is t ₁ , and the duty ratio is t ₁ /T; and a preset duty ratio range can be determined according to the duty ratio t ₁ /T; line phenomenon), there will be a delay δ _t , at this time, the time for wire feeding in a cycle T is t ₂ , and the actual duty ratio is t ₂ /T; when the actual duty ratio is t ₂ /T, it does not belong to the preset If the duty cycle range is set, go to step S300.

In step S300, a sewing abnormality is prompted to the operator.

For the method of determining the preset duty ratio range, the following methods can be adopted:

Obtain the theoretical time taken by the upper thread during the feeding process during normal sewing;

calculating a theoretical duty ratio of the ratio of the theoretical duration to the preset time period;

The duty ratio range is determined according to the theoretical duty ratio.

Continuing to take the accompanying drawing 2 of the manual as an example, the theoretical time length occupied by the upper thread in the feeding process during normal sewing is t ₁ ; the calculated theoretical duty cycle of the ratio of the theoretical time length to the preset time period is t ₁ / T; and the theoretical duty ratio t ₁ /T is a definite value; according to the actual situation, the theoretical duty ratio t ₁ /T is determined as a range, that is, the duty ratio range, which is used as a criterion for judging the actual sewing Whether the actual duty cycle in the process is within the duty cycle range.

If the actual duty cycle is not within the duty cycle range, the following steps can also be performed:

Judging whether the duration is zero, if yes, proceed to step S010; if not, proceed to step S02;

S010, giving a disconnection prompt to the operator;

S02. Judging whether to change the needle distance within the current preset time period; if not, proceed to step S020;

S020. Prompt the operator for jumper wires.

That is to say, as long as the above-mentioned duration is zero, it means that the upper thread has been disconnected, so the actual duty cycle should also be zero, and step S010 is performed to remind the operator of disconnection; if the duration is not zero, it means that it has not occurred. If the thread is broken, go to step S02, judge whether to change the stitch distance within the current preset time period; if not, go to step S020; prompt the operator for thread jumping.

In the step S02, if the needle distance is changed within the current preset time period, step S03 is also executed; the time length is compensated according to the changed needle distance, and the time length after compensation is determined to be consistent with the preset time. Whether the segment ratio is within the range of the duty cycle; if not, execute the step S020.

Specifically, the program flow chart shown in Figure 4 of the specification;

After step S10 starts, execute step S20 to obtain the sensor waveform, that is, obtain the piezoelectric sensor to start working, obtain the waveform, and obtain the waveform shown in Figure 2 of the specification; in step S30, filter and reshape the acquired actual waveform, This step can refer to the prior art; step S40 calculates the duty ratio, and step S50 judges whether the duty ratio is too small; step S40 and step S50 are the above-mentioned step S200, judging the difference between the duration and the preset time period ratio is within the preset duty ratio range; if it is not within the preset duty ratio range, that is, the duty ratio is too small, then enter step S60 to determine whether the duty ratio is zero (as in step judgment Whether the duration is zero), if so, output a disconnection alarm signal and end, such as step S70 and step S80. If the actual duty ratio is within the preset duty ratio range, the sewing cycle is defined as a normal cycle and stored, and the next cycle detection is performed, such as step S51.

In step S60, if the actual duty cycle is not zero, proceed to step S61 to judge whether to change the stitch distance, if not, it means that the thread skipping phenomenon does occur, output a skipped stitch alarm signal and end, as in step S71 and Step S90; in step S61, if the stitch length has been changed, the compensation value of the changed stitch length should be added to the calculation process of the duty ratio (the specific compensation method can be determined according to actual needs), and the calculation can be obtained after judging the compensation Whether the duty cycle is still too small, if so, then output a skipping alarm signal and end, such as step S62, step S72 and step S90; if the duty cycle calculated after compensation is within the preset duty cycle range, Then return to step S20, and repeat the loop judgment.

It can be seen that the present invention can install the piezoelectric sensor 101 on the tensioner stud 3, and when the piezoelectric sensor 101 detects that the tension rises, the waveform signal is output, and the waveform signal becomes as shown in Figure 2 after processing. Square wave signal, compare the rising edge time of each cycle of the waveform (the reverse case is the falling edge time), you can judge whether there is a needle jump. In a stable sewing process, the thread feeding process is relatively stable without changing the sewing parameters. There will be a great possibility of misjudgment at this time.

The invention compares the detection method of the duty cycle of the waveform. As shown in Figure 2, the state of the line transmission is shown as a high level waveform. The upper part of the figure is the waveform of normal sewing, and the lower part is the waveform after skipped stitches occur. The duty cycle of the normal waveform is t ₁ /T, and the The duty ratio of the waveform of the cycle behind the needle is t ₂ /T. The cycle T of the waveform can be calculated by the rotating speed of the spindle electronic control. As long as the high level time t of each spindle cycle is detected, it can be judged whether the needle skipping occurs by comparison. Even in variable stitch length sewing, it is still applicable as long as the parts with stitch length changes are compensated accordingly. Among them, the duty cycle refers to the time ratio of the high level in one cycle to the entire cycle. Of course, the waveform is not necessarily at the time of the rising edge, but also at the time of the falling edge, which can be determined according to the needs.

The present invention also provides a skipped stitch detection device for sewing machines, as shown in Figure 5 of the specification, which mainly includes:

Piezoelectric sensor 101: used to obtain the duration of the upper thread during the feeding process within the preset time period;

Controller 102: for judging whether the ratio of the duration to the preset time period is within a preset duty ratio range;

Alarm 103: for prompting the operator that the sewing is abnormal when the ratio of the duration to the preset time period is not within the preset duty cycle range.

Preferably, the alarm is specifically a disconnection alarm that prompts the operator for a disconnection when the duration is zero, and when the ratio of the duration to the preset time period is not in a preset duty cycle A jumper alarm that prompts the operator when the time is within the range and the duration is not zero.

Preferably, it also includes:

Memory: used to obtain the theoretical time taken by the upper thread during the feeding process during normal sewing;

A duty ratio range determination unit: used to calculate a theoretical duty ratio of a ratio between the theoretical duration and the preset time period, and determine the duty ratio range according to the theoretical duty ratio.

Preferably, the piezoelectric sensor 101 is arranged around the thread tensioner stud 3 . The installation position of the piezoelectric sensor 101 can also be set at the stud of the small wire clamp or other wire passing parts.

The skipped stitch detection device mentioned above has less changes to the original mechanism of the sewing machine. It only needs to install a piezoelectric sensor 101 on the thread clamp or other thread passing parts, which has less influence on the thread passing path and will not affect the existing The aesthetics of sewing stitches. At the same time, the tension level is used to represent the state of the sewing machine's thread transmission, and the data collected by the piezoelectric sensor 101 is converted into high and low level switching values, which can reduce the accuracy requirements of the sensors used and control costs. Since the form of detecting the duty cycle is adopted, the accuracy of recognition can be improved, and it is still applicable especially when sewing with variable stitch length; the skipped stitch detection device can also distinguish and detect skipped stitches and broken threads.

A sewing machine with a skipped stitch detection device provided by the present invention includes the skipped stitch detection device described in the above specific embodiments; other parts of the sewing machine can refer to the prior art, and will not be expanded here.

It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any such relationship between these entities. Actual relationship or sequence.

The sewing machine provided by the present invention and its skipping stitch detection device and detection method have been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present invention, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. A skipped stitch detection method for sewing machine, characterized in that, comprising: Obtain the duration occupied by the upper thread during the feeding process within the preset time period; Judging whether the ratio of the duration to the preset time period is within a preset duty cycle range; if not, go to the next step; Notify the operator of sewing abnormalities. 2. The jumping needle detection method according to claim 1, wherein the judging whether the ratio of the duration to the preset time period is within a preset duty ratio range; if not, proceed Before the next steps also include: Obtain the theoretical time taken by the upper thread during the feeding process during normal sewing; calculating a theoretical duty ratio of the ratio of the theoretical duration to the preset time period; The duty ratio range is determined according to the theoretical duty ratio. 3. The jumping needle detection method according to claim 1, wherein the judging whether the ratio of the duration to the preset time period is within a preset duty ratio range; if not, proceed Next steps also include: Judging whether the duration is zero, if yes, proceed to step S010; if not, proceed to step S02; S010, giving a disconnection prompt to the operator; S02. Judging whether to change the needle distance within the current preset time period; if not, proceed to step S020; S020. Prompt the operator for jumper wires. 4. The jumping stitch detection method according to claim 3, characterized in that, in said step S02, if so, step S03 is also performed; S03. Compensate the duration according to the changed needle distance, and judge whether the ratio of the compensated duration to the preset time period is within the duty ratio range; if not, execute the Step S020. 5 . The skipped needle detection method according to any one of claims 1 to 4 , wherein the preset time period is specifically the time required for the main shaft to rotate one revolution. 6 . 6. A skipped stitch detection device for a sewing machine, characterized in that it comprises: Piezoelectric sensor: used to obtain the length of time occupied by the upper thread during the feeding process within the preset time period; Controller: for judging whether the ratio of the duration to the preset time period is within a preset duty ratio range; Alarm: used to prompt the operator that the sewing is abnormal when the ratio of the duration to the preset time period is not within the preset duty cycle range. 7. The needle skipping detection device according to claim 6, wherein the alarm is specifically a wire-break alarm that prompts the operator to disconnect when the duration is zero, and when the duration is zero When the ratio to the preset time period is not within the preset duty cycle range, and the time length is not zero, the jumper alarm is used to prompt the operator to jump the wire. 8. The needle jump detection device according to claim 6, further comprising: Memory: used to obtain the theoretical time taken by the upper thread during the feeding process during normal sewing; A duty ratio range determination unit: used to calculate a theoretical duty ratio of a ratio between the theoretical duration and the preset time period, and determine the duty ratio range according to the theoretical duty ratio. 9. The device for detecting skipped needles according to any one of claims 5-8, characterized in that the piezoelectric sensor is arranged around the stud of the thread tensioner. 10. A sewing machine, characterized by comprising the device for detecting skipped stitches according to any one of claims 5-9.