JPS6154438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a feed-out body that operates to feed out a fixed amount of needle thread from a bobbin spool in synchronization with the operation of a stitch forming mechanism, and a feed-out detector that detects the amount of needle thread fed out from the bobbin spool. A needle that allows a required amount of thread to be paid out from a bobbin winder and supplied to a thread take-up each time one stitch is formed, using a device and a holding means that prevents the feeding body from feeding out needle thread when a predetermined amount of thread is fed out. Regarding a sewing machine having a thread supply device, in particular, the above-mentioned feed-out detection device can detect needle thread breakage and needle thread consumption, and upon such detection, an alarm device is activated and power supply to the sewing machine motor is cut off. Regarding safety devices for sewing machines.

As is well known, if you continue to operate the sewing machine when the sewing thread runs out, perforations will appear in the material to be sewn, especially in the case of materials other than textiles such as leather or pseudo-leather.
The marks of the perforations remain clearly, which significantly impairs the commercial value of the product.

Therefore, devices for detecting thread breakage have been developed, but they require a dedicated space to install the device and are expensive to manufacture, so they cannot be installed on machines other than special industrial sewing machines. I couldn't do that.

It is an object of the present invention to solve the above-mentioned conventional drawbacks by using some of the elements constituting the needle thread supply device in combination.

Embodiments of the present invention will be described below with reference to the drawings.
About the configuration of the mechanical part The sewing machine has a main shaft 2 that rotates in conjunction with the drive source.
A needle bar 4 that fixes a needle 3 with a needle thread T at its lower end and moves up and down in conjunction with the main shaft 2, a bobbin 5 as a needle thread supply source, and a needle thread T between the needles 3 that supports and tensions/relaxes the needle thread T. It operates in conjunction with the thread take-up 6, which reciprocates between two positions in conjunction with the main shaft 2, and also with thread cutting signals generated as appropriate, to cut the needle thread T connected to the fabric below the bed. Thread cutting device (not shown)
This is a known type which is equipped with a thread winding device 93 for winding the bobbin thread bobbin, etc., and in which the swing width of the needle bar 4, the feed amount of the feed dog, and the direction thereof are controlled based on information stored in advance in a storage device. . Further, as shown in FIG. 2, the needle thread T is suspended from the bobbin 5 to the thread take-up lever 6 via the thread tension device 7, first holding means 8, feed-out detection device 9, second holding means 11, and well-known thread take-up spring. ing.

The feeding device 10 has a feeding arm 12, and has a first feeding arm 12.
The length of the needle thread path between the second holding means 8 and 11 is increased when the needle 3 is located below the bed surface as shown in FIG. This is to make it as short as possible. The feeding arm 12 has a vertically inclined transmission surface 12a and a U-shaped thread holding groove 12b located below it, and has two vertically fixedly arranged thread holding grooves 12b located below it. Holes 13 formed in the guide plates 13 and 14
a, 14a, and its base is pivotally supported at each free end of a link 16 supported on a fixed shaft 15 and a link 19 supported on a fixed shaft 17.
The link 19 follows the cam surface of the cam body 18 via a spring 20 stretched between the link 19 and the machine frame.

The feed-out detection device 9 is for detecting the length of movement of the needle thread T from the bobbin spool 5 toward the feed-out arm 12, and includes a pulley 21 having a V groove 21a around which the needle thread T is wound, and a pulley 21 that is constant. It consists of an encoder 22 that generates one pulse every time the angle rotates.

The thread tension device 7 has a thread presser 23, which is used to provide a constant weak passing resistance in order to lightly tension the needle thread T so that it tightly wraps around the pulley 21. . As shown in FIG. 7, the thread presser 23 and the thread slip-out prevention plate 24 that cooperate with the thread presser 23 are slidably supported on support shafts 26 and 27 that project horizontally from a base plate 25 that is fixed perpendicularly to the machine frame. It has been done. The sliding movement of the thread drop prevention plate 24 is restricted by a ring 28 attached to the support shaft 26, and its free end 24a is diagonally inserted from above into the holes 23a and 25a formed in the thread presser 23 and the base plate 25. It is formed to enter downward. Further, the coil spring 29 presses the thread presser 23 toward the board 25, and the coil spring 30 mainly serves to press the thread presser 23 toward the board 25.
4, the free end 24a of which applies a rotational moment toward the hole 25a.

The first holding means 8 attracts and releases the holding plate 32 as an armature by energizing and de-energizing the electromagnet 31, and holds the needle thread T between the holding plate 32 and the opposing yoke 33 so as not to be able to pass through it. It is meant to be liberated. The holding plate 32 is a yoke 33
It is supported vertically by vertically disposed shafts 34 and 35, and a weak elastic force of a coil spring 36 is always applied downward, thereby accelerating the rise of the attractive force by the electromagnet 31.

Note that the upper surface of the yoke 33 of the above-mentioned holding means is connected to the V groove 21 of the pulley 21 in the feeding detection device 9.
a, the intersection point P (Fig. 7) of the thread pull-out prevention plate 24 and thread presser 23 in the thread tension device 7, and the straight line connecting the V groove 96a of the roller 96 pivotally supported on the machine frame, or above it. Place the needle thread T
In other words, the thread presser 32 is always pressed against the upper surface of the yoke 33 by the weak elastic force of the spring 36 so that the thread presser 32 does not float upward against the coil spring 36 due to the tension.

The second holding means 11 has basically the same structure as the first holding means 8, and attracts and attracts the holding plate 38 as an armature by energizing and de-energizing the electromagnet 37.
This is for releasing the needle thread T between it and the yoke 39 so that it cannot pass therethrough or it can be held and released. As shown in FIGS. 2 and 6, the holding plate 38 is swingably supported around the bifurcated protrusion 40a of the support frame 40 of the electromagnet 37 as a fulcrum, and always receives the elastic force of the coil spring 41 in the direction away from the yoke 39. ing. Further, a regulating member 42 that regulates the swinging position of the holding plate 38 due to this elastic force is formed integrally with the yoke 39 from synthetic resin, and keeps the distance S ₁ between the facing surfaces of the holding plate 38 and the iron core 43 constant at all times. I try to keep it. In addition, a certain gap S ₂ is provided between the facing surfaces of the iron core 43 and the retaining plate 38 when it is attracted to the yoke 39, so that when the electromagnet 37 is demagnetized, the retaining plate 38 is separated from the iron core 43 due to residual magnetism. Preventing delays.

The operating lever 44 is rotatably supported in three positions, A, R, and H, corresponding to push-up, neutral, and thread trimming modes. This operating lever 44 has a presser foot 4 with a presser foot (not shown) at the lower end.
5, a presser foot lifting cam 47 for lifting the presser foot against the spring 46, a thread tension device 7, and a first holding means 8.
A thread loosening cam 48 for releasing the clamping force on the needle thread T is integrally supported. The presser foot lifting cam 47 is provided with a presser foot 4 so as to raise the presser foot 45 when the operation lever 44 is rotated to the "A" position.
The lower surfaces of a presser bar holder 49, which is integral with the presser bar 5, are arranged to face each other. In addition, the thread loosening cam 48 moves the thread presser 23 against the spring 29 to the position indicated by the two-dot chain line in FIG. 7 when the operating lever 44 is rotated to the "A" or "C" position. The retainer plate 32 is disposed opposite to a follower 50 connected to a link mechanism that acts to push the retaining plate 32 upward against the spring 36. The follower 50 is swingable about a shaft 51, and this swinging motion is transmitted to the thread presser 23 via links 54 and 55 supported on shafts 52 and 53. In addition, the lower part of a connecting rod 56 having a forked portion into which the locking portion 32a of the holding plate 32 is loosely fitted at the upper end is vertically loosely fitted into the forked portion 54a of the link 54. 56 horizontal protrusions 57
A coil spring 58 having a larger spring constant than the spring 36 is arranged between the spring 36 and the coil spring 58 .

As shown in FIG. 1, the holding plate 3 of the first holding means 8
2 and the pulley 21 of the feeding detection device 9 protrude from the upper surface of the surface machine frame 59, and are covered by a hollow cover 60. The three side surfaces 60a, 60b, and 60c of the cover 60 are inclined so that the lower side faces inward, and the needle thread T is transferred to the cover 60.
By simply winding the needle thread T around the side surfaces 60a, 60b, and 60c of the needle thread T and pulling it, the needle thread T naturally slides down and is set against the first holding means 8 and the feeding detection device 9.

About the electric circuit As shown in FIG. 2, the position detection device 61 includes a rotary plate 61a fixed to the main shaft 2 and a detector 6 for detecting the rotary plate 61a.
1b, detects the rotation angle of the main shaft 2 from immediately after the needle 3 sticks into the bed plane to immediately after the needle 3 comes out of the bed plane, and generates a low level (hereinafter referred to as L) position signal. , and at other times, a high level (hereinafter referred to as H) position signal is generated.

As shown in FIGS. 3 and 4, the cloth thickness detection device 62 has a movable part 62 that rotates forward and backward in conjunction with the vertical movement of the presser bar 45.
a and the voltage corresponding to its rotational position (cloth thickness signal)
and a volume 62b that generates.

The presser foot lift switch 63 is disposed within the swinging path of the link 54 as shown in FIG. 3, and generates an H signal in connection with moving the operating lever 44 to the "A" or "C" position. .

The speed detection device 64 detects the rotational speed of the main shaft 2 and generates a corresponding number of pulses (speed signal). The error calculation device 65 includes first and second holding means 8,
This is to correct the error in the amount of yarn to be paid out due to the delay in the response operation of each holding plate 32, 38 in 11, and is the number obtained by multiplying the number of output pulses N of the speed detection device 64 by a constant k determined experimentally. B pulse (correction signal) is generated.

The memory circuit 66 stores information regarding the swing width of the needle 3 for each stitch (stitch width signal Y) and information about the horizontal movement amount of the cloth feed dog (not shown) (feed amount signal X).
The stored information corresponding to the next stitch is read out via the pattern control circuit 67 when the output of the position detection device 61 rises, and these pieces of information are input to the amplitude signal Y, At the same time that the feed amount signal X is sent to the latch circuit 68, the amplitude signal Y is also sent to the latch circuit 69, and the feed amount signal X is also sent to the latch circuit 70. Note that the latch circuit 69 is operated via the mono multivibrator (one shot) MS ₁ and the inverter I ₁ in relation to the rise of the output of the position detection device 61, and the latch circuit 68,
70 operates in relation to the fall of the position signal;
Furthermore, each latch circuit outputs its input as is by operation.

A needle swing stepping motor (ST.M) 71 is used to operate the needle bar swing mechanism, and is driven via a drive circuit 72 in response to the output of the latch circuit 69. Feed stepping motor (ST.M) 73
is for operating the feed mechanism, and is driven by receiving the output of the latch circuit 70 via the drive circuit 74.

The setting device 75 sets the amount of needle thread required for each stitch formation based on the signals X, Y, and D inputted through the latch circuit 68 and the latch circuit 76 operated in the same manner. It is the ninth
As shown in the figure, the value P ² , ^which is the _{sum of} the square value of ^the feed amount signal k ₂ multiplied by k ₂ P
are added to obtain "k ₁ P ² + k ₂ P", and the value obtained by multiplying the cloth thickness signal D by a constant k ₃ is added to this to obtain "k ₁ P ² + k ₂ P +
k ₃ D'' and further adds a constant k ₄ to this value to output a value (setting signal) A.

The subtraction device 77 outputs a value C obtained by subtracting the output value B of the error calculation device 65 from the output value A of the setting device 75 (theoretical value in FIG. 11) as a feed signal to the comparison circuit 78, and the comparison circuit 78 is a subtraction device. When the output values of counter 77 and counter 79 match, an H signal is generated. The counter 79 outputs a value obtained by counting the output pulses of the feeding detection device 9, and is set at the falling edge of the position signal.

Flip-flop _FF1 becomes active upon receiving the H signal from comparator circuit 78, and is reset to non-operational state in relation to the fall of the position signal, and its output is passed through AND gate _G1 and inverter _I2 . Sent to ANDGATE G ₂ . electromagnet 31,
37 is excited by the H output of the AND gates G ₁ and G ₂ via the corresponding operating circuits 80 and 81, and demagnetized by the L output.

The flip-flop FF ₂ holds both the holding means 8 and 11 during the stitch formation period for the first few stitches after the power is turned on and for the next first few stitches after the finished sewing material is removed from the sewing machine sewing section. This is to prevent the needle thread T from being drawn into the gap, and the initial setting circuit 8
It receives a signal instantaneously generated from MS 2 and is put into an operating state when the signal rises, and is reset to a non-operating state when the output of one-shot MS ₂ , which operates in response to a sewing machine stop signal that is generated in conjunction with the sewing machine stop operation, rises. At the same time, the terminal output is input to AND gates _G1 and _G2 via OR gate _G3 . Further, the counter 83 is connected to the position detection device 61.
The output is reversed from L to H when the value reaches a preset value (in the example, "5"), and when the sewing machine starts the sewing machine. It is reset in relation to the rising edge of the output of the one-shot MS ₃ , which operates in response to the generated sewing machine start signal, and its output is an OR gate.
It is input to AND gates _G1 and _G2 via _G3 .

In conjunction with raising the presser foot, the presser foot lifting switch 63 operates both holding means 8 and 11 in the upper stop zone where the hour hand 3 has come out of the bed surface.
The output is used as input to AND gates G ₁ and G ₂ via AND gate G ₄ and inverter I ₃ .

Flip-flop FF ₃ is used to determine that the needle thread T has been consumed or cut when there is no output from the feed-out detection device 9 from the start of sewing, and is set to the operating state upon receiving the output pulse from the feed-out detection device 9, and when the start is started. The one shot that operates upon receiving a signal
It is adapted to be reset to the inactive state in conjunction with the rise of the output of MS ₃ , and the Q terminal output is provided to AND gate G ₅ or the terminal output is provided as an input to AND gate G ₆ .

Flip-flop FF ₄ switches the needle thread T when the output from the feeding detection device 9 is no longer generated during sewing.
It is used to determine whether the Q terminal has been consumed or disconnected, and it is activated upon receiving the output pulse from the feed detection device 9, and is reset in relation to the fall of the output of the position detection device 61, and the Q terminal output is set to the inverter. It is via I ₄ as the input of gate G ₅ .

The counters 84 and 85 count the rise of the signal from the position detection device 61, and are related to when the value reaches a preset value (in the embodiment, the former is the "7" hand and the latter is the "3" hand). The output is inverted from L to H, and the counter 84 is reset by the rise of the one-shot _MS3 , and the counter 85 is reset by the rise of the output of the flip-flop _FF4 .

The counters 86 and 87 both count the output pulses of the feed-out detection device 9 and output their values, and the counter 86 controls the winding mode which is generated in conjunction with setting the known bobbin winding device 93 into operation. - The counter 87 is reset by the rising edge of the output of the one-shot MS ₄ which operates in response to an on signal, and the counter 87 operates in response to a bobbin winding mode off signal generated in connection with releasing the bobbin winding device 93 to the inactive state. It is reset by the rising edge of the one-shot _MS5 output.

The comparison circuit 88 is for automatically winding a desired amount of thread onto the bobbin thread bobbin 94 by the thread winding device 93, and is used to set the thread winding amount setting device 8 as appropriate.
When the output value of counter 9 and the output value of counter 86 match, the output is inverted, and the output at this time is used to stop the sewing machine motor via motor stop circuit 95. Instead of this, a solenoid is excited and the electromagnetic force causes the peg winder 9 to
3 may be moved to an inactive position.

The memory circuit 90 stores the amount of thread wound onto the bobbin thread bobbin 94 by the bobbin winding device 93, stores the counted value of the counter 86, and always outputs the stored value. The memory contents are cleared by the rising edge of output ₄ .

The comparator circuit 91 is for detecting when an amount of needle thread equivalent to the amount of thread wound on the bobbin thread bobbin 94 is consumed.
When the two outputs match, an H signal is output for a certain period of time. In addition,
Alarm devices 92 such as buzzers and lamps are Noah Gate
It is designed to operate for a certain period of time when the output of _G7 becomes L.

Note that the amount of thread required to form one stitch is determined by the feeding movement of the feeding arm 12 and the holding means 8, as will be described later.
This can be obtained by controlling the operation timing of the holding means 8, but especially the holding plate 3 of the holding means 8.
The delay in the second operation causes a feeding error. Therefore, as shown in FIG.
As shown in the figure, the cam surface of the cam body 18 is formed so that the feeding movement of the feeding arm 12 is slow at first and then gradually becomes faster in the latter half.

This invention has the above configuration, and its operation will be explained next.

The electromagnets 31 and 37 of both holding means 8 and 11 are energized when all four inputs of the corresponding gates G ₁ and G ₂ become H, and demagnetized when one of them becomes L, but in normal case. Since all three inputs from the gates G ₃ , G ₄ , and G ₇ are at H as described later, the output state of the flip-flop FF ₁ determines whether to energize or de-energize it.

Therefore, during normal sewing, the needle bar 4, thread take-up 6, and feeding arm 12 reciprocate along the timing curve shown in FIG. 10. The forward movement of the feeding arm 12 to the right in FIG. 2 increases the needle thread path between the two holding means 8 and 11, but just before the feeding arm 12 moves forward, the flip-flop FF ₁ detects the position detection device. 61
It is reset by the L output of gate _G1
The output of gate G2 becomes L, the output of gate _G2 becomes H, and at the same time as electromagnet 31 is demagnetized, electromagnet 37 is excited,
Since one holding means 8 releases the needle thread T and the other holding means 11 holds the needle thread T, the needle thread T corresponding to the needle thread path increased by the forward movement of the feeding arm 12 is It is drawn in between the two holding means 8 and 11 from the bobbin 5. At this time, the pulley 21 is
The feed detection device 9 rotates as the rotation angle moves, and the feed detection device 9 generates a number of clock pulses proportional to the rotation angle. This clock pulse is counted by a counter 79 and inputted to one input of a comparison circuit 78. In addition, the other input section of the comparison circuit 78 is connected to the feed amount signal The output (theoretical value) C of the subtraction device 77 corrected by subtracting the output value from the error calculation device 65 from the value is input, and the comparison circuit 78 outputs an H signal when the counted value of the counter 79 matches the theoretical value. do. As a result, the output of the flip-flop _FF1 is reversed from L to H, so that the electromagnet 31 is energized and the electromagnet 37 is demagnetized.

Therefore, the needle thread T of the predetermined length is held by both the holding means 8, 11.
After being fed in between, the first holding means 8 holds the needle thread T so that it cannot pass through and prevents it from being unwound from the bobbin 5, and the second holding means 11 allows the needle thread T to pass through freely. release. Note that if the needle thread T of the predetermined length is paid out during the forward movement of the feeding arm 12, the slack needle thread T between the second holding means 11 and the needle 3 will be removed during the subsequent forward movement of the feeding arm 12. It is temporarily pulled back between both holding means 8 and 11.

Further, since the feeding arm 12 returns to its original state before the needle thread T is next tensioned by the thread take-up lever 6, the first holding means 8 and the needle thread between the stitches are The T is gradually tightened, thereby tightening the seam with appropriate strength and knotting. Thereafter, the same operation is repeated every time one stitch is formed.

As mentioned above, feed amount signal X, amplitude signal Y,
The required amount of thread calculated based on the cloth thickness signal D is fed out each time one stitch is formed, but the regular amount of thread is not required for the first few stitches of sewing. Therefore, when sewing starts after turning on the power, flip-flop FF ₂ is preset and the counter 83 is reset by the start signal, so the position detection device 61 is reset.
Until the fall of the signal is counted 5 times, that is, until 5 stitches are formed, the output of the gate G ₃ becomes L, which closes the gates G ₁ and G ₂ , so that the electromagnets 31, 37 remains demagnetized and does not operate. Flip-flop FF ₂ is reset by stopping the sewing machine, but when the fabric is removed from the seam or the position is shifted, the needle thread T is let out from the bobbin 5 and reset again by the pulse signal from the feed-out detection device 9. When sewing is started after that, the electromagnets 31 and 37 remain demagnetized until five stitches are formed, as described above, and normal feeding is not performed.

When the sewing machine is stopped near the lowest point of the needle bar in order to rotate the cloth around the needle 3, the output of the gate _G4 remains at L even if the presser foot is raised, so both holding means 8 , 11 remains the same as before the sewing machine stopped, and if you start the sewing machine again, the scheduled stitches will continue to be formed, but if you stop the sewing machine near the top of the needle bar to take out the fabric from the seam, ,
When the presser foot is raised, the output of gate _G4 becomes H, which closes gates _G1 and _G2 .
The electromagnets 31 and 37 are demagnetized and both the holding means 8 and 11 release the needle thread T. Regarding the holding means 8, in the former case, since the holding plate 32 is attracted by electromagnetic force, the link 54 rotates clockwise in FIG. 2 in conjunction with the cam body 48, and the connecting rod 56 is pushed up. However, in the latter case, the electromagnetic force is not generated, so the retaining plate 32 is linked to the connecting rod 59 via the spring 58 and moves upward about the shaft 34. .

When the bobbin winder 93 is set to the operating state, the counter 86 and the memory circuit 90 are reset. Therefore, when the sewing machine is started after appropriately setting the thread winding amount setting device 89, the needle thread T is wound from the bobbin winder 5 onto the bobbin thread bobbin 94, and the thread amount is memorized via the feeding detection device 9 and the counter 86. It is stored in the circuit 90, and when the winding amount reaches the set amount, the motor stop circuit 95 is activated by the output of the comparator circuit 88.
The sewing machine motor will stop through. Further, the amount of thread consumed by sewing is detected by the feed-out detection device 9 and the counter 87, and when the amount of thread reaches the amount of thread previously wound on the bobbin thread bobbin 94, the amount of thread consumed by sewing is detected by the output of the comparison circuit 91. The alarm device 92 operates for a certain period of time, and the sewing machine motor is stopped via the motor stop circuit 95.

If the needle thread T is completely consumed or broken during sewing and the output of the feed detection device 9 stops, the flip-flop FF ₄ is not set, so the rising output of the position detection device 61 is detected by the counter 8.
5, and if the output of the feedout detection device 9 does not occur even once during the period corresponding to the set value, that is, during the three rotations of the main shaft 2, then the output of the gate _G5 becomes H. Therefore, the sewing machine is stopped via the motor stop circuit 95, the alarm device 92 is activated for a certain period of time, and the gate is activated.
G ₁ and G ₂ are closed and the electromagnets 31 and 37 are also demagnetized.

As mentioned above, the needle thread T may break when the power is not turned on, or even after the power is turned on, when the sewing machine is stopped near the top dead center of the needle bar and the presser foot is raised, or during sewing. Electromagnet 3 if consumed or
1 and 37 are demagnetized and the holding force of the needle thread by both holding means 8 and 11 is released, so when setting the needle thread T, in these conditions, first remove the end of the needle thread T from the bobbin spool 5. If you pick it up and pull it out, then wrap the middle part around the cover 60 and pull it lightly, a downward force will be generated on the needle thread T, so the middle part will slide down the sides 60a, 60b, 60c of the cover 60. If the end of the needle thread T is further pulled, the first holding means 8
It is pulled in between the holding plate 32 and the yoke 33, and is wound around the pulley 21 of the feeding detection device 9.

Furthermore, if the sewing machine is driven without setting the needle thread T, the output from the feed detection device 9 will not be input to the flip-flop FF ₃ after being reset by the sewing machine start signal and the output will become H, so the setting of the counter 84 will be When the main shaft 2 rotates by the number of rotations, the output of the gate _G4 becomes H. Therefore, in this case, the alarm device is activated after the main shaft 2 has rotated seven times, and the electromagnets 31 and 37 are demagnetized.

In the above embodiment, the set value of the counter 84 was set to "7"; however, this is true regardless of whether the needle thread T is set or not, and when five stitches have been made (in this embodiment) since the start of sewing. Until the set value of the counter 83 in the example) is formed, the electromagnets 31 and 37 remain demagnetized and normal feeding is not performed, so unless the set value of the counter 84 is made larger than the set value of the counter 83, the needle This is because it cannot be determined whether the thread T is set or not. Therefore, the counter 84
The set value of the counter 83 only needs to be larger than the set value of the counter 83.

Further, in the above embodiment, the feed signal and swing width signal stored in advance in the storage device are read out every rotation of the main shaft, and the movement of the feed mechanism and needle bar swinging mechanism is controlled for each stitch using these signals. In a sewing machine of a type that can sew a predetermined pattern using The feed signal was calculated and determined for each stitch formed based on the feed amount and needle swing amount, or the amount of thread that was experimentally determined in advance for each different condition of fabric thickness and stored in the storage device. Corresponding yarn amount data may be read out from the data group based on the feed signal and swing width signal, or these and the cloth thickness signal.

Further, in the above embodiment, the sewing machine controls the feed mechanism and the needle bar swinging mechanism based on the feed signal and swing width signal stored in the storage device, but the The invention may also be applied to a sewing machine in which the feed amount and needle swing amount are controlled manually. In this case, the feeding signal may be calculated in the same manner as described above from the detection signals corresponding to the setting modes of the feed amount and needle swing amount, or from these and the detection signal of the material thickness, or may be determined in advance by actual operation. Corresponding yarn amount data may be read out from a group of yarn amount data that has been randomly determined and stored.

In addition, in the above embodiment, the needle bar is applied to a zigzag stitch sewing machine in which the needle bar is oscillated in the direction crossing the cloth feeding direction, but the cloth is moved in the X-Y coordinate axis direction with respect to the needle bar that moves up and down in a fixed position. It may also be applied to a sewing machine that can sew a zigzag stitch pattern.

In this case, as is well known, two independent power sources, such as motors, are provided for moving the cloth in the X and Y coordinate directions. The amount of needle thread required to form one stitch is expressed as the square root of the sum of the square of the amount of fabric movement in the X-coordinate axis and the square of the fabric movement in the Y-coordinate axis, if the fabric thickness is ignored. Therefore, instead of the feed amount signal and swing width signal of this embodiment, signals for controlling the rotation direction and angle of each of the motors may be used.

As described above, the present invention includes a feeding body that operates to feed out a fixed amount of needle thread from a bobbin spool in synchronization with the operation of a stitch forming mechanism, and a feeding detection device that detects the amount of needle thread fed out from the bobbin spool. , a needle thread supplying device configured to pay out the required amount of thread from the bobbin winder and supply it to the take-up thread each time one stitch is formed, by means of a holding means that prevents the feeding body from feeding out when a predetermined amount of yarn is detected to be fed out. In the sewing machine, the feed-out detection device is also used to detect needle thread breakage and remaining needle thread, so there is no need to install a special device for the above detection, and the sewing machine equipped with the safety device of the present invention can be used at a low cost. It has the effect of being compact.

Note that in this embodiment, the flip-flop
FF ₁ , inverter I ₂ , gates G ₁ , G ₂ , and operating circuits 80 and 81 constitute a feeding control circuit, and flip-flop FF ₄ and counter 85 constitute a needle thread detection circuit.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of the sewing machine head, FIG. 2 is a perspective view of the needle thread supply device, FIG. 3 is a partial front view of the needle thread supply device, and FIG. 4 is a left side view of the needle thread supply device. 5 is a longitudinal sectional view of the first holding means, FIG. 6 is a longitudinal sectional view of the second holding means, FIG. 7 is a longitudinal sectional view of the thread tension regulator, FIG. 8 is a block diagram of the electric circuit, and FIG. The figure is a block diagram showing an example of a setting device, Figure 10 is a time chart, and Figure 11 shows the relationship between the theoretically determined required length of needle thread to be fed out and the length of the needle thread that is actually paid out. It is a diagram.

Claims (1)

[Scope of Claims] 1. Disposed on the needle thread path between the thread take-up and the needle thread supply source so as to be spaced apart from each other at the front and the front in the needle thread supply direction, so that the needle thread cannot pass through due to action and the needle thread cannot pass through due to non-action. Two holding means 6 and 7 act on the needle thread so that the needle thread can pass through the needle thread, and are arranged on the needle thread path between the two holding means, and change the needle thread path between the two holding means to change the needle thread path. a feeding body 12 that operates in synchronization with the thread take-up so as to increase the length of the needle thread at a time other than the tensioning period of the needle thread take-up and then reduce it to the shortest length by the time when the thread take-up reaches the maximum tension of the needle thread; The needle thread is engaged with the needle thread in front of the feeding body in the needle thread supply direction, and the operation of the feeding body is proportional to the increase in the length of the needle thread path between the two holding means or the length of the needle thread being fed out by the feeding body. and a feed-out detection device 16 that generates electrically different thread amount detection signals corresponding to the amount of displacement; A position detection device that detects and generates a position signal, a setting device 21 that can generate a setting signal corresponding to the length of needle thread required to form one stitch in response to different sewing conditions, and a thread amount. A comparison circuit 22 that compares the signal and the setting signal and generates a match signal when they match; and a comparison circuit 22 that makes the holding means on the bobbin winding side inactive in relation to the position signal and activates the holding means in relation to the match signal. At the same time, a feed-out control circuit associated with the position detection device and comparison circuit makes the holding means on the balance side inactive from when the coincidence signal is generated until at least the position signal disappears. In a sewing machine equipped with a needle thread supply device that feeds needle thread of the length required to form one stitch each time from a bobbin spool to a thread take-up, a position signal is generated and a thread amount detection signal is not generated. a needle thread detection circuit that operates in conjunction with the needle thread detection circuit; an alarm device that operates in conjunction with the needle thread detection circuit and generates sound or light; and an alarm device that operates in conjunction with the needle thread detection circuit and generates a signal to the sewing machine motor. A safety device for a sewing machine, comprising: a motor stop circuit that cuts off power supply.