JPH0322193B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a needle thread supply device for a sewing machine, which feeds out needle thread of a length corresponding to a feed signal from a supply source and actively supplies it to a thread take-up every time one stitch is formed. In particular, it relates to calculation of the feeding signal.

The amount of needle thread required to form one stitch is calculated by taking into account the amount of cloth feed, the amount of needle swing, or the thickness of the cloth and the length required for thread entanglement. However, there is a need for a feeding device that operates in synchronization with the thread take-up so that the needle thread path between the needle thread supply source and the thread take-up is increased at a time other than when the needle thread tension is applied by the thread take-up, and then is made as short as possible until reaching maximum tension. When the needle thread path is increased by the feeding device, the needle thread on the take-up side is held so that it cannot pass through, and the needle thread on the supply source side is released so that it can pass through. Two holding means act to hold the needle thread on the supply side as the length increases in response to the feed-out signal, and release the needle thread on the take-up side when the needle thread is tensioned by the thread take-up. In the needle thread supply device of a sewing machine, which feeds out the amount of needle thread corresponding to the feed signal from the supply source to the thread take-up every time one stitch is formed, the amount of needle thread is increased in proportion to the increase in the needle thread path due to the delay in the operation of the holding means. The needle thread is paid out even after the amount of needle thread actually paid out matches the theoretical amount of thread, resulting in poor sewing quality. Furthermore, this tendency becomes more pronounced as the sewing speed increases.

This invention calculates the needle thread payout error caused by the delay in the operation of the holding means from the sewing machine rotation speed, and corrects the theoretical thread amount calculated based on the feed amount, needle swing amount, fabric thickness, etc. It is an object of the present invention to solve the above-mentioned drawbacks by comparing the amount of thread with the amount of thread actually paid out and, when the two match, preventing the needle thread from being paid out from the supply source.

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 is used to pre-warm the thread presser 23 and to always 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 dropout prevention plate 24 is restricted by a ring 28 attached to the spindle 26.
The free end 24a is formed to enter holes 23a and 25a formed in the thread presser 23 and the substrate 25 obliquely downward from above, and the coil spring 29 presses the thread presser 23 toward the substrate 25. The coil spring 30 is mainly used to apply a rotational moment to the thread removal prevention plate 24 so that its free end 24a moves toward the hole 25a.

The first holding means 8 attracts and releases the holding plate 32 as an uncut 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 that it cannot pass through or passes 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 corresponds to the groove 21 of the pulley 21V 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 a manual 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 body 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 the distance between the opposing surfaces of the holding body 38 and the iron core 43 is
We try to keep S ₁ constant. Also iron core 4
A certain gap S ₂ is provided between the facing surfaces of the holding plate 38 when the electromagnet 37 is attracted to the yoke 39, and the separation of the holding plate 38 from the iron core 43 is delayed due to residual magnetism when the electromagnet 37 is demagnetized. is prevented.

The operating lever 44 has two positions corresponding to push-up, neutral, and thread trimming modes. B. It is rotatably supported in three positions (c). 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. Furthermore, when the operating lever 44 is rotated to the "A" or "C" position, 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. 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. Further, the lower part of a connecting rod 56 that removes the 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 will naturally slide down and be set against the first holding means 8 and the feeding detection device 9.

About the electric circuit The position detection device 61 includes a rotary plate 6a fixed to the main shaft 2 and a detector 61 for detecting it as shown in FIG.
b, 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 being 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 output pulse number N of the speed detection device 64 by an experimentally determined or constant k. 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).
When the output of the position detection device 61 rises, the stored information corresponding to the next stitch is read out via the pattern control circuit 67, 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 activated 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 it 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 value raised to the power of k ₂
k ₂ P is added to "k ₁ P ² - k ₂ P", and the value obtained by multiplying the cloth thickness signal D by the constant k ₃ is added to "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 the 11th) as a signal and sends it to the comparison circuit 7.
8, and the comparator circuit 78 generates an H signal when the output values of the subtractor 77 and the counter 76 match. The counter 79 outputs a value obtained by counting the output pulses of the feeding detection device 9, and is reset by the fall of the position signal.

The flip-flop _F1 becomes active upon receiving the H signal from the comparator circuit 78, and is reset to an inactive state in relation to the fall of the position signal, and these outputs are outputted via the AND gate _G1 and the inverter _I2 . Sent to ANDGATE G ₂ . Electromagnets 31, 37
are excited by the H output of the AND gates G ₁ and G ₂ via the corresponding operating circuits 80 and 81, respectively, and the L
Demagnetizes by 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 the sewing machine 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 the one shot MS ₂ , which operates in response to a sewing machine stop signal generated in connection with the sewing machine stop operation, rises. At the same time, the terminal output is input to OR gates _G1 and _G2 via OR gate _G3 . Further, the counter 83 counts the fall of the output of the position detection device 61, and when the value reaches a preset value (in the embodiment, it is "5"), the output is reversed from L to H. , is reset in relation to the rise of the output of one shot MS ₃ which operates in response to the sewing machine start signal generated in connection with the sewing machine start operation, and the output is sent to AND gates G ₁ and G ₂ via AND gate G ₃ . It has been entered.

The presser foot lifting switch 63 is used to release the needle thread T from both holding means 8 and 11 in the upper stop zone where the needle 3 has come out of the bed surface when the presser foot is raised. The output is 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 a non-operating state in conjunction with the rise of the output of MS ₃ , and the Q terminal output is provided to AND gate _G5 and the terminal output is provided as an input to AND gate _G6 .

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 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. Via I ₄ is 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 when the value reaches a preset value (in the embodiment, the former is the "7" hand and the latter is the "3" hand). Correspondingly, the output is inverted from L to H, and the counter 84 is reset by the rising edge of the one shot MS ₃ and the counter 85 is reset by the rising edge of the output of the flip-flop FF ₄ .

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 rotates as the needle thread T 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 a setting device 75 that calculates the feed amount signal A subtraction device 7 that corrects the value by subtracting the output value from the error calculation device 65
7 (theoretical value) C is input, and the comparison circuit 78 outputs an H signal when the count value of the counter 79 matches the theoretical value. 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.

Furthermore, since the feeding arm 12 returns to its original state before the needle thread T is tensioned by the thread take-up lever 6, as the thread thread take-up 6 subsequently rises, the first holding means 8 and the needle thread T between the stitches are is gradually tightened, which tightens the seam to the appropriate strength and knots it. 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. 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 _G3 becomes L, which closes the gates _G1 and _G2 , so that the electromagnets 31, 37 remains demagnetized and does not operate. Flip-flop FF ₂ is reset when the sewing machine is stopped, but when the fabric is removed from the seam or the position is shifted, the needle thread T is let out from the bobbin winder 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 the standard is not fed out.

When the sewing machine is stopped near the lowest point of the needle bar in order to rotate the cloth around needle 3, the output of gate _G4 remains at L and does not change even if the presser foot is raised.
The state of both holding means 8 and 11 remains the same as before the sewing machine stopped, and when the sewing machine is started again, the scheduled stitches will continue to be formed, but the sewing machine will be stopped near the highest point of the needle bar in order to take out the fabric from the seam part. In this case, when the presser foot is raised, the output of gate _G4 becomes H.
As a result, the gates G ₁ and G ₂ are closed, so that the electromagnets 1 and 37 are demagnetized and both the holding means 8 and 11 are connected to the needle thread T.
to release. Regarding the holding means 8, in the former case, since the holding plate 32 is attracted by the electromagnet, the link 54 is moved to the second position in conjunction with the cam body 48.
Even if the connecting rod 56 is pushed up by rotating clockwise in the figure, the spring 58 will only be compressed, but in the latter case, the electromagnet will not be generated, so the holding plate 56 will be pushed up.
2 is interlocked with a connecting rod 59 via a spring 58 and moves upward about the shaft 34 as a fulcrum.

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 feeding detection device 9 will not be input to the flip-flop FF ₃ after being reset by the sewing machine start signal and will become H, so the set number of the counter 84 will be reset. When spindle 2 rotates by
The output of _G4 becomes H. Therefore, in this case, the alarm device is activated after the main shaft 2 has rotated seven times, and
Electromagnets 31 and 37 are demagnetized.

As described above, the present invention provides a needle thread supply device for a sewing machine in which an amount of needle thread corresponding to a feed signal is paid out from a supply source and supplied to a thread take-up every time one stitch is formed. a setting device that generates a setting signal corresponding to the amount of feed and the amount of swing of the needle bar in the direction perpendicular to the cloth feed, or the required amount of yarn calculated based on these and the thickness of the cloth; a circuit detection device that outputs a speed signal corresponding to the rotational angular velocity of the needle, an error calculation device that outputs a correction signal corresponding to the needle thread amount as a function of the speed signal, and a value obtained by subtracting the value of the correction signal from the value of the setting signal. By using the output of the subtraction device as a feeding signal, errors in the amount of needle thread due to delays in the operation of the holding means are corrected, so the sewing speed of the sewing machine can be increased and sewing efficiency can be improved. In addition, good stitching quality can always be obtained even if the sewing speed of the sewing machine changes.

Note that in the above embodiment of the present invention, the feeding device 1
0 always increases the needle thread path by a constant amount,
The holding means 8 and 11 are shown to operate so that when one holds the needle thread, the other releases the needle thread, and when the other holds the needle thread, the other releases the needle thread. As described in Japanese Patent Application No. 57-151128, a holding means holds the needle thread on the thread take-up side and releases the needle thread on the supply source side when the needle thread path is increased by the feeding body, so that the necessary amount of thread is fed out. It acts to hold the needle thread on the supply side in relation to being held, and then releases the needle thread on the thread take-up side when the thread take-up is tensioned, and after both holding means hold the needle thread, In other words, after the required amount is paid out, the movement of the engaging portion of the feeding body with the needle thread is regulated by the needle thread tension between both holding means, and the needle thread path is prevented from increasing. It has the same effect when applied.

[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. 3 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 actual length of the needle thread to be fed out. It is a diagram.

Claims (1)

[Scope of Claims] 1. Operates in synchronization with the thread take-up so that the needle thread path between the needle thread supply source and the thread take-up is increased by a certain amount at a time other than when the needle thread is tensioned by the thread take-up, and then made shortest by the time of maximum tension. a feed-out device 10 for each stitch formation, and settings corresponding to the amount of fabric feed and the amount of swing of the needle bar in a direction perpendicular to the fabric feed, or the required amount of thread calculated based on these and the thickness of the fabric. A setting device 75 that generates a signal, a feed-out detection device 9 that generates a yarn amount signal corresponding to the amount of yarn paid out from the needle thread supply source in connection with the operation of the feed-out device, and a feed-out signal and a yarn amount signal. A comparator circuit 78 that generates a match signal when the two values match, and a comparator circuit 78 that is arranged on the needle thread path with the feeding device in between and prevents the needle thread on the take-up side from passing through when the needle thread path is increased by the feeding device. The needle thread on the supply source side is held in relation to the coincidence signal, and the needle thread on the thread take-up side is released when the needle thread take-up is tensioned. A needle thread supply device for a sewing machine is provided with two holding means 8 and 11 that act on a feed signal, and is arranged in relation to a main shaft, and feeds out an amount of needle thread corresponding to a feed signal from a supply source to a thread take-up every time one stitch is formed. a rotation detection device 64 that outputs a speed signal corresponding to the rotational angular velocity of the main shaft; an error calculation device 65 that outputs a correction signal corresponding to the amount of needle thread to be corrected as a function of the speed signal; A needle thread supply device for a sewing machine, comprising: a subtraction device 77 that outputs a value obtained by subtracting a signal value, and the output of the subtraction device is used as a feeding signal.