FR2572427A1 - APPARATUS FOR AUTOMATICALLY ADJUSTING THE SEWING PITCH IN A SEWING MACHINE. - Google Patents

Abstract

THE APPARATUS FOR ADJUSTING SEWING PITCHES ACCORDING TO THE PRESENT INVENTION ALLOWS TO POSITION THE LAST SEWING STITCH AT A PREDETERMINED PLACE. DURING THE SEWING OPERATION, A DEVICE DETECTS THE END OF THE SEWING PIECE AND THE APPARATUS ADJUSTS THE SEWING PIT BY DETECTING THE GAP BETWEEN THE NEEDLE HOLE AND THE STITCH STITCH.

Description

i Device for automatically adjusting the pitch of a seam in a

  sewing machine The present invention relates to an automatic sewing pitch adjustment device which makes it possible to precisely position and stop needle stitches at predetermined stitches and relates, more particularly, to the automatic adjustment of the sewing pitch so that the needle stitches end

at predetermined points.

  As an embodiment of a predetermined seam line on the inner side of a piece of sewing fabric, a seam along a neck portion has been chosen as the seam lines AB, BC, CD shown in the figure 1 at a distance "a" from the end of the

fabric sewing piece.

  In this case, each seam line is determined beforehand for each part of the collar, so as to effect the seams as indicated in the request.

  of published Japanese patent 53-38646.

  According to the present invention, two kinds of seams are made. Each sewing step is different, but the total length of the seam line is equal, and these two seams, which are set beforehand, are mixed so that the desired sewing is carried out, the last

  needle point being positioned at the predetermined point.

  Because we first fix the sewing stitch seeond which is chosen to adjust or adjust the seam,

  the needle stitches are not at the predefined stitches

  completed when the first needle point is not in

  place or when the elasticity of the part is different.

  For example, if the second seam pitch was i mm and the gap caused by the elasticity of the workpiece was 0.5 mm, it would be difficult to adjust the seam pitch within limits less than i mm in modifying the number of stitches and the quality of the sewn item would be reduced. In addition, in real sewing, the fact of precisely setting the first stitch for each piece and in the case where it is necessary to sew large pieces, the efficiency of the work is reduced and the cost price increased. The present invention proposes to improve these weak points. The present invention makes it possible to stop sewing with precision and this automatically at the predetermined location or point by detecting the required length of the sewing line and by calculating the necessary number of sewing steps to complete the sewing.

to the edge line.

  Based on this number of sewing stitches and this length of the sewing line, the revised number of sewing stitches and the sewing pitch are calculated, and the sewing machine is automatically adjusted so as to sew according to said pitch, the sewing carried out with this step and according to the above-mentioned revised number of sewing stitches

  thus ending at the predetermined point.

  We will now describe an embodiment of the present invention with reference to the accompanying drawings, in which: Figure 1 shows the seam of a collar with a margin "a"; Figure 2 is a schematic view of the present invention; FIG. 3 shows the way in which the sewing pitch is adjusted using a stepping motor and a solenoid; Figure 4 shows the formation of a seam line when using the apparatus according to the present invention; Figure 5 is a flow diagram of the present invention; Figure 6 is a block diagram of the present invention; and Figure 7 is a block diagram showing

  how the Pl / p ratio is calculated.

  Referring to FIG. 2, it can be seen that the reference 1 designates a conventional claw advance mechanism which is located under a bench and performs a movement of appearance and disappearance on the surface of a plate to

gorges, advancing four steps.

  Reference 2 designates a main shaft, reference 3 a conventional advance adjustment device which is connected to the main shaft 2 via

  of a crank and which transmits a component of movement-

  horizontal in the form of a horizontal advance. Reference 4 designates an adjustable screw which is rotated from the outside of the sewing machine, advancing

  or thus moving its end back.

  The reference 5 designates a conventional adjustment cam which is in contact with the end of said adjustment screw 4 and which is rotated by the end of this adjustment screw, the middle part of the cam being

held in the center.

  Reference 6 designates an oscillating shaft which is

  attached to the rear end of said adjustment cam.

  The reference 7 designates a link which is connected to said oscillating shaft 6 and which regulates the sewing pitch by modifying the horizontal component of displacement at the end of the advance adjustment device 3 as a function of the

cam position 5.

  Referring to Figures 2 and 3, we see that the - reference 9 designates a feed lever and -a qua part o30 of this feed lever 9 is fixed a finger 9a making

protrudes horizontally.

  The reference 8 designates a spring connected to the end of the advance lever 9 and fixed at its other end to the frame of the machine, this lever being thus urged so

  to move up normally.

  The reference 10 designates a shaft supporting a support section of the advance lever 9 which has an opening, said shaft being inserted with clearance in this opening and thus acting as an adjustment shaft arranged

  rotatingly against the machine frame.

  The reference 11 designates an oscillating lever which is fixed to the adjustment shaft 10 and which extends horizontally

  to the base of finger 9a of lever 9.

  When the lever 9 rotates downward, the finger 9a pushes the oscillating shaft 11 and, consequently, the adjusting shaft 10 rotates in an anticlockwise direction. The end of the adjustment shaft 10 is connected to the oscillating shaft 6 via a link 12 and, depending on the angle of rotation of this shaft.

  setting 10, the feed is reduced or reversed.

  The reference 13 designates a lever in the shape of an "L" whose bent part is rotatably supported by

  the adjustment shaft 10 (see fig. 3).

  At the free end of this lever 13 in the shape of an "L" is fixed an actuating finger 13a which projects

above the swingarm 11.

  Reference 14 designates a link arm or link which rotatably supports one of the ends

lever 13 in the shape of an "L".

  The reference 15 designates an actuating lever in the shape of an "L", the middle part of which is rotatably supported by the frame of the machine and the end of which is rotatably connected to another end of the

link 14.

  Another end of the "L" shaped actuating lever is supported by a movable core 16a of a

solenoid 16.

  The upward and downward movement of the movable core 16a causes the link between the actuating lever 15 to move to the right and to the left.

"L" shape and the connecting rod 14.

  The reference 17 designates a cam body of which one of the end surfaces forms a cam 17a and which is

  attached to a shaft 18 of a stepping motor.

  The distance between the circumference of the cam 17a and another end of the cam body differs according to

the circumferential position.

  The projecting end of the rod 14 forms a contact element 14a and this contact element 14a is located opposite the surface of the cam 17a, so that the distance between the contact element 17a and the surface of the cam 17a differs according to the angle of rotation

of this cam 17a.

  The link arm or link 14 therefore comes into contact with the surface of the cam 17a when it moves

to the right.

  Since the contact position differs as a function of the rotation of the surface of the cam 17a, the distance by which the contact element 14a moves also differs and this distance of movement has the effect of making the arm rotate downwards oscillating ll under the push of an actuating finger 13a of the lever

  in the shape of an "L" and to reduce the pitch of the seam.

  In short, the distance by which the rod 14 moves is defined by the angle of rotation of the body 17 of the cam which is driven in relative rotation by a stepping motor 18 and by the solenoid 16 when it is excited, the reduction sewing pitch being thus obtained in

  response to the distance by which the link moves 14.

  Reference 19 designates a potentiometer which is

  connected to the free end of the swinging arm ll by the inter-

  linkage linkage and swingarm rotation

  lt is converted into an electrical signal.

  When solenoid 16 is not energized, the potentio-

  meter 19 detects the seam pitch designated by the screw

  setting 4. When the solenoid 16 is energized, the potentio-

  meter 19 detects the sewing pitch designated by the motor

step by step 5.

  A sensor 20 (not shown in FIG. 2) for detecting the end of the sewing piece is disposed forward (in a direction opposite to the direction of advance) relative to the hole in the needle. The sensor 20 detects the end of the workpiece and is at a predetermined distance from the needle hole. The sewing end detection sensor consists of a projector 20a which is placed on the upper side and a photodetector which is placed

on the lower side.

  Any type of sewing piece end sensor can be used as long as it performs the same function, although its configuration

may be different.

  Referring to FIG. 6, it can be seen that the reference 21 designates an associated pulse generator

to the main tree.

  A disc with slots is mounted on the main shaft and, when the main shaft rotates, the passage

  of the slots is transformed into a pulsed signal.

  Reference 22 designates a main shaft detector and, during one revolution of the main shaft, a low level signal "L" is emitted during the advance operation and a high level signal "H" is emitted after

an advance transaction.

  We will now describe the operation of the

  sewing machine according to the invention. -

  Referring to the arrangement described above, we will explain using the latter's control circuit how sewing can be finished with precision at the preset edge line and how the sewing machine

  stops automatically thanks to this arrangement.

  In Figure 4, one of the examples is shown

  of a real seam made according to the present invention.

  The seam starts from the point and ends at the edge line which is i mm away from the end of the workpiece, this edge line being a straight line. In this example, the feed (no seam) for each needle point is set at 2 mm, and when the seam has reached 20 mm from the end of the workpiece, the workpiece end detector 20 to sew

sends a detection signal.

  Therefore, the required length of the seam after detecting the end of the workpiece is (20-1 = 19) 19 mm, and the required number of sewing stitches is 19/2 = 9.5 stitches . If the workpiece is advanced P1 mm after detection of the end of the workpiece, the required number of sewing stitches is

(9.5-P1 / 2) stitches.

  For example, if P1 = 0.4 mm as in figure 4, 9.5 - (Pl / p) = 9.5 (0.4 / 2) = 9.3 (sewing stitches) Thus, if we carry out 9 sewing stitches at the initial step of 2 mm and the last sewing point at a step of 0,) times the initial step (2x0.3 = 0.6 mm), sewing ends at the

edge line.

  Referring to Figure 5 which represents a flowchart and to Figure 6 which represents a block diagram, we will explain in more detail the principle

mentioned above.

  When the circuit is turned on, the preset sewing pitch, adjusted using the adjusting screw 4, is detected by the potentiometer 19 and a circuit 23 for determining the seam calculates the required number of sewing stitches after sensor 20 has detected the end

of the piece of sewing material.

  In the example above, the distance between the needle hole of the edge line is 19 mm and the pitch is 2 mm. Circuit 23 therefore calculates 9.5 stitches

(19 + 2 = 9.5).

  In the next phase, when the piece of sewing material from the point has advanced Until its end has reached a point 20 mm from the

  needle hole, the sensor 20 detects this position.

  When the end of the piece of sewing material is detected, the pulse generator 21, which is mounted on the main shaft, detects the angular position

of the last.

  According to this angle, the stitching pitch P1 necessary to make the next stitching point after detection by the sensor and the ratio between the pitch of the unfinished stitching and the stitching pitch P, i.e.

Pl / p, are calculated.

  In the present example, p = 2 mm, Pl-0.4 mm, the step 0 4 of the unfinished seam is then = 20%, as detected

  by the sensor when the step taken represents 80%.

  Referring to FIG. 7, it can be seen that to detect the ratio Pl / p (see fig. 4 for P1, P being the seam pitch) the detector 22 of the main shaft generates a low level signal "L" during the operation

  in advance and this signal is applied to a Gate 1.

  The sensor 20 for detecting the end of the sewing piece of fabric is connected to the reverse input of Door 1 and to the input of a Door 2 as well as to the input

  for validating the output of the table ROM 24.

  The pulse train from the main shaft pulse generator 21 is applied to a counter

  phase in the form of a clock signal via the

door 2.

  The phase counter detects the angular position or phase position of the main shaft when the sensor

  detected the end of the sewing piece.

  When the piece of fabric to be sewn covers the fabric piece detection sensor and a high level signal "H" is emitted, the pulse train from the main shaft pulse generator 21 is applied to phase counter 25, and this counter counts Until

Door 2 opens.

  Under these conditions, if the sensor 20 has detected the end of the piece of sewing material, the outlet passes

from level "H" to level "L".

  Then, Door 2 closes and the pulse train ceases to be applied to the input of the phase counter

, so that the counting stops.

  When the output of the end piece sewing fabric sensor 20 changes to the "L" level, although the advance operation is finished and the main shaft detector emits a "H" level signal , the phase counter 25 is not reset, and the phase at the time when the sensor has detected the end of the

  sewing cloth is maintained.

  The relation between the phase of the main shaft and P1 / P is not linear but follows a curve and this curve is particular to the seam step, so that to obtain the Pl / p ratio according to the phase of the tree

  main, the table is necessary.

  The phase value of the main shaft is entered in the ROM ROM 24 of the table in the form of an address, and the parameter of the sewing pitch from the potentiometer after passing through the A / D converter (analog / digital) and a temporary memory is registered

at this address.

  The sewing pitch parameter is temporarily stored when the end detection sensor 20

  of piece of sewing material goes from level "H" to level "L".

  The output of the end-of-sewing piece detection sensor 20 is applied to the input validation output of the table ROM 24 and, when the sensor has detected the end of the piece of sewing fabric , the signal goes from level "H" to level "L" and the ratio

P1 / p is issued.

  The calculation device 26 subtracts Pl / p from the aforementioned designated number of sewing stitches and calculates the number 0lo of sewing stitches from the first sewing stitch after the detection carried out by the end piece detection sensor to sew until the

sewing machine stops.

  For example, in the example described above, the designated number of sewing stitches is 9.5 and P1 / p is

  0.2 (0.4 * 2 = 0.2). Then the calculation gives 9.5 - 0.2 = 9.3.

  In other words, a seam comprising 9 sewing stitches with a sewing pitch of 2 mm plus a sewing point with a sewing pitch of 2 mm x 0.3 = 0.6 mm is

  ends at the preset position.

  On this subject, the decimal part a (in this case 0.3) is sent to the calculation device 27 and, by application of the formula below, the last step pl is obtained at the output (pl = P xa) In l example described above, the decimal part is 0.3 and the seam pitch is 2 mm, so pl is

0.6 mm (2 mm x 0.3 = 0.6 mm).

  The stepper motor control circuit (STM) 28 receives the output pl and it rotates the stepper motor 18 and positions the cam 17a so that the length of the

no sewing either pl.

  The calculation device 29 calculates the sum of the number of sewing stitches, namely the first sewing point with a sewing pitch of Pl / D x 2 mm and the last sewing point with a sewing pitch corresponding to the decimal part (in this case 0.3) as well as the stitches with a regular pitch. In this example, the total number of stitches is 11 (9 + 2 = 11), and this

number 11 is taken into account.

  The reduction counter 30 starts counting the number of sewing stitches when the sewing piece end detection sensor intervenes and, in this example, the number 11 (number of sewing stitches n ') is decreased by one unit for each stitch and. when it has been reduced to 1 (n '= 1), the speed of the sewing machine decreases, and a solenoid signal 31 is generated, this signal acting on the solenoid 16 (SOL) (see fig. 3) by via solenoid control circuit 16f

(see fig. 6).

  The stepping motor 18 has already rotated so as to establish the last predetermined pitch pl (0, 6 mm), the predetermined pitch being thus obtained. When the solenoid 16 intervenes, the electric current supplied to the stepping motor 18 increases in intensity, so as to reinforce

  the contact between the cam 17 and the contact element 14a.

  When the sewing machine performs the last stitch, does not take a zero value at 31a, the solenoid control circuit 16f opens and the stepping motor

18 returns to its original position.

  When the solenoid 16 ceases to be excited, the movable core 16a falls under the effect of gravity and the link 14 returns to its initial position Therefore, when the sewing operation resumes, it is carried out

at the initial pitch of 2 mm.

  When the solenoid control circuit 16f opens, the sewing machine stops in the position

low needle 32.

  On the other hand, if the operating mode is mode 33 with thread cutting, the sewing machine stops, when the thread has been cut, in the needle up position.

35.

  In the example described above, a pulse motor is used to obtain the necessary pitch, but it is also possible to use, for adjusting the sewing pitch, a linear motor instead of a

o30 pulses.

  In the embodiment described above, only the last step is adjusted, but it is possible to adjust the last two or three sewing steps. If the number of sewing stitches increased is increased, the difference between the set sewing pitch and the initial sewing pitch decreases, which results in positioning

more precise of the cam.

  The present invention allows adjustment of the sewing pitch during the sewing operation, after detection of the end of the workpiece and calculation of the necessary number of sewing stitches, which means that contrary-

  if the sewing step is adjusted before performing

  kill the seam, it is not necessary to precisely position the first needle point, and the seam is considerably improved because the margin is

  performed neatly and has an aesthetic appearance.

Claims (1)

CLAIM   Apparatus for automatically adjusting the pitch of a seam in a sewing machine comprising an automatic advance apparatus for modifying the pitch of the seam for a predetermined time during the sewing operation, apparatus characterized in that it comprises: a claw feed mechanism (1) for advancing the workpiece in synchronism with the rotation of the main drive shaft (2) of the machine; lO a regulating device (3) which can rotate and connected to the claw feed mechanism (1) for regulating the amount of feed of this mechanism in response to its rotational position; a connecting means which can move within the limits of a predetermined range and connected to the regulating device (3) in order to gradually modify the amount of advance of the claw advance mechanism in response to the movement of the connecting means in a direction; first drive means for moving the connecting means in said direction; adjusting means which can come into contact with the connecting means in the course of the latter and which can move the contact position in said direction; second drive means for moving said adjusting means; a first circuit for calculating a drive control time of the first drive means; a - second circuit for calculating the displacement of the second drive means so as to adjust the amount of advance which must vary when the first drive means performs a drive; a third circuit for controlling the first drive means at the time calculated by the first circuit and for controlling the second drive means so as to move the adjustment means towards the position calibrated by the second circuit before said calculated time.