GB2066508A - Automatic electronic sewing machine - Google Patents

Abstract

An automatic electronic sewing machine is capable of automatically sewing a button hole by shifting a needle while moving a work forward and backward. An indication means is provided to indicate whether the work is being moved forward or backward. The indication means may be a lamp which is continuously illuminated when the work is fed in one direction, and intermittently illuminated when the work is fed in the reverse direction.

Description

SPECIFICATION Automatic electronic sewing machine This invention relates to an automatic electronic sewing machine and, more particularly, to a machine which is capable of sewing buttonholes by shifting a needle and feeding a work forward and backward.

In accordance with the invention there is provided an automatic electronic sewing machine which can perform a buttonhole operation by shifting a needle position and moving a work forward and backward in response to an output signal of a control system, said automatic electronic sewing machine having: indicator means for indicating whether said work is being driven forward or backward.

Arrangements embodying the invention will now be described by way of example with reference to the accompanying drawings, in which: FIGURE 1 is a schematic front view of an embodiment of an automatic electronic sewing machine of the present invention; FIGURE 2 is a perspective view of an essential part of a mechanical portion of the automatic electronic sewing machine of FIGURE 1; FIGURE 3 is a perspective view of a linear motor employed within the mechanical portion of FIGURE 2 FIGURE 4 is a partially sectional view of a needle penetration drive mechanism employed within the mechanical portion of FIGURE 2, wherein a clutch mechanism is in the ON condition; FIGURE 5 is a sectional view of the clutch mechanism employed within the needle penetration drive mechanism of FIGURE 4, wherein the clutch mechanism is in the OFF condition;; FIGURES 6(A) and 6(B) are block diagrams of an embodiment of a control system of an automatic electronic sewing machine of the present invention; FIGURE 7 is a plan view of a buttonhole stitch pattern; FIGURES 8 and 9 are charts showing digital data stored in a read only memory (ROM) for conducting buttonhole operation; FIGURES 10 and 11 are charts of a buttonhole stitch pattern; FIGURE 12 is a chart showing coordinates of a needle position and a work feed plate position; FIGURE 13 is a block diagram of a portion of another embodiment of a control system of the automatic electronic sewing machine of the present invention; FIGURE 14 is a block diagram of a portion of still another embodiment of a control system of the automatic electronic sewing machine of the present invention; and FIGURE 1 5 is a block diagram of a portion of yet another embodiment of a control system of the automatic electronic sewing machine of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (I) CONTROL PANEL FIGURE 1 shows an embodiment of an automatic electronic sewing machine of the present invention and, more specifically, shows a control panel of the electronic sewing machine of the present invention.

An automatic electronic sewing machine body M includes indication lamps LA and LB for indicating a manual buttonhole operation mode and an automatic buttonhole operation mode, respectively. A manual mode selection switch KA is provided adjacent to a label EA for conducting the buttonhole operation in the manual mode. An automatic mode selection switch KB is provided adjacent to a label EB for conducting the buttonhole operation in the automatic mode. The body M further includes a keyboard panel K which includes various stitch pattern selection keys and control instruction selection keys as disclosed in copending application, AUTOMATIC ELECTRONIC SEWING MACHINE, Ser. No. 843,639, filed October 19, 1977 by Tousaku Nakanishi, Kazuo Suzuki, Masayasu Makino, Nobuyoshi Miyao and Hirokazu Koda and assigned to the same assignee as the present application.

(II) MECHANICAL PORTION FIGURE 2 shows a mechanical portion of the automatic electronic sewing machine of the present invention.

A main shaft 1 is driven to rotate by a motor 2. A needle 3 is driven to reciprocate through a needle shaft 5, and a crank shaft 6 associated with the main shaft 1. A work feed plate 4 is provided for feeding the work.

A linear motor 7 is provided for positioning the needle 3 at a desired position through the needle shaft 5. An output arm 8 of the linear motor 7 is associated with one end of an L-shaped lever 10 which is rotatably supported around a pin 9. The other end of the L-shaped lever 10 is connected to the needle shaft 5.

When the output arm 8 of the linear motor 7 is rotated in the direction shown by the arrow a of FIGURE 3, the L-shaped lever 1 9 is rotated around the pin 9 in the direction shown by the arrow b. With this rotation the position of the needle 3 is shifted along the X-axis as shown by the arrow c. The position of the needle 3 is detected by a potentiometer 11 which rotates in unison with the arm 8 of the linear motor 7.

A clutch cylinder 12 is slidably secured around the needle shaft 5 as shown in FIGURES 4 and 5. A clutch solenoid 1 3 and a clutch click 14 are disposed within the needle shaft 5. The clutch click 14 is rotatably secured around a pin 1 5, and one end of the clutch click 14 can be extruded outside through the surface of the needle shaft 5. The clutch cylinder 1 2 is connected to an arm 6a of the crank shaft 6.

When the clutch solenoid 13 is energized, the one end of the clutch click 14 is placed within the needle shaft 5 as shown in FIGURE 5. The clutch click 14 is not engaged with the clutch cylinder 12 and, therefore, the clutch cylinder 12 is reciprocated by the crank shaft 6 without transporting the reciprocating movement to the needle shaft 5. The needle shaft 5 is positioned at the uppermost position by a spring 16.

When the clutch solenoid 1 3 is deenergized, the one end of the clutch click 14 is extruded through the surface of the needle shaft 5 as shown in FIGURE 4. The extruded end of the clutch click 14 is engaged with the bottom surface of the clutch cylinder 1 2, whereby reciprocating movement of the clutch cylinder 12 is transported to the needle shaft 5. The needle shaft 5 is driven to travel downward by the clutch cylinder 12, and driven to travel upward by the spring 1 6. That is, when the clutch solenoid 13 is deenergized, the needle shaft 5 reciprocates in response to the rotation of the crank shaft 6. This condition is referred to as the condition where the clutch 12 is ON hereinafter.Contrarily, when the clutch solenoid 1 3 is energized, the needle shaft 5 is stationary at its uppermost position without regard to the rotation of the crank shaft 6. This condition is referred to as the condition where the clutch 12 is OFF, hereinafter.

A work feed drive shaft 1 7 rotates in synchronization with the main shaft 1. A cam 18 is secured to the work feed drive shaft 1 7 for driving the work feed plate 4 to move downward and upward in synchronization with the rotation of the main shaft 1. The bottom surface of the work feed plate 4 is supported by an arm 21, which is communicated to the cam 1 8 via an L-shaped lever 20 which is rotatable around a pin 19.

An arm 22 is provided for shifting the location of the work feed plate 4 along the Y-axis, or, in the direction shown by the arrow d. One end of the arm 22 is communicated to a shaft 23 which rotatably supports the feed plate 4, and the other end of the arm 22 is rotatably secured to a pin 24. The other end of the arm 22 is also rotatably communicated to an arm 26 which is engaged with a cam 25 fixed to the main shaft 1. A protrusion 29 is secured to the arm 26. The protrusion 29 is slidably associated with a C-shaped guide 30, which is rotatably connected to an output arm 28 of a linear motor 27 for determining the shift length of the work feed plate 4. The engaged condition of the protrusion 29 and the C-shaped guide 30 is shown in the circular A of FIGURE 2.

When the groove of the C-shaped guide 30 is substantially parallel with the course of movement of the protrusion 29 which rotates around a fulcrum lo the position of the fulcrum 1o is not changed even when the arm 26 changes its position in response to the rotation of the cam 25. When the C-shaped guide 30 is rotated by the linear motor 27 so that the groove of the C-shaped guide 30 crosses the course of movement of the protrusion 29 with a certain angle, the arm 26 is shifted its location in response to the rotation of the cam 25 in such a manner that the protrusion 29 is forced to accommodate the groove of the C-shaped guide 30.

The shift operation of the arm 26 functions to rotate the arm 22 around the pin 24, whereby the shaft 23 is shifted its position in the direction shown by the arrow e by the length corresponding to the rotation value of the arm 22. In this way, the work feed plate 4 is shifted along the Y-axis by a desired length. The shift value is controlled by the linear motor 27 and the shift operation is synchronized with the rotation of the main shaft 1. The shift operation of the work feed plate 4 along the Y-axis is conducted when the work feed plate 4 is pushed upward by the arm 21. A synchronization signal generator 31 is fixed to the main shaft 1 so that a synchronization signal p is developed in synchronization with the penetration operation of the needle 3.When the clutch 1 2 is ON and the needle 3 is positioned above the work, the synchronization signal P bears the high level, or ss = 1. When the point of the needle 3 is positioned below the work. p = O. When the clutch 12 is OFF, the needle 3 is stationary at the uppermost position and the synchronization signal P is developed in synchronization with the rotation of the main shaft 1.

A stopper 32 functions to lock the needle 3 at the center of the shift range of the needle 3 along the X-axis. The stopper 32 comprises a stationary solenoid 32a and a plunger 32b. The plunger 32b is inserted into a hole 33 formed in the lever 10 in order to lock the lever 10 at a predetermined position.

Therefore, the needle 3 is locked at the center of the shift range of the needle 3 when the plunger 32b is inserted into the hole 33.

The stitches are formed by the penetration operation of the needle 3 as in the case of the conventional sewing machine. The stitch formation speed is controllable by the depression force applied to a foot switch as in the case of the conventional sewing machine.

(III) SUMMARY OF CONTROL SYSTEM FIGURES 6(A) and 6(B) show an embodiment of a control system of the present invention.

DM represents the above-discussed mechanical portion of the automatic electronic sewing machine. The control system is incorporated in an LSI (large scale integrated circuit). A read only memory ROM stores digital data related to various stitch patterns. Desired stitch pattern information is read out in accordance with selection operation conducted through the selection keys. The thus read out pattern information is introduced into a random access memory RAM, and temporarily stored therein.

The thus stored pattern information corresponds to the selected stitch pattern. For example, when the buttonhole stitch as shown in FIGURE 7 is selected, the digital information related to the buttonhole stitch as shown in FIGURE 8 is introduced into the random access memory RAM. The pattern data indicate the positioning coordinates of the respective stitches along the X-axis and the Y-axis. The X section represents the position coordinates of the needle 3, and the Y section represents feed values of the work feed plate 4.

The pattern data stored in the RAM are developed step by step in synchronization with the synchronization signal B and converted into analog signals for shifting the needle 3 and the work feed plate 4 for achieving the stitch formation at predetermined positions.

The shift operation of the needle 3 and the work feed plate 4 is conducted when the needle 3 is separated from the work.

(IV) STITCH COORDINATES The needle position can be selected from thirty-two (32) positions X0 through X3t, and the work position can be selected from thirty-two (32) positions Y0 through Y31. That is, the stitch pattern can be formed in a matrix of 32 x 32 as shown in FIGURE 12.

More specificaily, the RAM stores the positioning information in the following manner.

X COORDINATES NEEDLE POSITION RAM DATA XO maximum shift in the 00000 positive direction Xlt5 center 01111 xal maximum shift in the 11111 negative direction Y COORDINATES WORK FEED PLATE POSITION RAM DATA Y0 maximum feed in the 00000 negative direction Y15 center 01111 Y31 maximum feed in the 11111 positive direction (V) CONSTRUCTION OF CONTROL SYSTEM Referring again to FIGURES 6(A) and 6(B), the control system mainly comprises a key input unit KU including the stitch pattern selection keys (not shown), the manual mode buttonhole operation selection key KA and the automatic mode buttonhole operation selection key KB.

The read only memory ROM includes plural sections PA, PB-1, PB-2, PC, ---------. and Pn, each of which stores pattern data of different kinds. The pattern data stored in the read only memory ROM are read out in accordance with selection commands derived from a ROM section selection circuit SC, and the thus read out pattern data are introduced into the random access memory RAM through a gate circuit GR. The section PB-1 of the read only memory ROM stores the pattern data related to the buttonhole operation in the forward direction (in the direction 0 of FIGURE 7) as shown in FIGURE 8.

The section PB-2 stores the pattern data related to the buttonhole operation in the backward direction (in the direction 0 of FIGURE 7) as shown in FIGURE 9.

The random access memory RAM includes sections RX and RY for storing the pattern data in the X-direction and the Y-direction, respectively.

An address register AC is associated with the random access memory RAM for addressing the random access memory RAM via an address decoder AD. The address register AC is controlled to count up upon every provision of the synchronization signal p which is developed in synchronization with the penetration operation of the needle 3 driven by a foot switch SF. That is, an address register incrementing circuit CO is connected to receive the synchronization signal S for increasing the contents stored in the address register AC in response to the synchronization signal ,B.

Output signals of the random access memory RAM are temporarily stored in registers BX and BY, respectively. The register BX comprises six (6) bits. The first bit B0 stores information "1" when a section nA of the buttonhole data shown in FIGURES 8 and 9 are addressed, and stores information "0" when another section nB of the buttonhole data are addressed. The digital data temporarily stored in the register BX are converted into an analog signal by a digital-to-analog converter DAX and applied to a linear motor LMX for swinging the needle 3 in the X-direction. The digital data temporarily stored in the register BY are converted into an analog signal by a digital-to-analog converter DAY and applied to a linear motor LMY for driving the work feed plate 4 in the Y-direction.

A judge circuit JA is connected to receive the output signal of the address register AC for developing a detection output "1" when the last address ACm of the random access memory RAM shown in FIGURE 8 is selected by the address register AC. The judge circuit JA is placed in the operative condition only when a set output signal F, of a flip-flop f1 or a set output signal F2 of a flip-flop f2 is applied through an OR gate OR,. The detection output of the judge circuit JA is applied to an address determination circuit AP in order to set the address of the address register AC at the address ACn shown in FIGURE 8.

A register NC is provided for storing the stitch number of the buttonhole stitch when the buttonhole operation is conducted in the direction (i) shown in FIGURE 7. A count-up circuit CUC is provided for increasing the contents stored in the register NC, and a clear circuit CLO is provided for clearing the contents stored in the register NC. The counted contents stored in the register NC are applied through a gate G1 to a register ND. A count-down circuit CDC is provided for decreasing the contents stored in the register ND. A judge circuit JO is connected to the register ND in order to develop a detection output "1" when the contents stored in the register ND are "0".

The control system further comprises flip-flops f3 through f6, which develop set output signals F3 through F6, respectively, AND gates A, through Ag, OR gates OR1 through OR3, an inverter Ii, and one- - shot pulse generators qA, qB and qC, which develop output signals QA, QB and QC, respectively.

The indication lamp LA is connected to receive a drive signal through the AND gates A6 and A7, which are connected to receive the set output signal F1 derived from the flip-flop f1, which is set when the manual mode buttonhole operation is performed. The AND gate A6 further receives the set output signal F5 of the flip-flop f5, which is placed in the set condition when the buttonhole operation is conducted in the forward direction, or in the direction d) qf FIGURE 7. The AND gate A7 further receives an inverted set output signal F5 through the inverter I,, and a pulse signal SS of a predetermined frequency. The output signals of the AND gates A6 and A7 are applied to the indication lamp LA through the OR gate OR2.

The indication lamp LB is connected to receive a drive signal through the AND gates A9 and Ag.

The AND gates A8 and A9 receive the set output signal F2 derived from the flip-flop f2, which is set when the automatic mode buttonhole operation is performed. The AND gate A8 further receives the set output signal F6 of the flip-flop f6. The AND gate A9 further receives a reset output signal of the flip-flop f6 and the pulse signal ss. The output signals of the AND gates A9 and A9 are applied to the indication lamp LB through the OR gate OR3.

(VI) OPERATION Now assume that the flip-flops f1 and f2 are in the reset states. When the manual mode buttonhole operation selection key KA is depressed, the one-shot pulse generator qA develops the one-shot pulse signal OA to set the flip-flop f1. A signal S1 is developed under the condition F5.OA before the T-type flipflop f5 is set, whereby the ROM section selection circuit SC selects the section PB-1, which stores the buttonhole data in the direction (3). By this selection, the data shown in FIGURE 8 stored in the section PB-i of the read only memory ROM are transferred to the random access memory RAM through the gate circuit GR.

The inverted set output signal F5 and the one-shot pulse signal QA are applied to the AND gate A to clear the counter NC through the clear circuit CLC. The flip-flop f5 is set by the one-shot pulse signal QA. The set output signals F, and F5 of the flip-flops f, and f5 are applied to the AND gate A6 to continuously enable the indication lamp LA.

Under these conditions, when the foot switch SF is actuated, the main shaft 1 is driven to rotate by the motor 2, whereby the synchronization signal p is developed.

The address data stored in the address register AC are applied to the random access memory RAM. The bottom most data shown in FIGURE 8 are read out, that is, the data "25" and "15" are introduced into the registers BX and BY, respectively. The linear motor LMX rotates by the value corresponding to the data "25", and the needle 3 penetrates the uppermost end 40a of a buttonhole 40 shown in FIGURE 7, thereby forming the first stitch. When the needle 3 is separated from the work in response to the rotation of the main shaft 1, the synchronization signal p is developed to increase the contents of the address register AC by one. The second data stored in the random access memory RAM, that is, the second data from the bottom of FIGURE 8 "4" and "1 5" are introduced into the registers BX and BY, respectively.The needle 3 is shifted left by the amount corresponding to the data "4", and the stitch is formed at a point 40b of FIGURE 7. At this moment the work feed plate 4 is not driven to move because the data in the Y-direction are "15".

The similar operation is repeated to form plural stitches at the uppermost end of the buttonhole 40. When the contents of the address register AC reach the data corresponding to the address ACn shown in FIGURE 8, the bit B0 of the register BX receives the signal "1", which shows that the RAM section is advanced from the section nB to the section nA. The signal "1" derived from the bit B0 is applied to the AND gate A2, which functions to apply the synchronization signal p to the count-up circuit CUC. Therefore, the conents of the register NC are increased one by one in response to the provision of the synchronization signal.

The data stored in the section nA of the random access memory RAM shown in FIGURE 8 are read out. The needle 3 is driven to swing between two positions corresponding to the data "4" and "13", respectively. And the work feed plate 4 is driven to move by two pitches for every stitch. Therefore, the stitches are formed at points 40b and 40C on the side Ol of FIGURE 7. That is, the zigzag stitch pattern is formed as shown in FIGURE 10. During these operations, the indication lamp LA is continuously enabled to indicate that the buttonhole operation is conducted in the direction 0.

When the contents of the address register AC reach the last address ACORN of FIGURE 8, the judge circuit JA develops the detection output toward the address determination circuit AP to set the contents of the address register AC at a value corresponding to the address ACn. The formation of the zigzag stitch pattern on the side 0 of FIGURE 7 is repeated as long as the foot switch SF is actuated.

Since the judge circuit JA is controlled by the set output signal F1 or F2 applied through the OR gate OR1, the above-mentioned repeat operation is performed only when the buttonhole operation is selected.

When the zigzag stitch pattern is formed in the direction Ol by a desired length, the foot switch SF is released and the manual mode buttonhole operation selection key KA is again depressed. Now assume that the stitch formation is conducted to a point 40d of FIGURE 7 at this moment. The one-shot pulse generator qA again develops the output signal QA. A signal S2 is applied to the ROM section selection circuit SC to select the section PB-2. Thereafter, the flip-flop f5 is reset to turn on the AND gate A7 and to turn off the AND gate A6. Accordingly, the indication lamp LA is driven to flicker at a frequency determined by the pulse signal SS.

The data stored in the section PB-2 of the read only memory ROM are transferred to the random access memory RAM. That is, the random access memory RAM stores the pattern data shown in FIGURE 9. The gate G1 is turned on by a signal F5.CA, whereby the contents stored in the register NC are transferred to the register ND. The contents stored in the register NC are remained in the register NC.

When the foot switch SF is again actuated, the contents of the address register AC are increased upon every provision of the synchronization signal P. The data stored in the random access memory RAM shown in FIGURE 9 are read out from the bottom. Accordingly, the stitches are formed between the points 40d and 40e of FIGURE 7 by the data stored in the section below the address ACn' of FIGURE 9, and the zigzag stitches are formed between the points 40e and 40a in the direction O2 of FIGURE 7 by the data stored between the addresses ACn' and ACm' of FIGURE 9. That is, the stitches are formed at the side O2 of the buttonhole 40 as shown in FIGURE 11.

In case where the foot switch SF is continuously actuated when the address ACm' of the random access memory RAM is selected, the judge circuit JA and the address determination circuit AP function to repeat the operation in accordance with the data stored in the section LN of FIGURE 9.

When the automatic mode buttonhole operation selection key KB is depressed at a time when the stitch formation is conducted to the point 4.ova of FIGURE 7 after passing the side (2), the one-shot pulse generator qB develops the output signal QB to set the flip-flop f2 and to reset the flip-flop f1. The AND gates A6 and A7 are turned off to disable the indication lamp LA. The flip-flop f6 is set to turn on the AND gate A8, whereby the indication lamp LB is continuously enabled to indicate that the operation is changed to the automatic mode.

The signal S, is developed because of the provision of the output signal QB, whereby the section PB-1 of the read only memory ROM is selected. The data stored in the section PB--l of the read only memory ROM are transferred to the random access memory RAM as shown in FIGURE 8.

When the foot switch SF is actuated under those conditions, the stitch pattern formation is conducted in accordance with the data stored in the random access memory RAM in response to the synchronization signal ,ss. When the stitch formation is advanced to the section nA of FIGURE 8, the bit B0 becomes "1" and, hence, the AND gate A3 functions to transfer the synchronization signal p toward the count-down circuit CDC in order to reduce the contents stored in the register ND one by one.

When the contents stored in the register ND reach zero (0), that is, when the stitch formation is conducted in the direction O by the length 11 preselected at the manual mode, the judge circuit JO develops the detection output "1" to turn on the AND gate A4. The one-shot pulse generator qC develops the output signal OC to set the flip-flop f3. At this moment the signal S2 (= F5,OA + QC) is developed to transfer the data stored in the section PB-2 of the read only memory ROM to the random access memory RAM. At the same time, the gate G1 is turned on by the output signal QC to transfer the contents stored in the register NC to the register ND.In this way, the stitch formation is conducted in the direction 0 of FIGURE 7.

When the operation is advanced to the section LN, the AND gate A3 functions to pass the synchronization signal P to count down the contents stored in the register ND. At a time when the stitch formation is conducted to the point 40,, the contents stored in the register ND become zero (0). The judge circuit JO develops the detection output, and the one-shot pulse generator qC develops the signal QC. Accordingly, the AND gate As develops a signal to reset the flip-flop f6, whereby the indication lamp LB is driven to flicker at a frequency determined by the pulse signal SS. By this flickering of the indication lamp LB, the operator reorganizes that the buttonhole operation in the automatic mode is completed.

The output signal of the AND gate As is also applied to the flip-flop f4 to set it. The set output signal of the flip-flop f4 is applied to the clutch solenoid 1 3 to turn off the clutch mechanism. The needle 3 is held stationary even though the main shaft 1 rotates. The stitch formation is not conducted till instructions are developed from the control panel. In this way, one cycle of the buttonhole operation is completed.

The buttonhole operation is performed without any guide plates, because the zigzag stitch length It of the section PB-2 is automatically selected to equal that of the section PB-1.

If the automatic mode buttonhole operation is desired to be again performed, the automatic mode buttonhole operation selection key KB is again depressed. The signal QB is developed to set the flip-flop f6. The AND gate A9 is turned on to continuously enable the indication lamp LB. The flip-flop f3 is reset.

And, the signal S1 is developed to transfer the digital data stored in the section PB-1 of the read only memory ROM to the random access memory RAM. Also, the gate G1 is turned on to transfer the contents stored in the register NC to the register ND. Following operation is similar to that is discussed above.

(via) OTHER EMBODIMENTS In the embodiment of FIGURES 6(A) and 6(B), the buttonhole length i1 is counted by the register NC. FIGURE 13 shows a portion of another embodiment of the control system, which is applicable to the case where the buttonhole length exceeds the capacity of the register NC. Like elements corresponding to those of FIGURES 6(A) and 6(B) are indicated by like numerals.

A judge circuit JOV is connected to receive the output signal of the register NC to develop a detection output when the contents stored in the register NC exceeds the capacity of the register NC.

The detection output signal of the judge circuit JOV is applied to a flip-flop f7 to enable an alarm lamp LOV. When the alarm LOV is enabled, the buttonhole operation must be performed in the manual mode only. The flip-flop f7 is reset upon depression of the manual mode buttonhole operation selection key KA.

FIGURE 14 shows still another embodiment of the control system, wherein the stitch formation length is varied in the direction 2) as compared with that in the direction (!) to compensate for the work slip. Like elements corresponding to those of FIGURES 6(A) and 6(B) are indicated by like numerals.

A register NC1 stores the stitch number in the direction (3), and another register NC2 stores the stitch number in the direction G3. An electronic switch SNC is provided for selectively applying the output signal of the count-up circuit CUC to the registers NC1 and NC2. Gates G2 and G3 are provided for controlling the application of the contents stored in the registers NCg and NC2 to the register ND.

When the buttonhole operation is conducted in the direction 01, the set output signals F1 and F6 are "1" and, therefore, the AND gate A6 is ON. At this moment, the electronic switch SNC is switched to the side of the register NC1. Accordingly, the contents of the register NC1 are increased in response to the synchronization signal 23 when the zigzag stitch pattern is formed in the direction 0. In this way, the stitch number in the direction Ol is stored in the register NC1.

When the manual mode buttonhole operation selection key KA is again depressed, the stitch formation is conducted in the direction Q2 in accordance with the data stored in the section PB-2 of the read only memory ROM. At this moment, the AND gate A, is turned on and the AND gate A6 is turned off. Therefore, the electronic switch SNC is switched to the side of the register NC2, whereby the register NC2 stores the stitch number.

Usually, the contents stored in the register NC2 are greater than that stored in the register NC by the amount corresponding to the work slip and the work slack. Under these conditions when the automatic mode buttonhole operation selection key KB is depressed, the one-shot pulse generator qB develops the output signal QB to turn on the gate G2, thereby transferring the contents stored in the register NC1 to the register ND.

The stitch formation is automatically conducted in the direction 0 upon actuation of the foot switch SF. When the stitch formation is conducted by the number determined by the register ND, the judge circuit JO develops the detection output, and the one-shot pulse generator qC develops the output signal QC. Accordingly, the gate G3 is turned on to transfer the contents stbred in the register NC2 to the register ND. The stitch formation is conducted in the direction 0 by the number determined by the contents stored in the register ND to complete the automatic mode buttonhole operation.

Upon completion of one cycle of the buttonhole operation, the clutch solenoid 13 is enabled to turn off the clutch mechanism. When the automatic mode buttonhole operation selection key KB is again depressed, the one-shot pulses generator qB is enabled to turn on the gate G2. The contents stored in the register NC, are transferred to the register ND. Following operation is similar to that as discussed above.

FIGURE 1 5 shows a portion of yet another embodiment of the control system of the present invention. Like elements corresponding to those of FIGURES 6(A) and 6(B) are indicated by like numerals.

The output signals of the register BY are introduced into a judge circuit JY, which judges whether the contents stored in the register BY are greater than fifteen (15) or smaller than fifteen (1 5). When the contents stored in the register BY are greater than fifteen (15), a signal Y > 15 is applied to an OR gate OR4. When the contents stored in the register BY are smaller than fifteen (15), a signal Y < 1 5 is applied to an AND gate A10. Another input terminal of the AND gate A10 is connected to receive the pulse signal SS of the predetermined frequency. The output signal of the AND gate A10 is applied to the OR gate OR4, of which the output signal is applied to the indication lamp LA or the indication lamp LB.

The indication lamp LA is continuously enabled when the signal Y > 1 5 is developed, or when the work feed plate 4 is driven to move in the positive direction. Contrarily, when the signal Y- < 5 is developed, or when the work feed plate 4 is driven to move in the negative direction, the indication lamp LA flickers at a frequency determined by the pulse signal SS.

The invention being thus described, it will be obvious that the same may be varied in many ways.

Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.

Claims (5)

1. I. An automatic electronic sewing machine which can perform a buttonhole operation by shifting a needle position and moving a work forward and backward in response to an output signal of a control system, said automatic electronic sewing machine having: indicator means for indicating whether said work is being driven forward or backward.
2. 2. An automatic electronic sewing machine as claimed in claim 1, wherein said indication means comprise an indication lamp.
3. 3. An automatic electronic sewing machine as claimed in claim 1 or 2, further comprising: a detection means for developing a first control signal when said work is being driven forward, and developing a second control signal when said work is being driven backward; and driver means for activating said indication means in two different modes in response to said first and second control signals.
4. 4. An automatic electronic sewing machine as claimed in claim 3, wherein said driver means continuously activates said indication means when said first control signal is developed, and intermittently activates said indication means when said second control signal is developed.
5. 5. An automatic electronic sewing machine as claimed in any preceding claim, including means for determining whether or not a signal which determines the amount of work feed is greater than a predetermined value, the indication means being arranged to operate in response to the result of the determination.