Control system for sewing machine

A semiautomatic sewing system (10) comprises a sewing machine (12), a drive unit (42) including a variable speed motor and encoder for counting stitches sewn, material edge sensors (40) mounted in spaced relationship in front of the needle (22) of the sewing machine, and a microprocessor controller (51) coupled to the sewing machine controls. Accurate control of seam lengths and end points is achieved by initiating countdown of a variable preprogrammed number of final stitches responsive to material edges detected by the sensors (40) only when the stitch count falls within a predetermined window of values so that inaccuracies from stitch counting are limited to a small portion of the overall seam length. If the sensors (40) do not detect a material edge within the window of stitch values, the sewing system (10) reverts to pure stitch counting to determine seam length.

We claim:

1. In a sewing machine for performing a sewing operation involving a series of seam segments and having a reciprocable needle for stitching material advanced in a feed direction and controls for operating the sewing machine, the improvement which comprises:

means for counting the number of stitches being sewn;

material detection means mounted in spaced relationship with said needle for detecting a material edge following a seam segment;

memory means for storing a plurality of stitch counts corresponding to different seam segments in the sewing operation to be performed;

processing means responsive to said material detection means, said stitch counting means and said memory means for generating first and second output signals, said first output signal stopping said sewing machine a preprogrammed number of stitches after detection of the edge of said material, said preprogrammed number of stitches corresponding to the stitch count stored in said memory means for the particular seam segment being sewn; and

means responsive to said second output signal for performing control of the sewing machine.

2. The sewing machine of claim 1, wherein said material detection means comprises at least one on/off sensor mounted ahead of said needle in a direction opposite the material feed direction.

3. The sewing machine of claim 1, wherein said material detection means comprises a pair of on/off sensors mounted in mutually spaced relationship ahead of said needle in a direction opposite the material feed direction.

4. The sewing machine of claim 1, wherein said material detection means comprises a lamp/photosensor and reflector mounted in vertically spaced relationship ahead of said needle in a direction opposite the material feed direction.

5. The sewing machine of claim 1 wherein said material detection means comprises an infrared emitter and sensor mounted in vertically spaced relationship ahead of said needle in a direction opposite the material feed direction.

6. The sewing machine of claim 1, wherein said processing and memory means is responsive to a preprogrammed total stitch count beyond said stored stitch counts to generate a signal stopping said sewing machine by said total stitch count.

7. In a semiautomatic sewing system including a sewing machine with a reciprocable needle for stitching material advanced in a feed direction and controls for operating said sewing machine, with means for counting stitches being sewn, and with sensors for detecting manipulation of the sewing machine controls, the improvement which comprises:

means mounted in spaced relationship with said needle for detecting the material periphery following a seam; and

a microprocessor controller with plural operational modes coupled to said sewing machine controls and responsive to said stitch counting means and said material detection means, said microprocessor controller in one mode being operable to record the operational sequence of said sewing machine controls as a function of stitch count and to compute the terminal number of stitches for each seam between detection of the material periphery and the end point of said seam;

said microprocessor controller in another mode being responsive to said material detection means to operate said sewing machine controls and halt said sewing machine said terminal number of stitches after detection of the material periphery following the seam.

8. The semiautomatic sewing system of claim 7, wherein said material detection means comprises at least one on/off sensor mounted ahead of said needle in a direction opposite the material feed direction.

9. The semiautomatic sewing system of claim 7, wherein said material detection means comprises a lamp/photosensor and reflector mounted in vertically spaced relationship ahead of said needle in a direction opposite the material feed direction.

10. The semiautomatic sewing system of claim 7, wherein said material detection means comprises an infrared emitter of variable output and an associated sensor mounted in vertically spaced relationship ahead of said needle in a direction opposite the material feed direction.

11. The semiautomatic sewing system of claim 7, wherein said material detection means comprises a pair of on/off sensors mounted in mutually spaced relationship ahead of said needle in a direction opposite the material feed direction.

12. The semiautomatic sewing system of claim 7, wherein said microprocessor controller in said other mode is responsive to said material detection means only during a preprogrammed range of stitch counts to avoid spurious signals.

13. The semiautomatic sewing system of claim 7, wherein said microprocessor controller in said one mode stores the total number of stitches required for each seam, and wherein said microprocessor controller in said other mode reverts to said total stitch count for determining seam length absent of detection of the material periphery within a preprogrammed range of stitch counts.

14. The semiautomatic sewing system of claim 7, further including:

means for selectively controlling the acceleration and deceleration rates of said needle in said other mode.

15. The semiautomatic sewing system of claim 7, further including:

means for selectively controlling the maximum speed of said needle in said other mode.

16. The semiautomatic sewing system of claim 7, wherein said material is multiply material and said material detection means comprises a lamp/photosensor located above said material, and further including:

a reflector associated with said lamp/photosensor; and

means for supporting said reflector on the opposite side of the material ply whose periphery is relevant to the seam being sewn.

17. A semiautomatic sewing system, comprising:

a sewing machine;

said sewing machine including a reciprocable needle for stitching a seam in material advanced along a feed direction, and controls for operating said sewing machine;

auxiliary means for performing a predetermined function associated with operation of said sewing machine;

means for counting stitches being sewn by said sewing machine;

means mounted in spaced relationship with said needle for detecting the material periphery following a seam;

a microprocessor controller responsive to said stitch counting means and said material detection means, and being coupled to said sewing machine controls and said auxiliary means;

said microprocessor controller having plural operational modes, and being operable in one mode to record the operational sequence of said sewing machine controls as a function of stitch count and to compute the terminal number of stitches for each seam between detection of the material periphery and the end point of said seam;

said microprocessor controller in said one mode being further operable to record the operational sequence of said auxiliary means as a function of stitch count;

said microprocessor controller in another mode being responsive to said material detection means to operate said sewing machine controls and halt said sewing machine said terminal number of stitches after detection of the material periphery following the seam; and

said microprocessor controller in said other mode further being operable to control said auxiliary means.

18. The semiautomatic sewing system of claim 17, wherein said material detection means comprises at least one on/off sensor mounted ahead of said sewing machine needle in a direction opposite the material feed direction.

19. The semiautomatic sewing system of claim 17, wherein said material detection means comprises an infrared emitter with variable sensitivity and associated sensor mounted in vertically spaced relationship ahead of said sewing machine needle in a direction opposite the material feed direction.

20. The semiautomatic sewing system of claim 17, wherein said microprocessor controller in said other mode is responsive to said material detection means only during a preprogrammed window of stitch counts to avoid spurious signals.

21. The semiautomatic sewing system according to claim 20, wherein said microprocessor controller in said one mode stores the total number of stitches required for each seam, and wherein said microprocessor controller in said other mode reverts to said total stitch count for determining seam length absent detection of the material periphery within said preprogrammed window of stitch counts.

22. The semiautomatic sewing system of claim 17, wherein said sewing machine includes a second reciprocable needle and throw-out mechanisms for selectively controlling said needles, and wherein said auxiliary means comprises:

actuators coupled to the throw-out mechanisms of said sewing machine needles.

23. The semiautomatic sewing system of claim 17, further including:

means for commanding said sewing machine to sew a single stitch in said one mode and thereby incrementing the stitch count stored in said microprocessor controller.

24. A method of controlling seam lengths and end points sewn in material with a sewing machine, comprising the steps of:

providing a sensor for detecting the presence of material a predetermined distance ahead of the needle of said sewing machine;

storing a stitch count value X corresponding to a point near the end of each seam where a sensor status change should occur;

storing a stitch count value Y corresponding to the total number of stitches in each seam, at least a portion of said stitch count value Y being manually entered and stored by actuation of a one-stitch switch;

positioning the material for sewing under the needle of said sewing machine;

starting the sewing machine;

accelerating the sewing machine and operating the sewing machine at substantially constant speed over that portion of the seam where the stitch count value Y was manually incremented before stopping;

counting the number of stitches sewn in each seam beginning with the first stitch in the seam;

controlling auxiliary devices associated with the sewing machine as a function of stitch count;

comparing the stitch count with the stored stitch count values;

initiating countdown of Y-X stitches responsive to a status change in said sensor; and

stopping the sewing machine upon completion of the countdown of Y-X stitches to complete each seam.

25. A method of controlling seam lengths and end points sewn in material with a sewing machine, comprising the steps of:

manually operating said sewing machine and each auxiliary device to sew seams on a similar piece of material;

sensing manual operation of auxiliary devices associated with the sewing machine to generate control input signals;

storing the control input signals of said auxiliary devices as a function of stitch count;

providing a sensor for detecting the presence of material a predetermined distance ahead of the needle of said sewing machine;

storing a stitch count value X corresponding to a point near the end of each seam where a sensor status change should occur;

storing a stitch count value Y corresponding to the total number of stitches in each seam;

positioning the material for sewing under the needle of said sewing machine;

starting the sewing machine;

counting the number of stitches sewn in each seam beginning with the first stitch in the seam;

controlling said auxiliary devices as a function of stitch count by generation of control output signals;

comparing the stitch count with the stored stitch count values;

initiating countdown of Y-X stitches responsive to a status change in said sensor;

stopping the sewing machine upon completion of the countdown of Y-X stitches to complete each seam; and

generating subsequent control output signals for said auxiliary devices responsive to stitch count.

26. The method of claim 25, further including the steps of:

computing a window of stitch counts surrounding the stitch count value X;

comparing the stitch count with the stitch count value Y; and

stopping said sewing machine absent a status change of said sensor within said window when said stitch count reaches said stitch count value Y.

27. The method according to claim 26, wherein said predetermined range of stitch counts is approximately 0.75X to 1.05X.

28. The method of claim 25, wherein the step of sensing the presence of material is carried out by at least one on/off sensor located ahead of the sewing needle.

29. The method of claim 25, wherein the steps of storing the stitch count values X and Y are carried out by:

manually operating said sewing machine to sew seams on an initial piece of material of similar shape;

counting the number of stitches sewn in each seam beginning with the first stitch in the seam;

setting X equal to the stitch count value upon a status change in said sensor; and

setting Y equal to the stitch count value at the end of each seam.

30. The method according to claim 29, wherein said initial piece of material is relatively larger in size than subsequent pieces of material.

31. A method of performing a sewing operation involving a series of seams with a sewing machine having a reciprocable needle for stitching material advanced in a feed direction and controls for operating the sewing machine, the method comprising the steps of:

counting the number of stitches being sewn by the sewing machine;

detecting an edge of material following a seam;

storing a plurality of stitch counts corresponding to different seams in the sewing operation to be performed;

generating first and second output signals in response to the detection of said material edge, said counted number of stitches and said stored plurality of stitch counts;

stopping said sewing machine in response to said first output signal a preprogrammed number of stitches after detection of the material edge, said preprogrammed number of stitches corresponding to the stitch count stored for the particular seam being sewn; and

performing control of the sewing machine in response to said second output signal.

32. The sewing machine of claim 1 and further comprising:

means for storing a maximum stitch count for each seam segment;

said processing means operable to stop said sewing machine at said maximum stitch count in the event said sensor does not detect the material edge within said maximum stitch count.