This application is based upon and claims the benefit of priority from the prior Japanese Patent Application 2005-174940, filed on, Jun. 15, 2005 the entire contents of which are incorporated herein by reference.
The present disclosure relates to a zigzag sewing machine including a needle swing mechanism that swings a needle bar, a cloth feed mechanism moving a feed dog in vertical and longitudinal directions, and a feed dog lateral transfer mechanism moving the feed dog in the lateral direction.
A conventional zigzag sewing machine has an arm including a needle bar drive mechanism that vertically moves a needle bar having a sewing needle attached thereto and a needle swing mechanism that swings the needle bar; and a sewing machine bed including a needle plate and a feed dog that projects/retracts from the needle plate in order to move a workpiece cloth.
The feed dog is generally provided with a plurality of longitudinally extending teeth, and is fed in a four-step cycle by a cloth feed mechanism provided inside the sewing machine bed. Formed on the needle plate disposed on the sewing machine bed upper surface is a needle hole extending laterally so as to correspond to the lateral swing of the sewing needle; and a plurality of longitudinally extending square holes for projecting/retracting a plurality of teeth therethrough.
The zigzag sewing machine of the aforementioned type moves the feed dog in plurality directions to provide for sewing complex sewing patterns. For example, JP-Y1-S54-135263 discloses a cloth feed dog having four rows of teeth which not only perform four-step feed, but also move in the lateral direction as well. Under such construction, the widths of the four rows of square holes are widened, allowing the teeth to move in the lateral direction. Thus, the workpiece cloth is moved by the teeth in both longitudinal and lateral directions, as well as in the oblique direction which is a combination of the aforementioned two directions.
However, under such construction, there is an increased possibility of defective stitches being formed upon forming straight stitches on the workpiece cloth. That is, since the widths of the square holes are widely arranged with respect to the four rows of teeth, depending upon the position of the needle drop point, the cloth presser and the teeth fail to clamp the straight stitches formed on the workpiece cloth. Hence, there are increased instances where cloth feed is carried out with a stitchless portion of the workpiece cloth being fed by being clamped between the cloth presser and the teeth. At this time, since tension is applied on a needle thread by cloth-feed, seam puckering is observed on the stitches of the workpiece cloth, forming defective seams in which the stitches are drawn up. Defective seams become more prominent especially upon sewing a thin workpiece cloth, or sewing with thicker sewing thread or with increased sewing speed. Reducing the thread tension of the thread tension regulator is a possible solution to the above problem. However, in such case, repetitive trial sewing needs to be performed in order to obtain the suitable thread tension for various types of workpiece cloth, sewing thread and sewing speed. This calls for a complex and time consuming preparatory work, which does not satisfy practical use.
Therefore, an object of the present disclosure is to provide a zigzag sewing machine capable of clamping a stitch formed on a workpiece cloth by one of the teeth formed on the feed dog and a cloth presser in order to prevent the formation of defective seams and seam puckering to the possible extent.
The zigzag sewing machine of the present disclosure is characterized in including a needle bar having a sewing needle attached thereto, a needle swing mechanism that laterally swings the needle bar, a needle plate disposed on the upper surface of a sewing machine bed, and a feed dog constituted by a plurality of teeth that feed a workpiece cloth by projecting/retracting from the needle plate. The zigzag sewing machine further includes a feed dog longitudinal transfer mechanism longitudinally moving the feed dog, a feed dog lateral transfer mechanism that laterally moves the feed dog, and a control unit that controls the feed dog lateral transfer mechanism so that one of the teeth is associated with a needle drop point of the sewing needle.
One of the teeth can be moved to a position corresponding to the needle drop point of the sewing needle by the control unit. Thus, since the stitch formed on the workpiece cloth can be clamped by one of the feed dog teeth and the cloth presser, no seam puckering occurs even if tension is applied to the needle thread by cloth feed. Thus, defective seams can be prevented to the possible extent without thread tension regulation.
Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the illustrative aspects with reference to the accompanying drawings, in which,
At least one of a plurality of embodiments according to the present invention will be described hereinafter with reference to
The electronic zigzag sewing machine 9, as shown in
A laterally extending sewing machine main shaft (not shown) and a sewing machine motor 78 (refer to
A needle bar 8 having a sewing needle 7 in the lower end thereof is provided in the head 4 which is formed in the left portion of the arm 3. The needle bar 8 is vertically moved by the rotation of the sewing machine main shaft via a needle bar drive mechanism (not shown). Provided in the arm 3 is a thread take-up drive mechanism (not shown) that vertically moves the thread take-up (not shown) in synchronization with the vertical transfer of the needle bar 8, and the like. Various switches such as a start/stop switch 12 that instructs the start and stop of a sewing operation are provided on the front side of the arm 3.
On the other hand, an oblong needle plate 5 is mounted on the upper surface of the bed 1 by a fixing screw 5f (refer to
A vertically oriented liquid crystal display 10 is provided on the front surface of the foot 2. Plurality types of utility stitches for linear sewing and zigzag sewing, for example, are displayed in the liquid crystal display 10 upon pattern selection. Also, function names that represent various functions required in a sewing operation and various guidance messages and other items are displayed in the liquid crystal display 10.
A transparent touch panel 11 (refer to
Provided in the arm 3 is a needle swing mechanism 15 that swings the needle bar in the lateral direction perpendicular to the cloth feed direction of the needle bar 8. The structure of the needle swing mechanism 15 will be described herein after.
As shown in
A vertically extending swing lever 18 is disposed in the left side of the needle bar base 16. The substantial center of the swing lever 18, which is disposed in the left side of the substantial center of the needle bar base 16, is rotatably supported by the machine frame 14 via a pivot pin 19. The lower end of the swing lever 18 abuts the cam body 20. Also, a longitudinally extending abutting pin 21 is fixed on the upper end of the swing lever 18.
A swing cam 22 abutting the abutting pin 21 is pivoted on the sewing machine frame 14. Formed on the swing cam 22 is a large-radius cam portion 22a disposed away from the rotational shaft center and a small-radius cam portion 22b disposed close to the rotational shaft center of the swing cam 22. The large- and small-radius cam portions 22a and 22b form a smooth and continuous curved cam-surface on the swing cam 22. On the other hand, the lower end of the needle bar base 16 is leftwardly (clockwise direction in
A gear is formed on the outer periphery of the swing cam 22. A drive gear 24 in mesh engagement with the gear is attached to the drive shaft of a needle swing motor 23 mounted on the sewing machine frame 14. Thus, the rotation of the needle swing motor 23 is conveyed to the gear via the drive gear 24, consequently rotating the swing cam 22 in the clockwise or the counterclockwise direction.
As shown in
On the other hand, as shown in
Also, the needle swing width of the sewing needle 7 ranging from the left baseline position 7a to the right baseline position 7b is set at approximately 7 mm. The intermediate position between the left baseline position 7a and the right baseline position 7b is defined as the middle baseline position 7c (refer to
Thus, since the sewing needle 7 is laterally moved, the needle hole 5e provided in the needle plate 5 is in a laterally extending form (refer to
Also, longitudinally extending square holes 5a to 5d are formed in the needle plate 5. A plurality of first to fourth teeth 6a to 6d formed on the feed dog 6 project/retract from the square holes 5a to 5d. More specifically, the feed dog 6 comprises a second and third teeth 6b and 6c provided in the cloth feed direction side of the needle hole 5e (direction of arrow B in
The lateral widths of the square holes 5a to 5d are set at approximately 3.0 mm. The longitudinal lengths of the square holes 5a to 5d are set at such length that ensures the longitudinal transfer of the first to fourth teeth 6a to 6d.
Next, a feed dog mechanism 26 and a feed dog longitudinal transfer mechanism 28 will be described herein after. The feed dog mechanism 26 includes a feed dog vertical transfer mechanism 27 that vertically moves the feed dog 6. The feed dog longitudinal transfer mechanism 28, on the other hand, longitudinally moves the feed dog 6. First, a description will be given on the feed dog vertical transfer mechanism 27. As shown in
On the other hand, a height adjustment bolt 36 is provided in the rear end of the feed base 32. The lower end of the height adjustment bolt 36 abuts the upper end of a vertically moving pin 37 extending in the vertical direction. The vertically moving pin 37 is provided vertically movably on the frame and is vertically moved by a vertical feed cam 31 and a vertical feed contact 39.
That is, a vertical feed cam 31 provided integrally with an eccentric cam 31a and a concentric cam 31b is disposed in front of the lower end of the vertically moving pin 37. The vertical feed cam 31 is fixed on a rotatable lower shaft 30 extending in the lateral direction, and the concentric cam 31b is disposed concentric with respect to the lower shaft 30. On the other hand, the eccentric cam 31a is provided eccentric with respect to the lower shaft 30 so that a part of the eccentric cam 31a surface becomes coplanar with a part the concentric cam 31b surface. The lower shaft 30 is connected to the sewing machine main shaft and is rotated integrally with the vertical feed cam 31 when the rotation of the main shaft is transmitted thereto.
The vertical feed contact 39 is disposed between the lower end of the vertically moving pin 37 and the lower shaft 30. The upper portion of the vertical feed contact 39 is rotatably supported by a cam shaft 38 provided in parallel with the lower shaft 30. A cam contact 39a that selectively contacts the eccentric cam 31a and the concentric cam 31b are formed in the right portion of the vertical feed contact 39. The vertical feed contact 39 is biased by a compression coil spring not shown so that the cam contact 39a is in consistent contact with the eccentric cam 31a.
An upwardly oriented abutting portion 39b that abuts the lower end of the vertically moving pin 37 is formed on the left portion of the vertical feed contact 39. The rear end of the feed base 32 is consistently biased downward by a helical extension spring not shown. Hence, the abutment between the height adjustment bolt 36 and the vertically moving pin 37, and between the vertically moving pin 37 and the abutting portion 39b are maintained consistently.
Thus, a circular motion of the eccentric cam 31a is conveyed to the rear end of the feed base 32 via the vertical feed contact 39, vertically moving pin 37 and the height adjustment bolt 36. Hence, the feed dog 6 is moved vertically between a feeding position shown in
Next, a description will be given on the feed dog longitudinal transfer mechanism 28. As shown in
On the other hand, a feed regulator 46 made of metal is provided in the upper portion of the swing link 41. The feed regulator 46 is rotatably supported by a rightwardly extending shaft member 47 provided on the frame not shown. A guide groove 46a forwardly inclined with respect to the vertical direction is formed on the left side surface of the feed regulator 46. The sliding block 45 is slidably engaged with the guide groove 46a so as to be guided by the guide groove 46a. Thus, the circular motion of the longitudinal feed cam 43 is conveyed to the swing link 41 and the distal end of the wing link 41 in a reciprocating manner in the guiding direction of the sliding block 45. Consequently, the longitudinal swing lever 33 is swung longitudinally about the pivot pin 35. The feed base 32 and the feed dog 6 are swung longitudinally by the above described swing movement, thus rearwardly feeding the sewing object, that is, the workpiece cloth.
Also, the feed dog longitudinal transfer mechanism 28 is capable of regulating the longitudinal feed amount of the feed dog 6. That is, as shown in
Next, the feed dog lateral transfer mechanism 50 that laterally moves the feed dog 6 will be described hereinafter. As shown in
As shown in
Also, a laterally extending operation lever 57 is disposed on the upper side of the frame 51. The right end of the operation lever 57 is connected to an upper corner of the swing lever 54 via a first connection mechanism 58, while the left end thereof is connected to a right side leg 32b of the feed base 32 via a second connection mechanism 60.
The first connection mechanism 58 is constituted as a free joint comprising a tapered recess 54a formed on the upper corner of the swing lever 54 and a spherical member 57a fixed to the right end of the operation lever 57 and contained in the recess 54a. Also, the first connection mechanism 58 is equipped with a plate spring member 59 biased so as to prevent the spherical member 57a from being removed from the recess 54a.
The second connection mechanism 60 is constituted as a free joint comprising a connection plate 61 provided on the front end of the right side leg 32b and formed with a tapered recess 61a; and a spherical member 57b fixed to the left end of the operation lever 57 and contained in the recess 61a. Also, the second connection mechanism 60 is equipped with a plate spring member 62 biased so as to prevent the spherical member 57b from being removed from the recess 61a. Therefore, the movement of the feed base 32 in the longitudinal and the lateral direction by the cloth feed mechanism 26 is enabled by providing the first and second connection mechanisms 58 and 60 on both ends of the operation lever 57 of the feed base 32.
Thus, when the lateral transfer motor 52 is rotated counterclockwise in rear view (refer to
As shown in
The feed dog 6 is arranged to be moved by the feed dog lateral transfer mechanism 50 in a span of approximately 1.6 mm at maximum. The lateral width of the first to fourth teeth 6a to 6d is set at approximately 1.4 mm. That is, when the feed dog 6 is moved from the leftmost position (refer to
Next, the configuration of a control system of the electronic zigzag sewing machine 9 will be described with reference to a block diagram in
A control device 65 of the zigzag sewing machine 9 is configured mainly by a microcomputer including therein a CPU 67, ROM 68, RAM 69, electrically-rewritable nonvolatile flash memory 70, bus 72 such as a data bus that connects the foregoing, input interface 66, and an output interface 71, and the like.
A start/stop switch 12, touch panel 11, rotational position detection sensor 77 that detects the rotational position of the sewing machine main shaft at every small predetermined angle, and the like are connected to the input interface 66.
Connected to the output interface 71 are drive circuits 73, 74, 75 and 76 for the sewing machine motor 78, the needle swing motor 23, the longitudinal transfer motor 49, and the lateral transfer motor 52 respectively, and a display controller (LCDC) 79, or the like for a liquid crystal display (LCD).
The RAM 69 contains a pattern number memory that stores the selected stitch pattern number; various memories, pointers, counters, and the like for storing calculation results of the CPU 67 on required basis. Various preset parameters and sewing conditions, and the like, are stored in the flash memory 70.
The ROM 68 stores a control program for driving the feed dog mechanism 26, a pattern selection control program for selecting a desired stitch from plurality types of utility stitches and decorative stitches, a display control program for displaying various images on the liquid crystal display 10, a feed dog lateral transfer control program which will be described in detail hereinafter, and the like. Furthermore, a needle drop point position/feed dog position mapping table shown in
The needle drop point position/feed dog position mapping table stores the distance of each sewing needle 7 drop point position from the left baseline position 7a and the corresponding feed dog 6 movement distance from the leftmost position. For example, as can be observed from
Subsequently, the feed dog lateral transfer control program executed by the control device 65 will be described with reference to
In the pattern selection process, if a straight stitch is not selected (S12: No), the control device 65 terminates the process. If a straight stitch is selected (S12: Yes), the control device 65 executes the setting control (refer to
In this control, the sewing needle 7 drop point position is set to the intended position by operating a “+” key 11f or a “−” key 11g associated with “swing width” on the liquid crystal display 10. The control is started whenever the “+” key 11f or the “−” key 11g is operated. When the “+” key 11f is operated (S21: Yes) and the swing width value is maximized to “7.0 mm” (S22: Yes), the control device 65 terminates the needle drop point position setting control. If a swing width value smaller than the maximum value is set (S22: No), the control device 65 increments the swing width setting by “0.5 mm” (S23). The incremented value overwrites the setting and is displayed to the liquid crystal display 10 as the current swing width setting (S24) Subsequently, the control device 65 swings (moves) the sewing needle 7 drop point position to the right by “0.5 mm” (S25) and terminates the needle drop point position setting control.
When the “−” key 11g is operated (S21: No, S26: Yes) and the swing width value is minimized to “0.0 mm” (S27: Yes), the control device 65 terminates the needle drop point position setting control. If a swing width setting greater than the minimum value is set (S27: No), the control device 65 decrements the swing width setting by “0.5 mm” (S28). The decremented value overwrites the setting and is displayed to the liquid crystal display 10 as the current swing width setting (S29). Subsequently, the control device 65 swings (moves) the sewing needle 7 drop point position to the left by “0.5 mm” (S30) and terminates the needle drop point position setting control.
Thereafter, in the feed dog lateral transfer control, when sewing is started (S14: Yes) by pressing the start/stop switch 12, the control device 65 identifies the needle drop of the first stitch based on a sensor signal outputted from the rotational position detection sensor 77. More specifically, when the sewing needle 7 is lowered from the uppermost position to the first stitch needle drop point, that is, when it is determined that the feed dog 6 is lowered below the needle plate 5 (S15: Yes), the control device 65 laterally moves the feed dog 6 (S16) based on the position of the needle drop point and terminates the feed dog lateral transfer control. In S16, the lateral transfer motor 52 is driven based on the swing width setting specified in S24 or S29 and the needle drop point position/feed dog position mapping table in
Next, the operation and effect of the electronic zigzag sewing machine 9 having the above construction will be described hereinafter.
When the sewing needle 7 drop point position is set at the “left baseline position” in which the swing width setting is “0.0 mm”, the feed dog 6 is moved to the leftmost position (refer to
When the needle drop point position is “0.5 mm” in which the swing width setting is set at “0.5 mm”, the feed dog 6 is moved rightward from the leftmost position by “0.5 mm”. Similarly, as the swing width setting is incremented by “0.5 mm” and the needle drop point position is rightwardly moved up to the “3.0 mm” position near the middle baseline position 7c, the feed dog 6 is rightwardly moved accordingly in small amounts (0.5 mm) until finally reaching the rightmost position (refer to
When the swing width setting is set at “4.0 mm” and the needle drop point position is “4.0 mm” which is beyond the middle baseline position 7c, the feed dog 6 is moved so as to be returned to the leftmost position at “0.0 mm” (refer to
Since the second and third teeth 6b and 6c are moved in association with the needle drop point position of the sewing needle 7, the stitch formed on the workpiece cloth can be clamped between either the second tooth 6b or the third tooth 6c and the cloth presser. Therefore, no seam puckering is observed even if tension is applied to the needle thread by cloth feed, thereby preventing defective seams. Since the second and third teeth 6b and 6c are moved so as to intersect the longitudinally extending vertical plane 25 that includes the needle drop point, the stitch can be clamped reliably even in case the lateral widths of the second and third teeth 6b and 6c are small.
Also, the needle drop point position of the sewing needle 7 (swing width setting) can be set by the user. The control device 65 controls the needle swing mechanism 15 so that the sewing needle 7 is dropped to the specified needle drop point position and the feed dog lateral transfer mechanism 50 is controlled based on the needle drop point position. Therefore, no separate control units are required for the needle swing mechanism 15 and the feed dog lateral transfer mechanism 50, thereby providing a simple construction.
Also, since the control device 65 controls the feed dog lateral transfer mechanism 50 to move the feed dog 6 when the feed dog 6 is below the needle plate 5, the second and the third teeth 6b and 6c can be moved to the needle drop point position without laterally moving the workpiece cloth.
Also, the control device 65 controls the feed dog lateral transfer mechanism 50 from the first sewing needle 7 drop after sewing start. Thus, a high-quality stitch with no seam puckering involved can be formed from the very first stitch after sewing start.
Furthermore, the control of the feed dog lateral transfer mechanism 50 is activated only when a straight stitch is selected in the pattern selection process. Thus, while enabling the formation of straight stitches free from seam puckering, the feed dog lateral transfer mechanism 50 is reliably inactivated when forming non-straight stitches such as decorative stitches.
Next, one of a plurality of modifications of the present embodiment will be described based on
Instead of controlling the feed dog lateral transfer mechanism 50 based on the needle drop point position, a needle drop point detection unit is provided that detects the needle drop point. The feed dog lateral transfer mechanism 50 is controlled based on the needle drop point position detected by the needle drop point detection unit.
As shown in
When the sewing needle 7 is disposed in the needle drop point corresponding to the glass fiber pair 82, the light injected from the light emitting glass fiber 82a reflects off the'sewing needle 7 and is received by the light receiving glass fiber 82b, rendering the detection of the needle drop point. The needle drop point detection unit is constructed by 15 sets of glass fiber pairs 82, or the like. Such construction provides the effect similar to the embodiment described earlier.
Modifications of the foregoing embodiments will be described hereinafter.
The teeth formed on the feed dog 6 are not limited to the first to fourth teeth 6a to 6d. A first to fifth teeth may be formed on the feed dog 6 and one of the plurality of the first to fifth teeth may be arranged to intersect the vertical plane 25.
If the electronic zigzag sewing machine is provided with a workpiece lateral feed mechanism that laterally feeds the workpiece cloth, the feed dog 6 may be controlled so as to be capable of laterally moving the workpiece cloth.
The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limited sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the invention as defined by the appended claims.
Number | Date | Country | Kind |
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2005-174940 | Jun 2005 | JP | national |
Number | Name | Date | Kind |
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3026832 | Taketomi | Mar 1962 | A |
4226199 | Adams | Oct 1980 | A |
4691654 | Meier | Sep 1987 | A |
4958580 | Asaba et al. | Sep 1990 | A |
5063867 | Horie | Nov 1991 | A |
5195442 | Meier | Mar 1993 | A |
Number | Date | Country |
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U 54-135263 | Sep 1979 | JP |
Number | Date | Country | |
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20060283365 A1 | Dec 2006 | US |