Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the illustrative examples with reference to the accompanying drawings, in which:
A first illustrative example of the present disclosure will be described with reference to
The arm 3 has a front on which a start/stop switch 7 is mounted for instructing start and stop of sewing. The pillar 2 has a front on which a color liquid crystal display 6 is mounted. The liquid crystal display 8 displays stitch patterns of various ordinary patterns, various function names, pattern names, various messages and the like. A touch key 8a (see
A color image sensor 9 is mounted on the underside of the head 4 so as to be located in front of the needlebar 5 and so as to be directed downward. The image sensor 9 is adapted to image workpiece cloth W substantially from above. The workpiece cloth W is placed on an upper face of a needle plate 10 of the bed 1. The image sensor 9 comprises a charge coupled device (CCD) image pickup device. In this arrangement, when workpiece cloth W to be sewn is placed on the upper face of the bed 1, a part of the workpiece cloth W near to the sewing needle 6 is adapted to be imaged by the image sensor 9 within a substantially circular image area.
Referring to
The needlebar driving mechanism 15 will firstly be described with reference to
On the other hand, a thread take-up crank 19 is secured to a distal end of a main shaft 18 rotated by a sewing machine motor 66 (see
The connecting mechanism 22 will be described in brief. The needlebar block 21 is slidably supported on the needlebar 5. A fixing member 23 is secured to the needlebar 9, and a vertically directed swinging member 24 has an upper end pivotally mounted on the fixing member 23. The swinging member 24 has a lower end with an engagement convex portion 24a which is elastically biased by a coil spring 25 so as to engage an engagement concave portion 21a of the needlebar block 21. More specifically, the needlebar 5 is vertically reciprocated via the connecting mechanism 22 when the main shaft 18 is rotated by the sewing machine motor 66 so that the needlebar block 21 is vertically moved via the thread take-up crank 19 and the needlebar crank rod 20.
Next, the following describes a needlebar releasing mechanism 30 for blocking connection between the needlebar 5 and the main shaft 18. A vertically directed pivoting shaft 31 is fixed to a substantially left lower half of the needlebar support 16 as shown in
The driving lever 34 has a distal end to which the engagement pin 35 is secured so that the engagement pin 35 is capable of abutting against a blocking cam 44b of the first cam member 44 from behind. The blocking cam 44b will be described in detail later. Furthermore, the blocking plate 32 is biased 25, counterclockwise by the spring force of the coil spring 36 as viewed on a plane. The operating plate 33 is engageable with the engagement protrusion 24b of the swinging member 24 from behind. More specifically, the blocking plate 32 is caused to pivot clockwise when the first cam member 44 is rotated clockwise so that the engagement pin 35 is moved rearward by the blocking cam 44b. Consequently, the engagement convex portion 24a of the swinging member 24 is disengaged from the engagement concave portion 21a of the needlebar block 21 via the engagement protrusion 24b in engagement with the operating plate 33, whereby the needlebar 5 under vertical drive is blocked off.
As a result, the needlebar 5 is slid to and held at the uppermost position by the spring force of a tension coil spring 38 hooked on a spring-receiving plate 37 mounted to the needlebar support 16. On the other hand, the needlebar block 21 is moved upward when the blocking plate 32 has been returned to a standby position as shown in
Furthermore, the drive motor 40 comprising a stepping motor is provided on a heightwise middle of the head 4 as shown in
Upon application of power to the lockstitch sewing machine M, the drive motor 40 is driven for initialization such that the machine M is set in an initial condition. Subsequently, when a sewing process is carried out in the initial condition, the needlebar 5 is vertically driven, and the drive motor 40 is driven according to a swing width so that the needlebar 5 is swung, whereby stitches are formed on the workpiece cloth W by the needle thread applied with an optimum tension.
When the needlebar 5 is swung within a predetermined swing range as described above, the blocking cam 44b of the first cam member 44 and the engagement pin 35 are in such a positional relation that the blocking cam 44b does not engage the engagement pin 35. When the drive motor 4 is driven so that the first cam member 44 is rotated to the needlebar release position which exceeds the predetermined swing range, the blocking cam 44b engages the engagement pin 35. Accordingly, the engagement pin 35 is moved rearward by the blocking cam 44b such the blocking plate 32 is caused to pivot clockwise. As a result, the engagement convex portion 24a of the swinging member 24 is disengaged from the engagement concave portion 21a of the needlebar block 21, whereupon the needlebar 5 is disconnected from the main shaft 18. Consequently, the needlebar 5 is slid to the uppermost position by the tension coil spring 38 thereby to be held in position.
When the needlebar released state is to be canceled, the drive motor 40 is driven so that the first cam member 44 is returned to an original position. Accordingly, the engagement convex portion 24a automatically engages the engagement concave portion 21a of the needlebar block 21 assuming the uppermost position, whereby the needlebar 5 is re-connected to the main shaft 18 so as to be vertically driven.
The pressing force adjusting mechanism 14 will now be described with reference to
The pressing force adjusting motor 52 is fixed on the frame F so as to be located just on the right of the rack member 50. The middle gear 53 has a pinion 53a provided integrally therewith and having a smaller diameter. The pinion 53a is in mesh engagement with a rack of the rack member 50. Furthermore, a presser lifting lever 56 is provided near the pressing force adjusting mechanism 14. The presser lifting lever 56 is manually operable to move the presser bar 13 so that the presser bar 13 is allowed to rise and fall. The presser lifting lever 56 is supported so that one end thereof is vertically pivotable on a pivot pin 56a. A potentiometer 57 is also provided near the pressing force adjusting mechanism 14 so as to be located just on the left of the presser bar 13.
The potentiometer 57 includes a pivot shaft from which a shaft portion 57a extends rightward. The shaft portion 57a abuts against an upper surface of the leftwards protruding protrusion 54b of the presser bar guide bracket 54. The shaft portion 57a is caused to pivot in response to rise or fall of the presser bar 13 and presser bar guide bracket 54 thereby to change a resistance value thereof. The control device 60 which will be described later computes the difference between a resistance value obtained when the workpiece cloth W is located below the presser foot 12 and a resistance value obtained when no workpiece cloth W is located below the presser foot 12, thereby detecting the difference of height of the presser bar 12 or a cloth thickness of the workpiece cloth W.
A pressing force adjustment will now be described with reference to
However, the height of the presser foot 12 in contact with the surface of the workpiece cloth W changes depending upon the cloth thickness t of the workpiece cloth W. Accordingly, the number of steps of the pressing force adjusting motor 52 (a heightwise position of the rack member 50) is suitably changed in proportion to an increase of cloth thickness t based on step number A in the case of cloth thickness t=0. More specifically, the heightwise position of the rack member 50 is adapted to change according to cloth thickness t detected by the potentiometer 57. For example, the number of steps in the case of cloth thickness t=1 mm is set at “A-b” and the heightwise position of the rack member 50 is rendered higher by 1 mm. In other words, even when cloth thickness t of the workpiece cloth W takes any value, the operator can freely move the workpiece cloth W without receiving any movement resistance in the case where the pressing force P is at 0 [N], whereupon a free-motion sewing can be realized. In this case, it is assumed that the weight of the presser bar 13, presser foot 12 and the like has substantially no influence upon the movement of the workpiece cloth W.
However, as shown in
The height position of the rack member 50 becomes lowest when the counterclockwise rotation of the pressing force adjusting motor 52 is maximized during sewing as shown in
The control system of the lockstitch sewing machine M will be described. Referring to
The ROM 62 stores a control program for cloth movement limiting control and the like in addition to a sewing control program on which various ordinary patterns and embroidery patterns are sewn and a general control program for display control. The RAM 63 is provided with memories necessary in execution of various control manners (memories such as flags, pointers, counters and the like, registers, buffers and the like) if needed.
The ROM 62 also stores a step number table in which the pressing force P [N] and the reference number of driving steps in the case of cloth thickness t=0 mm are interrelated, as shown in
The ROM 62 still further stores a pressing force change table as shown in
The cloth movement limiting control carried out by the control device 60 of the lockstitch sewing machine M will be described with reference to the flowchart of
A cloth thickness computing control for cloth thickness computing process is carried out in the cloth movement limiting control (S12). In the cloth thickness computing control, since the workpiece cloth W to be sewn is placed on the needle plate 10, the pressing force adjusting motor 52 is driven so that the pressing bar 13 is once lowered on the workpiece cloth W. In this case, a resistance value delivered from the potentiometer 57 is read, and the cloth thickness t of the workpiece cloth W is obtained from the resistance value.
Subsequently, a stitch pitch setting control (see
Subsequently, a start/stop control (see
However, in the case where the sewing machine motor 66 is being driven (S32: No) when the start/stop switch 7 has been operated (S31: Yes), the sewing machine motor 66 is stopped (S35). Subsequently, the pressing force P is changed to 0 [N] so that the workpiece cloth W can be taken out (S36). The needlebar release canceling instruction is delivered (S37) and the control device 60 then terminates the control, returning to the cloth movement limiting control.
Subsequently, a limiting control (see
Subsequently, the pressing force P is switched to 0 [N] (S46) and the control terminates. The cloth movement limiting control is carried out at the next time when the control device 60 has determined in the affirmative (Yes) at S42 and S43. When the pressing force P is not set at 20 [N] (S47: No), obtained image data is stored (S48) in the same manner as in S45. Subsequently, a movement amount of the workpiece cloth W is computed based on the image data in S45 and image data produced in S48 (S49).
In the movement amount computing process, image data obtained at the first and second times are compared and computation is carried out so that a movement amount of the workpiece cloth W is obtained. The obtained movement amount is sequentially integrated and stored. Subsequently, the obtained cloth movement amount WD is compared with the size of stitch pitch PD. When the cloth movement amount WD is smaller than the stitch pitch PD (S50: No), S41 to S50 are repeatedly carried out so that the workpiece cloth W is freely moved by the operator.
On the other hand, when the cloth movement amount WD is equal to or larger than the stitch pitch PD (S50: Yes), the pressing force P is set at 20 [N] (S51). As a result, since such a large pressing force as 20 [N] is applied to the workpiece cloth W, the operator can no longer move the workpiece cloth W. When the needlebar is not being released (S52: No), the control device 60 terminates the movement amount computation process, returning to the cloth movement limiting control.
However, cancel of the needlebar release is instructed (S54) when the needlebar is being released (S52: Yes) and the needlebar release canceling instruction has not been delivered (S53: No). The control then terminates. Upon start of the control, the needlepoint of the sewing needle 6 is currently located in the space below the needle plate 10 (S42: No) and was previously located in the space above the needle plate 10. That is, the control device 60 advances to S56 when the sewing needle 6 has been moved from the upper space to the lower space relative to the needle plate 10 (S55: Yes). The control terminates when the pressing force P is at 20 [N] in S56 and the workpiece cloth W has been moved by a distance corresponding to the stitch pitch PD (S56: Yes).
On the other hand, when the pressing force P is not at 20 [N], that is, when the workpiece cloth W has not been moved by the distance corresponding to the stitch pitch PD ((S56: No), the control device 60 advances to S57. When the needlebar 5 is not being released (S57: No), instruction is delivered to release the needlebar releasing mechanism 30 (S58). S48 and subsequent steps are repeatedly carried out. The control device 60 determines in the affirmative in S57 when the cloth movement limiting control is carried out next time and at subsequent times. Accordingly, S51 to S54 are carried out when the cloth movement amount WD is equal to or larger than the stitch pitch PD (S50: Yes) as the result of movement amount computation at S49 based on the image data obtained at S48. The control then terminates.
Next, the operation of the cloth movement limiting control thus configured will now be described. In this case, the stitch pitch PD is set at “3 mm” and the cloth thickness t is set at “1 mm.” The pressing force P is changed from 20 [N] to 0 [N] at cloth movement start time T1 when the needlepoint of the sewing needle 6 has been moved about 1 mm above the needle plate 10, for example at a tenth stitch, as shown in
When the operator moves the workpiece cloth W slowly for a twelfth stitch, the cloth movement amount does not reach the stitch pitch PD after the cloth movement termination time T2 has passed. In this case, the needlebar release is carried out at time T2. Thus, the operator can move the workpiece cloth in the needlebar released state continuously until the cloth movement amount reaches the stitch pitch PD. When, at time T3, the cloth movement amount becomes “about 3 mm” which is substantially the same as the stitch pitch PD, the pressing force P is changed from 0 [N] to 20 [N] at time T3 and the needlebar release is cancelled.
Thus, the movement amount of the workpiece cloth W manually moved by the operator is computed for every sewing cycle without change in the rotational speed of the sewing machine motor 66, based on the image data obtained by the image sensor 9. The pressing force adjusting motor 52 is controlled according to the result of comparison in which the movement amount is compared with the stitch pitch PD. Accordingly, the movement amount of the workpiece cloth W can be limited substantially to the stitch pitch PD by the pressing force adjusting mechanism 14. Consequently, even a beginner who is unfamiliar with a sewing work can carry out free-motion sewing such as quilting without any anxiety while enjoying sewing.
The sewing machine motor 66 is being driven (S61: Yes) when the limiting control starts. The needlepoint of the sewing needle 6 is currently located above the needle plate 10 and was previously located below the needle plate 10. That is, the control device 60 advances to S64 when the sewing needle 6 has been moved from the lower space to the upper space relative to the needle plate 10 (S63: No). In S64, a part of the workpiece cloth W near to the sewing needle 6 is imaged by the image sensor 9. Obtained image data is read to be stored on the predetermined memory of the RAM 63 (S64) and the control then terminates.
The control device 60 determines in the affirmative in S62 and S63 when the limiting control is carried out next time. The control then terminates. After this is repeated some times, the needlepoint of the sewing needle 6 is moved below the needle plate 10. The control device 60 then determines in the negative (No) in S62 and in the affirmative (Yes) in S65. Furthermore, when the image has been read in S64 (S66: Yes), the control device 60 advances to S67, where the obtained image data is read and stored in the same manner as in S64. Subsequently, a movement amount of the workpiece cloth W is computed based on the image data obtained in S64 and the image data read in S67 (S68).
Subsequently, based on the obtained cloth movement amount WD and stitch pitch PD, a movement amount difference ΔD obtained by subtracting the stitch pitch PD from the cloth movement amount WD is computed (S69). Subsequently, based on a cloth pressing force change table of
Next, the operation of the cloth movement limiting control thus configured will now be described. In this case, the stitch pitch PD is set at “3 mm” and the cloth thickness t is set at “1 mm.”
The pressing force P is set at 0 [N] at cloth movement start time T1 when the needlepoint of the sewing needle 6 has been moved about 1 mm above the needle plate 10, for example at a tenth stitch, as shown in
When the cloth movement amount becomes “about 2 mm” at the next twelfth stitch, the movement amount difference ΔD is “−1 mm” and the changed pressing force ΔP is “−0.5.” Accordingly, the pressing force adjusting motor 52 is rotated clockwise by the number of steps corresponding to “−1α” and the pressing force P is set at 2.5 [N]. When the cloth movement amount becomes “about 3 mm” at the next thirteenth stitch, the movement amount difference ΔD is “0” and the changed pressing force ΔP is “0.” Accordingly, the pressing force P remains unchanged at 3 [N].
As obvious from the foregoing, a movement amount of the workpiece cloth W to be manually moved by the operator is computed for every sewing cycle without changing the rotational speed of the sewing machine motor 66 based on image data obtained by the image sensor 9. The computed movement amount is compared with the stitch pitch PD. The pressing force adjusting motor 52 is controlled according to the results of comparison. Furthermore, the pressing force P the presser foot 12 applies to the workpiece cloth W is adjusted so that a movement amount of the workpiece cloth W manually moved by the operator becomes substantially equal to the stitch pitch PD. As a result, a movement amount of the workpiece cloth W by the operator can be accurately limited by a simple mechanism.
The pressing force P rendering the workpiece cloth W immovable by the operator should not be limited to 20 [N] in the above-described limiting control as shown in
The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limiting 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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2006-265761 | Sep 2006 | JP | national |