Thread routing mechanism for sewing machine

Abstract

 A thread routing mechanism for sewing machine includes a cylindrical needle bar case having a rotation axis and holding multiple spaced needle bars that are equally distant from the rotation axis and respectively carry a needle having an eye; a locating disk moving synchronously with the needle bar case and having multiple thread guide holes spaced around the rotation axis; and a thread take-up lever having a thread take-up end with multiple thread holes and movable upward and downward in a space directly above the needle bar case. Each thread hole together with a corresponding thread guide hole and a corresponding eye define a thread course, such that threads respectively routed through the thread courses have the same length even when the needle bars are changed from one to another. A thread pinching unit is also included to pinch or release the threads in or from the thread guide holes.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a thread routing mechanism located on a sewing head of a sewing machine to stabilize multiple threads for sewing operation, and more particularly to a thread routing mechanism that defines multiple thread courses and keeps multiple threads in the thread courses in the same length when multiple needle bars on one sewing head of the sewing machine are changed from one to another. The thread routing mechanism further includes a thread pinching unit for pinching or releasing the threads in the sewing operation and needle bar changing operation, respectively.

BACKGROUND OF THE INVENTION

[0002] Generally, a sewing machine must include an upper horizontal arm, a lower machine bed and a needle plate. An arm shaft in the upper horizontal arm actuates a thread take-up mechanism and a crank unit synchronously, so as to drive a needle bar mechanism in a sewing head to move upward and downward. A fabric feeding mechanism is provided on the lower machine bed, and a loop taker is provided below the needle plate. In a sewing operation, a needle carried by the needle bar mechanism is driven to move upward and downward reciprocatingly to pierce through the fabric, so that a thread extended through an eye of the needle is also brought to downward extend through the fabric; meanwhile, the thread take-up mechanism and the loop taker are coordinately moved in correct time sequence to take up and release the thread.

[0003] The thread take-up mechanism is normally arranged above the needle bar mechanism to ensure proper tension of the thread and minimize a resistance to the thread when the same passes through the thread take-up mechanism. In the market, except some multi-needle bar embroiders, there are few sewing machines that allow direct changing of the needle bars thereof. Since the multi-needle bar embroiders generally have the drawbacks of having a bulky volume and requiring an extended travel distance for a fabric feeding surface on a driving unit, it is necessary to develop a sewing machine that allows direct change of multiple needle bars from one to another in sewing operation while the sewing reference point and the needle plate for those needle bars are unchanged.

[0004] However, once the sewing machine adopts a cylindrical needle bar case on the sewing head to enable needle bar changing operation, the thread take-up mechanism must also be able to handle multiple threads. In this case, with the thread take-up mechanism located above the needle bars as in the conventional design, the length of the threads in the thread courses can not maintain same after the needle bar changing operation, resulting in change of the tension of the threads to adversely affect the subsequent sewing operation.

SUMMARY OF THE INVENTION

[0005] A primary object of the present invention is to provide a thread routing mechanism, which is installed on a sewing machine having changeable needle bars to define multiple thread courses, so that multiple threads respectively routed through the defined thread courses can maintain in the same length even when the needle bars on the sewing head of the sewing machine are changed from one to another.

[0006] Another object of the present invention is to provide the above thread routing mechanism and a thread pinching unit. Before changing the needle bars on the sewing machine, the thread pinching unit cooperates with other parts to release the threads, which are routed through the thread courses, for needle bar changing operation. After the needle bar changing operation and before the sewing operation, the thread pinching unit cooperates with other parts to pinch the threads, lest the threads should move out of the eyes on the needles carried by the needle bars.

[0007] To achieve the above and other objects, the thread routing mechanism for sewing machine according to the present invention mainly includes a thread take-up lever, a locating disk, and a cylindrical needle bar case. The cylindrical needle bar case has a rotation axis and a plurality of axially extended and circumferentially spaced needle bar holes. The rotation axis is equally distant from all needle bar holes; each of the needle bar holes has a needle bar received therein, and the needle bars respectively carry a needle having an eye formed thereon. The locating disk is assembled to a bottom of the cylindrical needle bar case to move synchronously with the latter, and is provided closely around the rotation axis with a plurality of circumferentially spaced thread guide holes. The thread take-up lever is located above the cylindrical needle bar case and close to the rotation axis, and includes a sway control end and a thread take-up end brought by the sway control end to move upward and downward. The thread take-up end is provided with a plurality of thread holes, through each of which a thread is extended; and the thread take-up end in moving is always located in a space that is upward extended from a cylindrical space enclosed in the cylindrical needle bar case. Each of the thread holes on the thread take-up lever together with a corresponding one of the thread guide holes on the locating disk and a corresponding one of the eyes on the needles define a course along which a thread is routed.

[0008] Each of the thread guide holes on the locating disk may be located on a line extended between the rotation axis and the axis of a corresponding needle bar, such that sections of the threads extended between the thread guide holes and the eyes may be radially outward arrayed from top to bottom, and the threads having been routed through the thread courses are substantially equally spaced.

[0009] The thread routing mechanism for sewing machine according to the present invention may further include a thread pinching unit, which includes a pinching member located beneath the locating disk to correspondingly cover the thread guide holes and including a thread pinching surface and an engaging section downward extended from the thread pinching surface. The thread pinching surface covers the thread guide holes, and is provided on an outer edge thereof with a notch, which is aligned with one of the thread guide holes. The thread pinching unit may further include a shaft member connected to a lower side of the pinching member, a nut tightened to a lower end of the shaft member, and a spring fitted around the shaft member with two ends pressed against the nut and the pinching member, so that the pinching member is normally pushed upward by the spring to tightly contact with the locating disk and pinch the threads in the thread guide holes. The thread pinching unit may further include a driving lever, which has an end engaged with the engaging section of the pinching member for moving the pinching member against the spring to separate from the locating disk and accordingly, release the threads for the same to freely move through the thread guide holes.

[0010] The present invention is characterized in that the thread holes on the thread take-up lever, the thread guide holes on the locating disk, and the eyes on the needles together form a thread routing structure defining a plurality of radially arrayed thread courses, so that sections of the threads routed through the thread courses are substantially equal in length even when the needle bars on the sewing machine are changed from one to another. Further, the thread pinching unit cooperates with other parts to form means for pinching and releasing the threads in sewing operation and needle bar changing operation, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

Fig. 1 is an assembled perspective view of a thread routing mechanism for sewing machine according to a first preferred embodiment of the present invention, showing its position on a sewing head of a sewing machine;

Fig. 2 is a partially cutaway view of the sewing machine of Fig. 1 showing a cylindrical needle bar case thereof;

Fig. 3 is a front view of the sewing machine of Fig. 2;

Fig. 4 is a partially sectioned side view of the thread routing mechanism according to a second preferred embodiment of the present invention;

Fig. 5 is a partially enlarged view of Fig. 4 showing a thread routed through a locating disk, a thread pinching unit and a needle bar included in the thread routing mechanism;

Fig. 6 is an exploded perspective view of the locating disk and the thread pinching unit of Fig. 5; and

Fig. 7 is a bottom view showing multiple threads are threaded through the thread routing mechanism according to the second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will now be described with some preferred embodiments thereof and with reference to the accompanying drawings. For the purpose of easy to understand, elements that are the same in the preferred embodiments are denoted by the same reference numerals.

[0013] Please refer to Figs. 1 and 2 that show a thread routing mechanism for sewing machine according to a first preferred embodiment of the present invention is installed on a needle bar changing mechanism 12 located at a sewing head 11 of a sewing machine 10. The thread routing mechanism includes a cylindrical needle bar case 20, a locating disk 21 and a thread take-up lever 22, on which holes for threads to extend through are provided. Corresponding thread extending holes on the cylindrical needle bar case 20, the locating disk 21 and the thread take-up lever 22 together define a course along which a thread 23 is routed.

[0014] As can be seen from Fig. 2, the cylindrical needle bar case 20 includes a cylindrical wall 201, a center of which defines a rotation axis 202. A plurality of axially extended needle bar holes 203 is spaced on the wall 201 of the cylindrical needle bar case 20 with the rotation axis 202 being equally distant from all needle bar holes 203. Each of the needle bar holes 203 has a needle bar 204 received therein, and the needle bars 204 respectively carry a needle 205 having an eye 206 formed thereon. When the cylindrical needle bar case 20 is driven by the aforesaid needle bar changing mechanism 12 to rotate, the position of every needle bar 204 on the cylindrical needle bar case 20 relative to the needle bar changing mechanism 12 is changed.

[0015] The locating disk 21 is assembled to a bottom of the cylindrical needle bar case 20 to move synchronously with the latter. The locating disk 21 is provided closely around the rotation axis 202 with a plurality of circumferentially spaced thread guide holes 211, and along an outer periphery thereof with a plurality of spaced needle bar holes 212 for the needle bars 204 to extend therethrough. Each of the thread guide holes 211 on the locating disk 21 is located on a line extended between the rotation axis 202 and a central axis of a corresponding needle bar 204 received in the needle bar hole 212.

[0016] The thread take-up lever 22 is movably mounted to a front end of the sewing head 11 of the sewing machine 10 to locate above the cylindrical needle bar case 20. The thread take-up lever 22 includes a sway control end 221 and a thread take-up end 222. The sway control end 221 is pivotally turnable to move the thread take-up end 222 upward and downward. The movable thread take-up end 222 is always located in a space 207, which is upward extended from a cylindrical space enclosed in the cylindrical wall 201 of the cylindrical needle bar case 20, and is located close to the rotation axis 202 of the cylindrical needle bar case 20. The thread take-up end 222 is provided with a plurality of thread holes 223, through each of which a thread 23 is extended.

[0017] The threads 23 having been extended through the thread holes 223 on the thread take-up lever 22 are first routed into the space enclosed in the wall 201 of the cylindrical needle bar case 20 and then further downward routed through the thread guide holes 211 on the locating disk 21 before being routed through the eyes 206 on the needles 205. Therefore, the thread holes 223 on the thread take-up lever 22, the thread guide holes 211 on the locating disk 21, and the eyes 206 of the needle 205 together define a plurality of thread courses.

[0018] Please refer to Fig. 3. In the illustrated first preferred embodiment, the thread take-up lever 22 is located in the space 207 upward extended from the cylindrical space enclosed in the wall 201 of the cylindrical needle bar case 20, such that the thread holes 223 on the thread take-up lever 22, the thread guide holes 211 on the locating disk 21, and the eyes 206 on the needles 205 are radially outward arrayed from top to bottom. Whereby, when the threads 23 have been respectively sequentially routed through the thread holes 223, the thread guide holes 211 and the eyes 206 of the thread routing mechanism, the sections of the threads 23 between the thread holes 223 and the eyes 206 are substantially equally spaced. With this arrangement, the length of the threads 23 in the thread courses can maintain stable after the needle bars 204 have been changed from one to another.

[0019] It is understood the first preferred embodiment is only illustrative to facilitate easy explanation of the present invention and not intended to limit same in any way. In a second preferred embodiment of the present invention shown in Fig. 4, the locating disk 21 further has a thread pinching unit 24 assembled thereto for selectively pinching or releasing the threads 23 that are routed through the thread guide holes 211 of the locating disc 21. The thread pinching unit 24 includes a pinching member 241 located beneath the locating disk 21 corresponding to the thread guide holes 211 for pinching the threads 23; a shaft member 242 connected to a lower side of the pinching member 241; a spring 243 fitted around the shaft member 242; a nut 244 tightened to a lower end of the shaft member 242; and a driving lever 245 having an end engaged with the pinching member 241. The spring 243 has a lower end pressed against the nut 244 and an upper end pressed against the pinching member 241, so that the pinching member 241 is normally pushed by the spring 243 to tightly contact with a lower surface of the locating disk 21 and pinches the threads in the thread guide holes 211. The driving lever 245 is used to drive the pinching member 241 downward against the spring force of the spring 243 and accordingly separate the pinching member 241 from the lower surface of the locating disk 21, so that the threads 23 are released to allow changing of the needle bars from one to another.

[0020] Please refer to Figs. 5 and 6. In the illustrated second preferred embodiment, the pinching member 241 includes a thread pinching surface 241a, which covers the thread guide holes 211; and an engaging section 241b, with which the driving lever 245 is engaged to prevent the whole pinching member 241 from rotating about the rotation axis 202. The thread pinching surface 241a is provided on an outer edge thereof with a notch 241c, which is aligned with one of the thread guide holes 211 to allow one of the threads 23 that is currently in use to freely pass therethrough, while all other thread guide holes 211 that are not aligned with the notch 241c cooperate with the thread pinching surface 241a to pinch the currently unused threads 23 therebetween. With this arrangement, the currently unused threads 23 are prevented from moving out of the eyes 206 when the sewing operation starts after the needle bar changing operation.

[0021] Please refer to Fig. 7. As can be found from the above two preferred embodiments, the present invention is characterized in routing the plurality of threads 23 through respective thread courses defined by the thread holes 223 on the thread take-up lever 22, the thread guide holes 211 on the locating disk 21 and the eyes 206 on the needles 205, so that the sections of the threads 23 extended between the thread guide holes 211 and the eyes 206 are radially outward arrayed from top to bottom, and the sections of the threads 23 routed through the thread holes 223 and the thread guide holes 211 to the eyes 206 are substantially equally spaced. Thus, the length of the threads 23 in the thread courses can maintain stable after the needle bars 204 have been changed from one to another on the sewing machine 10.
The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.

Claims

1. A thread routing mechanism for sewing machine, comprising:

a cylindrical needle bar case having a rotation axis and a plurality of axially extended and circumferentially spaced needle bar holes; the rotation axis being equally distant from all needle bar holes; each of the needle bar holes having a needle bar received therein, and the needle bars respectively carrying a needle having an eye formed thereon;

a locating disk being assembled to a bottom of the cylindrical needle bar case to move synchronously with the latter, and being provided closely around the rotation axis with a plurality of circumferentially spaced thread guide holes; and

a thread take-up lever being located above the cylindrical needle bar case and close to the rotation axis; the thread take-up lever including a sway control end and a thread take-up end brought by the sway control end to move upward and downward; the thread take-up end being provided with a plurality of thread holes, through each of which a thread is extended; and the thread take-up end in moving being always located in a space that is upward extended from a cylindrical space enclosed in the cylindrical needle bar case;

wherein each of the thread holes on the thread take-up lever together with a corresponding one of the thread guide holes on the locating disk and a corresponding one of the eyes on the needles define a course along which a thread is routed.

2. The thread routing mechanism for sewing machine as claimed in claim 1, wherein each of the thread guide holes on the locating disk is located on a line extended between the rotation axis and an axis of a corresponding needle bar.

3. The thread routing mechanism for sewing machine as claimed in claim 1, wherein sections of the threads routed from the thread guide holes to the needle eyes are radially outward arrayed from top to bottom, so that the threads having been routed through the thread courses are substantially equally spaced.

4. The thread routing mechanism for sewing machine as claimed in claim 1, further comprising a thread pinching unit, which includes a pinching member located beneath the locating disk to correspondingly cover the thread guide holes; the pinching member including a thread pinching surface for covering the thread guide holes, and the thread pinching surface being provided on an outer edge thereof with a notch, which is aligned with one of the thread guide holes.

5. The thread routing mechanism for sewing machine as claimed in claim 4, wherein the thread pinching unit further includes a shaft member connected to a lower side of the pinching member, a nut tightened to a lower end of the shaft member, and a spring fitted around the shaft member with two ends pressed against the nut and the pinching member, so that the pinching member is normally pushed upward by the spring to tightly contact with the locating disk and pinch the threads in the thread guide holes.

6. The thread routing mechanism for sewing machine as claimed in claim 5, wherein the thread pinching unit further includes a driving lever, which has an end engaged with the pinching member for moving the pinching member against the spring, so that the pinching member is separated from the locating disk to release the threads for the same to freely move through the thread guide holes.

Drawing