THREAD TRIMMER OF POST-BED SEWING MACHINE

Abstract

 A thread trimmer (2) of post-bed sewing machine is assembled to a feed wheel support post (231) of the sewing machine and includes a cutter set (30), a transmission device (40) and a lower shaft (24). The cutter set (30) includes a fixed cutter (31) located behind a needle hole (271) formed on a top of the feed wheel support post (231) for a sewing thread to extend therethrough, and a movable cutter (32) movably assembled to the feed wheel support post (231) and driven by the transmission device (40) to swing about a swing axis (231e) in parallel with the lower shaft (24), such that the movable cutter (32) can swing from a thread-hooking position adjacent to the needle hole (271) to a thread-trimming position for cutting the sewing thread. With these arrangements, only a relatively short loose thread end will be left on the workpiece being sewed when the sewing thread is cut by the fixed and the movable cutter.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a thread trimmer of post-bed sewing machine, and more particularly to a thread trimmer of post-bed sewing machine, with which only a relatively short loose thread end of a sewing thread will be left on a workpiece being sewed when the sewing thread is cut.

BACKGROUND OF THE INVENTION

[0002] A sewing machine is used to pass a sewing thread through several layers of materials to join the materials together. With the constant development in the sewing industrial field, different types of sewing machines have been available in the market. Each type of sewing machine can be applied to a sewing operation involving some specific workpieces. Currently, there is a post-bed sewing machine suitable for sewing shoes, bags or other products generally in the shape of a long sleeve.

[0003] To conveniently cut the sewing thread when the sewing operation is completed on the post-bed sewing machine, a thread trimmer is provided on the post-bed sewing machine for this purpose. Fig. 1 shows a conventional thread trimmer 1, which includes a fixed cutter 10 and a movable cutter 11. The fixed cutter 10 is mounted on a fixed cutter holder 13, which is arranged in a shuttle holding base 12. The movable cutter 11 is pivotally connected at an end to a top of the shuttle holding base 12 via a pivot shaft 14, and a swing arm 15 is assembled to a lower end of the pivot shaft 14. The swing arm 15 is connected to an actuator (not shown), which can bring the movable cutter 11 to swing about the pivot shaft 14 (i.e. the z-axis shown in the drawing) to hook and cut the sewing thread.

[0004] Since both of the fixed cutter 10 and the movable cutter 11 are mounted on the shuttle holding base 12, their blades are located relatively distant from a needle hole on the sewing machine. As a result, when the sewing thread is cut by the movable cutter 11, a relatively long loose thread end will be left on the surface of the workpiece. In this case, the relatively long loose thread end must be manually cut shorter even though the sewing thread has been cut.

[0005] In view that the conventional thread trimmer for the post-bed sewing machine has the above-mentioned disadvantage, it is tried by the inventor to develop an improved thread trimmer, so that only a relatively short loose thread end is left on the workpiece after the sewing thread is cut.

SUMMARY OF THE INVENTION

[0006] A primary object of the present invention is to provide a thread trimmer of post-bed sewing machine, with which only a relatively short loose thread end will be left on a workpiece being sewed when the sewing thread is cut, so that a sewing operator does not need to trim the loose thread end for a second time and the time for sewing operation can be shortened to enable increased productivity.

[0007] Another object of the present invention is to provide a thread trimmer of post-bed sewing machine, with which a swing distance between a thread-hooking position and a thread-trimming position of a movable cutter can be adjusted according to the material and nature of the sewing thread, so that the time difference set for cutting the sewing thread can be shortened or lengthened, making the post-bed sewing machine more practical for use.

[0008] To achieve the above and other objects, the thread trimmer of post-bed sewing machine according to the present invention is assembled to a feed wheel supporting base on a machine bed of the post-bed sewing machine. The feed wheel supporting base is upward extended in the direction of z-axis to form a feed wheel supporting post and has a lower shaft rotatably connected thereto. Preferably, the feed wheel supporting post includes a feeding stand, a needle plate holder assembled to a top of the feeding stand, and a movable cutter holder assembled to the feeding stand, a needle plate formed with a needle hole being assembled to the needle plate holder, allowing a needle and a sewing thread to extend through the needle hole on the needle plate, and the movable cutter holder including a curved rail. The thread trimmer mainly includes a cutter set and a transmission device.

[0009] The cutter set is arranged in the vicinity of the needle hole, and includes a fixed cutter and a movable cutter. Preferably, the cutter set further includes a thread-clamping spring plate. The fixed cutter is fixedly mounted on the feed wheel supporting post to be located behind the needle hole. The movable cutter is movably connected to the feed wheel supporting post. Preferably, the movable cutter includes a hooking recess adapted to receive the sewing thread therein and a guiding section for guiding the sewing thread to the hooking recess; and a movable blade being formed at an end of the hooking recess to correspond to the fixed cutter. Preferably, the thread-clamping spring plate has an end assembled to the movable cutter holder on the feed wheel supporting post and another opposite end elastically pressing against the movable cutter. In a preferred embodiment, the movable cutter is received in the curved rail to swing along the curved rail.

[0010] The transmission device is assembled to the movable cutter. The transmission device drives the movable cutter to swing about a swing axis that is extended in parallel with the lower shaft, such that the movable cutter is sequentially movable between an initial position adjacent to the needle hole, a thread-hooking position far away from the initial position, and a thread-trimming position corresponding to the needle hole for sewing thread trimming. Preferably, the transmission device includes a cam set, a swing arm, a return spring and an actuator, the cam set being mounted on the lower shaft to rotate synchronously with the lower shaft and including a rise path and a return path, the rise path serves to drive the movable cutter to swing from the thread-hooking position to the thread-trimming position, while the return path serves to drive the movable cutter to swing from the initial position to the thread-hooking position.

[0011] In a preferred embodiment, the cam set includes a first cam and a second cam. The first cam is rotatable relative to the lower shaft to allow an adjustment of a relative position between the first cam and the second cam and accordingly, a change of a relative position between the rise path and the return path. With this arrangement, it is able to adjust a swing time difference set for the movable cutter to swing from the thread-hooking position to the thread-trimming position.

[0012] Preferably, the swing arm of the transmission device has an end connected to the movable cutter via a link and another opposite end pivotally connected to the feed wheel supporting base, such that the swing arm can move to and fro between a contact position, in which the swing arm is in contact with the cam set, and a separation position, in which the swing arm is separated from the cam set.

[0013] In a preferred embodiment, the link includes a first link bar and a second link bar connected to the first link bar; and an adjustment device is provided between the first link bar and the second link bar for changing a relative position between the first link bar and the second link bar and accordingly, adjusting an overall length of the link. The adjustment device includes a plurality of screw holes and a plurality of elongated slots formed on the first link bar and the second link bar, respectively. The screw holes can be aligned with selected ones of the elongated slots using at least one screw.

[0014] Preferably, the return spring is mounted to between the swing arm and the feed wheel supporting base to ensure that the swing arm is normally located at the separation position. The actuator has an extendable rod, which can be extended toward and pushed against the swing arm, so that the swing arm is swung from the separation position to the contact position.

[0015] The present invention is characterized in that the fixed cutter of the cutter set is located behind the needle hole and the movable cutter of the cutter set can swing about a swing axis in parallel with the lower shaft to swing to and fro between the initial position, the thread-hooking position and the thread-trimming position. With these arrangements, only a relatively short loose thread end will be left on a workpiece being sewed when the sewing thread is cut by the movable cutter located at the thread-trimming position, so that a sewing operator does not need to trim the loose thread end for a second time.

[0016] Further, the present invention is characterized in that the relative position between the first cam and the second cam of the cam set can be selectively changed to thereby change the relative position between the rise path and the return path, allowing the adjustment of the swing time difference set for the movable cutter to swing from the thread-hooking position to the thread-trimming position.

[0017] Moreover, the present invention is characterized in that the adjustment device of the link enables change of a relative distance between the first and the second link bar to lengthen or shorten the overall length of the link and accordingly, to adjust a relative distance between the movable cutter at the initial position and the needle hole.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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 embodiment and the accompanying drawings, wherein

Fig. 1 is an exploded perspective view of a conventional thread trimmer for a post-bed sewing machine;

Fig. 2 is a cutaway view of a post-bed sewing machine, on which a thread trimmer according to the present invention is mounted;

Fig. 3 is an assembled perspective view showing a part of the mechanisms of the post-bed sewing machine of Fig. 2;

Fig. 4 is a fragmentary cutaway view showing the arrangement of the thread trimmer according to the present invention in a feed wheel supporting base of the post-bed sewing machine;

Fig. 5 is an exploded perspective view of the thread trimmer according to the present invention;

Fig. 6A shows a movable cutter of the thread trimmer according to the present invention is located at an initial position;

Fig. 6B shows the movable cutter of the thread trimmer according to the present invention is located at a thread-hooking position;

Fig. 6C shows the movable cutter of the thread trimmer according to the present invention is located at a thread-trimming position;

Figs. 7A and 7B show the manner of changing a relative position between a first cam and a second cam of the thread trimmer according to the present invention;

Fig. 8A shows a roller of the thread trimmer according to the present invention is located at a separation position without touching the first and second cams;

Fig. 8B shows the roller of the thread trimmer according to the present invention is located at a contact position to touch the first and second cams;

Figs. 9A and 9B show the manner of changing an overall length of a link of the thread trimmer according to the present invention;

Fig. 10 shows a return spring of the thread trimmer according to the present invention pulls a swing arm to a home position thereof;

Fig. 11 shows an actuator of the thread trimmer according to the present invention pushes the swing arm to swing upward;

Fig. 12A shows the thread trimmer of the present invention is in a state without performing a thread trimming operation;

Fig. 12B shows the thread trimmer of the present invention is in a state of performing a thread hooking operation; and

Fig. 12C shows the thread trimmer of the present invention is in a state of performing a thread trimming operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will now be described with a preferred embodiment thereof and by referring to the accompanying drawings.

[0020] Please refer to Fig. 2. The present invention provides a thread trimmer 2 to be mounted on a post-bed sewing machine 20. The post-bed sewing machine 20 includes a sewing head (not shown), a vertical stand (not shown) and a machine bed 21. The machine bed 21 forms a work table top 211, on which there are mounted a shuttle drive shaft base 22 adjustably movable in the x-axis direction and a feed wheel supporting base 23 located to a lateral side of the shuttle drive shaft base 22. A relative position between the shuttle drive shaft base 22 and a needle on the sewing head can be selectively changed.

[0021] Please refer to Figs. 2 and 3 at the same time. A lower shaft 24 and a lower feeder shaft 25 are provided inside the machine bed 21. The lower shaft 24 and the lower feeder shaft 25 can rotate about an axis in parallel with the x-axis. The shuttle drive shaft base 22 is upward extended in the direction of z-axis to form a shuttle drive shaft post 221. A shuttle drive shaft 222 is arranged in the shuttle drive shaft post 221 and is brought by the lower shaft 24 to rotate about an axis in parallel with the z-axis. The shuttle drive shaft 222 in turn rotates a shuttle 26 that is assembled to the shuttle drive shaft post 221.

[0022] As shown, the feed wheel supporting base 23 is upward extended in the direction of z-axis to form a feed wheel supporting post 231, which includes a feeding stand 231a, a needle plate holder 231b and a movable cutter holder 231c. The needle plate holder 231b is assembled to a top of the feeding stand 231a, and a needle plate 27 is assembled to the needle plate holder 231b. The needle plate 27 is formed with a needle hole 271, which is communicable with an interior of the feeding stand 231a. The needle (not shown) of the post-bed sewing machine 20 is extended through the needle hole 271 to move up and down in the direction of z-axis in a reciprocating motion. Further, the movable cutter holder 231c is fixedly connected to the feeding stand 231a of the feed wheel supporting post 231 by means of bolts and includes a curved rail 231d. The curved rail 231d has an open side oriented in a direction substantially in parallel with the x-axis, such that the curved rail 231d faces the shuttle 26. A lower transmission element 232 is arranged inside the feed wheel supporting post 231 of the feed wheel supporting base 23 and is brought by the lower feeder shaft 25 to rotate. Via a gearset, the lower transmission element 232 brings a lower feed wheel 28 assembled to the needle plate holder 231b to rotate about an axis in parallel with the x-axis. Further, the lower feed wheel 28 has an outer periphery that is partially protruded beyond a top surface of the needle plate holder 231b, such that the lower feed wheel 28 functions during a sewing operation to move a workpiece to be sewed up.

[0023] Please refer to Figs. 4 and 5, in which the machine bed 21, the shuttle drive shaft base 22, the shuttle drive shaft 222, the lower feeder shaft 25, the shuttle 26 and the lower feed wheel 28 of the post-bed sewing machine 20 are omitted from the drawings to better show the structural configuration of the thread trimmer 2. As shown, the thread trimmer 2 is assembled to the feed wheel supporting base 23 and mainly includes a cutter set 30 and a transmission device 40.

[0024] The cutter set 30 is arranged in the vicinity of the needle hole 271 on the needle plate 27, and is located between the shuttle 26 and the lower feed wheel 28. The cutter set 30 includes a fixed cutter 31, a movable cutter 32, and a thread-clamping spring plate 33. The fixed cutter 31 is mounted on the needle plate holder 231b to be located below the needle plate 27 and has a fixed blade 311 located close to the needle hole 271.

[0025] As shown, the movable cutter 32 of the cutter set 30 is located below the needle hole 271, such that the movable cutter 32 and the fixed cutter 31 are vertically aligned with each other. The movable cutter 32 includes a connecting pin 321, a hooking recess 322 formed near a tip of the movable cutter 32, a guiding section 323 formed on one side of the movable cutter 32 near the tip thereof, and a movable blade 324 formed behind the hooking recess 322. The movable cutter 32 is movably fitted in the curved rail 231d of the movable cutter holder 231c, such that the movable cutter 32 can swing in the curved rail 231d about a swing axis 231e, which is in parallel with the lower shaft 24. In the illustrated preferred embodiment, two pressing brackets 34 are mounted to the movable cutter holder 231c to partially cover the curved rail 231d, so that the movable cutter 32 is prevented from separating from the curved rail 231d.

[0026] Please refer to Figs. 6A to 6C, which respectively show the movable cutter 32 fitted in the curved rail 231d is located at an initial position 325 adjacent to the needle hole 271, a thread-hooking position 326 far away from the initial position 325, and a thread-trimming position 327 corresponding to the needle hole 271. The movable cutter 32 swings about the swing axis 231e to move between the above three positions. When the movable cutter 32 swings from the thread-hooking position 326 to the thread-trimming position 327, the hooking recess 322 on the movable cutter 32 is brought to pass a position immediately below the needle hole 271, so that the movable blade 324 is in contact with the fixed blade 311 to cut a sewing thread L that is extended through the needle hole 271, as shown in Fig. 12C.

[0027] Please refer to Figs. 4 and 5 again. The thread-clamping spring plate 33 of the cutter set 30 includes a mounting section 331 for mounting to the movable cutter holder 231c and a thread-clamping section 332 upward extended from an end of the mounting section 331. The thread-clamping spring plate 33 possesses a degree of elasticity, enabling the thread-clamping section 332 to elastically press against the movable cutter 32. Whereby, when the movable cutter 32 cuts the sewing thread L, the thread-clamping section 332 of the thread-clamping spring plate 33 is able to clamp a loose end of the sewing thread L released from the shuttle 26 between it and the movable cutter 32.

[0028] The transmission device 40 serves to bring the movable cutter 32 of the cutter set 30 to swing up and down about the swing axis 231e. That is, the movable cutter 32 is driven by the transmission device 40 to move from the initial position 325 to the thread-hooking position 326 and then the thread-trimming position 327 sequentially. As can be seen in Figs. 4 and 5, the transmission device 40 includes a fixing seat 41, a cam set 42, a link 43, a return spring 44, and an actuator 45. The fixing seat 41 is fixedly connected to the feed wheel supporting base 23, and the cam set 42 is mounted on the lower shaft 24 to rotate synchronously with the lower shaft 24 about an axis in parallel with the x-axis.

[0029] In the illustrated preferred embodiment, the cam set 42 includes a first cam 421 and a second cam 422, which is located to one side of the first cam 421. The first cam 421 has a first through hole 421a, through which the lower shaft 24 is extended, and a rise path 421b, which is located on an outer periphery of the first cam 421. The second cam 422 has a second through hole 422a, through which the lower shaft 24 is extended, and a return path 422b, which is located on an outer periphery of the second cam 422. The rise path 421b serves to drive the movable cutter 32 to swing from the thread-hooking position 326 to the thread-trimming position 327, while the return path 422b serves to drive the movable cutter 32 to swing from the initial position 325 to the thread-hooking position 326.

[0030] Please refer to Figs. 7A and 7B. A plurality of screws can be radially extended through a hub of the first cam 421 into the first through hole 421a, such that free end surfaces of the screws are simultaneously pressed against a circumferential surface of the lower shaft 24 to hold the first cam 421 immovable on around the lower shaft 24. Similarly, the second cam 422 is held immovable on around the lower shaft 24 by a plurality of screws in the same manner as the first cam 421.

[0031] However, when the screws are not fully extended into the first through hole 421a to press their free end surfaces against the surface of the lower shaft 24, the first cam 421 is able to rotate relative to the lower shaft 24. Accordingly, a relative position between the first cam 421 and the second cam 422 can be adjusted through rotating the first cam 421 relative to the lower shaft 24. At this point, a relative angular position between the rise path 421b and the return path 422b is simultaneously changed, which allows an adjustment of a swing time difference set for the movable cutter 32 to swing from the initial position 325 to the thread-hooking position 326, or from the thread-hooking position 326 to the thread-trimming position 327.

[0032] In the illustrated preferred embodiment, an included angle is formed between the rise path 421b and the return path 422b. When the first cam 421 is rotated relative to the lower shaft 24 to adjust the relative position between the first and the second cam 421, 422 and increase the included angle between the rise path 421b and the return path 422b, as shown in Fig. 7B, a swing time sequence for the movable cutter 32 to swing from the initial position 325 to the thread-hooking position 326 shall occur earlier, or a swing time sequence for the movable cutter 32 to swing from the thread-hooking position 326 to the thread-trimming position 327 shall be delayed. On the other hand, when the first cam 421 is rotated relative to the lower shaft 24 to adjust the relative position between the first and the second cam 421, 422 and decrease the included angle between the rise path 421b and the return path 422b, the swing time sequence for the movable cutter 32 to swing from the initial position 325 to the thread-hooking position 326 shall be delayed, or the swing time sequence for the movable cutter 32 to swing from the thread-hooking position 326 to the thread-trimming position 327 shall occur earlier.

[0033] Referring to Figs. 4 and 5, the link 43 of the transmission device 40 consists of a first link bar 431 and a second link bar 432. The first link bar 431 of the link 43 is assembled to the connecting pin 321 of the movable cutter 32; and the second link bar 432 is connected to a swing arm 434 via a link pin 433. The swing arm 434 is pivotally connected to the fixing seat 41 and includes a roller 435 for selectively pressing against the cam set 42. In the illustrated preferred embodiment, the second link bar 432 is pivotally connected to the link pin 433; and the roller 435 is able to press against the first cam 421 and the second cam 422 at the same time.

[0034] Please refer to Figs. 8A and 8B. Since the swing arm 434 is pivotally connected to the fixing seat 41, the roller 435 can rotate about an axis in parallel with the x-axis to move to and fro between a separation position 435a, in which the roller 435 is separated from the cam set 42, and a contact position 435b, in which the roller 435 is in contact with the cam set 42. During the to-and-fro movement of the roller 435 between the separation position 435a and the contact position 435b, the swing arm 434 can bring, via the link pin 433, the link 43 to move. In the illustrated preferred embodiment, the roller 435 in the contact position 435b is able to press against the rise path 421b or the return path 422b.

[0035] Please refer to Figs. 9A and 9B. An adjustment device 436 is provided between the first link bar 431 and the second link bar 432 for changing a relative position between the first link bar 431 and the second link bar 432. That is, with the adjustment device 436, the link 43 can be adjusted to an extended or a shortened overall length. As shown, the adjustment device 436 includes a plurality of screw holes 436a, a plurality of elongated slots 436b, and a plurality of screws 436c. The screw holes 436a and the elongated slots 436b are formed on the first link bar 431 and the second link bar 432, respectively. With this arrangement, the relative position between the first link bar 431 and the second link bar 432 can be finely adjusted to change a distance between the connection pin 321 and the link pin 433, and accordingly, to adjust a relative distance between the movable cutter 32 at the initial position 325 and the needle hole 271.

[0036] Please refer to Figs. 4, 10 and 11 at the same time. The return spring 44 has an end hooked to the link pin 433 on the swing arm 434 and another end hooked to a connecting plate 46 of the fixing seat 41. The return spring 44 serves to ensure that the roller 435 is normally located at the separation position 435a. However, it is understood the hooking of the two ends of the return spring 44 to the link pin 433 and the connecting plate 46, respectively, is only illustrative. In other operable embodiments, the return spring 44 can have its two ends hooked to the link 43 and the connecting plate 46, respectively, to achieve the same effect of keeping the roller 435 at the separation position 435a. The actuator 45 is assembled to the fixing seat 41 and has an extendable rod 451, which can be extended toward the swing arm 434 to push against the roller 435, so that the roller 435 is swung from the separation position 435a to the contact position 435b. In the illustrated preferred embodiment, the actuator 45 is configured as an electromagnet, which can be supplied with an electric current to produce a magnetic force for pushing the extendable rod 451 outward to an extended position.

[0037] Fig. 12A shows the post-bed sewing machine 20 is performing a sewing operation but not a thread trimming operation. In this state, the actuator 45 does not drive the extendable rod 451 to extend toward the swing arm 434 and the extendable rod 451 is not in contact with the roller 435. Meanwhile, the swing arm 434 is elastically pulled by the return spring 44 to bias downward, so that the roller 435 remains at the separation position 435a and is not in contact with the cam set 42 that is rotating now. When the roller 435 is located at the separation position 435a, the link 43 of the transmission device 40 also keeps the movable cutter 32 at the initial position 325.

[0038] Fig. 12B shows the post-bed sewing machine 20 has finished the last stitch in the sewing operation and is going to start the thread trimming operation. At this point, the needle is upward moved in the direction of z-axis to extend the sewing thread L through the workpiece and separate the sewing thread L from the needle hole 271. Thereafter, the actuator 45 is actuated, i.e., an electric current is supplied to the electromagnet, so that the actuator 45 drives the extendable rod 451 outward to push against the roller 435, bringing the roller 435 to swing from the separation position 435a to the contact position 435b.

[0039] At this point, an outer profile of the cam set 42 and the return path 422b sequentially press against the roller 435 and the upward moved extendable rod 451 causes the end of the swing arm 434 connected to the link 43 to bias and swing upward. Via the link 43, the upward biased swing arm 434 brings the movable cutter 32 to turn counterclockwise about the swing axis 231e from the initial position 325 to the thread-hooking position 326. At the thread-hooking position, the guiding section 323 of the movable cutter 32 automatically guides the sewing thread L to the hooking recess 322, so that the sewing thread L falls into the hooking recess 322.

[0040] Please refer to Fig. 12C, which shows the cam set 42 keeps rotating while the actuator 45 is disabled (i.e. current supply to the electromagnet is cut off), so that the extendable rod 451 is no longer pushed outward. At this point, the rise path 421b of the cam set 42 presses against the roller 435, bringing the end of the swing arm 434 connected to the link 43 to bias and swing downward. Therefore, via the link 43, the downward biased swing arm 434 brings the movable cutter 32 to turn clockwise about the swing axis 231e from the thread-hooking position 326 to the thread-trimming position 327, so that the movable blade 324 and the fixed blade 311 together cut the sewing thread L. Meanwhile, the thread-clamping section of the thread-clamping spring plate 33 is elastically pressed against the movable cutter 32, so that a loose thread end of the sewing thread L released from the shuttle 26 can be clamped between the thread-clamping section 332 and the movable cutter 32 when movable cutter 32 cuts the sewing thread L.

[0041] After completion of the thread trimming operation, the swing arm 434 is pulled by the return spring 44 to return to its home position and the movable cutter 32 is moved to the initial position 325 again.

[0042] The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment 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 trimmer of post-bed sewing machine, being assembled to a feed wheel supporting base of the post-bed sewing machine, the feed wheel supporting base including a feed wheel supporting post extended in the direction of z-axis and a rotatable lower shaft, and the feed wheel supporting post being provided with a needle hole, through which a sewing thread is extended; the thread trimmer comprising:

a cutter set including a fixed cutter fixedly mounted on the feed wheel supporting post and a movable cutter movably connected to the feed wheel supporting post, and the fixed cutter being located behind the needle hole; and

a transmission device being assembled to the movable cutter for driving the movable cutter to swing about a swing axis in parallel with the lower shaft, such that the movable cutter is sequentially movable between an initial position adjacent to the needle hole, a thread-hooking position far away from the initial position, and a thread-trimming position corresponding to the needle hole for sewing thread trimming.

2. The thread trimmer of post-bed sewing machine as claimed in claim 1, wherein the feed wheel supporting post includes:

a feeding stand;

a needle plate holder being connected to between the feeding stand and the fixed cutter with a needle plate assembled thereto, and the needle hole being formed on the needle plate; and

a movable cutter holder being fixedly connected to the feeding stand and including a curved rail, and the movable cutter being received in the curved rail to swing along the curved rail.

3. The thread trimmer of post-bed sewing machine as claimed in claim 1, wherein the movable cutter includes a hooking recess adapted to receive the sewing thread therein and a guiding section for guiding the sewing thread to the hooking recess; and a movable blade being formed at an end of the hooking recess to correspond to the fixed cutter.

4. The thread trimmer of post-bed sewing machine as claimed in claim 1, wherein the cutter set further includes a thread-clamping spring plate, which has an end assembled to the feed wheel supporting post and another opposite end elastically pressing against the movable cutter.

5. The thread trimmer of post-bed sewing machine as claimed in claim 1, wherein the transmission device includes:

a cam set being mounted on the lower shaft to rotate synchronously with the lower shaft;

a swing arm having an end connected to the movable cutter via a link and another opposite end pivotally connected to the feed wheel supporting base; and

an actuator having an extendable rod, which can be extended toward and pushed against the swing arm, so that the swing arm is swung from a separation position, in which the swing arm is separated from the cam set, to a contact position, in which the swing arm is in contact with the cam set.

6. The thread trimmer of post-bed sewing machine as claimed in claim 5, wherein the cam set includes a first cam and a second cam; and the first cam being rotatable relative to the lower shaft to selectively change a relative position between the first cam and the second cam.

7. The thread trimmer of post-bed sewing machine as claimed in claim 5, wherein the link consists of a first link bar and a second link bar connected to the first link bar; and an adjustment device being provided between the first link bar and the second link bar for changing a relative position between the first link bar and the second link bar and accordingly, adjusting an overall length of the link.

8. The thread trimmer of post-bed sewing machine as claimed in claim 5, wherein the transmission device further includes a return spring; and the return spring having an end connected to the feed wheel supporting base and another opposite end connected to the swing arm or the link to ensure that the swing arm is normally located at the separation position.

Drawing