CN214992295U - Feed dog assembly, thread cutting mechanism and presser foot lifting mechanism of sewing machine - Google Patents

Abstract

The application provides a feed dog assembly and a thread cutting and presser foot lifting mechanism of a sewing machine, in particular to the technical field of sewing machine manufacture, which is provided with the feed dog assembly, the thread cutting and presser foot lifting mechanism, an up-down lifting power source and a front-back feed power source, the feed dog assembly of the application only adopts the up-down lifting power source to execute the thread cutting action and the presser foot lifting action of the thread cutting and presser foot lifting mechanism under the common drive of the up-down lifting power source and the front-back feed power source, realizes that the thread cutting action and the presser foot lifting action are executed by a single up-down lifting power source, and the cloth feeding action is continuously executed after the up-down lifting power source and the front-back cloth feeding power source jointly execute the cloth feeding action, thereby not only improving the utilization rate of the power device of the sewing machine, but also further improves the intelligent control level of the power system of the sewing machine, saves power sources required by thread cutting action and presser foot lifting action, and has higher popularization and use values.

Description

Feed dog assembly, thread cutting mechanism and presser foot lifting mechanism of sewing machine

Technical Field

The application provides a feed dog subassembly, thread trimming mechanism and lift presser foot mechanism of sewing machine, concretely relates to sewing machine makes technical field.

Background

The feed dog is one of essential parts for sewing machine to realize sewing work. The company previously provides a cloth feeding tooth assembly of a separate sewing machine, and the specific scheme is that a non-lateral swinging source is applied to the cloth feeding tooth by an up-down motor and a front-back cloth feeding motor which are arranged on the cloth feeding tooth assembly, the up-down motor and the front-back cloth feeding motor indirectly act on the cloth feeding tooth to perform cloth feeding action, the front-back cloth feeding motor drives a turntable and then drives a connecting rod, the connecting rod is movably connected to the eccentric position of the turntable, and the connecting rod is movably connected with a cloth feeding tooth connecting frame. The cloth feeding tooth assembly is transmitted to a swing source by utilizing an up-down lifting motor and a front-back cloth feeding motor, and the cloth feeding tooth assembly can be additionally arranged on a bottom thread mechanism and can be manufactured into a modularized matching manner to be used on various sewing machines. In the sewing machine, a thread cutting and presser foot lifting device needs to be additionally arranged, and power for driving the thread cutting and presser foot lifting is required to be additionally arranged, so that the manufacturing cost of the sewing machine is increased.

Disclosure of Invention

The cloth feeding tooth assembly is driven by the up-down lifting power source and the front-back cloth feeding power source together, the up-down lifting power source and the front-back cloth feeding power source act on the cloth feeding tooth assembly together to execute cloth feeding action of the sewing machine, and the up-down lifting power source starts to drive the cloth cutting mechanism and the presser foot lifting mechanism successively to execute the wire cutting action and the presser foot lifting action after the cloth feeding action of the cloth feeding tooth assembly is completed.

Preferably, the front and rear cloth feeding power source has an output shaft provided with a crank; the cloth feeding mechanism is characterized in that a synchronous belt wheel is mounted on an output shaft of the up-and-down lifting power source, the crank indirectly acts on the cloth feeding tooth frame to realize front and back cloth feeding actions of the cloth feeding tooth assembly, the synchronous belt wheel indirectly acts on the multi-stage cam I and the multi-stage cam II to realize up-and-down lifting cloth feeding actions of the cloth feeding tooth assembly, a front output shaft of the up-and-down lifting power source executes a wire cutting action of the wire cutting mechanism, and a rear output shaft of the up-and-down lifting power source executes a presser foot lifting action of the presser foot lifting mechanism.

Preferably, the crank mounted on the output shaft is hinged to the oscillating rod, the crank drives the oscillating rod to operate, the oscillating rod is hinged to the cloth feeding dental frame, a support shaft is arranged on the cloth feeding dental frame, the support shaft is in clearance fit with the cloth feeding dental frame, the support shaft extends out of the cloth feeding dental frame and extends to two ends of the support, and the cloth feeding dental frame operates in the support.

Preferably, a synchronous pulley is mounted on a front output shaft of the up-down lifting power source, the synchronous pulley drives a synchronous pulley II and a synchronous pulley III to be connected with a multi-stage cam I and a multi-stage cam II through a synchronous belt, the multi-stage cam I and the multi-stage cam II are respectively arranged at two ends of the bottom of the support, and the multi-stage cam I and the multi-stage cam II are provided with a salient point I and a salient point II.

Preferably, the first multi-stage cam is fixed on the first rotating shaft and the second multi-stage cam is fixed on the second rotating shaft, and the first rotating shaft and the second rotating shaft are sleeved on the feed dog fixing support.

Preferably, the feed dog fixing support is further provided with a first limiting support and a second limiting support, the first limiting support and the second limiting support can fix an up-down lifting power source and a front-back feed power source, the first limiting support and the second limiting support are further provided with a first limiting block and a second limiting block, the first limiting block and the second limiting block are used for limiting the running position of the feed dog frame and/or the support, the feed dog assembly is further provided with a swing arm, and the feed dog fixing support is provided with a swing arm hole.

Preferably, the trimming crank is installed to the preceding output shaft of oscilaltion power supply, the trimming crank acts on the trimming fork arm, the trimming fork arm has trimming pole and return pole, the trimming crank has the axle sleeve, the axle sleeve is located between trimming pole and the return pole, is used the trimming end by the trimming fork arm again and carries out the end realization trimming action.

Preferably, the shaft sleeve of the thread cutting shaft sleeve pushes the thread cutting rod to cut threads, the shaft sleeve of the thread cutting shaft sleeve pushes the return rod to return the threads, and the thread cutting rod and the return rod can be interchanged in the upper position and the lower position of the thread cutting fork rod.

Preferably, a pressure foot lifting cam is mounted on a rear output shaft of the up-down lifting power source, a cam part of the up-down lifting power source for driving the pressure foot lifting cam acts on a pressure foot lifting ejector rod, and then the pressure foot lifting ejector rod acts on an end execution end of the pressure foot lifting to execute pressure foot lifting action.

Preferably, a first gear is mounted on a front output shaft of the up-down lifting power source, the multi-stage cam is mounted on a first rotating shaft, a second multi-stage cam is mounted on a second rotating shaft, the first rotating shaft and the second rotating shaft penetrate through the feed dog fixing support, a fourth gear and a third gear are mounted on the first rotating shaft and the second rotating shaft of the feed dog fixing support, and the fourth gear is meshed with the third gear.

Preferably, a second gear is additionally arranged behind the fourth gear of the first rotating shaft or the third gear of the second rotating shaft, the additionally arranged second gear is meshed with the first gear, and the second gear is driven by the second gear and is connected with the fourth gear and the third gear in parallel.

Compared with the prior art, the cloth feeding tooth assembly fully embodies the cloth feeding function of the cloth feeding tooth assembly for executing the sewing machine under the common drive of the up-down lifting power source and the front-back cloth feeding power source, and simultaneously, only the up-down lifting power source is adopted for executing the thread cutting action of the thread cutting mechanism and the presser foot lifting action of the presser foot lifting mechanism, so that the thread cutting action and the presser foot lifting action are executed by a single up-down lifting power source, and the thread cutting action and the presser foot lifting action are continuously executed after the up-down lifting power source and the front-back cloth feeding power source jointly execute the cloth feeding action.

Drawings

FIG. 1 is a general view of a feed dog assembly, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine of the present application;

FIG. 2 is a front view of a feed dog assembly of a sewing machine, a thread trimming mechanism and a presser foot lifting mechanism of the present application;

FIG. 3 is a view showing a feed dog assembly of a sewing machine according to the present application;

FIG. 4 is an exploded view of a feed dog assembly of a sewing machine, a thread trimming mechanism and a presser foot lifting mechanism of the present application;

FIG. 5 is a view of the feed dog swing lever position of the feed dog assembly, thread trimming mechanism and presser foot lifting mechanism of a sewing machine according to the present application;

FIG. 6 is a view of the support structure of a feed dog assembly, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine according to the present application;

FIG. 7 is a gear scheme diagram of a second embodiment of a feed dog assembly, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine according to the present application.

Reference numerals: the cloth feeding tooth assembly 10, the cloth feeding tooth frame 11, a multi-stage cam I12, a rotating shaft I121, a multi-stage cam II 13, a rotating shaft II 131, a swing amplitude rod 14, a supporting shaft 15, a support 16, a convex point I161, a convex point II 162, a swing amplitude hole 163, a limiting block I164, a limiting block II 165, a limiting support I166, a limiting support II 167, a swing rod 18, a thread cutting mechanism 20a, a presser foot lifting mechanism 20b, a presser foot lifting cam 21, a presser foot lifting ejector rod 22, a thread cutting crank 23, a shaft sleeve 231, a thread cutting fork rod 24, a thread cutting rod 241, a return rod 242, a thread cutting end execution end 25, an up-and-down lifting power source 30, a front output shaft 31, a rear output shaft 32, a front-back cloth feeding power source 40, an output shaft 41, a crank 42, a synchronous belt wheel 51, a synchronous belt wheel II 52, a synchronous belt wheel III 53, a cloth feeding tooth fixing support 6, a gear I71, a gear II 72, a gear III 73 and a gear IV 74.

Detailed Description

Preferred embodiments of the present application will be described in detail below with reference to fig. 1 to 7, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the scope of protection of the present application will be clearly and clearly defined, and these embodiments are only for illustrating the present invention and are not limited thereto.

Example one

In fig. 1-6, the present application provides a feed dog assembly, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine, which comprises a feed dog assembly 10, a thread trimming mechanism 20a, a presser foot lifting mechanism 20b, an up-down lifting power source 30 and a front-back feed power source 40. The feed dog assembly 10 is driven by the up-down power source 30 and the front-back feed power source 40, and the up-down power source 30 and the front-back feed power source 40 act on the feed dog assembly 10 together to perform the feed operation of the sewing machine, so that the feed dog assembly 10 has a feed function which is necessary for the sewing machine. After the cloth feeding action of the cloth feeding tooth assembly 10 is completed, the vertical lifting power source 30 starts to drive the thread cutting mechanism 20a and the presser foot lifting mechanism 20b to execute the thread cutting action and the presser foot lifting action, firstly, a front output shaft 31 installed on the vertical lifting power source 30 executes the thread cutting action of the thread cutting mechanism 20a, and then, a rear output shaft 32 installed on the vertical lifting power source 30 executes the presser foot lifting action of the presser foot lifting mechanism 20 b. According to the sewing machine, the front and rear cloth feeding power sources 40 of the cloth feeding tooth assembly 10 are used for executing the presser foot lifting action and the thread cutting action after the cloth feeding action is completed, the power utilization rate of the sewing machine is improved, the power required for executing the presser foot lifting action and the thread cutting action in the prior art is saved, and the manufacturing cost of the sewing machine is greatly reduced.

A crank 42 is attached to an output shaft 41 of the front and rear cloth feeding power source 40; the synchronous pulley 51 is mounted on the output shaft 41 of the up-down movement power source 30, the crank 42 indirectly acts on the feed dog frame 11 to realize the front-back feed motion of the feed dog assembly 10, the synchronous pulley 51 indirectly acts on the multi-stage cam one 12 and the multi-stage cam two 13 to realize the up-down movement of the feed dog assembly 10, and the front-back feed motion and the up-down movement simultaneously realize the feed motion of the sewing machine.

In the cloth feeding action corner area of the front and rear cloth feeding power source 40, a crank 42 mounted on an output shaft 41 is hinged to the oscillating rod 18, the crank 42 drives the oscillating rod 18 to rotate, and the oscillating rod 18 is hinged to the cloth feeding tooth frame 11 to enable the output shaft 41 to generate a front-and-back oscillating source for the cloth feeding tooth frame 11. The cloth feeding tooth rack 11 is provided with a support shaft 15, the support shaft 15 is in clearance fit with the cloth feeding tooth rack 11, the support shaft 15 extends out of the cloth feeding tooth rack 11 and extends to two ends of a support 16, and the cloth feeding tooth rack 11 operates in the support 16. The front and rear feed power sources 40 drive the crank 42 to swing the swing lever 18 and thus the feed dog 11 forward and backward.

A synchronous pulley 51 is mounted on the front output shaft 31 of the up-down lifting power source 30, the synchronous pulley 51 drives a second synchronous pulley 52 and a third synchronous pulley 53 through a synchronous belt to be connected and act on the first multi-stage cam 12 and the second multi-stage cam 13 to realize the up-down lifting cloth feeding action of the whole cloth feeding tooth assembly 10, and the first multi-stage cam 12 and the second multi-stage cam 13 are respectively positioned at two ends of the bottom of the bracket 16. The up-down lifting power source 30 drives the second synchronous pulley 52 and the third synchronous pulley 53 in a power source cloth feeding action corner area, specifically, the first multi-stage cam 12 is fixed on the first rotating shaft 121 and the second multi-stage cam 13 is fixed on the second rotating shaft 131, and the first rotating shaft 121 and the second rotating shaft 131 are sleeved on the cloth feeding tooth fixing support 6. The first multi-stage cam 12 and the second multi-stage cam 13 are provided with a first protruding point 161 and a second protruding point 162, and the first protruding point 161 and the second protruding point 162 are driven by the vertical lifting power source 30 to enable the bracket 16 to generate a vertical lifting swing source to the whole feed dog assembly 10.

The feed dog subassembly 10 of this application is fixed on feed dog fixed bolster 6, and above-mentioned feed dog subassembly 10 still has a pendulum width of cloth pole 14, pendulum width of cloth pole 14 is the cylinder type. The feed dog fixing support 6 has a swing hole 163, the swing hole 163 is provided to the swing rod 14 to provide a space for the vertical movement, and the swing of the swing source of the multi-stage cam one 12 and the multi-stage cam two 13 is limited by the swing hole 163 of the feed dog fixing support 6. In addition, the feed dog fixing support 6 is also provided with a first limit support 166 and a second limit support 167 which can fix the up-down lifting power source 30 and the front-back feed power source 40, and the first limit support 166, the second limit support 167 and the feed dog fixing support 6 body form a whole. The feed dog fixing support 6 is further provided with a first limiting block 164 and a second limiting block 165, and the first limiting block 164 and the second limiting block 165 are used for limiting the operation position of the feed dog frame 11 and/or the support 16, so that the feed dog assembly 10 has a fixed operation structure.

After the cloth feeding operation of the sewing machine is completed, the vertical lifting power source 30 starts to perform the thread cutting operation and the presser foot lifting operation. The front output shaft 31 of the up-down lifting power source 30 is provided with a thread cutting crank 23, the thread cutting crank 23 acts on the thread cutting fork rod 24, and then the thread cutting fork rod 24 acts on the thread cutting end execution end 25 to realize thread cutting action. The thread cutting fork rod 24 is provided with a thread cutting rod 241 and a return rod 242, the thread cutting crank 23 is provided with a shaft sleeve 231, the shaft sleeve 231 is positioned between the thread cutting rod 241 and the return rod 242, the shaft sleeve 231 pushes the thread cutting rod 241 to cut threads, and the shaft sleeve 231 pushes the return rod 242 to return the threads. The above-mentioned thread trimming rod 241 and the return rod 242 can be interchanged in the up-down position of the thread trimming fork rod 24, and the technical effects achieved by the above-mentioned thread trimming rod 241 and the return rod 242 are the same.

The presser foot lifting cam 21 is attached to the rear output shaft 32 of the up-down power source 30, the cam portion of the presser foot lifting cam 21 is acted on the presser foot lifting jack 22 by the driving of the up-down power source 30, and the presser foot lifting jack 22 acts on the presser foot end execution end to execute the presser foot lifting action.

The operation corners of the front and rear cloth feeding power source 40 where the cloth feeding action, the presser foot lifting action and the thread cutting action are located are a cloth feeding action corner area, a presser foot lifting action corner area and a thread cutting action corner area, respectively. The sewing operation sequence executed by the front and rear cloth feeding power source 40 is a cloth feeding operation, a thread cutting operation and a presser foot lifting operation. It is worth mentioning that after the front and back cloth feeding power source 40 finishes the cloth feeding action and the sewing machine stops, the front and back cloth feeding power source 40 shifts the operation corner to execute the thread cutting action and the presser foot lifting action, in other words, the cloth feeding action, the presser foot lifting action and the thread cutting action are not overlapped in the corner area where the front and back cloth feeding power source 40 operates, and after the sewing machine stops, the thread is firstly cut and then the presser foot is lifted.

In the feed operation corner region, the crank 42 is hinged to the swing lever 18 to generate a forward and backward feed swing source to the feed dog 11. When the sewing is finished, the front and rear cloth feeding power sources 40 leave from the cloth feeding action corner area and enter the presser foot lifting action corner area and the thread cutting action corner area. Since the idle circular arc surfaces of the first multi-stage cam 12 and the second multi-stage cam 13 contact under the support 16 when the vertical lifting power source 30 performs the corner region of the presser foot lifting action and the corner region of the thread cutting action, the vertical lifting power source 30 does not generate vertical lifting action on the support 16, and the front and rear cloth feeding power sources 40 are in a stop state, the whole cloth feeding dog assembly 10 is stationary. Similarly, when the front and rear cloth feeding power sources 40 operate in the cloth feeding operation corner region, the shaft sleeve 231 of the thread cutting crank 23 idles back and forth between the thread cutting rod 241 and the return rod 242 at the thread cutting fork rod 24; the circular arc surface of the presser foot lifting cam 21 also idles back and forth to the presser foot lifting mandril 22, so that the cloth feeding action, the presser foot lifting action and the thread cutting action executed by the front and back cloth feeding power source 40 are not influenced mutually, and the actions are clear and distinct.

Example two

The second embodiment is basically the same as the first embodiment, but different from the first embodiment in that the vertical lifting/lowering power source 30 generates a swing source for the feed dog assembly 10. In fig. 7, the vertical movement power source 30 also performs the sewing operation of the feed dog assembly 10 by means of gear transmission. The first gear 71 is mounted on the front output shaft 31 of the up-down lifting power source 30, the first multi-stage cam 12 is mounted on the first rotating shaft 121, and the second multi-stage cam 13 is mounted on the second rotating shaft 131. The first rotating shaft 121 and the second rotating shaft 131 penetrate through the feed dog fixing support 6, a fourth gear 74 and a third gear 73 are installed on the first rotating shaft 121 and the second rotating shaft 131 penetrating through the feed dog fixing support 6, and the fourth gear 74 is meshed with the third gear 73. In this embodiment, a second gear 72 is additionally installed behind the fourth gear 74 of the first rotating shaft 121 or the third gear 73 of the second rotating shaft 131, the additional second gear 72 is meshed with the first gear 71, and the first gear 71 drives the second gear 72 to be connected with the fourth gear 74 and the third gear 73 in parallel.

Alternatively, the first gear 71 directly meshes with the second gear 72, and the second gear 72 is omitted, so that the above-mentioned technical effects can be achieved. Under the driving of the up-down lifting power source 30, the gear i 71 mounted on the front output shaft 31 drives the rotating shaft i 121 or the rotating shaft ii 131 through the gear ii 72 mounted additionally, so that the technical effects of the swing source generated by the feed dog assembly 10 are the same.

The above description is only a preferred embodiment of the present application, and not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application, or which are directly or indirectly applied to other related technical fields, are also included in the scope of the present application.

Claims (11)

1. The cloth feeding tooth assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine are provided with the cloth feeding tooth assembly (10), the thread cutting mechanism (20a), the presser foot lifting mechanism (20b), an up-down power source (30) and a front-back cloth feeding power source (40), and are characterized in that the cloth feeding tooth assembly (10) is driven by the up-down power source (30) and the front-back cloth feeding power source (40) together, the up-down power source (30) and the front-back cloth feeding power source (40) act on the cloth feeding tooth assembly (10) together to execute the cloth feeding action of the sewing machine, and the up-down power source (30) starts to drive the thread cutting mechanism (20a) and the presser foot lifting mechanism (20b) to execute the thread cutting action and the presser foot lifting action after the cloth feeding action of the cloth feeding tooth assembly (10) is completed.

2. The feed dog assembly, thread trimming mechanism and presser foot lifting mechanism of the sewing machine according to claim 1, wherein the front and rear feed power sources (40) have output shafts (41) to which cranks (42) are attached; a synchronous belt wheel (51) is installed on an output shaft (41) of the up-and-down lifting power source (30), the crank (42) indirectly acts on the cloth feeding tooth rack (11) to realize the front-and-back cloth feeding action of the cloth feeding tooth assembly (10), the synchronous belt wheel (51) indirectly acts on the multi-stage cam I (12) and the multi-stage cam II (13) to realize the up-and-down lifting cloth feeding action of the cloth feeding tooth assembly (10), a front output shaft (31) of the up-and-down lifting power source (30) executes the wire shearing action of the wire shearing mechanism (20a), and a rear output shaft (32) of the up-and-down lifting power source (30) executes the pressure lifting action of the pressure lifting foot mechanism (20 b).

3. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 2, wherein a crank (42) mounted on the output shaft (41) is hinged to the swing lever (18), the crank (42) drives the swing lever (18) to operate, the swing lever (18) is hinged to the feed dog frame (11), a support shaft (15) is arranged on the feed dog frame (11), the support shaft (15) is in clearance fit with the feed dog frame (11), the support shaft (15) extends out of the feed dog frame (11) and extends to two ends of the support (16), and the feed dog frame (11) operates in the support (16).

4. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 1, wherein a synchronous pulley (51) is mounted on a front output shaft (31) of the up-down lifting power source (30), the synchronous pulley (51) drives a synchronous pulley II (52) and a synchronous pulley III (53) to connect a multi-stage cam I (12) and a multi-stage cam II (13) through a synchronous belt, the multi-stage cam I (12) and the multi-stage cam II (13) are respectively arranged at two ends of the bottom of the support (16), and the multi-stage cam I (12) and the multi-stage cam II (13) are provided with a salient point I (161) and a salient point II (162).

5. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 2 or 4, wherein the first multi-stage cam (12) is fixed on the first rotating shaft (121) and the second multi-stage cam (13) is fixed on the second rotating shaft (131), and the first rotating shaft (121) and the second rotating shaft (131) are sleeved on the feed dog fixing support (6).

6. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 5, wherein the feed dog fixing bracket (6) further comprises a first limit bracket (166) and a second limit bracket (167) which can fix the ascending and descending power source (30) and the front and rear feed power sources (40), the feed dog fixing bracket (6) further comprises a first limit block (164) and a second limit block (165), the first limit block (164) and the second limit block (165) are used for limiting the running position of the feed dog frame (11) and/or the bracket (16), the feed dog assembly (10) further comprises a swing arm (14), and the feed dog fixing bracket (6) is provided with a swing arm hole (163).

7. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine according to claim 1, wherein the thread cutting crank (23) is mounted on a front output shaft (31) of the up-down power source (30), the thread cutting crank (23) acts on the thread cutting fork rod (24), the thread cutting fork rod (24) is provided with a thread cutting rod (241) and a return rod (242), the thread cutting crank (23) is provided with a shaft sleeve (231), the shaft sleeve (231) is positioned between the thread cutting rod (241) and the return rod (242), and then the thread cutting action is realized by the action of the thread cutting fork rod (24) acting on the thread cutting end actuating end (25).

8. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine according to claim 7, wherein the bushing (231) pushes the thread cutting rod (241) to perform thread cutting, the bushing (231) pushes the return rod (242) to perform thread cutting return, and the thread cutting rod (241) and the return rod (242) are interchangeable in the up-down position of the thread cutting fork rod (24).

9. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 7, wherein a presser foot lifting cam (21) is attached to a rear output shaft (32) of the up-down and down-down power source (30), and a cam portion of the presser foot lifting cam (21) driven by the up-down and down-down and up-down power source (30) acts on a presser foot lifting jack (22), and further acts on a presser foot lifting end execution end by the presser foot lifting jack (22) to execute a presser foot lifting action.

10. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 2, wherein a first gear (71) is mounted on a front output shaft (31) of the up-down lifting power source (30), the first multi-stage cam (12) is mounted on a first rotating shaft (121), the second multi-stage cam (13) is mounted on a second rotating shaft (131), the first rotating shaft (121) and the second rotating shaft (131) penetrate through the feed dog fixing support (6), a fourth gear (74) and a third gear (73) are mounted on the first rotating shaft (121) and the second rotating shaft (131) of the feed dog fixing support (6), and the fourth gear (74) and the third gear (73) are meshed.

11. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 10, wherein a second gear (72) is additionally provided behind a fourth gear (74) of the first rotating shaft (121) or a third gear (73) of the second rotating shaft (131), the additional second gear (72) is meshed with the first gear (71), and the first gear (71) drives the second gear (72) and links the fourth gear (74) and the third gear (73).

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