CN115369578A - Feed dog assembly, thread cutting mechanism and presser foot lifting mechanism of sewing machine - Google Patents

Abstract

The application provides a work feed tooth subassembly, thread trimming mechanism and lift presser foot mechanism of sewing machine, concretely relates to sewing machine makes technical field, including work feed tooth subassembly, oscilaltion power supply and front and back work feed power supply, work feed tooth subassembly is driven by oscilaltion power supply and front and back work feed power supply jointly, the work feed action that work feed tooth subassembly carried out sewing machine is acted on to work feed tooth subassembly around the oscilaltion power supply and the front and back work feed power supply, the preceding output shaft that the work feed power supply had carries out the thread trimming action of thread trimming mechanism around, the back output shaft that the work feed power supply had around carries out the presser foot action of lifting of presser foot mechanism. This application single power device just can realize the trimming action and lift the presser foot action under sewing machine's electrical system control, has effectively improved the availability factor of sewing machine power, has reduced sewing machine's manufacturing cost by a wide margin for sewing machine's intelligent control level can further improvement, has higher use spreading value.

Description

Cloth feeding tooth 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 an essential part for realizing sewing work. The scheme is that a non-lateral swinging source is applied to the feed dog by an up-down driving source and a front-back feed driving source which are arranged on the feed dog assembly, the up-down driving source and the front-back feed driving source indirectly act on the feed dog to carry out feed action, the front-back feed driving source drives a turntable to drive 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 feed dog connecting frame. The cloth feeding tooth component transmits a swing source by utilizing an up-and-down lifting driving source and a front-and-back cloth feeding driving source, and the cloth feeding tooth component can be additionally arranged on a bottom thread mechanism and can be manufactured into a modularized matching mode 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 a power device for driving the thread cutting and presser foot lifting action needs to be additionally arranged, so that the manufacturing cost of the sewing machine is increased.

Disclosure of Invention

The sewing machine comprises a cloth feeding tooth assembly, an up-down power source, a front cloth feeding power source and a back cloth feeding power source, and is characterized in that the cloth feeding tooth assembly is driven by the up-down power source and the back cloth feeding power source together, the up-down power source and the back cloth feeding power source act on the cloth feeding tooth assembly to execute cloth feeding action of the sewing machine, a front output shaft of the back cloth feeding power source executes thread cutting action of the thread cutting mechanism, and a back output shaft of the back cloth feeding power source executes thread lifting action of the thread lifting mechanism.

Preferably, a synchronizing wheel is mounted on the front output shaft, the synchronizing wheel indirectly drives a first multi-stage cam and a second multi-stage cam to achieve cloth feeding component up and down lifting and cloth feeding actions, a cam is mounted on an output shaft of the up and down lifting power source, the cam indirectly acts on a cloth feeding tooth frame to achieve front and back cloth feeding actions of the cloth feeding tooth component, a thread cutting crank is mounted on the front output shaft, the thread cutting crank acts on a thread cutting fork rod and then performs thread cutting actions through a thread cutting tail execution end, a presser foot lifting cam is mounted on the rear output shaft, the presser foot lifting cam acts on a presser foot lifting ejector rod and then performs presser foot lifting actions through a presser foot lifting tail execution end.

Preferably, the up-down lifting power source realizes the front-back cloth feeding action of the cloth feeding tooth assembly by means of a connecting rod or a synchronizing wheel or a gear; the front and back cloth feeding power sources realize the up-and-down cloth feeding action of the cloth feeding tooth assembly by the technical means of a cam, a connecting rod or a synchronizing wheel.

Preferably, the cam is matched with a swing rod, the cam drives the swing rod, the swing rod is hinged with the cloth feeding tooth rack, the operation positioning groove of the cam is matched with a swing shaft sleeve of the swing rod, and the swing shaft sleeve of the swing rod idles at the operation positioning groove.

Preferably, the first multi-stage cam and the second multi-stage cam are respectively arranged at two ends of the bottom of a support of the sewing machine, the first multi-stage cam and the second multi-stage cam are respectively fixed on the first rotating shaft and the second rotating shaft, the first multi-stage cam and the second multi-stage cam are provided with a first salient point and a second salient point, and the first salient point and the second salient point act on the bottom of the support.

Preferably, a synchronous belt is sleeved on the first synchronous belt wheel, and the first synchronous belt wheel drives a second synchronous belt wheel of the first multi-stage cam; the second synchronous belt wheel drives a third synchronous belt wheel of the multi-stage cam.

Preferably, the feed dog assembly is fixed on a feed dog fixing support, the feed dog assembly is further provided with a swing amplitude rod, the swing amplitude rod is cylindrical, the swing amplitude hole is provided with a space for the swing amplitude rod to ascend and descend, the ascending and descending power source and the front and rear feed power sources are provided with a first fixing support and a second fixing support, the first fixing support, the second fixing support and the feed dog fixing support body form a feed dog fixing support whole, the feed dog fixing support is further provided with a first limiting block and a second limiting block, the first limiting block and the second limiting block are used for the feed dog support and/or the support, a support shaft is arranged on the feed dog support, the support shaft is fixed on the feed dog support and extends to two ends of the support, and the support shaft is positioned at two ends of the support in a clearance fit mode.

Preferably, the front output shaft of the front and rear cloth feeding power sources is provided with a wire cutting crank, the wire cutting crank acts on a wire cutting fork rod, the wire cutting fork rod is provided with a wire cutting rod and a return rod, the wire cutting crank is provided with a shaft sleeve, the shaft sleeve is positioned between the wire cutting rod and the return rod, and the shaft sleeve idles back and forth between the wire cutting rod and the return rod at the wire cutting fork rod.

Preferably, a rear output shaft of the front and rear cloth feeding power source is provided with a presser foot lifting cam, a cam part of the presser foot lifting cam acts on a presser foot lifting push rod, and the presser foot lifting push rod acts on a presser foot lifting tail end execution end to execute a presser foot lifting action.

Preferably, the operation turning angles of the front and rear cloth feeding power sources are respectively a cloth feeding action turning angle area, a presser foot lifting action turning angle area and a thread cutting action turning angle area, the sewing actions performed by the front and rear cloth feeding power sources are respectively a cloth feeding action, a thread cutting action and a presser foot lifting action, and the operation positioning groove formed by the presser foot lifting action turning angle area and the thread cutting action turning angle area is concentric with the rear output shaft.

Compared with the prior art, the cloth feeding tooth assembly is driven by the up-down power source and the front-back cloth feeding power source to execute the cloth feeding action of the sewing machine together, the front-back cloth feeding power source executes the thread cutting action and the presser foot lifting action by utilizing the vacant time of executing the cloth feeding tooth action, and a single power device can realize the thread cutting action and the presser foot lifting action under the control of an electric control system of the sewing machine, so that the use efficiency of the power of the sewing machine is effectively improved, the manufacturing cost of the sewing machine is greatly reduced, the intelligent control level of the sewing machine is further improved, and the cloth feeding tooth assembly has high use and popularization values.

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 side 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 structural view of a cam mounted on the front output shaft of the feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to the present application;

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

FIG. 7 is a view of the thread trimming mechanism configuration of the feed dog assembly, thread trimming mechanism and presser foot lifting mechanism of a sewing machine according to the present application;

FIG. 8 is a schematic view of a feed dog assembly of a sewing machine, a thread trimming mechanism and a feed dog assembly of a presser foot lifting mechanism according to the present application;

FIG. 9 is a view showing the construction of a feed dog fixing bracket 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 are as follows: the cloth feeding tooth assembly 1a, the thread cutting mechanism 1b, the presser foot lifting mechanism 1c, the up-down lifting power source 10, the cam 11, the positioning groove 111, the cloth feeding tooth frame 12, the output shaft 13, the support shaft 15, the support 16, the swing rod 17, the swing rod 18, the swing shaft sleeve 181, the front-back cloth feeding power source 20, the cloth feeding action corner area 2a, the presser foot lifting action corner area 2b, the thread cutting action corner area 2c, the front output shaft 21, the synchronous pulley one 211, the multi-stage cam one 212, the salient point one 2121, the multi-stage cam two 213, the salient point two 2131, the synchronous pulley two 214, the synchronous pulley three 215, the rotating shaft one 216, the rotating shaft two 217, the rear output shaft 22, the thread cutting crank 23, the shaft sleeve 231, the thread cutting fork rod 24, the thread cutting rod 241, the return rod 242, the thread cutting end execution end 25, the presser foot lifting cam 26, the presser foot push rod 27, the thread feeding tooth presser foot fixing support 30, the swing hole 31, the fixing support one 32, the fixing support two limiting blocks 33, the first limiting block 34 and the second limiting block 35.

Detailed Description

Preferred embodiments of the present application will be described in detail below with reference to the accompanying fig. 1-9, 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 more clearly defined, and these embodiments are only used for illustration of the present invention, and are not limited to the present invention.

Example one

The application provides a feed dog assembly, a thread trimming mechanism and a presser foot lifting mechanism of a sewing machine, which are provided with a feed dog assembly 1a, a thread trimming mechanism 1b, a presser foot lifting mechanism 1c, an up-down lifting power source 10, a front-back feed power source 20 and the like. The feed dog assembly 1a is driven by the up-down lifting power source 10 and the front-back feed power source 20 together, and the up-down lifting power source 10 and the front-back feed power source 20 act on the feed dog assembly 1a together to execute the feed motion of the sewing machine, so that the feed dog assembly 1a has the feed function of realizing sewing. After the cloth feeding operation is completed, the front and rear cloth feeding power source 20 starts to drive the thread cutting mechanism 1b and the presser foot lifting mechanism 1c to perform the thread cutting operation and the presser foot lifting operation. First, the front output shaft 21 of the front and rear cloth feeding power source 20 performs the thread cutting operation of the thread cutting mechanism 1b, and then the rear output shaft 22 of the front and rear cloth feeding power source 20 performs the presser foot lifting operation of the presser foot lifting mechanism 1 c. According to the sewing machine, the front and rear cloth feeding power sources 20 of the cloth feeding tooth assemblies 1a are utilized to perform the thread cutting action and the presser foot lifting action after the cloth feeding action is completed, the utilization rate of the power device of the sewing machine is improved, and the manufacturing cost of the sewing machine is greatly reduced.

A cam 11 is mounted on a front output shaft 21 of the front and rear cloth feeding power source 20; the output shaft 13 of the up-down lifting power source 10 is provided with a synchronous pulley I211, the cam 11 indirectly acts on the feed dog frame 12 to realize the front-back feed action of the feed dog assembly 1a, the synchronous pulley I211 indirectly acts on the bracket 16 to realize the up-down feed action of the feed dog assembly 1a, and the front-back feed action and the up-down feed action simultaneously realize the feed action of the sewing machine.

The cam 11 has a work positioning groove 111, and the work positioning groove 111 has a cloth feeding operation corner area 2a, a presser foot raising operation corner area 2b, and a thread cutting operation corner area 2c. In a cloth feeding action corner area 2a of a front and back cloth feeding power source 20, a cam 11 mounted on an output shaft 13 is matched with a swing rod 18, the cam 11 drives the swing rod 18 in the cloth feeding action corner area 2a, and the swing rod 18 is hinged with a cloth feeding retainer 12 to enable the output shaft 13 to generate a swing source for moving cloth back and forth to the cloth feeding retainer 12. The presser foot lifting operation corner region 2b and the thread cutting operation corner region 2c of the cam 11 are idle strokes, and the thread cutting operation and the presser foot lifting operation are performed by the front and rear cloth feeding power source 20 using the idle strokes of the cam 11.

The feed dog frame 12 is provided with a support shaft 15, the support shaft 15 is fixed on the feed dog frame 12, the support shaft 15 extends to two ends of a support 16, the support shaft 15 is positioned at two ends of the support 16 in a clearance fit mode, and the feed dog frame 12 operates in the support 16.

The front output shaft 21 is provided with a first synchronous pulley 211, and the first synchronous pulley 211 indirectly drives the first multi-stage cam 212 and the second multi-stage cam 213 to realize the up-and-down cloth feeding action of the whole cloth feeding tooth assembly 1 a.

The first multi-stage cam 212 and the second multi-stage cam 213 are respectively arranged at two ends of the bottom of the bracket 16. A synchronous belt is sleeved on the synchronous pulley I211, and the synchronous pulley I211 drives a synchronous pulley II 214 of the multi-stage cam I212; the second timing pulley 214 drives the third timing pulley 215 of the multi-stage cam 213. The vertical movement power source 10 drives the first timing pulley 211 and the third timing pulley 215 in the cloth feeding operation corner region 2a, thereby driving the first multi-stage cam 212 and the second multi-stage cam 213 to generate a swing source.

The feed dog assembly 1a of the present application is fixed to the feed dog fixing bracket 30, and specifically, the first multi-stage cam 212 is fixed to the first rotating shaft 216, the second multi-stage cam 213 is fixed to the second rotating shaft 217, and the first rotating shaft 216 and the second rotating shaft 217 are sleeved on the feed dog fixing bracket 30. The first multi-stage cam 212 and the second multi-stage cam 213 are provided with a first salient point 2121 and a second salient point 2131, and the first salient point 2121 and the second salient point 2131 are arranged to enable the bracket 16 to generate an up-and-down lifting and swinging source to the whole feed dog assembly 1 a. The feed dog assembly 1a further comprises a swing arm 17, and the swing arm 17 is cylindrical. The feed dog fixing support 30 is also provided with a swing hole 31, the swing hole 31 is provided with a space for the swing rod 17 to move up and down, and the swing of the swing source of the multi-stage cam I212 and the multi-stage cam II 213 is limited by the swing hole 31 of the feed dog fixing support 30. In addition, the feed dog fixing bracket 30 is also provided with a first fixing bracket 32 and a second fixing bracket 33 which can fix the up-down lifting power source 10 and the front-back feed power source 20, and the first fixing bracket 32, the second fixing bracket 33 and the feed dog fixing bracket 30 body form a whole and are fixed on the sewing machine. The feed dog fixing support 30 is further provided with a first limiting block 34 and a second limiting block 35, and the first limiting block 34 and the second limiting block 35 are used for limiting the operation position of the feed dog frame 12 and/or the support 16, so that the feed dog assembly 1a has a fixed operation structure on the feed dog fixing support 30.

After the cloth feeding operation of the sewing machine is completed, that is, the sewing is finished, the front and rear cloth feeding power sources 20 start to perform the thread cutting operation and the presser foot lifting operation. The front output shaft 21 of the front and rear cloth feeding power source 20 is provided with a thread cutting crank 23, the thread cutting crank 23 acts on a thread cutting fork rod 24, and then the thread cutting fork rod 24 acts on a thread cutting end execution end 25 to execute thread cutting. 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 located 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 positions of the thread cutting rod 241 and the return rod 242 on the thread cutting fork rod 24 can be interchanged, and the technical effects achieved by the thread cutting fork rod are the same.

The rear output shaft 22 of the front and rear cloth feeding power source 20 is provided with a presser foot lifting cam 26, the cam part of the presser foot lifting cam 26 driven by the front and rear cloth feeding power source 20 acts on a presser foot lifting push rod 27, and the presser foot lifting push rod 27 acts on a presser foot end executing end to execute the presser foot lifting action.

The operation corners of the front and rear cloth feeding power sources 20 where the cloth feeding action, the presser foot lifting action and the thread cutting action are respectively a cloth feeding action corner area 2a, a presser foot lifting action corner area 2b and a thread cutting action corner area 2c, and the sequence of the sewing actions performed by the front and rear cloth feeding power sources 20 is the cloth feeding action, the thread cutting action and the presser foot lifting action. It is worth mentioning that after the front and back cloth feeding power source 20 finishes the cloth feeding action and the sewing machine stops, the front and back cloth feeding power source 20 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 20 operates, and after the sewing machine stops, the thread is firstly cut and then the presser foot is lifted.

In the cloth feeding operation corner area 2a, the front and rear cloth feeding power sources 20 push the cam 11 against the swing boss 181 located in the cloth feeding operation corner area 2a, so that the swing lever 18 generates the front and rear cloth feeding swing source. When the sewing is finished, the front and rear cloth-feeding power sources 20 are separated from the cloth-feeding operation corner region 2a, and enter the presser foot lifting operation corner region 2b and the thread-cutting operation corner region 2c. Since the operation positioning groove 111 formed by the presser foot raising operation corner region 2b and the thread cutting operation corner region 2c is concentric with the rear output shaft 22 (or the front output shaft 21), the front and rear cloth feeding power source 20 entering the operation positioning groove 111 does not generate a front and rear cloth feeding swing source to the swing lever 18, and the swing shaft sleeve 181 of the swing lever 18 only idles in the operation positioning groove 111. Similarly, when the front and rear cloth feeding power sources 20 are operated in the cloth feeding operation corner region 2a, the sleeve 231 of the crank 23 idles back and forth between the thread cutting lever 241 and the return lever 242 at the thread cutting fork 24; and, the circular arc surface of the presser foot lifting cam 26 is also idle running back and forth to the presser foot lifting mandril 27, 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 20 are not influenced mutually, and the actions are clear and distinct.

Example two

The second embodiment is basically the same as the first embodiment, except that the up-down lifting power source 10 and the front-back cloth feeding power source 20 are different from each other in the implementation means of the swing source generated by the feed dog assembly 1a, except that the up-down lifting power source 10 adopts the cam 11 for the feed dog assembly 1a, the up-down lifting power source 10 also adopts the technical means of a connecting rod, a synchronous wheel or a gear and the like to achieve the purpose; in addition to the front and rear cloth feeding power sources 20 using the first timing pulley 211, the front and rear cloth feeding power sources 20 may also use a cam, a link, a timing wheel, or the like to achieve the above-mentioned object.

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

Claims (10)

1. A cloth feeding tooth assembly, a thread cutting mechanism and a presser foot lifting mechanism of a sewing machine are provided with a cloth feeding tooth assembly (1 a), an up-and-down power source (10) and a front-and-back cloth feeding power source (20), and are characterized in that the cloth feeding tooth assembly (1 a) is driven by the up-and-down power source (10) and the front-and-back cloth feeding power source (20) together, the up-and-down power source (10) and the front-and-back cloth feeding power source (20) act on the cloth feeding tooth assembly (1 a) to execute cloth feeding actions of the sewing machine, a front output shaft (21) of the front-and-back cloth feeding power source (20) executes thread cutting actions of a thread cutting mechanism (1 b), and a rear output shaft (22) of the front-and-back cloth feeding power source (20) executes presser foot lifting actions of a presser foot mechanism (1 c).

2. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine according to claim 1 are characterized in that a synchronizing wheel (211) is mounted on the front output shaft (21), the synchronizing wheel (211) indirectly drives a multi-stage cam I (212) and a multi-stage cam II (213) to realize the up-and-down cloth feeding action of the feed dog assembly (1 a), an output shaft (13) of the up-and-down lifting power source (10) is provided with a cam (11), the cam (11) indirectly acts on a feed dog frame (12) to realize the front-and-back cloth feeding action of the feed dog assembly (1 a), the front output shaft (21) is provided with a thread cutting crank (23), the thread cutting crank (23) acts on a thread cutting fork rod (24) to perform the thread cutting action through a thread cutting end (25), the rear output shaft (22) is provided with a presser foot lifting cam (26), and the presser foot lifting cam (26) acts on a presser foot lifting rod (27) to perform the presser foot lifting action through a presser foot end presser foot lifting action.

3. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 1 or 2, wherein the up-down lifting power source (10) realizes the forward and backward feed actions of the feed dog assembly (1 a) by means of a connecting rod or a synchronizing wheel or a gear; the front and back cloth feeding power source (20) realizes the up-and-down cloth feeding action of the cloth feeding tooth assembly (1 a) by the technical means of a cam, a connecting rod or a synchronous wheel.

4. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of a sewing machine according to claim 2, wherein the cam (11) is matched with a swing lever (18), the cam (11) drives the swing lever (18), the swing lever (18) is hinged with the feed dog frame (12), the operation positioning slot (111) of the cam (11) is matched with a swing shaft sleeve (181) of the swing lever (18), and the swing shaft sleeve (181) of the swing lever (18) idles in the operation positioning slot (111).

5. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 2, wherein the first multi-stage cam (212) and the second multi-stage cam (213) are respectively arranged at two ends of the bottom of the support (16) of the sewing machine, the first multi-stage cam (212) and the second multi-stage cam (213) are respectively fixed on the first rotating shaft (216) and the second rotating shaft (217), the first multi-stage cam (212) and the second multi-stage cam (213) are provided with a first salient point (2121) and a second salient point (2131), and the first salient point (2121) and the second salient point (2131) act on the bottom of the support (16).

6. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 2, wherein a synchronous belt is sleeved on the first synchronous pulley (211), and the first synchronous pulley (211) drives a second synchronous pulley (214) of the multi-stage cam (212); the second synchronous pulley (214) drives a third synchronous pulley (215) of the multi-stage cam (213).

7. The feed dog assembly, the thread trimming mechanism and the presser foot lifting mechanism of the sewing machine according to claim 1 or 2, wherein the feed dog assembly (1 a) is fixed on a feed dog fixing support (30), the feed dog assembly (1 a) further comprises a swing arm (17), the swing arm (17) is cylindrical, the swing hole (31) has a space for the swing arm (17) to ascend and descend, the ascending and descending power source (10) and the front and rear feed power sources (20) have a first fixing support (32) and a second fixing support (33), the first fixing support (32), the second fixing support (33) and the feed dog fixing support (30) body form a feed dog fixing support (30) as a whole, the feed dog fixing support (30) further comprises a first limit block (34) and a second limit block (35), the first limit block (34) and the second limit block (35) are used for the feed dog support (12) and/or the feed support (16), the feed dog support (15) is provided on the feed dog support (12), and the support shaft (15) is positioned at the two support shafts (16) in a clearance fit.

8. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 1 or 3, wherein the front output shaft (21) of the front and rear feed power source (20) is provided with a thread cutting crank (23), the thread cutting crank (23) acts on a 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 the shaft sleeve (231) idles back and forth between the thread cutting rod (241) and the return rod (242) on 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 1 or 3, wherein a presser foot lifting cam (26) is mounted on a rear output shaft (22) of the front and rear feed power source (20), a cam portion of the presser foot lifting cam (26) acts on a presser foot lifting jack (27), and the presser foot lifting jack (27) acts on a presser foot end executing end to perform a presser foot lifting action.

10. The feed dog assembly, the thread cutting mechanism and the presser foot lifting mechanism of the sewing machine as claimed in claim 1 or 3, wherein the operation turning angles of the front and rear feed power sources (20) are respectively a feed operation turning angle area (2 a), a presser foot lifting operation turning angle area (2 b) and a thread cutting operation turning angle area (2 c), the sewing operation sequence performed by the front and rear feed power sources (20) is a feed operation, a thread cutting operation and a presser foot lifting operation, and the operation positioning groove (111) formed by the presser foot lifting operation turning angle area (2 b) and the thread cutting operation turning angle area (2 c) is concentric with the rear output shaft (22).

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