Feed mechanism for a sewing machine

Abstract

The utility model provides a kind of cloth feeding structure of sewing machine, belong to sewing machine technical field.It solves how to reduce abrasion while improving the problem of the feed amount adjustment convenience of differential feeding tooth.This sewing machine's cloth feeding structure, sewing machine includes base, there is the differential tooth frame with the active tooth frame of being pasted in base, active tooth frame is fixed with active feeding tooth, differential tooth frame is fixed with differential feeding tooth, cloth feeding structure includes the differential feeding shaft of being opposite active tooth frame, base outer dial, cam and adjusting wrench in base, differential tooth frame is fixed with adjusting part, with differential feeding shaft transmission connection, it can drive its relative active tooth frame transverse reciprocating movement, adjusting wrench one end is positioned with cam circumferentially, other end is slidably connected dial and can be positioned.This sewing machine's cloth feeding structure can reduce abrasion while improving the feed amount adjustment convenience of differential feeding tooth.

Description

Technical Field

[0001] This utility model belongs to the field of sewing machine technology and relates to a fabric feeding structure for a sewing machine. Background Technology

[0002] The feed dog is a very important component of a sewing machine. It is mainly used to assist in feeding the fabric during sewing. With the continuous development of technology, two feed dogs are integrated into the sewing machine. The two feed dogs can be driven to feed the fabric at different speeds, thereby creating a certain stretching effect on the fabric during the sewing process and preventing wrinkles in the sewn fabric.

[0003] For example, a feeding mechanism for a sewing machine disclosed in Chinese Patent (Application Publication No.: CN117265782A) includes a base, an active feed dog, a differential feed dog, and a feeding boss protruding from the side wall of the base. The feeding boss is provided with an active feed dog and a differential feed dog. Both the active feed dog and the differential feed dog are disposed inside the base. The feeding boss is provided with a main cantilever and a differential cantilever, both of which are strip-shaped. The inner end of the main cantilever extends into the base and is fixedly connected to the active feed dog. The inner end of the differential cantilever extends into the base and is fixedly connected to the differential feed dog. The outer end of the main cantilever is fixedly connected to the active feed dog, and the outer end of the differential cantilever is fixedly connected to the differential feed dog.

[0004] As can be seen from paragraph 0047 of the aforementioned comparative documents, a method is disclosed that uses a motor as a drive source and provides power to the main feed shaft, lifting shaft, and differential feed shaft in cooperation with the main shaft. In this process, the rectangular sliders at one end of the main shaft and the lifting shaft can move the active feed toother and the differential feed toother up and down. Secondly, one end of the main feed shaft is connected to the active feed toother through a crank and a main connecting rod, so that the active feed toother and the active feed toother can move in the back and forth direction. When the differential feed shaft swings back and forth, it can drive the other end of the adjusting rod to swing back and forth, and drive the differential toother to move through the differential connecting rod, so that the differential feed toother can move in the back and forth direction.

[0005] However, for fabrics of different materials and thicknesses, there are certain requirements for the feed rate of the differential feed tooth. To meet this requirement, the comparative document proposes to make the adjusting slider movably connected to the adjusting rod and to lock the position of the adjusting slider relative to the adjusting rod using a locking component, thereby limiting the swing of the adjusting slider and the forward and backward displacement of the differential feed tooth.

[0006] However, this arrangement has significant drawbacks. The differential feed shaft and differential tooth holder are hinged, and the presence of the adjusting slider and adjusting rod will inevitably increase the transmission resistance between them. After one working cycle, mechanical wear will be aggravated, which will seriously affect the service life of the sewing machine. Secondly, when it is necessary to adjust the differential feed tooth feed amount, the sewing machine base must be flipped open relative to the base to expose the adjusting slider and adjusting rod, which is very inconvenient to operate. Summary of the Invention

[0007] The purpose of this utility model is to address the aforementioned problems in the existing technology by proposing a fabric feeding structure for a sewing machine. The technical problem to be solved by this utility model is: how to improve the ease of adjusting the feed amount of the differential feed teeth while reducing wear.

[0008] The objective of this utility model can be achieved through the following technical solution: a fabric feeding structure for a sewing machine, the sewing machine including a base, wherein a driving feeder and a differential feeder are vertically arranged in the base with their sides in contact, a driving feeder extending from the front end of the base is fixed on one side of the driving feeder, and a differential feeder arranged parallel to the driving feeder is fixed on the differential feeder, the fabric feeding structure including a differential feed shaft with one end facing the other side of the driving feeder, characterized in that an adjusting member is fixed on the side of the differential feeder facing the driving feeder, the... The differential feed shaft is connected to the adjusting component and can drive the differential toothed carriage to move laterally reciprocally relative to the active toothed carriage. The feeding structure also includes a scale fixed outside the base and located below the active toothed carriage and the differential toothed carriage, a cam rotatably connected inside the base and capable of driving the differential feed shaft to rotate, and an adjusting wrench located outside the base and in the shape of a long strip. The adjusting wrench is arranged radially along the differential feed shaft and one end is circumferentially positioned with the cam, while the other end is slidably connected to the scale and can maintain its position relative to the scale.

[0009] It should be noted beforehand that the driving mechanisms for the active feed gear and the driven feed gear, as well as the differential feed gear, in this application can be referenced in prior art document CN117265782A. Both are achieved using a single main shaft in conjunction with a motor and various linkage mechanisms. However, the biggest difference between this application and the prior art lies in the modification of the adjustment mechanism for regulating the differential feed gear's stroke feed. Specifically, in driving the differential feed gear and the differential feed gear, the combination of the motor and the main shaft, along with the linkage mechanism, enables the differential feed to... The feed shaft rotates synchronously with the main shaft. During this process, the differential feed shaft drives the differential feed dog to reciprocate continuously, allowing the differential feed dog to repeatedly move closer to or away from the active feed dog, thus pulling the fabric. Compared to existing technologies, this eliminates the need for adjusting sliders and rods, avoiding excessive hinges that could cause jamming during power transmission and excessive mechanical wear, effectively ensuring the sewing machine's lifespan. Furthermore, it addresses the varying feed rates required by different fabrics. This application independently provides an adjustment mechanism for adjusting the differential feed rate. Specifically, this mechanism includes a dial, a cam, and an adjustment wrench. The cam is connected to the differential feed shaft for transmission. During adjustment, the adjustment wrench can be manually pushed or pulled, allowing it to slide and remain positioned on the dial. The other end of the wrench, driven by the applied force, rotates the cam by a certain amount, causing the cam to rotate the differential feed shaft slightly. The differential feed shaft then controls the differential feed rate. The toothed frame drives the differential feed tooth to adaptively translate relative to the active feed tooth, ensuring that the initial position and subsequent feed amount of the differential feed tooth can be adjusted according to the needs of different fabrics. Secondly, it is worth mentioning that the cam can effectively utilize the remaining space in the base for assembly, while the adjusting wrench and the scale for easy reference by the operator are located on the outer wall of the base. This not only prevents the internal space of the base from being too cramped, but also ensures that the operator can operate more conveniently and quickly when adjusting the differential feed tooth.

[0010] In the above-mentioned fabric feeding structure of the sewing machine, a connecting arm is fixed on the differential feeding shaft, a connecting rod is hinged to one side of the cam, the connecting rod and the connecting arm are hinged together by a connecting rod, a connecting shaft is rotatably connected inside the base, the cam is fixed on the connecting shaft, one end of the adjusting wrench is connected to the connecting shaft and circumferentially positioned, the scale is fan-shaped and has an elongated and curved adjusting hole on its surface, and an adjusting knob is screwed to the other end of the adjusting wrench by a screw, the adjusting knob can slide along the length of the adjusting hole and press against the surface of the scale. As a specific solution, the differential feed shaft and the cam are driven by the cooperation of three links: connecting rod one, connecting arm, and connecting rod two. The cam is fixedly connected to the connecting shaft rotatably within the base, thus enabling the cam to be rotatably connected within the base. Based on this structure, the adjusting wrench is circumferentially positioned via its inner end and the connecting shaft, and is slidably connected to the adjusting hole of the dial via a screw and adjusting knob. When the adjusting knob is loose, the screw passing through the adjusting hole can slide along the length of the adjusting hole, allowing the adjusting wrench to drive the cam to rotate slightly according to the scale on the dial. This causes the cam to drive the differential feed shaft, which in turn moves the differential feed carriage and differential feed tooth, through the cooperation of connecting rod one, connecting arm, and connecting rod two. When the adjusting knob is tightened and presses against the dial, it positions the outer end of the adjusting wrench to prevent free swinging during operation and to prevent the differential feed tooth feed rate limitation from failing.

[0011] In the fabric feeding structure of the sewing machine described above, one end of the adjusting wrench is positioned near the front end of the dial and secured to the connecting shaft with a screw. The adjusting hole is located near the rear end of the dial, and the rear end of the adjusting wrench protrudes beyond the rear edge of the dial. This ensures the stability of the connection between the adjusting wrench and the connecting shaft, thereby guaranteeing more precise control of the cam by the adjusting wrench. Furthermore, the protrusion of the rear end of the adjusting wrench beyond the rear end of the dial makes manual adjustment more convenient for the operator.

[0012] In the above-mentioned fabric feeding structure of the sewing machine, the cam is provided with a connecting rod three on one side. The base is rotatably connected to an adjusting handle that can extend or retract in length, and the adjusting handle is perpendicular to the center line of the connecting shaft. One end of the connecting rod three is hinged to the adjusting handle, and the other end is provided with a strip hole. A positioning pin is screwed onto the outer wall of the cam, and the positioning pin is slidably connected in the strip hole. As can be seen from the aforementioned scheme, using an adjusting wrench to adjust the feed amount of the differential tooth holder and differential feed tooth cannot achieve high precision, and the adjustment accuracy often fails to meet the standard. To address this, this application adds an adjusting handle to the base. In actual operation, the adjusting handle is manually turned to increase its length. During this process, the adjusting handle can push the connecting rod three to swing around the hinge, causing the connecting rod three to drive the cam to rotate slightly, ensuring the adjustment accuracy of the cam, and thus ensuring more precise adjustment of the feed amount of the differential tooth holder and differential feed tooth. It is worth mentioning that the end of the connecting rod three connected to the cam is specifically slidably engaged with the positioning pin on the cam through a strip hole, which ensures that the connecting rod three can also slide adaptively relative to the positioning pin during rotation, avoiding interference.

[0013] In the fabric feeding structure of the sewing machine described above, the adjusting handle includes an outer sleeve fixed in the base. A push block and a push rod with their inner ends fixed to the push block are slidably connected inside the outer sleeve. The connecting rod three is hinged to the push block. The outer end of the push rod is screwed to the outer sleeve and extends out of the base, and an operating button is fixed to the outer end of the push rod. Specifically, when adjusting using the adjusting handle, the operator manually turns the operating button, causing the operating button to move the push rod inward relative to the outer sleeve through a threaded connection. This causes the push rod to slide the push block inward, thereby achieving the purpose of the push block driving the connecting rod three to rotate. Alternatively, a bolt and nut can be used instead of the adjusting handle structure. Specifically, the nut is fixed in the base, and the bolt and nut are screwed together with their ends hinged to the connecting rod three.

[0014] In the fabric feeding structure of the sewing machine described above, a swing arm is fixed to the output end of the differential feed shaft, and the adjusting member is fixed to the center of the active feed plate. A strip-shaped clearance hole is provided on the active feed plate for the adjusting member to pass through. The adjusting member and the swing arm are connected by a four-way hinge via a connecting rod. This arrangement ensures that the connection position between the differential feed plate and the differential feed rod is more central, guaranteeing the stability of the connection and transmission between them. Furthermore, the strip-shaped clearance hole on the active feed plate allows the adjusting member used for driving to pass through it. During driving, the adjusting member can slide within the clearance hole, preventing interference and ensuring that the differential feed plate can reciprocate relative to the active feed plate. Specifically, the adjusting member can be a screw, or it can be replaced with a pin, shaft, or other similar structure.

[0015] Compared with existing technologies, the fabric feeding structure of this sewing machine has the following advantages:

[0016] 1. The drive mechanism for driving the differential feed tooth and the adjustment structure for adjusting the differential feed tooth feed amount are set up separately to avoid the problem of short service life caused by increased mechanical wear during operation. At the same time, it is adapted to the internal space of the base. The cam and the adjustment wrench are integrated inside, and the dial for the cooperation between the two is set outside the base. This effectively saves space and makes it easier for the operator to operate the adjustment wrench by referring to the dial, making it more convenient to use.

[0017] 2. An adjustment handle is also provided, which works in conjunction with the cam via a connecting rod. During operation, the cam can be roughly adjusted by a large range using an adjustment wrench, and then the cam can be precisely adjusted by a small range using the adjustment handle, so as to ensure more accurate adjustment of the feed rate of the differential feeder. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the fabric feeding mechanism of this sewing machine.

[0019] Figure 2 This is a schematic diagram of the fabric feeding mechanism of this sewing machine after the base has been removed.

[0020] Figure 3 This is a schematic diagram of the fabric feeding mechanism of this sewing machine from another perspective after the base has been removed.

[0021] Figure 4 This is a schematic diagram of the structure of the cam and the differential feed shaft.

[0022] Figure 5 This is a schematic diagram of the structure of the cam, adjusting wrench, and dial.

[0023] Figure 6 This is a schematic diagram of the cam and the adjusting handle.

[0024] Figure 7 This is a cross-sectional view of the adjusting handle.

[0025] Figure 8 This is a structural diagram of the differential feed shaft, the active feed gear, and the differential feed gear.

[0026] Figure 9 This is a schematic diagram of the active dental arch.

[0027] In the picture,

[0028] 1. Base; 11. Active feeder; 111. Active feeder; 112. Clearance hole; 12. Differential feeder; 121. Differential feeder; 122. Adjusting component; 13. Connecting shaft;

[0029] 2. Differential feed shaft; 21. Connecting arm; 22. Swing arm;

[0030] 3. Dial; 31. Adjustment hole;

[0031] 4. Cam; 41. Connecting rod one; 42. Connecting rod three; 421. Strip hole; 43. Positioning pin

[0032] 5. Adjusting wrench; 51. Adjusting knob;

[0033] 6. Linkage 2;

[0034] 7. Adjusting handle; 71. Outer sleeve; 72. Push block; 73. Push rod; 731. Operating button;

[0035] 8. Linkage 4. Detailed Implementation

[0036] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0037] like Figure 1-3As shown, in the fabric feeding structure of this sewing machine, the sewing machine includes a base 1. A drive feeder 11 and a differential feeder 12 are vertically arranged inside the base 1. The drive feeder 11 and the differential feeder 12 are horizontally slidably connected in the base 1, and one side of the drive feeder 11 and one side of the differential feeder 12 are in contact with each other. Feed teeth are fixed on the sides of both the drive feeder 11 and the differential feeder 12 facing the front end of the base 1. The feed tooth fixed on the drive feeder 11 is the drive feeder 111, and the feed tooth fixed on the drive feeder is the differential feeder 121. A feed tooth is provided inside the base 1. A drive mechanism drives the active feed tooth 111 and the differential feed tooth 121, thereby enabling the active feed tooth 111 and the differential feed tooth 121 to move up and down, and also enabling the active feed tooth 111 and the differential feed tooth 121 to move horizontally relative to each other. This achieves the purpose of conveying and tightening the fabric through the cooperation of the active feed tooth 111 and the differential feed tooth 121. The drive method of the main feed tooth 111 and the differential feed tooth 121 can adopt the existing technology, and the specific details can be found in the prior art CN117265782A. This application will not elaborate on this part of the structure.

[0038] It is worth mentioning that the translational drive of the differential gear 12 in the horizontal direction is an indispensable part of this embodiment, and its specific structure can be found in [reference]. Figure 8 and Figure 9 A differential feed shaft 2 is provided inside the base 1, with one end facing the side of the active tooth guide 11. A swing arm 22 is fixed to the output end of the differential feed shaft 2. An adjusting component 122 (specifically a screw, but bolts, threaded pins, etc. can also be used) is screwed to the side of the differential tooth guide 12 facing the active tooth guide 11 near the center. A clearance hole 112 is provided near the center of the active tooth guide 11, and the clearance hole 112 is elongated and arranged laterally. The adjusting component 122 passes through the clearance hole 112. The differential feed shaft 2 and the active tooth guide 11... A connecting rod 4 8 is provided, with one end of the connecting rod 4 8 hinged to the swing arm 22 and the other end hinged to the adjusting member 122. According to the prior art, when the differential feeding shaft 2 is driven, the swing arm 22 fixed on the differential feeding shaft 2 can swing in tandem. In this state, the connecting rod 4 8 hinged to it can swing adaptively around the hinge points at both ends, and can transmit force to the adjusting member 122 when rotating, so that the adjusting member 122 pulls or pushes the differential tooth frame 12, thereby achieving the translation of the differential feeding tooth 121 closer to or further away from the active feeding tooth 111.

[0039] Combination Figure 4 and Figure 5A connecting shaft 13 located below the differential feeding shaft 2 is rotatably connected inside the base 1. A cam 4 is also provided below the differential feeding shaft 2. The cam 4 is sleeved and locked to the outside of the connecting shaft 13 by screws, so that the cam 4 is rotatably connected inside the base 1. A connecting pin 1 is provided on one side wall of the cam 4. A connecting rod 41 is rotatably connected to the connecting pin 1. A connecting arm 21 is fixed on the differential feeding shaft 2. A connecting rod 6 is provided between the connecting arm 21 and the connecting rod 41. The connecting rod 41 is rotatably connected to the connecting pin 1 at one end and to the connecting pin 2 at the other end. One end of the connecting rod 6 is fixed to the connecting pin 2, and the other end is hinged to the swing arm 22 through the connecting pin.

[0040] Secondly, a fan-shaped dial 3 is provided on the outside of the base 1. The dial 3 is specifically locked to the outer wall of the base 1 by screws. A strip-shaped and curved adjustment hole 31 is opened on the outer wall of the dial 3 near the rear end. An elongated adjustment wrench 5 is provided on the outside of the base 1. One end of the adjustment wrench 5 is screwed and locked to the outer end of the connecting shaft 13, and the other end protrudes from the rear edge of the dial 3. An adjustment knob 51 is screwed to the outer wall of the adjustment wrench 5 near the rear end, and the screw passes through the adjustment hole 3. In section 1, the adjusting wrench 5 serves as a guide. As a further specific solution, a slotted groove is formed on the front side wall of the adjusting wrench 5, and a protruding slotted portion is formed on the outer wall of the end of the connecting sleeve. The protruding portion is embedded in the groove, thereby achieving circumferential pre-positioning of the connecting sleeve and the adjusting wrench 5, facilitating subsequent screw tightening. Secondly, the adjusting knob 51 primarily functions to lock and unlock the adjusting wrench 5. In the locked state, the adjusting knob 51 presses against the surface of the dial 3, thereby achieving adjustment... The positioning of the outer end of the wrench 5 prevents it from driving the connecting shaft 13 and the cam 4 to rotate. In other words, in this state, the wrench 5 cannot drive the connecting shaft 13, and therefore the connecting shaft 13 cannot drive the cam 4 to rotate accordingly. Conversely, when the adjusting knob 51 is unlocked, in this state, the operator can pull up or press down the outer end of the adjusting wrench 5 according to the scale on the dial 3, causing the adjusting wrench 5 to drive the cam 4 to rotate via the connecting shaft 13. The cam 4 then cooperates with connecting rod 1 41 and connecting rod 2 6 to... The connecting arm 21 drives the differential feed shaft 2 to perform an adaptive rotation action, and the differential feed shaft 2 drives the differential feed dog 12 to move left or right relative to the active feed dog 11 through the swing arm 22 and the connecting rod 8 in conjunction with the adjusting component 122. This achieves the adjustment of the initial position of the differential feed dog 121 relative to the active feed dog 111. Furthermore, when the candidate sewing machine is working, due to the limitations of the aforementioned swing arms 22 and connecting rods, the feed amount of the differential feed dog 121 relative to the active feed dog 111 can also be limited.

[0041] Combination Figure 6 and Figure 7The base 1 also includes an adjusting handle 7, which is arranged laterally and perpendicular to the axis of the connecting shaft 13. Specifically, the adjusting handle 7 includes an outer sleeve 71 fixed in the base 1 and a push rod 73 screwed into the outer sleeve 71. A push block 72 is slidably connected to the inner end of the outer sleeve 71. The inner ends of the push block 72 and the push rod 73 are fixedly connected. The outer end of the push rod 73 extends out of the outer sleeve 71 and is fixed with an operating button 731. A long, narrow connecting rod 42 is provided inside the base 1. One end of the connecting rod 42 is hinged to the push block 72, and the other end has a slotted hole 421. A positioning pin 43 is fixed to one end of the connecting rod 41 on the cam 4, and the positioning pin 43 is slidably connected to the slotted hole 42. In section 1, the purpose of setting the adjustment handle 7 is that the simple adjustment wrench 5 and dial 3 cannot achieve precise adjustment of the position and feed amount of the differential feed tooth 121. Therefore, in the actual adjustment process, the operator often controls the cam 4 by adjusting the wrench 5 first, so that the position of the differential feed tooth 121 is initially adjusted over a large range. After adjusting to a certain value, the operator can turn the operation button 731, so that the push rod 73 and the outer sleeve 71 are threaded together to push the push block 72 inward or pull it outward. The push block 72 and the connecting rod 3 42 work together to pull the cam 4 to make a further slight rotation, thereby ensuring that the position of the differential feed tooth 121 is further precisely adjusted.

[0042] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

[0043] Although this document frequently uses terms such as base 1, active feeder 11, active feeder 111, clearance hole 112, differential feeder 12, differential feeder 121, adjusting component 122, connecting shaft 13, differential feeder shaft 2, connecting arm 21, swing arm 22, dial 3, adjusting hole 31, cam 4, connecting rod one 41, connecting rod three 42, strip hole 421, positioning pin 43, adjusting wrench 5, adjusting knob 51, connecting rod two 6, adjusting handle 7, outer sleeve 71, push block 72, push rod 73, operating knob 731, and connecting rod four 8, the possibility of using other terms is not excluded. The use of these terms is merely for the convenience of describing and explaining the essence of this utility model; interpreting them as any additional limitation would contradict the spirit of this utility model.

Claims

1. A fabric feeding structure for a sewing machine, the sewing machine comprising a base (1), wherein the base (1) is provided with an active feed dog (11) and a differential feed dog (12) with their sides attached together along a vertical direction, an active feed dog (111) extending out of the front end of the base (1) is fixed on one side of the active feed dog (111), and a differential feed dog (121) arranged parallel to the active feed dog (111) is fixed on the differential feed dog (121), the fabric feeding structure comprising a differential feed shaft (2) with one end facing the other side of the active feed dog (11), characterized in that, An adjusting member (122) is fixed on one side of the differential tooth frame (11) facing the active tooth frame (11). The differential feeding shaft (2) and the adjusting member (122) are connected by a transmission and can drive the differential tooth frame (12) to move laterally back and forth relative to the active tooth frame (11). The feeding structure also includes a scale (3) fixed outside the base (1) and located below the active tooth frame (11) and the differential tooth frame (12), a cam (4) rotatably connected inside the base (1) and capable of driving the differential feeding shaft (2) to rotate, and an adjusting wrench (5) located outside the base (1) and in the shape of a long strip. The adjusting wrench (5) is arranged radially along the differential feeding shaft (2) and one end is circumferentially positioned with the cam (4), and the other end is slidably connected to the scale (3) and can be positioned relative to the scale (3).

2. The thread feeding structure of the sewing machine according to claim 1, wherein A connecting arm (21) is fixed on the differential feeding shaft (2). A connecting rod (41) is hinged to one side of the cam (4). The connecting rod (41) and the connecting arm (21) are hinged together by a connecting rod (6). A connecting shaft (13) is rotatably connected inside the base (1). The cam (4) is fixed on the connecting shaft (13). One end of the adjusting wrench (5) is connected to the connecting shaft (13) and circumferentially positioned. The dial (3) is fan-shaped and has an elongated and curved adjusting hole (31) on its surface. An adjusting knob (51) is screwed to the other side wall of the adjusting wrench (5) by a screw. The adjusting knob (51) can slide along the length of the adjusting hole (31) and press against the surface of the dial (3).

3. The thread feeding structure of the sewing machine according to claim 2, wherein One end of the adjusting wrench (5) is located near the front end of the dial (3) and is locked to the connecting shaft (13) by a screw. The adjusting hole (31) is opened near the rear end of the dial (3). The rear end of the adjusting wrench (5) protrudes from the rear edge of the dial (3).

4. The thread feeding structure of a sewing machine according to claim 2 or 3, wherein The cam (4) is provided with a connecting rod three (42) on one side of the connecting rod one (41). The base (1) is rotatably connected to an adjusting handle (7) of extendable length, and the adjusting handle (7) is perpendicular to the center line of the connecting shaft (13). One end of the connecting rod three (42) is hinged to the adjusting handle (7), and the other end is provided with a strip hole (421). A positioning pin (43) is screwed onto the outer wall of the cam (4), and the positioning pin (43) is slidably connected in the strip hole (421).

5. The thread feeding structure of the sewing machine according to claim 4, wherein The adjusting handle (7) includes an outer sleeve (71) fixed in the base (1), a push block (72) is slidably connected inside the outer sleeve (71), and a push rod (73) whose inner end is fixed to the push block (72). The connecting rod (42) is hinged to the push block (72). The outer end of the push rod (73) is screwed to the outer sleeve (71) and extends out of the base (1). An operating button (731) is fixed to the outer end of the push rod (73).

6. The thread feeding structure of the sewing machine according to claim 5, wherein The output end of the differential feed shaft (2) is fixed with a swing arm (22). The adjusting member (122) is fixed to the plate surface of the active tooth frame (11) near the middle. The active tooth frame (11) has a strip-shaped clearance hole (112) that allows the adjusting member (122) to pass through. The adjusting member (122) and the swing arm (22) are hinged together by a connecting rod (8).

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