Synchronous control structure of sewing machine
By using limit blocks and ejection sections in the sewing machine to form limit channels, combined with the driving of the first spring, the problem of needle pitch adjustment rolling member and cam abutment is solved, ensuring the complete action of the cloth feeding teeth, and improving the sewing machine Stability and efficiency.
Patent Information
- Application Number
- CN202323664057.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2033-12-29
AI Technical Summary
In existing sewing machines, after a long time of use, the elastic coefficient of the needle distance adjustment roller and the needle distance adjustment cam cannot be ensured that the needle distance adjustment roller always abuts the needle distance adjustment cam, resulting in the inability to feed the cloth. Move reset.
The limiting block and the ejection section are used to form a limiting channel, and the pin distance adjusting member is driven into the limiting channel through the first pulling spring, and the pin distance adjusting cam is connected to the pin distance adjusting cam, which converts the rotation force into a compressive force to ensure the needle. The distance adjuster and the needle adjusting cam are always abutted.
When the tension spring is insufficient, the needle distance adjustment member can still abut the needle distance adjustment cam, ensuring smooth cloth feeding action and improving the stability and efficiency of the sewing machine.
Smart Images
Figure CN222139459U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of sewing machines and relates to a synchronous control structure of a sewing machine. Background Art
[0002] Sewing machines are clothing sewing devices that are widely used in today's life. In recent years, with the continuous improvement of technical levels, the functions of sewing machines have become more and more diverse. For example, a stitch length adjustment and automatic presser foot lifting device disclosed in a Chinese patent (authorization announcement number: CN217628851U) is provided, wherein a stitch length adjustment cam and a presser foot lifting adjustment cam are arranged on the motor shaft of the driving motor, one end of the feed control crank is connected to the control rotating shaft, and the other end is connected to the stitch length adjustment mechanism, one end of the presser foot lifting control crank is connected to the control rotating shaft, and the other end is connected to the presser foot lifting mechanism, a stitch length adjustment rolling member is arranged on the feed control crank, and a presser foot lifting rolling member is arranged on the presser foot lifting control crank, the cam surface of the stitch length adjustment cam includes a stitch length adjustment section, a presser foot lifting idling section and a first transition section, and the cam surface of the presser foot lifting cam includes a presser foot lifting section, a stitch length adjustment idling section and a second transition section; when the stitch length is adjusted and the presser foot is lifted, the presser foot lifting mechanism and the stitch length adjustment mechanism do not interfere with each other.
[0003] Combined with the contents of paragraphs 0036 and 0039 of the description of the comparative document, it can be known that for the presser foot lifting action and stitch length adjustment action in the sewing machine, the motor shaft of the driving motor drives the stitch length adjustment cam and the presser foot lifting cam to rotate together, and the stitch length adjustment cam drives the stitch length adjustment roller to drive the feed dog in the stitch length adjustment mechanism to move the fabric, and the presser foot lifting cam drives the presser foot lifting roller to drive the presser foot lifting mechanism to move the presser foot to flatten the fabric.
[0004] During use, since both the stitch length adjustment cam and the presser foot lifting cam are special-shaped wheels, when they rotate with the motor shaft, they push the stitch length adjustment roller and the presser foot lifting roller respectively, and there may be separation between the stitch length adjustment cam and the stitch length adjustment roller, and between the presser foot lifting cam and the presser foot lifting roller. In other words, there may be a situation where the presser foot and the feed dog cannot be moved and reset. In response to this defect, a solution is given in paragraphs 0037-0038 of the description of the comparative document, namely, a fixed base plate is provided in the casing, and the base plate and the swing seat reset pin are connected by a tension spring, so that the elastic force of the tension spring can realize the separation of the stitch length adjustment cam and the stitch length adjustment roller, and then pull the stitch length adjustment roller to move and abut against the stitch length adjustment cam again. Similarly, this structure is also applied to the presser foot lifting cam and the presser foot lifting roller.
[0005] But in fact, in order to ensure smooth driving of the feed dog, the elastic coefficient of the selected tension spring needs to be adapted to the overall transmission component, and the cam structure used in the prior art is generally a special-shaped wheel, that is, the outer wall of the cam has a convex structure protruding outward and a concave structure recessed inward. Therefore, when the stitch length adjustment cam cooperates with the stitch length adjustment roller through the concave surface on its own outer wall, even when the sewing machine is used for a long time and the elastic coefficient of the tension spring is reduced (that is, the elastic force of the tension spring is reduced), there will be a phenomenon that the tension force applied by the tension spring to the stitch length adjustment roller cannot ensure that the stitch length adjustment roller is always in contact with the stitch length adjustment cam, which in turn causes the feed dog to be unable to push the cloth to move. Summary of the invention
[0006] The utility model aims at the above problems in the prior art and proposes a synchronous control structure for a sewing machine. The technical problem to be solved by the utility model is: how to achieve that the stitch length adjustment rolling element and the stitch length adjustment cam always abut against each other.
[0007] The purpose of the utility model can be achieved through the following technical solutions: a synchronous control structure of a sewing machine, comprising a presser foot lifting and adjusting mechanism with a presser foot lifting and adjusting member, a stitch length adjusting mechanism with a stitch length adjusting member, a presser foot lifting and adjusting cam and a stitch length adjusting cam fixed on the driving end of a motor, a presser foot lifting and adjusting reset assembly capable of driving the presser foot lifting and adjusting member to always abut against the presser foot lifting and adjusting cam, and a first tension spring capable of driving the stitch length adjusting member to always abut against the presser foot lifting and adjusting cam, the outer side wall of the stitch length adjusting cam is recessed inwardly to form an ejection section, characterized in that a limiting block is connected to the stitch length adjusting cam, and a limiting channel is formed between the limiting block and the ejection section, and the stitch length adjusting cam can be rotated so that the stitch length adjusting member is embedded in the limiting channel and abuts against the ejection section and the limiting block.
[0008] On the premise that the stitch length adjusting member is always abutted against the presser foot lifting and adjusting cam by the first tension spring, the synchronous control mechanism of the present sewing machine has the advantage over the prior art that a limit block is assembled on the stitch length adjusting cam, which is relative to the ejection section on the outer wall of the stitch length adjusting cam, and a limit channel capable of accommodating the stitch length adjusting member is formed between the limit block and the ejection section. Under normal circumstances, the tension of the first tension spring can ensure that the stitch length adjusting member is always abutted against the outer wall of the stitch length adjusting cam, so that the stitch length adjusting mechanism drives the feed dog to complete the complete cloth feeding action under the pushing action of the stitch length adjusting cam. If the tension of the first tension spring is insufficient due to the elastic coefficient of the first tension spring itself or long-term use, the pressure of the first tension spring will not be able to make the stitch length adjusting cam rotate to the ejection section with the motor shaft. The stitch length adjusting member is in abutment with the outer wall of the ejection section. At this time, the tension of the first tension spring can still pull the stitch length adjusting member into the limiting channel. Moreover, the limiting block is connected to the stitch length adjusting cam, that is to say, the stitch length adjusting cam can drive the limiting block to rotate synchronously, and make this part of the rotational force be converted into a compressive force by the limiting block on the stitch length adjusting member, and cooperate with the limiting channel for the stitch length adjusting member, so that when the tension of the tension spring is insufficient, the stitch length adjusting member can still always be in abutment with the outer wall of the ejection section of the stitch length adjusting cam, thereby realizing that the stitch length adjusting member and the stitch length adjusting cam are always in abutment. On this basis, in this case, a presser foot lifting and resetting assembly is also used to realize the timely resetting action of the sewing machine presser foot after being lifted, so as to ensure that the fabric to be sewn can be pressed and positioned by the presser foot in time.
[0009] In the above-mentioned synchronous control structure of the sewing machine, the limit block is in the shape of a strip plate, one end of the limit block is detachably connected to the stitch length adjustment cam through a fastener, the other end of the limit block protrudes from the ejection section, the end of the limit block protruding from the ejection section is folded along the width direction of the limit block to form a limit portion, and the limit channel is formed between the limit portion and the ejection section. Through this arrangement, the connection between the limit block and the stitch length adjustment cam is stable, and a structurally stable limit channel is formed by the cooperation between the limit portion and the outer wall of the ejection section of the stitch length adjustment cam.
[0010] In the above-mentioned synchronous control structure of the sewing machine, the stitch length adjustment cam is located on the outer side wall in front of the ejection section and also protrudes outward to form a retracted section. One end of the limiting section has a guide portion extending outward, and a guide channel is formed between the guide portion and the outer wall of the retracted section. The stitch length adjustment cam can rotate so that the stitch length adjustment member is embedded in the guide channel and abuts against the retracted section and the guide portion. Through this arrangement, when the stitch length adjustment member abuts against the outer wall of the retracted section of the stitch length adjustment cam, the tension of the first tension spring cooperates with the outer wall of the retracted section to guide the stitch length adjustment member, so that the stitch length adjustment member can be embedded in the guide channel. When the stitch length adjustment cam continues to rotate to transition to the ejection section, the stitch length adjustment member can quickly pass through the guide channel and enter the limiting channel.
[0011] In the above-mentioned synchronous control structure of the sewing machine, the guide part is in the shape of a long strip and is curved outward from the front end to the rear end, so as to avoid interference between the needle distance adjusting member and the outer wall of the retracted section or the inner wall of the guide part in the guide channel.
[0012] In the above-mentioned synchronous control structure of the sewing machine, the front inner wall of the guide part is provided with a guide surface so that the port of the guide channel is expanded, which can guide the needle distance adjusting member to ensure that it can enter the guide channel more smoothly.
[0013] In the above-mentioned synchronous control structure of the sewing machine, a plurality of strip holes are provided at one end of the limit block detachably connected to the stitch length adjustment cam, and each of the strip holes extends along the length direction of the limit block, and a fixing hole is provided on the stitch length adjustment cam corresponding to each of the strip holes, and the limit block is fixed by fasteners passing through the strip holes and screwed with the fixing holes. In this way, the limit block can adjust its position while ensuring the locking effect, and further the guide channel and the limit channel can be expanded or reduced according to the size of the stitch length adjustment member used, ensuring higher applicability.
[0014] In the above-mentioned synchronous control structure of the sewing machine, the stitch length adjustment mechanism includes a stitch length adjustment crank and a crank pin for connecting to the frame, one end of the stitch length adjustment crank is hinged to the crank pin, and the other end is rotatably connected to the stitch length adjustment member, and the side wall of the stitch length adjustment crank has a connection portion protruding downward, and the first tension spring is connected to the connection portion. In this way, the installation and positioning of the first tension spring is achieved, and under the holding action of the crank pin, it is ensured that the first tension spring can pull the stitch length adjustment crank by pulling the connection portion, so that the stitch length adjustment member abuts against the outer wall of the stitch length adjustment cam.
[0015] In the above-mentioned synchronous control structure of the sewing machine, the presser foot lifting adjustment mechanism includes a presser foot lifting short connecting rod, the presser foot lifting adjustment member is a ball bearing, the inner ring of the presser foot lifting adjustment member is fixedly connected to the presser foot lifting short connecting rod through a screw and a nut, and the outer ring of the presser foot lifting adjustment member is in abutment with the presser foot lifting adjustment cam. The presser foot lifting adjustment mechanism is connected to the presser foot lifting adjustment member through a short connecting rod, and as a specific solution, the presser foot lifting adjustment member is specifically a ball bearing, that is, its inner ring can be fixed to the presser foot lifting short connecting rod by a screw, and its outer ring can roll when it contacts and is subjected to force with the presser foot lifting adjustment cam, thereby reducing the wear on the presser foot lifting adjustment member and the presser foot lifting adjustment cam. In addition, as an alternative solution, the presser foot lifting adjustment member can also have a rotating disk on the outer wall, which is screwed to the presser foot lifting short connecting rod by a screw and can rotate circumferentially around the screw.
[0016] In the above-mentioned synchronous control structure of the sewing machine, the synchronous control device of the sewing machine also includes a presser foot lifter reset assembly capable of making the presser foot lifter adjustment member always abut against the presser foot lifter adjustment cam, the presser foot lifter reset assembly includes a second tension spring and a spring pin for fixing in the frame, the presser foot lifter adjustment mechanism also includes a presser foot lifter plate fixedly connected to the presser foot lifter short connecting rod and a rear lever hinged to the presser foot lifter plate, one end of the second tension spring is connected to the spring pin, and the other end is connected to the rear lever. As a further solution, the presser foot lifter and reset assembly in the present application is also different from the reset structure in the prior art. Specifically, the presser foot lifter and reset assembly includes a spring pin and a second tension spring, wherein the spring pin is fixed on the frame of the sewing machine, one end of the second tension spring is connected to the rear lever in the presser foot lifter and adjusting mechanism, and the other end is connected to the spring pin. After the connection is completed, the spring is always in a tensioned state. After the presser foot lifter and adjusting mechanism lifts the presser foot, when the elastic force acting on the rear lever is greater than other forces, the rear lever and even the entire presser foot lifter and adjusting mechanism can be pulled downward to reset, thereby realizing the movement and reset of the presser foot. In addition, compared with the prior art, the original base plate structure is replaced by the setting of a spring pin, which can effectively reduce the installation space required for the presser foot lifter and reset assembly, thereby avoiding affecting the installation of other components. As an alternative solution, the tension spring in the presser foot lifter and reset assembly can be replaced by an elastic metal sheet.
[0017] Compared with the prior art, the synchronous control structure of the sewing machine has the following advantages:
[0018] By installing a limit block protruding from the ejection section on the stitch length adjusting cam corresponding to the ejection section, and forming a limit channel between the limit block and the ejection section, during the operation of the sewing machine, through the pulling force of the first tension spring, when the position of the stitch length adjusting member corresponds to the position of the ejection section of the stitch length adjusting cam, the limit block can limit the stitch length adjusting member in the limit channel and press it against the stitch length adjusting cam, so that the stitch length adjusting member and the stitch length adjusting cam are always in contact with each other. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is a structural diagram of the synchronous control structure of this sewing machine.
[0020] Figure 2 yes Figure 1 A partial enlarged view of point A in the middle.
[0021] Figure 3 It is a structural diagram of the synchronous control structure of the sewing machine from another perspective.
[0022] Figure 4 yes Figure 3 A partial enlarged view of point B in the middle.
[0023] Figure 5 It is a schematic diagram of the structure of the limit block and the needle distance adjustment cam.
[0024] Figure 6 It is a structural diagram of the limit block.
[0025] Figure 7 It is a structural schematic diagram of the needle distance adjustment cam.
[0026] Figure 8 It is a structural schematic diagram of the presser foot lifting and resetting assembly.
[0027] In the figure,
[0028] 1. Presser foot lifting adjustment mechanism; 11. Presser foot lifting adjustment member; 12. Presser foot lifting short connecting rod; 13. Presser foot lifting plate; 14. Rear lever;
[0029] 2. needle distance adjustment mechanism; 21. needle distance adjustment member; 22. needle distance adjustment crank; 221. connecting part; 23. crank pin;
[0030] 3. Lift the presser foot to adjust the cam;
[0031] 4. Stitch length adjustment cam; 41. Ejection section; 42. Limiting block; 421. Limiting portion; 422. Guide portion; 4221. Guide surface; 423. Strip hole; 43. Retracting section; 44. Fixing hole;
[0032] 5. The first tension spring;
[0033] 6. Presser foot lifting and resetting assembly; 61. Second tension spring; 62. Spring pin;
[0034] 7. Limit channel;
[0035] 8. Guidance Channel
[0036] 9. Reverse and forward sewing control mechanism. DETAILED DESCRIPTION
[0037] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
[0038] like Figure 1 and Figure 3 As shown, the synchronous control structure of the sewing machine includes a presser foot lifting adjustment mechanism 1 connected to the presser foot of the sewing machine, a stitch length adjustment mechanism 2 connected to the feed dog of the sewing machine, a reverse and forward sewing driving mechanism 9 respectively connected to the stitch length adjustment mechanism and the feed dog, and a presser foot lifting adjustment cam 3 and a stitch length adjustment cam 4 used to be fixedly connected to the motor shaft of the driving motor.
[0039] The presser foot lifting and adjusting mechanism 1, the needle length adjusting mechanism 2 and the reverse and forward sewing driving mechanism 9 are all prior arts, among which the specific structures of the presser foot lifting and adjusting mechanism 1 and the needle length adjusting mechanism 2 are disclosed in paragraphs 0036 and 0039 of the specification of Chinese patent CN217628851U, and the working principles are disclosed in paragraphs 0042 to 0045 of the specification. The specific structure and working principle of the reverse and forward sewing driving mechanism 9 are disclosed in paragraphs 0026 and 0035 of Chinese patent CN109056197A. Therefore, the specific structures and working principles of the presser foot lifting and adjusting mechanism 1, the needle length adjusting mechanism 2 and the reverse and forward sewing driving mechanism 9 are not described in detail in this case.
[0040] But it is worth mentioning that Figure 2 and Figure 4 The presser foot lifting and adjusting mechanism 1 specifically includes a presser foot lifting short connecting rod 12 and a presser foot lifting plate 13 which are screwed and locked together by a bolt and a nut. A presser foot lifting and adjusting member 11 is rotatably connected to the presser foot lifting and adjusting short connecting rod 12, and is specifically a ball bearing. As an alternative, it can also be a rotating disk rotatably connected to the presser foot lifting and adjusting short connecting rod 12, and the presser foot lifting and adjusting member 11 abuts against the outer side wall of the presser foot lifting and adjusting cam 3. The stitch length adjustment mechanism 2 specifically includes a stitch length adjustment crank 22 hinged in the sewing machine casing, and a stitch length adjustment member 21 is installed on the stitch length adjustment crank 22, which is specifically a bolt and a roller rotatably connected to the outside of the bolt. One end of the bolt is positioned on the stitch length adjustment crank 22, and the other end abuts against the outer wall of the stitch length adjustment cam 4. As an alternative, the stitch length adjustment member 21 can also be a bolt fixed with a ball bearing.
[0041] In addition, the presser foot lifting and adjusting mechanism 1 further comprises a rear lever 14 hingedly connected to the presser foot lifting plate 13, and a hanging hole is provided on the rear lever 14. Figure 8The synchronous control device of the sewing machine also includes a presser foot lifting and resetting component 6, which specifically includes a second tension spring 61 and a spring pin 62. One end of the spring pin 62 is fixed in a reserved hole opened on the frame, and a hanging groove is opened on the outer wall of the other end along the circumferential direction. One end of the second tension spring 61 is hung in the hanging hole, and the other end is hung in the hanging groove.
[0042] In addition, a first tension spring 5 is provided between the frame of the sewing machine and the stitch length adjustment crank 22. A downwardly protruding connecting portion 221 is provided near the middle of the stitch length adjustment crank 22. A connecting hole is provided on the connecting portion 221. One end of the first tension spring 5 is hooked to the reserved hole provided on the frame, and the other end is hooked in the connecting hole.
[0043] Combination Figure 5-7 The outer side wall of the stitch length adjustment cam 4 has a retraction section 43 that is protruding outward and used to control the stitch length adjustment mechanism 2 to drive the feed dog to retract downward, and an ejection section 41 that is concave inward and used to control the stitch length adjustment mechanism 2 to drive the feed dog to eject upward, and the two are arranged adjacent to each other. Two fixing holes 44 are provided on the plate surface of the stitch length adjustment cam 4. In addition, a limit block 42 in the form of a strip plate is detachably connected to the stitch length adjustment cam 4, and two strip holes 423 arranged at intervals are provided at the lower end along the length direction, and the opening direction of the two strip holes 423 is the same as the length direction of the limit block 42. The limit block 42 is fixed by two screws. The limit blocks 42 are passed through the strip holes 423 in a one-to-one correspondence and tightened into the fixing holes 44, so that the limit block 42 is positioned on the stitch length adjustment cam 4 and the upper end of the limit block 42 corresponds to the ejection section 41 and protrudes from the outer wall of the stitch length adjustment cam 4. The upper end of the limit block 42 is bent inward along the width direction of the limit block 42 itself to form a limit portion 421, and a limit channel 7 is formed between the limit portion 421 and the outer wall of the ejection section 41. In addition, a receiving groove located in the limiting channel 7 is opened on the plate surface at the upper end of the limit block 42 along the width direction. Through the setting of the receiving groove, interference between the fixed shaft or bolt used to maintain the stitch length adjustment member 21 and the limit block 42 is avoided.
[0044] Working principle: when the needle distance adjustment cam 4 rotates to make the needle distance adjustment member 21 abut against the retracted section 43, the tension of the first tension spring 5 drives the needle distance adjustment member 21 to abut against the outer wall of the retracted section 43, and slides into the guide channel 8 under the guidance of the outer wall of the retracted section 43 and the guide surface 4221. In this state, the needle distance adjustment member 21 always abuts against the outer wall of the retracted section 43 under the action of the first tension spring 5 and the guide portion 422. When the needle distance adjustment cam 4 continues to rotate in this direction, making the needle distance adjustment member 21 slide along the retracted section 43 toward the ejection section 41, at this time, although the tension of the first tension spring 5 is not enough to drive The needle distance adjusting member 21 is abutted against the outer wall of the ejection section 41, but it can still be ensured that the needle distance adjusting member 21 is positioned in the guide channel 8, and as the needle distance adjusting cam 4 drives the limit block 42 to continue to rotate eccentrically, the eccentric force generated is transmitted to the needle distance adjusting member 21 through the groove wall of the limit portion 421. In addition, the needle distance adjusting crank 22 is connected to the crank pin 23 in a hinged manner, so that the limit block 42 can push the needle distance adjusting member 21 downward through the groove wall of the limit portion 421, so that the needle distance adjusting member 21 abuts against the outer wall of the ejection section 41 while moving into the limit channel 7.
[0045] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.
[0046] Although the present invention uses more terms such as presser foot lifting adjustment mechanism 1, presser foot lifting adjustment member 11, presser foot lifting short connecting rod 12, presser foot lifting plate 13, rear lever 14, stitch length adjustment mechanism 2, stitch length adjustment member 21, stitch length adjustment crank 22, connecting portion 221, crank pin 23, presser foot lifting adjustment cam 3, stitch length adjustment cam 4, ejection section 41, limit block 42, limit portion 421, guide portion 422, guide surface 4221, strip hole 423, retracted section 43, first tension spring 5, presser foot lifting reset assembly 6, second tension spring 61, spring pin 62, limit channel 7, guide channel 8, etc., the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the utility model; interpreting them as any additional restrictions is contrary to the spirit of the utility model.
Claims
1. A synchronous control structure of a sewing machine, comprising a presser foot lifting adjustment mechanism (1) having a presser foot lifting adjustment member (11), a stitch length adjustment mechanism (2) having a stitch length adjustment member (21), a presser foot lifting adjustment cam (3) and a stitch length adjustment cam (4) fixed to a motor driving end, a presser foot lifting reset assembly (6) capable of driving the presser foot lifting adjustment member (11) to always abut against the presser foot lifting adjustment cam (3), and a first tension spring (5) capable of driving the stitch length adjustment member (21) to always abut against the presser foot lifting adjustment cam (3), the outer side wall of the stitch length adjustment cam (4) being inwardly recessed to form an ejection section (41), characterized in that: The needle distance adjustment cam (4) is connected to a limit block (42), and a limit channel (7) is formed between the limit block (42) and the ejection section (41); the needle distance adjustment cam (4) is capable of rotating so that the needle distance adjustment member (21) is embedded in the limit channel (7) and abuts against the ejection section (41) and the limit block (42).
2. The synchronous control structure of a sewing machine according to claim 1, characterized in that: The limit block (42) is in the shape of a strip plate, one end of the limit block (42) is detachably connected to the stitch length adjustment cam (4) via a fastener, the other end of the limit block (42) protrudes from the ejection section (41), one end of the limit block (42) protruding from the ejection section (41) is folded along the width direction of the limit block (42) to form a limit portion (421), and the limit channel (7) is formed between the limit portion (421) and the ejection section (41).
3. The synchronous control structure of a sewing machine according to claim 2, characterized in that: The needle distance adjustment cam (4) is located on the outer side wall in front of the ejection section (41) and also protrudes outward to form a retracted section (43); one end of the limiting portion (421) has a guide portion (422) extending outward, and a guide channel (8) is formed between the guide portion (422) and the outer wall of the retracted section (43); the needle distance adjustment cam (4) can be rotated so that the needle distance adjustment member (21) is embedded in the guide channel (8) and abuts against the retracted section (43) and the guide portion (422).
4. The synchronous control structure of a sewing machine according to claim 3, characterized in that: The guide portion (422) is in the shape of an elongated strip and is curved outwards from the front end to the rear end in an arc shape.
5. The synchronous control structure of a sewing machine according to claim 4, characterized in that: The front end inner wall of the guide portion (422) is provided with a guide surface (4221) so that the port of the guide channel (8) is expanded.
6. The synchronous control structure of a sewing machine according to any one of claims 2 to 5, characterized in that: One end of the limit block (42) detachably connected to the stitch length adjustment cam (4) is provided with a plurality of strip holes (423), and each of the strip holes (423) extends along the length direction of the limit block (42); a fixing hole (44) is provided on the stitch length adjustment cam (4) corresponding to each of the strip holes (423); the limit block (42) is fixed by fasteners passing through the strip holes (423) and being screwed to the fixing holes (44).
7. The synchronous control structure of a sewing machine according to any one of claims 1 to 5, characterized in that: The stitch length adjustment mechanism (2) comprises a stitch length adjustment crank (22) and a crank pin (23) for connecting to a frame, one end of the stitch length adjustment crank (22) is hinged to the crank pin (23), and the other end is rotatably connected to the stitch length adjustment member (21), a connecting portion (221) protruding downward is provided on a side wall of the stitch length adjustment crank (22), and the first tension spring (5) is connected to the connecting portion (221).
8. The synchronous control structure of a sewing machine according to claim 7, characterized in that: The presser foot lifting and adjusting mechanism (1) comprises a presser foot lifting short connecting rod (12); the presser foot lifting and adjusting member (11) is a ball bearing; the inner ring of the presser foot lifting and adjusting member (11) is fixedly connected to the presser foot lifting short connecting rod (12) via a screw and a nut; and the outer ring of the presser foot lifting and adjusting member (11) is in abutment with the presser foot lifting and adjusting cam (3).
9. The synchronous control structure of a sewing machine according to claim 8, characterized in that: The presser foot lifting and resetting assembly (6) comprises a second tension spring (61) and a spring pin (62) for fixing in a frame, the presser foot lifting and adjusting mechanism (1) also comprises a presser foot lifting plate (13) fixedly connected to the presser foot lifting short connecting rod (12) and a rear lever (14) hinged to the presser foot lifting plate (13), one end of the second tension spring (61) is connected to the spring pin (62), and the other end is connected to the rear lever (14).