Needle distance adjustment mechanism

Abstract

The present invention provides a stitch length adjustment mechanism, which belongs to the technical field of sewing machines. It solves the problems that the existing stitch length adjustment mechanism is prone to collision accidents caused by the motor rotating beyond the range, resulting in insufficient reliability. The stitch length adjustment mechanism is installed on the casing of the sewing machine, and a feed shaft is penetrated on the casing. The stitch length adjustment mechanism includes a swing plate seat, a motor and a rotatable sleeve mounted on the feed shaft. A first crank and a second crank connected to the swing plate seat are fixed on the sleeve. A rotating part capable of full-circle rotation is fixedly connected to the output shaft of the motor. A driving boss is eccentrically arranged on the rotating part. A strip-shaped driving hole is arranged on the first crank. The driving boss is inserted into the driving hole and can act on the hole wall of the driving hole to rotate the first crank around the feed shaft. The hole wall of the driving hole includes a swing-reducing surface that can abut against the driving boss and is concave outward. The stitch length adjustment mechanism improves the reliability of operation.

Description

Technical Field

[0001] The invention belongs to the technical field of sewing machines and relates to a needle distance adjusting mechanism. Background Art

[0002] A sewing machine is a machine that sews materials together through sewing threads. A sewing machine includes a needle bar mechanism, a thread picking mechanism, a feeding mechanism, a thread hooking mechanism, a clamping mechanism, a presser foot lifting mechanism, a stitch length adjustment mechanism, a thread trimming mechanism, etc. With the development of automation, these mechanisms are gradually improved and equipped with driving parts, including motors, electromagnets, cylinders, and oil cylinders, etc. Among them, motors are the most commonly used driving parts for driving parts to rotate.

[0003] A stitch length changing mechanism of a sewing machine disclosed in Chinese patent literature [application number: CN201320577992.5; announcement number: 203513991 U] comprises a tooth lifting shaft, a feed shaft and a swing plate seat, wherein a feed crank is fixedly connected to the feed shaft, a feed eccentric wheel is fixedly connected to the tooth lifting shaft and a feed connecting rod is sleeved on the feed eccentric wheel, the swing plate seat is hinged to the casing of the sewing machine, a swing plate assembly is arranged in the swing plate seat so that the feed connecting rod can drive the feed crank to swing, the feed connecting rod is connected to the feed crank through the swing plate assembly, a motor is also fixedly arranged on the casing and rotatably connected to a feed changing shaft, the feed changing shaft is transmission-connected to the output shaft of the motor through a transmission structure, a stitch length changing crank is fixedly connected to the feed changing shaft, and an adjusting connecting rod is connected between the stitch length changing crank and the swing plate seat so that the two can swing together. When the stitch length is adjusted to a positive value in the stitch length changing mechanism, the sewing machine realizes forward stitching, and when the stitch length is adjusted to a negative value, the sewing machine realizes reverse stitching.

[0004] In the above-mentioned needle pitch conversion mechanism, the transmission structure includes synchronous pulley 1 and synchronous pulley 2, synchronous pulley 1 is fixedly connected to the output shaft of the motor, synchronous pulley 2 is fixedly sleeved on the cloth feed conversion shaft, and a synchronous belt is connected between synchronous pulley 1 and synchronous pulley 2. Or the transmission structure includes a coupling, one end of the coupling is connected to the output shaft of the motor, and the other end of the coupling is connected to the cloth feed conversion shaft. In theory, the motor can rotate one circle to drive the swing plate seat to swing, and the motor will drive the needle pitch conversion crank to rotate one circle when it rotates one circle. However, in actual use, since the needle pitch conversion crank will interfere with other parts during the rotation of one circle, it can only rotate within a certain range. Therefore, the motor often does not need to rotate one circle. When in use, the rotation angle of the motor is usually limited to ensure the normal operation of the mechanism. However, during the movement of the mechanism, if the device that limits the rotation angle of the motor fails, the motor rotation is likely to exceed the allowed range, thereby causing a collision accident, causing the sewing machine to stop for maintenance, thereby affecting production efficiency. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to propose a needle distance adjustment mechanism, which solves the technical problem that the prior needle distance adjustment mechanism is prone to collision accidents caused by motor rotation out of range, resulting in insufficient reliability.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A stitch length adjustment mechanism is installed on a casing of a sewing machine, wherein a feed shaft is provided on the casing, and the stitch length adjustment mechanism comprises a swing plate seat hinged on the casing and a motor capable of driving the swing plate seat to swing, wherein the stitch length adjustment mechanism further comprises a rotatable sleeve mounted on the feed shaft, a first crank and a second crank transmission-connected to the swing plate seat are fixed on the sleeve, a rotating member capable of full-circle rotation is fixedly connected to the output shaft of the motor, a driving boss is eccentrically provided on the rotating member, a strip-shaped driving hole is provided on the first crank, the driving boss is inserted into the driving hole and can act on the hole wall surface of the driving hole to rotate the first crank around the feed shaft, and the hole wall surface of the driving hole comprises a swing-reducing surface that can abut against the driving boss and is concave outward.

[0008] The rotating part can rotate in a full circle, that is, the motor can rotate in a full circle. When the motor rotates one circle, the driving boss rotates one circle around the motor output shaft with the rotating part. Since the driving boss is located in the driving hole, according to the mechanical principle, the driving boss acts on the hole wall of the driving hole to drive the first crank to swing once around the feed shaft, and the second crank swings once around the feed shaft synchronously. Since the swing reduction surface is concave outward, compared with the plane or the convex surface convex inward when the swing reduction surface is not set, the swing angle of the first crank and the second crank can be controlled in a smaller range, thereby avoiding the first crank and the second crank from colliding with other parts, ensuring that the first crank and the second crank will not collide when the motor rotates one circle. Since the swing angle of the first crank and the second crank is limited by the cooperation of the driving boss and the driving hole on the first crank, rather than limiting the rotation angle of the motor, the problem of the motor rotation angle exceeding the range is fundamentally solved, thereby avoiding the collision accident caused by the motor rotating beyond the range, and improving the reliability of the needle distance adjustment mechanism.

[0009] Moreover, since the sleeve is mounted on the feed shaft, that is, the first crank and the second crank are positioned and installed on the feed shaft, on the one hand, the first crank and the second crank are supported and positioned by the feed shaft to avoid collision between the first crank and the second crank and the feed shaft, and at the same time, the first crank and the second crank are accurately positioned and rotated stably, ensuring the consistency between the designed running trajectory of the mechanism and the actual running trajectory, thereby improving the reliability of the stitch length adjustment mechanism, and on the other hand, it can also reduce the internal space of the sewing machine occupied by the sleeve, so that the various mechanisms of the sewing machine form an orderly and compact whole.

[0010] In addition, the driving boss is inserted into the driving hole for cooperation, which increases the overlapping part between the rotating part and the first crank in the direction of the feed axis. When the motor rotates one circle, compared with other transmission structures, the rotating part and the first crank occupy a relatively small movement space in the sewing machine, which reduces the possibility of interference between the rotating part and the first crank and other components, and is beneficial to improving the reliability of the operation of the stitch adjustment mechanism.

[0011] In the above-mentioned needle distance adjustment mechanism, a clearance groove is arranged on the hole wall surface of the driving hole at the position closest to the sleeve, and the two side walls of the clearance groove are arranged in parallel and can be abutted against the driving boss at the same time. When the driving boss and the two side walls of the clearance groove are abutted at the same time, there is a gap between the driving boss and the bottom surface of the clearance groove.

[0012] The two side walls of the give way groove are parallel, and when the driving boss abuts against the two side walls of the give way groove at the same time, there is a gap between the driving boss and the bottom surface of the give way groove, so that the give way groove has a give way effect, avoiding the driving boss from being stuck at the closest point to the sleeve due to the interference structure between the driving boss and the hole wall of the driving hole, so that the driving boss can move smoothly in the driving hole; at the same time, since the two side walls of the give way groove are arranged in parallel and can abut against the driving boss at the same time, the driving boss can make a smooth transition in the give way groove, avoiding the sudden change of the first crank swing caused by the sudden change of the driving boss at the abutment point, that is, avoiding the sudden change of the needle distance during the adjustment process, so that the needle distance adjustment mechanism runs smoothly when adjusting the needle distance, which is beneficial to improving the stability and reliability of the operation of the needle distance adjustment mechanism and ensuring the accuracy of the needle distance adjustment.

[0013] In the above-mentioned needle distance adjustment mechanism, the swing reduction surface is connected to the side wall surface of the clearance groove, and an arc transition surface is provided between the swing reduction surface and the side wall surface of the clearance groove. The arc transition surface allows the driving protrusion to smoothly transition between the swing reduction surface and the side wall surface of the clearance groove, so that the needle distance adjustment mechanism can be operated stably when adjusting the needle distance, avoiding sudden changes in the needle distance, which is beneficial to improving the stability and reliability of the operation of the needle distance adjustment mechanism and ensuring the accuracy of needle distance adjustment.

[0014] In the above-mentioned needle distance adjustment mechanism, the swing reduction surface is in an arc shape, and when the driving boss abuts against the swing reduction surface, the center of the swing reduction surface remains concentric with the rotation center of the motor output shaft.

[0015] The setting of the above-mentioned sway reduction surface makes it impossible for the driving boss acting on the sway reduction surface to drive the first crank and the second crank to rotate around the feed shaft, that is, the rotation of the motor is no longer transmitted to the first crank when the driving boss acts on the sway reduction surface. Therefore, if the needle distance adjustment mechanism still needs to use the motor angle limitation during use, after setting the above-mentioned sway reduction surface, even if the motor rotation angle exceeds the range, the rotation of the motor will not be transmitted, thereby avoiding the occurrence of collision accidents caused by the motor rotation angle exceeding the range, thereby improving the reliability of the operation of the needle distance adjustment mechanism.

[0016] Moreover, the above-mentioned swing reduction surface structure can also be used to cooperate with other actions of the sewing machine, such as cutting the thread or lifting the presser foot when the driving boss acts on the swing reduction surface, which can improve the coordinated use of various mechanisms in the sewing machine.

[0017] In the above-mentioned needle distance adjustment mechanism, the first crank has an imaginary symmetry axis perpendicular to the central axis of the feed shaft, the give way groove is symmetrically arranged about the imaginary symmetry axis, the two anti-sway surfaces are symmetrically arranged about the imaginary symmetry axis, and the two arc transition surfaces are symmetrically arranged about the imaginary symmetry axis.

[0018] After the wall surface of the driving hole is symmetrically arranged about the imaginary symmetry axis, the swing angle of the first crank generated by the driving boss acting on the wall surface of the driving hole is also symmetrically distributed about the imaginary symmetry axis, which facilitates the needle distance adjustment mechanism to adjust the needle distance.

[0019] In the above-mentioned needle distance adjustment mechanism, an avoidance groove or a through opening is provided on the hole wall surface of the driving hole at the position farthest from the sleeve, and the driving boss never abuts against the side wall surface of the avoidance groove or the through opening during one rotation of the rotating member; or an additional giveway groove is provided on the hole wall surface of the driving hole at the position farthest from the sleeve, and the two side walls of the additional giveway groove are arranged in parallel and can abut against the driving boss at the same time, and when the driving boss abuts against the two side walls of the additional giveway groove at the same time, there is an additional gap between the driving boss and the bottom surface of the additional giveway groove.

[0020] The avoidance groove and the through opening have a giving way function, which prevents the driving boss from getting stuck at the farthest point from the shaft sleeve due to the interference structure between the driving boss and the hole wall of the driving hole, so that the driving boss moves smoothly in the driving hole, which is beneficial to improving the stability and reliability of the operation of the stitch length adjustment mechanism. The additional giving way groove has the same function as the giving way groove, which avoids the sudden change of the stitch length of the sewing machine during the adjustment process, so that the stitch length adjustment mechanism runs smoothly when adjusting the stitch length, which is beneficial to improving the stability and reliability of the operation of the stitch length adjustment mechanism.

[0021] In the above-mentioned needle distance adjustment mechanism, a connecting rod is hinged between the second crank and the swing plate seat, and an adjustment structure for adjusting the distance from the hinge point of the second crank and the connecting rod to the rotation center of the second crank is provided between the connecting rod and the second crank.

[0022] The distance from the hinge point of the second crank and the connecting rod to the rotation center of the second crank is the effective length of the second crank. The effective length of the second crank can be changed by setting an adjustment structure. After the effective length of the second crank is changed, the swing angle range of the swing plate seat can be changed while the swing angle range of the second crank remains unchanged, thereby changing the limit range of the stitch length adjustment, that is, adjusting the size of the maximum stitch length. Therefore, when the swing angle range of the first crank is limited due to the cooperation between the driving hole and the driving boss, the size of the maximum stitch length can be adjusted by the above-mentioned adjustment structure, so that the stitch length of the sewing machine can meet the sewing requirements. Therefore, after the swing angle range of the first crank is limited by the cooperation between the driving hole and the driving boss, the swing angle range of the swing plate seat can be enlarged or reduced to meet the sewing requirements through the adjustment structure between the second crank and the connecting rod, thereby ensuring the use range of the sewing machine.

[0023] In the above-mentioned needle distance adjustment mechanism, the adjustment structure includes a plurality of adjustment holes arranged on the second crank, and the distance from each adjustment hole to the rotation center of the second crank is different. The second crank can be hinged with the connecting rod through any adjustment hole.

[0024] Since the distance from each adjustment hole on the second crank to the rotation center of the crank is different, and the second crank can be hinged to the connecting rod through any adjustment hole, when the second crank and the connecting rod are hinged through different adjustment holes, the effective length of the second crank is different, so that the swing angle range of the swing plate seat is different. In this way, by selecting different adjustment holes to make the second crank and the connecting rod hinged, the stitch adjustment limit range of the stitch adjustment mechanism can be changed, that is, the maximum stitch length can be changed.

[0025] In the above-mentioned needle distance adjustment mechanism, positioning retaining rings are fixedly connected to both ends of the shaft sleeve on the feed shaft, and both end surfaces of the shaft sleeve are respectively abutted against the corresponding positioning retaining rings.

[0026] The shaft sleeve is axially positioned on the feed shaft by a positioning retaining ring to prevent the shaft sleeve from axial sliding, so that the needle distance adjustment mechanism works stably.

[0027] In the above-mentioned needle pitch adjustment mechanism, the first crank is integrally formed or separately fixed on the shaft sleeve, and the second crank is integrally formed or separately fixed on the shaft sleeve. Integral forming can better ensure the processing accuracy, thereby ensuring the accuracy and reliability of the needle pitch adjustment mechanism. Separate fixing facilitates the maintenance and replacement of the first crank and the second crank.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The sleeve is sleeved on the feed shaft, a driving hole is set on the first crank fixed on the sleeve, and a driving boss is eccentrically set on the rotating member fixedly connected to the motor output shaft. The driving boss acts on the hole wall of the driving hole to make the first crank rotate around the feed shaft, and the wall of the driving hole includes a swing reduction surface that abuts against the driving boss and is concave outward. The swing angle of the first crank and the second crank is limited by the cooperation of the driving boss and the driving hole, and the swing angle range of the first crank and the second crank is further reduced by the swing reduction surface. The rotation angle of the motor is not limited, which improves the reliability of the operation of the stitch length adjustment mechanism. The swing reduction surface is optimized to an idle stroke surface, which improves the reliability of the operation of the stitch length adjustment mechanism and provides the possibility of cooperation with other actions of the sewing machine. The setting of the clearance groove improves the stability and reliability of the operation of the stitch length adjustment mechanism. An adjustment structure is set between the second crank and the connecting rod for adjusting the effective length of the second crank. When the angle range of the first crank and the second crank is limited, the swing angle limit range of the swing plate seat can be adjusted by the adjustment structure, thereby ensuring the use range of the sewing machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a three-dimensional diagram of the first embodiment of the needle distance adjustment mechanism. Figure 1 ;

[0031] Figure 2 It is a three-dimensional diagram of the first embodiment of the needle distance adjustment mechanism. Figure 2 ;

[0032] Figure 3 This is a disassembled stereoscopic diagram of the first embodiment of the needle distance adjustment mechanism;

[0033] Figure 4 is a three-dimensional diagram of the first embodiment of the stitch length adjustment mechanism when it is installed on a sewing machine;

[0034] Figure 5 This is a position relationship diagram when the driving boss is located in the yielding groove in the first embodiment of the needle distance adjustment mechanism;

[0035] Figure 6 This is a position relationship diagram when the driving convex column acts on the swing reduction surface in the first embodiment of the needle distance adjustment mechanism.

[0036] In the figure, 1, casing; 2, feed shaft; 3, motor; 3a, output shaft; 4, swing plate seat; 5, rotating part; 5a, driving boss; 6, bushing; 6a, center hole; 7, first crank; 7a, driving hole; 7b, swing reduction surface; 7c, give way groove; 7d, arc transition surface; 7e, imaginary symmetry axis; 7f, avoidance groove; 8, connecting rod; 8a, hinge hole; 9, second crank; 9a, adjustment hole; 9b, fixing hole; 10, hinge shaft; 11, swing shaft; 12, pin shaft; 13, gap. 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] Embodiment 1

[0039] like Figure 1-Figure 6 As shown, a stitch length adjustment mechanism is installed on the casing 1 of the sewing machine. The casing 1 of the sewing machine is provided with a feed shaft 2. The stitch length adjustment mechanism includes a motor 3 fixed on the casing 1 and a swing plate seat 4 hinged on the casing 1. The casing 1 includes a body and a base. A swing shaft 11 is inserted on the left and right ends of the swing plate seat 4. The swing shaft 11 is provided on the base and fixed. The swing plate seat 4 rotates around the swing shaft 11. The feed shaft 2 is provided on the base. The swing shaft 11 is located above and slightly behind the feed shaft 2. The swing shaft 11 is arranged parallel to the feed shaft 2. The motor 3 is fixed on the base at a position slightly below the left side of the swing shaft 11, and the motor 3 is located behind the feed shaft 2. The output shaft 3a of the motor 3 extends to the right and is arranged parallel to the feed shaft 2. A rotating member 5 capable of full-circle rotation is fixedly connected to the output shaft 3a of the motor 3. A driving boss 5a is eccentrically arranged on the rotating member 5. The driving boss 5a is located on the right end surface of the rotating member 5 and is cylindrical.

[0040] The needle pitch adjustment mechanism also includes a sleeve 6 rotatably mounted on the feed shaft 2, and the sleeve 6 is located between the swing plate seat 4 and the motor 3. A first crank 7 is fixed to the left end of the sleeve 6, and a second crank 9 is fixed to the right end of the sleeve 6. The first crank 7 and the second crank 9 are both located behind the feed shaft 2 and tilted downward. A center hole 6a is provided on the sleeve 6, and the feed shaft 2 is inserted into the center hole 6a, and the center hole 6a and the feed shaft 2 form a gap 13 to cooperate. Positioning retaining rings [not shown in the figure] are fixed on the left and right sides of the sleeve 6 on the feed shaft 2, and the two end faces of the sleeve 6 are respectively abutted against the corresponding positioning retaining rings, and the sleeve 6 is axially fixed to the feed shaft 2 through the positioning retaining rings. The sleeve 6 and the first crank 7 can be integrally formed or separately fixed. When they are separately fixed, a positioning socket is provided on the first crank 7, and a positioning boss is provided on the left end surface of the sleeve 6. The positioning boss is inserted into the positioning socket. The first crank 7 is also provided with two fixing parts, which are respectively located on both sides of the positioning socket. The fixing parts are provided with fixing screws, and the fixing parts are fixedly connected to the sleeve 6 by the fixing screws. The sleeve 6 and the second crank 9 can be integrally formed or separately fixed. When they are separately fixed, a positioning groove is provided on the right end surface of the sleeve 6. The second crank 9 is embedded in the positioning groove and fixedly connected to the sleeve 6 by the fastening screws.

[0041] The first crank 7 is provided with a strip-shaped driving hole 7a, the driving boss 5a is inserted into the driving hole 7a and can act on the hole wall of the driving hole 7a to make the first crank 7 rotate around the feed shaft 2, and the hole wall of the driving hole 7a includes a swing-reducing surface 7b that can abut against the driving boss 5a and is concave outward, and the swing-reducing surface 7b is arched. Preferably, the swing-reducing surface 7b is in an arc shape, and when the driving boss 5a abuts against the swing-reducing surface 7b, the center of the swing-reducing surface 7b is kept concentric with the rotation center of the output shaft 3a of the motor 3. The first crank 7 has an imaginary symmetry axis 7e perpendicular to the central axis of the feed shaft 2, and a clearance groove 7c is provided on the hole wall of the driving hole 7a at the position closest to the sleeve 6, and the clearance groove 7c is symmetrically arranged about the imaginary symmetry axis 7e. The two side walls of the clearance groove 7c are arranged in parallel and can abut against the driving boss 5a at the same time. When the driving boss 5a abuts against the two side walls of the clearance groove 7c at the same time, there is a gap 13 between the driving boss 5a and the bottom surface of the clearance groove 7c. The hole wall surface of the driving hole 7a is provided with an avoidance groove 7f at the place farthest from the shaft sleeve 6. When the driving boss 5a is located at the place farthest from the shaft sleeve 6 of the driving hole 7a, the maximum distance from the outer side surface of the driving boss 5a to the rotation center of the output shaft 3a of the motor 3 is less than the minimum distance from the groove wall surface of the avoidance groove 7f to the rotation center of the output shaft 3a of the motor 3. In this way, during the process of the rotating member 5 rotating one circle, the driving boss 5a never abuts against the side wall surface of the avoidance groove 7f. The swing reduction surface 7b is located between the avoidance groove 7f and the clearance groove 7c. There are two swing reduction surfaces 7b and they are symmetrically arranged about the imaginary symmetry axis 7e. The swing reduction surface 7b is connected to the side wall surface of the avoidance groove 7c, and a circular arc transition surface 7d is arranged between the swing reduction surface 7b and the side wall surface of the avoidance groove 7c, and there are two circular arc transition surfaces 7d and they are symmetrically arranged about the imaginary symmetry axis 7e. The swing reduction surface 7b and the side wall surface of the avoidance groove 7f have a smooth transition, and preferably, the swing reduction surface 7b is tangent to the side wall surface of the avoidance groove 7f.

[0042] A connecting rod 8 is hinged between the second crank 9 and the swing plate seat 4. The connecting rod 8 is located on the left side of the swing plate seat 4, and the second crank 9 is located on the left side of the connecting rod 8. An adjustment structure is provided between the connecting rod 8 and the second crank 9, and the adjustment structure is used to adjust the distance from the hinge point of the second crank 9 and the connecting rod 8 to the rotation center of the second crank 9. One end of the connecting rod 8 is hinged on the left side surface of the rear end of the swing seat plate through a pin 12, and the other end of the connecting rod 8 is provided with a hinge hole 8a. The adjustment structure includes several adjustment holes 9a provided on the second crank 9, and the distance from each adjustment hole 9a to the rotation center of the second crank 9 is different. The second crank 9 can be hinged with the connecting rod 8 through any one of the adjustment holes 9a. All the adjustment holes 9a are arranged in sequence along a straight line on the second crank 9. There are three adjustment holes 9a, and the number of adjustment holes 9a can be appropriately increased or decreased as needed, such as two or four. An articulated shaft 10 is provided between the connecting rod 8 and the second crank 9, one end of the articulated shaft 10 is inserted into the articulated hole 8a of the connecting rod 8, and the other end of the articulated shaft 10 can be inserted into any one of the adjustment holes 9a. In order to facilitate the installation of the articulated shaft 10, the apertures of all the adjustment holes 9a are equal, and the articulated shaft 10 can be inserted into the adjustment hole 9a after passing through the articulated hole 8a. The aperture of the articulated hole 8a is equal to the aperture of the adjustment hole 9a, and the articulated shaft 10 is an optical axis; or the aperture of the articulated hole 8a is larger than the aperture of the adjustment hole 9a, and the articulated shaft 10 is a stepped shaft, and the diameter of the section inserted into the articulated hole 8a matches the aperture of the articulated hole 8a, and the diameter of the section inserted into the adjustment hole 9a matches the aperture of the adjustment hole 9a. The side of the second crank 9 is provided with fixing holes 9b corresponding to the adjusting holes 9a one by one, and the inner ends of the fixing holes 9b penetrate the hole wall of the adjusting holes 9a, and each fixing hole 9b can be threadedly connected with a set screw, and the hinge shaft 10 is fixed to the second crank 9 by the set screw. A positioning plane is provided on one end of the hinge shaft 10 inserted into the adjusting hole 9a, and the end face of the set screw abuts against the positioning plane. The positions of the adjusting hole 9a and the hinge hole 8a can be interchanged between the second crank 9 and the connecting rod 8.

[0043] When the motor 3 rotates, the rotating member 5 is driven to rotate in a full circle. The rotation of the rotating member 5 drives the driving boss 5a to rotate around the rotation center of the output shaft 3a of the motor 3. The driving boss 5a abuts against the hole wall of the driving hole 7a of the first crank 7, thereby driving the first crank 7 to rotate around the feed shaft 2. The second crank 9 rotates synchronously with the first crank 7 through the shaft sleeve 6, and drives the swing plate seat 4 to swing through the connecting rod 8. The swing of the swing plate seat 4 will change the stitch length of the sewing machine. When the motor 3 stops rotating, the sewing machine will sew with the adjusted stitch length. In order to ensure that the driving boss 5a can stably abut against the hole wall of the driving hole 7a after and during the stitch length adjustment, a spring can be fixed on the shaft sleeve 6 to keep the driving boss 5a abutting against the hole wall of the driving hole 7a. For example, a limit seat is fixed on the outer surface of the rear side of the sleeve 6, and a downward driving spring is fixedly connected to the upper surface of the limit seat, and an upward driving spring is fixed on the lower surface of the limit seat. When the driving boss 5a abuts against the upper side wall of the driving hole 7a, the upper end of the downward driving spring abuts against the base to generate a downward pressure, so that the upper side wall of the driving hole 7a is tightly attached to the driving boss 5a. When the driving boss 5a abuts against the lower side wall of the driving hole 7a, the lower end of the upward driving spring abuts against the base to generate an upward pressure, so that the lower side wall of the driving hole 7a is tightly attached to the driving boss 5a, wherein the upper side wall of the driving hole 7a and the lower side wall of the driving hole 7a are divided by the imaginary symmetry axis 7e. Alternatively, a downward pulling tension spring is arranged on the rear end of the swing plate seat 4, and an upward driving spring is fixed on the lower surface of the limit seat of the sleeve 6. When the driving boss 5a abuts against the upper side wall of the driving hole 7a, the tension spring generates a downward pressure, so that the upper side wall of the driving hole 7a is tightly attached to the driving boss 5a. When the driving boss 5a abuts against the lower side wall of the driving hole 7a, the lower end of the upward driving spring abuts against the base to generate an upward pressure, so that the lower side wall of the driving hole 7a is tightly attached to the driving boss 5a.

[0044] When the motor 3 rotates one circle, the driving boss 5a rotates one circle around the output shaft 3a of the motor 3 along with the rotating member 5, and the driving boss 5a acts on the hole wall surface of the driving hole 7a to drive the first crank 7 to swing once around the feed shaft 2, and the second crank 9 swings once around the feed shaft 2 synchronously. Since the swing reduction surface 7b is concave outward, compared with the plane or the convex surface convex inward when the swing reduction surface 7b is not provided, the swing angle of the first crank 7 and the second crank 9 can be controlled within a smaller range, thereby avoiding the first crank 7 and the second crank 9 from colliding with other parts, and ensuring that the first crank 7 and the second crank 9 will not collide when the motor 3 rotates one circle. Since the swing angle of the first crank 7 and the second crank 9 is limited by the cooperation of the driving boss 5a and the driving hole 7a on the first crank 7, instead of limiting the rotation angle of the motor 3, the problem that the rotation angle of the motor 3 may exceed the range is fundamentally solved, thereby avoiding the collision accident caused by the motor 3 rotating beyond the range, and improving the reliability of the mechanism operation. Moreover, since the sleeve 6 is sleeved on the feed shaft 2, that is, the first crank 7 and the second crank 9 are positioned and installed on the feed shaft 2, on the one hand, the first crank 7 and the second crank 9 are supported and positioned by the feed shaft 2, so as to avoid the first crank 7 and the second crank 9 from colliding with the feed shaft 2, and at the same time, the first crank 7 and the second crank 9 are accurately positioned and rotated stably, so as to ensure the consistency between the designed running track of the mechanism and the actual running track, thereby improving the reliability of the stitch length adjustment mechanism, and on the other hand, it can also reduce the internal space of the sewing machine occupied by the sleeve 6, so that the various mechanisms of the sewing machine are orderly and compactly formed into a whole. In addition, the driving boss 5a is inserted into the driving hole 7a for matching, which increases the overlapping part between the rotating member 5 and the first crank 7 in the direction of the feed shaft 2. When the motor 3 rotates one circle, compared with other transmission structures, the movement space occupied by the rotating member 5 and the first crank 7 in the sewing machine is still relatively small, which reduces the possibility of interference between the rotating member 5 and the first crank 7 and other parts, which is conducive to improving the reliability of the mechanism operation. After the swing angle range of the first crank 7 is limited by the cooperation between the driving hole 7a and the driving boss 5a, the swing angle range of the swing plate seat 4 can be enlarged or reduced through the adjustment structure between the second crank 9 and the connecting rod 8 to meet the sewing requirements, thereby ensuring the use range of the sewing machine.

[0045] Embodiment 2

[0046] A through opening is provided on the wall surface of the driving hole 7a at the position farthest from the shaft sleeve 6, and during one rotation of the rotating member 5, the driving boss 5a never abuts against the side wall surface of the through opening. The other structures are the same as those in the first embodiment.

[0047] Embodiment 3

[0048] An additional clearance groove is provided on the hole wall of the driving hole 7a at the place farthest from the shaft sleeve 6. The two side walls of the additional clearance groove are arranged in parallel and can abut against the driving boss 5a at the same time. When the driving boss 5a abuts against the two side walls of the additional clearance groove at the same time, there is an additional gap 13 between the driving boss 5a and the bottom surface of the additional clearance groove. An additional fillet transition surface is provided between the side wall surface of the additional clearance groove and the swing reduction surface. The other structures are the same as those in the first embodiment.

[0049] 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.

Claims

1. A stitch length adjustment mechanism, mounted on a housing (1) of a sewing machine, wherein a feed shaft (2) is provided on the housing (1), the stitch length adjustment mechanism comprising a swing plate seat (4) hinged on the housing (1) and a motor (3) capable of driving the swing plate seat (4) to swing, characterized in that: The needle distance adjustment mechanism further comprises a shaft sleeve (6) which is rotatably mounted on the feed shaft (2), a first crank (7) and a second crank (9) which is transmission-connected to the swing plate seat (4) being fixed on the shaft sleeve (6), a rotating member (5) which is capable of full-circle rotation being fixedly connected to the output shaft (3a) of the motor (3), a driving protrusion (5a) being eccentrically arranged on the rotating member (5), a strip-shaped driving hole (7a) being arranged on the first crank (7), and a driving protrusion (5a) being arranged on the output shaft (3a) of the motor (3). The movable boss (5a) is inserted into the driving hole (7a) and can act on the hole wall surface of the driving hole (7a) to make the first crank (7) rotate around the feeding shaft (2); the hole wall surface of the driving hole (7a) includes a swing reduction surface (7b) that can abut against the driving boss (5a) and is recessed outward; the hole wall surface of the driving hole (7a) is provided with a clearance groove (7c) at a position closest to the shaft sleeve (6); the two side walls of the clearance groove (7c) are arranged in parallel and can simultaneously abut against the driving boss (5a). 5a), when the driving boss (5a) and the two side walls of the clearance groove (7c) are in contact at the same time, a gap (13) is provided between the driving boss (5a) and the bottom surface of the clearance groove (7c), the swing reduction surface (7b) is connected to the side wall surface of the clearance groove (7c), and an arc transition surface (7d) is provided between the swing reduction surface (7b) and the side wall surface of the clearance groove (7c), the swing reduction surface (7b) is in an arc shape, and when the driving boss (5a) is in contact with the swing reduction surface (7b), the swing reduction surface (7d) is provided between the driving boss (5a) and the side wall surface of the clearance groove (7c). The center of the swing surface (7b) is kept concentric with the rotation center of the output shaft (3a) of the motor (3); the first crank (7) has an imaginary symmetry axis (7e) perpendicular to the central axis of the feed shaft (2); the clearance groove (7c) is symmetrically arranged about the imaginary symmetry axis (7e); there are two swing reduction surfaces (7b) and they are symmetrically arranged about the imaginary symmetry axis (7e); there are two arc transition surfaces (7d) and they are symmetrically arranged about the imaginary symmetry axis (7e).

2. The needle distance adjustment mechanism according to claim 1, characterized in that: An avoidance groove (7f) or a through opening is provided on the hole wall surface of the driving hole (7a) at the position farthest from the shaft sleeve (6), and the driving boss (5a) never abuts against the side wall surface of the avoidance groove (7f) or the through opening during one rotation of the rotating member (5); or an additional clearance groove is provided on the hole wall surface of the driving hole (7a) at the position farthest from the shaft sleeve (6), and the side wall surfaces of the additional clearance groove are arranged in parallel and can abut against the driving boss (5a) at the same time, and when the driving boss (5a) abuts against the side wall surfaces of the additional clearance groove at the same time, an additional gap exists between the driving boss (5a) and the bottom surface of the additional clearance groove.

3. The needle distance adjustment mechanism according to claim 1, characterized in that: A connecting rod (8) is hinged between the second crank (9) and the swing plate seat (4), and an adjustment structure is provided between the connecting rod (8) and the second crank (9) for adjusting the distance from the hinge point between the second crank (9) and the connecting rod (8) to the rotation center of the second crank (9).

4. The needle distance adjustment mechanism according to claim 3, characterized in that: The adjustment structure comprises a plurality of adjustment holes (9a) arranged on the second crank (9), the distance between each adjustment hole (9a) and the rotation center of the second crank (9) being different, and the second crank (9) can be hinged to the connecting rod (8) through any one of the adjustment holes (9a).

5. The needle distance adjustment mechanism according to claim 1, characterized in that: Positioning retaining rings are fixedly connected to the two ends of the shaft sleeve (6) on the feeding shaft (2), and the two end surfaces of the shaft sleeve (6) are respectively abutted against the corresponding positioning retaining rings.

6. The needle distance adjustment mechanism according to claim 1, characterized in that: The first crank (7) is integrally formed or separately fixed on the shaft sleeve (6), and the second crank (9) is integrally formed or separately fixed on the shaft sleeve (6).

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