CN212688405U - Sewing machine - Google Patents

Abstract

The utility model provides a sewing machine, which comprises a main shaft, a feeding mechanism with a feeding swing seat, a presser foot lifting mechanism, a driving motor, a needle pitch adjusting power transmission mechanism and a presser foot lifting transmission mechanism with an avoiding structure; the needle pitch adjusting power transmission mechanism comprises a transmission eccentric wheel and a transmission connecting rod, wherein the transmission eccentric wheel is fixed on an output shaft of the driving motor; the corner of the output shaft of the driving motor is provided with a needle pitch active adjusting area and a presser foot lifting area; when the driving motor operates in the active stitch length adjusting area, the sewing machine has effective stitch length, and the driving motor and the presser foot lifting mechanism are in unpowered transmission; when the driving motor operates in the presser foot lifting area, power is transmitted between the driving motor and the presser foot lifting mechanism, and the absolute value of the needle pitch corresponding to the angle of the feeding swing seat is not more than the maximum absolute value of the effective needle pitch. The needle pitch adjusting mechanism is timely in response, capable of suspending stitches and good in needle pitch adjusting stability.

Description

Sewing machine

Technical Field

The utility model relates to a sewing machine.

Background

At present, a sewing machine is provided with a main motor, a main shaft connected with a motor shaft of the main motor, a tooth frame, feeding teeth arranged on the tooth frame, a feeding mechanism connected between the main shaft and one end of the tooth frame, a tooth lifting mechanism connected between the main shaft and the other end of the tooth frame, a presser foot and a presser foot lifting mechanism connected with the presser foot, wherein the main shaft drives the tooth frame and the feeding teeth to do composite motion of back-and-forth reciprocating motion and up-and-down reciprocating motion through the feeding mechanism and the tooth lifting mechanism, and the motion trail of the feeding teeth is elliptical.

Further, the structure of the presser foot lifting mechanism can be seen in a sewing machine disclosed in the chinese patent application with application publication No. CN107858790A, and the power source for the presser foot lifting is derived from a push rod and an electromagnet, so that the manual knee leaning and the automatic presser foot lifting can be realized. Firstly, when an operator manually pushes against a knee rest part knee rest disc connected below a push rod, the push rod can move upwards to drive a lever part in a presser foot lifting mechanism to rotate, finally, the pressure of a spring arranged at the upper end of a pressing rod is overcome, a pressing rod is driven to move upwards, the pressing rod upwards lifts the presser foot, and manual knee rest is achieved. However, the manual control strengthens the labor intensity of people and reduces the working efficiency. Secondly, when the electromagnet is electrified, the iron core of the electromagnet extends upwards to drive a lever component in the presser foot lifting mechanism to rotate, the pressure of a spring sleeved at the upper end of the pressure rod is overcome finally, the pressure rod is driven to move upwards, the pressure rod lifts the presser foot upwards, and automatic presser foot lifting is achieved. However, the electromagnet only has the telescopic characteristic, so that the stroke of the electromagnet is unique and cannot be adjusted, the lifting height of the presser foot is unique and cannot be adjusted, and the diversified sewing requirements cannot be met; and, the part collision is produced when the electro-magnet iron core stretches out and retracts, and then produces the noise.

Further, the sewing machine is also provided with a stitch length adjusting mechanism and a backstitch mechanism, the stitch length adjusting mechanism is used for adjusting the stitch length of the sewing machine, and the backstitch mechanism is used for switching a front sewing mode and a backstitch mode, for example, the sewing machine disclosed in the chinese patent application with application publication No. CN 108796841A. Generally, when the needle pitch is adjusted, the sewing machine needs to be stopped, then a needle pitch adjusting stud in a needle pitch adjusting mechanism is manually rotated, the needle pitch adjusting stud moves forwards or rightwards while being rotated, a feeding swing seat in a feeding mechanism is driven to rotate around a fulcrum of the feeding swing seat through the needle pitch adjusting mechanism, the position angle of the feeding swing seat is changed, and corresponding needle pitch adjustment is achieved. The power source of the backstitch mechanism can be an electromagnet or a backstitch wrench; the backstitch mechanism also acts on the feeding swing seat, so that the angle of the feeding swing seat exceeds a certain specific angle, and then reverse feeding can occur during subsequent sewing of the sewing machine, thereby realizing backstitch; when the power source of the backstitch mechanism is an electromagnet, the stroke of the electromagnet is unique and unadjustable, so that the backstitch and the front stitch can be switched, and the stitch length cannot be adjusted.

In order to overcome the problems caused by the electromagnet when the presser foot lifting mechanism acts and the needle pitch adjusting mechanism and the backstitch mechanism act, some sewing machines start to adopt a stepping motor to realize the automatic control of the lifting height of the presser foot and realize the switching of backstitch, normal stitch, closed stitch and backstitch, namely: the power source of the presser foot lifting mechanism is a stepping motor, the power source of the needle pitch adjusting mechanism is also a stepping motor, and the presser foot lifting mechanism and the needle pitch adjusting mechanism are independent and do not influence each other. However, since the presser foot lifting mechanism and the needle pitch adjusting mechanism are separately controlled and two stepping motors are required, on one hand, the complexity of the sewing machine is greatly increased, and it is difficult to add two large stepping motors in the sewing machine which is not sufficient in terms of space, and the complexity and cost of the electric control program are increased.

With the development of the technology, the sewing machine starts to adopt the same stepping motor to realize the needle pitch adjusting function and the presser foot lifting function, but the needle pitch adjusting function and the presser foot lifting function are not simply connected in series and combined together. Such as: due to the development of the sewing process, the needle pitch adjusting process is not only needed after the machine is stopped, but also is often accompanied with the needle pitch adjustment in the sewing process to realize pattern sewing, dense needle sewing, backstitch and the like, the angle of the feeding swing seat needs to be adjusted when the needle pitch is adjusted, the rotating angle of a motor shaft of the stepping motor also needs to be controlled, if the presser foot lifting mechanism is directly connected with the stepping motor, the presser foot is lifted, the sewing cannot be carried out, and obviously, the allowance is not allowed. For another example: after sewing is finished and sewing materials are taken out, if an operator manually rotates the upper shaft, if the angle of the feeding swing seat is changed too much due to the rotation angle of the corresponding stepping motor when the presser foot is lifted, the problem that the feeding teeth collide with the needle plate due to too large needle pitch change can occur.

Based on the above problems, in the sewing machine which adopts the same stepping motor to realize the needle pitch adjusting function and the presser foot lifting function, the avoiding mechanism (or the clutch mechanism) is arranged in the needle pitch adjusting mechanism connected between the stepping motor and the feeding swing seat and the presser foot lifting transmission mechanism connected between the stepping motor and the presser foot lifting mechanism, such as the sewing machine disclosed in the chinese invention patent application with the application publication number of CN111118752A and the sewing machine disclosed in the chinese utility model patent with the authorization publication number of CN 210177083U. The avoiding mechanism can realize the separation state between the stepping motor and the feeding swing seat during the action of the stepping motor driving presser foot lifting mechanism and the separation state between the stepping motor and the presser foot lifting mechanism during the position angle change of the feeding swing seat, namely: the needle distance adjusting mechanism is fixed when the presser foot is lifted, and the presser foot lifting mechanism is fixed when the needle distance is adjusted. Therefore, the actions of the needle pitch adjusting mechanism and the presser foot lifting mechanism are not influenced mutually, and the independence of function switching between the presser foot lifting and the needle pitch adjustment by adopting the same stepping motor can be realized.

Furthermore, the avoiding mechanism is usually in the form of an outer cam matched with a roller or a crank connecting rod matched with a sliding chute, and a tension spring is arranged between the feeding swinging seat and the sewing machine shell to keep the relative connection between the feeding swinging seat and the sewing machine shell. Meanwhile, in the aspect of control, generally, the motor rotates forwards (or backwards) to perform needle distance adjustment control, and when the functions of lifting the presser foot and adjusting the needle distance need to be switched, the motor rotates backwards (or forwards) to run out of a needle distance adjusting area, and then the presser foot lifting control is performed. However, the avoidance mechanism having the above-described structure is employed in a pitch adjusting portion where the operating conditions are relatively high, and the following problems arise: when the stitch length is switched at a high speed, the stitch length adjusting mechanism cannot respond in time due to the tension spring; when the needle pitch is switched, the avoidance mechanism of the chute structure has a collision phenomenon, so that noise is generated; the tension of the tension spring is used as the holding force for holding the feeding swing seat, and the tension spring has the risk of disengagement and poor stability; suspension sewing can not be realized, the presser foot is required to be always kept at a specific height for sewing during suspension sewing, but the needle pitch is greatly changed at the moment, and the problem that the feeding tooth collides with the needle plate can occur.

SUMMERY OF THE UTILITY MODEL

In view of the above prior art's shortcoming, the to-be-solved technical problem of the utility model is to provide a sewing machine, it adopts same driving motor to realize gauge needle regulatory function and lift presser foot function to realize gauge needle regulatory mechanism response on this basis in time, suspension seam and very good gauge needle regulation stability.

In order to achieve the above purpose, the utility model provides a sewing machine, which comprises a main shaft, a tooth frame, feeding teeth arranged on the tooth frame, a feeding mechanism connected between the main shaft and the tooth frame, a presser foot, and a presser foot lifting mechanism connected with the presser foot, wherein the feeding mechanism is internally provided with a feeding swing seat capable of rotating around a first fixed swing fulcrum, and the angle of the feeding swing seat determines the needle pitch of the sewing machine; the sewing machine also comprises a driving motor, a needle pitch adjusting power transmission mechanism connected between an output shaft of the driving motor and the feeding swing seat, and a presser foot lifting transmission mechanism connected between the output shaft of the driving motor and the presser foot lifting mechanism; the needle pitch adjusting power transmission mechanism comprises a transmission eccentric wheel and a transmission connecting rod, the transmission eccentric wheel is fixed on an output shaft of a driving motor, one end of the transmission connecting rod is rotatably sleeved on the periphery of the transmission eccentric wheel, and the other end of the transmission connecting rod is hinged with the feeding swing seat; an avoidance structure is arranged in the presser foot lifting transmission mechanism; the corner of the output shaft of the driving motor is provided with a needle pitch active adjusting area, a needle pitch passive adjusting area except the needle pitch active adjusting area and a pin lifting area contained in the needle pitch passive adjusting area; when the output shaft of the driving motor operates in the active needle pitch adjusting area, the sewing machine has an effective needle pitch, and the avoiding structure enables the driving motor and the presser foot lifting mechanism to have no power transmission; when the output shaft of the driving motor operates in the presser foot lifting area, the presser foot lifting transmission mechanism enables power transmission between the driving motor and the presser foot lifting mechanism, the needle pitch corresponding to the angle of the feeding swing seat changes, and the absolute value of the needle pitch is not greater than the maximum absolute value of the effective needle pitch.

Furthermore, the presser foot lifting transmission mechanism comprises a transmission cam, a transmission crank with a second fixed swing fulcrum, a roller rotatably arranged at one end of the transmission crank, and a transmission pull rod, wherein the transmission cam is fixed on an output shaft of the driving motor, and two ends of the transmission pull rod are respectively hinged with one of the transmission crank and the presser foot lifting mechanism; the outer peripheral surface of the transmission cam is provided with a pressure lifting pin driving section consisting of a diameter-variable surface and an avoidance section consisting of an equal-diameter surface; when the output shaft of the driving motor runs in the active needle pitch adjusting area, the roller is in contact fit with the avoiding section of the transmission cam; when the output shaft of the driving motor operates in the presser foot lifting area, the roller is in contact fit with the presser foot lifting driving section of the transmission cam.

Further, the presser foot lifting mechanism comprises a right lever with a third fixed swing fulcrum, a presser foot lifting pull rod, a left lever with a fourth fixed swing fulcrum, a presser foot lifting plate, a pressure lever guide frame and a pressure lever extending up and down, the transmission pull rod is hinged to one end of the right lever, the other end of the right lever is hinged to one end of the presser foot lifting pull rod, the other end of the presser foot lifting pull rod is hinged to one end of the left lever, the other end of the left lever is hinged to the upper end of the presser foot lifting plate, a lifting hook portion is arranged on the presser foot lifting plate, a connecting protruding portion clamped with the lifting hook portion is arranged on the pressure lever guide frame, the pressure lever guide frame is fixed to the upper end of the pressure lever, and the presser foot is installed at the lower end of the pressure.

Furthermore, a torsion spring is sleeved on a third fixed swinging fulcrum of the right lever, two ends of the torsion spring are respectively connected with the sewing machine shell and the right lever, and the acting force applied to the right lever by the torsion spring can enable the roller to be tightly attached to the peripheral surface of the transmission cam.

Furthermore, a split structure is arranged between the transmission eccentric wheel and the transmission cam.

Furthermore, the transmission eccentric wheel and the transmission cam are of an integrated structure.

Further, the feeding mechanism comprises a feeding shaft parallel to the main shaft, a first feeding transmission unit connected between the main shaft and the feeding shaft, and a second feeding transmission unit connected between the feeding shaft and the tooth rack; the first feeding transmission unit comprises a feeding eccentric wheel, a feeding connecting rod, a first feeding swing plate, a second feeding swing plate and a feeding crank, wherein the feeding eccentric wheel, the feeding connecting rod, the first feeding swing plate and the second feeding swing plate are fixed on a main shaft, the upper end of the feeding connecting rod is rotatably sleeved on the periphery of the feeding eccentric wheel, the lower end of the feeding connecting rod, one end of the first feeding swing plate and one end of the second feeding swing plate are coaxially hinged, the other end of the first feeding swing plate is hinged to a feeding swing seat, and the other end of the second feeding swing plate is hinged to the feeding crank.

Further, the sewing machine further comprises a machine shell, the machine shell comprises an upper machine shell section and a lower machine shell section which are fixedly connected, the main shaft is rotatably installed in the upper machine shell section, the feeding swinging seat is rotatably installed in the lower machine shell section, and the driving motor is fixedly installed in the upper machine shell section.

As described above, the sewing machine of the present invention has the following advantageous effects:

above-mentioned sewing machine adopts a driving motor to realize the gauge needle regulatory function simultaneously and lifts the presser foot function, its compact structure, occupy small to simplify automatically controlled procedure, and adopt driving motor as the driving source, driving motor's output corner is controllable, for adopting the electro-magnet as the driving source, can avoid producing part collision, greatly reduced noise for this application, has still realized that gauge needle is adjusted, the front end is sewed up, close stitch, backstitch and the presser foot lifts the adjustable of height simultaneously.

Particularly, the needle pitch adjusting power transmission mechanism adopts a structure of a transmission eccentric wheel and a transmission connecting rod, and the structure enables power transmission between the driving motor and the feeding swing seat to be continuously realized, namely, an avoiding structure is not arranged in the needle pitch adjusting power transmission mechanism, and the power transmission between the driving motor and the feeding swing seat is always realized, or different rotating angles of an output shaft of the driving motor correspond to different position angles of the feeding swing seat, namely, different needle pitches, so that the position angle of the feeding swing seat can timely respond to the rotating angle of the output shaft of the driving motor, and the needle pitch adjusting power transmission mechanism can timely respond. Moreover, the position angle of the feeding swing seat is kept by the driving motor through the needle pitch adjusting power transmission mechanism, when an electric control module of the sewing machine controls an output shaft of the driving motor to be kept at a corner, the feeding swing seat can be kept at a position angle through the needle pitch adjusting power transmission mechanism, so that the needle pitch at the moment is kept, an avoiding mechanism is not arranged in the needle pitch adjusting power transmission mechanism, a tension spring structure does not need to be arranged between the feeding swing seat and a sewing machine shell, the condition that the position angle of the feeding swing seat is unstable does not exist, and the stability of needle pitch adjustment is greatly improved.

Further, when the drive motor enables the presser foot lifting mechanism to lift the presser foot upwards through the presser foot lifting transmission mechanism, the position angle of the feeding swing seat can be changed along with the operation of the drive motor, the needle pitch of the sewing machine can also be changed, but the absolute value of the needle pitch at the moment is not larger than the maximum absolute value of the effective needle pitch, so that the problem that the feeding teeth collide with the needle plate is avoided, and the needle pitch adjusting function and the presser foot lifting function can be combined together by adopting the same drive motor.

Further, when the needle pitch adjusting function is switched to the presser foot lifting function, the driving motor runs the active needle pitch adjusting area firstly, and then continues to run to the presser foot lifting area along the same direction, so that the whole running rhythm is smooth.

Furthermore, when the drive motor enables the presser foot lifting mechanism to lift the presser foot upwards through the presser foot lifting transmission mechanism, the presser foot can be kept at a specific height through controlling the rotating angle of the motor shaft of the drive motor, at the moment, the sewing machine has a relatively fixed needle distance, and the absolute value of the needle distance is not more than the maximum absolute value of the effective needle distance, so that the sewing machine can perform sewing at the moment, the problem that the feeding tooth collides with the needle plate is avoided, and the suspended sewing is realized.

Drawings

Fig. 1 is a schematic view of a sewing machine according to the present application.

Fig. 2 is a schematic structural view of fig. 1 with the chassis omitted and at another view angle.

Fig. 3 is an enlarged view of circle a of fig. 2.

FIG. 4 is a schematic structural view of a stitch length adjusting power transmission mechanism in the sewing machine.

Fig. 5 is a schematic structural view of a presser foot lifting transmission mechanism in the sewing machine.

Fig. 6 is a schematic structural view of the drive cam in fig. 5.

Fig. 7 is a schematic view showing a rotation angle range of a motor shaft of a driving motor in the sewing machine.

FIG. 8 is a graph showing the relationship between the rotation angle of the motor shaft of the driving motor and the needle pitch and the height of the presser foot in the sewing machine.

Fig. 9 is a schematic view of the sewing machine after the presser foot is lifted.

FIG. 10 is a schematic view of the sewing machine in a floating seam configuration.

FIG. 11 is a diagram showing the relationship between the driving eccentric wheel and the driving link in the process of adjusting the stitch length of the sewing machine.

Fig. 12 and 13 are relationship diagrams between the transmission eccentric wheel and the transmission connecting rod in the process of lifting the presser foot of the sewing machine.

Fig. 14 and 15 are process views of the sewing machine during stitch length adjustment.

Fig. 16 and 17 are process views of the sewing machine when lifting the presser foot.

Fig. 18 is a schematic structural diagram of the present application when the driving eccentric wheel and the driving cam are of an integrated structure.

Description of the element reference numerals

10 spindle

20 dental articulator

30 feeding tooth

40 feeding mechanism

41 feeding swing seat

411 left arm part

412 right arm

42 feeding shaft

43 feeding eccentric wheel

44 feeding connecting rod

45 first feeding swing plate

46 second feeding swing plate

47 feeding crank

48 first support shaft

50 presser foot

60 lift presser foot mechanism

61 Right lever

62 lifting presser foot pull rod

63 left lever

64 Lift presser foot lifting plate

65 pressure bar guide frame

66 pressure lever

67 torsion spring

70 driving motor

71 Motor shaft

80-stitch-length-adjusting power transmission mechanism

81 transmission eccentric wheel

82 drive connecting rod

90 lift presser foot drive mechanism

91 drive cam

911 lifting presser foot driving section

912 avoidance segment

92 driving crank

93 roller

94 drive draw bar

96 second support shaft

97 crank support

Upper segment of 121 case

122 lower section of the casing

Detailed Description

The following description is provided for illustrative purposes, and other advantages and features of the present invention will become apparent to those skilled in the art from the following detailed description.

It should be understood that the drawings of the present application are only used to match the contents disclosed in the specification, so as to be known and read by those skilled in the art, and not to limit the practical limitations of the present invention, so that the present application does not have any technical significance, and any modification of the structure, change of the ratio relationship, or adjustment of the size should still fall within the scope of the present application without affecting the function and the achievable purpose of the present application. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle", and the like used in the present specification are for convenience of description, and are not intended to limit the scope of the present invention, and changes or adjustments of the relative relationship thereof may be considered as the scope of the present invention without substantial changes in the technical content.

The present application provides a sewing machine of the type being a flat bed sewing machine. As shown in fig. 1 and 2, the sewing machine has a housing, a main shaft 10 rotatably installed in the housing, and a main motor driving the main shaft 10 to rotate. The sewing machine frame has a frame upper section 121 and a frame lower section 122 fixedly connected, the main shaft 10 is rotatably installed in the frame upper section 121, and a lower shaft parallel to the main shaft 10 and a rotating shuttle installed at the left end of the lower shaft in the sewing machine are located in the frame lower section 122. For convenience of description, in the following examples, the directions are defined as follows: defining the axial direction of the main shaft 10 as a left-right direction, wherein the direction of the main shaft 10 towards the machine head is a left direction, and the direction towards the machine tail is a right direction; defining the moving direction of the sewing material when the sewing machine is used for sewing as a front direction; a direction orthogonal to both the left-right direction and the front-rear direction is defined as an up-down direction.

The sewing machine related to the application can adopt one driving motor 70 to realize the needle pitch adjusting function and the presser foot lifting function at the same time, and the needle pitch adjusting function comprises several sewing modes of switching a normal sewing mode, a closed sewing mode, a backstitch mode and a backstitch mode. Based on this, as shown in fig. 1 and fig. 2, the sewing machine comprises a tooth frame 20, a feeding tooth 30 fixedly mounted on the tooth frame 20, a feeding mechanism 40 connected between the main shaft 10 and the front end of the tooth frame 20, a presser foot 50, a presser foot lifting mechanism 60 connected with the presser foot 50, a driving motor 70, a needle distance adjusting power transmission mechanism 80 connected between an output shaft of the driving motor 70 and a feeding swing seat 41, and a presser foot lifting transmission mechanism 90 connected between an output shaft of the driving motor 70 and the presser foot lifting mechanism 60, wherein the feeding mechanism 40 is provided with the feeding swing seat 41 capable of rotating around a first fixed swing fulcrum O1, the feeding swing seat 41 is rotatably mounted in a lower section 122 of the machine shell, and the angle of the feeding swing seat 41 determines the needle distance of the sewing machine. Specifically, as shown in fig. 2 and 4, the pitch power transmission mechanism 80 includes a transmission eccentric 81 and a transmission connecting rod 82, the transmission eccentric 81 is fixed to the output shaft of the driving motor 70 by a screw, the upper end of the transmission connecting rod 82 is rotatably fitted around the outer periphery of the transmission eccentric 81, and the lower end of the transmission connecting rod 82 is hinged to the feed oscillating base 41 by a pin extending left and right. The transmission eccentric wheel 81 and the transmission connecting rod 82 form a geometric closed model, the needle pitch adjusting power transmission mechanism 80 formed by the transmission eccentric wheel 81 and the transmission connecting rod has stable and reliable structure, and power is continuously transmitted between the driving motor 70 and the feeding swing seat 41. An avoiding structure is arranged in the presser foot lifting transmission mechanism 90. Preferably, the driving motor 70 can be a stepping motor, and the driving motor 70 is connected to an electronic control module of the sewing machine.

In the sewing machine related to the present application, the needle pitch adjusting power transmission mechanism 80 is composed of a transmission eccentric wheel 81 and a transmission connecting rod 82, so that power transmission is continuously provided between the driving motor 70 and the feeding swing seat 41, or the needle pitch adjusting power transmission mechanism 80 has no avoidance structure, so that the rotation angle of the output shaft of the driving motor 70 has a one-to-one correspondence relationship with the angle of the feeding swing seat 41, that is, any angle of the rotation angle of the output shaft of the driving motor 70 in the circle range of 0-360 degrees is uniquely corresponding to the swing angle of the feeding swing seat 41. When the rotation angle of the output shaft of the driving motor 70 rotates through different angles within the range of 0 to 360 degrees, the output shaft of the driving motor 70 enables the feeding swing seat 41 to rotate around the first fixed swing fulcrum O1 through the needle pitch adjusting power transmission mechanism 80, so that the feeding swing seat 41 is in different angles. Therefore, in the range of the rotation angle of the output shaft of the drive motor 70 from 0 ° to 360 °, as shown in fig. 7, the rotation angle of the output shaft of the drive motor 70 has a needle pitch active adjustment region W1, a needle pitch passive adjustment region W2 other than the needle pitch active adjustment region W1, and a foot lifting region W3 included in the needle pitch passive adjustment region W2, and the needle pitch active adjustment region W1 and the needle pitch passive adjustment region W2 are collectively 0 ° to 360 °. Specifically, in the view shown in fig. 8, the curve S1 is a needle pitch variation curve, and the curve S2 is a presser foot height variation curve. As can be seen from fig. 8: when the output shaft of the driving motor 70 runs in the needle pitch active adjusting area W1, the sewing machine has an effective needle pitch, the effective needle pitch is the needle pitch required by the sewing machine during normal sewing, and the avoiding structure enables no power transmission between the driving motor 70 and the presser foot lifting mechanism 60; when the output shaft of the driving motor 70 runs in the presser foot lifting area W3, the presser foot lifting transmission mechanism 90 enables power transmission between the driving motor 70 and the presser foot lifting mechanism 60, and the needle pitch corresponding to the angle of the feeding swing seat 41 changes, and the absolute value of the needle pitch is not greater than the maximum absolute value of the effective needle pitch. In the embodiment, the needle pitch active adjusting area W1 is alpha 1-alpha 2, the needle pitch passive adjusting area W2 is 0-alpha 1 and alpha 2-360 degrees, the presser foot lifting area W3 is alpha 3-alpha 4, and alpha 1 is more than 0 degrees and less than alpha 2 and less than alpha 3 and less than alpha 4 and less than 360 degrees.

Further, the effective gauge of the sewing machine includes a positive gauge corresponding to a positive stitch mode, a small gauge (typically 0.5mm-1mm) corresponding to a dense stitch, a zero gauge, and a negative gauge corresponding to a reverse stitch mode. The positive needle pitch is in a direct proportion relation with the needle pitch value, namely: the larger the needle pitch value is, the larger the needle pitch corresponding to the positive needle pitch value is. The negative gauge is inversely related to the gauge value, i.e.: the smaller the stitch length value is, the larger the stitch length corresponding to the negative value stitch length is. In this embodiment, as shown in FIG. 8, the effective stitch length of the sewing machine has a stitch length value of-5 mm to +5mm, -5mm to 0 being a negative value stitch length corresponding to the reverse sewing mode, and 0 to +5mm being a positive value stitch length corresponding to the positive sewing mode. In addition, when the output shaft of the driving motor 70 runs in the active needle pitch adjustment area W1, the rising height of the presser foot 50 is zero.

When the sewing machine is used for normal sewing, the rotating angle of the output shaft of the driving motor 70 is a certain rotating angle value in the needle pitch active adjusting area W1, the driving motor 70 enables the feeding swing seat 41 to be kept at a swing angle through the needle pitch adjusting power transmission mechanism 80, and the needle pitch value of the sewing machine at the moment is a certain needle pitch value within the range of effective needle pitch-5 mm- +5 mm. After the main motor of the sewing machine is operated, the sewing machine performs sewing according to the current stitch length value; if the current stitch length value is a positive stitch length, the sewing machine performs positive sewing; if the current stitch length value is a small stitch length, the sewing machine performs close stitch sewing; if the current stitch length value is a negative value, the sewing machine performs backstitch. In the presser foot 50, the raised height of the presser foot 50 is zero, and the presser foot 50 is in a lowered state.

When the needle pitch is required to be adjusted, the electric control module of the sewing machine sends a signal to the driving motor 70 after receiving a needle pitch adjusting instruction, the output shaft of the driving motor 70 rotates by an angle in the needle pitch active adjusting area W1, the driving motor 70 acts on the feeding swing seat 41 through the needle pitch adjusting power transmission mechanism 80 to enable the feeding swing seat 41 to rotate by an angle around the first fixed swing fulcrum O1, the swing angle of the feeding swing seat 41 is changed, and the needle pitch value of the sewing machine is changed, so that the functions of needle pitch adjustment, normal sewing, backstitch, closed stitch, backstitch and the like are realized.

When the presser foot needs to be lifted, the electronic control module of the sewing machine sends a signal to the driving motor 70 after receiving a presser foot lifting instruction, the output shaft of the driving motor 70 rotates to α 3 from the current turning angle value, and then continues to rotate to a turning angle value in the presser foot lifting area W3 from α 3 along the same direction, when the output shaft of the driving motor 70 rotates to a turning angle value in the presser foot lifting area W3 from α 3, the avoidance mechanism (i.e. the presser foot lifting driving section 911 and the roller 93 on the driving cam 91 described below) is in a power transmission state, so that the whole presser foot lifting transmission mechanism 90 is in a power transmission state, the driving motor 70 acts on the presser foot lifting mechanism 60 through the presser foot lifting transmission mechanism 90, and the presser foot lifting mechanism 60 drives the presser foot 50 to move upwards to realize presser foot lifting, as shown in fig. 9.

Further, the sewing machine has the following five scenes that need to lift the presser foot during the use: in a scene I, when sewing is finished, the presser foot 50 is lifted to take out sewing materials; in the second scenario, before sewing, the presser foot 50 is lifted and a sewing material is put in; in the third scene, in the midway of sewing, the presser foot 50 is lifted up by stopping to rotate the sewing material direction, and corner sewing is carried out; in the scene IV, when starting sewing, slightly lifting the presser foot 50 for a short time to ensure that the upper thread is rolled under the sewing material; scene fifthly, the presser foot 50 keeps a lower height for carrying out suspension sewing. When the presser foot is lifted under the above-mentioned several scenarios, even if the needle pitch is changed due to the change of the angle of the feeding swing seat 41, the influence is not generated, and the specific analysis is as follows.

For the above scenario (r): after the sewing machine is finished, the presser foot 50 is lifted to enable the feeding swing seat 41 to swing, so that the needle pitch is changed, but the influence is not caused; even if the operator manually rotates the main shaft 10 after the sewing material is taken out, the absolute value of the needle pitch corresponding to the swing angle of the feeding swing seat 41 in the presser foot lifting area W3 does not exceed the maximum absolute value of the effective needle pitch, so that the problem that the feeding dog 30 collides with the needle plate does not occur.

For the above scenario 2: before sewing is started, the presser foot 50 is lifted and then sewing materials are put in, the change of the needle pitch cannot be influenced at the moment, and the needle pitch can be returned to the normal needle pitch value within the effective needle pitch range when the presser foot 50 is in a certain put-down state in the subsequent sewing.

For the above scenario c: the presser foot 50 is lifted in the midway of sewing, due to the related synchronous relation of the sewing machine, the needle is positioned at the highest point when the sewing machine is stopped in the midway, the feeding tooth 30 is positioned below the needle plate at the moment, the needle distance change cannot influence at the moment, and the presser foot 50 is put down during the subsequent sewing, so that the needle distance can return to the normal needle distance value within the effective needle distance range.

For scenario iv above: the time control of the seam-starting slight lifting has a certain requirement relatively, the seam-starting slight lifting presser foot is matched with the electronic thread clamping device to roll the upper thread below the seam material, the power for rolling the upper thread into the seam material comes from the rotating shuttle to enlarge the thread loop, the feeding tooth 30 is positioned below the needle plate when the rotating shuttle enlarges the thread loop, and the change of the needle pitch does not influence at the moment.

For the above scenario (v): as required by some special sewing processes, the presser foot 50 is raised to a lower height L1, as shown in fig. 10, and sewing is then continued. When the motor shaft 71 of the driving motor 70 rotates into the presser foot lifting area W3, the presser foot 50 will be lifted, when the presser foot 50 is just lifted, the electric control module controls the motor shaft 71 of the driving motor 70 to stop and maintain the rotation angle, the motor shaft 71 of the driving motor 70 keeps the feeding swing seat 41 at an angle through the needle pitch adjusting power transmission mechanism 80, at this time, the angle of the feeding swing seat 41 corresponds to a determined needle pitch value, which corresponds to a certain positive value between +5mm and 0 in the embodiment, and the size of the needle pitch is completely determined by the rotation angle of the motor shaft 71 of the driving motor 70, the size of the needle pitch is not changed, so that the presser foot 50 can be sewn at a stable needle pitch on the premise of lifting to a lower height L1, and thus, the suspended sewing is realized. Moreover, the application can also realize different stitch length requirements of different suspension heights, namely, the lifting height of the presser foot 50 corresponds to the stitch length one by one when the seam is suspended, namely: the presser feet are different in height and different in stitch length during suspension.

From the above, it can be seen that: in the sewing machine related to the present application, on one hand, the avoiding structure in the presser foot lifting transmission mechanism 90 avoids influencing the height of the presser foot during adjustment; on the other hand, after the presser foot 50 is lifted, the swing angle of the feeding swing seat 41 is changed under the action of the driving motor 70 and the needle pitch adjusting power transmission mechanism 80, but the absolute value of the needle pitch corresponding to the swing angle of the feeding swing seat 41 in the presser foot lifting area W3 does not exceed the maximum absolute value of the effective needle pitch, so that the problem that the feeding tooth 30 collides with the needle plate does not occur, and the needle pitch adjusting function and the presser foot lifting function are realized simultaneously by adopting one driving motor 70. Based on this, the sewing machine that this application relates to compact structure, occupy smallly to simplify automatically controlled procedure, and adopt driving motor 70 as the driving source, driving motor 70's output corner is controllable, for adopting the electro-magnet as the driving source, this application can avoid producing part collision, greatly reduced noise, has still realized that the gauge needle is adjusted, the front end is sewed up, the dense needle seam, the backstitch, and presser foot 50 lifts up the adjustable of height simultaneously.

In particular, the needle pitch adjusting power transmission mechanism 80 enables power transmission to be continuously performed between the driving motor 70 and the feeding swing seat 41, that is, the needle pitch adjusting power transmission mechanism 80 does not have an avoiding structure such as an avoiding groove and a cam surface, and power transmission is always performed between the driving motor 70 and the feeding swing seat 41, or different rotation angles of the output shaft of the driving motor 70 correspond to different position angles of the feeding swing seat 41, that is, different needle pitches, so that the position angle of the feeding swing seat 41 can timely respond to the rotation angle of the output shaft of the driving motor 70, and the needle pitch adjusting power transmission mechanism 80 can timely respond. Moreover, the position angle of the feeding swing seat 41 is kept by the driving motor 70 through the needle pitch adjusting power transmission mechanism 80, when an electric control module of the sewing machine controls an output shaft of the driving motor 70 to be kept at a corner, the feeding swing seat 41 can be kept at a position angle through the needle pitch adjusting power transmission mechanism 80, so that the needle pitch at the moment is kept, and the needle pitch adjusting power transmission mechanism 80 is not provided with an avoiding mechanism, so that a tension spring structure does not need to be arranged between the feeding swing seat 41 and a sewing machine shell, the condition that the position angle of the feeding swing seat 41 is unstable does not exist, and the stability of needle pitch adjustment is greatly improved.

In addition, the needle pitch adjusting power transmission mechanism 80 is composed of a transmission eccentric wheel 81 and a transmission connecting rod 82, compared with the structural form of a crank connecting rod, the transmission eccentric wheel 81 and the transmission connecting rod 82 enable the motor operation angle to be not limited from 0 degree to 360 degrees, the crank connecting rod structure enables the motor operation angle to be limited, and meanwhile, the phenomenon that the reaction torque of the driving motor 70 acting on a crank is large in the normal sewing stage of the sewing machine due to the fact that the length of the crank is long can be avoided, the phenomenon that the holding torque of the driving motor 70 is insufficient is avoided, and the needle pitch stability is guaranteed.

Further, when the drive motor 70 lifts the presser foot mechanism 60 upwards to lift the presser foot 50 through the presser foot lifting transmission mechanism 90, the position angle of the feeding swing seat 41 can be changed along with the operation of the drive motor 70, the needle pitch of the sewing machine can also be changed, but the absolute value of the needle pitch at the moment is not more than the maximum absolute value of the effective needle pitch, so that the problem that the feeding tooth 30 collides with a needle plate is avoided, the needle pitch adjusting function and the presser foot lifting function can be combined together by adopting the same drive motor 70, and stable suspension sewing is also realized.

Further, as shown in fig. 8, when the output shaft of the driving motor 70 operates in the presser foot lifting area W3, the lifting height of the presser foot 50 is in inverse proportion to the stitch length value of the sewing machine, that is: the higher the elevation height of the presser foot 50 is, the smaller the stitch length value of the sewing machine is. In this embodiment, in the presser foot lifting area W3, the height of the presser foot corresponding to the rotation angle α 3 of the output shaft of the driving motor 70 is 0, and the corresponding needle pitch value is +4.5 mm; the presser foot height corresponding to the rotation angle α 4 of the output shaft of the driving motor 70 is 13mm, and the corresponding needle pitch value is-4 mm. Therefore, when the output shaft of the driving motor 70 is operated in the presser foot lifting area W3, the absolute value of the needle pitch of the sewing machine is always smaller than the maximum absolute value of the effective needle pitch by 5 mm.

Preferably, as shown in fig. 1 and 2, the driving motor 70 is fixedly installed at the right end of the upper section 121 of the housing, and the motor shaft 71 of the driving motor 70 is located at the lower side of the main shaft 10 but at the upper side of the feeding swing seat 41.

Further, the preferred embodiment of the feeding mechanism 40 is: as shown in fig. 2 and 3, the feeding mechanism 40 includes a feeding shaft 42 parallel to the main shaft 10, a first feeding transmission unit connected between the main shaft 10 and the feeding shaft 42, and a second feeding transmission unit connected between the feeding shaft 42 and the dental articulator 20. The first feeding transmission unit comprises a feeding eccentric wheel 43 fixed on the main shaft 10 through a screw, a feeding connecting rod 44, a first feeding swinging plate 45, a second feeding swinging plate 46 and a feeding crank 47 fixed on the right end of the feeding shaft 42, the upper end of the feeding connecting rod 44 is rotatably sleeved on the periphery of the feeding eccentric wheel 43, the lower end of the feeding connecting rod 44, one end of the first feeding swinging plate 45 and one end of the second feeding swinging plate 46 are coaxially hinged through a pin extending left and right, the other end of the first feeding swinging plate 45 is hinged with the feeding swinging seat 41 through a pin extending left and right, and the other end of the second feeding swinging plate 46 is hinged with the feeding crank 47 through a pin extending left and right.

Preferably, as shown in fig. 3 and 4, the feeding swing seat 41 has a concave structure and has a left arm portion 411 and a right arm portion 412 which are parallel; two second feeding swing plates 46 are distributed on the left side and the right side of the lower end of the feeding connecting rod 44; the first feeding swing plate 45 is also provided with two pieces, which are respectively positioned between the left arm portion 411 and the left second feeding swing plate 46, and between the right arm portion 412 and the right second feeding swing plate 46. Both the left arm portion 411 and the right arm portion 412 of the feed swing base 41 are rotatably mounted to a first support shaft 48 extending leftward and rightward, the first support shaft 48 being fixed in the housing lower joint portion 122 of the sewing machine, the first support shaft 48 constituting a first fixed swing fulcrum O1 of the feed swing base 41. Alternatively, both the left arm 411 and the right arm 412 of the feed swing base 41 are fixedly attached to a first support shaft 48 extending left and right, the first support shaft 48 is rotatably attached to the lower housing portion 122 of the sewing machine, and the first support shaft 48 constitutes a first fixed swing fulcrum O1 of the feed swing base 41. The lower end of the transmission link 82 is hinged with the right arm part 412 of the feeding swing seat 41 through a pin extending left and right, and the hinged point of the transmission link 82 and the feeding swing seat 41 is positioned at the rear end of the right side surface of the right arm part 412.

Further, the preferred embodiment of the presser foot lifting mechanism 60 is: as shown in fig. 2, the presser foot lifting mechanism 60 includes a right lever 61 having a third fixed swing fulcrum O3, a presser foot lifting pull rod 62, a left lever 63 having a fourth fixed swing fulcrum O4, a presser foot lifting plate 64, a presser foot guide frame 65, and a presser foot 66 extending vertically, the right end of the right lever 61 is connected to the presser foot lifting transmission mechanism 90, the left end of the right lever 61 is hinged to the right end of the presser foot lifting pull rod 62, the left end of the presser foot lifting pull rod 62 is hinged to one end of the left lever 63, the other end of the left lever 63 is hinged to the upper end of the presser foot lifting plate 64, the presser foot lifting plate 64 is provided with a lifting hook portion, the presser foot guide frame 65 is provided with a connection engaged with the lifting hook portion, the protrusion presser foot guide frame 65 is fixed to the upper end of the presser foot 66, and the presser foot 50 is. Taking the view angle shown in fig. 2 as an example, when the presser foot needs to be lifted, the motor shaft 71 of the driving motor 70 rotates from the current rotation angle to a rotation angle value in the presser foot lifting area W3, the driving motor 70 drives the right lever 61 to rotate clockwise around the third fixed swing fulcrum O3 through the presser foot lifting transmission mechanism 90, the right lever 61 pulls the presser foot lifting pull rod 62 rightwards, so that the left lever 63 rotates anticlockwise around the fourth fixed swing fulcrum O4, the left lever 63 drives the press rod 66 to move upwards through the presser foot lifting plate 64 and the press rod guide frame 65 and overcomes the elastic force of the presser foot spring sleeved on the upper end of the press rod 66, and the press rod 66 drives the presser foot 50 to move upwards together, so as to lift the presser foot.

Preferably, the right lever 61 is rotatably mounted to the housing upper section 121 by a shaft screw extending back and forth, which constitutes a third fixed swing fulcrum O3 of the right lever 61. The left lever 63 is rotatably attached to the housing upper joint 121 by a shaft screw extending forward and backward, which constitutes a fourth fixed swing fulcrum O4 of the left lever 63.

Further, the presser foot lifting transmission mechanism 90 preferably adopts the following structure: as shown in fig. 2 and 5, the presser foot lifting transmission mechanism 90 includes a transmission cam 91, a transmission crank 92 having a second fixed swing fulcrum O2, a roller 93 rotatably mounted at the rear end of the transmission crank 92, and a transmission pull rod 94, the transmission cam 91 is fixed on the output shaft of the driving motor 70 by a screw, the front end of the transmission crank 92 is hinged to the lower end of the transmission pull rod 94 by a pin extending left and right, and the upper end of the transmission pull rod 94 is hinged to the right end of the right lever 61 by a shaft position screw extending forward and backward; as shown in fig. 6, the outer peripheral surface of the transmission cam 91 has a pressure raising/pressing pin driving section 911 formed of a diameter-variable surface and an escape section 912 formed of an equal-diameter surface. When the output shaft of the driving motor 70 runs in the active stitch length adjusting area W1, the roller 93 is in contact fit with the avoiding section 912 of the transmission cam 91, and at this time, when the output shaft of the driving motor 70 drives the transmission cam 91 to rotate, because the avoiding section 912 is an equal diameter surface, the transmission cam 91 cannot drive the transmission crank 92 to rotate through the roller 93, the transmission pull rod 94 does not act, the presser foot lifting mechanism 60 does not act, and therefore the avoiding section 912 of the transmission cam 91 and the roller 93 form an avoiding structure of the presser foot lifting transmission mechanism 90, and influence on the presser foot height during stitch length adjustment is avoided. When the output shaft of the driving motor 70 runs in the presser foot lifting area W3, the roller 93 is in contact fit with the presser foot lifting driving section 911 of the transmission cam 91, and at this time, when the output shaft of the driving motor 70 drives the transmission cam 91 to rotate, because the presser foot lifting driving section 911 is a diameter-variable surface, the transmission cam 91 upwardly supports the roller 93, so that the transmission crank 92 rotates around the second fixed swing fulcrum O2, the front end of the transmission crank 92 downwardly pulls the transmission pull rod 94, and further the right lever 61 clockwise rotates around the third fixed swing fulcrum O3, the presser foot 50 moves upward, and the presser foot lifting mechanism 60 performs a presser foot lifting action.

In addition, in the presser foot lifting driving section 911 of the same transmission cam 91, the lifting height of the presser foot 50 during the floating sewing corresponds to the needle pitch; however, if the contour dimension of the presser foot lifting drive section 911 of the transmission cam 91 is designed differently, the presser foot 50 may be lifted at the same height and have different needle pitches during floating sewing.

Preferably, as shown in fig. 2 and 4, a torsion spring 67 is sleeved on an axis screw of the third fixed swing fulcrum O3 constituting the right lever 61, two ends of the torsion spring 67 are respectively connected to the upper section 121 of the housing and the right lever 61, an acting force applied by the torsion spring 67 to the right lever 61 makes the right lever 61 have a tendency of counterclockwise rotation, the acting force is transmitted to the roller 93 and is reflected in a movement tendency that the roller 93 moves downward, so that the roller 93 is tightly attached to the outer circumferential surface of the transmission cam 91, and accuracy and stability of force transmission in the pressure foot lifting process are ensured. The presser foot lifting and driving mechanism 90 further includes a crank bracket 97 fixed in the upper section 121 of the housing, and a second support shaft 96 extending in the left-right direction and fixed to the crank bracket 97, the driving crank 92 is rotatably attached to the second support shaft 96, and the second support shaft 96 constitutes a second fixed swing fulcrum O2 of the driving crank 92. Of course, in other embodiments, the second support shaft 96 may be directly fixed to the housing upper section 121.

Further, when the output shaft of the driving motor 70 is operated in the needle pitch active adjustment area W1 for normal needle pitch adjustment and backstitch, there is a certain angle between the driving eccentric 81 and the driving connecting rod 82

The swing angle of the feeding swing seat 41 is θ, as shown in fig. 11, the swing angle θ of the feeding swing seat 41 corresponding to the rotation angle value of the output shaft of the driving motor 70 in the needle pitch active adjusting area W1 does not exceed the working stroke, and the needle pitch of the sewing machine is always within the effective needle pitch range. When the presser foot is required to be lifted, the output shaft of the driving motor 70 rotates to a rotation angle value in the presser foot lifting area W3 from the current rotation angle, the transmission eccentric wheel 81 rotates along with the output shaft of the driving motor 70, in the process, the transmission eccentric wheel 81 passes through a position collinear with the transmission connecting rod 82, as shown in fig. 12, the position is defined as a polar position, when the transmission eccentric wheel 81 is in the polar position state, the swing angle theta of the feeding swing seat 41 is maximum, the corresponding needle pitch has a maximum value, and the maximum needle pitch value is slightly larger than the maximum value of the effective needle pitch by 5 mm. In this embodiment, when the driving eccentric wheel 81 is in the polar position, the maximum needle pitch is 5.42 mm. Then, as the driving eccentric 81 continues to rotate, the driving eccentric 81 crosses the polar position, as shown in fig. 13, the swing angle θ of the feeding swing seat 41 is reduced, the corresponding needle pitch is also reduced, and the absolute value of the needle pitch of the sewing machine does not exceed the maximum absolute value of the effective needle pitch when the presser foot is lifted. Therefore, in this application, when the presser foot is lifted by the sewing machine, the variation trend of the needle pitch is as follows: the needle pitch gradually increases from the current needle pitch value to the maximum value in the effective needle pitch, increases to the maximum needle pitch value and gradually decreases, so that the needle pitch in the presser foot lifting area W3 changes to be the large needle pitch of the front sewing → the small needle pitch of the front sewing → the zero needle pitch → the small needle pitch of the back sewing → the large needle pitch of the back sewing, namely: a positive gauge and a negative gauge occur in the presser foot lifting area W3. In addition, when the transmission eccentric wheel 81 is in a polar position state, the maximum needle pitch of the sewing machine is slightly larger than the maximum value of the effective needle pitch by 5mm, so that the influence of the processing error on the maximum value of the effective needle pitch can be prevented, and a space is reserved for processing.

Further, taking the view angle of fig. 2 viewed from the left side of the sewing machine as an example, the current stitch length of the sewing machine is a negative stitch length, and when the driving motor 70 is rotated counterclockwise in the active stitch length adjustment area W1, as shown in fig. 14 and 15, the stitch length of the sewing machine changes in a tendency of a large backstitch → a small backstitch → a zero stitch → a small forward stitch → a large forward stitch; in this process, the transmission cam 91 rotates along with the output shaft of the driving motor 70, but the roller 93 is in contact fit with the escape section 912 of the transmission cam 91, so the transmission cam 91 does not drive the presser foot lifting mechanism 60 to operate, and the presser foot 50 is not lifted. When the presser foot is automatically lifted, the output shaft of the driving motor 70 continuously rotates anticlockwise from the current rotation angle to a rotation angle value in the presser foot lifting, as shown in fig. 16 and 17, in the process, the transmission eccentric wheel 81 rotates along with the output shaft of the driving motor 70, passes through a polar position, then crosses a maximum needle pitch corresponding to the polar position, then a presser foot lifting driving section 911 of the transmission cam 91 is in contact fit with the roller 93, the driving presser foot 50 is lifted, the needle pitch corresponding to the swing angle of the feeding swing seat 41 is gradually reduced, but is always within an effective needle pitch range, and the problem that the needle pitch is changed too greatly due to too large angle change of the feeding swing seat 41 does not occur.

Further, the following two structural configurations can be provided between the driving eccentric 81 and the driving cam 91: firstly, as shown in fig. 2, 4 and 5, the transmission eccentric wheel 81 and the transmission cam 91 are in a split structure, and the two parts are two independent parts and are respectively fixed on the output shaft of the driving motor 70 through screws; secondly, as shown in fig. 18, the driving eccentric 81 and the driving cam 91 are combined into an integral structure.

In conclusion, the present invention effectively overcomes various disadvantages in the prior art, and can be implemented in batch with high industrial utilization value.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (8)

1. A sewing machine comprises a main shaft (10), a tooth frame (20), a feeding tooth (30) arranged on the tooth frame (20), a feeding mechanism (40) connected between the main shaft (10) and the tooth frame (20), a presser foot (50), and a presser foot lifting mechanism (60) connected with the presser foot (50), wherein a feeding swing seat (41) capable of rotating around a first fixed swing fulcrum is arranged in the feeding mechanism (40), and the angle of the feeding swing seat (41) determines the needle pitch of the sewing machine, and is characterized in that: the needle pitch adjusting mechanism comprises a driving motor (70), a needle pitch adjusting power transmission mechanism (80) connected between an output shaft of the driving motor (70) and the feeding swing seat (41), and a presser foot lifting transmission mechanism (90) connected between the output shaft of the driving motor (70) and the presser foot lifting mechanism (60); the needle pitch adjusting power transmission mechanism (80) comprises a transmission eccentric wheel (81) and a transmission connecting rod (82), the transmission eccentric wheel (81) is fixed on an output shaft of the driving motor (70), one end of the transmission connecting rod (82) is rotatably sleeved on the periphery of the transmission eccentric wheel (81), and the other end of the transmission connecting rod (82) is hinged with the feeding swinging seat (41);

an avoiding structure is arranged in the presser foot lifting transmission mechanism (90);

the corner of the output shaft of the driving motor (70) is provided with a needle pitch active adjusting area (W1), a needle pitch passive adjusting area (W2) except for the needle pitch active adjusting area (W1), and a foot lifting area (W3) contained in the needle pitch passive adjusting area (W2);

when the output shaft of the driving motor (70) runs in the active stitch length adjusting area (W1), the sewing machine has an effective stitch length, and the avoiding structure enables no power transmission between the driving motor (70) and the presser foot lifting mechanism (60);

when the output shaft of the driving motor (70) runs in the presser foot lifting area (W3), the presser foot lifting transmission mechanism (90) enables power transmission to be realized between the driving motor (70) and the presser foot lifting mechanism (60), the needle pitch corresponding to the angle of the feeding swing seat (41) is changed, and the absolute value of the needle pitch is not more than the maximum absolute value of the effective needle pitch.

2. The sewing machine of claim 1, wherein: the presser foot lifting transmission mechanism (90) comprises a transmission cam (91), a transmission crank (92) with a second fixed swing fulcrum, a roller (93) rotatably arranged at one end of the transmission crank (92), and a transmission pull rod (94), wherein the transmission cam (91) is fixed on an output shaft of the driving motor (70), and two ends of the transmission pull rod (94) are respectively hinged with the transmission crank (92) and one component of the presser foot lifting mechanism (60);

the outer peripheral surface of the transmission cam (91) is provided with a pressure lifting and pressing foot driving section (911) formed by a diameter-variable surface and an avoidance section (912) formed by an equal-diameter surface;

when the output shaft of the driving motor (70) runs in the active needle pitch adjusting area (W1), the roller (93) is in contact fit with the avoidance section (912) of the transmission cam (91); when the output shaft of the driving motor (70) runs in the pressure lifting foot area (W3), the roller (93) is in contact fit with the pressure lifting foot driving section (911) of the transmission cam (91).

3. The sewing machine of claim 2, wherein: the presser foot lifting mechanism (60) comprises a right lever (61) with a third fixed swing fulcrum, a presser foot lifting pull rod (62), a left lever (63) with a fourth fixed swing fulcrum, a presser foot lifting plate (64), a press rod guide frame (65) and a press rod (66) extending up and down, wherein the transmission pull rod (94) is hinged with one end of the right lever (61), the other end of the right lever (61) is hinged with one end of the presser foot lifting pull rod (62), the other end of the presser foot lifting pull rod (62) is hinged with one end of the left lever (63), the other end of the left lever (63) is hinged with the upper end of the presser foot lifting plate (64), a lifting hook part is arranged on the presser foot lifting plate (64), a connection part clamped with the lifting hook part is arranged on the press rod guide frame (65), and the press rod guide frame (65) is fixed at the upper end of the press rod (66), the pressure foot (50) is mounted at the lower end of the pressure rod (66).

4. The sewing machine of claim 3, wherein: the fixed swing fulcrum cover of third of right lever (61) is equipped with a torsional spring (67), the both ends of torsional spring (67) link to each other with sewing machine casing and right lever (61) respectively, the peripheral face of transmission cam (91) can be hugged closely in roller (93) to the effort that right lever (61) was applyed in torsional spring (67).

5. The sewing machine of claim 2, wherein: the transmission eccentric wheel (81) and the transmission cam (91) are of a split structure.

6. The sewing machine of claim 2, wherein: the transmission eccentric wheel (81) and the transmission cam (91) are integrated.

7. The sewing machine of claim 1, wherein: the feeding mechanism (40) comprises a feeding shaft (42) parallel to the main shaft (10), a first feeding transmission unit connected between the main shaft (10) and the feeding shaft (42), and a second feeding transmission unit connected between the feeding shaft (42) and the tooth rack (20); the first feeding transmission unit comprises a feeding eccentric wheel (43), a feeding connecting rod (44), a first feeding swinging plate (45), a second feeding swinging plate (46) and a feeding crank (47) fixed on a feeding shaft (42) which are fixed on a main shaft (10), wherein the upper end of the feeding connecting rod (44) is rotatably sleeved on the periphery of the feeding eccentric wheel (43), the lower end of the feeding connecting rod (44), one end of the first feeding swinging plate (45) and one end of the second feeding swinging plate (46) are coaxially hinged, the other end of the first feeding swinging plate (45) is hinged with a feeding swinging seat (41), and the other end of the second feeding swinging plate (46) is hinged with the feeding crank (47).

8. The sewing machine of claim 1, wherein: the feeding swing mechanism is characterized by further comprising a machine shell, the machine shell comprises an upper machine shell section (121) and a lower machine shell section (122) which are fixedly connected, the main shaft (10) is rotatably installed in the upper machine shell section (121), the feeding swing seat (41) is rotatably installed in the lower machine shell section (122), and the driving motor (70) is fixedly installed on the upper machine shell section (121).

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