Sewing machine

Abstract

To provide a sewing machine that has a cam-type balance, uses a plurality of needle threads, and can match sewing finishing of the threads.SOLUTION: A sewing machine comprises: a needle bar that holds a first sewing machine needle and a second sewing machine needle, and is vertically driven; a balance that allows a first needle thread fed to the first sewing machine needle and a second needle thread fed to the second sewing machine needle to be inserted, and operates in conjunction with the needle bar; a cam part including a first cam for adjusting thread tightness by guiding the first needle thread passing through the balance and a second cam for adjusting the tread tightness by guiding the second needle thread passing through the balance, provided apart from the first cam; and a sewing machine body in which the needle bar, the balance, and the cam part are provided. The first cam and the second cam are fitted to the sewing machine body so that positions thereof can be independently adjusted to the sewing machine body.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a sewing machine. [Background technology]

[0002] A cam-type thread take-up type sewing machine is known. As an example of a cam-type thread take-up type sewing machine, Patent Document 1 discloses a sewing machine equipped with a needle bar take-up and a thread take-up plate on which a cam surface is formed that enables the needle thread to be tightened with the reciprocating motion of the needle bar take-up. The sewing machine of Patent Document 1 is a two-needle sewing machine, and two upper threads, a right needle thread and a left needle thread, pass through the needle bar take-up. The thread take-up plate is a flat member on which two cam surfaces are formed, a cam surface for the right needle thread and a cam surface for the left needle thread. When the needle bar take-up reciprocates with the right needle thread and the left needle thread, the thread take-up plate moves the right needle thread and the left needle thread along their corresponding cam surfaces. Each cam surface is bent in a mountain shape. As the right needle thread and the left needle thread move toward the top of the mountain, the path length of the needle thread from the sewing machine needle to the cam surface changes, and the needle thread is pulled by the change in the path length, thereby performing thread tightening. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-96088 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned Patent Document 1, if it is desired to adjust the degree of thread tightness, it is possible to adjust the mounting position of the thread reeling plate. However, since the mounting position of the thread reeling plate affects the thread tightness of all needle threads, if the sewing states of the right needle thread and the left needle thread are different, for example, it is difficult to align the sewing states of the respective needle threads.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a sewing machine that is equipped with a cam-type thread take-up lever and uses multiple upper threads, and that is capable of matching the finished stitches of each thread. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a sewing machine comprising: a needle bar which holds a first sewing needle and a second sewing needle and is driven in an up and down direction; a thread take-up lever through which a first upper thread supplied to the first sewing needle and a second upper thread supplied to the second sewing needle are inserted and which operates in conjunction with the needle bar; a cam section including a first cam which guides the first upper thread passing through the thread take-up lever to adjust thread tightness; and a second cam which is provided separately from the first cam and guides the second upper thread passing through the thread take-up lever to adjust thread tightness; and a sewing machine body in which the needle bar, the thread take-up lever and the cam section are provided, wherein the first cam and the second cam are attached so that their positions can be adjusted separately relative to the sewing machine body. Effect of the Invention

[0007] According to the aspects of the present invention, in a sewing machine that is equipped with a cam-type thread take-up lever and uses a plurality of needle threads, the sewing finish of each thread can be matched. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing a schematic diagram of an example of a sewing machine according to the present embodiment. [Diagram 2] FIG. 2 is a side view showing a schematic example of an internal structure of the sewing machine according to the present embodiment. [Diagram 3] FIG. 3 is a perspective view for explaining a path of an upper thread according to the embodiment. [Figure 4] FIG. 4 is a diagram for explaining each stage (A)-(D) of the operation of the sewing needle and looper according to this embodiment. [Diagram 5] FIG. 5 is a schematic diagram of the shape of a stitch formed by a double chain stitch. [Figure 6]FIG. 6 is a perspective view of the balance and the cam portion according to the embodiment, as viewed from the -X direction. [Figure 7] FIG. 7 is a perspective view of the balance and the cam portion according to the embodiment, as viewed from the +X direction. [Figure 8] FIG. 8 is an exploded perspective view of the cam portion according to the embodiment. [Figure 9] FIG. 9 is a front view showing the cam portion with the screw member removed. [Figure 10] FIG. 10 is a schematic diagram showing the positional relationship between the balance and the cam portion when the balance is located near the lower inclined surface of the cam portion. [Figure 11] FIG. 11 is a schematic diagram showing the positional relationship between the balance and the cam portion when the balance is located near the top of the cam portion. [Figure 12] FIG. 12 is a schematic diagram showing a cross section of the balance and the cam portion in FIG. [Figure 13] FIG. 13 is a schematic diagram showing the positional relationship between the balance and the cam portion when the balance is located near the upper inclined surface of the cam portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be appropriately combined. In addition, some components may not be used.

[0010] In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each part is described with reference to this XYZ orthogonal coordinate system. The direction parallel to the X axis in a specified plane is the X-axis direction. The direction parallel to the Y axis in a specified plane perpendicular to the X axis is the Y-axis direction. The direction parallel to the Z axis perpendicular to the specified plane is the Z-axis direction. The direction of rotation or tilt around the X axis is the θX direction. The direction of rotation or tilt around the Y axis is the θY direction. The direction of rotation or tilt around the Z axis is the θZ direction. The plane including the X axis and the Y axis is appropriately referred to as the XY plane. The plane including the X axis and the Z axis is appropriately referred to as the XZ plane. The plane including the Y axis and the Z axis is appropriately referred to as the YZ plane. The XY plane is parallel to the specified plane. The XY plane, the XZ plane, and the YZ plane are perpendicular to each other. In the following description, the XY plane and the horizontal plane are parallel. The Z axis direction is the up-down direction. The +Z direction is the upward direction and the -Z direction is the downward direction. Note that the XY plane may be inclined with respect to the horizontal plane.

[0011] (sewing machine) Fig. 1 is a side view showing an example of a sewing machine 1 according to the present embodiment. Fig. 2 is a side view showing an example of an internal structure of the sewing machine 1 according to the present embodiment. Fig. 3 is a perspective view for explaining a path of an upper thread UT according to the embodiment. In the present embodiment, the sewing machine 1 is a double chainstitch sewing machine that performs double chainstitching.

[0012] As shown in Figures 1, 2 and 3, the sewing machine 1 comprises a sewing machine body 2, a needle bar 3 which holds a sewing needle 6 and moves back and forth in the Z-axis direction, a thread take-up lever 4 which supplies an upper thread to the sewing needle 6, and a cam portion 5 which adjusts the tension of the upper thread in cooperation with the thread take-up lever 4.

[0013] The sewing machine 1 also has a needle plate 8 having a needle hole 7 through which the sewing needle 6 can pass and supporting the object to be sewn, and a looper 9 that swings around a rotation axis AX parallel to the Y axis to scoop up the upper thread from the object to be sewn and the sewing needle 6 that has passed through the needle hole 7 and intertwine it with the lower thread (looper thread).

[0014] The sewing machine 1 also includes an upper thread tensioner 10 to which the upper thread is supplied from the thread supply source, a lower thread tensioner 11 to which the lower thread is supplied from the thread supply source, an actuator 12 that generates power, and a power transmission device 13 that transmits the power generated by the actuator 12 to each of the needle bar 3 and the looper 9.

[0015] The sewing machine body 2 is a structure in which various members including the needle bar 3, the thread take-up lever 4, and the cam portion 5 are provided. The sewing machine body 2 has a first arm 2A on which the actuator 12 is provided, a bed 2B facing the first arm 2A, a second arm 2C connecting one end of the first arm 2A on the +X side to the bed 2B, and a head 2D provided at the other end of the first arm 2A on the -X side and supporting the needle bar 3. Note that the first arm 2A, the second arm 2C, and the head 2D will be described as three separate parts, but are structurally integrated.

[0016] The first arm 2A extends in the X-axis direction. The bed 2B is disposed in the -Z direction from the first arm 2A and extends in the X-axis direction. The second arm 2C extends in the Z-axis direction and connects one end of the first arm 2A on the +X side to one end of the bed 2B on the +X side. The head 2D protrudes in the -Z direction from the other end of the first arm 2A on the -X side.

[0017] The needle bar 3 holds the sewing needle 6. In the embodiment, the sewing machine 1 can attach a plurality of sewing needles 6 to the needle bar 3 and form stitches in parallel with each sewing needle 6. That is, the needle bar 3 holds a first sewing needle 6A and a second sewing needle 6B and is driven in the vertical direction. In the embodiment, the needle bar 3 holds a third sewing needle 6C in addition to the first sewing needle 6A and the second sewing needle 6B. The sewing machine 1 is configured as a so-called three-needle double chain stitch sewing machine. Hereinafter, the three sewing needles are collectively referred to as the sewing needle 6. When distinguishing between the individual sewing needles 6, they are respectively referred to as the first sewing needle 6A, the second sewing needle 6B, and the third sewing needle 6C.

[0018] The needle bar 3 holds the sewing needle 6 so that the sewing needle 6 is parallel to the Z-axis. The needle bar 3 moves back and forth in the Z-axis direction. The needle bar 3 is supported by the head 2D. The sewing needle 6 has a threading hole through which the upper thread UT passes. The sewing needle 6 holds the upper thread UT on the inner surface of the threading hole. A separate upper thread UT is supplied to each sewing needle 6. That is, the first sewing needle 6A is supplied with the first upper thread UT1. The second sewing needle 6B is supplied with the second upper thread UT2. The third sewing needle 6C is supplied with the third upper thread UT3. The upper thread UT is a general term for the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3. As the needle bar 3 moves back and forth in the Z-axis direction, the sewing needle 6 moves back and forth in the Z-axis direction while holding the upper thread UT.

[0019] The thread take-up 4 supplies the upper thread UT to the sewing needle 6. The first upper thread UT1 supplied to the first sewing needle 6A, the second upper thread UT2 supplied to the second sewing needle 6B, and the third upper thread UT3 supplied to the third sewing needle 6C are passed through the thread take-up 4, and the thread take-up 4 operates in conjunction with the needle bar 3. The thread take-up 4 moves back and forth in the Z-axis direction. In this embodiment, the thread take-up 4 is a so-called needle bar thread take-up, which is fixed to the needle bar 3 and moves back and forth integrally with the needle bar 3. The thread take-up 4 moves back and forth in the Z-axis direction while holding each upper thread UT. The thread take-up 4 moves back and forth in the Z-axis direction to pay out and pull up the upper thread UT.

[0020] The needle plate 8 supports a sewing object. The needle plate 8 is positioned in the -Z direction relative to the needle bar 3. The needle plate 8 faces the sewing needle 6 held by the needle bar 3. The needle plate 8 has a needle hole 7 through which the sewing needle 6 can pass. After penetrating the sewing object supported by the needle plate 8, the sewing needle 6 passes through the needle hole 7.

[0021] The looper 9 scoops up the upper thread UT from the sewing needle 6 that has penetrated a sewing object supported by the needle plate 8 and passed through the needle hole 7 of the needle plate 8. The looper 9 is disposed in the -Z direction from the needle plate 8. The looper 9 is disposed inside the bed 2B. The looper 9 is supported by the bed 2B inside the bed 2B so as to be rotatable in the θY direction. The looper 9 holds the lower thread LT that is entangled with the upper thread UT to form a stitch. The loopers 9 are provided in the same number as the sewing needles 6. For convenience, only one looper 9 is shown in FIG. 2, but in the embodiment, the loopers 9 include a first looper 9A corresponding to the first sewing needle 6A, a second looper 9B corresponding to the second sewing needle 6B, and a third looper 9C corresponding to the third sewing needle 6C.

[0022] The upper thread tensioner 10 applies tension to the upper thread UT supplied to the sewing needle 6. The upper thread tensioner 10 is supported by the first arm 2A. A different upper thread tensioner 10 is provided for each upper thread UT. That is, the upper thread tensioner 10 includes a first upper thread tensioner 10A that applies tension to the first upper thread UT1 supplied to the first sewing needle 6A, a second upper thread tensioner 10B that applies tension to the second upper thread UT2 supplied to the second sewing needle 6B, and a third upper thread tensioner 10C that applies tension to the third upper thread UT3 supplied to the third sewing needle 6C. As shown in FIG. 3, each upper thread tensioner 10 has the same configuration. Each upper thread tensioner 10 includes a set of a thread guide 21, a thread tensioner 22, a thread tensioner 23, a thread tensioner 24, and a thread guide 25. A corresponding upper thread UT is supplied to each upper thread tensioner 10 from an upper thread stand 14 provided on the upper surface of the first arm 2A. The upper thread stand 14 includes an upper thread stand 14A that holds a first upper thread UT1, an upper thread stand 14B that holds a second upper thread UT2, and an upper thread stand 14C that holds a third upper thread UT3.

[0023] The upper thread tensioner 10 is disposed between the upper thread stand 14 and the thread take-up 4. The upper thread guide 15 is disposed between the thread take-up 4 and the sewing machine needle 6. The upper thread guide 15 is provided on the head 2D. The upper thread guide 15 has three holes through which each upper thread UT is individually inserted. The upper thread guide 15 guides the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3 to the corresponding first sewing machine needle 6A, the second sewing machine needle 6B, and the third sewing machine needle 6C.

[0024] As shown in FIG. 1, the lower thread tensioner 11 applies tension to the lower thread LT supplied to the looper 9. The lower thread tensioner 11 is supported by the first arm 2A. A lower thread tensioner 11 is provided for each lower thread LT. That is, the lower thread tensioners 11 include a first lower thread tensioner 11A that applies tension to a first lower thread LT1 supplied to the first looper 9A, a second lower thread tensioner 11B that applies tension to a second lower thread LT2 supplied to the second looper 9B, and a third lower thread tensioner 11C that applies tension to a third lower thread LT3 supplied to the third looper 9C.

[0025] The second arm 2C is provided with a plurality of lower thread guides 16. Each lower thread guide 16 guides a respective lower thread LT along a path from the lower thread tensioner 11 to the looper 9. Each lower thread LT is guided by the lower thread guide 16 from the lower thread tensioner 11 along the second arm 2C in the -Z direction and introduced into the bed 2B. Within the bed 2B, each lower thread LT is supplied to a corresponding looper 9 via a lower thread guide (not shown).

[0026] 2, actuator 12 generates power to reciprocate needle bar 3 in the Z-axis direction. Actuator 12 also generates power to swing looper 9 in the θY direction. Actuator 12 includes a pulse motor. Actuator 12 is supported by first arm 2A.

[0027] The power transmission device 13 transmits the power generated by the actuator 12 to each of the needle bar 3 and the looper 9. The power generated by the actuator 12 is transmitted to the needle bar 3 via the power transmission device 13. As a result, the needle bar 3, the thread take-up lever 4 fixed to the needle bar 3, and the sewing needle 6 held by the needle bar 3 move back and forth in the Z-axis direction. In addition, the power generated by the actuator 12 is transmitted to the looper 9 via the power transmission device 13. As a result, the looper 9 swings in the θY direction in synchronization with the reciprocating movement of the needle bar 3 in the Z-axis direction. The sewing machine 1 sews an object to be sewn by cooperation between the sewing needle 6 held by the needle bar 3 and the looper 9.

[0028] Fig. 2 shows a schematic configuration of the power transmission device 13. As shown in Fig. 2, the power transmission device 13 has an arm shaft 13A arranged inside the first arm 2A, a bed shaft 13B arranged inside the bed 2B, and a looper shaft 13C arranged inside the bed 2B.

[0029] The power transmission device 13 also includes a pulley 13D provided on the arm shaft 13A, a pulley 13E provided on the bed shaft 13B, and a timing belt 13F wound around the pulley 13D and the pulley 13E.

[0030] The arm shaft 13A extends in the X-axis direction. The actuator 12 is connected to one end of the arm shaft 13A on the +X side. By actuation of the actuator 12, the arm shaft 13A rotates in the θX direction.

[0031] The other end of the arm shaft 13A on the -X side is connected to the needle bar 3 via a power transmission mechanism 13G. The power generated by the actuator 12 is transmitted to the needle bar 3 via the arm shaft 13A and the power transmission mechanism 13G. This causes the needle bar 3, the thread take-up 4, and the sewing needle 6 to reciprocate in the Z-axis direction.

[0032] The bed shaft 13B extends in the X-axis direction. The bed shaft 13B is arranged in parallel with the arm shaft 13A. The bed shaft 13B can rotate in the θX direction. The power of the actuator 12 is transmitted to the bed shaft 13B via a pulley 13D provided on the arm shaft 13A, a pulley 13E provided on the bed shaft 13B, and a timing belt 13F stretched between the pulleys 13D and 13E.

[0033] The other end of the bed shaft 13B on the -X side is connected to the looper shaft 13C via the power transmission mechanism 13H. The power generated by the actuator 12 is transmitted to the looper shaft 13C via the arm shaft 13A, the bed shaft 13B, and the power transmission mechanism 13H. The power transmission mechanism 13H is an eccentric cam mechanism. The power transmission mechanism 13H connects the swing arm 13C1 connected to the looper shaft 13C to the bed shaft 13B. The power transmission mechanism 13H reciprocates the tip of the swing arm 13C1 up and down using the power generated by the actuator 12.

[0034] The looper shaft 13C is disposed in the +Z direction from the bed shaft 13B. The looper shaft 13C extends in the Y-axis direction. The looper shaft 13C is rotatable in the θY direction. The looper shaft 13C is supported by the bed 2B. The swing arm 13C1 extends in the radial direction from the looper shaft 13C. The looper shaft 13C reciprocates within a predetermined angle range in association with the reciprocating movement of the tip of the swing arm 13C1 in the up and down directions.

[0035] The loopers 9 (first looper 9A, second looper 9B, and third looper 9C) are fixed to the looper shaft 13C. As a result, the loopers 9 swing back and forth around the rotation axis AX (i.e., in the θY direction) integrally with the looper shaft 13C within a predetermined angular range. The rotation axis AX is the central axis of the looper shaft 13C. The loopers 9 swing back and forth so that their tips intersect in the X direction with the trajectory of the up and down reciprocating motion of the sewing needle 6. The loopers 9 have a hook-shaped tip. The loopers 9 have a threading hole at their tips through which the lower thread LT passes. The loopers 9 hold the lower thread LT on the inner surface of the threading hole. A separate lower thread LT is supplied to each looper 9.

[0036] (Sewing needle and looper operation) Fig. 4 is a diagram for explaining an example of the operation of the sewing needle 6 and the looper 9 according to this embodiment. Note that in Fig. 4, the needle plate 8 and the sewing object are omitted.

[0037] The sewing needle 6 moves back and forth in the Z-axis direction so that the tip of the sewing needle 6 alternates between one of a state in which it is in the +Z direction relative to the sewing object and a state in which it is in the -Z direction relative to the sewing object.

[0038] As the sewing needle 6 reciprocates, it penetrates the sewing object. In the following description, within the movable range of the sewing needle 6 in the Z-axis direction, the position of the sewing needle 6 when the tip of the sewing needle 6 is located furthest in the +Z direction will be referred to as the uppermost point, and the position of the sewing needle 6 when the tip of the sewing needle 6 is located furthest in the -Z direction will be referred to as the lowermost point.

[0039] Hereinafter, with reference to FIG. 4, a procedure for performing a double chainstitch using one sewing needle 6 holding an upper thread UT and one looper 9 holding a lower thread LT will be described.

[0040] As shown in Fig. 4(A), the sewing needle 6 passes through the sewing object, passes the upper thread through the loop of the lower thread LT, and reaches the lowest point. The loop of the lower thread LT is formed when the looper 9 passes through the loop of the upper thread UT that the sewing needle 6 formed in the previous stitch.

[0041] As shown in Fig. 4(B), when the sewing needle 6 rises from the lowest point, the upper thread UT below the sewing object is loosened and a loop of the upper thread UT is formed. The looper 9 enters into the loop of the upper thread UT formed by the sewing needle 6. At this time, the upper thread UT is tightened by cooperation between the thread take-up 4 and the cam portion 5, which will be described later. In other words, the upper thread UT that forms the loop is pulled by the thread take-up 4 and taken up above the sewing object, thereby narrowing the loop of the upper thread UT.

[0042] As shown in Fig. 4(C), when the sewing needle 6 reaches near the top point, the looper 9 advances to the most forward position within the loop of the upper thread UT. At this timing, the workpiece is fed by a feed mechanism (not shown). As the workpiece is fed, the upper thread UT is finally tightened.

[0043] As shown in Fig. 4(D), when the sewing needle 6 starts to move down again, the looper 9 moves back from within the loop of the upper thread UT. As the looper 9 moves back from the most forward position, a loop of the lower thread LT is formed. The sewing needle 6 enters into this loop of the lower thread LT and scoops up the lower thread LT. After this, the operation of the sewing needle 6 and the looper 9 returns to that shown in Fig. 4(A).

[0044] Fig. 5 is a schematic diagram of the shape of a stitch formed by double chainstitching. The sewing object located between the upper thread UT and the lower thread LT is omitted in Fig. 5. In double chainstitching, the upper thread UT and the lower thread LT are entangled in a chain shape below the sewing object, forming a stitch as if the upper thread UT and the lower thread LT are knitted together.

[0045] 4 and 5, a stitch is formed by a pair of sewing needles 6 and a looper 9. In the embodiment, three stitches are formed in parallel by three pairs of sewing needles 6 and loopers 9. The first upper thread UT1, the second upper thread UT2, and the third upper thread UT3 are each used to form stitches by different pairs of sewing needles 6 (6A, 6B, 6C) and loopers 9 (9A, 9B, 9C), but all of them are tightened by the same thread take-up lever 4 and cam unit 5. The degree of thread tightening can be adjusted by adjusting the position of the cam unit 5, but if the sewing conditions of the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3 vary, it is difficult to reduce the variation by adjusting the overall position of the cam unit 5. Therefore, in the embodiment, even if the cam unit 5 is provided in common to each of the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3, the degree of thread tightening can be adjusted independently for each upper thread UT.

[0046] (Balance and cam) Fig. 6 is a perspective view of the balance 4 and the cam portion 5 according to the embodiment as viewed from the -X direction. Fig. 7 is a perspective view of the balance 4 and the cam portion 5 according to the embodiment as viewed from the +X direction.

[0047] As shown in Figs. 3, 6 and 7, the cam section 5 is attached to the sewing machine body 2 so as to protrude in the -Y direction from the side surface of the head 2D in the -Y direction. The cam section 5 is disposed in the vicinity of the thread take-up 4 so that the upper thread UT held by the thread take-up 4 comes into contact with the cam section 5. The cam section 5 has a cam guide section 35 having holes 35A, 35B and 35C (see Fig. 7) through which the upper thread UT passes, a first cam 31, a second cam 32 and a third cam 33, and a fixed member 34. The thread take-up 4 has inlet holes 41A, 41B and 41C, outlet holes 42A, 42B and 42C, and an attachment section 43. Each member constituting the cam section 5 is made of, for example, metal.

[0048] The first needle thread UT1 is supplied from the needle thread stand 14A shown in Fig. 3 through the first needle thread tensioner 10A, the hole 35A of the cam guide portion 35 (see Fig. 7), the entrance hole 41A of the thread take-up 4 (see Fig. 7), the first cam 31, the exit hole 42A of the thread take-up 4 (see Fig. 6), and the guide hole 15A of the needle thread guide 15 (see Fig. 6) to the first sewing machine needle 6A. The second needle thread UT2 is supplied from the needle thread stand 14B through the second needle thread tensioner 10B, the hole 35B of the cam guide portion 35, the entrance hole 41B of the thread take-up 4, the second cam 32, the exit hole 42B of the thread take-up 4, and the guide hole 15B of the thread guide 15 to the second sewing machine needle 6B. The third upper thread UT3 is supplied from the upper thread stand 14C through the third upper thread tensioner 10C, the hole 35C of the cam guide portion 35, the entrance hole 41C of the thread take-up lever 4, the third cam 33, the exit hole 42C of the thread take-up lever 4, and the guide hole 15C of the upper thread guide 15 to the third sewing machine needle 6C.

[0049] The balance 4 is attached to the needle bar 3 at an attachment portion 43 provided at one end. The balance 4 has a shape that extends from the attachment portion 43 in the -Y direction and bends around the cam portion 5. That is, the balance 4 has a first portion 4A extending from the attachment portion 43 in the -Y direction, a second portion 4B bending from the end of the first portion 4A in the +X direction, and a third portion 4C extending from the end of the second portion 4B in the +Y direction. The end of the third portion 4C is the other end of the balance 4. The first portion 4A is located in the -X direction with respect to the cam portion 5, and the third portion 4C is located in the +X direction with respect to the cam portion 5. The first portion 4A and the third portion 4C face each other in the X-axis direction via the cam portion 5. In the third portion 4C, inlet holes 41A, 41B, and 41C are formed at intervals in the Y-axis direction. In the first portion 4A, outlet holes 42A, 42B, and 42C are formed at intervals in the Y-axis direction. The inlet holes 41A, 41B, and 41C face the outlet holes 42A, 42B, and 42C, respectively, in the X-axis direction. This allows the thread take-up 4 to bring each upper thread UT into contact with the cam portion 5 between the inlet holes 41A, 41B, and 41C and the outlet holes 42A, 42B, and 42C.

[0050] The first cam 31, the second cam 32, and the third cam 33 of the cam portion 5 are disposed in an inner area surrounded by the first portion 4A, the second portion 4B, and the third portion 4C of the balance 4.

[0051] The first cam 31 guides the first upper thread UT1 passing through the thread take-up 4 to adjust the thread tightness. The second cam 32 guides the second upper thread UT2 passing through the thread take-up 4 to adjust the thread tightness. The third cam 33 guides the third upper thread UT3 passing through the thread take-up 4 to adjust the thread tightness. The first cam 31, the second cam 32, and the third cam 33 are provided separately. The first cam 31, the second cam 32, and the third cam 33 are independent members from one another.

[0052] The first cam 31 is disposed on the passage path of the first upper thread UT1 between the inlet hole 41A and the outlet hole 42A of the thread take-up 4. The first cam 31 has a first guide surface 31A. The first cam 31 guides the first upper thread UT1, which moves in the vertical direction together with the thread take-up 4, along the first guide surface 31A. The second cam 32 is disposed on the passage path of the second upper thread UT2 between the inlet hole 41B and the outlet hole 42B of the thread take-up 4. The second cam 32 has a second guide surface 32A. The second cam 32 guides the second upper thread UT2, which moves in the vertical direction together with the thread take-up 4, along the second guide surface 32A. The third cam 33 is disposed on the passage path of the third upper thread UT3 between the inlet hole 41C and the outlet hole 42C of the thread take-up 4. The third cam 33 has a third guide surface 33A. The third cam 33 guides the third upper thread UT3, which moves up and down together with the thread take-up 4, along a third guide surface 33A.

[0053] Fig. 8 is an exploded perspective view of the cam portion 5 according to the embodiment. Fig. 9 is a front view showing the cam portion 5 with the screw member 37 removed.

[0054] As shown in FIG. 8, the first guide surface 31A is formed on a part of the outer circumferential surface of the first cam 31. The first guide surface 31A is a side surface of the first cam 31 on the -Y direction side. The first guide surface 31A is a surface of the first cam 31 that is open to the outside. In other words, the first guide surface 31A is not an inner circumferential surface of a through-hole (such as a through-hole or a slit) that penetrates the first cam 31, but is a surface exposed to the outside of the first cam 31. The first guide surface 31A is polished to have a smooth surface so as not to cause scratches or fraying on the upper thread UT due to contact with the upper thread UT. The first guide surface 31A is formed of a curved surface that extends in the Z-axis direction (up and down direction) as a whole and has an apex 31B that protrudes in the -Y direction. The apex 31B is formed at a position on the lower end side between the upper end and the lower end of the first guide surface 31A. The first guide surface 31A has a lower inclined surface 31C inclined from the lower end thereof toward the apex 31B, and an upper inclined surface 31D inclined from the upper end thereof toward the apex 31B.

[0055] The first cam 31 has a screw insertion portion 36A at one end (upper end) and the other end (lower end). The screw insertion portion 36A is a through hole that penetrates the first cam 31. The screw insertion portion 36A is an oblong hole that is long in the Y-axis direction.

[0056] The second guide surface 32A is formed on a part of the outer peripheral surface of the second cam 32. The second guide surface 32A is a side surface of the second cam 32 on the -Y direction side. The second guide surface 32A is a surface of the second cam 32 that is open to the outside. In other words, the second guide surface 32A is a surface exposed to the outside of the second cam 32. The second guide surface 32A is polished to be a smooth surface so as not to cause scratches or wear on the upper thread UT due to contact with the upper thread UT. The second guide surface 32A is formed of a curved surface that extends in the Z axis direction (up and down direction) as a whole and has an apex 32B that protrudes in the -Y direction. The apex 32B is formed at a position on the lower end side between the upper end and the lower end of the second guide surface 32A. The second guide surface 32A has a lower inclined surface 32C that is inclined from the lower end of the second guide surface 32A toward the apex 32B, and an upper inclined surface 32D that is inclined from the upper end toward the apex 32B.

[0057] The third cam 33 has a screw insertion portion 36B at one end (upper end) and the other end (lower end). The screw insertion portion 36B is a through hole that penetrates the third cam 33. The screw insertion portion 36B is an oblong hole that is long in the Y-axis direction.

[0058] The third guide surface 33A is formed on a part of the outer peripheral surface of the third cam 33. The third guide surface 33A is a side surface on the -Y direction side of the third cam 33. The third guide surface 33A is a surface of the third cam 33 that is open to the outside. In other words, the third guide surface 33A is a surface exposed to the outside of the third cam 33. The third guide surface 33A is polished to be a smooth surface so as not to cause scratches or wear on the upper thread UT due to contact with the upper thread UT. The third guide surface 33A is formed as a curved surface that extends in the Z axis direction (up and down direction) as a whole and has an apex 33B that protrudes in the -Y direction. The apex 33B is formed at a position on the lower end side between the upper end and the lower end of the third guide surface 33A. The third guide surface 33A has a lower inclined surface 33C that is inclined from the lower end of the third guide surface 33A toward the apex 33B, and an upper inclined surface 33D that is inclined from the upper end toward the apex 33B.

[0059] The third cam 33 has a screw insertion portion 36C at one end (upper end) and the other end (lower end). The screw insertion portion 36C is a through hole that penetrates the third cam 33. The screw insertion portion 36C is an oblong hole that is long in the Y-axis direction.

[0060] The first cam 31, the second cam 32, and the third cam 33 are each separately attached to a fixed member 34. The fixed member 34 includes a first fixed member 34A that fixes one end (upper end) of each cam, and a second fixed member 34B that fixes one end (lower end) of each cam. The first fixed member 34A and the second fixed member 34B are each fixed to the head 2D of the sewing machine body 2.

[0061] The first fixing member 34A is provided with a cam guide portion 35. The first fixing member 34A has a first screw hole 34A1 for fixing one end of the first cam 31, a second screw hole 34A2 for fixing one end of the second cam 32, and a third screw hole 34A3 for fixing one end of the third cam 33. The first screw hole 34A1, the second screw hole 34A2, and the third screw hole 34A3 are aligned along the Y-axis direction. The second fixing member 34B has a first screw hole 34B1 for fixing the other end of the first cam 31, a second screw hole 34B2 for fixing one end of the second cam 32, and a third screw hole 34B3 for fixing one end of the third cam 33. The first screw hole 34B1, the second screw hole 34B2, and the third screw hole 34B3 are aligned along the Z-axis direction.

[0062] The first cam 31, the second cam 32 and the third cam 33 are attached to a fixed member 34 so that their positions can be adjusted in an adjustment direction to move closer to or away from the needle bar 3. In this embodiment, the adjustment direction is the Y-axis direction. Since the sewing needle 6 is attached to the lower end of the needle bar 3, when the distance in the Y-axis direction between the first cam 31, the second cam 32 and the third cam 33 and the needle bar 3 changes, the path length of the upper thread UT from the first cam 31, the second cam 32 and the third cam 33 to the corresponding sewing needle (first sewing needle 6A, second sewing needle 6B, third sewing needle 6C) changes.

[0063] The first cam 31 is attached to the fixed member 34 by a screw member 37 passed through the screw insertion portion 36A. One end of the first cam 31 is fastened to the first fixed member 34A by the screw member 37 attached to the first screw hole 34A1 via the screw insertion portion 36A. The other end of the first cam 31 is fastened to the second fixed member 34B by the screw member 37 attached to the first screw hole 34B1 via the screw insertion portion 36A.

[0064] The second cam 32 is attached to the fixed member 34 by a screw member 37 passed through the screw insertion portion 36B. One end of the second cam 32 is fastened to the first fixed member 34A by the screw member 37 attached to the second screw hole 34A2 via the screw insertion portion 36B. The other end of the second cam 32 is fastened to the second fixed member 34B by the screw member 37 attached to the second screw hole 34B2 via the screw insertion portion 36B.

[0065] The third cam 33 is attached to the fixed member 34 by a screw member 37 passed through the screw insertion portion 36C. One end of the third cam 33 is fastened to the first fixed member 34A by the screw member 37 attached to the third screw hole 34A3 via the screw insertion portion 36C. The other end of the third cam 33 is fastened to the second fixed member 34B by the screw member 37 attached to the third screw hole 34B3 via the screw insertion portion 36C.

[0066] As shown in FIG. 9, the first cam 31, the second cam 32, and the third cam 33 are arranged side by side. The first cam 31, the second cam 32, and the third cam 33 are arranged side by side in the Y-axis direction. The length in the Y-axis direction of each screw insertion portion (36A, 36B, 36C) of the first cam 31, the second cam 32, and the third cam 33 is larger than the diameter of each screw hole of the first fixing member 34A and the second fixing member 34B (i.e., the diameter of the shaft portion of the screw member 37). Therefore, the first cam 31 can change the mounting position of the first cam 31 in the Y-axis direction (adjustment direction) within the range of the gap CL between the screw member 37 and the screw insertion portion 36A by loosening each screw member 37. Similarly, the second cam 32 can change the mounting position of the second cam 32 in the Y-axis direction (adjustment direction) within the range of the gap between the screw member 37 and the screw insertion portion 36B by loosening each screw member 37. The mounting position of the third cam 33 can be changed in the Y-axis direction (adjustment direction) within the range of the gap between the screw members 37 and the screw insertion portion 36C by loosening each screw member 37. With this configuration, the first cam 31, the second cam 32, and the third cam 33 are mounted so that their positions can be adjusted separately.

[0067] The second cam 32 has an opposing surface 32E (see FIG. 8) that faces the first cam 31 on the opposite side of the outer circumferential surface to the second guide surface 32A. The opposing surface 32E faces the first guide surface 31A in the Y-axis direction at a distance from the first guide surface 31A. As a result, the cam portion 5 forms a slit-shaped yarn passage TP1 surrounded by the inner circumferential surface, with the first guide surface 31A and the opposing surface 32E as inner circumferential surfaces. In other words, the first guide surface 31A is the outer circumferential surface of the first cam 31 that is open to the outside, but the first cam 31 (first guide surface 31A) and the second cam 32 (opposing surface 32E) in combination form a closed yarn passage TP1 (see FIG. 9).

[0068] Similarly, the third cam 33 has an opposing surface 33E (see FIG. 8) opposing the second cam 32 on the opposite side of the outer circumferential surface to the third guide surface 33A. The opposing surface 33E is spaced apart from the second guide surface 32A and faces the second guide surface 32A in the Y-axis direction. As a result, the cam portion 5 forms a slit-shaped yarn passage TP2 (see FIG. 9) surrounded by an inner circumferential surface, with the second guide surface 32A and the opposing surface 33E as inner circumferential surfaces.

[0069] When the position of the first cam 31 is adjusted in the +Y direction or the position of the second cam 32 is adjusted in the -Y direction, a gap is formed between the upper end of the first guide surface 31A and the upper end of the opposing surface 32E, but this gap is closed by the lower surface BS (see FIG. 8) of the first fixed member 34A. Therefore, even if the first cam 31 and the second cam 32 are shifted in the Y-axis direction, the yarn passage TP1 remains closed. The same is true for the yarn passage TP2.

[0070] (Function of the balance and cam) Next, the function of the balance 4 and the cam portion 5 will be described. Fig. 10 is a schematic diagram showing the positional relationship between the balance 4 and the cam portion 5 when the balance 4 is located near the lower inclined surface of the cam portion 5. Fig. 11 is a schematic diagram showing the positional relationship between the balance 4 and the cam portion 5 when the balance 4 is located near the top of the cam portion 5. Fig. 12 is a schematic diagram showing a cross section of the balance 4 and the cam portion 5 in Fig. 11. Fig. 13 is a schematic diagram showing the positional relationship between the balance 4 and the cam portion 5 when the balance 4 is located near the upper inclined surface of the cam portion 5. In Figs. 10, 11 and 13, the balance 4 is indicated by dotted lines.

[0071] The thread take-up 4 moves up and down in conjunction with the needle bar 3, bringing the upper thread UT it holds into contact with the cam portion 5 and moving it up and down. The movement of the thread take-up 4 changes the contact position between the cam portion 5 and the upper thread UT. The cam portion 5 changes the path length of the upper thread UT (the path length from the upper thread tensioner 10 to the sewing machine needle 6) for each contact position with the upper thread UT. The cam portion 5 achieves thread tightening by changing the path length of the upper thread UT.

[0072] As shown in Fig. 10 and Fig. 4(B), when the sewing needle 6 starts to rise from near the lowest point, the thread take-up 4 moves the forming position of the lower inclined surface (31C, 32C, 33C) of the cam portion 5 in the +Z direction. In Fig. 10, the positions of the inlet holes 41A, 41B, 41C and the outlet holes 42A, 42B, 42C of the thread take-up 4 have not yet reached the corresponding lower inclined surface (31C, 32C, 33C), so that each upper thread UT follows a straight path connecting the inlet hole and the outlet hole. When the thread take-up 4 moves in the +Z direction from Fig. 10, each upper thread UT comes into contact with the corresponding lower inclined surface 31C, 32C, 33C, and each upper thread UT is bent along the lower inclined surface 31C, 32C, 33C. As each of the upper threads UT approaches the tops 31B, 32B, and 33B, the contact positions between each of the upper threads UT and the lower inclined surfaces 31C, 32C, and 33C are offset in the -Y direction.

[0073] As shown in Figs. 11 and 12, after the looper 9 enters the loop of the upper thread UT (see Fig. 4(B)), each upper thread UT passing through the thread take-up lever 4 reaches the position of each apex 31B, 32B, 33B of the cam portion 5. At this time, as shown in Fig. 12, the magnitude of the offset of the contact position (P1, P2, P3) between the upper thread UT and the cam portion 5 becomes maximum. Each upper thread UT is bent by the amount of the offset between the inlet hole (41A, 41B, 41C) and the outlet hole (42A, 42B, 42C), so that the path length to the sewing needle 6 becomes longer. The upper thread UT is taken up in slack (loop) from the sewing needle 6 in accordance with the increment of the path length from the thread take-up lever 4 and the cam portion 5 to the sewing needle 6. As a result, the upper thread UT is gradually taken up from the sewing needle 6 until the thread take-up 4 passes from the lower inclined surface (31C, 32C, 33C) of the cam portion 5 to the top portion (31B, 32B, 33B), thereby tightening the thread.

[0074] 13, after the thread take-up 4 passes the top of the cam portion 5, the upper thread UT is guided along the upper inclined surfaces 31D, 32D, and 33D until it reaches the highest point. During this process, the offset of the contact position between the upper thread UT and the cam portion 5 becomes smaller, so that the tension of the upper thread UT is gradually relaxed.

[0075] In this embodiment, the positions of the first cam 31, the second cam 32, and the third cam 33 can be adjusted separately, so that the magnitude of the offset in Fig. 12 can be adjusted individually for each upper thread UT. That is, by adjusting the position of the first cam 31, the distance in the Y-axis direction from the inlet hole 41A and the outlet hole 42A of the thread take-up lever 4 to the contact position P1 between the first upper thread UT1 and the first cam 31 can be adjusted. As a result, the degree of thread tightening can be adjusted according to the amount of change in the path length of the first upper thread UT1 passing through the inlet hole 41A, the contact position P1, and the outlet hole 42A.

[0076] Similarly, by adjusting the position of the second cam 32, the distance from the entrance hole 41B and the exit hole 42B of the thread take-up 4 to the contact position P2 between the second upper thread UT2 and the second cam 32 can be adjusted. As a result, the degree of thread tightening can be adjusted according to the amount of change in the path length of the second upper thread UT2 passing through the entrance hole 41B, the contact position P2, and the exit hole 42B. By adjusting the position of the third cam 33, the distance from the entrance hole 41C and the exit hole 42C of the thread take-up 4 to the contact position P3 between the third upper thread UT3 and the third cam 33 can be adjusted. As a result, the degree of thread tightening can be adjusted according to the amount of change in the path length of the third upper thread UT3 passing through the entrance hole 41C, the contact position P3, and the exit hole 42C. As a result, even if the sewing finish of each upper thread UT varies, it is possible to independently adjust the sewing finish of each of the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3.

[0077] If the tightening of any of the first top thread UT1, the second top thread UT2, and the third top thread UT3 is too tight, the sewing worker adjusts the position of the corresponding cam among the first cam 31, the second cam 32, and the third cam 33 in the +Y direction. If the tightening of any of the first top thread UT1, the second top thread UT2, and the third top thread UT3 is too loose, the sewing worker adjusts the position of the corresponding cam among the first cam 31, the second cam 32, and the third cam 33 in the -Y direction. This makes it possible to align the finish of the stitches of the first top thread UT1, the second top thread UT2, and the third top thread UT3, and form a uniform stitch.

[0078] (effect) As described above, according to this embodiment, the sewing machine 1 comprises: a needle bar 3 which holds a first sewing needle 6A and a second sewing needle 6B and is driven in an up and down direction; a thread take-up 4 through which a first upper thread UT1 supplied to the first sewing needle 6A and a second upper thread UT2 supplied to the second sewing needle 6B are inserted and which operates in conjunction with the needle bar 3; a cam section 5 which includes a first cam 31 which guides the first upper thread UT1 passing through the thread take-up 4 to adjust the thread tightness, and a second cam 32 which is provided separately from the first cam 31 and guides the second upper thread UT2 passing through the thread take-up 4 to adjust the thread tightness; and a sewing machine main body 2 in which the needle bar 3, the thread take-up 4, and the cam section 5 are provided, and the first cam 31 and the second cam 32 are attached to the sewing machine main body 2 so that their positions can be adjusted separately.

[0079] This allows the adjustment of the thread tightness of the first upper thread UT1 by adjusting the position of the first cam 31 and the adjustment of the thread tightness of the second upper thread UT2 by adjusting the position of the second cam 32 to be performed independently. This allows the adjustment of the sewing finish by the first sewing needle 6A and the first upper thread UT1 and the sewing finish by the second sewing needle 6B and the second upper thread UT2 to be aligned with each other. As a result, in a sewing machine 1 equipped with a cam-type thread take-up lever and using multiple upper threads UT, the sewing finish of each thread can be aligned. In the embodiment, the cam section 5 further includes a third cam 33, and the first cam 31, the second cam 32, and the third cam 33 are separately attached to the sewing machine body 2 so that their positions can be adjusted, so that the sewing finish of each of the first upper thread UT1, the second upper thread UT2, and the third upper thread UT3 can be adjusted to be aligned.

[0080] In this embodiment, the first cam 31 has a first guide surface 31A that is open to the outside on a part of its outer circumferential surface, and guides the first upper thread UT1 that moves up and down together with the thread take-up 4 along the first guide surface 31A. The second cam 32 has a second guide surface 32A that is open to the outside on a part of its outer circumferential surface, and guides the second upper thread UT2 that moves up and down together with the thread take-up 4 along the second guide surface 32A. This allows the first guide surface 31A and the second guide surface 32A to be formed on the outer circumferential surface that is open to the outside, rather than on the inner circumferential surface of a slit or the like. This allows the first guide surface 31A and the second guide surface 32A, which smooth the first guide surface 31A and the second guide surface 32A that slide the upper thread UT, to be polished easily and uniformly. For example, when forming a guide surface on the inner circumferential surface of a long and narrow slit, polishing work using a precision grinder (a buff provided on the tip chuck of an electric drill) is required, whereas in this embodiment in which a guide surface is formed on the outer circumferential surface, polishing can be performed using a buff polishing device that can polish a wide range easily and uniformly.

[0081] In this embodiment, the second cam 32 has an opposing surface 32E opposing the first cam 31 on the opposite side of the outer circumferential surface to the second guide surface 32A, and the cam portion 5 forms a slit-shaped thread passage surrounded by the inner circumferential surface, with the first guide surface 31A and the opposing surface 32E as the inner circumferential surface. As a result, the first guide surface 31A is formed on the outer circumferential surface of the first cam 31, and the area where the first upper thread UT1 is guided along the first guide surface 31A can be configured as a closed thread passage TP1. This makes it possible to prevent a situation in which, for example, an operator erroneously moves the upper thread UT during sewing preparation, causing the first upper thread UT1 to unintentionally move toward the second guide surface 32A.

[0082] In this embodiment, the cam section 5 has a fixed member 34 fixed to the sewing machine body 2 and to which the first cam 31 and the second cam 32 are attached, and the first cam 31 and the second cam 32 are attached to the fixed member 34 so as to be positionally adjustable in an adjustment direction (Y-axis direction) in which they approach and move away from the needle bar 3. The first cam 31 and the second cam 32 can be easily attached and adjusted in position to the common fixed member 34. The first cam 31 and the second cam 32 each have screw insertion portions 36A, 36B, and 36C formed to extend in the adjustment direction (Y-axis direction), and are attached to the fixed member 34 by a screw member 37 that passes through the screw insertion portions 36A, 36B, and 36C. This allows the positions of the first cam 31 and the second cam 32 to be adjusted individually with a simple structure.

[0083] The technical scope of the present disclosure is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the present disclosure.

[0084] For example, in the above embodiment, an example was shown in which three cams, the first cam 31, the second cam 32, and the third cam 33, were provided, but the cam section 5 may be provided with only two cams, the first cam 31 and the second cam 32, or may be provided with four or more cams. The number of cams may be determined according to the number of upper threads (the number of sewing machine needles) to be used.

[0085] For example, in the above embodiment, the first guide surface 31A is provided on a part of the outer circumferential surface of the first cam 31 so as to be open to the outside, and the second guide surface 32A is provided on a part of the outer circumferential surface of the second cam 32 so as to be open to the outside, but the first guide surface 31A may be formed by the inner circumferential surface of a through hole (slit) formed in the flat plate-like first cam 31. The second guide surface 32A may be formed by the inner circumferential surface of a through hole (slit) formed in the flat plate-like second cam 32. [Explanation of symbols]

[0086] Reference Signs List 1... sewing machine, 2... sewing machine body, 2A... first arm, 2B... bed, 2C... second arm, 2D... head, 3... needle bar, 4... thread take-up lever, 4A... first part, 4B... second part, 4C... third part, 5... cam portion, 6... sewing machine needle, 6A... first sewing machine needle, 6B... second sewing machine needle, 6C... third sewing machine needle, 7... needle hole, 8... needle plate, 9... looper, 9A... first looper, 9B... second looper, 9C... third looper, 10... thread tension adjuster, 10A... first thread tension adjuster, 10B... second thread tension adjuster, 10C... third thread tension adjuster, 11... bobbin thread Tensioner, 11A...first lower thread tensioner, 11B...second lower thread tensioner, 11C...third lower thread tensioner, 12...actuator, 13...power transmission device, 13A...arm shaft, 13B...bed shaft, 13C...looper shaft, 13C1...oscillating arm, 13D...pulley, 13E...pulley, 13F...timing belt, 13G...power transmission mechanism, 13H...power transmission mechanism, 15...upper thread guide, 15A, 15B, 15C...guide hole, 16...lower thread guide, 21, 25...thread guide, 22, 23, 24...thread tensioner, 31...first cutter cam, 31A...first guide surface, 31B...top, 31C...lower inclined surface, 31D...upper inclined surface, 32...second cam, 32A...second guide surface, 32B...top, 32C...lower inclined surface, 32D...upper inclined surface, 32E...opposing surface, 33...third cam, 33A...third guide surface, 33B...top, 33C...lower inclined surface, 33D...upper inclined surface, 33E...opposing surface, 34...fixing member, 34A...first fixing member, 34A1...first screw hole, 34A2...second screw hole, 34A3...third screw hole, 34B...second fixing member, 34B1...first screw hole, 3 4B2...second screw hole, 34B3...third screw hole, 35...cam guide portion, 35A, 35B, 35C...hole, 36A, 36B, 36C...screw insertion portion, 37...screw member, 41A, 41B, 41C...entrance hole, 42A, 42B, 42C...exit hole, 43...mounting portion, AX...rotation axis, BS...lower surface, LT...lower thread, LT1...first lower thread, LT2...second lower thread, LT3...third lower thread, P1, P2, P3...contact position, TP1, TP2...thread path, UT...upper thread, UT1...first upper thread, UT2...second upper thread, UT3...third upper thread.

Claims

1. a needle bar that holds the first sewing needle and the second sewing needle and is driven in a vertical direction; a thread take-up lever through which a first needle thread supplied to the first sewing machine needle and a second needle thread supplied to the second sewing machine needle are inserted and which operates in conjunction with the needle bar; a cam portion including a first cam that guides the first upper thread passing through the lever to adjust thread tightness, and a second cam that is provided separately from the first cam and guides the second upper thread passing through the lever to adjust thread tightness; a sewing machine body in which the needle bar, the thread take-up and the cam portion are provided, The first cam and the second cam are attached to the sewing machine body so as to be separately positionally adjustable. sewing machine.

2. the first cam has a first guide surface that is open to the outside on a part of an outer circumferential surface, and guides the first upper thread that moves in a vertical direction together with the thread take-up along the first guide surface; the second cam has a second guide surface that is open to the outside on a part of an outer circumferential surface, and guides the second upper thread that moves in the vertical direction together with the thread take-up along the second guide surface.

2. The sewing machine according to claim 1.

3. The first cam and the second cam are arranged side by side, the second cam has an opposing surface facing the first cam on an opposite side of an outer circumferential surface to the second guide surface, The cam portion defines an inner circumferential surface, the inner circumferential surface being the first guide surface and the opposing surface, and forms a slit-shaped yarn passage surrounded by the inner circumferential surface.

3. The sewing machine according to claim 2.

4. the cam portion includes a fixed member that is fixed to the sewing machine body and to which the first cam and the second cam are attached, the first cam and the second cam are attached to the fixed member so as to be positionally adjustable in an adjustment direction in which the first cam and the second cam approach and move away from the needle bar; A sewing machine according to any one of claims 1 to 3.

5. The first cam and the second cam each have a screw insertion portion formed to extend in the adjustment direction, and are attached to the fixed member by a screw member passing through the screw insertion portion.

5. The sewing machine according to claim 4.

6. the needle bar further holds a third sewing needle; The third needle thread is further inserted through the thread take-up lever, the third needle thread being supplied to the third sewing needle. the cam portion further includes a third cam that guides the third upper thread passing through the lever to adjust thread tension, The first cam, the second cam, and the third cam are attached to the sewing machine body so as to be separately positionally adjustable. A sewing machine according to any one of claims 1 to 3.

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