JPH0154073B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises a hook that grips an upper thread loop, a rotation axis parallel to the needle, and a hook that is supported in a hook so as not to rotate relative to the sewing machine. A rotatably driven hook having a bobbin case for supplying bobbin thread to a needle passage hole, and a thread catcher provided on a blade holder that is movable and swingable between the hook and the needle passage hole. The cutting edge of this thread catcher cooperates with the substantially fixed mating blade, and the thread catcher has a cut that grasps one side of the processed part of the lower thread and upper thread, and a leg with a pointed end on the leading side in the direction of movement. The leg side is movable between the needle side part of the needle thread, the processing side part of the needle thread, and the bobbin thread, and the direction of movement of the thread catcher is from the non-operating position to the mating blade. This invention relates to a thread cutting device for a lockstitch sewing machine, which is oriented in the opposite direction to the direction of rotation of the lockstitch sewing machine.

[Conventional technology]

In such a thread cutting device known from German Patent No. 3303032 (corresponding to U.S. Patent Application No. 570865), the threads do not move together in the direction of rotation of the shuttle, but are gripped in the opposite direction and are Subject to tension while being held. Immediately after the needle thread loop is captured by the hook tip of the hook, the processed half of the needle thread and the bobbin thread are approximately at the same height relative to the axis of the hook and are therefore in a common plane rising towards the needle passage hole. , the part of the upper thread where the thread is grabbed and passed under the hook to the needle is very low. It is therefore possible to grasp both thread sections on one side of the process relatively easily. In this known sewing machine, when the thread take-up is in its uppermost position, as usual, and the needle, which is usually slightly advanced than the thread take-up, is again in a position below the top dead center,
Thread cutting is performed. This thread take-up position during thread cutting makes it possible to prevent the free end of the thread from being pulled out of the needle eye at the beginning of the next stitch. A disadvantage in this case is that the free passage space between the suture support piece and the needle tip is reduced.

In order to eliminate the above-mentioned problems, the needle thread between the thread take-up and the needle or needle hole is held by a special thread gripping piece during thread cutting, so that the thread take-up only takes out a new thread section from the supply thread during its upward movement. It is already known from German Patent No. 276 162 to prevent the free end of the thread from being pulled out of the needle eye.

From German Utility Model No. 812,481 (corresponding to U.S. Pat. No. 4,515,098), it is known to solve this problem by providing a so-called reversing device, which returns the needle to the upper position. be.

Both solutions are technically expensive, require additional control costs and further increase cycle times.

[Problem that the invention seeks to solve]

The object of the present invention is therefore to improve a thread cutting device of the type mentioned in the first place in order to prevent, by technically simple means, the upper thread from slipping out of the needle after cutting the thread, and at the same time The object is to provide maximum passage space between the needle tip and the suture material placement piece.

[Means for solving problems]

In order to solve this problem, according to the invention, the blade holder is provided with a thread tensioning piece that extends up to the upper surface of the bobbin case near the blade holder, so that the thread tensioning piece can hold the bobbin in the inoperative position of the thread catcher. The part of the upper thread that is located outside the case and is located above the bobbin case at the position of the thread catcher that has swung toward the mating blade, and therefore is on the top surface of the bobbin case, is exposed to the thread tension piece when the hook rotates. around, so that at the same time the needle thread is pulled out by the needle.

〔Effect of the invention〕

With the measures according to the invention, after the thread cutting device has been swung into its operating position, an additional upper thread is withdrawn immediately before the start of the thread cutting process. It is therefore possible to carry out the thread cutting process at a high position on the needle. Thus, in this case, without the need to further change the needle position,
The maximum possible passage space for the suture material is obtained between the needle and the needle passage hole. At the beginning of a new sewing process, the needle is lowered and the balance is still rising upwards.
In this case, some or all of the needle thread that is additionally drawn out by the thread tensioning piece can be drawn through the needle hole without the risk of slipping out. Therefore, by using an additional means that is structurally very simple, a reversing device is no longer necessary.
Alternatively or additional thread gripping pieces can be omitted. Additional control costs for such devices are eliminated. Furthermore, no time is required for the operation of known devices, thereby reducing the overall sewing time.

The means according to claim 2 extends the thread tensioning piece to below the surface formed by the upper surface of the bobbin case, so that the upper thread portion guided on the upper surface of the bobbin case is reliably captured, so that the thread tensioning piece is attached to the bobbin case. Collision with the top surface of the case can be prevented.

Claim 3 defines the position that the thread tensioning piece assumes with respect to the hook when drawing out the additional needle thread immediately before thread cutting, and this position of the thread tensioning piece is in accordance with the tension of the needle thread being drawn out. Also determine the length.

By means of the measures according to claim 4, it is possible to ensure that the needle thread is gripped and held by the thread tension piece during the drawing process.

With the arrangement according to claim 5, the thread tensioning piece can be swung over the top surface of the bobbin case in a timely manner to hold the appropriate portion of the upper thread during the formation of the last stitch before cutting the thread. You can hang it around the string tension piece and pull it out.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

The sewing machine shown in FIG.
It has a support 2 standing upright on one side of the support support 2, and an arm 3 freely projecting from the support support 2 parallel to and above the base plate 1. An upper shaft 4 is supported within the arm 3, and a needle bar 6 is supported via a crank transmission 5 to drive the needle bar 6 via the crank transmission 5. This needle bar 6 has a needle 7 at its lower end. The upper shaft 4 has a handle wheel 8 at the end on the column side. In addition to a handle wheel 8, a belt pulley 9 is also provided on the upper shaft 4, and the sewing machine is driven by a belt 10 via the upper shaft 4 from an electric motor (not shown).

A hook drive shaft 11 is rotatably supported on the base plate 1 and is synchronously driven from the upper shaft 4 via a belt transmission device 12 . This hook drive shaft 11 is supported horizontally.
The vertically arranged hook shaft 13 of the lockstitch hook 14 is
is driven. This drive is performed via a gear 16 mounted on the shuttle shaft 13 with a set screw 15.

A hook body 17 of the hook 14 is fixedly provided at the upper end of the hook shaft 13. The pot body 17 is generally shaped like a pot. The internal space that opens upwards in the pot body 17 includes a rotation axis 1 of the pot 14.
bobbin case 19 provided concentrically with respect to 8;
is supported to be freely rotatable with respect to the hook 14. Similarly, a bobbin 20 is provided within the bobbin case concentrically with respect to the rotation axis 18, and a bobbin thread 21 is provided.
is wrapped around it. This bobbin 20 is axially fixed in the bobbin case 19 by a strip 22 which can be pivoted upwards.

The needle 7 has a needle thread 23 mounted on the arm 3.
4 via a balance 25, which can be driven by the upper shaft 4 in the usual manner.

A needle plate 26 having a needle passage hole 28 on the top surface of the base plate 1
is provided, and during the downward movement of the needle 7, this needle 7 passes through the needle passage hole 28 together with the upper thread 23. Pot body 17
A hook point 30 is formed on the outer periphery of the needle thread 23, which is sharp in the direction of rotation, and grips the needle thread 23, which spreads out to form a loop when passing by the needle 7 passed through the needle passage hole 28, to form a loop. while guiding it around the hook 14 together with the bobbin thread 21.

Sewing machines having the lockstitch hook 14 described above are generally known in practice.

The upper edge of the bobbin case 19 has a recess 31 on the side diametrically opposite to the needle passage hole 28, and the rotation axis 1
The free end of the stop finger 32, which is arranged radially at right angles to 8, extends into this recess 31.
This stop finger 32 is adjustably mounted on a suitable projection 33 of the base plate 1 by means of a screw 34. The recess 31 has enough clearance to allow the needle thread 23 to pass through the stop finger 32. Note that the stop finger 32 is configured to be flush with the top surface of the hook 14, and therefore does not protrude upwards from this top surface, so that the entire space above the hook 14, particularly in the range of the needle passage hole 28, is completely filled. I'm meeting you. For this reason, pot 14
The blade arm 35 of the thread cutting device 36 can swing in the entire upper space. This blade arm 35 is the blade holder 3
7 by screws 38, and the blade holder 37
It is mounted on a shaft 39 supported by the base plate 1. The oscillating drive of the shaft 39 and thus of the thread cutting device 36 is driven by an electromagnet 40 and the shaft 3
This is carried out in the usual manner by means of a push rod 41 connected to 9.

A square lever 42 is coupled to the shaft 39 in substantially the same plane as the push rod 41 of the electromagnet 40 by a tightening screw 43. The rounded end 45 of the shorter lever arm 44 of the square lever 42 is connected to the push rod 41
It's hitting. The longer lever arm 46 of the square lever 42 likewise has a rounded end 47. When the electromagnet 40 is energized so that the push rod 41 is pushed out, the rounded end 47 of the longer lever arm 46 can swing against the guide surface 48 of the cam plate 49 . This cam plate 49 is coupled to the lower end of the hook shaft 13 by a set screw 50 so as to prevent relative rotation. The cam plate 49 causes the blade arm 35 to move after the thread cutting device 36 is operated by excitation of the electromagnet 40.

A projection 51 that projects upward is formed on the longer lever arm 46 of the square lever 42.
A buffer piece 52 made of, for example, rubber is attached to the lever and is attached to a protrusion 53 attached to the base plate 1, so that it is cushioned when the rectangular lever 42 returns to its non-operating position as shown in FIG. and hit the protrusion.

The rectangular lever 42 is provided with a torsion spring 54 with an initial stress applied, one end 55 of which abuts against the rectangular lever 42 and the other end 56 fixed to the base plate 1. Rounded end 4 of the longer lever arm 46
The swinging of the rectangular lever 42 so that the cam guide surface 48 comes into contact with the cam guide surface 48 is performed against the force of this torsion spring 54, and after the rectangular lever 42 is separated from the guide surface 48, this torsion spring 54 Return the lever 42 to the inoperative position again.

At the free end of the blade arm 35 opposite to the blade holder 37, a thread catcher 57 is provided which is bent downward and has a cutting edge 58. In order to capture the upper thread 23 and the bobbin thread 21, the thread catcher 57 has a V-shaped cut 60 on the leading edge in the swing direction 59 opposite to the rotation direction 29, and this cut 60 has a V-shaped cut 60 in the upper leg. It is divided by a side 61 and a lower leg side 62, and the lower leg side 62 ends at a tip 63 on the advancing side in the swing direction 59. The bottom of the V-shaped cut 60 is formed by a rounded part 64 from which a slit-like recess 65 extends through the thread catcher 57 opposite to the pivoting direction 59 as far as the cutting edge 58 .
The cutting edge 58 is formed by a hole 66 in the thread catcher 57 which is suitably made obliquely.
The inner surface 67 of the thread catcher 57 closer to the shaft 39
has a wedge-shaped portion 69 which becomes thinner towards the outer surface 68 in the direction of oscillation 59.

A fixed mating blade 70 is attached to the thread catcher 57,
attached to the blade holder 71, while this blade holder 7
1 is attached by screws 72 to appropriate projections 73 of the base plate 1. The mating blade 70 has a cutting edge 74, and when the blade arm 35 swings together with the thread catcher 57, this cutting edge 74 touches the outer surface 68 of the thread catcher 57.
, and in particular cooperates with its cutting edge 58 .

The mating blade 70 is provided with an elastic thread gripping piece 75, which has a tip 76 bent into a substantially semicircular shape in the range of the cutting edge 74 of the mating blade 70. The thread catcher 57 has a wedge-shaped portion 69 of its inner surface 67 in the region of its leading end, so that the thread catcher 5
The thread catcher 57 enters between the mating blade 70 and the thread gripping piece 75 while bringing the outer surface 68 of the thread gripping piece 75 into contact with the cutting edge 74 of the mating blade 70, and the rounded tip 76 of the thread gripping piece 75 then catches the thread. It hits the inner surface 67 of the capture body 57.

The bobbin thread 21 exits the bobbin case 19 through an outlet opening 77 located in the area of the upper edge of the bobbin case 19 in the immediate vicinity of the needle passage hole 28 and from there directly into the needle passage hole, as shown in dashed lines in FIG. It extends towards 28.

From the upper surface 78 of the hook 30 of the hook 14 to the hook body 17
A recess 79 is formed at the transition point, and when the hook 30 grips the upper thread 23 and then rotates in the direction of rotation 29, the upper thread 23 is pulled over the upper surface of the bobbin 20 by this recess 79. A round recess 81 is formed at the transition from the underside 80 of the hook 30 to the hook body 17, and the needle thread 23 is guided within this recess 81.

As can be seen from FIGS. 2, 4a to 4f, and 6, the blade arm 35 swings in its direction 59.
It has a protrusion 85 on the rear side, and a pin-shaped thread tensioning piece 86 is provided on this protrusion. This thread tensioning piece 86 extends towards the bobbin 20 and has a constriction 87 halfway from the projection 85 to its free end.
According to FIG. 6, the free end of the thread tensioning piece 86 projects below the plane formed by the upper surface 88 of the bobbin case 19. In order to allow the blade arm 35 with the thread tensioning piece 86 to swing without hindrance, the bobbin case 19 has a notch 89 in the path of movement of the thread tensioning piece 86. As can be seen from FIG. 2, the depth of this notch is determined so that it is substantially flush with the top surface of the bobbin 20. As can be seen from FIGS. 4a and 4b, the thread tensioning piece 86 is not on the bobbin 20 or the bobbin case 19 that accommodates it in the non-operating position of the blade arm 35, but in the radially outer area of the hook body 17. , so that during normal sewing movements, when the blade arm 35 of the thread cutting device is in the inactive position, the shuttle 14 can operate unhindered.

In the embodiments of the invention described above, the hook was inserted into an integral bobbin case. Instead of such a hook, a two-part bobbin case consisting of a lower bobbin case and an upper bobbin case can also be used.

[Effect]

The operation is as follows.

It is assumed that the seams shown in FIG. 5 are formed on a work piece (not shown). This seam is connected to the bobbin thread 2, which is always below the seam, as shown by the chain line in Figure 5.
1 and an upper thread 23 that is always above the seam and entwined with the lower thread 21, and the upper thread 23 is in the range of the seam and from the needle passage hole 28 to the upper surface 78 of the hook 30, that is, as shown in FIG. The range of solid lines and dotted lines is indicated by reference numeral 82, and the range of other broken lines is indicated by reference numeral 23.
It is shown in The solid line portion is the processed one side portion of the needle thread 23.

In order to form the stitch shown in FIG. 5, the needle 7 pierces the workpiece (not shown) and, after reaching its lowest position, is raised upwards by a certain distance, the so-called loop stroke, so that it is threaded through the hole of the needle 7. Upper thread 23 forms a loop. The upper part, shown in solid and dotted lines in FIG.
The dashed line leading to is below. At this moment, this loop is grabbed by the hook 30, and this loop is grabbed by the hook 30.
0 along the bobbin 20 and is in this case twisted once around the bobbin thread 21, thereby producing the stitch shown. This loop then falls out of the hook 14 again, with the excess needle thread 23 being pulled upwards by the thread take-up 25. The formation of such seams is generally known.

Thread cutting is performed as follows.

Immediately after the hook 30 is inserted into the loop as shown in FIG. 5, the portion 82 of the needle thread 23 forms a triangle;
At this time, the needle thread portion 82 is threaded from the needle passage hole 28 to the hook tip 3.
The part of the needle thread 23 that forms the side extending to the upper surface 78 of the hook 30 and is indicated by a broken line is the vertical side that extends from the upper surface 78 of the hook 30 to the lower surface 80 and the lower surface 80 of the hook 30.
A side extending obliquely upward from the needle passage hole 28 to the needle passage hole 28 is formed. The bobbin thread 21 extends from the outlet opening 77 of the bobbin case 19 to the needle passage hole 28 slightly above the triangle formed by these sides.

During the swinging movement of the blade arm 35 in the swinging direction 59, the tip 63 of the lower leg side 62 of the thread catcher 57 is in the horizontal plane between the upper surface 78 and the lower surface 80 of the hook 30, and in no case It is also located above the round recess 81. The V-shaped notch 60 extends upwards from the tip 63 in any case above the outlet opening 77, so that during the oscillating movement of the thread catcher 57 this notch 60
The lower thread 21 is rotated in the opposite direction to the rotation direction 29 of the hook 30.
and the needle thread portion 82, and thus the needle thread portion closer to the seam or workpiece, the portion of the needle thread 23 that wraps around the underside 80 of the hook 30 and returns to the needle 7 is caught by the thread catcher 57. Not caught by.

In FIG. 4a the thread cutting device 36 is shown in its inactive position and is in this position during sewing. In the position shown in FIG. 4a, the needle thread loop is gripped by the hook 30 and stretched into the triangle described above, the substantially vertical base of which is determined by the recess 79 and the rounded recess 81. At the earliest, the round recess 81 and the recess 79 correspond to the needle passage hole 28 and the rotation axis 18 of the hook 14.
The thread cutting device 36 can be operated when the thread cutting device 36 is at the line connecting the threads (for example, the initial position A). However, this operation is preferably carried out only when the hook 30 has moved further in the direction of rotation 29 by an angle b to position B, as shown in FIG. 4b. This angle b is between 20° and 60°. This angular position B of the hook tip 30
As shown in FIG. 4c, the electromagnet 40 is excited by a pulse, so that the blade arm 35 swings together with the thread catcher 57 in a direction opposite to the rotational direction 29 while grasping the upper thread 82 and the lower thread 21. The swinging direction 59 is started. The moment the upper thread 82 and lower thread 21 are caught is shown in FIG. 4c. The rocking movement is carried out up to the position shown in FIG. 4d. At this position of the thread catcher 57, the V-shaped cut 60 has already been closed by the mating blade 70, so the upper thread portion 82 and the lower thread 2
1 is guided in the rounded part 64 of the thread catcher 57. Furthermore, the rounded tip 76 of the thread gripping piece 75 rests on the inner surface 67 of the thread catcher 57 via the wedge-shaped portion 69 . In this position the thread catcher 57 stops, in other words the two thread ends leading towards the workpiece and thus the seam are guided precisely. Pot 14 is approx.
Rotate further to angle c of 160° to 170° and thread upper thread 2.
3 is pulled over the bobbin case 19 under the action of the recess 79 and, when position C is reached, is passed through the recess 31 and under the stop finger 32.

During the course of the subsequent movement of the hook 14, the bobbin 20
The lower thread portion 23a guided above the blade arm 35
After swinging, the thread hits the thread tension piece on the upper surface 88 of the bobbin 20. Since this thread tension piece has a constriction 87, this lower thread portion 23a is reliably held in the center of the thread tension piece 86. This capture of the needle thread section 23a by the thread tensioning piece 86 takes place approximately between the rotational position of FIG. 4d and the rotational position of FIG. 4e.

When the hook 14 further rotates, the upper thread loop is further moved by the hook body 17 to the bobbin case 1 as usual.
Guided around 9. In this case an additional needle thread 23
is pulled out from the spool 24. This is because the needle thread 23 is pulled around the thread tension piece 86 and the 4th d
This is because, as can be seen in the figures and in FIG. 4e, the thread tension piece is close to the axis of rotation 18 of the shuttle 14 during this stage of operation. As a result, another needle thread portion 23b is formed between the thread tension piece 86 and the hook point 30. As can be seen from FIG. 4c, in the position of the hook body 17 shown therein, the upper thread section 23b and the upper thread section 82 have not yet been completely guided around the bobbin case 19, so that they continue to the upper thread section 23b. A portion of the needle thread section 82 is still above the bobbin case 19.

When the base of the hook 30 subsequently reaches a point D, which is separated from point A by an angle of d=270°, the cutting arm 35 together with the thread catcher 57 is swung further. The beginning of this rocking motion is shown in FIG. 4e and the end is shown in FIG. 4f, the base of the hook 30 having rotated through an angle e of about 340 DEG, so that point E is reached.

Furthermore, as can be seen from Figure 4f, the needle passage hole 28
Since the cutting edge 58 of the thread catcher 57 is relatively close to each other, both upper thread portions 23a and 23b are
Immediately before the actual thread cutting process of the thread cutting device 36, an acute angle is formed with the thread pulling piece 86 as the apex. At this moment, the balance 25 has not reached its highest position yet.
In addition to the lower thread 21, the needle thread section 82 to be cut and the following lower thread sections 23a and 23b are under tension due to the action of the thread tensioning piece 86. Cutting edges 74 and 58
As a result of the joint action, the lower thread 21 and the upper thread portion 82 and thus the processed half of the upper thread 23 are cut. Usually this is done at a high position of the needle where the balance 25 is not yet in its uppermost position. Next, the blade arm 35 together with the thread catcher 57
is swung back to the initial position shown in Figure 4a.

During this return swing, the free end of the upper thread portion 23b is
The thread gripping piece 75 is pulled out from the gripping position between the tip 76 and the mating blade 70. On the other hand, the bobbin case side end of the bobbin thread 21 is connected to the tip 76 of the thread gripping piece 75.
and the mating blade 70 remain tightened.
The bobbin thread 21 indicated by reference numerals 21a and 82a in Fig. 4f
The thread end on one side of the needle thread portion 82 is removed together with the thread end when the workpiece is taken out of the sewing area. At the same time, the upper thread portions 23a, 23b, which were freed from the work piece during thread cutting, are pulled out through the needle passage hole 28. Thereafter, from the hole 90 of the needle 7, at this position of the needle 7, i.e. at the high position of the needle, the needle thread portion 2 is longer than in the case without thread tension by the length of the needle thread portions 23a and 23b.
3c hangs down. The needle thread section is also fixed so that the needle thread 23 is prevented from slipping out of the needle 7 even at the beginning of the next sewing process, when the needle moves downwards but initially the thread take-up 25 is still moving upwards as usual. A length of 23c has been chosen. Since the mating blade 70 is in front of the outlet opening 77 in the direction of rotation 29, the bobbin thread is also in the ideal position for the new sewing.

The above-mentioned movement of the thread cutting device 36 takes place as follows.

The push rod 41 is pushed out by the excitation of the electromagnet 40, and the rounded end 4 of the shorter lever arm 44 is pushed out.
5 causes the rectangular lever 42 to swing from the inoperative position shown in FIG. This is done when the base of the hook 30 of the hook 14 is in position B. The rounded end 47 of the longer lever arm 46 then comes into contact with the guide surface 48 of the cam plate 49, which now moves the blade arm 35 and thus the thread catcher 57, causing the longer lever arm to move. Persistent contact between the rounded end 47 of the arm 46 and the guide surface 48 is ensured without subsequent energization of the electromagnet 40.

For purposes of illustration, as is usual in transmission theory, the operating position 83 of the longer lever arm 46 relative to the cam plate 49 will be depicted as if the cam plate 49 were stationary and the longer lever arm 46 rotated. It is shown. Therefore, the position of the base of the hook 30 is from B to E.
The relative positions of the longer lever arm 46 and the cam plate 49 are also indicated by B' to E'. The short-term excitation of electromagnet 40 takes place approximately at point B, which corresponds to B' in FIG. In this case, the tip 47 of the longer lever arm 46 is only brought into the active area of the guide surface 48 of the cam plate 49 and does not come into contact with the guide surface 48 at this point. Hook 14 and therefore cam plate 4
Further rotation of 9 causes its guide surface 48 to engage the tip 47 of the lever arm 46 approximately at C'. Therefore, forced guidance of the blade arm 35 together with the thread catcher 57 takes place from here. The blade arm 35 may be held up to point C' by excitation of the electromagnet 40. In this position, where the V-shaped cut 60 is closed by the mating blade 70, the thread catcher 57 is held until just before the position E or E'. As can be easily seen, the thread cutting process between hook tip base positions D and E in FIG. 4, which correspond to positions D' and E' in FIG.
4, and this cam 84 is connected to the longer lever arm 46.
This is therefore done by deflecting the thread catcher 57. After getting over the cam 84, the square lever 42 receives the return force of the torsion spring 54 and moves to its fourth position.
Return to the inoperative position shown in Figure a. This return movement is damped by the buffer piece 52.

In the embodiment shown and described above, two
A lockstitch hook 14 is used which rotates at double the number of rotations and has a bobbin case held by a stop finger 32 diametrically opposite the needle passage hole 28. However, it is also possible to use a hook in which the bobbin case is prevented from rotating in the area of the needle passage hole, and the thread on one side of the process, as well as the upper and lower threads, can be captured immediately after the thread loop is received by the hook. It is possible.

Further, the above-mentioned thread cutting device is provided with a thread tension loosening device, and the thread tension loosening device is operated at an appropriate moment by the electric motor driving the sewing machine via the belt 10 or its control part to tension the thread of the thread catcher 57. It is also possible to apply a reaction force to the yarn at the moment of yarn cutting.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the sewing machine, Fig. 2 is a front view with a part of the lockstitch hook cut away and seen in the direction of the arrow in Fig. 1, and Fig. 3 is a thread drawn along the cutting line - in Fig. 2. 4a to 4f are plan views of the driving range of the cutting device; FIGS. 4a to 4f are plan views of the lockstitch hook and the thread cutting device in different operating positions as seen in the direction of the arrow in FIG. 2; FIG. 6 is an elevational view of the thread catcher of the thread cutting device seen in the direction of the arrow in FIG. 4a; FIG.
FIG. 3 is a cross-sectional view of the thread catcher taken along the cutting line in the figure. 7... Needle, 14... Hook, 18... Rotation axis, 1
9...Bobbin case, 21...Lower thread, 23...Upper thread, 28...Needle passing hole, 29...Rotation direction, 30
... Hook tip, 37 ... Blade holder, 57 ... Thread catcher, 58 ... Cutting blade tip, 60 ... Cut, 61,
62... Leg side, 63... Tip, 70... Opponent blade,
86... Thread tension piece, 88... Upper surface.

Claims (1)

[Scope of Claims] 1. A hook that grips the needle thread loop, a rotational axis parallel to the needle, and a bobbin case that is supported within the shuttle so as not to rotate relative to the sewing machine and supplies the bobbin thread to the needle passage hole. A thread catcher is provided on a blade holder that is movably swingable between the hook and the needle passage hole, and the cutting edge of the thread catcher is approximately The thread catcher works together with the fixed mating blade, and has a notch that grabs one side of the bobbin thread and the upper thread to be processed, and a leg side that has a pointed end on the advancing side in the direction of movement, and this leg side is on the needle side of the upper thread. It is movable between the part and the upper thread processing part and the bobbin thread, and the direction of movement of the thread catcher is directed from the non-operating position towards the mating blade, opposite to the direction of rotation of the hook. In the blade holder 35, the blade holder 35 is attached to the blade holder 35.
A thread tensioning piece 86 is provided which extends to an upper surface 88 of the bobbin case 19 which is closer to the thread catcher 57 and is outside the bobbin case 19 in the non-operating position of the thread catcher 57 and which swings towards the mating blade 70. Yarn catcher 57
The part of the upper thread 23 that is above the bobbin case 19 in the position , and thus on the upper surface 88 of the bobbin case 9, is guided around the thread tension piece 86 during the rotation 29 of the shuttle 14, so that the upper thread is at the same time A thread cutting device for a lockstitch sewing machine, characterized in that a thread 23 is pulled out by a needle 7. 2 Notch 8 for the thread tensioning piece 86 where the upper surface 88 of the bobbin case 19 reaches approximately this upper surface 88
9. The thread cutting device according to claim 1, characterized in that the thread cutting device comprises: 9. 3. The thread cutting device according to claim 1, wherein the thread tensioning piece 86 is swingable to a position close to the rotational axis 18 of the hook 14. 4. The thread tension piece 86 is characterized in that it has a constriction 87 which points towards the blade holder 35 from the free end of the thread tension piece 86 which is closer to the upper surface 88 of the bobbin case 19. Yarn cutting device according to item 1. 5 After the thread catcher 57 grabs the thread, the mating blade 70
The thread according to claim 1, characterized in that it can be stopped in an intermediate position in which the cut 60 is closed by a thread tensioner, and the thread tensioning piece 86 is located on the bobbin case 19 for thread tensioning in this intermediate position. Cutting device.