JPH01207097A - Cycle sewing machine thread trimming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention switches a clutch mechanism disposed between a sewing machine main shaft and a drive source to at least two positions in order to switch between a power cutoff state and a drive connection state. a switching member to be moved; a speed control cam that is rotated at a reduced speed in conjunction with the main shaft of the sewing machine; and a speed control cam that is capable of switching the arrangement position of the switching member in accordance with the rotation; A feed control cam that controls the feed of the work cloth as it rotates, a movable blade that swings back and forth across the vertical movement path of the needle, and a fixed blade placed on one side of the vertical movement path of the needle work together. a thread trimming mechanism that cuts sewing thread; a thread trimming cam that is rotated in conjunction with the sewing machine main shaft to reciprocate the movable blade; and a cam follower that is detachably disposed on the thread trimming cam. , a biasing means for biasing the cam follower in the direction of engagement with the thread trimming cam, and a connecting member for operatively connecting the cam follower and the movable blade of the thread trimming mechanism.
;Relating to a thread cutting device for an improved cycle sewing machine.

(Prior art) Conventionally, as this type of device, for example, the Japanese Patent Publication No. 53'-3
As described in Publication No. 0054, a stop body and a thread trimming cam are provided on the main shaft of the sewing machine, and a stop pawl that engages with the stop body to stop the rotation of the main shaft of the sewing machine has a thread trimming cam follower. A pressing body is provided for engaging and disengaging the child from the thread trimming cam, and - the rotational speed of the sewing machine main shaft is switched and controlled according to the cam shape of the speed control cam rotated in each sewing cycle, so that the stop claw is moved to the outer periphery of the stop body. When engaged, power transmission between the drive source and the main shaft of the sewing machine is interrupted, and the cam follower is engaged with the thread trimming cam via the pressing body by the biasing force of the spring. Subsequently, when the main shaft of the sewing machine is rotated by inertia, the movable blade of the thread trimming mechanism is oscillated back and forth according to the cam shape of the thread trimming cam, and during this forward movement, a thread sorting operation is performed based on the biasing force of the spring. At the same time, a light cutting operation is performed by the movable blade and the fixed blade during the backward movement, and thereafter, the stop groove of the stop body engages with the stop pawl, so that the rotation of the main shaft of the sewing machine is stopped.

(Problem to be Solved by the Invention) However, in the conventional device described above, after the speed control cam performs stop control, the rotational speed due to inertia of the main shaft of the sewing machine is lower than the preset speed (due to various loads, etc.). When this occurs, the rotation of the main shaft of the sewing machine may be stopped due to frictional contact with the outer periphery of the stop member before the stop pawl engages with the stop groove of the stop member.To prevent this, the speed relative to the main shaft of the sewing machine may be stopped. By adjusting the phase relationship of the control cams, the stop control timing is delayed (as a result, the timing at which the cam follower engages with the thread trimming cam on the main shaft of the sewing machine is also delayed. The movable blade is suddenly engaged with the part by the biasing force of the spring, and the movable blade is rapidly moved forward, and the sewing thread may be accidentally cut when the movable blade performs a thread handling operation.

(Object of the Invention) The present invention has been made to solve the above problems, and its purpose is to accurately control the timing at which the cam follower engages the thread trimming cam in relation to the feed operation of the work cloth. It is an object of the present invention to provide a thread cutting device for a cycle sewing machine, which can be set to a thread cutting cam and can therefore reliably perform a thread sorting operation and an optical cutting operation based on the cam shape of the thread cutting cam.

(Means for solving problems) In order to achieve the above objectives, this invention:

A thread trimming activation section provided on the feed control cam is disposed so as to be removable from the thread trimming activation section, and when disengaged from the thread trimming activation section, it is placed in an operating position and a cam follower is activated by a biasing means. A blocking member is provided that prevents engagement with the thread trimming cam and is disposed in an inactive position when engaged with the thread trimming activation section to permit engagement between the cam follower and the thread trimming cam. .

(Function) Therefore, when the blocking member is disengaged from the thread trimming activation part when the feed control cam rotates, the blocking member is placed in the operating position, and the blocking member causes the cam follower and the thread trimming cam to engagement is prevented. Further, when the thread trimming activation section is engaged with the blocking member as the feed control cam rotates, the blocking member is placed in the inactive position, and the blocking member prevents the engagement between the cam follower and the thread trimming cam. is allowed.

Then, the thread trimming mechanism is operated by the action of the thread trimming cam and the urging means.

(Example) Hereinafter, an example in which the present invention is embodied in a bar-tacking cycle sewing machine will be described in detail with reference to the drawings.

As shown in FIGS. 2 and 3, a clutch mechanism 3 is attached to an end of a sewing machine main shaft 2 disposed within a sewing machine frame 1. As shown in FIGS. That is, this clutch mechanism 3 includes a pair of clutch plates 4 fixed on the main shaft 2 of the sewing machine at a predetermined distance.
, 5, and the sliding tube 6 which is slidably mounted along the sewing machine main shaft 2 between the temporary latch 4.5 and is biased to move to the right in FIG. A low-speed pulley 7 and a high-speed pulley 8 are rotatably mounted on the clutch plate 4. A fixed position stop cam 9 is formed on one clutch plate 4, and a sphere 10 is supported on the sliding tube 6.

Further, a switching member 11 is rotatably supported on the sewing machine frame 1 by a support shaft 12, and the switching member 11 is normally connected to a stop control section of a cam surface 13 formed on the upper end thereof (see FIG. 3(b)). Based on the engagement between 13a and the sphere IO,
It is placed at the power cutoff position A shown in FIG. 3(a).

Then, by rotating the switching member 11 from the power cutoff position A in the counterclockwise direction in the figure, the switching member ll
The upper locking protrusion 14 disengages from the recess 9a of the fixed position stop cam 9, allowing the sewing machine main shaft 2 to rotate. Further, based on the rotation of the switching member 11, the low speed control portion 13b of the cam surface 13 is engaged with the sphere 10, and when the switching member 11 is placed at the low speed drive position B, the low speed pulley 7 is moved to one side. The belt 7a of the low speed pulley 7 is connected to the clutch plate 4.
The main shaft 2 of the sewing machine is connected to a low-speed drive source via. or,
When the high-speed control portion 13C of the cam surface 13 is engaged with the sphere IO and the switching member 11 is placed in the high-speed drive position C, the high-speed pulley 8 is joined to the other clutch plate 5, and the high-speed pulley 8 is connected to the other clutch plate 5. The sewing machine main shaft 2 is connected to a high-speed drive source via a bell) 8a.

As shown in FIGS. 2 and 3, an operating lever 15 is rotatably supported on the sewing machine frame 1 by a support shaft 16, and is normally placed at a rest position P shown in FIG. 4. The operating lever 15 has an arc-shaped elongated hole 17 centered around the support shaft 16 . Further, an intermediate operating lever 18 is rotatably supported on the support shaft 16, and a connecting pin 19 protruding from one end thereof is fitted into the elongated hole 17.
The intermediate operating lever 18 is connected to the switching member 11 via the connecting pin 19 and the connecting rod 20.

As the operating lever 15 rotates, the switching member 11 is rotated through the engagement between the elongated hole 17 and the connecting pin 19 and the connecting rod 20.

On the other hand, a speed control cam 21 and a feed control cam 22 are disposed within the sewing machine frame 1 so as to be integrally rotatable around a vertical axis, and rotate once per sewing cycle in conjunction with the rotation of the sewing machine main shaft 2. As the speed control cam 21 rotates, a transmission member (not shown) is actuated based on the shape of the cam, and the position of the switching member 11 is switched via the transmission member. Also, the feed system '+111 cam 2
2, a feed mechanism (not shown) is formed based on the shape of the cam groove 22a (partially shown only on the top side) on both the upper and lower surfaces.
is operated, and the feed mechanism applies feed to the work cloth.

A fixed blade 24 is disposed in an example of the needle passage hole 23 located on the vertical movement path of the needle in the head portion a of the sewing machine frame 1, and a movable blade that constitutes a thread cutting mechanism together with the fixed blade 24. 25 is rotatably supported by a support shaft 26, and the movable blade 25 crosses the vertical movement path of the needle from the standby position shown in FIGS. 1 and 6(a) to the tip shown in FIG. 6(c). By moving forward to the side position, a well-known forward side turning operation is performed, and by moving back from the forward side position to the standby position, a thread cutting operation is performed.

As shown in FIG. 2, FIG. 4, and FIG. 7, a first system cutting cam 30 is attached to the main shaft 2 of the sewing machine, and has an equal radius portion 30a on its outer periphery, and a center of the same radius portion 30a than the equal radius portion 30a. A yarn handling portion 30b biased toward the side is formed. A first cam follower lever 31 is rotatably supported at its center on one side of the first system cutting cam 30, and a follower 31a that engages and disengages from the first system cutting cam 30 projects from one end thereof. has been done.

On the other hand, an intermediate lever 32 is located near the feed control cam 22.
is rotatably supported at its center by a support shaft 32a, connected to the cam follower 31 by a connecting rod 33, and connected to the movable blade 25 via a rod 343, a rotating lever 35, and a link 36. has been done. Further, the intermediate lever 32 is urged to rotate clockwise in FIG. 2 by the spring 32b, and due to the urging force, the first cam follower lever 3
1 is biased in the direction of engagement with the -th system cutting cam 30, and the movable blade 25 is biased to rotate clockwise in FIG.

As shown in FIG. 1, FIG. 2, FIG. 4, and FIG. 6, on the uniform radius outer peripheral surface 37 of the feed control cam 22,
A thread trimming activation piece 38 is attached to a position opposite to the cam groove portion that generates the feed between the last stitch of the +'U cycle and the previous stitch. A protrusion 39 is formed from the outer circumferential surface 37 of the feed control cam 22 toward the rear side in the rotation direction of the feed control cam 22 and includes a guide surface 39a that slopes outward.

Further, between the feed control cam 22 and the intermediate lever 32, a tri-arm-shaped blocking member 40 is rotatably supported at its center by a support shaft 40a, and is rotated counterclockwise in FIG. 1 by a spring 41G. is biased to rotate.

This blocking member 40 has a blocking claw 43 that can be engaged with and detached from an engaging protrusion 42 provided on the intermediate lever 32, and a blocking claw 43 that can be engaged with and detached from the protrusion 39 of the thread trimming activation piece 38 and the outer circumferential surface 37 of the feed control cam 22. A following piece 44 is integrally formed.

Then, the follower piece 44 of the blocking member 40 moves toward the feed control cam 22.
When the blocking member 40 is engaged with the outer peripheral surface 37 of the first
The engaging protrusion 4 of the intermediate lever 32 is placed in the operating position shown in FIG.
2 is engaged, and the first cam follower lever 31 is moved by the spring 32b.
It is placed in the standby position shown in FIG. 7(a) against the urging force of , and is separated from the first system cutting cam 30. Also, follower piece 4
4 is engaged with the protrusion 39 of the thread trimming activation piece 38,
The blocking member 40 is placed in the inactive position shown in FIG. 6(b), the blocking claw 43 of the blocking member 40 is disengaged from the engagement protrusion 42 of the intermediate lever 32, and the first cam follower lever 31 is moved to the spring 32b. 7(b), and is engaged with the first series cutting cam 30.

As shown in FIGS. 2, 4, and 5, a power pulley 46 and a second thread trimming cam 47, which are connected to a low-speed drive source, are attached to a support shaft 45 provided on the sewing machine frame 1 at a predetermined interval. It is rotatably supported. power pulley 46
On the support shaft 45 between the second thread trimming cam 47 and the inner clutch surface 48 of the power pulley 46, an actuating body 51 is rotatably and slidably provided with a latch plate 49 and a locking piece 50. It is mounted so that it can be mounted, and is biased by springs 52 to move in the direction of cracking and pre-joining. Further, a drive lever 53 having a pair of locking protrusions 53a and 53b at both ends is swingably supported at the center of the sewing machine frame 1 so as to be located on the outer peripheral edge of the operating body 51. Drive lever 53
While the positions of the locking protrusions 53a and 53b are switched between the position shown in FIG. 7(a) and the position shown in FIG. 7(d) with the rocking of the A clutch plate 49 is connected to a clutch surface 48 of a power pulley 46, and each time the clutch plate 49 is switched, the second thread cutting cam 47 is drivingly connected to the power pulley 46 and rotates approximately half a rotation.

The lower end of the drive lever 53 is provided with the intermediate actuation lever 18.
An engaging body 54 that engages with the tip of the operating lever 15 is provided in a protruding manner.
8 is urged to rotate in the direction of engagement. Further, on the outer periphery of the second thread cutting cam 47, there is an equal radius portion 47a, and a thread handling recess 4 that is biased toward the rotation center side with respect to the equal radius portion 47a.
7b, the equal radius portion, and a thread cutting protrusion 47G that is biased toward the outer circumferential side than 17a are formed in series.

An example of the second thread trimming cam 47 is a second cam follower lever 56.
is rotatably supported at its center, and a follower 56a provided at its lower end is engaged with and disengaged from the second thread trimming cam 47, and a long hole 56b formed at its upper end and a pin 57 on the connecting rod 33 are connected to each other. The second cam follower lever 56 is connected to the connecting rod 33 by engagement with the second cam follower lever 56 . Then, as shown in FIG. 7(c), the follower 31a of the first cam follower lever 31 moves to the -
When engaged with the thread handling portion 30b of the system cutting cam 30, the follower 56a of the second cam follower lever 56 is activated via the connecting rod 33.
enters the thread handling recess 47b of the second thread cutting cam 47.

Now, the operation of the cycle sewing machine configured as described above will be explained. With the low speed pulley 7 and the power pulley 46 being rotated at low speed and the high speed pulley 8 being rotated at high speed, the operating lever 15 shown in FIGS. 3(a) and 4 is rotated counterclockwise. It is switched to the first operation position Q. and,
Through engagement between its tip and the engaging body 54 of the drive lever 53, the drive lever 53 is swung clockwise in FIG. 4 against the biasing force of the spring 55, and the upper locking protrusion 53a is activated. body 5
1, and the lower locking protrusion 53b enters into the rotation locus of the locking piece 50.

Then, due to the biasing force of the spring 52 shown in FIG. 5, the clutch plate 49 is joined to the inner clutch surface 48 of the power pulley 46, and the rotation of the power pulley 46 is transmitted to the operating body 51 and the second thread trimming cam 47. Both 51 and 47 are rotated approximately half a turn together with the power pulley 46 until the locking piece 50 engages with the lower locking protrusion 53b. Thereby, as shown in FIG. 7(a), the thread handling recess 47b of the second thread cutting cam 47 is disposed relative to the follower 56a of the second cam follower lever 56.

Next, when the operating lever 15 is switched to the second operating position R shown in FIG.
9, and through this engagement and the connecting rod 20, the switching member 11 is switched from the power cutoff position A to the low speed drive position B shown in FIG. 3(a). Therefore, the locking projection 14 of the switching member 11 is disengaged from the recess 9a of the fixed position stop cam 9, and the low speed pulley 7 is connected to one clutch plate 4, and the sewing machine main shaft 2 is connected to the low speed drive source, and the sewing machine main shaft 2 is connected to the low speed drive source. The main shaft 2 is rotated at low speed.

Then, the speed control cam 21 and the feed control cam 22 are rotated at a reduced speed in conjunction with the sewing machine main shaft 2, and based on the cam shape of the speed control cam 21, the arrangement position of the switching member 11 is switched, and the rotational speed of the sewing machine main shaft 2 is changed. is switched from low speed to high speed and from high speed to low speed. Also, the feed control cam 22
The feeding device is operated based on the shape of the cam groove 22a. During sewing of a predetermined number of stitches, the following piece 4 of the blocking member 40 is attached to the outer peripheral surface 37 of the feed control cam 22.
4 are engaged, and the blocking member 40 is rotated as shown in FIGS. 1 and 6(a).
Based on the engagement between the blocking pawl 43 and the engaging protrusion 42 of the intermediate lever 32-, the position shown in FIG.
), the follower 31a of the first cam follower 31 is held at a position where it separates from the first system cutting cam 30 via the intermediate lever 32 and the connecting rod 33.

Based on the subsequent rotation of the feed control cam 22, when the feed operation between the last stitch of the sewing cycle and the previous stitch is performed with the main shaft 2 of the sewing machine being driven at a low speed, the thread trimming activation piece 38 is activated. When the protrusion 39 engages with the follower piece 44 of the blocking member 40, the blocking member 40 moves along the guide surface 39a of the protrusion 39, against the spring 41, in the clockwise direction in FIG. 1 [FIG. 6(a)
6 (b) and 7 (
As shown in b), the blocking pawl 43 separates from the intermediate lever 32. Then, due to the biasing force of the spring 32b shown in FIG. 2, the first cam follower lever 31 is moved from the I release position shown in FIG.
) is rotated to the engagement position shown in ).

At this time, the switching member 11 is rotated from the low speed drive position B to the power cutoff position A shown in FIG. 3(a) by the action of the speed control cam 21, and the sewing machine main shaft 2 is rotated by inertia. As the switching member 11 rotates, the locking protrusion 14
engages with the uniform radius outer peripheral surface of the fixed position stop cam 9.

Then, together with the main shaft 2 of the sewing machine, the 7th system cutting cam 30
When the thread handling portion 30b of the first system cutting cam 30 faces the follower 31a of the first cam follower lever 31, the spring 32b is rotated from the position shown in Figure (b) to the position shown in Figure (c). The force causes the first cam follower lever 31 to rotate counterclockwise in FIG. 7(b), and as a result, the follower 56a of the second cam follower lever 56 moves to the second position as shown in FIG. 7(C). Thread handling recess 47b of thread cutting cam 47
go inside. At the same time, the connecting lever 33° intermediate lever 3
2 and the rod 34, etc., the movable blade 25 is
), and the movable blade 25 performs the thread handling operation. At this time, the blocking member 40
As shown in Figure (C), the thread trimming activation piece 38 is held in the inactive position by engagement with the protrusion 39.

Thereafter, as the first system cutting cam 30 rotates, its equal radius portion 30a is again engaged with the follower 31a, and thereby the intermediate lever 32 and the movable blade 25 are slightly rotated back. With this return rotation of the intermediate lever 32, as shown in FIG.
), the return rotation of the blocking member 400 toward the operating position is regulated, and the protrusion 39 of the thread trimming activation piece 38 moves toward the blocking member 4.
Even after separating from the following piece 44 of 0, the blocking member 4
0 is held in the inactive position.

Further, when the follower 31a is re-engaged with the equal radius section 30a of the first thread trimming cam 30, the locking protrusion 14 of the recess 9alC of the fixed position stop cam 9 is engaged at the same time. At this time,
The switching member 11 is rotated slightly clockwise in FIG. 3(a), and the connecting rod 20 is raised. Therefore, the intermediate operating lever 18 is rotated clockwise, the drive lever 53 is rotated counterclockwise in FIGS. 4 and 7(C), and the lower locking protrusion from the locking piece 50 is 53b leaves.

Thereby, the clutch plate 49 of the actuating body 51 is joined to the inner clutch surface 48 of the power pulley 46.

Therefore, the rotation of the power pulley 46 is transmitted to the operating body 51 and the second thread trimming cam 47, and these 51 degrees 47 are rotated approximately half a turn in the counterclockwise direction in FIG. 7(d). Based on this rotation, the second cam follower lever 56 moves clockwise in FIG. Rotated, connecting rod 33. The movable blade 25 is rotated back to the position shown in FIG. 6(e) via the intermediate lever 32, rod 34, etc.

The sewing thread is then cut by the movable blade 25 and the fixed blade 24. Further, due to the upward movement of the linking rod 33 following the rotation of the second cam follower lever 56 and the return rotation of the intermediate lever 32 in the counterclockwise direction in FIG. 2, as shown in FIG. 7(e), The follower 31a of the first cam follower lever 31 is in the -th position.
At the same time as it separates from the system cutting cam 30, the engagement protrusion 42 separates from the blocking claw 43 of the blocking member 40 as shown in FIG. is engaged with the outer circumferential surface 37 of the feed control cam 22 and held at the operating position.

Thereafter, as the actuating body 51 and the second thread trimming cam 47 rotate, the thread trimming protrusion 47c of the second thread trimming cam 47 is completely separated from the follower 56a of the second cam follower lever 56. As shown in FIG. 7(f), the intermediate lever 32 is slightly rotated clockwise in FIG. 2 by the biasing force of the spring 32b, and as shown in FIG. The end face is engaged with the blocking claw 43 of the blocking member 40,
The follower 31a of the first cam follower lever 31 is held at a position spaced apart from the first system cutting cam 30.

Further, as shown in FIG. 7(f), the locking piece 5 of the actuating body 51
0 engages with the upper locking protrusion 53a, its rotation is blocked, power transmission between the power pulley 46 and the operating body 51 is cut off, and the rotation of the second thread trimming cam 47 is also stopped. .

As described above, in this embodiment, the thread cutting operation is not started in accordance with the stop control timing of the sewing machine main shaft 2 by the speed control cam 21, but by the thread cutting activation piece 38 attached to the feed control cam 22. Since the start timing of the thread handling operation is set, it is possible to eliminate fluctuations in the timing caused by fluctuations in the inertial force of the main shaft 2 of the sewing machine. The thread handling operation can be performed reliably, and the risk of the sewing thread being accidentally cut during the thread handling operation can be avoided.

- When replacing the feed control cam 22 with another one in order to change the number of stitches in the sewing cycle, the thread trimming activation piece 3
8 can be accurately positioned and fixed to the feed control cam 22 in advance, and after assembling both 22 and 38 to the sewing machine, the installation of the thread trimming activation piece 38 does not require the troublesome work of adjusting the position. There's no need. Furthermore, the optical cutting operation after the thread handling operation is performed by a cutting cam 30 on the main shaft 2 of the sewing machine.
Since this is carried out by the second thread cutting cam 47 on a different shaft from the sewing machine main shaft 2, malfunctions caused by fluctuations in the inertial force of the main shaft 2 of the sewing machine can be avoided.

Note that this invention is not limited to the above embodiments,
It is also possible to perform the thread sorting operation and the thread cutting operation only by the first system cutting cam 30.

(Effects of the Invention) As described in detail above, the present invention allows the timing at which the cam follower engages with the thread trimming cam to be accurately set in relation to the feed operation of the workpiece cloth, and thus the thread trimming cam It exhibits an excellent effect in that the thread handling operation and the light cutting operation can be performed satisfactorily based on the cam shape.

[Brief explanation of the drawing]

16 is a plan view showing the main parts of a cycle sewing machine embodying the present invention, FIG. 2 is a partial side view, FIG. 3(a) is a partial rear view, and FIG. 3(b) is a cam surface of the switching member. FIG. 4 is a partial rear view showing the thread trimming cam mechanism; FIG. 5 is a partially enlarged sectional view showing the installation state of the second thread trimming cam;
FIGS. 6(a) to (f) are partially reduced bottom views showing the operating state of the thread trimming mechanism, and FIGS. 7(a) to (f) are partially reduced rear views showing the operating states of each thread trimming cam. . 2... Sewing machine main shaft, 3... Clutch mechanism, 11...
- Switching member, 21... Speed control cam, 22... Feed control cam, 24... Fixed blade, 25... Movable blade, 3
0... Third system cutting cam, 31... First cam follower lever, 38... Thread cutting activation piece, 40... Blocking member, 4
7...Second thread trimming cam, 56...Second cam follower lever.

Claims (1)

[Claims] 1. A switch that is switched and moved to at least two positions in order to switch the clutch mechanism (3) disposed between the sewing machine main shaft (2) and the drive source to a power cutoff state and a drive connection state. The member (11) is rotated at a reduced speed in conjunction with the sewing machine main shaft (2), and as the member (11) rotates, the switching member (11)
) a speed control cam (21) whose arrangement position can be changed;
A feed control cam (22) is rotated at a reduced speed in conjunction with the main shaft (2) of the sewing machine, and controls the feed of the workpiece cloth as it rotates.
), and a movable blade (25) that swings back and forth across the vertical movement path of the needle.
) and a fixed blade (24) placed on one side of the vertical movement path of the needle.
a thread trimming mechanism that cuts the sewing thread in cooperation with the thread trimming mechanism; a thread trimming cam (30) that rotates in conjunction with the sewing machine main shaft (2) to reciprocate the movable blade (25); A cam follower (31) detachably disposed on the cam (30), and a biasing means (32b) that biases the cam follower (31) in a direction to engage the thread trimming cam (30). ), the cam follower (31) and the movable blade (2) of the thread cutting mechanism.
5) connecting members (32, 33, 34) that operatively connect the
, 35, 36), and a thread trimming activation section (38) provided on the feed control cam (22).
The cam follower (31) is arranged to be detachable from the thread trimming starting part (38), and when the thread cutting starting part (38) is not engaged, it is placed in the operating position and the cam follower (31) is moved by the biasing means (32b). ) and the thread trimming cam (30), and when engaged with the thread trimming activation section (38), the cam follower (31) and the thread trimming cam (30) are disposed in an inactive position. A thread cutting device for a cycle sewing machine, comprising a blocking member (40) that allows engagement with the thread cutting device.