CZ302749B6 - Tread cutting device - Google Patents

Abstract

In the present invention, there is disclosed a thread cutting device (11) in a buttonhole stitching machine using a needle thread and a bobbin thread, said thread cutter comprising freely opening and closing scissors (15) arranged for cutting off the needle thread and for holding a cut off needle thread by their closing from the opened state, and freely opening and closing scissors (52) arranged for cutting off the bobbin thread and for holding a cut off bobbin thread by their closing from the opened state. The thread cutting device (11) of the present invention further comprises solenoids (38, 72, 73) and a pulse motor (101) both arranged for driving scissors (15) for cutting off the needle thread from closed state in open state without mutual connection with the movement of a fabric feeding mechanism, and a driving mechanism comprising a solenoid (66) and a pulse motor (131), both arranged for driving scissors (52) for cutting of bobbin thread from a closed state in the open state without mutual connection with the movement of a fabric feeding mechanism.

Description

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a thread-stitching device which is arranged in a sewing machine for sewing buttonhole using a predetermined number of bound stitches.

BACKGROUND OF THE INVENTION

A buttonhole sewing machine with lock stitches comprises a needle that is pivotable in the transverse direction and movable in the vertical direction, and a rotary looper.

Furthermore, a sewing machine of this type comprises a device for cutting the needle thread, attached to the fabric and to the hook.

A device for cutting the needle thread is described, for example, in JP-B-61-5258U. A bobbin thread cutting device is described, for example, in JP-B-7 59266.

In the needle thread cutting device described in JP-B-61-5258U, the openable bobbin thread cutting shears are connected to the operating lever via various mechanisms. The operating lever is connected to the sewing machine presser lifting mechanism.

If the operating lever is pulled out after sewing is complete, when the fabric pressing device is lifted up from the fabric, the needle thread cutting shears are closed to cut the needle thread. If the operating lever is then returned to its original position after the needle thread is cut, the needle thread shears hold the needle thread in the closed state.

In the bobbin trimming apparatus disclosed in JP-B7-59266, the bobbin trimming shears are connected to the operating lever via various mechanisms. In the same manner as the needle thread cutting device, the carriage lever is pulled out such that the bobbin thread cutting shears are closed to cut the bobbin thread. Although the operating lever is returned to its initial position, the bobbin thread shears hold the bobbin thread in the closed state.

After the sewing operation has commenced in the next cycle, the needle thread shears and the bobbin thread shears must be in the open state. For this purpose, there is provided a mechanism for opening the scissors for cutting the needle thread and a mechanism for opening the scissors for cutting the bobbin thread, the mechanisms being controlled in conjunction with the fabric feeding mechanism of the sewing machine.

The needle thread shear opening mechanism and the bobbin thread shear opening mechanism have such a construction that the cam portion disposed in the presser foot of the fabric feed mechanism pushes the protruding portion disposed on the movable scissor blade, thereby causing to open the needle thread cutting shears and the bobbin thread cutting shears in the initial stage of the presser foot arm movement at the start of the sewing operation.

After the sewing operation has commenced, the fabric feeding mechanism is then moved to a constant position so that the needle-opening shearing mechanism opens the needle-cutting shears and the bobbin-shearing mechanism to open the needle-cutting shears. opens the shears for cutting the bobbin thread.

In the known yarn cutting device, however, the opening operations for opening the needle thread shears and the bobbin thread shears are interconnected with the movement of the fabric feeding mechanism.

Therefore, the fabric feeding mechanism must be moved to a constant position after the start of the sewing operation in order to open the needle-cutting scissors and the bobbin thread scissors, thereby releasing the needle thread and the bobbin thread.

In addition, there is also the problem that the needle thread and the bobbin thread are released immediately after the thread trimming is complete, and the sewing operation in the next cycle cannot be performed if the fabric feeding mechanism is moved to a different position from the predetermined end a position, e.g. a constant position, spaced a distance from a predetermined end position, whereby the sewing operation is completed.

It is therefore necessary to always move the fabric feeding mechanism to the same position in order to allow the sewing machine to start the sewing operation. In other words, the opening operation of the scissors is performed in conjunction with the movement of the fabric feeding mechanism, so that these operations are very limited to one another.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the aforementioned problems and to provide a yarn cutting device driven independently of the press bar lifting device and the fabric feeding mechanism.

In order to accomplish the above object, a buttonhole sewing machine for sewing a buttonhole sewing machine for sewing a buttonhole with a needle thread and a bobbin thread has been developed, comprising a sewing machine thread sewing machine for sewing a buttonhole sewing machine by means of a needle thread and a bobbin thread comprising needle scissors and bobbin threads comprising needle thread scissors which are openable and collapsible and are arranged to cut the needle thread and to hold the cut needle thread by its clamping condition from the open , and spool yarn scissors that are openable and collapsible and are arranged to cut the spool yarn and to hold the cut spool yarn in the middle by gripping them from the open state.

The yarn splicing apparatus further comprises a drive device configured to drive the scissors for cutting the needle thread from the clamped state to the open state without interconnecting the movement of the fabric feeding mechanism, and a drive device arranged to drive the scissors for cutting the bobbin thread from the clamped state to the open. a condition without interconnection with the movement of the fabric feeding mechanism.

The drive device is further arranged to drive the scissors for cutting the needle thread from the opened state to the clamped state.

Preferably, the drive device is one pulse motor, wherein the yarn shearing apparatus further comprises control means for operating the shears for shearing the needle yarn to bring the shears for shearing the needle yarn from the clamped state to the open state by rotating the pulse motor in one direction. for trimming the needle thread / open state into the clamped state by rotating the pulse motor in the opposite direction.

. 9 GB 302749 B6

Preferably, the yarn cutting device further comprises a drive device configured to drive the shears for cutting the spool yarn from an open condition to a closed condition.

Preferably, the drive device is a pulse motor, wherein the yarn shearing apparatus further comprises control means for operating the shears for shearing the bobbin thread to bring the shears for shearing the bobbin thread from clamped to open by rotating the pulse motor in one direction; trimming the spool yarn from the open to the closed state by rotating the pulse motor in the opposite direction.

The at least one drive speed of the pulse motor by which the spool yarn shears are brought into a closed state, and the drive speed of the pulse motor by which the spool yarn shears are brought into an open state is preferably variable.

Preferably, each drive means is selected from the group consisting of a solenoid, an air cylinder, and a pulse motor.

Accordingly, a first aspect of the present invention is directed to a yarn cutting device

2o in a buttonhole sewing machine for sewing a buttonhole with a needle thread and a bobbin thread, which includes a needle thread shear to close it to cut the needle thread and hold the needle thread in a closed condition, to cut the bobbin thread closing the bobbin thread and holding the cut bobbin thread in the closed state, and a drive mechanism for driving the open state of at least one needle thread clipper set in the closed state or the bobbin thread clipper set in the closed state.

The yarn cutting device of the present invention further comprises a drive mechanism for driving the closed state of the needle thread shears set in the open state and for driving the open state of the needle thread shears set in the closed state.

The yarn cutting device of the present invention further comprises one pulse motor forming the drive train and means for operating the needle thread cutting shears to bring the needle thread cutting shears set in the open state closed by rotating the pulse motor in one direction, and for opening the needle thread shears set in the closed state by rotating the pulse motor in the opposite direction.

The yarn cutting device of the present invention further comprises a drive mechanism for driving the closed state of the bobbin thread shears set in the open state and for driving the open state of the bobbin thread shears set in the closed state.

The yarn cutting device of the present invention further comprises one pulse motor forming the drive train and means for actuating the spool yarn shears for bringing the yarn shears in the open state closed by rotating the pulse motor in one direction, and for opening the shears for trimming

The bobbin threads set in the closed state by rotating the pulse motor in the opposite direction.

The speed of driving the at least one pulse motor at which the bobbin shears are to be closed and the speed of driving the pulse motor at which the bobbin shears are to be opened are variable.

The yarn trimming apparatus of the present invention further comprises a drive mechanism for driving the closed state of the needle thread shears set in the open state and for driving the open state of the needle thread shears set in the closed state and for driving the closed state. scissors for trimming bobbin threads set in the open state and for driving into the open condition scissors for trimming bobbin threads set in the closed state

The drive device is preferably selected from the group consisting of a solenoid, an air cylinder and a pulse motor.

Accordingly, in accordance with a first aspect of the present invention, the yarn cutting device is provided with a drive device, the drive device being driven to bring the at least one needle thread shears or spool thread shears to a closed state.

As a result, the opening operation of the scissors is in no way connected to the movement of the fabric feeding mechanism of the sewing machine.

Therefore, if the sewing machine commences a sewing operation in the next cycle, the position of the fabric feeding mechanism is not affected by the opening operation of the scissors.

Even if the fabric feeding mechanism is not moved to the sewing start position at the start of the sewing operation in the next cycle, the respective scissors will release the thread within a predetermined period.

In addition, the opening operation of the scissors is performed without interconnection with the movement of the fabric feeding mechanism. The scissors are therefore opened in the desired period of time without affecting the direction of movement of the fabric feeding mechanism.

In addition, the scissors carry out the opening operation so that they are driven by a drive device which is initially provided with a fabric cutting device. Thus, the time sequence of the scissor operations of the scissors is not in any way affected by the operations of the other sewing machine mechanisms.

A second aspect of the present invention is directed to a yarn cutting device according to the first aspect of the present invention, further comprising a drive device (solenoids or pulse motor) for driving the closed state of the needle thread shears set in the open state, and for driving into the open condition of the needle thread shears set in the closed condition.

According to a second aspect of the present invention, the yarn cutting device is provided with a drive device. This drive means drives the needle thread shears into the closed state and the open state. As a result, the operations of closing and opening the needle thread shears are not performed in conjunction with the operation of the press bar lifting device and the operation of the fabric feeding mechanism.

Therefore, if the sewing machine terminates the sewing operation and starts a new sewing operation in the next cycle after the needle thread cutting shears have performed the cutting operation, the position of the fabric feeding mechanism is not affected by the opening operation of the needle thread cutting shears.

In addition, the needle thread shears perform the closing and opening operations in such a way that they are driven by a driving device which is already incorporated in the thread cutting device.

Thus, the sequence of the opening operation of the needle thread shears is not affected by the operation of the other sewing machine mechanisms.

A third aspect of the present invention is directed to a yarn shearing apparatus according to the second aspect of the present invention, the apparatus further comprising a pulse motor that forms a drive train and means for controlling the operation of the needle thread shears (cam mechanism) for introducing to the closed state of the needle thread shears, set in the open state, by rotating the pulse motor in one direction, and to bring the needle thread shears open. in the closed state, even with the pulse motor rotating in the opposite direction.

In accordance with a third aspect of the present invention, the means for controlling the operation of the needle thread cutting scissors provides for closing the needle thread cutting scissors by rotating the pulse motor in one direction while ensuring the opening of the

2o trimming the needle thread by rotating the pulse motor in the opposite direction.

Therefore, only one pulse motor is entirely sufficient as a driving source for opening and closing the needle shears. As a result, a reduction in production costs can be achieved, as well as a reduction in the number of components in the thread cutting device.

2?

A fourth aspect of the present invention is directed to a thread cutting apparatus according to the first aspect of the present invention, the apparatus further comprising a drive device (solenoids or pulse motor) for driving into the closed state of the bobbin thread shears set in the open condition and driving into the open condition the scissors for cutting the bobbin thread, set in the closed condition.

In accordance with a fourth aspect of the present invention, the yarn cutting device is provided with a drive device. This drive means drives the shears for cutting the bobbin thread into a closed state and an open state. Therefore, the closing and opening operations of the spool yarn shear are not performed in conjunction with the operation of the press bar lifting device and the operation of the fabric feeding mechanism.

Therefore, if the sewing machine terminates the sewing operation and starts a new sewing operation in the next cycle after the bobbin thread shears have performed the trimming operation, the position of the fabric feeding mechanism 40 is not affected by the opening operation of the bobbin thread shears.

In addition, the bobbin thread shears perform closing and opening operations by being driven by a drive device which is already incorporated in the yarn cutting device.

Thus, the sequence of the opening operation of the bobbin shears is not affected by the operation of the other sewing machine mechanisms.

A fifth aspect of the present invention is directed to a thread cutting apparatus according to the fourth aspect of the present invention, the apparatus further comprising one pulse motor forming a drive train and means for controlling the operation of the spool yarn cutting shears (operating means) a condition of the spool yarn scissors set in the open state by rotating the pulse motor in one direction, and for opening the spool yarn scissors set in the closed state by rotating the pulse motor in the opposite direction,

In accordance with a fifth aspect of the present invention, the means for controlling the operation of the spool yarn scissors provides for closing the spool yarn scissors by rotating the pulse motor in one direction while providing for opening the spool yarn scissors by rotating the pulse motor in the opposite direction.

Therefore, only one pulse motor is entirely sufficient as a driving source for opening and closing the shears for cutting the bobbin thread. As a result, a reduction in production costs can be achieved, as well as a reduction in the number of parts of the thread cutting device.

A sixth aspect of the present invention is directed to a yarn shearing apparatus according to the fifth aspect of the present invention, wherein at least one pulse motor driving speed at which the bobbin thread shears are to be closed and a pulse motor driving speed at which the scissors for trimming the bobbin thread into the open state is variable.

In accordance with a sixth aspect of the present invention, the drive speed of the pulse motor is variable. Therefore, if the bobbin shears are to cut and hold the bobbin thread, the drive speed can be reduced to reliably cut the bobbin thread, while preventing the bobbin thread from slipping off the bobbin thread shears.

A seventh aspect of the present invention is directed to a thread cutting apparatus according to the first aspect of the present invention, the apparatus comprising a drive device (solenoids or pulse motors) for driving into the closed state of the needle thread cutting scissors set in the open condition and for driving to the open state of the needle clipping shears set in the closed state, and to drive the closed state of the bobbin shears set in the open state, and to drive the open state of the bobbin shears set in the closed state.

In accordance with a seventh aspect of the present invention, the yarn cutting device is provided with a drive device. This drive means drives the needle thread shears and the bobbin thread shears into the closed state and the open state.

Therefore, the operations for closing and opening the respective scissors are not performed in conjunction with the operation of the press bar lifting device and the operation of the fabric feeding mechanism.

If the sewing machine starts the sewing operation in the next cycle, the position of the fabric feeding mechanism is not affected by the opening operation of the scissors. In other words, even if the fabric feeding mechanism is not moved to the sewing start position at the start of the sewing operation in the next cycle, the respective scissors will release the thread.

In addition, the respective shears perform the closing and opening operations by being driven by a drive device which is already incorporated in the yarn cutting device. The sequence of operations of the respective scissors is therefore in no way affected by the operation of the other sewing machine mechanisms.

An eighth aspect of the present invention is directed to a thread cutting device according to any preceding aspect of the present invention from one to seven, wherein the drive device is any device selected from the group consisting of a solenoid, an air cylinder and a pulse motor.

In accordance with an eighth aspect of the present invention, the drive train is any device selected from the group consisting of a solenoid, an air cylinder, and a pulse motor that are electrically operated.

-6 CZ 302749 Bo

It is therefore very easy to change the time sequences for closing and opening the needle thread shears and the bobbin thread shears.

Until now, the needle thread cutting shears and the bobbin thread cutting shears have been commonly interconnected with the press bar lifting device and the fabric feeding mechanism. As a result, the time sequence for closing and opening the needle thread shears and the bobbin thread shears was mechanically controlled by changing the cam position.

However, in the case of the present invention, the closing and opening operations of the aforementioned shears are carried out by driving a solenoid, an air cylinder or a pulse motor. It is thus very easy to regulate the sequence of operations for closing and opening the respective scissors.

Overview of the drawings

The invention will now be explained in more detail by way of examples of specific embodiments thereof, the description of which will be given with reference to the accompanying drawings, in which:

Fig. 1 is an exploded perspective view showing a yarn cutting device according to a first embodiment of the present invention;

Fig. 2 is a side elevational view showing a yarn cutting device according to a first embodiment of the present invention;

Fig. 3 is a plan view showing a yarn cutting device according to a first embodiment of the present invention:

Fig. 4 is a partial front elevational view showing a yarn cutting device according to a first embodiment of the present invention;

Fig. 5 is a bottom view showing a bobbin thread cutting device according to a first embodiment of the present invention;

Fig. 6 is an exploded perspective view showing a thread cutting device according to a second embodiment of the present invention;

Fig. 7 is a plan view showing a needle thread cutting device according to a second embodiment of the present invention;

Fig. 8 is a bottom view showing a bobbin thread cutting device according to a second embodiment of the present invention;

Fig. 9 is a plan view showing a needle thread cutting device according to a third embodiment of the present invention;

Fig. 10 is an exploded perspective view showing a needle thread cutting device according to a third embodiment of the present invention;

Fig. 11 is a side elevational view showing a cam mechanism arranged in a needle thread cutting device according to a third embodiment of the present invention;

Fig. 12 is a bottom view showing a bobbin thread cutting device according to a third embodiment of the present invention;

FIG. 13 is an exploded perspective view showing a bobbin thread cutting device according to a third embodiment of the present invention;

FIG. 14 is a timing diagram illustrating the operation and operation of a bobbin thread cutting device according to a third embodiment of the present invention; and Fig. 15 is a block diagram showing the entire construction of a buttonhole sewing machine in an exemplary embodiment of the present invention.

-7 GB 302749 B6

DETAILED DESCRIPTION OF THE INVENTION

The yarn cutting apparatus according to each embodiment of the present invention will now be described in more detail below with reference to the accompanying drawings.

First embodiment

Before fully explaining the yarn cutting device 11 according to the first embodiment of the present invention, a schematic construction of a buttonhole sewing machine for forming a knotted stitch containing the same yarn cutting device will first be described.

As shown in FIG. 2, the sewing machine frame 4 arranged on the sewing machine board comprises a base portion 1 having a nearly rectangular housing shape, a longitudinal cylindrical portion 2 erected from the rear of the base portion I, and an arm body 3, protruding from the upper part of the longitudinal cylindrical part 2 and located opposite the base part 1.

A needle bar (not shown in the figures), provided with a needle 5 attached to its lower end, is disposed on the upper part of the arm body 3 and can be moved vertically and pivoted in the transverse direction.

The hook device (not shown in the figures) is arranged in the base part 1, opposite to the needle bar. A bobbin is embedded in the looper, on which the bobbin thread is wound to form the bound stitch in cooperation with the needle 5.

The presser foot arm 7, arranged in the longitudinal direction in FIG. 2, is located below the arm body 3.

The presser 6 for sewing the fabric during sewing is attached to the front end of the presser foot 7, the lower end of the presser rod 9, located in the vertical direction, connected to the front end of the presser foot 7 by means of a roller 8.

The pressure bar 9 is movable vertically and always presses down the fabric pressing device 6 due to the downwardly acting resilient force of a resilient member (not shown) arranged relative to the pressure bar 9 so that the fabric is held between the pressure device 6 and a fabric feed plate (not shown).

In addition, the pressure bar 9 is connected to the operating lever 10. When the operating lever 10 is actuated, the pressure bar 9 is raised against the action of a resilient force so that the fabric held by the pressure device 6 is released.

The presser foot arm 7 has a rear end attached to a fabric feeding mechanism (not shown). This fabric feeding mechanism actuates the fabric feeding plate and the presser foot arm 7 in the longitudinal direction due to the driving force of the motor, feeding the fabric held between the presser 6 and the fabric feeding plate.

The sewing machine is further provided with a cloth cutting mechanism for forming a buttonhole on the fabric in the rearward direction of the needle 5 of Fig. 2. This fabric cutting mechanism comprises a knife stand (not shown) arranged on the upper side of the knife stand and movable vertically and a knife control mechanism provided with a cloth cutting cylinder (not shown) to provide vertical movement of the movable knife.

The sewing machine is further provided with a thread cutting device 11 according to the invention (see FIG. 1).

The sewing machine further comprises a control device (not shown) for controlling the operation of each mechanism based on predetermined parameters. As a result, the sewing machine performs a number of operations to sew the buttonhole.

The thread cutting device 11 will now be described in more detail with reference to the illustration of Figures 1 to 5.

The yarn cutting device 11 comprises a needle thread cutting device 12 and a bobbin thread cutting device 50.

First, the construction of the needle thread cutting device 12 will be described with reference to the illustration of Figures 1 to 4.

The needle thread cutting device 12 comprises a needle thread cutting section 11 for performing the needle thread cutting operation and a needle thread cutting section 14 for driving the needle thread cutting portion 13.

The needle thread trimming portion 13 comprises an openable needle cutting shears 11.

2o of the thread, a support arm 16 for receiving the scissors 15 for cutting the needle thread, and a support shaft 17 for attaching the support arm 16 to the apex. The bearing member 24 is supported on support portions 23 attached to the lower portion of the arm body 3 rotatably about a pivot axis in the transverse direction of FIG. 1. The support shaft 17 is supported so as to penetrate the bearing member 24 slidingly and rotatably, arm body 3.

The support arm 16 has a lower end attached to the upper portion of the support shaft 17, the apex 16a being attached to the lower end of the pressure bar 9. As a result, the support shaft 17 is movable vertically around the bearing member 24 due to the vertical movement of the pressure bar 9. The arm 11 extends from the upper portion of the support shaft 17 to the left in Fig. 1, being further bent and extending downwardly forward and at an angle as shown in Fig. 1. The upper portion of the support arm 11 is provided with scissors 15 for cutting the needle thread. are rotatable towards the top of the presser foot arm 7.

The needle thread cutting scissors 15 comprise a fixed blade 20 attached to the upper portion of the support arm 11, a movable blade 11 rotatably arranged about the pin 22 relative to the fixed blade 20, and a pressure plate 11 attached to the fixed blade 20. In addition, it is movable. the blade 19 is provided with a cam support portion 19a projecting from its upper surface.

The drive portion 14 for cutting the needle thread will now be described.

The needle thread cutting drive portion 14 includes means for closing the needle thread cutting shears to ensure that the needle thread cutting portion 13 performs the function of pinching the needle thread cutting scissors 15 (needle thread cutting operation) and means for cutting the needle thread. opening the needle thread cutting scissors 15 to operate the needle thread cutting portion 11 while performing the needle thread cutting scissors operation 11 (needle thread release operation).

The details of this feature will now be described in more detail below.

The means for clamping the needle thread cutting scissors 11 causes the needle thread cutting scissors 11, in the open state, in a standby position, distant from the vertical path of the needle 5 and the vertical path of the fabric cutting knife, to begin to clamp. More specifically (to say that the means for clamping the needle thread clipping scissors 11 close the needle thread clipping scissors J while moving the needle thread clipping scissors J from the standby position.

302749 B6 toward the shear position opposite the vertical path of the needle 5, after the sewing operation of the sewing machine is completed.

As a result, the needle thread cutting shears 50 cut the needle thread and hold the needle thread cut off. The means for clamping the needle thread shears 15 further move the needle thread shears 15 from the shear position to the final standby position (which is located at a distance from the vertical path of the needle 5 but not at a distance from the vertical path of the cutting knife. fabric).

After the sewing machine commences the sewing operation and the needle 5 then performs several stitches, the means for opening the needle-cutting scissors 15 will move the needle-threading scissors 15 in the closed state in the ending standby position to this standby position. they open the scissors 15 for cutting the needle thread. As a result, the needle thread cutting shears 15 release the holding of the needle thread. The standby position, the shear position and the final standby position will be described in more detail below.

The construction of the means for clamping the needle shears 15 will now be described in more detail below.

The lower end (right end) of the operating lever 10 extending transversely is attached to the longitudinal cylindrical portion 2 rotatable about an axis of rotation in the longitudinal direction. One of the ends of the tension spring 31 is connected to the central portion of the operating lever W, the other end of the tension spring 31 is connected to the arm body 3. The tension spring 31 activates the operating lever 10 clockwise (i.e., opposite to the arrow) d in FIG. 1) viewed from the front.

The fastening portion 26 of the roller 27 extends upwardly from the base end of the operating lever 10, the roller 27 being disposed at the upper end of the fastening portion 26. The pivot member 28 is arranged to rest against the roller 27. The pivot member 28 extends transversely, the end (right end) of the pivot member 28 is attached to the arm body 3 such that it is pivotable about an axis of rotation in a vertical direction.

In addition, the cam 28a is formed on the rear of the pivot member 28 with the roller 27 resting on the cam 28a. The front of the pivot member 28 rests on the base end of the pivot arm 29. The base end of the pivot arm 29 is attached to the rear end of the support shaft Γ7. A compression spring 30 is wound on a support shaft 17 between the pivot arm 29 and the bearing member 24. The compression spring 30 activates the support shaft 17 rearwardly together with the pivot arm 29.

The right portion of the cam member 32 is attached to the central portion of the operating lever 10, and is rotatable about an axis of rotation in the longitudinal direction. The left end of the cam member 32 is connected to the central portion of the bobbin thread cutting lever 33 and is rotatable about a pivot axis in the longitudinal direction. The bobbin thread cutting lever 33 extends vertically with the lower portion extending into the base portion 1. The upper end (the base end) of the bobbin thread cutting lever 33 is attached to the longitudinal cylindrical portion 2, rotatable about the axis of rotation in the longitudinal direction .

The pressing body 34 is fixedly arranged in the middle part of the bobbin thread cutting lever 33. The engagement mechanism 35 is disposed adjacent the apex portion 34a of the pressing body 34.

The engagement mechanism 35 comprises a support body 35a, an engagement body 35b, and a compression spring 35d. The support body 35a is attached to the support arm 7a. The base end of the engagement body 35b is connected to the support body 35a and is pivotable about an axis of rotation in the longitudinal direction. The apex end of the engagement body 35b is provided with an engagement portion 35c that is bent upward. A compression spring 35d is coupled between the support body 35a and the engagement body 35b. The compression spring 35d activates the engagement body 35b upwards relative to the support body 35a.

- 10 GB 302749 Β6

The apex portion 34a of the pressing body 34 is arranged near the upper surface of the engagement body 35b. When the bobbin thread cutting lever 33 rotates clockwise around its upper end as seen from the front, the apex portion 34a of the pressing body 34 pushes the engagement body 35b downwardly against the force of the compression spring 35d,

The pivot arm 29 extends downward from its base end. The roller 36 is disposed in the central portion of the pivot arm 29. In addition, one of the ends of the tension spring 37 is hinged to the central portion of the pivot arm 29, with the other end of the tension spring 37 hinged at the upper end of the spool 33. The tension spring 37 activates the pivot arm 29 clockwise as seen from the front. Then, the roller 36 is supported on the cam portion 32a and the cam portion 32b formed on the right side of the cam member 32. As a result, the rotation of the arm 29 in the clockwise direction is suppressed.

The corner portion 32c is formed at the right end of the cam member 32 by the cam portion 32a and the cam portion 32b. In addition, the engaging pawl 29a extending forwardly is provided at the apex portion (at the lower end) of the pivot arm 29. The engaging pawl 29a may be freely engaged and disengaged from the engagement portion 35c on the engagement body 35b.

The closure plate 25, which is formed by an almost rectangular member that is elongated in the longitudinal direction, extends downwardly and is fixed to the front end of the presser foot arm 7.

The means for opening the scissors for cutting the needle thread will now be described in more detail.

In the known needle thread cutting device, the needle thread cutting shears of the needle thread cutting part are opened in interaction with the forward movement of the presser foot arm. In the thread cutting device 11 of the present invention, however, the needle thread cutting shears 15 of the needle thread cutting portion 13 are opened by operation of the drive device, without being interconnected with the presser foot arm 7.

First, the construction of the means for opening the scissors for cutting the needle thread will be described in more detail.

The means for opening the scissors for cutting the needle thread comprises driving means for opening the scissors 15 for cutting the needle thread and movement means for moving the scissors 15 for cutting the needle thread from the ending standby position to the standby position.

The drive means for opening the scissors 15 for cutting the needle thread comprises a solenoid 38 which constitutes the driving device, a lever 21 for attachment to the support arm 16 rotatably about a pivot axis in the transverse direction in the central portion, and a tension spring 39 to activate the lever 21.

The solenoid 38 is attached to the lower portion of the arm body 3 and serves to provide longitudinal movement of the rod 38a extending forward. The front end of the rod 38a is supported on one of the ends of the lever 21. One of the ends of the tension spring 39 is hinged to the central portion of the lever 21, the other end of the tension spring 39 being hinged to the frame 4 of the sewing machine. The tension spring 39 activates the rod 38a rearwardly together with one of the ends of the lever 2T. The other end of the lever 21 is provided with an opening cam portion 21a that extends to the right.

The opening cam portion 21a is disposed on the left side of the cam support portion 19a. The first cam face 21b and the second cam face 21c are formed at the right end of the opening cam portion

21a. The first cam face 21b extends in the longitudinal direction. The second cam face 21c is connected to the first cam face 21b and is inclined to the left towards the rear.

-IICZ 302749 B6

When the needle thread cutting shears 15 are set in the closed state and the solenoid 38 is switched from the off state to the on state, the rod 38a is pushed outwards forwards against the action of the tension spring 39. As a result, the lever 21 rotates counterclockwise. (in the direction of the arrow f in FIG. 1) as seen from the side (from the right).

Together with the rotation of the lever 21, the second cam face 21c is supported on the cam support portion 19a, and finally the first cam face 21b is supported on the cam support portion 19a. As a result, the cam abutment portion 19a is pressed by the opening cam portion 21a, wherein the movable blade 19 is rotated such that the needle thread cutting shears 15 perform the opening operation.

When the solenoid 38 is switched off, the tension spring 39 and the rod 38a are restored to the original state, while the needle thread cutting shears 15 are kept open.

The movement means of the needle thread shear comprises a solenoid 40 which forms the drive device, a coupling 41 to be connected to the apex of the solenoid rod 40a, a pressure body 42 to be coupled to the coupling 41, and a tension spring 37.

The solenoid 40 is rigidly arranged on the base portion J and is arranged on the left side of the engagement mechanism 35. The rod 40a extends to the right of the solenoid body 40. The solenoid 40 serves to provide lateral movement of the rod 40a. One of the ends of the coupling 41 is connected to the tip portion of the rod 40a and is pivotable about a pivot axis in the longitudinal direction. One of the ends of the pressing body 42 is connected to the other end of the coupling 41 and is rotatable about an axis of rotation in the longitudinal direction.

The pressing body 42 extends vertically from one of its ends towards the central portion, bending to the right in the central portion. The pressing body 42 is arranged in the longitudinal cylindrical part 2, being rotatable about an axis of rotation in the longitudinal direction in its central part. The pressing body 42 extends transversely from its central portion towards the apex portion, the apex portion being arranged near the upper surface of the engagement body 35b.

In the case where the engagement pawl 29a is arranged below the engagement portion 35c of the engagement body 35b and engages the engagement portion 35c by the biasing force of the tension spring 37, the function of the movement means of the scissors for cutting the needle thread is as follows.

When the solenoid 40 is switched from the off state to the on state, the rod 40a is pulled out to the left (in the direction of arrow e in Fig. 1). As a result, the pushing body 42 rotates in a clockwise direction as seen from the front. Together with the rotation of the pressing body 42, the apex portion of the pressing body 42 pushes the engagement body 35b downwards. As a result, the engagement body 35b rotates clockwise as seen from the front portion, the engagement portion 35c being disengaged from the engagement pawl 29a.

When disengaged, the pivot arm 29 rotates clockwise around the support shaft 17 under the biasing force of the tension spring 37. Together with the pivot arm 29 rotation, the needle thread shears 15 attached to the top of the support arm move. J6, through the support shaft Γ7 from the ending standby position to the standby position. In this case, the pivot arm 29 is stopped by the roller 36 against the cam member 32.

The construction of the bobbin thread cutting device 50 will now be described in more detail with reference to the illustration of Figures 1 and 5.

The bobbin thread cutting device 50 is formed by the base 51 of the needle plate 55, by the scissors 52 for cutting the bobbin thread, which are controllable relative to the base 51 of the needle plate.

- 12 GB 302749 Β6

55, the scissor closing means 53 for bringing the open scissors 52 to a closed state, and the scissor opening means 54 for bringing the closed scissors 52 to an open state.

The base 51 of the needle plate 55 is formed by a plate-like member and is rigidly arranged in the base part I almost horizontally. The suture plate 55 is attached to the upper surface of the base 51 of the suture plate 55. The suture plate 55 is provided with an insertion opening for insertion of the needle 5, the hook device being arranged below the suture plate base 55.

The bobbin thread shears 52 include an upper knife 56, a lower knife 57 and a leaf spring 58. The lower knife 57 is disposed at the front of the base 51 of the needle plate 55. The base end 57a of the lower knife 57 is connected to the bottom surface of the base 51 wherein it is rotatable about an axis of rotation in a vertical direction. The upper blade 56 and the leaf spring 58 are arranged in the lower blade 52 and are rotatable about an axis of rotation in a vertical direction relative to the lower blade 57.

The pin 56a is arranged to protrude from the lower surface of the upper knife 56. The front protruding portion 56b is formed in the front of the upper knife 56. The leaf spring 58 is attached to the lower knife 57.

The closure means 53 of the bobbin shear 52 serves to rotate the lower knife 57 around the base end 57a, thereby closing the bobbin shear 52. The construction of the closure means 53 of the scissors 52 for cutting the bobbin thread will now be described.

The closure means 53 of the bobbin shearing shear 52 comprise a drive arm 60, a coupling member 61. a bobbin shear coupling member 62, a bobbin winding winding arm 63, a coupling member 64 and a coupling member 65. is provided at the lower end of the bobbin thread cutting lever 33.

The rear end of the driving arm 60 extending in the longitudinal direction is connected to the ball pin 59 by means of a ball bearing. The driving arm 60 is arranged in the base part 1, the pivoting arm of the axis of rotation being vertical in its central part.

The front end of the drive arm 60 is connected to one of the ends (to the left end) of the linker 61, being rotatable about an axis of rotation in a vertical direction. The other end of the coupling 61 is connected to one of the ends (to the rear end) of the coupling for cutting the bobbin thread, being rotatable about an axis of rotation in a vertical direction.

The spool yarn connecting member 62 is attached to the bottom surface of the base 51 of the needle plate 55 and is rotatable about an axis of rotation in a vertical direction in its central portion. The top portion of the spool yarn splicing member 62 is connected to the central portion of the spool yarn winding arm 63 and to one of the ends of the spool yarn closure member 64, being rotatable about a pivot axis in a vertical direction. The other end of the coupling 64 is connected to the lower blade 57 and is rotatable about an axis of rotation in a vertical direction.

The rear end of the spool winding arm 63 is connected to one of the ends of the coupling 65 is connected to the base 51 of the needle plate 55, being rotatable about an axis of rotation in a vertical direction. The winding arm 63 serves to wind the bobbin yarn fed from the bobbin with the help of its tip portion.

The bobbin thread shears 52, which are set in the open condition, are closed as follows.

When the drive arm 60 rotates, the lower blade 57 rotates forward about its base end

57a with the help of the connecting member 62 for cutting the bobbin thread, the winding arm 63 for

As a result, the upper knife 56 moves forward together with the lower knife 57, with the protruding portion 56b of the upper knife 56 resting on the opening portion 51a of the base 51 of the needle plate 55.

Thereafter, the forward movement of the upper knife 56 is suppressed, with the lower knife 57 further rotating forward so that the upper knife 56 rotates relatively rearwardly relative to the lower knife 57. As a result, the bobbin thread shears 52 are closed while the bobbin thread is cut. fed from the coil. In addition, when the spools 52 for cutting the bobbin thread are closed, the bobbin thread is held by the leaf spring 58 and the upper knife 56.

lo

The opening means 54 of the bobbin shear 52 serves to press the pin 56a by actuating the drive train, thereby opening the bobbin shear 52. The construction of the opening means 54 of the scissors 52 for cutting the bobbin thread will now be described.

The spool opening means 54 includes a solenoid 66 which constitutes a drive member, a coupling member 67, an operating member 68, and a tension spring 69. The solenoid 66 is fixedly positioned in the base portion L The solenoid 66 serves to move the rod 66a in the longitudinal direction .

The forward end of the rod 66a is connected to the rear end of the link member 67 and is rotatable about an axis of rotation in a vertical direction. The forward end of the coupling 67 is connected to one of the ends of the operating member 68 and is rotatable about an axis of rotation in a vertical direction. In addition, one of the ends of the tension spring 69 is connected to one of the ends of the operating member 68, the other end of the tension spring 69 being connected to the base portion 1.

The middle portion of the operating member 68 is attached to the base 51 of the needle plate 55 and is rotatable about an axis of rotation in a vertical direction. The tension spring 69 activates the operating member 68 in a clockwise direction as seen from the underside. The other end of the operating member 68 extends toward the pin 56a.

When the solenoid 66 is switched from the off state to the on state, the rod 66a is pushed out. As a result, the operating member rotates counterclockwise as seen from the underside, with the apex portion of the operating member 68 pressing on the pin 56a. When the pin 56a is pushed so that the engagement of the protruding portion 56b on the opening portion of the stator is released, the upper knife 56 rotates forward relative to the lower knife 57. As a result, the bobbin thread cutting shears 52 open and hold the bobbin thread is released.

When the solenoid 66 is switched from the on state to the off state, the operating member 68 rotates clockwise due to the biasing force of the tension spring 69.

The operation of the yarn cutting device 11 and the sequence of operations will now be described. The sewing machine control device controls the solenoids 38, 40 and 66 so that the device 11. for thread cutting is operated as follows.

During the sewing operation of the sewing machine, the machine 11 is. for thread trimming, set into the following initial conditions:

(1) The operating lever 10 is placed in the position A shown in Fig. 4 by the biasing force of the tension spring 31.

(2) The support shaft 17 and the pivot arm 29 are located rearwardly by the action of the biasing force of the compression spring 30.

(3) Rotation of the pivot arm 29 clockwise by the action of the tension spring 37, as seen from the front, is suppressed by the abutment of the roller 36 on the cam portion 32b of the cam member 32.

(4) The solenoid 40 is set to the off state, wherein the pressing body 42 is set to the state in which the engagement body 35b is not pressed downwards.

(5) The press body 34 is also placed in a state in which the engagement body 35b is not pressed downwards.

(6) The engagement pawl 29a is positioned on the upper surface of the engagement body 35b.

(7) The solenoid 38 is set to the off state, wherein the needle thread shears 15 are set away from the open state.

(8) The needle thread cutting scissors 15 are placed in a standby position, spaced apart from the vertical path of the needle 5 to the left, obliquely and backward as viewed in plane (oo).

(9) The solenoid 66 is set to the off state, wherein the bobbin thread shears 52 are set to the open state.

(10) The protruding portion 56b of the upper knife 56 does not extend into the open portion of the base 51 of the stitch plate 55, wherein the bobbin thread shears 52 are located at an initial position 5 which is located outside the vertical path of the needle 5.

After the sewing machine has completed one sewing of the buttonhole, the operator actuates the operating lever 10. As a result, the operating lever 10 rotates counterclockwise (in the direction of arrow d in FIG. 1) around its base end, with the shearing device 12 the needle thread is actuated in the following manner before the rotation of the operating lever 10 reaches position B.

Specifically, the roller 27 rotates around the base end of the operating lever 10 counterclockwise as seen from the front, thereby moving along the cam 28a of the pivot member 28. As a result, the roller 27 rotates the pivot member 28 towards the front. As it rotates forward, the pivot member 28 pushes the support shaft 17 forward together with the pivot arm 29. As a result of the forward movement of the support shaft 17, the needle thread cutting shears 15 move forward.

The cam member 32 rotates about its left end clockwise as viewed from the front by rotating the operating lever 10. As a result of the rotation of the cam member 32, the bobbin thread cutting lever 33 rotates about its base end clockwise. The cam portion 32b pushes the roller 36 to the right.

Together with the rotation of the bobbin thread cutting lever 33, the pressing body 34 pushes the engagement body 35b downwards. The roller 36 is pushed to the right so that the support shaft 17 rotates counterclockwise when viewed from the front together with the pivot arm 29. The pressure body 34 pushes the engagement body 35 downward so that the engagement body 35 does not interfere with the movement of the engagement pawl 29a. The support shaft se rotates counterclockwise until the roller 36 abuts the corner portion 32c of the cam member 32. Due to the rotation of the support shaft 17 counterclockwise, the needle thread cutting shears 15 move to the right.

As described above, the scissors J5. For trimming the needle threads, they move from the standby position to the trimming position by rotating the support shaft 17 counterclockwise and by moving it forward.

When the needle thread shears 15 are to be moved from the standby position to the shear position, the cam support portion 19a of the movable blade 19 abuts the closure plate 25, thereby being relatively pressed against the closure plate 25. As a result, the movable blade 19 rotates relative to By rotating the movable blade 19, the needle thread cutting shears 15 are closed in order to cut the needle thread and to hold the needle laterally from the needle thread thus cut.

- 15 GB 302749 B6

When the operating lever 10 is positioned in position B, the roller 36 is held in abutment on the corner portion 32c of the cam member 32, wherein the needle thread cutting shears 15 are set in the closed position in the shearing position.

The operating lever 10 further rotates counterclockwise, the needle thread cutting device 12 being actuated in the following manner before the operating lever 10 is moved from position B to position C.

Specifically, the roller 27 rotates around the base end of the operating lever 10 counterclockwise as viewed from the front and passes over the top of the cam 28a of the pivot member 28. As a result, the support shaft 17 and the pivot arm 29 move rearwardly before the frothing. the pressure spring 30, wherein the needle thread cutting shears 15 are further moved back to the closed state.

The cam member 32 rotates clockwise around its left end by rotating the operating lever 10. As a result of the rotation of the cam member 32, the bobbin thread cutting lever 33 further rotates in the clockwise direction, the roller 36 to abut the corner the portion 32c, moves to the cam portion 32a.

When the roller 36 moves towards the cam portion 32a, the support shaft 17 rotates slightly clockwise as seen from the front, together with the pivot arm 29 under the biasing force of the tension spring 37. Due to the rotation of the support shaft 17 in the clockwise direction, the needle thread shears 15 move slightly to the left to the closed state.

If the operating lever W is moved from position A to position C, the bobbin thread cutting device 50 is operated as follows.

The bobbin thread cutting lever 33 rotates clockwise around its base portion by the cam member 32 due to rotation of the operating lever 10 so that the drive arm 60 rotates about its central portion clockwise as seen from below.

By rotating the drive arm 60 in the clockwise direction, the spool yarn connecting member 62 rotates about its central portion counterclockwise, as seen from below, via the connecting member 6L.

Due to the rotation of the bobbin thread cutting member 62 counterclockwise, the bobbin winding arm 63 rotates about its central portion counterclockwise as seen from below while winding the bobbin thread fed from the bobbin.

The lower blade 57 rotates about its base portion in a clockwise direction, as seen from below, by rotating the spool yarn connecting member 62 counterclockwise.

When the lower knife 57 rotates, the projecting portion 56b of the upper knife 56 abuts the opening portion 51a of the needle plate base 51 so that the upper knife 56 rotates relative to the lower knife 57.

As a result, the bobbin thread shears 52 close and cut the bobbin thread wound by the winding arm 63 for winding the bobbin thread. Thereafter, the bobbin thread cutting shears 52, in the closed state, retain the bobbin side of the bobbin thread thus cut.

- 16GB 302749 B6

Furthermore, if the operating lever 10 rotates counterclockwise, the fabric pressing device 6 is raised so that the fabric can be inserted or removed.

When the operator releases the operating lever JO, the operating lever JO rotates upward to position A through position C by applying the biasing force of the tension spring 31. When the operating lever 10 rotates from position C to position A, the needle thread cutting device 12 is controlled by the following way.

Due to the rotation of the operating lever 10 in the clockwise direction, the roller 27 returns to its initial state. As a result, the pivot member 28 first rotates forward and then rotates backward and returns to its initial state. Together with the rotation of the pivot member 28, the support shaft 17 and the pivot arm 29 first move forward and then move backward so that their longitudinal positional relationship returns to their initial state. Therefore, the longitudinal positional relationship of the needle thread shears 15 is brought to a position that is identical to the standby position.

The cam member 32 rotates counterclockwise about its left end by rotating the operating lever 10 clockwise. Together with the rotation of the cam member 32, the bobbin thread cutting lever 33 rotates counterclockwise about its base end. As a result, the pressing body 34 releases pressure on the engagement body 35b so that the engagement body 35b returns to its initial state.

The roller 36 moves from the cam portion 32a to the corner portion 32c and subsequently to the cam portion 32b in accordance with the anti-clockwise rotation of the cam member 32. When the roller 36 moves toward the cam portion 32b, the engagement pawl 29a of the pivot arm 29 abuts the side surface of the engagement portion 35c of the engagement body 35b, since the engagement body 35b has returned to its initial state.

As a result, the rotation of the pivot arm 29 in the clockwise direction is suppressed so that the relative abutment of the roller 36 and the cam portion 32b is released. As a result, the movement of the needle thread shears 15 to the left is also suppressed.

As described above, when the operating lever 10 is returned from position C to position A, the longitudinal positional relationship of the needle thread shears 15 is returned to the standby position and their transverse positional relationship is not returned to the standby position. This position is the ending standby position described above.

As described above, the ending standby position is located on the vertical path of the cloth cutting knife. The needle thread cutting scissors 15, located in the ending standby position, are set in such a state that they are closed and hold the needle thread.

When the operating lever 10 is rotated from position C to position A, the bobbin thread cutting device 50 is operated as follows.

The bobbin thread cutting lever 33 rotates counterclockwise about its base end by the cam member 32 due to the rotation of the operating lever 10. Due to the rotation of the bobbin thread cutting lever 33 counterclockwise, the drive arm 60 rotates about its central portion counterclockwise, as can be seen from below.

As a result, the bobbin thread cutting member 62 rotates clockwise around its central portion via the link member 6k. As the bobbin thread cutting member 62 rotates clockwise, the bobbin winding arm 63 rotates in the direction of rotation. clockwise around its center, returning to its initial state.

- 17GB 302749 B6

The lower knife 57 rotates counterclockwise around its base end as a result of rotating the bobbin thread cutting member 62 clockwise such that the engagement of the protruding portion 56b of the upper knife 56 and the opening portion 51a of the needle plate base 51 is released . As a result, the bobbin thread shears 52 are returned to their initial position in the closed state.

The operator further controls the sewing machine pedal so that the sewing machine initiates the sewing operation in the next cycle. After the sewing machine commences the sewing operation, the machine 11 is. for cutting the yarn, operated as follows.

In the needle thread cutting device 12, the solenoid 38 is switched from the off state to the on state, so that the lever 21 is rotated counterclockwise as seen from the side. Together with the rotation of the lever 21, the second cam face 21c then abuts the cam abutment portion 19a, with the cam abutment portion 19a finally abutting on the first cam face 21b.

As a result, the opening cam portion 21a (second cam face 21c and first cam face 21b) urges the cam support portion 19a so that the movable blade 19 rotates. The needles 15 for cutting the needle thread are thus opened, further loosening the holding of the needle thread.

Upon opening of the needle thread cutting shears 15, the solenoid 38 is brought to the off state, while the needle thread cutting shears 15 are kept open.

Then, the solenoid 40 is switched from the off state to the on state so that the rod 40a is attracted to the left. As a result, the pressing body 42 pushes the engagement body 35b down, the engagement pawl 29a being disengaged from the engagement body 35b.

As a result, the pivot arm 29 rotates clockwise by the biasing force of the tension spring 37 until the roller 36 abuts and the cam portion 32b of the cam member 32. The support shaft 17 rotates together with the rotation of the pivot arm 29. The support shaft 17 rotates together with the rotation of the pivot arm 29, wherein the needle thread cutting shears 15 move to the left and are finally returned to the standby position.

After the needle thread cutting shears 15 are returned to the standby position, the solenoid 40 is switched off so that the downward pressure exerted on the presser body 42 is released.

The solenoid 66 in the bobbin thread cutting device 50 switches from the off state to the on state so that the bar 66a is pushed outwardly forward. As a result, the operating member 68 rotates counterclockwise as seen from below, with the apex portion of the operating member 68 pressing on the pin 56a.

As a result, the upper knife 56 rotates so that the bobbin thread shears 52, set in the closed state, open and release the bobbin thread. Upon opening of the bobbin thread shears 52, the solenoid 66 is brought to the off state so that the operating member 68 rotates clockwise and the operating member 68 returns to its initial state.

In the thread cutting device 11 according to the first embodiment of the present invention, the lever 21 to be actuated by the solenoid 38 is arranged in the support arm 16 and is movable with the scissors 15 for cutting the needle thread. Therefore, even if the needle thread cutting shears 15 are positioned in any relative position with respect to the presser foot arm 7, the lever 21 rotates so that the needle thread cutting shears 15 can be opened.

- 18 GB 302749 B6

Furthermore, since the yarn cutting device 12 comprises an original solenoid 38, the needle thread cutting shears 15 are opened without being related to the movement of the presser foot arm 7, i.e. the movement of the fabric feeding mechanism.

Similarly, since the bobbin thread cutting device 50 comprises the original solenoid 66, the bobbin thread cutting shears 52 may open without being related to the movement of the fabric feeding mechanism.

Thus, if the sewing machine is to commence the sewing operation in the next cycle, the position of the fabric feeding mechanism is not limited by the opening movement of the needle thread shears 15 and the bobbin thread shears 52.

Thus, for example, in the case where the sewing operation can be performed by moving the fabric feeding mechanism itself, even if the positional relationship between the fabric feeding mechanism and the sewing object is not set, if the sewing operation in the next cycle is the same as the sewing operation in the last cycle, where the buttonhole is to be sewn in different parts, it is not necessary to re-adjust the sewn object. As a result, increased productivity can be achieved.

Furthermore, since the scissors 15 and the scissors 52 are opened by means of solenoids 38 and 66 already arranged, their function is in no way affected by the action of other sewing machine mechanisms. In addition, the solenoids 38 and 66 are electrically driven. As a result, their functional timing can be set relatively easily.

In addition, the needle thread shears 15 are moved from the shear end position to the standby position by driving the original solenoid 40. The movement is therefore not related to the movement of the fabric feeding mechanism.

The closure plate 25 is further provided as a longitudinal elongate member. The longitudinal range in which the cam support portion 19a can rest on the closure plate 25 is therefore large. In other words, the longitudinal range is not influenced in any way by the longitudinal position of the presser foot 7 when the needle thread cutting shears 15 perform the closing operation.

In a first embodiment of the present invention, it will be understood that certain detailed constructions may be suitably altered and not limited to the particular embodiment. For example, instead of solenoids 38, 40 and 66, air cylinders can be used to move the rod back and forth. The needle thread cutting shears 15 or the bobbin thread cutting shears 52 may be opened with the aid of air cylinders.

In addition, the solenoids 38, 40 and 66 may be pulsed motors. For example, in the case where the solenoid 38 is a pulse motor, the drive shaft of the pulse motor extends in a transverse direction, wherein the pivoting member extends almost perpendicularly, the pivoting member extending almost perpendicular to the drive shaft is fixedly mounted on the drive the shaft. The pivot member rests on one of the ends of the lever 21.

When the pulse motor normally rotates, the pivot member pushes one of the ends of the lever 21 forward so that the needle thread cutting shears 15 open and release the needle thread as described above. Conversely, if the pulse motor rotates in the opposite direction, the pressing is released and the needle thread shears 15 are kept in an open condition.

Furthermore, in the case where the solenoid 66 is a pulse motor, the coupling 67 is pushed forward as a result of the conventional rotation of the pulse motor, so that the bobbin thread shears 52 open as described above. Conversely, if the coupling member 67 is pulled backward as a result of the reverse rotation of the pulse motor, the bobbin thread shears 52 are kept open.

- 19 GB 302749 B6

In the case where the solenoid 40 is a pulse motor, the coupling 44 is pulled to the left due to the conventional rotation of the pulse motor, and the needle thread cutting shears 15 are returned to the standby position as described above. Conversely, the coupling 41 is pushed to the right by reverse rotation of the pulse motor.

Second embodiment

Next, the yarn cutting apparatus according to the second embodiment of the present invention will be described with reference to the Figures 6 and 8.

The thread cutting device of the second embodiment is arranged in a buttonhole sewing machine in the same manner as the first embodiment. As in the first embodiment, the sewing machine comprises a sewing machine frame, a needle, a hook mechanism, a drive mechanism for moving the needle bar vertically, a mechanism for pivoting the needle bar, a fabric pressing device, a presser foot 2 (shown in FIG. 6 and 7), the fabric feeding mechanism, the pressing bar and the fabric cutting mechanism.

In a second embodiment of the present invention, the same structural elements and features as in the first embodiment are designated by the same reference numerals, and their detailed description will be omitted.

The yarn cutting device according to the second embodiment comprises a needle thread cutting device 71 and a bobbin thread cutting device 90.

First, the needle thread cutting device 21 will be described in more detail.

As shown in FIGS. 6 and 7, the needle thread cutting device 71 is formed by the solenoids 72 and 73 forming the driving mechanism, the opening needle thread cutting scissors 15 and the needle thread cutting mechanism 74 for cutting the needle thread. for opening and closing the scissors 15 by controlling the solenoids 72 and 73.

The needle cutting shear drive mechanism 74 is formed by a solenoid arm 25 to be connected to the solenoid 22, a needle thread cutting base 76 that can be engaged with and disengaged from the solenoid arm 75 by a rotating shaft 22 for receiving it. the needle thread trimming base 26 movably in the longitudinal direction, by the rotary bearing bases 78 and 79 by a lever 21 rotatably arranged in the needle thread trimming base 76, the lever 80 for engaging the needle thread trimming base 76, the tension spring 81 for actuating the lever 80, tension springs 82 and 83 for actuating the needle thread cutting base 76, a stop 85 for suppressing the forward movement of the needle thread cutting base 76, and a closing plate 25 arranged at the apex of the presser foot arm 2.

The bases 78 and 22 are rigidly attached to the arm body and lie in a vertical direction with respect to each other. The rotating shaft 22 is inserted vertically and is fixed between the bases 78 and 79 so as to be rotatable about an axis of rotation in the vertical direction. The square piece 84 is attached to the central portion of the pivot shaft 77 and is pivotable about a pivot axis in the transverse direction.

The needle thread cutting base 76 extends in the longitudinal direction. The central portion of the needle thread trimming base is provided with a through hole 76b extending transversely of the needle thread trimming base 76. The through hole 76b extends longitudinally, wherein the square piece 84 is longitudinally slidably mounted in the through hole 26b. As a result, the needle thread cutting base 76 is movable longitudinally.

- 20GB 302749 B6

In addition, the front end of the needle thread cutting base 76 is transversely rotatable about the rotary shaft 78, being vertically rotatable about a square piece 84.

The needle thread cutting shears 15 are arranged at the front end of the needle thread cutting base 76. The needle thread cutting scissors 15 have the same construction as in the first embodiment, comprising a fixed blade 20, a movable blade 19, a thrust plate 18, and a cam support portion 19a.

One of the ends of the tension spring 82 is hinged to the front of the base 76 for cutting the needle thread and the other end of the tension spring 82 is hinged to the arm body. Extended part

76a extending to the right is formed at the rear end of the needle thread cutting base 78. The stop 85 is attached to the arm body in front of the extended portion 76a.

The solenoid 72 is attached to the bottom of the arm body behind the needle thread cutting base 76, the rod 72a extending forward from the solenoid 72 body. The solenoid 72 serves to move the rod 72a in the longitudinal direction. The solenoid arm 75 is fixedly mounted on the bar 72a. Extended part 75a. extending to the left is formed at the front end of the solenoid arm 75. The elongated portion 75a is disposed in front of the elongated portion 76a of the needle thread cutting base.

When the solenoid 72 is in the off state, the solenoid arm 75 is pushed outwardly together with the bar 72a, the elongated portion 75a resting against the elongated portion 76a. In this state, the needle thread trimming base 76 is activated forwardly by the tension spring 82. The elongated portion 76a is supported against the stop 85 so that the forward movement of the needle thread trimming base 76 is limited.

Conversely, if the solenoid 72 is switched from the off state to the on state, the solenoid arm 75 is retracted together with the bar 72a. In this state, the elongated portion 75a is supported on the elongated portion 76a, the needle thread cutting base 76 moves rearwardly together with the solenoid arm 75, against the biasing force of the tension spring 82.

The lever 21 is attached to the needle thread cutting base 76 so that it is pivotable about a pivot axis in a transverse direction in its central portion. The support portion 21d extending upwardly is formed at one end of the lever 21. The cam portion 21a is formed at the other end of the lever 21 in the same manner as the first embodiment, wherein the first cam face 21b and the second cam face 21c are the opening cam portion 21a.

In the same manner as in the first embodiment, the opening cam portion 21a presses the cam support portion 19a to set the needle yarn shears 15, when closed, into the open condition.

The solenoid arm 73 is fixedly mounted on the arm body behind the support portion 21d of the lever 21 The solenoid 73 serves to move the rod 73a in the longitudinal direction.

The lever 80, which is almost L-shaped, is arranged in plan view in front of the support portion 21d of the lever 21 and to the right of the needle thread cutting base 76. The lever 80 is attached to the arm body pivotally about an axis of rotation in a vertical direction in its bent portion. One of the ends of the tension spring 81 is hinged at one of the ends of the lever 80, the other end of the tension spring 81 is hinged to the arm body.

The tension spring 81 is biased to rotate one of the ends of the lever 80 rearwardly. Due to the biasing force of the tension spring 81, one of the ends of the lever 80 is supported on the support portion 21d of the lever 21, the support portion 21d being supported on the front end of the rod 73a.

- 21 GB 302749 B6

In addition, one end of the tension spring 83 is hinged to the central portion of the needle thread cutting base 76, the other end of the tension spring 83 is hinged to the arm body. By applying the biasing force of the tension spring 83, the right surface of the needle thread cutting base 76 rests against the other end of the lever 80.

When the solenoid 73 is set off, the front end of the needle thread cutting base 76 is activated in the direction of rotation to the right by the tension spring 83. The cam support portion 19a is supported on the closure plate 25. As a result, the front end of the base 76 cutting the needle thread to the right is prevented. In this state, the needle thread shears 15 are set in the closed state.

When the solenoid 73 is switched from the off state to the on state, the lever 21 rotates counter-clockwise, as seen from the side (from the right), against the biasing force of the tension spring 80, the lever 80 rotating in the clockwise direction. hands, as can be seen in the top view.

When the lever 80 rotates clockwise, the other end of the lever 80 rotates the front end of the needle threading base 76 to the left. In addition, the opening cam portion 21a presses the cam support portion 19a together with the rotation of the lever 21 counterclockwise so that the needle thread cutting shears 15 are opened.

In addition, the forward end of the needle thread cutting base 76 is attached to the push rod, moving vertically along with the vertical movement of the push rod.

The bobbin thread cutting device 90 will now be described in more detail. As shown in FIG. 8, the bobbin thread cutting device 90 has nearly the same construction as the bobbin thread cutting device 50 of the first embodiment of the present invention.

Thus, when describing the bobbin cutting device 90 according to the second embodiment of the present invention, the same components as the bobbin cutting device 50 according to the first embodiment of the present invention are referred to by the same reference numerals, in particular only different structures will be described.

In the bobbin thread cutting device 50 according to the first embodiment of the present invention, the drive arm 60 of the closure means 53 of the bobbin shears 52 is connected to the bobbin thread cutting lever 33, the closing means 53 being actuated depending on the rotation of the bobbin cutting lever 33. threads.

However, in the bobbin thread cutting device 90 according to the second embodiment of the present invention, the means 53 for closing the bobbin thread cutting shears 52 is provided with the original driving device.

Thus, the closure means 53 for closing the bobbin thread cutting shears 52 comprises a solenoid 91 which is a driving device. The solenoid 91 is mounted in the base portion 1, the rod 91a extending to the right of the solenoid body 91. The solenoid 91 serves to move the rod 91a in the transverse direction.

In the bobbin thread cutting device 50 according to the first embodiment of the present invention, the drive arm 60 is connected to the left end of the coupling 61.

However, in a bobbin thread cutting device 90 according to the second embodiment of the present invention, the bar 91a is attached to the left end of the coupling 61. The left end of the coupling 61 is pivotable about an axis of rotation in a vertical direction with respect to the bar 91a.

-22 GB 302749 B6

When the solenoid 91 is set to the off state, the coupling 61 is set to be pulled to the left under the force of the tension spring 92, wherein the bobbin thread shears 52, set in the open state, are placed in the initial position.

When the solenoid 11 is switched from the off state to the on state, the coupling 61 moves to the right against the force of the tension spring 92, while the spool yarn coupling 62 rotates counterclockwise as seen from below.

In the same manner as the bobbin thread cutting device 50 of the first embodiment of the present invention, the bobbin thread cutting shears 52 are closed together with the counterclockwise rotation of the link 62.

When the solenoid 9J is then switched from the on state to the off state, the coupling 61 moves to the left, the bobbin thread shears 52 being returned to their initial position in the closed state.

The functions of the yarn cutting device according to the second embodiment of the present invention will now be described. The sewing machine control unit controls the solenoids 66, 72, 73 and 91 so that the yarn cutting device is operated as follows.

During the sewing operation of the sewing machine, the thread cutting device is set in the following initial state.

(1) The solenoid 72 is in the on state, the needle thread cutting base 76 and the solenoid arm 75 being held backwardly retracted against the force of the tension spring 82. The needle thread cutting base extension 76a does not rest against stop 85.

(2) The solenoid 73 is engaged, the rod 73a being held to push the support portion 21d and one of the ends of the lever 80 forward against the force of the tension spring 81. As a result, the other end of the lever 80 is held to push the front end of the needle thread cutting base 76 to the left against the force of the tension spring 83. As a result, the needle thread cutting scissors 15 are positioned in the ready position.

(3) The first cam face 21 is maintained so as to rest against the cam support portion 19a. wherein the needle thread cutting shears 15 are set in the open condition.

(4) The solenoids 66 and 11 are set to the off state, with the bobbin thread shears 52 being set in the open state.

(5) The protruding portion 56b of the upper knife 56 does not rest against the opening portion 51a of the base 11 of the needle plate 55, wherein the bobbin thread shears 52 are positioned in the initial position.

After the sewing machine has completed the buttonhole sewing operation, the solenoid 72 is switched off. Consequently, when the elongated portion 75a of the solenoid arm 75 engages with the elongated portion 76a of the needle thread cutting base 76, the needle thread cutting base 76 moves forward together with the needle thread cutting scissors 11 by applying the biasing force of the tension spring 82 wherein the elongated portion 76a is supported against the stop 85 so that the forward movement of the needle thread cutting base 76 is stopped.

Further, the solenoid 73 is switched off. As a result, the rod 73a and the support portion 21d come into contact with each other. The lever 80 then rotates counterclockwise (in the opposite direction to the arrow h in FIG. 6) due to the biasing force of the tension spring 81, while the lever 21 further rotates clockwise (in the opposite direction). direction as shown by arrow q in FIG. 6).

Together with the rotation of the lever 80, the front end of the needle thread cutting base 76 rotates to the right due to the biasing force of the tension spring 83, so that the scissors 11 for shearing

-23 GB 302749 Β6 the needle threads move to the right. Thereafter, the cam support portion 19a is supported on the closure plate 25, the cam support portion 19a being relatively pressed against the closure plate 25.

As a result, the needle thread cutting shears 15 close to cut the needle thread and insert and maintain the needle thread on the needle side. When the needle thread cutting scissors 15 are brought into a fully closed state, the movement of the scissors 15 and the forward end of the needle thread cutting base 76 to the right is suppressed by the closure plate 25. In a second embodiment of the present invention state, placed in the ending standby position.

The solenoid 91 is further energized. As a result, the bobbin thread cutting link 62 rotates counterclockwise as seen from below.

Due to the counterclockwise rotation of the link 62, the bobbin thread cutting device 90 performs the bobbin thread cutting operation in the same manner as the bobbin thread cutting device 50 of the first embodiment of the present invention.

Specifically, the bobbin winding arm 63 winds the bobbin thread, the upper knife 56 rotating relative to the lower knife 52 together with the rotation of the lower knife 57.

As a result, the bobbin thread shears 52 and the bobbin thread wound by the winding arm 63 are closed. Then, the bobbin thread shears 52, when closed, retain the bobbin side of the bobbin thread thus cut.

The solenoid 91 is then switched off, with the link 61 being pulled to the left by the tension spring 92. As a result, the bobbin thread cutting link 62 rotates clockwise, the bobbin thread cutting shears 52 returning. to its initial position in the closed state. Thus, the fabric can be inserted or removed through a manual or automatic operator operation.

Then the operator presses the sewing machine pedal so that the sewing machine starts the sewing operation in the next cycle. After the sewing operation of the sewing machine has commenced, the thread cutting device is operated as follows.

First, the solenoid 72 is energized, wherein the solenoid arm 75 is pulled back together with the needle thread cutting base 76 against the biasing force of the tension spring 82. Along with the rear thread cutting base 76, the scissors 55 are also provided for shearing. trimming needle threads move backwards.

Then, the solenoid 73 is energized, wherein the rod 73a pushes the lever 80 forward together with the support portion 21d. As a result, the lever 21 rotates counterclockwise, with the lever 80 rotating clockwise.

Together with the rotation of the lever 80, the needle thread cutting shears 50 rotate to the left together with the front end of the needle thread cutting base 76. The opening cam portion 21a pushes the cam support portion 19a together with the rotation of the lever 21. As a result, the needle thread cutting shears 15 open and release the needle thread. Thus, the solenoid 73 is brought on, causing the needle thread shears 15 to move to the standby position in the open state.

Subsequently, the solenoid 66 is energized so that the apex portion of the operating member 68 urges the pin 56a. As a result, the upper knife 56 rotates, wherein the bobbin thread shears 52, when closed, open and release the bobbin thread. After the bobbin thread shears 52 are opened, the solenoid 66 is switched off, with the operating member 68 rotating clockwise and returning to the initial state.

-24EN 302749 B6

In the thread cutting device according to the second embodiment of the present invention, the lever 21 to be driven by the solenoid 73 is arranged on the needle thread cutting base 76 and can move together with the needle thread cutting shears 15. therefore, even when the needle thread cutting shears 15 are positioned relatively at any position relative to the presser foot arm 7, the needle thread cutting shears 15 may open by rotating the lever 21.

Furthermore, since the needle thread cutting device 71 comprises the original solenoid 72, the needle thread cutting shears 15 are opened without interdependence with the movement of the arm 7 to the presser foot.

Similarly, since the bobbin cutting device 90 includes the original solenoid 66, the bobbin cutting shears 52 may open without interdependence on the movement of the fabric feeding mechanism.

Therefore, if the sewing machine is to start the sewing operation in the next cycle, the position of the fabric feeding mechanism is not limited by the opening operation of the needle thread shears 15 and the bobbin thread shears 52.

In addition, the needle thread cutting shears 15 are opened and closed by operating the original solenoids 72 and 73 in the needle thread cutting device 71, wherein the bobbin thread cutting shears 52 are opened and closed by operating the original solenoids 66 and 91 in the device 90 trimming bobbin thread. As a result, the timing of the operation of the thread-cutting device is in no way influenced by the operation of the other machine parts.

In a second embodiment of the present invention, it will be understood that certain particular constructional details may be appropriately changed since they are not limited to the exemplary embodiments.

For example, the solenoids 66, 72, 73, and 91 may be formed by air cylinders to move the rod forwards and backwards.

In addition, solenoids 66, 72, 73 and 91 may be pulsed motors. For example, in the case where the solenoid 73 is an impulsion motor, the drive shaft of the pulse motor extends in the transverse direction, wherein the pivot member extending almost perpendicular to the drive shaft is fixedly mounted on the drive shaft. The pivot member abuts one end of the lever 2L

When the pulse motor normally rotates, the pivot member pushes one of the ends of the lever 21 forward so that the needle thread cutting shears 15 move to the left, opening as described above. Conversely, if the pulse motor rotates in the opposite direction, the end of the lever 21 is pushed backward by the force of a tension spring 81 disposed at one end of the lever 80. As a result, the needle thread cutting shears 15 move to the right while closing. as described above.

Third embodiment

The yarn cutting apparatus according to the third embodiment of the present invention will now be described.

The thread cutting device of the third embodiment is embedded in a buttonhole sewing machine in the same manner as the first embodiment. As in the first embodiment, the sewing machine comprises a sewing machine frame, a needle, a hook mechanism, a drive mechanism for ensuring the vertical movement of the needle bar, a mechanism for ensuring the pivoting movement of the needle bars, a presser for pressing the fabric, a presser arm 7. the feet (shown in Fig. 9 and Fig. 10), the fabric feeding mechanism, the pressing bar and the fabric cutting mechanism.

In a third embodiment of the present invention, the same structural elements and features as in the first embodiment are designated by the same reference numerals, and their detailed description will be omitted.

The yarn cutting device according to the third embodiment comprises a needle thread cutting device 100 (shown in Figures 9 and 10) and a bobbin thread cutting device 130 (shown in Figures 12 and 13). .

As shown in the figures of FIG. 9 and FIG. 10, the needle thread cutting device 100 is comprised of one pulse motor 101, which constitutes the drive device, of the expander. with the needle thread shear drive mechanism 102 intended to open and close the needle thread shears 15 and to move them by driving the pulse motor 101.

The base 103 is arranged on the side surface of the arm body 3 (on the rear face of the arm body 3 in Fig. 2), wherein the pulse motor 101 and the drive mechanism 102 for operating the needle shears 15 are connected to the base 103. the pulse motor 101 extends to the right of the base 103 and is rotatable relative to the base 103.

The drive mechanism 102 for operating the needle thread cutting shears 15 comprises a lever 21, a cam mechanism 104, a needle thread cutting base 105, cam members 107 and 110, latch cams 108 and 111, and tension springs 109 and 110.

The pivot base 106 is disposed at the rear end at the bottom of the base 103 and is pivotable about a pivot axis in a vertical direction. The rear end of the needle thread trimming base 105 extending in the longitudinal direction is connected to the pivot base 106. The needle thread trimming base 105 is movable in the longitudinal direction relative to the pivot base 106.

In addition, the cam member 107 is attached to the left face of the base 103. The cam face 107a is formed on the left face at the front end of the cam member 107. The cam face 107a is inclined forward from left to right.

In addition, the base end of the latch cam 108 is attached to the left face of the base 103. The latch cam 108 is pivotable about a pivot axis in a transverse direction at its base end.

One of the ends of the tension spring 109 is connected to the latch cam 108 and the other end of the tension spring 109 is connected to the base 103. The tension spring 109 activates the latch cam 108 to rotate counterclockwise as seen from the side (right) .

The cam face 108a is formed on the right face at the other end of the latch cam 108. The cam face 108a is inclined upwards from left to right. The left surface of the second end of the latch cam 108 is planar.

The cam member 10 is attached to the right face of the needle threading base 105. The cam face 110a is formed on the right face at the rear end of the cam member U0. The cam face 110a is inclined rearward from left to right. Due to the longitudinal movement of the needle thread cutting base 105, the cam face 110a approaches or moves away from the cam face 107a.

-26GB 302749 Β6

In addition, the latch cam 111 is attached to the left face of the needle threading base 105. The latch cam 111 extends upward from left to right. The right surface of the latch cam 111 is planar.

When the latch cam 111 moves to the left in a state where the cam face 111a of the latch cam 111 rests against the cam platen 108a of the latch cam 108, the latch cam 108 rotates upward about its base end. Finally, the cam face 108a and the cam face 111a are brought into abutment with the left face of the latch cam 108 abutting the right face of the latch cam 111.

A tension spring 112 for activating the needle thread trimming base 105 towards the right is attached to the central portion of the needle thread trimming base 105. By means of the tension spring 112, the needle thread trimming base 105 is activated in the rotational direction to the right around the pivot base 106. The right surface of the latch cam 111 rests against the left surface of the latch cam 108, so rotating the needle thread trimming base to the right.

In addition, the lever 21 is attached to the right face of the needle thread cutting base 105 and is pivotable about a pivot axis in the transverse direction in its central portion. As in the first embodiment, the opening cam portion 21a is disposed at one end of the lever 21, wherein the first cam face 21b and the second cam face 21c are formed on the opening cam portion 21a. The lever 21 is actuated rearwardly by the tension spring 39.

The needle thread cutting shears 15 are arranged at the front end of the needle thread cutting base 105. The needle thread cutting scissors 15 comprise a pressure plate ,8, a movable blade 19, a fixed blade 20, and a cam abutment portion 9a, as in the first embodiment of the present invention.

In addition, the pressure bar 9 is attached to the front end of the needle threading base 105. The closure plate 25 is arranged on the top of the presser foot arm 7 in the same manner as in the first embodiment.

The cam mechanism 104 is further coupled to the drive shaft 101a of the impulse motor 101. The cam mechanism 104 comprises a drive cam 113 intended to be coupled to the drive shaft 101a of the impulse motor 101, a longitudinal cam arm 114 of the drive cam 113 to be coupled to the drive cam 113, 116 arranged in the longitudinal cam arm 114 of the drive cam 113, and a pin 117 arranged in the cam arm 115 of the shears 15,

The drive cam 113 is disposed on the right side of the base 103. The drive cam 113 is formed by an almost disc-shaped member whose center portion is attached to the drive shaft 101a of the pulse motor 101. The drive cam 113 rotates with rotation of the drive shaft 101a.

The detection portion 113a is formed on the outer peripheral portion of the drive cam 113, the sensor 118 detecting the edge 113b of the detection portion 113a. The sensor 118 detects the edge 113d, thereby detecting that the rotation angle of the drive cam 113 is set in the initial state. The drive cam 113 is provided with a first cam opening 113b and a second cam opening 113c.

The cam follower 114a is disposed at one end of the longitudinal cam arm 114 of the drive cam 113, and the pin 116 is disposed at the other end of the longitudinal cam arm 114 of the drive cam 113. In addition, the middle portion of the longitudinal cam arm 114 is attached to the base 103 about the axis of rotation in the transverse direction. The cam follower 114a is slidably inserted into the second cam opening 113c.

The pin 116 is inserted into the through hole 105a formed in the needle threading base 105. The through hole 105a is elongated obliquely longitudinally, the pin 116 being movable

In the longitudinal direction of the through hole 105a. The longitudinal cam arm 114 is pivotable about its central portion such that the needle thread cutting base 105 is movable longitudinally.

On the other hand, the cam follower 115a is disposed at one end of the cam arm 115 of the scissors 15, the pin 17 being disposed at the other end of the cam arm 115 of the scissors 15. In addition, the middle portion of the cam arm 115 of the scissors 15 is attached to the base 103; rotatable about the axis of rotation in the transverse direction. The cam follower 115a is movable in the first cam opening 11b. The pin 112 is near the other end of the lever 21.

The cam arm 115 of the scissors 15 rotates clockwise as seen from the side so that the pin 117 presses the other end of the lever 21 against the force of the tension spring 39, causing the lever 21 to rotate. On the other hand, the cam arm 115 the shears 15 rotate counterclockwise so that the lever 21 rotates in the opposite direction due to the biasing force of the tension spring 39.

Also in the third embodiment of the present invention, the lever 21 rotates against the force of the tension spring 39 in the same manner as in the first embodiment. As a result, the opening cam portion 21a presses on the cam support portion 19a so that the needle thread cutting shears 15 set to the closed state are opened.

The drive cam 113 will now be described in more detail with reference to the illustration of Figure 11. In this Figure 11, the first cam opening 113b and the second cam opening 113d are shown only by their axes.

When the needle thread cutting device 100 is initialized (during the sewing operation of the sewing machine), the first cam hole 11b is positioned in front of the second cam hole 113c as shown in FIG. 11. The first cam hole 113b lies opposite the second cam hole 113c around the center of rotation of the drive cam 113.

The first cam opening 113b is formed by a cam part 1A, a cam part 1B connected to the cam part 1A, and a cam part 1C connected to the cam part 1B.

The distance between the cam portion 1A and the center of rotation of the drive cam 113 is constant at any angle.

The distance between the cam portion 1B and the center of rotation of the drive cam 113 decreases from the cam portion 1A towards the cam portion IC.

The distance between the cam portion 1C and the center of rotation of the drive cam 113 is constant at any angle.

The second cam opening 113c is formed by a cam part 2A, a cam part 2B connected to the cam part 2A, a cam part 2C connected to the cam part 2B, a cam part 2D connected to the cam part 2C, and a cam part 2E connected to the cam part 2D .

The distance between the cam portion 2A and the center of rotation of the drive cam 113 is constant at any angle.

The distance between the cam portion 2B and the center of rotation of the drive cam 113 decreases from the cam portion 2A towards the cam portion 2C.

The distance between the cam portion 2C and the center of rotation of the drive cam 113 is constant at any angle.

The distance between the cam portion 2D and the center of rotation of the drive cam 113 increases from the cam portion 2C towards the cam portion 2E.

The distance between the cam portion 2E and the center of rotation of the drive cam 113 is constant at any angle.

In addition, the sensor 118 is connected to the sewing machine control. When sensing the edge 113d of the detection portion 113a, the sensor 118 sends a detection signal from the sewing machine control. Based on this signal from the sensor 118, the sewing machine control unit detects whether or not the needle thread cutting device 100 is in its initial state.

Only when the detection signal from the sensor 118 is sent to the sewing machine control can the sewing machine control decide that the rotation position of the drive shaft 101a of the pulse motor 101 is set to its initial state.

In the case where the detection signal is not supplied below the sensors 118, and in the case where the detection signal is maintained as an input, it is decided that the rotation position is not set to the initial state.

In addition, the sewing machine control device varies and controls the rotation speed of the pulse motor 101 via the motor control circuit based on the set value.

The bobbin thread cutting device 130 will now be described in more detail.

As shown in Figures 12 and 13, the bobbin thread cutting device 130 is of nearly the same construction as the bobbin thread cutting device 50 of the first embodiment of the present invention. To this end, the same construction elements as the bobbin thread cutting device 50 are designated with the same reference numerals, in particular the constructional differences will be described.

In the bobbin thread cutting device 50 of the first embodiment of the present invention, the drive arm 60 of the closing means 53 for closing the bobbin thread shears 52 is connected to the bobbin thread cutting lever 33, the closing means 53 being controlled in conjunction with the rotation of the lever 33 for cutting bobbin thread.

In addition, the opening means 54 of the bobbin thread shears 52 are controlled by driving the solenoid 66.

However, L1 of the bobbin thread cutting device 130 of the third embodiment of the present invention are the bobbin thread cutting means 53 and the scissor opening means 54

52 is driven by the driving force of one pulse motor

131

The bobbin thread cutting device 130 comprises opening spools 52 for cutting the bobbin thread, the closing means 53 of the scissors 52 for bringing the scissors 52 set in the closed state, the opening means 54 of the scissors 52 for putting the scissors 52 set in the open state closed, a pulse motor 131 (not shown in FIG. 12) that constitutes the driving means, operating means 133 for controlling the operation of the shutter means 53 of the scissors 52 by one of the rotary operations of the pulse motor 131 and operation of the pulse motor 131 and a base 132 (not shown in FIG. 12) to receive the pulse motor 131.

The base 132 is a plate-shaped member and is mounted almost horizontally in the base portion. The pulse motor 131 is attached to the bottom surface of the base 132. The drive shaft 131a of the pulse motor 13I projects upwardly from the base 132, rotating relative to the base 132.

-29EN 302749 B6

The operating means 133 comprises a second drive cam 134, a first coupling member 135 and a second coupling member 136. The second drive cam 134 is disposed above the base 132. The second drive cam

134 is formed by an almost plate-shaped member whose center portion (pivot center) is attached to the drive shaft 131a. The second drive cam 134 rotates together with the rotation of the drive shaft 131a.

The detection portion 134a is formed on the outer peripheral portion of the second drive cam 134, the sensor 137 detecting the edge 134d of the detection portion 134a. The sensor 137 detects the edge 134d. thereby actually detecting whether the rotation angle of the second drive cam 134 is set in the initial state.

The second drive cam 134 is provided with a first cam hole 134b and a second cam hole 134c. The first cam opening 134b is opposed to the second cam opening 134c about the center of rotation of the second drive cam 134.

The first cam opening 134b is formed by a cam portion 3A, a cam portion 3B connected to the cam portion 3A, and a cam portion 3C connected to the cam portion 3B.

The distance between the cam portion 3A and the center of rotation of the second drive cam 134 is constant at any angle.

The distance between the cam portion 3B and the center of rotation of the second drive cam 134 increases from the cam portion 3A towards the cam portion 3C.

The distance between the cam portion 3C and the center of rotation of the second drive cam 134 is constant at any angle.

The second cam opening 134c is formed by the cam portion 4A, the cam portion 4B connected to the cam portion 4A, and the cam portion 4C connected to the cam portion 4B.

The distance between the cam portion 4A and the center of rotation of the second drive cam 134 is constant at any angle.

The distance between the cam portion 4B and the center of rotation of the second drive cam decreases from the cam portion 4A towards the cam portion 4C.

The distance between the cam portion 4C and the center of rotation of the second drive cam 134 is constant at any angle.

The cam follower 135a is disposed at one of the ends of the first L-shaped coupling member 135 and is displaceably received in the first cam opening 134b. First coupling member

135 is attached to the base portion pivotally about an axis of rotation in a vertical direction in its bent portion.

The other end of the first connecting member 135 is pivotally connected to the rear end of the connecting member 61 of the closure means 53 of the scissors 52 for cutting the bobbin thread. The coupling 61 of the first embodiment of the present invention is disposed transversely while the coupling 61 of the third embodiment of the present invention is disposed longitudinally. The leading end of the link member 61 is pivotally connected to one of the ends of the link member 62 for cutting the bobbin thread.

The cam follower 136a is disposed at one end of the second L-shaped coupling member and is displaceably received in the second cam opening 134c. Second coupling member

136 is attached to the base portion pivotally about an axis of rotation in a vertical direction in its bent portion.

-30 GB 302749 Β6

The other end of the second connecting member 136 is pivotally connected to the rear end of the connecting member 67 of the opening means 54 of the scissors 52 for cutting the bobbin thread.

In addition, the sensor 137 is connected to the sewing machine control. When sensing the edge 134d of the detection portion 134a, the sensor 137 sends a detection signal to the sewing machine control. Based on this detection signal received from the sensor 137, the sewing machine controller detects whether or not the bobbin thread cutting device 130 is in its initial state, in the same manner as the needle thread cutting device 100.

In addition, the sewing machine controller varies and controls the rotation speed of the pulse motor 131 via the motor drive circuit based on the set value.

FIG. 15 is a block diagram illustrating the construction of a sewing machine used for the third embodiment of the present invention.

The sewing machine has a structure such that each drive source is connected to a control circuit 210.

The control circuit 210 is such that the ROM ROM 212, the random access RAM 213, the drive mechanism 214 of the pulse motor 220 for feeding in the Y direction to drive each pulse motor, the pulse motor drive 215 for positioning the needle, the drive device 216 a pulse motor for pivoting needle movement, a needle threading device drive mechanism 217, a bobbin threading device drive mechanism 218, a sewing machine engine drive unit 219, and a cylinder drive unit 228 are connected to a CPU 211 as shown 15.

In addition, the control panel 220, which will be described in more detail below, the trigger switch 225 for issuing instructions to start the sewing operation, and the sensor 137 for the bobbin thread cutting device 130 are connected to the CPU central controller 211.

The Y-direction feed pulse motor 220, driven by the Y-direction pulse motor 220 drive mechanism 214, feeds in a predetermined direction the fabric on which the buttonhole stitches are to be formed during the sewing operation.

The pulse needle swing motor 222, driven by the drive mechanism 216 of the pulse needle swing motor 222, serves to provide a needle swing movement that moves in the hole width direction by a predetermined distance.

The needle positioning pulse motor 221, driven by the drive mechanism 215 of the needle positioning pulse motor 221, serves to change the needle position when the needle is pivoted.

A pulse motor 101 (a needle thread cutting machine), driven by the drive mechanism 217 of the needle thread cutting machine, serves to drive the needle thread cutting machine to cut the needle thread inserted into the needle after completion of the sewing operation. it may be, for example, a motor or a solenoid.

The pulse motor 131, driven by the drive mechanism 218 of the bobbin thread cutting device, serves to cut the bobbin thread running from the hook to the fabric after completion of the sewing operation, which will now be described in more detail below.

The sewing machine motor 150, driven by the drive mechanism 219 of the sewing machine motor 150, serves to rotate the main shaft to drive the needle and the hook.

The control data 212 and buttonhole control program 212a are stored in the permanent ROM 212.

-31 CZ 302749 Βή

In addition, the ROM 212 is provided with a sewing database 212b in which the pattern data sets for determining the shape and size of the buttonhole to be created are stored.

The CPU central controller 211 controls each engine and drive train via a drive train based on signals inputted via the control panel 200 and various switches and detection signals sent from different sensors not shown, in accordance with the control program 212a, stored in non-volatile ROM 212 by setting a predetermined region of random access memory RAM 213 as a work area.

When the trigger switch 225 is pressed, the CPU central controller 211 drives the sewing machine motor 150, the pulse motor 220 to feed in the Y direction, the pulse motor 221 to lock the position of the needle, and the pulse motor 222 to swing the needle through each drive. whereby a buttonhole stitch is formed.

In addition, the CPU central controller 211 drives the knife cutting roller 229 through the drive mechanism 228 of the roller 229, whereby a buttonhole is formed with the knife cutting knife.

Further, the pulse motor 101 and the pulse motor 131 for cutting the needle thread and bobbin thread are respectively driven after completion of the buttonhole forming operation.

The operation of the thread cutting device will now be described with reference to the graph shown in FIG. 14.

In the graph shown in Fig. 14 (a), the horizontal coordinate axis represents the number of revolutions of the drive shaft 101a that is reached when the pulse motor 101 is set to its initial state.

The vertical coordinate axis means the distance of the longitudinal movement of the needle thread trimming base 105 from the initial state, the distance of the transverse movement of the front end of the needle thread trimming base 105 from the initial state, and the magnitude opening the scissors 15 for cutting the needle thread.

In the graph shown in Fig. 14 (b), the horizontal coordinate axis indicates the number of revolutions of the drive shaft 13a. This is achieved when the pulse motor 131 is set to its initial state.

The perpendicular coordinate axis means the distance of movement of the bobbin thread shears 52 (lower blade 57) from the initial state, and the amount of rotation of the operating member 68 from the initial state.

First, the needle thread cutting device 100 is initialized during the sewing operation of the sewing machine, as follows:

(1) The edge 113d of the detection portion 113a is sensed by the sensor 118, wherein the drive shaft 101a of the pulse motor 101 and the drive cam 113 form an angle in the initial state. As a result, the cam follower 114a is located at the point P of the first cam opening 113b (see FIG. 11).

(2) One of the ends of the lever 21 is located in the rear portion by the action of the biasing force of the tension spring 39. For this purpose, the opening cam portion 21a does not rest against the cam support portion 19a. In addition, the needle thread shears 15 are kept open.

(3) The right surface of the latch ratchet cam is held so that it rests on the left surface of the latch cam 108. As a result, the rotation of the needle thread cutting base 105 to the right by the action of the tension spring 112 is prevented.

(4) The cam face 110a of the cam member 110 does not rest against the cam face 107a of the cam member 107.

(5) The needle thread cutting scissors 15 are positioned at a distance from the vertical needle path and the vertical path of the cloth cutting knife. Specifically, the needle thread shears 15 are positioned in the open position in the open condition.

In addition, the bobbin thread cutting device 130 is set to its initial state during the sewing operation of the sewing machine as follows:

(1) The edge 134d of the detection portion 134a is sensed by the sensor 137, wherein the drive shaft 131a of the pulse motor 131 and the second drive cam 134 form an angle of rotation in the initial state.

(2) The cam follower 135a is positioned at the R point (see FIG. 12) of the first cam hole 134b, wherein the cam follower 136a is positioned at the S point (see FIG. 12) of the second cam hole

134c.

(3) The protruding portion 56b of the upper knife 56 does not rest against the opening portion 51a of the base 51 of the needle plate 55, wherein the spools 52 for cutting the bobbin thread are placed in the initial state.

As a result, the bobbin thread shears 52 are kept open.

If the control gear normally rotates the pulse motor 101 after the sewing operation has been completed, the drive cam ΐ 13 rotates clockwise (in the direction of the arrow k shown in Fig. 11), with the cam follower 115a sliding along the cam portion LA.

However, since the distance between the cam portion 1A and the center of rotation of the drive cam 113 is constant, the cam arm 115 of the needle thread shears 115 does not rotate.

If, on the other hand, the cam follower a 14a slips on the cam part 2D due to the rotation of the drive cam 113 counterclockwise, the distance between the center of rotation> 5 of the cam follower 113 and the cam follower 114a increases according to this slip.

As a result, the cam follower 114a moves rearwardly, with the longitudinal cam arm 114 of the drive cam 113 rotating clockwise as seen from the side. As a result, the pivot 116 rotates forward with the needle thread cutting base 105 moving forward.

When the latch cam 111 moves forward together with the forward movement of the needle thread cutting base 105, the abutment of the right surface of the latch cam 111 and the left surface of the latch cam 108 is released, the distance between the cam face 107a and the cam face 108a also increasing.

When the right surface of the ratchet cam v 1 and the left surface of the ratchet cam 108 are released, the forward end of the needle thread cutting base 105 rotates to the right around the pivot base 106 by applying the biasing force of the tension spring 112.

By rotating the needle thread cutting base 105 to the right, the cam support portion 19a is supported on the closure plate 25. In the same manner as the first embodiment, the needle thread cutting shears 15 are closed. The needle thread cutting shears 15 are thus closed to cut the needle thread and to hold the needle thread cut off.

Furthermore, if the drive cam 113 rotates counterclockwise, the cam follower 114a moves along the cam portion 2E, with the distance between the cam portion 2E and the center of rotation of the drive cam 113 constant.

Therefore, even when the cam follower 114a is moved along the cam portion 2E, the longitudinal cam arm 114 of the drive cam 113 does not rotate, and the forward movement of the needle thread cutting base 105 is also stopped.

Thereafter, the control device ensures reverse rotation of the pulse motor 101.

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If the drive shaft 101a of the pulse motor 101 returns to its initial state (rotated back by the same number of pulses as the number of pulses during normal rotation), the control device stops the reverse rotation of the pulse motor 101.

As a result of the reverse rotation of the pulse motor 101, the drive cam 11 rotates clockwise (in the direction of arrow j in Figure 11), with the cam follower 115a moving the cam portion 1A and the cam follower 114a moving the cam portion 2E and subsequently the cam portion 2D .

Consequently, the cam arm 15 of the needle thread shears 15 does not rotate, while the longitudinal cam arm 114 of the drive cam 113 rotates counterclockwise, and the needle thread trimming base 105 moves rearward.

When the cam member 110 moves rearward together with the needle thread trimming base 105, the cam face 110a is supported on the cam face 107a. If the cam member i? 1 10 moves backward together with the needle thread cutting base 105, so the front end of the needle thread cutting base 105 rotates to the left due to the action of the cam member 110 and the cam member 107 against the biasing force of the tension spring 1112.

Further, if the control device normally rotates the pulse motor 101, the second drive cam 134 rotates

2o in the clockwise direction (in the direction of arrow n in FIG. 12) with the cam follower 136a moving the cam portion 4A. However, since the distance between the cam portion 4A and the center of rotation of the second drive cam 134 is not constant, the second coupling 136 does not rotate.

On the other hand, the cam follower 135a moves the cam portion 3B by rotation

2? the second drive cam 134 clockwise, so the distance between the center of rotation of the second drive cam 134 and the cam follower 13a decreases due to this displacement. Therefore, the cam follower 135a moves to the right, with the first coupling 135 rotating counterclockwise as seen from below.

Together with the rotation of the first coupling member 135, the bobbin winding arm 63 rotates counterclockwise as seen from below, with the lower blade 57 rotating clockwise. During rotation, the take-up arm 63 winds the bobbin thread onto the lower knife 57 after it contacts the bobbin thread.

On the other hand, the bobbin thread shears 52 close due to the rotation of the lower knife 57 to cut the wound bobbin thread and to hold the bobbin thread thus cut. Immediately before the spool yarn winding arm 63 contacts the spool yarn, the control device reduces the rotational speed of the pulse motor 131.

As a result, the rotational speed of the winding arm 63 for winding the bobbin thread will decrease after the winding arm 63 winds the bobbin thread. Therefore, it is possible to prevent the bobbin winding arm 63 from accidentally cutting the bobbin thread.

The rotational speed of the bobbin thread cutting shears 52 is also further reduced, so that the retained bobbin thread can be prevented from sliding off the bobbin thread cutting shears 52.

Furthermore, if the second drive cam 134 rotates clockwise, the cam follower 135a moves the cam part 3A. The distance between the cam part 3A and the center of rotation of the second drive cam 134 is constant. Therefore, even if the cam follower 135a moves the cam portion 3A, the first coupling member 135 does not rotate.

As a result, the bobbin thread shears 52 do not rotate. Specifically, the spools 52 for cutting the bobbin thread are located in the shear position in the closed state.

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Thereafter, the control device ensures reverse rotation of the pulse motor 13_L. If the drive shaft 131a of the pulse motor 131 returns to its initial state (rotated back by the same number of pulses as the number of pulses during normal rotation), the control device stops the reverse rotation of the pulse motor 131.

By reversing the pulse motor, the second drive cam 134 rotates counterclockwise, with the cam follower 136a moving the cam portion 4A and the cam follower 135a moving the cam portion 3A and subsequently the cam portion 3B.

Consequently, the second coupling 136 does not rotate, with the first coupling 135 rotating in a clockwise direction. Together with the rotation of the first coupling member 135, the bobbin thread shears 52 return to their initial position in the closed state.

The operator then depresses the sewing machine pedal so that the sewing machine commences the sewing operation in the next cycle, even after the sewing machine commences the sewing operation, the yarn cutting device operates as follows.

First, when the control device provides for the reverse rotation of the pulse motor 101, the drive cam 113 rotates clockwise, the cam follower 114a shifting the cam portion 2C, while the cam follower 115a shifts the cam portion 1B.

Since the distance between the cam portion 2C and the center of rotation of the drive cam 113 is constant, the longitudinal cam arm 114 of the drive cam 113 does not rotate, and the needle thread cutting base 105 does not move forward.

Since, on the other hand, the cam follower 115a shifts the cam portion 1B, the distance between the center of rotation of the drive cam 113 and the cam follower 115a decreases. Therefore, the cam follower 115a moves rearwardly.

As a result, the cam arm 115 of the needle thread cutting scissors 15 rotates clockwise as seen from the side, the pin 117 moving forward. The pin 117 therefore pushes the other end of the lever 21 forward, with the lever 24 rotating counterclockwise as seen from the side.

By rotating the lever 21, the opening cam portion 21a then presses on the cam support portion 19a, the needle thread cutting shears 15 opening and releasing the needle thread.

Further, if the drive cam 113 rotates in a clockwise direction, the cam follower 114a moves the cam portion 2B and then the cam portion 2A, with the cam follower 115a moving the cam portion IC.

Since the distance between the cam portion IC and the center of rotation of the drive cam 113 is constant, the cam arm 115 of the needle cutting shear 15 does not rotate. Therefore, the cam arm 115 of the scissors 15 stops when the lever 21 is pushed forward.

Since, on the other hand, the cam follower 114a moves the cam portion 2B, the distance between the center of rotation of the drive cam 113 and the cam follower 114a decreases. Therefore, the cam follower 114a moves forward.

As a result, the longitudinal cam arm 14 of the drive cam 113 rotates counterclockwise, with the pivot 116 rotating rearwardly. The cam member 110 therefore moves rearwardly together with the needle thread trimming base 105. Thus, the needle thread cutting base 105 rotates to the left against the biasing force of the tension spring 112 due to the action of the cam member 107 and the cam member 10.

CZ 302749 Β6

When the needle thread trimming base 105 rotates to the left, the cam face 111a of the ratchet cam 11 rests against the cam face 108a of the ratchet cam 108. Further, when the needle thread cutting base 105 rotates counterclockwise, the cam face 111a pushes the cam face. the face 108a, wherein the latch cam 108 rotates upward about its base end.

Finally, the latch cam 111 moves to the left of the latch cam 108 so that the cam face 11a of the latch cam 11 and the cam face 108a of the latch cam 108 is released. As a result, the latch cam 108 rotates downward about its base end under the action of the biasing force of the tension spring 109.

Further, if the control device provides for the conventional rotation of the pulse motor 101, the drive cam 113 rotates counterclockwise, with the cam follower 11a moving the cam portion 2A and then the cam portion 2B, with the cam follower 115a moving the cam portion IC.

Since the distance between the cam portion IC and the center of rotation of the drive cam 113 is constant, the cam arm 15 of the needle thread shears 15 does not rotate. Therefore, the cam arm 115 of the scissors 5 is stopped when the lever 21 is pushed forward.

Since the cam follower 14a, on the other hand, moves the cam portion 2B, the longitudinal cam arm 114 of the drive cam 113 rotates clockwise, with the pivot 116 rotating forward. The cam member 110 therefore moves forward together with the needle thread trimming base 105, wherein the longitudinal position of the needle thread trimming base 105 coincides with the longitudinal position in the initial state.

When the needle thread trimming base 105 moves rearwardly, the needle thread trimming base 105 rotates to the left due to the biasing force of the tension spring 112. If the needle thread trimming base rotates to the left, the left surface of the latch cam 108 rest against the right surface of the latch cam 111.

As a result, turning the needle thread trimming base to the right is prevented, and the transverse position of the needle thread trimming base 105 becomes identical to the initial position in the initial state.

Specifically, when the cam follower 114a moves from the cam portion 2B to the cam portion 2C, the needle thread trimming base 105 is positioned in the initial state, the needle thread trimming shears 15 being positioned in the open position in the open state.

Further, if the drive cam 113 rotates counterclockwise, the cam follower 114a moves the cam portion 2C, while the cam follower 115a moves the cam portion LB.

Since the distance between the cam portion 2C and the center of rotation of the drive cam 113 is constant, the longitudinal cam arm 114 of the drive cam 113 does not rotate. As a result, the needle thread trimming base 105 does not move to the initial state, and the needle thread trimming shears 15 do not move from the standby position.

As the cam follower 115a on the other hand moves the cam portion 1B, the cam arm 115 of the scissors 15 rotates counterclockwise, with the pivot 117 rotating rearwardly. As a result, the lever 21 is rotated clockwise by the biasing force of the tension spring 39, the opening cam portion 21a being separated from the cam support portion 19a.

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If a conventional rotation of the same number of pulses as the number of reverse rotation pulses is performed, the control device stops the normal rotation of the pulse motor 101, so that the needle thread cutting device 100 is brought into the initial state.

Further, if the control device provides for the reverse rotation of the pulse motor 131, the second drive cam 134 rotates counterclockwise (in the direction of arrow m in Fig. 12), the cam follower 135a shifting the cam portion 3C, and the cam follower 136a shifting the cam portion 4B and then the cam portion 4C.

Since the distance between the cam portion 3C and the center of rotation of the second drive cam 134 is constant, the first coupling member 135 does not rotate, while the spools 52 for cutting the bobbin thread do not move.

Since on the other hand the cam follower 136a moves the cam portion 4B, the distance between the center of rotation of the second drive cam 134 and the cam follower 136a decreases. As a result, the second coupling 136 rotates clockwise as seen from below.

Together with the rotation of the second link member 136, the operating member 68 rotates counterclockwise as seen from below. The operating member 68 pushes the pin 56a through its apex portion as a result of rotation. Accordingly, the upper knife 56 is rotated, with the spools 52 for cutting the bobbin thread set in the closed state opening and releasing the bobbin thread.

Further, if the second drive cam 134 rotates counterclockwise, the cam follower 136a moves the cam portion 4C. However, since the distance between the cam portion 4C and the center of rotation of the second drive cam 134 is constant, the second coupling 136 does not rotate. Therefore, the bobbin thread cutting shears 52 are therefore kept in an open condition.

Further, if the control device provides for the conventional rotation of the pulse motor 131, the second drive cam 134 rotates clockwise such that the cam follower 135a moves the cam portion 3C, and the cam follower 136a moves the cam portion 4C and then the cam portion 4B.

Since the distance between the cam portion 3C and the center of rotation of the second drive cam 134 is constant, the first coupling member 135 does not rotate, while the spools 52 for cutting the bobbin thread do not move.

The cam follower 136a, on the other hand, moves the cam portion 4B such that the second coupling member 136 rotates counterclockwise as seen from below. Along with the rotation of the second link member 136, the operating member 68 rotates clockwise as seen from below, the contact of the apex of the operating member 68 and the pin 56a released.

Further, if a conventional rotation of the same number of pulses as the number of pulses during the reverse rotation is performed, the control device stops the normal rotation of the pulse motor 131, and the bobbin thread cutting device 130 is reset.

In the thread cutting device according to the third embodiment of the present invention, the lever 21 to be driven by the pulse motor 101 is arranged on the basis of the needle thread cutting 105, wherein the lever 21 can move together with the thread cutting shears 15.

Therefore, even when the needle thread cutting shears 15 are located in any relative position with respect to the presser foot arm 7, the needle thread cutting shears 15 may open due to the rotation of the lever 21.

The needle thread cutting device 100 further comprises an original pulley motor 101, the bobbin thread cutting device 130 comprising an original pulse motor 131.

The needle thread trimming and the bobbin thread cutting shears 52 are therefore opened without interconnection with the presser foot arm 7.

Thus, if the sewing machine is to start the sewing operation in the next cycle, the position of the fabric feeding mechanism is not limited by the opening operation of the needle thread shears 55 and the bobbin thread shears 52.

In addition, the needle thread cutting device 100, as well as the bobbin thread cutting device 130, performs the opening and closing operations of the scissors by driving one pulse motor. As a result, the number of parts as well as the cost of the thread cutting device can be reduced.

In a third embodiment of the present invention, it will be understood that particular detailed constructions may also be suitably altered, without being limited to the particular embodiment.

Industrial applicability

In accordance with the present invention, the yarn cutting device is provided with a drive device. The drive means drives the needle thread shears and the bobbin thread shears into the open state. As a result, the opening operation of the scissors is not performed in conjunction with the movement of the fabric feeding mechanism.

Thus, when the sewing machine operation is completed, the needle thread cutting shears perform a shearing operation, after which the sewing machine then starts the sewing operation in the next cycle, wherein the position of the fabric feeding mechanism is not affected by the opening operation of the needle thread cutting shears.

For example, in the case where the sewing operation can be carried out by the actual movement of the fabric feeding mechanism, even if the relative position between the fabric feeding mechanism and the sewing object is not adjusted if the sewing operation in the next cycle is the same as in the previous cycle wherein the buttonhole sewing is performed in different parts, it is not necessary to re-adjust the seamed object. As a result, increased labor productivity can be ensured.

In addition, the scissors carry out the opening and closing operation by driving the drive train, which initially provided with a thread cutting device. Thus, the timing of the opening and closing operations of the scissors is not affected by the operation of the other sewing machine mechanisms. This makes it very easy to change the opening time of the scissors for the respective sewing conditions.

Claims (7)

PATENT CLAIMS -381. A buttonhole sewing machine (11) for sewing a buttonhole using a needle thread and a bobbin thread, comprising: needle thread shears (15) that are openable and collapsible and are arranged to cut the needle thread and hold the cut needle thread by clamping it from its open condition, and spool thread cutters (52) that are openable and collapsible arranged to cut the spool yarn and to hold the cut spool yarn by clamping them from the open condition, characterized in that the yarn cutting device (11) further comprises: 5, a drive device configured to drive the scissors (15) to cut the needle thread from the clamped state to the open state without interconnecting the movement of the fabric feeding mechanism, and a drive device arranged to drive the scissors (52) to cut the bobbin thread from the clamped state to an open condition without interconnecting with the movement of the tissue feed mechanism. The thread cutting device (11) according to claim 1, characterized in that the drive device is further arranged to drive the needle thread shears (15) from the opened to the clamped state. The yarn cutting device (11) according to claim 2, characterized in that the drive device is a pulse motor (101), the yarn cutting device (11) further comprising: control means (104) for actuating the scissors (15) for cutting the needle thread for introduction 20 scissors (15) for trimming the needle thread from the clamped state to the open state by rotating the pulse motor (101) in one direction, and for bringing the scissors (15) for trimming the needle thread from the opened state to the clamped state by rotating the pulse motor (101) in the opposite direction. 25 The yarn cutting device (11) of claim 1, further comprising a drive device configured to drive the shears (52) to cut the spool yarn from an open condition to a closed condition. The yarn cutting device (11) according to claim 1, characterized in that the driving device (30) is a pulse motor (131), the yarn cutting device (11) further comprising: control means (133) for actuating the spool yarn (52) for shearing the spool yarn (52) for shearing the spool yarn (52) from the closed state to the open state by rotating the pulse motor (131) in one direction; cutting the spool yarn from the open to the closed state by rotating the pulse motor (131) in the opposite direction. Thread cutting device (11) according to claim 5, characterized in that the at least one driving speed of the pulse motor, which is a spool shear (52) 40, and the speed of drive of the pulse motor by which the bobbin shears (52) are brought into the open state is variable. A thread cutting device (11) according to any one of claims 1 to 6, wherein each of the drive means is a device selected from the group consisting of a solenoid, an air cylinder and a pulse motor.