JPH067683U - Sewing machine thread trimmer - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a thread trimming device for a sewing machine, which is capable of optimizing a length of a thread connected to a seam start end. According to the present invention, the sewing machine is configured to bend the yarns I1 and I3 to be cut by a yarn pulling arm 11 to generate tension and then to cut the yarn with a movable knife 4 directly below the needle drop hole 1a. In the thread cutting device, the groove 12 for introducing the thread to be cut is formed at the tip of the thread winding arm 11, and the holding plate 13 for holding the thread inserted in the groove with the thread winding arm. By being provided, a sufficient tension can be generated in the yarn with a minimum necessary amount of boring.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thread cutting device of a sewing machine, which reciprocates a movable knife and a thread winding arm in opposite directions to cut a thread from a needle plate to a sewing machine hook in a bent state.

[0002]

[Prior art]

 At present, thread cutting devices for sewing machines are roughly classified into those having a movable knife and a fixed knife and those having only a movable knife. Among these, as a thread trimming device equipped with a fixed knife and a movable knife, the movable knife horizontally reciprocates below the needle plate to capture and withdraw the thread from the needle plate to the sewing machine hook, and between it and the fixed knife. It is generally known that the thread is sheared by a needle, but with this type of thread trimmer, the shape of the knife can be simplified, but the fixed knife is set at a position away from the needle drop path, so long cloth There is a problem that the thread remains and the quality of the sewn product is impaired.

On the other hand, as a thread cutting device for cutting a thread using only a movable knife, for example, a rotary type thread cutting device is known, and in this device, a rotary type thread cutting device is held on a side of a sewing machine hook. The movable knife is rotated along the arc-shaped path set around the sewing machine hook to cut the thread just below the needle plate, and the thread remaining on the cloth can be greatly reduced. It has the advantage of

4 to 7 are views showing this rotary type thread cutting mechanism. In FIG. 4, reference numeral 1 denotes a needle plate mounted on the sewing machine bed, and the needle plate 1 has a needle drop hole 1a through which a sewing needle N is inserted. Reference numeral 2 denotes a known sewing machine hook housed in a sewing machine bed, and a bobbin bobbin (not shown) is housed inside the sewing machine via a bobbin case 3.

Reference numeral 4 denotes a movable knife having an arc shape and having a blade portion 4a at one end as shown in FIG. Reference numeral 5 denotes a thread winding arm 5 having an arcuate shape having a diameter smaller than that of the movable knife 4, and a tip portion 5a has a shape as shown in FIG. The movable knife 4 and the thread hoisting arm 5 are adapted to move around the circumference of the sewing machine hook 2 along arcuate paths having different curvatures, as shown in FIG. 4 during the sewing operation. It is held at the initial position set on both sides of the sewing machine hook 2.

During the thread cutting operation, the thread plucking arm 5 rotates in the clockwise direction in the drawing and the movable knife 4 rotates in the counterclockwise direction in conjunction with the rotation of the sewing machine lower shaft 5. As a result, first, the thread hoisting arm 5 selects only the upper thread I1 and the lower thread I3 connected to the cloth from the two upper threads and the lower thread I3 located between the sewing machine hook 2 and the needle plate 1. It is captured and bent (see FIG. 6), and then the blade portion 6a of the movable knife 4 contacts the upper thread I1 and the lower thread I3 located between the needle plate 1 and each thread I1 just below the needle drop hole. , I3 is cut.

As described above, in the rotary type thread cutting device that cuts the thread only with the movable knife 4, the threads I1 and I3 are bent by the thread winding arm 5 so that the threads I1 and I3 to be cut can be obtained. A tension force is generated, and the tension force increases the pressure contact force between the blade portion 6a of the movable knife 4 and the thread to cut the thread.

[0008]

[Problems to be solved by the device]

 However, in the conventional thread cutting device described above, in order to obtain the tension required for cutting, as shown in FIG. 7, the thread is unwound until the bending angle of the lower thread I3 in the thread winding arm 5 becomes an acute angle. It was necessary to sufficiently increase the frictional resistance between the thread hoisting arm 5 and the threads I1 and I3. Therefore, in this type of thread trimming device, the length of the remaining thread that is continuous with the end of the seam can be shortened, but the length of the bobbin thread from the bobbin case 3 to the cut end is conversely long, and In the sewing operation, the long bobbin thread was entangled with the bottom surface of the cloth in a bird's nest shape or was largely led out to the bottom surface of the cloth, resulting in deterioration of the quality of the sewn product.

This invention has been made in view of the above-mentioned conventional problems, and it is possible to shorten the length of the residual thread which is continuous with the seam end portion of the cloth, and of course, the length of the thread which is continuous with the seam start end portion. An object of the present invention is to provide a thread cutting device for a sewing machine that can also optimize the sewing machine.

[0010]

[Problems to be solved by the device]

 This invention reciprocates the movable knife and the thread plucking arm, which are arranged according to both rules of the sewing machine hook, in opposite directions, and the upper thread and the needle thread positioned between the needle plate and the sewing hook are moved by the thread plucking arm. A rotary type thread of a sewing machine in which the bobbin thread is caught and bent, and the thread cutting operation is performed by bringing the upper thread and the bobbin thread from the thread bobbin arm to the sewing machine hook into contact with the blade portion of the thread trimming knife. In the cutting device, a groove is formed at the tip of the thread hoisting arm to allow the upper thread and the lower thread to be caught, and at the same time, the upper and lower surfaces of the thread hoisting arm are always pressed into contact with the groove. A holding plate is provided to hold the invading upper thread and lower thread between the thread winding arm and the arm.

[0011]

[Action]

 In this invention, since the thread hoisting arm intrudes the thread into the groove formed at the tip of the arm and then further intrudes the thread between the arm and the clamping plate to clamp the thread, the thread does not have to be bent at an acute angle. A high frictional force is generated between the thread plucking arm and the thread, and a large tension can be generated in the thread from the thread plucking arm to the needle plate. For this reason, an appropriate thread cutting operation can be obtained, and the length of the thread from the cut end portion to the bobbin case and the like held in the sewing machine hook can be kept to a necessary minimum, and the next sewing is performed. It is possible to prevent a long thread from being left at the seam start end of the sewn product.

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. The same or corresponding parts as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in the side view of FIG. 1, the thread cutting device according to this embodiment is provided with a thread winding arm 11 shown in FIGS. 2 and 3 instead of the thread winding arm 5 in the conventional rotary type thread cutting device. It is a thing.

As shown in the figure, the thread plucking arm 11 has an L-shaped bent shape, and its rear end is attached to a fixed base 10 that rotates in conjunction with the sewing machine lower shaft during thread cutting operation. There is. Further, as shown in FIG. 3, a groove 12 extending in the forward movement direction (arrow A direction) is formed at the tip of the thread winding arm 11, and one side forming one side of the groove 12 is formed. A thread dividing inclined surface 11A that is inclined outward is formed at the tip of the portion, and a thread introducing inclined portion 11B that is inclined inward is formed on the other side of the groove 12. Has been formed. The width of the groove 12 is formed so that a thread can be inserted therein.

Further, 13 is a sandwiching plate made of a flexible member. The holding plate 13 has its rear end fixed to the upper surface of the rear end of the thread winding arm 11, and is always in pressure contact with the upper surface of the thread winding arm 11 to cover the latter half of the groove 12. ing. The other structures including the movable knife 4 are the same as those of the above-mentioned conventional technique, and the duplicate description will be omitted.

In this embodiment having the above-mentioned configuration, during thread cutting operation, the thread plucking arm 11 moves clockwise (forward direction A) and the movable knife 4 moves counterclockwise (forward direction) as in the conventional device. Each rotate in direction B). In this forward movement process, the thread hoisting arm 11 firstly, as shown in FIG. 3 (a), the two upper threads I1 and I2 existing between the sewing machine hook 2 and the needle plate 1 and one lower thread. The needle thread I2 connected to the sewing needle N is excluded from the thread I3 to the outside by the thread dividing inclined surface 11A, and the needle thread I1 and the bobbin thread I3 are introduced into the groove by the thread introducing inclined surface. The upper threads I1 and I3 introduced at a point slightly passing through the dropping path are intruded between the nipping plate 13 and the nipping plate 13 (see FIG. 3 (b)), and then rotated to the backward movement start position shown in FIG. The yarns I1 and I3 that are moved and caught are pulled out to the side.

Due to this hopping operation, the length of the lower thread I1 from the bobbin case 3 to the needle plate 1 becomes the minimum length required for the next sewing operation, and the thread I 1, in the thread hoisting arm 11 is obtained. The bending angle of I3 is an obtuse angle as shown in FIG. Therefore, when the same amount of boring operation is performed in the conventional device, the frictional resistance generated between the tip portion 5a of the thread hoisting arm 5 and the threads I1 and I3 becomes extremely low, and the bobbin bobbin moves The yarn I 1 is unwound more than necessary, and sufficient tension cannot be generated on the yarns I 1 and I 3 extending from the yarn hoisting arm 5 to the needle plate 1.

However, in this embodiment, since the yarns I1 and I3 are sandwiched between the sandwiching plate 13 and the yarn hoisting arm 11, the yarn hoisting arm can be engaged despite the minimum amount of hoisting as described above. A large tension can be generated in the yarns I1 and I3 extending from 11 to the needle plate 1.

On the other hand, in the movable knife 4 which has started the forward rotation in the counterclockwise direction, when the thread plucking arm 11 reaches the backward movement start position, the blade portion formed at the tip end thereof has the needle drop position. It reaches the cutting position directly below and contacts the upper threads I1 and I2 captured by the thread hoisting arm. At this time, since a large tension is generated in the yarns I1 and I3, the blade portion 4a of the movable knife 4 can be brought into contact with the yarns I1 and I3 with a sufficient pressure contact force, and the yarns I1 and I3 can be surely obtained. I3 can be cleaved. Also, since the length of the lower thread I3 from the bobbin case 3 to the cut end portion is the minimum required length set in advance, in the next sewing, a long lower thread is attached to the seam start end portion of the cloth. I2 will not be left.

Therefore, according to this embodiment, a long residual thread is not formed at both the start end portion and the rear end portion of the seam, and excellent quality can be obtained. After the thread cutting operation, the thread hoisting arm 11 returns to the initial position while holding the threads I1 and I3, but the threads I1 and I3 are pulled up to the upper thread loop at the first needle after the start of the sewing operation. And both members 11 and 13 are naturally removed.

In the above embodiment, the holding plate 13 is fixed to the upper surface of the thread plucking arm 11, but the holding plate 13 may be attached to the lower surface of the thread plucking arm 11, and its shape is also shown in the embodiment. It is not limited to what you eat. Further, in the above embodiment, the rotary type thread trimming device has been described as an example, but the present invention can be applied to a device in which the movable knife and the thread plucking arm move horizontally, and is particularly limited to the rotary type thread trimming device. Not done.

[0021]

[Effect of device]

 As explained above, this invention is a thread trimmer for a sewing machine in which the thread to be cut is bent by the thread-guiding arm to generate tension and then the thread is cut by a movable knife directly below the needle drop hole. In the device, a groove for introducing the thread to be cut is formed at the tip of the thread hoisting arm, and a clamping plate for clamping the thread inserted in the groove with the thread hoisting arm is provided. It is possible to generate sufficient thread tension on the thread with a limited amount of traverse. Therefore, according to this thread trimming device, the length of the residual thread connected to the seam end portion of the cloth can be shortened as well as the conventional device, and the length of the residual thread connected to the seam start end portion can be reduced. It can be optimized and the quality of sewn products can be significantly improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a plan view of an essential part of what is shown in FIG.

FIG. 3 is a partially enlarged plan view of what is shown in FIG.
(A) shows the state before the thread hopping operation, and (b) shows the state during the thread hopping operation.

FIG. 4 is a side view showing an initial state in a conventional rotary type thread cutting device.

FIG. 5 is a plan view showing tip portions of the thread plucking arm and the movable knife shown in FIG.

FIG. 6 is a side view showing a state in which the thread winding arm has captured the thread from the state shown in FIG.

FIG. 7 shows a state in which the movable knife contacts the yarn from the state shown in FIG.

[Explanation of symbols]

 1 Needle plate 2 Sewing hook 4 Movable knife 4a Blade portion 11 Threading arm 12 Groove 13 Clamping plate I1, I2 Upper thread I3 Lower thread

Claims (1)

[Scope of utility model registration request] 1. A movable knife that reciprocates from a predetermined initial position separated from the needle drop path to a cutting position set in the vicinity of the needle drop path, and a predetermined thread catching position beyond the needle drop path from the initial position. A thread bobbin arm that reciprocates over the thread, and reciprocates the thread bobbin arm and the movable knife in opposite directions, whereby the upper thread and the bobbin thread located between the needle plate and the sewing machine hook are threaded. In a thread trimming device of a sewing machine, wherein the movable knife is brought into contact with the upper thread and the bobbin thread from the needle plate to the thread hoisting arm while performing the thread cutting operation while bending the thread hoisting arm. A groove for allowing the upper thread and the lower thread to enter is formed at the tip portion, and the upper thread and the lower thread that have entered the groove are always pressed against one of the upper and lower surfaces of the thread hoisting arm. A clamping plate was provided to clamp it between the arm Thread cutting device of a sewing machine characterized by and.