JPH0153078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thread cutting device for a sewing machine that can reliably hold only the cut end of a bobbin thread after thread cutting.

[Prior art]

Conventionally, there have been devices of this type as shown in FIGS. 1 and 2. In the figure, 101 is a feed dog in which a needle hole 102 is formed. 103 is an inner pot, 104 is a movable blade, and 105 is this movable blade 10
4, upper thread 106 and lower thread 107
After cutting, the thread holding surface is a flat spring that holds the thread between the movable blade 104 and the movable blade 104, as shown in the second figure.

At this time, for horizontal hook-type sewing machines equipped with an automatic thread trimming device, the upper and lower threads remaining on the back side of the fabric after the thread is cut should be as short as possible, and the stitches should not be skipped during the next sewing. In order to form a reliable stitch, it is necessary to leave only the required amount of needle thread on the needle side, and to securely hold the cut end of the bobbin thread until the first stitch is formed. It is said that

Conventionally, this type of thread cutting device is constructed as described above, so when the back surface of the movable blade 104 is flat, the upper thread 106 is cut after thread cutting as shown in FIGS. 1 and 2.
and the bobbin thread 107 are the back side of the movable blade 104 and the movable blade 1.
05 and the leaf spring 105 located below, but if the upper thread 106 is thicker than the lower thread 107, the upper thread 106 can be held securely, but the important lower thread 107 The problem was that it became unstable and fell from the leaf spring 105 and could not be held. Further, if sewing is performed without the bobbin thread 107 being held, there are drawbacks such as not being able to form many stitches or not forming a stitch at all.

[Summary of the invention]

This invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and a concave or convex surface is provided near the thread catching hook part on the back surface of the movable blade to form a bobbin thread holding part relatively. To provide a thread cutting device for a sewing machine which can securely hold the bobbin thread after the thread is cut by holding only the bobbin thread between a bobbin thread holding part and a leaf spring, and can perform sewing smoothly and reliably. The purpose is to

[Embodiments of the invention]

An embodiment of the present invention suitable for a horizontal hook type sewing machine will be described below with reference to FIGS. 3 to 10. 1
As shown in FIG. 3, the needle plate is fixed to the sewing machine bed with screws. 2 is the feed dog,
It moves up and down reciprocally within the opening 1a of the throat plate 1. A needle hole 3 is formed in this feed dog 2, and a needle 4 passes through this needle hole 3 and moves up and down. Reference numeral 5 denotes a hook that rotates in a horizontal plane and cooperates with the needle 4 to form a regular stitch, and includes an outer hook 6 that captures the needle thread;
A bobbin for bobbin thread (not shown) is supported inside.
It has an inner pot 7 that houses the. Reference numeral 8 denotes a hook mounting base which is fixed to the bed with screws and is equipped with the hook 5 and a thread cutting device. Reference numeral 9 denotes a movable body to which a movable blade 10 is attached and moves back and forth, and is slidably fitted into the hook mount 8. Reference numeral 10 denotes a movable blade fixed to the movable body 9, which has a thread cutting part 11 at its tip;
A hook portion 12 for catching a thread and a cutting blade 13 are formed, and a convex surface (bobbin thread holding portion) 14 for holding a bobbin thread is formed on the back surface as shown in FIG. This convex surface 14 is characterized in that it is located at a position through which the lower thread 36 can pass, and at a position where the upper thread 35 is blocked. A leaf spring 15 is located below the movable blade 10, and after the thread is cut, the lower thread 36 is held by the movable blade convex surface 14 and the leaf spring 15, as shown in FIGS. 7 and 8. A fixed blade 16 is fixedly arranged near the movable plate 10, and cooperates with the movable blade 10 to simultaneously cut the upper thread 35 and the lower thread 36 captured by the movable blade 10. Reference numeral 17 denotes a knife stand on which the fixed blade 16 is attached, and is attached to the hook mount 8 so as to be vertically adjustable. 18 is the hook mounting base 8
The swinging arm is rotatably supported by the swing arm, has a roller at its tip, and fits into a groove of the movable body 9.

FIG. 4 is a view of the sewing machine bed seen from the back side, and FIG. 5 is a sectional view taken along the line W--W in FIG. 4, showing a device for reciprocating the movable blade 10. Reference numeral 19 denotes an operating arm that transmits the displacement of the thread cutting cam 20 to the movable body 9 via the swing arm 18. Reference numeral 21 denotes a support fixed to the sewing machine bed, which carries a guide shaft 22, into which a cam follower arm 23 is inserted and slidably guided by the guide shaft 22. The cam follower arm 23 has a roller 24 that is formed to be able to engage and detach freely. 25 is a spring for disengaging the roller 24 from the thread cutting cam groove 26 after thread cutting is completed. Reference numeral 27 denotes a rotary solenoid attached to the support body 21, which rotates in response to a thread trimming signal, and transmits the rotation to a swing lever 28 fixed to the shaft of the rotary solenoid 27. The tip of the swing lever 28 has a roller 30 that fits into the groove 29 of the cam follower arm 23 and is slidable thereon.

Further, the thread trimming cam 20 has a cam groove 26 on its outer periphery for reciprocating the movable blade 10, and is fixed to the lower shaft 32 and constantly rotates during operation of the sewing machine. A universal joint 33 connects the cam follower arm 23 and the operating arm 19.

Next, the insertion and operation of this invention will be explained.

When a pedal (not shown) installed at the bottom of the table is operated to stop the sewing machine, a signal is sent to the control circuit of the needle position stop motor.
The sewing machine will stop operating when the needle bar is near its lowest point.

Next, when the pedal is operated to perform automatic thread trimming, the sewing machine receives the thread trimming signal and starts rotating at a low speed. At the same time, the rotary solenoid 27 that receives the thread trimming signal rotates, and the swing lever 2
8. Push down the cam follower arm 23 via the roller 30. The roller 24 supported by the cam follower arm 23 fits into the thread cutting cam groove 26 and moves in accordance with the phase of the cam, swinging the cam follower arm 23 and interlocking with the operating arm 19 via the universal joint 33. do. The swinging arm 18 fixed to the operating arm 19 swings, and the movable body 9 is moved by a roller 34 protruding from the swinging arm 18.
The movable body 9 fitted to the hook mount 8 moves straight on a horizontal plane, and the movable blade 10 attached to the movable body 9 moves forward. The movement of the movable blade 10 at this time is such that the needle 4 rises from the lowest position, and immediately after the hook thread catching section captures the upper thread 35, it begins to move and pushes the movable blade thread sabbling section 11 into the upper thread loop. The upper thread is separated into the needle thread to be left on the needle side and the upper thread to be left on the back side of the fabric, and as shown in FIG. 9, the movable blade 10 passes under the lower thread and moves forward.

Next, when the sewing machine rotates and the phase of the thread trimming cam 20 becomes opposite to the forward movement, each mechanism operates in the opposite direction, and the upper thread 35, which is sorted in the forward movement, is operated in the opposite direction as shown in FIG. The bobbin thread 36 is caught by the movable blade thread catching hook part 12, and when the bobbin thread 36 is further moved double-handedly, as shown in FIGS. passes outside the convex surface 14 and enters the concave surface 14a. Then, in cooperation with the fixed blade 16, the two threads are cut to an appropriate length at a position just before the starting point, and the sewing machine stops at the highest level of the thread take-up. At this time, the cut end after cutting is the convex surface 1 of the movable blade 10.
The lower thread 36 that has passed through the lower thread 4 is held by the leaf spring 15 located below the movable blade 10, but since the upper thread 35 enters the back surface 14a of the movable blade, there is a gap between it and the leaf spring 15 and it is not held. become. Then, preparation for forming the next stitch is made in a state in which the bobbin thread 36 is not securely held.

〔Effect of the invention〕

As described above, according to the present invention, a lower thread clamping part is relatively formed with a concave or convex surface near the thread catching hook part on the back surface of the movable blade, and the lower thread clamping part and the leaf spring are connected to each other. Since the structure is such that only the bobbin thread is held between the two threads, the bobbin thread 36 is securely held after the thread is cut, so that there is no support for the next sewing and smooth and reliable stitches can be formed. be.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the conventional thread holding state after cutting the thread, Fig. 2 is an enlarged cross-sectional view taken along line X-X in Fig. 1, and Fig. 3
The figure is a plan view showing the area around the hook and movable blade on the first side of the sewing machine, Figure 4 is a drawing showing the thread cutting device section seen from the back of the sewing machine bed, and Figure 5 is Y-Y in Figure 2.
6 is a perspective view of the movable blade of an embodiment of the present invention seen from the back side; FIG. 7 is an enlarged view showing the thread holding state after cutting the thread of the embodiment of the present invention; FIG. 8 7 is a sectional view taken along the line W-W in FIG. 7, and FIGS. 9 and 10 are perspective views for explaining the state of yarn sorting and yarn catching. 1... Throat plate, 5... Hook, 10, 104... Movable blade, 15, 105... Leaf spring, 16... Fixed blade,
35,106... Upper thread, 36,107... Lower thread.

Claims (1)

[Claims] 1. A needle that passes through the throat plate attached to the sewing machine bed and reciprocates up and down, a hook that cooperates with this needle to form stitches, and the required amount of upper thread and bobbin thread provided near the hook. In a thread cutting device for a sewing machine having a movable blade and a fixed blade for cutting thread, the bobbin thread holding portion is relatively cut by a concave or convex surface provided near the thread catching hook portion on the back surface of the movable blade. A thread cutting device for a sewing machine, characterized in that only the bobbin thread is held by the bobbin thread holding portion and a plate spring located on the lower surface of the movable blade.