JPH0217570Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a bobbin case for a full-rotation hook in a sewing machine, and particularly to a mechanism for applying tension to a bobbin thread led out from the bobbin case.

Conventionally, this type of tension applying mechanism applies tension to the bobbin thread by sandwiching the bobbin thread between the bobbin outer circumferential surface and the bobbin outer circumferential surface using the elastic force of a leaf spring provided along the bobbin outer circumferential surface. Since this leaf spring has a large spring constant, for example, when changing the bobbin thread and the thickness of the bobbin thread changes, the amount of tension applied to the bobbin thread changes greatly, and each time it applies tension to the needle thread. It becomes necessary to adjust the thread tension device or the elastic force of the leaf spring, which reduces the efficiency of sewing work.In addition, it is necessary to adjust the upper and lower thread tension to obtain a good stitch with a good balance of the upper and lower thread tensions. There were drawbacks such as the need for considerable skill on the part of the operator to be able to make appropriate adjustments.

This invention aims to eliminate the above-mentioned conventional drawbacks.

Hereinafter, an embodiment of this invention will be described with reference to the drawings. Reference numeral 1 denotes a bobbin case, and inside there is a hole 3 that supports the bobbin 2 on the outer periphery and loosely fits into a support shaft (not shown) of an inner pot (not shown). As shown in FIG. 3, the front end surface has a U-shaped groove 5 parallel to the end surface and facing each other, and the left end of the groove 5 as shown in FIGS. 1 and 2. A hole 6 is formed on the side of the bobbin case 1 by penetrating the front end surface and the inside of the bobbin case 1. Reference numeral 7 designates a latch, which is slidably and loosely fitted into the groove 5 of the bobbin case 1 on both upper and lower sides, and has a pawl 8 on the right end that locks the collar of the bobbin 2, and a latch 7 on the left end that allows the latch 7 to slide. A pair of support parts 10a and 10b are formed to support both ends of the pin 9, which have axes perpendicular to the directions (left and right) (up and down) and parallel to the front end surface of the bobbin case 1.

Reference numeral 11 denotes a helical spring, which is inserted into a hole 12 formed on the front end side of the bobbin case 1 parallel to the sliding direction of the latch 7, and its both ends are connected to the bottom of the hole 12 and the spring receiver 13 formed on the latch 7. It is placed in a compressed state between. Reference numeral 14 denotes a latch lever, whose left end is rotatably connected to a pin 9 supported on the support parts 10a and 10b of the latch 7, and has a cam 15 formed at its base that projects into the hole 6 of the bobbin case 1. , the free end extends parallel to the outer surface of the latch 7. Reference numeral 16 denotes a thread guide groove formed in the vertical direction on the front end surface of the bobbin, and as shown in FIG. , are guided upward through the lower thread guide groove.

This invention has the above-mentioned structure, and FIGS. 1 and 3 show a state in which tension is applied to the bobbin thread A.

That is, the helical spring 11 shown in FIG. 1 pushes the latch 7 to the right in FIGS. 1 and 2, and the latch lever 14 connected by the pin 9 is thereby pushed to the right in FIG. The cam 6 is pressed against the right end surface of the hole 6 of the bobbin case 1 at a position above the pin 9 by the action of the helical spring 11 . As a result, a counterclockwise rotation moment is applied to the latch lever 14 about the pin 9 in FIG. 2, and the lower thread A is moved to the latch 7 as shown in FIGS.
The bobbin thread A is held between the outer end surface of the latch lever 14 and the inner end surface of the latch lever 14 by the acting force of the helical spring 11.
Apply tension to.

Furthermore, if the bobbin thread A is changed to a thicker thread, for example, the diameter of the bobbin thread A in FIG. Pinch the bobbin thread at this position.
This slight rotation of the latch lever 14 causes its cam 15 to push against the right end surface of the hole 6, and the pin 9 moves slightly to the left from the position indicated by the solid line. As the pin 9 moves to the left, the latch 7 supporting the pin 9 also moves slightly to the left in FIG. Since the spring has a small spring constant, the force exerted by the helical spring 11 to pinch the bobbin thread between the outer surface of the latch 7 and the inner surface of the latch lever 14 is smaller than that of a leaf spring even when the bobbin thread is thicker. It only changes slightly, and the same is true even if the thickness of the bobbin thread becomes thinner.

As mentioned above, this invention uses a helical spring with a small spring constant to give tension to the bobbin thread, so even if the type of bobbin thread is changed and its thickness changes, the bobbin thread Since tension changes are extremely small compared to conventional leaf springs, there is no need to adjust the needle thread tension device in response to changes in bobbin thread tension, which is required in the past, improving sewing work efficiency and making it easier for even the most experienced workers. Good seams can be easily obtained, and good seams can always be obtained even when the thickness of a single thread varies locally, improving the commercial value of sewn products. There is.

In the illustrated embodiment, the existing helical spring 11 that presses the latch lever to the latch is used, but in other embodiments, a helical spring dedicated to imparting tension to the bobbin thread, separate from the helical spring 11, may be used on the bobbin. A similar effect can be obtained by providing the tensioner at an appropriate location in the case 1 and applying tension to the bobbin thread by its acting force.

[Brief explanation of drawings]

Figure 1 is a front view of the bobbin case, Figure 2 is the front view of the bobbin case.
FIG. 3 is a sectional view taken from FIG. 1. In the figure, 1 is a bobbin case, 2 is a bobbin, 7 is a latch, 14 is a latch lever, and 11 is a helical spring.

Claims (1)

[Scope of Claim for Utility Model Registration] A bobbin case with a thread hole 17 opening on the lower outer circumferential surface, a clutch with a claw 8 formed at one end and slidable relative to the bobbin case, and a latch at the base. A latch lever 14 is rotatably provided at the other end, a coil spring 11 is formed in the longitudinal direction of the front surface of the bobbin case, and the coil spring 11 applies an acting force to the latch lever in a direction parallel to the outer surface of the latch. A bobbin case for a full-rotation hook in a sewing machine, which is provided with a thread guide hole 16 for guiding a bobbin thread A between a latch and a latch lever.