Description

ROTARY SHUTTLE DEVICE FOR SEWING MACHINES

CONFIGURED FOR EASY INSTALLATION OF DILATED

DIAMETER BOBBIN THEREIN

Technical Field

[1] The present invention relates, in general, to rotary shuttle devices for sewing machines and, more particularly, to a rotary shuttle device for sewing machines configured for the easy installation of a dilated diameter bobbin therein, in which the structure of the stud of a bobbin case base is improved such that, when a bobbin is installed in the bobbin case base, the bobbin can avoid interference with a hook holder bracket, so that both the radius of flanges of the bobbin and the under thread winding capacity of the bobbin can be maximized, thus increasing the productivity of sewing work. Background Art

[2] As shown in FIG. 1, a conventional sewing machine is provided with a rotary shuttle device 100 for the supply of under thread. The rotary shuttle device 100 comprises a hook body 20, which is mounted to a drive shaft 10, rotatably coupled to a drive unit, and is called an "outer hook" in the art, a bobbin case BC, received in the hook body 20, and a bobbin 40 with an under thread wound around the bobbin 40. The bobbin case BC comprises a bobbin case base 30, which is received in the hook body 20 and is called an "inner hook", and a bobbin case body 50 for holding the bobbin 40 at a location outside the bobbin case base 30.

[3] A stud 31 is axially provided at the center of the bottom of the bobbin case base 30 such that it is perpendicular to the bottom. The bobbin 40 is rotatably fitted over the stud 31. A track groove 21 is formed in the inner surface of the hook body 20, and a hook 22 is formed in one end of the track groove 21. A cutout 23, having a gentle radius of curvature, is formed in the sidewall of the hook body 20 at a location near the hook 22, such that the under thread can pass by the cutout 23 while being in contact therewith.

[4] At a location near the bobbin case BC comprising the bobbin case base 30 and the bobbin case body 50, a hook holder bracket 2 is installed in the body of the sewing machine and is inserted into a holding slot 33 in the bobbin case base 30, thus holding the bobbin case BC so as to prevent the bobbin case BC from moving. Further, a needle passing hole 34 is formed in the bobbin case base 30 at a location near the holding slot 33, and allows a needle to pass therethrough when the needle descends.

[5] The bobbin 40 comprises a winding shaft 41, around which the under thread is

wound, and opposite flanges 43 and 45, formed in both ends of the winding shaft 41.

[6] If the under thread winding capacity of the bobbin 40 for sewing machines is increased, the frequency with which an empty bobbin must be changed with a full bobbin can be reduced, and thus the productivity of sewing work can be increased. However, to increase the under thread winding capacity of bobbins for sewing machines, it is necessary to change both the basic construction and the design standard of sewing machines, which are compatibly used throughout the world. Thus, in practice, it is very difficult to increase the under thread winding capacity of bobbins in the related art.

[7] In recent years, a variety of techniques for increasing the under thread winding capacity of bobbins while satisfying the compatible design standard of sewing machines has been actively studied. One of the attempts to increase the under thread winding capacity of bobbins is intended to increase the diameter of the flanges 43 and 45 of bobbins, installed in the bobbin case base 30, as large as possible.

[8] In the related art, bobbins having a flange diameter of 021mm have been widely used. However, according to the study of techniques for increasing the under thread winding capacity of bobbins, new bobbins having a flange diameter of 023mm or larger have reached commercialization.

[9] However, as shown in FIG. 2, when the hook holder bracket 2 is inserted into the bobbin case base 30 and holds the bobbin case base 30, it encroaches on part of the upper space inside the bobbin case base 30. Thus, when the radius of the flanges 43 and 45 of a bobbin is increased, the bobbin may interfere with the hook holder bracket 2. In the above case, the bobbin may be difficult to install in the bobbin case base 30.

[10] Therefore, the increase in the radius of the flanges of the bobbin 40 has been limited to a size that causes no interference between the bobbin 40 and the hook holder bracket 2 in the process of installing the bobbin in the bobbin case base 30. This limitation on the bobbin flange radius results in an inefficiency wherein the radius of the bobbin flange must be set to a small size compared to the actual space defined in the bobbin case base for receiving bobbins therein. Disclosure of Invention Technical Problem

[11] Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and is intended to provide a rotary shuttle device for sewing machines configured for the easy installation of a dilated diameter bobbin therein, in which the structure of the stud of a bobbin case base is improved such that, when a bobbin is installed in the bobbin case base, the bobbin can avoid interference with a hook holder bracket, so that both the radius of flanges of the bobbin and the

under thread winding capacity of the bobbin can be maximized, thus increasing the productivity of sewing work. Technical Solution

[12] In an aspect, the present invention provides a rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein, comprising: a hook body mounted to a drive shaft; a bobbin case, which comprises a bobbin case base, received in the hook body, and a bobbin case body for holding a bobbin at a location outside the bobbin; and the bobbin, which is installed in the bobbin case and around which an under thread is wound,

[13] wherein the bobbin case base is provided with a stud, which has a latch locking groove formed around an upper end of the stud and is axially formed on a bottom of the bobbin case base and holds the bobbin fitted thereover, with a holding slot formed on an upper end of the bobbin case base at a predetermined location so as to hold the bobbin case base to a body of a sewing machine,

[14] wherein the stud is provided within a predetermined region thereof with a stepped part having a reduced diameter so that, when the bobbin is installed in the bobbin case base, the bobbin can be fitted over the stud in a state in which the bobbin is tilted to one side so as to avoid interference with a hook holder bracket.

Advantageous Effects

[15] As described above, the rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the present invention is advantageous in that the stud of a bobbin case base, having an improved structure, allows a bobbin to avoid interference with a hook holder bracket when the bobbin is installed in a bobbin case, so that the radius of bobbin flanges and the under thread winding capacity of bobbins can be maximized, thus realizing increased productivity of sewing work. Brief Description of the Drawings

[16] FIG. 1 is an exploded perspective view of a conventional rotary shuttle device for sewing machines;

[17] FIG. 2 is a plan view illustrating the conventional rotary shuttle device in a state in which a hook holder bracket is inserted into a bobbin case;

[18] FIG. 3 is a perspective view of a bobbin case base according to an embodiment of the present invention;

[19] FIG. 4 is a cross-sectional view of FIG. 3;

[20] FIG. 5 is a view illustrating the operation of FIG. 3;

[21] FIG. 6 is a cross-sectional view of a bobbin case base according to another embodiment of the present invention;

[22] FIG. 7 is a view illustrating the operation of FIG. 6; and

[23] FIG. 8 is a cross-sectional view of a bobbin case base according to a further embodiment of the present invention.

[24] *Description of the elements in the drawings*

[25] 1: rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the present invention

[26] 2: hook holder bracket 3: upper thread

[27] 4: under thread 10: drive shaft

[28] 20: hook body 30: bobbin case base

[29] 300: bobbin case base of the present invention

[30] 31 : stud 311: latch locking groove

[31] 312: upper end 313: stepped part

[32] 317: inclined surface 33: holding slot

[33] 40: bobbin 50: bobbin case body

[34] 100: conventional rotary shuttle device

Mode for the Invention

[35] Hereinbelow, preferred embodiments of a rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the present invention will be described in detail with reference to the accompanying drawings.

[36] FIG. 3 is a perspective view of a bobbin case base according to an embodiment of the present invention. FIG. 4 is a cross-sectional view of FIG. 3. FIG. 5 is a view illustrating the operation of FIG. 3.

[37] As shown in FIG. 3 through FIG. 5, the rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the embodiment of the present invention comprises a hook body 20, which is mounted to a drive shaft 10, a bobbin case BC, which comprises a bobbin case base 300, received in the hook body 20, and a bobbin case body 50 for holding a bobbin 40 at a location outside the bobbin 40, and the bobbin, which is installed in the bobbin case BC and around which an under thread is wound. A stud 31, with a latch locking groove 311 formed around an upper end of the stud 31, is axially formed at the center of the bottom of the bobbin case base 300 such that it is perpendicular to the bottom. The bobbin 40 is rotatably fitted over the stud 31. The rotary shuttle device 1 further comprises a holding slot 33, which is formed on an upper end of the bobbin case base 300 at a predetermined location and holds the bobbin case base 300 to the body of a sewing machine.

[38] The stud 31 of the bobbin case base 300 is provided in a predetermined region

thereof with a stepped part having a reduced diameter so that, when a bobbin 40 is installed in the bobbin case base 300, the bobbin 40 can be fitted over the stud 31 in a state in which the bobbin 40 is tilted to one side so as not to interfere with a hook holder bracket 2.

[39] The stepped part of the stud 31 may comprise a flat stepped part 313, which is formed on the side surface of the stud 31 by axially cutting the stud 31 within a predetermined region from the upper end such that the flat stepped part 313 faces the holding slot 33.

[40] The cross-section of the stud 31 at a part having the flat stepped part 313 is a D- shaped cross-section, and the cutting depth of the flat stepped part 313 is set to a depth that can remain completely the latch locking groove 311.

[41] In another embodiment of the present invention, the stepped part of the stud 31 may comprise an annular stepped part 315, which is formed around the entire circumference of a middle portion of the stud 31, as shown in FIG. 6.

[42] It is preferred that the depth of the annular stepped part 315 be 0.3 ~ 0.6 mm and that the width thereof be 1.5 - 4 mm.

[43] Further, it is preferred that the upper end 312 of the stud 31 above the latch locking groove 311 be inclined around the edge thereof, unlike a conventional stud having a rounded upper end.

[44] To make the edge of the upper end 312 of the stud 31 be inclined, the upper end

312 is preferably chamfered.

[45] Further, the inclined surface 317, which is formed around the edge of the upper end of the stud through chamfering, preferably has a degree θ of inclination of about 100°.

[46] In a further embodiment of the present invention, the stud 31 may have both the flat stepped part 313 and the annular stepped part 315, as shown in FIG. 8.

[47] The operation of the rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the present invention having the above-mentioned construction will be described hereinbelow with reference to FIG. 5 and FIG. 7.

[48] As shown in FIG. 5, in the present invention, the stud 31 of the bobbin case base

300 is provided with the stepped part, so that the bobbin 40 can be fitted over the stud 31 in a state in which the bobbin 40 is tilted to one side so as to avoid interference with the hook holder bracket 2.

[49] In other words, when the bobbin 40 is fitted over the stud 31 of the bobbin case base 300, the winding shaft 41 of the bobbin 40 can be temporarily tilted due to the flat stepped part 313 and/or the annular stepped part 315 of the stud 31, so that the bobbin 40 can be fitted over the stud 31 in the state in which the bobbin 40 is tilted to one side.

[50] Here, the upper end 312 of the stud 31 is inclined around the edge thereof, so that

the upper end 312 does not interfere with the winding shaft 41 when the winding shaft 41 is fitted over the stud 31 so as to be tilted.

[51] After the bobbin 40 enters the bobbin case base 300 in the tilted state, in which the bobbin 40 can avoid interference with the hook holder bracket 2, as described above, the bobbin 40 is stood upright in the bobbin case base 300 to finish installation thereof. Thus, the radius of the flanges 43 and 45 of the bobbin 40 can be sufficiently increased to an extent that efficiently utilizes the space inside the bobbin case base 300 and increases the under thread winding capacity of the bobbin 40.

[52] In the above description, the embodiments of the present invention have been disclosed for illustrative purposes with reference to the accompanying drawings. Here, the technical terms and words used in the specification and claims must not be interpreted according to limited definitions thereof, such as ordinary or dictionary meanings, but must be understood to represent meanings and concepts corresponding to the technical scope and spirit of the invention. Thus, those skilled in the art will appreciate that the construction of the embodiments and drawings of the invention has been disclosed as that of preferred embodiments, and thus various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Industrial Applicability

[53] As described above, the rotary shuttle device for sewing machines configured for easy installation of a dilated diameter bobbin therein according to the present invention is advantageous in that the structure of the stud of a bobbin case base is improved such that, when a bobbin is installed in the bobbin case, the bobbin can avoid interference with a hook holder bracket, so that both the radius of flanges of the bobbin and the under thread winding capacity of the bobbin can be maximized, thus increasing productivity of sewing work.