Oscillating loop taker for a sewing machine

Abstract: This invention relates to an oscillating loop taker featuring that a needle thread guiding projection (26) which forms a recess (29) in which the driver member (40) of bobbin case holder (20) is fit together with the wedge (30) is so formed that the inner radius R1 of the leading edge portion (31) of the projection (26) is made shorter than that R2 of the space in which the bobbin case (37) at the base end portion (28) of the projection (26) is housed, the inclination of the needle thread guiding face (31) at the recess side of the projection (26) is set to a desired comparatively large value and further the length in the circumferential direction of the needle thread guiding face (31) is made comparatively long to cause the needle thread (46) to be easily transferred onto the outer circumferential face (47) of the bobbin case (37), thereby causing the bobbin thread (38) to be permitted to pass through between the inner peripheral face in the vicinity of the base end portion and the outer peripheral end portion of the bobbin case (37), causing the bobbin case (37) in the bobbin case holder (20) to be enlarged, causing the diameter of the bobbin, which is accommodated in the bobbin case holder (20), to be enlarged, and causing the winding capacity of the bobbin thread (38), which is wound in a bobbin (39), to be increased.

Description: This invention relates to an oscillating loop taker according to the preamble of claim 1. Such a known oscillating loop taker is shown in Figs 1 to 3. An oscillating loop taker 1 provided in a sewing machine for household and industrial uses includes a bobbin case holder 3 supported by a bobbin case holder rib 2 being inserted in a hook groove formed on an inner peripheral surface of a cup-shaped hook body not illustrated herein, a driver member 4 by which the bobbin case holder 3 is driven for half turn in the direction of arrows A1 and A2 and a bobbin case 7 in which a bobbin in which a bobbin thread is wound is accommodated. A rotating restraining member 7a is integrally formed together with the bobbin case 7. This rotating restraining member 7a is fit in a fitting recess of a bobbin case holder clamper not illustrated herein, thereby preventing rotation of the bobbin case 7 upon rotation of the bobbin case holder. A lower spindle of a sewing machine is coaxially fixed at a mounting portion 8 of the driver member 4 and is driven for half turn around the rotary axis line ℓ. When the driver member 4 rotates in the direction of an arrow A1, one end portion 9 in the peripheral direction thereof is brought into contact with a contacting portion of the bobbin case holder 3, thereby causing the bobbin case holder 3 to rotate in the direction of arrow A1, with the bobbin case 7 however being prevented from rotating. As end portion 9 of the driver member 4 reaches the upper dead point, the direction of rotation thereof is reversed to cause the driver member 4 to be driven for rotation from the direction of arrow A1 to the direction of arrow A2. At this time, the other end portion in the peripheral direction of the driver member 4 is brought into contact with the inner surface of a recess formed in the vicinity of a wedge 12 of the bobbin case holder 3, thereby causing the bobbin case holder 3 to rotate in the direction of arrow A2, with the bobbin case 7 however being prevented from rotating. In the oscillating loop taker 1 which can be driven for half turns as described above, a needle thread carried by a needle 14 which can vertically, reciprocate is caught by the wedge 12 and the bobbin case holder 3 is rotated by a half turn in the direction of arrow A1 by the driver member 4, thereby causing a needle thread loop to be formed. At this time, the needle thread is arranged at a lower portion as shown by the dashed line 15 and moves in the direction of an arrow 18, sliding along with a guiding face 17 of a thread guiding projection 16 which forms the recess 13 together with the wedge 12. Then the needle thread 15 transfers to the outer peripheral surface of the bobbin case 7 by vertical movements of a balance (not illustrated) of the sewing machine body. Thus, as the balance is elevated, the needle thread 15 shifts over, sliding on the outer peripheral surface of the bobbin case 7. The needle thread 15 which is thus pulled upwards by the balance is engaged with the bobbin thread which is drawn out from the bobbin 6 in the bobbin case 7, thereby causing a sewing joint to be formed. When the needle thread 15 transfers to the outer peripheral surface of the bobbin case 7 from the wedge 12, the bobbin case holder 3 reversely turns in the direction of arrow A2 and returns to the initial position (the solid line position shown in Fig. 1). And the bobbin case holder 3 is again driven in the direction of arrow A1 and catches the needle thread carried to the vicinity of the wedge 12 by a downstroke movement of the needle 14, thereby causing a needle thread loop to be formed. A series of movements as mentioned above is repeated, thereby causing consecutive sewing joints to be formed. When the oscillating loop taker 1 is utilized in a sewing machine for household or industrial use, then when the bobbin thread 5 of the bobbin case 6 is consumed, the bobbin 6 in which the bobbin thread 5 has been consumed must be replaced with a bobbin in which new bobbin thread has been wound. Especially, in a sewing machine for industrial use, the sewing speed of which is fast and the sewing volume of which is large, the bobbin 6 must be replaced frequently, and the sewing efficiency thus will be reduced. The winding capacity of the bobbin thread 5 can be increased by enlarging the diameter D of the bobbin 6 and the width B in the axial direction of the bobbin 6. However, if the diameter D of the bobbin 6 is enlarged, the bobbin case holder 3 must be accordingly enlarged. If the bobbin case holder 3 is enlarged, the needle thread loop is also enlarged, thereby causing not only the thread tightness to be worsened and the likely production of balls of thread but also vibrations accompanying the half turn movements of the bobbin case holder will be increased and noise accordingly will be increased. Also, if the width B of the bobbin 6 is enlarged, it will become difficult for the needle thread loop to transfer onto the bobbin case 7. As a result, undesirable tension operates on the needle thread to cause the thread tightness to be worsened, and balls of thread may be produced with a reduction in sewing quality. From US-A-1 394 039 a sewing machine is known having an oscillating shuttle for carrying the underthread which is interlooped with the needle thread to form a stitch. The shuttle comprises a circular body part having a cavity fitted with the central pivot upon which a bobbin case is mounted. A bobbin for the underthread is contained within the bobbin case. The oscillating movement of the shuttle is caused by an oscillating shuttle driver having two horns, one of which bears against the butt of the shuttle when driving it forward, and the other acts to drive the shuttle backward. In order to enable a larger bobbin to be used for the underthread, the point about which the shuttle oscillated is eccentric to the axis of the driving shaft of the shuttle driver. This enables the shuttle driver to have a longer radius, so that the shuttle itself and the bobbin for the underthread can be increased. In the sewing machine known from DE-PS 38 118 an oscillating bobbin case holder is held by an angular plate which is fixed to a stop member of a sewing plate. In the bobbin case holder a bobbin is housed on which the bobbin thread is wound. The bobbin case holder will be rotated by a forked steering arm engaging on the rear side of the bobbin case holder. A hook is provided on the bobbin case holder engaging in a loop of the upper thread formed on a needle. It is an object of the invention to provide an oscillating loop taker, of simple construction, which can solve the above problems and by which the winding capacity of the bobbin thread to be wound in the bobbin can be increased by enlarging the bobbin without enlarging the bobbin case holder. This object will be solved by the features of claim 1. Dependent claims are directed on preferred embodiments of the invention. According to the invention, as the needle thread is easily transferred to the outer peripheral surface of the bobbin case by setting the inclination of the needle thread guiding surface at the recess side of the needle thread guiding projection to a desired value and by increasing peripheral length thereof, the needle thread caught by the wedge of the bobbin case holder is guided along the needle thread guiding surface of the recess as the bobbin case holder rotates, thereby enabling the needle thread to be easily transferred from the needle thread guiding face onto the outer peripheral surface of the bobbin case and ensuring smooth thread transfer Therefore, it is possible to form good sewing joints without unnecessary high tension operating on the needle thread and without producing thread balls. As the base end portion of the projection is so formed that the inner leading edge portion of the projection is radially inward of the inner surface defining the bobbin case accommodating space, the bobbin thread is permitted to pass between the inner peripheral face in the vicinity of the base end portion and the outer peripheral end portion of the bobbin case and it is possible to enlarge the bobbin case in the bobbin case holder. Thereby, the diameter of the bobbin, accommodated in the bobbin case holder, may be enlarged, and accordingly the winding capacity of the bobbin thread wound in a bobbin can be increased. Therefore, it is possible to reduce the frequency of replacement of bobbins and to greatly increase the sewing efficiency. Also according to the invention, even though the outer diameter of the bobbin case accommodated in the bobbin case holder is made larger, since a portion of the outer diameter of the bobbin case is reduced to prevent the interference with the needle thread guiding projection, there is no possibility that the leading edge portion of the needle thread guiding projection will be brought into contact with the outer peripheral surface of the bobbin case. Thereby, the bobbin case holder will not interfere with the bobbin case and the bobbin case holder will be oscillated smoothly. These and other objects of the invention and advantages and features thereof will be made more apparent in the ensuing detailed description with reference to the accompanying drawings, wherein: Fig. 1 is a front elevational view of conventional oscillating loop taker; Fig. 2 is perspective disassembled view of the oscillating loop taker of Fig. 1; Fig. 3 is a sectional view of the oscillating loop of Fig 1; Fig. 4 is a front elevation view of one of the preferred embodiments of the invention;, Fig. 5 is a side view of the oscillating loop taker 20 from the right side in Fig. 4; Fig. 6 is a plan view of the oscillating loop taker 20 shown in Fig. 4; Fig. 7 is an enlarged sectional view taken along with the cutting lines VII-VII of Fig. 5; Fig. 8 is a partially enlarged bottom plan view showing the vicinity of the needle thread guiding projection from the side of an arrow M of Fig. 7; Fig. 9 is a perspective view of an oscillating loop taker 21 furnished with the bobbin case holder 20 shown in Figs. 4 through 8; Fig. 10 is a partially enlarged sectional view of an oscillating loop taker 21; and Fig. 11 is a front elevational view off the bobbin case holder 20 to explain the transfer movements of the needle thread 46 onto the bobbin case 37. With reference to the accompanying drawings, one of the preferred embodiment of the invention is described in details. As shown in Figs. 4 to 6 a bobbin case holder 20 provided in an oscillating loop taker according to the invention has a bottom portion 23 from which a stud 22 projects and a peripheral edge portion 24 defining a bobbin case accomodating space 29 therein. A wedge 25 is formed at the peripheral edge portion 24, and a needle thread guiding projection 26 is also formed radially inwardly of wedge 25 A recess 27, into which a driver member 40 described hereinafter is engaged, is formed between the wedge 25 and the needle thread guiding projection 26. As shown in Figs. 7 and 8, a radial dimension R1 between the rotational center of stud 22 and a leading edge portion 30 of the needle thread guiding projection 26 is formed to be less than a radial dimension between such center of stud 22 and an inner surface of a base end portion 28 of the projection 26 (R1 < R2). Thereby, even though the peripheral length ℓ1 of the needle thread guiding projection 26 is lengthened, the strength of projection 26, can be prevented from being lowered by maintaining a sufficient thickness. Also the angle ϑ1 formed between a needle thread guiding surface 31 of the projection 26 adjacent recess 27 and direction tangential to the base end portion 28 of the projection 26 can be made larger than would be possible if radial dimensions R1 and R2 were equal R2 (R1 = R2). Moreover, by increasing the length ℓ1 in the peripheral direction of the needle thread guiding face 31, it is possible for the needle thread caught by the wedge 25 to be easily transferred onto an outer peripheral surface 47 of a bobbin case 37, as mentioned hereinafter. In view of the above structure, it is possible to make a smooth and reliable transfer of the needle thread caught by the wedge 25. Again with reference to Fig. 1, on a line (ℓ-P) of a radius connecting the rotary axial line ℓ of the bobbin case holder 3 to a base end portion of the needle thread guiding projection 16, it is necessary that an interval W1 is usually 1 mm or so because this position defines a channel from which the bobbin thread is drawn out of the bobbin case 7 and is introduced to a needle hole by the control spring. As the bobbin case 7 is placed at a fixed position and the bobbin case holder 3 is driven by half turns, this interval must always meet a requirement of W1 ≧ 1 mm at the downstream side in the direction of arrow A2 from the position of P1 on the line ℓ - P shown in Fig. 1. However, an interval W2 is never subjected to the above restriction at all at the downstream side (in the direction of the leading edge of the projection 16) in the direction of arrow A1. Therefore, the radial dimension R1 may be drawn near the outer periphery of the bobbin case. To the contrary, if only the radial dimension R2 is enlarged with R1 remained unchanged, the radius of the bobbin case can be enlarged to a value which is near to the radial dimension R1 and furthermore, the angle ϑ1 (Refer to Fig. 7) of the projection can be retained at a desired value which is not different from the conventional one at all, thereby causing the bobbin case 37 accommodated in the bobbin case holder 20 to be enlarged. Therefore, a bobbin 39 which will be accommodated in the bobbin case 37 can be enlarged, thereby increasing the winding capacity of the bobbin thread. Fig. 9 illustrates an oscillating loop taker 21 furnished with the bobbin case holder 20 shown in Figs. 4 through 8. An oscillating loop taker 21 furnished with the bobbin case holder 20 is arranged beneath a needle plate 35 on a sewing machine bed. In the oscillating loop taker 21, the bobbin case holder 20 is supported with a bobbin case holder rib 36 inserted in a hook groove formed on the inner peripheral surface of a cup-shaped hook body not illustrated herein, and the bobbin case 37 is attached to stud 22 which extends from the bottom portion 23 of bobbin case holder 20. Bobbin 39 in which bobbin thread 38 is wound is housed in the bobbin case 37. Driver member 40 is arranged at the opposite side of a rotary axis ℓ2 relative to the bobbin case holder 20. The driver member 40 has a rotary axis coincident with the rotary axis ℓ2 of the bobbin case holder 20, and a lower spindle 43 of the sewing machine is fixed at a mounting portion 42 integral with the driver member body 41. The rotary axis of the lower spindle 43 is coincident with the rotary axes of the bobbin case holder 20 and the driver member 40. As a sewing operation is started, the lower spindle 43 is driven and reciprocated for half turn in the direction of arrows D1 and D2 around the rotary axis thereof. At the same time, a needle 44 is vertically reciprocated in association with the lower spindle 43, thereby causing a needle thread 46 to be brought to the vicinity of the wedge 25 of the bobbin case holder 20 through a needle hole 45 formed in the needle plate 35. The bobbin thread wound in the bobbin 39 housed in the bobbin case 37 is elastically pushed to the outer circumferential surface 47 of the bobbin case 37 through a bobbin thread inserting hole by means of a bobbin thread regulating spring 48 and is led upwardly through the needle plate hole 45 in needle plate 35. A rotating restraining member 37a is formed integrally with the bobbin case 37, and is fit in a fitting recess of a bobbin case holder clamper (not illustrated herein), thereby preventing the rotation of the bobbin case 37 upon oscillation of the bobbin case holder 20. The driver member 40 is driven and reciprocated by half turns in the directions of arrows D1 and D2 by half-turn drive of the lower spindle 43. When the driver member 40 is rotated in the direction of arrow D1, one end portion 49 thereof is brought into contact with the bobbin case holder 20 and is pushed in the same direction, thereby causing the bobbin case holder 20 to be driven and turned by a half revolution direction of arrow D1, with the rotation of the bobbin case 37 being prevented. Also, when the driver member 40 is rotated in the direction of arrow D2, the other end portion of the driver member 40 is brought into contact with the inner surface of the recess 27 and is pushed, thereby causing the bobbin case holder 20 to be driven and rotated by a half revolution in the direction of arrow D2, reverse to the direction D1 of rotation, with the rotation of the bobbin case being prevented. Thus, as the bobbin case holder 20 is driven and reciprocated in the directions of arrows D1 and D2, there is a possibility for the needle thread guiding projection 26 of the bobbin case holder 20 to be brought into contact with the outer circumferentiai face 47 of the bobbin case 37 since the needle thread guiding projection 26 is inclined inwardly of the radial dimension, as shown in Figs. 7 and 8. For this reason, as shown in Fig. 10, on a roughly straight cylindrical body 51 of the bobbin case 37, a staged face 52 whose outer diameter is shorter than the outer diameter of the cylindrical body 51 is circumferentially formed, at least in the area in which the projection 26 moves. The reason why the bobbin thread regulating spring 48 does not interfere with the inner circumferential face of the bobbin case holder 20 is that the radial dimension R1 of the leading edge portion 30 of the projection 26 and the radial dimension R2 of the base end portion 20 thereof are such that R2 > R1 and R2 is a value such that the inner circumferentiai face of the base end portion 28 will not interfere with the bobbin thread pushed by the bobbin thread regulating spring 48. Thereby even though the bobbin case holder 20 is reciprocated in the directions of arrows D1 and D2, the vicinity of the leading edge portion 30 of the projection 26 is not brought into contact with the outer circumferential face 47 of the bobbin case 37 and the bobbin thread regulating spring 48 attached to the outer circumferential face 47 and does not disturb the reciprocation of the bobbin case holder 20. As the bobbin case holder 20 is driven in the direction of arrow D1 by the driver member 40 by the structure discussed above, the needle thread 46 caught by the wedge 25 forms a loop as shown in Fig. 11, and the needle thread is guided in the direction of an arrow F, which is the passing-through direction of the needle thread. Then, at a position such that the leading edge of the wedge 25 vertically intercrosses with the rotary axis ℓ2 and reaches the axis ℓ3 parallel to the moving channel of the needle 44, the needle thread 46 in the recess 27 is guided in the direction of an arrow G in Fig. 11 along with the needle thread guiding face 31 and is transferred to the outer circumferential face 47 of the bobbin case 37. At this time, as the needle thread guiding face 31 is so formed as to cover the length ℓ1 as described with reference to Fig. 7, the needle thread 46 which moves in the direction of an arrow G along with the needle thread guiding face 31 is guided to the position beyond the axis ℓ3 in the circumferential direction. Then, the needle thread 46 can be transferred onto the outer circumferential face 47 of the bobbin case 37, thereby providing reliable thread transfer. In addition, as the angle ϑ1 is set to a desirable value, that is, such a valued that the needle thread 46 can smoothly slide and can be guided in the direction of arrow G along the needle thread guiding face 31, in accompanying with the upward movement of a balance, not illustrated herein, the needle thread 46 can be easily transferred from the guiding face 31 onto the outer circumferential face 47 at further left side from the axis ℓ3 of Fig. 11 of the bobbin case 37. Thereby, unnecessary tension may not be imported to the needle thread. Therefore, the thread tightness may not be worsened and thread cutoff will not be caused. Thus, the configuration of needle thread guiding projection 26 enables guiding and transfer of the needle thread 46 to be smooth and reliable. In the case that any staged face 52 is not provided on the outer circumferential face 47 of the bobbin case and the width B 10 of the bobbin is enlarged, an upper end corner portion 70 on the outer circumferential face 47 comes more upwards as shown by an imaginary line 71 as the width B 10 increases. On the other hand, it is necessary for the needle thread to be moved reasonably in the direction of arrow F, which is the passing-through direction of needle thread in Fig. 10. However, if the corner portion 70 is enlarged, it will become difficult for the needle thread to transfer onto the outer surface 53 of the bobbin case and finally the needle thread is wound on the outer circumferential face 47. In order to avoid the above phenomenon it is necessary that the corner portion 70 is set below the distance H1. To realize this condition, in this preferred embodiment, the radius of the outer circumferential face 47 of the bobbin case is enlarged in the height area in which the outer circumferential face 47 does not interfere with the projection 26, to such a degree that it may not exceed the radial dimension R2 in Fig. 7, thereby achieving the desired position of the corner portion 70. Namely, as with the relationship between the staged face 52 and the outer circumferential face 47, the position of the corner portion 70 can be lowered by enlarging the outer circumferential face 47. Therefore, the distance H2 from the bobbin case holder rib 36 to the outer surface of the bobbin case 37 can be enlarged, thereby enabling the width B 10 of the bobbin 39 to be enlarged. In an oscillating loop taker comprising such a bobbin 39, the distance H2 of the bobbin case 37 can be made larger than the distance h2 in Fig. 3 when the distance h1 from the bobbin case holder rib 2 of the bobbin case holder 3 in the prior art shown in Fig. 3 is equal to the distance H1 of the invention (i.e., h1 = H1) The width B 10 of the bobbin 39 which is housed in such a bobbin case 37 can be made larger by, for instance 3 mm than the width B of the prior art, thereby increasing the winding capacity of the bobbin thread 38 wound in the bobbin 39.

Claims: An oscillating loop taker comprising a bobbin case holder (20) having a bottom portion (23) and a peripheral edge portion (24) defining a bobbin case accommodating space (29) therein, said peripheral edge portion (24) having a radially outer, circumferentially extending wedge (25) and a radially inner, circumferentially extending needle thread guiding projection (26) forming a recess (27) therebetween, a driving member (40) engaging the recess (27) for reciprocally rotating the bobbin case holder (20) about a rotation axis (l₂) and a bobbin case (37) supported within the bobbin case accommodating space (29) by a stud (22) fixed on the bottom portion (23) of the bobbin case holder (20), characterized in that a radial dimension R1 from the rotation axis (l₂) to an inner leading edge portion (31) of the needle thread guiding projection (26) is less than a radial dimension R2 from the rotation axis (l₂) to an inner surface defining the bobbin case accommodating space (29) at a base end (28) of the needle thread guiding projection (26) and that the needle thread guiding projection (26) has a radially outer surface (31) defining the recess (27) and inclined radially inwardly toward the leading edge portion (30). An oscillating loop taker according to claim 1, characterized in that the bobbin case (37) has a cylindrical body (51) having formed in a portion thereof a circumferential stage (52), whose outer diameter is less than the outer diameter of the cylindrical body (51). An oscillating loop taker according to claim 1, characterized in that the outer surface (47) of the bobbin case (37) is so formed as to be protruded by about 3 mm outwardly from the open end of the bobbin case holder (20) in axial direction.

Inventors: SHIMIZU HIROMITSU, SHIMIZU, HIROMITSU
Applicants: BROTHER IND LTD, HIROSE MFG CO LTD, BROTHER KOGYO KABUSHIKI KAISHA, HIROSE MANUFACTURING COMPANY LIMITED
Application year: 1990
Main classification: D05B57
IPC codes: D05B57