Full rotary hook

Abstract: The invention provides a full rotary hook wherein amount of a bobbin thread wound in a bobbin (4) is increased by making a circumferential portion (12a) between a thread separating portion (21) and a thread releasing portion (22) thinner than the remainder of the circumferential portion (12b) to increase an inner diameter of a bobbin case holder (3). Thereby, the inner diameter of the bobbin (4) housed in the bobbin case holder (3), and further the inner diameter of the cylindrical portion (12) housing the bobbin case (5) can be increased and consequently an outer diameter of a flange (8) of the bobbin (4) can be increased, thereby increasing the amount of the bobbin thread wound around a winding drum of the bobbin.

Description: 1. Field of the invention The present invention relates to a full rotary hook of a sewing machine. 2. Description of the Prior Art US-A-3,682,121 describes a full rotary hook according to the preamble of claim 1. It is necessary to increase the quantity of bobbin thread wound on a bobbin in view of improving the productivity. In a full rotary hook of a sewing machine, it is desired to provide a construction where the quantity of bobbin thread wound on a bobbin is increased as much as possible while the remainder of the structure, such as the structure for installing a bobbin case by latching it in a bobbin case holder, remains the same. In the operation of a sewing machine, it is necessary that a looped needle thread passes smoothly through a contact portion between a rotation restraining notch of the bobbin case holder and a rotation restraining member which enters the notch and prevents the bobbin case holder from rotating together with the hook body, in order to improve the sewing performance. This is desired also in the case of a full rotary hook where the quantity of bobbin thread wound on a bobbin is increased. SUMMARY OF THE INVENTION An object of the invention is to provide a full rotary hook which enables to increase the quantity of bobbin thread wound on a bobbin. Another object of the invention is to provide a full rotary hook which enables to increase the quantity of bobbin thread wound on a bobbin and to simplify the assembling operation of the constitution of installing the bobbin case by latching thereof in the bobbin case holder. Further another object of the invention is to provide a full rotary hook which enables it to increase the quantity of bobbin thread wound on bobbin and to improve the sewing performance by making it possible for the looped needle thread to pass smoothly between the bobbin case holder rotation restraining notch and the rotation restraining member which is fitted in the notch. The invention provides a full rotary hook according to claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Other and further objects, features, and advantages of the invention will be apparent from the following detailed description taken with reference to the drawings, wherein: Fig. 1 is a fragmentary perspective view of an embodiment of the invention. Fig. 2 is a front view of a bobbin case holder. Fig. 3 is a rear view of a bobbin case holder. Fig. 4 is a side view of a bobbin case holder. Fig. 5 is a plan view of a bobbin case holder. Fig. 6 is a sectional view of a bobbin case holder along line VI-VI in Fig. 5. Fig. 7 is a longitudinal sectional view of a full rotary hook. Fig. 8 is a fragmentary perspective view of a bobbin case. Figs. 9(1) and 9(2) are plan views showing an assembled condition of the bobbin case. Fig. 10 is a sectional view in the direction X-X of the bobbin case along line X-X in Fig. 9(1). Fig. 11 is a partial view illustrating the fitting of a latch member in guide grooves. Figs. 12(1)-12(4) are sectional views showing a sequence of assembly of the latch member. Fig. 13 is a fragmentary perspective view of an end of a cylindrical portion of the bobbin case holder and an end of a cylindrical portion of the bobbin case. Fig. 14 is a plan view showing the bobbin case mounted in the bobbin case holder. Fig. 15 is a plan view of a portion adjacent the ends of the cylindrical portions, and Fig. 16 is a similar plan view according to another embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, preferred embodiments of the invention will be described below. Fig. 1 is a fragmentary perspective view of an embodiment of the invention. Fixed on a shaft 1 which is driven to rotate is a hook body 2 wherein a bobbin case holder 3 is housed. A bobbin case 5 which houses a bobbin 4 is housed in the bobbin case holder 3. Fig. 2 is a front view of the bobbin case holder 3, Fig. 3 is a rear view of the bobbin case holder 3, Fig. 4 is a side view of the bobbin case holder 3, Fig. 5 is a plan view of the bobbin case holder and Fig. 6 is a sectional view along line VI-VI of Fig. 5. A longitudinal and horizontal cross section of a full rotary hook including bobbin case holder 3 is shown in Fig. 7. The bobbin 4 includes a winding drum 7 of a straight cylinder shape whereon bobbin thread is wound, and flanges 8 which are fixed to opposite axial ends of the winding drum 7. Extending perpendicularly from a bottom 9 of the bobbin case holder 3 is a stud 10 which passes through the winding drum 7 of the bobbin 4. On the outer periphery of a cylindrical portion 12 of the bobbin case holder 3 is formed a bobbin case holder rib 13 which fits in a hook groove 14 formed in the hook body 2. Fitted in a rotation restraining notch 15 of the bobbin case holder 3 is a rotation restraining member 66 which is fixed to the body of the sewing machine. Thus, when the hook body 2 is rotating in the direction shown by an arrow 16, the bobbin case holder 3 is prevented from rotating. The bobbin case holder rib 13 has formed thereon a thread hook portion 21 for hooking the needle thread loop and a thread releasing portion 22. In order to increase the quantity of bobbin thread wound on bobbin 4 the outer diameter of the flanges 8 is increased. Accordingly, the diameter of a cylindrical portion 23 of the bobbin case 5 may be increased and the wall thickness of the cylindrical portion 12 of the bobbin case holder 3 must be decreased. When the inner diameter of the bobbin case holder 3 is increased and overall wall thickness is decreased, the strength of the cylindrical portion 12 is lowered. According to the invention, a thickness tl of a part 12a of cylindrical portion 12 extending circumferentially from the thread hook portion 21 to the thread releasing portion 22 is less than a thickness t2 of a remainder portion 12b of cylindrical portion 12. Inner diameters of the portions 12a, 12b are equal and uniform and the difference between the thickness tl of the portion 12a and the thickness t2 of the portion 12b is Δt. The needle thread is present in a zone W1 corresponding to portion 12a and having reduced thickness tl. Thus, the needle thread does not receive undesirably large friction forces in the space between the outer periphery of the portion 12a and the inner periphery of the hook body 2. The remainder portion 12b has thickness t2 which is sufficient to maintain the necessary strength of the cylindrical portion 12. For example, inner diameter 2R of the cylindrical portion 12 of the bobbin case holder 3 may be greater than the inner diameter of the conventional bobbin case holder by 0.6 mm, the outer diameter of the portion 12a may be equal to the outer diameter of the cylindrical portion of the conventional bobbin case holder, and outer diameter of the remainder portion 12b may be greater than the outer diameter of the cylindrical portion of the conventional bobbin case holder by 0.6 mm. Fig. 8 is a fragmentary perspective view of the bobbin case 5 of the invention, and Fig. 9(1) and 9(2) are front views showing conditions of assembly of the bobbin case 5. The cylindrical portion 12 of the bobbin case holder 3 and the cylindrical portion 23 of the bobbin case 5 axially overlap along a portion of the circumferential dimensions thereof. An upstream end 26 relative to the direction 16 of rotation of hook body 2 of the cylindrical portion 12 of the bobbin case holder 3 and a downstream end 27 relative to direction 16 of the cylindrical portion 23 of the bobbin case 5 are opposingly disposed near the rotation restraining notch 15 of the bobbin case holder 3. An outward flange 29 is formed in the body 28 of the bobbin case 5 to guide the needle thread loop and to control the slack of the needle thread to a small amount. In an end face of the body 28 of the bobbin case 5 at the side of the open end of the bobbin case holder 3 are formed a pair of opposing guide grooves 31, 32 defined by guide portions 33, 34. The guide grooves 31, 32 extend parallel to the radial direction of the bobbin case 5 and opposite sides of a latch member 35 are fitted in and freely movable along the guide grooves 31, 32. Formed at an end of the latch member 35 is a bent tail portion 36 which passes through a hole 37 formed in the body 28 of the bobbin case 5 and enters the bobbin case 5 in the axial direction of the body 28. The hole 37 extends in the radial direction of the bobbin case 5. The tail portion 36 contacts the outer periphery of the flange of bobbin 4 that is disposed at the open end side of the bobbin case holder 3. Such contact enables the bobbin case 5 and the bobbin 4 to be removed together from the bobbin case holder 3, when bobbin 4 is locked in bobbin case 5. In an end of the latch member 35, opposite the tail portion 36 is formed a through hole 39 e.g. by bending a part of the latch member 35, thus forming supports 44 of a hinge 38. On an end of an operating piece 40 is formed a through hole 45 e.g. by bending the material of member 40, thus forming a support 41 of hinge 38. A hinge pin 42 passes through one hole 39 of the latch member 35, through the hole 45 of the member 40 and through the other hole 39 of member 35. Thereby the latch member 35 and the operating member 40 are connected for relative angular displacement around the axis of the hinge pin 42. Formed on a side of the latch member 35 is a spring receiving element 43 which projects outwardly. The latch member 35 has also formed therein a latch hole 46 extending in the longitudinal direction thereof. An end 46a of the latch hole 46 is engaged with a small diameter portion 47 formed at an end of the stud 10 and latched thereby. The latched condition is released by movement of the latch member 35. The guide groove 31 formed by the guide portion 33 is parallel to a diameter 48 of the bobbin case 5. The guide portion 34 has a part 34a which is near the hole 37 and a part 34b which is spaced from the hole 37, and accordingly the guide groove 32 has a portion 32a which is near the hole 37 and a part 32b which is spaced from the hole 37. The guide groove portions 32a, 32b have a step 50 formed therebetween. Fig. 10 is a sectional view along line X-X of Fig. 9(1). Installed in the guide groove portion 32a is a coil spring 51 one end of which is in contact with the step 50 and other end of which is in contact with the spring receiving element 43. Thus, the spring 51 forces the latch member 35 in the direction of arrow 52 in Fig. 9(1) and (2), namely outwardly in the radial direction of the body 28 of the bobbin case 5. The part 34a of the guide portion 34 near hole 37 is recessed in a direction away from guide groove 31. In mounting the latch member 35 on the body 28 of the bobbin case 5, one side of the latch member 35 is inserted in the guide groove 31 as shown in Fig. 11, and the latch member 35 is caused to make an angular displacement in the direction of the arrow 53 such that the tail portion 36 is located in the hole 37, whereby the latch member 35 is in the position shown in Fig. 9(1) and Fig. 10. In this condition, the side of the latch member 35 which includes the spring receiving element 43 is exposed from the guide groove 32. The operating member 40 has a cam 54 formed at an end thereof. The cam 54 pulls the latch member 35 in the direction of an arrow 55, against the force of the spring 51 as shown in Fig. 12(1), when the operating member 40 is angularly displaced in the direction of an arrow 57a. By locating the bobbin case 5 which houses the bobbin 4 in the bobbin case holder 3 such that the cam 54 extends into an operating hole 56 formed in the body 28 of the bobbin case 5 as shown in Fig. 12(2), an edge 46a of the latch member 35 is pressed against a spherical end 80 of the stud 10. Accordingly the latch member 35 is displaced in the direction of an arrow 55a and fits into the small diameter portion 47 of the stud 10. Thus, the bobbin case 5 which houses the bobbin 4 is latched in the bobbin case holder 3, and unintentional release therefrom is prevented. When the operating member 40 makes an angular displacement in the direction of an arrow 57, the spring 51 urges the operating member 40 to make an angular displacement in the direction of the arrow 57. Therefore, in the condition shown in Fig. 12(1), as shown in Fig. 9(2), the spring receiving element 43 is in the guide groove portion 32a, the corresponding side of the latch member 35 is in the guide groove portion 32b and the other side of the latch member 35 is in the guide groove 31. Accordingly the latch member 35 can stably move along the guide grooves 31, 32. When the operating member 40 is released by hand, the operating member 40 make an angular displacement in the direction of the arrow 57 by the spring force of the spring 51 and makes an angular displacement from the position shown in Fig. 12(3) to the position shown in Fig. 12(4), with the end 46a of the latch hole 46 of the latch member 35 within the small diameter latching portion 47 of the stud 10, thereby achieving a latched state. When the operating member 40 is raised in the direction 57a reverse to the arrow 57, the cam 54 comes into contact with the end 56a of the operating hole 56 and the latch member 35 displaces in the direction of an arrow 59 (Fig. 12(3)). Thereby the tail portion 36 presses the flange 8 of the bobbin 4 inwardly in the radial direction and holds it, while the end portion 46a of the latch hole 46 departs from the small diameter portion 47 of stud 10. Therefore, the bobbin case 5 and the bobbin 4 can be removed from the bobbin case holder 3 together, by pulling the bobbin case 5 in the direction of an arrow 60 shown in Fig. 12(3). The latch member 35 has a stopper 62 formed thereon. Displacement of the latch member 35 in the direction of an arrow 59 is restricted by the stopper 62 coming into contact with an end 37a of the hole 37. Fig. 13 is a perspective view of a part of the bobbin case holder 3 and the bobbin case 5. Fig. 14 is a front view of the bobbin case holder 3 housing the bobbin case 5. Near the rotation restraining notch 15 of the bobbin case holder 3, end 26 of the cylindrical portion 12 of bobbin case holder 3 and end 27 of the cylindrical portion 23 of bobbin case 5 oppose each other as described above. As clearly shown in Fig. 14, the end 26 is located further outwardly in the radial direction of the bobbin case holder 3 than the end 27 of the bobbin case 5, that is, a step dl is formed between the end 26 and the end 27. Fig. 15 is an enlarged front view of the vicinity of the ends 26 and 27. When the hook body rotates in the direction 16, the needle thread loop is in the position as indicated by reference 63 in Fig. 14, where the needle thread loop is guided by the flange 29 and controlled so that slackness of the needle thread loop is decreased. When the needle thread loop 63 is lifted by the upward motion of a thread take-up lever (not shown) to the position indicated by reference 64, the needle thread passes over the outer periphery of the flange 29, and comes into contact with a part 26a of the end 26. When the needle thread 64 is further pulled by the thread take-up lever, the needle thread passes between the rotation restraining notch 15 of the bobbin case holder 3 and the rotation restraining member 66. In this manner, when the hook body 2 is rotating at a low speed, in particular, the needle thread loop is hooked on the part 26a of the end 26 and then the needle thread 64 passes between the rotation restraining notch 15 and the rotation restraining member 66. Therefore, the motion of passing through is made smoothly without the needle thread being touching other parts or being caught, and with the needle thread tension being stabilized. Sewing performance thus can be improved. The ends 26, 27 are parallel to the direction of diameter 48 (Fig. 8) of the bobbin case holder 3.

Claims: A full rotary hook, including a bobbin case holder (3) to be mounted in a rotatable hook body (2) and a bobbin case (5) to receive a bobbin (4) removably mounted in said bobbin case holder (3) such that the bobbin case (5) and the bobbin (4) together are mountable on and removable from said bobbin case holder (3), further comprising means to latch said bobbin case (5) and the bobbin (4) in said bobbin case holder (3), said latch means comprising a stud (10) extending coaxially from said bobbin case holder (3) and means on said bobbin case (5) for holding said bobbin (4) to said stud (10), said holding means comprising a pair of opposed guide grooves (31, 32) formed in an end (28) of said bobbin case (5), a latch member (35) having first and second opposite edges slidably received in said first and second guide grooves (32, 31) respectively, said first edge having extending outwardly therefrom a spring receiving element (43) slidable within a recessed portion (32a) of said first guide groove (32), a spring (51) positioned within said first guide groove (32) and having an end abutting said spring receiving element (43) thereby urging said latch member (35) to slide in said guide grooves (31, 32) in a direction causing the surface of said latch member (35) to catch on said stud (10), and said latch member (35) having a bent portion (36) at a longitudinal first end thereof, to abut the bobbin (4), an operating member (40) being pivotally connected to a second end of said latch member (35) and having a cam (54) abuttable against said bobbin case (5) to thereby move said latch member (35) relative to said bobbin case (5) against the force of said spring (51) to release said latch member (35) from said stud (10), said movement being limited by a stopping member (62), extending from said latch member (35) in a direction towards and abuttable against said bobbin case (5), characterized in that the first and second guide grooves (31, 32) enable that said second edge of said latch member (35), with said operating member (40) being pivotally connected thereto, is allowed first to be inserted obliquely into said second guide groove (31), next said latch member (35) is allowed to be angularly displaced in the direction (53) towards said bobbin case (5) and finally to be pushed back against the force of said spring (51) abutting said spring receiving element (43), until said latch member (35) is slidably locked by said cam (54) against movement by the spring (51), said cam (54) extending into an operating hole (56) formed in said bobbin case (5), said receiving element (43) being confined to said first guide groove (32).

Inventors: SHIMIZU HIROMITSU, SHIMIZU, HIROMITSU
Applicants: HIROSE MFG CO LTD, HIROSE MANUFACTURING COMPANY LIMITED
Application year: 1991
Main classification: D05B57
IPC codes: D05B57