LOOP TAKER FOR SEWING MACHINE

Abstract: The invention concerns a loop taker characterized by a bobbin case holder (24) in which is housed a bobbin (32) whose axis (36) is inclined relative to the rotational axis (37) of a cup-shaped hook body (18) in such a way that the bobbin (32) is kept away from a path of needle (41) movement, and also a sewing machine equipped with the loop taker. Thereby, it is possible to increase the outer diameter of the bobbin (32) or increase the length of the bobbin (32), and it is possible to increase the quantity of bobbin thread (32) wound on the bobbin (32).

Description: This invention relates to a loop taker for a sewing machine. A typical prior art arrangement is shown in FIG.1. A horizontal axis full rotary loop taker has a cup shaped hook body 1 which supports a bobbin case holder 2 in position. In the bobbin case holder 2 there is mounted a bobbin case 5 shown by a virtual line for housing a bobbin 4 on which a bobbin thread 3 is wound. The hook body 1 is fixedly mounted on a horizontal rotary shaft 6 for rotation therewith. A needle 7, as arrows 8 show, is reciprocatingly up and down movable, the lowermost point of the path of its movement being shown by reference numeral 9. The rotation axis of the bobbin 4 is on a straight line coaxially or in parallel with the rotary shaft 6. FIG.2 is a sectional view of the hook body 1 in which the bobbin case holder 2 is housed. A bobbin case holder rib 10 formed on the outer periphery of the holder 2 is fitted in a hook groove 11 formed in the hook body 1. A loop 13 of a needle thread 12 is seized by a loop seizing point 17, and as the hook body 1 rotates, the thread 12 progresses from its loop condition as shown in FIG.3(1) into a loop state as shown in FIG.3 (2). The needle thread 12 passes itself through the loop while being in contact with a lower portion 14a of the bottom 14 of the bobbin case holder 2, and further it slides around the bottom 14 of the holder 2 as FIG.3(3) shows. In such prior art arrangement, if the quantity of the bobbin thread wound on the bobbin 4 is to be increased, it is necessary either to (a) increase the outer diameter D of the bobbin 4 or to (b) increase the axial length H of the bobbin 4. (a) In case that the outer diameter D of the bobbin 4 is increased, the hook groove 11 in the hook body 1 and the rib 10 on the holder 2 are necessarily diametrically enlarged. Therefore, if the rotational speed of the hook body 1 is constant, the peripheral speed of the hook groove 11 will be increased. Accordingly, the frictional force between the hook groove 11 and the rib 10 will be increased. As a consequence, there will be an increase in the value of heat release involved. As a result of the increase in frictional force, considerable tension will be exerted on the needle thread 12 when the thread 12 passes through an abutment surface between a rotation restraining notch 15 of the bobbin case holder 2 and a stopper member which is in engagement with the notch 15. Thus, stitches are unfavorably affected in tightness, which fact is likely to lead to incidental knotted needle thread or looping. (b) For the purpose of increasing the axial length H of the bobbin 4, two approaches may be considered: (b1) the bobbin 4 is extended toward the open end side (right ward in FIG.1) of the bobbin case holder 2, and (b2) the bottom 14 of the bobbin case holder 2 is extended leftward in FIG.1, while the bobbin 4 is extended toward the bottom 14 side. In case that the (b1) approach of extending the bobbin 4 toward the open end side of the case holder 2 is adopted, the trouble is that in the up and down reciprocating movement of the needle 7, the needle point will be lowered radially inwardly of the radially outer side of the bobbin thread 3 wound on the bobbin 4, when it is lowered to the lowermost point 9 of needle movement, so that the needle 7 will run into the bobbin thread 3 wound on the bobbin 4, whereby breakage may be caused to the bobbin thread 3 wound on the bobbin 4. In case that the (b2) approach of extending the bottom 14 of the bobbin case holder 2 leftward in FIG.1 is adopted, as FIG.4 shows, the resulting configuration is such that the prior arrangement bottom 14 shown by a virtual line is extended leftward in FIG. 4. As such, the needle thread 12 is caught in the lower portion 14a of the bottom 14 of the bobbin case holder 2 and thus thread passing is rendered impossible, with the result that sewing is made impossible. A loop taker for a sewing machine, comprising a bobbin case holder in which is housed a bobbin, whose axis is inclined relative to the rotational axis of a cup-shaped hook body is already known from US-A-1,484,624. In this known loop taker the path of the needle movement is directed to about the center of the bobbin, positioned in the bobbin case holder, with the end planes of the bobbin being positioned at opposite sides of the path of needle movement. For this reason the diameter of the race plate or bobbin case holder rib is necessarily much larger than the diameter of the bobbin, in order to avoid that the lower point of the needle will run into the bobbin thread wound on the bobbin. The object of the invention is to provide a loop taker for a sewing machine, which eliminates the above mentioned problems arising from increasing the outer diameter or the length of the bobbin and enables the increase of the quantity of bobbin thread, wound on the bobbin, without increasing substantially the diameter of the bobbin case holder rib. According to the invention this object is accomplished by a loop taker in which the axis of the bobbin is inclined in such a way that the bobbin is kept away from a path of needle movement, said path being along a needle axis, which intersects a plane containing one axial end of the bobbin the plane being perpendicular to the axis of the bobbin and the path of needle movement terminating at a point spaced from the axis of the bobbin by a distance less than the distanc between the axis of the bobbin and a radially outermost point of the bobbin. With a loop taker according to the invention, it is possible to increase the outer diameter of the bobbin and/or the axial length of the bobbin by inclining the axis of the bobbin relative to the rotational axis of the hook body. Thus, it is possible to increase the quantity of bobbin thread wound on the bobbin. In this case, it is unnecessary to substantially increase the outer diameter of the rib of the bobbin case holder for housing the bobbin. Therefore, the hook body of an existing arrangement may be employed as it is. The needle thread delivery of any existing needle thread take-up may also be used as it is and need not be changed. Therefore, the invention eliminates all such problems as increased heat generation, unfavorable stitch tightness, thread breakage, and needle thread passing difficulty, which have been earlier mentioned in conjunction with the prior art arrangement. These and other objects, features and advantages of the invention will become more apparent upon a reading of the following detailed specification and drawing, in which: FIG.1 is a sectional view showing a prior art arrangement; FIG.2 is a sectional view in side elevation showing a bobbin case holder 2 in the prior art arrangement in FIG.1; FIG.3 is a side view illustrating aspects of operation of the prior art arrangement; FIG. 4 is a side view of the bobbin case holder 2 for illustration of problems of the prior art arrangement; FIG.5 is a sectional view showing one embodiment of the invention; FIG.6 is a perspective view of the embodiment shown in FIG.5; FIG.7 is a perspective view of a bobbin 32; and FIG.8 is a side view of a bobbin case holder 24. Referring now to the drawings, embodiments of the invention are described below. FIG.5 is a sectional view showing one embodiment of the invention, and FIG.6 is a perspective view thereof. A cup-shaped hook body 18 includes a hook body proper 19 and a mounting portion 20. The mounting portion 20 is fixed to a rotary shaft 21 having a horizontal mounting axis. A rotating hook section 22 is fixed to the hook body proper 19 to define a hook groove 23. The hook groove 23 extends circumferentially within an imaginary plane perpendicular to the rotational axis of the rotary shaft 21. On the outer periphery of bobbin case holder 24 there is formed a bobbin case holder rib 25 which fits in the hook groove 23 so as to be supported by the hook body 18, the rib lying in a plane C, which is substantially parallel to the path of needle movement. The hook body 18 has a loop seizing point 26 and a spring 27. A protrusion 30 of a rotating restraining member 29 fixed to a sewing machine body or the like is fitted in a rotation restraining notch 28 formed in the bobbin case holder 24, being thereby retained. In a recess 31 of the holder 24 there is mounted a bobbin case 53 housing a bobbin 32 shown in FIG.7. A bobbin thread 33 is wound on the bobbin 32. The bobbin 32 has a center hole 34 through which a stud 35 extends, said stud 35 being mounted on a bottom 31a of a housing recess 31 of the bobbin case holder 24 in perpendicular relation thereto. The axis of the stud 35, that is, a rotational axis 36 of the bobbin 32, is inclined at an angle of ϑ relative to a rotational axis 37 of the hook body 18. The bobbin 32 has a right circular cylindrical body 38 on which bobbin thread 33 is wound and which is formed with the center hole 34 through which the stud 35 extends, and also has a pair of flanges 39, 40 fixed to the cylindrical body 38 at both ends thereof. A needle 41 is up and down movable in the directions of arrows 42, the lowermost point of the needle 41 in the path of its movement being shown by reference numeral 43. Flanges 39, to extend in respective planes B, E inclined to the path of needle movement at an angle. The angle ϑ of the axis 36 of the bobbin 32 is determined in such a way that the bobbin 32 is kept away from the path of movement of the needle 41 which extends upward and downward in FIG. 5 and such that the needle 41 may not strike the flange 39 at the lowermost point 43 of needle movement, the path of needle movement being along a needle axis A which intersects a plane B containing one axial end of the bobbin, the plane being perpendicular to the axis of the bobbin and the path of needle movement terminating at a point spaced from the axis of the bobbin by a distance D less than a distance D¹ between the axis of the bobbin and a radially outermost point of the bobbin, for example, the angle ϑ is 5 degrees or above. By inclining the axis 36 of the bobbin 32 at angle ϑ relative to the rotational axis 37 of the hook body 18 in this way it is possible to increase the outer diameter of flanges 39,40 of the bobbin 32 or increase the length of the bobbin 32, that is, the axial length of the cylindrical body 38 to which the flanges 39,40 are coupled and on which bobbin thread 33 is wound; and thus it is possible to increase the quantity of bobbin thread winding 33 by some 50%, for example, over aforesaid prior art arrangement. The bottom 44 of the bobbin case holder 24 is generally flat and the upper end 44a of the bottom 44 is only required to have a very small gap d enough to permit the passage of the needle thread. Therefore, it is possible to utilize a comparatively large gap d1 present in a conventional arrangement as shown in FIG.1 for the purpose of the invention, thus ensuring most effective and advantageous utilization of any available idle space. In the prior art, the flange side surfaces of the bobbin 32 on the open end side of the bobbin case holder 24 can not be allowed to extend beyond the up and down needle position on said open end side. In the present embodiment, on the other hand, the flange side surfaces of the bobbin 32 can be allowed to extend on said open end side at a level lower than the lowermost point 43 of needle movement, irrespective of the path of needle 41 movement. In this respect, too, any idle space can be advantageously utilized for the purpose of the invention. According to the invention, the hook body may be of any conventional construction; it is only necessary that the bobbin case holder 24, the bobbin 32, and the bobbin case 53 should be replaced by those according to the invention. Thus, the invention provides the advantage that the amount of bobbin thread winding can be remarkably increased. Furthermore, the bottom 44 of the bobbin case holder 24, as FIG. 8 shows, is configuredly expanded on the base end side of the hook body 18 (left-hand side in FIGS.5 and 8) toward the upper end 44a. This enables the needle thread 45 to smoothly slide on the bottom 44 in the direction of arrow 46 without the needle thread 45 being caught at the lower portion 47 of the bottom 44, accurate thread passage being thus made possible. The invention provides a further advantage that, as already mentioned, when the bobbin case holder 24, bobbin 32, and bobbin case 53 according to the invention are mounted in a conventional sewing machine in order to increase the amount of bobbin thread 33 winding, there is no necessity of changing the amount of thread delivery of the needle thread take-up in the machine. This assures easy application of the invention in conjunction with any conventional sewing machine. In another embodiment of the invention, this invention can be applied in conjunction with a sewing machine in which the bobbin case holder 24 and the bobbin case 53 are integrally incorporated. The bobbin case holder 24 need not be provided with a stud 35.

Claims: A loop taker for a sewing machine, comprising a bobbin case holder (24) in which is housed a bobbin (32), whose axis (36) is inclined relative to the rotational axis (37) of a cup-shaped hook body (18), characterised in that the axis (36) is inclined in such a way that the bobbin (32) is kept away from a path of needle movement, said path being along a needle axis (A), which intersects a plane (B) containing one axial end (39) of the bobbin (32) the plane (B) being perpendicular to the axis (36) of the bobbin (32) and the path of needle movement (A) terminating at a point (43) spaced from the axis (36) of the bobbin (32) by a distance (D) less than the distance (D¹) between the axis (36) of the bobbin (32) and a radially outermost point of the bobbin (32).

Inventors: SHIMIZU, HIROMITSU
Applicants: HIROSE MANUFACTURING COMPANY LIMITED
Application year: 1987
Main classification: D05B57
IPC codes: D05B55, D05B57