THREAD TAKE-UP LEVER DEVICE FOR SEWING MACHINES

Abstract: An upper thread (6) is guided to extend vertically by a pair of thread guides (4) vertically opposed to each other. A thread take-up lever (9, 9a, 9b, 9c, 46) is installed so that it is horizontally reciprocated across the space between the pair of thread guides. When the thread take-up lever is reciprocated, it engages the thread positioned between the thread guides to draw it in V-form during its forward travel and stops drawing the thread to form a slack in the thread in its return travel. To prevent this slacked thread portion from clinging to the thread take-up lever, a thread holding member (28, 29, 30, 31, 32, 33) or thread braking member (36, 37, 38, 41, 45, 49) made of easily deformable material and adapted to contact the thread to thereby prevent the thread from following the movement of the thread is installed at at least one position along the path of travel of the thread engaging portion (10, 10a, 10b, 10c, 50) of the thread take-up lever.

Description: This invention relates to a thread take-up lever device for sewing machines and particularly to improvements for enhancing the performance of the thread take-up lever itself included in a thread take-up lever device. In the most common sewing machine, the thread take-up lever has an eyelet through which thread is passed. In operative association with the upper shaft or main shaft housed in the sewing machine frame and driven for rotation, the thread take-up lever is vertically reciprocated to tighten or loosen the thread to form a stitch. Usually the thread take-up lever is reciprocated in a vertically extending slit formed in the frame. The eyelet extends beyond the frame over at least a portion of the range of reciprocating motion of the thread take-up lever to permit thread to be passed through the eyelet. For this reason, it has been impossible to house the thread take-up lever completely within the frame. An eyeletless thread take-up lever is disclosed in United States Patent No. 3,782,312 which describes a thread take-up lever formed with a hook portion adapted to engage the thread. Thus, the threading of the eyelet is unnecessary and hence the thread take-up lever can be completely housed within the frame. A thread take-up lever functions to tighten or loosen the thread in accordance with its reciprocating motion. In this connection, it is to be noted that because of its tightening action on the thread, the thread take-up lever often causes the thread to break. On such occasions, the thread suddenly loosens and clings to the thread take-up lever and in extreme cases it coils itself around the thread take-up lever. In such instances it is very difficult to release the thread, particularly in a sewing machine of the type in which the thread take-up lever is housed completely in the frame. Furthermore, such clinging to the thread take-up lever may occur frequently even when the thread has not broken, for example, when using a fluffy or hard-twist thread. US 4,413,578 describes a complex device, adapted to overcome the problems described above, which comprises a vertically reciprocating take-up member and a thread handling device which includes a rod, a fibre pile member and cams. The thread engaging portion of the take-up member does not at any point contact the fibre pile member and it is the combination of the shape of the cams and the fibre pile member which prevent slack formation. An object of this invention is to provide a thread take-up lever device for sewing machines which is capable of preventing a thread from clinging to the thread take-up lever. Accordingly, the present invention seeks to provide a thread take-up device for sewing machines comprising a thread take-up lever having a portion adapted to engage a thread and being reciprocable along a predetermined path to draw the thread during its forward travel along that path, and a thread braking means comprising a skirt of flexible material fixed in at least one position and which is adapted to contact the thread engaged by the thread engaging portion and to separate therefrom the slack which forms in the thread during the return travel of the thread engaging portion and to prevent the thread from clinging to the thread engaging portion during its return travel, characterised in that the skirt intersects the path of travel of the thread engaging portion such that the thread engaging portion projects underneath the skirt at least at the end of its forward travel, and retracts from that position at least at the end of its return travel. Therefore, the thread braking means is in a fixed position and contacts a portion of the thread held the thread take-up lever. Therefore, even if a thread break occurs, the thread is not permitted to follow the return travel of the thread take-up lever because of the presence of the thread braking means, which separates from the thread from the thread take-up lever. Further, when a thread clings to the thread take-up lever and will not break, a slack in the thread which forms during the return travel of the thread take-up lever tends to be separated from the thread take-up lever because of its contact with the thread braking means. Therefore, the clinging of the thread to the thread take-up lever and the thread coiling problem are advantageously prevented. Various embodiments of the present invention will now be described by ways of example only with reference to the accompanying drawings in which: Fig. 1 is a perspective view of a portion of a sewing machine showing an embodiment of the invention; Fig. 2 is a top view showing a thread take-up lever 9 provided with an engaging portion 10 adapted to be reciprocated within a thread guide member 4 shown in Fig. 1; Figs. 3A through 3F illustrate the operation of the thread take-up lever 9, a needle 8 and a shuttle hook 19 when the engaging portion 10 is positioned at positions A through F shown in Fig. 2; Figs. 4 through 8 show sequentially the process of a thread 6 coiling itself around the thread take-up lever 9 following a thread break; Figs. 9D and 9E correspond to Figs. 3D and 3E respectively, and illustrate the thread 6 clinging to the thread take-up lever 9 which occurs when using hard-twist thread; Figs. 10D and 10E correspond to Figs. 3D and 3E respectively, and illustrate the thread 6 clinging to a thread take-up lever 9 which retains the thread 6 even during its return travel; Fig. 11 is a top view of the principal portion of a sewing machine having an embodiment of the invention, the thread guide member 4 being shown in section; Fig. 12 is a front, partly broken view of the thread guide member 4 shown in Fig. 11; Figs. 13 and 14 are perspective views which show the thread take-up lever 9 acting on a cover 34 shown in Fig. 11; Fig. 15 is a top view showing the engaging portion of a thread take-up lever 9b used in another embodiment; Fig. 16 is a top view showing the thread take-up lever 9b of Fig. 15 acting on a skirt member 41; Fig. 17 is an enlarged perspective view showing the relationship between the thread take-up lever 9b and the skirt member 41; Fig. 18 is a top view showing the principal portion of a sewing machine having another embodiment of the invention; Fig. 19 is a front view showing the relationship between a skirt member 45 and a thread take-up lever 9c shown in Fig. 18; and Fig. 20 is a top view showing the principal portion of a sewing machine having another embodiment of the invention. The invention is applicable to a thread take-up lever device having a thread take-up lever formed with an eyelet for receiving a thread, as is usually found in the more common sewing machines, but effective particularly when applied to a thread take-up lever device disclosed in the copending application, European Patent Application No. 86303340.3 (Patent No. 0204426). European Patent No. 0204426 describes a pair of thread guide means spaced a predetermined distance from each other on opposite sides of the path of travel of a thread engaging portion of the thread take-up lever. The pair of thread guide means are respectively formed with through-passages to allow a thread to pass therethrough in a direction which is substantially orthogonal to that path. While being reciprocated between the pair of thread guide means, the engaging portion of the thread take-up lever engages a portion of thread located between the thread guide means and draws the thread during its forward travel and releases the thread in its return travel. Fig. 1 is a perspective view of a portion of a sewing machine having that described in EP 0204426. In Fig. 1, the upper wall and front wall of the arm head 1 of a sewing machine frame are formed with a slit 2, a portion of which is shown, extending in a vertical plane. As shown a tension regulator device 3 and a thread guide member 4 are disposed within the arm head 1 in positional association with the slit 2. The thread guide member 4 itself forms the "pair of thread guide means," and the "through-passage" is realized by a single groove 5 continuously extending over the upper, front and lower walls of the thread guide member 4. An upper thread 6 fed from a thread supply source, such as a bobbin (not shown), is engaged by a thread guide element 7 and inserted in the slit 2, and then it is passed through the eyelet of a needle 8. When the thread 6 is inserted in the slit 2, it is held between a pair of tension disks provided in the tension regulator device 3 while it is received in the groove 5 of the thread guide member 4. The thread guide member 4 has a horizontally extending opening in its rear side, and the engaging portion of a thread take-up lever (not shown in Fig. 1) adapted to engaged the thread 6, projects into the opening, the engaging portion being horizontally reciprocated within said thread guide member 4. Fig. 2, is a top view of the type of thread take-up lever described above. The thread take-up lever 9 shown therein has an engaging portion 10 in the form of a hook formed on the front end thereof. The engaging portion 10 is reciprocated in such a manner that the path of its forward travel differs from the path of its return travel. A disk 12 operatively associated with the main shaft (not shown) housed in the sewing machine frame is rotated in the direction of arrow 11, the disk 12 having a pin 13 mounted at an eccentric position thereon. The thread take-up lever 9, which is L-shaped, is pivotally connected at one end thereof to the pin 13. A connecting link 15 is pivotally supported at one end thereof on a pin 14 fixed to the frame. The other end of the connecting link 15 is pivotally connected to the angled portion of the thread take-up lever 9 by a pin 16. In such an arrangement, when the disk 12 is rotated in the direction of arrow 11, the thread take-up lever 9 performs a swing motion such that the engaging portion 10 moves along a path 17 during its forward travel and along a path 18 during its return travel. In Fig. 2, the position of the groove 5 is illustrated to clarify the positional relationship between the range of movement of the thread take-up lever 9 and the thread guide member 4 shown in Fig. 1. The path followed by the thread take-up lever 9, particularly by its engaging portion 10 are shown at A , B , C , D , E , and F . Figs. 3A through 3F illustrate the operational relationship between the engaging portion 10 or the thread take-up lever 9, the needle 8 and the shuttle hook 19. The suffixes A through F in Figs. 3A through 3F correspond to A through F , respectively, shown in Fig. 2. In Fig. 3A, the engaging portion 10 during its forward travel engages the thread 6. The needle 8 is moving upward. The shuttle hook 19, arresting the thread 6, is rotated clockwise to the limit angle while drawing the thread 6 downward. In Fig. 3B, the engaging portion 10 quickly draws upwards the thread 6 disengaged from the shuttle hook 19. The shuttle hook 19 is rotated anti-clockwise as soon as it releases the thread 6. In Fig. 3C, the engaging portion 10 reaches the extreme right during its forward travel to pull the thread 6 taut. The needle 8 is lowering. The shuttle hook 19 is rotated anti-clockwise in order to arrest the thread 6. Fig. 3D, shows the engaging portion 10 switching from forward to return travel. The speed of the engaging portion 10 in its return travel corresponds substantially to the speed at which the thread 6 is pulled downward by the needle 8. The needle 8 reaches its lowest point and then starts to rise, At which time, the thread slackens and forms a loop to be arrested by the shuttle hook 19 during its clockwise rotation. In Fig; 3E, the return travel of the engaging portion 10 is faster than the rate at which the thread 6 is pulled downward. As a result, the thread 6 is left behind by the thread take-up lever 9 whilst slacking in the vicinity of the engaging portion 10. Prior to the needle 8 being extracted from the fabric 20, the shuttle hook 19 arrests the loop of the thread 6. In Fig. 3F, the engaging portion 10 completes its return travel and turns to its forward travel. The needle 8 further rises. The shuttle hook 19 pulls the thread 6 downward as it is rotated. Thereafter, the state of Fig. 3A is restored and the operation is repeated. The operation described is the normal operation. However, if a thread break occurs, then the thread 6 clings to the thread take-up lever 9 and will eventually coil itself around the thread take-up lever 9 as illustrated by Figs. 4 to 8. If a thread break occurs as the thread take-up lever 9 draws the thread 6, then a slack will form in the thread 6 during the return travel of the thread take-up lever 9, as shown in Fig. 5. When the thread take-up lever 9 has completed its return travel, the thread 6 clings to the thread take-up lever 9 and, as shown as shown in Figs. 7 and 8, when the thread take-up lever 9 starts its forward travel, the thread 6 coils around the thread take-up lever 9. The above-described problem of the thread 6 clinging to or coiling around the thread take-up lever 9 is not limited to situations when a thread break has occured. For example, fluffy or hard-twist thread tends to cling to the thread take-up lever 9. Figs. 9D and 9E shows operating steps corresponding to Figs. 3D and 3E, respectively. In Fig. 9D, the thread 6, released from the thread take-up lever 9, forms a one-sided slack. In Fig. 9E, the one-sided slack in the thread 6 causes the thread 6 to cling to the thread take-up lever 9 during the return travel of the thread take-up lever 9. As shown in Figs. 6 to 8, the thread 6 will still cling to the thread take-up lever 9 during its forward travel. The clinging of the thread 6 to the thread take-up lever 9 described with reference to Figs. 4 through 8, and 9D and 9E also occurs with a thread take-up lever adapted to retain the thread during its return travel. Figs. 10D and 10E (corresponding to Figs 3D and 3E) show the operation of a thread take-up lever 9a adapted to retain the thread 6 during its return travel. The thread take-up lever 9a shown in Figs. 10D and 10E is designed so that its engaging portion 10a receives the thread 6 from the side and does not readily release the thread 6 therefrom even during return travel. The hook which comprises the engaging portion 10a of the thread take-up lever is formed with a clearance 21 which allows only passage of the thread 6, the engaging portion 10a being closed except for the clearance 21. In Fig. 10D, a slack is formed in the thread. The thread 6 then has a tendency to untwist, and the slack portion of the thread 6 tends to deform in response to this untwisting. In Fig. 10D, the slack in the thread 6 having been formed below the thread take-up lever 9a is indicated at 22. The slack 22 deforms as a result of the untwisting and runs on to the thread take-up lever 9a. In Fig. 10E, as a result of the shuttle hook 19 arresting the thread 6, the thread clings firmly to the thread take-up lever 9a. The ways in which the thread 6 may cling to the thread take-up lever 9 or 9a as shown in Figs 4 to 8, Figs. 9D and 9E and Figs 10D and 10E are by way of example only. The aforementioned problems of the thread 6 clinging to or coiling around the thread take-up lever 9 or 9a, disrupts the normal operation of the sewing machine. Further, when clinging occurs in the absence of a thread break, normal stitches cannot be formed and missed stitches often occur. Thus, it is necessary to prevent such clinging of the thread 6 to the thread take-up lever 9 or 9a. A thread take-up device which is designed to prevent clinging thread is shown in Figs. 11 to 14. In the embodiment shown in Figs. 11 to 14, a cover 34 is attached to a thread guide member 4 with the main portion of the cover 34 positioned within the thread guide member 4. The cover 34 is formed with a slot 35 which receives the engaging portion 10 of a thread take-up lever 9 to allow the reciprocating motion of the engaging portion 10. A skirt member 36 is attached at its upper edge to the cover 34 and extends over the slot 35. The skirt member 36 is formed of a flexible sheet material such as a fabric, resin sheet, leather or the like. The thread take-up lever 9 arrests the vertically extending thread 6 in the groove 5, by its engaging portion 10 during its forward travel, and as shown in Fig. 19. As it draws the thread 6 the engaging portion 10 projects beneath the skirt member 36. During the return travel of the thread take-up lever 9, as shown in Fig. 20, the engaging portion 10 retracts from its projecting position and the thread 6 is separated from the thread take-up lever 9 by the skirt member 36. The skirt member 36, therefore, functions as thread braking means which acts to contact the thread engaged by the thread engaging portion and to separate therefrom the slack which forms in the thread during the return travel of the thread engaging portion to prevent the thread from clinging to the thread engaging portion during its return travel. Such thread braking means need only be positioned to extend across the path of travel of the engaging portion 10. The embodiment shown in Figs. 15 to 17 is characterized by the construction of the engaging portion of a thread take-up lever. The engaging portion 10b of the thread take-up lever 9b is closed by a plate spring 39 which can be deformed by a relatively light force. Therefore, the thread is received by the engaging portion 10 by deforming the plate spring 39. However, the thread once held by the engaging portion 10b cannot escape readily therefrom. The thread take-up lever 9b shown in Fig. 15, similar to the thread take-up lever 9a shown in Fig. 10D, retains the thread during its return travel. Figs. 16 and 17 show a device having, a cover 40 of substantially the same construction as that of the cover 34 shown in Fig. 11 and a skirt member 41 installed in substantially the same manner the skirt member 36. In the embodiment described above, the skirt member 41 acts to pull the thread 6 from the engaging portion 10b to straighten the slack in the thread 6 so that the thread is tensioned. Therefore, the problem of the thread 6 clinging to the take-up lever 9b is advantageously prevented. The embodiment shown in Figs. 18 and 19 comprises a thread take-up lever 9c which is reciprocated about the axis of a fixed pin 42, so that its engaging portion 10c is moved along the same arcuate path both in its forward and return motion. In this embodiment, a cover 44 having a slot 43 is attached to a thread guide member 4. A skirt member 45 is attached to the cover 44 as shown in Fig. 13. According to this embodiment, engaging portion 10c of the thread take-up lever 9c extends beneath the skirt member 45 during both forward and return travel. The thread take-up lever 46 shown in Fig. 28 is linearly reciprocated as it is guided by a straight rod 47. The device has a cover 48 formed with a slot, a thread guide member 4 and a skirt member 49, similar to that shown in Fig. 19. In the embodiment described above, when the thread take-up lever 46 is reciprocated, its engaging portion 50 passes beneath the skirt member 49 both in its forward and return travels. The devices described above prevent the thread from not only clinging to the thread take-up lever but also from entering the mechanism which drives the thread take-up lever; thus, it prevents the thread from being entangled in such a mechanism or from breaking as a result of such entanglement.

Claims: A thread take-up device for sewing machines comprising a thread take-up lever (9, 9b, 9c, 46) having a portion (10, 10b, 10c, 50) adapted to engage a thread (6) and being reciprocable along a predetermined path to draw the thread during its forward travel along that path, and a thread braking means comprising a skirt of flexible material (36,41,45,49) fixed in at least one position and which is adapted to contact the thread engaged by the thread engaging portion and to separate therefrom the slack which forms in the thread during the return travel of the thread engaging portion and to prevent the thread from clinging to the thread engaging portion during its return travel, characterised in that the skirt intersects the path of travel of the thread engaging portion such that the thread engaging portion projects underneath the skirt at least at the end of its forward travel, and retracts from that position at least at the end of its return travel. A thread take-up device according to claim 1, further comprising a thread guide (4) disposed on both sides of the predetermined path to define a passage through which the thread can pass in a direction substantially orthogonal to the predetermined path. A thread take-up device according to claim 2, wherein the thread guide (4) also comprises a cover (34,40,44,48) formed with a slot (35,43) for receiving the thread engaging portion (10,10b,10c,50). A thread take-up device according to claim 3, wherein the skirt (36,41,45,49) is attached to the cover (34) and extends over the slot (35,43). A thread take-up lever according to any preceding claim, wherein the skirt is of fabric, resin sheet or leather. A thread take-up device according to any preceding claim, wherein the thread engaging portion (10b) is adapted to engage the thread in both its forward and return travels, and wherein the thread braking means is adapted to pull the thread slack from the thread engaging portion during return travel. A thread take-up device according to claim 6, wherein the engaging portion (10b) is closed by a plate spring (39) and can be opened by a relatively light force. A thread take-up device according to any one of claims 1 to 6, wherein the thread take-up lever (9c) is mounted for rotation about a fixed axis so that the thread engaging portion moves along the same-arcuate path in both its forward and return travels. A thread take-up device according to any one of claims 1 to 6, wherein the thread take-up lever is reciprocated along a linear path.

Inventors: MIKUNI, YOSHIO, TANAKA, OSAMU
Applicants: JAGUAR CO., LTD.
Application year: 1987
Main classification: D05B49
IPC codes: D05B49