JPS6052839B2 - Sewing machine thread tensioning device - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a thread tensioning device for a sewing machine, and in particular, the present invention relates to a thread tensioning device for a sewing machine, and in particular, it ensures that thread is inserted into the device during threading, and that the thread passing through the device is used by the sewing machine. The present invention relates to a device that stably applies tension to the thread without causing it to come loose.

[Prior art]

In the thread tensioning device of a conventional sewing machine, in order to prevent the thread passing through the device from coming off the pair of tension discs during use of the sewing machine, for example,
As shown in Fig. 0, a recess is provided at the periphery of one of the tension discs, and the thread passes between the two tension discs through the recess, or as disclosed in Japanese Patent Publication No. 40-28064. As shown in FIG. 1, pressure is applied to intensively urge one tension plate toward the other tension plate at a position closer to the outside of the sewing machine frame than the thread passage path.

However, in order to apply a weak tension to the thread, if the spring force of the thread tension spring that presses the two tension discs is adjusted to a small value, the thread may not move between the two tension discs while the sewing machine is running, despite the above-mentioned measures. There were times when I fell out of line. In addition, in conventional devices, when there is no thread between both tension discs, both tension discs are pressed against each other by the action of a thread tension spring, and when the thread is inserted between both tension discs, The tension disc is configured to release the spring force of the thread tension spring against the tension disc so that the tension disc can be separated.

However, since each upper thread clamping surface of both tension discs is finished with precision polishing, even after the spring force is released, both tension discs often remain in close contact without separating, especially for a long period of time. This tendency is strong when the spring force of the thread tension spring is left unreleased.

For this reason, when inserting the upper thread between the tension discs at the start of sewing or when the thread breaks, it is necessary to insert the upper thread between the tension discs in a taut state. However, if the operator neglects to tension the upper thread, the upper thread will not be inserted securely between the two tension discs, and as a result,
The desired tension is not applied to the upper thread, resulting in the inconvenience that a tight and correct seam cannot be formed.

[Object] The object of the present invention is to completely eliminate the above-mentioned drawbacks, and more specifically, to make it extremely easy to thread the thread so that it passes through the device, and to To provide a thread tension applying device in which thread passing through the device always passes along a fixed course and does not come off during use of a sewing machine.

[Embodiment] An embodiment in which the present invention is embodied in a needle thread tensioning device for a household sewing machine will be described below with reference to the drawings.

A mounting plate 2 is fixed to the end opening of the hollow arm 1,
A face plate 3 for covering the opening is attached to the mounting plate 2 so as to be openable and closable, and the face plate 3, the hollow arm 1, etc. constitute a sewing machine frame.

Inside the face plate 3, there is a known needle bar 5, which has a needle 4 attached to its lower end and which moves vertically and reciprocally and oscillates in the horizontal direction in conjunction with the main shaft (not shown) of the sewing machine. Presser foot 6 at the bottom end
A presser bar 8 is fixed to the presser bar 8 and is normally applied with a downward pressing force by the action of a compression spring 7. The presser foot lifting lever 9 has a known cam portion (not shown) that faces the protruding piece of the protrusion 10 fixed to the presser bar 8 from below via an operating rod 11 which plays a role to be described later. When the lever 9 is rotated upward, the presser bar 8 is lifted up against the action of the compression spring 7. The mounting plate 2 also includes a first thread guide 12, a guide pin 13, a second thread guide 15 having a thread take-up spring 14, and a guide piece for sequentially guiding the thread T paid out from the needle thread supply source. 16, the third thread guide 17 is fixed. Further, a fourth thread guide 18 is fixed to the lower end of the needle bar 5 together with the needle 4.
A slot 19 is formed between the front end of the hollow arm 1 and the mounting plate 2, and the tip of the thread holding hole 20 projects outward through the slot 19. It constitutes 21 vertical movement passages. Reference numeral 22 denotes a needle thread tension applying device according to the present invention disposed in the needle thread passing path, and its details will be explained with reference to FIGS. 2 to 5.

A pair of elongated plate-like members 23 and 24 whose side edges are bent in a direction away from each other are loosely fitted into pins 25 implanted in the mounting plate 2 at their lower portions.
The plate-shaped member 24 adjacent to the mounting plate 2 is fixed with its side edge in contact with the mounting plate 2 by a support shaft 26, and the other plate-shaped member 23 is also free from the support shaft 26. It is fitted.

Therefore, the plate-like member 23 has a support shaft 26 and a pin 2.
5 and are movable in their axial direction. The opposing surfaces of both the plate members 23 and 24 are formed smoothly, and the movable plate member 23 has a plane including the axis of the support shaft 26 and the axis of the pin 25. A pair of protrusions 27 and 28 are arranged so that their tips are located within a plane that is perpendicular to each other and located slightly above the support shaft 26.
are formed to face the fixed plate member 24 and have different protruding amounts. That is, the protrusion 27 located relatively inwardly
The protrusion amount is slightly larger than the protrusion amount of the other protrusion 28 located relatively outward. The support shaft 26 also includes an actuation plate 29 that also serves as a spring holder, a compression spring 30, a slider 31, and an adjustment knob 3.
2. The stoppers 33 are each supported and are prevented from coming off the support shaft 26 by a pair of nuts 35 and 36 that are screwed into thread grooves 34 provided on the free end side of the support shaft 26.

An actuating plate 2 whose upper end is fitted into the support shaft 26
9, as is clear from FIG. 37, 38 are formed, and the springing force of the compression spring 30 acts intensively on the movable plate member 23 via the pair of protrusions 37, 38, causing the plate member 23 to become a fixed plate. The shaped member 24 is polymerized. As shown in FIGS. 1 and 2, the upper thread T paid out from the upper thread supply source is guided by the first thread guide 12 and the guide pin 13, and passes through both the plate members 23 and 23. 24, is bent around the support shaft 26, is guided by the pin 25, comes out from between the plate-like members 23 and 24, is bent upward by the second thread guide 15, and then is moved to the thread take-up 21. It passes through the thread holding hole 20, is bent downward, passes through the third thread guide 17 and the fourth thread guide 18, and reaches the eye of the needle 4.
, 24, the guide pin 13, the support shaft 26,
It is guided by the pin 25 and passes through the gap substantially along its longitudinal direction.

By the way, due to the presence of the pair of protrusions 27 and 28, the gap between the plate members 23 and 24 along the passage path of the needle thread T is larger on the needle thread supply source side, as is clear from FIG. It is formed into a certain approximate wedge shape, and the upper thread T
Both plate-like members 2 along the direction substantially perpendicular to the passage path of
Due to the difference in the amount of protrusion of the pair of protrusions 27 and 28, the gap between the two protrusions 27 and 24 is formed into a substantially wedge shape, with the outer side of the sewing machine frame being smaller, as shown in FIG.

Therefore, the upper thread T paid out from the supply source by the vertical movement of the thread take-up 21 passes smoothly between the two plate-like members 23 and 24, and the upper thread T is slackened between the two plate-like members. Even if it does, it will not come off from between the two plate-like members 23 and 24. Note that the protrusion amount of the pair of protrusions 27 and 28 formed on the plate member 23 is, for example, 0.35.
T! r! R and 0.2WL, and the approximately wedge-shaped gap formed between the plate members 23 and 24 is extremely thin. Further, the actuating plate 29 extends downward, and its intermediate portion is bent toward the mounting plate 2 to form an abutting portion 39 to the mounting plate 2.
is formed, and the actuating plate 29 is prevented from rotating inadvertently by fitting the fork-shaped portion 40 into the upper edge of an upright portion 41 formed by bending the mounting plate 2. Further, a sloped portion 42 serving as a cam surface is formed at the lower end of the operating plate 29, and the base end is loosely fitted to the presser bar 8, and the intermediate portion is connected to the presser foot lifting lever 9. A horizontally extending pin 43 is implanted at the tip of the actuating rod 11 that engages with the cam surface.
It passes through a vertically extending slot 44 provided in the upright portion 41 and faces the inclined portion 42 of the actuating plate 29 from below. Therefore, when the presser bar 8 is lifted by rotating the lever 9 for lifting the presser foot, the operating rod 11 rises in conjunction with the operation of the lever 9, and the horizontal pin 43 is guided into the slot 44. be and rise. At this time, the horizontal pin 43 engages with the inclined part 42 of the actuating plate 29 and presses the inclined part 42, and the actuating plate 29 is rotated in the opposite direction in FIGS. 3 and 4 using the abutting part 39 as a fulcrum. The spring force of the compression spring 30 that was pressing the plate member 23 is removed from the plate member 23 by rotating it clockwise. Furthermore, a flat surface 45 is formed on the support shaft 26, and the slider 3
1 has a fitting hole corresponding to the cross-sectional shape of the support shaft 26 at a portion where the flat surface 45 is present, and the support shaft 2
It is movable in the axial direction on 6, but cannot rotate.

Further, a cam surface inclined in the circumferential direction is formed on the front end surface 46 of the slider 31, and engages with a cam surface inclined in the circumferential direction formed on the rear end surface 47 of the adjustment knob 32. The slider 3 is adjusted by rotating the adjustment knob 32.
1 moves in the axial direction, and the tension force of the compression spring 30 is adjusted. Furthermore, an annular groove 48 extending over an angular range of about 330 degrees is provided on the front end surface of the adjustment knob 32, and the tongue piece 49 of the stopper 33, which is prevented from rotating like the slider 31, The adjustment knob 32 is fitted into the annular groove 48 so that the adjustment knob 32 can rotate within an angular range of about 300 degrees. By the way, when the upper thread T passes through the approximately wedge-shaped thin gap between the plate members 23 and 24, a predetermined tension is automatically applied to the upper thread T depending on its thickness. It is.

That is, to explain with reference to FIG. 6, FIG. 6 is an explanatory diagram for explaining the principle of the thread tension applying device according to the present embodiment, in which a line is drawn along the passage path of the upper thread T. Diagrammatically shown. Among these, a indicates a state in which the upper thread T is not passed.
The two plate members 23 and 24 are connected to the pair of protrusions 27 described above.
, 28 form a narrow wedge-shaped gap A and are in contact at point B. Therefore, it is considered that in the gap A, there actually exists a virtual protrusion D that forms a fixed gap C at a position corresponding to the part where the needle thread T crosses the line segment connecting the pair of protrusions 27 and 28. , the movable plate member 23 may be considered to be movable with its virtual protrusion D as a fulcrum. Further, the spring force of the compression spring 30 acts intensively on the plate-like member 23 via the pair of protrusions 37 and 38 on the actuating plate 29, and this causes P in a of FIG. It is shown as. This position of action is
This corresponds to the part where the upper thread T crosses the line segment connecting the pair of protrusions 37 and 38, and in this embodiment, it is about 3 minutes from the contact point B.
It is located at a distance of 5m. Furthermore, the amount of protrusion of the virtual protrusion D immediately after the fixed gap C1 is approximately 0.25w in this embodiment.
It is about t. FIG. 6b shows the state when the extremely fine needle thread T1 passes between the two plate-like members 23 and 24, and the needle thread T1 passes through the movable plate-like member 2 in the area A1.
3, and the entire contact area receives the action of a springing force P1, and a frictional resistance proportional to the springing force P1 acts on the upper thread T1, and a tension corresponding to that size is applied. be done.

Next, when the medium-thin needle thread T2 passes between the plate members 23 and 24, as shown in FIG.
is wider than the case of the above-mentioned ultra-fine T1, and the upper thread T2
receives a springing force P2 greater than P1 in the entire area A2. This phenomenon occurs because the thread itself is not a rigid body.Moreover, the fulcrum is D, and the force acting on the point of effort is the spring force P. Similar to the principle of a lever, the closer the point of action to the needle thread is to the point of force, the greater the force it receives. However, in the case of a thread that is not a rigid body, the point of action is not determined as a point, but is replaced by an area of action, but the closer the area of action is to the point of force, the greater the two-strand force acting on the upper thread becomes. . Therefore, the upper thread T2 has the upper thread T1.
Greater frictional resistance acts than in the case of , and a relatively large tension is applied. Furthermore, when the needle thread 1T3 of standard thickness, which is thicker than the needle thread T2, passes between the plate-like members 23 and 24, as shown in FIG. However, the springing force P does not substantially act on the portion of the plate member 23 on the needle thread supply source side beyond the protrusion D, and the needle thread T3 The area on which the spring force P acts is A3.

This can be understood from the fact that the protrusion D does not rise. Further, it is clear from the above description that the tension is greater than the springing force P2 that the upper thread T3 receives in the region A3, and that a greater tension is applied to the upper thread T3 than in the case of the upper thread T2. Further, FIG. 6e shows a state in which a thread thicker than T3 (thick thread or very thick thread) passes between the plate members 23 and 24.

In this case, the region A4 on which the springing force P acts is substantially equal to the above-mentioned region A3, and the springing force P4 that the upper thread T4 receives in that region is almost the same as the springing force P3. However, since a greater resistance due to deformation acts on the upper thread T4 than in the case of the upper thread T3, a greater tension is applied to the upper thread T4. That is, as mentioned above, there is a substantially fixed gap C in the part where the protrusion D is present, and when an upper thread having a thickness larger than this fixed gap C passes through, The thread passes through the gap C in a compressed state. The amount of crushing, that is, the amount of deformation, increases as the needle thread passes through the fixed gap C, and the resistance due to deformation increases, making it difficult to pass through the fixed gap C. Therefore, a larger tension acts on the upper thread T4 than in the case of the upper thread T3. In short, both plate members 23,
If the thickness of the needle thread passing between 24 and 24 is different, the above-mentioned spring force P
As the area of action changes, the frictional resistance applied to the upper thread changes, and the resistance due to deformation when passing through the fixed gap changes, and due to the frictional resistance and the resistance due to deformation, both plate-like members When the upper thread passes between 23 and 24, the passing resistance acting on the upper thread is automatically determined according to the thickness of the upper thread, and a predetermined tension is applied to the upper thread. The thicker the upper thread passing between the plate members 23 and 24, the greater the tension applied to the upper thread.

Moreover, the tension applied at this time is significantly influenced by the size of the fixed gap C.
The magnitude of the tension applied to the needle thread in other parts of the needle thread passage path, for example, the thread guides 12, 15, 17, 1
It is necessary to determine this by considering the tension applied due to the resistance generated when passing through the 8th grade, etc. Furthermore, it goes without saying that the tension applied to the needle thread can be changed by changing the spring force P, and the tension can be finely adjusted as necessary by rotating the adjustment knob 32. It is possible to do this.

Incidentally, the gap A between the plate-like members 23 and 24 is extremely narrow, and the area in which the springing force P acts on the needle thread becomes sensitive depending on the thickness of the needle thread T passing through the gap A. Needless to say, the tension applied to the needle thread changes significantly and the tension applied to the needle thread increases or decreases. As described in detail above, in this embodiment, when the upper thread passes between the two plate-like members 23 and 24, a predetermined tension depending on the thickness of the upper thread is automatically applied to the upper thread. Although the present invention is applied to an upper thread tension applying device, it is also applicable to a conventional type of device that manually adjusts the tension applied to the upper thread.

Therefore, in the needle thread tension applying device in this embodiment, a gap always exists between both plate-like members 23 and 24, and the gap is large on the thread supply source side of the needle thread passage path. When threading, the needle thread is inserted between the two plate-like members 23 and 24 by the spring force of the compression spring 30 acting on the movable plate-like member 23 by rotating the presser foot lifting lever 9 upward. This can be done reliably and easily by removing.

Further, the upper thread T, which is sequentially paid out during the sewing operation, can be threaded very smoothly between the plate members 23 and 24 because the gap between the two plate members 23 and 24 is formed in a substantially wedge shape, which is larger on the thread supply source side as described above. It can pass between the plate-like members, thereby imparting a stable tension to the needle thread. If the gap along the needle thread passage path between the two plate-like members were formed to be smaller on the thread supply source side, contrary to this embodiment, then the needle thread T would pass between the two plate-like members. When it is introduced between the shaped members 23 and 24, it is suddenly crushed at its introduction end. Coupled with the fact that the movable plate-like member 23 floats with a relatively small force at its end, the plate-like member 23 tends to move erratically, and stable tension is not applied to the needle thread passing through it. . Furthermore, the gap between the plate-shaped members 23 and 24 is formed in a substantially wedge shape that is smaller on the outside of the sewing machine frame than the normal needle thread passage path due to the difference in the amount of protrusion of the protrusions 27 and 28. , both plate-like members 23, 24
The needle thread T passing between the threads does not deviate from the regular needle thread passage path shown in Fig. 2, and always passes through a constant path, and a stable tension is applied to the needle thread T. . In this embodiment, the fixed plate member 24 is provided separately from the mounting plate 2, but when forming the mounting plate 2 by press processing, the portion corresponding to the plate member 24 may be extruded. Of course, this member can be omitted and the mounting plate 2 can also be used.

〔effect〕

In the thread tension applying device according to the present invention, the gap between the two plate-shaped members in the direction substantially perpendicular to the thread passage path is located on the outside of the sewing machine frame from the thread passage path even in a state where no thread is present. Since the thread is formed to be approximately wedge-shaped and thin so as to be small, the thread passing between the two plate-like members always passes along a fixed path, and the thread passes between the two plate-like members during use of the sewing machine. There is no way to separate from it.

In addition, even when there is no space between the two plate-like members, a gap is formed that becomes larger toward the yarn supply source in the thread passage path, so the two plate-like members do not come into close contact with each other, and when threading The yarn can be reliably and easily inserted between the two plate-like members from the yarn supply source side without having to hold the yarn in a tensioned state. Moreover, since one of the two plate-like members is fixedly arranged on the sewing machine frame, the thread engaging surface of the one plate-like member is held at a constant position with respect to the sewing machine frame, which allows the thread to be transferred between the two plate-like members. It can be inserted more reliably and easily between the shaped members.

Therefore, the occurrence of phenomena such as the thread coming off from between the pair of tension discs during use of the sewing machine, or the thread not being reliably inserted between the tension discs when threading, as in conventional devices, is completely prevented. A regular tension is always applied to the thread, and a normal stitch can always be formed.

[Brief explanation of the drawing]

The drawings show an embodiment in which the present invention is embodied in a needle thread tensioning device for a household sewing machine, and FIG. 1 is for explaining the outline of the embodiment device in relation to other mechanisms of the sewing machine. 2 is a front view showing the needle thread tensioning device, FIG. 3 is an enlarged side view of FIG. 2, and FIG. 4 is an enlarged cross section taken along the line ■-■ of FIG. 2. Fig. 5 is an enlarged sectional view taken along the line ■-V in Fig. 2, and Fig. 6 is an explanatory view for explaining the principle of the needle thread tension applying device. Diagrams b to e are diagrams showing states in which needle threads of different thicknesses pass through. In the figure, 12 is a first thread guide, 13 is a guide pin, 15 is a second thread guide, 22 is an upper thread tension applying device, 23 is a movable plate member, 24 is a fixed plate member, and 25 is a 26 is a support shaft, 27 and 28 are a pair of protrusions, 29 is an actuation plate, 30 is a compression spring, and 37 and 38 are a pair of protrusions.

Claims (1)

[Claims] 1. A first elongated plate-like member 24 fixedly arranged on the sewing machine frame, a second elongated plate-like member 23 arranged so as to be movable relative to the first plate-like member 24, and a thread supply. Yarn guide means (13, 15, 25, 26, etc.) for guiding the yarn T unwound from the source so that it passes between the two plate-like members substantially along the longitudinal direction thereof, and the both plate-like members 23 . Both plate-like members are arranged such that the gap becomes larger toward the thread supply source and becomes smaller toward the outside of the sewing machine frame from the thread passing route. A pair of protrusions 27 and 28 are provided on opposing surfaces of both the plate-like members 23 and 24 to form a thin substantially wedge-shaped gap between the plates 23 and 24 against the action of the urging means. established,
A thread tension applying device for a sewing machine, characterized in that the thread always passes along a constant path between both plate-like members 23 and 24.