JPH0884884A - Bobbin thread controllable sewing machine - Google Patents

Abstract

PURPOSE: To provide a sewing machine by which any kind of sewing pattern can be finished finely by automatically changing the thread tensile force of bobbin thread by the sewing pattern and obtaining stitch balancing thread tension for the bobbin thread fitted in the sewing pattern. CONSTITUTION: A pattern cam to form plural kinds of sewing patterns is provided, and when the sewing pattern is changed from straight stitch to zigzag stitch, a part where a can follower part 32b is engaged is moved from a cam 18a for straight stitch to a cam 18b for needle rocking sewing pattern. Since a tensile force applied to the bobbin thread is weakened by such movement of the part, the optimum stitch balancing thread tension for selected zigzag stitch can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewing machine for sewing an arbitrary sewing pattern selected from at least two kinds of sewing patterns.

[0002]

2. Description of the Related Art In a sewing machine, after the upper thread and the lower thread are entangled with each other, the upper thread is pulled up together with the lower thread by a balance so that the connecting point of the upper thread and the lower thread is located at the center of the cloth. It is configured. In order to determine the position of the binding point, there is also a method of pulling out the bobbin thread in advance before pulling up the balance, but the position of the binding point is the tension between the upper thread and the lower thread when the thread is pulled up by the balance. Since it is decided based on the balance, no matter how much the predetermined feeding amount is set to an appropriate amount, if the balance of the tension is broken when the balance is pulled up, the lower thread is additionally fed, On the contrary, since the lower thread may be left over, it is treated as an auxiliary method for controlling the lower thread. Furthermore, since the bobbin thread is pulled out in advance before being pulled up by the balance, there is a risk that the bobbin thread may become slack and become entangled or get caught in the internal mechanism of the sewing machine.

Further, since different tensions are generated in the upper thread depending on the sewing method (sewing pattern) such as straight line stitching and zigzag stitching, a sewing machine provided with an adjusting member for adjusting the tension of the lower thread is disclosed. It is described in JP-A-63-6033. Japanese Patent Publication No. 61-34360 discloses a sewing machine that controls thread tension by selecting information stored in an electronic storage device for a combination of sewing pattern selection and cloth thickness selection. . Further, as disclosed in Japanese Patent Publication No. 54359/1993, a structure is provided in which the bobbin thread is prohibited from being pulled out when the balance is pulled up by restraining the rotation of the bobbin, and the tension applied to the upper thread by the balance and the lower thread are applied. There is also a method of satisfactorily determining the position of the connection point between the upper thread and the lower thread by balancing the tension.

[0004]

However, as described in the conventional Japanese Unexamined Patent Publication No. 63-6033,
In the sewing machine where the user adjusts the tension applied to the bobbin thread, each time the sewing pattern and the cloth thickness change, the user adjusts the bobbin thread tension from the outside of the machine frame while performing trial sewing and Since it is necessary to perform the selection operation and the thread tension switching operation, it is very troublesome and the operability is poor. Furthermore, Japanese Patent Publication Sho 61-34
In the sewing machine which is set and stored in the electronic storage device for the combination by the selection of the sewing pattern and the selection of the cloth thickness as described in Japanese Patent Publication No. 360, the combination of the sewing pattern and the cloth thickness is selected for the combination. Need to perform a calculation process to select the thread tension information stored and stored in the electronic memory device and set the thread tension, or a cam for centralized thread tension control and a drive for driving it. Therefore, an electronic storage device, an arithmetic processing unit, and a drive unit are additionally provided in the conventional sewing machine, and a computer is required to be mounted on the sewing machine to drive them. For this reason, the sewing machine becomes expensive or large in size. In addition, Japanese Patent Fair 5-5
In the method described in Japanese Patent No. 4359, since the bobbin thread is controlled by restraining the bobbin, the bobbin actually spins idle when the sewing machine rotates at a high speed in which the thread is being unreeled. It is not an effective thread control method.

The present invention has been made in order to solve the above-mentioned problems, and a sewing machine operator can select a sewing pattern to be sewn and does not perform other operations. Another object of the present invention is to provide a sewing machine which can surely control the supply of the bobbin thread so as to be optimum for the sewing pattern and can obtain an appropriate bobbin thread tension even in various sewing patterns.

[0006]

In order to achieve this object, the bobbin thread controllable sewing machine according to claim 1 of the present invention is a sewing pattern selection for selecting one from at least two kinds of sewing patterns. Means, a sewing pattern detecting means for detecting the sewing pattern selected by the sewing pattern selecting means, and at least the lower thread so as to accompany the sewing pattern selected by the pattern selecting means based on the detection result by the sewing pattern detecting means. A lower thread tension setting means for setting two or more kinds of tension is provided.

According to another aspect of the present invention, a bobbin thread controllable sewing machine has a constant tension imparting means for constantly imparting a constant tension to the bobbin thread, and a constant tension by the constant tension imparting means. The thread tension setting means includes a variable tension applying means for applying tension to the bobbin thread.

Further, in the bobbin thread controllable sewing machine according to a third aspect of the present invention, the bobbin thread tension setting is such that, when a pattern without needle swing is selected, a higher tension is set than when a pattern with needle swing is selected. Equipped with means.

Further, the lower thread controllable sewing machine according to claim 4 is provided with a sewing pattern detecting means which is moved by the sewing pattern selecting means.

According to a fifth aspect of the present invention, the bobbin thread controllable sewing machine detects sewing pattern selection means for selecting one of at least two types of sewing patterns and the sewing pattern selected by the pattern selection means. Based on the sewing pattern detecting means and the detection result of the sewing pattern detecting means, the lower thread is grasped and released according to the pattern selected by the sewing pattern selecting means, and at least two kinds of lower thread thread amounts are set. And a bobbin thread amount setting means.

According to another aspect of the present invention, there is provided a bobbin thread controllable sewing machine which sets a bobbin thread amount which is larger when a pattern with needle swing is selected than when a pattern without needle swing is selected. A yarn amount setting means is provided.

[0012]

In the bobbin thread controllable sewing machine according to claim 1 of the present invention having the above structure, the sewing pattern selecting means selects one from at least two kinds of sewing patterns.
The bobbin thread tension setting means sets at least two kinds of tensions to the bobbin thread according to the sewing pattern selected by the sewing pattern selecting means based on the detection result of the sewing pattern detecting means.

In the sewing machine capable of controlling the bobbin thread according to a second aspect, the constant tension applying means always applies a constant tension to the bobbin thread. The variable tension imparting means imparts to the bobbin thread a variable tension whose strength can be varied, in addition to the constant tension applied by the constant tension imparting means.

Further, in the bobbin thread controllable sewing machine according to claim 3, when the bobbin thread tension setting means is selected for a pattern without needle swing, the tension is higher than that for a pattern with needle swing. To set.

In the sewing machine capable of controlling the bobbin thread according to the fourth aspect, when the sewing pattern is selected, the sewing pattern detecting means is moved by the sewing pattern selecting means, and the bobbin thread tension suitable for the sewing pattern is obtained. It can occur.

Then, in the bobbin thread controllable sewing machine according to a fifth aspect, the sewing pattern selecting means selects one from at least two kinds of sewing patterns. The bobbin thread amount setting means sets and sets at least two kinds of bobbin thread amounts by grasping and releasing the bobbin thread according to the sewing pattern selected by the sewing pattern selecting means based on the detection result of the sewing pattern detecting means. To do.

Further, in the sewing machine capable of controlling the bobbin thread according to a sixth aspect of the present invention, the bobbin thread amount setting means is more selected when the pattern with needle swing is selected than when the pattern without needle swing is selected. Set the bobbin thread amount.

[0018]

EXAMPLE A first example of a lower thread controllable sewing machine in which the tension of the lower thread is set by the passage resistance to the lower thread will be described below.

As shown in FIG. 1, in the sewing machine, an upper shaft 6 fixed to the sewing machine frame 2 is rotationally driven by an electric motor 4 which is a drive source fixed to the sewing machine frame 2, and a drive transmission belt is further provided. The lower shaft 10, which is also fixed to the sewing machine frame 2 by means of 8, is rotationally driven at the same rotational speed as the upper shaft 6.
A gear 12 is fixed to the lower shaft 10 so as to rotate integrally with the lower shaft 10, and the rotational movement is transmitted to an outer hook 14 fixed to the sewing machine frame 2. At this time, the outer pot 14 is moved to the lower shaft 10.
On the other hand, it is rotated at a double speed, whereby the upper thread is smoothly captured and intersects with the lower thread 16 to form a seam.

A cam set 18, which is a component of variable tension imparting means, is fixed to the lower shaft 10 so as to rotate together with the lower shaft 10 before the gear 12 for driving the outer hook 14. There is. The cam set 18 includes a linear sewing pattern cam 18a and a needle swing sewing pattern cam 18b. The needle swing sewing pattern cam 18b is slidable in the thrust direction of the lower shaft 10. A force is constantly applied to the linear sewing pattern cam 18a and the needle swing sewing pattern cam 18b so as to be separated from each other in the thrust direction of the lower shaft 10, and the lower shaft 10 is held so as to be in a separated position separated by a predetermined distance. Rotates together with.

Further, a sewing pattern selection handle 20 is rotatably fixed to the sewing machine frame 2 so that a sewing pattern can be selected from the outside of the sewing machine frame 2. By rotating this, a sewing pattern selecting means is sewn. The pattern selection cam 22 rotates to obtain pattern information of cloth feed and needle swing, and the sewing pattern is determined. This sewing pattern selection cam includes a sewing pattern identification cam 24.
Are integrally formed, and the switching lever 26 is in contact with the outer periphery of the sewing pattern identification cam 24 at the cam contact portion 26a. The switching lever 26 works so that the cam contact portion 26a is always pressed against the outer circumference of the sewing pattern selection cam 22. The sewing pattern identification cam 24 has an outer diameter dimension changed according to the needle swing pattern among the selected sewing patterns, and when a sewing pattern with needle swing is selected, the cam contact portion 26a of the switching lever 26 has the sewing pattern. The identification cam 24 is designed to fall in the inner diameter direction. The movement of the switching lever 26 is transmitted to the cam sliding member 30 via the rod 28 as shown in FIG.

The tip portion 30a of the cam sliding member 30 is fitted in the groove portion 18c below the needle swing sewing pattern cam 18b. In other words, the needle swing sewing pattern cam 18b is slid in the thrust direction of the lower shaft 10 by the operation of the cam sliding member 30, and can be positioned at the approaching position and the isolated position with respect to the linear sewing pattern cam 18a. On the other hand, a cam follower portion 32b, which is a part of the lower thread tension body 32 which is a component of the lower thread tension setting means, is in contact with the outer peripheral portion of the cam set 18. The bobbin thread tension body 32 is swingably supported by a base member 34, and the base member 34 is fixed to the sewing machine frame 2.

As shown in FIG. 2, the sewing product is a sewing machine frame 2
It is fed by the feed dog 38 on the needle plate 36 fixed to the. A needle hole 36a is formed in the needle plate 36 so that the lower thread 16 can be pulled out above the needle plate 36. Outer pot 14
An inner pot 40 is housed inside. The bobbin thread tension lever 32a, which is a part of the bobbin thread tension member 32, and the upper surface 40a of the inner hook 40 sandwich the bobbin thread 16 to provide pull-out resistance. The bobbin thread tension body 32 is swingably supported by a base member shaft portion 34a which is a part of the base member 34, and the cam follower portion 32b is in contact with the outer periphery of the cam set 18 and is swingable along the cam surface. Has become. The spring 42 constantly presses the cam follower portion 32b against the outer peripheral portion of the cam set 18, and at the same time functions to push the bobbin thread tension lever portion 32a downward.

As shown in FIG. 3, the inner hook 40 has a lower thread 16
The bobbin 44 around which is wound is stored and the lower thread 16 is supplied for forming a stitch. Bobbin thread 16 from bobbin 44
Is an inner hook leaf spring portion 4 as a constant tension applying means for the inner hook 40.
The lower thread 16 is sandwiched by 0b, and a constant passing resistance (pressure contact force) that can be pulled out is always provided. Further, the lower thread 16 is guided to the needle hole 36a of the needle plate 36, reaches the sewn product, and forms a stitch together with the upper thread. In the middle of this lower thread supply path, the lower thread tension body 3
The lower thread tension lever portion 32a, which is a part of 2, and the upper surface portion 40a of the inner hook 40 sandwich the lower thread 16 so that the lower thread 16 can be pulled out to provide a lower thread additional tension.

Further, the respective parts during one rotation of the sewing machine operate as shown in the timing chart of FIG. The horizontal axis of the timing chart represents the rotation angle of the upper shaft 6 during one rotation of the sewing machine, and the rotation angle 0 ° is the needle bar uppermost point, and the rotation angle 1
80 ° is the lowest point of the needle bar, and the rotation angle of 360 ° returns to the highest point of the needle bar again to form one stitch.
The vertical axis represents the vertical movement of the balance, the horizontal movement of the feed dog, the vertical movement of the feed dog, the vertical movement of the needle bar, and the lower thread tension lever portion 32 of the bobbin thread tension body 32 when straight, at each upper axis rotation angle.
The vertical movement amount of a and the vertical movement amount of the lower thread tension lever portion 32a of the lower thread tension body 32 at the time of needle swing sewing are shown. The needle bar gradually descends from the highest point when the upper shaft rotation angle is 0 °. At the same time, the balance is raised to tighten the upper thread, and the feed dog 38 is configured to start feeding the cloth.

Next, the details of the operation of each element described above will be described.

At the time of sewing the needle swing sewing pattern, the bobbin thread tension lever portion 32a is in the raised position, that is, the separated position where the bobbin thread 16 does not receive additional passing resistance. When the needle swing sewing pattern is sewn, the tension of the bobbin thread 16 becomes weaker than that when the linear sewing is performed due to only the passage resistance of the inner hook leaf spring portion 40b.
It is known in advance from experiments and the like. That is, as a result, the tightening of the thread is not so strong and a soft seam is formed.

2 and 4, the lower shaft 1 when the sewing machine is driven
When 0 rotates, the cam set 18 fixed to the lower shaft 10 rotates together with it. At this time, the lower shaft 10
Always makes one revolution per stitch formation. Therefore, since the cam set 18 also makes one rotation, this mechanism completes one cycle of operation for one stitch. The bobbin thread tension body 32 swings according to the unevenness of the outer circumference of the cam set 18 because the cam follower portion 32b is in contact with the outer peripheral surface of the cam set 18.
Then, the bobbin thread tension lever portion 32a moves up and down, and the inner hook 4
A change in the relative positional relationship occurs with the upper surface portion 40a of 0.

When the linear sewing pattern is selected by the sewing pattern selection handle 20, as shown in FIG.
Also, the cam follower portion 32b of the lower thread tension body 32 meshes. The left side surface is the outer peripheral cam shape of the cam 18a for linear sewing pattern,
The right side surface shows the outer peripheral cam shape of the needle swing sewing pattern cam 18b. At this time, since the switching lever 26 is in contact with the maximum outer diameter portion of the sewing pattern identifying cam 24, the needle swing sewing pattern cam 18b is held at the isolated position via the rod 28 and the cam sliding member 30. Therefore, the cam follower portion 32b is controlled only by the linear sewing pattern cam 18a.

In FIG. 2, since the cam follower portion 32b is in contact with the concave portion on the outer peripheral surface of the linear sewing pattern cam 18a,
The bobbin thread tension lever portion 32a is in an approaching position in contact with the inner hook upper surface portion 40a. At this time, the bobbin thread 16 is sandwiched between the lower thread tension lever portion 32a and the inner hook upper surface portion 40a, and the lower thread tension lever portion 32a is pressed downward by the spring 42, that is, the inner hook upper surface portion 40a, This force causes the lower thread 16
Give passage resistance to. On the other hand, since the passage resistance by the inner hook leaf spring portion 40b is always working, two are added and the bobbin thread 16
A strong withdrawal resistance will be added to.

When the switching lever 26 is moved by the sewing pattern selection handle 20 to select a sewing pattern with needle swing, as shown in FIG. 6, the cam set 18 and the cam of the bobbin thread tension body 32 are cammed. It meshes like a follower part 32b. The left side surface is the outer peripheral cam shape of the cam 18a for linear sewing pattern,
The right side surface shows the outer peripheral cam shape of the needle swing sewing pattern cam 18b. At this time, since the switching lever 26 is in contact with the outer diameter portion of the sewing pattern identification cam 24 which is depressed in the inner diameter direction, the needle swing sewing pattern cam 18b is held at the approach position via the rod 28 and the cam sliding member 30. are doing. Therefore, the cam follower portion 32b is controlled by a combined cam curve of both the linear sewing pattern cam 18a and the needle swing sewing pattern cam 18b.

In FIG. 4, the cam follower portion 32b is located at the phase angle of the concave portion on the outer peripheral surface of the linear sewing pattern cam 18a, but is also in contact with the needle swing sewing pattern cam 18b. Become. For this reason, the bobbin thread tension lever portion 32a is in a separated position apart from the inner hook upper surface portion 40a. At this time, the bobbin thread 16 is not sandwiched between the bobbin thread tension lever portion 32a and the inner hook upper surface portion 40a, and the passage resistance is not given to the bobbin thread 16. On the other hand, since the passage resistance due to the inner hook leaf spring portion 40b is always working, the lower thread 16 is added with the passage resistance that can be pulled out only by the inner hook leaf spring portion 40b, which is weaker than the straight stitch pattern.

At the time of sewing the straight stitch pattern, the bobbin thread tension lever portion 32a is in the lowered position, that is, in the approaching position for giving additional passing resistance to the bobbin thread 16, and the tension of the bobbin thread 16 becomes strong. As a result, a strong tightening effect is obtained and a firm seam is formed. When the thread tightening is completed, the cam follower portion 32b of the bobbin thread tension body 32 comes into contact with the convex portion on the outer peripheral surface of the linear sewing pattern cam 18a with the rotation of the bobbin thread 10, and the bobbin thread tension lever part 32a rises to pull out the upper thread. Prepare for When the upper shaft 6 rotates from here, the needle bar crosses the lowest point and the upper thread forms a thread loop, and the upper thread is caught by the outer hook 14, and the upper thread thread loops through the hook to cross the upper thread and the lower thread 16. . Further, the upper shaft 6 rotates to complete one cycle of stitch formation by one rotation of the sewing machine.

When the upper shaft 6 rotates from here as in the case of straight line sewing, the needle bar crosses the lowest point and the upper thread forms a thread loop, which is caught by the outer hook 14 and the thread loop of the upper thread passes through the hook. The upper thread and the lower thread 16 are crossed. Further, the upper shaft 6 rotates to complete one cycle of stitch formation by one rotation of the sewing machine.

As described above, in the sewing machine capable of controlling the bobbin thread tension, the sewing machine operator can simply set the sewing pattern to be sewn and does not perform any other operation.
A sewing machine can be manufactured in which the thread tension of the bobbin thread can be reliably controlled to be optimal for the sewing pattern, and a stable thread tension can be obtained for a stable sewing pattern even in various sewing patterns.

Further, since the position of the connecting point between the upper thread and the lower thread 16 is determined by the balance between the tension of the upper thread and the tension of the lower thread 16, the tension of the lower thread 16 is set as in this embodiment. If the pattern is changed according to the sewing pattern, the connecting point can be appropriately positioned according to the sewing pattern. Further, since a tension for balancing the tension of the upper thread is generated in the lower thread 16, it can be an appropriate method for determining the lower thread, unlike the method of feeding the lower thread 16 in advance before pulling out by the balance. Further, the lower thread 16 is tensioned when it is pulled up by the balance,
Since the bobbin thread 16 is not slack, unlike the method in which the bobbin thread 16 is reeled out in advance before being pulled out by the balance, the bobbin thread 16 is prevented from being entangled or caught before the balance is pulled up.

In the above-described embodiment, the bobbin thread tension setting means is composed of the inner hook leaf spring portion, the lower thread tension lever portion, and the inner hook. , For example, outer hook, bobbin, needle plate, hook stopper, feed dog,
It may be constituted by a thread cutting member or a part of the machine frame of the sewing machine, or tension may be applied to the bobbin thread by a rotational resistance of a bobbin or the like by utilizing magnetic force instead of thread passing resistance. Further, in the present embodiment, the bobbin thread tension is set in two steps, but it may be set in three steps or more.

Next, a second embodiment of a lower thread controllable sewing machine for controlling the lower thread amount by grasping the lower thread so that it cannot be pulled out will be described with reference to FIGS. 8 to 12. The same configurations as those in the above-described embodiment are designated by the same names and numbers, and the description thereof will be omitted.

A cam set 48 for controlling the lower thread restraining body is fixed to the lower shaft 10 so as to rotate integrally with the lower shaft 10 before the gear 12. The cam set 48 includes a linear pattern cam 48a and a needle swing pattern cam 48b, and the needle swing pattern cam 48b is slidable in the thrust direction of the lower shaft 10. Always straight cam 48
A force is applied to the a and the needle swing pattern cam 48b so as to be separated from each other in the thrust direction of the lower shaft 10, and the a and the cam 48b are held so as to be in a separated position separated by a predetermined distance and rotate integrally with the lower shaft 10.

The tip portion 30a of the cam sliding member 30 is fitted into the groove portion 48c below the needle swinging cam 48b. That is, the operation of the cam sliding member 30 causes the needle swing pattern cam 48b to slide in the thrust direction of the lower shaft 10,
The linear pattern cam 48a can be located at the approaching position and the separating position. On the other hand, a cam follower portion 32b which is a part of the lower thread restraint body 32 which is one lower thread restraint body is in contact with the outer peripheral portion of the cam set 48. This lower thread restraint body 32
Is swingably supported by a base member 34, and the base member 34 is fixed to the sewing machine frame 2.

Inside the outer hook 14, there is an inner hook 40 which is a lower thread restraining body paired with the lower thread restraining body 32. The lower thread grip portion 32a, which is a part of the lower thread restraint body 32, and the upper surface portion 4 of the inner hook 40.
With 0a, the lower thread 16 is held so that it cannot be pulled out. The lower thread restraint body 32 is a part of the base member 34 and is a base member shaft portion 3.
The cam follower portion 32b is swingably supported by 4a, contacts the outer circumference of the cam set 48, and is swingable along the cam surface. The spring 42 constantly presses the cam follower portion 32b against the outer peripheral portion of the cam set 48, and at the same time, functions to push the lower thread grip portion 32a downward.

Next, the details of the operation of each element described above will be described.

8 and 7, the lower shaft 1 when the sewing machine is driven
When 0 rotates, the cam set 48 fixed to the lower shaft 10 rotates together with it. At this time, the lower shaft 10 is 1
One rotation is always made for forming one seam. Therefore, since the cam set 48 also makes one rotation, this mechanism also makes one stitch for one stitch.
The cycle operation is complete. Since the cam follower portion 32b is in contact with the outer peripheral surface of the cam set 48, the bobbin thread restraint body 32 swings according to the unevenness of the outer periphery of the cam set 48. Then, the lower thread grip portion 32a moves up and down, and a relative positional relationship with the upper surface portion 40a of the inner hook 40 changes. When the linear pattern is selected by the pattern selection handle 20, the cam follower portion 32b is provided with the linear pattern cam 48a.
Controlled only by.

In FIGS. 8 and 11, since the cam follower portion 32b is in contact with the concave portion on the outer peripheral surface of the linear pattern cam 48a, the lower thread gripping portion 32a is in an approaching position in contact with the inner hook upper surface portion 40a. At this time, the lower thread 16 is sandwiched between the lower thread grip portion 32a and the inner hook upper surface portion 40a, and the lower thread grip portion 32a is moved downward by the spring 42, that is, the inner hook upper surface portion 40a.
The lower thread 16 is gripped by the force so that it cannot be pulled out. Further, when the pattern with the needle swing is selected by the pattern selection handle 20, the cam follower portion 32b is provided with the linear pattern cam 48a and the needle swing pattern cam 4.
8b is controlled by both composite cam curves.

In FIGS. 9 and 10, the cam follower portion 32b is at the phase angle of the concave portion on the outer peripheral surface of the linear pattern cam 48a, but is also in contact with the needle swing pattern cam 48b. Become. Therefore, the lower thread gripping portion 3
2a is a separated position separated from the inner hook upper surface portion 40a. At this time, the lower thread 16 is not sandwiched between the lower thread grip portion 32a and the inner hook upper surface portion 40a, and the lower thread 16 is pulled out only by a length necessary for sewing.

When sewing a sewing pattern with a needle swing, the bobbin thread gripping portion 32a is in the separated position for a longer period of time (V1 to W> V2 to W) than when straight line sewing is performed. In other words, since the amount of lower thread consumed is large, thread tightening is not performed too strongly, and a soft seam is obtained. On the contrary, since the lower thread consumption is reduced during straight line sewing, a strong tightening effect can be obtained and a firm seam can be obtained.

FIG. 12 is a timing chart showing the movement of each part during one rotation of the sewing machine. The horizontal axis represents the rotation angle of the upper shaft 6 during one rotation of the sewing machine, and the rotation angle 0 ° is the needle bar highest point,
The rotation angle of 180 ° is the lowest point of the needle bar, and the rotation angle of 360 ° returns to the highest point of the needle bar again to form one stitch. The vertical axis represents the vertical movement of the balance, the horizontal movement of the feed dog, the vertical movement of the feed dog, the vertical movement of the needle bar, and the lower thread holding portion 32a of the lower thread restraining body 32 at each upper axis rotation angle.
Vertical movement amount (during linear pattern sewing and needle swing pattern sewing)
Represents

When the upper shaft rotation angle is 0 °, the needle bar gradually descends from the uppermost point. At the same time, the balance is lifted to tighten the upper thread, and the feed dog 38 starts feeding the cloth. At this time, the bobbin thread gripping portion 32a is in the lowered position, that is, the approaching position for holding and constraining the bobbin thread 16, and the bobbin thread 16 is not consumed. As a result, the bobbin thread tightening is performed at the same time as the upper thread tightening to form a seam and the slack of the lower thread and the upper thread is eliminated.

When the thread tightening is completed, the cam follower portion 32b of the lower thread restraining body 32 comes into contact with the convex portion on the outer peripheral surface of the cam 16 as the lower shaft 10 rotates, and the lower thread gripping portion 32a rises (V1 point, V2 point). (Point) An isolation position where the lower thread 16 is released is reached. The bobbin thread 16 is released and is supplied and consumed by a required amount by cloth feeding. At this time, at the time of straight line sewing, the lower thread grip portion 32a
Is close to the point V2, and the lower thread grip portion 32a is at the point V1 when the needle swing pattern is sewn. That is, the period (time) in which the lower thread is released is longer in the needle swing pattern sewing than in the linear pattern sewing.

When the upper shaft 6 rotates and the cloth feeding is completed, the cam follower portion 32b of the lower thread restraining body 32 comes into contact with the concave portion of the outer peripheral surface of the cam 16 as the lower shaft 10 rotates, and the lower thread gripping portion 3
2a descends again (point W) and comes to an approach position where the lower thread 16 is clamped and restrained. The bobbin thread 16 is grasped and unnecessary thread for sewing is not consumed. As a result, unnecessary thread is not supplied and the seam is not disturbed. The roller bar reaches the cloth.

Further, when the upper shaft 6 rotates, the needle bar exceeds the lowest point and the upper thread forms a thread loop, which is caught by the outer shuttle 14 and passes through the shuttle by the upper thread. However, at this time, if the lower thread grip portion 32a remains in the lowered position, the upper thread loop cannot pass through the shuttle. For this reason, the cam follower portion 32b of the lower thread restraining body 32 is temporarily brought into contact with the convex portion of the outer peripheral surface of the cam 16 only when the upper thread loop passes through the shuttle, and the lower thread gripping portion 32a is raised (X point). ) Cross the upper thread and the lower thread 16. When the upper thread finishes passing through the shuttle, the cam follower portion 32b of the lower thread restraint body 32 is again brought into contact with the concave portion of the outer peripheral surface of the cam 16, and the lower thread grip portion 32a is returned to the lowered position (Y
(Point) The lower thread 16 is in a restrained state. Further, the upper shaft 6 rotates to complete one cycle of stitch formation by one rotation of the sewing machine.

In the first embodiment, if the upper thread tension is not the expected value, the balance between the tensions of the upper thread and the lower thread will be lost. According to the control of No. 1, since it is not affected by the needle thread tension, a more stable thread tension can be obtained. Further, in controlling the thread amount, the bobbin thread is directly restrained and released without an intermediate inclusion so that the bobbin thread supply amount can be reliably controlled.

Further, when the lower thread is needed, the thread is smoothly supplied with a very small force, so that the cloth is not contracted without exerting an excessive force on the cloth, and a clean seam can be obtained even in a thin cloth. . On the other hand, even when an unexpected situation occurs on the upper thread side or when a large tension is applied when the lower thread is unnecessary due to other factors, the lower thread is not consumed unnecessarily and a seam trouble does not occur. Even at the time of thread tightening, which is the most important in forming a seam, the necessary thread amount is secured in advance, the bobbin thread is locked out, and then the upper thread is tightened, so that the seam is reliably formed.

Since various operations are not necessary in terms of configuration, it is not necessary to install an arithmetic unit such as a computer, an extra actuator or a sensor other than the driving of the sewing machine, and it is possible to achieve a very small size at low cost. Also in terms of timing, processing time, various actuators, time loss from operation start command of sensor to operation start, and timing deviation to the stitch due to detection at a position away from the seam does not occur, so sewing from the first stitch to the end of sewing Even and clean seams are guaranteed.

In the second embodiment, a cam is attached to the lower shaft as the lower thread amount setting means, but instead of this, any method capable of controlling the operation of the lower thread restraining body may be used. For example, a solenoid or a motor may be used. Further, instead of obtaining the sewing machine rotation information from the lower shaft, it is possible to use the upper shaft, the vertical axis, the shuttle shaft, the motor and the drive belt. Further, in the second embodiment, the bobbin thread amount setting means is constituted by the bobbin thread gripping portion and the inner hook, but instead of these, any method capable of gripping and releasing the lower thread may be used, such as an outer hook and a bobbin. , A needle plate, a hook stopper, a feed dog, a thread cutting member, or a part of a sewing machine frame.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. In both of the above-mentioned embodiments, the pattern detecting means is composed of the pattern identification cam and the switching lever, but it is sufficient if the selected pattern can be identified instead of these, for example, the use of a mechanical contact type switch, a non-contact type sensor, Computer identification is also acceptable. Further, in both the above-mentioned embodiments, the pattern detecting means, the bobbin thread tension setting means and the bobbin thread amount setting means are mechanically connected by the rod. Alternatively, a dedicated actuator such as a solenoid or a motor may be used.

Further, in both of the above-described embodiments, the method of fixing the cam on the lower shaft so as to rotate integrally with the sewing machine as the rotation phase information of the sewing machine is used. May be used,
It is also possible to obtain the information from the upper shaft other than the lower shaft, the vertical axis, the shuttle shaft, the motor, and the drive belt.

[0058]

As is apparent from the above description, in the bobbin thread controllable sewing machine according to claim 1 of the present invention, the sewing machine operator performs other operations only by setting the sewing pattern to be sewn. Since the tension corresponding to the sewing pattern can be applied to the bobbin thread without fail, the thread tension of the bobbin thread can be reliably controlled to be optimal for the sewing pattern, and the sewing pattern is stable even in various sewing patterns. A proper thread tension can be obtained.

In the sewing machine capable of controlling the bobbin thread according to the third aspect of the present invention, different tensions are applied to the bobbin thread by the pattern without needle swing, that is, the straight stitch and the pattern with needle swing, that is, the zigzag stitch. , A pattern with needle swing can be sewn favorably with a weaker tension than a pattern without needle swing.

In the bobbin thread controllable sewing machine according to claim 4 of the present invention, the sewing pattern detecting means is moved by the sewing pattern selecting means in accordance with the selection of the sewing pattern to set the tension of the lower thread. Therefore, it is not necessary to provide an arithmetic unit, an actuator, or the like based on the information corresponding to the cloth thickness, the sewing pattern, etc., so that the cost of the sewing machine can be reduced and the construction of the sewing machine can be simplified and downsized.

In the lower thread controllable sewing machine according to the fifth aspect of the present invention, the sewing machine operator does not perform any other operation merely by setting the sewing pattern to be sewn and is influenced by the tension of the upper thread. Since the amount of bobbin thread corresponding to the sewing pattern can be set for the bobbin thread, the thread tension of the bobbin thread can be reliably controlled to be optimal for that sewing pattern, and stable even in various sewing patterns. A proper thread tension can be obtained for the sewing pattern.

In the bobbin thread controllable sewing machine according to the sixth aspect of the present invention, the pattern with needle swing is more preferable than the pattern without needle swing, that is, the straight stitch without being influenced by the tension of the upper thread. Since a large amount of bobbin thread is set at the time of zigzag stitching, it is possible to sew a pattern with a needle swing, which has a weaker thread tension, than that of a pattern without needle swing.

[Brief description of drawings]

FIG. 1 is an overall view of a sewing machine showing a first embodiment embodying the structure of a lower thread controllable sewing machine of the present invention.

FIG. 2 is a side view showing a detailed configuration of a main part of the first embodiment, showing a state in which a strong tension is applied to a bobbin thread.

FIG. 3 is a top view showing a detailed configuration of a main part of the first embodiment.

FIG. 4 is a side view showing a detailed configuration of a main part of the first embodiment, showing a state in which a lower thread is given a weak tension.

FIG. 5 is a diagram showing a detailed configuration of a main part of FIG. 4 in the first embodiment.

FIG. 6 is a diagram showing a detailed configuration of a main part of FIG. 2 in the first embodiment.

FIG. 7 is a timing chart showing the movement of each part during one rotation of the sewing machine of the first embodiment.

FIG. 8 is a side view showing a detailed configuration of a main part of the second embodiment, showing a state in which a lower bobbin thread amount is set.

FIG. 9 is a side view showing a detailed configuration of a main part of the second embodiment, showing a state in which a larger bobbin thread amount is set.

FIG. 10 is a diagram showing a detailed configuration of a main part of FIG. 9 in a second embodiment.

FIG. 11 is a diagram showing a detailed configuration of a main part of FIG. 8 in a second embodiment.

FIG. 12 is a timing chart showing the movement of each part during one rotation of the sewing machine of the second embodiment.

[Explanation of symbols]

 16 bobbin thread 18 cam set 18a cam for straight line sewing pattern 18b needle cam for sewing pattern 20 sewing pattern selection handle 22 sewing pattern identification cam 26 switching lever 26a cam contact part 32 bobbin thread tension body 32a bobbin thread tension lever part 32b cam follower Part 40 Inner hook 40a Upper surface part 40b Inner hook leaf spring part

Claims (6)

[Claims] 1. A sewing machine for sewing an arbitrary sewing pattern selected from at least two types of sewing patterns while applying tension to a lower thread, wherein 1 out of the at least two types of sewing patterns is sewn. A sewing pattern selecting means for selecting one of the sewing patterns, a sewing pattern detecting means for detecting the sewing pattern selected by the pattern selecting means, and a bobbin thread tension setting means for setting at least two kinds of tensions on the bobbin thread. The bobbin thread control is possible, in which the bobbin thread tension setting means sets a tension to the bobbin thread according to the pattern selected by the sewing pattern selection means based on the detection result of the sewing pattern detection means. Na sewing machine. 2. The bobbin thread tension setting means, a constant tension applying means for constantly applying a constant tension to the bobbin thread, and a constant tension applied to the bobbin thread by the constant tension applying means, and a variable strength. 2. The bobbin thread controllable sewing machine according to claim 1, further comprising variable tension applying means for applying variable tension. 3. The lower thread tension setting means sets a higher tension when a pattern without needle swing is selected than when a pattern with needle swing is selected. Sewing machine with lower thread controllable. 4. The bobbin thread controllable sewing machine according to claim 1, wherein the sewing pattern detecting means is moved by the sewing pattern selecting means. 5. A sewing machine for sewing an arbitrary sewing pattern selected from at least two kinds of sewing patterns while setting the amount of bobbin thread, wherein one of the at least two kinds of sewing patterns is sewn. A sewing pattern selecting means for selecting one of the two, a sewing pattern detecting means for detecting the sewing pattern selected by the pattern selecting means, and a bobbin thread amount setting means for setting at least two kinds of bobbin thread amounts. A lower thread control, wherein the lower thread thread amount setting means grips and releases the lower thread so as to accompany the pattern selected by the sewing pattern selection means based on the detection result of the sewing pattern detection means. Possible sewing machine. 6. The bobbin thread amount setting means sets a bobbin thread amount that is larger when a pattern with needle swing is selected than when a pattern without needle swing is selected. A sewing machine capable of controlling the lower thread according to claim 5.