YARN TENSION ADJUSTING DEVICE

Abstract

 In a yarn tension adjusting device (2) that adjusts tension exerted on a yarn (Y) held between opposing surfaces (211 and 221) of first and second disks (21 and 22) opposing each other, the first disk (21) is movable toward or away from the second disk (22) on the same shaft (23). A permanent magnet (24) is disposed on the first disk (21), whereas an electromagnet (25) coupled to a power source to be capable of changing a magnetic pole and electric current is disposed on the second disk (22). A coil spring (27) that constantly urges the opposing surface (211) of the first disk (21) toward the opposing surface (221) of the second disk (22) is contracted between a screw member (28) screwed at a first end of the shaft (23) and a surface of the first disk (21) opposite to the opposing surface (211).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a yarn tension adjusting device that adjusts tension exerted on a yarn held between opposing surfaces opposing each other.

2. Description of the Related Art

[0002] A yarn tension adjusting device of this type may generally be installed in a top tension device of a flat knitting machine to prevent excessive pullout of a yarn from a yarn cone. The yarn tension adjusting device exerts appropriate tension on a yarn held between opposing surfaces opposing each other. A first one of the opposing surfaces is movable toward or away from a second one of the opposing surfaces, and constantly urged toward the second one of the opposing surfaces by a coil spring disposed on the first one of the opposing surfaces. The coil spring includes a screw member screwed on an end of a shaft extending in an expansion/contraction direction. When the screw member has its length in the expansion/contraction direction changed by being fastened or unfastened, the urging force of the first one of the opposing surfaces exerted on the second one of the opposing surfaces is increased or decreased to adjust tension exerted on a yarn between opposing surfaces.

[0003] Other examples of a yarn tension adjusting device of this type known thus far include a device that adjusts tension exerted on a needle yarn on a yarn feed path of a sewing machine along which the needle yarn is fed from a yarn spool to a needle (see Japanese Unexamined Patent Application Publication No. 2002-210279). This yarn tension adjusting device includes a coil spring constantly urging the first one of the opposing surfaces opposing each other toward the second one of the opposing surfaces, and a plunger that presses with an electromagnetic solenoid. Adding the pressing force of the plunger to the urging force of the coil spring allows the pressing force not being fulfilled by the urging force of the coil spring to be exerted on the second one of the opposing surfaces, to adjust tension of the needle yarn over a wide range.

SUMMARY OF THE INVENTION

[0004] Although the urging force of urging means, such as the coil spring, is increased with the pressing force of the plunger, the above-described existing yarn tension adjusting device fails to decrease the urging force of the urging means. To decrease the urging force of the urging means, the existing yarn tension adjusting device needs to additionally have a mechanism including a plunger that moves the first one of the opposing surfaces in a direction away from the second one of the opposing surfaces by pushing it with an electromagnetic solenoid. Providing two mechanisms including a plunger that pushes the first one of the opposing surfaces toward the second one of the opposing surfaces with an electromagnetic solenoid and a plunger that pushes the first one of the opposing surfaces away from the second one of the opposing surfaces with an electromagnetic solenoid, to increase or decrease the urging force of the urging means, would significantly increase the size of the device and increase the cost.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a yarn tension adjusting device that can move a first one of opposing surfaces toward or away from a second one of the opposing surfaces to increase or decrease urging force of urging means without using two mechanisms each including an electromagnetic solenoid and a plunger to reduce the cost while avoiding size increase of the device.

[0006] In order to achieve the above object, the present invention is to provide a yarn tension adjusting device including a yarn tension adjusting device body that adjusts tension exerted on a yarn held between opposing surfaces opposing each other. A first opposing surface of the opposing surfaces is movable toward or away from a second opposing surface of the opposing surfaces. A permanent magnet is disposed at the first opposing surface, and an electromagnet coupled to a power source to be capable of changing a magnetic pole and electric current is disposed at the second opposing surface. Urging means for constantly and elastically urging the first opposing surface toward the second opposing surface is disposed at the first opposing surface.

[0007] The urging means may include urging force changing means for changing urging force of the urging means.

[0008] The urging force changing means may change urging force of the urging means with electric means using electricity.

[0009] The yarn tension adjusting device body may be installed in a top tension device of a flat knitting machine.

[0010] As described above, the permanent magnet is disposed at the first opposing surface, which opposes the second opposing surface with the yarn interposed therebetween, and the urging means for constantly urging the first opposing surface toward the second opposing surface is disposed, whereas the electromagnet that can change the magnetic pole is disposed at the second opposing surface. Thus, changing the magnetic pole of the electromagnet obtains attraction force and repulsive force with respect to the polarity of the permanent magnet. Thus, the urging force of the urging means is increased by the attraction force caused when the magnetic pole of the electromagnet is changed to the polarity different from that of the permanent magnet, whereas it is decreased by the repulsive force caused when the magnetic pole of the electromagnet is changed to the polarity the same as that of the permanent magnet. Thus, the permanent magnet and the urging means at the first one of the opposing surfaces, and the electromagnet, at the second one of the opposing surfaces, capable of changing the magnetic pole and the electric current form a yarn tension adjusting device. Thus, two-direction movement of a first one of opposing surfaces toward or away from a second one of the opposing surfaces to increase or decrease urging force of urging means is performed by switching between attraction force and repulsive force with the change of the magnetic pole of the electromagnet and depending on the size of the attraction force and the repulsive force corresponding to the electric current to the electromagnet. This structure eliminates the need of using two mechanisms each including an electromagnetic solenoid and a plunger. Thus, the size increase of the yarn tension adjusting device is suppressed, and the cost can be reduced.

[0011] In addition, the urging force of the urging means enables exertion of certain tension on the yarn held between the opposing surfaces without depending on the magnetic force. This structure can thus reduce power consumption.

[0012] In addition, although having the permanent magnet mounted thereon, the first one of the opposing surfaces that moves toward or away from the second one of the opposing surfaces while including the urging means is lighter in weight than the second one of the opposing surfaces that has the electromagnet mounted thereon. Thus, the mechanism that increases or decreases the urging force of the urging means is light in weight. The first one of the opposing surfaces can thus quickly respond in accordance with attraction force and repulsive force caused by changing the magnetic pole and the electric current of the electromagnet.

[0013] The urging means may include urging force changing means for changing the urging force. Thus, the urging force can be changed without depending on the magnetic force between the permanent magnet and the electromagnet, so that tension can be exerted on the yarn as intended. This structure is preferable for uniform tension control or for controlling tension exerted at intended timing with reference to the urging force of the urging means, and thus can further reduce power consumption.

[0014] When the urging force changing means includes electric means for electrically changing the urging force of the urging means, the urging force of the urging means of each yarn tension adjusting device can be electrically changed, which can eliminate manual operations performed to change the urging force of the urging means. In addition, changing of the urging force of the urging means with the electric means is performed on the basis of the tension value detected by a tension sensor. Thus, the thread tension can be monitored with a tension sensor, so that tension changes due to external causes such as accumulation of yarn dust can be also managed.

[0015] The yarn tension adjusting device body may be installed in the top tension device. Thus, the yarn tension adjusting device body can be readily installed in each top tension device around which is relatively spacious, instead of an existing yarn tension adjusting device that urges the opposing surfaces with only the urging force of the urging means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 

Fig. 1 is a perspective view of a top tension device including a yarn tension adjusting device according to an embodiment of the present invention;

Fig. 2 is a perspective view of the yarn tension adjusting device illustrated in Fig. 1; and

Fig. 3 is a sectional view of a yarn tension adjusting device illustrated in Fig. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of the present invention will now be described with reference to the drawings.

[0018] Fig. 1 is a perspective view of a top tension device including a yarn tension adjusting device according to an embodiment of the present invention. Multiple top tension devices 1 each illustrated in Fig. 1 are installed in a flat knitting machine, not illustrated. Each top tension device 1 includes a yarn tension adjusting device 2. Each yarn tension adjusting device 2 individually adjusts tension exerted on a yarn Y pulled out from a yarn package. Each yarn tension adjusting device 2 is attached to a base end (upstream side of the yarn feed path) of a frame 10 of the top tension device 1.

[0019] Multiple side tensioners that remove, for example, the slack when the yarn Y tensioned by the top tension device 1 is fed to a knitting needle are disposed on the side surface of the flat knitting machine. These side tensioners form a cluster of a large number of yarn feed paths.

[0020] The top tension device 1 also includes a tension arm 11, which extends toward the tip, above the frame 10. Reference signs 12 to 17 denote yarn guide portions that allow the yarn Y to be inserted therethrough to guide the yarn Y. While being tensioned by the yarn tension adjusting device 2, the yarn Y pulled out from the yarn package is fed to a carriage (not illustrated) from the yarn guide portion 16 of the tension arm 11 and the yarn guide portion 17 via the yarn guide portions 12 to 15. Here, the yarn guide portion 13 is disposed at the tip of an arm that swings in an up-down direction as a rotation shaft around the base end of the frame 10. Thus, when the yarn Y is broken, the yarn breakage can be detected with a swing of the arm.

[0021] Fig. 2 is a perspective view of the yarn tension adjusting device 2 illustrated in Fig. 1, and Fig. 3 is a sectional view of the yarn tension adjusting device 2 illustrated in Fig. 2. As illustrated in Fig. 2 and Fig. 3, the yarn tension adjusting device 2 includes a yarn tension adjusting device body 20, which exerts tension on a yarn Y held between opposing surfaces 211 and 221 of first and second disks 21 and 22 opposing each other for adjustment.

[0022] The first and second disks 21 and 22 are disposed on the same shaft 23, and the second disk 22 of both disks 21 and 22 is fixed to a second end (right end in Fig. 3) of the shaft 23. The first disk 21 is movable on the shaft 23. Specifically, the first disk 21 is disposed on the shaft 23 so that the opposing surface 211 (first one of the opposing surfaces) is movable toward or away from the opposing surface 221 (second one of the opposing surfaces) of the second disk 22.

[0023] A substantially annular permanent magnet 24 is disposed on the surface of the first disk 21 opposite to the opposing surface 211. On the other hand, an electromagnet 25 is disposed on the surface of the second disk 22 opposite to the opposing surface 221. The electromagnet 25 is coupled to a power source, not illustrated, via a converter (not illustrated) that changes the current direction and the electric current to be capable of changing the magnetic pole and the electric current. These changes are controlled by a controller of the flat knitting machine, not illustrated.

[0024] The electromagnet 25 includes an iron core 251 and a coil 252, wound around the iron core 251. The opposing surface 221 of the second disk 22 is a magnetic pole surface. The first and second disks 21 and 22 are formed from a nonmagnetic material such as stainless steel. The shaft 23 has its second end fitted on the iron core 251.

[0025] The shaft 23 has a substantially circular insertion hole 231 at a portion between the opposing surfaces 211 and 221 of the first and second disks 21 and 22. The insertion hole 231 has a communication groove 232 communicating with the outside. Tension is exerted on the yarn Y inserted through the insertion hole 231 via the communication groove 232, between the opposing surfaces 211 and 221 of the first and second disks 21 and 22.

[0026] A coil spring 27, which is urging means for constantly and elastically urging the opposing surface 211 of the first disk 21 toward the opposing surface 221 of the second disk 22, is disposed on the first disk 21. The coil spring 27 is contracted between a screw member 28, which is screwed on a first end (left end in Fig. 3) of the shaft 23, and the surface of the first disk 21 opposite to the opposing surface 211 while having its expansion/contraction direction aligned with the shaft 23. Here, the screw member 28 has a function of urging force changing means for moving on the shaft 23 in the expansion/contraction direction of the coil spring 27 with a manual fastening/unfastening operation (change operation) to change the urging force of the coil spring 27.

[0027] Thus, in the present embodiment, the permanent magnet 24 is disposed on the first disk 21, which opposes the second disk 22 with the yarn Y interposed therebetween, and the coil spring 27 is provided that constantly urges the opposing surface 211 of the first disk 21 toward the opposing surface 221 of the second disk 22, whereas the electromagnet 25 that can change the magnetic pole is disposed on the second disk 22. Thus, changing the magnetic pole of the electromagnet 25 with a converter obtains attraction force and repulsive force with respect to the polarity of the permanent magnet 24. Besides, the electromagnet 25 is coupled to the power source to be capable of changing the electric current. Thus, the attraction force and repulsive force with respect to the permanent magnet 24 can be changeable in accordance with the electric current.

[0028] Thus, the urging force of the coil spring 27 is increased with the attraction force that occurs when the magnetic pole of the electromagnet 25 is changed to the polarity different from that of the permanent magnet 24, whereas it is decreased by the repulsive force that occurs when the magnetic pole of the electromagnet 25 is changed to the polarity the same as that of the permanent magnet 24. Thus, the permanent magnet 24 and the coil spring 27 on the first disk 21, and the electromagnet 25, on the second disk 22, capable of changing the magnetic pole and the electric current form the yarn tension adjusting device 2. Thus, two-direction movement of the opposing surface 211 of the first disk 21 toward or away from the opposing surface 221 of the second disk 22 to increase or decrease the urging force of the coil spring 27 is performed by switching between attraction force and repulsive force with the change of the magnetic pole of the electromagnet 25 and depending on the size of the attraction force and the repulsive force corresponding to the electric current fed to the electromagnet 25. This structure eliminates the need of using two mechanisms each including an electromagnetic solenoid and a plunger. Thus, the size increase of the yarn tension adjusting device 2 is suppressed, and the cost can be reduced.

[0029] In addition, the urging force of the coil spring 27 enables exertion of certain tension on the yarn Y held between the opposing surfaces 211 and 221 of the first and second disks 21 and 22 without depending on the magnetic force. This structure eliminates the need of constant power feed to the electromagnet 25, and thus can reduce power consumption.

[0030] In addition, although having the permanent magnet 24 mounted thereon, the first disk 21 that moves with the coil spring 27 toward or away from the opposing surface 221 of the second disk 22 is lighter in weight than the second disk 22 that has the electromagnet 25 mounted thereon. Thus, the mechanism that increases or decreases the urging force of the coil spring 27 is light in weight. At the timing that requires speed, such as when the flat knitting machine switches the thread tension between a push knit and a pull knit, that is, when a carriage is reversed, the first disk 21 can quickly respond in accordance with attraction force and repulsive force caused by changing the magnetic pole of the electromagnet 25.

[0031] The screw member 28 that contracts the coil spring 27 between itself and the first disk 21 functions as urging force changing means for changing the urging force of the coil spring 27 by being fastened and unfastened. Thus, the urging force can be changed without depending on the magnetic force between the permanent magnet 24 and the electromagnet 25, so that tension can be exerted on the yarn Y as intended. This structure is preferable for uniform tension control or for controlling tension exerted at intended timing with reference to the urging force of the coil spring 27, and thus can further reduce power consumption.

[0032] The yarn tension adjusting device body 20 is installed in the top tension device 1 of a flat knitting machine. Thus, the yarn tension adjusting device body 20 can be readily installed in each top tension device 1 on the upper portion that is more spacious than the portion, such as the side surface of the flat knitting machine, where multiple side tensioners form a cluster of a large number of yarn feed paths, instead of an existing yarn tension adjusting device that urges the opposing surfaces with only the urging force of the urging means.

[0033] The present invention is not limited to the above embodiment, and includes various other modification examples. For example, in the above embodiment, the screw member 28 is manually fastened or unfastened to change the urging force of the coil spring 27. However, the screw member may be electrically fastened or unfastened by electric means such as a motor. Thus, the urging force of the coil spring of each yarn tension adjusting device can be electrically changed, which can eliminate manual fastening/unfastening operations performed on the screw member. In addition, the urging force of the coil spring is changed by the electric means on the basis of the value of tension detected by a tension sensor. Thus, the thread tension can be monitored with a tension sensor, so that tension changes due to external causes such as accumulation of yarn dust can be also managed.

[0034] Here, the urging force of the coil spring is changed by fastening or unfastening the screw member in accordance with the rotation rate of a motor at the timing before knitting with the flat knitting machine, not during knitting. Thus, a quick tension control, such as that required during knitting, is not required, so that a compact inexpensive motor is used.

[0035] In the above embodiment, the coil spring 27 is used as the urging means. Instead, an N-shaped or M-shaped flat spring may be used as the urging means, and such a flat spring may be contracted between the screw member at the first end of the shaft and the surface of the first disk opposite to the opposing surface.

[0036] In the above embodiment, the yarn tension adjusting device 2 is installed in the top tension device 1 of a flat knitting machine. However, the yarn tension adjusting device 2 may be installed anywhere, not to mention on the side surface of a flat knitting machine while bypassing the side tensioners on a yarn feed path along which a yarn pulled out from a yarn package is fed to a knitting needle.

Claims

1. A yarn tension adjusting device (2), comprising a yarn tension adjusting device body (20) that adjusts tension exerted on a yarn (Y) held between opposing surfaces (211 and 221) opposing each other,
wherein a first opposing surface (211) of the opposing surfaces (211 and 221) is movable toward or away from a second opposing surface (221) of the opposing surfaces (211 and 221),
wherein a permanent magnet (24) is disposed at the first opposing surface (211), and an electromagnet (25) coupled to a power source to be capable of changing a magnetic pole and electric current is disposed at the second opposing surface (221), and
wherein urging means (27) for constantly and elastically urging the first opposing surface (211) toward the second opposing surface (221) is disposed at the first opposing surface (211).

2. The yarn tension adjusting device (2) according to Claim 1, wherein the urging means (27) includes urging force changing means (28) for changing urging force of the urging means (27).

3. The yarn tension adjusting device (2) according to Claim 2, wherein the urging force changing means (28) changes urging force of the urging means (27) with electric means using electricity.

4. The yarn tension adjusting device (2) according to any one of Claim 1 to Claim 3, wherein the yarn tension adjusting device body (20) is installed in a top tension device (1) of a flat knitting machine.

Drawing