Thread breakage detection device for sewing machine

Information

  • Patent Grant
  • 6802273
  • Patent Number
    6,802,273
  • Date Filed
    Wednesday, June 12, 2002
    22 years ago
  • Date Issued
    Tuesday, October 12, 2004
    20 years ago
Abstract
A stitch balancing thread tension 11 of a sewing machine 1 includes a rotary disk 17 having a surface extending perpendicular to an axial direction of a shaft 16 on which the rotary disk 17 is mounted. The thread breakage detection device includes a permanent magnet member 21 attached to the surface of the rotary disk 17, a hole element 22 that detects a magnetic field generated at the permanent magnet member 21 and outputs detection signals, and a detection unit that detects the thread breakage based on the detection signals from the hole element 22. Because the thread breakage detection device is integrally formed to the stitch balancing thread tension 11, the thread breakage detection device can be provided to the sewing machine 1 without increasing a number of components and the size of the sewing machine 1.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a thread breakage detection device for sewing machines, and more specifically to a thread breakage detection device including a permanent magnet member and a hole element provided to a stitch balancing thread tension having a rotary disk.




2. Related Art




There have been provided sewing machines for industrial use capable of stitching multicolor embroidery patterns. One type of such sewing machines includes a needle-bar casing that houses a plurality of needle bars each mounting a needle at its lower end. During embroidery operation, the needle-bar casing is moved right and left to select one of the needles to use. A plurality of thread spools for supplying needle threads are provided on a thread spool stand that is fixed behind the needle-bar casing. A frame, to which a plurality of thread breakage detection sensors and a plurality of stitch balancing thread tensions are attached, is formed to an upper part of the needle-bar casing. The needle threads from the thread spools are supplied to the corresponding needles via the corresponding thread breakage detection sensors and stitch balancing thread tensions.




Each thread breakage detection sensor includes, for example, a shaft that rotates in association with the supply of the needle thread, a photo-interrupter supported on the frame, and an encode disk formed with a plurality of slots. The encode disk is fixed to and integrally rotatable with the shaft, and detects thread breakage based on detection signals from the photo-interrupter.




However, the above conventional configuration requires an increased number of components because of the thread breakage detection sensor provided to the frame, whereby the manufacturing costs of the sewing machine are increased, and the overall configuration becomes complex. This problem is particularly striking in a multi-needle sewing machine for industrial use where a plurality of needles are provided since in this case a plurality of thread breakage detection sensors are required. Also, dust raised during embroidery operation often causes detection error.




SUMMARY OF THE INVENTION




It is an object of the present invention to overcome the above problems, and also to provide a thread breakage detection device that can be used in a sewing machine without increasing the number of components, the manufacturing costs, or the size of the sewing machine.




In order to achieve the above and other objects, there is provided a thread breakage detection device used in a stitch balancing thread tension having a shaft and a rotary disk having a surface extending perpendicular to an axial direction of the shaft and rotating in accordance with a supply of a thread. The thread breakage detection device including a permanent magnet member attached to the surface of the rotary disk and generating a magnetic field, a hole element that detects the magnetic field generated in the permanent magnet member and outputs a detection signal based on the detected magnetic field, and a detection unit that detects a thread breakage of the thread based on the detection signal.




There is also provided a stitch balancing thread tension including a stationary member, a shaft relatively rotatable with respect to the stationary member, a rotary disk that applies a tension to a thread, the rotary disk being mounted on the shaft and having a surface that extends perpendicular to an axial direction of the shaft, a permanent magnet member attached to the surface of the rotary disk, and a hole element mounted on the stationary member, the hole element detecting a magnetic field generated in the permanent magnet member.




Further, there is provided a sewing machine including a stationary member, a shaft, a rotary disk, a permanent magnet member, a hole element, a measuring unit, a counting unit, and a detector. The shaft is relatively rotatable with respect to the stationary member. The rotary disk applies a tension to a thread. The rotary disk is mounted on the shaft and has a surface that extends perpendicular to an axial direction of the shaft. The permanent magnet member is attached to the surface of the rotary disk. The hole element mounted on the stationary member, detects a magnetic field generated in the permanent magnet member, and outputs a detection signal based on the detected magnetic field. The measuring unit measures a time duration during an embroidery operation. The counting unit counts a number of times the detection signal changes. The detector detects a thread breakage of the thread when the counting unit does not count a predetermined number within a predetermined time duration during the embroidery operation.











BRIEF DESCRIPTION OF THE DRAWINGS




In the drawings:





FIG. 1

is a perspective partial view of a sewing machine including a thread breakage detection unit according to an embodiment of the present invention;





FIG. 2

is a partially cross-sectional view of the sewing machine of

FIG. 1

;





FIG. 3

is an enlarged view of a stitch balancing thread tension of the sewing machine integrally formed with the thread breakage detection unit;





FIG. 4

is a front view of the stitch balancing thread tension integrally formed with the thread breakage detection unit;




FIG.


5


(


a


) is a front view of a permanent magnet member of the thread breakage detection unit;




FIG.


5


(


b


) is a simplified side view of the permanent magnet member;




FIG.


6


(


a


) is an explanatory view of a detection signal output when a needle thread is broken;




FIG.


6


(


b


) is an explanatory view of a detection signal output when a bobbin thread is broken;





FIG. 7

is a block diagram showing a control mechanism of the sewing machine;





FIG. 8

is a flowchart representing a thread breakage detection process;




FIG.


9


(


a


) is a front view of an alternative permanent magnet member;




FIG.


9


(


b


) is a simplified side view of the permanent magnet member of FIG.


9


(


b


);




FIG.


10


(


a


) is a graph showing an actual expending amount expended during ordinary operations;




FIG.


10


(


b


) is a graph showing an actual expending amount when a needle thread is broken during operations; and




FIG.


10


(


c


) shows irregular data appearing in a data pattern, when a bobbin thread is broken, indicating an actual expending amount of the needle thread.











PREFERRED EMBODIMENT OF THE PRESENT INVENTION




Next, a preferred embodiment of the present invention will be described while referring to the attached drawings. In the present embodiment, a thread breakage detecting unit of the present invention is applied to a multi-needle sewing machine having a plurality of needles capable of stitching multicolor embroidery patterns. First, an overall configuration of the multi-needle sewing machine will be described.




As shown in

FIG. 1

, a multi-needle sewing machine


1


includes an arm


2


, a needle-bar casing


4


provided on a front end of the arm


2


, and a thread-spool stand


5


fixedly provided to an upper part of the arm


2


behind the needle-bar casing


4


. The needle-bar casing


4


is freely movable right and left and houses a plurality of needle bars


3


arranged in a line from the right to the left. The thread-spool stand


5


is provided with a plurality of arm spool pins


7


each mounting a thread spool


6


.




The plurality of needle bars


3


and a plurality of thread take-up levers


8


are vertically movably provided to the lower part of the needle-bar casing


4


. A support frame


9


is formed to the upper part of the needle-bar casing


4


. Provided on the front surface of the frame


9


are a plurality of tension generators


10


aligned horizontally, a plurality of stitch balancing thread tensions


11


aligned horizontally, a bobbin winder tension member


12


, and a plurality of stitch balancing thread tensions


13


aligned horizontally, arranged in this order from the above to the bottom. Needle threads


14


from the corresponding thread spools


6


are led to corresponding needles


15


via the tension generators


10


, the stitch balancing thread tensions


11


, the stitch balancing thread tensions


13


, the bobbin winder tension member


12


, the thread take-up levers


8


, and the like. A bobbin thread


60


is extending from a bobbin (not shown).




Next, description will be provided for the stitch balancing thread tensions


11


and


13


. Because the stitch balancing thread tensions


13


have the same configuration as the stitch balancing thread tensions


11


, only the stitch balancing thread tensions


11


will be described. As shown in

FIG. 2 and 3

, each stitch balancing thread tension


11


includes a shaft


16


, a rotary disk


17


, a regulation unit


18


, a thread take-up spring


19


, a body


20


, and the like. The body


20


is made of metal and, as shown in

FIG. 4

, has a flange


20




a


formed with a hole


20




b


in an elongated round shape. As shown in

FIG. 3

, the body


20


is fixed to the frame


9


by a screw


26


inserted through the hole


20




b


. In this configuration, the relative position of the stitch balancing thread tension


11


to the frame


9


can be controlled by moving the body


20


with respect to the screw


26


.




The shaft


16


is formed of a small-diameter portion


16




a


, a large-diameter portion


16




b


, a medium-diameter portion


16




c


, and a small-diameter portion


16




d


, arranged in this order from the rear side to have a stepped configuration. The small-diameter portion


16




a


and the large-diameter portion


16




b


are housed inside the body


20


with the thread take-up spring


19


mounted on the outer periphery of the large diameter portion


16




b


. The small-diameter portion


16




a


is tightly engaged to an engaging hole


20




c


formed in the rear portion of the body


20


, and is fixed to the body


20


by a screw


27


. A ground locking screw


28


is also provided to the body


20


.




The shaft


16


is formed with an expanding slot


25




a


extending from a tip end of the medium-diameter portion


16




c


across the entire length of the small-diameter portion


16




d


in its axial direction. A thin-plate member


29


, a circular felt member


30


, the rotary disk


17


, and a circular felt member


31


are mounted on an outer periphery of a base end of the medium-diameter portion


16




c


. The thin-plate member


29


, the circular felt member


30


, the rotary disk


17


, and the circular felt member


31


are integrally rotatable. Here, a user can, after loosing the screw


27


, rotate the shaft


16


around its axis using a flat head driver inserted into the expanding slot


25




a


. In this manner, the user can adjust the urging force of the thread take-up spring


19


.




The regulation unit


18


is for regulating the rotation resistance of the rotary disk


17


and includes a tension disk


32


, a turning dial


33


, a helical compression spring


34


, and a circular spring bearing


35


. The tension disk


32


is formed of a compound resin to a sleeve shape with a front side open, and is mounted on the periphery of a rear half portion of the medium-diameter portion


16




c


such that the tension disk


32


is movable in the axial direction of the shaft


16


. A rear side of the tension disk


32


contacts and applies relatively small pressing force to the circular felt members


31


,


30


, which are for applying the rotation resistance to the rotary disk


17


. The turning dial


33


is formed of a compound resin to a tapered sleeve shape with its rear side open, which is engaged inside the tension disk


32


Inside a front half portion of the turning dial


33


is integrally formed with a sleeve portion


33




a


whose inner periphery defines a female screw that engages a male screw


25




b


formed to an outer periphery of the small-diameter portion


16




d.






The spring bearing


35


is housed inside the turning dial


33


and mounted on the small-diameter portion


16




d


so as to be movable in the axial direction. The helical compression spring


34


provided between a flange


35




a


formed to the, front end of the spring bearing


35


and the tension disk


32


urges the flange


35




a


to contact the sleeve portion


33




a


and urges the tension disk


32


to press the rotary disk


17


. In this configuration, when a user rotates the turning dial


33


with his fingers, the spring bearing


35


moves forward and backward in the axial direction, thereby changing the urging force of the helical compression spring


34


applied onto the tension disk


32


. In this manner, the rotation resistance of the rotary disk


17


is adjusted.




Here, the rotary disk


17


is formed of a pair of thin metal disks engaged each other back to back to define on its outer periphery a thread guide groove


37


having a V-shaped cross section. The needle thread


14


is wound around the thread guide groove


37


to make a single complete circle. As shown in

FIG. 4

, the rotary disk


17


is formed of a plurality of through holes


36




a


aligned equidistance from each other along the outer periphery for preventing slippage between the rotary disk


17


and the needle thread


14


wound therearound. In this configuration, the rotary disk


17


rotates as the needle thread


14


is supplied to the needles


15


during embroidery operations.




The sewing machine


1


also includes a thread breakage detection unit


40


shown in FIG.


3


. The thread breakage detection unit


40


detects thread breakage of the needle thread


14


and the bobbin thread


60


and includes a permanent magnet member


21


, a hole element


22


, and a control device


43


(FIG.


7


). The permanent magnet member


21


is attached to the rear surface of the rotary disk


17


by sintering (pore into a casing and sinter) so that the permanent magnet member


21


rotates integrally with the rotary disk


17


when the needle thread


14


is supplied. FIG.


5


(


a


) shows a rear surface of the hole element


22


opposite to a front surface fixed to the rotary disk


17


. The permanent magnet member


21


is formed of sintered metal to have a ring shape with a thickness of 2 mm to 3 mm and a diameter that is approximately the half of the diameter of the rotary disk


17


. As shown in

FIG. 5

, a plurality of north poles and a plurality of south poles are arranged in the rear surface of the permanent magnet


21


in alternation.




As shown in

FIG. 3

, the hole element


22


is mounted on a rectangular-shaped substrate


41


that is attached to the front surface of the flange


20




a


of the body


20


by an adhesive. The hole element


22


is positioned close to the permanent magnet member


21


and facing one of the north poles and the south poles of the permanent magnet member


21


. The flange


20




a


is formed with a through hole


20




d


through which a lead wire


42


extends from the hole element


22


to the control device


43


.




As shown in FIG.


5


(


b


), the magnetic field generated at the permanent magnet member


21


has a direction parallel to the thickness direction of the permanent magnet


21


, i.e., to the axial direction of the stitch balancing thread tension


11


and selectively reaches to the hole element


22


. As the rotary disk


17


rotates, a pole that confronts the hole element


22


switches from a north pole to a south pole and vice versa, so that the direction of the magnetic field projected to the hole element


22


is reversed in short period of time. As a result, a sinusoidal wave signal is generated in the hole element


22


and output as a detection signal to the control device


43


via the lead wire


42


. The CPU


44


shapes this sinusoidal wave signal and then converts into a rectangular pulse signal having a value of “0” and “1” as shown in

FIG. 6

, wherein the pulse signal of “0” indicates the magnetic field with a forward direction, for example, and the pulse signal of “1” indicates the magnetic field with a reversing direction.




When the needle thread


14


is broken during the operation, supply of the needle thread


14


from the thread spool


6


completely stops, and therefore the rotary disk


17


stops rotating. Because the permanent magnet member


21


stops rotating also, the direction of the magnetic field projected to the hole element


22


stays constant. The resultant pulse signal becomes either a signal a or a signal b shown in FIG.


6


(


a


) depending on the direction at this time. Accordingly, it is possible for the CPU


44


to detect the occurrence of the thread breakage based on the detection signal from the hole element


22


.




On the other hand, when the bobbin thread


60


is broken during the operation, a resultant pulse signal becomes as shown in FIG.


6


(


b


). This is because the needle thread


14


and the bobbin thread


60


become out of balance, disrupting a stable rotation of the rotary disk


17


. The rotary disk


17


may rotate faster and slower than a regular speed to increase and decrease the needle-thread supply speed. In this case also, the CPU


44


can detect the occurrence of the thread breakage based on the detection signal from the hole element


22


.




Next, a control mechanism will be described while referring to FIG.


7


. The control device


43


includes a microcomputer


49


, an I/O interface


47


, a driver


48


connected one another via a bus B. Although not shown in the drawings, the I/O interface


47


includes the above-mentioned waveform shaping circuit that shapes a sinusoidal wave signal from the hole element


22


and the above-mentioned converter that converts the signal that has been shaped by the waveform shaping circuit into a rectangular pulse signal having the value of “0” and “1” (FIG.


6


).




Connected to the I/O interface


47


are an operation panel


50


, a start/stop (S/S) switch


51


, the hole element


22


, an upper needle sensor


52


for detecting an upper needle position of the needle


15


, a lower needle sensor


53


for detecting a lower needle position of the needle


15


, a sewing motor


54


for rotating a main shaft (not shown) of the sewing machine


1


, and the like. The sewing motor


54


is driven by the driver


48


.




The microcomputer


49


includes a central processing unit (CPU)


44


, a read only memory (ROM)


45


, and a random access memory (RAM)


46


. The ROM


45


stores a thread breakage detection control program (described later) and various control programs for processing the detection signal from the hole element


22


and detecting the breakage of the thread


14


,


60


. The RAM


46


is provided with work memories, such as various flags, buffers, registers, and counters.




Next, a control process of the thread breakage detection executed by the control device


43


will be described while referring to a flowchart of FIG.


8


. This process is started when the S/S switch


51


is turned ON. When the process starts, first in S


1


, a counter I, which is for counting the detection signal from the hole element


22


, is initialized to zero, and a timer TM is started. Both the counter I and the timer TM are stored in the RAM


46


. Next in S


2


, detection signals from the hole element


22


, the upper needle sensor


52


, and the lower needle sensor


53


are detected, and it is determined in S


3


whether or not the embroidery operation is currently performed. If not (S


3


:NO), then the process returns to S


2


. If so (S


3


:YES), then the process proceeds to S


4


where it is determined whether or not the detection signal from the hole element


22


shown in

FIG. 6

has changed from “0” to “1”. If so (S


4


:YES), then in S


5


, the counter I is incremented by one, and process proceeds to S


6


. If not (S


4


:NO), the process directly proceeds to S


6


.




In S


6


, it is determined whether or not the timer TM has measured a predetermined time duration To, for example, 1 minute. If not (S


6


:NO), then the process returns to S


2


. On the other hand, if so (S


6


:YES), then in S


7


, it is determined whether or not the counter I has counted a predetermined count value Co. If so (S


7


:YES), this means that the thread breakage has not occurred. The counter I is reset to zero and the timer TM restarts in S


8


(FIG.


6


), and the process returns to S


2


. Here, the count value Co is set in accordance with the diameter of the rotary disk


17


, i.e., of the hole element


22


, the number of the poles (the north poles and the south poles (dividing number)), and an expending rate of the needle thread


14


during ordinary embroidery operation, which is in proportion to the rotation number of the sewing motor


54


. The count value Co can be set sufficiently small value, such as 10 or 50.




If a negative determination is result in S


7


(S


7


:NO), this means that the rotary disk


17


has stopped rotating in the middle of the embroidery operation, indicating that the thread breakage has occurred. The thread breakage is detected in S


9


, and the sewing motor


54


stops driving the main shaft in S


10


so as to stop the embroidery operation. Then, in S


11


, a control signal is output to a buzzer driving circuit (not shown) to notify a user the thread breakage.




As described above, the thread breakage is detected based on the detection signal from the hole element


22


that is generated based on the magnetic field reaching to the hole element


22


from the permanent magnet member


21


. Because the permanent magnet member


21


and the hole element


22


are integrally provided in the stitch balancing thread tension


11


, there is no need to provide a thread-breakage detection device as a separate component from the stitch balancing thread tension


11


,


13


. This realizes a small-sized inexpensive thread-breakage detection unit, and thus reduces the overall size and production costs of the sewing machine


1


. This is particularly striking in the multi-needle sewing machine


1


for industrial use that includes the plurality of needles


15


, that is, the plurality of stitch balancing thread tensions


11


,


13


on the single frame


9


. Because there is no need to provide a plurality of thread-breakage detection units separate from the stitch balancing thread tensions


11


,


13


, the number of components is reduced, so that small-sized frame


9


and thus the small-sized sewing machine


1


can be provided.




Because the permanent magnet


21


is attached to the rotary disk


17


which is a component of the existing tension unit


11


,


13


, an available area to attach the permanent magnet


21


is limited. This requires designing the permanent magnet


21


in accordance with the limited area. However, it is easy to form the permanent magnet member


21


of a sintered metal into a desired shape. Here, it is conceivable to attach the conventional detection sensor including the photo interrupter and the encode disk to the existing tension unit. However, in this case, the configuration of the electric circuit becomes complex because of space limitations.




Also, the arrangement of the north poles and the south poles is easily changed in the above embodiment. For example, increasing the number of the north poles and the south poles increases detection accuracy.




Because the rotary disk


17


rotates relative to the body


20


whose positioning is adjustable with respect to the frame


9


, it is possible to adjust the relative position of the tension units


11


to the frame


9


without changing the relative positional relationship between the permanent magnet member


21


and the hole element


22


.




Moreover, erroneous detection due to dust raised during the embroidery operation does not occur in the detection device using the permanent magnet


21


and the hole element


22


. This contrast to the above-described conventional detection device that uses the photo interrupter and the encode disk.




It should be noted that it is possible to detect, when a thread breakage occurs, whether the needle thread


14


was broken or the bobbin thread


60


was broken. Specifically, the expending amount of the needle thread


14


during ordinary embroidery operation can be calculated based on stitching data. During the ordinary operation, the actual expending amount of the needle thread


14


, which is calculated based on the rotation of the rotary disk


17


, matches the theoretical expending amount calculated based on the stitching data as shown in FIG.


10


(


a


). However, when the needle thread


14


breaks, the actual expending amount stops increasing as shown in FIG.


10


(


b


). On the other hand, when the bobbin thread


60


breaks, irregular data, which indicating the actual expending amount, appear in the data pattern as shown in FIG.


10


(


c


). This is because the thread breakage of the bobbin thread


60


disrupts the stable rotation of the rotary disk


17


, so that the rotary disk


17


rotates faster and slower than the regular speed to increase and decrease the needle-thread supply speed. Accordingly, when the irregular data appears, it is detected that the thread that was broken is the bobbin thread


60


. Otherwise, it is detected that the thread that was broken is the needle thread


14


.




While some exemplary embodiments of this invention have been described in detail, those skilled in the art will recognize that there are many possible modifications and variations which may be made in these exemplary-embodiments while yet retaining many of the novel features and advantages of the invention.




For example, as shown in FIGS.


9


(


a


) and


9


(


b


), a permanent magnet member


21


A rather than the permanent magnet member


21


can be used. The permanent magnet member


21


A includes a ring-shaped non-magnetic base


21


B with one or more permanent magnet


21


C. Also, the permanent magnet member


21


is not necessarily formed of a sintered metal, but could be formed of one or more permanent magnet.




Although the above embodiment is described for the multi-needle sewing machine


1


having the plurality of needles


15


, the present invention can be applied to other type of sewing machines.




Moreover, although the broken-thread detecting unit


40


is provided to the tension unit


11


that applies a tension to the needle thread


14


, the broken-thread detecting unit


40


could be provided to a tension unit (not shown) that applies a tension to a bobbin thread if a sewing machine includes such a tension unit.



Claims
  • 1. A thread breakage detection device used in a stitch balancing thread tension having a shaft and a rotary disk having a surface extending perpendicular to an axial direction of the shaft and rotating in accordance with a supply of a thread, comprising:a permanent magnet member attached to the surface of the rotary disk and generating a magnetic field; a hole element that detects the magnetic field generated in the permanent magnet member and outputs a detection signal based on the detected magnetic field; and a detection unit that detects a thread breakage of the thread based on the detection signal, wherein the hole element is disposed on one side of the permanent magnet member and the rotary disk is disposed on an opposite side of the permanent magnet member.
  • 2. The thread breakage detection device according to claim 1, wherein the permanent magnet member has a surface in which a plurality of north poles and a plurality of south poles are arranged in alternation to give the permanent magnet member a ring shape.
  • 3. The thread breakage detection device according to claim 2, wherein the permanent magnet member is formed of a sintered metal.
  • 4. The thread breakage detection device according to claim 2, wherein the hole element is located confronting the surface of the permanent magnet member.
  • 5. The thread breakage detection device according to claim 1, wherein the permanent magnet member rotates along with the rotary disk, and the detection unit detects the thread breakage by detecting whether or not the rotary disk has stopped rotating during an embroidery operation based on the detection signal.
  • 6. The thread breakage detection device according to claim 1, wherein the thread is a needle thread.
  • 7. The thread breakage detection device according to claim 1, wherein the rotary disk is rotatable with respect to a stationary member of the stitch balancing thread tension, and a position of the stationary member is adjustable with respect to a frame of a sewing machine.
  • 8. A stitch balancing thread tension comprising:a stationary member; a shaft relatively rotatable with respect to the stationary member; a rotary disk that applies a tension to a thread, the rotary disk being mounted on the shaft and having a surface that extends perpendicular to an axial direction of the shaft; a permanent magnet member attached to the surface of the rotary disk; and a hole element mounted on the stationary member, the hole element detecting a magnetic field generated in the permanent magnet member, wherein the hole element is disposed on one side of the permanent magnet member and the rotary disk is disposed on an opposite side of the permanent magnet member.
  • 9. The stitch balancing thread tension according to claim 8, further comprising a detector that detects a thread breakage of the thread, wherein the hole element outputs a detection signal based on the detected magnetic field, and the detection unit detects the thread breakage based on the detection signal.
  • 10. The stitch balancing thread tension according to claim 8, wherein the permanent magnet member has a surface in which a plurality of north poles and a plurality of south poles are arranged in alternation to give the permanent magnet member a ring shape.
  • 11. The stitch balancing thread tension according to claim 8, wherein the permanent magnet member is formed of a sintered metal.
  • 12. The stitch balancing thread tension according to claim 8, wherein the thread is a needle thread.
  • 13. The stitch balancing thread tension according to claim 8, wherein the rotary disk is rotatable relative to the stationary member, and a position of the stationary member is adjustable with respect to a frame of a sewing machine.
  • 14. A sewing machine comprising;a stationary member; a shaft relatively rotatable with respect to the stationary member; a rotary disk that applies a tension to a thread, the rotary disk being mounted on the shaft and having a surface that extends perpendicular to an axial direction of the shaft; a permanent magnet member attached to the surface of the rotary disk; a hole element mounted on the stationary member, the hole element detecting a magnetic field generated in the permanent magnet member and outputting a detection signal based on the detected magnetic field; a measuring unit that measures a time duration during an embroidery operation; a counting unit that counts a number of times the detection signal changes during the embroidery operation; and a detector that detects a thread breakage of the thread when the counting unit does not count a predetermined number within a predetermined time duration during the embroidery operation, wherein the hole element is disposed on one side of the permanent magnet member and the rotary disk is disposed on an opposite side of the permanent magnet member.
  • 15. The sewing machine according to claim 14, wherein the permanent magnet member has a surface in which a plurality of north poles and a plurality of south poles are arranged in alternation to give the permanent magnet member a ring shape.
  • 16. The sewing machine according to claim 14 further comprising a frame, wherein the stationary member is relatively movably attached to the frame.
  • 17. The sewing machine according to claim 14, wherein the thread is a needle thread.
Priority Claims (1)
Number Date Country Kind
2001-181231 Jun 2001 JP
US Referenced Citations (4)
Number Name Date Kind
4196685 Tamura Apr 1980 A
5018465 Hager et al. May 1991 A
5322028 Hashiride et al. Jun 1994 A
6341426 Okumura Jan 2002 B1
Foreign Referenced Citations (2)
Number Date Country
A 7-148373 Jun 1995 JP
A 9-327585 Dec 1997 JP