Thread guide threading apparatus and sewing machine provided therewith

A threading apparatus for threading a thread guide of a sewing machine includes a moving member, a pivot arm, and a hook member pivotally mounted on the moving member and coupled to the pivot arm so as to be operated in synchronization with the pivot arm. The hook member has a threading hook and performs a first rocking switching the hook member from a standby position where the threading hook is not threaded to an operating position, based on action of an operating force upon rotation of the pivot arm. The hook member further performs a sliding movement in which the hook member is slid from the operating position together with the pivot arm and the moving member to thread the thread guide and a second rocking in which the hook member is rocked to be returned to the standby position after having threaded the thread guide.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a thread guide threading apparatus for threading a thread guide of a needle bar provided in a lower portion of a sewing head and a sewing machine provided with the thread guide threading apparatus.

2. Description of the Related Art

In conventional sewing machines, a needle bar is often provided with a thread guide guiding a thread extending from a needle thread take-up lever through a needle eye, along a needle bar. The thread guide needs to be threaded before the thread is passed through the eye of the needle supported on the lower end of the needle bar. In the conventional sewing machines, however, threading the thread guide is manually carried out by the user. On the other hand, the thread guide is often formed with a thread guard which is open only at one side in order that the thread may be prevented from easily disengaging from the thread guide during sewing.

In the preparation for sewing, however, the thread guide is sometimes close to the sewing head depending on a position of the needle bar stopped. In such a case, the needle bar needs to be located near an uppermost position in order that the thread may be passed through the needle eye, whether or not the sewing machine is provided with a threading apparatus. Accordingly, when the thread guide is threaded, a thread guide provided above the needle is located near the sewing head or the thread guide is located close to the sewing head when the needle bar is moved upward so that cloth is put into or taken out of a spaced defined between the needle and the sewing bed.

Under the foregoing condition where the thread guide is close to the sewing head, the operator has a difficulty in viewing the thread guide and it is difficult for the operator to thread the thread guide since a space between the thread guide and the sewing head is too narrow. Furthermore, even when the sewing machine is constructed so that the thread guide is automatically threaded after the sewing machine has been threaded, the thread guard of the thread guide is open only at one side in many cases, whereupon there is a possibility that the thread guide may not be threaded reliably.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a thread guide threading apparatus which can thread the thread guide of the needle bar automatically and reliably and a sewing machine provided with the thread guide threading apparatus.

The present invention provides a thread guide threading apparatus threading a thread guide provided in a lower part of a sewing machine head. The apparatus comprises a moving member mounted on the sewing machine head so as to be slid, a pivot arm pivotally mounted on the moving member so as to be caused to pivot and so as to slide the moving member when an operating force is applied thereto, and a hook member. The hook member is pivotally mounted on the moving member and coupled to the pivot arm so as to be operated in synchronization with the pivot arm. The hook member has a threading hook and performs a first rocking switching the hook member from a standby position where the threading hook is not threaded to an operating position, based on action of an operating force upon pivoting of the pivot arm. The hook member further performs a sliding movement in which the hook member is slid from the operating position together with the pivot arm and the moving member to thread the thread guide and a second rocking in which the hook member is rocked to be returned to the standby position after having threaded the thread guide.

The thread is engaged with the threading hook by the first rocking when the operating force acts on the pivot arm. The thread engaged with the threading hook is pulled toward the thread guide side by the sliding movement, whereby the thread guide is threaded. Finally, the second rocking disengages the thread from the threading hook. Thus, the thread guide can automatically be threaded reliably by a three-step operation of the hook member.

The invention provides another thread guide threading apparatus threading a thread guide provided in a lower part of a sewing machine head and having an open end an inner end, the apparatus comprising an operating force applying member receiving an external operating force, and a hook member having a threading hook and moved by the operating force received by the operating force applying member between a standby position where the threading hook is not threaded and an operating position where the threading hook can be threaded. The movement of the hook member includes a first movement in which the hook member is switched from the standby position to the operating position, a second movement in which the hook member is moved a predetermined distance so that the thread caught on the threading hook by the first movement is moved from the open end of the thread guide to the inner end side of the thread guide, and a third movement in which the hook member is switched from the operating position to the standby position.

When the operating force acting on the operating force applying member is transmitted to the hook member, the hook member is switched from the standby position to the operating position by the first movement, so that the thread engages the threading hook. The thread caught on the threading hook is moved from the open end of the thread guide to the inner end side by the second movement. Finally, by the third movement, the threading hook is disengaged from the thread. Thus, since the thread can be caught on the thread guide while the thread is being moved from the open end of the thread guide to the inner end side, the thread guide can reliably be threaded.

The invention provides further another thread guide threading apparatus for use in a sewing machine which includes a thread cassette detachably attached to a cassette mount and a thread guide provided below a needle bar supporting a sewing needle. The threading apparatus comprises a hook member having a threading hook and moved between a standby position where the thread drawn from the thread cassette is not caught on the threading hook and an operating position where the threading hook is threaded, the hook member being switched between the standby position and the operating position, whereby the thread is caught on the thread guide, and an operating force applying member applying an operating force for switching the hook member between the standby position and the operating position in synchronization with attachment of the thread cassette.

The thread guide is automatically threaded in synchronization with attachment of the thread cassette. This can avoid the operator's manually threading the thread guide after the thread has been passed through the needle eye and accordingly, the working efficiency can be improved.

The invention provides a still another thread guide threading apparatus for use in a sewing machine which includes a first thread guide provided at a lower portion of a needle bar supporting a sewing needle and a second thread guide away from the first thread guide by a predetermined distance. The apparatus comprises a hook member having a threading hook and being moved between a standby position where the threading hook is not threaded and an operating position where the threading hook is allowed to be threaded, the hook member being switched between the standby position and the operating position thereby to thread the first and second thread guides, and an operating force applying member applying an operating force for switching the hook member between the standby position and the operating position.

When the operating force for operating the hook member is applied to the operating force applying member, the operating force is transmitted to the hook member so that the hook member is switched between the standby position and the operating position. In this case, the thread is caught not only on the first thread guide below the needle bar but also on the second thread guide away from the first thread guide by the predetermined distance. Consequently, since an individual work for threading the second thread guide is avoided, the working efficiency can be improved.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention will be described with reference to the accompanying drawings. In the embodiment, the invention is applied to a household sewing machine in which a thread is automatically passed through a needle eye in synchronization with attachment of a thread cassette.

Referring toFIGS. 1 and 2, the household sewing machine M includes a sewing bed1having a horizontal plane, a pillar2standing from a right end of the bed1, a sewing arm3extending leftward from an upper end of the pillar2so as to be opposed along the bed1, and a machine head4located at a left end of the arm3. The head4is provided with a cassette mount5to which a thread cassette10is detachably attached. A thread drawn from the thread cassette10attached to the cassette mount5serves as a needle thread. The arm3or the head4thereof includes operation switches (not shown) such as a sewing start switch, sewing finish switch, etc. The arm3further includes a liquid crystal display7.

Referring now toFIGS. 2 and 3, in the head4are provided a needle bar12, a needle thread take-up lever13(seeFIG. 10) and a thread tensioning mechanism14adjusting a thread tension of the needle thread drawn from the thread cassette10. In the head4are further provided a threading mechanism16for automatically passing the needle thread12through an eye15aof the needle15supported on the needle bar12when the thread cassette10is attached to the cassette mount5, a principal portion of a thread holding mechanism17holding the needle thread11near the needle eye15afor the threading by the threading mechanism16, a thread guide threading mechanism18automatically threading a first thread guide19mounted on a lower end of the needle bar12and a second thread guide20provided near the lower end of the head4.

The two thread guides19and20are separated away from each other in the lower portion of the head4by a predetermined distance. The thread guides19and20have thread guards19aand20aon which the needle thread11is caught, respectively (seeFIGS. 24 to 27). The thread guards19aand20aare open substantially in the same direction (rightward) and substantially horizontal. In the head4are further provided a needle bar vertically moving mechanism for vertically moving the needle bar12, a needle bar rocking mechanism for rocking the needle bar12, and a needle thread take-up lever driving mechanism for vertically rocking the needle thread take-up lever13.

The needle thread11drawn from the thread cassette10attached to the cassette mount5is caught, from above, on a thread tension shaft (not shown) between a pair of thread tension discs of the thread tensioning mechanism14. The needle thread11extending downstream from the thread tension shaft is further guided to be caught on the needle thread take-up lever13. Furthermore, the needle thread11extending downstream from the needle thread take-up lever13is passed through the needle eye15aby the threading mechanism16after having been held near the needle eye15aby the thread holding mechanism17. The needle thread11is then caught on the thread guides19and20by the thread guide threading mechanism18, whereupon the needle thread is set for the sewing operation. Each of the threading mechanism16, thread holding mechanism17and thread guide threading mechanism18is automatically operated in synchronization with attachment of the thread cassette10.

On the other hand, the bed1is provided with a bobbin mount (not shown) to which a bobbin is detachably attached. A thread extending from the bobbin serves as a bobbin thread. The bed1is further provided with a shuttle mechanism (not shown). When the needle and bobbin threads are set for the sewing operation and a sewing machine motor (not shown) is then driven, the needle bar12is vertically moved by the needle bar vertically moving mechanism. The shuttle mechanism is driven in synchronization with the vertical movement of the needle bar12so that the needle thread11is caught by the shuttle mechanism near the needle15lowered below a needle plate1aof the bed1, whereupon the needle and bobbin threads are entangled to be formed into stitches.

The thread cassette10will now be described in detail. The thread cassette10includes a cassette body30and a lid31pivotally mounted on the cassette body as shown inFIGS. 4 to 7. The cassette body30with the lid31defines therein a thread accommodating cavity33for accommodating a thread spool32serving as a supply of thread. A spool pin34is mounted on the lid31. When the lid31is opened forward as shown inFIG. 5, the thread spool32is allowed to be attached to and detached from the spool pin34. When the lid31is closed with the thread spool32attached to the spool pin34, the thread spool is enclosed in the thread accommodating cavity33.

The needle thread11is set in the following state when the thread cassette10has been attached to the cassette mount5. The needle thread11extends upward from the thread spool32to be drawn out of the thread accommodating cavity33. The thread11further extends through a thread path35defined between the cassette body30and a left-hand end of the lid31. The thread11is then put on a first thread guard36aat a left lower end of the thread cassette10, further extending rightward thereafter to be put on a second thread guard36bat a lower end of a partition wall37and a third thread guard36cat a right lower end of the thread cassette10. The thread11further extends forward to be put on a fourth thread guard36dand is then returned to extend leftward. The thread11is then retained on a thread retainer38. Furthermore, the thread11extending leftward is cut by a left blade29of the thread retainer38and the resultant thread end is put on a fifth thread guard36enear the blade39.

A needle thread take-up lever guide space40defined at a right end of the thread cassette10extends substantially over the length of the cassette. The guide space40is open at the rear and the lower portion of the cassette. A thread tensioning space41is defined at a central lower end of the thread cassette10and open at a lower portion thereof. These spaces40and41are partitioned by a partition wall37. A pair of right and left escape grooves43aand43bare formed in the right-hand front of the thread cassette10. The escape grooves43aand43bprevent a holding member70of the thread holding mechanism17from interference with the right-hand front of the thread cassette10.

The thread cassette10is descended to be inserted into the cassette mount5. In this case, the needle thread take-up lever13enters the guide space40from below the cassette, whereas the thread tensioning mechanism14enters the thread tension space31from below the cassette. When the thread cassette10has been inserted slightly into the cassette mount5, a thread part11abetween the thread guards36band36cis caught by the needle thread take-up lever13in the guide space40.

Subsequently, when the thread cassette10is further inserted into the cassette mount5, a thread part11bbetween the thread guards36aand36bis held by the thread tensioning mechanism14in the thread tension space41. On the other hand, a thread part11cbetween the thread guard36dand the thread retainer38is drawn near the needle eye15aby the thread holding mechanism17to be held as shown inFIG. 22. A cam member42which will be described later is provided between the thread guard36dand the thread retainer38. The cam member42rocks a thread nipping member74of the thread holding mechanism17.

The threading mechanism16will be described. Referring toFIG. 8, the threading mechanism16includes a threading shaft50and a slider guide shaft51both provided on the left of the needle bar12for vertical movement, a threading slider52fitted with upper ends of the shafts51and52so as to be moved up and down, a hook mechanism53for passing the needle thread11through the needle eye15ain synchronization with rotation of the threading shaft50coupled with the upper ends of the shafts50and51, and a threading shaft driving member54for driving the threading shaft50in synchronization with the attaching operation of the thread cassette10.

The threading shaft50and the slider guide shaft51are supported on the needle bar mount55together with the needle bar12. The needle bar12, threading shaft50and slider guide shaft51are rocked together by a needle bar rocking mechanism. The needle bar12(or needle15) needs to be located at a predetermined position where the needle thread11held by the thread holding mechanism17can be passed through the needle eye15aby the hook mechanism53. For this purpose, the needle bar12is located at a leftmost position immediately before the threading operation by the threading mechanism16(immediately before attachment of the thread cassette10). Furthermore, regarding the vertical position, the needle bar12is located at a position where the needle thread11can be passed through the needle eye15aor more specifically, a predetermined position slightly lower than the uppermost position.

Two upper and lower pins56aand56bprotrude from an upper portion of the threading shaft50and a vertically middle portion of the shaft. When the threading shaft50is lowered a predetermined amount, the pin56bengages a limiting member12cfixed to the vertically middle portion of the threading shaft2. Furthermore, a coil spring57is provided around the threading shaft50for urging the threading slider52upward. Another coil spring58is provided around an upper half of the slider guide shaft51for urging the threading slider52upward. The threading slider52is formed with a cam groove52aincluding an upper half straight groove and a lower half spiral groove. Furthermore, the threading slider52is provided with an upwardly protruding plate59. The backside of the protruding plate59is formed into a horizontal plane (not shown).

Referring toFIGS. 8 and 9, the hook mechanism53includes a threading hook60for catching the needle thread11, two guide members61and62disposed at both sides of the threading hook60, a thread holding wire horizontally extending through the threading hook60and the guide members61and62, and a hook holding member64fixed to the lower end of the threading shaft50and holding the threading hook60and guide members61and62. The threading hook60has a distal end formed with a hook portion60aas shown inFIG. 9. In the threading, the hook portion60ais passed through the needle eye15aand the threading hook60is guided by the two guide members61and62. Under these conditions, the needle thread11held near the needle eye15aby the thread holding mechanism17is caught by the threading hook60.

A threading shaft driving member54is rotatably coupled to a slide member66fitted with a guide shaft65so as to be vertically slidable. The threading shaft driving member54is urged by a torsion coil spring67in the clockwise direction as shown inFIG. 8A. On the other hand, the slide member66is urged upward by a coil spring68. The threading shaft driving member54has an upper end formed with a driving force transmitting portion54aabutting the horizontal plane of the plate59to transmit a driving force to the threading slider52for the attachment of the thread cassette10. The threading shaft driving member54has a lower end formed with a cam portion54bfor preventing the driving force from transmitting to the threading slider54. The guide shaft65has a lower end to which a cam member69is fixed. The cam member69has an inclined distal cam portion69a. The cam portion54babuts against the distal cam portion69awhen the threading shaft driving member54is moved downward a predetermined amount.

The threading operation by the threading mechanism16will now be described. When the threading shaft driving member54is driven downward against the urging force of the coil spring68in synchronization with attachment of the thread cassette10, the driving force transmitting portion54aabuts the horizontal plane of the plate59so that the driving force is transmitted to the plate59, whereupon the threading shaft51and the slider15, guide52are moved downward, too. When the threading shaft50is moved downward a predetermined amount, the pin member56bengages the limiting member12cthereby to prevent further downward movement of the threading shaft50. However, the threading slider52is further moved downward against the urging force of the coil spring58. Since the pin member56aof the threading shaft50is moved along the cam groove52aof the threading slider52relative to the threading shaft50, the downward movement of the threading slider52relative to the threading shaft50is converted to rotational movement of the threading shaft50, whereby the shaft50pivots a predetermined angle. In this case, as shown inFIG. 9A, the hook mechanism53provided at the lower end of the threading shaft50is also rotated with the threading shaft, whereupon the hook portion60aof the threading hook60is passed through the needle eye15aand catches the needle thread11.

While the needle thread11is caught on the hook60a, the threading shaft driving member54is moved downward to a predetermined position and the cam portion54babuts the distal cam portion69aof the cam member69, as shown inFIG. 9A. Furthermore, when the thread cassette10is further pushed into the cassette mount5such that the threading shaft driving member54is moved downward, the threading shaft driving member54is rotated counterclockwise against the urging force of the torsion coil spring67as shown inFIG. 8A. Consequently, since the driving force transmitting portion54adeparts from the horizontal plane of the protruding plate59, the driving force for driving the threading shaft50downward is not transmitted. Accordingly, the threading shaft50is rotated in the opposite direction and returned upward by the urging force of the coil spring58. With this, since the hook mechanism53is rotated in such a direction as to depart from the needle15, the threading hook60catching the needle thread11is pulled through the needle eye15aas shown inFIG. 9B, thereby completing the threading operation.

The thread holding mechanism17will now be described. The thread holding mechanism17includes a holding member70having a pair of spaced-apart thread holding portions71and72capable of holding the needle thread11, a synchronous moving mechanism73for moving the thread holding portions71and72near the needle eye15ain synchronization with attachment of the thread cassette10, a thread holding portion74releasably holding the needle thread11between the left thread holding portion71and itself, a torsion coil spring75(urging member) elastically urging the thread holding portion74toward the holding portion71, and a cam member42mounted on the cassette body30of the thread cassette10and rocking the thread holding portion74to a side where the needle thread11is temporarily released in synchronization with a predetermined stage of the step of attaching the thread cassette.

The thread holding mechanism17further includes a base frame76fixed to the head4and a moving frame77supported so as to be moved upward and downward. The holding member70is fixed to the moving frame77which is moved by a sequential moving mechanism73. The base frame76has guide members78located at both sides of the vertical movement path of the needle thread take-up lever13and a pair of guide plates79aand79b(seeFIG. 3) provided on the left of the guide members for guiding the moving frame77. The moving frame77comprises a pair of moving plates80aand80bprovided between the guide plates79aand79b. The moving plates80aand80bare connected to each other by a plurality of connecting pins.

The holding member70and the thread nipping member74will be described with reference toFIGS. 11A to 11C. The thread holding portions71and72of the holding member70are connected to each other by a connecting member81. The connecting member81has a right end extending horizontally rightward and is fixed to a holding member support104further fixed to a second wire101of the interlock transfer mechanism73. The thread holding portions71and72are formed with recesses71aand72afor catching the needle thread11in the attachment of the thread cassette10respectively. The thread nipping member74is mounted on a pivot shaft82further pivotally mounted on the left-hand thread holding portion71. A torsion coil spring is provided around the pivot shaft82.

The thread nipping member74has a lower end including a front portion formed with a recess74aholding the needle thread11in cooperation with the left thread holding portion71therebetween. A driven pin84is provided on the lower end so as to be operated by a cam member42as will be described later. On the other hand, the thread nipping member74has an upper end (which is opposed to the driven pin84relative to the pivot shaft82) on which a limit pin85is provided. The limit pin85limits a rocking motion of the thread nipping member74to a thread holding side over a predetermined range. The driven pin84protrudes leftward and the limit pin85protrudes rightward.

The interlock transfer mechanism73will be described. Referring toFIGS. 11A to 12, the interlock transfer mechanism73comprises a cassette contact90made of a synthetic resin and coming into contact with the thread cassette10to be lowered with the cassette during attachment of the thread cassette. The interlock transfer mechanism73further includes first and second running blocks91and92moving the holding member70by an amount four times larger than an amount of movement of the cassette contact90. The cassette contact90is vertically movable between right and left guide plates79aand79bof the base frame76. The cassette contact90has a contact portion90aformed on the left end side thereof so as to protrude leftward from the left-hand guide plate79a. The lower end of the thread cassette10is brought into contact with the contact portion90a.

The first running block91comprises a pulley93coupled with the cassette contact90so as to be vertically moved together, a first wire94wound on the pulley93and having one end fixed to the guide plate79b, and a pulley95connected to the other end of the first wire94. The pulley93is enclosed in a pulley enclosing member96made of a synthetic resin. The pulley enclosing member96is vertically movable together with the pulley93between the paired guide plates79aand79bbelow the cassette contact90. A coil spring97is provided between the cassette contact90and the pulley enclosing member96for urging the cassette contact90upward relative to the pulley93. On the other hand, the pulley93(and the pulley enclosing member96) is urged upward by a coil spring98which returns the moving frame77upward. The coil spring98has a lower end connected to a lower end of the left moving plate80a.

The first wire94has one end fixed to a portion of the guide plate79located above the cassette contact90and the other end fixed to a pin member99connecting the upper ends of the moving plates80aand80b. The pin member99is supported by the guide plates79aand79bso as to be moved vertically along a guide groove100. The pulley95is rotatably supported on the pin member99. Accordingly, the pulley95and the moving plates80aand80b(or moving frame77) are vertically movable relative to the guide plates79aand79b(or fixed frame76) under the condition where the pin member99is guided by the guide groove100.

When the cassette contact90comes into contact with the thread cassette10to be pushed downward during attachment of the thread cassette, the pulley93is also pushed downward together with the thread cassette10. Since the pulley93serves as a running block in this case, the pulley95and accordingly the moving frame77are moved downward by an amount twice as large as an amount of movement of the cassette contact90.

The second running block92comprises a second wire101having both ends fixed to the guide plate79band two pulleys102and103on both of which the second wire is wound. The pulleys102and103are rotatably supported on the lower and upper ends of the moving plates80aand80brespectively. The one end of the second wire101is fixed to the upper end of the guide plate79b, whereas the other end of the second wire101is fixed to the lower end of the guide plate79bwhile the second wire is wound on the pulleys102and103.

Referring toFIGS. 12 to 13B, a holding member support104made of a synthetic resin is fixed to a portion of the second wire101located between the pulleys102and103. The connecting member81of the holding member70is connected to the holding member support104. The connecting member81and the holding member support104are supported so as to be movable vertically along the guide groove105between the paired moving plates80aand80b.

When the moving plates80aand80bare moved downward by the first running block91, the pulleys102and103are also moved downward with movement of the moving plates80aand80b. The pulley102thus serves as a running block in this case. When a portion of the wire101wound on the pulley102is thrust downward, the second wire101is moved from the front side of the pulley102(right side as viewed inFIG. 12) to the rear side (left side as viewed inFIG. 12) by an amount twice as large as an amount of movement of the pulley102. In other words, the holding member70connected to the portion of the second wire101between the pulleys102and103is also moved downward by an amount twice as large as an amount of movement of the pulley102. Accordingly, an amount of movement of the holding member70becomes four times larger than an amount of movement of the thread cassette10.

The cam member42will now be described. Referring toFIGS. 4,6,7and10, the cam member42is formed integrally in the right rear end of the cassette body30so as to protrude from the front of the cassette body. The cam member42includes a protruding portion110protruding forward from the front of the cassette body30and a cam portion111extending rightward from the front end of the protrusion110. A pin passage112is defined between the cam portion111and the front of the thread cassette10. The drive pin84is passed through the pin passage112relative to the thread cassette10during attachment of the cassette.

The cam portion111has a cam face111aformed in the rear thereof. The driven pin84is moved or slid along the cam face11aduring attachment of the thread cassette10. The cam face111ahas an upper inclined face inclined downwardly rearward and a lower inclined face continuous to the lower end of the upper inclined face and inclined downwardly forward. Thus, the cam face111afacing the front of the thread cassette10is formed so as to protrude rearward. A boundary portion of the upper and lower inclined faces is bent, and the cam face111aprotrudes rearmost at the bent portion. Accordingly, the driven pin84is passed through the pin passage112along the cam face111aas the thread cassette10is moved downward. Thus, the driven pin84is operated by the cam member42so that the thread nipping member74is rocked back and forth. At this time, the needle thread11is held between the thread holding portion71and the thread nipping member74.

Referring toFIGS. 10 and 14to23, the thread holding operation of the thread holding mechanism17will be described with main attention to the holding of the needle thread11by the thread holding portion71and the thread nipping member74. The thread nipping member74is urged to the thread holding side by the torsion coil spring75immediately after the thread cassette10comes into contact with the cassette contact90. When the thread cassette10is then thrust into the cassette mount5, the holding member70is moved downward in synchronization with attachment of the threads cassette10, as shown inFIG. 15. The holding member70is moved downward relative to the thread cassette10since a movement amount of the holding member70is rendered four times larger than a movement amount of the thread cassette10by the first and second running blocks91and92.

The driven pin84is thrust rearward by the cam face111awhen reaching the pin passage112formed inside the cam member42, as shown inFIG. 16. With this, the thread nipping member74starts to be rocked about the pivot shaft82to the hold releasing side. Upon further downward movement of the holding member70, the thread nipping member74is rocked to the hold releasing side to the maximum extent when the driven pin84reaches a rearmost protruding portion of the cam face111a, as shown inFIG. 17. At this time, the portion11c(seeFIGS. 4 and 7) of the needle thread11extending in front of the thread cassette10enters a space between the recesses71aand74aof the thread holding portion71and the thread nipping member74.

When the driven pin84is further moved downward along the cam face111aand passes a farthest protruding portion of the cam face111awithin the pin passage112, the thread nipping member74is urged by the torsion coil spring75(seeFIG. 11B) to be rocked to the thread holding side. When the driven pin84passes through the pin passage112thereby to loose contact with the cam face111a, the needle thread11is held between the recesses71aand74aof the thread holding portion71and the thread nipping member74, as shown inFIG. 18. The limit pin85is upwardly spaced away from the recesses71aand74a.

Thus, the moving frame77is further moved downward as shown inFIG. 19while the needle thread11is held as described above. The needle thread11is held near the needle eye15aby the thread holding portions71and72. At this time, the hook mechanism53of the threading mechanism16is rotated clockwise such that the threading hook60passes through the needle eye15aas shown inFIG. 20.

When the holding member70is moved near the needle eye15a, the cassette contact90thrust downward in contact with the lower end of the thread cassette10departs from the thread cassette, and the pulley93is moved upward by the urging force of the return coil spring98. With this return movement, the moving frame77and the holding member70are moved upward. The needle thread11held by the thread holding portions71and72is caught on the threading hook60. The hook mechanism53is returned counterclockwise inFIG. 20while the needle thread11is caught on the threading hook60. As a result, the needle thread11is passed through the needle eye15aas shown inFIGS. 21 and 22.

The holding member70is moved upward with the moving frame70when the needle thread11has been passed through the needle eye15a. In this case, as shown inFIG. 23, the position where the connecting member81engages the guide groove105differs from that in the case where the holding member70is moved downward (seeFIG. 18). Accordingly, since the driven pin84is spaced away from the cam face111aof the cam member42, these are prevented from interference. Consequently, the holding member70is smoothly moved upward. The limit pin85is located on the right of the thread nipping member74and spaced away from the cam member42rightward. Accordingly, the limit pin85does not prevent the vertical movement of the holding member70.

The thread guide threading mechanism18will be described with reference toFIGS. 3 and 24to31. The thread guide threading mechanism18includes a horizontal plate-shaped base member120fixed to the lower portion of the head4, a moving member121slidably mounted on the underside of the base member120and a pivot arm122pivotally mounted on the underside of the moving member121.

The thread guide threading mechanism18further includes a thread hook member123pivotally mounted on the underside of the moving member121and having a thread hook123aformed on the distal end thereof. The hook member123is coupled to the pivot arm122so as to be rockable between a standby position (seeFIGS. 24 and 28) where the needle thread11drawn from the thread cassette10is not caught on the thread hook123aand an operating position (seeFIGS. 25 and 29) where the needle thread11can be caught on the thread hook123a. The thread guide threading mechanism18further includes an operating force applying member124(seeFIGS. 28 and 29) for applying to the hook member123an operating force for switching the hook member123between the standby position and the operating position. The thread guide threading mechanism18further includes an operating force transmitting mechanism125for transmitting to the pivot arm122an operating force applied to the operating force applying member124.

The thread guide threading mechanism18performs a first rocking switching the hook member123from a standby position to an operating position by an operating force the thread cassette10applies to the operating force applying member124in synchronization with attachment of the thread cassette. The thread guide threading mechanism18also performs a sliding movement in which the hook member123switched to the operating position and the pivot arm122are slid from the operating position together with the moving member121so that the first and second thread guides19and20are threaded. The thread guide threading mechanism18further performs a second rocking in which the hook member123is rocked to be returned to the standby position after the thread guides have been threaded.

The standby position includes a first standby position (seeFIGS. 24 and 28) which is near the thread guides19and20before attachment of the thread cassette10and a second standby position (seeFIGS. 27 and 31) which is farther from the thread guides19and20than the first standby position.

The base member120is suspended from two support members131and132(seeFIG. 28) mounted on a frame member130constituting a part of the thread tensioning mechanism14. The base member120has a stopper133integrally formed thereon so as to protrude downward. The stopper133receives the pivot arm122moving leftward during the sliding movement thereby to stop the arm.

The moving member121comprises a generally rectangular horizontal plate-shaped member and is mounted on two pin members134and135further mounted on the base member120so that the moving member is slid right and left. The moving member121is formed with a guide groove121aextending in a right-and-left direction. The pin members134and135are engaged with each other so that the moving member121is slid relative to the base member120. The guide groove121aguides the sliding movement of the moving member121. More specifically, the moving member121is mounted on the base member120so as to be slid by a predetermined distance between a first condition where the left pin member134is located at the left end of the guide groove121a(seeFIG. 24) and a second condition where the right pin135is located at the right end of the guide groove (seeFIG. 27). The moving member121has a slit121bformed in the rear of the guide groove121aso as to be parallel to the guide groove. A return coil spring136is provided in the slit121bto elastically urge the moving member121rightward (guide start end position inFIG. 24).

The pivot arm122has a proximal end which is pivotally mounted via a pin137(seeFIG. 28) on the front right end of the moving member121. A torsion spring138is provided around the pin137to elastically urge the pivot arm122counterclockwise inFIG. 24(in the direction of standby position of the hook member123). The pivot arm122has an operating force input portion122aformed at a central right portion thereof. An operating force for switching the hook member123by the operating force transmitting mechanism125is supplied to the operating force input portion122a. The pivot arm122has a distal end including a left-hand portion formed with a horizontally projecting abutment portion122bwhich abuts against a stopper member133when the pivot arm122is slid by a predetermined distance together with the moving member121as will be described later.

The hook member123has a proximal end pivotally mounted via a pin139on the moving member121. The distal end of the pivot arm122and a portion of the hook member123near the proximal end are interlocked by an interlock mechanism140which will be described later. Accordingly, the proximal ends of the hook member123and the pivot arm122are pivotally mounted on the moving member121so as to maintain a predetermined positional relation. The interlock mechanism140includes a notch122cformed in the distal end of the pivot arm122and a pin141provided in the rear of the pin139near the proximal end of the hook member123so as to project downward and engage the notch122c. The hook member123has a guide hook123awhich is away from the needle thread11when the hook member123is at the first standby position as shown inFIGS. 24 and 28. In this state, when the pivot arm122pivots clockwise inFIG. 25about the pin137by a predetermined angle θ1(for example, θ1≈20°) against the urging force of the torsion spring138, the notch122cis also turned by the angle θ1. At this time, the pin141is turned about the pin139by the notch122c.

The distance between the pins137and141is longer than the distance between the pins139and141. Accordingly, when the hook member123is rocked in the horizontal state by the turning of the pin141, the turning of the pin141is enlarged such that the guide hook123ais rocked substantially horizontally clockwise inFIG. 25about the pin139by a predetermined angle θ2(for example, θ2≈90°) which is larger than the pivot angle of the pivot arm122. The hook member123reaches the operating position as shown inFIGS. 25 and 29, whereupon the guide hook123aengages the needle thread11. However, the hook member123is located below the pivot arm122and the moving member121and has an upwardly protruding portion (not shown) formed integrally therewith. The protruding portion is also turned with turn of the hook member123. The moving member121partially overhangs a turning path of the protruding portion. When the hook member123pivots the predetermined angle θ2, the protruding portion of the hook member engages the overhang (not shown) of the moving member121, whereupon a further pivot of the hook member123is prevented.

Referring toFIGS. 28 to 31, an operating force applying member124is pivotally mounted on a frame member130of the thread tensioning mechanism14so as to be rocked. The operating force applying member124has a forwardly projecting cassette contact124aprovided on the distal end side (right-hand end side) thereof. The lower end of the thread cassette10comes into contact with the cassette contact124a. In attachment of the thread cassette10, an operating force is transmitted from the thread cassette10to the cassette contact124ain synchronization with attachment of the thread cassette so that the hook member123is switched between the standby position and the operating position. As a result, the operating force applying member124is rocked clockwise inFIG. 28.

An operating force transmitting mechanism125comprises a link member145pivotally mounted at its middle portion on the lower end of the operating force applying member124, a distal end arm145aformed on the distal end (right-hand end) of the link member145so as to be bent downward, a driven pin146provided on the proximal end (left-hand end) of the link member145, and a cam plate147having an arc cam groove147athe driven pin146engages. The link member145extends in the right-and-left direction and is moved in the right-and-left direction. When the operating force is applied from the thread cassette10to the cassette contact124a, the operating force applying member124is rocked clockwise inFIG. 28. The link member145is moved leftward with the rocking of the operating force applying member124. As described above, the moving member121is urged rightward by the coil spring136. Since the pivot arm122is pivotally mounted on the moving member121, the lower end of the distal end arm portion140ais usually in abutment with the operating force input portion122aof the pivot arm122.

More specifically, the operating force is transmitted through the link member145extending in the right-and-left direction to the operating force input portion122aof the pivot arm122. Since the proximal end of the link member145is guided via the driven pin146along the cam groove147aof the cam plate147, the driven pin146is moved in an arc of the cam groove147asubstantially corresponding with an arc in which the lower end of the operating force applying member124is moved. Consequently, the overall link member145can smoothly be moved in the right-and-left direction. In other words, the link member145has no center of rotation when it is rotated. Accordingly, the distal end arm portion145apresses the operating force input portion122asubstantially horizontally leftward, whereupon sliding friction can be prevented from occurring between the distal end arm145aand the operating force input portion122a.

A threading operation carried out by the thread guide threading mechanism18will now be described. Before attachment of the thread cassette, as shown inFIGS. 24 and 28, the hook member123is at the first standby position where the needle thread11is not caught on the threading hook123a. In this state, when the thread cassette10is pushed into the cassette mount5, the lower end of the cassette body20abuts against the cassette contact124asuch that the thread cassette applies an operating force to the cassette contact124athereby to rock the cassette contact clockwise inFIG. 28. At this time, when the operating force is transmitted from the operating force applying member124via the distal end arm portion145aof the link member145to the operating force input portion of the pivot arm122, a first rocking movement is carried out in which the pivot arm122is turned by the predetermined angle θ1and the hook member123is switched from the standby position to the operating position.

More specifically, the operating force supplied to the operating force input portion122aturns the pivot arm122about the pin137by the predetermined angle θ1clockwise inFIG. 24. As a result, the hook member123is also rocked about the pin139clockwise inFIG. 24between the first and second thread guides19and20by the interlock mechanism140. The threading hook123ais turned by the predetermined angle θ2thereby to be switched to the operating position as shown inFIG. 25, engaging the needle thread11. In order that the needle thread11may reliably be caught by the threading hook123a, the operating position of the hook member123as shown inFIG. 25is located rightward (opening direction of the thread guide portions19aand20a) relative to the first standby position as shown inFIG. 24. With turn of the pivot arm122, the abutment portion122bformed in the distal end of the pivot arm122projects leftward.

When the operating force is further transmitted to the pivot arm122after the first rocking movement, further turn exceeding the predetermined angle θ1is prevented by the engagement of the overhang of the moving member121and the projecting portion of the hook member123. Accordingly, as shown inFIGS. 26 and 30, the hook member123switched to the operating position and the pivot arm122are slid leftward a predetermined distance together with the moving member121against the urging force of the coil spring136until the abutment portion122babuts against the stopper member133. In the sliding movement, the needle thread11engaging the threading hook123ais drawn leftward together with the hook member123such that the needle thread is caught on the threading portions19aand20aof the first and second thread guides19and20respectively.

The threading portions19aand20aof the respective thread guides19and20are open substantially rightward as shown inFIGS. 24 to 27. The hook member123is moved between the standby position and the operating position which are further between the two thread guides19and20. Accordingly, the needle thread11engaging the threading hook123ais reliably caught on the thread guides19and20by the sliding movement. Furthermore, the needle thread11engaging the threading hook123ais moved from the open ends (right ends) of the threading portions19aand20aof the thread guides19and20to the inner ends (left ends), whereupon the needle thread11is reliably caught on the inner ends of thread guides19and20.

Referring toFIGS. 26 and 30, when the abutment122babuts against the stopper member133, the pin141is unable to move leftward (a part of the pivot arm122is temporarily stopped relative to the moving member121). In this state, when the thread cassette10is further thrust into the cassette mount such that an operating force is further supplied to the input portion122a, the second rocking movement is carried out to return the hook member123to the stand by position. More specifically, the moving member121is moved leftward relative to the base member120until the right-hand pin135engages the right end of the guide groove121a. Accordingly, the pivot arm122is caused to pivot about the pin141counterclockwise inFIG. 27. The interlock mechanism140is operated by the pivot of the arm122so that the hook member123is rocked about the pin141counterclockwise inFIG. 27thereby to be switched to the second standby position.

The abutment122bis slid on the stopper member133with pivot of the arm122. On this occasion, the needle thread11is disengaged from the threading hook123ato be detached from the hook, whereupon catching the needle thread11on the thread guides19and20is completed. When the hook member123is switched to the second standby position, the threading hook123ais located farther away from the needle bar12and needle thread11than when the hook member123is at the first standby position.

The sequential operation of the sewing machine M in the attachment of the thread cassette10will now be described with main concern to the threading operation of the threading mechanism16, thread holding operation of the thread holding mechanism17and thread guiding operation of the thread guide mechanism18. When the thread cassette10is inserted into the cassette mount5from above, the lower end of the cassette body30thrusts the cassette contact90downward as shown inFIGS. 14 to 19. As a result, the interlock mechanism73is operated so that the holding member70is moved downward in synchronization with attachment of the thread cassette10. When reaching the pin passage112inside the cam member42of the thread cassette10, the driven pin84provided on the thread nipping member74is moved downward along the cam face111a. Consequently, the driven pin84is operated by the cam member42so that the thread nipping member74is rocked about the pivot shaft82to the releasing side against the urging force of the torsion spring75.

The thread nipping member74is rocked to the maximum releasing side when the holding member70is moved downward such that the driven pin84abuts against the rearmost projecting portion of the cam face111aas shown inFIG. 17. At this time, the portion11c(FIGS. 4 and 7) of the needle thread11extending along the front of the thread cassette10enters the space between the left thread holding portion71and the thread nipping member74. Thereafter, when the driven pin84is moved downward along the cam face111a, the thread nipping member74is rocked to the holding side by the torsion spring75. When the driven pin84gets out of the pin passage112to be completely detached from the cam face111a, the needle thread11is held between the holding member71and the thread nipping member74as shown inFIG. 18. In this state, the moving frame77and the holding member70are further moved downward with attachment of the thread cassette10, so that the needle thread11is held near the needle eye15aby the paired thread holding portions71and72of the holding member70.

The threading operation is also carried out by the threading mechanism16synchronously. More specifically, the threading shaft50, slider guide51and threading slider52are moved downward in synchronization with attachment of the thread cassette10, as shown inFIG. 8. When moved downward a predetermined distance, the threading shaft50is prevented from further downward movement by the pin member56and limiting member12c. However, the threading slider52is further moved downward against the urging force of the coil spring58. Thus, the threading slider52is further moved downward relative to the threading shaft50. The relative movement of the threading slider52is converted to turn of the threading shaft50by the pin member56aand cam groove52aof the threading slider52, whereby the threading shaft50is turned by a predetermined angle.

The hook mechanism53provided on the lower end of the threading shaft50is also turned with the threading shaft as shown inFIG. 20. As a result, the hook portion60aof the threading hook60is passed through the needle eye15a. At this time, the holding member70of the thread holding mechanism17starts to move upward from the lowermost position, so that the needle thread11held by the thread holding portions71and72is caught by the hook60a. At this time, the cam portion54bof the threading shaft driving member54abuts against the distal end cam portion69aof the cam member69so that the threading shaft driving member54is driven counterclockwise inFIG. 8against the urging force of the torsion spring67. Accordingly, since the drive force for driving the shaft50downward is not transmitted to the threading slider52, the shaft50is turned in the opposite direction and returned upward by the urging force of the coil spring58. With this, the hook mechanism53is turned together with the shaft50, whereupon the hook member123on which the needle thread11is caught is returned through the needle eye15aas shown inFIG. 21. Thus, the threading operation is completed.

Thus, when the thread cassette10is further pushed into the cassette mount5with the needle thread11having been passed through the needle eye15a, the needle thread is caught on the two thread guides19and20by the threading mechanism18. More specifically, as shown inFIGS. 24 and 28, the lower end of the cassette body30abuts against the cassette contact124aof the operating force applying member124when the thread cassette10is thrust into the cassette mount5under the condition where the hook member123is at the first standby position where the needle thread11is not caught on the threading hook123a. Consequently, the operating force from the thread cassette10is applied to the cassette contact124a.

The operating force applied to the operating force applying member124is transmitted to the input portion122aof the pivot arm122by the operating force transmitting mechanism125. Then, the first rocking movement is carried out in which the hook member123is switched from the first standby position to the second standby position so that the needle thread11engages the threading hook123a, as shown inFIGS. 25 and 29. The sliding movement is then carried out in which the hook member123switched to the operating position and the pivot arm122are slid together with the moving member121, as shown inFIGS. 26 and 30, whereupon the needle thread11is caught by the thread catching portions19aand20aof the thread guides19and20. Furthermore, the second rocking movement is carried out in which the hook member123is returned to the second standby position after the needle thread has been caught by the thread guides19and20, as shown inFIGS. 27 and 31. Consequently, the needle thread11is disengaged from the threading hook123aand the threading operation is completed.

The following effects can be achieved from the above-described sewing machine M. The thread guide threading mechanism18switches the hook member123between the standby position and the operating position by the operating force the thread cassette10applied to the operating force applying member124in synchronization with attachment of the thread cassette, thereby catching the needle thread11on the first thread guide19. Consequently, the needle thread can automatically be caught on the first thread guide19in synchronization with attachment of the thread cassette to the cassette mount.

The needle bar12is located at a position near the uppermost position after the needle thread has been passed through the needle eye15a. The first thread guide19is located beneath the head4so as to be close to the head. Accordingly, it is difficult for the user to thread the first guide19when the sewing machine is threaded or when cloth is put into and taken out of the sewing machine. In the foregoing embodiment, however, the needle thread11can be caught on the first thread guide19in synchronization with attachment of the thread cassette10. Consequently, the aforesaid troublesome work can be eliminated and the working efficiency can be improved. Furthermore, the needle thread11can also be caught on the second thread guide20when caught on the first thread guide19.

The proximal end of the link member145is guided via the driven pin146along the cam groove147a. Accordingly, the operating force is transmitted via the link member145to the operating force input portion122aof the pivot arm122in synchronization with attachment of the thread cassette10. On this occasion, the link member145can smoothly be moved in the right-and-left direction horizontally. Accordingly, the distal end arm portion145acan press the input portion122aof the pivot arm122substantially horizontally rightward. Consequently, occurrence of sliding friction can be prevented between the distal end arm portion145aand the input portion122a. In other words, a force required to attach the thread cassette can be rendered smaller.

The thread catching portions19aand20aof the thread guides19and20are open substantially in the same direction (rightward). The operating position of the hook member123is located so as to be directed to the opening direction of the thread catching portions19aand20aas compared with the standby position thereof. Between the thread guides19and20, the hook member123is moved between the standby and operating positions. Accordingly, the needle thread11can be prevented from being caught on the threading hook123awhen the hook member123is at the standby position. When the hook member123is switched to the operating position, the thread catching portions19aand20acan catch the needle thread11located in the opening direction of thread catching portions19and20.

Furthermore, between the first and second thread guides19and20, the hook member123is moved between the standby and operating positions as described above. Accordingly, the hook member123is moved to the side opposed to the opening direction of the thread catching portions19aand20awhile the needle thread11is caught by the threading hook123a. Consequently, since the needle thread11goes into the inner ends of the thread catching portions19aand20a, the needle thread11can reliably be caught on the first and second thread guides19and20.

When the operating force is transmitted via the transmitting mechanism125to the input portion122aof the pivot arm122, the needle thread11is engaged with the thread catching hook123aby the first rocking movement. The needle thread11in engagement with the hook123ais drawn toward the thread guides19and20by the sliding movement, thereby being caught on the thread guides. Finally, the needle thread11is disengaged from the hook123aby the second rocking movement. Thus, the needle thread11can automatically be caught on the thread guides19and20reliably. Furthermore, in the sliding movement (second movement), the needle thread11in engagement with the hook123ais moved from the open ends of the threading portions19aand20atoward the inner end side. Consequently, the needle thread11can reliably be caught on the inner ends of the thread guides19and20.

The hook member123is located at the first standby position near the thread guides19and20when the thread cassette10is not attached to the cassette mount5. Upon attachment of the thread cassette10, the hook member123is switched from the first standby position to the operating position. Consequently, threading the thread guides19and20can quickly be initiated. On the other hand, upon completion of the attachment of the thread cassette10, the hook member123is located at the second standby position farther away from the thread guides19and20than the first standby position. Since the hook member123is located away from the needle bar12, the needle thread11can be prevented from being stuck to the hook member123.

The cassette mount5is provided in the head4of the sewing machine M. The thread cassette10is attached to the cassette mount5from above the sewing machine M. When the user pushes the thread cassette10with both hands to attach it to the cassette mount5, the hands of the user are located over the head4. In other words, the user's hands are located away from the thread guides19and20which are provided below the head4. In the foregoing embodiment, however, the needle thread11is caught on the thread guides19and20in synchronization with attachment of the thread cassette10. Accordingly, the user need not pass his or her hands from above the head4to the thread guides19and20after the thread cassette10has been attached to the cassette mount5. Consequently, the preparation for the sewing work can smoothly be carried out.

Several modified forms will be described. The supply of thread includes a thread spool and bobbin in the foregoing embodiment. However, various types of thread supply may be used. For example, a mere mass of thread may be used. Furthermore, the thread cassette may be constructed so that the thread spool or mass of thread is exposed and mounted on the spool pin.

In the foregoing embodiment, the user thrusts the thread cassette into the cassette mount5with his or her hand or hands other driving means such as rubber rollers or an electric motor may be used so that the thread cassette10is automatically be attached to the cassette mount5. The aforesaid drive means may be used to drive the thread holding mechanism17and the thread guide mechanism18. Furthermore, when the needle thread is caught on the two thread guides19and20, the thread holding mechanism17and the thread guide mechanism18may be driven by a manually operated lever.

The thread guides19and20are open rightward and have horizontally formed thread catching portions19aand20ain the foregoing embodiment. The hook member123is moved substantially horizontally between the standby position and the operating position, whereby the needle thread11is caught on the catching hook123a. However, the hook member123amay be moved from the right to the left obliquely downward at 45 degrees. On the other hand, the thread catching portions19aand20aof the thread guides19and20may be open rightward and may extend obliquely upward substantially at 45 degrees so that the hook member123is moved horizontally from the left to the right.

The base member of the thread guide mechanism may be integral with a sewing machine frame or a cover covering the sewing machine frame. In this case, the moving member, stopper member, stopper member or coil spring is provided directly on the sewing machine frame or a cover covering the sewing machine frame.

The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limiting sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the invention as defined by the appended claims.