Patent Description:
Conventionally, a sewing machine capable of performing a double chain stitch (multi thread chain stitch) defined as <NUM>, <NUM> and the like in JIS-L0120 is known. In the above described sewing machine, when an upper decoration mechanism is attached, it is possible to perform a double chain stitch with an upper decoration thread (hereafter, referred to as "upper decoration sewing") defined as indication signs <NUM>, <NUM> (seam of the indication sign <NUM> is shown in <FIG>) and the like where the decoration is added to the seam of the indication sign <NUM> and the like. Note that the thread hatched in <FIG> is the decoration thread.

In the sewing machine capable of performing the above described two kinds of double chain stitches, if the upper decoration mechanism is attached when performing the double chain stitch not using the decoration thread, the upper decoration mechanism located near the needles becomes obstructive and workability is reduced. Therefore, the upper decoration mechanism is detached when performing the double chain stitch not using the decoration thread while the upper decoration mechanism is attached when performing the upper decoration sewing. <CIT> proposes that counter-marks are provided on a spreader, which functions as the upper decoration mechanism, and a driving arm of the sewing machine for positioning them with each other when mounting the spreader on the driving arm.

<CIT> discloses an upper decorative stitching spreader that is switched active or inactive by an upper decoration switching mechanism. By placing the spreader in active state, upper decorative stitches which are formed from above the fabric are added to the conventional over-edge chain stitches and lower decorative stitches which are formed from below the fabric. On the other hand, by placing the spreader in an inactive state; that is, by stopping the spreader, over-edge chain stitching without upper decorative stitching, and lower decorative stitching which is performed from below the fabric are performed without interference with the spreader.

<CIT> discloses an arm shaft, with a clutch on the arm shaft comprising a cam ring, an actuating ring, and a revolution transmission mechanism, and the lower end of a rocking lever which laterally rocks by fitting an engaging element in a cam groove provided on the cam ring, and a spreader which is laterally rockably provided, connected by a connecting rod to impart a specified amplitude to the spreader. Then, the leading end part of a switching lever is fitted in a peripheral groove of the actuating ring, and the clutch is turned on/off by a switching operation of the switching lever, and by doing so, a balance-sewing and a flat sewing are switched.

<CIT> discloses an upper decorative stitching device which is designed to make it possible to convey precisely the swing movement of the first lever which shows swing movements widthwise in a pendulum manner to the horizontal reciprocating motion of the second lever provided with a spreader, to make it possible to reduce the cost of the device by simplifying the structure of the upper decorative stitching device, and also to facilitate the operation of switching between the case of upper decorative stitching and the case of no upper decorative stitching. The device is constructed so that a connecting rod provided at both ends with spherical bearings is used to make connection between the first lever which shows swing movements widthwise in a pendulum manner in front of the sewing machine and the second lever provided at the front end with a spreader which reciprocates horizontally along the needle position, thereby converting the rotation of the upper shaft into the reciprocal movements of the spreader.

Although the operation of positioning the upper decoration mechanism can be simplified in the sewing machine of <CIT>, the operator should perform the operation while visually confirming the counter-marks. Thus, the operation itself cannot be omitted. In addition, the upper decoration mechanism detached from the sewing machine may be lost, the upper decoration mechanism may be erroneously broken during the storage and other faults may occur.

Considering the above described problems, the present invention aims for providing an upper decoration mechanism not requiring the operation of removing the upper decoration mechanism from the sewing machine without reducing the workability even when performing the double chain stitch not using the decoration thread and a sewing machine having the upper decoration mechanism.

The present invention relates to a double chain stitch sewing machine comprising an upper decoration mechanism and the features of claim <NUM>.

In the above described double chain stitch sewing machine, it is preferred to further provide a transmission mechanism configured to transmit a force for driving the needle from a main shaft to the spreader in the expanded state while the force is interrupted in the retracted state.

In the above described double chain stitch sewing machine, it is preferred that the transmission mechanism includes a positioning mechanism configured to adjust operations of the needle and the spreader to a predetermined timing when switching the spreader from the retracted state to the expanded state.

In the above described double chain stitch sewing machine, it is preferred to further provide a guide mechanism configured to move the spreader in a predetermined path with a predetermined posture when switching the spreader between the expanded state and the retracted state.

In the above described double chain stitch sewing machine, it is preferred to further provide an upper decoration thread guide configured to be switched between the expanded state for performing the upper decoration sewing by guiding an upper decoration thread to the spreader and the retracted state where the spreader is separated from the needle interlocking with the expansion retraction mechanism.

By using the upper decoration mechanism of the present invention, the spreader is switched to the expanded state by the above described expansion retraction mechanism to perform the upper decoration sewing without detaching the spreader from the sewing machine. Namely, there is no risk of losing and breaking the spreader, and the workability is improved since the operation of attaching and detaching the spreader is no required. In addition, when the spreader is switched to the retracted state by the expansion retraction mechanism, the spreader can be separated from the needles. Thus, the double chain stitch not using the decoration thread can be performed with high workability.

Hereafter, an embodiment of an upper decoration mechanism of the present invention and an embodiment of a sewing machine having the upper decoration mechanism will be explained with reference to the drawings. In the following explanation, the explanation will be made using the directions of right, left, front, rear, up, down, X, Y and Z for convenience.

<FIG> shows a sewing machine <NUM> realizing a sewing machine of the present invention. An upper decoration mechanism <NUM> realizing an upper decoration mechanism of the present invention is mounted on the sewing machine <NUM>. A main shaft <NUM> rotated by a not-illustrated sewing machine motor is provided on an arm portion 1a of the sewing machine <NUM>. A not-illustrated lower shaft rotated by the sewing machine motor is provided on a bed portion 1b of the sewing machine <NUM>. The upper decoration mechanism <NUM> (including a later-described spreader <NUM>) and needles (comprised of three needles: a first needle <NUM>; a second needle <NUM>; and a third needle <NUM> in the present embodiment) are connected to the main shaft <NUM>. A looper mechanism (not-illustrated) and a feed mechanism (not-illustrated) provided on the bed portion 1b are connected to the lower shaft. In addition, a first needle thread T1, a second needle thread T2, a third needle thread T3, a decoration thread T4 and a looper thread T5 wound around thread reels are attached to the sewing machine <NUM>. The sewing machine motor is rotated and the elements connected to the upper shaft <NUM> and the lower shaft are cooperated with each other. Thus, the seams are formed by the first needle thread T1 and the like so that the cloth is sewn. By using the sewing machine <NUM> of the present embodiment, an upper decoration sewing shown in <FIG> can be performed and the double chain stitch not using the decoration thread T4 can be also performed. Note that a needle thread guide <NUM> and other members are attached to the sewing machine <NUM> around the third needle <NUM> and the like.

A partially enlarged view of <FIG> shows an expanded state where the spreader <NUM> is moved near to the third needle <NUM> and the like. When the sewing machine motor is rotated in this state, the upper decoration sewing can be performed. An entire perspective view of <FIG> shows a retracted state where the spreader <NUM> is moved upward and separated from the third needle <NUM> and the like. When the sewing machine motor is rotated in this state, the double chain stitch not using the decoration thread T4 can be performed. In the upper decoration mechanism <NUM> of the present embodiment, when a later described expansion lever <NUM> is pressed downward in the retracted state, the spreader <NUM> can be switched to the expanded state. When a retraction lever <NUM> is pressed from front to rear in the expanded state, the spreader <NUM> can be switched to the retracted state.

<FIG> shows the upper decoration mechanism <NUM> and the main shaft <NUM> in the retracted state. An upper decoration cam <NUM> is attached to the main shaft <NUM> so that the upper decoration cam <NUM> is rotated together with the main shaft <NUM>. In addition, the upper decoration mechanism <NUM> includes a base plate <NUM>. The base plate <NUM> is fixed to a not-illustrated sewing machine frame. Furthermore, the upper decoration mechanism <NUM> includes an upper decoration shaft <NUM> having a long columnar (cylindrical) shape, a connection plate <NUM> having a plate shape, and a follower pin <NUM> having a short columnar (cylindrical) shape. Here, the base plate <NUM> supports the upper decoration shaft <NUM> so that the upper decoration shaft <NUM> is rotatable. As shown in the drawing, one end of the connection plate <NUM> is connected to the upper decoration shaft <NUM> while the other end of the connection plate <NUM> is connected to the follower pin <NUM>. Note that the upper decoration shaft <NUM> is energized by a not-illustrated spring in the direction of an arrow A (clockwise in the view from up to down) and the follower pin <NUM> is always in contact with the upper decoration cam <NUM>. Therefore, the main shaft <NUM> is rotated in accordance with the upper decoration cam <NUM>, and the upper decoration shaft <NUM> is rocked in accordance with the rotation of the main shaft <NUM>.

<FIG> is an exploded view of the upper decoration mechanism <NUM>. The upper decoration mechanism <NUM> of the present embodiment further includes a mechanism core <NUM>, an upper decoration thread guide <NUM>, a spreader <NUM>, an upper coupler <NUM>, a lower coupler <NUM>, an expansion lever <NUM>, a retraction lever <NUM> and a stepped screw <NUM>. In <FIG>, <FIG>, <FIG>, <FIG>, a cover <NUM> and some other components are omitted for the convenience of the illustration.

The mechanism core <NUM> is formed in a substantially hollow shape. The mechanism core <NUM> is inserted around the upper decoration shaft <NUM> and supported by the upper decoration shaft <NUM> so as to be rotatable and slidable in the axial direction with respect to the upper decoration shaft <NUM>. In addition, the mechanism core <NUM> includes a slide portion 12a protruded from an outer peripheral surface of the mechanism core <NUM>.

The upper decoration thread guide <NUM> includes a pair of support portions 13a provided at an interval in the vertical direction. Each of the pair of support portions 13a has a hole into which the upper decoration shaft <NUM> can be inserted. The interval between the support portions 13a is substantially identical to a whole length of the mechanism core <NUM>. In addition, the upper decoration thread guide <NUM> includes a release portion receiver 13b having a plate shape extended from left to right and a positioning portion 13c provided on an upper end of the release portion receiver 13b so as to be protruded from front to rear.

The spreader <NUM> includes a hole capable of being inserted around the upper decoration shaft <NUM> and a pair of support portions 14a provided at an interval in the vertical direction. The interval between the support portions 14a is substantially identical to the length from an upper surface of one of the support portions 13a located on the upper side to a lower surface of the other of the support portions 13a located on the lower side. In addition, the spreader <NUM> includes a spreader retreat cam follower 14b protruded from left to right.

The upper coupler <NUM> has a short columnar shape. An upper end of the upper coupler <NUM> is connected to the spreader <NUM> in a state that the upper coupler <NUM> is directed in the vertical direction. Namely, the upper coupler <NUM> is integrally operated with the spreader <NUM>. Note that a lower end of the upper coupler <NUM> is formed in a semispherical shape.

The lower coupler <NUM> includes a connection hole 16a connected to the lower end of the upper decoration shaft <NUM>. Since the lower coupler <NUM> and the upper decoration shaft <NUM> are attached with a predetermined angle relation, the rocking angle of the lower coupler <NUM> is uniquely determined by the rotation angle of the upper decoration cam <NUM>. In addition, the lower coupler <NUM> includes a spreader angle determining cam portion 16b having a groove shape extended in the vertical direction at an outside of the connection hole 16a in the radial direction. Note that the width of the groove of the spreader angle determining cam portion 16b is substantially identical to the outer diameter of the upper coupler <NUM>. A pair of inclined portions 16c is provided on the upper part of the spreader angle determining cam portion 16b so that the interval is gradually increased from the lower part to the upper part.

The expansion lever <NUM> is formed in an approximately L shape. A slide portion fixing hole 17b and a stepped screw slide portion 17c located at the lower part of the slide portion fixing hole 17b are provided on a plate-shaped portion 17a which is vertically extended. In addition, a rotary pin 17d having a columnar shape extended to the right side is provided on the plate-shaped portion 17a.

The retraction lever <NUM> is located at a center part in the longitudinal direction. The retraction lever <NUM> includes a pin hole 18a into which the rotary pin 17d can be inserted. A positioning release portion 18b protruded from rear to front is provided on the upper end portion of the retraction lever <NUM>.

Note that the upper decoration mechanism <NUM> includes not-illustrated springs for energizing the upper decoration thread guide <NUM>, the spreader <NUM>, the expansion lever <NUM> and the retraction lever <NUM> respectively. The upper decoration thread guide <NUM> is energized in the direction of an arrow B (clockwise in the view from up to down), the spreader <NUM> is energized in the direction of an arrow C (counterclockwise in the view from up to down), the expansion lever <NUM> is energized in the direction of an arrow D (direction from down to up), and the retraction lever <NUM> is energized in the direction of an arrow E (counterclockwise in the view from right to left).

Here, the above described base plate <NUM> will be explained. The base plate <NUM> of the present embodiment includes a hole into which the upper decoration shaft <NUM> can be inserted and a pair of support portions 8a provided at an interval in the vertical direction. In addition, a slide groove 8c is provided on a plate-shaped portion 8b located at the right side of the base plate <NUM> so that the slide groove 8c penetrates through the base plate <NUM> and extends in the vertical direction. In addition, a spreader slide groove 8d is provided on the plate-shaped portion 8b so that spreader slide groove 8d extends in the vertical direction at the front side of the slide groove 8c. A spreader retreat cam portion 8e gradually increased from the upper part to the lower part in the front-rear direction is provided on the lower part of the spreader slide groove 8d. In addition, an upper decoration thread slide cam portion 8f extending in the vertical direction is provided on the front end portion of the plate-shaped portion 8b. A stopper <NUM> protruded from rear to front is provided on the upper part of the upper decoration thread slide cam portion 8f. A positioning groove <NUM> is provided on the lower part of the upper decoration thread slide cam portion 8f so that the positioning groove <NUM> cuts the plate-shaped portion 8b from front to rear.

The above described components forming the upper decoration mechanism <NUM> can be assembled by the following procedures, for example. First, the pin hole 18a is inserted around the rotary pin 17d so that the retraction lever <NUM> is rotatably supported on the expansion lever <NUM>. Note that the retraction lever <NUM> is held on the expansion lever <NUM> while preventing retraction lever <NUM> from slipping off by a not-illustrated slip-off preventing mechanism (e.g., narrow groove is formed on a tip end portion of the rotary pin 17d and an E-ring is fitted into the narrow groove after the pin hole 18a is inserted). Then, the stepped screw <NUM> inserted into the stepped screw slide portion 17c is screwed and fixed to the base plate <NUM>. Consequently, the expansion lever <NUM> is supported on the base plate <NUM> so as to be movable in the vertical direction.

For attaching the mechanism core <NUM>, the upper decoration thread guide <NUM> and the spreader <NUM> to the base plate <NUM>, after the mechanism core <NUM> is sandwiched by the pair of support portions 13a and the pair of support portions 13a is sandwiched by the pair of support portions 14a, the upper decoration shaft <NUM> inserted into one of the support portions 8a of the base plate <NUM> is inserted into the support portions 14a and other portions. When the mechanism core <NUM> and other members are assembled with the base plate <NUM>, the slide portion 12a is inserted through the slide groove 8c and inserted into the slide portion fixing hole 17b. Then, the lower end portion of the upper decoration shaft <NUM> is inserted into the connection hole 16a of the lower coupler <NUM>. Thus, the lower coupler <NUM> is attached to the upper decoration shaft <NUM>.

In the above described assembled state, the mechanism core <NUM>, the upper decoration thread guide <NUM>, the spreader <NUM>, the expansion lever <NUM> and the retraction lever <NUM> are supported so as to integrally move in the vertical direction with respect to the base plate <NUM> and the upper decoration shaft <NUM>. In addition, since the expansion lever <NUM> is energized in the direction of the arrow D, the mechanism core <NUM>, the upper decoration thread guide <NUM>, the spreader <NUM>, the expansion lever <NUM> and the retraction lever <NUM> are positioned in the vertical direction when the positioning portion 13c abuts on the lower end portion of the stopper <NUM>. In addition, since the decoration thread guide <NUM> is energized in the direction of the arrow B, the positioning portion 13c is positioned in the circumferential direction when the positioning portion 13c abuts on the upper decoration thread slide cam portion 8f. Furthermore, since the spreader <NUM> is energized in the direction of the arrow C, the spreader retreat cam follower 14b is positioned in the circumferential direction in a state that the spreader retreat cam follower 14b is inserted into the spreader slide groove 8d. Here, although the retraction lever <NUM> is energized in the direction of the arrow E, the retraction lever <NUM> is covered with the cover <NUM> shown in <FIG>. Thus, the retraction lever <NUM> is not rotated excessively in the direction of the arrow E even when it is energized. Although the upper coupler <NUM> is a portion to be inserted into the spreader angle determining cam portion 16b of the lower coupler <NUM> as described later, the upper coupler <NUM> is located above the lower coupler <NUM> in a state that the positioning portion 13c abuts on the lower end part of the stopper <NUM>.

Next, the retracted state and the expanded state of the upper decoration mechanism <NUM> of the present embodiment will be explained. The retracted state and the expanded state of the upper decoration thread guide <NUM> will be explained with reference to <FIG>. In <FIG>, the base plate <NUM> and the expansion lever <NUM> are partly shown. In addition, <FIG> is a drawing showing the retracted state while <FIG> is the drawing showing the expanded state.

As shown in <FIG>, the expansion lever <NUM> is energized in the direction of the arrow D in the retracted state. Therefore, the upper decoration thread guide <NUM> which integrally moves in the vertical direction with the expansion lever <NUM> is also energized in the direction of the arrow D. Accordingly, the positioning portion 13c abuts on the lower end portion of the stopper <NUM> and the upper decoration thread guide <NUM> is not moved in the vertical direction. In addition, since the upper decoration thread guide <NUM> is energized in the direction of the arrow B, the positioning portion 13c abuts on the upper decoration thread slide cam portion 8f.

When the expansion lever <NUM> is pressed downward, the upper decoration thread guide <NUM> which integrally moves in the vertical direction with the expansion lever <NUM> is moved downward in a state that the positioning portion 13c abuts on the upper decoration thread slide cam portion 8f. When the positioning portion 13c comes to the positioning groove <NUM>, the positioning portion 13c is fitted to the positioning groove <NUM> by the energizing force in the direction of the arrow B. Namely, since the upper decoration thread guide <NUM> is positioned in the vertical direction by the positioning portion 13c and the positioning groove <NUM>, the upper decoration thread guide <NUM> and the expansion lever <NUM> are kept in the state of being moved below (the expanded state) even if the user releases the expansion lever <NUM>.

As described above, when the upper decoration thread guide <NUM> is switched from the retracted state to the expanded state by pressing down the expansion lever <NUM>, the upper decoration thread guide <NUM> is lowered while keeping the angle around the upper decoration shaft <NUM> and rotated in the direction of the arrow B when the positioning portion 13c is fitted to the positioning groove <NUM>. Namely, the upper decoration thread guide <NUM> is located near the third needle <NUM> and the like in the expanded state as shown in partially enlarged view of <FIG>. However, when switching from the retracted state to the expanded state, the upper decoration thread guide <NUM> is lowered while keeping the angle rotated in the direction of separating from the third needle <NUM> and the like. Thus, the upper decoration thread guide <NUM> can be prevented from colliding with the third needle <NUM> and the like and the needle thread guide <NUM> and the like provided on the periphery of the third needle <NUM>.

On the other hand, when switching from the expanded state to the retracted state, as shown in <FIG>, the lower end portion of the retraction lever <NUM> is pressed from front to rear.

By the above described operation, the retraction lever <NUM> is rotated in the reverse direction of the arrow E. Thus, the positioning release portion 18b abuts on the release portion receiver 13b of the upper decoration thread guide <NUM>. Consequently, since the upper decoration thread guide <NUM> is rotated in the reverse direction of the arrow B, the engagement between the positioning portion 13c and the positioning groove <NUM> is released. After that, the upper decoration thread guide <NUM> is moved upward while the positioning portion 13c abuts on the upper decoration thread slide cam portion 8f by the energizing force in the direction of the arrow B and the energizing force in the direction of the arrow D. Then, the upper decoration thread guide <NUM> is stopped at the position where the positioning portion 13c abuts on the lower end portion of the stopper <NUM>.

As described above, when switching from the expanded state to the retracted state, the upper decoration thread guide <NUM> is raised after rotated in the reverse direction of the arrow B. Namely, as shown in partially enlarged view of <FIG>, the upper decoration thread guide <NUM> located near the third needle <NUM> and the like in the expanded state is separated from the third needle <NUM> and the like and then raised while keeping the angle. Thus, the upper decoration thread guide <NUM> can be prevented from colliding with the third needle <NUM> and the like and the needle thread guide <NUM> and the like provided on the periphery of the third needle <NUM>.

Then, the retracted state and the expanded state of the spreader <NUM> will be explained with reference to <FIG>. In <FIG>, the base plate <NUM> and the expansion lever <NUM> are partly shown. In addition, <FIG> is a drawing showing the retracted state while <FIG> is the drawing showing the expanded state.

As described above, the spreader <NUM> is integrally moved with the expansion lever <NUM> and the like in the vertical direction. In the retracted state, the expansion lever <NUM> and the like are stopped in a state that the positioning portion 13c abuts on the lower end portion of the stopper <NUM> by the energizing force in the direction of the arrow D as shown in <FIG>. Therefore, the spreader <NUM> is also stopped in the vertical direction in the retracted state shown in <FIG>. In addition, since the spreader retreat cam follower 14b is inserted into the spreader slide groove 8d in the retracted state, the movement of the spreader <NUM> in the rotation direction is restricted. As described above, since the energizing force is acted on the spreader <NUM> in the direction of the arrow mark C, the spreader retreat cam follower 14b abuts on the wall surface of the front side of the spreader slide groove 8d.

When the expansion lever <NUM> is pressed downward, the spreader <NUM> is interlocked with the expansion lever <NUM> and moved downward in a state that the spreader retreat cam follower 14b is inserted into the spreader slide groove 8d. The spreader retreat cam portion 8e having an inclined shape is provided on the lower part of the spreader slide groove 8d so that the width of the groove is gradually increased from the upper part to the lower part in the front-rear direction. Namely, although the operation of the spreader <NUM> in the rotation direction is restricted in the retracted state shown in <FIG>, the restriction of the operation of the spreader <NUM> in the rotation direction is released in the expanded state shown in <FIG>.

Incidentally, since the upper coupler <NUM> is connected to the spreader <NUM>, the upper coupler <NUM> is also lowered when the spreader <NUM> is lowered. Here, the lower coupler <NUM> connected to the upper decoration shaft <NUM> is located at the lower part of the upper coupler <NUM>. Therefore, when the spreader <NUM> is lowered, the upper coupler <NUM> is inserted into the lower coupler <NUM> and the lower end part of the upper coupler <NUM> is fitted to the spreader angle determining cam portion 16b. In the present embodiment, since the width of the groove of the spreader angle determining cam portion 16b and the outer diameter of the upper coupler <NUM> are substantially identical, the spreader <NUM> is integrally rocked with the lower coupler <NUM> when the upper coupler <NUM> is fitted to the spreader angle determining cam portion 16b.

As shown in <FIG>, since the follower pin <NUM> is in contact with the upper decoration cam <NUM>, the upper decoration shaft <NUM> to which the lower coupler <NUM> is connected is always rocked in a state that the main shaft <NUM> is rotated. Therefore, when the spreader <NUM> is lowered, the spreader angle determining cam portion 16b of the lower coupler <NUM> may not be located immediately below the upper coupler <NUM> in some cases. On the other hand, the lower coupler <NUM> of the present embodiment includes the pair of inclined portions 16c which is inclined so that the interval is gradually increased from the lower part to the upper part at the upper part of the spreader angle determining cam portion 16b. Thus, when the lowered upper coupler <NUM> is in contact with the inclined portions 16c, the spreader <NUM> is rotated in accordance with the inclined portions 16c and the upper coupler <NUM> is moved toward the spreader angle determining cam portion 16b. Namely, the angle deviation between the spreader <NUM> and the lower coupler <NUM> is eliminated by the inclined portions 16c. Thus, the upper coupler <NUM> can be smoothly fitted to the spreader angle determining cam portion 16b when the spreader <NUM> is lowered.

As described above, when the expansion lever <NUM> is pressed downward to switch the spreader <NUM> from the retracted state to the expanded state, the spreader <NUM> is lowered while keeping the angle around the upper decoration shaft <NUM> and then rotated by a predetermined angle at a portion where the upper coupler <NUM> is fitted to the lower coupler <NUM>. Namely, the spreader <NUM> is located near the third needle <NUM> and the like in the expanded state as shown in partially enlarged view of <FIG>. However, when switching from the retracted state to the expanded state, the spreader <NUM> is lowered while keeping the angle rotated in the direction of separating from the third needle <NUM> and the like. Thus, the spreader <NUM> can be prevented from colliding with the third needle <NUM> and the like and the needle thread guide <NUM> and the like provided on the periphery of the third needle <NUM>.

When the retraction lever <NUM> is pressed for switching from the expanded state to the retracted state as shown in <FIG>, the spreader <NUM> is raised (shown in <FIG>) by the energizing force in the direction of the arrow D. Thus, the engagement between the upper coupler <NUM> and the lower coupler <NUM> is released. When the engagement between the upper coupler <NUM> and the lower coupler <NUM> is released, the spreader <NUM> is rotated by the energizing force in the direction of the arrow C until the spreader retreat cam follower 14b abuts on the wall surface located at the front side of the spreader slide groove 8d. Even when the spreader <NUM> is raised before the rotation is finished, the spreader retreat cam follower 14b is in contact with the spreader retreat cam portion 8e and the spreader <NUM> is rotated in the direction of the arrow C. Thus, the spreader <NUM> can be prevented from colliding with the third needle <NUM> and the like and the needle thread guide <NUM> and the like provided on the periphery of the third needle <NUM>. After that, in a state that the spreader retreat cam follower 14b is inserted into the spreader slide groove 8d, the spreader <NUM> is raised while keeping the angle and switched to the retracted state.

As described above, when switching from the expanded state to the retracted state, the spreader <NUM> is rotated in the direction of separating from the third needle <NUM> and the like and then raised while keeping the angle. Thus, the spreader <NUM> can be prevented from colliding with the third needle <NUM> and other members provided on the periphery of the third needle <NUM>.

When the upper decoration mechanism <NUM> is switched to the retracted state, the upper decoration thread guide <NUM> and the spreader <NUM> are separated from the third needle <NUM> and the like and moved upward. In the retracted state, since the upper coupler <NUM> is separated from the lower coupler <NUM>, the spreader <NUM> is not rocked even when the main shaft <NUM> is rotated. Therefore, the double chain stitch not using the decoration thread T4 can be performed with high workability. When the upper decoration mechanism <NUM> is switched to the expanded state, the upper decoration thread guide <NUM> and the spreader <NUM> are lowered to near the third needle <NUM> and the like, the upper coupler <NUM> is fitted to the spreader angle determining cam portion 16b, and the spreader <NUM> is rocked in synchronization with the rotation of the main shaft <NUM>. Thus, the upper decoration sewing shown in <FIG> can be performed. Here, the processes of forming the seams of the upper decoration sewing shown in <FIG> will be explained with reference to <FIG>.

In <FIG>, the first needle thread T1, the second needle thread T2 and the third needle thread T3 are inserted into the first needle <NUM>, the second needle <NUM> and the third needle <NUM> respectively. The looper thread T5 is inserted into a looper (not illustrated). The decoration thread T4 is inserted into a hole-shaped portion located at the tip portion of the upper decoration thread guide <NUM>. The drawing located at the left side of <FIG> shows the state that the first needle <NUM>, the second needle <NUM> and the third needle <NUM> are moved to the uppermost position and the spreader <NUM> is moved to the leftmost position. In the above described state, the tip portion of the spreader <NUM> captures the decoration thread T4 and holds the captured decoration thread T4 so that the decoration thread T4 crosses the first needle <NUM> and the like.

Then, as shown in the drawing located at the upper side of <FIG>, when the first needle <NUM> and the like are lowered, the third needle <NUM> passes through the rear side of the decoration thread T4. At this time, the spreader <NUM> moved to the right releases the decoration thread T4.

Then, as shown in the drawing located at the right side of <FIG>, the first needle <NUM> and the like are moved to the lowermost position and cooperate with a not-illustrated looper mechanism, feed mechanism and the like for sewing the decoration thread T4 into the first needle thread T1, the looper thread T5 and the like. Thus, the seams of the upper decoration sewing are formed. At this time, the spreader <NUM> passes through the decoration thread T4 held by the upper decoration thread guide <NUM> and moves to the lower right of the hole-shaped portion located at the tip of the upper decoration thread guide <NUM> (i.e., rightmost position).

After that, as shown in the drawing located at the lower side of <FIG>, the first needle <NUM> and the like are raised and the spreader <NUM> is moved to the left while capturing the decoration thread T4. After the cloth is fed by the feed mechanism, the first needle <NUM> and the like and the spreader <NUM> are moved to the position shown in the drawing located at the left side of <FIG>.

After that, the upper decoration sewing shown in <FIG> is performed by repeating the above described processes.

The embodiment embodying the present invention is exemplified above. However, the present invention is not limited to the above described specific embodiment. Various variations and modifications are possible within the content of the present invention described in the claims unless particularly limited in the above described explanation. In addition, the above described effects of the embodiment merely exemplify the effects raised from the present invention. The effects of the present invention are not limited to the above described effects.

For example, "expansion retraction mechanism" of the present specification is realized by the configurations mainly formed by the upper decoration shaft <NUM> and the sliding structure of the support portions 14a of the spreader <NUM> in the upper decoration mechanism <NUM> of the present embodiment. In addition, the configuration of switching between the expanded state and the retracted state is realized by the interlocking operation of the upper decoration thread guide <NUM> and the spreader <NUM> using the sliding structure of the support portions 13a of the upper decoration thread guide <NUM> and the upper decoration shaft <NUM> and the structure of sandwiching the support portions 13a by the support portions 14a. However, the present invention is not limited to the above described embodiment. Other configurations can be added or some configurations can be replaced with alternative configurations. For example, instead of the mechanism of switching between the expanded state and the retracted state by the sliding operation in the vertical direction, the spreader <NUM> and the upper decoration thread guide <NUM> can be switched between the expanded state and the retracted state by the mechanism of rocking them in the front-rear direction. Alternatively, it is also possible that the spreader <NUM> is switched between the expanded state and the retracted state by the sliding operation in the vertical direction while the upper decoration thread guide <NUM> is switched between the expanded state and the retracted state by the rocking motion in the front-rear direction without interlocking with the motion of the spreader <NUM>. In addition, "transmission mechanism" of the present specification is realized by the upper coupler <NUM> and the spreader angle determining cam portion 16b of the lower coupler <NUM>. However, the present invention is not limited to the above described configuration. For example, it is also possible that a member integrally moved with the expansion lever <NUM> in the vertical direction is provided and the member is interposed between the upper decoration cam <NUM> and the follower pin <NUM> to separate the follower pin <NUM> from the upper decoration cam <NUM> when the expansion lever <NUM> is raised. Thus, the transmission of force from the main shaft <NUM> can be switched. It is also possible that a clutch is provided between the upper decoration shaft <NUM> and the lower coupler <NUM>, the lower coupler <NUM> is rocked by the force from the main shaft <NUM> when the clutch is enabled, and the lower coupler <NUM> is stopped when the clutch is disabled. It is also possible that two motors: one is a motor for vertically moving the first needle <NUM>; and the other is a motor for rocking the spreader <NUM> are provided, the two motors are driven in the expanded state, and the motor for rocking the spreader <NUM> is stopped in the retracted state.

In the present embodiment, the outer diameter of the upper coupler <NUM> and the width of the groove of the spreader angle determining cam portion 16b are substantially identical, and the upper coupler <NUM>, the spreader angle determining cam portion 16b and the inclined portions 16c also function as "positioning mechanism" of the present specification. For example, it is also possible that the width of the groove of the spreader angle determining cam portion 16b is longer than the outer diameter of the upper coupler <NUM> to function as "transmission mechanism. " In such a case, "positioning mechanism" is separately provided. Regarding "positioning mechanism," it is also possible that two motors: one is a motor for vertically moving the first needle <NUM> and the like; and the other is a motor for rocking the spreader <NUM> are provided, encoders for measuring the rotation angle of the two motors are provided respectively, the rotation angles of the two motors are measured by the encoders and synchronized with each other to adjust the operation of the first needle <NUM> and the operation of the spreader <NUM> to a predetermined timing.

In addition, "guide mechanism" of the present specification is realized by the spreader retreat cam follower 14b provided on the spreader <NUM>, the spreader slide groove 8d provided on the base plate <NUM>, and the spring energizing the spreader <NUM> in the direction of the arrow C or the spreader retreat cam portion 8e in the present embodiment. However the present invention is not limited to the above described embodiment. For example, it is also possible that the equivalent of the spreader slide groove 8d and the spreader retreat cam portion 8e is provided for the spreader <NUM> and the equivalent of the spreader retreat cam follower 14b is provided for the base plate <NUM>. In the present embodiment, for ensuring the operation of the spreader <NUM>, both the spring for energizing the spreader <NUM> in the direction of the arrow C and the spreader retreat cam portion 8e are provided. However, when at least one of the spring for energizing the spreader <NUM> in the direction of the arrow C and the spreader retreat cam portion 8e is provided, the spreader <NUM> can be rotated in the direction of the arrow C after the engagement between the upper coupler <NUM> and the lower coupler <NUM> is released.

Claim 1:
A double chain stitch sewing machine (<NUM>) comprising an upper decoration mechanism (<NUM>), the upper decoration mechanism (<NUM>) comprising:
an expansion retraction mechanism configured to switch a spreader (<NUM>) between an expanded state where the spreader (<NUM>) cooperates with needles (<NUM>, <NUM>, <NUM>) for performing an upper decoration sewing and a retracted state where the spreader (<NUM>) is separated from the needles (<NUM>, <NUM>, <NUM>) for performing sewing without an upper decoration thread (T4),
wherein when the upper decoration mechanism (<NUM>) is switched to the retracted state, the spreader (<NUM>) is separated from the needles (<NUM>, <NUM>, <NUM>) and is moved upward, and
wherein when the upper decoration mechanism (<NUM>) is switched to the expanded state, the spreader (<NUM>) is moved downward and is lowered near to the needles (<NUM>, <NUM>, <NUM>),
characterized in that the upper decoration mechanism (<NUM>) is housed inside the cover of the double chain stitch sewing machine (<NUM>) in the retracted state.