Patent Description:
In a sewing machine including a feed dog in the related art, when an upper thread is captured by a shuttle and drawn below a throat plate, a loop of the upper thread formed by the shuttle may go into disorder until the upper thread is drawn up by a thread take-up lever. As a result, the loop of the upper thread may be caught on a corner portion of a top plate of the feed dog and cause a sewing failure.

In a sewing machine described in <CIT>, a corner portion of a top plate of a feed dog is rounded in an arc shape to reduce catching of a loop of an upper thread, thereby solving the above problem. <CIT> discloses a sewing machine according to the preamble of claim <NUM> with a transporter for transporting sewing material while operation a sewing machine. <CIT> describes a feeding device of a sewing machine. A sewing machine is known from <CIT>.

However, in the sewing machine described in <CIT>, when the corner portion of the top plate of the feed dog is rounded, the contact area between an upper surface of a throat plate and a workpiece is reduced, and the stable feeding of the workpiece may be affected.

An object of the present embodiment is to form excellent seams while feeding a workpiece well.

This object is solved by a sewing machine as defined by claim <NUM>.

As described above, according to the present embodiment, the wall portion of the feed dog prevents a loop of the upper thread from going into disorder. Accordingly, it is not necessary to cut a corner portion of the top plate, and excellent seams can be formed while the workpiece is fed well.

The following description is an embodiment of the present invention and does not limit the present invention.

<FIG> is a perspective view of a sewing machine <NUM> according to the present embodiment. <FIG> is an enlarged perspective view illustrating a configuration in the vicinity of a throat plate <NUM>, which will be described later.

In the present embodiment, a post-bed unison-feed sewing machine, which is a double-needle sewing machine and includes a horizontal shuttle, is described as an example of the sewing machine <NUM>.

To implement the present invention, none of double-needle, unison-feed, the horizontal shuttle, and post-bed are necessary and these are only preferred examples.

The sewing machine <NUM> includes a needle up-and-down movement mechanism that moves up and down two needle bars <NUM> each holding a sewing needle <NUM> at lower end portions, a feed mechanism that feeds a workpiece in a predetermined feed direction (X-axis direction described later) by a feed dog <NUM> (see <FIG>) from below the throat plate <NUM> (described later), an upper feed mechanism that feeds the workpiece on the throat plate <NUM> in the feed direction (X-axis direction) by a feed foot <NUM> (see <FIG>) from above, a needle-feed mechanism that feeds the sewing needles <NUM> in the feed direction (X-axis direction) of the workpiece, a feed adjustment mechanism that adjusts a sewing pitch, a shuttle mechanism including two horizontal shuttles <NUM>, and a sewing machine frame <NUM> holding these components. Each of the above-described mechanisms has a known configuration in a sewing machine, and thus description thereof will be simplified.

The sewing machine <NUM> also has a general configuration for a sewing machine such as a thread tensioner and a thread take-up lever, and description thereof will be omitted since the configuration is known.

The sewing machine frame <NUM> includes a sewing machine bed portion <NUM>, an upright body portion <NUM>, and a sewing machine arm portion <NUM>.

The sewing machine bed portion <NUM> is located at a lower portion of the sewing machine frame <NUM> and supports the entire sewing machine frame <NUM>. The sewing machine bed portion <NUM> extends along a Y-axis direction described later, and includes a post bed <NUM> erected on an upper surface of one end portion thereof and the throat plate <NUM> (see <FIG>) on which stitch points are performed on an upper end surface of the post bed <NUM>.

The upright body portion <NUM> is erected from the other end portion of the sewing machine bed portion <NUM>. The sewing machine arm portion <NUM> extends from an upper end portion of the upright body portion <NUM> in the same direction as the sewing machine bed portion <NUM> along the Y-axis direction.

The sewing machine arm portion <NUM> supports the needle bars <NUM>, a presser foot <NUM>, and the feed foot <NUM> at a lower portion of a distal end thereof in the extending direction.

In the following description, a longitudinal direction of the sewing machine bed portion <NUM> parallel to the upper surface of the sewing machine bed portion <NUM> is referred to as the Y-axis direction, a direction parallel to the upper surface of the sewing machine bed portion <NUM> and orthogonal to the Y-axis direction is referred to as the X-axis direction, and a direction perpendicular to the upper surface of the sewing machine bed portion <NUM> is referred to as a Z-axis direction. As illustrated in <FIG>, one side in the Y-axis direction is defined as "left", the other side is defined as "right", one side in the X-axis direction is defined as "front", the other side is defined as "rear", one side in the Z-axis direction is defined as "upper", and the other side is defined as "lower". Downstream of the workpiece in the feed direction is referred to as "front".

The sewing machine <NUM> normally performs sewing with the sewing machine frame <NUM> installed such that the X-axis direction and the Y-axis direction are horizontal and the Z-axis direction is the vertical direction.

Directions of components of the sewing machine <NUM> will be described on these premises.

The needle up-and-down movement mechanism applies a reciprocating up-and-down movement to the two needle bars <NUM>, which are adjacent in the Y-axis direction, via a crank mechanism from an upper shaft that rotates by using a sewing machine motor (not illustrated) as a drive source. The thread take-up lever is assembled into the needle up-and-down movement mechanism and pivots reciprocally in synchronization with the needle bars <NUM>.

The needle-feed mechanism includes a needle bar oscillating base that supports the two needle bars <NUM> to be movable up and down and is supported to be oscillatory about a Y axis in the sewing machine arm portion <NUM>, and a power mechanism that applies reciprocating oscillation to the needle bar oscillating base using the sewing machine motor as a drive source. When the needle bar oscillating base oscillates about the Y axis, the sewing needles <NUM> located at the lower end portions of the needle bars <NUM> reciprocate in the X-axis direction.

The power mechanism obtains power of the reciprocating movement from the sewing machine motor via a feed mechanism described later, thereby synchronizing the feed oscillation of the sewing needles <NUM> and the feed movement of the feed dog.

The sewing needles <NUM> perform a revolving movement about the Y axis by combining the reciprocating movement in the X-axis direction by the needle-feed mechanism and the reciprocating up-and-down movement by the needle up-and-down movement mechanism, enabling the forward feeding of the sewing needles <NUM> while performing stitch points on the workpiece on the throat plate <NUM>.

<FIG> is a side view schematically illustrating a configuration above and below the throat plate <NUM>. As illustrated in <FIG> and <FIG>, the upper feed mechanism includes the presser foot <NUM> that presses the workpiece on the throat plate <NUM> from above, the feed foot <NUM> that feeds the workpiece forward, a presser bar <NUM> that supports the presser foot <NUM> at a lower end portion thereof, and a feed foot bar <NUM> that supports the feed foot <NUM> at a lower end portion thereof.

The upper feed mechanism further includes a triangular link to which upper end portions of the presser bar <NUM> and the feed foot bar <NUM> are coupled to be pivotable about the Y axis, a presser spring that presses the triangular link downward, and a power mechanism that applies reciprocating oscillation to the triangular link from the sewing machine motor via a cam.

The presser bar <NUM> is supported by the sewing machine arm portion <NUM> to be movable up and down, and a downward pressing force is applied to the presser bar <NUM> by the presser spring via the triangular link. Accordingly, the presser foot <NUM> applies pressing pressure from above to below to the workpiece on the throat plate <NUM>.

On the other hand, since the triangular link is given the reciprocating oscillation, the triangular link alternately moves the presser foot <NUM> and the feed foot <NUM> up and down via the presser bar <NUM> and the feed foot bar <NUM> so that the presser foot <NUM> and the feed foot <NUM> step. Since the feed foot bar <NUM> is supported by the triangular link to be oscillatory about the Y axis, the workpiece is sandwiched from above and below between the feed foot <NUM> and the feed dog <NUM> when the feed foot <NUM> lands, and the feed foot <NUM> oscillates in the feed direction and feeds the workpiece. The feed foot <NUM> has serrated teeth formed on a bottom surface thereof to easily hold the workpiece.

The feed mechanism includes the feed dog <NUM> whose tooth tips are seen through two openings of the throat plate <NUM> provided at the upper end portion of the post bed <NUM>, and a power mechanism that applies a feed operation to the feed dog <NUM>.

A detailed structure of the feed dog <NUM> will be described later.

The power mechanism takes out reciprocating movements in the X-axis direction and the Z-axis direction from the rotation of the sewing machine motor via a cam mechanism, combines the reciprocating movements in the two directions, and transmits the combined reciprocating movements to a feed dog bracket disposed below the post bed <NUM>. The feed dog bracket is given the combined reciprocating movements in two directions of the X-axis direction and the Z-axis direction, thereby performing a revolving movement about the Y axis. The feed dog bracket transmits the revolving movement about the Y axis to the feed dog <NUM> disposed below the throat plate <NUM> via a feed lever member inserted up and down through the post bed <NUM>.

Accordingly, the feed dog <NUM> can move in the feed direction and feed the workpiece on the throat plate <NUM> while keeping the tooth tips partially protruding out from the two openings of the throat plate <NUM>.

The feed adjustment mechanism can adjust a reciprocating movement component (feed pitch) in the X-axis direction transmitted to the feed dog bracket by changing and adjusting a movement direction of a part of link members of a multi-joint link mechanism that transmits the reciprocating movement in the X-axis direction from the cam mechanism constituting the power mechanism of the feed mechanism to the feed dog bracket. The feed adjustment mechanism can also switch positive feed (forward feed) of the workpiece to reverse feed (backward feed).

The feed adjustment mechanism may adjust the feed pitch by manually operating an operation unit such as a dial, and may adjust the feed pitch by a motor that controls an operation amount. When the feed adjustment mechanism includes a motor, for example, the motor is controlled to have a feed pitch set and input from an operation panel.

The shuttle mechanism is provided in the vicinity of the upper end portion of the post bed <NUM>, and includes the two horizontal shuttles <NUM> arranged side by side in the Y-axis direction, and a power mechanism that transmits rotation from the sewing machine motor to the horizontal shuttles <NUM>.

The power mechanism includes a lower shaft that extends along the Y-axis direction and rotates via a timing belt stretching in the upright body portion <NUM> from the upper shaft, two shuttle shafts provided in the post bed <NUM> along the Z-axis direction, and a gear mechanism using a bevel gear that transmits rotation from the lower shaft to the shuttle shafts. The gear mechanism accelerates the rotation of the sewing machine motor to double speed and transmits the rotation to the shuttle shafts.

The two horizontal shuttles <NUM> are disposed on two sides in the Y-axis direction with the feed dog <NUM> disposed below the throat plate <NUM> sandwiched in between.

Each horizontal shuttle <NUM> includes an outer shuttle <NUM> that is coupled to an upper end portion of the corresponding shuttle shaft and rotates about the Z axis, and an inner shuttle <NUM> that stores a bobbin of a lower thread D while maintaining a non-rotating state inside the outer shuttle <NUM>.

During sewing, each sewing needle <NUM> is inserted into a corresponding one of two insertion holes <NUM> (see <FIG>) provided in the feed dog <NUM> from above, and a hook <NUM> (see <FIG>) of the outer shuttle <NUM> of each horizontal shuttle <NUM> captures an upper thread loop from the corresponding sewing needle <NUM>, and largely draws the loop below the throat plate <NUM> to pass through the inner shuttle <NUM>. Accordingly, the lower thread D drawn out from a lower thread feed port <NUM> (see <FIG>) of the inner shuttle <NUM> is inserted into a loop of an upper thread U to form a knot.

<FIG> is a perspective view of the feed dog <NUM>. <FIG> is a side view of the feed dog <NUM>.

The feed dog <NUM> includes a top plate <NUM> and a support portion <NUM> that is integrally coupled to the top plate <NUM> and to which a feed operation is transmitted.

The top plate <NUM> is a rectangular flat plate body along an X-Y plane, and the support portion <NUM> is a rectangular flat plate body along an X-Z plane. An upper end portion of the support portion <NUM> is integrally coupled to a middle portion of a lower surface of the top plate <NUM> in the Y-axis direction. Accordingly, when viewed from the X-axis direction, the feed dog <NUM> has a substantially T-shape by the top plate <NUM> and the support portion <NUM>, in which the top plate <NUM> extends to left and right from the upper end portion of the vertically erected support portion <NUM>.

A lower end portion of the support portion <NUM> is supported by an upper end portion of the feed lever member of the feed mechanism inserted up and down through the post bed <NUM>, so that a feed operation is input to the support portion <NUM>.

The top plate <NUM> is formed with a groove extending along the X-axis direction in a middle portion of an upper surface thereof in the Y-axis direction, so that the upper surface is divided into right and left two parts corresponding to the two sewing needles <NUM>. The top plate <NUM> is further formed with serrated teeth as viewed in the Y-axis direction at a front end portion and a rear end portion of the upper surface. Tooth tips of the teeth are slightly inclined forward relative to a vertically upward direction, so that friction forward relative to a lower surface of the workpiece is increased.

At the middle portion of the top plate <NUM> in the X-axis direction, the substantially circular insertion holes <NUM>, through which the sewing needles <NUM> are inserted, penetrate the top plate <NUM> up and down on left and right two sides with the support portion <NUM> sandwiched in between. The sewing needles <NUM> are inserted into the corresponding insertion holes <NUM>, and the upper thread U is caught by the horizontal shuttles <NUM> below the throat plate <NUM> and the top plate <NUM>.

The top plate <NUM> includes, on a lower surface side thereof, a pair of wall portions <NUM> extending in an up-and-down direction on one side (front side) and the other side (rear side) in the X-axis direction (feed direction of the workpiece) relative to the insertion holes <NUM>.

The wall portions <NUM> each have a plate shape along a Y-Z plane. In the present embodiment, the wall portions <NUM> are located at a front end portion and a rear end portion of the top plate <NUM>, and may also be close to the insertion holes <NUM> in the X-axis direction. One wall portion <NUM> is provided on the front side and one wall portion <NUM> is provided on the rear side for the left and right insertion holes <NUM> together. Alternatively, one wall portion may be provided on the front side or the rear side for each of the left and right insertion holes <NUM>.

Each wall portion <NUM> has an inner side surface <NUM> (surface facing a lower side of the insertion hole <NUM>) on the insertion hole <NUM> side, and the inner side surface <NUM> is inclined in a direction away from the insertion hole <NUM> as approaching downward.

The wall portion <NUM> further has, at a lower portion of each end portion (end portion separated from the support portion <NUM>) thereof in a width direction (Y-axis direction) of the top plate <NUM>, an inclined surface <NUM> that is inclined inward (toward the support portion <NUM>) in the width direction of the top plate <NUM> as approaching downward. The inclined surface <NUM> reaches the support portion <NUM>.

Behaviors of the upper thread U and the lower thread D extending from the horizontal shuttles <NUM> to the insertion hole <NUM> of the feed dog <NUM> in a series of hand movement and feed operation will be described with reference to the drawings. <FIG>, <FIG>, <FIG>, <FIG>, and <FIG> are perspective views of the throat plate <NUM> and the horizontal shuttle <NUM>, and <FIG>, <FIG>, <FIG>, <FIG>, and <FIG> are cross-sectional views of the feed dog <NUM> as viewed from a right side.

The sewing needle <NUM> performs reciprocating up-and-down movement of one stroke and the horizontal shuttle <NUM> performs two rotations per rotation of the upper shaft of the needle vertical movement mechanism. When an upper shaft angle when the needle bar <NUM> is located at a top dead center is <NUM>°, <FIG> illustrate a state in which the upper shaft angle is <NUM>°. The upper shaft angle of <NUM>° is a timing at which the downward sewing needle <NUM> generally starts to enter the insertion hole <NUM>,
and the feed dog <NUM> moves upward and forward to start feeding the workpiece.

At this timing, the lower thread D extends straight from a lower thread feed port <NUM> to the insertion hole <NUM>, and is not in contact with the inner side surface <NUM> of the feed dog <NUM> on the lower thread feed port <NUM> side.

The upper thread U is inserted into an eye hole of the sewing needle <NUM>, and has not yet been drawn by the horizontal shuttle <NUM>. The feed dog <NUM> is located in the vicinity of a rear end portion in a front and rear stroke range in the forward movement.

Next, <FIG> show a state in which the upper shaft angle is <NUM>°. The upper shaft angle of <NUM>° is a state in which the sewing needle <NUM> passed through a bottom dead center and starts to rise. The upper thread U starts to form a loop due to slack as the sewing needle <NUM> starts to rise below the insertion hole <NUM>. Further, the hook <NUM> of the horizontal shuttle <NUM> is in a state immediately before the hook <NUM> captures the loop of the upper thread U.

The feed dog <NUM> is located in the vicinity of a middle position in the front and rear stroke range in the forward movement. The lower thread D extends straight from the lower thread feed port <NUM> to the insertion hole <NUM>. The forward inclination of the lower thread D increases as the feed dog <NUM> moves forward, and the lower thread D approaches the inner side surface <NUM> on the lower thread feed port <NUM> side. However, since the inner side surface <NUM> is inclined forward and upward (rearward and downward), the inner side surface <NUM> maintains a non-contact state with the lower thread D.

Next, <FIG> show a state in which the upper shaft angle is <NUM>°. The upper shaft angle of <NUM>° is a state in which the sewing needle <NUM> left the insertion hole <NUM> due to the upward movement thereof and the upper thread U is captured by the hook <NUM> of the horizontal shuttle <NUM> below the insertion hole <NUM> and is largely drawn to a side opposite to the lower thread D along an outer periphery of the inner shuttle <NUM>.

The feed dog <NUM> is located at a most forward position in the front and rear stroke range, and the lower thread D approaches the inner side surface <NUM> on the lower thread feed port <NUM> side in a state in which the lower thread D extends straight from the lower thread feed port <NUM> to the insertion hole <NUM> and the forward inclination is largest. However, since the inner side surface <NUM> is inclined forward and upward (rearward and downward), the inner side surface <NUM> maintains a non-contact state with the lower thread D.

Next, <FIG> show a state in which the upper shaft angle is <NUM>°. At the upper shaft angle of <NUM>°, the sewing needle <NUM> is located substantially at the top dead center due to the upward movement, and the upper thread U is captured by the hook <NUM> of the horizontal shuttle <NUM> below the insertion hole <NUM> and is largely drawn to the lower thread D side along the outer periphery of the inner shuttle <NUM>. Immediately thereafter, the loop of the upper thread U passes through the entire inner shuttle <NUM> and is released from the horizontal shuttle <NUM>.

The feed dog <NUM> moves slightly downward from the most forward position in the front and rear stroke range, and the lower thread D approaches the inner side surface <NUM> on the lower thread feed port <NUM> side in a state in which the lower thread D extends straight from the lower thread feed port <NUM> to the insertion hole <NUM> and the forward inclination is reduced, and maintains the non-contact state.

Next, <FIG> show a state in which the upper shaft angle is <NUM>°. The upper shaft angle of <NUM>° is a state in which the thread take-up lever fully draws up the upper thread U. Below the insertion hole <NUM>, the loop of the upper thread U that was drawn to a maximum extent disappears due to the drawing of the thread take-up lever. On the other hand, the loop of the upper thread U is reduced at once from a state in which the lower thread D is inserted into the loop of the upper thread U, and thus the lower thread D is drawn up by the upper thread U to form a knot.

In a series of hand movement and feed operation illustrated in <FIG>, the upper thread U leaves the horizontal shuttle <NUM> immediately after the upper shaft angle exceeds <NUM>°, and starts to be drawn up by the thread take-up lever. At this timing, the loop of the upper thread U is maximized and is likely to go into disorder. At this time, since the pair of wall portions <NUM> are provided at the front and rear portions on a lower side of the top plate <NUM> of the feed dog <NUM>, the disorder of the loop of the upper thread U is prevented from moving forward and rearward even when the upper thread U goes into disorder.

Since the pair of wall portions <NUM> prevent the disorder of the loop of the upper thread U, it is not necessary to cut a corner portion of the top plate <NUM>, and the contact area between the workpiece and the feed dog <NUM> can be sufficiently ensured. Accordingly, excellent seams can be formed while the workpiece is fed well.

<FIG> is a perspective view illustrating the vicinity of the feed dog <NUM> by cutting out a part of the throat plate <NUM>.

As illustrated in the drawing, as described above, each of the pair of wall portions <NUM> has, at the lower portion of each end portion in the Y-axis direction (width direction of the top plate <NUM>), the inclined surface <NUM> that is inclined inward in the Y-axis direction (support portion <NUM> side) and downward.

When the pair of wall portions <NUM> are provided and the loop of the upper thread U goes into disorder in the direction of an arrow in <FIG>, the upper thread U may be caught by the lower end portion of the wall portion <NUM>, and sewing failures such as sewing unevenness and bunches (loops of the upper thread remaining due to a drawing failure of the thread take-up lever) may occur. However, when the inclined surface <NUM> is formed at the lower end portion of the wall portion <NUM>, the catching can be prevented, sewing failures can be reduced, and excellent seams can be formed.

In particular, when a lower end portion of the inclined surface <NUM> reaches the support portion <NUM>, no corner portion is formed at the lower end portion of the wall portion <NUM>, and thus the loop of the upper thread U can be more effectively prevented.

The inclined surface <NUM> further has a function of guiding the upper thread U to the insertion hole <NUM> while preventing the upper thread U from being caught when the loop of the upper thread U is drawn up by the thread take-up lever, so that the upper thread U can be drawn up smoothly. Therefore, seams can be formed in accordance with the set tension and the sewing quality can be improved.

When the sewing machine <NUM> is a post-bed sewing machine, the internal space of the post bed <NUM> is narrow, and thus it is required to reduce the size of the feed dog <NUM> in the X-axis direction (feed direction). However, when the feed dog <NUM> is reduced in size in the X-axis direction, the loop of the upper thread U is likely to be caught on the corner portion of the top plate <NUM> and the lower end portions of the pair of wall portions <NUM>. However, the pair of the wall portions <NUM> can effectively prevent the catching of the upper thread U on the corner portion of the top plate <NUM>, and the inclined surface <NUM> can effectively reduce the catching of the upper thread U on the lower end portions of the pair of wall portions <NUM>.

The case in which the sewing machine <NUM> is a post-bed sewing machine is described as an example. When the sewing machine <NUM> is a cylinder bed sewing machine, an upper surface of a cylinder bed is similarly narrow and a reduction in size in the feed direction of the feed dog is required. Accordingly, the feed dog <NUM> having the above-described configuration can also be suitably applied to the cylinder bed sewing machine.

The shuttle mechanism of the sewing machine <NUM> includes the horizontal shuttle <NUM>. In a so-called vertical shuttle, a rotary circle of the shuttle is disposed along the vertical direction, and is disposed below the needle hole and the insertion hole. Accordingly, the direction in which the loop of the upper thread U released from the hook of the shuttle is directed toward an eye and the insertion hole coincides with the drawing-up direction by the thread take-up lever, and thus the disorder of the loop of the upper thread U is less than in the horizontal shuttle.

In contrast, a rotary circle of the horizontal shuttle <NUM> is disposed along the horizontal direction, and the loop of the upper thread U is captured and released from a lateral side (Y-axis direction) relative to the insertion hole <NUM>. For this reason, the direction in which the loop of the upper thread U released from the hook of the shuttle is directed toward the insertion hole <NUM> is the Y-axis direction, which does not coincide with the drawing-up direction by the thread take-up lever that is the Z-axis direction. Accordingly, the disorder of the loop of the upper thread U is more likely to occur than in the vertical shuttle.

However, since the feed dog <NUM> includes the pair of wall portions <NUM> and each of the wall portions <NUM> has the inclined surface <NUM>, the loop of the upper thread U can be prevented from being caught and the sewing quality can be improved.

In the series of hand movement and feed operation, the lower thread D maintains a state of extending linearly from the lower thread feed port <NUM> to the insertion hole <NUM>. On the other hand, since the feed dog <NUM> having the insertion hole <NUM> performs the feeding by the front-and-rear and up-and-down revolving operation, the inclination angle of the lower thread D constantly fluctuates.

In contrast, the wall portion <NUM> of the feed dog <NUM> is inclined in a front-and-rear direction (X-axis direction) in which the inner side surface <NUM> is separated from the insertion hole <NUM> as approaching downward. As seen from the insertion hole <NUM> side, the lower thread D extends in a direction away from the insertion hole <NUM> as approaching downward, similarly to the inclination direction of the inner side surface <NUM>. Accordingly, the inner side surface <NUM> along the inclination direction can reduce the contact with the lower thread D.

In particular, by setting an inclination component of the inner side surface <NUM> in the front-and-rear direction to be equal to or larger than an inclination component of the lower thread D in the front-rear direction that may occur (increasing the inclination in the front-rear direction), the contact with the bobbin thread D can be more effectively prevented.

When the lower thread D can be prevented from coming into contact with the feed dog <NUM> in the series of hand movement and feed operation, the variation in the tension of the lower thread D during sewing is reduced. Then, seams formed by the sewing are homogenized, and the effect of improving the sewing quality is expected.

As illustrated in <FIG>, it is preferable that a length L in the X-axis direction (feed direction) from the center of the insertion hole <NUM> of the feed dog <NUM> to a lower end portion of the inner side surface <NUM> is <NUM>/<NUM> or more of a maximum pitch that can be set by the feed adjustment mechanism relative to the feed mechanism.

A length l in the X-axis direction from the center of the insertion hole <NUM> of the feed dog <NUM> to an upper end portion of the inner side surface <NUM> is preferably <NUM>/<NUM> or more of the maximum pitch. In this case, the length l to the upper end portion of the inner side surface <NUM> is preferably smaller than the length L to the lower end portion.

Even when the feed pitch of the feed dog <NUM> is set to the maximum, the lower thread D extending from the lower thread feed port <NUM> to the insertion hole <NUM> can be prevented from coming into contact with the inner side surface <NUM>.

The sewing machine <NUM> is a needle-feed sewing machine including a needle-feed mechanism that reciprocates the needle bar <NUM> in the X-axis direction in synchronization with the feed dog <NUM>, and is also a unison-feed sewing machine including the feed foot <NUM> that applies a feed operation to the workpiece on the throat plate <NUM> from above in synchronization with the feed dog <NUM>.

In the case of the needle-feed sewing machine and unison-feed sewing machine, no eye is formed in the throat plate <NUM>, an opening through which the top plate <NUM> of the feed dog <NUM> is exposed is formed, and the insertion hole <NUM> that is a needle hole is formed in the feed dog <NUM>.

In this case, the position and behavior of the lower thread D inserted into the insertion hole <NUM> vibrate back and forth below the top plate <NUM> by the reciprocating front-and-rear movement of the feed dog <NUM>, and the lower thread D is likely to come into contact with the wall portion <NUM> of the feed dog <NUM>. However, since the wall portion <NUM> has the inclined inner side surface <NUM>, the contact with the lower thread D is prevented, and the tension fluctuation of the lower thread D is effectively reduced in the needle-feed sewing machine and unison-feed sewing machine. Then, an effect of suitably improving the sewing quality by homogenization of seams is expected.

The embodiment of the present invention is described above. However, the present invention is not limited to the above-described embodiment.

For example, although a double-needle sewing machine is described as an example of the sewing machine <NUM>, the sewing machine <NUM> is not limited thereto, and may be a single-needle sewing machine. In this case, the feed dog <NUM> may be divided into two in a middle position in the Y-axis direction by a division cross section along the X-Z plane.

Although the inner side surface <NUM> inclined in the predetermined direction is formed on both of the front and rear wall portions <NUM>, the inclined inner side surface <NUM> may be provided only on the wall portion <NUM> on the lower thread feed port <NUM> side of the horizontal shuttle <NUM>.

Although the post-bed sewing machine is described as an example of the sewing machine <NUM>, the present invention can be applied to any sewing machine as long as the sewing machine feeds a workpiece by a feed dog. For example, the present invention is not limited to the cylinder bed described above, and the feed dog <NUM> including the wall portion <NUM> may be provided in a flat bed sewing machine. Also in the case of the flat bed sewing machine, the loop of the upper thread U may go into disorder. Accordingly, it is effective to provide the pair of wall portions <NUM> below the feed dog <NUM>, and the inclined surface <NUM> is also effective. The inner side surface <NUM> is also effective to prevent the contact with the lower thread D.

In the case of the flat bed sewing machine, the support portion <NUM> of the feed dog <NUM> may not have a plate-shaped structure along the X-Z plane. For example, the support portion <NUM> may be coupled to a feed dog bracket to which a front-and-rear and up-and-down reciprocating movement is input. In this case, the support portion <NUM> may have a plate shape along the X-Y plane. The feed dog <NUM> may have a configuration in which the plate-shaped support portion <NUM> along the X-Y plane is coupled with the top plate <NUM>.

The unison-feed sewing machine is described as an example of the sewing machine <NUM>, and the sewing machine <NUM> is not limited thereto. The present invention is also applicable to a sewing machine that does not have an upper feed mechanism and/or a needle-feed mechanism. In this case, the insertion hole of the feed dog is not a circular hole as the insertion hole <NUM>, but may be a rectangular opening or a slit having a larger opening, and an eye may be provided in the throat plate separately from the feed dog.

However, even in the case of such a sewing machine, the loop of the upper thread U may go into disorder, and thus it is effective to provide the pair of wall portions <NUM> below the feed dog, and the inclined surface <NUM> is also effective. Since the feed dog performs a revolving operation along the front-and-rear direction, the inner side surface <NUM> is also effective to prevent the contact with the lower thread D.

Although the shuttle mechanism of the sewing machine <NUM> includes the horizontal shuttle as an example, the shuttle mechanism is not limited thereto, and the shuttle may be a vertical shuttle. The shuttle is not limited to a full rotary shuttle, and may be a half rotary shuttle.

Claim 1:
A sewing machine (<NUM>) comprising:
a feed dog (<NUM>) partially protruding out up and down from a throat plate (<NUM>) to feed a workpiece;
a sewing needle (<NUM>) configured to perform stitch points on the workpiece by moving up and down; and
a shuttle (<NUM>) configured to capture an upper thread (U) passed through the sewing needle (<NUM>) below the throat plate (<NUM>) to be entwined with a lower thread (D),
wherein the feed dog (<NUM>) includes a top plate (<NUM>) having teeth formed on an upper surface thereof, and a support portion (<NUM>), integrally coupled to the top plate (<NUM>), to which a feed operation is input,
wherein the top plate (<NUM>) includes an insertion hole (<NUM>) that the sewing needle (<NUM>) penetrates up and down, and a pair of wall portions (<NUM>) extending in an up-and-down direction (Z) and width direction (Y) respectively on one side and another side in a feed direction (X) of the workpiece relative to the insertion hole (<NUM>) on a lower surface side of the top plate (<NUM>),
characterized in that
each of the pair of wall portions (<NUM>) has an inner side surface (<NUM>) facing a lower side of the insertion hole (<NUM>), wherein at least one inner side surface (<NUM>) is inclined in a direction away from the insertion hole (<NUM>) as approaching downward, and the inner side surfaces (<NUM>) of the pair of wall portions (<NUM>) face each other in the feed direction (X).