sewing machine

Abstract

To feed an object to be sewn favorably.SOLUTION: A sewing machine includes: a feed dog 40 appearing / disappearing vertically from a needle plate 212, and for feeding an object to be sewn; a sewing needle 11 for performing needle location on the object to be sewn by the vertical movement; and a shuttle 17 for supplementing a needle thread put through the sewing needle 11 on the lower side of the needle plate 212 and entangling a bobbin thread. The feed dog 40 includes: a top plate 41 in which teeth are formed on an upper surface; and a support part 42 where a feed operation with respect to the top plate 41 is inputted. The top plate 41 includes: an insertion hole 43 of the sewing needle 11 penetrated vertically; and a pair of wall parts 44 extending in the vertical direction in one and the other of the feed direction of the object to be sewn with respect to the insertion hole 43 on a lower surface side of the top plate 41.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sewing machine having a feed dog. [Background technology]

[0002] In conventional sewing machines with a feed dog, when the needle thread is caught by the shuttle and pulled under the needle plate, the loop of the needle thread formed by the shuttle can become loose until it is pulled up by the thread take-up lever. As a result, the loop of the needle thread can get caught on the corner of the top plate of the feed dog, which can cause poor stitching. The sewing machine of Patent Document 1 attempts to solve the above problem by rounding the corners of the top plate of the feed dog into an arc shape to reduce the likelihood of the upper thread loop getting caught. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4913575 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the sewing machine described in Patent Document 1, if the corners of the top plate of the feed dog are rounded, the contact area between the top surface of the needle plate and the workpiece is reduced, which could affect the stable feeding of the workpiece.

[0005] An object of the present invention is to form a good stitch while feeding a sewing material well. [Means for solving the problem]

[0006] The present invention relates to a sewing machine, A feed dog that moves up and down from the needle plate to feed the sewing material; A sewing needle that moves up and down to drop into the sewing material; a hook that catches the upper thread passed through the sewing needle below the needle plate and winds a bobbin thread therearound; The feed dog has a top plate having teeth formed on an upper surface thereof and a support portion to which a feed operation is inputted with respect to the top plate, The top plate has a needle insertion hole that penetrates vertically, and a needle insertion hole that is provided on the underside of the top plate on one side and the other side in the feeding direction of the sewing material relative to the needle insertion hole. , facing the direction in which the sewing material is fed, It is characterized by having a pair of walls extending in the vertical direction. [Effects of the Invention]

[0007] As described above, according to the present invention, the wall portion of the feed dog suppresses the movement of the upper thread loop, so there is no need to grind the corners of the top plate, and it is possible to feed the sewn material well while forming good stitches. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing the overall configuration of a sewing machine according to an embodiment of the present invention; [Figure 2] FIG. 2 is an enlarged perspective view showing the configuration of the needle plate and its surroundings. [Figure 3] FIG. 10 is a side view showing a simplified configuration of the upper and lower parts of the needle plate. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 6(A) is a perspective view showing the behavior of the upper thread and the lower thread passing from the horizontal shuttle to the insertion hole of the feed dog during sewing, and FIG. 6(B) is a cross-sectional side view of FIG. 6(A). [Figure 7] 7(A) is a perspective view following FIG. 6(A) showing the behavior of the upper thread and lower thread passing from the horizontal shuttle to the insertion hole of the feed dog during sewing, and FIG. 7(B) is a cross-sectional view as seen from the side. [Figure 8] 8(A) is a perspective view subsequent to FIG. 7(A) showing the behavior of the upper thread and lower thread passing from the horizontal shuttle to the insertion hole of the feed dog during sewing, and FIG. 8(B) is a cross-sectional view as seen from the side. [Figure 9]9(A) is a perspective view showing the behavior of the upper thread and the lower thread passing from the horizontal shuttle to the insertion hole of the feed dog during sewing, following FIG. 8(A), and FIG. 9(B) is a cross-sectional view as seen from the side. [Figure 10] 10(A) is a perspective view showing the behavior of the upper thread and lower thread passing from the horizontal shuttle to the insertion hole of the feed dog during sewing, following FIG. 9(A), and FIG. 10(B) is a cross-sectional view as seen from the side. [Figure 11] FIG. 2 is a perspective view showing the periphery of the feed dog with a part of the needle plate cut away. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiments of the Invention] An embodiment of the present invention will be described below with reference to the drawings. The following is an embodiment of the present invention and is not intended to limit the present invention. FIG. 1 is a perspective view of a sewing machine 100 according to this embodiment, and FIG. 2 is an enlarged perspective view showing the configuration around a needle plate 212, which will be described later. In this embodiment, the sewing machine 100 is exemplified as a twin-needle, post-bed, integrated feed sewing machine equipped with a horizontal shuttle. However, in order to carry out the invention, it is not essential that the machine has two needles, a comprehensive feed, a horizontal hook, and a post bed, and these are merely preferred examples.

[0010] The sewing machine 100 is equipped with a needle up-and-down movement mechanism that moves up and down two needle bars 12 that hold sewing needles 11 at their lower ends, a feed mechanism that feeds the workpiece from below a needle plate 212 (described later) in a predetermined feed direction (the X-axis direction) using a feed dog 40 (see FIG. 2), an upper feed mechanism that feeds the workpiece on the needle plate 212 in the feed direction (the X-axis direction) from above using a feed foot 14 (see FIG. 3), a needle feed mechanism that feeds the sewing needles 11 in the feed direction (the X-axis direction) of the workpiece, a feed adjustment mechanism that adjusts the stitch pitch, a shuttle mechanism having two horizontal shuttles 17, and a sewing machine frame 20 that holds these components. Note that each of the above mechanisms is well known in sewing machines, so their description will be brief. The sewing machine 100 also includes components common to sewing machines, such as a thread tensioner, thread take-up lever, etc., but these are well-known components and therefore will not be described here.

[0011] [Sewing machine frame] The sewing machine frame 20 has a sewing machine bed portion 21, a vertical body portion 22, and a sewing machine arm portion 23. The sewing machine bed section 21 is located below the sewing machine frame 20 and supports the entire sewing machine. The sewing machine bed section 21 extends along the Y-axis direction, which will be described later, and has a post bed 211 standing on the upper surface of one end thereof, and a needle plate 212 (see FIG. 2) where the needle drops is provided on the upper end surface of the post bed 211.

[0012] The upright body portion 22 stands upright from the other end of the sewing machine bed portion 21, and a sewing machine arm portion 23 extends from the upper end thereof in the same direction as the sewing machine bed portion 21 along the Y-axis direction. The sewing machine arm portion 23 supports the needle bar 12, the presser foot 13, and the feed foot 14 at the lower end in the extension direction.

[0013] In the following description, the longitudinal direction of the sewing machine bed 21 that is parallel to the upper surface of the sewing machine bed 21 is referred to as the Y-axis direction, the direction that is parallel to the upper surface of the sewing machine bed 21 and perpendicular to the Y-axis direction is referred to as the X-axis direction, and the direction that is perpendicular to the upper surface of the sewing machine bed 21 is referred to as the Z-axis direction. Also, as shown in Fig. 1, one side of the Y-axis direction is referred to as the "left" and the other as the "right", one side of the X-axis direction is referred to as the "front" and the other as the "rear", and one side of the Z-axis direction is referred to as the "up" and the other as the "down". The downstream side in the feed direction of the sewing material is referred to as the "front". Furthermore, the sewing machine 100 is normally configured to perform sewing with the sewing machine frame 20 set so that the X-axis direction and the Y-axis direction are horizontal and the Z-axis direction is vertical. Based on these assumptions, the directions of the components in the sewing machine 100 will be described.

[0014] [Needle vertical movement mechanism] The needle up / down movement mechanism applies reciprocating up / down movement to two adjacent needle bars 12 in the Y-axis direction via a crank mechanism connected to an upper shaft that rotates using a sewing machine motor (not shown) as a drive source. The thread take-up lever is incorporated into the needle up / down movement mechanism and rotates reciprocatingly in synchronization with the needle bars 12.

[0015] [Needle feed mechanism] The needle feed mechanism has a needle bar rocking base that supports the two needle bars 12 so that they can move up and down and is supported so that it can rock around the Y axis within the sewing machine arm portion 23, and a power mechanism that uses the sewing machine motor as a drive source to impart reciprocating rocking motion to the needle bar rocking base. When the needle bar rocking base rocks around the Y axis, the sewing needle 11 located at the lower end of the needle bar 12 moves back and forth in the X axis direction. The power mechanism receives power for reciprocating motion from the sewing machine motor via a feed mechanism, which will be described later, thereby synchronizing the feed swing of the sewing needle 11 with the feed motion of the feed dog.

[0016] The sewing needle 11 moves in a circular motion around the Y axis by combining the reciprocating motion in the X axis direction by the needle feed mechanism and the reciprocating up and down motion by the needle up and down movement mechanism described above, enabling the needle to be fed forward while making a needle drop on the workpiece on the needle plate 212.

[0017] [Upper feed mechanism] Fig. 3 is a side view showing a simplified configuration above and below the needle plate 212. As shown in Figs. 1 and 3, the upper feed mechanism has a presser foot 13 that presses down on the workpiece on the needle plate 212 from above, a feeding foot 14 that feeds the workpiece forward, a presser bar 15 that supports the presser foot 13 at its lower end, and a feeding foot bar 16 that supports the feeding foot 14 at its lower end. Furthermore, the upper feed mechanism has a triangular link to which the upper ends of the presser bar 15 and the feed foot bar 16 are connected so that they can rotate around the Y axis, a presser spring that presses the triangular link downward, and a power mechanism that imparts a reciprocating swing to the triangular link via a cam from the sewing machine motor.

[0018] The presser bar 15 is supported by the sewing machine arm portion 23 so as to be movable up and down, and a downward pressing force is applied by a presser spring via a triangular link, so that the presser foot 13 applies a pressing force from above downward to the workpiece on the needle plate 212. Meanwhile, the triangular link is given a reciprocating swing motion, which causes the presser foot 13 and the walking foot 14 to move up and down alternately, as if stepping, via the presser bar 15 and the walking foot bar 16. The walking foot bar 16 is supported by the triangular link so that it can swing about the Y axis, so when the walking foot 14 lands, it sandwiches the workpiece from above and below together with the feed dog 40, and swings in the feed direction to feed it. The bottom surface of the walking foot 14 is formed with sawtooth teeth to make it easier to hold the workpiece.

[0019] [Feed mechanism] The feed mechanism includes a feed dog 40 whose tip is visible through two openings in a needle plate 212 provided at the upper end of the post bed 211, and a power mechanism that applies a feed motion to the feed dog 40. The detailed structure of the feed dog 40 will be described later.

[0020] The power mechanism extracts reciprocating motion in the X-axis and Z-axis directions from the rotation of the sewing machine motor via a cam mechanism, combines these two reciprocating motions, and transmits them to the feed table located below the post bed 211. The feed table performs orbital motion around the Y-axis by combining and applying the two reciprocating motions in the X-axis and Z-axis directions. The feed table then transmits the orbital motion around the Y-axis to the feed dog 40 located below the needle plate 212 via a feed lever member inserted vertically inside the post bed 211. As a result, the feed dog 40 moves in the feed direction while the tooth tip appears and disappears through the two openings in the needle plate 212, and can feed the sewing material on the needle plate 212.

[0021] [Feed adjustment mechanism] The feed adjusting mechanism can adjust the reciprocating motion component in the X-axis direction (feed pitch) transmitted to the feed table by changing and adjusting the direction of motion of some link members of the multi-joint link mechanism that transmits the reciprocating motion in the X-axis direction from the cam mechanism that constitutes the power mechanism of the feed mechanism to the feed table. The feed adjusting mechanism can also switch the forward feed (forward feed) of the sewing workpiece to reverse feed (rearward feed). The feed adjusting mechanism may be configured to adjust the feed pitch by manually operating an operating means such as a dial, or may be configured to adjust the feed pitch by a motor whose movement amount is controllable. If the feed adjusting mechanism is configured to include a motor, the motor is controlled to adjust the feed pitch to the value input from the operation panel, for example.

[0022] [Shuttle mechanism] The shuttle mechanism is built in near the upper end of the post bed 211 and has two horizontal shuttles 17 arranged side by side in the Y-axis direction, and a power mechanism that transmits rotation from the sewing machine motor to each of the horizontal shuttles 17. The power mechanism has a lower shaft along the Y-axis direction that rotates via a timing belt stretched from the upper shaft inside the vertical body portion 22, two shuttle shafts that are provided along the Z-axis direction inside the post bed 211, and a gear mechanism using bevel gears that transmits rotation from the lower shaft to each shuttle shaft. The gear mechanism doubles the rotation speed of the sewing machine motor and transmits the rotation to the shuttle shafts.

[0023] The two horizontal shuttles 17 are arranged on either side in the Y-axis direction, sandwiching the feed dog 40 arranged below the needle plate 212. Each horizontal hook 17 has an outer hook 171 connected to the upper end of the hook shaft and rotating around the Z axis, and an inner hook 172 that stores a bobbin of lower thread D while remaining non-rotating inside the outer hook 171. During sewing, each sewing needle 11 enters from above into two insertion holes 43 (see FIG. 4) provided in the feed dog 40, and the point 173 (see FIG. 6(A)) of the outer hook 171 of each horizontal hook 17 captures the upper thread loop from the corresponding sewing needle 11, pulls it far below the needle plate 212, and passes it through the inner hook 172. As a result, the lower thread D pulled out from the lower thread feed opening 174 (see FIG. 6(A)) of each inner hook 172 is inserted into the loop of the upper thread U, forming a knot.

[0024] [Feed dog] FIG. 4 is a perspective view of the feed dog 40, and FIG. 5 is a side view. The feed dog 40 has a top plate 41 and a support portion 42 that is integrally connected to the top plate 41 and to which the feed operation is transmitted. The top plate 41 is a rectangular flat plate that extends along the XY plane, and the support portion 42 is a rectangular flat plate that extends along the XZ plane. The upper end portion of the support portion 42 is integrally connected to a middle portion in the Y-axis direction on the underside of the top plate 41. As a result, the feed dog 40, consisting of the top plate 41 and the support portion 42, has a generally T-shape when viewed from the X-axis direction, with the top plate 41 extending to the left and right from the upper end portion of the support portion 42 that is set up vertically. The lower end of the support portion 42 is supported by the upper end of the feed lever member of the feed mechanism described above, which is inserted vertically inside the post bed 211, and a feed operation is input thereto.

[0025] A groove is formed along the X-axis direction in the middle of the top surface of the top plate 41 in the Y-axis direction, dividing the top surface into left and right halves corresponding to the two sewing needles 11. Furthermore, teeth that are sawtooth-shaped when viewed in the Y-axis direction are formed on the front and rear ends of the top surface of the top plate 41. The tips of the teeth are slightly inclined forward relative to the vertically upward direction, and are structured to increase friction to the front side against the underside of the sewing material.

[0026] Furthermore, in the middle of the top plate 41 in the X-axis direction, on both the left and right sides of the support portion 42, substantially circular insertion holes 43 are formed penetrating vertically, through which each sewing needle 11 is inserted. Each sewing needle 11 enters this insertion hole 43, and the upper thread U is captured by the horizontal shuttle 17 below the needle plate 212 and the top plate 41. The underside of the top plate 41 is provided with a pair of wall portions 44 extending vertically on one side (front side) and the other side (rear side) of the X-axis direction (feed direction of the sewing material) relative to each insertion hole 43.

[0027] Each wall portion 44 has a plate shape along the YZ plane. In the present embodiment, the wall portions 44 are located at the front end and rear end of the top plate 41, but they may be provided closer to each insertion hole 43 in the X-axis direction. Also, although the configuration in which one wall portion 44 is provided on the front side and one wall portion 44 is provided on the rear side common to the left and right insertion holes 43 is exemplified, one wall portion may be provided on the front side or one wall portion on the rear side for each of the left and right insertion holes 43.

[0028] Each wall portion 44 has an inner surface 441 (surface facing the lower side of the insertion hole 43) on the insertion hole 43 side, and each inner surface 441 is inclined in a direction away from the insertion hole 43 as it extends downward.

[0029] Furthermore, at the lower portions of the ends (ends remote from the support portions 42) of these wall portions 44 in the width direction (Y-axis direction) of the top plate 41, inclined surfaces 442 are provided that are inclined inward in the width direction of the top plate 41 (toward the support portions 42) as they extend downward. Each of these inclined surfaces 442 reaches the support portions 42.

[0030] [Upper and lower thread behavior] The behavior of the upper thread U and lower thread D passing from the horizontal shuttle 17 to the insertion hole 43 of the feed dog 40 during a series of stitching and feeding operations will be explained with reference to the drawings. Figures 6(A), 7(A), 8(A), 9(A), and 10(A) are perspective views of the needle plate 212 and the horizontal shuttle 17, and Figures 6(B), 7(B), 8(B), 9(B), and 10(B) are cross-sectional views of the feed dog 40 as viewed from the right side.

[0031] The upper shaft of the needle up-and-down movement mechanism described above moves the sewing needle 11 up and down by one stroke per rotation, and the horizontal shuttle 17 rotates two times. If the upper shaft angle is 0° when the needle bar 12 is at the top dead center, Figures 6(A) and 6(B) show a state where the upper shaft angle is 120°. An upper shaft angle of 120° is approximately the timing when the descending sewing needle 11 begins to enter the insertion hole 43 and the feed dog 40 moves forward while rising, starting to feed the workpiece. At this timing, the lower thread D passes straight from the lower thread reel-out opening 174 to the insertion hole 43 and is not in contact with the inner surface 441 of the feed dog 40 on the lower thread reel-out opening 174 side. The upper thread U is inserted through the eye of the sewing needle 11 and has not yet been pulled out by the horizontal shuttle 17. The feed dog 40 is moving forward and is located near the rear end of its front and rear stroke range.

[0032] 7(A) and 7(B) show the state where the upper shaft angle is 203°. At an upper shaft angle of 203°, the sewing needle 11 has passed the bottom dead center and has begun to rise, and as the sewing needle 11 starts to rise, the upper thread U begins to form a loop due to slack below the insertion hole 43. Also, this is the state where the point 173 of the horizontal shuttle 17 is about to catch the loop of the upper thread U. Furthermore, the feed dog 40 is moving forward and is located near the middle position of its front and rear stroke range. The lower thread D runs straight from the lower thread reel-out opening 174 to the insertion hole 43, and as the feed dog 40 moves forward, the forward inclination increases, and the lower thread D approaches the inner surface 441 on the lower thread reel-out opening 174 side. However, since the inner surface 441 is inclined upward toward the front (downward toward the rear), the lower thread D remains out of contact.

[0033] 8(A) and 8(B) show the state where the upper shaft angle is 270°. At the upper shaft angle of 270°, the sewing needle 11 has risen and escaped from the insertion hole 43, and below the insertion hole 43, the upper thread U is caught by the point 173 of the horizontal shuttle 17 and is pulled out largely in the opposite direction from the bobbin thread D along the outer periphery of the inner shuttle 172. Furthermore, the feed dog 40 is at the most forward position within its front-to-rear stroke range, and the bobbin thread D extends straight from the bobbin thread reel-out opening 174 to the insertion hole 43, and approaches the inner surface 441 on the bobbin thread reel-out opening 174 side with the bobbin thread D inclined forward at its largest angle. However, since the inner surface 441 is inclined upward toward the front (downward toward the rear), the bobbin thread D remains out of contact.

[0034] 9(A) and 9(B) show the state where the upper shaft angle is 350°. At an upper shaft angle of 350°, the sewing needle 11 has risen to a position almost at the top dead center, and the upper thread U is caught by the point 173 of the horizontal shuttle 17 below the insertion hole 43 and pulled out largely toward the bobbin thread D along the outer periphery of the inner shuttle 172. The loop of the upper thread U then passes through the entire inner shuttle 172 and is released from the horizontal shuttle 17. In addition, the feed dog 40 moves slightly downward from its most forward position in the front-to-back stroke range, and the bobbin thread D passes straight from the bobbin thread retraction port 174 to the insertion hole 43, with the forward inclination reduced as it approaches the inner surface 441 on the bobbin thread retraction port 174 side but maintains a non-contact state.

[0035] 10(A) and 10(B) show the state when the upper shaft angle is 60°. A 60° upper shaft angle is the state in which the thread take-up is pulling up the upper thread U to its maximum. Below the insertion hole 43, the upper thread U has been pulled out to its maximum, and the loop is then pulled up by the thread take-up, eliminating it. Meanwhile, the lower thread D is inserted into the loop of the upper thread U, and the loop of the upper thread U suddenly becomes smaller, so the lower thread D is pulled up by the upper thread U and forms a knot.

[0036] [Effects based on the feed dog structure] 6(A) to 10(B), the upper thread U leaves the horizontal shuttle 17 immediately after the upper shaft angle passes 350°, and the loop of the upper thread U becomes maximum around the time when the thread take-up begins to pull up the upper thread U, making it prone to wild movement. At this time, because a pair of walls 44 are provided at the front and back below the top plate 41 of the feed dog 40, the loop of the upper thread U is prevented from wild movement forward and backward, even if wild movement occurs. Furthermore, since the pair of wall portions 44 suppress the movement of the loop of the upper thread U, there is no need to grind down the corners of the top plate 41, and a sufficient contact area between the sewn material and the feed dog 40 can be secured, making it possible to feed the sewn material well while forming good stitches.

[0037] FIG. 11 is a perspective view showing the periphery of the feed dog 40 with a part of the needle plate 212 cut away. As shown in the figure, the pair of wall portions 44 have, as described above, an inclined surface 442 at the lower part of the end portion in the Y-axis direction (width direction of the top plate 41) that slopes inward in the Y-axis direction (towards the support portion 42) as it extends downward.

[0038] If a pair of walls 44 is provided, and if the loop of the upper thread U moves wildly in the direction of the arrow in Fig. 11, the lower end of the wall 44 may get caught, which may result in poor stitching such as uneven stitching or lanterns (loops of upper thread remaining due to improper lifting of the thread take-up). However, if the lower end of the wall 44 is formed with the above-mentioned inclined surface 442, the catch is suppressed, poor stitching is reduced, and good stitches can be formed. In particular, when the lower end of the inclined surface 442 reaches the support portion 42, no corner is formed at the lower end of the wall portion 44, making it possible to more effectively prevent the loop of the upper thread U from getting caught. Furthermore, the inclined surface 442 has a function of guiding the loop of the upper thread U to the insertion hole 43 while preventing it from getting caught when the loop is pulled up by the thread take-up lever, thereby enabling the upper thread U to be pulled up smoothly. Therefore, a stitch is formed according to the set tension, and it is possible to improve the stitching quality.

[0039] Furthermore, if the sewing machine 100 is a post bed sewing machine, the internal space of the post bed 211 is small, and therefore it is necessary to reduce the size of the feed dog 40 in the X-axis direction (feed direction). However, if the feed dog 40 is reduced in size in the X-axis direction, the loop of the upper thread U is more likely to get caught on the corners of the top plate 41 or the lower ends of the pair of wall portions 44. However, the pair of wall portions 44 effectively prevent the loop from getting caught on the corners of the top plate 41, and the provision of the inclined surface 442 makes it possible to effectively reduce the loop from getting caught on the lower ends of the pair of wall portions 44. Although the above-mentioned sewing machine 100 is an example of a post bed sewing machine, in the case of a cylinder bed sewing machine, the upper surface of the cylinder bed is also narrow and miniaturization of the feed dog in the feed direction is required, so the feed dog 40 of the above-mentioned configuration can also be suitably applied to a cylinder bed sewing machine.

[0040] The shuttle mechanism of the sewing machine 100 is configured to have a horizontal shuttle 17. In a so-called vertical shuttle, the rotation circle of the shuttle is arranged along the vertical direction and is located below the needle eye or insertion hole, so the direction in which the loop of the upper thread U released from the point of the shuttle moves toward the needle eye or insertion hole coincides with the direction in which the thread take-up lever pulls the loop of the upper thread U up and down, and this results in less movement of the loop of the upper thread U than in a horizontal shuttle. In contrast, the horizontal shuttle 17 is configured such that the rotation circle of the shuttle is arranged horizontally, and the loop of the upper thread U is captured and released from the side (Y-axis direction) of the insertion hole 43. For this reason, the direction in which the loop of the upper thread U released from the tip of the shuttle moves toward the insertion hole 43 is the Y-axis direction, and the direction in which the thread take-up lever pulls it up is the Z-axis direction, which do not coincide, and the loop of the upper thread U is more likely to move wildly than in a vertical shuttle. However, since the feed dog 40 has a pair of wall portions 44, and each wall portion 44 has an inclined surface 442, it is possible to prevent the loop of the upper thread U from getting caught, thereby improving the sewing quality.

[0041] Furthermore, during the series of stitching and feeding operations described above, the lower thread D maintains a state in which it passes in a straight line from the lower thread payout opening 174 to the insertion hole 43. On the other hand, the feed dog 40 having the insertion hole 43 feeds by moving back and forth and up and down in a circular motion, so the inclination angle of the lower thread D constantly fluctuates. In contrast, each wall portion 44 of the feed dog 40 is inclined in the front-rear direction (X-axis direction) such that its inner surface 441 moves downward and away from the insertion hole 43. When viewed from the insertion hole 43 side, the lower thread D extends in a direction moving away from the insertion hole 43 as it moves downward, similar to the inclination direction of the inner surface 441. Therefore, the inner surface 441 along the inclination direction can reduce contact with the lower thread D. In particular, by setting the inclination component of the inner surface 441 in the front-to-back direction to be equal to or greater than the inclination component of the lower thread D that may occur in the lower thread D (increasing the inclination in the front-to-back direction), contact with the lower thread D can be more effectively suppressed. If the lower thread D can be prevented from coming into contact with the feed dog 40 during a series of stitching and feeding operations, fluctuations in the tension of the lower thread D during sewing can be reduced. This is expected to result in more uniform stitches formed by sewing, thereby improving the sewing quality.

[0042] As shown in FIG. 5, it is preferable that the length L in the X-axis direction (feed direction) from the center of the insertion hole 43 of the feed dog 40 to the lower end of each inner surface 441 is at least half the maximum pitch that can be set by the feed adjustment mechanism for the feed mechanism. Furthermore, it is preferable that the length l in the X-axis direction from the center of the insertion hole 43 of the feed dog 40 to the upper end of each inner surface 441 be equal to or greater than ¼ of the maximum pitch. In this case, it is preferable that the length l to the upper end of the inner surface 441 be shorter than the length L to the lower end. Even when the feed pitch of the feed dog 40 is set to the maximum, it is possible to prevent the lower thread D extending from the lower thread reel-out port 174 to the insertion hole 43 from coming into contact with each inner surface 441.

[0043] The sewing machine 100 is a needle feed sewing machine equipped with a needle feed mechanism that moves the needle bar 12 back and forth in the X-axis direction in synchronization with the feed dog 40, and is also an integrated feed sewing machine equipped with a feed foot 14 that applies a feed motion from above to the sewing material on the needle plate 212 in synchronization with the feed dog 40. In the case of these needle feed sewing machines and integrated feed sewing machines, no needle hole is formed in the needle plate 212, but an opening is formed to expose the top plate 41 of the feed dog 40, and an insertion hole 43 is formed in the feed dog 40 as a needle hole. In this case, the bobbin thread D inserted through the insertion hole 43 is likely to come into contact with the wall portion 44 of the feed dog 40 due to the reciprocating movement of the feed dog 40, which causes its position and behavior to fluctuate back and forth below the top plate 41. However, since the wall portion 44 has the inclined inner surface 441 described above, contact of the bobbin thread D is suppressed, and fluctuations in the tension of the bobbin thread D are effectively reduced in needle feed sewing machines and integrated feed sewing machines. This is expected to have the effect of suitably realizing improved seam quality by making the stitches more uniform.

[0044] [others] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, although the sewing machine 100 is illustrated as a twin-needle sewing machine, the present invention is not limited to this and may be a single-needle sewing machine. In this case, the feed dog 40 may be configured to be divided into two at a midpoint in the Y-axis direction by a cut surface along the XZ plane.

[0045] In addition, both the front and rear wall portions 44 have inner surfaces 441 that are inclined in a predetermined direction, but this inclined inner surface 441 may be provided only on the wall portion 44 that faces the bobbin thread reel-out port 174 of the horizontal shuttle 17.

[0046] Furthermore, although the sewing machine 100 is exemplified as a post-bed sewing machine, the present invention is applicable to any sewing machine that uses a feed dog to feed the sewing material. For example, the present invention is not limited to the cylinder bed sewing machine described above, and the feed dog 40 having the wall portion 44 described above may be provided in a flat-bed sewing machine. In the case of a flat-bed sewing machine, since the loop of the upper thread U may become unruly, it is effective to provide a pair of wall portions 44 below the feed dog 40, and an inclined surface 442 is also effective. Furthermore, the configuration of the inner surface 441 is also effective in suppressing contact with the bobbin thread D.

[0047] In the case of a flatbed sewing machine, the support portion 42 of the feed dog 40 may not have a plate-like structure along the XZ plane. For example, the support portion 42 may have a structure that can be connected to a feed base to which back-and-forth and up-and-down reciprocating motions are input. In that case, the support portion 42 may be plate-like along the XY plane. Furthermore, the feed dog 40 may have a structure in which such a plate-like support portion 42 along the XY plane is connected to the top plate 41 described above.

[0048] Furthermore, although the sewing machine 100 is an integrated feed sewing machine, the present invention is not limited to this and can be applied to a sewing machine that does not have an upper feed mechanism and / or a needle feed mechanism. In this case, the feed dog insertion hole is not a circular hole like insertion hole 43, but is a larger rectangular opening or slit, and a needle hole can be provided in the throat plate separately from the feed dog. However, even in such a sewing machine, the loop of the upper thread U may become unruly, so it is effective to provide a pair of walls 44 below the feed dog, and the inclined surface 442 is also effective. In addition, since the feed dog moves in a circular motion in the front-to-rear direction, the configuration of the inner surface 441 is also effective in suppressing contact with the lower thread D.

[0049] Furthermore, although the embodiment has been described in which the shuttle mechanism of the sewing machine 100 has a horizontal shuttle, the present invention is not limited to this, and the shuttle may be a vertical shuttle. Furthermore, the shuttle is not limited to a full-rotary shuttle, and may be a half-rotary shuttle. Even in these cases, the loop of the upper thread U may become unruly, so it is effective to provide a pair of walls 44 below the feed dog 40, and the inclined surface 442 is also effective. Furthermore, since the feed dog 40 moves in an orbit along the front-to-rear direction, the configuration of the inner surface 441 is also effective in suppressing contact with the lower thread D. [Explanation of symbols]

[0050] 11 Sewing Needle 12 Needle bar 13 Presser foot 14 Oriashi 17 Horizontal pot 171 Outer pot 172 Inner pot 173 Tip of the Sword 174 Line reel 20 Sewing machine frame 211 Post Bed 212 needle plate 40 feed dog 41 Top plate 42 Support part 43 Insertion hole 44 Wall 441 Inner surface 442 Slope 100 sewing machines D Lower thread U Upper thread

Claims

1. A feed dog that moves up and down from the needle plate to feed the sewing material; A sewing needle that moves up and down to drop into the sewing material; a hook that catches the upper thread passed through the sewing needle below the needle plate and winds a bobbin thread therearound; The feed dog has a top plate having teeth formed on an upper surface thereof and a support portion to which a feed operation is inputted with respect to the top plate, The sewing machine is characterized in that the top plate has an insertion hole for the sewing needle that penetrates from top to bottom, and a pair of wall portions that extend in the vertical direction on the underside of the top plate, on one side of the insertion hole in the feed direction of the sewn material and on the other side, facing the feed direction of the sewn material.

2. 2. The sewing machine according to claim 1, wherein the surface of at least the wall portion on the bobbin thread outlet side of the hook facing the insertion hole is inclined downward in a direction away from the insertion hole.

3. The sewing machine according to claim 1 or 2, characterized in that each of the pair of wall portions has an inclined surface at the lower part of the widthwise end of the top plate that slopes inward in the widthwise direction as it extends downward.

4. 4. The sewing machine according to claim 1, further comprising a needle feed mechanism that moves a needle bar holding the sewing needle back and forth in the feed direction of the workpiece in synchronization with the feed dog.

5. 5. The sewing machine according to claim 1, further comprising a feed foot that applies a feed motion from above to the workpiece on the needle plate in synchronization with the feed dog.

6. 6. The sewing machine according to claim 1, wherein the shuttle is a horizontal shuttle.

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