sewing machine

Abstract

To prolong the time taken by a retainer to hold a looper thread without setting a reciprocation stroke of the retainer larger.SOLUTION: A sewing machine has a needle that holds a needle thread and vertically moves by penetrating a needle plate, a looper that holds a looper thread and entangles the looper thread with the needle thread by reciprocating in a space below the needle plate, a retainer 5 that reciprocates in the space below the needle plate and captures the looper thread, and a retainer motion mechanism 6 that transmits a driving force from a driving source to the retainer 5 and changes the motion state of the retainer 5. The retainer motion mechanism 6 causes the retainer 5 to continue a state of capturing the looper thread by making the retainer reciprocate so as to move at lower speed for a certain time than before and after the certain time at a position in a certain range in the space below the needle plate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sewing machine that can form a circular stitch with a looper thread that is spread out without using a retainer needle that penetrates the fabric. [Background technology]

[0002] Sewing machines capable of forming a circular stitch with a spread looper thread have existed for some time. For example, there is the sewing machine described in Patent Document 1. The sewing machine described in Patent Document 1 is configured to form a circular stitch with a spread looper thread in the double loop portion by providing a retainer that moves below the needle plate without penetrating the needle plate, and the retainer holds the looper thread, without using a retainer needle that penetrates the fabric and creates holes. According to the illustrations in Patent Document 1, the stitch shown in Figure 3 corresponds to the stitch shown in Figure 4 (viewed from the back side of the fabric) (however, a hole caused by the retainer needle penetrating the fabric is not created as in Figure 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-314681 Summary of the Invention [Problem to be solved by the invention]

[0004] In the sewing machine described in Patent Document 1, a retainer is configured to reciprocate within a predetermined range along an arc-shaped path upon receiving a driving force from a main shaft provided inside (see FIG. 2 of Patent Document 1). Because this reciprocating motion is a simple reciprocating motion, when the reciprocating motion turns around, the movement speed of the retainer momentarily becomes zero as the movement direction is changed. However, the movement speed of the retainer during forward and backward movements changes in relation to time to follow a sine curve of a certain shape. For this reason, for example, in order to form a circular stitch with a desired spread of the looper thread, it is necessary to lengthen the time for the retainer to continuously hold the looper thread (the time from capturing the looper thread to releasing it). To achieve this, in order for the retainer to hold the looper thread while moving at a speed that follows the sine curve, it is necessary to set the reciprocating stroke of the retainer (the range of reciprocating motion) to be large in accordance with the extension of the holding time. This is because the retainer captures the looper thread, moves to the turning point, reverses its movement direction, and then releases the looper thread. However, in a small sewing machine, for example, there is a limit to how large the internal volume of the cylinder can be made, so even if the retainer is made to hold the looper thread for a period of time sufficient to produce the desired stitch, it may not be possible to accommodate the reciprocating range of the retainer within the cylinder due to space constraints, making it impossible to increase the reciprocating stroke.

[0005] Therefore, an object of the present invention is to provide a sewing machine that can lengthen the time that the retainer holds the looper thread without setting a large reciprocating stroke of the retainer, thereby achieving stitches with the looper thread having a desired spread. [Means for solving the problem]

[0006] The present invention is a sewing machine comprising: a needle that holds a needle thread and moves up and down through a needle plate; a looper that holds a looper thread and moves back and forth in the space below the needle plate to entangle the looper thread with the needle thread; a retainer that moves back and forth in the space below the needle plate to capture the looper thread; and a retainer movement mechanism that changes the movement state of the retainer while transmitting driving force from a drive source to the retainer, wherein the retainer movement mechanism performs the reciprocating movement so that the retainer moves at a position within a certain range within the space below the needle plate for a certain period of time at a slower speed than before and after that range, thereby causing the retainer to maintain a state in which it captures the looper thread.

[0007] According to this configuration, the retainer movement mechanism causes the retainer to reciprocate within a certain range of positions in the space below the needle plate for a certain period of time at a slower speed than before and after, thereby maintaining the state in which the retainer captures the looper thread. Therefore, compared to a configuration in which the retainer is not moved at a slower speed, the looper thread can be held for a longer period of time during slow-speed movement due to the reduced speed, so there is no need to increase the range of reciprocating movement of the retainer. Note that the "movement at a slower speed" also includes a case in which the speed is zero (a stopped state). Furthermore, to separate the case in which the speed is zero, the phrase "the retainer movement mechanism causes the retainer to reciprocate within a certain range of positions in the space below the needle plate for a certain period of time at a slower speed than before and after, or causes the retainer to wait at a speed of zero."

[0008] The certain range for the low-speed movement of the retainer by the retainer movement mechanism can be a range between a turning position where the direction of movement of the retainer is reversed and a position near the turning position that is away from the turning position in the direction in which the retainer retreats.

[0009] The retainer movement mechanism may move the retainer backward from the folded-back position within the certain range, then move the retainer forward to the folded-back position again, and then move the retainer backward again.

[0010] With these configurations, the retainer repeatedly moves forward and backward at a low speed near the turning position. This allows the configuration of the retainer movement mechanism to be simplified compared to a mechanism that comes to a complete stop after a certain period of time. Note that the "completion of the stop after a certain period of time" does not include a momentary stop due to the turning position.

[0011] The retainer motion mechanism comprises a link mechanism in which two link units are combined, and the link mechanism is configured so that, when a reciprocating motion is input, the relationship between the lines connecting the input side connection points and the output side connection points of both link units repeatedly changes within a range of part or all between a straight state in which they are lined up in a straight line and a bent state in which they are bent, and at least while the bent state of the link mechanism is eliminated, the change is reversed, and the link mechanism begins to bend again, the retainer can continue to capture the looper thread.

[0012] With this configuration, the retainer can be reciprocated over a small distance when the link mechanism is in a straight line or before and after the turning point in the change, so the retainer can be moved at a slower speed than before and after that. This allows the link mechanism to achieve low-speed movement.

[0013] The retainer movement mechanism includes a link mechanism in which two link units are combined, and the link mechanism is configured so that, when a reciprocating motion is input, it repeats a proximal bent state in which the link units are bent in one direction, a straight state in which the link units are arranged in a straight line, and a distal bent state in which the link units are bent in the other direction, in relation to the straight lines connecting the input side connection points and the output side connection points of both link units.The proximal bent state has a bent point between both link units closer to it than the distal bent state, and the retainer can continue to capture the looper thread at least until the link mechanism moves from the straight state, through the proximal bent state, and then returns to the straight state.

[0014] With this configuration, the retainer can be reciprocated over a small distance from the straight state through the proximal bent state until the link mechanism returns to the straight state, allowing the retainer to move at a slower speed than before and after that. This allows for slow movement with the link mechanism.

[0015] The retainer movement mechanism comprises an input side rotating member provided on the input side and rotating within a certain range, an output side rotating member provided on the output side and rotating within a certain range, and a displacement transmission mechanism that transmits displacement from the input side rotating member to the output side rotating member, and the displacement transmission mechanism can be configured to temporarily reduce the amount of displacement transmitted from the input side rotating member to the output side rotating member depending on the angle between the tangential component of the rotational displacement of the input side rotating member and the tangential component of the rotational displacement of the output side rotating member.

[0016] According to this configuration, the retainer can be moved at a low speed due to the relationship between the angle formed by the tangential component of the rotational displacement of the input side rotation member and the tangential component of the rotational displacement of the output side rotation member.

[0017] The input side rotation member has a first input arm and a first output arm extending in different radial directions from a first rotation center, and outputs the driving force input from the first input arm from the first output arm as a rotation force about the first rotation center, and the output side rotation member has a second input arm and a second output arm extending in different radial directions from a second rotation center, and outputs the driving force input from the second input arm from the second output arm as a rotation force about the second rotation center, The displacement transmission mechanism may include a groove portion provided on the first output arm portion or the second input arm portion, extending parallel to a radial direction passing through the first rotation center or the second rotation center, and a slide member provided on the second input arm portion or the first output arm portion, which moves along the groove portion.

[0018] According to this configuration, the combination of the groove and the slide member allows the retainer to move at a low speed. [Effects of the Invention]

[0019] In the present invention, the looper thread can be held for a long period of time during low-speed movement compared to a configuration in which the retainer does not move at variable speeds, so there is no need to increase the range of reciprocating movement of the retainer. Therefore, the time that the retainer holds the looper thread can be extended without setting a large reciprocating stroke of the retainer, and as a result, a stitch with the looper thread having the desired spread can be achieved. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a sewing machine incorporating a mechanism according to an embodiment of the present invention; [Figure 2] 1 is a perspective view showing an area including a retainer movement mechanism (link mechanism) according to a first embodiment, in which the retainer is in its most advanced (advanced) position. FIG. [Figure 3] 1 is a perspective view showing an area including a link mechanism according to a first embodiment, with a retainer in its most retracted (evacuated) position. FIG. [Figure 4] 4A and 4B are perspective views of the main part showing the positional relationship between the periphery of the retainer and the looper of the link mechanism according to the first embodiment, where FIG. 4A corresponds to the state in FIG. 3 and FIG. 4B corresponds to the state in FIG. 2. [Figure 5] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, and a looper thread (retainer not shown) in the order of operation in the first embodiment. [Figure 6] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, a needle thread, and a looper thread (a retainer is not shown) in the order of operation in the first embodiment. [Figure 7] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, a retainer, a needle thread, and a looper thread in the order of operation in the first embodiment. [Figure 8] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, a retainer, a needle thread, and a looper thread in the order of operation in the first embodiment. [Figure 9] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, a retainer, and a looper thread (needle thread not shown) in the order of operation in the first embodiment. [Figure 10] FIG. 2 is a perspective view showing the positional relationship of a needle, a looper, a retainer, and a looper thread (needle thread not shown) in the order of operation in the first embodiment. [Figure 11] 4 is a graph showing changes in the advanced state of the retainer in the first embodiment. [Figure 12] 10 is another graph showing changes in the advanced state of the retainer in the first embodiment. [Figure 13] FIG. 10 is a perspective view showing an area including a retainer movement mechanism (link mechanism) according to a second embodiment, in which the retainer is in a normal speed state (when the needle is at the top dead center position). [Figure 14] FIG. 10 is a perspective view showing an area including a link mechanism according to a second embodiment, in which the retainer is in a low speed state (when the needle is at the bottom dead center position). [Figure 15] 10 is a graph showing changes in the advanced state of the retainer in the second embodiment. [Figure 16] FIG. 11 is a perspective view showing an area including a retainer movement mechanism according to a third embodiment. [Figure 17] 17 is a perspective view showing a retainer movement mechanism according to a third embodiment, seen from the opposite side to that of FIG. 16. FIG. [Figure 18] FIG. 11 is an exploded perspective view showing a retainer movement mechanism according to a third embodiment. [Figure 19] 10A and 10B are explanatory views showing the operation of the retainer movement mechanism according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, the present invention will be described with reference to an embodiment. The sewing machine 1 of this embodiment is capable of creating a stitch in which the looper thread Lb is spread out into a loop, and is primarily used to create double chainstitches, but can also be used to create other stitches using looper threads, such as interlock stitches. The "double chainstitch" mentioned above includes both single-needle double chainstitches and multi-needle double chainstitches. In the following description, the up-down direction refers to the direction in this embodiment.

[0022] [First embodiment] As shown in FIG. 1, a sewing machine 1 incorporating a mechanism according to this embodiment (first embodiment) has a cylindrical cylinder 2 that supports the fabric during sewing. Note that a sewing machine 1 incorporating a mechanism according to a second embodiment, described later, has the same external appearance. The fabric is fed along the longitudinal direction of the cylinder 2. In this embodiment, the fabric is fed and sewn from right to left in FIG. 1. A sewing section where a needle 3 moves up and down to perform sewing is provided at the tip of the cylinder 2 (the reference numeral "3" in FIG. 1 does not represent the needle 3 itself, but is used to indicate its approximate position). The worker (operator) performing the sewing work is positioned to the right of the sewing machine 1 in FIG. 1 (in the direction of the arrow OP shown in the figure). It should be noted that the sewing machine 1 of this embodiment is specialized for sewing fabric into a cylindrical shape. Therefore, compared to a sewing machine in which the fabric is fed perpendicular to the longitudinal direction of the cylinder, the cylinder 2 needs to be formed narrower, and the internal space of the cylinder 2 is also smaller, which places spatial limitations on the arrangement of internal components. The symbol "OP" is attached to the figures necessary for explanation, but even in figures without this symbol, the positional relationship is the same as in the figures with this symbol.

[0023] In the sewing machine 1 of this embodiment (as well as the second embodiment described later), the main parts involved in forming stitches are the needle 3, looper 4, and retainer 5 shown in FIG. 4. The configurations of the needle 3 and looper 4 are the same as those known in the art. The needle 3 holds the needle thread La (see FIG. 6, etc.) and moves up and down while passing through the needle plate 21. In this embodiment, multiple needles 3 are provided (specifically, four needles 3). Note that, while a retainer needle has conventionally been provided in parallel with the sewing needle, in this embodiment, there is no retainer needle, and only the sewing needle 3 is provided as the needle that passes through the fabric.

[0024] The looper 4 has a shape shown in, for example, FIGS. 5 to 10. It holds a looper thread Lb (see FIG. 5, etc.) and reciprocates within the space below the needle plate 21 of the cylinder 2, entangling the looper thread Lb with the needle thread La as shown in FIGS. 6 to 8. The looper 4 has a curved shape that is slightly convex upward as shown, and as shown in FIG. 5, the looper thread Lb is movably threaded through the interior of the looper 4 from its base end to its tip end. The looper 4 of this embodiment reciprocates in a direction perpendicular to the direction in which the fabric is fed relative to the cylinder 2 (the width direction of the cylinder 2). Therefore, in this embodiment, the looper 4 can swing the looper thread Lb left and right relative to the fabric feed direction, so that a seam can be formed even without the retainer 5. Therefore, the retainer 5 described below is not an essential component for forming a seam. The retainer 5 of this embodiment is configured to hold the looper thread Lb pulled out by the looper 4 when forming a double chainstitch or the like, thereby achieving a stitch in which the looper thread Lb has the desired spread.

[0025] The retainer 5 reciprocates within the space below the needle plate 21 in the cylinder 2, capturing the looper thread Lb held by the looper 4. The retainer 5 in the mechanism according to this embodiment is connected to a link mechanism 6 serving as a retainer movement mechanism shown in FIGS. 2 and 3, and reciprocates as the driving force of a main shaft (not shown) is converted and transmitted. Unlike conventional retainer needles, the retainer 5 does not penetrate the fabric during the reciprocating motion. The retainer 5 is formed by bending a plate-like body as shown in FIG. 7. The flat base 51 is attached to a retainer support 8 that swings via the link mechanism 6. In this embodiment, the retainer 5 is attached so that the fixing hole 511 coincides with the mounting portion 82 of the retainer support 8. The center of rotation of the retainer 5 coincides with the rotation support portion 81 of the retainer support 8 (the rotation center related to the swinging motion). A connecting portion 52 is formed at the upper end of the base portion 51 by being bent in the plate thickness direction, and a tip portion 53 is formed at the tip of the connecting portion 52, protruding perpendicular to the direction in which the connecting portion 52 extends. The base portion 51, connecting portion 52, and tip portion 53 are integral. The retainer 5 captures the looper thread Lb by hooking the looper thread Lb at this tip portion 53 (more specifically, the portion of the tip portion 53 closer to the connecting portion 52). The tip portion 53 of the retainer 5 reciprocates in a direction perpendicular to the reciprocating direction of the looper 4 (a direction along the longitudinal direction of the cylinder 2). Therefore, the moving direction of the tip portion 53 of the retainer 5 that hooks the looper thread Lb is perpendicular to the moving direction of the looper 4 (see the moving direction indicated by the arrow in Figure 7).

[0026] The link mechanism 6 changes the motion state of the retainer 5 while transmitting the driving force from the driving source (motor, not shown) of the sewing machine 1 to the retainer 5. The link mechanism 6 of this embodiment connects a transmission rod 7 that receives driving force from the main shaft and moves reciprocally in the axial direction (up and down), to a retainer support body 8 that supports the retainer 5. The main shaft rotates, and its rotation is converted into reciprocating motion by a conversion mechanism, such as an eccentric mechanism, interposed between the main shaft and the transmission rod 7. The link mechanism 6 is made up of a first member 61 to a sixth member 66 that are rotatably connected to each other from the base end side to the tip end side of the cylinder 2.

[0027] The first member 61 and the third member 63 are each formed into a different V-shape, with each tip of the V-shape rotating around a pivot point at the folded-back portion of the V-shape. The first member 61 is connected to the end of the transmission rod 7. The second member 62 and the fourth member 64 to the sixth member 66 are each formed into an I-shape (straight rod shape), with both ends in the longitudinal direction connected to the other members so as to be able to rotate. The fifth member 65 is a member that extends between the base end and tip end of the cylinder 2 and is longer than the other members.

[0028] What is important in this embodiment is the relationship between the driving force transmission between the vertically moving transmission rod 7 and the first member 61 to the third member 63 when the retainer 5 captures the looper thread Lb. The first member 61 (the output arm 611, which is the portion of the V-shape opposite the transmission rod 7) and the second member 62 as a link unit are aligned on the same straight line as in the connection direction X shown in FIG. 2, based on the relationship between the lines connecting the input-side connecting points and the output-side connecting points of both members 61 (611), 62. This corresponds to the state in which the retainer 5 is most advanced (advanced). The bending state and its changes between the output arm 611 of the first member 61 and the second member 62 can be set in various ways without particular limitations. However, according to the bending state first described in this embodiment, the straight state appears twice in one cycle of the reciprocating motion of the transmission rod 7, which is the input side. In the first straight state, the transmission rod 7 is continuing to descend at that moment. When the transmission rod 7 further descends and reaches the bottom end, the output arm 611 of the first member 61 and the second member 62 assume a "<" shape (or a right-leaning "V" shape), which is a proximal bent state, from the state shown in FIG. 2. Note that the bend of the "<" shape in the proximal bent state is slight (a few degrees) and is difficult to distinguish from a straight state visually, so it is not shown. When the transmission rod 7 begins to ascend, the angle of the "<" shape increases, and after a second straight state, the output arm 611 of the first member 61 and the second member 62 change into an inverted "<" shape (or a left-leaning "V" shape), and assume a state bent in the connection direction Y, which is a distal bent state shown in FIG. 3. At this point, the transmission rod 7 has reached the top end. When the transmission rod 7 begins to descend, the angle of the inverted "<" shape increases, and the transmission rod 7 returns to the straight state shown in FIG. 2. This operation is repeated as the transmission rod 7 reciprocates up and down. In this case, the states where the bending change turns around are the proximal bending state and the distal bending state. Note that, compared to the straight state, the bending point between the first member 61 (output arm 611) and the second member 62 is set closer in the proximal bending state than in the distal bending state.

[0029] The link mechanism 6 configured to operate in this manner allows the retainer 5 to move at a slower speed within a certain range of positions in the space below the needle plate 21 for a certain period of time relative to the speeds before and after the reciprocating movement of the retainer 5, thereby creating a slight movement state and maintaining a state in which the looper thread Lb is captured. The certain period of time related to the slow-speed movement is included in the time from when the retainer 5 captures the looper thread Lb (the moment shown in FIG. 7) to when the looper 4 starts to reverse the direction of movement related to the reciprocating movement (immediately after the moment shown in FIG. 10). The certain range related to the slow-speed movement is the range between a turn-back position where the direction of movement of the retainer 5 reverses to the retreating (retracted) direction with the tip end 53 in the most advanced (advanced) state, and a position near the turn-back position that is away from the turn-back position in the direction in which the retainer 5 retracts. Here, "nearby" refers to a range of less than 3% of the total stroke amount related to the reciprocating movement of the retainer 5 (corresponding to the distance from the most advanced position to the most retracted position), as will be described in detail later.

[0030] Before and after the first member 61 (output arm 611) and the second member 62 of the link mechanism 6 are in a straight line, they share a tangent to the rotational locus of each member 61 (611), 62 (a tangent perpendicular to the axial direction of each member 61 (611), 62). While this relationship is established, nearly 100% of the driving force transmitted from the first member 61 (the driving side) to the second member 62 (the driven side) is a force with a directional component along the tangent direction. In other words, the force with a directional component perpendicular to the tangent direction is nearly 0%. Meanwhile, the V-shaped third member 63 is configured so that the branch receiving the driving force from the second member 62 is perpendicular to the axial direction of the second member 62 (see FIG. 2). Therefore, the third member 63 hardly rotates due to the driving force of the second member 62 in the aforementioned directional component. Therefore, the retainer 5, which is connected to the link mechanism 6 (downstream of the third member 63 in the force transmission direction), can be moved at a low speed (to a state where it hardly moves). As described above, in this embodiment, the directional component of the force accompanying the rotation of the members that make up the link mechanism 6 reduces the amount of driving force transmitted to other members, thereby allowing the retainer 5 to move at a low speed.

[0031] Furthermore, when focusing on the proximal bent state, the retainer 5 can be reciprocated over a smaller distance during the period when the link mechanism 6 changes from the straight state to the proximal bent state and then back to the straight state compared to the period when the link mechanism 6 changes from the straight state to the distal bent state and then back to the straight state, and therefore the retainer 5 can be moved at a slower speed than before and after that.

[0032] The retainer 5, to which the driving force is transmitted by the link mechanism 6, is in the fine-motion state during the time period including the turning back operation on the side holding the looper thread Lb during the reciprocating movement. Here, the fine-motion state refers to a state in which the retainer 5 does not turn back instantly as in the conventional technique (Patent Document 1), but moves back and forth within a certain range while moving at a low speed for a certain period of time (as if the retainer 5 were "tapping" within a limited range). The "certain range" is a very small range compared to the entire range in the direction of the reciprocating movement. In this embodiment, the "very small range" is defined as follows: when the rotation angle of the main shaft of the sewing machine 1 is 47° or more, the amount of reciprocating movement of the retainer 5 within that rotation angle is less than 3% of the total stroke amount of the movement (corresponding to the distance from the most advanced position to the most retracted position).

[0033] For this reason, in this embodiment, the change in the movement position of the retainer 5 does not follow a constant sine curve. Instead, the speed of the retainer 5 drops dramatically on one side of the two turns, resulting in the aforementioned slight movement state. In particular, in FIG. 11 , there are two “peaks” corresponding to the turns with a small “valley” between them, resulting in the aforementioned “treading” state. Note that “0°” on the horizontal axis in FIG. 11 corresponds to the highest position of the needle 3 (the top dead center of the needle bar, not shown, that supports the needle 3). And “180°” corresponds to the lowest position of the needle 3 (the bottom dead center of the needle bar). Note that by changing the configuration of the link mechanism 6, the movement position of the retainer 5 can be changed as shown in FIG. 12. In this case, even in the same “treading” state, as shown in the figure, there is only one “peak” corresponding to the turns, and the movement position of the retainer 5 changes so that, for example, the sine curve becomes partially gentler or a “flat” portion appears within the sine curve.

[0034] The link mechanism 6 is provided with a bending movable portion (in this embodiment, a combination of a first member 61 and a second member 62, which are link units), which, in response to the reciprocating motion of the transmission rod 7, changes between a most bent state on one side (a proximal bent state (not shown) / a dogleg bent in the opposite direction from the state in FIG. 2 to that in FIG. 3) and a most bent state on the other side (a distal bent state / an inverted dogleg shape shown in FIG. 3). In this embodiment, the time (moment) at which the up-and-down reciprocating motion of the transmission rod 7 is changed from downward to upward does not coincide with the time at which the extension directions of the output arm 611 of the first member 61 and the second member 62 of the bending movable portion provided in the link mechanism 6 become linear (a linear state). In this embodiment, the tip end 53 of the retainer 5 is set to protrude most when the bending movable portion is in a linear state (the state in FIG. 2), and the tip end 53 is set to retract when the bending movable portion is in a bent state (both the dogleg shape and the inverted dogleg shape). Figure 3 shows the most retracted state. Therefore, even after the directions in which the output arm 611 of the first member 61 and the second member 62 extend become aligned, they continue to bend due to being pushed by the transmission rod 7. The output arm 611 of the first member 61 and the second member 62 become aligned twice, once before and once after they become bent (specifically, V-shaped). The time between these two alignments is the time it takes for the retainer 5 to enter the fine-motion state. Due to this relationship between the first member 61 (output arm 611) and the second member 62, the link mechanism 6 moves the retainer 5 (particularly the tip end 53 that captures the looper thread Lb) backward once from the turn-back position, then forward again to the turn-back position, and then further backward within the certain range, as shown by two peaks on the graph in FIG. 11 (horizontal axis 0° to 90°).

[0035] Here, a case will be described in which the bending states and changes thereof of the output arm 611 of the first member 61 and the second member 62 are set differently. The bending states described above are set so that the output arm 611 of the first member 61 and the second member 62 can change to three states: a straight state, a proximal bending state (a "L" shape), and a distal bending state (an inverted "L" shape). In contrast to this, as another setting, for example, they can be set so that they can change to two states: a straight state and a bending state. In this case, the states at which the bending change turns back are the straight state and the bending state. The "bent state" is the distal bending state in the first embodiment (the state shown in FIG. 3). Even with this configuration, low-speed movement of the retainer 5 can be achieved.

[0036] As another alternative, the link mechanism 6 can be configured to change between two states: a bent state and a quasi-linear state (referred to as a "quasi-linear state") that is bent in the same direction as the bent state but more gently than the bent state, rather than the straight state. In this case, the states where the change in bending is reversed are the quasi-linear state and the bent state. Even with this configuration, the low-speed movement of the retainer 5 can be achieved in the same way. Therefore, the link mechanism 6 can be configured in various ways so that it repeatedly changes over part or all of the range between the straight state and the bent state.

[0037] Next, Figures 5 to 10 show the needles 3 (four needles), looper 4, retainer 5, needle thread La, and looper thread Lb, and explain the positional relationship of each part in the order of operation. Note that in some figures, the retainer 5 and needle thread La are omitted for the purpose of simplifying the explanation and avoiding complication of the illustrations. Also, arrows attached to each part indicate the direction of movement. Also, arrows with horizontal bars indicate that the part is at the return position. Each figure is viewed from the perspective of looking from the tip end of the cylinder 2 toward the base end, that is, from the opposite side of the operator toward the operator (the side of arrow OP shown in Figure 5, etc.). Directions are also expressed based on that perspective.

[0038] FIG. 5 shows the state in which the looper 4 is moving to the right in the figure. At this time, the needle 3 is lowered (needle thread La is not shown). FIG. 6 shows the state after the movement direction of the looper 4 has reversed from the right in the figure to the left in the figure. At this time, the needle 3 is raised after reaching the bottom dead center (lowest position). The needle thread La is then picked up by the looper 4, which has entered below the needle 3. At this time, the looper thread Lb passes through the loop of the needle thread La from right to left. FIG. 7 shows the state in which the looper 4 is moving to the left in the figure. The retainer 5 moves closer to the looper 4, hooks and captures the looper thread Lb that has passed through the loop of the needle thread La, and begins to hold the looper thread Lb. FIG. 8 shows the state in which the looper 4 has moved further left in the figure and reached the leftmost position in the figure. At this time, the needle 3 is at the top dead center (highest position). The retainer 5 is held within a certain range of positions and continues to capture the looper thread Lb. Figure 9 shows the state after the movement direction of the looper 4 has reversed from the left to the right in the figure. At this time, the needle 3 is lowered (needle thread La is not shown) and crosses the looper 4. Even at this point, the retainer 5 is held within a certain range of positions and continues to capture the looper thread Lb. Figure 10 shows the state after the looper 4 has moved further to the right in the figure and reached its rightmost position in the figure. At this time, the needle 3 is at the bottom dead center (needle thread La is not shown). The retainer 5 then moves back and releases the looper thread Lb. Incidentally, the position at which the retainer 5 captures the looper thread Lb is set to the same position as the retainer needle that was conventionally provided together with the needle and captured the looper thread while penetrating the fabric.

[0039] With regard to the movement of the retainer 5, the retainer 5 is set to a state in which it moves at an extremely slow speed, at least from the time the looper 4 reaches its leftmost position in the drawing (Fig. 8) until the needle 3 crosses the looper 4 (Fig. 9). As a result, the position of the portion of the looper thread Lb held by the retainer 5 hardly fluctuates relative to the needle thread La, and so as the looper thread Lb moves to the left, more of the looper thread Lb is pulled out, forming a loop of the looper thread Lb that is wider (i.e., "loose") than conventionally. Therefore, as the looper thread Lb is captured by the retainer 5, a circular stitch with the desired width can be formed.

[0040] At this time, the retainer 5 is in a state of moving at an extremely slow speed, so the amount of movement of the retainer 5 while holding the looper thread Lb can be made smaller than in the conventional configuration (Patent Document 1) in which the retainer holds the looper thread while continuing to reciprocate at a constant speed. Therefore, since the amount of movement of the retainer 5 can be made smaller, the volume occupied by the retainer 5 inside the cylinder 2 can be made smaller, and the retainer 5 can be stored compactly relative to the cylinder 2.

[0041] The movement trajectory of the retainer 5 is shown schematically in the graph of Figure 11. The horizontal axis of the graph is the time axis (more specifically, the angle based on the top dead center and bottom dead center of the needle 3 and the needle bar that supports it), and the vertical axis is the displacement related to the reciprocating movement. As an example of a conventional retainer 5, the retainer 5 described in Patent Document 1 performs a simple reciprocating movement, and although not shown, the movement trajectory of the retainer 5 is a simple sine curve. If it is attempted to hold the looper thread Lb for a long period of time with such a simple reciprocating movement, it is necessary to increase the stroke of the reciprocating movement of the retainer 5. This may result in the reciprocating range of the retainer 5 not being able to fit inside the cylinder 2.

[0042] On the other hand, the movement locus of the retainer 5 in this embodiment is, for example, as shown in Figure 11. As is clear from the graph, two small, low peaks are formed in the range from 0° to 90° on the horizontal axis. The formation of two small peaks on the graph means that the tip 53 of the retainer 5 reciprocates within a very small range. In this way, by "treading" the retainer 5 within a limited range relative to the looper 4, the retainer 5 does not immediately turn back, but can remain within a narrow range within the reciprocating range for a certain period of time. In this way, the looper thread Lb can be held without increasing the reciprocating range of the retainer 5.

[0043] Although the first embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made within the scope that does not deviate from the gist of the present invention.

[0044] For example, the low-speed movement mechanism, which is configured to move the retainer 5 at a low speed within a certain range of positions for a certain period of time, is not limited to the link mechanism of the above-described embodiments and can be implemented in various configurations. For example, mechanical configurations may include a cam, a gear with no teeth on some parts, a combination of multiple gears that move toward and away from each other, a clutch mechanism, or a brake mechanism that decelerates by friction. Furthermore, electrical configurations may include an electrical circuit that connects and disconnects the transmission of driving force at a predetermined time interval. Furthermore, while the above-described embodiments describe a low-speed movement mechanism provided at one location along the driving force transmission path, separate low-speed movement mechanisms may be provided at multiple locations, and each separate mechanism may be configured to operate simultaneously or with a time lag.

[0045] [Second embodiment] In addition, the driving force for moving the retainer 5 can be obtained from the looper shaft, which is the shaft for driving the looper 4, or the feed base. Also, the retainer 5 can be moved by a drive mechanism independent of the mechanism for driving other parts of the sewing machine. A "second embodiment" will be illustrated below.

[0046] As a second embodiment, an example of a configuration in which the driving force of the retainer 5 is obtained from the looper shaft 11 is shown in FIGS. 13 and 14. The movement trajectory of the retainer 5 in the second embodiment is also shown in the graph of FIG. 15. In the second embodiment, the retainer shaft 12 is provided so that its axial direction is parallel to the looper shaft 11, which is driven by a main shaft (not shown) connected to the base end. A retainer support portion 14 is provided integrally with the tip of the retainer shaft 12. The axial directions of the looper shaft 11 and the retainer shaft 12 are aligned with the longitudinal direction of the cylinder 2, and the distance between the centers of the respective shafts is constant. The looper shaft 11 and the retainer shaft 12 are connected to each other by a link mechanism 13 so that a driving force can be transmitted. The link mechanism 13 includes a looper-side link body 131 and a connecting link body 132 as link units. The connecting link body 132 is connected to a link receiving portion 121 provided integrally with the base end of the retainer shaft 12. The looper shaft 11 rotates within a predetermined angular range to move the looper 4 forward and backward. Correspondingly, the link mechanism 13 repeats between the state shown in Fig. 13 and the state shown in Fig. 14 (more specifically, a state beyond the state shown in Fig. 14 in which the looper side link body 131 and the connecting link body 132 are slightly bent in the opposite direction to that shown in Fig. 13).

[0047] The retainer 5 in the second embodiment is a rod-shaped body bent into an "L" shape to form a crochet hook. The retainer 5 has a base 54 extending in the radial direction attached to the retainer support part 14, and captures the looper thread Lb by hooking it at a tip 55 provided integrally on the radially outer side of the base 54. As described above, the looper shaft 11 and the retainer shaft 12 are parallel, and the looper 4 and the retainer 5 rotate (swing) at the tips of the respective shafts, so that the tip 55 of the retainer 5 reciprocates in the direction along the looper 4 (i.e., in the direction perpendicular to the longitudinal direction of the cylinder 2).

[0048] By adjusting the timing at which the link mechanism 13 changes from the bent state to the linear state, the retainer 5 of the second embodiment can be in the slightly moving state during a time period that includes the turning back operation on the side that holds the looper thread (not shown) during reciprocation, as in the first embodiment. In the second embodiment, as shown in FIG. 15, the time period corresponds to the period that includes the lowest position of the needle 3 (bottom dead center of the needle bar), which corresponds to "180°" on the horizontal axis, and two small, low peaks are formed there. This state corresponds to the period between the state shown in FIG. 14 and the reversely bent state. The capture of the looper thread Lb by the tip 55 of the retainer 5 is similar in timing to capture by a conventional retainer needle. The reason for the position of the peaks being different from the first embodiment is that the reciprocating directions of the looper 4 and the retainer 5 are perpendicular to each other in the first embodiment, whereas they are parallel in the second embodiment, resulting in different timings for holding the looper thread. This concludes the description of the second embodiment.

[0049] [Third embodiment] In the first embodiment, the adjacent members 61-66 are connected by a combination of a round hole and a round rod-shaped shaft, as shown in FIGS. 2 and 3, allowing rotation around a fixed axis. However, this is not limited to this. A rotation shaft (round rod-shaped) may be located inside a long hole or groove formed at one or more connection locations, and the rotation shaft may shift within the extension of the long hole or groove as the member rotates. This configuration ensures that even if one of the adjacent members 61-66 (the upstream side of the drive force transmission path) moves, the displacement is not transmitted to the other member (the downstream side of the drive force transmission path), or is transmitted only slightly. This allows the retainer 5, located at the most downstream side of the drive force transmission path, to move at an extremely slow speed, as in the previous embodiment. As a specific example, a configuration in which a groove is provided will be described below as a "third embodiment." In the third embodiment, components common to those in the first embodiment will be described using the same reference numerals (for convenience of description, some components will be given names different from those in the first embodiment).

[0050] The retainer movement mechanism 6 in the third embodiment includes, in the order of transmission of the driving force for operating the retainer 5, an input-side rotation member 61 that is provided on the input side and rotates within a certain range, an output-side rotation member 63 that is provided on the output side and rotates within a certain range, and a displacement transmission mechanism 67 that transmits displacement from the input-side rotation member 61 to the output-side rotation member 63. The displacement transmission mechanism 67 temporarily reduces the amount of displacement transmitted from the input-side rotation member 61 to the output-side rotation member 63 due to the angular relationship between the tangential component of the rotational displacement of the input-side rotation member 61 and the tangential component of the rotational displacement of the output-side rotation member 63.

[0051] The angular relationship of the tangential components mentioned above will now be explained. When the tangential component of the rotational displacement of the input side rotation member 61 and the tangential component of the rotational displacement of the output side rotation member 63 are orthogonal to each other, even if the input side rotation member 61 rotates, the component of the rotational force of the input side rotation member 61 that corresponds to the tangential component of the rotational displacement of the output side rotation member 63 is zero, and therefore is not transmitted as rotational force to the output side rotation member 63. In other words, the amount of displacement transmitted from the input side rotation member 61 to the output side rotation member 63 temporarily decreases (becomes zero in this case). Note that the rotational force of the input side rotation member 61 is simply absorbed by misalignment within the displacement transmission mechanism 67.

[0052] In the third embodiment, in order to correspond to the orthogonal relationship between the tangential components in the rotational displacements of the input side rotating member 61 and the output side rotating member 63, at the end of the rotation range of the input side rotating member 61 (the position where the first output arm 613 is at the upper end (top dead center) of the rotation range), the tangential component in the rotational displacement of the input side rotating member 61 is set to be approximately along the extension direction of the groove portion 671 (see the rotation trajectory of the first output arm 613 shown in Figure 19).

[0053] Incidentally, the fact that the amount of displacement transmitted from the input-side rotation member 61 to the output-side rotation member 63 is temporarily reduced due to the angular relationship of the tangential direction component also applies to the relationship between the first member 61 as the input-side rotation member and the third member 63 as the output-side rotation member in the link mechanism 6 as the retainer motion mechanism of the first embodiment, and the second member 62 in the first embodiment corresponds to the displacement transmission mechanism 67 described in the third embodiment. In this first embodiment, the first member 61 (including the output arm 611) and the second member 62 are bent to cause a positional misalignment, thereby absorbing the rotational force of the input-side rotation member 61. Similarly, this also applies to the relationship between the looper-side link body 131 and the link receiver 121 in the link mechanism 13 as the retainer motion mechanism of the second embodiment, and the connecting link body 132 in the second embodiment corresponds to the displacement transmission mechanism 67 described in the third embodiment. Here, in the second embodiment, the looper side link body 131 corresponds to the input side rotating member 61 of the third embodiment, and the retainer shaft 12 corresponds to the output side rotating member 62 of the third embodiment. In this second embodiment, the looper side link body 131 and the connecting link body 132 are bent to cause a positional deviation and absorb the rotating force of the looper side link body 131. Therefore, even though the first and second embodiments have different specific configurations, at least a part of the actions achieved by the third embodiment are common to both.

[0054] The third embodiment is specifically configured as shown in Figures 16 to 19. Note that the fourth member 64 and the fifth member 65 in particular differ greatly in shape from those of the first embodiment (see Figure 2), but there is no significant difference in function. The input-side rotation member 61 has a first input arm 612 and a first output arm 613 (rotational movement is indicated by curved arrows in Figure 19) that extend in different radial directions from a first rotation center 61c, and the driving force input from the first input arm 612 by movement of the transmission rod 7 is output from the first output arm 613 as a rotational force about the first rotation center 61c. The output side rotating member 63 has a second input arm 631 and a second output arm 632 (the rotational movement is indicated by curved arrows in Figure 19) extending in different radial directions from 63c, and outputs the driving force input from the second input arm 631 from the second output arm 632 as a rotational force around the second rotation center 63c.

[0055] The displacement transmission mechanism 67 has a groove 671 provided in the second input arm 631, which extends parallel to a radial direction passing through the second rotation center 63c, and a slide member 672 provided in the first output arm 613, which moves along the groove 671. The groove 671 has a rectangular cross-sectional shape and is a constant shape in the extension direction. The slide member 672 is composed of a shaft 6721 provided integrally with the first output arm 613, and a slide block 6722 provided rotatably around the shaft 6721. The shaft portion 6721 is in the shape of a round bar, and the slide block portion 6722 is in the shape of a rectangular parallelepiped, with a hole (the illustrated form is a through hole, but it may also be a bottomed hole) provided in the center into which the shaft portion 6721 fits, and the slide block portion 6722 moves along the extension direction of the groove portion 671 while abutting against the inner surface of the groove portion 671. In other words, the slide member 672 slides relative to the groove portion 671.

[0056] As shown in FIG. 19, the displacement transmission mechanism 67, which is formed by combining the groove 671 and the slide member 672, allows the input rotation member 61 and the output rotation member 63 to rotate while the linear distance between the first rotation center 61c of the input rotation member 61 and the second rotation center 63c of the output rotation member 63 remains constant. In other words, the displacement transmission mechanism 67 is configured to transmit displacement from the input rotation member 61 to the output rotation member 63 while allowing for misalignment between the input rotation member 61 and the output rotation member 63. This change in position can temporarily reduce the amount of transmitted displacement. The movement position of the retainer 5 can be changed in the same manner as in FIG. 12.

[0057] Note that the displacement transmission mechanism 67 is not limited to the above-described configuration in terms of the relationship between the input-side rotation member 61 and the output-side rotation member 63. The portions where the groove 671 and the slide member 672 are provided may be reversed from the configuration described above. In other words, the displacement transmission mechanism 67 can be configured to have a groove 671 that is provided in the first output arm 613 or the second input arm 631 and extends parallel to a radial direction passing through the first rotation center 61 c or the second rotation center 63 c, and a slide member 672 that is provided in the second input arm 631 or the first output arm 613 and moves along the groove 671. [Explanation of symbols]

[0058] 1 sewing machine 2 cylinders 21 Throat plate 3 needles 4. Roopa 5 Retainer 6. Retainer movement mechanism (first and third embodiments), link mechanism (first embodiment) 61 Link unit (first embodiment), first member (first embodiment), input side rotation member (third embodiment) 61c First rotation center 612 First input arm 613 First Output Arm 62 Link unit, second member (first embodiment) 63 Third member (first embodiment), output side rotating member (third embodiment) 63c Second center of rotation 631 Second input arm 632 Second output arm 67 Displacement transmission mechanism (third embodiment) 671 Groove 672 Slide member 13 Retainer movement mechanism (second embodiment), link mechanism (second embodiment) 131 Link unit body (second embodiment), looper side link body (second embodiment) 132 Link unit body (second embodiment), connecting link body (second embodiment) La needle thread Lb Looper thread OP Side facing the operator

Claims

1. A needle that holds a needle thread and moves up and down through a needle plate; a looper that holds a looper thread and reciprocates within a space below the needle plate to entangle the looper thread with the needle thread; a retainer that reciprocates within a space below the needle plate and captures the looper thread; a retainer movement mechanism that changes the state of motion of the retainer while transmitting a driving force from a driving source to the retainer, The retainer movement mechanism causes the retainer to reciprocate so as to move within a certain range of positions in the space below the needle plate for a certain period of time at a slower speed than before and after the position, thereby allowing the retainer to continue to capture the looper thread, A sewing machine in which the certain range for the low-speed movement of the retainer by the retainer movement mechanism is a range between a turn-around position where the movement direction of the retainer is reversed and a position near the turn-around position that is away from the turn-around position in the direction in which the retainer retreats.

2. 2. The sewing machine according to claim 1, wherein the retainer movement mechanism moves the retainer backward once from the folded position within the given range, then moves the retainer forward again to the folded position, and then moves the retainer backward again.

3. The retainer movement mechanism includes a link mechanism in which two link units are combined, the link mechanism is configured such that, when a reciprocating motion is input, the relationship between the lines connecting the input-side connecting points and the output-side connecting points of both link units repeatedly changes within a range between a linear state in which they are aligned in a straight line and a bent state in which they are bent, 2. The sewing machine according to claim 1, wherein the retainer continues to capture the looper thread at least while the link mechanism is released from the bent state, turns around, and starts to bend again.

4. The retainer movement mechanism includes a link mechanism in which two link units are combined, The link mechanism is configured such that, when a reciprocating motion is input, the link mechanism repeats a proximal bent state in which the link units are bent in one direction, a straight line state in which the link units are arranged in a straight line, and a distal bent state in which the link units are bent in the other direction, in relation to the relationship between the straight lines connecting the input side connection points and the output side connection points of the link units, and the bending point between the link units in the proximal bent state is set closer to the straight line state than in the distal bent state, 2. The sewing machine according to claim 1, wherein the retainer continues to capture the looper thread at least while the link mechanism moves from the straight state through the proximal bent state and then back to the straight state.

5. the retainer movement mechanism comprises an input-side rotation member provided on the input side and rotating within a certain range, an output-side rotation member provided on the output side and rotating within a certain range, and a displacement transmission mechanism that transmits displacement from the input-side rotation member to the output-side rotation member, 2. The sewing machine according to claim 1, wherein the displacement transmission mechanism temporarily reduces the amount of displacement transmitted from the input side rotating member to the output side rotating member based on the angular relationship between the tangential component of the rotational displacement of the input side rotating member and the tangential component of the rotational displacement of the output side rotating member.

6. the input side rotation member has a first input arm and a first output arm extending in different radial directions from a first rotation center, and outputs a driving force input from the first input arm as a rotation force about the first rotation center from the first output arm, the output-side rotation member has a second input arm and a second output arm extending in different radial directions from a second rotation center, and outputs a driving force input from the second input arm as a rotation force about the second rotation center from the second output arm; 6. The sewing machine according to claim 5, wherein the displacement transmission mechanism includes a groove provided on the first output arm or the second input arm and extending parallel to a radial direction passing through the first rotation center or the second rotation center, and a slide member provided on the second input arm or the first output arm and moving along the groove.

Images