SEWING MACHINE

Abstract

 Provided is a sewing machine including: a needle configured to hold a needle thread and move up and down through a stitch plate; a looper configured to hold a looper thread and entangle the looper thread with the needle thread by reciprocally moving within a space below the stitch plate; a retainer configured to reciprocally move within the space below the stitch plate to capture the looper thread; and a retainer motion mechanism configured to change a motion state of the retainer while transmitting driving force from a driving source to the retainer, in which the retainer motion mechanism is configured to allow the retainer to reciprocally move at a lower speed within a specific position range in the space below the stitch plate for a specific period of time than speeds before and after the specific period of time to keep the retainer capturing the looper thread.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to Japanese Patent Application No. 2022-125579 and Japanese Patent Application No. 2022-188995, the disclosures of which are incorporated herein by reference in their entirety.

FIELD

[0002] The present invention relates to a sewing machine capable of making stitches with a looper thread formed into wide loops, without the use of a retainer needle configured to perforate a fabric.

BACKGROUND

[0003] Sewing machines capable of making stitches with a looper thread formed into wide loops have been conventionally available. Examples thereof include a sewing machine described in JP 2001-314681 A (Patent Literature 1). The sewing machine described in Patent Literature 1 includes a retainer configured to move below a stitch plate without passing through the stitch plate, and allows the retainer to hold a looper thread, thereby being capable of making stitches with the looper thread formed into wide loops in a portion of double-thread chain stitches, without the use of a retainer needle configured to perforate a fabric and make holes therethrough. According to the drawings of Patent Literature 1, the above configuration is applicable to stitches shown in Fig. 3 of Patent Literature 1, in contrast to stitches shown in Fig. 4 of Patent Literature 1 (as viewed from a back side of the fabric), although no holes as shown in Fig. 3 made by the retainer needle having perforated the fabric are made.

CITATION LIST

Patent Literature

[0004] Patent Literature 1: JP 2001-314681 A

SUMMARY

Technical Problem

[0005] In the sewing machine described in Patent Literature 1, the retainer is configured to reciprocally move along an arc-shaped trajectory within a specific range in response to driving force of an internally equipped main shaft (see Fig. 2 of Patent Literature 1). Since this reciprocating motion is a simple reciprocation, the retainer reduces its moving speed to 0 for a moment when a direction in which the retainer moves changes at the time of returning during the reciprocating motion, but the retainer in forward motion and in backward motion changes its moving speed so as to conform to a sine curve having a certain shape in relation to time. To make, for example, stitches with the looper thread formed into loops each having a desired size, therefore, the retainer needs to be configured to continuously hold the looper thread for a long period of time (i.e., period of time from when the retainer captures the looper thread to when it releases the looper thread), for the purpose of which a stroke of the reciprocally moving retainer (i.e., a range within which the retainer reciprocally moves) needs to be increased depending on the prolonged period of time to allow the retainer to hold the looper thread while moving at such a speed as to conform to the sine curve. This is due to the configuration that the retainer moves to a returning point after capturing the looper thread, and releases the looper thread after reversing the moving direction. However, a small-sized sewing machine, for example, can have a cylinder with only a limited internal volume, which may be in some cases too small for the range of the reciprocally moving retainer to be accommodated within the cylinder and too small to set a large reciprocating stroke when the retainer is caused to hold the looper thread for a period of time long enough to achieve desired stitches.

[0006]  It is therefore an object of the present invention to provide a sewing machine capable of prolonging a period of time for which a retainer holds a looper thread and achieving stitches with the looper thread formed to have a desired size, without the necessity of setting a large stroke of the reciprocally moving retainer.

Solution to Problem

[0007] Provided in the present invention is a sewing machine including: a needle configured to hold a needle thread and move up and down through a stitch plate; a looper configured to hold a looper thread and entangle the looper thread with the needle thread by reciprocally moving within a space below the stitch plate; a retainer configured to reciprocally move within the space below the stitch plate to capture the looper thread; and a retainer motion mechanism configured to change a motion state of the retainer while transmitting driving force from a driving source to the retainer, in which the retainer motion mechanism is configured to allow the retainer to reciprocally move at a lower speed within a specific position range in the space below the stitch plate for a specific period of time than speeds before and after the specific period of time to keep the retainer capturing the looper thread.

[0008] The configuration can be such that the specific position range within which the retainer is caused to move at the low speed by the retainer motion mechanism is a range between a returning position at which the retainer reverses a moving direction from a forward direction to a backward direction and a position close to the returning position and away in the backward direction from the returning position.

[0009] The configuration can be such that the retainer motion mechanism is configured to allow, within the specific position range, the retainer to once move backward from the returning position, thereafter move forward to the returning position again, and then further move backward.

[0010] The configuration can be such that the retainer motion mechanism includes a link mechanism formed of two link units combined together; when reciprocating motion is input, the link mechanism is configured to change repeatedly in all or part of a range between a linear state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units are arranged linearly and a bent state where the straight lines are arranged to form a bent shape; and the retainer is configured to keep capturing the looper thread at least while the link mechanism is released from the bent state to a point at which the state changes, and then begins being bent again.

[0011] The configuration can be such that the retainer motion mechanism includes a link mechanism formed of two link units combined together; when reciprocating motion is input, the link mechanism is configured to change repeatedly into a proximally bent state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units are arranged to form a bent shape in one direction, a linear state where the straight lines are arranged linearly, and a distally bent state where the straight lines are arranged to form a bent shape in an other direction, wherein a bent point between the two link units in the proximally bent state is closer to the bent point in the linear state than the bent point in the distally bent state is to the bent point in the linear state, and the retainer is configured to keep capturing the looper thread at least while the link mechanism is brought from the linear state back into the linear state again through the proximally bent state.

[0012] The configuration can be such that the retainer motion mechanism includes: an input-side pivoting member disposed on an input side and configured to pivotally move within a specific range; an output-side pivoting member disposed on an output side and configured to pivotally move within a specific range; and a displacement transmission mechanism configured to transmit displacement from the input-side pivoting member to the output-side pivoting member, and the displacement transmission mechanism is configured to temporarily reduce an amount of displacement transmitted from the input-side pivoting member to the output-side pivoting member, depending on an angle between a tangential component of a pivotal displacement of the input-side pivoting member and a tangential component of a pivotal displacement of the output-side pivoting member.

[0013] The configuration can be such that the input-side pivoting member includes a first input arm and a first output arm, which extend from a first pivoting center in different radial directions, and driving force that is input from the first input arm is output from the first output arm as pivoting force about the first pivoting center, the output-side pivoting member includes a second input arm and a second output arm, which extend from a second pivoting center in different radial directions, and driving force that is input from the second input arm is output from the second output arm as pivoting force about the second pivoting center, and
the displacement transmission mechanism is disposed on the first output arm or the second input arm, and includes: a groove part extending in parallel with a radial direction passing the first pivoting center or the second pivoting center; and a sliding member disposed on the second input arm or the first output arm and configured to move along the groove part.

BRIEF DESCRIPTION OF DRAWINGS

[0014] 

Fig. 1 is a perspective view showing a sewing machine with a built-in mechanism according to one embodiment of the present invention.

Fig. 2 is a perspective view of an extracted portion including a retainer motion mechanism (link mechanism) according to a first embodiment, the view showing a state where a retainer is at a foremost position (i.e., has advanced the most).

Fig. 3 is a perspective view of the extracted portion including the link mechanism according to the first embodiment, the view showing a state where the retainer is at a rearmost position (i.e., has retracted the most).

Fig. 4A is a perspective view of an essential part of the link mechanism according to the first embodiment showing a positional relationship between a looper and the retainer and related members, the view corresponding to the state in Fig. 3.

Fig. 4B is a perspective view of the essential part of the link mechanism according to the first embodiment showing a positional relationship between the looper and the retainer and related members, the view corresponding to the state in Fig. 2.

Fig. 5 is a perspective view showing a positional relationship among needles, the looper, and a looper thread (with the retainer not shown) in order of operation in the first embodiment.

Fig. 6 is a perspective view showing a positional relationship among the needles, the looper, needle threads, and the looper thread (with the retainer not shown) in order of operation in the first embodiment.

Fig. 7 is a perspective view showing a positional relationship among the needles, the looper, the retainer, the needle threads, and the looper thread in order of operation in the first embodiment.

Fig. 8 is a perspective view showing a positional relationship among the needles, the looper, the retainer, the needle threads, and the looper thread in order of operation in the first embodiment.

Fig. 9 is a perspective view showing a positional relationship among the needles, the looper, the retainer, and the looper thread (with the needle threads not shown) in order of operation in the first embodiment.

Fig. 10 is a perspective view showing a positional relationship among the needles, the looper, the retainer, and the looper thread (with the needle threads not shown) in order of operation in the first embodiment.

Fig. 11 is a graph showing changes in the state where the retainer advances in the first embodiment.

Fig. 12 is another graph showing changes in the state where the retainer advances in the first embodiment.

Fig. 13 is a perspective view showing an extracted portion including a retainer motion mechanism (link mechanism) according to a second embodiment, the view showing the case where the retainer moves at a normal speed (i.e., when the needles are located at the top dead center).

Fig. 14 is a perspective view showing the extracted portion including the link mechanism according to the second embodiment, the view showing the case where the retainer moves at a low speed (i.e., when the needles are located at the bottom dead center).

Fig. 15 is a graph showing changes in the state where the retainer advances in the second embodiment.

Fig. 16 is a perspective view showing an extracted portion including a retainer motion mechanism according to a third embodiment.

Fig. 17 is a perspective view of the retainer motion mechanism according to the third embodiment, as viewed from the opposite side to Fig. 16.

Fig. 18 is an exploded perspective view showing the retainer motion mechanism according to the third embodiment.

Fig. 19 is an explanatory view showing an operation of the retainer motion mechanism according to the third embodiment.

DESCRIPTION OF EMBODIMENTS

[0015] A description will be hereinafter given on the present invention by taking embodiments. A sewing machine 1 of this embodiment is a sewing machine 1 capable of making stitches with a looper thread Lb formed into wide loops, and is mainly used for double chain stitching, but can also be used for making other stitches using a looper thread, such as flat stitching. The term "double chain stitching" includes both single-needle double chain stitching and multiple-needle double chain stitching. A vertical direction described hereinafter defines a direction in the embodiments.

[First embodiment]

[0016] As shown in Fig. 1, the sewing machine 1 with a built-in mechanism according to this embodiment (first embodiment) includes a cylinder 2 in a cylindrical shape for supporting a fabric during sewing. The sewing machine 1 with a built-in mechanism according to the second embodiment, which will be described later, has the same appearance. The fabric is fed along a longitudinal direction of the cylinder 2. In this embodiment, the fabric is fed from a right side toward a left side in Fig. 1 for sewing. A sewing part in which a needle 3 moves up and down for sewing is disposed at a distal end portion of the cylinder 2 (the reference sign "3" in Fig. 1 is represented not for denoting the needle 3 itself but for indicating its approximate position). An operator engaging in sewing operation is located on the right side in Fig. 1 of the sewing machine 1 (i.e., at a position directed by the illustrated arrow OP) to perform the operation. It should be noted that the sewing machine 1 of this embodiment, which is dedicated to sewing a fabric into a tubular shape, needs to have the cylinder 2 formed in a thinner shape with a smaller internal space than the cylinder of, for example, a sewing machine configured to feed a fabric in a direction orthogonal to a longitudinal direction of the cylinder, and thus allows only limited space for accommodating parts or members inside the cylinder 2. The reference sign "OP" is added to those figures for which the reference sign is necessary for explanation, but the positional relationship defined by the reference sign still applies to those other figures without the reference sign.

[0017] In the sewing machine 1 of this embodiment (and also the sewing machine 1 according to the second embodiment to be described later), the main parts or members involved in forming stitches include the needle 3, a looper 4, and a retainer 5 shown in Fig. 4A and Fig. 4B. The needle 3 and the looper 4 each have a conventionally known configuration. The needle 3 holds a needle thread La (see, e.g., Fig. 6), and moves up and down through a stitch plate 21. In this embodiment, the needle 3 includes a plurality of (specifically four) needles 3. Although a conventionally known sewing machine includes a retainer needle disposed in parallel with a sewing needle, the sewing machine 1 of this embodiment includes no retainer needle but only includes the sewing needle 3 as the needle that perforates a fabric.

[0018] The looper 4 has a shape shown in, for example, Fig. 5 to Fig. 10, and is configured to hold a looper thread Lb (see, e.g., Fig. 5) and reciprocally move within a space below the stitch plate 21 of the cylinder 2 to entangle the looper thread Lb with the needle thread La as shown in Fig. 6 to Fig. 8. The looper 4 has a curved shape slightly projecting upward as illustrated, and the looper thread Lb passes through the inside of the looper 4 from a proximal end portion to a distal end portion thereof, as shown in Fig. 5. The looper 4 of this embodiment reciprocally moves in a direction orthogonal to the direction of feeding the fabric relative to the cylinder 2 (i.e., a width direction of the cylinder 2). In this embodiment, since the looper 4 is configured to be capable of swinging the looper thread Lb right and left relative to the fabric feeding direction, stitches can still be formed without use of the retainer 5. Thus, the retainer 5 to be described hereinbelow is not an essential feature for making stitches. The retainer 5 of this embodiment is configured to hold the looper thread Lb drawn out by the looper 4 during, for example, double chain stitching to consequently achieve stitches with the looper thread Lb formed to have a desired size.

[0019] The retainer 5 reciprocally moves within the space below the stitch plate 21 in the cylinder 2 to capture the looper thread Lb held by the looper 4. The retainer 5 in the mechanism according to this embodiment is connected to the link mechanism 6 as a retainer motion mechanism shown in Fig. 2 and Fig. 3, and is configured to reciprocally move with driving force of a main shaft (not shown) being converted and transmitted to the retainer 5. Unlike conventional retainer needles, this retainer 5 does not perforate the fabric when reciprocally moving as above. As shown in Fig. 7, the retainer 5 is formed by bending a plate-like body. A base part 51 having a flat plate shape is attached to a retainer support 8 configured to be swung by the link mechanism 6. In this embodiment, the base part 51 is attached to locate a fixing hole 511 in conformity with a mounting part 82 of the retainer support 8. A pivot center of the retainer 5 coincides with a pivot supporting part 81 of the retainer support 8 (i.e., a pivot center of the swinging). A connecting part 52 formed by bending the plate in its thickness direction lies at an upper end of the base part 51, and a distal end part 53 projecting orthogonal to a direction in which the connecting part 52 extends is formed at a distal end of the connecting part 52. The base part 51, the connecting part 52, and the distal end part 53 are integrated with each other. The distal end part 53 (more specifically, a portion of the distal end part 53 close to the connecting part 52) hooks the looper thread Lb to thereby allow the retainer 5 to capture the looper thread Lb. The distal end part 53 of the retainer 5 reciprocally moves in a direction orthogonal to the direction in which the looper 4 reciprocally moves (i.e., a direction along the longitudinal direction of the cylinder 2). Thus, a direction in which the distal end part 53 of the retainer 5 for hooking the looper thread Lb moves is orthogonal to a direction in which the looper 4 moves (see the moving directions shown in the respective arrows in Fig. 7).

[0020] The link mechanism 6 changes a motion state of the retainer 5 while transmitting driving force from a 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 reciprocally moves in an axial direction (vertically) in response to the driving force of the main shaft, and the retainer support 8 supporting the retainer 5. The main shaft is configured to rotate, and the driving force of the main shaft is converted to reciprocating motion by a conversion mechanism such as an eccentric mechanism laid between the main shaft and the transmission rod 7. This link mechanism 6 is composed of a first member 61 to a sixth member 66 pivotally connected to each other from a proximal end side to a distal end side of the cylinder 2.

[0021] The first member 61 and the third member 63 have different shapes from each other while resembling the letter V, and each have distal end portions of the V shape pivotally moving about a pivotal supporting point at a supporting point of the V shape. The first member 61 is connected to an end of the transmission rod 7. The second member 62 and the fourth member 64 to the sixth member 66 each have an I shape (straight rod shape) with both ends in its longitudinal direction pivotally connected relative to other members. The fifth member 65 extends between the proximal end part and the distal end part of the cylinder 2, and is longer than the other members.

[0022] What is important in this embodiment is the relationship in transmitting driving force between the transmission rod 7 moving up and down and the first member 61 to the third member 63 while the retainer 5 captures the looper thread Lb. When the first member 61 (an output arm 611 being a portion of the V shape opposite to a side of the transmission rod 7) and the second member 62, which serve as link units, are each represented as a straight line obtained by connecting its input-side connecting point and its output-side connecting point to each other, a linear state where the straight lines of the members 61 (611) and 62 are lined up on the same straight line as in a connection direction X shown in Fig. 2 corresponds to a state where the retainer 5 is at a foremost position (i.e., has advanced the most). A bent state formed between the output arm 611 of the first member 61 and the second member 62 and how the bent state changes can be set variously with no particular limitations, but according to the bent state to be described first in this embodiment, the linear state occurs twice per cycle of the reciprocating motion of the transmission rod 7 being the input side. At the moment when the first linear state occurs, the transmission rod 7 is continuously descending. When the transmission rod 7 further descends and reaches a bottommost end, the output arm 611 of the first member 61 and the second member 62 form a "<" shape (or a "V" shape tilted to the right), which is a proximally bent state, from the state shown in Fig. 2. It should be noted that the bending of the "<" shape in the proximally bent state is not illustrated as it is too slight (at an angle of a few degrees) to be visually distinguishable from the linear state. When the transmission rod 7 turns ascending, the angle of the "<" shape increases, the second linear state occurs, and then the shape formed between the output arm 611 of the first member 61 and the second member 62 changes to a ">" shape (or a "V" shape tilted to the left) to be bent in a connection direction Y being a distally bent state shown in Fig. 3. At this time, the transmission rod 7 has reached an uppermost end. When the transmission rod 7 turns descending, the angle of the ">" shape increases and returns to the linear state shown in Fig. 2. This operation is repeated as the transmission rod 7 reciprocally moves up and down. In this case, the proximally bent state and the distally bent state are each a point at which the bending changes. A bending point in the proximally bent state between the first member 61 (output arm 611) and the second member 62 is set closer to the bending point in the linear state than the bending point in the distally bent state is.

[0023] The link mechanism 6 configured to thus operate allows the retainer 5 to reciprocally move at a lower speed within a specific position range in the space below the stitch plate 21 for a specific period of time than speeds before and after the specific period of time to bring the retainer 5 into a micromotion state to thereby keep capturing the looper thread Lb. The specific period of time associated with the movement at a lower speed is included in the period of time between when the retainer 5 captures the looper thread Lb (i.e., the moment shown in Fig. 7) and when the looper 4 starts reversing its moving direction in association with the aforementioned reciprocating motion (immediately after the moment shown in Fig. 10). The specific position range associated with the lower-speed movement is a range between a returning position at which the retainer 5 with the distal end part 53 located at the foremost position (i.e., having advanced the most) reverses its moving direction into a backward (retracting) direction and a position close to the returning position and away in the backward direction from the returning position. The term "vicinity" herein, which will be described in details later, refers to a range less than 3% of the total stroke (corresponding to a distance between the most advanced position and the most retracted position) of the reciprocally moving retainer 5.

[0024] Before and after the first member 61 (output arm 611) and the second member 62 of the link mechanism 6 are brought into the linear state, the first member 61 (output arm 611) and the second member 62 are in such a relationship that tangential lines of pivoting trajectories of the members 61 (611) and 62 (i.e., tangential lines respectively orthogonal to axial directions of the members 61 (611) and 62) are substantially shared. While this relationship is established, substantially 100% of the driving force transmitted from the first member 61 on a driving side to the second member 62 on a driven side is the force of a direction component along the tangential direction. That is, the force of a direction component orthogonal to the tangential direction is substantially 0%. Of the third member 63 having a V shape, an axial direction of a branch portion subjected to the driving force from the second member 62 is set to be orthogonal to the axial direction of the second member 62 (see Fig. 2). With the aforementioned direction components, therefore, the driving force of the second member 62 hardly causes the third member 63 to pivotally move. This configuration enables the retainer 5 connected to the link mechanism 6 (on a downstream side of the third member 63 in a direction in which the force is transmitted) to move at a low speed (i.e., in a substantially stationary state). As described above, in this embodiment, the direction component of the force associated with the pivotal movement of a member of the link mechanism 6 reduces the amount of the driving force transmitted to the other members to thereby enable the retainer 5 to move at a low speed.

[0025] When focusing on the proximally bent state, the retainer 5 can reciprocally move within a smaller distance for a period of time for which the link mechanism 6 turns from the linear state to the proximally bent state and turns back to the linear state, than for a period of time for which the link mechanism 6 turns from the linear state to the distally bent state and turns back to the linear state; thus, the retainer 5 can move at a lower speed for the period of time involving the proximally bent state than before and after the period of time.

[0026] The retainer 5 to which the link mechanism 6 has transmitted the driving force is in the micromotion state within a time interval including a returning operation of the reciprocally moving retainer 5 on a side at which the retainer 5 holds the looper thread Lb. The micromotion state herein means a state where the retainer 5 reciprocally moves within a specific range while moving at a low speed for a specific period of time (i.e., the retainer 5 is brought into a "stepping in place" state within a limited range), rather than a state where the retainer 5 returns instantaneously as in the known art (Patent Literature 1 (JP 2001-314681 A)). The "specific range" is a minute range as compared with the entire range in a direction of the reciprocating motion. In this embodiment, the "minute range" is defined such that, when the main shaft of the sewing machine 1 rotates at a rotation angle of 47° or more, the corresponding amount of the reciprocating motion of the retainer 5 within the rotation angle is less than 3% of the total stroke (corresponding to the distance between the most advanced position and the most retracted position) of the movement.

[0027] Thus, the change in position of the moving retainer 5 in this embodiment does not draw a constant sine curve, but the micromotion state occurs at one of the two returning points where the speed of the retainer 5 is extremely reduced. Fig. 11 in particular shows that the position changes so that the curve has two "peaks" corresponding to the one returning point with a small "valley" therebetween, during which the "stepping in place" state occurs. The degree "0°" on the horizontal axis shown in Fig. 11 corresponds to the position at which the needle 3 has ascended to the uppermost position (i.e., the top dead center of the needle bar, which is not shown, supporting the needle 3). The degree "180°" corresponds to the position at which the needle 3 has descended to the bottommost position (i.e., the bottom dead center of the needle bar). The change in position of the moving retainer 5 can be made as shown in Fig. 12 by altering the configuration of the link mechanism 6. In this case, even in the same "stepping in place" state, the position of the moving retainer 5 changes so that the sine curve has one "peak" at the returning point or has a gently curved portion or a "flat" portion, as illustrated.

[0028] The link mechanism 6 includes a bent movable portion (in this embodiment, a combination of the first member 61 and the second member 62 being the link units), which is configured to change between a most bent state on one side (proximally bent state (not shown) / having a "<" shape bent from the state in Fig. 2 to the opposite side to the state in Fig. 3) and a most bent state on the other side (distally bent state / having a ">" shape shown in Fig. 3) in response to the reciprocating motion of the transmission rod 7. In this embodiment, the setting is such that the time (moment) at which the transmission rod 7 reciprocally moving up and down changes its movement from the downward movement to the upward movement does not coincide with the time at which the output arm 611 of the first member 61 and the second member 62, which are the bent movable portion of the link mechanism 6, extend linearly (i.e., are brought into a linear state). Further in this embodiment, the setting is such that the distal end part 53 of the retainer 5 has projected the most when the bent movable portion is in the linear state (state in Fig. 2) and the distal end part 53 moves backward when the bent movable portion is in the bent state (having both a "<" shape and a ">" shape). Fig. 3 shows the state where the distal end part 53 is located at the rearmost position. This configuration allows the output arm 611 of the first member 61 and the second member 62 to be pushed by the transmission rod 7 and keep being bent even after the output arm 611 of the first member 61 and the second member 62 are in the linear state. The output arm 611 of the first member 61 and the second member 62 are brought into the linear state twice, i.e., before and after they are in the bent state (specifically, in a "<" shape). The period of time for which they are in the linear state twice coincides with the period of time for which the retainer 5 is in the micromotion state. With such a relationship between the first member 61 (output arm 611) and the second member 62, the link mechanism 6 causes the retainer 5 (in particular the distal end part 53 capturing the looper thread Lb) to once move backward from the returning point within the specific range, thereafter again moves forward to the returning point, and then further move backward, as shown in Fig. 11 in which the graph (with the horizontal axis of 0° to 90°) has two peaks.

[0029] A description will be given hereinbelow on the case where a different setting is employed for the bent state of the output arm 611 of the first member 61 and the second member 62 and for how the bent state changes. The bent state described above is set such that the state between the output arm 611 of the first member 61 and the second member 62 changes to three states, namely: the linear state, the proximally bent state (having a "<" shape), and the distally bent state (having a ">" shape). A different setting, in contrast, can be such that the state between the members changes to, for example, two states, namely: the linear state and the bent state. In this case, the linear state and the bent state are each a point at which the bending changes. The "bent state" is the distally bent state in the first embodiment (i.e., the state shown in Fig. 3). This configuration also enables the retainer 5 to move at a low speed.

[0030] Further, yet another setting can be employed such that the state between the members changes to two states, namely: a state where the members are bent in the same direction as the above bent state but more gently than the above bent state without being in the linear state (the state is referred to as a "quasi-linear state"); and the bent state. In this case, the quasi-linear state and the bent state are each a point at which the bending changes. This configuration also enables the retainer 5 to move at a low speed in a similar manner. Accordingly, the link mechanism 6 can be set variously so as to repeatedly change its state in all or part of the range between the linear state and the bent state.

[0031] Next, the needles 3 (four needles), the looper 4, the retainer 5, the needle thread La, and the looper thread Lb are shown in Fig. 5 to Fig. 10 to give a description on their positional relationship in order of their operation. In some figures, the retainer 5 and/or the needle threads La are not illustrated in order to facilitate explanation or avoid the illustrations from being complicated. The arrow provided for each part or member indicates its moving direction. The arrow with a horizontal bar indicates that the part or member with the arrow has reached the returning position. Each figure is based on a view from the distal end side toward the proximal end side of the cylinder 2, i.e., a view from an opposite side to the operator side toward the operator (side of the arrow OP shown in, e.g., Fig. 5). Directions are also expressed on the basis of the same view.

[0032] Fig. 5 shows a state where the looper 4 is moving in the right direction in the figure. At this time, the needles 3 are descending (the needle threads La are not illustrated). Fig. 6 shows a state after the moving direction of the looper 4 is reversed from the right direction to the left direction in the figure. At this time, the needles 3 are ascending after reaching the bottom dead center (the bottommost position). The needle threads La are hooked by the looper 4 entering below the needles 3. At this time, the looper thread Lb is caused to pass through loops formed of the needle threads La from right to left. Fig. 7 shows a state where the looper 4 is moving to the left in the figure. The retainer 5 moves to approach the looper 4, hooks and captures the looper thread Lb passing through the loops of the needle threads La, and starts holding the looper thread Lb. Fig. 8 shows a state where the looper 4 moves further to the left in the figure and has reached the leftmost position in the figure. At this time, the needles 3 are at the top dead center (the uppermost position). The retainer 5 is held within a specific position range to keep capturing the looper thread Lb. Fig. 9 shows a state after the moving direction of the looper 4 is reversed from the left direction to the right direction in the figure. At this time, the needles 3 are descending (the needle threads La are not illustrated) and cross the looper 4. Even at this point, the retainer 5 is still held within the specific position range to keep capturing the looper thread Lb. Fig. 10 shows a state where the looper 4 moves further to the right in the figure and has reached the rightmost position in the figure. At this time, the needles 3 are at the bottom dead center (the needle threads La are not illustrated). Thereafter, the retainer 5 moves backward to release the looper thread Lb. The position at which the retainer 5 captures the looper thread Lb is set in the same manner as the position at which a retainer needle, which is conventionally provided together with the needle for capturing the looper thread while perforating a fabric.

[0033] As to the movement of the retainer 5, the retainer 5 is in the state of moving at an extremely low speed at least from when the looper 4 is at the leftmost position in the figure (Fig. 8) to when the needles 3 cross the looper 4 (Fig. 9). This configuration allows the position of a portion of the looper thread Lb held by the retainer 5 to hardly vary relative to the needle threads La, and thus enables the looper thread Lb to be drawn out by a greater length as the looper 4 moves to the left, to form a larger and wider loop (i.e., "with sufficient space therein") than the loop formed by the known technique. Thus, stitches with the looper thread Lb formed into loops having a desired size can be made depending on the capturing of the looper thread Lb by the retainer 5.

[0034] In so doing, the configuration that the retainer 5 moves at an extremely low speed can reduce the moving amount of the retainer 5 while holding the looper thread Lb as compared with the known art (Patent Literature 1 (JP 2001-314681 A)) in which the retainer is configured to hold a looper thread while continuously moving reciprocally at a constant speed. Thus, the retainer 5 configured to reduce its moving amount can have a reduced volume occupied inside the cylinder 2, and can be compactly stored in the cylinder 2.

[0035] Fig. 11 is a graph schematically showing the moving trajectory of the retainer 5. The horizontal axis of the graph represents a time axis (specifically representation by angle based on the top dead center and the bottom dead center of the needles 3 and the needle bars supporting the needles 3), and the vertical axis represents displacement in association with the reciprocating motion. As an example of the known art, the retainer 5 of Patent Literature 1 is configured to reciprocally move in a simple manner, and thus draws a simple sine curve as the moving trajectory, although not shown. If the retainer 5 reciprocally moving in such a simple manner is caused to hold the looper thread Lb for a long period of time, the retainer 5 needs to increase its stroke for the reciprocating motion. Such a configuration leads to a possibility that the range in which the retainer 5 reciprocally moves cannot be accommodated inside the cylinder 2.

[0036] In contrast, the moving trajectory of the retainer 5 in this embodiment is, for example, as shown in Fig. 11. As is evident from the graph, two small low hills are formed within a range of the horizontal axis from 0° to 90° inclusive. The fact that the graph has the two small hills means that the distal end part 53 of the retainer 5 reciprocally moves within the minute range. Such a configuration that the retainer 5 is brought into the "stepping in place" state relative to the looper 4 within a limited range enables the retainer 5 to stay in a small range within the range in which the retainer 5 reciprocally moves, rather than causing the retainer 5 to reverse its movement direction instantaneously. Accordingly, the retainer 5 can hold the looper thread Lb without increasing the range in which the retainer 5 reciprocally moves.

[0037] The description has been given on the first embodiment of the present invention, but the present invention is not limited to the aforementioned embodiment, and various modifications can be made without departing from the gist of the present invention.

[0038] For example, a low-speed moving mechanism, which is configured to move the retainer 5 at a low speed within the specific position range for the specific period of time, is not limited to the link mechanism of each of the aforementioned embodiments, but can be achieved with various configurations. For example, as a mechanical configuration, there can be such a configuration equipped with a cum, a gear partially having no teeth, a combination of a plurality of gears that come close to or separate from each other, a clutch mechanism, or a brake mechanism configured to reduce speed by friction. As an electrical configuration, there can be such a configuration including an electric circuit for connecting and disconnecting transmission of the driving force at a specific time cycle. Each of the aforementioned embodiments has been described by taking, for example, the case where the low-speed moving mechanism is located at one position in a driving force transmission path, but the configuration can be such that the low-speed moving mechanism has separated portions located at a plurality of positions and the separated portions of the mechanism operate concurrently or sequentially with time lag.

[Second embodiment]

[0039] The driving force for moving the retainer 5 can also be obtained from a looper shaft, which is a shaft for driving the looper 4, or a feed bar. The retainer 5 can also be moved with a driving mechanism independent of the mechanism for driving other portions of the sewing machine. A "second embodiment" will be described as an example below.

[0040] Fig. 13 and Fig. 14 each show an example of a configuration as the second embodiment that the driving force of the retainer 5 is obtained from a looper shaft 11. Fig. 15 is a graph schematically showing the moving trajectory of the retainer 5 in the second embodiment. In the second embodiment, a retainer shaft 12 is disposed with its axial direction parallel to the axial direction of the looper shaft 11 which is driven by a main shaft (not shown) connected on the proximal end side. A retainer support part 14 is integrally provided at a leading end of the retainer shaft 12. The looper shaft 11 and the retainer shaft 12 have their axial directions extending along the longitudinal direction of the cylinder 2, with a constant distance between their axial centers. The looper shaft 11 and the retainer shaft 12 are connected to each other via a link mechanism 13 so as to be capable of transmitting the driving force. 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 receiver 121 integrally provided on the proximal end side of the retainer shaft 12. The looper shaft 11 rotatally moves within a specific angle range to allow the looper 4 to move forward and backward. Corresponding thereto, the link mechanism 13 is repeatedly brought into the state shown in Fig. 13 and the state shown in Fig. 14 (specifically, the state where, beyond the state shown in Fig. 14, the looper-side link body 131 and the connecting link body 132 form a slightly reverse-bent state to an opposite side to the state shown in Fig. 13).

[0041] The retainer 5 in the second embodiment is formed in a hook shape by bending a rod-shaped body into an "L" shape. The retainer 5 has a radially extending base part 54 mounted to the retainer support part 14, and is configured to allow a distal end part 55 integrally provided radially outside the base part 54 to hook and thereby capture the looper thread Lb. As described above, the looper shaft 11 and the retainer shaft 12 are parallel to each other, and the looper 4 and the retainer 5 pivotally move (swing) at ends of the respective shafts; thus, the distal end part 55 of the retainer 5 reciprocally moves in a direction along the looper 4 (i.e., a direction orthogonal to the longitudinal direction of the cylinder 2).

[0042] Adjusting the timings at which the link mechanism 13 is in the bent state and in the linear state can bring the retainer 5 of the second embodiment into the micromotion state within a time section involving a returning operation of a side of the reciprocally moving retainer 5 holding the looper thread (not shown), as in the case of the first embodiment. In the second embodiment, as shown in Fig. 15, a section involving the moment at which the needles 3 have descended to the bottommost position (i.e., are located at the bottom dead center of the needle bars) corresponding to "180°" of the horizontal axis, corresponds to the above time section, in which the graph has two small low hills. This state corresponds to a state between the state shown in Fig. 14 and the reverse-bent state. The timing at which the distal end part 55 of the retainer 5 captures the looper thread Lb conforms to the timing at which the conventionally known retainer needle captures the thread. The hills in the graph of the second embodiment are located at different positions from those in the first embodiment because the timings at which the retainer 5 holds the looper thread are different between the first embodiment in which the directions in which the looper 4 and the retainer 5 reciprocally move are orthogonal to each other and the second embodiment in which they are in parallel with each other. The second embodiment has been hereinabove described.

[Third embodiment]

[0043] In the first embodiment, as shown in Fig. 2 and Fig. 3, the members 61 to 66 adjacent to each other are connected to each other so as to pivotally move about an axis at a certain position (in combination of a round hole and a shaft having a round rod shape). However, the configuration is not limited thereto, and can also be such that a pivotally movable shaft (having a round rod shape) is located in an elongated hole or groove part formed at one or more connecting portions and is displaced within a range in which the elongated hole or groove part extends as the pivotal movement occurs. With such a configuration, when one of each adjacent ones of the members 61 to 66 (on an upstream side of the driving force transmission path) moves, the displacement resulting from the movement can be made not to be transmitted or to be hardly transmitted to the other one of the members (on a downstream side of the driving force transmission path), and the retainer 5, which is located on the most downstream side of the driving force transmission path, can be brought into the state of moving at an extremely low speed as in the preceding embodiments. As a specific example, a description will be hereinafter given on a configuration with a groove part as a "third embodiment". Any features common to those in the first embodiment are provided with the same reference signs in the third embodiment for explanation (some of which are named differently from the first embodiment for the convenience of explanation).

[0044] A retainer motion mechanism 6 in the third embodiment includes, in order of transmitting the driving force for operating the retainer 5: an input-side pivoting member 61 disposed on an input side and pivotally moving within a certain range; an output-side pivoting member 63 disposed on an output side and pivotally moving within a certain range; and a displacement transmission mechanism 67 configured to transmit displacement from the input-side pivoting member 61 to the output-side pivoting member 63. The displacement transmission mechanism 67 is configured to temporarily reduce the amount of displacement transmitted from the input-side pivoting member 61 to the output-side pivoting member 63, depending on an angular relationship between a tangential component of the pivotal displacement of the input-side pivoting member 61 and a tangential component of the pivotal displacement of the output-side pivoting member 63.

[0045] A description will be given on the aforementioned angular relationship between the tangential components. When the tangential component of the pivotal displacement of the input-side pivoting member 61 and the tangential component of the pivotal displacement of the output-side pivoting member 63 are orthogonal to each other, no pivoting force of the pivotally moving input-side pivoting member 61 is transmitted to the output-side pivoting member 63 since no component out of the pivoting force of the input-side pivoting member 61 corresponds to the tangential component of the pivotal displacement of the output-side pivoting member 63. That is, the amount of displacement transmitted from the input-side pivoting member 61 to the output-side pivoting member 63 is temporarily reduced (in this case it becomes 0). The pivoting force of the input-side pivoting member 61 is only absorbed by misalignment within the displacement transmission mechanism 67.

[0046] In the third embodiment, the tangential component of the pivotal displacement of the input-side pivoting member 61 substantially conforms to a direction in which a groove part 671 extends at an end of a pivoting range of the input-side pivoting member 61 (i.e., position at which a first output arm 613 is located at an upper end (top dead center) of the pivoting range), so that the tangential components of the pivotal displacements of the input-side pivoting member 61 and the output-side pivoting member 63 are orthogonal to each other (see the pivoting trajectory of the first output arm 613 shown in Fig. 19).

[0047] Temporarily reducing the amount of displacement transmitted from the input-side pivoting member 61 to the output-side pivoting member 63 depending on the angular relationship between the tangential components is applicable also between the first member 61 as an input-side pivoting member and the third member 63 as an output-side pivoting member, of the link mechanism 6 as the retainer motion mechanism of the first embodiment, in which case the second member 62 of the first embodiment corresponds to the displacement transmission mechanism 67 described in the third embodiment. In this first embodiment, the first member 61 (output arm 611 thereof) and the second member 62 form the bent state to thereby cause misalignment and absorb the pivoting force of the input-side pivoting member 61. The same is applicable also between the link receiver 121 and the looper-side link body 131 of the link mechanism 13 as the retainer motion mechanism of the second embodiment, in which case the connecting link body 132 of the second embodiment corresponds to the displacement transmission mechanism 67 described in the third embodiment. In the second embodiment, the looper-side link body 131 corresponds to the input-side pivoting member 61 of the third embodiment, and the retainer shaft 12 corresponds to the output-side pivoting member 63 of the third embodiment. In this second embodiment, the looper-side link body 131 and the connecting link body 132 form the bent state to thereby cause misalignment and absorb the pivoting force of the looper-side link body 131. Thus, the first embodiment and the second embodiment having different specific configurations still share at least a part of the same operational effects to be produced by the third embodiment.

[0048] The third embodiment is specifically configured as shown in Fig. 16 to Fig. 19. The fourth member 64 and the fifth member 65 in particular are formed significantly differently from those of the first embodiment (see Fig. 2), but have functions not significantly different therefrom. The input-side pivoting member 61 includes a first input arm 612 and the first output arm 613 (with their pivoting motion indicated by a curved arrow in Fig. 19), which extend from a first pivot center 61c in radially different directions, and is configured to allow the driving force that is input from the first input arm 612 by the movement of the transmission rod 7 to be output from the first output arm 613 as a pivoting force about the first pivot center 61c. The output-side pivoting member 63 includes a second input arm 631 and a second output arm 632 (with their pivoting motion indicated by a curved arrow in Fig. 19), which both extend from a second pivot center 63c in radially different directions, and is configured to allow the driving force that is input from the second input arm 631 to be output from the second output arm 632 as a pivoting force about the second pivot center 63c.

[0049] The displacement transmission mechanism 67 includes: the groove part 671 disposed in the second input arm 631 and extending in parallel with a radial direction passing the second pivot center 63c; and a sliding member 672 disposed on the first output arm 613 and configured to move along the groove part 671. The groove part 671 has a rectangular shape in cross section, the shape being constant in a direction in which the groove part 671 extends. The sliding member 672 includes a shaft part 6721 integrally provided on the first output arm 613 and a sliding block 6722 rotatably arranged around the shaft part 6721. The shaft part 6721 has a round rod shape, and the sliding block 6722 has a rectangular parallelepiped shape with a hole at the center thereof in which the shaft part 6721 is placed (the hole illustrated has a through hole, but the hole can be a bottomed hole). The sliding block 6722 is configured to move along the direction in which the groove part 671 extends while being in abutting contact with an inner surface of the groove part 671. That is, the sliding member 672 slides relative to the groove part 671.

[0050] The displacement transmission mechanism 67 formed in combination of the groove part 671 and the sliding member 672 allows, as shown in Fig. 19, the input-side pivoting member 61 and the output-side pivoting member 63 to pivotally move while a linear distance between the first pivot center 61c of the input-side pivoting member 61 and the second pivot center 63c of the output-side pivoting member 63 remains constant. That is, the displacement transmission mechanism 67 is configured to transmit displacement from the input-side pivoting member 61 to the output-side pivoting member 63 while allowing misalignment between the input-side pivoting member 61 and the output-side pivoting member 63. The change involving this misalignment enables the amount of displacement transmission to be temporarily reduced. The change in position of the moving retainer 5 can be made in the same manner as shown in Fig. 12.

[0051] The configuration of the displacement transmission mechanism 67 is not limited to the aforementioned configuration in terms of the relationship between the input-side pivoting member 61 and the output-side pivoting member 63. The portions where the groove part 671 and the sliding member 672 are disposed can be opposite to the portions in the configuration described above. That is, the configuration can be such that the displacement transmission mechanism 67 is disposed on the first output arm 613 or the second input arm 631, and includes: the groove part 671 extending in parallel with the radial direction passing the first pivot center 61c or the second pivot center 63c; and the sliding member 672 disposed on the second input arm 631 or the first output arm 613 and configured to move along the groove part 671.

[0052] The configurations and operational effects of the aforementioned embodiments will be summarized below. Provided in the aforementioned embodiments is a sewing machine 1 including: a needle 3 configured to hold a needle thread La and move up and down through a stitch plate 21; a looper 4 configured to hold a looper thread Lb and entangle the looper thread Lb with the needle thread La by reciprocally moving within a space below the stitch plate 21; a retainer 5 configured to reciprocally move within the space below the stitch plate 21 to capture the looper thread Lb; and a retainer motion mechanism 6 configured to change a motion state of the retainer 5 while transmitting driving force from a driving source to the retainer 5, in which the retainer motion mechanism 6 is configured to allow the retainer 5 to reciprocally move at a lower speed within a specific position range in the space below the stitch plate 21 for a specific period of time than speeds before and after the specific period of time to keep the retainer 5 capturing the looper thread Lb.

[0053] According to this configuration, the retainer 5 is caused to reciprocally move by the retainer motion mechanism 6 at a lower speed within the specific position range in the space below the stitch plate 21 for the specific period of time than the speeds before and after the specific period of time, to thereby keep the retainer 5 capturing the looper thread Lb. As compared with the configuration that the retainer 5 is not caused to move at a low speed, the above configuration that the retainer 5 moves at a lower speed during low-speed movement can achieve a longer period of time for which the retainer 5 holds the looper thread Lb, and thus eliminates the necessity of increasing a range within which the retainer 5 reciprocally moves. The "low-speed movement" includes the case where the speed is 0 (a stopped state). The above definition can be paraphrased by separating the case where the speed is 0 to read: "the retainer motion mechanism 6 is configured to allow the retainer 5 to reciprocally move at a lower speed or to wait at a speed of 0 within a specific position range in the space below the stitch plate 21 for a specific period of time than speeds before and after the specific period of time".

[0054] The configuration can be such that the specific position range within which the retainer 5 is caused to move at the low speed by the retainer motion mechanism 6 is a range between a returning position at which the retainer 5 reverses a moving direction from a forward direction to a backward direction and a position close to the returning position and away in the backward direction from the returning position.

[0055] The configuration can be such that the retainer motion mechanism 6 is configured to allow, within the specific position range, the retainer 5 to once move backward from the returning position, thereafter move forward to the returning position again, and then further move backward.

[0056] According to these configurations, the retainer 5 repeatedly moves forward and backward at a low speed near the returning position. Thus, the configuration of the retainer motion mechanism 6 can be simplified as compared with the configuration that the retainer 5 completely stops for the specific period of time. The above "complete stoppage for the specific period of time" does not include any instantaneous stoppage that occurs when the retainer 5 reverses its moving direction.

[0057] The configuration can be such that the retainer motion mechanism 6 includes a link mechanism 6 formed of two link units 62 combined together; when reciprocating motion is input, the link mechanism 6 is configured to change repeatedly in all or part of a range between a linear state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units 62 are arranged linearly and a bent state where the straight lines are arranged to form a bent shape; and the retainer 5 is configured to keep capturing the looper thread Lb at least while the link mechanism 6 is released from the bent state to a point at which the state changes, and then begins being bent again.

[0058] This configuration allows the retainer 5 to reciprocally move within a small distance during the period for which the link mechanism 6 is in the linear state or during the periods before and after the point at which the bent state of the link mechanism 6 changes, and thus enables the retainer 5 to move at a lower speed than the speeds before and after the bent state changes. Thus, the link mechanism 6 can achieve the low-speed movement.

[0059] The configuration can be such that the retainer motion mechanism includes a link mechanism 6 formed of two link units 61 combined together; when reciprocating motion is input, the link mechanism 6 is configured to change repeatedly into a proximally bent state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units 61 are arranged to form a bent shape in one direction, a linear state where the straight lines are arranged linearly, and a distally bent state where the straight lines are arranged to form a bent shape in an other direction, wherein a bent point between the two link units 61 in the proximally bent state is closer to the bent point in the linear state than the bent point in the distally bent state is to the bent point in the linear state, and the retainer 5 is configured to keep capturing the looper thread Lb at least while the link mechanism 6 is brought from the linear state back into the linear state again through the proximally bent state.

[0060] This configuration enables the retainer 5 to reciprocally move within a small distance during the period at which the link mechanism 6 is brought from the linear state back into the linear state again through the proximally bent state, and thus enables the retainer 5 to move at a lower speed than the speeds before and after the period. Thus, the link mechanism 6 can achieve the low-speed movement.

[0061] The configuration can be such that the retainer motion mechanism 6 includes: an input-side pivoting member 61 disposed on an input side and configured to pivotally move within a specific range; an output-side pivoting member 63 disposed on an output side and configured to pivotally move within a specific range; and a displacement transmission mechanism 67 configured to transmit displacement from the input-side pivoting member 61 to the output-side pivoting member 63, and the displacement transmission mechanism 67 is configured to temporarily reduce an amount of displacement transmitted from the input-side pivoting member 61 to the output-side pivoting member 63, depending on an angle between a tangential component of a pivotal displacement of the input-side pivoting member 61 and a tangential component of a pivotal displacement of the output-side pivoting member 63.

[0062] This configuration enables the retainer 5 to achieve the low-speed movement depending on the angle between the tangential component of the pivotal displacement of the input-side pivoting member 61 and the tangential component of the pivotal displacement of the output-side pivoting member 63.

[0063] The configuration can be such that the input-side pivoting member 61 includes a first input arm 612 and a first output arm 613, which extend from a first pivoting center 61c in different radial directions, and driving force that is input from the first input arm 612 is output from the first output arm 613 as pivoting force about the first pivoting center 61c, the output-side pivoting member 63 includes a second input arm 631 and a second output arm 632, which extend from a second pivoting center 63c in different radial directions, and driving force that is input from the second input arm 631 is output from the second output arm 632 as pivoting force about the second pivoting center 63c, and the displacement transmission mechanism 67 is disposed on the first output arm 612 or the second input arm 632, and includes: a groove part 671 extending in parallel with a radial direction passing the first pivoting center 61c or the second pivoting center 63c; and a sliding member 672 disposed on the second input arm 632 or the first output arm 612 and configured to move along the groove part 671.

[0064] This configuration enables the retainer 5 to move at a low speed by combination of the groove part 671 and the sliding member 672.

[0065] According to the aforementioned embodiments, the retainer 5 can hold the looper thread Lb for a longer period of time than the configuration that the retainer 5 does not move at different speeds, and can thus eliminate the necessity of increasing the range in which the retainer 5 reciprocally moves. Thus, the period of time for which the retainer 5 holds the looper thread Lb can be prolonged without increasing the stroke of the reciprocally moving retainer 5, as a result of which it is possible to produce the effect that stitches with the looper thread Lb formed to have a desired size are achieved without necessity of setting a large stroke of the reciprocally moving retainer 5.

REFERENCE SIGNS LIST

[0066] 

1: Sewing machine

2: Cylinder

21: Stitch plate

3: Needle

4: Looper

5: Retainer

6: Retainer motion mechanism (first and third embodiments), link mechanism (first embodiment)

61: Link unit (first embodiment), first member (first embodiment), input-side pivoting member (third embodiment)

61c: First pivot center

612: First input arm

613: First output arm

62: Link unit, second member (first embodiment)

63: Third member (first embodiment), output-side pivoting member (third embodiment)

63c: Second pivot center

631: Second input arm

632: Second output arm

67: Displacement transmission mechanism (third embodiment)

671: Groove part

672: Sliding member

13: Retainer motion mechanism (second embodiment), link mechanism (second embodiment)

131: Link unit (second embodiment), looper-side link body (second embodiment)

132: Link unit (second embodiment), connecting link body (second embodiment)

La: Needle thread

Lb: Looper thread

OP: Side directed to operator

Claims

1. A sewing machine comprising:

a needle configured to hold a needle thread and move up and down through a stitch plate;

a looper configured to hold a looper thread and entangle the looper thread with the needle thread by reciprocally moving within a space below the stitch plate;

a retainer configured to reciprocally move within the space below the stitch plate to capture the looper thread; and

a retainer motion mechanism configured to change a motion state of the retainer while transmitting driving force from a driving source to the retainer, wherein

the retainer motion mechanism is configured to allow the retainer to reciprocally move at a lower speed within a specific position range in the space below the stitch plate for a specific period of time than speeds before and after the specific period of time to keep the retainer capturing the looper thread.

2. The sewing machine according to claim 1, wherein the specific position range within which the retainer is caused to move at the low speed by the retainer motion mechanism is a range between a returning position at which the retainer reverses a moving direction from a forward direction to a backward direction and a position close to the returning position and away in the backward direction from the returning position.

3. The sewing machine according to claim 2, wherein the retainer motion mechanism is configured to allow, within the specific position range, the retainer to once move backward from the returning position, thereafter move forward to the returning position again, and then further move backward.

4. The sewing machine according to claim 1, wherein the retainer motion mechanism comprises a link mechanism formed of two link units combined together,

when reciprocating motion is input, the link mechanism is configured to change repeatedly in all or part of a range between a linear state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units are arranged linearly and a bent state where the straight lines are arranged to form a bent shape, and

the retainer is configured to keep capturing the looper thread at least while the link mechanism is released from the bent state to a point at which the state changes, and then begins being bent again.

5. The sewing machine according to claim 1, wherein the retainer motion mechanism comprises a link mechanism formed of two link units combined together,

when reciprocating motion is input, the link mechanism is configured to change repeatedly into a proximally bent state where straight lines each connecting an input-side connecting point and an output-side connecting point of each of the two link units are arranged to form a bent shape in one direction, a linear state where the straight lines are arranged linearly, and a distally bent state where the straight lines are arranged to form a bent shape in an other direction, wherein a bent point between the two link units in the proximally bent state is closer to the bent point in the linear state than the bent point in the distally bent state is to the bent point in the linear state, and

the retainer is configured to keep capturing the looper thread at least while the link mechanism is brought from the linear state back into the linear state again through the proximally bent state.

6. The sewing machine according to claim 1, wherein the retainer motion mechanism comprises: an input-side pivoting member disposed on an input side and configured to pivotally move within a specific range; an output-side pivoting member disposed on an output side and configured to pivotally move within a specific range; and a displacement transmission mechanism configured to transmit displacement from the input-side pivoting member to the output-side pivoting member, and
the displacement transmission mechanism is configured to temporarily reduce an amount of displacement transmitted from the input-side pivoting member to the output-side pivoting member, depending on an angle between a tangential component of a pivotal displacement of the input-side pivoting member and a tangential component of a pivotal displacement of the output-side pivoting member.

7. The sewing machine according to claim 6, wherein

the input-side pivoting member comprises a first input arm and a first output arm, which extend from a first pivoting center in different radial directions, and driving force that is input from the first input arm is output from the first output arm as pivoting force about the first pivoting center,

the output-side pivoting member comprises a second input arm and a second output arm, which extend from a second pivoting center in different radial directions, and driving force that is input from the second input arm is output from the second output arm as pivoting force about the second pivoting center, and

the displacement transmission mechanism is disposed on the first output arm or the second input arm, and comprises: a groove part extending in parallel with a radial direction passing the first pivoting center or the second pivoting center; and a sliding member disposed on the second input arm or the first output arm and configured to move along the groove part.

Drawing