Buttonholing machine

Abstract

 The invention relates to a buttonholing machine (10). The buttonholing machine (10) includes a needle bar turning base which is arranged inside an arm portion (2c) of a frame (2), and a looper base (47) and a turning mechanism (60) which are arranged inside a bed portion (2a). The turning mechanism (60) includes a turning motor (61) which serves as a turning drive source, a driving pulley (62) coupled to the turning motor (61), a first driven pulley (63) coupled to the looper base (47), a transmission shaft (64) which transmits a rotational force to the needle bar turning base inside the arm portion (2c) from the inside of the bed portion (2a), a second driven pulley (65) coupled to the transmission shaft (64), and a timing belt (66) which transmits the rotational force from the driving pulley (62) to each of the first and second driven pulleys (63, 65). A rotation ratio of two of the driving pulley (62), the first driven pulley (63), and the second driven pulley (65) is other than 1:1. An origin detecting means (68, 69) for detecting an origin position of the turning motor (61) is provided on each of said two pulleys.

Description

[0001] The invention relates to a buttonholing machine having a function of turning a needle bar and a looper.

[0002] A buttonholing machine includes a turning mechanism which synchronously turns a needle bar, which can perform needle swing, and a looper base, on which a looper is mounted, by using a turning motor. For example, when eyelet buttonhole sewing is performed, the buttonholing machine can turn the needle bar and the looper while performing needle swing in an eyelet hole portion of an end of a buttonhole, thereby radially forming needle swing stitches.

[0003] When performing the eyelet buttonhole sewing, the buttonholing machine can perform the turning of the needle bar and the looper also at the other end of the buttonhole opposite the eyelet hole portion, thereby radially forming stitches smaller than those on the eyelet hole side to perform round bar tacking (see, e.g., Fig. 16 of JP2004-008519A).

[0004] The conventional buttonholing machine includes a needle bar turning base which is rotatable while supporting the needle bar so as to allow the needle swing, a looper base which is rotatable while supporting the looper, a turning motor serving as a turning drive source, a driving pulley provided on the turning motor, a first driven pulley which transmits the rotation to the looper base, and a second driven pulley which transmits the rotation to the needle bar turning base. The needle bar turning base and the looper base are synchronously turned via a timing belt.

[0005] Meanwhile, when the round bar tacking is performed while performing eyelet buttonhole sewing as described above, the needle bar turning base and the looper base make a turn of 180° at the eyelet portion and make an additional turn of 180° at the round bar tacking portion. Thus, a turn of 360° in total is performed.

[0006] On the other hand, in order to make an extra turn of the needle bar turning base and the looper base at the round bar tacking portion so as to overlap the stitches of a stitching start end and a stitching finishing end in a sewn product, it is necessary to turn the needle bar turning base and the looper base 360° or more.

[0007] In the conventional buttonholing machine described above, the transmission ratio of the driving pulley and a driven pulley is set to 1:1. Thus, in order to turn the needle bar turning base and the looper base 360° or more, the turning motor also needs to rotate 360° or more. However, since the angle control of the turning motor is executed based on an origin position of 0°, which is obtained by an origin sensor provided at a predetermined origin position of the driving pulley, 0° and 360° cannot be distinguished from each other. Thus, there has been a problem in that the driving range of the turning motor cannot be made 360° or more.

[0008] In order to solve the problem described above, it can be considered to set the rotation ratio of the driving pulley and the driven pulley so as to increase speed, so that the rotation of the driving pulley can be made less than 360°. However, in the buttonholing machine, there also exists a situation where the turning speed is increased to enhance sewing productivity. If the transmission ratio is set so as to increase speed, the influence of inertia becomes great particularly in a case where the turning speed is increased to enhance productivity. This adversely affects the engaging operations of the sewing needle and the looper at the start and the end of stitching. Thus, it has been difficult to increase the transmission ratio.

[0009] In addition, the turning operation at both ends of a buttonhole is also performed in sewing methods other than the eyelet buttonhole sewing, and the problems described above occurs not only in the eyelet buttonhole stitching but also, for example, in an circular eyelet stitching.

[0010] The ratio of 1:1 as the transmission ratio of the driving pulley and the driven pulley is merely an example, and the transmission ratio may be set to increase speed as long as it is within a range in which the influence of inertia is permissible. That is, the transmission ratio of the driving pulley and the driven pulley need not be limited to 1:1. In other words, the problem of the conventional sewing machine is that the turning motor is driven only within a range of less than 360°.

[0011] It is object of the present invention is to allow a turning motor to rotate 360° or more, thereby allowing a turning mechanism to rotate 360° or more.

[0012] According to a first aspect of the invention, a buttonholing machine includes: a needle bar which holds a sewing needle and performs a needle swing; a needle bar turning base on which the needle bar is supported to pivot the needle bar; a looper which catches an upper thread, which is passed through the sewing needle, to interlace the upper thread and a lower thread; a looper base on which the looper is swingably supported; and a turning mechanism which synchronously turns the needle bar turning base and the looper base. The needle bar turning base is arranged inside an arm portion of a frame of the buttonholing machine. The looper base and the turning mechanism are arranged inside a bed portion of the frame. The turning mechanism includes: a turning motor which serves as a turning drive source; a driving pulley coupled to the turning motor; a first driven pulley coupled to the looper base; a transmission shaft which transmits a rotational force to the needle bar turning base inside the arm portion from the inside of the bed portion; a second driven pulley coupled to the transmission shaft; and a timing belt which transmits the rotational force from the driving pulley to each of the first and second driven pulleys. A rotation ratio of two of the driving pulley, the first driven pulley, and the second driven pulley is other than 1:1. An origin detecting means for detecting an origin position of the turning motor is provided on each of said two pulleys.

[0013] According to a second aspect of the invention, a rotation ratio of the driving pulley and the first driven pulley is 1:1.

[0014] According to a third aspect of the invention, a regulating member is provided on the timing belt to limit a rotational range of the turning motor, and the turning motor is rotatable within a range in a forward rotating direction from the origin position and a range in a backward rotating direction from the origin position.

[0015] According to a fourth aspect of the invention, the origin detecting means includes: a first rotation detecting plate mounted on one of said two pulleys; a second rotation detecting plate mounted on the other of said two pulleys; a first sensor which detects a rotational state of the first rotation detecting plate; and a second sensor which detects a rotational state of the second rotation detecting plate. The buttonholing machine further includes a control means which controls a rotating direction of the turning motor based on detection outputs from the first sensor and the second sensor, and which returns the turning motor to the origin position.

[0016] According to a fifth aspect of the invention, respective detection parts of the first rotation detecting plate and the second rotation detecting plate are configured such that different rotational angles of the turning motor are detectable.

[0017] According to a sixth aspect the invention, one of the first rotation detecting plate and the second rotation detecting plate has a detection width based on which a rotational range in the backward rotating direction from the origin position is detectable.

[0018] According to the first aspect of the invention, with respect to each of the two pulleys (for example, a combination of the driving pulley and the second driven pulley or a combination of the first driven pulley and the second driven pulley) whose rotation ratio is not 1:1, the origin detecting means for detecting the origin position of the turning motor is provided. Thus, even in a case in which the turning motor and the driving pulley have made a rotation of 360° or more while the origin position of the turning motor being a position which is simultaneously indicated by the two origin detecting means, the two origin detecting means do not simultaneously indicate an origin at the position of 360°. Accordingly, it is possible to distinguish between 0° and 360° of the turning motor.

[0019] The rotation ratio of the driving pulley and the first driven pulley may not be set to 1:1 as long as it is within a range in which the influence of inertia is permissible. That is, the present invention enables the turning motor to be rotated 360° or more, and the turning angles of the needle bar turning base and the looper base can be enlarged in accordance with the transmission ratio.

[0020] According to the second aspect of the invention, since the rotation ratio of the driving pulley and the first driven pulley is 1:1, the rotational angle of the turning motor and the turning angles of the needle bar turning base and the looper base can be made to coincide with each other. Thus, control can be simplified, and the influence of inertia can be further reduced.

[0021] According to the third aspect of the invention, since the regulating member which limits the rotational range of the turning motor is provided, a thread is prevented from being entangled with the needle bar, the looper, etc. due to the excessive rotation of the turning motor.

[0022] According to the fourth aspect of the invention, since the first sensor and the second sensor which respectively detect the rotational states of the first rotation detecting plate and the second rotation detecting plate are provided, and the turning motor is returned to the origin position based on the detection outputs from the sensors, the turning motor can be smoothly returned to the origin.

[0023] According to the fifth aspect of the invention, the respective detection parts of the first rotation detecting plate and the second rotation detecting plate are configured so as to detect different rotational angles of the turning motor. Thus, the turning motor can be easily returned to the origin position.

[0024] According to the sixth aspect of the invention, since one of the first rotation detecting plate and the second rotation detecting plate has the detection width based on which the rotation range in the backward rotating direction from the origin can be detected, the turning motor can be easily returned to the origin position.

[0025] Other aspects and advantages of the present invention will be apparent from the following description, the drawings and the claims.

[0026] The following description of a preferred embodiment of the invention serves to explain the invention in greater detail in conjunction with the drawings. These show:

Fig. 1:

a perspective view of a buttonholing machine according to an embodiment of the invention, illustrating a state in which a bottom cover is removed;

Fig. 2:

a bottom view of the buttonholing machine without the bottom cover;

Fig. 3:

an explanatory view of a turning mechanism;

Fig. 4:

a perspective view of a configuration inside a bed portion;

Fig. 5:

a block diagram of a control configuration of the buttonholing machine; and

Fig. 6:

an explanatory diagram illustrating an example of operations for returning a turning motor to an origin position.

[0027] Overall Configuration of Buttonholing Machine

[0028] As shown in Fig. 1, a buttonholing machine 10 includes a frame 2 having a bed portion 2a which is located in a lower part of the whole sewing machine and is formed in the shape of a substantially rectangular box, a vertical drum portion 2b which is provided at one end of the bed portion 2a, and an arm portion 2c which is provided so as to extend from the vertical drum portion 2b in the same direction as the bed portion 2a. In the following description, a direction in which the vertical drum portion 2b is set upright is defined as a Z-axis direction, a longitudinal direction of the bed portion 2a and the arm portion 2c which is orthogonal to the Z-axis direction is defined as a Y-axis direction, and a direction orthogonal to both the Y-axis direction and the Z-axis direction is defined as an X-axis direction.

[0029] The buttonholing machine 10 includes a needle bar 12 which holds a sewing needle 11 through which an upper thread passes, a needle bar turning base (not shown) which swingably supports the needle bar 12, an up-and-down movement mechanism (not shown) which moves the needle bar 12 up and down, a swinging mechanism (not shown) which swings the needle bar 12, a looper mechanism 40 which forms overlock stitches, a turning mechanism 60 which turns the needle bar turning base and a looper base 47 of the looper mechanism, a stitching motor 20 serving as a drive source for sewing operation, a cloth feeding mechanism (not shown) which conveys cloth in the X-axis direction and in the Y-axis direction, and a control means which performs control of the respective parts.

[0030] Since the up-and-down movement mechanism, the swinging mechanism, the cloth feeding mechanism, and the looper mechanism have similar configurations as the conventionally known mechanisms, the detailed description thereof are omitted.

[0031] Needle Bar

[0032] The needle bar 12 is supported by a needle bar swinging base (not shown) inside the vicinity of the distal end of the arm portion 2c so as to be movable up and down. The needle bar swinging base is supported by the needle bar turning base so as to be swingable in the X-axis direction. The needle bar turning base is supported so as to be able to turn about the Z-axis direction within the frame. The needle bar turning base supports the needle bar 12 so that the needle bar 12, which is in the state of being at a reference position (a state along the Z-axis direction) which is not inclined, is exactly located at a pivoting center position.

[0033] This enables the needle bar 12 to perform the up-and-down movement operation by the up-and-down movement mechanism, and the swinging operation by the swinging mechanism. In the buttonholing machine 10, a needle swinging direction is set such that the needle bar 12 performs the needle swing in a direction orthogonal to a progression direction (a direction along a buttonhole) of the sewing, whereby needle swing stitches are formed.

[0034] The up-and-down movement mechanism and the swinging mechanism transfer the up-and-down movement and swinging movement to the needle bar 12 by using a crank mechanism from an upper shaft (not shown) whose rotational driving is performed by the stitching motor 20.

[0035] Looper Mechanism

[0036] The looper mechanism 40, as shown in Figs. 2 and 4, includes a grooved cam 42 provided at a lower shaft 21 which is rotationally driven by the stitching motor 20, an eccentric cam 41 provided at the lower shaft 21, a spreader swinging arm 43 to which swinging operation is transferred by the eccentric cam 41, a looper swinging arm 44 which swings in engagement with the grooved cam 42, a spreader driving shaft 45 which is moved up and down by the spreader swinging arm 43, a looper driving shaft 46 which is moved up and down by the looper swinging arm 44, a looper base 47 which is rotatably supported by the frame 2 in a state where the driving shafts 45 and 46 are arranged on a center position, a throatplate 48 which is attached to the upper end of the looper base 47, a left looper 49 and a left spreader 50 which interlaces a lower thread D to an upper thread and performs a double chainstitch, and a right looper and a right spreader (both are not shown in Fig. 4) which perform a single thread chainstitch by the upper thread.

[0037] A cam groove is formed on the front side of the grooved cam 42. A cam roller (not shown) provided in the looper swinging arm 44 engages a cam groove so that swinging is performed on the looper swinging arm 44 at a specified angle by the rotation of the lower shaft 21.

[0038] The eccentric cam 41 enables the pivot of the spreader swinging arm 43 to be reciprocally rotated by the crank mechanism, and enables the spreader swinging arm 43 which is fixed to and connected with the pivot to be swung.

[0039] Both the spreader driving shaft 45 and the looper driving shaft 46 have a cylindrical tubular form, the external diameter of the spreader driving shaft 45 is smaller than the internal diameter of the looper driving shaft 46, and the spreader driving shaft 45 is mounted so as to be inserted into the looper driving shaft 46. A lower thread D is inserted into the spreader driving shaft 45 from a lower end thereof to an upper end thereof, and the lower thread D is guided to the left looper 49 and the left spreader 50 which are provided in an upper part of the looper base 47.

[0040] The spreader driving shaft 45 and the looper driving shaft 46 are arranged at a turning center of the looper base 47 along the Z-axis direction.

[0041] The lower end of the spreader driving shaft 45 is coupled to the spreader swinging arm 43 to give up-and-down movement, whereby the operation required for sewing is transferred to each spreader.

[0042] The lower end of the looper driving shaft 46 is coupled to the looper swinging arm 44 to give up-and-down movement, whereby the operation required for sewing is transferred to each looper.

[0043] The looper base 47 is supported by a frame so as to be turnable around the Z-axis in the vicinity of its lower part, and a looper-side pulley 63 serving as a first driven pulley of the turning mechanism 60 which will be described later is mounted below the supported portion so as to be fixed concentrically with the looper base 47.

[0044] Stitching Motor

[0045] As shown in Fig. 2, the stitching motor 20 is arranged at an end opposite to the needle bar 12 and at the bottom of the bed portion 2a such that an output shaft is parallel to the Y-axis direction.

[0046] The output shaft of the stitching motor 20 is mounted with a motor pulley 22 which gives torque to the lower shaft pulley 24 via a timing belt 23. The lower shaft 21 is rotatably supported along the Y-axis direction at the center of the bottom of the bed portion 2a. A transmission pulley 25 is mounted on the lower shaft 21 adjacent to the lower shaft pulley 24 to transmit torque to the upper shaft (not shown) via the timing belt 26.

[0047] Turning Mechanism

[0048] As shown in Figs. 2 and 3, in the buttonholing machine 10, for example, when overlock sewing is performed on a buttonhole having a shape composed of a straight portion and a droplet-like portion in a straight line like an eyelet hole, it is necessary to perform sewing by turning the needle swing direction while performing the needle swing along the edge of the hole of the droplet-like portion. Further, in addition to the eyelet hole, there is also a case where sewing is performed by turning the needle swing direction at both ends of a normal buttonhole, or a case where a round bar tacking is performed.

[0049] Accordingly, the turning mechanism 60 which turns the needle swing direction, and turns and moves the looper base 47 is provided on the bottom side of the bed portion 2a.

[0050] The turning mechanism 60, as shown in Fig. 2, includes the turning motor 61 that is a stepping motor used as a drive source for the turning operation, a driving pulley 62 which is fixed and mounted on an output shaft 61a of the turning motor 61, a looper-side pulley 63 serving as a first driven pulley which is fixed and mounted on the looper base 47, a needle-bar-side pulley (not shown) which is fixed and mounted on the needle bar turning base, a transmission shaft 64 which is built from the inside of the bed portion 2a to the inside of the arm portion 2c, an intermediate pulley 65 serving as a second driven pulley which is fixed and mounted on a lower end of the transmission shaft 64, a transmission pulley (not shown) which is fixed and mounted on an upper end of the transmission shaft 64, a looper-side timing belt 66 which is stretched over the driving pulley 62, the looper-side pulley 63, and the intermediate pulley 65, a timing belt 77 which is stretched over the transmission pulley and the needle-bar-side pulley, and a tension roller 67 which gives tension to the looper-side timing belt 66.

[0051] A regulating member 70 is fixed and mounted on the stretched timing belt 66. The regulating member 70 includes an extending portion (not shown) which extends in the Z-axis direction (both upper and lower directions), and is arranged between the driving pulley 62 and the looper-side pulley 63. As shown in Figs. 2 and 3, the turning motor 61 rotates from an origin position in a forward rotating direction (clockwise direction) or in a backward rotating direction (counterclockwise direction). Although the regulating member 70 moves with the rotation of the turning motor 61, a motor bracket 71, which serves as a first stopper, and a second stopper 72 are arranged on a movement locus of the extending portion.

[0052] The motor bracket 71 is fixed to a frame to support the turning motor 61 at a predetermined position, and an extending portion of the regulating member 70 which extends downward (upwardly perpendicular to the plane of the sheet) abuts on the motor bracket 71. The second stopper 72 is cylindrical, and is fixed to a frame with screws (not shown), and an upwardly extending portion of the regulating member 70 abuts on the second stopper 72. Fig. 2 shows a state where the turning motor 61 has rotated in the forward rotating direction several times from the origin position. If the turning motor makes a rotation of 365 degrees in the forward rotating direction, the regulating member 70 abuts on the motor bracket 71, and if the turning motor makes a rotation of 140 degrees in the backward rotating direction, the regulating member 70 abuts on the second stopper 72. Thereby, the turning motor 61 is able to rotate within a predetermined range of -140 degrees (the backward rotating direction) to +365 degrees (the forward rotating direction) with the origin position as a basis, and makes two or more rotations to prevent a thread from being entangled in the looper or the needle.

[0053] The turning motor 61 is fixed and mounted on the lower part of the bed portion 2a such that its output shaft is parallel to the Z-axis direction and is directed downward.

[0054] The driving pulley 62 and the looper-side pulley 63 have an external diameter ratio (rotation ratio) of 1:1. The number of teeth of the driving pulley 62 and the number of teeth the looper-side pulley 63 are both 2628. On the other hand, the intermediate pulley 65 has a smaller diameter than the driving pulley 62, and its number of teeth thereof is set to 2426. The external diameter of the intermediate pulley 65 is not particularly limited, and may be greater than that that of the driving pulley 62 so long as multiples of the external diameter of the intermediate pulley 65 does not coincide with the external diameter of the driving pulley 62.

[0055] The external diameter of the transmission pulley which performs simultaneous rotation via the intermediate pulley 65 and the transmission shaft 64 is equal to the external diameter of the intermediate pulley 65. This inhibits the influence of inertia on the intermediate pulley 65 which performs accelerating rotation with respect to the driving pulley 62.

[0056] The external diameter of the needle-bar-side pulley is equal to the external diameter of the driving pulley 62. This enables the needle bar turning base and the looper base 47 to be simultaneously turned at an angle equal to the rotational angle of the turning motor 61.

[0057] An origin detecting means which detects the origin of the turning mechanism 60 includes a first rotation detecting plate 73, a first sensor 68 which detects the rotational state of the first rotation detecting plate, a second rotation detecting plate 74, and a second sensor 69 which detects the rotational state of the second rotation detecting plate.

[0058] The first rotation detecting plate 73 has a main body 73a and a fan-like detection part 73b. The main body 73a is formed with long holes 73ab and 73ab which have a circular arc shape about the driving shaft 61a of the turning motor 61, and is adjusted in position and mounted on the driving pulley 62 with screws 75 and 75 serving as fixing members. The detection part 73b is fan-shaped and is formed so as to protrude from the main body 73a. The detection part 73b protrudes in a horizontal direction from the driving pulley 62, and is formed with a width of 60 degrees about the driving shaft 61a of the turning motor 61.

[0059] The first sensor 68 serving as a proximity sensor is arranged below the detection part 73b of the first rotation detecting plate 73. The first sensor 68 is fixed to a frame, detects the detection part 73b of the first rotation detecting plate 73 to output a detection signal to a CPU 80 serving as a control means, when the driving pulley 62 is at a certain angle.

[0060] The second rotation detecting plate 74 has a main body 74a and a fan-like detection part 74b. The main body 74a is formed with long holes 74ab and 74ab which have a circular arc shape about the transmission shaft 64, and is adjusted in position and mounted on the intermediate pulley 65 with screws 76 and 76 serving as fixing members. The detection part 74b is fan-shaped, and is formed so as to protrude from the main body 74a. The detection part 74b protrudes in the horizontal direction from the intermediate pulley 65, and is formed with a width (detection width) of 167.2 degrees about the transmission shaft 64.

[0061] The second sensor 69 serving as a proximity sensor is arranged below the detection part 74b of the second rotation detecting plate 74. The second sensor 69 is fixed to a frame, detects the detection part 74b of the second rotation detecting plate 74 to output a detection signal to the CPU 80 serving as a control means, when the intermediate pulley 65 is at a certain angle.

[0062] At the origin position of the turning motor 62, the first rotation detecting plate 73 and the second rotation detecting plate 74 are adjusted in position so that the first sensor 68 detects a right end face 73c (a downstream end in the clockwise direction in Figs. 2 and 3) of the detection part of the first rotation detecting plate 73, and the second sensor 69 detects a left end face 74c (an upstream end in the clockwise direction in Figs. 2 and 3) of the detection part of the second rotation detecting plate 74. Thus, the detection signals of the first sensor 68 and the second sensor 69 are reversed on the basis of the origin position.

[0063] The control means performs origin search control so that the main-shaft angle of the turning motor 61 when the first and second sensors 68, 69 simultaneously perform origin detection output is regarded as a motor origin (0°).

[0064] Control Means

[0065] In Fig. 5, a ROM 81 and a RAM 82 are connected to the CPU 80. Further, an operation panel 83, a start switch 84, the first sensor 68, and the second sensor 69 are connected to the CPU via an interface 85. Furthermore, the stitching motor 20 (a servo-motor) is connected to the CPU via an interface 86 and a drive circuit 87. Furthermore, the turning motor 61 (a stepping motor) is connected to the CPU 80 via an interface 88 and a drive circuit 89.

[0066] Origin Search Control

[0067] An example of origin search will be described on the basis of the above configuration, and an origin search method shown in Fig. 6.

[0068] In Fig. 6, the rotational angle of the turning motor 61 is described. With the rotation of the turning motor 61, the regulating member 70 abuts on the first stopper 71 or second stopper 72. Accordingly, the turning motor 61 rotates within a certain range, e.g., -140 degrees (the backward rotating direction) to +365 degrees (the forward rotating direction) from the origin position. This range is divided into six sections A, B, C, D, E, F in accordance with the output state of sensors. The angle range of respective sections and the output state of the first sensor 68, and the second sensor 69 are as follows.

Section A:	Angle range: -140 degrees to 0 degree (origin)
	First sensor 68: OFF, Second sensor 69: ON
Section B:	Angle range: 0 degree to 60 degrees
	First sensor 68: ON, Second sensor 69: OFF
Section C:	Angle range: 60 degrees to 167.2 degree
	First sensor 68: OFF, Second sensor 69: OFF
Section D:	Angle range: 167.2 degrees to 334.3 degrees
	First sensor 68: OFF, Second sensor 69: ON
Section E:	Angle range: 334.3 degrees to 360 degrees
	First sensor 68: OFF, Second sensor 69: OFF
Section F:	Angle range: 360 degrees to 365 degrees
	First sensor 68: ON, Second sensor 69: OFF

[0069] The CPU 80 executes the origin search control when a main power supply of the sewing machine 10 is turned on. The rotating direction and origin return operation of the turning motor 61 in the respective sections A to F will be described.

[0070] In the section A, the first sensor 68 is OFF, the second sensor 69 is ON, and these detection outputs coincide with those in the section D which will be described later. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, the CPU 80 rotates the turning motor 61 in the forward rotating direction. Then, if the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an ON state and the second sensor 69 is brought into an OFF state), it can be recognized that the rotational angle has not been in the section D but in the section A, and the switching position is the origin O. Thus, the turning motor 61 is stopped and returned to the origin.

[0071] In the section B, the first sensor 68 is ON, the second sensor 69 is OFF, and these detection outputs coincide with those in the section F which will be described later. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, the CPU 80 rotates the turning motor 61 in the backward rotating direction. Then, if the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state), it can be recognized that the rotational angle has not been in the section F but in the section B, and the switching position is the origin O. Thus, the turning motor 61 is stopped and returned to the origin.

[0072] In the section C, the first sensor 68 is OFF, the second sensor 69 is OFF, and these detection outputs coincide with those in the section E which will be described later. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, the CPU 80 rotates the turning motor 61 in the backward rotating direction. Then, since it can be recognized that the rotational angle has not been in the section E but in the section C if the first sensor 68 is first switched to an ON state, the turning motor is further rotated in the backward rotating direction. Then, in the origin position O where the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state), the turning motor 61 is stopped and returned to the origin.

[0073] In the section D, the first sensor 68 is OFF, and the second sensor 69 is ON. As mentioned above, these detection states are the same as those in the section A. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, as mentioned above, the CPU 80 rotates the turning motor 61 in the forward rotating direction. Since it can be recognized that the rotational angle has not been in the section A but in the section D if only the second sensor 69 is first switched to an OFF state, the turning motor is rotated in the backward rotating direction by changing the rotating direction. Then, in the origin position O where the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state), the turning motor 61 is stopped and returned to the origin.

[0074] In the section E, the first sensor 68 is OFF, and the second sensor 69 is OFF. These detection states are the same as those in the section C mentioned above. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, as mentioned above, the CPU 80 rotates the turning motor 61 in the backward rotating direction. Since it can be recognized that the rotational angle has not been in the section C but in the section E if only the second sensor 69 is first switched to an ON state, the turning motor is rotated in the backward rotating direction. Then, in the origin position O where the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state), the turning motor 61 is stopped and returned to the origin.

[0075] In the section F, the first sensor 68 is ON, and the second sensor 69 is OFF. These detection states are the same as those in the section B mentioned above. If the detection outputs of the first and second sensors 68, 69 are obtained when the main power supply is ON, as mentioned above, the CPU 80 rotates the turning motor 61 in the backward rotating direction. Since it can be recognized that the rotational angle has not been in the section B but in the section F if only the first sensor 68 is first switched to an OFF state, the turning motor is rotated in the backward rotating direction. Then, in the origin position O where the first and second sensors 68, 69 are almost simultaneously switched (if the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state), the turning motor 61 is stopped and returned to the origin.

[0076] As described above, the CPU 80 controls the rotating direction of the turning motor 61 from the detection outputs of the first sensor 68 and the second sensor 69 in the respective sections A to F, and returns the turning motor 61 to the origin position O.

[0077] The control means 80 executes the aforementioned origin search control when the main power supply of the sewing machine 10 is turned on. In the origin search control, the rotational driving of the turning motor 61 is performed, and an origin detection signal output from each of the origin sensors 68, 69 is monitored for every pulse. Simultaneously, when there are origin detection signals output (the first sensor 68 is brought into an ON state and the second sensor 69 is brought into an OFF state if the rotational range is in the section A, and the first sensor 68 is brought into an OFF state and the second sensor 69 is brought into an ON state if the rotational range is in the sections B to F) almost simultaneously from the two origin sensors 68, 69, the output shaft angle of the turning motor 61 is stored as an origin. At this time, since the driving pulley 62 and the intermediate pulley 65 have different diameters, origin detection signals are not output simultaneously from the two origin sensors 68, 69 again unless the turning motor 61 makes a rotation equivalent to the least common multiple of the above diameters. Thus, it is possible to detect a unique origin unless the aforementioned rotation equivalent to the least common multiple is not performed in both the forward rotating direction and the backward rotating direction from a current origin position.

[0078] Additionally, the control means performs the angle control of the turning motor 60 on an open loop basis. That is, after the origin angle of the turning motor 61 is obtained, the control means gives a rotation command equivalent to a pulse number which becomes a target angle to the turning motor 61 on the basis of the origin angle, and executes angle control.

[0079] In the buttonholing machine 10, setting is made so that the origin position of the turning motor 61 and a sewing start angle (a direction in which a direction in which needle swing is performed is parallel to the X-axis direction) coincide with each other.

[0080] On this premise, for example, when eyelet buttonhole sewing is controlled by the control means, on one side of a buttonhole formed along the Y-axis direction, sewing is performed along the Y-axis direction at predetermined feed pitches while needle swing sewing is performed with the turning motor 61 being kept at the origin. The turning motor 61 is controlled around an eyelet hole formed at the end of the buttonhole so as to make a turn of 180°. At this time, as for the rotational speed of the turning motor 61, the turning motor is driven at a speed at which the turning motor is rotatable such that an angle obtained by dividing 180° by the number of stitches set in a turning section matches the rotational cycle of the stitching motor 20.

[0081] On the opposite side of the buttonhole, sewing is performed in the opposite direction along the Y-axis direction at predetermined feed pitches while needle swing sewing is performed with the turning motor 61 being kept at 180°. Moreover, in the case where the setting of round bar tacking is performed, the turning motor 61 is controlled at the opposite end of the eyelet hole of the buttonhole so as to make a turn up to 360°. The rotational speed of the turning motor 61 at this time is also determined according to the number of stitches set and the rotational speed of the stitching motor 20. The turning motor may make a turn up to 360°+α, and sewing which overlaps with a stitching start position can be performed.

[0082] After the completion of sewing, the control means performs the control of returning the turning motor 61 to the origin. At this time, the origin detection is performed by the two origin sensors 68, 69 while the turning motor 61 is rotated in a direction opposite to the rotating direction during sewing. That is, simultaneous origin detection signal output reception is monitored while backward rotation is performed, and motor driving is stopped using an angle at which the simultaneous detection has been performed as the origin of the turning motor 61. In addition, as mentioned above, even in a case where turning by 360° or more has been performed during sewing, the process by the two origin sensors 68, 69 of setting the simultaneous detection position as an origin is performed. Thus, it is possible to make a distinction between 0° and 360°, and 360° or more turning become possible during sewing.

[0083] Additionally, the above embodiment is configured such that the turning motor 61 can be rotated in the backward rotating direction and the forward rotating direction on the basis of the origin position. For this reason, after the turning motor is first rotated by several tens of degrees in the backward rotating direction from the origin position and a portion of a left bar tacking portion is sewn, sewing can be performed in order of a right bar tacking portion, a right sewing portion, an eyelet portion, a left sewing portion, and a left bar tacking portion. Thus, an overlapping portion of the bar tacking portions is beautiful.

[0084] Advantageous Effect of Embodiment

[0085] As described above, in the buttonholing machine 10, the first and second origin sensors 68, 69 are respectively disposed in the two pulleys 62 and 65 whose rotation ratio is a ratio other than 1:1. Thus, even in a case where the turning motor 61 and the driving pulley 62 have made a rotation of 360° or more in a case where an origin position simultaneously indicated by the two origin sensors 68, 69 is used as the origin of the turning motor 62, the two origin detection sensors do not indicate an origin simultaneously at the position of 360°. Accordingly, it is possible to distinguish between 0° and 360° of the turning motor. Additionally, as mentioned above, the distinction between the angles of integral multiples of 0° and 360° is also possible within a range of a least common multiple of the external diameter of the driving pulley 62 and the transmission pulley 65 × ±360°.

[0086] Further, since the rotation ratio of the driving pulley 62 and the looper-side pulley 63 is set to 1:1, the rotational angle of the turning motor 61, and the turning angles of the needle bar turning base and the looper base 47 can be made to coincide with each other, control can be simplified, and the influence of inertia can be further reduced.

[0087] Furthermore, since the regulating member 70 which limits the rotational range of the turning motor 61 is provided, a thread is prevented from being entangled in the needle bar, the looper, etc. due to the excessive rotation of the turning motor 61.

[0088] Furthermore, since the first sensor 68 and the second sensor 69 which respectively detect the rotational states of the first rotation detecting plate 73 and the second rotation detecting plate 74 are provided and the turning motor is returned to the origin position from both the sensor detection outputs, the turning motor can be quickly returned to the origin.

[0089] Furthermore, since the detection part of each of the first rotation detecting plate 73 and the second rotation detecting plate 74 is formed so as to detect different rotational angles of the turning motor 61, the turning motor 61 can be easily returned to the origin position. Additionally, since one of the first rotation detecting plate 73 and the second rotation detecting plate 74 has a detection width such that the rotational range in the backward rotating direction from the origin can be detected, the turning motor 61 can be easily returned to the origin position.

[0090] In the above buttonholing machine 10, the external diameter ratio (the rotation ratio) of the driving pulley 62 and the looper-side pulley 63 (a first driven pulley) is set to 1:1. However, the rotation ratio may be a ratio other than 1:1 within a range in which the influence of inertia is in a permissible range. In that case, the two origin sensors 68, 69 may be provided to the driving pulley 62 and the looper-side pulley 63.

[0091] Further, instead of the intermediate pulley 65, the second origin detection sensor 69 may be provided to the transmission pulley having the same external diameter as the intermediate pulley 65.

Claims

1. A buttonholing machine (10) comprising:

a needle bar (12) which holds a sewing needle (11) and performs a needle swing;

a needle bar turning base on which the needle bar (12) is supported to pivot the needle bar;

a looper (49) which catches an upper thread, which is passed through the sewing needle, to interlace the upper thread and a lower thread (D);

a looper base (47) on which the looper (49) is swingably supported; and

a turning mechanism (60) which synchronously turns the needle bar turning base and the looper base (47),

wherein the needle bar turning base is arranged inside an arm portion (2c) of a frame (2) of the buttonholing machine (10), and
the looper base (47) and the turning mechanism (60) are arranged inside a bed portion (2a) of the frame (2),
characterized in that the turning mechanism (60) comprises:

a turning motor (61) which serves as a turning drive source;

a driving pulley (62) coupled to the turning motor (61);

a first driven pulley (63) coupled to the looper base (47);

a transmission shaft (64) which transmits a rotational force to the needle bar turning base inside the arm portion (2c) from the inside of the bed portion (2a);

a second driven pulley (65) coupled to the transmission shaft (64); and

a timing belt (66) which transmits the rotational force from the driving pulley (62) to each of the first and second driven pulleys (63, 65),

wherein a rotation ratio of two of the driving pulley (62), the first driven pulley (63), and the second driven pulley (65) is other than 1:1, and
an origin detecting means (68, 69) for detecting an origin position of the turning motor (61) is provided on each of said two pulleys.

2. The buttonholing machine (10) according to claim 1, wherein a rotation ratio of the driving pulley (62) and the first driven pulley (63) is 1:1.

3. The buttonholing machine (10) according to claim 1 or 2, wherein a regulating member (70) is provided on the timing belt (66) to limit a rotational range of the turning motor (61), and the turning motor (61) is rotatable within a range in a forward rotating direction from the origin position and a range in a backward rotating direction from the origin position.

4. The buttonholing machine (10) according to any one of claims 1 to 3, further comprising a control means (80),
wherein the origin detecting means (68, 69) comprises:

a first rotation detecting plate (73) mounted on one of said two pulleys;

a second rotation detecting plate (74) mounted on the other of said two pulleys;

a first sensor (68) which detects a rotational state of the first rotation detecting plate (73); and

a second sensor (69) which detects a rotational state of the second rotation detecting plate (74),

wherein the control means (80) controls a rotating direction of the turning motor (61) based on detection outputs from the first sensor (68) and the second sensor (69), and returns the turning motor (61) to the origin position.

5. The buttonholing machine (10) according to claim 4, wherein respective detection parts (73b, 74b) of the first rotation detecting plate (73) and the second rotation detecting plate (74) are configured such that different rotational angles of the turning motor (61) are detectable.

6. The buttonholing machine (10) according to claim 4 or 5, wherein one of the first rotation detecting plate (73) and the second rotation detecting plate (74) has a detection width based on which a rotational range in the backward rotating direction from the origin position is detectable.

Drawing