Apparatus for disconnecting a needle bar and threading on a sewing machine

In a device for disconnecting a needle bar from a needle-bar connecting stud on a sewing machine, a drive source drives a moving board. The moving board lowers a predetermined distance until a threading hook goes through an eye in a needle. A disconnecting member rotates a clutch click and disconnects the clutch click from a needle-bar connecting stud. The needle bar thus disengages from the needle-bar connecting stud. The moving board further lowers, an actuating rod lowers, the actuating rod in turn lowers a threading rod, the threading rod further rotates, and the threading hook goes through the eye. The needle is thus threaded. The disconnecting operation and the threading operation are carried out by using the drive source in common. Consequently, the device is simple in structure and compact in size. Since the needle bar only rises to disengage from the needle-bar connecting stud, no scratches are given on the fabric. The sewing machine can effectively execute pattern-sewing, basting and other operations.

BACKGROUND OF THE INVENTION 
This invention relates to a needle-bar disconnecting device on a sewing 
machine for connecting and disconnecting a needle bar to and from a 
needle-bar connecting stud moving vertically synchronously with the 
rotation of an arm shaft. 
When fabric is embroidered, basted, or sewn, the movement of the needle bar 
is stopped temporarily and fabric is fed without being sewn. For that 
purpose, a device for stopping the movement of the needle bar is used. A 
device for stopping the rotation of an arm shaft is known. A device for 
stopping a counterbalancing crank with a clutch provided between the arm 
shaft and the counterbalancing crank is also known. However, the inertia 
of stopped components of these known devices is so large that at the time 
of restart a large load is applied to the clutch and other components. To 
solve this problem, Japan Published Examined Utility Model Application No. 
S61-25752 and Japan Published Unexamined Patent Application No. S59-194792 
are proposed. In these related-art references, a clutch is provided 
between a needle-bar connecting stud and a needle bar, and only the needle 
bar is stopped. Another related-art device proposed in Japan Published 
Unexamined Utility Model Application No. S62-139472 is applied to a zigzag 
sewing machine. In this device a needle bar is rotated in a width larger 
than that of a zigzag form sewn. The rotation of the needle bar actuates a 
clutch for disconnecting the needle bar from a needle bar connecting stud. 
Further, threading the needle of a sewing machine presents related 
problems. To facilitate threading, various threading devices are proposed. 
For example, in Japan Published Unexamined Patent Application No. 
H1-113092, a spring exerts an upward force on an actuating rod. The 
actuating rod is lowered by an air cylinder. A threading rod interlocks 
with the actuating rod, lowers, and rotates. A threading hook thus goes 
through an eye in a needle and catches a thread. Subsequently, when the 
threading hook is drawn from the eye, thread is also drawn and the needle 
is threaded. 
In the related art, some sewing machines are provided with both the 
needle-bar disconnecting device and the threading device. However, when 
these related-art devices are both used in a sewing machine, a drive 
source for actuating the clutch and disconnecting the needle bar must be 
mounted separately from the drive source required for threading. 
Therefore, the devices occupy excessive space in the sewing machine. At 
the same time, since the devices must be controlled separately, a 
complicated control device is required. 
The needle bar is disconnected from the needle-bar connecting stud through 
a pulse motor, and the pulse motor can also be used for the rotating of 
the needle bar. However, every time the needle bar disengages from the 
needle-bar connecting stud, the needle bar laterally moves. The resulting 
problem is that the relative position among a thread guide, an eye in a 
needle, and stitches causes variances in thread amount and tension. At the 
same time, the lateral movement of the needle bar may mar the fabric. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide a device with a simple structure 
that can securely disconnect a needle bar from a needle-bar connecting 
stud and thread a needle. 
To attain this and other objects, this invention provides a device for 
disconnecting a needle bar from a needle-bar connecting stud and threading 
a needle on a sewing machine. The sewing machine comprises a needle, a 
vertically moving needle bar having the needle on its lower end, a spring 
for exerting an upward force on the needle bar, a rotating arm shaft, a 
needle-bar connecting stud being driven through the arm shaft for moving 
vertically along the needle bar, and a clutch click provided on the needle 
bar for rotating and engaging in the needle-bar connecting stud. The 
clutch click engages in the needle-bar connecting stud, and the needle-bar 
connecting stud together with the needle bar moves vertically to sew. The 
sewing machine further comprises an actuating rod for vertically moving in 
parallel with the needle bar, a moving board for vertically moving in 
parallel with the actuating pin, a drive source for moving the moving 
board and lowering the actuating rod, and a disconnecting means for 
rotating the clutch click and disconnecting the needle bar from the 
needle-bar connecting stud. The drive source drives the moving board, the 
actuating rod lowers and the threading hook enters the eye to thread the 
needle. The moving board moves by the predetermined distance until the 
threading hook goes through the eye, and the clutch click rotates and 
disengages from the needle-bar connecting stud.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 1, a device for disconnecting a needle bar on a sewing 
machine is connected to an arm shaft 1. The arm shaft 1 is driven and 
rotated through a sewing-machine motor (not shown). A crankpin 4 is set on 
a counterbalance 2 on the arm shaft 1. One end of a connecting rod 6 is 
rotatably inserted into the crankpin 4, and a needle-bar connecting stud 8 
is rotatably inserted into the other end of the connecting rod 6. The 
needle-bar connecting stud 8 is slidably engaged on a needle bar 10. As 
shown in FIG. 3, a groove 12 radially and horizontally extends in the 
needle-bar connecting stud 8. 
A needle bar frame 14 is attached to the needle bar 10. A stud 16 is 
inserted into the needle bar frame 14 and slidably supports a click 18 in 
the needle bar frame 14. One end of a torsion spring 22 is attached to the 
stud 16, and the other end of the torsion spring 22 is engaged on a clutch 
pin 20 inserted into the click 18 perpendicularly to the needle bar 10. 
The torsion spring 22 applies a force to the click 18 so that the end of 
the click 18 engages the groove 12 in the needle-bar connecting stud 8. 
The click 18 can be engaged to and disengaged from the groove 12 through 
the torsion spring 22. As shown in FIG. 3, a positioning stopper 24 is 
secured through a screw 25 onto the needle bar 10 at a predetermined 
position above the needle-bar connecting stud 8. A projection 24a projects 
from the positioning stopper 24 perpendicularly to the axial direction of 
the needle bar 10. 
A needle bar support 26 supports the needle bar 10 such that the needle bar 
10 can vertically slide. A needle 32 is attached through a needle 
connecting stud 28 and a clamp screw 30 to the lower end of the needle bar 
10. A threading mechanism 33 adjoins the needle bar support 26. The 
threading mechanism 33 includes a threading rod 34 provided in parallel 
with the needle bar 10 on the needle bar support 26. The threading rod 34 
can rotate about its axis and slide vertically. As shown in FIG. 2, the 
threading rod 34 has a threading hook 36 on its lower end. When the 
threading rod 34 rotates about its axis, the threading hook 36 is rotated 
through a known linkage 38 toward an eye 32a in the needle 32. 
As shown in FIG. 3, an actuating pin 40 is inserted and secured in its 
axial direction through the upper part of the threading rod 34. When the 
threading rod 34 lowers, the actuating pin 40 lowers and contacts the 
projection 24a of the positioning stopper 24. The positioning stopper 24 
is secured through the screw 25 to the predetermined position of the 
needle bar 10 so that when the actuating pin 40 contacts the projection 
24a, the threading hook 36 is lowered to the eye 32a in the needle 32. 
As shown in FIG. 3, an actuating rod 42 is slidably inserted onto the 
threading rod 34, and a compression spring 44 is interposed between the 
actuating pin 40 and the actuating rod 42. As shown in FIG. 2, an S-shaped 
guide slot 46 extends upward in the outer periphery of the actuating rod 
42. One end of the actuating pin 40 engages the guide slot 46. A contact 
surface 48 is formed on the upper end of the actuating rod 42 and projects 
along the radius of the threading rod 34. A hook 49 is formed on the outer 
periphery of the actuating rod 42. A spring 50 extends between the hook 49 
and a hook (not shown) formed as one piece with the needle bar support 26. 
The spring 50 exerts an upward force on the actuating rod 42. 
As shown in FIG. 1, one end of an L-shaped member 51 is rotatably inserted 
to the upper end of the needle bar support 26. The other end of the 
L-shaped member 51 is rotatably attached through a screw 54 into a 
threading housing 52 secured to a sewing-machine housing (not shown). A 
spring 55 extends between the L-shaped member 51 and the needle bar frame 
14, and exerts an upward force through the needle bar frame 14 to the 
needle bar 10. 
A guide bar 56 is secured onto the threading housing 52 in parallel with 
the threading rod 34. A moving board 58 is slidably attached to the guide 
bar 56, separately from the actuating rod 42. The moving board 58 includes 
a slot 60 extending along the sliding direction of the moving board 58. A 
pin 62 on the guide bar 56 engages the slot 60, thus preventing the moving 
board 58 from rotating. A projection 64 is formed on the upper end of the 
moving board 58. When the moving board 58 slides down toward the actuating 
rod 42, the projection 64 can touch the contact surface 48 of the 
actuating rod 42. When the moving board 58 is in its uppermost position as 
shown in FIG. 2, the projection 64 is a predetermined distance L away from 
the contact surface 48. However, the projection 64 can be in contact with 
the contact surface 48. The actuating rod 42 can be formed as one piece 
with the moving board 58. 
A disconnecting pin 66 is provided in parallel with the pin 20 on the lower 
end of the moving board 58. A rotating shaft 70 is secured through two 
screws 68 in parallel with the guide bar 56 onto the needle bar support 
26. A disconnecting board 72, which is supported on the rotating shaft 70, 
can rotate. A torsion spring 74 wound around the rotating shaft 70 puts 
the disconnecting board 72 in parallel with the axis of the pin 20 and 
that of the disconnecting pin 66. A ridge 76, which is formed on the 
disconnecting board 72, slopes away from the disconnecting pin 66. When 
the moving board 58 and the disconnecting pin 66 rotate and lower, the 
disconnecting pin 66 presses down the ridge 76 and the disconnecting board 
72 is rotated. While the needle bar 10 is vertically moving, the 
disconnecting board 72 can rotate and contact the clutch pin 20, thereby 
pressing up the clutch pin 20. The clutch pin 20 disconnects the click 18 
from the groove 12. 
The moving board 58 includes a rack 78. The teeth of the rack 78 are formed 
transverse to the sliding direction of the moving board 58. The rack 78 
meshes with a pinion 80. The pinion 80 and a helical gear 82 form one 
member and are rotatably supported on the threading housing 52. A worm 
gear 86 is attached to a rotating shaft of a pulse motor 84 on the 
threading housing 52 and meshes with the helical gear 82. The pulse motor 
84 composes a drive source for threading the needle 32. 
On the other hand, a stopper 88 is a gap S away from the upper end of the 
needle bar 10. When a solenoid 90 is energized, the stopper 88 can 
protrude toward the needle bar 10 against the force of a coil spring 92 
and lower the needle bar 10. 
As shown in the electric circuit schematic diagram in FIG. 5, an electronic 
controller 100 controls the threading mechanism 33. A start-stop switch 
102 and a threading switch 104 are connected to the electronic controller 
100. An NP1 arm-shaft phase detector 106, an NP2 arm-shaft phase detector 
108, and a presser-foot detecting switch 110 are also connected to the 
electronic controller 100. When the arm shaft 1 rotates and the needle bar 
10 rises to its uppermost position, the NP1 arm-shaft phase detector 106 
detects the corresponding rotational position of the arm shaft 1 and sends 
out an NP1 signal. The NP2 arm-shaft phase detector 108 detects that the 
arm shaft 1 rotates by 30 degrees further from the rotational position 
detected by the NP1 arm-shaft phase detector 106 and sends out an NP2 
signal. The presser-foot detecting switch 110 detects when a presser foot 
(not shown) lowers and sends out a signal. The electronic controller 100 
transmits a control signal to the solenoid 90, a pulse-motor driver 112, 
and a sewing-machine motor driver 116. The pulse-motor driver 112 
transmits pulses to the pulse motor 84 corresponding to the control signal 
from the electronic controller 100. The sewing-machine motor driver 116 
transmits pulses to a sewing-machine motor 114 corresponding to the 
control signal from the electronic controller 100. The sewing-machine 
motor 114 drives and rotates the arm shaft 1. 
In operation, as shown in the flowchart of FIG. 6, after a power switch on 
the sewing machine is turned on, step S200 initializes the pulse motor 84. 
An operator presses the threading switch 104 so that the eye 32a in the 
needle 32 is threaded with thread 94 prior to sewing operation. When step 
S210 determines that the threading switch 104 is turned on, step S220 
executes threading procedure. 
Specifically, first the pulse motor 84 receives a drive signal with the 
predetermined pulses from the pulse-motor driver 112 and rotates. The 
rotation of the pulse motor 84 is transmitted through the worm gear 86, 
the helical gear 82, the pinion 80 and the rack 78 to the moving board 58, 
thereby lowering the moving board 58 along the guide bar 56. 
The moving board 58 lowers the predetermined distance L, and the projection 
64 of the moving board 58 contacts the contact surface 48 of the actuating 
rod 42 and presses down the actuating rod 42 against the force of the 
compression spring 50. At the same time, the compression spring 44 and the 
guide slot 46 lower. The actuating pin 40 lowers the threading rod 34. 
Therefore, the linkage 38 and the threading hook 36 also lower. 
In this embodiment, when the moving board 58 lowers the predetermined 
distance L, as shown in FIG. 8, the disconnecting pin 66 presses down the 
ridge 76 of the disconnecting board 72 and the disconnecting board 72 
rotates. Subsequently, since the pin 20 of the click 18 is raised, the 
click 18 is disconnected from the groove 12. The spring 55 exerts upward 
force on the needle bar 10, thereby raising the needle bar 10 until the 
upper end of the needle bar 10 touches the stopper 88. When the click 18 
is disengaged from the groove 12, the needle bar 10 is higher by the gap S 
than its uppermost position to which the rotation of the arm shaft 1 
brings the needle bar 10. Therefore, if the needle-bar connecting stud 8 
returns to its uppermost position through the rotation of the arm shaft 1, 
the click 18 fails to engage in the groove 12. The predetermined gap S 
prevents the needle bar 10 from contacting the stopper 88 with noise every 
time the needle bar 10 rises at the time of the sewing operation. 
Consequently, the gap S should be more than zero. 
On the other hand, when the needle bar 10 rises through the force of the 
spring 55, the NP1 arm-shaft phase detector 106 transmits the NP1 signal 
to the electronic controller 100, and the arm shaft 1 is stopped at the 
rotational position where the needle bar 10 is at its uppermost position. 
When the threading rod 34 lowers, the actuating pin 40 lowers. The end of 
the actuating pin 40 contacts the projection 24a of the positioning 
stopper 24. On the other hand, the click 18 is disengaged from the groove 
12 by means of the disconnecting board 72. The actuating pin 40 in contact 
with the projection 24a can lower the needle bar 10 against the force of 
the spring 55. When the needle bar 10 is lowered by the gap S, the click 
18 engages in the groove 12 in the needle-bar connecting stud 8 stopped at 
its uppermost position. Since the arm shaft 1 is stopped, no rotation is 
transmitted through the connecting rod 6 to the needle-bar connecting stud 
8. The needle bar 10 is thus held at its uppermost position, and the 
threading rod 34 fails to lower further. When the threading rod 34 is 
stopped, the pulse motor 84 lowers the moving board 58. The actuating rod 
42 lowers against the force of the compression spring 44, and the 
actuating pin 40 moves along the guide slot 46, thereby rotating the 
threading rod 34. The rotation of the threading rod 34 is transmitted 
through the linkage 38 to the threading hook 36. The threading hook 36 
rotates and enters the eye 32a in the needle 32. 
As shown in FIG. 4, the threading hook 36 goes through the eye 32a and 
catches the thread 94. When the pulse motor 84 reverses, the moving board 
58 rises. The compression spring 50 exerts tensile force on the actuating 
rod 42. The actuating rod 42 and the guide slot 46 rise. The actuating pin 
40 rotates the threading rod 34 in reverse. The reverse rotation of the 
threading rod 34 is transmitted through the linkage 38 to the threading 
hook 36. The threading hook 36 is rotated and drawn from the eye 32a. The 
thread 94 caught in the threading hook 36 is also drawn from the eye 32a. 
After step S220 executes the above-mentioned threading procedure, or if 
step S210 determines that the threading switch 104 is not turned on, step 
S230 determines the threading switch 104 is not turned on, step S230 
determines whether the NP1 arm-shaft phase detector 106 detects that the 
arm shaft 1 is in its uppermost position and issues the NP1 signal. If at 
step S230 the NP1 arm-shaft phase detector 106 does not issue the NP1 
signal, step S240 drives the sewing-machine motor 114. If at step S230 the 
NP1 arm-shaft phase detector 106 sends the NP1 signal to the electronic 
controller 100, step S250 stops the sewing-machine motor 114. 
Subsequently, step S260 energizes the solenoid 90 so that the stopper 88 
protrudes against the force of the coil spring 92, and stops the solenoid 
90 to disengage the stopper 88 from the coil spring 92. 
Through the processes from step S230 through S260, the needle bar 10 is put 
in its uppermost position, and the click 18 is almost engaged in the 
groove 12. After the click 18 is firmly engaged in the groove 12, the 
needle bar 10 is kept in its upper position. 
Subsequently, when at step S270 the operator confirms that the start-stop 
switch 102 is turned on, step S280 determines whether the presser-foot 
detecting switch 110 is turned on and the presser-foot is lowered. If at 
step S280 the presser-foot detecting switch 110 is turned on, step S290 
determines whether pattern-sewing operation is instructed or not. If at 
step S290 a pattern-sewing key (not shown) is operated and the 
pattern-sewing operation is instructed, step S300 executes pattern-sewing 
procedure in response to the instruction of the pattern-sewing key and 
according to pattern program stored in advance. If at step S290 the 
pattern-sewing key is not operated, step S310 determines whether basting 
operation is instructed. If at step S310 the basting operation is 
instructed, step S320 executes the basting procedure according to basting 
program stored in advance. 
Unless the start-stop switch 102 is turned on or the presser-foot detecting 
switch 110 is turned on, processes of and after step S290 are skipped and 
the process ends. 
When stitches are skipped without being sewn in the course of the pattern 
sewing and the basting, the vertical movement of the needle bar 10 is 
interrupted through needle-bar disconnecting procedure under the control 
of the electronic controller 100. The needle-bar disconnecting procedure 
will now be explained with reference to FIGS. 7 and 9. 
First, step S400 determines according to disconnecting signal stored in 
advance in the pattern program and the basting program whether the 
disconnecting of the needle bar 10 from the needle-bar connecting stud 8 
is executed or not. If step S400 determines that the disconnecting is 
executed, step S410 rotates the pulse motor 84 according to the pulses 
from the pulse-motor driver 112. 
Therefore, as aforementioned, the moving board 58 lowers by the 
predetermined distance L. As shown in FIG. 8, the disconnecting pin 66 
presses down the ridge 76 of the disconnecting board 72 and the 
disconnecting board 72 is rotated, thereby raising the pin 20 of the click 
18. The click 18 is usually raised and lowered through the rotation of the 
arm shaft 1. The click 18 is thus disengaged from the groove 12. The 
needle bar 10 is raised by means of the force of the spring 55 until the 
upper end of the needle bar 10 touches the stopper 88. In this embodiment, 
when the click 18 is off the groove 12, the needle bar 10 is higher by the 
gap S than its uppermost position to which the needle bar 10 is raised 
through the rotation of the arm shaft 1. If the needle-bar connecting stud 
8 returns to its uppermost position through the rotation of the upper 
shaft 1, the click 18 fails to engage in the groove 12. As shown by a 
broken line in FIG. 9, even if the needle-bar connecting stud 8 rises up 
and down through the rotation of the arm shaft 1, the needle bar 10 fails 
to rise. 
As aforementioned, when the needle bar 10 is disconnected from the 
needle-bar connecting stud 8, fabric is fed without being sewed. 
Subsequently, step S420 determines whether to finish disconnecting the 
needle bar 10 from the needle-bar connecting stud 8 according to LAST1 
signal corresponding to program stored in advance. If at step S420 the 
LAST1 signal is issued, step S430, contrary to step S410, sends pulses to 
the pulse motor 84, thereby rotating the pulse motor 84 in reverse. 
Specifically, when the pulse motor 84 reverses, the moving board 58 rises. 
The disconnecting pin 66 is detached from the ridge 76 of the 
disconnecting board 72. The disconnecting board 72 is rotated through the 
force of the torsion spring 74, and disengaged from the pin 20. 
Subsequently, step S440 determines whether the NP2 signal is issued or not. 
If at step S440 the NP2 signal is issued, step S450 energizes the solenoid 
90, thus thrusting the stopper 88 and lowering the needle bar 10 by the 
gap S. On the other hand, the needle-bar connecting stud 8 slides up and 
down the needle bar 10 according to the rotation of the arm shaft 1. When 
the needle-bar connecting stud 8 slides up close to its uppermost 
position, the click 18 lowers by the force of the torsion spring 22. The 
click 18 thus engages in the groove 12. The needle bar 10 is connected to 
the needle-bar connecting stud 8. The rotation of the arm shaft 1 is 
transmitted to the needle bar 10, and as shown by a solid line in FIG. 9 
the needle bar 10 moves up and down. 
Step S460 determines whether another NP2 signal is issued or not. If at 
step S460 the NP2 signal is issued, step S470 stops the solenoid 90 and 
the process ends. From the time the first NP2 signal is issued until 
another NP2 signal is issued, the arm shaft 1 rotates once and the 
needle-bar connecting stud 8 moves up and down once. During the time 
period between the NP2 signals, since the solenoid 90 is energized, the 
click 18 as well as the needle bar 10 are lowered to such a position that 
the click 18 can engage in the groove 12. By raising the needle-bar 
connecting stud 8, the click 18 is firmly engaged in the groove 12. 
Solenoid 90 need not be provided, in which case the stopper 88 is secured 
to such a position that the gap S is zero. In this structure, by stopping 
the moving board 58 where the disconnecting pin 66 rotates the 
disconnecting board 72, the click 18 is disengaged from the groove 12. 
In this embodiment, the moving board 58 lowers by the predetermined 
distance L, the disconnecting board 72 rotates the click 18, the click 18 
is disengaged from the groove 12, and the needle bar 10 is thus 
disconnected from the needle-bar connecting stud 8. The moving board 58 
further lowers, the actuating rod 42 also lowers itself and the threading 
rod 34, the threading rod 34 rotates, and the threading hook 36 is put 
through the eye 32a in the needle 32. 
Specifically, when the moving board 58 lowers by the predetermined distance 
L, the needle bar 10 disengages from the needle-bar connecting stud 8. 
While the needle bar 10 is disengaged in the course of the pattern-sewing 
operation or the basting operation, stitches are skipped. When the moving 
board 58 further lowers, the threading mechanism 33 threads the eye 32a in 
the needle 32. Through the pulse motor 84 the needle bar 10 can be firmly 
disconnected from the needle-bar connecting stud 8 and the needle 32 can 
be threaded. For both the disconnecting operation and the threading 
operation, only the pulse motor 84 need be controlled. Therefore, the 
control circuit is simplified, and the threading mechanism as well as the 
disconnecting mechanism can be compact. While the needle bar 10 is rising 
without rotating, the needle bar 10 can disengage from the needle-bar 
connecting stud 8 without doing damage to the fabric. The pattern-sewing 
operation as well as the basting operation can be smoothly carried out. 
To disconnect the needle bar 10 from the needle-bar connecting stud 8, the 
moving board 58 moves the predetermined distance L, but the actuating rod 
42 does not lower although the pulse motor 84 is used in common for the 
disconnecting operation and the threading operation. Consequently, the 
operator never feels that improper operation is carried out. The needle 
bar 10 can be disconnected from the needle-bar connecting stud 8 in time 
before the threading hook 36 enters the eye 32a. The predetermined 
distance L can be between the start point of the moving board 58 and the 
point where the threading hook 36 is put through the eye 32a. The 
actuating rod 42 may lower, which causes no substantial problem. 
This invention has been described above with reference to the preferred 
embodiment. Modifications and alterations may become apparent to one 
skilled in the art upon reading and understanding the specification. It is 
intended to include all such modifications and alterations within the 
scope of the appended claims.