Lock stitching and overlock stitching sewing machine

A sewing machine having lock stitching device incorporated in a frame and driven by a primary driving member comprising a detachable overlock stitching device having its own needle bar driving mechanism spaced apart from the stitch forming part of the lock stitching device and driven by the same primary driving means. Preferably, a switching mechanism provides for the actuation of one stitching device while the other is at rest.

BACKGROUND OF THE INVENTION 
This invention relates generally to sewing machines, and more specifically 
it relates to a home sewing machine selectively operable for making lock 
stitches and overlock stitches. 
In the mass production of sewn clothes, the lock stitches and the overlock 
stitches are most used. The former is for stitching edges of the cloth, 
and the latter is for darning and in addition for ordinary stitching when 
the clotch is very elastic such as knitted material. 
In general home sewing activity, however, the lock stitches are most 
frequently used and not the overlock stitches. This fact does not mean 
that the overlock stitching is not desired in domestic sewing but it 
merely means that due to the different formations of these two kinds of 
stitches an additional cost, maintenance and storage made the machine for 
overlock stitching impractical. 
Consequently, the zigzag stitching or so-called three-folded edge stitching 
has been substituted for the edge darning. However, the sewing technique 
has recently become diversified due to prevailing knitted materials, or 
because fashion has been taken into account, and the edge darning 
utilizing the lock stitching has not coped with the requirements. 
Especially, in very elastic materials such as jersey it is necessary to 
use stitches capable of matching the elasticity of the material. Also in 
this regard, the overlock stitching is desired. 
SUMMARY OF THE INVENTION 
The present invention has been devised to facilitate the overlock stitching 
in the home sewing work and to satisfy the requirements in this field. 
A primary object of this invention is to enable an easy overlock stitching 
operation in a device having a simplified structure. 
Another object of the invention is to broaden the utilization of the lock 
stitching sewing machine by detachably attaching thereto an overlock 
stitching device. 
A further object of the invention is to drive the lock stitching device and 
the overlock stitching device either by means of respective driving 
members or by means of the same driving member. 
Many other features and actual embodiments according to the invention will 
be apparent from the following explanation with reference to the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Two stitching devices, namely the lock stitching device and the overlock 
stitching device are incorporated within a single sewing machine frame and 
driven by a common driving member. These devices have, respectively, their 
own needles, feeding teeth, needle plates and thread taking levers. The 
two types of stitches are formed respectively in different parts of the 
sewing machine. Since a common machine frame is used for the both 
stitchings, the structure of this invention is more economical than that 
using two separate sewing machines which are specialized for the lock 
stitching and the overlock stitching respectively, and it is also more 
convenient for use and storage. 
In FIGS. 1-6 the overlock stitching device is shown with an overlock 
stitching needle 1 and a looper 2 incorporated in different positions in 
the lock stitching sewing machine. It is, therefore, easy for an operator 
to handle and operate the lock stitching device as it is. 
A reference will be made to a first embodiment of this invention as shown 
in FIGS. 7 to 11 where the overlock stitching device is provided in a 
position shown in FIG. 1. In this embodiment, the stitching part of the 
overlock stitching device is provided in a stepped flat portion 4 formed 
on the upper part of the free arm 6 and of the stand 5 of the lock 
stitching sewing machine 3, and the sewing machine is driven via a pulley 
8 by a belt 7. The pulley 8 is secured on a driving shaft 9 which is 
furnished with a pair of mechanical clutches 10. The clutch 10 is composed 
of a follower clutch 13 for the lock stitching, which has a gear 12 
integrated with a belt wheel 11 for driving the lock stitching device and 
which is axially restrained with respect to the driving shaft 9 but free 
in rotation, a driving clutch 14 which is restrained in rotation by a key 
but slidable axially, and a follower clutch 15 for the overlock stitching, 
which is axially restrained with respect to the follower clutch 13 and the 
driving shaft 9 and which is of the same shape as the follower clutch 13. 
The driving clutch 14 is formed with gears 16 at its both edges, and is 
geared with any one of the follower clutches 13 or 15 by operation of a 
knob 20 via a guiding pin 18 and a guiding lever 19 engaging in a guiding 
groove 17 formed at a center of the clutch 14. Therefore, according to 
this embodiment, the sewing machine is used either for the lock stitching 
or the overlock stitching operation by adjusting the control knob 20, 
whereby one stitching device is actuated and the other device is at rest. 
The lock stitching device of this embodiment is in principle the same as 
that of the normal lock stitching sewing machine, and the thread taking 
lever, the needle bar and others are driven by the belt 21 and the belt 
wheel 22, and a lower shaft 191 (shown in FIG. 44) is driven via sprocket 
24 and a timing belt 25, and a loop taker and a feeding mechanism are 
driven via the lower shaft. 
The overlock stitching device is driven via the belt 26 and the belt wheel 
27 by means of the overlocking shaft 28 to form stitches with an upper and 
a lower thread. The overlocking shaft 28 is fixed with an upper gear 32 
integrated with an upper cam 31 for driving loopers 29, 30, and the upper 
gear 32 is engaged with a lower gear 34 integrated with a lower cam 33 for 
driving the loopers 29, 30. The lower gear 34 is secured on a hollow shaft 
35 which is held at its hollow part by an upper shaft 23, and the hollow 
shaft 35 drives an eccentric feeding cam 36 fixed on an end portion 
thereof to deliver horizontal and tilting movements to a feeding gear 38 
via a feeding shaft 35 gives a forward movement to the feeding gear 38, it 
rotates in a direction opposite to rotation of the upper shaft 23 of the 
lock stitching device, that is, in a clockwise direction, viewing from the 
pulley 8. The overlocking shaft 28 is secured with a crank 39 at its end 
portion, and a needle holder 43 is turned around a pin 44 secured to the 
arm 6 via a pin 40, a crank rod 41 and a pin 42 to drive an overlocking 
needle 45. The upper cam 31 and the lower cam 33 drive an upper looper 
holder 49 via rollers 48 (shown in FIG. 9) engaging in grooves 46, 47. The 
holder 49 transmits movement required for forming stitches to the upper 
looper 30 which is secured to an end portion of the holder 49, and it 
engages a pin 51 of a lower looper rod clamp 50 to give linear 
reciprocating movement to a lower looper 29 via the lower looper rod clamp 
50 and a lower looper rod 52. The lower looper rod 52 is supported by the 
arm 6 and is slidably held by bushes 53, 54 and is restrained in rotation 
by an edge 55 of the lower looper bar clamp 50. The upper looper 30 is 
formed with a V-shaped groove 57 at its end portion to catch the lower 
thread passed through a thread hole 58. 
A process of forming stitches by the upper and lower loopers 30, 29 is 
shown in FIG. 11. When knob 20 is moved to the right in FIG. 7 to urge the 
driving clutch 14 to engage the overlocking stitching follower clutch 15 
for driving the belt wheel 27, the driving shaft 9 is rotated in the 
clockwise direction in FIG. 7 and the upper gear 32 is rotated in the same 
direction by the belt 26, but the lower gear 34 is rotated in the 
counterclockwise direction. The overlock stitching needle 45 turns 
vertically thereby, and the upper looper supporter 49 is moved by rotation 
of the grooves 46, 47 of the upper and lower cams 31, 33 so that the lower 
looper 29 makes a linear reciprocating movement. The upper looper 30 
reciprocates horizontally together with the lower looper 29 while the 
looper 30 is turning in accordance with the turning movement of the upper 
looper supporter 49. Therefore, the upper looper 30 carries out a 
resultant movement similar to a movement shown in FIG. 31, and feeds a 
thread loop of the lower looper 29 onto a left side of the needle 45. The 
eccentric feeding cam 36 rotates in the counterclockwise direction in FIG. 
7, and gives an elliptical movement to the teeth 38 for a forward feeding. 
A process of forming overlock stitches will be referred to in FIG. 11. At 
first in (a), the upper looper 30 above the left side of the needle 45 
holds the thread loop of the lower looper 29, and the needle 45 falls as 
passing through the thread loop so that the thread loop of the needle 45 
is passed through the thread loop of the lower looper 29, and the thread 
loop rises a little above a lower dead point and swells, and the lower 
looper 29 starts to move to the right. When coming to (b), the upper 
looper 30 moves to the right as holding the thread loop, and the lower 
looper 29 moves to the right into the thread loop of the needle 45. When 
reaching (c), the upper looper 30 is under a moving path of the lower 
looper 29 and starts to rise, and then the lower looper 29 finishes to 
cause the thread loop to pass through the thread loop of the needle 45. At 
(d), the upper looper 30 catches the thread loop of the lower looper 29 
and rises, and the lower looper 29 starts to move to the left, and then 
the feeding teeth 38 feeds the cloth and the stitches move. At (e), the 
feeding is completed and the thread loop of the lower looper 29 passes 
through said thread loop, and the thread loop of the needle 45 gets out of 
the lower looper 29 and the upper looper 30 feeds the thread loop of the 
lower looper 29 above the left side of the thread 45 and continues to move 
to the left, and the needle 45 again passes through the thread loop and 
falls down. In (f), the thread loop of the needle 45 reaches the lower 
dead point, and the upper looper 30 and the lower looper 29 still continue 
to move to the left. Again returning back to the (a) condition to repeat 
the above movements, the overlocking stitches are formed. In the above 
process, the lock stitching device is completely stopped. 
For carrying out the lock stitching, the knob 20 is moved to the left to 
urge the driving clutch 14 to engage the lock stitching follower clutch 13 
so that the upper shaft 23 is rotated in the clockwise direction in FIG. 7 
via the belt wheel 8, the belt 21 and the sprocket 24. In the above 
process, the overlocking stitching device is completely stopped. 
In this embodiment, a cutting edge which is employed in conventional 
overlock stitching is not incorporated because the home sewing does not 
require so much efficiency. The operator has to cut out the cloth in 
advance, and it is enough to use an appropriate means for guiding the 
cloth, and for the safety it is desirable to furnish the machine without 
the cutting edge. A thread taking lever for forming stitches for the sake 
of clarity is omitted in the drawing. 
In this embodiment, the lock stitching device and the overlock stitching 
device are operated each in the different place of the machine. When one 
device is at work, the other is at rest, and therefore the operator cannot 
be injured by the needle or looper of the resting device. Thus, one of the 
features of the invention is that the clutch mechanism drives only one 
stitching device and stops the other. For this reason the invention 
contributes substantially to the safety of operation. 
Also, the device of this embodiments changes the diameters of the two 
pulleys between the follower clutches 13 and 15 to increase the reduction 
ratio of the overlock stitching device in comparison with the lock 
stitching, because the moving torque of the overlock stitching device is 
in general lesser than that of the lock stitching device and rotates at 
high speed. Thus, it is also one of the features of the invention that the 
driving reduction ratio of the overlock stitching device is larger than 
that of the lock stitching device, so that the overlock stitching device 
may provide the optimum rotating speed. 
Further, with respect to the feeding mechanism, the feeding rate is not 
changed and the structure is fairly simplified. The feeding movement is 
given to the teeth 38 in the structure shown in FIG. 7 by means of the 
eccentric feeding cam 36 fixed on the hollow shaft 35 which is mounted on 
the upper shaft 35. To provide easy and exact feeding is also one of the 
features of this invention. 
A second embodiment of this invention is illustrated in FIGS. 12 to 15 
where the overlock stitching device is provided in a position shown in 
FIG. 2. In the embodiment, the stitching part 1 and 2 of the overlock 
stitching device is located on a recess formed on an edge of the bed 59 on 
the rear side of the lock stitching sewing machine 66. Height (h) of the 
bed 59 is higher than that of the ordinary sewing machine. The mechanism 
of the overlock stitching device is housed in the bed 59. This second 
embodiment is suitable for the so-called free arm type sewing machine 
having a horizontal loop taker, and the overlock stitching device is 
detachably housed under the auxiliary bed 62, and it is possible to use 
this sewing machine as the flat bed type sewing machine, as the lock 
stitching device is attached. The overlock stitching device may be easily 
attached to the flat bed type sewing machine. 
The overlock stitching device is incorporated under the auxiliary bed 62 
and is connected to the sewing machine by guiding pins 63, 64 and a 
stopper 65. A switching lever 69 is positioned at the left in FIG. 12, and 
an upper cover 67 of the auxiliary bed 62 as well as a side cover 68 are 
closed, so that the sewing machine may be used as a lock stitching sewing 
machine of the flat bed type. Conversely, when the upper cover 67 as well 
as the side cover 68 are opened and the switching lever 69 is positioned 
at the right, the sewing machine may be used as an overlock stitching 
sewing machine. If the auxiliary bed 62 is taken off, the sewing machine 
may be used as an ordinary lock stitching sewing machine of the free arm 
type. Also in this embodiment, the mechanical clutch may drive the 
stitching device as in the first embodiment. 
In FIG. 13, the sewing machine 66 is driven via the pulley 7 by the belt 7, 
and the driving shaft 9 secured to the pulley 8 is provided with the 
mechanical clutch 10. In the clutch 10, the driving clutch 14 is geared 
with the lock stitching follower clutch 13 by a spring 70 via a connecting 
arm 71 and a guiding arm 73, and drives the lock stitching device by the 
belt 21. When the auxiliary bed 62 is attached to the machine frame and 
the switching lever 69 is positioned at the pulley side, a switching rod 
74 cooperating with the switching lever 69 pushes out an intermediate rod 
75 to push the connecting rod 71 against force of a spring 70, so that the 
driving clutch 14 is geared with the overlock stitching follower clutch 15 
to interrupt gearing with the lock stitching device and driven an overlock 
driving shaft 76 via a belt 26. When the auxiliary bed 62 is attached, an 
overlock shaft 77 is connected with the overlock driving shaft 76 by means 
of couplings 78, 79, and the overlock stitching device is driven. 
An outer appearance of the auxiliary bed 62 where the overlock stitching 
device is built in, is shown in FIG. 14, and FIG. 15 shows an inner 
structure of the overlock stitching device. The essential parts are the 
same as in the first embodiment. The switching lever 69 is secured to a 
switching rod 74 and is always pressed down by a plate spring 80. This 
spring pressure causes a stem 83 to be fixed in notches 81 and 82. 
The lock stitching device and the overlock stitching device are attachable 
and detachable, and in an operative condition each of the devices may be 
driven by the same driving source. This is one of the features of the 
invention. In the device of this second embodiment, partial mechanisms 
other than the needle bar may be used in common, for example, the feeding 
mechanism (see the third to fifth embodiments). Further, it is possible to 
install different driving sources for the lock stitching and the overlock 
stitching devices, which rotate in opposite directions. In the lock 
stitching sewing machine of the free arm type, the invention makes it 
possible to incorporate the overlock stitching device into the auxiliary 
bed 62 to form a compact unit. 
A third embodiment of this invention is shown in FIGS. 16-33. In this 
embodiment, the stitching part of the overlock stitching device 1 and 2 is 
located on an edge between an upper face of base 86 and a recess in bed 85 
of the locking stitching sewing machine 87 (FIG. 3) of the free arm type, 
and the mechanism of the overlock stitching device is built in the arm 84, 
the bed 85 and the base 86. A sewing machine 87 in this embodiment is 
provided with a lock stitching flywheel 88 and an overlock stitching 
flywheel 89. A cover 90 shields non-used flywheel 88 or 89, and the cover 
90 is fixed to one of the flywheels by means of a braking device 91 (FIG. 
20), thereby to selectively drive the device to be used. The embodiment 
shown in FIG. 16 where a projection 92 formed on the cover 90 does not 
push a button 94 of a switch 93 provided on the sewing machine 87, makes 
use of a motor driving circuit as shown in FIG. 17, and the modification 
shown in FIG. 18 where the projection 92 pushes the button 94, uses a 
driving circuit as shown in FIG. 19 which drives the motor in the opposite 
direction than in the embodiment shown in FIG. 16. When the motor rotates 
in the normal direction, one of the stitching devices is driven by a pair 
of clutches in the same direction, and when the motor rotates in the 
opposite direction, the other stitching device is driven. In the cover 90 
shown in FIG. 20, an interposed rib 95 is secured to a braking device 91 
of an elastic material, and this braking device 91 elastically acts on a 
groove 96 or 98 to stop rotation of the flywheel 88 or 89 and also serves 
for positioning of the cover 90. 
In FIG. 21, the sewing machine 87 is driven by a belt 98 via a pulley 99. A 
driving shaft 100 which is secured on the pulley 99 and held to the 
machine frame, is provided with lock stitching and overlock stitching 
clutch rings 103 and 104 rotating in one direction and axially restrained 
by rings 101, 102 and the pulley 99. The lock stitching clutch ring 103 is 
integrated with a lock stitching driving pulley 105, and the overlock 
stitching clutch ring 104 is integrated with an overlock stitching driving 
pulley 106. The clutch ring 104 comprises, as shown in FIGS. 22 and 23, a 
roller 107, a spring 108 and a groove 109. When the driving shaft 100 is 
rotated in the clockwise direction (reverse direction), the clutch ring 
104 and the pulley 99 are rotated together with the driving shaft 100 
(FIG. 22), and when the driving shaft 100 is rotated in the 
counterclockwise direction (normal direction), the clutch ring 104 is 
released from the driving shaft 100, and the driving shaft 100 rotates 
idly (FIG. 23). The lock stitching clutch ring 103 has, as shown in FIGS. 
24 and 25, quite an opposite action with respect to the rotation of the 
driving shaft 100. Only when the driving shaft 100 is rotated in the 
counterclockwise direction (normal direction), the clutch ring 103 is 
rotated therewith. 
In this embodiment, the rotating direction of the driving motor is switched 
by means of the cover 90, switch 93, flywheels 88, 89 and clutch rings 
103, 104 to selectively drive the stitching device only. The stitching 
device is the same as in the first embodiment. 
The overlocking device in this embodiment forms the stitches with the two 
threads as shown in FIG. 8, and a piece of looper 110 whose shape is shown 
in FIGS. 26 and 27 is employed. The looper 110 is formed with a hole 112 
at its end 111 for the under thread and has a hook 113 for catching the 
thread 114 as shown in FIGS. 26 and 27. An overlocking shaft 115 shown in 
FIG. 28 is driven via the belt 116 and the pulley 117 by the overlocking 
clutch ring 104. The overlocking shaft 115 is shaped in accordance with 
FIG. 29 and is held by the bushes 118, 119. A ball crank 120 is connected 
to one end of a crank rod 121 to drive a looper shaft 123 via a looper rod 
121 having a ball pin. The looper link 124 is connected to a looper shaft 
link 125 secured to a looper shaft 123 by a connecting pin 127, and to a 
guiding rod link 126' secured to a guiding rod 126 held to the machine 
frame by a connecting pin 127' to constitute a four-articulation link 
mechanism which is rotated around the looper shaft 123 and the guiding 
shaft 126. The looper 110 is fixedly screwed to a lower end of the looper 
link 124 to provide movements as shown in FIG. 31. The overlocking shaft 
115 is formed with a crank portion 128 to give vertical movement to the 
needle bar 135 secured to the needle bar clamp 134 via the crank rod 129, 
crank arm 130, needle bar shaft 131, needle bar moving rod 132 and 
intermediate link 133. Further, the overlocking shaft 115 is mounted with 
an eccentric cam 136, and the eccentric cam 136 engages a feeding part 137 
to give feeding movement to the feeding teeth 138 as shown in FIG. 10. The 
needle bar 135 has a slight inclination in the feeding direction with 
respect to horizontal movement of the looper 110, and this inclination is 
conventional in the art of forming the overlocking stitches. 
Movements of the looper mechanism in the third embodiment may be explained 
by means of a simplified diagram shown in FIG. 31, since the looper shaft 
123 and the guiding shaft 126 of the rotational centers are at the same 
side of the needle bar 135 with respect to the needle plate 139, a space 
under the needle plate 139 may be small. Thereby, it is possible to 
provide a holding and moving part of the cloth to be sewn on a thin base 
86 as seen in the sewing machine in this embodiment. In other words, it is 
one of the features of the invention to arrange the basic mechanism such 
as the driving portion of the looper mechanism be on the same side of the 
needle bar 135 as the needle plate 139. 
An arrangement of the needle bar 135 under the needle plate 139 as shown in 
FIGS. 32 and 33 may be effectively applied to the first embodiment as 
shown in FIG. 1, and in this case the height of an upper surface of a 
stand 5 of the machine frame can be lowered. It is apparent that this 
feature is not limited to the looper mechanism of the third embodiment but 
applied to a looper mechanism of a later-mentioned embodiment. 
The two rotating clutches rotating in one direction are used as mentioned 
above to change the rotating direction of the motor for driving one of the 
stitching devices, the flywheels 88, 89 are provided for the respective 
stitching devices and the cover 90 for the pulley of the non-used device 
switches the switch 93. 
The stitches in the third embodiment are formed as shown in FIG. 30. For 
forming the overlocking stitches, the cover 90 is pushed up as shown in 
FIG. 18 to make the circuit shown in FIG. 19, and the machine motor is 
rotated reversely to drive the overlock stitching device by the clutch 
rotating in one direction, so that the overlocking shaft 115 is rotated in 
the counterclockwise direction shown in FIG. 28 to vertically move the 
needle bar 135 and at the same time the looper 110 moves as shown in FIG. 
31 and the feeding part 137 carries out the feeding movement. FIG. 30-(a) 
shows that the needle 45 falls and rises a little to form a thread loop, 
and the looper 110 is positioned at the lower left edge, and at (b) the 
looper 110 moves to the right and catches the thread loop. Coming to (c) 
the looper 110 rises at the right of the needle 45 and feeds the caught 
thread loop under the cloth, and then the feeding teeth 138 feed the 
cloth. In (d) the looper 110 rises above the cloth and moves to the left, 
and releases the thread loop of the needle 45 and forms a new thread loop 
of the looper 110 through which the needle 45 passes, and a thread loop 
formed by the needle 45 is passed through the thread loop of the looper 
110. In (e), the looper 110 moves to the right of the needle 45 and passes 
through the thread loop which has been left in (d), and falls down. At 
(f), the needle 45 reaches the lower dead point and the loop 110 moves to 
the lower left oblique direction. Thus, one stitch is formed. When the 
overlocking shaft 115 is further rotated, formation of a thread loop is 
returned to (a) condition for a subsequent stitch. 
For forming the lock stitches, the cover 90 is pushed down as shown in FIG. 
16 to make the electric circuit shown in FIG. 17, and the machine motor is 
rotated in the normal direction, so that the upper shaft 23 is rotated in 
the clockwise direction in FIG. 21 via the clutch rotating in one 
direction, thereby to enable to perform the lock stitching. In this case, 
the pulley 89 is controlled by the braking device 91, and the overlock 
stitching device is stopped. 
A fourth embodiment of this invention is shown in FIGS. 34-37 where the 
overlock stitching device is provided in a position shown in FIG. 4. In 
this embodiment, the stitching part of the overlock stitching device is 
positioned in the rear side of a stand 5 connecting the arm 6 and a bed 59 
of the lock stitching sewing machine 141 (FIG. 4), and the mechanism of 
the overlock stitching device is built in the stand and the bed 59. In the 
sewing machine 141 of this embodiment, a switching lever 142 exposed on 
the arm 6 is operated, thereby to drive the stitching device to be used 
and to stop the needle bar of the other stitching device nearly at the 
upper dead point. Therefore, the mechanisms of the both devices are 
operated concurrently except for the needle bars, and since the thread 
taking levers of the lock and overlock stitching devices and the loopers 
are at operation, a danger of injury is more or less present. By 
furnishing safety covers or shields, the danger of injury of the operator 
may be eliminated. 
The lock stitching device is the same as that of the ordinary lock 
stitching sewing machine, but the driving mechanism of the needle bar 143 
is different as shown in FIGS. 36 and 37, and the lower needle bar clamp 
146 and the needle bar 143 are engageable in the axial direction of the 
needle bar 143 by means of a pawl 145 pivoted on an upper needle bar clamp 
144 which is secured on the needle bar 143. The pawl 145 is always urged 
by a spring 147 as shown in FIG. 36 to connect the needle bar 143 of the 
lower needle bar clamp 146, but a switching plate 148 which is vertically 
movable is pushed up to rotate the pawl 145 in the clockwise direction 
against pressure of the spring 147 at a projection 149, thereby to release 
connection between the needle bar 143 and the lower needle bar clamp 146. 
After having released said connection by the switching plate 148 and when 
the plate 148 is made to fall, the needle bar 143 drops due to its own 
weight until the upper needle bar clamp 144 contacts to the lower needle 
bar 146 and the pawl 145 is caused to connect to the lower needle bar 
clamp 146, or when such connection is impossible because of little 
falling, the sewing machine 141 is driven to raise the needle bar 143 via 
the lower needle bar clamp 146 and to act on the upper needle bar clamp 
144 nearly at the upper dead point of the needle bar 143 so that the pawl 
145 is engaged with the lower needle bar clamp 146 by pressure of the 
spring 147 rotating the upper needle bar clamp 144 in the counterclockwise 
direction. 
The overlock stitching device in this fourth embodiment is driven by an 
upper shaft 151 in common to the lock stitching device, and turns the 
upper looper shaft 155 via a crank rod 153 whose one end is connected to a 
first crank portion 152 provided on the upper shaft 151, an upper looper 
rod arm 154, an upper looper shaft 155, an upper gear 156, and a lower 
gear 157 for imparting movement to the looper 110 in the same structure as 
in the third embodiment. A second crank portion 159 provided on the upper 
shaft 151 is connected to a rod 160 for driving a needle bar 161 of the 
same structure as in the lock stitching device. The feeding mechanism is 
common to the lock device in the basic mechanism, and feeding is effected 
by a feeding part 163 for the overlocking of the same shape as the feeding 
part 162. The lock stitching needle bar 143 and the overlock stitching 
needle bar 161 form the same angle with the feeding direction (bed face), 
and the angle with the feeding direction may be a right angle. The 
overlocking stitches are formed in the same manner as in the third 
embodiment shown in FIG. 30. 
This fourth embodiment is different from the first to third embodiments, 
and the non-used stitching device stops only the movement of the needle 
bars 143 or 161 while the other parts of the mechanism are running. In 
FIG. 35, the switching lever 142 is supported for rotation around a 
switching lever shaft 165 and is urged to the front or to the back of the 
sewing machine by means of a spring 164, and its position can be selected 
at will. When the switching lever 142 is made to fall to the front of the 
sewing machine in FIG. 35 a connecting rod 166 lets the lock stitching 
switching plate 148 fully descend so that the needle bar 143 and the lower 
needle bar clamp 146 are connected to provide an operating condition of 
the needle bar 143. The connecting rod 167 fully pushes up the overlock 
stitching switching plate 168 to release connection between the needle bar 
161 and the lower needle bar clamp 169 by means of a needle bar releasing 
mechanism (same as in the lock stitching device), and to stop the needle 
bar 161 above the upper dead point by means of the switching plate 168 and 
a projection 170. 
Reversely, when the switching lever 142 is made to fall to the back of the 
sewing machine the overlock stitching needle bar 161 is driven and the 
lock stitching needle bar 143 is stopped. Thus, when one stitching device 
is operative, the other is inoperative. 
A fifth embodiment is shown in FIGS. 38-40 where the overlock stitching 
device is provided also in the position shown in FIG. 4. In this 
embodiment the stitching part 1 of the overlock stitching device is 
located on a flat portion of a recess formed in the stand connecting the 
arm and the bed of the lock stitching sewing machine 171. A cover 172 is 
furnished for shielding exposed moving parts of the overlock stitching 
device. When the cover 172 is closed, both stitching devices are driven 
simultaneously, and when the cover 172 is opened, the needle bar 143 of 
the lock stitching device is stopped and only the overlock stitching 
device is driven. 
This fifth embodiment is the same as the fourth embodiment as shown in FIG. 
40 except that the needle bar 173 of the overlock stitching device is 
directly connected to the needle bar clamp 174, and the mechanism of the 
lock stitching switching plate is different. The exposed moving parts of 
the overlock stitching device can be shielded with the cover 172 to avoid 
danger caused by the non-used stitching device. That is, safety is 
maintained by stopping the needle bar (as seen in the fourth embodiment) 
when the lock stitching device is inoperative and when the overlock 
stitching device is inoperative the cover 172 shields the exposed moving 
parts. More specifically, the lock stitching switching plate 148 is always 
pushed up via a bell crank 176 and a rod 177 by a spring 175 for stopping 
the needle bar 143 as shown in the fourth embodiment. The rod 177 is 
connected to a switching arm 180 via a connecting arm 178 and a connecting 
shaft 179. When the cover 172 is closed firmly by a fastener 181, a wall 
182 of the cover 172 pushes the switching arm 18 against pressure of a 
spring 175 and pushes down the switching plate 148 via the rod 177 and the 
bell crank 176 to provide a driving condition for the lock stitching 
needle bar 143. When the cover 172 is opened as shown in FIG. 39 and 
strength against the pressure of the spring 175 is cancelled, rod 177 is 
pulled to the back of the sewing machine by the spring 175 and the 
switching plate 148 rises to stop the lock stitching needle bar 143. Thus, 
when one stitching device is driven, the needle bar of the other stitching 
device is stopped, and when the other stitching device is driven, the 
exposed dangerous moving parts of the non-used device are shielded with a 
cover. 
In a sixth embodiment of this invention the overlock stitching device is 
arranged at the position shown in FIG. 5. In this embodiment, the 
stitching part of the overlock stitching device is located on a stepped 
flat portion of a recess formed on arm 6 and a bed of the lock stitching 
sewing machine. The element part of the overlock stitching device is 
housed under the arm 6 and the bed 59. This sixth embodiment is a 
modification of that shown in FIG. 4 (the fourth and fifth embodiments), 
and the mechanisms of the fourth and fifth embodiments may be applied as 
they are. 
It is, of course, possible to modify the embodiments according to the 
invention to form flat parts on an upper face of the arm 84 and on an 
upper face of the base 86. 
In a seventh embodiment the overlock stitching device is installed at a 
position shown in FIG. 6. In this embodiment, the stitching part of the 
overlock stitching device is located on an enlarged and elongated portion 
of the back edge of the lock stitching sewing machine, and the arm 185 of 
the sewing machine 184 and the wall of the pulley side of the bed 186 are 
partially enlarged, and in this enlarged portion the mechanism of the 
overlock stitching device is incorporated. It is sufficient to reverse the 
right side and the left side of the ordinary overlock stitching sewing 
machine for this overlock stitching device. If the wall of the pulley side 
is enlarged a variation of the third and fifth embodiments will be 
provided. The cloth feeding direction of the overlock stitching is turned 
reversely to that of the lock stitching, that is, if the sewing machine is 
turned 180.degree. when the lock stitching and the overlock stitching are 
switched, the ordinary overlock stitching mechanism may be incorporated as 
it is. 
This seventh embodiment will be explained with reference to FIGS. 41-44. In 
the sewing machine 184, both the lock stitching device and the overlock 
stitching device are always driven, and the exposed dangerous moving parts 
of the non-used stitching device are shielded by a cover 188 to relevate 
the safety. The cover 188 as shown in FIG. 43 is held on a guiding rod 189 
provided on the surface of the bed 186, and is always pressed to an arm 
185 (in the counterclockwise direction). The displacement of the cover 188 
from one device to the other device is effected by pulling the cover 188 
against pressure of the spring 190 along the guiding rod 189. 
The inner mechanism of the sewing machine 184 relating to the seventh 
embodiment is seen in FIG. 44, and the ordinary one is sufficient for the 
lock stitching device. The overlock stitching device forms stitches with 
three theads as shown in FIGS. 45 and 46, and a common low shaft 191 of 
the lock stitching device is used to drive an upper looper 192, a lower 
looper 193, the needle bar 194 and the thread taking lever (not shown) for 
moving feeding teeth (not shown) by means of an eccentric cam 196 secured 
to the lower shaft 191 and a horizontal feeding shaft 195 of the lock 
stitching device. A ball crank rod 198 is connected at its one end to a 
first bell crank portion 197 of the lower shaft 191 and connected at its 
other end to an upper looper 199 having a ball pin. The upper looper arm 
199 is fixed to an upper looper shaft 200, the upper looper shaft 200 is 
connected to one end of an upper looper actuating arm 201, a pin 202 fixed 
to one of the upper looper actuating arm 201 is connected to an upper rod 
203, and the upper looper rod 203 imparts the resultant sliding and 
turning movement to the upper looper 192 via an upper looper guide 205 
whose center shaft is pivoted in a bush 204 fixed to the machine frame. A 
second ball crank portion 206 of the lower shaft 191 is connected to one 
end of a ball crank rod 207, this ball crank rod 207 is connected at its 
other end to a ball crank pin 208 which is formed in a lower looper arm 
209 as one part thereof; the lower looper arm 209 is secured to the lower 
looper shaft 210 and the lower looper shaft 210 is rotatably connected to 
the machine frame, the lower looper shaft 210 is secured at its one end 
with a lower looper actuating arm 211, and the lower looper actuating arm 
211 is secured with a lower looper 193 to turn around the lower looper 
shaft 210. A crank portion 212 of the lower shaft 191 gives vertical 
movement to the needle rod 194 via a crank rod 213, needle bar shaft arm 
214, needle shaft 215, needle bar actuating arm 216, intermediate link 217 
and needle bar clamp 218. The horizontal movement of the feeding teeth is 
effected via a feeding arm 220 and a feeding portion 219 by a horizontal 
feeding shaft 195. 
For the looper mechanism and the needle bar mechanism of the overlock 
stitching device in this seventh embodiment, the mechanism of the ordinary 
overlock stitching sewing machine is incorporated as it is in the reverse 
condition of right and left. The stitches shown in FIGS. 45 and 46 seem 
different, but actually only the tension effected by the three threads is 
changed. The stitches in FIG. 45 are formed in that the upper thread is 
made strong in tension, and those in FIG. 46 are formed in that the upper 
thread is made weak in tension, the thread taking lever 222 is shielded 
with a cover 223. 
The overlocking stitches according to this invention will be discussed with 
reference to FIGS. 49 to 51. The overlocking stitches vary according to 
the use of one thread to four threads, and these stitches are another 
objective of the invention. These stitches may be provided by making minor 
changes on each of the embodiments as it will be explained below. 
Stitches shown in FIG. 47 are formed with one thread by exchanging the 
looper 224 in the third and fifth embodiments with a looper 224 shown in 
FIG. 48. 
Stitches shown in FIG. 49 are formed with two threads by changing the 
thread tension of the stitches shown in FIG. 8 to make the upper thread 
225 weak. It is often desirable to change the tension of the thread in 
accordance with different overlock stitching for effecting variances on 
the stitches. FIGS. 45 and 46 show examples thereof. 
Stitches shown in FIG. 50 are called as interlock stitches, and double 
chain stitches 227 are formed concurrently besides the overlocking 
stitches 226, which may be easily put into practice by installing a double 
chain stitching device in addition to the embodiments of the invention. In 
this regard, the needle bar may be common with the overlocking stitching 
device. 
Stitches shown in FIG. 51 are formed with two needles and four threads of 
an upper looper thread 228 passing through an upper looper, a lower looper 
thread 229 passing through a lower looper, a right upper thread passing 
through a right needle, and a left upper thread passing through a left 
needle, for example, these stitches may be effected by providing the two 
needles in the sixth embodiment. There are many overlocking stitches by 
the two needles, but those may be formed by exchanging the looper without 
changing the others. 
In each of the above-mentioned embodiments, the feeding direction of the 
cloth is the same as that of the ordinary lock stitching sewing machine, 
but the invention is not limited to them, and a direction to the upper 
shaft may be permitted, or it is possible to turn the sewing machine 
around the upper shaft to make the cloth feeding part horizontal, and all 
such modifications similar to the disclosed embodiments are apparently 
included in the present invention. 
In summation, the lock stitches and the overlock stitches may be formed by 
one sewing machine, and the device according to the invention is very 
convenient. Especially the edge darning which has been conventionally 
performed by the zig-zag stitching, may be effected by the overlock 
stitching, and therefore the possible range of the home sewing is 
broadened and the quality of the sewn production is improved. 
In the invention, the lock stitching and overlock stitching is selectively 
used. During operation of the one stitching device, the needle bar of the 
other stitching device is stopped to make noise low and prevent the 
operator's fingers or the cloth from being damaged. There are provided 
switching means which make it possible to rotate the machine motor in the 
normal and reverse directions and the two sets of the clutches rotating in 
one direction which selectively transmit rotation of the driving shaft 
rotated by the machine motor to the respective devices, and the first 
device is only driven without any complicated movement for selecting the 
stitches. The first device is selected by shielding the pulley with the 
cover, and the switch is operated by the cover to reverse the rotating 
direction of the machine motor. 
Further, the moving torque of the lock stitching sewing machine for moving 
the mechanism is large while that of the overlock stitching sewing machine 
is small, and in order that the power is transmitted from the same driving 
source, both devices may be rotated at the same speed, since the reduction 
ratio for the overlock stitching device has been in advance made large. If 
the reduction ratio be equal, the overlock stitching device would rotate 
inconveniently at high speed. 
Besides, since the looper driving portion of the overlock stitching device 
is provided at the same side as the needle bar with respect to the needle 
plate, the mechanical part under the needle plate (when the needle bar is 
provided under the needle plate, the mechanical part is above the needle 
plate) may be small, and the stitching part of the overlock stitching is 
positioned at disposal. 
The upper shaft and the lower shaft of the lock stitching device are 
provided with the hollow shaft having the eccentric cam, and the full 
rotation in one direction of the eccentric cam gives the elliptical 
movement to the feeding portion to provide the feeding for the overlock 
stitching, and therefore it does not make it necessary to prepare another 
feeding mechanism for the overlock stitching mechanism. Thus, the 
structure is simplified for providing the excellent feeding in function. 
In addition, the overlock stitching device according to the invention is 
made compact to be attachable to the lock stitching device, thereby to 
carry out the overlock stitching by attaching the overlock stitching 
device thereto if necessary, while using it as the lock stitching sewing 
machine ordinarily, paying attention to the safety measures. 
Furthermore, the overlock stitching device is incorporated under the 
auxiliary bed of the free arm type sewing machine for operating the 
overlock stitching, and when the overlock stitching device is not used, 
the lock stitching sewing machine is used as the flat bed sewing machine. 
When the overlock stitching device is taken out, it may be used as the 
free arm sewing machine. As is seen from the above, the present invention 
offers an advancement in the industrial field concerned.