Double purpose looper for overlocking sewing machine

A looper for a sewing machine capable of making overlocked stitches has a unitary distal portion which is operable for the selective production of overlocked stitches with one needle and three threads or one needle and two threads. The unitary distal portion of the looper includes an upper looper portion and a spreader portion. A holder is provided in connection with driving means for supporting the looper, and a positioning arrangement is provided to selectively position the unitary distal portion of the looper in a first position for movement along a first path or in a second position for movement along a second path for the selective production of the stitches.

BACKGROUND OF THE INVENTION 
The present invention relates to a looper for use in an overlocking sewing 
machine, and more particularly to a double-purpose looper capable of 
forming overlocked stitches with one needle and two threads and one needle 
and three threads. 
Conventional overlocking sewing machines for producing overlocked stitches 
with one needle and three threads include a sewing needle, a lower looper 
and an upper looper secured to a looper holder, which cooperate to form 
such overlocked stitches. Overlocking sewing machines for forming 
overlocked stitches with one needle and two threads have a sewing needle, 
a lower looper and a spreader, which are cooperatively actuatable to 
produce such overlocked stitches. 
In the conventional machine, as many differently shaped loopers and 
spreaders are needed as the stitches produced by their use. Formation of 
overlocked stitches with one needle and three threads or one needle and 
two threads on a single sewing machine requires two different loopers 
which are to be replaced with each other as demands dictate, an 
arrangement which is quite tedious and time-consuming. 
Recently, as seen in U.S. Pat. No. 4,237,804 a sewing machine was proposed 
for stitching fabric edges with an overlocked stitch with one needle and 
three threads, the sewing machine including an upper looper and a separate 
movble member attached thereto, which together define a hook portion for 
overcasting a fabric edge with one needle and two threads as with a single 
spreader. When forming overlocked stitches with one needle and three 
threads, the movable member is brought away from the upper looper to 
release the hook portion and allow the upper looper to function as 
intended. In this machine, the combined hook portion moves along the same 
path as that of the upper looper when forming overlocked stitches with one 
needle and three threads, so that the hook portion and the upper looper 
will meet a lower looper at the same position to produce the respective 
stitches. The separate movable member which is necessary to cooperate with 
the upper looper in providing the combined hook portion for formation of 
overlocked stitches with one needle and two threads must be retracted, 
when not in use, into a position in which the movable member does not 
interfere with operation of the sewing machine, and hence a space must be 
reserved for retracting the movable member therein. Furthermore, when the 
combined hook portion picks up a thread from the lower looper, the thread 
therefrom tends to be caught in a gap defined between the upper looper and 
the separate movable member. 
Thus, the known overlocking sewing machines even with the combined hook 
portion upper looper and movable member, are unable to form overlocked 
stitches of at least two types, reliably and smoothly, while permitting 
the change between stitch types to be quickly made. 
It is therefore an object of the present invention to solve the foregoing 
problems encountered with the prior apparatus by providing a single looper 
element which enables the production of both one needle, three thread 
overlocked stitches and one needle, two thread overlocked stitches upon 
cooperation with a needle and a lower looper in a sewing machine. 
This object and other objects, features and advantages of the present 
invention will become apparent from the following description when 
considered in connection with the accompanying drawings. 
SUMMARY OF THE INVENTION 
In general, the objects and advantages of the present invention are 
achieved by providing an improved looper having a unitary distal portion 
which serves as an upper looper and as a spreader, thus serving the 
functions of two different elements. In the present invention, the upper 
portion of the distal portion of the improved looper serves as an upper 
looper to produce overlocked stitches with one needle and three threads 
while the lower portion of the distal portion of the improved looper 
serves as a spreader for producing overlocked stitches with one needle and 
two threads. The unitary distal portion of the improved looper, includes 
upper and lower distal end portions jointly defining a hook portion 
therebetween. The hook portion can be considered to be a spreader portion 
which is operable to function as a spreader as described herein. The 
unitary distal portion preferably is curved toward the lower looper in the 
sewing machine, and is operable with a sewing needle and a lower looper, 
both of which are capable of carrying threads for the selective production 
of overlocked stitches with one needle and three threads or one needle and 
two threads. The improved looper of the present invention preferably 
includes an aperture in its unitary distal portion which is capable of 
supporting a thread for movement with the looper. 
The improved looper of the invention is supported by holder means, 
preferably a looper holder, which in turn is mounted to driving means for 
the looper for movement therewith. The supporting of the improved looper 
to the holder means and to the driving means is accomplished at least in 
part by positioning means mounted on said holder means or said driving 
means for selectively positioning the improved looper with its unitary 
distal portion with respect to the driving means in a first or second 
position at which the looper driving means drives the looper along 
different paths, and thereby meets the lower looper at different 
positions. In its first position, the unitary distal portion of the 
improved looper is moved by the driving means along a first path and in 
its second position the unitary distal portion is moved along a second 
path. As will be hereinafter described, the positioning of the improved 
looper with its unitary distal portion in either of the two positions and 
moving the portion along the respective paths will determine the formation 
of overlocked stitches with either one needle and three threads or one 
needle and two threads. 
Upon movement along one of its two paths, the improved looper, in 
cooperation with a needle carrying a thread and a lower looper also 
carrying a thread, will serve as an upper looper to pick up the lower 
looper thread for producing, with a third thread carried by it, overlocked 
stitches with one needle and three threads; while upon movement along the 
other of its two paths, the improved looper, again in cooperation with the 
needle and lower looper, each carrying a thread, will serve as a spreader 
having a front hook portion to catch and retain the lower looper thread 
for forming overlocked stitches with one needle and two threads. 
More specifically, the improved looper in the first position is movable to 
cause the distal or hook portion to move along one path across the lower 
looper for forming, with a thread carried by the improved looper, an 
overlocked stitch with one needle and three threads, and the improved 
looper in the second position is movable to cause the distal or hook 
portion to move along a second path across the lower looper so as to pick 
up and spread a lower thread loop from the lower looper for forming an 
overlocked stitch with one needle and two threads.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings where like elements have the same reference 
numbers, and specifically to FIGS. 1-4, the numeral 20 designates 
generally a looper constructed in accordance with the present invention, 
the looper having a unitary distal end portion bifurcated with upper and 
lower distal end portions 21, 22 which jointly define a hook portion 23 
therebetween. Lower distal end portion 22 and hook portion 23 serve as a 
spreader portion to catch and retain lower looper thread 56, (FIG. 14), so 
as to assist in forming overlocked stitches with one needle and two 
threads. Upper looper portion 33 formed by upper distal end portion 21 
having an upper surface 34 of said unitary distal portion serves as an 
upper looper to produce overlocked stitches with one needle and three 
threads. The upper distal end portion 21 has adjacent thereto in suitable 
position in looper 20 an aperture 24 for passage of a thread therethrough. 
The distal end portions are curved toward the back of a lower looper 27 as 
shown. 
As best illustrated in FIGS. 2 and 3, looper 20 has a mounting flange 25 on 
one side of a rear or lower portion of the looper, flange 25 in this 
embodiment having an elongated aperture, preferably a slot, 26 extending 
longitudinally of the flange. 
As shown in FIG. 4, the lower looper 27 is angularly movable about a shaft 
(not shown) disposed downwardly thereof for reciprocal movement in the 
directions of the arrows 28. A sewing needle 29 is movable downwardly in 
front of the lower looper 27 as it is withdrawn. The lower looper 27 has 
in its distal end an aperture 30 for passage of a thread therethrough. 
Designated in FIG. 4 as 31 is a looper holder on which is mounted the 
flange 25 of the looper 20. The looper 20 is secured to the distal end 
portion of (as shown) looper holder 31 by a screw 32 extending through the 
elongated slot 26 into a threaded hole in the looper holder 31 in at least 
two positions which are determined by the positioning of the flange 25 on 
the looper holder, and screw 32 in slot 26. To selectively position looper 
20 in position for the formation of overlocked stitches with one needle 
and three threads, the looper 20 is first moved forward toward the lower 
looper 28 into the solid-line position illustrated in FIG. 4 until the 
right end of the elongated aperture 26 abuts against the screw 32. The 
looper 20 is then fixed to the looper holder 31 by tightening the screw 
32. In order to selectively position looper 20 in position for the 
formation of overlocked stitches with one needle and two threads, the 
screw 32 is loosened to allow the looper 20 to be retracted on the looper 
holder 31 until the left end of the elongated aperture 26 abuts against 
the screw 32. Then, the screw 32 is tightened to fix the looper 20 to the 
looper holder 31. 
FIGS. 5-8 illustrate another embodiment of the present invention, reference 
numeral 40 generally designating the improved looper thereof with its 
unitary distal end portion. The unitary distal end portion of looper 40 is 
bifurcated with upper and lower distal portions 21, 22 jointly defining a 
hook portion 23 therebetween, and is curved toward the back of the lower 
looper 27. The looper 40 includes an aperture 24 for receiving a thread in 
the manner described above. Further in this embodiment, looper 40 is 
mounted on a looper holder 41, which in turn is fixedly mounted to an 
elongated member 42 of the looper driving means. Thus, whereas in the 
first embodiment, the elongated member served as the looper holder 31 to 
which looper 20 was mounted, in this embodiment the flanged member 41 
serves as the looper holder to which looper 40 is mounted and which in 
turn is mounted on the elongated member 42. 
Looper 40 has in its portion distant from the unitary distal end described 
above, a horizontally elongated aperture 43 through which a screw 44 
extends into threaded engagement in a threaded hole in the looper holder 
41. The looper 40 can be selectively positioned thereon by advancing the 
looper 40 to a first position or retracted to a second position upon 
loosening the screw 44, and can be secured in place in the first or second 
position by tightening the screw 44. To selectively position looper 40 in 
position for the formation of overlocked stitches with one needle and 
three threads, the looper 40 is displaced toward the lower looper 27 into 
the first solid-line position, in which the looper 40 is fastened by the 
screw 44. In order to selectively position looper 40 in position for the 
formation of overlocked stitches with one needle and two threads, screw 44 
is loosened to allow looper 40 to be retracted on looper holder 41 away 
from lower looper 27, and the screw 44 then tightened. 
FIG. 8 shows apparatus for driving a looper of the present invention. 
Although looper 40 is utilized in FIG. 8, the apparatus applies as well to 
looper 20. The driving apparatus comprises a drive shaft 45 located in a 
lower portion of the sewing machine, a crank 46 fixed to the shaft 45, and 
a swingable lever 47 connected at its distal end to one end of a connector 
link 48 by a pin 49. The other end of connector link 48 is connected by a 
pin 50 to an end of the crank 46. The swingable lever 47 is connected at 
its proximal end thereof to a shaft 51 rotatably journalled in a bearing 
(not shown) disposed downwardly of a bed of the sewing machine. 
The looper holder 31 in the embodiment of FIGS. 1-4 is in the form of an 
elongated rod to which flange 25 is mounted, whereas in FIG. 8 the 
elongated member 42 is an element of the driving apparatus. Thus, looper 
holder 31 can be considered in relation to FIG. 8 as 42 and, like member 
42, as having a lower end rotatably coupled to pin 49 and having an 
intermediate portion slidably inserted through a guide hole 52 in a guide 
member 53 that is angularly movably mounted on shaft 54 attached to a 
support (not shown) disposed downwardly of the sewing machine bed. 
When the drive shaft 45 rotates, the lever 47 is caused by the connector 
link 48 to turn about the shaft 51, whereupon the elongated member 42 
moves up and down as it swings about the shaft 54 causing the upper and 
lower distal ends 21, 22 of the looper to follow the path a or b shown in 
FIGS. 4 and 5. 
The manner in which the looper 20, 40 of the invention is utilized to form 
an overlocked switch with one needle and three threads will now be 
described. 
With the looper 20, 40 selectively positioned in the first solid line 
position in FIGS. 4 and 5, as described above, an upper thread 55 is 
threaded through the hole 24 in the looper 20, 40, a lower thread 56 is 
threaded through the hole 30 in the lower looper 27, and a sewing thread 
57 is threaded through a thread hole in the sewing needle 29. 
As the sewing machine is put into operation, the upper distal end portion 
21 of the looper 20, 40 moves along the path a as the distal end portion 
21 traverses the lower looper 27. At this time, the upper distal end 
portion 21 passes under the lower thread 56 as shown progressively in 
FIGS. 9, 10 and 11, and is raised with the lower thread 56 carried on 
upper surface 34. The looper 20, 40 continues to move upwardly to pass the 
upper thread 55 extending through the hole 24 under the lower thread 56 
and until the upper thread 55 meets the sewing needle 29. The upper thread 
55 is now caught by the sewing needle 29 as the latter is lowered. 
Thereafter, the looper 20, 40 is moved downwardly and the lower looper 27 
is retracted forming an overlocked stitch with one needle and three 
threads (Japanese Industrial Standards: Classification B9070, 
Identification E13, E13A). 
The manner in which the looper 20, 40 of the invention is utilized to form 
an overlocked stitch with one needle and two threads will now be 
described. 
The looper is retracted to the second, broken line position in FIGS. 4 and 
5 and secured in that position as heretofore described. In this position, 
the driving apparatus will cause the upper distal end portion 21 and hook 
portion 23 to follow the path b across the lower looper to form an 
over-locked stitch with one needle and two threads. 
The sewing machine is operated with the lower thread 56 and the needle 
thread 57, but without the upper thread 55 in the looper 20, 40. The hook 
portion 23 of the distal portion of the looper 20, 40 as it moves upwardly 
picks up the lower thread 56 extending through the lower looper 27 as 
shown successively in FIGS. 12, 13 and 14. The looper 20, 40 continues to 
move upwardly with the lower thread 56 retained in hook portion 23, i.e. 
between the distal end portions 21, 22, and more particularly by lower 
distal end portion 22 as shown in FIG. 14, until the lower thread 56 is 
taken by the sewing needle 29 as the latter descends. The looper 20, 40 
and the lower looper 27 are then retracted to form an overlocked stitch 
with one needle and two threads (Japanese Industrial Standards: 
Classification B9070, Identification E12, E12A). 
Stated otherwise, the upper distal end portion 21 of the looper 20, 40 
moves along the path b which is different from the path described by the 
upper distal end portion 21 as it is in the first position, as shown in 
FIGS. 4 and 5, and hence the upper distal end portion 21 does not move 
into the lower thread 56 carried by the lower looper 27. Instead, the 
lower distal end portion 22 portion follows a path b', as illustrated in 
FIG. 12, to pick up the lower thread 56, thus producing an overlocked 
stitch with one needle and two threads. 
The looper 20, 40 of the present invention can be attached to the looper 
holder 31, 41, respectively, at front and rear positions with little 
difficulty, such that the looper will move across the lower looper 27 at 
different positions. When the looper 20, 40 is in the forward position, 
the looper serves as an upper looper in a sewing machine for forming 
overlocked stitches with one needle and three threads, and when the looper 
20, 40 is in the rearward position, the looper serves as a spreader in a 
sewing machine for producing overlocked stitches with one needle and two 
threads. The arrangement of the present invention is highly advantageous 
in that it can form two kinds of overlocked stitches without the expense 
of having two different looper elements as with earlier sewing machines. 
With the present invention, as described above, the unitary looper 20, 40 
is easily movable from the first to the second position or vice versa in 
order to cause the distal end portions 21, 22 of the distal or hook 
portion to traverse the lower looper at different positions for the 
formation of overlocked stitches with one needle and two threads or one 
needle and three threads. 
While in the illustrated embodiments the looper 20, 40 has been shown as 
being movable generally horizontally, it may be arranged so as to move 
generally vertically between first and second positions, and various 
manners of movement such as angular movement or sliding movement may be 
employed for shifting the looper. 
The looper 20, 40 moves across the lower looper 27 at different positions 
simply by changing paths of movement of the distal or hook portion of the 
looper 20, 40. The arrangement of the invention is advantageous in that no 
additional member for defining a hook portion with the upper looper is 
needed resulting in smooth and reliable formation of overlocked stitches, 
a construction which is different from conventional arrangements in which 
upper loopers move along a single, fixed path. Since there is no need for 
reserving an additional space for withdrawing therein a separate member 
out of interference with the operation of the machine for forming 
overlocked stitches with one needle and three threads, as with the 
recently proposed apparatus, the present invention is readily applicable 
to small-size sewing machines having limited space available therein.