Overcast sewing machine for forming a multiple-thread overcast seam

An overcast sewing machine in which a plurality of different stitch types can be sewn. Various designs are disclosed for sewing alternatingly the stitch types 512 and 514, which consist of two needle threads, one lower looper thread and one overcast looper thread. In one design, the holder of the overcast looper can be fixed in a first working position, in which both needle threads are interlinked with the overcast looper thread, and can be displaced into a second working position, in which only one needle thread is interlinked with the overcast looper thread. According to another design, two thread eyes are provided in the overcast looper and the overcast looper thread is threaded through one of these thread eyes to form one of the stitch types and through the other thread eye to form the other stitch type. In addition, stitch type 504, consisting of three threads, can be formed by removing one needle. To form a stitch type 502 consisting of one needle thread and one lower looper thread, an overcast looper with a fork-shaped catching tip can be moved on the looper holder from a resting position into a working position, in which the lower looper thread is laid around the edge of the material being sewn and is fed to the needle for penetration. The stitch-forming devices mentioned above are associated with additional stitchforming devices for forming a double chain stitch seam stitch type 401, DIN 61400, U.S. Federal Standard Catalogue Number 751.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention pertains to an overcast sewing machine for forming 
multiple-thread overcast seams, the sewing machine including at least two 
thread-carrying needles arranged at spaced locations from each other, one 
thread carrying lower looper taking up and throwing off the needle thread 
loops, and one thread-carrying overcast looper arranged on a looper holder 
for taking up the looper thread carried by the needle thread loops and 
laying the overcast looper thread around the edge of the material being 
sewn and feeding it for inserting the needles into a triangle formed by 
the leg of the overcast looper thread extending from the thread eye to the 
interlacing of the lower looper thread with the overcast looper thread at 
the edge of the material being sewed, by the needle-side leg of the lower 
looper thread line around the overcast looper, and by the overcast looper 
and, to an improvement of the design according to West German 
Offenlegungsschrift No., DE-OS36,36,390. 
2. Background Art 
The West German Offenlegungsschrift No., DE-OS 36, 39,390 discloses an 
overcast sewing machine with at least three thread-carrying needles, which 
are arranged next to each other, are aligned in a straight direction at 
right angles to the direction of feed of the material to be sewn and are 
arranged in a needle holder from which one needle or more needles can be 
removed. The sewing machine includes a thread-carrying lower looper, which 
cooperates with all needles; and an overcast looper, to which a limited 
pivoting movement is imparted, and which cooperates with all the needles 
except for the needle located farthest away from the edge of the material 
to be sewn. 
This overcast sewing machine forms an overcast stitch type not covered by 
either U.S. Federal Standard Catalogue No. 751 or German DIN Specification 
No. 61400, which consists of at least five threads, including three needle 
threads, which penetrate the material being sewn during sewing and are 
subdivided, depending on the distance from the edge of the material being 
sewn, into first needle threads and one last needle thread, as well as one 
lower looper thread and one overcast looper thread, which are interlaced 
at the edge of the material being sewn and are interlinked with all needle 
threads in the material being sewn. The overcast looper thread extends 
between the lower looper thread, with which it is interlinked at the edge 
of the material being sewn, and the first needle threads, which extend in 
parallel to the edge of the material being sewn and next to each other at 
spaced locations, and all of them are interlinked with the overcast looper 
thread. However, the last needle thread is interlinked only with the lower 
looper thread. 
By inserting another thread-carrying needle in the needle holder, it is 
possible to make a stitch type consisting of six threads, namely, four 
needle threads, one lower looper thread, and one overcast looper thread, 
in which stitch type the needle thread located farthest away from the edge 
of the material being sewn is interlinked only with the lower looper 
thread, and all others are interlinked with the lower looper thread and 
the overcast looper thread. 
If sewing is performed with only two thread-carrying needles, stitch type 
514 is formed, which consists of two needle threads, one lower looper 
thread, and one overcast looper thread, and the latter is interlinked with 
both needle threads in the fabric being sewn and is interlaced with the 
lower looper thread at the edge of the material being sewn. 
To form stitch type 504, which consists of one needle thread, one lower 
looper thread, and one overcast looper thread, which are interlaced with 
each other at the edge of the material being sewn and are interlinked with 
the needle thread in the material being sewn, the second needle must be 
removed. 
If, among the three thread-carrying needles, the needle located farthest 
away from the edge of the material being sewn is retained, and the first 
or second needle is optionally removed, it is possible to form stitch type 
512, in which the needle thread located farthest away from the edge of the 
material being sewn is interlinked only with the lower looper thread in 
the material being sewn, while the lower looper thread and the overcast 
looper thread are interlinked with the other needle thread in the material 
being sewn, and the latter threads are interlaced with each other at the 
edge of the material being sewn. 
The changeover from one stitch type to another is consequently carried out 
by adding or removing certain needles. Even though it is thus possible to 
make several stitch types on one sewing machine, when adding one or 
several needles, it is necessary to rethread the needle thread, usually 
through a number of thread guide eyes and the eye of the needle, which is 
relatively time-consuming, in addition to insertion into the needle holder 
and fixing. 
SUMMARY AND OBJECT OF THE INVENTION 
It is primary object of the present invention to design an overcast sewing 
machine of this class such that several stitch types can be sewn with 
minimum effort for changeover. 
According to the present invention, various designs are provided to 
accomplish this task. The design according to the invention including 
providing a shutter looper which may be fixed in a first working position, 
in which both needles penetrate into the above mentioned triangle, and can 
be displaced into and fixed in a second working position, in which only 
one needle, adjacent to the edge of the material being sewn penetrates 
into the triangle, makes it unnecessary to reroute the threading or to 
rethread the thread if the stitch types 512 and 514 are sewn 
alternatingly. To achieve this, the overcast looper only needs to be 
brought from one working position into another. 
Stitch type 504 can also be prepared, as in the state of the art, by 
removing one of the needles. 
Advantageous designs of the overcast looper, its holder and its guide bar 
are provided in which the overcast looper includes a shaft which is 
arranged displaceable in a transverse hole of a guide bar and is fastened 
to the looper holder, which is arranged at a free end of the guide bar 
such that it can be displaced between the first and second working 
positions and can be fixed there. 
The design including two locking grooves for receiving a spring clip which 
is fastened on the guide bar, provided on the looper holder ensures 
reliable fixation of the overcast looper in both working positions in a 
simple manner. 
The measure of the invention including providing the looper holder with a 
hand grip, facilitates handling during the changeover from one stitch type 
to the other. 
The design according to the invention in which the overcast looper has two 
thread eyes, located at spaced locations at a distance corresponding to 
the distance between the needles, through which thread eyes the thread 
carried by the overcast looper can be lead optionally to form two 
different overcasts seams, so that one needle penetrates into the above 
mentioned triangle when the overcast looper thread is lead through one 
thread eye and both needles penetrate into the triangle when the overcast 
looper thread is lead through the other thread eye, requires only 
transferring the overcast looper thread from one thread guide eye into the 
other in order to sew the stitch types 512 and 514 alternatingly. 
The measures according to the invention in which the overcast looper is 
overlaid by a looper with a fork shaped catching tip formed by two legs of 
unequal length such that the leg of the looper farther away from the 
needle supplements the tip of the overcast looper and the looper can be 
displaced on the looper holder from a shut-off position into a working 
position and can be fixed there, in which working position it catches, 
together with the tip of the overcast looper, the lower looper thread, 
lays it around the edge of the material being sewed and feeds it to the 
point of insertion of the needle between the overcast looper and its leg 
extending from the bottom of the fork to the edge of the material being 
sewed, expands the field of use of the overcast sewing machine by the 
possibility of sewing stitch type 502. 
The design according to the invention in which the fork shaped looper has 
an angularly bent end with an essentially rectangular opening, through 
which a projection of the looper holder extends to secure the position, 
serves to secure the position of the overcast looper with the fork-shaped 
catching tip and the design according to the invention in which the 
fork-shaped looper has a hand grip, serves to facilitate the changeover of 
this looper when changing over from the resting position to the working 
position and vice versa. 
The characteristics of an overcast sewing machine as described so far make 
it possible to change over a sewing machine for forming a plurality of 
different overcast stitch types. As a result, a number of users, 
especially small entities and the household, can do without purchasing 
several special machines, which are designed to form only one or two 
overcast stitch types, and which are consequently suitable only for 
special types of fabric and for corresponding stitch type requirements. 
All overcast stitch types share the common feature that they can be used 
in a time-saving and highly efficient manner to sew together two fabric 
layers while hemming in or cleaning and securing the fabric edges against 
fraying, and seams prepared with these stitch types are characterized by 
high longitudinal extensibility. In contrast, the tensile strength of the 
seam and the stability under higher stresses are not very good compared 
with seams prepared with other stitch types. 
Under the type designation "Hobbylock 795", the applicant markets an 
overcast sewing machine published in Pfaff Company's Booklet "Fur's 
Atelier", Document No. 23369 3.87 Kala), which has stitch-forming devices 
for forming an overcast seam of stitch type 503 according to DIN 61400, 
U.S. Federal Standard Catalogue No. 751, in combination with 
stitch-forming devices for forming a double chain stitch seam, stitch type 
401 according to 61400, U.S. Federal Standard Catalogue No. 751, at a 
laterally spaced location from the overcast seam. The combination of the 
overcast seam with the double chain stitch seam unites high longitudinal 
extensibility with high tensile strength of the seam. However, for 
processing knitted goods, the overcast seam of stitch type 503 is too 
narrow to sufficiently secure the edges of the fabric layers. 
The measure according to the invention in which the stitch-forming means 
performing the respective overcast seam (stitch types numbers 504, 512, 
514, DIN61400, U.S. Federal Standard Catalogue Number 751) are associated 
with additional stitch-forming means performing a double chain stitch seam 
(stitch type number 401, DIN61400, U.S. Federal Standard Catalogue Number 
751) to the side of the overcast seam (stitch types numbers 504, 512, 
514,), is suggested to expand the possible applications of such a sewing 
machine. To achieve higher strength of the connection and higher 
resistance to stresses, each overcast seam to be formed with the means 
according to the intention specified in the paragraphs above is 
supplemented with a double chain stitch seam of stitch type 401, so that 
the existing possibilities for forming different stitch types are 
expanded. 
Because of the extremely limited space available under the needle plate, it 
is advantageous to arrange the additional stitch-forming devices, 
according to the invention such that the additional stitch forming means 
are arranged in front of the stitch forming means performing the overcast 
seams (stitch type numbers, 504, 512, 514). 
The measures according to the invention in which the stitch forming tools 
performing: 
(A) A thread overcast seam stitch type number, 504, DIN61400, U.S. Federal 
Standard Catalogue Number 751; 
(B) An imitation four-thread overcast safety seam, stitch type number, 512, 
DIN61400 U.S. Federal Standard Catalogue Number 751; and 
(C) A four-thread overcast seam, stitch type number, 514, DIN61400, U.S. 
Federal Standard Catalogue Number 751, are always activated in combination 
with the stitch forming means for forming the double chain stitch seam, 
stitch type number, 401 which also can be used alone or activated alone, 
ensures versatile possibilities of application for a single sewing 
machine. As a result, the machine can be used for nearly all the 
sewing-together and hemming-in operations that occur in practice. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which 
preferred embodiments of the invention are illustrated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
As is shown in FIG. 1, the needle drive lever 2, whose fork-shaped end 3 is 
hinged to the needle holder 4, in which two thread-carrying needles 5 and 
6 are fastened interchangeably, is fastened on the oscillating shaft 1. 
The needle holder 4 is guided longitudinally movably on a sliding bar 7 
corresponding to arrow 8, and the sliding bar is mounted on a pin 9 that 
is a permanent part of the housing. A thread-carrying lower looper 10, 
which is fastened in a looper holder 12 clamped on the oscillating shaft 
11, cooperates with the needles 5 and 6. The lower looper 10 performs an 
oscillating movement according to arrow 13. 
The overcast looper guide bar 14, which is guided longitudinally movably in 
a revolute and sliding joint 15, is driven by an oscillating shaft 16 via 
a drive lever 17, which is hinged to the lower, fork-shaped end 18 of the 
guide bar 14. The upper end of the guide bar 14 has a reduced diameter, as 
can be seen in FIGS. 2 and 5. An angular looper holder 19 has in one of 
its legs 20 a longitudinal slot 21 and is placed onto the narrowed end of 
the guide bar 14. A hole for the passage of the shaft 23 of an overcast 
looper 24, in which hole it is fastened with a screw 25, is provided in 
the downwardly extending leg 22 of the looper holder 19. The looper 24 has 
a thread catching shoulder 26. A hole directed obliquely relative to the 
longitudinal axis of the guide bar 14, in which the overcast looper 24 is 
guided displaceably with its shaft 23, is provided in the guide bar 14. 
The overcast looper 24 has a thread hole 27 (See FIGS. 2 and 5) and a 
thread guiding groove 28, from which two transverse holes, which are 
arranged at spaced locations from each other and will hereinafter be 
called thread eyes 29 and 30, and whose purpose will be described later, 
traverse the overcast looper 24. In practice, the overcast looper 24 has 
only one thread eye. To show another design, it is represented with two 
thread eyes 29 and 30 in the drawings. 
The leg 20 of the looper holder 19 has a projection 31, in which two 
V-shaped locking grooves 32 and 33 are provided for a spring clip 34, 
wherein the legs 35 and 36 of the spring clip are in contact with the 
front side of the guide bar 14, and the spring clip is associated with a 
clamping disk 37 provided on the underside with corresponding grooves for 
the legs 35 and 36 of the spring clip 34. The looper holder 19 is provided 
with a handgrip 38 for displacing the looper holder 19 from one working 
position of the overcast looper 24 fastened in the looper holder 19 into 
the other working position, which positions are determined by the spring 
clip 34 in conjunction with the locking grooves 32 and 33. This 
arrangement provides a looper holder adjustor means. 
Stitch type 512 (FIGS. 4 and 8), is formed in one working position of the 
overcast looper 24, in which the spring clip 34 snaps into the locking 
groove 33, due to the cooperation of the needles 5 and 6, which are 
movable in the direction of the arrow 8, of the lower looper 10, which is 
driven such that it performs oscillating movements in the direction of 
arrow 13, and of the overcast looper 24, which is movable in the direction 
of arrow 39, and stitch type 514 (FIGS. 7 and 9), is formed in the other 
working position of the overcast looper 24, in which the spring clip 34 
snaps into the locking groove 32. 
To form stitch type 502 (FIGS. 10 and 11), an overcast looper 41 made from 
a thin spring plate with a catching tip 44 formed by two legs 42 and 43 of 
unequal length is mounted by inserting a spacing plate 40. The overcast 
looper 41 has an angularly bent end 45 with an essentially rectangular 
opening 46, through which the projection 31 of the looper holder 19 
extends to secure the position of the overcast looper 41. 
By inserting a spring washer 47, the overcast looper 41 is fastened, 
together with the spring clip 34 and the clamping disk 37, to the guide 
bar 14 by means of a screw 49 passing through the spring washer, a 
longitudinal slot 48 in the overcast looper 41, the spacing plate 40, and 
the clamping disk 37, such that it can be displaced from a resting 
position into a working position, in which the leg 43 of the catching tip 
44 that is farther away from the needle 5 supplements by the catching tip 
50 of the overcast looper 24 by overlapping it. To facilitate handling, 
the overcast looper 41 is provided with a handgrip 51. 
As is shown in FIG. 12, the needle drive lever 102, whose fork-shaped end 
103 is connected by a connecting rod 104 to the needle bar pin 106 
fastened to the needle bar 105, is fastened on the oscillating shaft 101. 
The needle bar 105 can be moved up and down in bearing bushes 107 and 108, 
which are permanent parts of the housing, as is indicated by arrow 109 in 
FIG. 12. A needle holder 110, in which three thread-carrying needles 111, 
112, and 113 are inserted and fastened, is fastened at the lower end of 
the needle bar 105. The needle 113 is arranged laterally offset from the 
needles 112 and 113, which are arranged in one line extending at right 
angles to the direction of feed of the material to be sewn, and in front 
of the latter needles. A thread-carrying lower looper 114 and a 
thread-carrying overcast looper 115 cooperate with the needles 111 and 
112, and a thread-carrying double chain stitch looper 116 cooperates with 
the needle 113. The lower looper 114 is fastened in a looper holder 118 
clamped onto the oscillating shaft 117, and it performs an oscillating 
movement corresponding to arrow 119. 
The overcast looper guide bar 120, which is guided longitudinally 
displaceably in a revolute sliding joint 121, is driven by an oscillating 
shaft 122 via a drive lever 123, which is hinged to the lower, fork-shaped 
end 124 of the guide bar 120. The upper end of the guide bar 120 has 
reduced diameter, as is indicated in FIGS. 12, 13, and 16. An angular 
looper holder 125, which has a longitudinal slot 127 in one of its legs 
126, is mounted on the end of the guide bar 120. In the downwardly 
extending leg 128 of the looper holder 125, a hole for the passage of the 
shaft 129 of the overcast looper 115, in which hole the shaft is fastened 
with a screw 130, is provided. In the vicinity of its catching tip 131, 
the overcast looper 115 has a thread eye 132, which begins in a thread 
guide groove 133 which joins a thread feed hole 134 passing through the 
looper body. To support the lower looper thread taken up by the overcast 
looper 115, the overcast looper 115 has a thread catching shoulder 135. It 
performs a movement around the edge of the material to be sewn, W, 
corresponding to arrow 136 in FIG. 12. 
The leg 126 of the overcast looper holder 125 has a projection 137, in 
which two V-shaped locking grooves 138 and 139 are provided for a spring 
clip 140, which is fastened to the guide bar 120 by inserting a clamping 
disk 143 having corresponding grooves on its underside for the legs 141 of 
the spring clip 140. A handgrip 144 for displacing the looper holder 125 
from one working position of the overcast looper fastened in the looper 
holder 125 into another working position, which working positions are 
determined by the spring clip 140 in conjunction with the locking grooves 
138 and 139, is provided on the looper holder 125. 
The double chain stitch looper 116, which cooperates with the needle 113 to 
form stitch type 401, DIN 61400 (U.S. Federal Standard Catalogue No. 751), 
is fastened on a looper holder 145, which is clamped on an oscillating 
shaft 146. In addition to its oscillating movements in the direction of 
arrow 147 in FIG. 12, axial displacing forces in the direction of arrow 
148 are also imparted to the oscillating shaft 146. The two movement 
components result in an elliptical movement path 150 (FIGS. 19 and 20) of 
the catching tip 149 of the double chain stitch looper 116 around the path 
of movement of the needle 113 to catch and throw off the loop 153 of the 
needle thread 151. 
In one working position (FIGS. 13 and 14) of the overcast looper 115, in 
which the spring clip 140 snaps into the locking groove 139, a stitch type 
512, DIN 61400, U.S. Federal Standard Catalogue No. 751, is formed due to 
the cooperation of the needles 111 and 112, which can be moved in the 
direction of the arrow 109; of the overcast looper 115, which can be moved 
in the direction of the arrow 136 around the edge of the material being 
sewn W; and of the lower looper 114, which is driven to perform an 
oscillating movement in the direction of the arrow 119. This is an 
imitation four-thread safety seam. FIGS. 15 and 19 show this seam together 
with the double chain stitch seam, stitch type 401. 
The four-thread overcast seam stitch type 514, DIN 61400, U.S. Federal 
Standard Catalogue No. 651, is formed in the other working position (FIGS. 
16 and 17) of the overcast looper 115, in which the spring clip 140 snaps 
into the locking groove 138. FIGS. 18 and 20 show this seam together with 
the double chain stitch seam, stitch type 401. 
Mode of Operation 
For the stitch type 512 shown in FIG. 4, which consists of the sewing 
threads 60 and 61, the lower looper thread 62, and the overcast looper 
thread 63, and for its formation, which is illustrated in FIG. 8, the 
overcast looper thread 63, which, coming from a thread reserve, is fed, 
according to one design, through the thread hole 27 and the thread groove 
28, is threaded through the thread eye 30, and the looper holder 19 is 
brought into its first, retracted working position shown in FIGS. 2 and 3, 
in which the spring clip 34 has snapped into the locking groove 33, and 
the thread eye 29 is located to the right of the path of movement of the 
needle 5 in FIGS. 2, 3 and 8, and the thread eye 30 is located to the left 
of the path of movement of the needle 5. Stitch formation takes place such 
that the lower looper 10 penetrates into the loops 68 and 69 of the needle 
threads 60 and 61, respectively, during the forward oscillating movement. 
During its upwardly and laterally directed arc-shaped movement 
corresponding to arrow 39,(See FIG. 1) the overcast looper 24 takes up the 
lower thread 62 emerging from the thread eye 10a of the lower looper 10 on 
the rear side of the lower looper 10 in FIG. 8 behind the thread eye 10a. 
This lower thread is caught by the catching shoulder 26 of the overcast 
looper 24, so that, as is shown in FIG. 8, it lies as a loop over the 
overcast looper 24, whose needle-side leg 64 extends to the interlacing 65 
with the overcast looper thread 63 at the edge of the material being sewn, 
and whose leg 66, which is farther away from the needle, extends from the 
catching shoulder 26 to the interlacing 67 with the two needle thread 
loops 68 and 69. The part 70 of the overcast looper thread 63, which 
emerges from the thread eye 30 on the needle side and extends to the 
interlacing 67, is fed by the material feed of the needle 5 with the 
thread 60 such that it penetrates into the triangle formed by the leg 70 
of the overcast looper thread, which leg extends from the thread eye 30 to 
the interlacing 65 of the lower looper thread 62 with the overcast looper 
thread at the edge of the material being sewn, by the needle-side leg 64 
of the lower looper thread 62 lying around the overcast looper 24 in its 
catching shoulder 26, and by the overcast looper 24 proper, while the 
needle 6 with the needle thread 61 passes only through the material being 
sewn W. During its back-swinging movement, the lower looper 10 throws off 
the needle thread loops 68 and 69, which are then pulled by the thread 
layer, so that the lower looper thread 62 is interlinked by the needle 
threads 60 and 61 on the underside of the workpiece W. On the top side of 
the workpiece W, the overcast looper thread 63 is interlinked only with 
the needle thread 60. 
To change over from stitch type 512 to stitch type 514, the looper holder 
19 with the overcast looper 24 only need be pushed forward into the second 
working position to the needles 5 and 6 to the extent that the spring clip 
34 will snap into the locking groove 32. In this second working position 
(FIGS. 5, 6 and 9), the path of movement of the needles 5 and 6 is to the 
right of the thread eye 30. After the lower looper 10 has penetrated into 
the needle thread loops 68 and 69, after the lower looper thread 62 
carried by the lower looper has been taken up by the overcast looper 24 on 
the needle side behind the thread eye 10a, and after the overcast looper 
thread leg 70 emerging from the thread eye 30 of the overcast looper 24 on 
the needle side has been fed to the needles 5 and 6, both of the needles 5 
and 6 with the threads 60 and 61 penetrate into the triangle formed by the 
leg 70 of the overcast looper thread 63, by the leg 64 of the lower looper 
thread 62, and by the overcast looper 24, and pass through the material 
being sewn W. The overcast looper thread 63 is now interlinked with the 
two needle threads 60 and 61 on the top side of the material being sewn, 
and on the underside of the material being sewn, the lower looper thread 
62 interlaced with the overcast looper thread 63 at the edge of the 
material being sewn is also interlinked with both of the needle threads 60 
and 61 by throwing off the two needle thread loops 68 and 69 caught by the 
lower looper thread, which are pulled by the thread layers to the 
underside of the material being sewn. 
As in the state of the art, stitch type 504 can be formed by removing the 
right-hand needle 5 with the looper holder 19 of the overcast looper 24 in 
the second working position or by omitting the left-hand needle 6 with the 
looper holder 19 and with the overcast looper 24 in the first working 
position. 
According to the other design, stitch type 512 (FIG. 4) is formed by 
leaving the overcast looper 41 with the catching tip 44 in its resting 
position and fixing the looper holder 19 with the overcast looper 24 in 
its second working position displaced toward the needles 5 and 6 (FIGS. 5 
and 6), in which the spring clip 34 has snapped into the locking groove 
32. The overcast looper thread 63, fed in through the thread hole 27 and 
the thread groove 28, is threaded through the thread eye 29, which is 
located to the left of the path of movement of the needle 5 and to the 
right of that of the needle 6 in FIG. 5. 
After the lower looper 10 has penetrated into the loops 68 and 69 of the 
needle threads 60 and 61 at the beginning of the upward movement of the 
inserted needles 5 and 6, after the lower thread 62 carried by it has been 
taken up by the overcast looper 24 on the needle side behind the thread 
eye 10a, and after the leg 70 emerging on the needle side from the thread 
eye 29 of the overcast looper 24 has been brought to the feed position 
over the material being sewn W, only the needle 5 with the needle thread 
60 penetrates into the triangle formed during the feed of the material 
being sewn by the leg 70 of the overcast looper thread 63, by the leg 64 
of the lower looper thread 62, and by the overcast looper 24, whereas the 
needle 6 with the needle thread 61 penetrates only the material being sewn 
W, as a result of which the overcast looper thread 63 is interlinked with 
the needle thread 60 on the underside of the material being sewn, and the 
lower looper thread 62, which is interlaced with the overcast looper 
thread 63 at the edge of the material being sewn, is interlinked with both 
of the needle threads 60 and 61 on the underside of the material being 
sewn due to the needle thread loops 68 and 69 being thrown off during the 
swing-back movement off the lower looper 10 and to the loops 68 and 69 
being tensioned by the thread layer of the sewing machine. 
To sew stitch type 514 (FIG. 7), only the overcast looper thread 63 needs 
be pulled out of the thread eye 29 and be threaded through the thread eye 
30, without changing the position of the looper holder 19 with the 
overcast looper 24 and the overcast looper 41. The paths of movement of 
both of the needles 5 and 6 are now to the right of the thread eye 30 in 
FIG. 5. After the loopers 10 and 24 have reached the above-mentioned "feed 
position", both of the needles 5 and 6 penetrate into the triangle formed 
during the feed of the material being sewn by the leg 70 of the overcast 
looper thread 63, the leg 64 of the lower looper thread 62, and the 
overcast looper 24, so that both threads, namely, the overcast looper 
thread 63 on the top side of the material being sewn and, on the underside 
of the material being sewn, the lower looper thread 62 interlaced with the 
overcast looper thread 63 at the edge of the material being sewn, are 
interlinked with the needle threads 60 and 61 after the needle thread 
loops 68 and 69 have been thrown off during the back-swinging movement of 
the lower looper 10 and pulled by the thread layer of the sewing machine 
toward the material being sewn. 
After removal of one needle, stitch type 504 can be formed with the second 
design as well. 
To form stitch type 502 (FIGS. 10 and 11), one needle, e.g., needle 6, is 
removed, the overcast looper thread 63 is pulled out of the thread eye 30, 
the looper holder 19 with the overcast looper 24 is brought into its 
working position farther away from the needle 5, in which position the 
spring clip 34 has snapped into the locking groove 33, and the overcast 
looper 41 is pushed toward the tip 50 of the overcast looper 24 into a 
working position, in which the fork leg 43 of the catching tip 44 covers 
part of the looper tip 50, and this the looper tip forms an extension of 
the fork leg 43, as is shown in FIG. 10. 
Stitch formation is now performed such that the lower looper 10 with the 
lower looper thread 62 penetrates into the needle thread loop 68 formed at 
the beginning of the upward movement of the inserted needle 5, the 
fork-shaped catching tip 44 of the looper 41 catches, together with the 
catching tip 50 of the overcast looper 24, the lower looper thread 62 
emerging from the needle lug 10a on the needle side to the left of the 
thread eye 10a in FIG. 10, and feeds it around the edge of the material 
being sewn over the workpiece W in front of the needle 5. The needle 5 
with the needle thread 60 then penetrates between the leg 71 of the lower 
looper thread 62 extending between the bottom of the catching tip 44 to 
the needle thread loop 68 and the overcast looper 41. During the return of 
the overcast looper 41 and of the lower looper 10, the lower looper thread 
62 is released by the catching tip 44 and is brought by the lower looper 
10 to the underside of the workpiece around the edge of the material being 
sewn, and the loop 68 of the needle thread 60 is thrown off and pulled by 
the thread layer of the sewing machine to the underside of the material 
being sewn. The lower looper thread 62 is thus interlinked with the needle 
thread 60 on the top side of the material being sewn and on the underside 
of the material being sewn. 
To form the double chain stitch seam 401, stitch type 401 according to DIN 
61400, U.S. Federal Standard Catalogue No. 751, which consists of the 
needle thread 151 and the looper thread 152, the needle 131 carrying the 
needle thread 151 is inserted into the triangle that is formed by the loop 
153 of the needle thread 151, which loop is caught by the double chain 
stitch looper 116 during the forward oscillation and lies around it, by 
the leg 152a of the looper thread 152 extending to the stitch hole in 
front of the thread eye 116a, and by the double chain stitch looper 116. 
During the back-swinging of the double chain stitch looper 16, the loop 
153 is thrown off and pulled by the known thread layer toward the 
underside of the material being sewn. 
To form the imitation safety seam shown in FIGS. 15 and 19, stitch type 512 
according to DIN 61400, U.S. Federal Standard Catalogue No. 751, which 
consists of the needle threads 154 and 155, the lower looper thread 156, 
and the overcast looper thread 157, the looper holder 125 with the 
overcast looper 115 carrying the overcast looper thread 157 is brought 
into the first working position shown in FIGS. 13 and 14, in which the 
spring clip 140 snaps into the locking groove 139, and the thread eye 132 
of the overcast looper 115 is located between the paths of movement of the 
two needles 111 and 112 as shown in FIGS. 13 and 14 "when the needle 154 
enters into the triangle formed by the leg 164 of the overcast looper 
thread 157, the needle side of the overcast looper 115 and the interlacing 
of said lower looper thread 156 with said overcast looper thread 157 at 
the edge of the material being sewn". Stitch formation is performed such 
that the lower looper 114 penetrates into the loops 158 and 159 of the 
needle threads 154 and 155 during the forward oscillating movement. During 
its upwardly and laterally directed arc-shaped movement according to the 
arrow 136 (FIG. 12), the overcast looper 115 takes up the lower looper 
thread 156 emerging from the thread eye 114a on the rear side of the lower 
looper 114 behind the thread eye 114a. This lower looper thread is caught 
by the catching shoulder 135 of the overcast looper 115, so that it lies, 
as is shown in FIG. 19, over the overcast looper 115 as a loop, whose 
needle-side leg 160 extends to the interlacing 161 formed with the 
overcast looper thread 157 at the edge of the material being sewn, and 
whose leg 162 away from the needle extends from the catching shoulder 135 
to the thread eye 114a through the interlacing 163 formed with the two 
needle thread loops 158 and 159. The part 164 of the overcast looper 
thread 157, which emerges from the thread eye 132 on the needle side and 
extends to the interlacing 161, is introduced by the material feed of the 
needle 111 into the triangle formed by the leg 164 of the overcast looper 
thread 157, which extends from the thread eye 132 to the interlacing of 
the lower looper thread 156 with the overcast looper thread 157 at the 
edge of the material being sewn, by the needle-side leg 160 of the lower 
looper thread 156 lying around the overcast looper 115 in its catching 
shoulder 135, and by the overcast looper 115 proper, while the needle 112 
with the needle thread 155 penetrates only through the material being sewn 
W. During its back-swinging movement, the lower looper 114 throws off the 
needle thread loops 158 and 159, which are then tensioned by the known 
thread layer, so that the lower looper thread 156 is interlinked by the 
needle threads 154 and 155 on the underside of the material being sewn. On 
the top side of the material being sewn, the overcast looper thread 157 is 
interlinked only with the needle thread 154. 
To change over from stitch type 512 to stitch type 514, the looper holder 
125 with the overcast looper 115 only needs to be pushed forward into the 
second working position toward the needles 111 and 112 to the extent that 
the spring clip 140 will snap into the locking groove 138. In the second 
working position (FIGS. 16, 17 and 20), the path of movement of the 
needles 111 and 112 are located to the right of the needle eye 132. After 
the lower looper 114 has penetrated into the needle thread loops 158 and 
159, after the lower looper thread 156 carried by it has been taken up by 
the overcast looper 115 on the needle side behind the thread eye 114a, and 
after the overcast looper thread leg 164 emerging on the needle side from 
the thread eye 132 of the overcast looper 115 has been fed to the needles 
111 and 112, both of the needles 111 and 112 with the threads 154 and 155 
penetrate into the triangle formed by the leg 160 of the lower looper 
thread 156 and the overcast looper 115 during the feed of the material 
being sewn, and pass through the material being sewn W. The overcast 
looper thread 157 on the top side of the material being sewn is 
interlinked with both of the needle threads 154 and 155, and the lower 
looper thread 156, interlaced with the overcast looper thread 157 at the 
edge of the material being sewn, is also interlaced with both of the 
sewing threads 154 and 155 on the underside of the material being sewn by 
the two needle thread loops 158 and 159, which are caught by the lower 
looper thread and pulled by the thread layer to the underside of the 
material being sewn. 
Stitch type 504 (FIG. 21) is formed by removing the needle 111 with the 
looper holder 125 of the overcast looper 115 in the second working 
position or by omitting the left-hand needle 112 with the looper holder 
125 and the overcast looper 115 in the first working position. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.