Improvements in Double Chain Stitch Sewing Machines.
Year: 1896

page_text: Date of Application, 7th Aug., 1896-Accepted, 12th Sept., 1896
COMPLETE SPECIFICATION.
Improvements in Double Chain Stitch Sewing Machines.
I, BERNHARD KÖHLER, Engineer, of Zwickauerstrasse, Chemnitz, in the
Kingdom of Saxony, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
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One of the recent developments of the glove trade is the use as
material of looped fabrics, made from very thin threads which form very fine
meshes.
Now, as the fineness of the seam should correspond to that of the looped fabric,
I have constructed a double chain stitch sewing machine which is capable of
producing a seam with very short stitches (about 17 or 18 stitches per centimetre)
and of using a very fine needle; for even the finest needles adapted for use on
ordinary sewing machines may cut the fine knitting threads and cause the meshes
to burst.
A needle suitable for such work must not only be fine, but it should also have a
short stroke, because a long and fine needle would vibrate too much; and care
must be taken, that even with the shortest stitch the needle enters accurately into
the loop of the lower thread.
In the double chain stitch machines hitherto used, the lower needle or looper
waits till the upper or sewing needle has passed through the loop; consequently
the upper or sewing needle must remain with its eye below the looper until the
latter has made a backward and a forward oscillation, which in the case of quick-
running machines can only be effected by a comparatively long needle and a long
stroke of the same.
eye las
In order that a short and very thin needle may be used, I have constructed the
machine in such a manner, that the looper need not wait until the needle's
passed it, and that ample time is afforded for the looper to get ready to enter the
needle loop, when the needle begins its upward motion.
In the accompanying drawings,
Fig. 1 is a side elevation of a machine embodying my invention;
Fig. 2 is a plan of the lower part;
Fig. 3, a front view; and Figs. 4 to 7 are diagrams on a larger scale showing
the formation of the seam.
The horizontal shaft b receives an oscillating motion from the main shaft a by
means of a grooved disc or cam c, friction roller r and lever h.
mounted the looper d which carries the lower thread f'.
On this shaft b is
A tooth e serving to deflect or lead off the looper thread f' is screwed on to a
lever g which has its fulcrum at x and receives its motion from a grooved drum i
mounted on the main shaft a. The motion of the sewing needle and of the cloth
feeder are produced in the usual manner by the ordinary means.
The process of sewing is illustrated by Figs. 4 to 7, and is as follows.―
After the sewing needle n with the thread f' has formed a loop, the looper d
carrying the thread f' enter the said loop, as shown in elevation by Fig. 4 and in
plan by Fig. 44, and the needle n re-ascends (Figs. 5 and 54).
Now the feed motion of the material takes place, while the tooth e seizes the
looper thread f' and guides it sideways, holding it in such a manner, that the
needle n cannot stab the thread f. This takes place even with the shortest
Finally
stitch and without requiring the looper d to wait for the needle n.

page_text: the tooth e again recedes (Figs. 7, 74), and the threads are tightened or
-drawn in.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
In double chain-stitch sewing machines, the combination of a looper d adapted
to move in the direction of the seam, with a tooth e adapted to deflect the looper
thread sideways, that is at an angle to the seam, before the sewing needle passes
through the material, substantially as described and for the purpose specified.
Dated this 7th day of August 1896.
FAIRFAX & WETTER,
433, Strand, London, Agents.