Improvements in Thread Feeds for Double-lockstitch Sewing Machines.
Year: 1891

page_text: Date of Application, 6th May, 1891
Complete Specification Left, 29th Jan., 1892-Accepted, 5th Mar., 1892
PROVISIONAL SPECIFICATION.
Improvements in Thread Feeds for Double-lockstitch Sewing
Machines.
I, SIEGFRIED NOTHMANN of the firm of Gebr. Nothmann, Sewing Machine
Makers of 20 Neue Hochstrasse Berlin N. in the Empire of Germany, do hereby
declare the nature of this invention to be as follows:-
It is known that in double lockstitch sewing machines the upper thread should be
kept taut whilst the needle is descending until it pierces the fabric to prevent a
loop of thread being formed and brought under the needle.
The improved thread feed hereindescribel is intended to effect this purpose and
has the further advantage over other thread feeds that it also accelerates the
drawing up the thread after passage of the shuttle and thus also the drawing up of
the stitch.
The thread feed lever pivoted at one end and carrying the thread at the other
end in the known manner is according to this invention provided on its under side
with a projecting nose. The needle bar is provided with an upwardly directed
hook or lifter or with a laterally projecting pin for the same purpose, namely, to
lift the thread feed lever and govern the descent thereof. When the needle bar is
in its highest position the hook or pin prevents the lever from descending until the
said hook or pin has arrived at the lower end of the nose on the said lever, which
will occur as the needle enters the cloth, the lever is then free to move and thence-
forth is caused by its spring to follow the movement of the needle bar until the
latter reaches its lowest position. As the needle bar moves upward from its lowest
position the said hook or pin presses and moves upon the inside of the nose on the
lever and lifts the latter, the movement of the lever being controlled by the needle
bar in this manner so that when the latter has attained the point where during the
downward stroke the thread lever began to fall, the latter will have been moved up
into its highest position and during the remainder of the upward stroke and first
portion of the downward stroke, be there maintained by the hook or pin moving in
front of the outer incline of the nose thereon.
Dated this 6th day of May 1891
HERBERT & Co.,
Agents to Applicant.
COMPLETE SPECIFICATION.
Improvements in Thread Feeds for Double-lockstitch Sewing
Machines.
1, SIEGFRIED NOTHMANN of the firm of Gebr. Nothmann, Sewing Machine
Makers of 20 Neue Hochstrasse Berlin N. in the Empire of Germany 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:-
In double lockstitch sewing machines while the needle is descending from its
highest position through the first part of its stroke, that is to say until the point of
the needle has at least commenced to pierce the fabric to be sewn, the upper thread
should be kept taut to prevent a loop of thread being formed and brought under the
needle which would prevent the proper formation of the stitch.
While effecting this general purpose of the thread feed lever, the improved
thread feed which is the object of this invention has the further advantage over
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page_text: other such feeds that by its action the thread is drawn up more quickly from
around the end of the shuttle and consequently the formation of the stitch is
accelerated.
The invention consists broadly in placing on the thread feed lever a projection or
nose, or in other words so shaping the contour of the under side of the thread lever
that when lifted by a projection or part of the needle bar, it rises to its greatest
height, or substantially so, before the needle bar has reached its highest position,
the further upward movement of the needle bar being without any further lifting
action, or with but very slight lifting action on the thread lever, and on the descent
of the needle bar, the thread lever is still prevented from descending until the
needle is piercing the fabric sewn.
The construction by which this is effected is shown in the annexed drawing in
which―
Figs. 1 and 2 are vertical sections of the head of the sewing machine, Fig. 1
showing the needle bar and thread lever in the lowest position, Fig. 2 the same in
the highest position.
Figs. 3 to 6 are detail views of a modified construction.
The thread lever a pivoted at i is formed with the necessary shape of contour
on its under side to act as described, by the addition of the nose c. The thread
lever which usually passes through a slot in the needle bar A is raised by a hook
like projection on the needle bar, the upper end of which projection rides on the
under side of the thread lever, so that the latter is raised more or less relatively to
the needle bar according to the shape of its under contour as it passes over the
projection. The spring a pressing on the piston e depresses the lever a causing it
to follow the movements of the projection 6 of the needle bar.
The shape of the nose c is such that when the needle bar is in its highest position
as in Fig. 2, the projection 6 lies in front of the nose c and prevents the lever a
from falling until during the descent of the needle bar the upper end of the
projection b arrives just below the point of the nose c. At this moment the thread
lever a becomes free to fall from its highest position and thereupon falls with an
accelerated motion until the needle bar is in its lowest position Fig. 1. When the
needle bar again rises the projection lifts the lever a into its highest position
before the needle bar has attained its highest position, the latter part of the upward
movement of the needle bar being performed while the thread lever remains at rest
in its highest position.
In place of a hook like projection b as in Figs. 1 and 2, a cross pin b¹ supported
by a lug or lugs on the needle bar may be used with the same effect as shown in
Figs. 3 to 6, this pin occupying the same relative position as the upper end of
the projection b.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what.
I claim is:
In a double lockstitch sewing machine, an upper thread feed lever having the
nose c or equivalent under face contour in combination with a lifting projection or
part on the needle bar or equivalent reciprocating bar whereby the thread lever
attains its highest position previous to the needle bar and descends from such
position subsequent to the needle bar, or whereby the movement of the thread lever
when nearing or departing from its highest position is retarded substantially as and
for the purpose described.
Dated tuis 29th day of January 1892.
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.