Variable Positive Feed-motion for Sewing Machines.WING-MACHI
Year: 1890

page_text: ate of Application, 4th Oct., 1890-Accepted, 8th Nov., 1890
COMPLETE SPECIFICATION.
Variable Positive Feed-motion for Sewing Machines.
1 JULIUS KÖHLER of Limbach, Saxony, Manufacturer of Sewing Machines do
hereby declare the nature of my invention for "VARIABLE POSITIVE FEED-MOTION
FOR SEWING-MACHINES "and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement and
accompanying drawings:
:-
My said invention relates to improvements in overhead sewing machines and has
for its object to provide means for positively varying the length of stitch. In over-
head sewing machines as usually constructed the fabric operated upon is fed past a
horizontal needle by the intermittent rotation of a pair of feed rolls and in order to
adjust the extent of the rotation of the said feed rolls at each stitch for the purpose
of obtaining stitches of a suitable length it has heretofore been usual to employ a feed
motion consisting of a friction driven disc on the same axis as one of the feed rolls
and to regulate its action by adjusting the stroke of the lever which actuates it.
Owing however to the gradual wear of the friction driving surfaces the friction
between them diminishes and the feed becomes uncertain in its action and in con-
sequence there is a lack of uniformity in the length of the stitches. In order to
obviate such a defect I make use of ratchet wheels in the manner hereinafter described
which while enabling a positive feed of variable rate to be obtained possess the
advantage that the seam may be fastened off at the end by any desired number of
stitches.
In order that my said invention may be more fully understood I will at once
proceed to describe the same with reference to the accompanying sheet of drawings
in all the figures of which the same letters refer to the same parts.
In the said drawings Fig. 1 is a longitudinal sectional elevation of so much of
an overhead sewing machine as is necessary to illustrate and to show the application
of my said invention.
Fig. 2 is a plan as seen from underneath.
Fig. 3 is a front view partly in section.
Figures 4, 5 and 6 illustrate modifications of my said invention which will be herein-
after described.
The
On the vertical shaft C of the feed roll B are four ratchet wheels D¹ D² D³ and D'
preferably arranged beneath the base E of the machine. The said ratchet wheels are
all of equal size but the pitch or size of teeth of each of the said ratchet wheels is
different from that in the other three. The pawl, by means of which the ratchet
wheels are rotated, is made to engage with one or other of the ratchet wheels according
to the length of stitch which it is desired to produce. In order to do this it is
necessary to be able to vary the height of the pawl at will without interfering with
its horizontal movement." This accomplish in the following manner.
horizontal slide bar G has a reciprocating movement imparted to it by the lever H H¹
suspended from a swinging bar Q and an excentric Y. In a vertical slot in the slide
bar G is an adjustable slide block indicated by dotted lines at F Fig. 2. An inner
prolongation of the slide block F carries the pawl D and an outer prolongation of
the slide block F takes into the secondary slide bar L, Figs. 1, 2 and 3. The stem L'
of the secondary slide bar L projects upwards through the base of the machine and
may be fixed at any desired height by a set screw M. By means of the two slide
bars G and L the position of the pawl can be varied either horizontally or vertically
and may be caused to actuate whichever of the four ratchet wheels is best suited for the
length of stitch it is desired to produce.
To enable the adjustment to be effected I provide means for drawing the pawl out

page_text: of gear until it is brought opposite to the teeth of the ratchet wheel with which it
is intended to engage. For this purpose I employ the bell crank lever P, Fig. 2,
carrying a long stud P1 on its short arm. By pulling at the long arm of the lever P
the stud P¹ is caused to bear on the inside of the pawl in such a manner as to draw
the latter out of gear.
If this is done while the machine is in operation the feed rolls
cease to act and the needle can pass several times through the fabric at the same
place and fasten off the seam as in button holing.
When employing a feed motion such as hereinbefore described it is necessary to
vary the stroke of the pawl to suit the different pitches of the teeth in the different
wheels. This I may effect in various ways as for example by an adjustable excentric
but I prefer the method shown in the drawing in which the position of the fulcrum k
of the lever H H is varied by means of a slot in the lever H H¹. The ratchet
wheels are prevented from rotating backwards by the usual device employed with
ordinary feed motions, consisting of a friction brake R having an arm with lugs which
are caused to bear against the rim of the disc R by means of a spring in such a manner
as to bind against the said rim when it tends to rotate backwards in the direction of
the arrow as is well understood.
Instead of varying the height of the pawl in the manner hereinbefore described I
may allow it to remain constantly at the same height while varying the height of the
ratchet wheels on the vertical shaft C of the feed rolls by the means shown in Fig. 4.
In this case the ratchet wheels D1 D2 D3 D4 are capable of vertical displacement. A
vertical feather or key which fits both the shaft and the ratchet wheels prevents the
latter rotating except simultaneously with the former. A fork L at the foot of
the secondary slide bar L' takes into a groove in the boss of the ratchet wheels for
the purpose of raising and depressing them.
Another modification of my said invention is shown in Figs. 5 and 6. Here the
ratchet wheels are rigidly secured to the vertical shaft C and instead of a single
pawl being used I employ as many pawls as there are ratchet wheels and provide the
secondary slide bar L with two fingers S S' which being interposed between the pawls
and the ratchet wheels prevent more than one of the pawls acting at once.
extremities of the fingers are rounded or bevelled off so that as they are raised or
depressed they press against the inside of the pawls and withdraw them from the
ratchet wheels.
The
With both the arrangement shown in Figs. 4 and 6 I employ a bell-crank lever as
shown at P in Fig. 2 for the purpose of withdrawing the acting pawl from the ratchet
wheel to enable the seam to be fastened off.
In the foregoing description I have referred to four ratchet wheels only as I find
this number to furnish a convenient range of variation in the length of the stitches,
but I do not limit myself to the exact number of four ratchet wheels and more or less
than four may be used according to circumstances. The secondary slide bar L' is
provided with a pointer and an index as illustrated in the drawings for the purpose
of indicating the length of stitch for which the machine is set.
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
1. In an overhead sewing machine the use combination and arrangement of the
parts hereinbefore described and shown for producing a variable intermittent positive
feed substantially as set forth.
2. In an overhead sewing machine the use of ratchet wheels of different pitches
fixed to the shaft of one of the feed rolls in combination with one or more vertically
adjustable pawls for the purpose of obtaining a positive and variable intermittent
feed substantially as hereinbefore described and shown in the accompanying
drawings.
3. In an overhead sewing machine the use of several ratchet wheels of different pitches,
vertically adjustable on the shaft of one of the feed rolls in combination with a pawl
having a constant position for the purpose of obtaining a positive and variable

page_text: intermittent feed substantially as hereinbefore described and shown in the accompanying
drawings.
4. In an overhead sewing machine having a positive feed obtained by ratchet
wheels the means hereinbefore described for stopping the feed while the needle is in
operation for the purpose of fastening off substantially as set forth.
Dated this Third day of October 1890.
EDWARD TURNER WHITELOW,
70, Deansgate, Manchester, Agent for the Applicant.