Improvements in Lock Stitch Sewing Machines
Year: 1887

page_text: Date of Application, 24th June, 1887
Complete Left, 26th Mar., 1888
Complete Accepted, 27th Apr., 1888.
I, HORACE WILLIAM SNOW of 63 Seven Sisters Road Holloway in the County of
Middlesex, Sewing Machine Manufacturer and Dealer do hereby declare the nature
of this invention to be as follows:-
Improvements in Lock Stitch Sewing Machines whereby the upper tension requires
no adjustment and the lower tension can be regulated by moving a lever acting on
the throw or dip of the heart cam of the Shuttle carrier and driver.
This Invention relates to improvements in lock stitch Sewing Machines and more
especially to such Machines when adapted to be operated by hand but the said
improvements are also applicable to such Machines when adapted to be operated by a
treadle and driving band or otherwise. The said improvements consist as follows,
& may be applied to any Sewing Machine working with an upper and lower
shaft.
The Shuttle carrier & driver which holds the Shuttle oscillates on a pin screw and
is set in motion by means of a stud pin attached to a crank which is fixed to a rotating
shaft, the said Shuttle Carrier and driver working under the work plate in front of
the needle. The stud-pin works in a specially constructed heart-slot or heart cam.
The pin-screw on which the Shuttle carrier & driver oscillates is worked and adjusted
by a lever which lever is fixed to the Machine by means of a screw fitting into a
groove of a part attached to the pin screw. By raising or depressing this lever the
throw or dip of the heart cam can be varied as desired and the change of action
imparted to the pin screw and to the Shuttle carrier & driver can be regulated, thus
allowing the tension of the lower thread to be increased or lessened as desired. The
heart-cam slot of the shuttle carrier and driver is so constructed that the Shuttle
carrier & driver drops back a little releasing the cotton of the upper thread from the
heel of the Shuttle before working forward thus allowing the top thread to be tightly
taken up into the work. Thus when the needle is at its highest point the Shuttle
carrier & driver has also worked forward as far as it will go, but when it is

page_text: arranged that the dip or throw of the heart cam slot shall be less by raising
the lever, the tension of the lower thread is increased and a tighter tension of the
top thread is thereby effected, so that by raising or depressing the lever the
tensions of both threads can be accurately equalised according to the length of
stitch desired and the substance of the material sewn. The arrangement for the 5
tension of the top thread requires no adjustment or alteration.
Dated this 24th day of June 1887.
I, HORACE WILLIAM SNOW, of 63 Seven Sisters Road, Holloway, in the County of
Middlesex, Sewing machine manufacturer and dealer 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, reference being had to
the accompanying two sheets of drawings and to the letters and figures marked
thereon, that is to say :-
This invention relates to improvements in lock-stitch sewing machines whereby
the necessity for altering the adjustment of the tension of either the upper or lower
thread to suit various materials and various lengths of stitches is rendered unneces
sary. For this purpose the tensions of the upper and lower threads are adjusted
in relation to each other once for all for all kinds of material and for all lengths of
stitches for which the machine is to employed; and provision is made for giving out
more or less of the threads according to the requirements of the material and length
of stitch by, in the first place, causing the shuttle to move backward slightly after
having passed through the loop of the upper thread and then forward again; and in
the second place, by causing this second forward motion of the shuttle to reach the
same point as the first forward motion, to fall short of, or to go beyond that point,
according to circumstances. These effects may be produced by employing mechanical
arrangements of the kind illustrated by way of example in the accompanying
drawings, in which Figures 1, 2, and 3 are front views of the lower part of a sewing
machine, showing the shuttle carrier in various positions, and the mechanism for
effecting the variation in the length of stroke of the shuttle above referred to; and
Figure 4 is a partial side view of same with a portion of the shuttle carrier broken
away.

page_text: a is the shuttle carried by the shuttle carrier or holder which oscillates in a
vertical plane on a pin i, and is moved to and fro by the crank or wrist pin e carried
by the crank o fixed on the rotating shaft d. This crank pin e takes into a peculiarly
shaped slot n formed in the shuttle carrier b. The pin i, on which the shuttle carrier?
oscillates, is fixed in a lever the fulcrum or axis g of which is fitted into and turns
in a hole hored in the frame of the machine, being retained therein by a screw the
end of which enters a groove m formed in the fulcrum or axis g. The pin i being
placed on the lever h eccentrically with respect to the fulcrum or axis y of the said
lever, it is obvious that when the outer end of the lever is raised or lowered the
pin will be lowered or raised also, and with it the shuttle carrier b, and that as the
position of the path of the crank pin e remains unaltered its leverage on the cam
slot n, when in the position shown in Figure 2, varies according as the pin i is
brought nearer to it or is removed further from it, and consequently that the first
forward motion of the shuttle (which is produced by the action of the crank pin e on
the lower part of the cam slot n) is greater when the pin i is nearer to the crank
pin e than when it is further removed therefrom. Similarly, the leverage of the
crank pine on the cam slot n, when in the position shown in Figure 3, varies
according as the pin i is nearer to or further from the crank pin e, and consequently
the second forward motion of the shuttle (which is produced by the action of the
crank pin e on the upper part of the cam slot n) also varies according to the relative
positions of the pin and the crank pin e; but, in consequence of the peculiar form
of the upper part of the cam slot n when the pin i is further removed from the
crank pine the second movement of the shuttle is greater than when the pin is
nearer to the crank pin e and vice versa. These arrangements enable the amplitudes
of the first and second forward movements of the shuttle carrier to be so adjusted
to each other, by merely raising or lowering the outer end of the lever /, that the
amplitude of the. second forward movement of the shuttle may be made less than,
equal with, or greater than, that of the first forward movement.
P
It will now be understood that when the crank pin e (which rotates in the direction
of the arrow) has reached the position shown in Figure 2, the shuttle carrier has
made a stroke from right to left (so as to pass the shuttle a through the loop of the
upper thread) to a distance dependent upon, and defined by, the position of the lever /.
By the further revolution of the crank pin e it acts upon the part n of the cam slot n
and forces the shuttle carrier b to move backwards a little or from left to right.
When the crank pin e reaches the position shown in Figure 3 in which the needle
has reached its highest point and the upper thread has been drawn up, the shuttle
carrier bis again moved forward a little. Now according as this second forward
movement brings the shuttle a short of, up to, or beyond, the point it reached in the
first movement (Figure 2) which is determined by the position of the lever h, the
shuttle thread will hold back the upper thread less or more. If the shuttle carrier b
is moved forward further at the first movement (Figure 2) than at the second
(Figure 3) the under thread is by the first forward movement drawn a little out of
the shuttle, and the second forward movement being less than the first leaves a certain
amount of slack under thread which is easily drawn up through the material by the
upper thread and appears on the upper surface of the material.
On the other hand if the shuttle carrier is moved further at its second forward
movement than at its first the under thread tension which is contained in the shuttle a,
and adjusted in a definite fixed relation to the upper thread tension, again comes
into action, and holds the shuttle thread back so that the upper thread cannot draw
it up into the material, and it then lies along on the underside of the said material.
By placing the lever h in a correct position to suit the material being sewn, and the
length of stitch being made, both threads can be made to cross exactly in the middle
of the material as usual without it being necessary to alter the adjustment of the
tension of either the upper or lower thread.
The upper and lower thread tension devices may be constructed and arranged in
any suitable manner, and are permanently adjusted in relation to each other in such
manner that any alteration necessitated by a change of material or of length of stitch

page_text: can be effected by altering the position of the shuttle carrier b and its cam slot n
in relation to the driving pin e by merely altering the position of the lever h.
In the foregoing description and relative drawings, the invention is described, and
illustrated, in its application to a sewing machine having an oscillating shuttle carrier
actuated by a crank pin engaging in a cam slot in the said shuttle carrier; but it is
obvious that the invention can readily applied to any shuttle sewing machine by
arranging suitable mechanical devices whereby a secondary backward and forward
motion is imparted to the shuttle, and by which the amplitude of both the primary
and secondary forward movements thereof can be varied in relation to each other as
and for the purpose herein described.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what I
claim is :-
In lock-stitch sewing machines, mechanism for imparting two backward and
forward movements to the shuttle in the formation of each stitch, combined with
mechanism for varying the amplitude of the two forward movements of the shuttle in
relation to each other, for the purpose of regulating the quantity of thread delivered
for each stitch according to the nature of the material being operated upon, and the
length of stitch formed, without varying the permanently adjusted tensions of the
upper and lower threads, substantially as hereinbefore described, and illustrated in
the Drawings hereto annexed.