Improvements in Tension Devices for Sewing Machines.
Year: 1897

page_text: [Communicated from abroad by THE SINGER MANUFACTURING COMPANY of New York,
in the United States of America, Sewing Machine Manufacturers.]
Improvements in Tension Devices for Sewing Machines.
I, WILLIAM HARVEY INSLEE, Manager of The Singer Manufacturing Company,
Kilbowie, Dumbartonshire do hereby declare the nature of this invention and in
what manner the same is to be performed, as communicated to me to be particularly
described and ascertained in and by the following statement :-
My Invention relates to tension devices for sewing machines, and it has for its
object to provide means whereby the tension of the thread or threads may be
automatically varied from stitch to stitch for the purpose of producing ornamental
seams. In carrying my Invention into effect I preferably loosely mount the tension
discs and tension spring or springs on a movable rod or spindle provided with an
abutment or abutments between which and the tension discs the said spring or
springs are confined; and then by slowly reciprocating said rod or spindle so that the
same travels back and forth once only while a number of stitches are being made the
tension on the thread or threads will be automatically varied from stitch to stitch by
gradually compressing and then again gradually relaxing said spring or springs; the
tension discs, it being understood, remaining stationary while the rod or spindle
reciprocates through them. My Invention in its preferred form contemplates the
employment of two pairs of tension discs or two tension devices of any other suitable
form, one for the upper and the other for the lower thread, the tension springs of the
respective devices being reversely acted on, so that when the frictional hold of the
tension device on the upper thread is increased the tension on the lower thread is
relaxed, and vice versa.
In the accompanying drawings Fig. 1 is a plan view of a tension device embodying
my Invention, this view showing a part of the arm of a sewing machine on which the
said device is mounted. Fig. 2 is a side view of the same with the machine arm in
section to show the tension device operating mechanism. Fig. 3 is a detail view of
the reciprocating rod or spindle and its operating device, and Fig. 4 is a diagramatic
view of one form of ornamental overseam which may be made by the use of my
Invention.
A denotes a part of the overhanging bracket-arm of a sewing machine and B a
small bracket mounted thereon and having a barrel or bearing portion 6 through
which freely slides a rod or spindle C on which the tension discs d are loosely
mounted, two pairs of tension discs being herein shown. The tension discs are
pressed into yielding contact with each other, and held against the opposite ends of
the bearing or barrel b, by springs e loosely surrounding the said rod or spindle
and confined between said discs and nuts c, or other suitable abutments, adjustably
mounted on said rod or spindle.
F is a small rotating shaft having bearings in the arms b¹ of the bracket B and
provided with an eccentric f working in a yoke c² rigidly attached to or integral with

page_text: the rod or spindle C. The shaft F is provided with a ratchet-wheel f¹ engaged by a
spring-pressed pawl g mounted on a pawl carrying lever G pivoted on said shaft and
vibrated from a cam h on the machine driving shaft H through a reciprocating yoke h¹
on which rests a rod i attached at its upper end to the lever G, said rod being held
against said yoke by the coil-spring k.
.
From the foregoing it will be apparent that when a sewing machine to which my
Invention may be attached is in operation the cam or eccentric f will be slowly
rotated, to slowly reciprocate the rod or spindle C which alternately compresses and
relaxes the spring e, thus causing variations, from stitch to stitch, in the frictional
pressure of the tension discs on the thread or threads passing between them. Thus
when two reversely varied tension devices, one for an upper and the other for a lower
thread, are employed, as in the present instance, the tension on the upper thread will
be increased from stitch to stitch while the tension on the lower thread will be
diminished, and vice versa. With the tensions of the upper and lower threads of an
over-seaming edge-stitching machine thus reversely varied the result will be somewhat
as illustrated in Fig. 4, in which the lines t may be supposed to denote the upper
thread of one color, the lighter lines t¹ the lower thread of another color, and the
curved line p the 'purl' resulting from the concatenation of the upper and lower
threads. A somewhat similar ornamental effect can be secured by varying the
tension, from stitch to stitch, on one of the threads only; or in a four-thread overedge
seam, such for example as is made on a machine similar to that shown in the
Specification of Letters Patent No. 6512 dated April 5th, 1892, this ornamental effect
can be increased or varied by passing all the threads through the automatically varied
tension devices. The ornamental seams may also be varied by changing or adjusting
the feeding movements of the ratchet wheel f¹ to rotate the shaft F faster or slower;
by varying the adjustment of the nuts c to change the pressure of the springs e on the
tension discs, or by substituting a cam or pattern wheel of any desired form for the
eccentric f, as will be readily understood by any mechanic skilled in the art to which
my Invention relates.
I do not therefore wish to be understood as limiting my Invention to the particular
form of tension devices herein shown, or to the details of construction of the operating
mechanism or other parts as herein illustrated, as these may be widely varied without
departing from the spirit of my Invention. Although I have illustrated in Fig. 4 an
ornamental edging seam produced by the use of my Invention it will be understood
that similar ornamental seams may be produced in the bodies of fabrics back from
their edges by properly presenting the work to almost any kind of overseaming or
zig-zag stitch machine equipped with my Invention.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same has to be performed, I declare that what I claim is :-
1. The combination with a sewing machine tension device, of an automatic
mechanism constructed and operating to gradually increase the frictional drag
exerted on the thread by said tension device for a series of stitches and then to
gradually decrease said frictional drag for a series of stitches, whereby ornamental
seams, due to the varying action of said tension device, may be produced.
.
2. The combination with a plurality of sewing machine tension device, of automatic
mechanism for reversely varying the frictional drags exerted on the thread by the
same, from stitch to stitch; whereby the tension on an upper thread may be gradually
increased for a series of stitches while the tension on a lower thread is at the same
time gradually diminished, and vice versa.
3. In a sewing machine tension device, the combination with two pairs of tension
discs, of a movable rod or spindle on which said discs are loosely mounted, confined
-springs encircling said rod and oppositely pressing against said discs and means for
.slowly reciprocating said rod or spindle to cause the pressure of said springs against
said discs to be automatically and reversely varied from stitch to stitch.

page_text: 4. The combination with the bracket B, of a rod or spindle C fitted to reciprocate
in said bracket and provided with the adjustable nuts c and the yoke c², the tension
discs d and springs e mounted on said rod or spindle, the shaft F having a cam or
eccentric, as f, and means for slowly rotating said shaft.
WALLACE FAIRWEATHER,
Of the firm of Cruikshank & Fairweather, Chartered Patent Agents,
62 Saint Vincent Street, Glasgow, Agent for the Applicant.