IMPROVE- MENTS IN OVERHEAD SEWING MACHINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by William Walker at the Office of the
Commissioners of Patents on the 12th February 1878.
WILLIAM WALKER, of Dundee, in the County of Forfar, North Britain. "IMPROVE-
MENTS IN OVERHEAD SEWING MACHINES."
This Invention, which has for its object improvements in that class of machines
adapted for sewing over the edges or selvedges of fabrics, relates, firstly, to an
endless belt composed of two layers or thicknesses of leather or an equivalent
material, fastened together by sewing or otherwise. A spiral groove or screw
thread is cut through the outer layer of the belt, which layer is broader than the
inner layer, and projects over each edge of it. The outer layer has preferably a
thickness of about one-eighth of an inch, and the inner one a thickness of from
three-eighths to half an inch or thereby. A number of holes are punched or cut in
the inner layer at the parts exposed by the spiral groove, and in each hole a small
pulley is situated on an axis passing through and across the leather.
The pulleys are prevented from rubbing on the leather by thin discs of metal, and
each of them has a groove or channel cut in it circumferentially, which channel
guides the sewing thread or yarn, and prevents it from rubbing either on the sides
or bottom of the spiral groove.
The endless belt is driven by a number of flanched rollers, the width between the
flanches of which is equal to the breadth of the inner layer of the belt, which is
kept in position by passing between these flanches.
The rollers are placed at equal distances apart round a common centre, and each
of them is supported on a stud passing through a framing or "gable," and secured
by a nut or equivalent means. A pulley, whose breadth is equal to the width
between the flanches of the rollers, and whose periphery is covered with leather or
other material capable of increasing its hold or friction, is situated on the common
centre, around which the flauched rollers are arranged for the purpose of rotating
the said rollers, and through them the endless belt herein-before described.
Under a modification the said belt, instead of being composed of two thicknesses
of leather, may consist of one thickness only, cut and shaped and provided with
grooved rollers in the manner before specified,

page_text: The Invention relates, secondly, to a steel needle, which consists of one turn or
thereby of a helix, and which is preferably square in section. This needle fits the
spiral thread or groove in the endless belt tightly enough to give it a resistance
sufficient to cause it to penetrate the cloth or fabric being sewn, but not so tightly
as to prevent the needle from slipping back as the sewing yarn or thread is
expended.
The amount of resistance communicated to the needle is regulated by the appli-
cation of oil or other ungent to the endless belt, or by magnetising the needle and
attracting it by pieces of iron or metal inserted into the endless belt, or the resistance
may be regulated by other equivalent and suitable means.
The Invention relates, thirdly, to a fence or guide to be bolted to the edge of the
framing or main "gable" of overhead sewing machines, and employed to regulate
the distance from the selvedge to the point at which the needle is required to pene-
trate the fabric. The fence or guide also supports a "bending roller," which bends
back the endless belt so as to make it clear the cloth and the fence intervening
between the needle and the belt.
The Invention relates, fourthly, to means for preventing the needle from coming
out of the spiral groove in the endless belt by the action of its own centrifugal force
or otherwise. The apparatus employed for this purpose consists of a series of rollers
placed at equal distances apart outside the belt, and supported on studs fixed round
a common centre in the framing of the machine. These studs have the parts which
pass through the framing turned slightly eccentric so as to admit of adjustment of
the rollers, or to cause them to press the needle down upon the pulleys situated at
the bottom of the spiral groove of the endless belt, if required so to do.
Overhead sewing machines constructed with these improvements are also fur-
nished with driving pulleys, belt shifters, tables, cloth guides, and other apparatus.
usual in such machines.
In operating with the improved machine the sewing thread or yarn is hooked
into or through the eye of the needle, and the machine is then driven backwards.
by means of a hand wheel placed on the end of the main shaft. The backward
driving is continued until the needle reaches its starting point, which is at the left-
hand end of the groove as the operator faces the machine.
When the starting point has been reached the machine is driven forwards by the
hand wheel, or by power applied to the main shaft until all the thread is passed
over the grooved pulleys in the spiral groove of the belt. The end of the thread is
next knotted, and the machine is then ready to commence the seam.