IMPROVEMENTS IN LAING'S OVERHEAD SEWING MACHINE
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by James Graham at the Office of
the Commissioners of Patents on the 19th December 1881.
JAMES GRAHAM, of Dundee, in the County of Forfar, North Britain, Engineer.
"IMPROVEMENTS IN LAING'S OVERHEAD SEWING MACHINE:"
This Invention has for its object to simplify and improve the construction and
action of overhead sewing machines of the kind known as Laing's, and one
modification of which is described in the Specification of Letters Patent granted to
James Laing and dated 12 October 1874 (No. 3493).
The present improvements relate to details connected with the part of such
machines which is known as the thread barrel and forms a characteristic and
essential feature of Laing's machine distinguishing it from all previous attempts to
obtain mechanically what is known as the overhead, or overedge, or overcast
stitch. This thread barrel is an essential part not only of the original modification
of Laing's machines described in the Specification bereinbefore referred to, but
also of other modifications of Laing's machines which have been more recently
made public, and the present improvements are applicable to any of such
modifications.
The thread barrel has a longitudinal movement relatively to the needle which
moves round the barrel, and it is on the proper relation of this movement to the
others, and to the peculiarities of the materials which are being operated on in
each case that the satisfactory action of the machine largely depends.
In carrying out the present Invention the longitudinal movement is derived
from the rotation of the thread barrel itself in an automatic manner depending on
the tension of the thread or twine. The outer end of the thread barrel, which is
hollow, has a slightly smaller cylinder projecting a short distance from it, and on
this smaller cylinder or end core as it is hereinafter termed the loops of thread or
twine finally act as the stitches are being tightened in the cloth. The end core is
fitted in the end of the barrel with such degree of play or looseness as
to allow the loops when tightening to draw it to the side against the edge of the
cloth, and it is by this lateral movement of the end core that the longitudinal
movement of the barrel is brought about. A spindle passing through the thread
barrel or part of it, and extending some distance beyond the end opposite to that

page_text: having the end core, has a part of it which is outside of the barrel formed with a
screw thread; and it is by the action of this screw thread on a couple of stationary
engaging bits formed with segments of internal screw threads that the thread
barrel is moved longitudinally. The spindle is connected to the thread barrel by
collars allowing one to turn independently of the other but causing them to
move together longitudinally. When the end core is drawn to the side by
the tension of the loops on it, a frictional contact or gripping action takes
place between the spindle or a boss on it and the interior of the thread
barrel directly or between the spindle and one or more friction pieces fitted
inside of the barrel and turning with it. In one modification the spindle
is formed with a conical boss and a pair of segmental wedges are fitted between
such boss and the sides of the barrel, and when the end core, which in
this modification is separate from the spindle is turned to one side by the tension
of the loops its inner end bears on one of the wedges in a manner to make it act
frictionally on the spindle and carry it round with the barrel. When the spindle
is thus carried round the action of its screwed part effects the longitudinal
movement. Frictional weights are applied to the spindle, and can be varied to
obtain the tension or tightness of the stitches that may be desired, as the tension
of the loops on the end core required to bring about the longitudinal movement is
greater or less accordingly as the rotation of the spindle is resisted more or less by
Buch frictional weights.