IMPROVEMENTS IN 'LAING'S OVERHEAD SEWING MACHINE
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Robert Orchai at the Office of the
Commissioners of Patents on the 10th February 1877
ROBERT ORCHAR, of Dundee, in the County of Forfar, North Britain, Engineer
"IMPROVEMENTS IN 'LAING'S OVERHEAD SEWING MACHINE
This Invention, which relates to improvements in or upon the machine known as
"Laing's Overhead Sewing Machine," for which Letters Patent were granted to
James Laing, dated the Twelfth day of October, One thousand eight hundred and
seventy-four, and numbered 3493, has for its object to obtain positive motions or
actions throughout the several parts of the said machine, to dispense with the use
of a belt for diving the spiral needle in such machines, and to lessen the strain
upon the needle
The Invention consists in the first placo in airanging the driving pulleys at or
near the central part of the machine, upon the axis of which is a smaller pulley,
which dives by means of a belt, and with or without spur gearing, a horizontal
countershaft situated below or parallel to the thread barrel
Under one arrange-
ment, on the outer end of this countershaft is a spur wheel, which gears into another
spur wheel or pinion on the axis of the cylinder or tube which dives the thread
barrel, and within which the thread barrel slides In this arrangement the thread
barrel and tube are driven at the same speed
When it is desired to drive the thread barrel either faster or slower than the tube
then in that case a further spur pinion is placed beyond the spur wheel on the tube,
which gearing into a spur pinion on the shaft of the thread barrel drives it indepen-
dently of the tube, and at the required speed corresponding to the relations of the
spur gearing In either case the after portion of the thread barrel which projects
beyond the tube is formed with a key way, into which the key either in the tube
or spur pinion enters and so rotates it
To drive the spiral needle that portion of the tube around which it is situated is
formed with shallow ratchet teeth, and the interior of the needle is similarly formed
so that some of the teeth on the end of the tube engage with some of those at the
interior of the needle.
The needle, being larger in diameter than the ratchet circle at the end of the
tube, a guide is provided which partly surrounds the needle, and presses it at one
side against the ratchet teeth, by which arrangement the needle is not only pro-
jected forward so as to give the requisite clearance between its interior and the

page_text: ratchet teeth to enable the cloth being sewn to pass, but the needle being thereby
kopt in contact with the ratchet wheel is continuously rotated with the tube
In order to maintain the spiral of the needle at a constant pitch, or in other
words to maintain the helices at a constant distance apart, that end of the counter-
shaft herein-before referred to nearest to the needle end of the tube is provided with
& disc, upon the edge of which a screw thread is cut corresponding with the spirals
of the needle, so that the spuals of the needle may enter the spiral groove in the
dise By this arrangement another advantage is obtained, namely, that by driving
the feeding chain from the spiral groove in the disc, or from the countershaft, the
rate of feed is or may be made to correspond exactly with the degree of spiral of the
necdle
To enable the thread barrel of the machine to carry forward the thread positively
during the sewing operation, and that without straining the needle, a roller placed
horizontally on the stud or shaft parallel to the axis of the thread barrel is employed.
The periphery of this roller is sufficiently near that of tho thread barrel as to press
the thread against the barrel with sufficient force to enable the barrel by its fric-
tional contact with the thread to carry it forward, or the roller may be driven by
gearing which will impart to it a positive surface, speed, or motion equal to that of
the thread barrel.