IMPROVEMENTS IN SEWING MACHINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by William Dawes at the Office of the
Commissioners of Patents on the 28th May 1878.
WILLIAM DAWES, of Kingston Grove, Leeds, in the County of York, Engineer.
"IMPROVEMENTS IN SEWING MACHINES."
The first part of this Invention consists in a simplified method or system of
obtaining what is known as the " fast-and-loose "action, or the occasional disengaging
or freeing of the machine from the treadle and driving action and wheel, for the
purpose of enabling the operator to wind the shuttle bobbins or spools from or in
connection with the latter without working the machine. For this purpose I sub-
stitute, in lieu of the ordinary fast-and-loose band or balance wheel, a sliding,
lifting, or other movement to the entire machine, or to the main driving wheel,
whereby the distance between the centres of the large (driving) and the small
(driven) gut or band wheels can, by treadle, lever, wedge, or other convenient
action, be instantly altered by the operator, and this to an extent or degree suffi-
cient to destroy and restore at will the grip or driving power of the gut or band
upon the before-named wheels, the said gut or belt remaining at all times in or
upon the wheels effective or operative, or not, according to circumstances, as herein-
before explained.
In some cases I obtain the before-explained result by the use of a double top to
the table or stand, the upper part or board having a sufficient sliding movement or
action with the machine upon the lower part to give either grip and movement, or
slackness and quiescence, as desired, and herein-before explained.
As a further security against any accidental movement of the machine during the
time of bobbin winding, I cause the same movement or action which disengages or
frees the machine, by slackening the gut or belt, to also bring it into contact with
a fixed pad or break, which contact ceases when the re-tightening of the belt taken
place for working the machine.
As a means of obtaining additional convenience from or in connection with the
foregoing arrangements, I also construct and fix the shuttle, bobbin, or spool-
winding apparatus in such a manner that the same movement or action which
causes the machine to become disengaged or quiescent shall also put into "
Price 271
gear
"

page_text: or action the said winding apparatus, and thus the complete change, and both
benefits are realized by one simple movement or alteration.
It will be obvious that this part of my Invention is more especially applicable to
those machines in which the shuttle, spool-winding, and the band adjustment are
effected by or in connection with the main driving wheel, and that both its objects
and action are different and distinct from the mere occasional tightening of the gut
or belt by slackening the fixing screws, and altering the position of the machine
for that purpose only; also that it has reference to portable machines and stands,
and is not intended to apply to those which are driven by "power and
shafting.
"
The second part of this Invention consists in an improved automatic check or
"pawl" action, for preventing turning again" or backward movement at or near
the "dead centres," and at the same time possessing the additional feature or
capability of allowing the machine to be moved either forward or backward for
adjustment by hand or otherwise when necessary.
In constructing this pawl action I sometimes arrange it in such a manner that its
check power, the backward way, shall be definite and effective through two portions
only of each revolution of the crank and main. wheel, say, about ninety degrees
each, covering or including the two "dead centres," but shall cease entirely through
the remaining two portions.
In other cases I so construct it that, whilst possessing the ordinary check or grip
action through the entire revolution, it shall be so placed and arranged that the
natural action and position of the hand when moving the wheel for adjusting the
machine shall unconsciously, and therefore automatically remove or destroy its
action entirely whilst such movement or adjustment is being effected.
In other cases I construct the pawl in such a manner that, whilst possessing
sufficient check power to prevent the machine from turning again when the treadle
and crank are passing or near the dead centres, it shall also embrace the power or
capability of "giving way" or yielding, with a definite break or sliding friction
movement, on the application by hand or otherwise of more power than the feet
and treadle are then, that is, near the dead centres, able to exert, and thus in each
case the same effect and benefits, as herein-before explained, are realized.
The third part of this Invention consists in an assisting or compensating spring
action or attachment, for equalizing the circumferential or "pulling round" power
of the treadle upon the crank and main driving wheel. This action or attachment,
which may be placed to act upon or in connection with the crank pin, connecting
rod, main wheel, or other convenient part, is so constructed that during the best or
most effective.portion of each single stroke of the treadle, and half revolution of the
crank and wheel, the said spring shall be forced away from its natural or neutral
position, and allowed to recoil and give back, through its elasticity, this spring
power when the crank is passing the "dead centres," and thus, by this "giving and
taking," or compensating action and effect, a much steadier and smoother movement
is obtained, and the liability to stick on the centres is obviated.