IMPROVEMENTS IN SEWING MACHINES AND IN THE PROCESS OF HEMSTITCHING BY MACHINERY
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John Forbes at the Office of the
Commissioners of Patents on the 17th July 1882.
JOHN FORBES of the City of New York in the United States of America Book-
keeper "IMPROVEMENTS IN SEWING MACHINES AND IN THE PROCESS OF
HEMSTITCHING BY MACHINERY"
My invention consists of a Machine which is capable of being applied by the
substitution of different sets of cams to either plain stitching or Hemstitching and
which in so far as regards hemstitching produces the hemstitch by means of a
combination of lock and loop or chain stitches
For the purpose of applying the Machine to plain stitching I place upon the
driving Shaft a compound cam having wave grooves in the periphery and disc
which actuate the needle arm and Shuttle arm respectively so as to produce the
ordinary lock stitch and I also place on the driving shaft a small double cam to
actuate the feed-rack for passing the cloth under the needle in the ordinary way,
both cams being specially adapted to the arrangement of the needle and shuttle
arms and the feed Mechanism which are needed when the Machine is being used
for hemstitching
When I desire to apply the Machine to hemstitching I substitute for the
Compound cam already referred to another compound cam also having wave
grooves in the Periphery and disc and having in addition a depressed Periphery
cam and a facecam on the disc
The groove in the Periphery drives the needle arm so as to make three stitches
in each revolution of the cam, two of such stitches being locked by the aid of the.
groove in the disc by which the shuttle arm and shuttle carriage are actuated and
the shuttle is caused to pass through a loop of the needle thread in the ordinary
way and one being looped or chained by the aid of the depressed periphery cam
by which the looper arm is actuated and the looper is caused to pass into a loop of
the needle thread and to hold the loop and distend it so that the needle in its
subsequent descent enters the loop and forms the loop or chain stitch
The looper consists of two prongs slightly bent to form a kind of Slot and receive
a stationary pin which distends the prongs while being driven forward by the
looner arm

page_text: An arm actuated by the face cam already referred to takes up and tightens the
thread after each lockstitch
And instead of the small double cam used for plain stitching I employ a cam or
cams producing three motions. One motion of this cam raises the feed rack in the
ordinary way but at every third stitch only and another simultaneously advances
the feed rack, while the third actuates the feed rack laterally in both directions.
alternately at each of two out of three stitches
The presser foot is furnished with a Split Spring or Springs to hold both the hem
and single ply of the cloth and is hung loosely so as to move laterally with the
cloth
.
The hemstitch is produced by the needle passing through the hem of the cloth
and the needle thread being locked by the shuttle thread. The cloth is next fed
laterally so that the needle may enter the shire the thread being then caught by
the looper. The cloth is thereupon fed forward and the needle entering the loop
formed by the looper the needle thread is again caught by the shuttle thread and
locked, thereby completing the hemstitch.