In- PROVEMENTS IN SEWING MACHINES
Year: 1869

page_text: PROVISIONAL SPECIFICATION left by Friedrich Hohmann at the
Office of the Commissioners of Patents, with his Petition, on the
5th June 1869.
I, FRIEDRICH HOHMANN, of Ipswich, in the County of Suffolk,
Engineer, do hereby declare the nature of the said Invention for "In-
PROVEMENTS IN SEWING MACHINES," to be as follows:-
The said Invention consists partly in the novel arrangement of
devices for operating the shuttle of a sewing machine, and partly in
constructing the working parts of sewing machines of a material not
heretofore applied to such a purpose. The shuttle works to and fro
horizontally and in a straight line across the path of the needle below
the cloth plate, and is operated by a horizontal vibrating lever whose
fulcrum or pivot is fixed in some convenient part of the back of the
frame. The said lever is caused to vibrate by a cam fixed on a rotating.
shaft, which by toothed wheels or otherwise is operated from the driving
wheel, and which also carries the feed cam. The shuttle is supported
in a carrier or holder fitted to slide upon a straight horizontal bar or-
rod secured at its ends to the frame. The shuttle may be of the ordinary.
form and lies between two shoulders or projections on the ends of the.
carriage with its open side or face sliding against a guide plate arranged.

page_text: parallel with the slide bar on which the carrier is fitted. At the top
of the said carrier is fixed a stud or pin which projects upward between
the jaws of the vibrating lever, the said stud having a small anti-
friction roller turning freely thereon. The said lever is fitted to vibrate
freely upon a fulcrum pin or stud preferably fixed in a small bracket at
the rear of the machine above the rotating shaft. The part of the said
lever which lies above the cam is widened, and is formed with flat side
pieces which project downward, enclosing the cam between them and
fitting closely to its periphery. These pieces form the bearing or working
surfaces against which the cam acts as it rotates with its shaft. It is
preferable that these bearing pieces should be made adjustable, so that the
spaces between the two pieces may be adapted to the periphery of the cam,
which should work freely in the space or aperture between these
bearing surfaces, but without any unnecessary freedom or slackness
therein. For this purpose I pass a screw through the two pieces at
one side of the cam, and by turning this screw the said pieces will
yield or spring sufficiently to give the required adjustment. The
periphery or working surface of the cam should be curved, so that the
bearing surfaces of the lever throughout the angular changes in its
position will work freely and smoothly upon the cam. The latter
should be made adjustable upon the shaft so that its distance from the
fulcrum may be increased or diminished to allow the throw of the
shuttle to be properly regulated, and the side or bearing pieces should
be of such a length as to permit this adjustment to be made without
inconvenience, I prefer that the cam should be arranged between the
fulcrum of the horizontal lever and the shuttle, but if the machine
is generally so constructed as to render it more convenient or desirable
the fulcrum pin may be placed between the cam and the shuttle.
Hitherto the wheels, shafts, rods, the shuttles, shuttle boxes, and
carriers, and other working parts of sewing machines have been usually
constructed of iron and steel or other metal. To prevent the noise of
the working of the machine and for other reasons it is very desirable
to find some material to use as a substitute for metal. Such substance
should be capable of being cast, filed, turned and bored, and other-
wise worked by the instruments and apparatus used in this branch of
manufacture, and it should not be greatly more costly than the metal
and should be susceptible of finish to the degree required in these
machines. By numerous experiments I have found that the material
now commonly known as "vulcanite possesses these properties, and
"

page_text: that when properly applied to the construction of the devices herein-before
described and to the other working parts of a sewing machine will greatly
diminish the noise thereof and will render the same greatly superior
to a machine having its working parts constructed of metal. The
toothed wheels and pinions whereby motion is transmitted from the
driving wheel to the needle bar and feed motion run very rapidly
togother, and however well these wheels may be constructed and fitted
together when made of metal they will not work without noise, though
many expedients have been adopted to render such machines silent.
When however these wheels are formed of "vulcanite," according to
my Invention, they will be rendered almost noiseless. Another part of the
mechanism which occasions a disagreeable noise in working is the crank
which operates the needle bar, and which causes à clicking noise at
certain parts of the stroke. A similar noise is also produced between
the shuttle and the shuttle carrier, and in other parts of the machine
where two metal surfaces work together. I therefore make the needle
bar and crank, and also the shuttle and shuttle carrier, of "vulcanite"
I also make the shafts and rods, and other working parts, or some of
such parts, of the same material, which I have found not only furnishes
the means whereby I am enabled to construct a silent machine, but
which is more easy to work in forming the various parts of the machine,
is more durable than metal, requires no lubrication, and renders the
machine more cleanly and less liable to derangement. I have described
the application of the "vulcanite" only to the working or moving
parts of the machine, but if desired the frame and other fixed parts
may be made of the same material. I however prefer to construct
such fixed parts of cast iron or other metal ordinarly employed for the
purpose.