AN IMPROVED DIFFERENTIAL SCREW MOTION APPLICABLE TO PRESSES, PUNCHES, RAIL BENDERS, SHAFT STRAIGHTENERS, AND OTHER MECHANICAL CONTRIVANCES OF A SIMILAR CHARACTER
Year: 1872

page_text: PROVISIONAL SPECIFICATION left by John Edward Rogers at the
Office of the Commissioners of Patents, with his Petition, on the
23rd May 1872.
I, JOHN EDWARD ROGERS, of Smethwick, in the County of Stafford,
Machinist, do hereby declare the nature of the said Invention for "AN
IMPROVED DIFFERENTIAL SCREW MOTION APPLICABLE TO PRESSES, PUNCHES, RAIL
BENDERS, SHAFT STRAIGHTENERS, AND OTHER MECHANICAL CONTRIVANCES OF A
SIMILAR CHARACTER," to be as follows:-
My Invention consists of the arrangement of threads herein-after
described, forming a differential screw motion applicable to presses,
punches, rail benders, shaft straighteners, and other mechanical con-
trivances of a similar nature. I first take a piece of round iron or
steel of the required length and diameter, which is then turned, a collar
being formed in its centre or thereabouts. Two threads are then cut,
that is one on either side of the collar, and both running the same way
but being of different pitches.
Both of these threads are then fitted
with nuts which may be formed of any required shape. On the out-
side of one nut is cut a thread which runs in an opposite direction to
the internal thread, and is fitted into a suitable part of the machine
to which the motion is to be applied, proper allowance being made for

page_text: it to work over the distance it may be required to travel. On the
end of the main screw on which this nut works is keyed or screwed a
collar, so that the faces of this nut lock against a collar at either end
of the stroke. The other nut which has no rotary motion is kept from
turning round by a stud or key fitted into it. To work this motion a
wrench is fitted to the end which runs through the nut threaded on the
outside, and supposing the end collar to be down on the face of the nut
the wrench is turned so as to cause the centre collar to be brought
against the opposite face. By that time the other nut has made a direct
movement equal to the difference of the pitches of the two screws.
The power being still applied the collar locking against the nut causes
it to turn, and this being threaded in an opposite direction the other
nut is caused to move at an increased speed equal to the sum of the two
pitches the rest of the distance. The wrench being turned the reverse
way the nut is brought back to its first or normal position.
As a modification of my Invention I take two pieces of iron or steel
of different diameters, and the smaller being turned and threaded as
far up as necessary the larger piece is bored out and threaded to
receive the smaller piece, a thread also being cut on the outside of the
larger piece in the same direction as the inside but of different pitch.
This outside thread is fitted into a moveable nut similar to that I have
described in the first motion and with collars at either end for the
working of the said nut, the smaller piece working inside and acting in
a direct motion similarly to the plain nut described under the first
head of my Invention, and being kept from turning round in a similar
manner.
I desire it to be understood that I do not bind myself to use single
threaded screws only.
I may also in some cases use either of these motions to apply their
power in combination with what is commonly known as a toggle or lock