IMPROVEMENTS IN DIFFERENTIAL- SCREW, DEVICES FOR FASTENING OR ADJUSTING PURPOSES
Year: 1880

page_text: LETTERS PATENT to John Hastie, of Greenock, in the County of Renfrew, North
Britain, Engineer, for an Invention of "IMPROVEMENTS IN DIFFERENTIAL-
SCREW, DEVICES FOR FASTENING OR ADJUSTING PURPOSES."
PROVISIONAL SPECIFICATION left by the said John Hastie at the Office of
the Commissioners of Patents on the 1st July 1880.
JOHN HASTIE, of Greenock, in the County of Renfrew, North Britain, Engineer.
*IMPROVEMENTS IN DIFFERENTIAL-SCREW DEVICES FOR FASTENING OR ADJUSTING
PURPOSES."
This Invention has for its object by certain improved devices to render more
conveniently available and useful than heretofore the increased power and holding
security obtainable by employing differential screws.
In one arrangement, to be used in place of an ordinary screw bolt and nut or
otherwise, two nuts are employed, one of which is formed with an internal screw
thread to screw upon a bolt, stud, spindle, or rod, and with an external screw thread
to screw into the other nut, which latter is formed with an internal screw thread to
fit the external one of the first nut. The external screwed thread of the first or
doubly-screwed nut is upon a boss projecting from one face of the head of the nut,
and the external and internal threads have the same direction, being both right-
hand or both left-hand threads, but they are of different pitches. In applying the
device the doubly-screwed nut with the other one upon it is serowed upon the bolt,
stud, spindle, or rod, until the second nut which is placed undermost bears on the
surface of the object to which the fastening is applied; and then, whilst the
second or bearing nut is held by means of a screw key or otherwise, the doubly-
threaded nut is screwed backwards, and in consequence of the pitch of its external
thread being coarser than that of its internal thread it forces the second nut inwards
with a pressure depending on the difference between the pitches.
In a second-arrangement-the-second-or-bearing nut is provided with a pin on its
bearing face to enter a hole in the surface up to which it is screwed, and to prevent
it from turning whilst the final screwing action is being applied to the doubly-
screwed nut. Any convenient projection and its counterpart may be employed for

page_text: preventing the second or bearing nut from turning after reaching its bearing
position. In one modification radial or other grooves or indentations are formed
on the bearing faces of the nut, and on the surface up to which it is screwed, and a
washer of copper or other suitable material is interposed.
In a third arrangement the second or bearing nut is fixed by screw pins, or
rivets, or otherwise to the article to which the screw fastening or adjusting device
is applied; or the part constituting the second nut, or that into which the doubly-
screwed nut is to be screwed, may be solid with or part of the article to which
the fastening is applied. This arrangement has a feature which is of considerable
advantage in some applications; on unscrewing the doubly-screwed nut it forces
back or loosens the bolt, stud, spindle, or rod, or if such part is a fixture, it will
lift or loosen the cover or other article it held down when screwed up. The arrange-
ment is also advantageously applicable for adjusting and fixing a piece in different
positions on a spindle or rod.
In a fourth arrangement both nuts are doubly-screwed and form an improved
jam-nut device, the first being as in the other arrangements, and the second having
a part to screw on the first nut and a part to screw on the bolt, stud, spindle,
.or rod.
A fifth arrangement is for pipe couplings or similar fastenings. In it a single
coupling thimble is used, and part of it is internally screwed to screw on one pipe
end, whilst the other part is differentially screwed to screw on the other pipe end,
the effect of screwing on the coupling being to draw the pipe ends very forcibly
together.
In a sixth arrangement, which is also for pipe couplings, there are two coupling
thimbles, each of which is internally screwed to screw on its pipe end, whilst one is
also externally screwed to screw into an internally screwed part of the other
thimble. The three pairs of screw threads may be all different, or any two pairs
may be alike the other being different.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Hastie in the Great Seal Patent Office on the 31st December
1880.
JOHN HASTIE, of Greenock, in the County of Renfrew, North Britain, Engineer,
"IMPROVEMENTS IN DIFFERENTIAL-SCREW DEVICES FOR FASTENING OR ADJUSTING
PURPOSES."
My said Invention has for its object by certain improved devices to render more
conveniently available and useful than heretofore the increased power and holding
security obtainable by employing differential screws.
And in order that my said Invention and the manner of performing the same
may be properly understood, I will proceed to particularly describe examples of my
various improved differential-screw dovices, which examples are delineated on au
accompanying Sheet of explanatory Drawings. In these Drawings the saine
reference letters are used to mark the same or like parts wherever they are
repeated.
One arrangement or device is shown in plan and in vertical section in Figures 1
and 2 of the accompanying Drawings, and is to be used in place of an ordinary
screw bolt and nut, or otherwise. In this examplo two nuts A, B, are employed,
one of which A is formed with an internal screw thread to screw upon a bolt C, or
upon a stud, spindle, or rod, and with an external screw thread to screw into the
other nut B, which lutter is formed with an internal scrow thread to fit tho
external one of the first nut A. The external screw thread of the first or doubly-
screwed nut A is upon a boss projecting from one face of the head of the nut; and
the external and internal screw threads have the same direction, being both
right-hand or both left-hand threads, but they are of different pitches. In applying
the device the doubly-screwed nut A with the other one B upon it is screwed upon
the bolt, stud, spindle, or rod C, until the second nut B which is placed innermost
bears on the surface of the object to which the fastening is applied; and then,
whilst the second or bearing nut B is held by means of a screw key or otherwise,
the doubly-threaded nut A is screwed backwards, and in consequence of the pitch
of its external throad being coarser than that of its internal thread, it forces the
second nut B inwards with a pressure depending on the difference between tho
pitches.
The threads may be transposed, that is, the internal thread may be coarser in
pitch than the external thread, and in that case tho doubly-threaded nut A is
screwed inwards instead of outwards when being fixed.
In a second arrangement the second or bearing nut B is provided with a pin D,
as indicated by dotted lines in Figures 1 and 2 on its bearing face, to enter a hole
in the surface up to which it is to be screwed, and to prevent it from turning
whilst the final screwing action is being applied to the doubly-screwed nut A.
Any convenient projection and its counterpart may be employed for preventing the
second or bearing aut B from turning after reaching its bearing position. In one
modification, shown in Figures and 4, radial grooves (or it might be other
indentations) are formed on the bearing faces of the nut B, and on the surface E up
to which it is screwed, and a ring or washer H of copper or other suitablo material
is interposed.
In a third arrangement, shown in plan in Figure 5, and in vertical section in
Figure 6, the second or bearing nut B is fixed by screw pins, or rivets, or otherwise
to the article E to which the screw fastening or adjusting device is applied. Or
the part constituting the second nut, or that into which the doubly-screwed nut A
is to be screwed, may be solid with or part of the article J to which the fastening
is applied, as shown in vertical section in Figure 7. This arrangement has a

page_text: feature which is of considerable advantage in some applications. On unscrewing
the doubly-screwed nut A it forces back or loosens the bolt, stud, spindle, or rod C;
or if such part C is a fixture, it will lift or loosen the cover or other article J it
held down when scrowed up. The arrangement is also advantageously applicable
for adjusting and fixing a piece in different positions on a spindle or rod.
In a fourth arrangement, shown in vertical section in Figure 8, both nuts A and K
are doubly-screwed and form an improved jam-nut device, the first nut A being as
in my other arrangements, and the second nut K having a part to screw on the first
nut A, and also a part to screw on the bolt, stud, spindle, or rod C.
Figures 9 and 10 aro a side elevation and a transverse vertical section showing a
modification of my third arrangement or device as applied for securing railway fish
plates. The fish plato L, which is at the side of the rail where the fastening nut A
is applied, is formed with an internal screw thread to fit the external thread of the
nut A, and the grip or hold of the fastening device, and the consequent resistanco
to loosening, are such as would not be obtainable in the case of an ordinary screw
bolt and nut, excepting with an exceedingly fine pitch, which would be inconvenient
and unsuitable in other respects.
With reference to certain differential screw couplings for connecting pipes
described in my Provisional Specification relative hereto, I have to state that I do
not herein mako any claim therefor.
Having thus particularly described my said Invention and the manner of
performing the same, I have to state that I do not restrict myself to the precise
details herein described or delineated, but that what I believe to be novel and
original, and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is,-
1. The combination of a nut formed with internal and external screw threads
having different pitches, but the same helical direction, with a bolt, stud, spindle, or
rod, and with a second internally screwed uut, substantially as and for the purposes
herein before described.
2. The combination of a nut formed with internal and external screw threads
having different pitches, but the same helical direction, with a bolt, stud, spindle, or
rod, and with an internally screwed socket in a fixed nut, or in the part to which
the doubly-screwed nut is applied for fastening or adjusting purposes, as herein-
before described.
In witness whereof, J, the said John Hastie, have hereunto set my hand
and seal, this Thirtieth day of December, in the year of our Lord One
thousand eight hundred and eighty.