Improvements in Fastenings for Cranks and other Pieces to Shafts.
Year: 1897

page_text: Date of Application, 29th Mar., 1897
Complete Specification Left, 28th Dec., 1897-Accepted, 19th Feb., 1898
Improvements in Fastenings for Cranks and other Pieces to Shafts.
I, THOMAS ALFRED HEARSON, of Coopers Hill, Englefield Green, Surrey, Professor
of Engineering, do hereby declare the nature of this invention to be as follows:-
For the purpose of securing together a shaft and a crank or other piece which is
mounted on it, I drill a hole through the crank or other piece in a direction at right
angles, or approximately at right angles, to the axis of the shaft at such a distance
from the axis that, (the shaft being in place,) the drill will remove a portion of the
inaterial of the shaft. On the surface of the hole I cut a screw-thread, a portion of
the thread being formed in the material of the shaft. Into this hole I insert a
screwed plug. The hole and plug may each be of uniform diameter throughout,
or one or both may be slightly tapered. On one end of the screwed plug I form a
head or flats to facilitate tight insertion and removal.
For some purposes, in which it is desirable to readily unfasten the crank-piece
and axle, I cut away from one side of the plug such a portion that, when that side
of the plug is turned towards the shaft, by unscrewing the plug half a turn from the
tight position, the shaft will be able to revolve relatively to the crank.
Dated this 20th dow of Moroh 1007
Improvements in Fastenings for Cranks and other Pieces to Shafts.
I, THOMAS ALFRED HEARSON, of Coopers Hill, Englefield Green, Surrey, Professor
of Engineering, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement:-
-
For the purpose of securing together a shaft and a crank or other piece which is
mounted on it, I drill a hole through the crank or other piece in a direction at right
angles, or approximately at right angles, to the axis of the shaft at such a distance
from the axis that, (the shaft being in place,) the drill will remove a portion of the
material of the shaft. On the surface of the hole I cut a screw-thread a portion of
the screw-thread being formed in the material of the shaft. Into this hole I insert
a screwed plug.
The hole and plug may each be of uniform diameter throughout, or one or both
may be slightly tapered.
On one end of the screwed plug I form a head or flats to facilitate tight insertion
and removal.

page_text: To still further facilitate tight insertion and easy removal I sometimes make the
screwed plug hollow by means of a tapered hole throughout its length. Also by a
saw-cut or cuts along the whole or a portion of its length the plug is made capable of
expansion. On driving a tapered pin into the tapered hole the screwed plug will
be expanded and set up tightly in its place. On driving the pin the other way the
plug will be slackened and may easily be unscrewed.
For some purposes in which it is desirable to readily unfasten the crank-piece
and axle I cut away from one side of the plug such a portion that, when that side of
the plug is turned towards the shaft, by unscrewing the plug half a turn from the
tight position, the shaft will be able to revolve relatively to the crank.
Figs. 1 and 2 show the construction of the simplest form of the fastening as used
for fixing a bicycle crank to the pedal axle.
The axle being accurately fitted into the eye of the crank a hole is drilled at right
angles to the axle in such a position that the axis of the drill is approximately
tangential to the surface of the axle. Into the hole thus drilled a screw-tap is
inserted and a screw-thread is formed partly in the material of the axle and partly
in the crank.
The axle is then removed and a somewhat larger tap is inserted through the hole
formed in the crank. This will enlarge the hole a little.
A slightly tapered screw-plug is provided in which the smaller end is of the
diameter of the smaller tap and the larger end a little greater than the diameter
of the larger tap.
If this is tightly inserted it will bear hard on one side against the surface of the
hole formed in the crank and on the other side against the surface of the hole formed
in the axle and form a very rigid connection which will not work loose and yet is
easily removable by means of the hexagon head formed on one end of the screwed
plug.
Figs. 3 to 7 show an alternative construction intended to still further facilitate
tight insertion and easy removal. In this the screwed plug is made hollow by
forming a tapered hole in it. The hollow plug is shown separately in Figs. 5, 6
and 7. A slit is cut on one side which extends as far as the head of the screw but
is not taken through the head. When in place the slit is turned into the position
shown in Fig. 4, or into a position which would be arrived at by turning the plug
through half a revolution.
A tapered pin is fitted into the tapered hole and when it is driven in tightly by a
hammer the screwed plug will be pressed very closely against the axle. When
it is required to disconnect, the tapered pin is first driven back, the screwed plug
will then be slackened and may be readily un-screwed.
A nut is screwed on to the small end of the pin for the purpose first, of prevent-
ing it from falling out of place and being lost, if it should become loose, and
secondly, to protect the point of the pin from being injured when, by means of a
hammer, it is driven out of the tapered hole.
The following modifications may, under some circumstances, be adopted with
advantage.
The saw-cut may be continued through the whole length of the screwed plug.
The spanner-head on the end of the screwed-plug may be omitted and a screw-
driver slot be provided at one or both ends.
The tapered hole may be made somewhat eccentric to the screwed surface of the
plug and the saw-cut made at the thinnest part.
Such a fastening, or more than one, may advantageously be used to secure the end
of a shaft to a sleeve which is made to fit around it, and, if the sleeve is similarly
secured to the end of a second shaft, the two lengths of shafting will be rigidly
coupled together and yet in such a manner that they may be readily disconnected
and re-connected as firmly as before.
Further such a fastening as is shown in Figs. 3 to 7 may sometimes be advan-
tageously used in the place of an ordinary key of rectangular section, the axis of
the hollow screw being placed parallel to that of the shaft.

page_text: In this case the slit should be turned away from the shaft. On driving in the
tapered pin the screwed plug will be expanded sideways and make a very tight
connection. Unless the circumstances are such that the tapered pin can be driven
back by a blow struck on the small end, it will be necessary to provide a head on
the pin whereby it may be removed by the use of wedges or a wrench.
An expansible fastening constructed as described but without a screwed surface
may under some circumstances be used with advantage.
Figs. 8 and 9 show the modification of the construction which will facilitate rapid
disconnection. The construction is like that shown in Figs. 1 and 2 except that in
Figs. 8 and 9 a portion of the screwed plug has been cut away. In Fig. 9 the
screwed plug is tightly home and a rigid connection between the crank and axle is
provided. In Fig. 8 the plug has been unscrewed half a turn so that the hollow
which is formed in it is turned towards the shaft, giving freedom for the shaft to
revolve.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what I
claim is :-
1. A fastening for a crank or other piece to a shaft or axle consisting of a screwed
plug fitted into a screw-threaded hole which is drilled partly in the crank or other
piece and partly in the shaft or axle, the axis of the hole being approximately in
a direction at right angles to the axis of the shaft or axle.
2. A fastening for a crank or other piece to an axle constructed substantially as
described and shown in Figs. 3 to 7.
3. A fastening for a crank or other piece to an axle capable of rapid dis-connec-
tion substantially as described and shown in Figs. 8 and 9.
4. A sleeve or muff-coupling for two lengths of shafting in which the connection
of the sleeve to the end of each length of shafting is made by means of one or more
screwed plugs substantially as described.
1008