Improvements in Flexible Shafts.
Year: 1897

page_text: Date of Application, 4th May, 1897
La
OLL A
1
Date of Application, 4th May, 1897
1
Complete Specification Left, 20th Dec., 1897 Accepted, 12th Mar., 1898
PROTIONAL SPECIFICATION.
Improvements in Flexible Shafts.
I, MAX BUCHERER, of Koln-Ehrenfeld, in the Empire of Germany, Engineer,
do hereby declare the nature of this invention to be as follows:
:-
Flexible shafts usually consisting of wire ropes have been already frequently
employed in place of gearing or rigid shafts for conveying movement.
:
The advantages which such shafts afford in practice consist essentially in the
fact that they may be carried round more or less sharp curves according to their
flexibility without reducing their effectiveness and a certain mobility may thus
be given to the driven mechanism relative to the source of power which is entirely
impossible where rigid transfer mechanism is employed.
This circumstance makes the use of flexible shafts appear desirable to a greater
extent, but they have hitherto been limited only to such cases where the power
to be transmitted was not too great, such for instance as dental machines, sheep
shearing machines and the like, as the hitherto usual construction of flexible-
shafts was not equal to the deleterious action of torsion on their duration.
This invention has for its object a flexible shaft which, in consequence of its
peculiar construction, is suitable for transmitting movement or power even in
such cases where it is a question of great power, such for instance as in cycles.
for conveying the rotary movement of the pedal shaft to the driving wheels.
The invention consists in making long metal strips of suitable section and
sufficiently flexible or elastic material and in providing the edges of the same
with teeth by cutting notches or recesses. These toothed metal strips are then
wound spirally on a flexible core, such for instance as a wire rope, in such a way
that the toothed edges engage with one another, that is to say the teeth of one
edge engage in the notches of the adjacent edge. The two free ends of the metal
strips are soldered or otherwise suitably attached to the flexible core.
A metal band of T-section is preferably employed, the toothed notches being
cut on the arms of the T-shaped profile.
Of course any suitable section, such as cruciform, double T-shaped or the
like may be selected in place of the T-shaped section. Similarly the choice of a
flat metal band with toothed and notched edges is not excluded but the previously
mentioned section is to be preferred, as greater power of resistance is thereby
obtained.
The winding of the above mentioned metal band may be effected in a single
or multiple threaded spiral the band being preferably set up on edge in order
to increase as far as possible the power of resistance of the flexible shaft against
torsion or fracture during the transmission of power when turning on its own
axis.
The flexible core serves for guiding the spiral coils and as already stated may
be made of any suitable flexible material.
The mode of working of a flexible shaft made in this manner is as follows:-
At a small pressure the spring power of the spiral coils suffices to transmit
a small amount of work.

page_text: At a greater strain the teeth engaging one another prevent any diminution
of the diameter and a further twisting of the flexible shaft, and impart to the
same a higher capacity and therefore the possibility of a greater delivery of power,
presuming that the rotation is in the direction of the spiral coils.
In a rotation in the opposite direction, the teeth engaging with one another
prevent any increase in the diameter of the spiral coils so that such a shaft
retains its capability of working in either direction of rotation. In no case is
the elasticity of the flexible shaft called upon beyond a given extent, as the
teeth lying in some cases on the outermost periphery serve for transmitting the
power and prevent any deleterious greater spring tension.
Of course several spiral coils may also be employed one over the other, which
are preferably wound in opposite directions.
In place of the spiral coils, closed rings with the same profiles and teeth or
notchings may also be employed, arranged on a flexible core, the end rings being
firmly connected with the flexible core.
Intermediate rings may also be employed having holes for receiving the teeth
of the adjacent rings.
It is evident from the foregoing that a whole series of further modifications are
possible and that the essential feature of the invention is always to be sought
in projections or teeth engaging in notches or holes.
Dated this 30th
1 100%
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
I, MAX BUCHERER, of Koln-Ehrenfeld, in the Empire of Germany, Engineer,
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:
Flexible shafts usually consisting of wire ropes have been already frequently
employed in place of gearing or rigid shafts for conveying movement.
The advantages which such shafts afford in practice consist essentially in the
fact that they may be carried round more or less sharp curves according to their
flexibility without reducing their effectiveness and a certain mobility may thus
be given to the driven mechanism relative to the source of power which is entirely
impossible where rigid means of transmission is employed.
This circumstance makes the use of flexible shafts appear desirable to a greater
extent, but they have hitherto been limited only to such cases where the power
to be transmitted was not too great, such for instance as dental machines, sheep
shearing machines and the like, as the hitherto usual construction of flexible
shafts was not equal to the deleterious action of torsion on their durability.
This invention has for its object a flexible shaft which, in consequence of its
peculiar construction, is suitable for transmitting movement or power even in
such cases where it is a question of great power, such for instance as in cycles
for conveying the rotary movement of the pedal shaft to the driving wheels or
for avoiding bevel gearing and the like in transmission shafts.
The invention consists in making long shaped metal strips of suitable section
and sufficiently flexible or elastic material and in providing the flanges or edges of
the same with teeth by cutting notches or recesses therein. These toothed metal
strips are then wound spirally on a flexible core, such for instance as a wire rope,

page_text: in such a way that the toothed edges or flanges engage with one another, that is
to say the teeth of one edge or flange engage in the notches of the adjacent
edge or flange. The two free ends of the metal strips are soldered or otherwise
suitably firmly attached to the flexible core or even to the sleeves surrounding or
encasing the ends if there be no core.
In the accompanying drawings,-
!
Figure 1 is an elevation of a piece of metal of T-shaped section, such as may be
preferably employed, the toothed notches being cut on the arms of the T-shaped
profile.
Figure 2 is a longitudinal section of a flexible shaft which is made by spirally
winding the metal strip of T section shown in Figure 1 and has disconnected
flanges or edges.
Of course any suitable section, such as cruciform,. double T-shaped or the
like may be selected in place of the T-shaped section.
The winding of the above mentioned metal band may be effected in a single
or multiple threaded spiral, the band being preferably set up on edge in order
to increase as far as possible the power of resistance of the so formed flexible shaft
against torsion or fracture during the transmission of power when turning on its
own axis.
The flexible core if such be employed in a flexible shaft thus formed serves for
guiding the spiral coils and as already stated may be made of any suitable flexible
material.
:-
The mode of working of a flexible shaft made in this manner is as follows:-
At a small pressure the spring power of the spiral coils suffices to transmit
a small amount of work.
At a greater strain the teeth engaging one another prevent any diminution
of the diameter and a further twisting of the flexible shaft, and impart to the
same a higher capacity and therefore the possibility of a greater delivery of power,
presuming that the rotation is in the direction of the spiral coils.
In a rotation in the opposite direction, the teeth engaging with one another
prevent any increase in the diameter of the spiral coils so that such a shaft
retains its capability of working in either direction of rotation. In no case is
the elasticity of the flexible shaft called upon beyond a given extent, as the
teeth lying mainly on the outermost periphery serve for transmitting the power
and prevent any deleterious greater spring tension.
Of course several spiral coils may also be employed one over the other, which
then are preferably wound in opposite directions.
In order to prevent the teeth coming out of engagement whilst the shaft is
at work, they may be so shaped as to have at their base a smaller section than at
their ends. If then the notches or intervals between the teeth be formed to
correspond, the separation of the teeth from one another in the direction of the
centre line of the teeth is restricted and a disengagement of the same entirely
prevented, by which means the shaft may also be subjected to a pull and if encased
with elastic tubes with thin walls, piping, or the like, as a flexible casing, can
endure a high pressure and pull.
The form of teeth preferably employed for this object is that of a dovetail
but T-shaped, disc-shaped or other suitably shaped teeth may be employed.
Intermediate spirals may also be inserted having notches or recesses for receiving
the teeth or projections of the next or adjacent spirals.
It is evident from the foregoing that a whole series of further modifications are
possible and that the essential feature of the invention is always to be sought
in one or more shaped metal bands having the bar part set upon edge
being wound spirally, whilst the edges or flanges of the said metal bands have
teeth and dovetail or other suitable notches which engage in one another and
render a displacement of the coils impossible and yet retain great flexibility. For
large shafts such as are employed for transmission shafts in order to avoid bevel
gearing, the bars are placed suitably close together and strengthened.

page_text: 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:
A flexible shaft for transmitting power and movement, characterized by shaped
metal bands, which are spirally wound preferably on a flexible core and which
are of suitable composition, or section, being formed with projections or teeth or
dovetails to engage in the notches or recesses of the adjacent shaped flanges or
edges of the spiral coils, with the object of avoiding by means of these teeth, any
great tension, and of imparting to the shaft a higher capacity more particularly as
regards its flexibility, substantially as herein before described.
Dated this 24th day of December 1897
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.