Improvements in or relating to Flexible Transmission Shafting.
Year: 1899

page_text: Date of Application, 23rd Dec., 1899-Accepted, 19th May, 1900
COMPLETE SPECIFICATION.
Improvements in or relating to Flexible Transmission Shafting.
A communication from LA SOCIETE ANONYME DE TRANSMISSION, TRANSPORT,
TRACTION, of 1, Square Labruyere, Paris, in the Republic of France
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of London,
Chartered Patent Agent, 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:-
The use of flexible shafting for the purpose of transmitting movement, say
from a motor to a tool, by means of parts articulated together in various manners,
is well-known, but all the systems used at the present time are attended with
certain drawbacks. Such shafts cannot be lengthened or shortened so as to
follow the various curves which they ought to be able to follow. Owing to this
drawback the parts are exposed to abnormal stresses either as to traction or
compression, which causes rapid wear of the parts composing such shafts.
Then again in the case of flexible shafts where the component parts are articu-
lated, two by two on spheres, the parts being shaped like claws with two or more
arms, the arms of one claw engaging between those of the other, and embracing
the same sphere, at the beginning of the movement the lateral faces of the claws
of each element come in contact with the corresponding surfaces of the element
next to them. This results in a heavy shock and friction on the first named
claws and consequently a rapid wear or deterioration takes place. It is therefore
necessary to construct these parts near the driving end of the shaft, differently
from the others so as to avoid such shocks.
The present invention relates to a flexible shaft which meets the necesssary
requirements in every respect and may be employed in all cases where the em-
ployment of a flexible shaft is required.
In the accompanying drawings
Figure 1 is a longitudinal section of the flexible shaft with its component
parts.
Figure 2 is a transverse section on the line 2-2 of Figure 1, and
Figure 3 is a partial longitudinal section, the plane of which is perpendicular
to that of Figure 1.
Figs. 4 & 5 are detail views of the member g, Figs. 6 & 7 of the member h
and Figs. 8 & 9 of the member hereinafter referred to.
The movement of the motor or driving force is received by a shaft a ending
in a collar with a projection engaging with a slit in a square part 6 arranged
in a metallic sleeve c. Into the interior of the square part 6 passes a shaft/
the two being connected together by a pin, which is introduced through a hole
in the sleeve c. The shaft d passes freely through a sleeve attached to the
casing e of the flexible shaft and ends in a part having a diameter slightly
smaller than that of the surrounding casing and provided at its end with a square
triangular or polygonal hole, in which can slide, with slight friction, a rod f
of the same form carrying the first flexible element f¹. At one of its ends, the
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page_text: rod carries a cross key or bar f2 which can freely slide in slots d¹ d¹ arranged
diametrically opposite to each other in the hollow part of the shaft d, the
length of which slots limits the travel or play of the rod d.
The three or four first flexible elements consist of metallic parts g g, preferably
of cylindrical form, the ends of each of them being provided with a deep recess.
The two recesses of the same element are arranged relatively to each other at a
suitable angle, say of 45 degrees.
Each two adjoining elements are connected by means of a metallic prism h
fitting in one of the recesses of each of them and secured by means of two pins h¹ h¹
arranged at right angles to each other, that is to say one of these two pins passes
through two opposite faces of the prism h while the other passes, in another
plane, through the two other faces, in such a manner that the adjoining recesses
or cut away portions of two adjacent elements form with each other a right
angle also.
The other elements ii consist of cylindro-ovoidal parts terminating at each end
in two or more suitably curved or inwardly turned claws embracing a
sphere o, the claws at the ends of two adjacent elements being arranged, with a
certain amount of play, the one between the other, so as to embrace the same
sphere o and to be able to turn round the latter
As the shaft a receives its movement from the motor it involves in this
movement the elements b, c and d, and thus the rod f and the first element
connected with it. The three or four next elements g g are next involved in the
movement without shock and work in the manner of Cardan joints and are
exposed to the greatest torsional effect at the moment of starting. The
remaining elements ii are then similarly successively involved in the movement
owing to the free space or play between their respective claws, the conjugate
faces of which come in contact with each other. It will be easily understood,
that if these elements were placed first, i.e. in the place occupied by the ele-
ments g g the shocks between the claws would be much greater, and the wear
of the parts would be much more rapid, a drawback which is not experienced with
the elements g g. The latter elements could be employed for the whole length
of the flexible portion of the shaft but their cost being so much greater than that
of the spherical hinge parts it is preferable to limit their employment, in the
manner described. If during the working of the flexible shaft the curve should
be varied, as is often the case, although such may be necessitated only owing to
the forward movement of the tool, it might happen that the elements would be
exposed to abnormal effects of compression or traction which might soon wear
them out, while the friction of the shaft in its covering e would also increase,
from which would result a less effective working, heating and straining of the
whole system and a rapid wear of the flexible shaft. It is therefore necessary
that at least one of the connecting points should be movable, so as to allow the
shaft always to bend to the most favourable curve for working purposes.
This condition is realised in a perfect manner by the arrangement, in which
the bar of the first element f¹ can slide in the end of the shaft d, and the small
sides of the slots limiting the travel of the pin f prevent the bar f from
slipping out of its socket. The sliding of this bar f easily takes place during
the work of the flexible shaft, and the action on the parts is always assured in a
continuous manner.
Having now particularly described and ascertained the nature of the said
invention as communicated to me by my foreign correspondent and in what
manner the same is to be performed, I declare that what I claim is:-
1. A flexible shaft varying as regards length of which at least one of the
two terminal elements is connected with a rod capable of sliding, without turn-
ing, in a sleeve directly connected with the shaft receiving the rotary movement
from the motor or driving force so as to allow the shaft to lengthen or shorten
within two limits determined by the length of play of a pin of the rod in slots

page_text: in the sleeve, the first elements at least of the flexible shaft having no free play
the one relative to the other so as to avoid shocks and to lessen the wear and
tear of the shaft, substantially as described.
2. In a flexible shaft of the kind described, cylindrical parts hollowed or cut
away at their ends for the purpose of coupling and forming with each other a
certain angle and receiving rods articulated on pins passing through the cheeks
of the connections these parts having no free space with regard to each other, and
transmitting the movement without shock, substantially as described.
3. The complete flexible shafting substantially as described or illustrated in
the accompanying drawings.
Dated this 23rd day of December 1899.
BOULT, WADE & KILBURN,
Agents for the Applicant.