Improvements in Flexible Driving Shafts or Cables.
Year: 1889

page_text: Date of Application, 1st Aug., 1889-Accepted, 7th Sept., 1889
COMPLETE SPECIFICATION.
Improvements in Flexible Driving Shafts or Cables.
I, JOHN SMALLEY CAMPBELL, of 10 Park Square West, Regents Park, N.W., in
the County of Middlesex, 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:—
My invention relates more particularly to the flexible driving shafts or cables used
in dental engines, but it is also applicable to flexible shafts or cables of larger size,
such for example as those used in engineers shops for drilling holes in boiler plates, or
other like heavy work.
The flexible shafts or cables ordinarily employed are not capable of being bent to
and working at a curve of very short radius, and in dental engines, it has been
customary, in order to overcome the inconvenience caused thereby, to provide the
cable or arm at one or both ends, or in the centre, with a short length formed of
a single coil of spring wire, which is extremely flexible and will bend and work at
a sharp curve. These coils are however not sufficiently strong to drive such tools as
grinding wheels, and others which require extra power, without jarring, and un-
pleasant vibration, and the main object of my invention is to provide means for
converting such flexible coils into rigid shafts when required, and thus overcoming the
above objection.
The accompanying sheets of drawings represent the form in which I apply my
invention to a dental engine. The engine itself, which may be of any of the usual
forms, is not shown; Figs. 1, 2, 3, and 4, represent my arrangement as applied to
the engine end of the driving cable; Fig. 1 being a side elevation, Figs. 2 and 3
sectional side elevations, shewing the parts in different positions; and Fig. 4 a plan;
Fig. 5 is a sectional view shewing the arrangement applied to the handle or tool end
of the cable.
Similar letters of reference denote similar parts throughout the drawings.
Referring to Figs. 1, 2, 3, and 4, A is a shank fitting into the top of the pillar post
of the engine, and having a spherical, or other suitably shaped head B, within
which is journalled a short spindle C, carrying a pulley D, driven from the main
wheel of the engine in the usual manner. EE is a hollow box or bracket affixed
to or formed in one piece with the head B, and FF is a similar hollow box jointed
to EE by the pin H; a tube J is affixed to F F, carrying at its outer end the
sheath K of the ordinary flexible shaft or cable L. A spindle M is journalled in
bearings N and P within the tube J, and has the cable L affixed to one end. The
spindles C and M are connected by the flexible coiled spring Q, which transmits
the motion of the spindle C to the spindle M and cable L, and at the same tune
permits the box bracket joint F E, F F, to be turned down into the position shewn
by dotted lines in Fig. 1, so that the arm and cable can hang down against the pillar
post, of the engine. R is a tube which encircles the spindle M and can be slid
forward over the spring Q, when the said spring and bracket joint are extended out
in the horizontal position.
A ring S is provided to slide on the tube J, and the inner end of the set screw T in
the said ring enters the annular groove U in the end of the tube R, so that the said
tube can be slid back and forth by means of the ring S, while at the same time it
is free to rotate. A slot V is formed in the tube J, through which the screw T
passes, to allow the ring S to slide. A slot W is formed in the tube R for the
greater part of its length, and a pin X in the spindle M'engages with the said
slot. On the opposite side a short slot Y is formed in the end of the tube, and when
the tube is slid forward to cover the spring coil Q, this slot engages with a pin Z
on the spindle C, and the said spindle is then connected by means of the pins

page_text: and slots with the cable spindle M, so that the two spindles become practically one
continuous rigid spindle running in bearings B, N, and P, and the spring Q, although
it revolves with the spindles, no longer transmits any power, all the strain of driving
-being taken by the tube R. The slot W and pin X not only compel the tube R and
spindle M to rotate together, but also ensure the pin Z always entering the slot Y,
when the tube R is slid forward.
a is a flat spring, firmly secured to the half E E, of the box bracket joint, a slot bis
formed in the outer end, which passes over a projecting lug c on F F, and makes the
joint a rigid bracket, when in the horizontal position. A small bolt a passes over the
said spring and forces it always to engage with the lug c, and also holds it against
the bracket joint, so as to form a curve when the arm is turned down, and thus by its
resistance to prevent the arm from falling suddenly against the pillar post of the
engine, when the spring is released from the lug c.
In Fig. 2 the tube R is shewn drawn back within the tube J, so that the motion of
spindle is transmitted to spindle M by the coiled spring Q; and in Fig. 3 the
tube R is shewn slid forward, and engaged with spindle C, so that the said spring Q
is out of action.
The main advantages of my above described arrangement are, that I obtain the
benefit of a flexible spring for the purpose of folding the arm down against the pillar
post when not in use, combined with all the advantages of a strong cable when
required.
Referring to Fig. 5 which shews my invention as applied to the handle end of the
cable:
The arrangement is substantially the same as that shewn in the preceeding Figs.
with the exception of the box bracket joint EE, F F, which is not required. e is the
usual tool handle, having a spindle C, which in this case is connected to a spindle M
by a flexible coiled spring Q. The spindle M is carried in the tube J, to the end of
which is attached the sheath K of the cable L, this cable being attached to the end of
the spindle M. The spring coil Q is surrounded by a sheath f. Ris the tube actuated
by a ring S, and having a long slot W working on a pin X on the spindle M, and a
short slot Y to engage with the pin Z on the spindle C, when the tube is slid forward.
By this means the spring can be thrown out of action, when heavier work is
required, and the driving power be transmitted through the tube R to the spindle C.
In place of converting the spring Q into a rigid arrangement by means of a tube
sliding externally thereto, I may employ a pin or shaft to slide within the spring, but
in practice I prefer the use of the external tube.
Although I have shewn and described my invention as applied to a flexible shaft or
cable of a dental engine, it is obvious that its use is not confined thereto, but that it
may be applied to flexible driving shafts or cables of any other description.
I wish it to be understood that I make no claim to the use per se of flexible springs
such as Q, in a flexible driving shaft or cable, as the employment of such springs at
either or both ends, or in the middle of the cable, is quite old.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a flexible driving shaft or cable, having one or more flexible springs Q, the
combination, with such springs, of tubes capable of sliding over the said springs for
the purpose of converting them, when required, into rigid continuous shafts, sub-
stantially as herein set forth.
2. In a flexible driving shaft or cable, having one or more flexible springs Q, the
combination, with such springs, of pins capable of sliding within the said springs for
the purpose of converting them, when required, into rigid continuous shafts, sub-
stantially as herein set forth.
3. In a flexible driving shaft or cable, the arrangement of a box bracket joint,
consisting of the parts E E, F F, and having a flat spring a confined by a bar & and
engaging with a lug c, in combination with a flexible spring Q capable of conversion

page_text: into a rigid shaft as described in either of the preceeding claims, substantially as
herein set forth.
4. The flexible driving shaft or cable of a dental engine, or other apparatus, con-
structed substantially as and for the purposes herein described and shewn with
reference to the accompanying drawings.
Dated this 23rd day of Jul 1880
AMBROSE MYALL,
21, Cockspur Street, S.W., Agent for the Applicant.