An Improvement in Casing for Flexible Shafts.
Year: 1890

page_text: Date of Application, 13th May, 1890-Accepted, 14th June, 1890
COMPLETE SPECIFICATION.
An Improvement in Casing for Flexible Shafts.
I, FREDERIC SCHOFF of 3418 Boring Street, in the City and County of
Philadelphia, and State of Pennsylvania, United States of America, Gentleman, 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 object of my invention is to provide a flexible shaft with a flexible outer
casing or covering of such character as will restrict the bending of the shaft
beyond a predetermined limit, and this object 1 attain by providing the flexible
shaft with what may be termed a vertebrate casing or envelope, the joints, sections
or vertebrae of which are so constructed that they will bind one upon another
when the flexible shaft has reached the predetermined limit of flexion, and will. thus
prevent any further bending of the shaft in that direction.
In the accompanying drawing:
Figure 1 is a side view representing a flexible shaft having a casing or envelope
constructed in accordance with my invention ;
Figure 2 is a section, on a larger scale, showing an end portion of the flexible
shaft, its hand piece and fittings, and a number of the sections of the vertebrate casing
or envelope for the shaft; and
Figures 3 to 9 are views illustrating various methods of constructing the sections
or vertebrae of said casing or envelope.
A represents part of the flexible shaft, consisting of a number of spiral coils wound
tightly one upon another, as usual, a being the power receiving fitting connected to
one end of said shaft, and 6 the stem or spindle to be rotated, or through which the
power is to be imparted to any suitable implement.
At each end of the shaft are non-rotating sleeves or ferrules B, and these ferrules
must be connected by a flexible, tube forming a casing or envelope for enclosing
the flexible shaft, restricting the bending of the same and preventing injury to the
shaft, or to the person handling the tool or implement which is being driven.
Usually, this flexible casing or envelope consists of a single coil of special wire
and an outer covering of leather, rubber or equivalent material, but the objection
to a casing or envelope of this character is that it soon becomes more flexible than
the shaft itself, and consequently does not restrict the bending of the shaft to a
greater extent than is compatible with its economical and safe working.
In carrying out my invention therefore, I make the casing or envelope for the
flexible shaft in vertebrate form, each of the sections or vertebrae d fitting into one
and on to the other of the adjoining sections and having such play as will permit
the flexion of the shaft and its casing or envelope to any desired predetermined
extent, the sections or vertebrae binding one upon another when this degree of
flexion has been reached, so that further movement of the shaft in that direction is
prevented.
As shown in Fig. 2 each of the sections or vertebrae of the casing or envelope
consists of a shell having two cylindrical portions, one of which is of somewhat
greater diameter than the other, so that the small cylindrical portion of one shell may
enter the large cylindrical portion of an adjoining shell, the small portion having at
the end an external rib i and the large portion having at the end an internal rib m so
that when the sections or vertebrae are once fitted together, longitudinal seperation of
the vertebrae is effectually prevented by these ribs, but the vertebrae can yield upon
each other to an extent permitted by the contact of the rib i with the rib m, and with
the internal shoulder n formed where the internal diameter of the shell is reduced.
In order to permit the fitting of the vertebrae together the rib m may be
independent of the shell of the vertebrae, and may be in the form of a split ring

page_text: to be slipped over the small end of an adjoining vertebra and screwed into place
after the latter has been inserted, or the rib m may be secured in place by soldering,
brazing, or other means, or it may be of an elastic character, and may be sprung
into a groove formed in the large end of the shell, as shown in Fig. 4 for instance,
or the rib may be detachable as in Fig. 5, if desired, the rib being in the form
of a split ring, which can be first contracted so as to be passed through the ribbed
end of the shell and then allowed to expand inside the same for the reception
of the small cylindrical end of the next section, to which it may be secured by
brazing, soldering or otherwise, access being had to it through the open end of the
preceding section, or both ribs i and m may be detachable, in which case, neither of
them need be split.-Detachable ribs, however, are not absolutely essential to the
proper, carrying out of the invention, as the ribs may be integral with each shell,
and the small portion of the latter may be slotted longitudinally, so as to form a
series of ribbed fingers which may be sprung together, so as to permit the ribs i
to pass the ribs, m of the adjoining section, and may then be allowed to expand so
as to confine the two sections together-an instance of this construction being
shown in Fig. 6; or the large portion of the shell with its internal rib may be
slotted in the same manner, as shown in Fig. 7, the spring fingers being expanded
to permit, the ribbed end of the adjoining section to pass the samo.
In this case
however, it is advisable to provide an outer contracting ring m³, preferably screwed
on to the large end of the shell as in Fig. 8 so as to properly contract the internal
rib, and prevent the same from yielding to the strains to which it is subjected in
the subsequent use of the tool.
When it is not desired that the sections or vertebrae of the casing or envelope shall
be permitted to turn independently of each other the ribs may be dispensed with
altogether.
:
Fig. 9, showing a construction of this character in which the entering end of one
section has radial pins w adapted to slots w cut in the covering end of the adjoining
section, so as to permit the desired flexion of one section upon the other without
permitting the seperation of the sections, and a like pin and slot may be used in
connection with the other forms of joint shown, when it is desired to prevent
turning of the sections independently of each other.
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. The within described casing or envelope for a flexible shaft, the same consisting
of a series of sections or vertebrae, each consisting of a tube having one end of
larger. diameter than the other, the small end of one tube entering the large end
of the adjoining tube, and said tube sections being provided with stops whereby
the extent of flexion of the casing is limited, substantially as specified.
2. The within described casing or envelope for a flexible shaft, the same consisting
of a series of articulated sections or vertebrae, each consisting of a tube having
one end of larger diameter than the other, the small end of one tube entering the
large end of the adjoining tube, and the enlarged end of each section having an
internal rib, and the small end having an external rib whereby, when the sections
are fitted together, stops are formed for preventing seperation of the sections and
limiting the flexion of the casing substantially as specified.
3. The within described casing or envelope for a flexible shaft, the same
consisting of a series of articulated sections or vertebrae, the entering end of one
section having an external rib and the receiving end of the adjoining section
having an internal rib, one of which ribs is independent of the shell of the vertebrae
substantially as specified.