Improvements in Flexible Conduits for Electrical Conductors."
Year: 1897

page_text: Date of Application, 16th Nov., 1897-Accepted, 18th Dec., 1897
COMPLETE SPECIFICATION.
"Improvements in Flexible Conduits for Electrical Conductors."
I, EDWIN TRUMAN GREENFIELD, of No. 527 West 34th Street, New York,
United States of America, Electrician, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:--
This invention is directed particularly to a novel form of flexible armoured
conduit adapted especially for surrounding or protecting electrical conductors,
such for instance as are used in connection with systems of electric lighting and
the like, and its objects are;
First, to devise such an armoured conduit which may be cheaply constructed
and which will effectually protect such conductors under all conditions of usage;
Secondly, to devise a flexible armoured conduit which will possess such flexi-
bility as to enable it to be used in conveying conductors around corners or angles
where the curvatures are necessarily abrupt and without any danger of damaging
it, the conduit; and, Third, to construct a flexible armoured conduit in which the
armour shall be securely locked together so that it, the conduit, may be severed
at any point and the armour remain in locked position throughout its length and
at the points where it is severed, and also so that it will be given great flexibility
and withstand longitudinal strains without danger of rupture.
For a full and clear understanding of the invention reference is to be had to
the accompanying drawings, in which,
Figure 1 illustrates in side elevational view a short section of this improved
flexible conduit; and
Figure 2 a slightly enlarged sectional view thereof, illustrating also the elements
thereof slightly separated from each other for the purpose of enabling its structure
to be better understood.
Figure 3 is a side elevational view of a similar section of the conduit partially
completed; and
Figure 4 is a similar side elevational view of the interior insulating lining
therefor.
Figure 5 illustrates in side elevational view a short length of a modified form of
this novel flexible armoured conduit, illustrating also the manner of constructing
the same.
Figure 6 is a longitudinal sectional view of Figure 5; and
Figure 7 an enlarged end elevational view of the structure partly in section as
seen looking at Figure 5 from left to right.
Reference will first be had to Figures 1 to 4 inclusive, illustrating one form of
this novel flexible armoured conduit, which is constructed by first win King a
strip of soft rubber R, Figure 4, upon a flexible or expansible mandrel, the
adjacent edges of said strip being preferably coated with benzine, alcohol, or any
well known agent which will cause the same to adhere to each other when so
wound. Upon this strip of rubber is now wound a second strip, of thin sheet
metal M, such as iron, the convolutions or windings thereof being separated from
[Price 8d.]

page_text: each other and the body portion thereof breaking joints with the joints of the
rubber strip R¹, see Figure 3.
About the outer surface of the metal surface M is now wound a second strip of
rubber R, the convolutions or windings of which are separated from each other
by a definite space as were the like convolutions or windings of the metal strip M,
as clearly shown in Figure 2. Around the entire structure a third strip M³, of
metal, substantially like the first strip M is wound with the difference, however,
that this third strip is corrugated centrally, as shown at C, Figures 1 and 2, the
corrugation being of such a nature and so located that it fits accurately within
the space left by the edges of the adjacent windings or convolutions of the strip M,
and at the same time bears firmly down upon the rubber strip R in suc manner
as to cause its inner surface to abut firmly against the inner strip R¹ of rubber.
This central corrugation C serves also the additional and very important function
of preventing the outer metallic strip M¹ from unwinding from around the inner
strips when the conduit is severed at any point. Any number of alternate strips
of rubber and metal may be similarly wound and the same united together by
any adhesive paste, such for instance as rubber cement. After the conduit has
been constructed as described, the expansible mandrel is withdrawn and the com-
pleted conduit subjected to the well known process of vulcanization so as to thereby
vulcanize the rubber parts thereof to any desired degree, thus uniting the whole
structure firmly together. Under some conditions of usage, it might not be
deemed best to vulcanize at all, rubber cement being a sufficient binding agent,
but in case the conduit is to be used in positions surrounding steam pipes, boilers,
flues, and other places where unnatural heat exists, it should be vulcanized to
such a degree of hardness as will naturally suggest itself to those skilled in the
art.
In place of making the interior tube R¹ of spiral convolutions, the same might
be an ordinary flexible rubber tube with the convolutions of meta and rubber
alternately wound around it as before and the entire structure vulcanized together.
In this event the conduit might be constructed without the use of an interior
expansible sustaining mandrel.
Referring now to Figures 5 to 7 inclusive which illustrate the preferred
modified form of this invention, T represents a flexible lining, preferably com-
posed of vulcanized rubber. N and M represent spirally wound strips of metal,
such as iron or steel, although they may be of any metal having the desired
strength and flexibility. The inner strip M is so constructed that when wound
upon the lining tube T it presents an outward concave or curvilinear surface
throughout its length and is also constructed with a central line or row of pro-
jections or lugs I I, while the outer strip N which is wound upon it in such
manner as to break joints is curved in a reverse direction or inwardly, and has
constructed upon its inner surface a series of lateral indentations D; somewhat
similar indentations being shown between the lugs or projections I in the strip M.
S represents a strip of soft rubber or of elastic tape provided with an adhesive
agent on either or both surfaces, said elastic strip being wound between the
successive convolutions or spirals of the strip M. and the strip N wound thereon
in the manner shown, so as to cause the central portion of the elastic or rubber
strip S to adhere to the outer surface of the lining tube T. After the conduit is
thus constructed, it is subjected to any of the usual processes of vulcanization to
the desired degree, thereby causing the rubber strip S and rubber tube T. to
firmly adhere to each other and to the successive convolutions of the spiral
strips N and M, thus making an absolutely water tight and perfect insulating
flexible conduit.
It will be noticed that by virtue of the opposite curvature of the strips N and M
and the intervening row of projections or lugs I, there is formed a continuous
locking joint between all parts of the conduit or tube, such locking joint prevent-
ing the unwinding of the end portions of the tube and also any possibility of
separating the several convolutions by longitudinal strain upon the conduit or

page_text: tube. It will also be apparent that by virtue of the reverse curvature of the two
strips N and M, when in position, there is given greater flexibility to the entire
conduit or tube than is possible with the novel armoured conduit tube disclosed in
Figures 1 to 4 inclusive of the drawings herein before referred to.
It will of course be understood that the projections or lugs I might be replaced
by a continuous ridge or rib, but it is found in practice that better results are
obtained by the use of such lugs. It is also apparent that there might be a
similar series of lugs or projections extending inwardly in the strip N and adapted
to depress the elastic strip S and hold it firmly against the inner tube T and also
give additional longitudinal strength and locking security to the structure.
Although the insulating material of which the alternate layers of this improved
conduit are described as being made of soft rubber, it is to be understood that
the same may be of other pliable materials, such as fabrics coated with soft
rubber, or of such materials as when wound in the manner described could be
united together in one mass with one or more successive layers of spirally wound
armours and the entire mass still retain the desired flexibility and water resisting
and insulating qualities.
Ocean cables have heretofore been constructed in which the conductor itself was
surrounded with rubber, jute, and the like, and this in turn surrounded with a
spirally wound armour of wire, the spirals running either all in the same direc-
tion, or one layer in one direction and a second in a reverse direction, the alternate
layers being thus applied to the desired thickness, and no claim is hereinafter
made broad enough to include such structure, the broadest claim being to a
flexible conduit of the nature described and designed to cover or surround
removable conductors.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. An armoured conduit consisting of a flexible interior insulating tube and
one or more spirally wound layers of metal secured thereto.
2. An armoured conduit consisting of a flexible insulating lining and alternate
layers of spirally wound strips of metal separated from each other by layers of
insulating material and all united together.
3. An armoured conduit consisting of any insulating lining surrounded by alternate
layers of metal armour and insulating material, the entire structure being of a
flexible nature.
4. An armoured conduit consisting of alternate layers of spirally wound insulat-
ing material and metal armour breaking joints with each other and united
together so as to constitute a water-tight flexible conduit.
5. An armoured conduit consisting of alternating layers of spirally wound sheet
rubber or rubber cloth and metal armour, said layers being united together by
the process of vulcanization.
6. A flexible armoured conduit tube consisting of a flexible lining and two or
more metallic armour strips spirally wound thereon and curved in opposite
directions, substantially as shown in Figures 5 and 6 of the drawings.
7. A flexible armoured conduit tube consisting of a flexible lining and two or
more metallic armour strips spirally wound thereon, said armour strips being
curved in opposite directions and breaking joints with each other, substantially
as shown in Figures 5 and 6 of the drawings.
1 15th day of November 1897
HASELTINE LAKE & Co.
45 Southampton Buildings, London, W.C. Agents for the Applicant.