Remote control cable

A remote control cable comprises two conducting wires separated by a central element with reinforcing wires parallel to the conducting wires. At least one layer of lapping covers these elements and at least one external coating layer is applied. The central element separates and holds the conducting wires parallel and is in the form of a continuous element, comprising two longitudinal recesses arranged symmetrically relative to a solid central portion. Each recess encloses a conductor over more than half of the periphery of the conductor. This cable may be used for the transmission of control command for moving bodies traveling at high speed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a new remote control cable or wire, which 
is light, of small section, with high tensile strength, virtually 
inextensible, flexible and impervious, which can advantageously be used 
for the transmission of control commands for moving bodies traveling at 
high speed. 
More particularly, it relates to a new remote control cable intended to 
guide a moving body by means of commands which are in the form of 
rectangular electrical signals, a specific length of the cable being 
stored at the rear of the moving body and unwinding as the body moves. 
The invention also relates to a new process and a new device for making 
such a cable. 
2. Technical Considerations and Prior Art 
Numerous documents describe conducting wires or conducting cables which can 
be used to transmit commands to a moving body. Amongst these documents are 
French Pat. No. 1,477,500 and its two Patents of Addition No. 90,970 and 
No. 93,154. 
French Pat. No. 1,477,500 describes an inextensible conducting cable 
comprising a core containing at least two separate conductors situated 
virtually along the longitudinal axis of the said cable, the core being 
surrounded by a layer of lapping and the assembly covered by at least one 
thin coating layer. 
According to Addition No. 90,970, in order to hold the conductors apart, 
the conducts are arranged symmetrically relative to a bonded glass fibre 
core and bonded to the latter by heat sealing. Other reinforcing glass 
fibres are arranged parallel to the core/conductor assembly and, as in the 
principal patent, the whole structure is surrounded by a lapping wire and 
an external coating. Preferably, the conducting wires are slightly inlaid 
inside the central core. 
Addition No. 93,154 relates to improvements to the conducting cables 
produced according to the processes mentioned above, these improvements 
applying principally to, on the one hand, the nature and the method of 
lapping and, on the other hand, to the external coating of the said cable. 
The conducting cables described in the aforementioned documents exhibit 
very high qualities, particularly with respect to their fineness, their 
strength and, above all, with respect to their electrical properties and 
particularly to their time constant factor. 
However, the symmetrical positioning of the conducting wires relative to 
the core is rather difficult to achieve and, during manufacture and/or 
use, the wires can move slightly, which is prejudicial to good 
transmission of signals. Moreover, the use of glass fibres, as a 
separating element and as the core, increases the weight of the cable 
substantially, which leads to a reduction in the breaking coefficient of 
the cable determined by the ratio of the breaking strength of the cable to 
the weight of the cable. 
To overcome these disadvantages, it has been proposed, particularly in 
French Pat. No. 2,005,693, to hold and to separate the conducting wires of 
a cable of the type previously described by assembling them in parallel by 
bonding them with the same lacquer as that used to insulate each of the 
wires. If, in theory, such a solution is attractive, it must be recognized 
that, from the practical point of view, it is difficult to achieve and 
that it suffers from a certain number of disadvantages. Indeed with this 
method, it is virtually impossible to have a good bond between the two 
conductors along their whole length, since the bonding takes place over a 
very small part of the surface of each of the conductors. Moreover, this 
bonding is rather poor and the conductors may have a tendency to separate 
from one another in use. Finally, the spacing between the two conductors 
is provided by the thickness of the insulating layer which surrounds each 
conductor, which therefore requires the conductors to be covered with a 
relatively thick layer of insulating material if sufficient spacing 
between them is to be achieved. 
The prior art further includes the following patents: German Pat. No. 
1,540,626, filed Dec. 23, 1965 (Ser. No. 101,140); German Pat. No. 
1,665,605, filed Apr. 14, 1966 (Ser. No. 103,167); French Pat. No. 
1,564,336 (based on U.S. patent application Ser. No. 640,621), filed May 
23, 1967; and U.S. Pat. No. 3,536,548, filed Aug. 26, 1968 (Ser. No. 
755,296). 
SUMMARY OF THE INVENTION 
The present invention achieves an inextensible conducting cable which 
exhibits improved characteristics relative to the previous cables, 
particularly with respect to the spacing and holding of the conducting 
wires set in its central part. 
Another advantage of the cable according to the present invention resides 
in the fact that the volume occupied by the conducting wires in the cable 
is reduced to a minimum whilst retaining a spacing for the conducting 
wires, which is suitable for good electrical characteristics. 
The invention relates, therefore, to a remote control cable comprising two 
conducting wires separated by a central element, reinforcing wires 
parallel to the said conductors, at least one layer of lapping which 
covers these elements and at least one external coating layer. The 
invention is further characterized in that the central element separates 
and holds the conducting wires parallel and is in the form of a continuous 
element comprising two longitudinal recesses arranged symmetrically 
relative to a solid central portion. Each recess encloses a conductor over 
more than half of its periphery and the external surface of the separating 
element forms, with each of the free surfaces of each of the conductors, a 
continuous surface of generally elliptical cross-sectional shape. 
Preferably, the central element for separating and holding the conducting 
wires surrounds the latter over two-thirds of their periphery, the 
distance between the two conductors being between 0.03 and 0.06 mm. 
Advantageously, the material forming the central element is a heat-fusible, 
homogeneous material having a low dielectric constant, and is, for 
example, made up of a mixture of waxes, paraffins and low molecular weight 
polyethylene. As materials which give good results, there can be cited 
synthetic resins or waxes based on linear hydrocarbons, such as those 
marketed by EASTMAN KODAK, under the trademark "EPOLENE". 
The conducting wires are preferably enamelled copper wires. The reinforcing 
wires which are placed parallel to the core are preferably in the form of 
a bundle of parallel wires, arranged concentrically around the core so 
that the latter is perfectly enclosed. The choice of reinforcing wires 
will depend on the mechanical characteristics required, but it is obvious 
that wires which have the greatest strength in decitex should be used. 
Currently, as wires which are particularly suitable, there can be cited 
those known under the generic name of "ARAMID", which are based on an 
aromatic polyamide. 
The lapping and the external coating are carried out in a known manner, the 
lapping comprising, advantageously, two superimposed layers wound in 
opposite directions. 
According to a particular embodiment, the assembly made up of the core and 
the reinforcing parallel wires is surrounded by a loose lapping, which 
allows a quasi-circular section to be obtained and facilitates the 
penetration of a possible binding agent. The two external layers of 
lapping in opposite directions are made up of turns laid edge-to-edge 
around the complex thus formed, and the whole is covered with an external 
coating layer, preferably according to the same principle as that 
described in French Patent of Addition No. 93,154. 
Moreover, it is advantageous to make the lapping layers using 
multi-filament, zero twist wires, which allows very good covering of the 
assembly, for a minimum thickness since the filaments lie virtually flat 
when lapped. 
The invention also relates to a process and a device which make is possible 
to produce such a cable. 
The process according to the invention consists of passing the conducting 
wires into a bath of molten material, based on an insulating product 
having a low dielectric constant, then gauging the coated wires by passing 
them through a die of specific section, and it is characterized in that 
the conducting wires are held apart in the bath of molten material and are 
led horizontally to the gauging die whilst being held in contact with the 
walls of the said die. In this way, the fusible material holds the 
conductors separated by a rigidly fixed distance and, moreover, surrounds 
the conductors on only one part of their periphery. 
Advantageously, the conducting wires are led into the bath at a distance 
from one another, and converge near the gauging die where they are 
maintained at the desired spacing. The cable is then made by conventional 
means, by covering the core thus formed with a bundle of parallel 
reinforcing wires, providing the lapping and coating layers, and carrying 
out other appropriate treatments. 
To carry out the invention, advantageously a particular coating and gauging 
device is used, in the form of a tank containing the fusible material into 
which the conducting wires are led and held separate by means of guides, 
the tank being equipped with a horizontal gauging die and including 
positioning guides which allow the wires to converge near the die whilst 
maintaining them in the horizontal plane containing the axis of the die. 
Advantageously, the circular gauging part of the die is preceded by a 
convergent section which facilitates the passage of the wires, and the 
level of the fusible material is above the die.

DETAILED DESCRIPTION 
As can be seen in FIG. 1, the cable according to the invention comprises 
two conducting wires 1 and 2, separated by a central element 3, parallel 
reinforcing wires 4, a loose lapping 5, covered by two alternate layers of 
lapping 6 and 7 wound in opposite directions and preferably made from 
multi-filament, zero twist wires. This structure is coated by at least one 
external coating layer 8. 
In accordance with the invention, and as can be better seen in FIG. 2, the 
central element 3 for separating and holding the conducting wires 1 and 2 
is in the form of a continuous element comprising two longitudinal 
recesses 9 and 10, arranged symmetrically relative to a central solid 
portion 11. Each recess 9 and 10 encloses a conductor 1 or 2 over more 
than half of the periphery of the conductor. This conductor/center element 
assembly forms a complex with a continuous surface of generally elliptical 
cross-sectional shape. 
Thanks to this particular structure, there is obtained, on one hand, a good 
holding and a constant spacing of the conductors for the smallest possible 
volume occupied in the cable and, on the other hand, a minimum line 
capacity between conductors arising from the heat-fusible product used. 
The manufacture of the core of a cable according to the invention is 
illustrated by FIGS. 3 and 4, wherein the two conducting wires 1 and 2 are 
led into a tank 12 containing a molten material 20 based on an insulating 
product. Guides 13, 14 and 15 allow the wires to be held spaced apart in 
the bath 20 and to be led to a horizontal, gauging die 16 in such a way 
that they converge near this die whilst being held in a horizontal plane 
containing the axis of the die. The conducting wires rub against the 
lateral walls 17 and 18 of the said die 16 as they pass therethrough. 
The example which follows shows the advantages introduced by the invention. 
EXAMPLE 
In accordance with the invention, a cable as illustrated by FIGS. 1 and 2 
is made. This cable has the following structure: 
A core constituted by two copper, enamelled wires 1 and 2 of 0.07 
millimeter diameter, and by a separating and holding element 3, the 
assembly having an elliptical shape whose dimensions are 0.22 mm long and 
0.15 mm wide, 
a reinforcement 4 made from 4 aromatic polyamide yarns of 220 dtex/134 
strands, 
a loose lapping 5 made from a polyester yarn of 50 dtex/22 strands, 
two lappings 6 and 7 laid edge-to-edge in opposite directions, made from 
polyester of 72 dtex/22 strands, and 
a final heat-sealing coating 8. 
In the present instance, after forming the loose lapping 5, a coating is 
made using an acrylic resin in order to give cohesion to the reinforcing 
strands 4. Moreover, the final heat-sealing coating is made from a 
copolymer of vinyl chloride and vinyl propionate dissolved in ethyl 
acetate, the coating being controlled by gauging with a die. Finally, the 
lapping layers are made by conventional means with any appropriate 
material. The wire thus obtained exhibits the following characteristics: 
final diameter: 0.46 mm 
weight: 260 g/km 
tensile breaking strength: 18 da N, which gives a breaking coefficient of: 
EQU R/P = 69,000 m. 
The electrical characteristics are: 
resistance per conductor: 4.7 ohms/m 
capacity: 60 pF/m. 
With such a cable, it is possible to control a moving body traveling at a 
speed close to 330 meters per second and to do so over a distance which 
can exceed 4,000 meters.