FLEXIBLE CONDUIT

CONDUIT FLEXIBLE

English Abstract

A B S T R A C T
A flexible cable conduit having an anti-friction
liner adapted to surround a movable core. The liner
in turn is surrounded by a plurality of spiraled lay
wires. The lay wires in turn are surrounded by a
spiral wound overlap wrap where the wrap comprises a
plastic material to provide a sealing means for the
conduit and has high tension properties to constrain
the wires from moving radially on any bending of the
conduit.

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A flexible cable conduit comprising a plastic tubular
anti-friction liner adapted to surround a movable core and a
plurality of spiraled lay wires surrounding said liner and
adjoining one another; characterized in having a plastic film
spiral wound overlap wrap sealingly surrounding said lay wires
to prevent radial displacement thereof when said wires are
subjected to a compression load and to provide a continuous sealing
of said wires along the length of the conduit wherein the overlap
of one wrap with an adjacent wrap is substantially 50% of the
width of the wrap.
2. A flexible cable conduit according to claim 1 further
characterized in that at least one surface of said wrap has a
self-adhesive layer thereon whereby overlap portions of the wrap
will be affixed to one another.
3. A flexible cable conduit according to claim 1 further
characterized in that said wrap has a plurality of tension re-
sisting threads therein extending longitudinally of the wrap.
4. A flexible cable conduit according to claim 1 further
characterized in that said liner is surrounded and contacted by
a plastic tubular sheath to form a composite piece with said liner
adapted to withstand pressures exerted on said liner by said lay
wires.

Description

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IMPROVED FLEXIBLE CONDUIT
This invention relates to an improved flexible
conduit and more particularly, to a flexible cable
conduit adapted to surround a movable core, for
example a control cable.
5. Flexible cable conduits are known which utilize
a plastic sheath to surround a control cable and where
the sheath in turn is surrounded by a layer of
spiraled lay wires. In such installations the plastic
sheath serves as an anti-friction element for the
10. control cable while the spiraled lay wires provide
strength to the conduit to resist tension and
compression loads. The lay wires themselves are
enclosed or constructed by wires or rovings to prevent
the lay wires from spreading or "bird caging" on
15. application of compression loads to the conduit as may
occur when a control cable within the conduit is moved
in a direction to produce bends in the conduit. The
lay wires along with their constructing wires or
rovings in turn may be enclosed in an extruded plastic
20. sheath to seal the lay wires and rovings from
moisture. Such a construction is shown in U.S.Patent
No. 3,063,303.
In the type of construction as discussed the use
of separate wires or rovings to contain the lay wires
25. and of a separate plastic sheath to provide a seal for
tbe conduit necessarily increases expense of
manufacture since the separate steps in assembling the
plastic sealing sheath and the rovings to the lay
wires are required to produce the conduit.
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It ls thereEore an objec-t of my inven-tion to provide
for an improved flexible conduit construction wherein assembly
of a conduit involving any separate application of an outer sealiny
sheath and application of wires or rovings to constrain the lay
wires of a conduit is eliminated which at the same time will
provide a constraint means for the lay wires as well as a sealing
means to impart water tight integrity and proteetion against
foreign materials and abrasion to the conduit.
Further it is an object of my invention to provide for
an improved flexible conduit in which the conduit may have a
combined sealing means and lay wire constraint means applied
in a continuous in-line fabrication resulting in a more economical
manufacture of the conduit.
Broadly, according to my invention, there is provided
a flexible cable conduit comprising a plastic tubular anti-
friction liner adapted to surround a movable core and a plurality
of spiraled lay wires surrounding said liner and adjoining one
another; characterized in having a plastic film spiral wound
overlap wrap sealingly surrounding said lay wires to prevent
radial displacement thereof when said wires are subjected to
a compression load and to provide a continuous sealing of said
wires along the length of the conduit wherein the overlap of one
wrap with an adjacent wrap is substantially 50~ of the width of
the wrap. The tubular anti-~riction liner and an outer sheath
may together form a composite piece but if desired could be
formed by a unitary plastic piece provided -the plastic material
selected has both an anti-friction property as well as a sufficient
strength to withstand compression or crushing pressures exerted

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by the lay wires.
The wrap preferably has a self-adhesive or pressure
sensitive layer on one side thereof so tha-t the wrap may be spirally
wrapped around the lay wires in a continuous in-line fabrication.
The wrap also preferably has a plurality of tension
resisting threads, f or example glass f ibres, which extend
longitudinally of the wrap in order to add to the strength of the
wrap so as to provide the necessary constraint to the lay wires
when applied to a sheath in order to prevent any radial displace-
ment of the lay wires upon bending of the sheath.
In the accompanying drawings:
Figure 1 is a side broken view of a flexible conduit
constructed according to the invention;
Figure 2 is an enlarged cross-sectional view of the
conduit of Figure l; and
Figure 3 is an enlarged broken plan view of a plastic
wrap utilized in sealing the lay wires of the conduit of Figure 1.
Referring to Figure 1 there is illustrated a flexible
conduit 1 adapted to surround and guide a movable core 2 which
20 ~ is movable longitudinally and/or rotatably with respect to the
cGnduitl. The core 2 may normally comprise a control cable
operatively connecting an operating element, such as an accelerator
pedal of an automobile with an operable element, such as a
carburettor.
The conduit 1 includes a plastic tubular anti-friction
liner 3 made preferably of a TFE resin against the sides of which
the core 2 may move. The liner 3 in turn preferably has an
extruded plas-tic tubular outer sheath ~ made of a high temperature

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thermo plastic material to provide protection to the anti-friction
liner 3 and to also prevent crushing of the liner 3 upon later
application of metal lay wires 5. As shown a plurality of metal
lay wires 5 are wound in spiral form about the sheath 4 with the
lay wires providing protection against the conduit being crushed
as well as providing strength to the conduit to resist tension
and compression loads. While the liner 3 and sheath 4 are shown
as separate items joined together to form a composite piece
adapted to withstand pressures exerted on the liner by the lay
wires, they

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could be replaced by a single unitary tubular plastic
piece provided the plastic material had the
anti-friction and strength properties required.
The lay wires 5 are covered by an outer wrap
5. which comprises a plastic tape material which is
spirally wound about the lay wires with an appreciable
overlap on the order of substantially 50% of the
width of the wrap 6. The wrap 6 is a high -tensile
strength self-sealing tape such that the tape seals
10. upon itself as it is wrapped around the wires 5 to
provide a sealing means for the wires and to protect
them from moisture 9 foreign material and abrasion.
The high tensile properties of the wrap 6 resist
tension forces applied to it which may occur when
15~ individual lay wires are forced outwardly due to the
conduit 1 being bent. Such bending of the conduit 1
may occur during installation of the conduit between
two fi~ed points or may occur when bending forces are
applied to the core control cable 2 and thus to the
20. conduit around it.
Use of the spiral wound wrap as shown in
Figure 1 permits the assembly of the conduit in an
in-line manner with the tape being wound around the
wires after the wires have been in turn wound Gn to
25. the extruded sheath 4. Thus the single application of
the wrap perform two functions, namely sealing the lay
wires and constraining any radial displacement of
individual lay wires.

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The tape as more fully disclosed in Figure 3
comprises a layer 10 of a pressure sensitive adhesive
which contains a plurality of parallel longitudinally
e~tending threads 11 over which a plastic film 12
5. extends. A particular tape which I have found
applicable for use in a conduit constructed according
to the invention is one manufactured by the Devon Tape
Corporation of Carlstadt, New Jersey as their model
No.195. This tape comprises a black polyester film
10. having a layer of high tack pressure sensitive
adhesive thereon which is reinforced by glass
monofilaments. This tape has high scruff and abrasion
resistance properties to provide protection to the lay
wires against abrasion while the glass threads, 80 per
15. inch, provide necessary tensile strength. The high
tackiness of the adhesive as well as the polyester
film assure complete sealing of the lay wires to
protect them from moisture,
It is seen that a conduit constructed according
20. to the invention eliminates any need of separate
assembly o~ a lay wire constraint means and a sealing
means and thus reduces expense of manufacture.