Note: Descriptions are shown in the official language in which they were submitted.
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MASS TERMINABLE FLAT CABLE AND CABLE
ASSEMBLY INCORPORAT:[NG THE CABLE
The present invention relates to electrical
wiring components and, more specifically, to a cable
assembly incorporating a flat cable adapted for use with
mass termination, insulation displacement connectorsO
Backqround of the Invention
Mass termination, insulation displacement
connectors have come into increasing commerical
prominence because of the significant savings in time
and labor they offer compared to stripping and
individually terminating each conductor using a crimp
terminal. These connectors have an insulative housing
body holding a number of regularly spaced terminal
elements having slotted plates terminating in sharpened
free ends extending beyond a surface of the body. The
conductors also include covers having recesses in a
~ facing surface or receiving the free ends of the
:~ plates. After the insulated conductors are aligned with
their corresponding slotted plates, relative closing of
the housing body and cover results in displacement of
the insulation with the conductor cores contacting the
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metallic plates. For further information regarding the
operation and s~ructure of such mass termination
connectors, reference may be made to U.S. Patent Nos.
4,458,967 and 3,912r354.
: The most efficient form of conductors for use
with such connectors is the flat cable in which
conductors, running parallel and spaced to match the
spacing of the terminal elements in the connector, are
held by a layer of insulation. The use of a flat cable
avoids running the conductors one at a time and holding
them i~ position for termination. The flat cable can be
used for either a daisy chain connection (where the
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connector is applied intermediate the cable ends) or an
end connection. m e sharpened ends of the slotted
plates pierce the web material between the conductors in
the flat cable a~ the body and cov~r close so slitting
of the cable between conductors is not required.
While flat cables offer many advantages with
respect to efficiency in termination, they present
difficulties during routing. Flat cables have certain
dimensions larger than comparable round cables, the flat
cables do not bend as easily, they are more susceptible
to damage during routing, and the continuous presence of
the layer of insulation holding the discrete conductors
may result in somewhat increased weight o a flat
cable. Additionally, a flat cable is usually more
susceptible to electrical cross talk than a comparable
round cable.
There are several methods for manufacturing
flat cable. In one method, the insula~ion is extruded
` about parallel, coplanar conductors. In another, two
layers of in5ulation are bonded together with the
conductors held in parallel, coplanar relationship.
- Some of these methods require the use of large expensive
manufacturing equipment. One simpler manufacturing
method has been proposed wherein individual conductors,
each having a thermoplastic jacket, are positioned on a
layer of the same material as that used in the jackets~
Upon raising the temperature to the melting point of the
insulation, the jackets and layer will fuse, forming a
flat cable. Unfortunately, the most commonly used
insulating materials, such as polyvinyl chloride, have
poor dimensioned stability, particularly when the flat
cable is subjected to varying temperatures~
A method of forming flat cable using conductor
modules has also been suggested. In this method, pairs
of conductors are formed into modules by applying a
~ jacket of insulation about them. The modules are fed in
; edge-to-edge relationship between two webs of polyester
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material precoated with a hot-melt adhesive on their
facing surfaces. This assembly is then subjected to
heating and the application of pressure to form the
final flat cable assembly. For additional information
concerning this flat cable and its method of
manufacture, reference may be made to U.S. Patent No.
4,468,089.
Summary of the Invention
Among the se~eral aspects of the present
invention may be noted the provision of an improved flat
cable adapted for use with mass termination, insulation
displacement connectors. The cable has greater
strength, increased dimensional s~ability over a wide
temperature range, lighter weight, and smaller finished
cable thickness than conventional flat cables which
employ a carrier film of the same insulating material as
the jacket on the conductor cores. A cable embodying
features o the present invention can be reconfigured
from substantially round to flat, and has reduced
electrical cross talk~ The cable of the present
invention is reliable in use, has long servic~ life and
is simple and economical to manufacture. Other aspects
and features of the present flat cable will be, in part,
apparent and, in part, pointed out ~ereinafter in the
~ollowing specification and in the accompanying claims
and drawings.
Briefly, the flat cable of the present
invention includes a laminated carrier film and a
plurality of discrete conductors held in regularly
spaced parallel relationship by the carrier film to
match the terminal elements spacing of the connector.
Each conductor has an insulative jacket made of a
thermoplastic material. The carrier film includes an
attachment layer of thermoplastic insulation having a
melting temperature similar to that of the jacket
material. me carrier film also includes a dimensional
stabilization layer holding the attachment layer and
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made of an insulative material having a melting
temperature higher than those of the attachment layer
and the jacket material and displaying dimensional
stability at the melting temperatures of the attachment
layer and ~he jacket material. The jackets of the
conductors are fused to the attachment layer. The
carrier film can be longitudinally discon~inuous to form
first cable sections where the conductors are held
parallel for ease of termination and second cable
sections where the conductors are not held to increase
flexibility and reduce weight. The cable can be formed
into a round configuration to provide advantages d~ring
routing.
As a method of manufacturing a flat cable, the
present invention includes several steps: 1) The
~- jacketed conductors are positioned against the
attachment layer so that the spacing of the conductors
; matches that of the terminal elements in the connector.
2) The temperatures of the conductors jackets and the
- 20 attachment layer are raised until the jackets and the
attachment layers fuse. 3) The conductors have their
positions maintained on the attachment layer until the
temperatures of the jackets and the attachment layer
drop sufficiently so that the jackets are fixed.
Brief Description of the Drawin~s
FIG. 1 is an end view of the mass terminable
flat cable of the present invention;
FIG. 2 is an exploded perspective view showing
a mass termination insulation displacement connector
usable with the cable of FIGI l;
FIG. 3 is a simplified diagrammatic
representation of a method of manufacturing the cable of
FIG. 1.
FIG. 4 is a plan view of a cable assembly
incorporating an alternative e~bodiment of a cable
embodying various features of the present invention
w~erein the cable can be reconfigured from a round
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configuration to a flat configuration by removal of an
outer protective sheath, and wherein first cable
sections in which conductors run parallel and are held
by a carrier film are spaced by second cable sections
which do not have the carrier film and in which thP
conductors are paired and twisted;
FIG. 5 illustrates the cable assembly of FIG. 4
with certain components removed and with the cable in
its round configuration throughout its length;
FIG. 6 is a cross-sectional view taken
generally along line 6--6 of FIG. 5 through a first
cable section in which the cable is spiralled around a
central strength member;
FIG. 7 is a cross-sectional view taken
- 15 generally along line 7---7 of E'IG. 5 thxough a second
cable section, and
FIG. 8 is a cross-sectional view of an
-~ alternative emboaiment of the cable of FIG. 4 wherein
the flat cable is folded instead of spiralled.
Corresponding reference numbers indicate
corresponding components throughout the several views of
the drawings.
Description of the Preferred Embodiment
Referring now to the drawings, a flat cable of
the present invention adapted for use with a mass
termination, insulation displacement connector 22 ~shown
in FIG. 2), is generally indicated by reference numeral
20. The flat cable 20 includes a laminated carrier film
24 and a plurality of discrete conductors 26 held in
regularly spaced, parallel relationship by the carrier
film. Each conductor 26 includes a metallic, i.e.,
copper, core 28 and an insulating jacket 30 about the
core. While the particular flat cabl~ illustrated is
intended for carrying electrical signals and has the
cores on .050 inch centers, it will be appreciated that
the ~lat cable 20 of the present invention can be made
in larger si~es for use in supplying electrical power to
various electrical components.
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The mass termination connector 22 shown in FIG.
2 is of the high terminal density, signal conductor type
and includes an insulative body 32 having two rows of
terminal element cavities. A terminal element 33 is
disposed in each cavity with elements in each row having
a .100 inch pitch. Ad3acent terminal elements in each
row are staggered so that every other conductor 26 is
terminated by elements in one row while the remaining
conductors are terminated by the elements in the other
row. Each terminal element includes a slotted plate 34
extending beyond a surface 35 of the boay with the plate
terminating in sharpened ends for piercing the web
material of the flat cable between the conductors. The
plate edges defining the slot function to displace the
conductor jacket material so that by forcing a conductor
26 into a slotted plate 34, the conductor core 28 is
engaged by the metallic plate to establish an electrical
circuit. The connector 22 also includes a cover 36 held
in alignment with the body 32 by means of pins 38. The
cover, also formed of insulating material, includes a
facing surface 40 having pockets 42 for locating the
flat cable conductors 26 with respect to the terminal
elements 33, and a recess 43 for receiving the free ends
of the slotted plates 34. Thus after the flat cable 20
is positioned ~etween the cover 36 and the body 32,
relative closing of the two results in mass termination
of the conductors 26 of the flat cable 20.
Re~erring to FIG. 1, the carrier film 24
includes an àttachment layer 44 of a thermoplastic
insulation having a melting temperature similar to that
of the jacket material 30, and a dimensional
stabilization layer 46 made of an insulating material
having a melting temperature higher than those of the
attachment layer and the jacket material and displaying
dimensional stability at the melting temperatures of the
attachment layer and the jacket material. me jackets
30 of the conductors 26 are fused to the attachment
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layer 44 and the attach~ent layer is held by the
stabilization layer 46 preferably by bonding them
together with an adhesive 48, or the attachment layer
and the stabilization layex may themselves be fused.
Also preferably the attachment layer 44 and the
conductor jackets 30 are made of the same insulating
material. Among the several combinations of insulating
materials are the following: polyvinyl chloride jackets
and attachment layer with polyester stabilization l~yer;
fluorinated ethylene-propylene jackets and attachment
- layer with tetrafluoroethylene stabilization layer;
polyethylene iackets and attach~ent layer with polyester
stabilization layer; and polypxopylene jackets and
attachment layer with polyester stabilization layer.
With respect to the irst combination,
polyester offers a greater strength to weight ratio than
polyvinyl chloride~ Also polyester has better
dimensional stability over a wide range of thermal and
environmental conditions. The other combinations offer
similar characteristics. Thus the cable 20 can have
greater strength, better temperature stability, smaller
thickness and lighter weight than a conventional flat
cable which uses a carrier layer of the same insulating
material as the conductor jackets. Additionally, the
polyester stabilization layer 4~ serves a strain relief
function when mass termination connectors including
strain clips are employed. Upon tensioning of the flat
cable between connectoxs, the polyester layer resists
extension of the jackets and the metallic conductor
cores.
It will also be appreciated that the flat cable
20 has a side 50 which is undulating, with the
; undulations formed by the individual jackets 30. These
- undulations are received by the pockets 42 in the
connector cover 36 to properly locate the various cores
28 in alignment with their ~orresponding slotted plates
34. This is advantageous over a flat cable having flat
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sides becaus~ the connector ~oes not have to be provided
with alignment stops at the sides of the cover and/or
body to position the flat cable in position for
termination.
As shown diagrammatically in FIG~ 3, the flat
cable 20 of the present invention is relatively simple
to manufacture using a continuous process~ At a feed
station 52 are positioned a roll 54 of the carrier film
24 and a number of spools 56 of the conductors 26~ The
carrier film and the plurality of the conductors are
received by a positioning die 58 which aligns the
various conductors 26 in regularly spaced, parallel
relationship on the attachment layer 44 of the carrier
film. ~he die has conductor receiving passageways which
decrease in dimension from the die entrance side to its
exit side so that upon exit of the cable components, the
conductors are held firmly against the attachment
layer. The film and conductors next pass through a
heating zone 60 where the te~peratures of the jacket
material and the attachment layer are raised
sufficiently that the conauctors and attachment layer
fuseO ~ext downstream is a cooling ~one where another
~: aie 62 functions firmly to hold the conductors against
the attachment layer until the jackets are fixed onto
the attachement layer. Finally, the completed flat
; cable 20 is wound on a take up reel 64. The above
~escription assumes that the formation of the carri~r
layer has been completed. The carrier layer 24 can also
be formed as a preliminary operation in this
manufacturing proces~ by including an upstream station
where the attachment layer and stabilization layer are
bonded.
As a method of manufacturing a flat cable for
use with a mass termiation connector 22 having regularly
spaced terminal elements 33, the present invention
includes the following steps:
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1) The jacketed conductors 26 are posltioned in
parallel spaced relationship against the carrier film 24
so that the conductor engage the attachment layer 44
with the spacing between the conductors matching that of
the terminal elements in the connector.
2) The temperatures of the conductor jackets 3U
and the attachment layer 44 are raised so that the
jackets and the attachment layer fuse. ~owever, the
temperature of the stabilization layer 46 remains below
its melting temperature.
3) The positionin~ of the conductors is
maintained until the temperatures of the jackets and the
attachment layer drop sufficiently so that the jackets
become fixed on the attachment layer~
It will be appreciated that the particular
construction o~ the flat cable 20 allows the use of
diffexent insulating materials for the jackets 30 of the
conductor~ in the same manufacturing process without
requiring modification of expensive equipment
components. This is because of the great flexibility
offered by cable 20. I a particular insulation is
required for the conductor jacke~J only the attachment
; layer coating on the polyester film stabili~ation layer
need by changed to match the jacket.material used in the
'`~ 25 conductors 26.
While the flat cable is shown with the
; conductors running parallel throughout the leng~h of the
cabIe, the cable could alternatively have sections
wherein adjacent conductors form twisted pairs with
tho8e sections spaced by other sections wherein the
conductors run parallel to one another.
Referring now to FIGS. 4-8, a cable assembly 66
is shown which includes an alternative embodiment 20A of
the flat cable of the present invention. Components of
;~, 35 the flat cable 20A corresponding to components of the
flat cable 20 are indicated by the reference numeral
applied to the component of the flat cable 20 with the
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addition of the suffi~ "A". As shown in FIGo 4, the
flat cable 20A is longitudinally divided into a
plura]ity of spaced first cable sections 68 in which the
conductors 26A are held in regularly spaced, parallel
S relationship by carrier film 24A by means of the
attachment layer 44A being fused with the conductor
jackets, and a plurality of second cable s~ctions 70
wherein the conductors are not held. The conductors in
the second sections 70 are preferably disposed in
twisted pairs, ac shown in FIGS. 4 and 5, or the
conductors may be in an unpaired configuration~ A
second cable section 70 space~ each adjacent pair of
first cable sections 68. me irst cable sections 68
are preferably regularly spaced and are somewhat shorter
than the second cable sections 70. me first cable
sections are used for termination of the conductor cores
- 28A by the insulation displacement connectors 22 because
it is at the first cable sections w~ere the conductors
are held in a regularly spaced array having centers
matching those of the terminal elements 33 of the
connector. On the other han~, the presence of the
second cable sections 70 with the loose twisted pairs
provides greater flexibility, lighter weight, and
improves the electrical characteristics of the cable in
that cross t~lk is xeduced~
The flat cable 20A, when part of the cable
assembly 66, is deformed into a non-flat and preferably
substantially circular configuration. The cable
assembly 66 includes an outer jacket 72 constituting
means disposed about the periphery of the cable 20A for
holding the cable in its preferably circular
cross-sectional configuration. The outer jacket is
formed of a tough, abrasion resistant thermoplastic
material and the outer surface of the jacket 7~ carries
spaced indicia 74 (such as a circular stripes) to locate
the presence of the first cable sections 680 Thus, the
user can easily find a first cable section, strip the
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outer jacket therefrom and apply a connector 22 after
returning the cable section to its flat configuration.
The round configu~ation of the cable 20A when held in
the cable assembly 66 provides many advantages when the
cable asse~bly is routed. A round configuration has
smaller dimensions, is more flexible in certain
directions (a flat cable configuration has restricted
bending in the plane of the flat cable) and is more
resistan~ to damage during routing, for example, during
pulling of the cable assembly through a conduit,
The flat cable 20A can be deformed from its
flat, as-manufactured configuration to the substantially
round configuration by piralling, as shown in FIG~ 6,
or by folding, as shown in FIG. 8. A central strength
lS member 76, formed by a fiber or steel stranded rope, may
be provided. The spiralled configuration ofEers certain
advantages in that the deformed cable more closely
resembles a round configuration without extensive use of
fillers with the cable 20A inside the outer jacket 72,
and the cable 20A is not required to undergo severe
bending. On the other hand, the accordian folded cable
shown in FIG. 8 can quickly be returned to its flat
configuration by pulling apart the lateral sides of the
exposed first cable section.
Optionally, as shown in FIG~ 5, the cable
assembly 66 can include a metallic shield encompassing
the deformed flat cable 20A. m e shield comprises a
foil 78 which miyht be on Mylar ~Mylar is a registered
trademark of Dupont for polyester film) and/or a
metallic braid ~0. Optimum shielding is achieved using
the foil 78 disposed under the braid 80 and in contact
therewith, the use of the braid over the foil results in
the lowe~t radio frequency leakage and lowest
susceptibility to electrical noise. The braid functions
to limit penetration of low frequency noise while the
presence of the foil limits high frequency noise
penetration.
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In view of the above, it will be seen that the
several objects of the invention are achieved and other
advantageous results attained.
As various changes could be made ~ithout
departiny from the scope of the invention, it is
intended that all matter contained in the above
description shali be interpreted as illustrative and not
in a limiting senseO
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