Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to electrical connectors, and especially to
connectors for forming solder joints between conductors in such articles
as automotive harnesses and the like.
Electrical harnesses, for example as manufactured in the
automotive industry, are often quite complex. In some instances they
are manufactured by forming two ~ or more sub-assemblies of wires,
terminals, connectors and any other components, and then forming
electrical connections) between the sub-assemblies. In such a case the
assembly of the harness may be controlled by computer permitting, with
the aid of a monitor, the assembly operator to see schematically the lay
up and to check correct build-up of the assembly at each stage of the
harness manufacture. In order to enable this control process to operate
the ends of the conductors of the sub-assemblies axe connected, eg. by
means of spring contacts, and an electrical current or signal is passed
through the assembly in order to obtain verification that the harness is
°' correct. It is only after such verification is obtained that the
clips are
'~'a~emoved and a perananent electrical connection is formed.
According to the invention, there is provided a device for forming
an electrical connection at the end of a bundle of elongate electrical
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conductors, which comprises an electrically insulating sleeve, a
metallic connecting element located within the sleeve, and a quantity of
solder for forming a permanent electrical connection between the
conductors, the connecting element having a tapering internal surface
which has a screw thread, so that a temporary electrical connection can
be formed by screwing the bundle of conductors into the connecting
element.
Preferably the device includes an element for holding the bundle
before or while the permanent electrical connection is formed, For
example the element may resist withdrawal of the bundle so that the
connection will be able to withstand normal handling of the harness
during assembly without the connection inadvertently becoming loose or
. breaking, but can be removed if desired, for example in order to replace
one or more sub-assemblies. Such an element may, for example,
comprise a ring located inside the sleeve which is provided with one or
more teeth or gripping edges for engaging insulation of the conductors
forming the bundle. The teeth or gripping members preferably have
substantially the same axial inclination as has the screw thread of the
connecting element, so that the bundle can be inserted into the sleeve by
rotating the bundle within the sleeve and applying a forward pressure,
but that removal of the sleeve from the insulated conductors by pulling
and/or unscrewing is resisted. Alternatively, the element may be
provided in order to hold the bundle during or immediately before
recovery of the sleeve. For example, a fusible or infusible (cross-linked)
polymeric ring, preferably a heat-shrinkable polymeric ring may be
provided in the sleeve. Such a ring may be made to melt or recover
before recovery of the sleeve if its melting or recovery point is lower than
that of they recoverable sleeve. recovery of the ring in this way can be
used to reinforce the grip on the bundle and to eliminate or reduce the
risk of piercing of the sleeve wall by the conductor strands. Such an
element nnay, for example have a melting or softening point in the range
of from 60 to 100°C. Examples of materials from which the polymeric
ring may be formed include ionomers, eg. Surlyn, or from polyamides, .
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eg. nylon 6, 66, 11 or 12. After the installed device has cooled, the
element will assist in maintaining mechanical rigidity of the assembly.
The device according to the invention has the advantage that the
conductors can be electrically joined to form a temporary joint which is
disconnectable but is able to have a high degree of dependability, in
order, for example to test the connected conductors, and can then be
permanently joined with no further manipulation of the joint but simply
by heating the sleeve in order to melt the solder. In addition, the
tapering interior of the connecting element enables bundles formed from
a range of conductor sizes to be handled by the device.
In the broadest aspect of the invention the device includes a
connecting element having a single tapering internal surface so that a
stub splice can be formed between a bundle of conductors inserted into
one en~i of the sleeve, the other end of the sleeve for example being
closed. However, it is possible for devices according to the invention to
include connecting elements having more than one tapering internal
surface so that, for eaample an in-line splice may be formed between a
pair of bundles of conductors. Thus, according to another aspect, the
invention provides a device for forming a splice between a pair of
bundles of elongate electrical conductors, which comprises an
electrically insulating sleeve, a metallic connecting element located
within the sleeve and a quantity of solder for forming a permanent
electrical connection between the conductors of the bundles, the
connecting element having two end portions each of which has a
tapering internal surface and at least one of which has a screw thread
so that a temporary electrical connection can be formed by inserting one
of the bundles of conductors into each end portion of the connecting
element.
.. . ~ Where the end portions of the connecting element are rotatable
with xespect to each other it is often desirable to form the sleeve in two
parts, each part being located on one of the end portions of the
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connecting element so that the connecting element end portions can be
rotated by twisting the part of the sleeve it is located in.
Usually the sleeve will be dimensionally recoverable, and
especially dimensionally heat-recoverable, that is to say the article has a
dimensional configuration that may be made substantially to change
when subjected to heat treatment.
Usually these articles recover, on heating, towards an original
shape from which they hare previously been deformed but the term
"heat-recoverable", as used herein, also includes an article which, on
heating, adopts a new configuration, even if it has not been previously
deformed.
In their most common form, such articles comprise a heat-
shrinkable sleeve made from a polymeric material exhibiting the
property of elastic or plastic memory as described, for example, in US
Patents 2,027,962; 3,086,242 and 3,597,372. As is made clear in, for
example, US Patent 2,027,962, the original dimensionally heat-stable
form may be a transient form in a continuous process in which, for
ezample, an eztruded tube is ezpanded, whilst hot, to a dimensionally
heat-unstable form but, in other applications, a preformed
dimensionally heat-stable article is deformed to a dimensionally heat-
unstable form in a separate state.
In the production of heat-recoverable articles, the polymeric
material may be cross-linked at any stage in the production of the article
that will enhance the desired dimensional recoverability. One manner
of producing a heat-recoverable article comprises shaping the polymeric
mateaal into the desired heat-stable form, subsequently cross-linking
the polymeric material, heating the article to a temperature above the
crystalline melting point or, for amorphous materials the softening
post, as the case may be, of the polymer, deforming the article and
cooling the article whilst in the deformed state so that the deformed state
of the article is retained. In use, since the deformed state of the article is
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heat-unstable, application of heat will cause the article to assume its
original heat-stable shape.
Any material to which the property of dimensional recoverability
may be imparted may be used to form the sleeve. Preferred materials
include low, medium or high density polyethylene, ethylene copolymers,
eg. with alpha olefins such as 1-butane or 1-hexane, or vinyl acetate,
polyamides or fluorpolymers, eg. polytetrafluoroethylene, vinylidine
fluoride or ethylene-tetrafluoroethylene copolymer.
The fact that the ends of the conductors are enclosed in the
connection element will also reduce the risk of any strands of the
conductors piercing the sleeve during recovery thereof. Also, the
conducting element can act as a heat-sink thereby preventing
overheating of the device during recovery.
At least in the broadest aspect of the invention the connecting
element may generally have any form although it is preferred for it to be
formed by coiling a piece of wire into a tapering coil so that the windings
form the screw thread. Preferably the internal surface of the connecting
element is at least partly conical, for example it may be conical or frusto-
conical. If' the connecting element is formed from a wire, it can grip the
bundle of conductors introduced therein due to the resilience of the wire
and the fact that it will be enlarged radially to some extent by the
introduction of the bundle. However, in one advantageous form of device
it has been radially expanded from its relaxed state during manufacture
of the device and to be retained in its expanded state so that it will
..radially contract, or attempt radially to contract, when the permanent
connection is formed. Thus, for example, the spring may be held out
against its resilient recovery forces by the sleeve or by the solder, so that
softening of the sleeve or melting of the solder will allow the spring to
recover. For example, a boss may be formed on the internal surface of
. . the sleeve or ~n the internal surface of the solder which will disappear
when the device is heated. The degree of expansion need not be great,
for example it may be not more than 5% or even not more than 2%, since
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it may be desirable that the coil remains in contact with the solder
element when the device is heated.
The wire may be formed with a circular cross-.section, although it
is preferred_for the wire to have a relatively sharp ridge along its length,
eg. formed by cold drawing or cold rolling, which, when the wire has
been coiled, is directed toward the interior of the coil in order to form the
screw thread. In particular it is advantageous for the wire to be formed
with a polygonal, and especially a square, cross-section. The wire may
be formed from any appropriate metal or metal alloy, but preferably is
formed from copper, and especially from copper having substantially the
same purity as that conventionally employed for electrical conductors.
Other configurations of connecting element may, however, be
employed. For euample it may be formed from a solid block of metal that
has been tapped with a screw thread. In the case of the connecting
element used for the splice, it may be convenient, although it is not
essential, for both end portions to be formed in the same way. For
example, the entire connecting element may be formed from a single
piece of wire which has been wrapped so as to form a tapering internal
profile~at each end, it may be formed from a wire and a solid block that
has been tapped with a screw thread, or it may be formed from two solid
blocks of metal. Alternatively, connecting elements an which one end
does not have a screw thread could be employed, in which the bundle of
wires is simply pushed into the connecting element. Where the
connecting element is provided with a screw thread at each end, the
screw threads may both have the same handedness, or one may be right-
,handed while the ,other is left-handed. Since it is not normally
necessary . to twist the sleeve about the conductors by more than one
quarter to one half a revolution in order to for~an a temporary connection
the choice of thread sense does not cause any particular problem. It is,
however, possible for ;ths end portions of the connecting element to be .
. rotatable with respect to each other. For eaample, end portions formed
from a wire may both be supported on a small cylindrical connecting
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element by wrapping part of the wire into a circumferential groove in
the connecting element.
As mentioned above, the device includes a quantity of solder, ie. a
quantity of soft solder as distinct from brazing material, for forming a
permanent solder connection. The solder may, fox example, simply be
in the form of an Sn63Pb37 eutectic composition which will melt as the
device is heated and the sleeve recovers, or more than one solder
composition having differing melting points may be employed; as
described in International Application No. W088/09068. In this form of
device, melting of the higher melting point component, eg. Sngg,~Agg,5
eutectic will provide a visual indication.that the device has been heated
sufficiently to melt the lower melting point composition and to form a
satisfactory solder joint. If desired the lower melting point solder may
be a non-eutectic composition and, for example as described in
International Application No. PCT/GB90/00234, the higher and lower
melting point aolder compositions may together form a eutectic
composition. For ezample, a non-eutectic SnspPb4p lower melting point
component may be employed with a higher melting point component
formed frnm pure tin in relative amounts that an SnggPbg7 eutectic is
formed. The disclosures of these two patent applications are
incorporated herein by reference. An advantage of employing a two
component solder, and especially a tin, SnspPb4p combination is that it
reduces the possibility of "wicking" that is to say, travel of the solder
along the conductors and away from the joint area due to capillary
action by the stranded conductors, which can be caused by prolonged
heating of the-device.
The solder may be positioned anywhere where it will be able to
flow into the connecting element to form a solder joint. The solder may
be employed in the form of a ring or in any other form for example a ball,
and may be disposed symetrically about the sleeve axis or offset from it.
The solder element may, for instance, be located at the smaller diameter
'end of the connecting element in which case it may be in the form of a
ball or plug, or it may be located in the region of a large diameter end of
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the connecting element, for example in the form of a ring. Preferably
the solder is in the from of an element that surrounds the connecting
element, especially where the connecting element is in the form of a coil
so that the fused solder can flow through the windings of the coil to the
interior thereof. More than one quantity of solder may be employed, for
example where the connecting element has more than one tapering
internal surface for forming a splice.
According to another aspect, the invention provides a method of
forming an electrical harness from a plurality of insulated electrical
wires, which includes:
(a) gathering a number of the insulated wires together to form a
bundle at least at the end of the wires;
(b) inserting the bundle into a device as described above by means of a
screwing action in order to form a temporary electrical
connection;
(c) applying electrical signals to the harness so formed in order to
ascertain information about it; and
(d) heating the sleeve to form a permanent solder connection between
the wires.
The device may be heated by means of a hot air gun or infrared
lamp as commonly used to recover solder connector devices, or the
device may be heated by induction heating methods.
-_ Two forms of device according to the invention will now be
described by way of example with reference to the accompanying
drawings in which: . . ,
Figure 1 is a sectional elevation along the axis of a device
according to the present inventio~a;
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- Figure 2 is a cross-section of the wire employed to form the coil
of the device; ~
Figure 3 is a sectional elevation of the device shown in figure 1
with a bundle of wires inserted therein;
Figuxe 4 is a sectional elevation of the completed joint;
Figure 5 is a sectional elevation along the axis of a second form of
device;
Figures 6 and ? are sectional elevations along the axis of
connectors suitable for forming a splice; and
Figures 8 and 9 are elevations of two further forms of connecting
element that can be employed in the device of Figure ?.
Referring to the accompanying drawings a device 1 for forming a
connection between a number of electrically insulated wires 2 comprises
a dimensionally heat-recoverable sleeve 3 formed from crosslinked and
expanded polyvinylidine fluoride, and a connecting element 4 formed as
a frusto-conical apring or coil of hard temper wire. The copper wire 5
has a cross-section as shown in figure 2 which, as can be seen is
generally circular over part of ita circumference but which has two
flattened surfaces formed by cold rolling or cold drawing which meet to
form a relatively sharp ridge f. This ridge 6 is oriented so that it is
directed toward the interior of the frusto-conical coil 4 and forms a screw
thread. One end ? of the wire is located at the smaller diameter of the
connecting element 4 is bent so that it extends across the axis of the coil
and prevents over insertion of the conductor bundle. Tn some instances
it may be advantageous to expand the diameter of the coil ~ by opening
out the ends of the copper wire 5 and retaining them in their new
position, for example by means of a lip on the solder ring.
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A strip 8 of composite solder composition which has been formed
into a ring and swaged into a frusto-conical shape sits in contact with
the outer surface of the coil 4. The composite solder strip is formed from
a major quantity of Sn6pPb4p non-eutectic composition and has a small
temperature control ring 9 of pure tin on its outwardly directed surface.
The device is closed at one end by means of a spherical plug 10 of
sealing material, eg. irradiated or non-irradiated polyethylene, for
example as described in British Patent Application No. 9002093.4.
The sleeve 3 also contains a moulded ring 11 formed from
crosslinked nylon which is positioned between the connecting element 4
and the open end 12 of the sleeve. The internal surface of the ring 11 has
a number of elongate teeth 13 which are oriented at the same angel to
the ass of the device as the wire 5 in the coil 4.
In operation, during the manufacture of a harness, a number of
insulated wires 2 having their insulation stripped from the ends of the
wires, are bundled together and are inserted into the device 1. Complete
insertion is achieved by rotating the bundle (in fact, rotating the device
about the bundle) so that the end of the conductors are screwed into the
connecting element 4 and the teeth 13 on the ring 11 grip the insulation
of the wires and resist them being pulled out of the sleeve 3. At this
stage a dependable low resistance . joint has been formed, and the
harness may be tested by passing electrical signals along the wires 2
aad analysing the results by means of an appropriate microcomputer.
Once this has been performed, a permanent connection may be formed
between the wires 2 simply by heating the sleeve 3, for example by means
of an infrared lamp, a hot-sir gun or a small oven, so that it recovers
about the bundle of wires 2. During recovery the solder 8 melts and
flows through the windings of the coil 4 thereby forming a strong solder
joint between the conductors of the wires 2 and the connecting element 4.
At the same time the nylon ring softens and the teeth 13 collapse,
thereby allowing the ring 11 to be forced into conformity with the bundle
under the recovery forces of the sleeve 2. Heating is continued until the
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temperature control ring 9 of the solder strip has melted, thereby
allowing the overlying part of the sleeve 3 to recover fully. The completed
joint is shown in figure 4 without the solder, for the sake of clarity.
A second form of device 1 is shown in figure 5. This form of device
is generally similar to the device shown in figure 1 but with two
exceptions. First, the moulded polyamide ring 11 of figure 1 has been
replaced with a low recovery temperature polyamide ring that has been
formed by extruding a tube and chopping it into short lengths. Secondly,
the solder ring 8 of figure 1 has been replaced with a solder ring 8 which
is located adjacent to the larger diameter end of the coil 4. Tf desired the
internal surface of the ring 11 may be coated with a layer of adhesive,
preferably a hot-melt adhesive (not shown) in order to provide a seal
against moisture ingress to the device. In addition or alternatively, one
or more thermoplastic sesiing rings may be provided in the region of the
end 12 of the sleeve 3.
The wire bundle is inserted into the device as described with
respect to figure 1. When the device is heated in order to recover the
sleeve 3, the ring 11 will usually recovery slightly before the sleeve 3 and
thereby help to maintain the wires in position.
Figure 6 shows a device having two open ends which is suitable
for forming a splice between a pair of bundles of conductors. The device
comprises a dimensionally recoverable sleeve 3 formed from crosslinked
and expanded polyvinylidine fluoride, and a connecting eleL~nent 16
formed from hard temper copper wire. The connecting element 16 is
formed having two opposite halves 17 and 18 each of which has a
tapering internal surface for receiving a separate conductor bundle. As
shown, the connecting element 16 has been formed by wrapping a single
piece of wire in the same sense along its entire length so that the
internal surface of both halves 17 and 18 both have a right-handed
thread. ~ .Although the wire forming the connecting element is shown as
a circular wire that has been rolled to form two flat surfaces and an edge
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between them, it may be preferred to employ wire having a square cross-
section.
The device is substantially symmetrical about the centre of the
connecting element 16, each half of the device having the same general
configuration as that of the device shown in figure 5, in which a solder
ring $ located adjacent to each end of the connecting element 16. The
device has a pair of rings 11 which are constructed, and function,
exactly as those shown in Figure 5.
In operation, in order to form a splice, a bundle of conductors is
introduced into one open end of the device and into one end of the
connecting element 16, and the device is then twisted about the bundle to
secure it. The second bundle is then inserted into the other open end of
the device and connecting element. After securing the bundle in the
connecting element 16 by twisting , the electrical performance of the
harness bundle can be tested and the device then be heated to recover the
sleeve 3 and form a permanent solder connection.
Figure 7 shows a further form of device that is suitable for
forming an in-line splice between a pair of bundles of conductors. A
connecting element comprises a pair of generally frusto conical coiled
parts 20 and 21 which are formed from hard tempered copper wire. The
wire has a square cross-section and the edges of the wire form an
internal thread in each coiled part, one coiled part 21 having a right
handed thread and the other coiled part 20 having a left handed thread.
One of the coiled parts 20 is screwed into the end of a hub element 22 that
has an internal thread, and the other coiled part 21 is mounted over a
boss~23 of the hub element so that it is freely rotatable.
A ring of solder 24,25 is located about the external surface of each
coiled part 20 ~ and 21, and a heat-shrinkable polyvinylidine fluoride
sleeve~26 and 27 is partially recovered about the coiled parts, solder and a
pair~of fusible inserts 28 a~ad 29. The lengths and position of the sleeves
26 and 2? is such that they axially overlap for an extent, and a fusible
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ring 30 formed for example from polyethylene is located within the end
region of sleeve 27 within the region of overlap.
In operation, after a bundle of conductors has been introduced
into sleeve 26 and secured in the coiled part 20 of the connecting element,
a second bundle can be inserted into the sleeve 27 and secured within the
coiled part 21 by twisting the sleeve and coiled part about the conductors.
This twisting action does not affect the sleeve 26 and the coiled part 20
and so there is no liklihood of them beiag unscrewed from the bundle.
The splice may then be tested electrically as described above and a
permanent joint be formed.
Figures 8 and 9 show two alternative forms of connecting element
that may be employed in the device shown in Figure 7. In the element
shown in Figure 8 the ends of the coiled parts 20 and 21 are splayed
outwardly to form a waist, and a ring 32 having inwardly bent lateral
edges is positioned over the ends of the coiled parts to retain them
together while allowing them to rotate. In Figure 9 both coiled parts 20
and 21 are fitted over a pair of mating collars 33 and 34, one which has a
shaft 35 that extends through a hole 36 in the other end is retained
therein in such a way that it can rotate.
