FIELD OF THE INVENTION
[0001] The present invention relates to electrical connectors for insulated electrical conductors,
and more specifically relates to crimp connectors of the type comprising a metallic
crimp barrel and a heat-shrinkable sleeve.
BACKGROUND OF THE INVENTION
[0002] Crimp connectors are commonly used for establishing an electrical connection between
the ends of two electrical conductors. A typical crimp connector comprises a malleable
metallic crimp barrel surrounded by a heat-shrinkable sleeve, with a layer of heat-activated
adhesive being applied to the inner surface of the sleeve. The bared end portions
of two insulated conductors are inserted into the crimp barrel, which is then deformed
by a crimping tool to establish an electrical connection between the two conductors.
The sleeve is then heated, thereby activating the adhesive and shrinking the sleeve
onto the crimp barrel and the conductors to seal the connection. The sleeve of the
crimp connector is typically clear to allow visual confirmation that an electrical
connection has been made, and is longer than the crimp barrel so as to completely
cover the bared end portions of the conductors.
[0003] A typical crimp connector is described in U.S. patent No. 4,151,364 (Ellis), issued
on April 24, 1979. The crimp connector described in this patent comprises an insulating
sleeve having a metal crimp barrel permanently positioned therein. This type of crimp
connector is manufactured by inserting the crimp barrel into a heat-shrinkable sleeve
in its expanded state and then partially shrinking the sleeve down onto the crimp
barrel to permanently retain the crimp barrel in the sleeve. Since the sleeve and
the crimp barrel are permanently attached, the crimping force must be applied to the
crimp barrel through the heat-shrinkable sleeve. It is common to form the heat-shrinkable
sleeves of such crimp connectors from a polyolefin which has been crosslinked by electron
beam radiation. Sleeves made from this type of material generally have poor resistance
to the forces applied by the crimping tool, resulting in splitting of the sleeve to
expose the underlying conductors or reduction in the wall thickness of the tube to
a point where it is insufficient to provide the necessary physical and dielectric
strength.
[0004] One solution to this problem is proposed by U.S. patent No. 4,196,308 (Siden) issued
on April 1, 1980. The Siden patent provides a crimp connector comprising a metal crimp
barrel which is removably retained within a heat-shrinkable sleeve. A connection between
two conductors is formed by the following steps: the bared end portion of one conductor
is inserted into the crimp barrel and the sleeve, the sleeve is slid back from the
end of the conductor to expose the crimp barrel, the bared end portion of a second
conductor is inserted into the opposite end of the crimp barrel, the exposed crimp
barrel is crimped with a crimping tool, the heat-shrinkable sleeve is slid over the
connection and is then heated to cause it to shrink over the connection. While the
solution proposed by Siden overcomes the problem of splitting or otherwise damaging
the heat-shrinkable sleeve, such connectors are more difficult to use since additional
steps are required and the user must ensure that the sleeve is properly positioned
over the connection prior to heat shrinking. Further, there is the possibility that
the crimp barrel and sleeve can become separated and lost prior to use, resulting
in further inconvenience.
[0005] A number of other solutions have been proposed to make the use of crimp connectors
less problematic. One solution involves reduction of the strength of the crimping
forces to avoid damage to the sleeve. However, this may result in a crimp connection
of unacceptably low quality. Another solution involves shaping the crimping dies of
the tool to evenly distribute the crimping forces throughout the wall of the tube.
However, such crimping tools are frequently more expensive and consequently less likely
to be purchased by a user.
[0006] Presently, the most preferred solution for overcoming this problem is to form the
heat-shrinkable sleeve from a material which is more resistant to crimping forces
than conventional crosslinked polyolefin sleeves. For example, U.S. patent No. 4,444,816
(Richards et al.) issued on April 24, 1984, discloses radiation crosslinked polyamides
comprising substantial amounts of Nylon-11 and/or Nylon-12 units. These Polyamides
are heat-shrinkable and are able to withstand the forces applied by a crimping tool
without splitting or unacceptable reductions in wall thickness.
[0007] EP-0 384 053 which is considered to represent the closest prior Art discloses an
assembly for providing axial strain relief to a splice between two cables having an
apertured layer, accordingly a plurality of annular metallic spacer tubes which are
positioned over the insulating sheath and over the crimps which join the ends of the
conductors. The metallic braid layers of the cables are pulled over the spacer tubes
and are secured by tape on either side of the crimps. A tubular support sleeve is
then slid over the splice and is heat shrunk over the splice. The sleeve comprises
an outer heat recoverable fabric layer and a lining of thermoplastic bonding material.
Once it melts, this bonding material flows into the apertures of the braided layer,
thereby forming a mechanical and/or adhesive bond between the heat recoverable sleeve
and the braided layer of the cable.
[0008] However, the use of polyamides to form heat-shrinkable sleeves in crimp connectors
is not free from difficulties. These polymers have relatively high softening temperatures,
typically about 150°C. Heating the electrical connection to these temperatures can
damage the insulation of the conductors being joined or may result in excessive melting
of the heat activated adhesive, causing it to run out of the connection. There is
also the possibility that the user may not sufficiently heat the heat-shrinkable sleeve,
resulting in poor sealing of the connection. Furthermore, crimp connectors formed
with polyamide sleeves are typically more costly than those made with polyolefin sleeves,
and may not have an acceptable degree of clarity which is desired in crimp connectors.
Still further, polyamide polymers such as Nylon-11 and Nylon-12 tend to be very rigid,
with the result that the metallic conductors may be prone to fatigue failure at the
junction with the heat-shrinkable sleeve. It is preferable that the heat-shrinkable
sleeve be as flexible as possible in order to provide strain relief to the conductors.
SUMMARY OF THE INVENTION
[0009] The disadvantages of the prior art discussed above are overcome by the present invention
according to claims 1 and 10, which provides a crimp connector comprising a crimp
barrel and a heat-shrinkable sleeve which is formed from an ionic polymer.
[0010] Ionic polymers, also known as "ionomers", are based on copolymers of α-olefins with
ethylenically unsaturated, preferably α,β-ethylenically unsaturated, carboxylic acid
monomers in which a proportion of the acid groups of the copolymer are reacted with
metal ions to create ionic carboxylates.
[0011] One of the earlier patents disclosing ionomers is U.S. patent No. 3,264,272 (Rees),
issued August 2, 1966. As noted in the Rees patent, ionomers have surprising properties
which result from an ionic attraction between the metal ion and one or more ionized
carboxylic acid groups. This ionic attraction results in a form of crosslinking which
occurs in the solid state. However, when ionomers are heated above their melting point
and subjected to shear stresses, the ionic crosslinks are ruptured and the polymers
exhibit melt fabricability essentially the same as that of the uncrosslinked linear
base copolymer.
[0012] It has also been found that ionomer resins have high impact toughness, abrasion resistance
and chemical resistance, making them useful in a wide range of consumer and industrial
products where these properties are important. Some applications include automobile
body parts, bowling pins and cut-resistant golf ball covers. However, ionomers are
typically significantly less rigid than polyamide polymers.
[0013] The inventors have now found that heat-shrinkable tubing formed from ionomers has
high resistance to splitting when subjected to forces of the type applied to a crimp
connector by a crimping tool. The resistance to splitting possessed by ionomers is
in fact similar to that of presently preferred polyamide heat-shrinkable sleeves.
[0014] Thus, the inventors appear to be the first to appreciate that ionomers are suitable
for use in heat-shrinkable sleeves of crimp connectors. This is surprising since ionomers
are known to be suitable for use in wire coatings (disclosed by Rees) and are known
to be suitable for use in heat-shrinkable tubing, as disclosed in U.S. patent No.
3,816,335 (Evans) issued June 11, 1974, and in U.S. patent No. 5,573,822 (Nishikawa
et al) issued November 12, 1996. '
[0015] The failure of others to appreciate the suitability of ionomers as heat-shrinkable
sleeves in crimp connectors is particularly surprising in view of the fact that ionomers
are known to possess a number of other properties which are desirable in heat-shrinkable
sleeves for crimp connectors, and which render them equally or more suitable to this
application than polyamides. In particular, ionomers are known to possess a high degree
of transparency; they accept colorants which do not materially deteriorate transparency,
allowing for excellent color coding of products; they are typically less expensive
than nylon; and can be made with varying degrees of stiffness. Another important advantage
of ionomers is that they are heat-shrinkable at significantly lower temperatures than
polyamide connector sleeves, typically about 50°C lower. The lower heat shrink temperature
renders ionomers more compatible with commonly used heat activated adhesives, such
as ethylene-vinyl acetate- (EVA)-based hot melt adhesives, and lessens the likelihood
of insufficient heating of the sleeve during heat shrinking and of deterioration of
the wire coating due to excessive heating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention will now be described, by way of example only, with reference to the
accompanying drawings, in which:
[0017] Figure 1 is a perspective view of a crimp connector according to a first preferred
embodiment of the present invention;
[0018] Figures 2 to 4 are longitudinal cross-sectional views of the crimp connector of Figure
1, illustrating the steps involved in forming a connection between the ends of two
conductors;
[0019] Figure 5 is a perspective view of a crimp connector according to a second preferred
embodiment of the present invention; and
[0020] Figure 6 is a graph which compares the degree of shrinkage against temperature for
ionomer tubing, polyolefin tubing and polyamide tubing.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] Figure 1 illustrates a crimp connector 10 according to a first preferred embodiment
of the present invention. Connector 10 is of the type commonly referred to as a "butt"
connector since it is used to form an electrically conductive butt joint between the
ends of two electrical conductors.
[0022] The butt connector 10 shown in Figure 1 comprises a tubular metallic crimp barrel
12, and a heat-shrinkable polymeric sleeve 14.
[0023] Crimp barrel 12 has an outer surface 16, an inner surface 18 and first and second
open ends 20 and 22. The inner surface 18 defines a hollow interior 24 extending through
the crimp barrel 12 between the open ends 20 and 22. The crimp barrel 12 is preferably
comprised of a metal which is a good conductor and which is sufficiently malleable
such that barrel 12 is "crimpable", i.e. it can be deformed with a crimping tool.
Preferred metals are selected from the group comprising copper, aluminum and brass,
and alloys thereof.
[0024] The heat-shrinkable sleeve 14 is also of a generally cylindrical shape, having an
outer surface 26, an inner surface 28 and first and second open ends 30 and 32. The
inner surface 28 defines a hollow interior 34 of the sleeve 14 extending between its
open ends 30 and 32.
[0025] Preferably, as shown in the drawings, the heat-shrinkable insulating sleeve comprises
a hollow cylindrical tube having a length greater than a length of the crimp barrel
12, and is comprised of a pair of end portions 36 and 38, and a central portion 40
located therebetween. Central portion 40 has an inside diameter which is sized to
receive the crimp barrel 12 in a sufficiently close-fitting relationship such that
it is retained against substantial movement during normal use of the butt connector
10.
[0026] Each of the end portions 36 and 38 extends between the central portion 40 and a respective
one of the open ends 30 and 32 of the sleeve 14. Preferably, the end portions 36 and
38 have an inside diameter greater than a diameter of the central portion 40, and
form a gradual, sloped transition with the central portion 40. The diameter of the
end portions 36 and 38 is enlarged relative to the central portion to allow the ends
of the conductors to be easily inserted into the connector 10. The sloped transitions
of the end portions 36 and 38 also assist in guiding the ends of the conductors into
the crimp barrel 12.
[0027] Although the preferred connector shown in the drawings comprises a central portion
40 which closely receives the crimp barrel 12 and has flared, enlarged end portions
36 and 38, it will be appreciated that this configuration is not an essential feature
of the invention. Rather, the insulating sleeve 14 may be of constant diameter, with
the crimp barrel 12 being loosely held within the hollow interior 34 of the sleeve
14.
[0028] The heat-shrinkable insulating sleeve according to the invention preferably has an
adhesive layer 42 formed on the inner surface 28 thereof, with the adhesive layer
preferably being formed inside sleeve 14 by melt co-extrusion. The adhesive resin
composition is preferably a conventional hot-melt adhesive composition which melts
and flows at temperatures required for heat shrinking of the sleeve. Some examples
of hot-melt adhesives which can be employed in the connector of the present invention
include thermoplastic polyamide resins, thermoplastic saturated copolyester resins,
and resin compositions comprising such hot-melt adhesives as copolymers of ethylene,
ethyl acrylate, and carbon monoxide. The most preferred hot-melt adhesives are resin
compositions based on copolymers of ethylene and vinyl acetate, or those based on
polyamide polyers.
[0029] The connector 10 is formed by first inserting the crimp barrel 12 into sleeve 14,
it being understood that sleeve 14 is of constant cross-sectional radial diameter
prior to assembly. The crimp barrel 12 is positioned inside sleeve 14 so that it is
located centrally relative to the two open ends 30 and 32. The central portion 40
of sleeve 14 is then heated, causing recovery in central portion 40, i.e. shrinkage
of sleeve 14 into contact with the outer surface 16 of the crimp barrel 12. A suitable
process for forming the connector, and heat shrinking the central portion 40, is described
in U.S. Patent No. Re.33,591 (Feeny et al.), reissued on May 21, 1991. During recovery
of the central portion 40 of sleeve 14, the end portions 36 and 38 remain unrecovered,
i.e. they remain in their expanded state.
[0030] The heat-shrinkable insulating sleeve 14 according to the invention is contains at
least one ionic polymer, also referred to herein as an "ionomer". Preferably, the
ionomer content of sleeve 14 is sufficient to impart to the sleeve 14 the above-mentioned
desirable properties of ionomers, i.e. high impact toughness, high abrasion and chemical
resistance, high resistance to splitting by crimping tools, high degrees of flexibility
and transparency, and heat shrinkability at lower temperatures than polyamides. Preferably,
the sleeve 14 is primarily comprised of ionic polymer, and optionally contains other
polymers in lesser amounts than the ionic polymer. More preferably, the ionomer content
of sleeve 14 is greater than 50% by weight, even more preferably greater than 80%
by weight, and most preferably greater than 90% by weight. For example, where colorants
are employed, the ionomer is preferably prepared as a color masterbatch containing
an EVA carrier. Other optional ingredients include to be used in minor quantities
include EVA, metallocene polyethylene, etc. to prevent premature shrinking.
[0031] In some preferred embodiments of the present invention, the heat-shrinkable sleeve
may be comprised of a plurality of co-axially arranged polymeric layers and is formed,
for example, by co-extrusion of two or more different polymers. Where the sleeve 14
comprises a plurality of layers, at least one of the layers will be primarily comprised
of an ionic polymer as described above.
[0032] lonomers suitable for use in the present invention are derived from the polymerization
of at least one α-olefin and at least one ethylenically unsaturated carboxylic acid,
a proportion of whose acid groups have been reacted to create ionic carboxylates of
metal ions. Preferred ionomers for use in the heat-shrinkable sleeves of electrical
connectors according to the invention include those defined in the above-mentioned
Rees patent, which is incorporated herein by reference in its entirety.
[0033] The α-olefins incorporated in the ionomers of the present invention have the general
formula RCH=CH
2, wherein R is a radical selected from the group comprising hydrogen and alkyl radicals
having from 1 to 8 carbon atoms. Preferred α-olefins for use in the ionomers according
to the invention include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene,
3-methyl-1-butene and 4-methyl-1-pentene. Preferably, the α-olefin content of the
ionomer is greater than or equal to 50 mol percent based on the ionomer, and is more
preferably greater than or equal to about 80 mol percent.
[0034] The ethylenically unsaturated carboxylic acid component of the ionomer preferably
comprises one or more α,β-ethylenically unsaturated carboxylic acids, which are selected
from the group comprising α,β-ethylenically unsaturated monocarboxylic and dicarboxylic
acids having from 3 to 8 carbon atoms. Preferred examples of such carboxylic acids
include acrylic acid, methacrylic acid, monoesters of dicarboxylic acids such as methyl
hydrogen maleate, methyl hydrogen fumarate, ethyl hydrogen fumarate, maleic acid and
maleic anhydride. The amount of unsaturated carboxylic acid in the ionomer is preferably
from about 0.2 to 25 mol percent based on the ionomer, and more preferably from about
1 to about 10 mol percent.
[0035] The base copolymer employed in forming the ionomers of the present invention may
be prepared in several ways, including copolymerization of a mixture of the olefin
and the acid monomers, and grafting the acid monomer to a base polymer of the olefin.
However, direct copolymerization of the olefin and the acid component is preferred
as it ensures that the carboxylic acid groups are randomly distributed over all the
molecules comprising the ionic copolymer.
[0036] The most preferred base copolymers are those obtained by direct copolymerization
of ethylene with an α,β-ethylenically unsaturated monocarboxylic acid comonomer, which
is most preferably selected from the group comprising acrylic acid and methacrylic
acid.
[0037] The ionic base copolymer has a molecular weight, as defined by melt flow index, which
is preferably in the range of from about 0.1 to about 1,000 g/10 min., and more preferably
in the range of from about 1.0 to about 100 g/10 min.
[0038] Although the preferred base copolymers used in forming the ionomers according to
the invention comprise the above-described olefin and acid monomers, the base copolymer
may also contain additional components. For example, additional copolymerizable monoethylenically
unsaturated monomers can be employed in combination with the olefin and the acid monomer
described above.
[0039] The ionomers of the present invention are obtained by reacting (also referred to
herein as "neutralizing") a proportion of the acid groups of the base copolymer with
an ionizable metal compound. The metal ions which are useful in the ionomers of the
present invention include mono-, di- and trivalent ions of metals in Groups I, II,
III, IV-A and VIII of the Periodic Table of Elements. Preferred examples of monovalent
metal ions include Na
+, K
+, Li
+, Cs
+, Ag
+, Hg
+ and Cu
+, Preferred divalent metal ions include Be
2+, Mg
2+, Ca
2+, Sr
2+, Ba
2+, Cu
2+, Cd
2+, Hg
2+, Sn
2+, Pb
2+, Fe
2+, Co
2+, Ni
2+ and Zn
2+. Preferred trivalent metal ions include Al
3+, Sc
3+, Fe
3+ and Y
3+. The most preferred monovalent metal ions are alkali metals, more preferably selected
from the group comprising Na
+, K
+ and Li
+. The most preferred divalent metal ion is Zn
2+. It is not essential that only one metal ion be employed in the ionomers of the invention,
and more than one metal ion may be preferred in certain applications.
[0040] The degree of neutralization is preferably such that the metal ion neutralizes at
least 10% of the carboxylic acid groups of the base copolymer. More preferably, it
is desirable to neutralize from about 50% to about 90% of the acid groups.
[0041] After formation of the ionomer as described above, the ionomer resin composition
is shaped into a tube using a melt extruder or the like. The tube is then preferably
covalently crosslinked by any conventional method, for example irradiation with an
ionizing radiation such electron beams, gamma-rays and X-rays, or by heating.
[0042] In embodiments where crosslinking is conducted by ionizing radiation, a crosslinking
accelerator is preferably incorporated into the ionomer resin and a crosslinking inhibitor
is preferably incorporated into the adhesive layer.
[0043] The method for producing the heat-shrinkable insulating sleeve according to the present
is not particularly limited. For example, the ionomer resin composition may preferably
be shaped into a tube using a melt extruder or the like. The tube is then crosslinked
as described above, and the diameter of the crosslinked tube is expanded under high
temperature conditions by, for example, introducing compressed air into the tube.
The tube is then fixed in its expanded shape by cooling.
[0044] Particularly preferred ionomer resins for use in the connectors of the present invention
are sold by DuPont under the trademark Surlyn®. A number of different grades of Surlyn®
ionomer resins are commercially available. All are based on ethylene/methacrylic acid
copolymers, with Surlyn® 7930 and 7940 containing lithium ions; Surlyn® 8020, 8120,
8140, 8150, 8320, 8527, 8660, 8670, 8920, 8940, 8945, PC350 and PC100 containing sodium
ions; and Surlyn® 9020, 9120, 9150, 9320W, 9520, 9650, 9720, 9721, 9730, 9910, 9945,
9950 and 9970 containing zinc ions.
[0045] Surlyn® ionomer resins generally have a melt flow index of from about 0.7 to 20,
a density of about 0.94 to about 0.97, and a melting point of from about 70°C to about
100°C. Preferred for use in the connectors of the present invention are those Surlyn®
ionomer resins which have a melting point above about 80°C and which have high impact
toughness. Among the most preferred Surlyn® ionomer resins is Surlyn® 8940, commonly
used as a ski laminating film, which has a Notched Izod impact strength of 1025 Jm
and a melting point of 94°C as determined by differential scanning calorimetry (DSC).
[0046] As mentioned above, the melting temperatures, and consequently the expansion and
heat shrink temperatures, of preferred ionomer resins such as Surlyn® ionomer resins
are significantly lower than those of polyamides commonly used for heat-shrinkable
connector sleeves. This is advantageous for a number of reasons. Firstly, a lower
expansion temperature makes the manufacture of heat-shrinkable sleeves less expensive
in terms of equipment and energy costs. A lower heat shrink temperature lessens the
likelihood that insufficient heat will be applied by the user and allows the ionomer
sleeve to be heated to its heat shrink temperature more quickly than a conventional
polyamide sleeve. Furthermore, there is less chance that damage (eg. by creeping,
melting or cracking) will be caused to the insulating layer of the conductors being
joined, which are typically comprised of polyethylene or poly(vinyl chloride), and
less chance that the heat-activated adhesive will melt and run out of the connection
during heat shrinking. lonomer resins also tend to have better transparency than polyamide
resins, more readily accept colourants which do not deteriorate transparency, are
considerably less expensive, are less sensitive to alcohols and moisture than polyamides,
are easier to crosslink, and can be made to have varying degrees of stiffness which
is not possible with resins containing a large proportion of nylon.
[0047] A preferred method for forming a sealed connection between a pair of conductors using
the butt connector 10 according to the first preferred embodiment of the present invention
is now described below with reference to Figures 2 to 4. In the method described below,
an electrical connection is formed between a pair of electrical conductors 44. As
both conductors 44 are identical, the same reference numerals are used to describe
the components thereof. Each conductor 44 comprises an electrical wire 46, typically
comprised of copper, surrounded by an insulating layer 48 which is typically comprised
of a polymeric material such as poly(vinylchloride) or polyethylene. As shown, the
ends of the conductors 44 are stripped prior to connection to form bared end portions
50.
[0048] In Figure 2, the bared end portions 50 of conductors 44 have been inserted into the
enlarged end portions 36 and 38 of sleeve 14 and are about to be inserted into the
open ends 20 and 22 of the crimp barrel 12. As shown, the open ends 20 and 22 and
the hollow interior 24 of crimp barrel 12 are sized and shaped to closely receive
the bared end portions 50, and the diameter of insulating layer 48 is greater than
the inside diameter of crimp barrel 12 to prevent the insulated portions of conductors
44 from entering the crimp barrel 12.
[0049] Referring now to Figure 3, the bared end portions 50 of conductors 44 have been received
in the open ends 20 and 22 of the crimp barrel 12 so that the end of the insulating
layer directly abuts the ends 20 and 22 of crimp barrel 12, and so that a portion
of the insulating layer is received inside the end portions 36 and 38 of sleeve 14.
In this position, the bared end portions 50 extend inwardly into the crimp barrel
12 by a distance which is slightly less than half the length of the crimp barrel 12.
However, it will be appreciated that the length of bared end portions 50 may vary
to some extent. The bared end portions 50 may be somewhat shortened so long as they
extend into the crimp barrel 12 to a sufficient extent that they can be crimped. The
bared end portions may instead be longer than one half of the length of the crimp
barrel 12 in which case the end of the insulating layer 48 would not abut the ends
20 or 22 of the crimp barrel 12. However, the insulating layer 48 should extend somewhat
into the end portions 36 and 38 of the sleeve 14, such that a seal can be formed between
the sleeve 14 and the insulating layer 48, as described below. Furthermore, the crimp
barrel 12 may preferably be provided with a centrally located septum to prevent over-insertion
of the bared end portions 50 into the crimp barrel 12.
[0050] Once the bared end portions 50 are received inside crimp barrel 12 as shown in Figure
3, the central portion 40 of sleeve 14, the adhesive layer 42 contained therein, the
crimp barrel 12 and bared end portions 50 are all subjected to a crimping operation
using a conventional crimping tool. This operation results in crimps 52 and 54 being
formed for each of the bared end portions 50, thereby creating electrical contact
between the crimp barrel 12 and the bared end portions 50, and also retaining the
conductors against movement relative to the crimp barrel 12. It will be appreciated
that the crimps formed by various crimping tools may vary. Rather than forming a pair
of crimps 52 and 54 as illustrated in the drawings, the crimping tool may instead
form one centrally located crimp extending over parts of both end portions 50.
[0051] The end portions 36 and 38 of sleeve 14 are then heated, causing recovery of the
end portions 36 and 38 into an engaging relationship with the insulating layer 48,
and also activating the adhesive layer 42, causing it to flow and seal the connection
between the sleeve and the conductors 44. This seal prevents penetration of moisture
into the connection and also prevents relative movement of the conductors 44. The
completed electrical connection is shown in Figure 4.
[0052] Figure 5 illustrates an electrical connector according to a second preferred embodiment
of the present invention, which comprises a terminal connector 56 having an exposed
terminal fastener 58 for forming an electrical connection with a screw terminal or
the like. Although the exposed terminal fastener 58 is shown as having a U-shape,
it may instead have another suitable shape for use with such terminals, such as an
annular shape.
[0053] The structure and composition of terminal connection 56 is similar to that described
above in connection with the butt connector 10 according to the first preferred embodiment
of the invention, and is now briefly described below.
[0054] The terminal fastener 58 is formed at one end of a conductive member 60, the other
end of which comprises a crimpable, tubular metallic crimp barrel 62 with an open
end for receiving the bared end portion of an electrical conductor (not shown). The
metal from which the conductive member 60 is formed is preferably the same as that
described above for crimp barrel 12.
[0055] Terminal fastener 56 also includes a heat-shrinkable polymeric sleeve 64 which is
longer than the crimp barrel 62, sleeve 64 having a first end 66 and a second end
68. The crimp barrel 62 is received inside the first end 66 of sleeve 64 in a sufficiently
close-fitting relationship so as to retain the position of the crimp barrel 62 within
the sleeve 64 during normal use. The second end 68 of sleeve 64 extends past the open
end of the crimp barrel 62 and is sized to receive an insulated portion of the electrical
conductor. As in connector 10, first end 66 of sleeve 64 is recovered by heat shrinking
so as to closely receive the crimp barrel 62, and the second end 68 is of larger diameter
to assist in inserting the lead of the electrical conductor. The insulating sleeve
64 is primarily comprised of an ionomer having the composition and characteristics
described above with reference to the first preferred embodiment, or may preferably
be formed of a plurality of layers, at least one of which is primarily comprised of
ionomer, as described above.
[0056] The advantages of the present invention are further illustrated by the following
examples.
EXAMPLE 1 - Crimp Tests
[0057] A number of crimp connectors of various diameters were prepared by inserting metal
crimp barrels into sleeves comprised of heat-shrinkable tubing, followed by sufficient
heating of the sleeve to shrink the sleeve over the crimp barrel. Crimp connectors
were prepared using sleeves comprised of the following materials:
1. Standard polyolefin
Commercial name: MDKT
Manufacture location: Mechenheim, Germany
Manufacturer: DSG Canusa
Composition: MDPE, masterbatch colourant
2. lonomer
Commercial name: NiAC (proposed)
Manufacture location: Toronto, Canada
Manufacturer: DSG Canusa
Composition: Dupont Surlyn® 8940, masterbatch
3. Polyamide (identified herein as "Nylon")
Manufacturer: Raychem, division of Tyco Electronics
Composition: Nylon, grade and composition unkown
[0058] The connectors were each crimped by a standard crimping tool. It was observed that
the sleeves of all the polyolefin connectors fractured upon crimping. In contrast,
the ionomer and polyamide connectors performed equivalently as no fracture of the
sleeves was observed.
EXAMPLE 2 - Heat Shrink Time and Temperature
[0059] As shrink time and temperature are related, the standard industry test is to fix
the time and measure the percent recovery of the tubing. The percent recovery is typically
expressed as percentage of inside diameter (ID) of the tubing in its expanded state.
Figure 6 is a plot of percent recovery vs. temperature for each type of heat-shrinkable
sleeve of Example 1. The data shown in Figure 6 was obtained by measuring the inside
diameter of the tubing at two minute intervals while the tubing was heated at a constant
rate.
[0060] As can be seen from Figure 6, the ionomer (NiAC) sleeve attained full recovery between
90 and 100°C, which was considerably less than the temperatures required for full
recovery of the MDKT and Nylon sleeves. In fact, the Nylon sleeve only started to
shrink at relatively high temperatures of about 150°C.
EXAMPLE 3 - Product Clarity
[0061] In this example, the clarity of the tubing used in the connectors of Example 1 was
observed. The NiAC product was observed to have better clarity and surface finish
than either the MDKT or Nylon tubing.
[0062] Although the invention has been described in connection with certain preferred embodiments,
it is not limited thereto. Rather, it is intended that the invention include all embodiments
which may be within the scope of the following claims.
1. An electrical connector (10) for connecting two or more electrical conductors (44),
comprising:
a crimpable, tubular metallic crimp barrel (12) open at both ends (20, 22) to receive
bared end portions (50) of the electrical conductors (44) to be connected, and to
create electrical contact with and retain said electrical conductors (44) after crimping;
and
a heat-shrinkable polymeric sleeve (14) inside which said crimp barrel (12) is received
in a sufficiently close-fitting relationship so as to retain a position of said crimp
barrel (12) within said sleeve (14), said sleeve (14) being longer than said crimp
barrel (12) and having ends (30, 32) which extend beyond the ends (20, 22) of the
crimp barrel (12) to receive insulated portions (48) of the conductors (44) to be
connected;
characterised in that the heat-shrinkable sleeve (14) is comprised of one or more layers, at least one
said layer being a covalently crosslinked, heat-shrinkable layer primarily comprised
of an ionic polymer, said ionic polymer being derived from the polymerization of at
least one α-olefin and at least one ethylenically unsaturated carboxylic acid, a proportion
of whose acid groups have been reacted to create ionic carboxylates of metal ions.
2. The electrical connector according to claim 1, characterised in that a portion of said heat-shrinkable sleeve (14) has been recovered into a close-fitting
relationship with said barrel (12), and characterised in that the ends (30, 32) of the sleeve (14) extending beyond the ends (20, 22) of the crimp
barrel (12) remain unrecovered.
3. The electrical connector according to any one of the preceding claims, characterised in that said at least one layer of the heat-shrinkable sleeve (14) which is primarily comprised
of the ionic polymer comprises at least 50%, preferably at least 80%, and more preferably
at least 90%, by weight of the ionic polymer.
4. The electrical connector according to any one of the preceding claims, characterised in that said heat-shrinkable sleeve (14) is lined with a hot melt adhesive (42) which melts
and flows at a temperature required to shrink said sleeve (14), the hot melt adhesive
(42) preferably being based on a copolymer of ethylene and vinyl acetate, and more
preferably being based on a polyamide polymer.
5. The electrical connector according to any one of the preceding claims, characterised in that the heat-shrinkable sleeve (14) comprises a hollow cylindrical tube.
6. The electrical connector according to any one of the preceding claims, characterised in that said α-olefin comprises ethylene.
7. The electrical connector according to any one of the preceding claims, characterised in that said ethylenically unsaturated carboxylic acid is an α,β-ethylenically unsaturated
carboxylic acid which is preferably selected from the group comprising α,β-ethylenically
unsaturated monocarboxylic and dicarboxylic acids having from 3 to 8 carbon atoms,
and more preferably is selected from the group comprising acrylic acid and methacrylic
acid.
8. The electrical connector according to any one of the preceding claims, characterised in that said metal ions are selected from one or more members of the group comprising sodium,
lithium and zinc ions, and preferably comprise sodium ions.
9. The electrical connector according to any one of the preceding claims, characterised in that the heat-shrinkable insulating sleeve (14) is covalently crosslinked prior to expansion,
and is preferably covalently crosslinked by irradiation with an ionizing radiation.
10. An electrical connector (56) for forming a terminal connection with an electrical
conductor, comprising:
a conductive member (60), one end of which comprises a crimpable, tubular metallic
crimp barrel (62) open to receive a bared end portion of the electrical conductor
and another end of which comprises a terminal fastener (58);
a heat-shrinkable polymeric sleeve (64) inside which said crimp barrel (62) is received
in a sufficiently close-fitting relationship so as to retain a position of said crimp
barrel (62) within said sleeve (64), said sleeve (64) being longer than said crimp
barrel (62) and having one of its ends (68) extending past the open end of the conductive
member (60) to receive an insulated portion of the conductor while leaving the terminal
fastener (58) exposed; and
optionally comprising an adhesive layer provided on the inner surface of the heat-shrinkable
sleeve (64);
characterised in that the heat-shrinkable sleeve (64) is comprised of one or more layers, at least one
said layer being a covalently crosslinked, heat-shrinkable layer primarily comprised
of an ionic polymer, said ionic polymer being derived from the polymerization of at
least one α-olefin and at least one ethylenically unsaturated carboxylic acid, preferably
an α,β-ethylenically unsaturated carboxylic acid, a proportion of whose acid groups
have been reacted to create ionic carboxylates of metal ions.
1. Elektrischer Verbinder (10) zum Verbinden von zwei oder mehr elektrischen Leitern
(44), umfassend:
eine quetschbare, rohrförmige metallische Crimphülse (12), die an beiden Enden (20,
22) offen ist, um abisolierte Endabschnitte (50) der zu verbindenden elektrischen
Leiter (44) aufzunehmen und nach dem Crimpen den elektrischen Kontakt zwischen den
elektrischen Leitern (44) herzustellen und diese festruhalten; und
einen Warmschrumpfschlauch (14) aus einem Polymermaterial, in dem die genannte Crimphülse
(12) hinreichend eng sitzend aufgenommen wird, so dass die genannte Crimphülse (12)
in dem genannten Schrumpfschlauch (14) in ihrer Position gehalten wird, wobei der
genannte Schrumpfschlauch (14) länger als die genannte Crimphülse (12) ist und Enden
(30, 32) aufweist, die sich über die Enden (20, 22) der Crimphülse (12) hinaus erstrecken,
um isolierte Abschnitte (48) der zu verbindenden Leiter (44) aufzunehmen;
dadurch gekennzeichnet, dass der Warmschrumpfschlauch (14) eine oder mehrere Schichten umfasst, wobei wenigstens
eine der genannten Schichten eine kovalent vernetzte, wärmeschrumpfbare Schicht ist,
die überwiegend aus einem ionischen Polymer besteht, wobei das genannte ionische Polymer
aus der Polymerisation wenigstens eines α-Olefins und wenigstens einer ethylenisch
ungesättigten Carbonsäure gewonnen ist, von deren Säuregruppen ein gewisser Anteil
zur Reaktion gebracht worden ist, um ionische Carboxylate von Metallionen zu bilden.
2. Elektrischer Verbinder gemäß Anspruch 1, dadurch gekennzeichnet, dass ein Abschnitt des genannten Warmschrumpfschlauchs (14) eng anliegend auf die genannte
Hülse (12) aufgeschrumpft ist, und dadurch gekennzeichnet, dass die Enden (30, 32) des Schrumpfschlauchs (14), die sich über die Enden (20, 22) der
Crimphülse (12) hinaus erstrecken, ungeschrumpft bleiben.
3. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die genannte wenigstens eine Schicht des Warmschrumpfschlauchs (14), die überwiegend
aus dem ionischen Polymer besteht, wenigstens zu 50 Gew.-%, vorzugsweise zu mindestens
80 Gew.-% und noch bevorzugter zu 90 Gew.-% aus dem ionischen Polymer besteht.
4. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der genannte Warmschrumpfschlauch (14) mit einem Schmelzkleber (42) ausgekleidet
ist, der bei einer zum Schrumpfen des genannten Schrumpfschlauchs (14) erforderlichen
Temperatur schmilzt und fließt, wobei der Schmelzkleber (42) vorzugsweise auf einem
Copolymer von Ethylen und Vinylacetat und noch bevorzugter auf einem Polyamidpolymer
basiert.
5. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der Warmschrumpfschlauch (14) ein hohles zylindrisches Rohr umfasst.
6. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass das genannte α-Olefin Ethylen umfasst.
7. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die genannte ethylenisch ungesättigte Carbonsäure eine α,β-ethylenisch ungesättigte
Carbonsäure ist, die vorzugsweise aus der Gruppe ausgewählt ist, die α,β-ethylenisch
ungesättigte Mono- und Dicarbonsäuren mit 3 bis 8 Kohlenstoffatomen umfasst, und noch
bevorzugter aus der Gruppe ausgewählt ist, die Acrylsäure und Methacrylsäure umfasst.
8. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die genannten Metallionen aus einem oder mehreren Elementen aus der Gruppe ausgewählt
sind, die Natrium, Lithium und Zinkionen umfasst, und vorzugsweise Natriumionen umfassen.
9. Elektrischer Verbinder gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der Warmschrumpfschlauch (14) vor der Ausdehnung kovalent vernetzt wird und vorzugsweise
durch Einstrahlung von ionisierender Strahlung kovalent vernetzt wird.
10. Elektrischer Verbinder (56) zur Herstellung einer Klemmenverbindung mit einem elektrischen
Leiter, umfassend:
ein leitendes Element (60), dessen eines Ende eine quetschbare, rohrförmige metallische
Crimphülse (62) umfasst, die so geöffnet ist, dass sie einen abisolierten Abschnitt
eines elektrischen Leiters aufnehmen kann, und dessen anderes Ende eine Anschlusslasche
(58) umfasst;
einen Warmschrumpfschlauch (64) aus einem Polymermaterial, in dem die genannte Crimphülse
(62) hinreichend eng sitzend aufgenommen wird, so dass die genannte Crimphülse (62)
in dem genannten Schrumpfschlauch (64) in ihrer Position gehalten wird, wobei der
genannte Schrumpfschlauch (64) länger als die genannte Crimphülse (62) ist und sich
eins seiner Enden (68) über das offene Ende des leitenden Elements (60) erstreckt,
so dass es einen isolierten Abschnitt des Leiters aufnehmen kann und dabei die Anschlusslasche
(58) frei lässt; und
optional umfassend eine Kleberschicht auf der Innenfläche des Warmschrumpfschlauchs
(64);
dadurch gekennzeichnet, dass der Warmschrumpfschlauch (64) eine oder mehrere Schichten umfasst, wobei wenigstens
eine der genannten Schichten eine kovalent vernetzte, wärmeschrumpfbare Schicht ist,
die überwiegend aus einem ionischen Polymer besteht, wobei das genannte ionische Polymer
aus der Polymerisation wenigstens eines α-Olefins und wenigstens einer ethylenisch
ungesättigten Carbonsäure gewonnen ist, vorzugsweise einer α,β-ethylenisch ungesättigten
Carbonsäure, von deren Säuregruppen ein gewisser Anteil zur Reaktion gebracht worden
ist, um ionische Carboxylate von Metallionen zu bilden.
1. Un connecteur (10) électrique pour la connexion de deux ou plusieurs conducteurs électriques
(44) comprenant :
un fut à sertir (12) métallique tubulaire sertissable, ouvert aux deux extrémités
(20, 22) pour recevoir des parties d'extrémités dénudées (50) des conducteurs électriques
(44) destinés à être connectés, et pour créer un contact électrique avec lesdits conducteurs
et retenir lesdits conducteurs électriques (44) après le sertissage ; et
un manchon (14) en polymère qui se rétracte à la chaleur à l'intérieur dudit fût à
sertir (12) est reçu dans une relation suffisamment serrée pour retenir une position
dudit fût à sertir (12) à l'intérieur dudit manchon (14), ledit manchon (14) étant
plus long que ledit fût à sertir (12) et ayant des extrémités (30, 32) qui s'étendent
au-delà des extrémités (20, 22) du fût (12) de sertissage pour recevoir les parties
(48) isolées des conducteurs (44) destinées à être connectées ;
caractérisé en ce que le manchon (14) qui se rétracté à la chaleur est constitué d'une ou de plusieurs
couches, une couche au moins étant une couche covalente réticulée, qui se rétracte
à la chaleur constituée en premier lieu d'un polymère ionique, ledit polymère ionique
provenant de la polymérisation d'au moins d'une oléfine et d'au moins un acide carboxylique
à insaturation éthylénique; une partie de ces groupes d'acide ayant réagies pour créer
des carboxylates d'ions métalliques.
2. Le connecteur électrique selon la revendication 1, caractérisé en ce qu'une partie du manchon (14) qui se rétracte à la chaleur a été recouverte dans une
relation serrée par ledit fût (12), et caractérisé en ce que les extrémités (30, 32) du manchon (14) s'étendant au-delà des extrémités (20, 22)
du fût (12) sertissable restent découvertes.
3. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce qu'au moins ladite couche du manchon (14) qui se rétracte à la chaleur, constituée en
premier lieu du polymère ionique, comprend au moins 50%, de préférence au moins 80%,
et de préférence au moins 90% en poids du polymère ionique.
4. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que ledit manchon (14) qui se rétracte à la chaleur est recouvert d'une colle à chaud
(42) qui fond et s'écoule à une température nécessaire pour rétrécir ledit manchon
(14) ; la colle à chaud (42) se basant, de préférence, sur un polymère polyamide.
5. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que le manchon (14) qui se rétracte à la chaleur comprend un tube cylindrique creux.
6. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que ladite oléfine comprend de l'éthylène.
7. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que ledit acide carboxylique à insaturation éthylénique est un acide carboxylique insaturé
à insaturation éthylénique a, β qui est, de préférence, choisit parmi un groupe comprenant
des acides monocarboxyliques à insaturation éthylénique a, β et des acides dicarboxyliques
ayant de 3 à 8 atomes de carbone, et ledit acide carboxylique est, de préférence encore,
choisit parmi le groupe comprenant un acide acrylique et un acide méthacrylique.
8. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que lesdits ions métalliques choisis parmi un ou plusieurs éléments du groupe comprenant
du sodium, du lithium et des ions de zinc, et comprennent, de préférence, des ions
de sodium.
9. Le connecteur électrique selon n'importe laquelle des revendications précédentes,
caractérisé en ce que le manchon (14) qui se rétracte à la chaleur est réticulé de façon covalente avant
l'élargissement, et est, de préférence réticulé de façon covalente en étant irradié
par une radiation ionisante.
10. Un connecteur électrique (56) destiné à former une connexion terminale avec un conducteur
électrique, comprenant :
un élément conducteur (60), dont une extrémité comprend un fût (62) à sertir métallique
tubulaire ouvert pour recevoir une partie d'extrémité dénudée du conducteur électrique
et une autre extrémité duquel conducteur comprend un élément de fixation (58) terminal
;
un manchon (64) qui se rétracte à la chaleur à l'intérieur duquel fût à sertir (62)
est reçue dans une relation suffisamment serrée afin de retenir une position dudit
fût à sertir (62) dans ledit manchon (64), ledit manchon (64) étant plus long que
ledit fût à sertir (62) et ayant une de ses extrémités (68) s'étendant au-delà de
l'extrémité ouverte de l'élément conducteur (60) pour recevoir une partie isolée du
conducteur tout en laissant dénudé l'élément de fixation (58) terminal; et
comprenant en option une couche de colle fournie sur la surface intérieure du manchon
(64) qui se rétracte à la chaleur ;
caractérisé en ce que le manchon (64) qui se rétracte à la chaleur est constitué d'une ou de plusieurs
couches, au moins une desdites couches étant une couche réticulée de façon covalente,
qui se rétracte à la chaleur, constituée en premier lieu d'un polymère ionique, ledit
polymère ionique provenant de la polymérisation d'au moins une oléfine et d'au moins
un acide carboxylique à insaturation éthylénique, de préférence un acide carboxylique
à insaturation éthylénique a, β; une partie de ces groupes d'acide ayant réagis pour
créer des carboxylates ioniques d'ions métalliques.