[0001] The present invention relates to an electrical crimp type termination for aluminium
wire including an electrically conductive crimp barrel associated with means interposed
between the inside surface of the crimp barrel and the outside surface of the aluminium
wire to form a strong reliable electrical joint when crimped with the material of
the crimp barrel and the aluminium wire.
[0002] Aluminium wire typically is only about 60 % as electrically conductive as copper
wire of the same diameter but it is about one third the specific weight of copper
and much less expensive. There are thus economic and technical advantages to using
aluminium wire as electrical conductors. As a result aluminium wire has been used
in some electrical wiring applications where copper wire might normally have been
used.
[0003] However, aluminium wire has fallen out of favor as electrical conductor material
due to the unreliability of electrical connections made to aluminium. Specifically,
a non-electrically conductive aluminium oxide rapidly forms on the surface of clean
aluminium. Thus when an electrical joint is made to aluminium wire, some easy, convenient,
inexpensive and quick means must be employed to break up the surface non-conductive
aluminium oxide to expose the underlying aluminium and to simultaneously make a reliable
electrical joint before oxide has a chance to reform over the newly cleaned surfaces.
The prior art means include copper alloy terminations, where the word termination
includes connectors and the like, for aluminium wire having crimp barrels whose inner
diameters include internal protrusions or perforated sleeves which, upon crimping
the connector barrel, bite into the aluminium wire surface to break up and penetrate
the oxide layer to bring clean aluminium into immediate and intimate electrical contact
with the termination material. Another means used to make electrical connection to
aluminium wire has included a hard brittle plating, usually nickel, on the crimp barrel
interior surface. When the barrel is crimped onto the aluminium wire the brittle plating
breaks up into a large plurality of small hard sharp electrically conductive particles
to expose clean material beneath and also to abrade and bite through the oxide layer
into and to expose clean aluminium which comes into immediate and intimate electrical
contact with the connector.
[0004] Wire terminations are usually made of a relatively hard electrically conductive material,
such as brass, copper, steel, bronze or beryllium copper, having a yield strength
in excess of 1000 kg/cm
2. Unfortunately, the prior art means do not provide long term reliable electrical
joints between aluminium and such relatively hard materials so that high resistance
joints sometimes result producing a potentially dangerous condition. Primarily because
of this problem, aluminium wire has fallen into disfavor as electrical conductor material.
This is unfortunate in light of the current rising price and uncertain supply of copper.
[0005] The present invention overcomes the disadvantages and limitations of the prior art
arrangements by providing an electrical crimp type termination for aluminium wire
which includes interposed between the inside surface of a relatively hard electrically
conductive crimp barrel and the outside surface of the aluminium wire a sleeve made
of a relatively soft electrically conductive material and having a bore coated with
a thin hard brittle layer, the coated bore being adapted to fit over the aluminium
wire and the outside surface of the sleeve being adapted to fit into the crimp barrel,
so that crimping the crimp barrel causes the sleeve to be crimped with the material
of the crimp barrel and the aluminium wire, thereby forming a strong reliable electrical
joint by breaking the coated layer into many sharp particles to bite through and abrade
the oxide surface of the aluminium wire to bring clean aluminium into intimate electrical
contact with clean sleeve material and by additionally bringing the relatively hard
barrel material into intimate electrical contact with the relatively soft sleeve material.
[0006] One way of carrying out the invention is described in detail below with reference
to the drawings which illustrate one specific embodiment, in which :
Fig. 1 is an exploded isometric view of a crimp type connector termination made according
to the present invention.
Fig. 2 is a cross section of the connector of Fig. 1 taken along its longitudinal
axis.
Fig. 3 is a partial cross section of the connector termination of Fig. 1 as crimped
on an aluminium wire and taken along the wire longitudinal axis.
[0007] Referring first to Figs. 1 and 2, a termination such as connector 10 made according
to the present invention is comprised of a pin contact member 12 and a sleeve 14.
Pin contact member 12 is similar or identical to the pin contact member known in the
electrical connector art which terminates a single electrical lead or wire and which
is positioned in a block of insulating material, normally in spaced relationship with
a plurality of like pin contact members, to comprise an electrical connector. Pin
contact member 12 is designed to mate with a standard socket contact member (not shown)
which is similarly positioned in a second block of insulating material in spaced relationship
with a plurality of socket contact members to comprise the mating electrical connector.
As will be clear to one skilled in the art, the socket contact members can incorporate
the means of the present invention. Pin contact member 12 is a crimp connection device
which here is comprised of a pin end 12a, a barrel end 12b and an intermediate collar
12c. Pin contact member 12 is preferably formed in the usual manner, that is, machined
from a relatively hard electrically conductive rodstock such as brass or beryllium
copper as is standard in the art. Barrel end 12b has an internal round crimpwell 12d.
[0008] A sleeve 14 has an external dimension 14a which fits easily within crimpwell 12d
of pin contact member 12. Aluminium wire 15, either a single strand or multistranded
wire, has an external dimension such that wire 15 fits easily into bore 14b of sleeve14.
Sleeve 14 may be machined cylinder or, preferably, made of sheet stock which is rolled
into a cylindrical shape with seam 14c. Sleeve 14 is made of a relatively soft electrical
material such as copper alloy CA145, annealed to a DPH hardness of 65 maximum if machined
or copper alloy CA102 at 1/8 temper if rolled.
[0009] Bore 14b of sleeve 14 has deposited thereon a hard brittle and preferably continuous
coating 18 such as mekel which is suitably electroplated. Coating 18 not only provider
a frangible means which will break up into a large number of small sharp particles
when sleeve 14 is crimped but it also protects the underlying metal from corrosion
and other contamination so that when coating 18 is fractured a clean pure metallic
underlayer is exposed.
[0010] In embodiments of the invention actually made,coating 18 was nickel applied by a
standard
lelectroless nickel plating process at a thickness of 13/1000 mm to 14/1000 mm. As
might be expected, the hard brittle coating can be applied by other coating processes
such as electrolytic plating, metal cladding and vapor deposition, for example. Of
course, another coating than nickel can be used to practice the invention, so long
as the coating is hard and brittle, such as other brittle metals, ceramics, enamels
and the like.
[0011] Refer now to Fig. 3 where an aluminium wire 15 is seen assembled within sleeve 14
sandwiched within crimpwell 12d between the interior surface of the crimp barrel 12b
and the exterior surface of the,wire. Crimp barrel 12b is crimped in the conventional
manner, producing crimp deformation 20 and simultaneously crimping sleeve 14 in a
crimp deformation 22. As a result, pin contact member 12 is electrically crimped and
joined to sleeve 14 at interface 24. Simultaneously, coating 18 is shattered in a
large plurality of sharp particles 26 which dig into and through the aluminium oxide
layer to provide electrical communication between wire 15 and sleeve 14 (It should
be noted that coating 18 and particles 26 are shown exaggerated in size for. clarity
in this figure). When coating 18 is shattered, clean pure underlying sleeve material
is exposed. The shattered particles 26 also abrade the surface oxide layer of wire
15 to expose clean pure aluminium which, by crimping, is brought into high pressure
intimate electrical contact with the newly exposed sleeve material. The result is
the formation of an intermetallic and cold welding of the aluminium to the sleeve
material at interface 28, resulting in a strong reliable electrically sound joint.
[0012] Although the invention has been here embodied in a pin connector, it should be obvious
that it can be used in other terminations such as, for example, socket connectors,
spade lugs and the like.
1. An electrical crimp type termination for aluminium wire including an electrically
conductive crimp barrel (12b) associated with means (14,18) interposed between the
inside surface of the crimp barrel (12b) and the outside surface of the aluminium
wire (15) to form a strong reliable electrical joint when crimped with the material
of the crimp barrel (12b) and the aluminium wire (15), characterized in that said
interposed means (14,18) comprises a sleeve (14) made of a relatively soft electrically.
conductive material and having a bore (14b) coated with a thin hard brittle layer
(18), the coated bore (14b) being adapted to fit over the aluminium wire (15) and
the outside surface of the sleeve (14) being adapted to fit into the crimp barrel
(12b).
2. A termination as claimed in claim 1, characterized in that said layer (18) is of
an electrically conductive material.
3. A termination as claimed in claim 1 or 2, characterized in that the sleeve material
is relatively soft copper.
4. A termination as claimed in claim or 2, characterized in that said layer (18) is
nickel plated on the surface of the sleeve bore (14b).
5. A termination as claimed in claim 1 or 2, characterized in that the crimp barrel
12b is made of a material having a yield strength in excess of about 1000 kg/cm2.
6. A termination as claimed in claim 5, characterized in that the crimp barrel (12b)
is formed of a material chosen from the group consisting of brass, copper, steel,
bronze and beryllium copper.