Note: Descriptions are shown in the official language in which they were submitted.
ELC 77-22
~10469Z
BACKGROUND OF THE INVENTION
This invention relates to electrical contacts for an
electrical connector and a method of making the contacts.
More specifically, this invention relates to electrical
contacts of the type wherein a plurality of fine wires
are held together and axially-aligned in a bundle within
a sleeve and the wires provide surfaces for mating and
electrical conductivity with a second contact in another
connector. The second contact may be either a similar
contact or one of a plurality of conventional but dis-
similar contacts.
Electrical contacts of the type including a plurality
of axially-aligned fine wires held in a sleeve are old and
known in the prior art, as evidenced by U. S. Patent
3,725,844 issued April 3, 1973, to McKeown et al for
"Hermaphroditic Electrical ~ontact". Such a contact
typically includes a plurality of wires, each with acutely
angled forward end portions and held within a holder simply
by a crimp of the holder radially inwardly providing a
frictional retention among the wires and between the holder
and the plurality of wires.
The manufacture of electrical connectors of the type
described in the Brush Contact Patent is not the ultimate
in cost effectiveness. The manufacturing requires that the
individual wires be separately made, handled, and channeled
into a sleeve which is only fractionally larger internally.
Channeling the wires into such a sleeve may damage the wires
in some instances.
469Z
The crimping operation in the manufacture of the
prior art electrical connector is necessary to securely
hold all of the wires together and within the sleeve. This
presents an undesirable feature of requiring an undesirably
high force to secure all the wires within the sleeve.
~ The electrical resistance of the prior art contact
depends partially on the quality of the crimp, so a poor
crimp can significantly increase the electrical resistance
of the contact. Since a low resistance in a contact is
necessary, particular care (with resulting expense) was
directed to obtaining a good crimp.
In some instances it is desirable to verify that the
correct number of wires (perhaps within a small tolerance)
is included in the plurality of wires. In the prior art
methods of making such a contact, a mechanical way of
determining assembly with the wires in the comparatively
heavy sleevé against a nominal weight. The heavy sleeve makes
it difficult to determine the exact number of wires included.
The number of wires is important to the retention of wires
within the sleeve and to the electrical resistance of the
bundle in prior art applications.
Electrical contacts including a welded end are not
themselves new. One such contact including a welded end is
shown in a prior art U.S. patent Re 25,798, issued June 15,
1965 to Platz et al for-"Plug-In Connector". Such
a contact was formed to have a relatively
high mating force which is undesirable and a relatively
high manufacturing cost.
The foregoing and other limitations of the prior
art present problems in the manufacturing of the contact and
the subsequent reliability of such a contact.
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SUMMARY OF THE INVENTION
The present invention overcomes the limitations
of the prior art by providing an electrical contact
which includes a one-piece sub-assembly of a plurality
of axially-aligned electrically conduct;ng wires secured
together at one end. Such an assembly is easier to
handle, and, in some instances, less expensive to make
and assemble and one which has a higher reliability and
lower electrical resistance in use.
Thus, the invention relates to an electrical
contact comprising: a sleeve having an axial passage;
and several electrically conducting wires axially aligned
and axially mounted within the passage of the conduit,
the wires bonded one to another at a rear end, each of
the wires extending forwardly in the sleeve with the
forward end portion of each wire terminating in an
acutely angled end surface.
In another aspect, the invention relates to a
one-piece assembly for use in making an electrical contact
for an electrical connector, the assembly comprising:
a plurality of electrically conducting wires, each having
an acutely angled forward end portion, the plurality of
wires axially aligned parallel one to another and
arranged together in a bundle; and means located near
the rear end portion of the plurality of conducting wires
~or securing the wires together in a radial enlargement
for retention when assembled within a sleeve of electrically
conducting wires are joined together to form a one-piece
assembly.
The electrical contact of the present invention
obtains a higher reliability while reqlliring a smaller
force to secure the wires within the sleeve and has a
l~V~S~?2
signif;cantly lower mating force than the prior art
electrical contact described in the above-identified
U.S. patent Re 25,798.
In a particular embodiment a plurality of
straight fine wires each with an acutely angled forward
end portion are axially aligned to form a bundle. The
wires, at the rear end portion of the bundle, are secured
one to another by a weld to provide a contact with a
lower electrical impedance and a greater mechanical
resistance to disassembling forces. The welded bundle
is then inserted into an electrical connector sleeve
with the rear end of the bundle located rearwardly within
the sleeve, and a crimp in the sleeve secures the bundle
with the weld within the sleeve. The location of the
crimp is advantageously located in the portion of the
sleeve forward of the welded (or enlarged) portion or in
the portion of the sleeve including the welded portion.
Such a crimping arrangement coacts with the weld to
secure the wlres better within the sleeve and to provide
a lower electrical resistance and a higher mechanical
resistance to disassembly.
A welded brush bundle of the present invention
could be treated as a sub-assembly, and inventoried in
the bundle form, ready for insertion.
Such a sub-assembly could be easily weighed
(or balanced against an appropriate standard) to determine
whether the correct number of wires are included ~perhaps
within a given tolerance in the accepted number or wires),
Accordingly, it is an object of the present
invention to provide a novel electrical contact for an
electrical connector and a novel method of manufacturing
the contact which is economical and which has a low
mating force and low electrical resistance.
Further, it is an object of the present
invention to provide a one-piece sub-assembly including
a plurality of w;res with a rear welded portion which
may be separately manufactured, inspected and inventoried.
The foregoing and other objects and advantages
of the present invention will be apparent to one skilled
in the art in view of the foregoing description and
the accompanying drawings.
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92
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a partial cross-sectional view of an electrical contact of
the prior art with each of the wires forming the contact separately inserted
and held together and within a sleeve by a crimping of the sleeve inward.
FIGURE 2 is a magnified view of one of the contact wires of the electrical
contact of FIGURE 1.
FIGURE 3 is a partial crti~,~, sectional view of a bundle of fine wires used
in the electrical contacts held 111 a sleeve for welding but prior to being welded.
FIGURE 4 shows the bundle of FIGURE 3 looking in the direction ofthe
line 4-4 in FIGURE 3.
FIGURE 5 is a view of the bundle of fine wires following the step of welding
the wires together to form 8 welded bundle, prior to insertion into a sleeve.
FIGURE 6 shows a view of another, larger welded bundle of fine wires.
FIGUR~ 7 shows a bundle of wires welded together arld he]d within a sleeve.
FIGURE 8 is a view of the wires i71 the sleeve~ in PIGUR~; 7 looking in
the direction of line 8-8.
11~46~2
DETAILED DESCRIPTION OF THE DRAWINGS
FI~. 1 depicts in a partially cutaway view a form of a brush contact 10
for an electrical connector which is known in the art, similar to that describedin the Brush Contact Patent. The brush contact lû includes a sleeve or holder
20 and a plurality of fine wires 30 arranged in a bundle 40.
The sleeve or holder 20 has a forward axial passage or socket 21 (for receiving
the fine wires 30) and a rear portion 22 for an electrical connection (or termination).
The rear portion 22 as shown in FIGURE 1 is a socket for the insertion and attachment
of an electrical wire. Other configurations of the rear portion of the holder
20 are known ~nd may be substituted during the manufacturing of the holder,
such other configurations include a printed circuit board tail and a solderless
wire wrap tail, according to the type of electrical element which is being terminated
in (or connected to) the contacts. The contact provides an electrical connectionbetween the wire tor other termination) in the rear and the forward contact.
The fîne wires 30 have acutely angled end portions 32 on at least the forward
end of each wire. The rear portions 34 of the wires 3û are inserted in the holder
20 and held in place, typically by a crimped portion 25 of the holder to reduce
the cross-section dimension of the holder to thereby hold the wires fixed with
respect to the holder 20.
11~4~92
FIGURE 2 shows a single fine wire 30 of such a brush contact. The wire
is typically cylindrical and made of an electrically conducting material such
as berylium copper. For ease in manufacturing and assembling, the forward
end 32 and rear end 34 are typically formed with acutely angled end portions
to eliminate a requirement that the wires be directionally oriented. As is shown,
the end portions have an angle of 30 in this view, but a greater or lesser angle
could be used.
FIGURE 3 shows a bundle 40 of wires 30 which are in an electrically conducting
welding holder (or socket) 100 for welding but not yet welded. The bundle 40
shown consists of seven wires, although more or less could be used. The bundle
40 at this state is common to both the ~rior art and to the present invention,
at this stage of manufacture and assembly.
The holder 100 is generally cylindrical with an opening 102 at the top and
is used only in preparation for and during the welding operation. The wires
30 which make up a single bundle 40 are channeled (or funneled) into the holder
100 through the opening 102 in preparation for welding.
The holder 100 is formed with Q slot 104 which extends partially around
the periphery of the holder intermediate the height of the holder. The slot
104 accommodates a spring clip 110 which is inserted around the holder 100 and
which secures the wires 30 together with each other in a tight bundle and in
contact with a portion o~ the inside wall of the holder 100.
A welding system suitable for making the welded bundle of this invention
is shown generally in diagramatic form in FIGURE 3. The welding system is
a stored energy welding system which includes an electrode 200, a capacitor
210, a capacitor cha~ing system 220 and a switch 230. The capacitor 210 is
coupled with its cathode to the electrode through the switch 230 and with its
anode to the holder 100 and through the holder 100 to the wires 30 in the bundle40. The capacitor charging system 220 charges the capacitor to a predetermined,
possibly variable voltage.
The electrode 200 is spatially located with respect to the proximate end
portion of the bundle 40 to provide a suitable gap 300.
In operation of the welding system of FIGURE 3, the capacitor charging
system 220 charges capacitor 210 to a predetermined voltflge. The switch 230
is closed (either manually or automatically), creating a potential (voltage) difference
between the electrode 200 and the wires 30 in the bundle 40 approximately
e~ual to the predetermined voltage, which causes an arc to cross the gap and
bond the wires together.
One example of the apparatus used to accomplish the welding is as follows.
For a seven wire bundle of the berylium copper wire of .008 inch diameter,
a Superior Model 527A arc/percussive butt welder power supply was used. A
capacitor of approximately 6400 microfarads, charged to approximately 90
volts, and a gap of .û20 inches were used with good results. Other
ariations and modifications of such a we]ding schedule may be
easily determiined and are well within the skill of those working in
the f ield.
-~0-
FIGURE 4 shows a cross sectional view of the bundle of wires 30 held
by the spring clip in contact with each other and with the wall of the holder
100.
FIGURE 5 shows a bundle 40 of wires 30 after the welding process. One
end of the bundle is no longer the individual separate wire strands but rather
an enlarged porffon or nugget 50. As a result of the stored energy welding
process described above, the bundle 40 after welding is slightly shorter in length
than the wires 30 were originally. The enlarged welded portion or nugget 50
comprises a relatively small portion of the length (3-10%) of the welded assembly,
a percentage which depends in part upon the length of the wire.
If the nugget 50 is formed by the stored energy welding system described
previously, the nugget 50 is of the same material as the individual wires. This
system has the advantage of not consuming additional material (which could
change the weight of the bundle and make it difficult to determine the number
of wires included in a parffcular bundle) and of not requiring clean-up of the
welded bundle (i.e. excess solder and fluxes).
FIGUE~E 6 illustrates a larger bundle 40 of wires similarly prepared with
a forward acutely angled end portion 32 and a rear enlarged portion or nugget
~0. Such a bundle would be suitable for greater current carrying capacity.
FIGURE 7 shows a portion of an electrical contact lû of the present invention
with a welded bundle 40 of fine slraight brush wires 30 inserted into a holder
20.
The holder 20 has an ~xial passage 21 e~tending rearwardly from a forward
opening 22 to a rear stoL, 23 which may be formed in any one of several methods.
~11-
46~i2
The welded bundle 40 of wires 30 (e.g. as shown in FIGURE 5) is inserted
through the forward opening 22 with the enlarged portion leading until the rear
stop 23 is reached.
Therafter, a portion of the sleeve or holder 2G is crimped radially inwardly
to form a crimped portion 25. The crimped portion is advantageously formed
either at or forward of the enlarged portion 50 to thereby captivate the bundle
40 within the holder by restricting the forward movement of the nugget 50
and therefore the bundle 40. Such an arrangement of the nugget and the crimp
allows the use of a lower crimping force than would otherwise to required.
Other resulting benefits are that the wires are better secured to one another
and to the holder to provide both better mechanical attachment and a lower
electrical resistance connection.
Other objects and advantages of the present invention will be apparent
to those skilled in the art in view of the foregoing description. For example,
other forms of welding such as tungsten-inert gas (tig) welding or percussive
welding might be used, or a known substitute for welding (such as soldering)
might be employed to advantage. Further, a different method of securing the
bundle within the sleeve might be used without departing from the spirit of
the present invention. The foregoing description accordingly should be considered
as illustrative only and should not be interpreted to limit the scope of the present
invention, which is defined by the following claims.
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