Electrical terminal having wire-receiving slot for relatively small diameter wires and connectors containing such terminals

Electrical terminal having a wire-receiving slot comprises a pair of plate-like members in parallel side-by-side relationship. The plate-like members have aligned free ends and the space between the plate-like members serves as the wire-receiving slot for a wire which is to be connected to the terminal. The width of the slot is substantially less than the thickness of the material of the plate-like members and the terminal can be produced in sizes which are suitable for extremely fine wires having diameters of 0.2 mm or less. A connector is described containing terminals in accordance with the invention.

FIELD OF THE INVENTION 
This invention relates to electrical terminals having a wire-receiving slot 
for establishing contact with a wire inserted into the slot and to 
electrical connectors containing terminals having wire-receiving slots. 
The invention is particularly concerned with terminals which are intended 
for use with extremely fine wires. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 3,444,506 describes a multicontact electrical connector for 
flat cable having contact terminals therein which have wire-receiving 
slots into which the conductors of the cable are inserted when electrical 
contact is made. The terminals are of flat conductive sheet metal and have 
a free end into which the wire-receiving slot extends. The width of the 
slot is less than the conducting cores of the conductors so that as the 
conductor moves into the slot, the edges of the slot contact the conductor 
to form the electrical contact. 
Terminals of the type described in the above-identified U.S. patent are 
widely used for wires having a diameter of at least about 0.33 mm (0.013 
inches) which is the equivalent of an AWG 28 wire but they are not used to 
any significant extent for wires having a diameter less than about 0.33 
mm. The reason for this limitation on the use of wire-in-slot or 
insulation displacement terminals is that it is impractical to produce 
terminals having extremely narrow slots which are required for very fine 
wires. For example, an AWG 32 wire has a diameter of about 0.20 mm (0.008 
inches) and the slot required for a wire of this size must have a width of 
about 0.1 mm (0.004 inches). The wire-receiving slots are produced in the 
sheet metal from which the terminals are manufactured by means of 
conventional punch and die techniques, that is, a punch is provided having 
a width equal to the width of the slot and a die is also provided having a 
opening into which the punch moves. The sheet metal is supported on the 
die and when the punch moves into the die, the slot is formed. 
As a practical matter, it is not possible to produce slots in sheet metal 
of a given thickness which have a width which is significantly less than 
the thickness of the sheet metal. In other words, if the stock metal has a 
thickness of about 0.30 mm, it is impractical to punch a slot in the stock 
metal having a width which is much less than 0.30 mm. It follows that if 
the wire has a diameter of 0.20 mm, the slot width should be about 0.10 mm 
and a slot having this width cannot be produced in stock metal having a 
thickness of 0.30 mm. This limitation on slot width exists for the reason 
that if it is attempted to punch an extremely narrow slot in a relatively 
thick stock metal, the punch will break because of the extremely high 
stresses imposed on the punch when it moves against the stock metal. 
It might appear that the terminals for extremely fine wires might be 
produced from extremely thin stock metal thereby to permit the formation 
of extremely narrow slots in the stock metal. However, if the stock metal 
used for the terminals is extremely thin, the resulting terminals will be 
flimsy and will be useless for that reason. 
U.S. Pat. No. 4,293,177 shows another type of terminal having a 
wire-receiving slot which is produced by folding a flat piece of sheet 
metal to produce two side-by-side parallel sections of sheet metal 
connected by a fold or bight. The edges of the sections are coined and 
bent inwardly towards each other to define the wire-receiving slots. In 
the manufacture of this type of terminal it is not necessary to punch the 
slot and the problems discussed above which are encountered when narrow 
slots are punched are avoided. 
The present invention is directed to the achievement of an improved 
terminal which comprises a folded section of sheet metal to produce a pair 
of parallel plate-like members and particularly to a terminal which can be 
used in connectors intended for flat ribbon cable without stripping 
insulation from the cable. The invention is further directed to the 
achievement of terminals which are more compact than previously available 
terminals and which, for that reason, are desirable for use with extremely 
fine wires. 
THE INVENTION 
The invention comprises a sheet metal electrical terminal of the type 
having a shank portion which has an inner end and a free end. The shank 
portion has oppositely facing first and second major surfaces and has a 
wire-receiving slot extending inwardly from the free end. The terminal is 
characterized in that the shank portion comprises first and second 
plate-like members which are in side-by-side parallel relationship. The 
first and second major surfaces are on the first and second plate-like 
members respectively and the plate-like members have first and second 
internal surfaces which are opposed to each other. The shank portion has a 
contact section which extends from a free end towards the inner end, the 
first and second internal surfaces having opposed contact surface portions 
in the contact section which are spaced apart by a distance which is less 
than the diameter of the wire for which the terminal is intended. The 
wire-receiving slot is thus defined by the space between the first and 
second internal surfaces of the plate-like members and a wire can be 
connected to the terminal by aligning the wire with the slot and moving 
the wire laterally of its axis and into the slot. 
In accordance with the further embodiments, the shank portion has first and 
second side edges and comprises a folded section of flat sheet metal 
having a U-shaped cross section. The U-shaped cross section thus has a 
bight and walls extending from the bight. The bight is the first side edge 
and the walls are the first and second plate-like members. In accordance 
with a further embodiment, the bight extends from the contact section 
towards the inner end and does not extend into the contact section. 
In accordance with a further embodiment, the opposed contact surface 
portions extends from a location adjacent to, but spaced from, the free 
end towards the inner. The first and second internal surfaces are recessed 
in the contact section from the opposed contact surface portions so that a 
lead-in portion is provided in the slot to guide the wire into the space 
between the contact surfaces. 
In accordance with a further embodiment, a multicontact electrical 
connector is provided containing contact terminals as described above.

THE DISCLOSED EMBODIMENT 
One form of terminal 2 in accordance with the invention comprises a shank 
portion 4 having an arm 6 extending from an inner end 20 of the shank. The 
arm 6 may take the form of a solder post, for example, or other device for 
connecting the terminal to a complementary terminal or other conductor. 
The shank portion 4 comprises first and second generally rectangular 
plate-like members 8, 10 which have oppositely facing first and second 
major surfaces 12, 14. The shank portion has first and second side edges 
16, 18 which extend from the inner end 20 to the free end 22 thereof. 
As will be explained below, the terminal is produced by folding a flat 
blank so that the first side edge 16, has a fold or bight as shown at 24 
and the plate-like members 8, 10 are the sidewalls which extend from the 
bight. The bight 24 has one end, the lower end in FIG. 1, which is spaced 
from the free end 22 of the terminal. The bight extends from the one end, 
the lower end in FIG. 1, towards the inner end 20 and the portion of the 
shank between the bight and the free end 22 can be considered as a contact 
or conductor-receiving section 26. 
The plate-like members 8, 10 have opposed internal first and second 
surfaces 28, 30 and, in the contact or conductor-receiving section 26, 
these internal surfaces have opposed contact surface sections 32 which are 
on the right-hand side of the terminal as viewed in FIG. 3 so that they 
are adjacent to the bight 24. The significance of this feature will be 
explained below. 
The wire-receiving slot of the terminal is the space between the opposed 
plate-like members in the contact section 26 and a wire can therefore be 
aligned with this slot and moved laterally of its axis into the slot until 
it is between the opposed contact surface sections 32. It will be noted 
that the ends of these contact surfaces 32 are spaced from the free end as 
shown at 34 and the zones 36, 40 which surround the contact surface 
sections 32 are of reduced thickness as shown in FIG. 2. This reduced 
thickness is achieved by simply coining the flat blank as shown in FIG. 5 
prior to folding of the blank and this coining operation results in the 
provision of a wire lead-in section as shown at 36 in FIGS. 2 and 3. The 
distance between the opposed coined surfaces 36 is greater than the 
thickness of the conductor for which the terminal is extended so that the 
conductor can be moved easily into the slot until it encounters the end 34 
of the contact surface sections 32. It is also desirable to swage the ends 
of the plate-like members as shown at 38 to thereby provide tapered 
opposed surfaces at the slot which will guide the wire into the lead-in 
section 36. 
The leading edge 35 of each contact surface section 32 may be made 
relatively sharp if the wire for which the terminal is intended has a 
varnish-type insulation (if it is a magnet or coil wire) so that these 
sharp leading edges will penetrate the varnish-type insulation and 
establish electrical contact. On the other hand, if the wires are provided 
with conventional relatively soft plastic insulation, these leading edges 
35 should be smooth for best results. 
FIG. 5 shows the coined blank 43 from which the terminal of FIGS. 1 to 4 is 
produced. Ordinarily, a succession of blanks will be stamped from a 
continuous strip of conductive sheet metal and the finished terminals will 
be connected to a continuous carrier strip so that the terminals can be 
removed from the strip by an assembly machine and inserted into a 
multicontact connector as described below. The blank after being stamped 
from sheet metal is coined in the areas 36, 40 and swaged as shown at 38. 
Advantageously, dimples are provided as shown at 31 on one side of the 
fold line so that when the blank is folded to produce the terminal of FIG. 
1, the internal surfaces of the plate-like members will be spaced apart by 
a precisely predetermined amount and the width of the slot particularly as 
measured between the contact surface sections 32 is thereby precisely 
controlled. The blank shown is provided with lances 42 by means of which 
it is retained in the connector housing shown in FIG. 6. 
Terminals in accordance with the invention can be produced in a wide range 
of sizes for wires of varying diameters however, as noted above, the 
invention has particular advantages for relatively fine wires. In order to 
illustrate this advantage, the approximate dimensions of a terminal 
intended for an AWG 32 wire having a diameter of about 0.20 mm (0.008 
inches) will be described. 
The terminal is produced from sheet metal having a thickness of about 0.30 
mm (0.012 inches), the material preferably being a phosphor bronze in 
temper 5 or temper 6, that is to say, material which has been work 
hardened by extensive cold rolling. The blank is stamped as shown in FIG. 
5 and the swaging, coining and dimpling operations are carried out to 
produce the dimples 31, the reduced thickness areas 36, 40 and the lead-in 
surfaces 38 adjacent to the free end 22. Thereafter, the blank is folded 
along the fold lines indicated through an angle of 180.degree. until the 
internal surfaces are against or opposed to each other. The closeness of 
the opposed surfaces is controlled during manufacturing by the stamping 
and forming die with the air of the dimples 31 and the distance between 
the opposed internal surfaces can thus be very closely controlled. In the 
finished terminal, the distance between the opposed internal surfaces in 
the coined areas 36, 40 is approximately 0.20 mm (0.008 inches) and the 
spacing between the opposed contact surface sections 32 is approximately 
0.10 mm (0.004 inches). A wire-receiving slot of these dimensions is thus 
properly dimensioned to receive a wire having a diameter of 0.20 mm. It 
will be apparent from the discussion previously presented that it would be 
impossible to produce a slot having this width by conventional stamping 
operations with a punch and die for the reason that the punch would not 
withstand the forces developed. The overall length of the shank portion of 
the terminal described above is about 6.3 mm (0.25 inches) and the width 
is 1.3 mm (0.05 inches). 
A terminal as described above which is manufactured from stock metal having 
a thickness of 0.30 mm is sufficiently robust to withstand the handling to 
which it must be subjected when it is manufactured and assembled to an 
electrical connector. The disclosed form of the terminal is particularly 
strong in that the folded bight portion 24 of the shank is composed of 
material which has been severely work hardened by the folding operation. 
The material itself is preferably in a relatively hard temper and the 
added folding operation to produce the bight further hardens the material 
in the zone 24 of the terminal. It will be noted that the contact surface 
sections 32 are immediately adjacent to and in alignment with the bight 
24. The stresses thus imposed on the terminal during insertion of the wire 
can thus be transmitted to the strongest part of the terminal so that it 
is able to withstand these forces. 
FIG. 6 shows a connector assembly 50 containing terminals in accordance 
with the invention which is intended to be installed on a multiconductor 
cable 48 having a plurality of conductors 44 in side-by-side relationship 
contained in insulating material 46. The connector assembly comprises a 
housing body 52 and a cover 54 which is assembled to the housing 52 
against the conductor-receiving surface 56 thereof. The housing body has a 
plurality of openings 58 (FIG. 7) which receive the shank portions of the 
terminals in a manner such that the contact sections 26 extend beyond the 
surface 56 as shown in FIG. 7. Advantageously, the bight portions of the 
terminals are recessed slightly from the surface 56 as shown. 
The cover 54 has a scalloped surface as shown at 60 for supporting the 
cable and has a plurality of U-shaped openings 62 which receive the 
sections 26 of the terminals. Ribs 66 in these openings are dimensioned to 
be received in the coined zones 40 of the terminals and functions to 
support the conductor immediately adjacent to the wire contacting surface 
sections 32 when the wires are being pushed into the wire-receiving slots. 
Installation of the connector on the cable merely requires that the cable 
be placed on the surface 60 of the cover 54 and the connector body or 
housing 52 be aligned with the cable and assembled to the cover as 
illustrated in FIGS. 7 and 8. During such assembly, the conductors will 
move into the wire-receiving slots and will be received between the 
surface portions 32 which will establish electrical contact. The 
previously described lances 42 serve to retain the terminals in the cover 
54. The cover may be dimensioned so that the openings 62 will support the 
free ends of the plate-like members in the contact section 26 against 
outward flexure. In other words, the contact sections 26 may be 
dimensioned to have an interference fit in the openings 62 so that the 
contact surfaces will be held against the wire by the sidewalls of the 
housing cover. 
Terminals and connectors in accordance with the inventions can be of any 
desired dimensions, however, the principles of the invention offer 
particular advantages where the conductors are contained in a flat cable 
48 and the distance between adjacent conductors 44 is extremely small. 
Cables 48 are now being used which have a center-to-center spacing of 
0.025 inches (0.64 mm). Connectors of the type shown in FIG. 6 must also 
be capable of being installed on the cable 48 without stripping the 
insulation 48 from the cable. It follows that the terminals must be 
sufficiently strong to withstand the forces imposed when they are pushed 
through the cable insulation and when the conductors enter the terminals 
as shown in FIGS. 7 and 8. Terminals in accordance with the present 
invention are extremely robust as noted above by virtue of the fact that 
the bight 24 extends along one of the side edges of the shank portion and 
the contact surfaces 32 are immediately adjacent to the bight portion in 
the preferred embodiment. 
It will be apparent from the foregoing description that an electrical 
terminal has been described which can be produced from stock metal of 
substantial thickness and which nonetheless is capable of being produced 
with extremely narrow wire-receiving slots so that a sturdy and durable 
terminal can be manufactured which is capable of being used with extremely 
fine wires.