Terminal for establishing electrical contact with a shielded cable

A terminal for establishing electrical contact with the conductive shield of a cable having an aluminized Mylar.RTM. layer surrounded by an outer braid and then a layer of insulation forming a jacket. A ferrule is inserted between the outer braid and the Mylar.RTM. and is locked in place by an insulator displacement device which penetrates the insulation jacket to establish electrical contact with the shield.

BACKGROUND OF THE INVENTION 
This invention relates to an electrical connector for a shielded cable, and 
more particularly to a connector for electrically and mechanically 
terminating such a cable. 
Numerous connectors have been disclosed by the prior art for electrically 
and mechanically terminating shielded cable. For example, U.S. Pat. No. 
3,406,373 discloses an inner-sleeve member having a plurality of barbed 
arms folded back over the sleeve. The barbs are adapted to penetrate a 
Mylar.RTM. coating which has been exposed to stripping away the outer 
insulation. U.S. Pat. No. 3,744,007 discloses a serrated crimping washer 
penetrating the outer insulation sheath of a coaxial cable in order to 
provide electrical connection with a braided outer conductor. U.S. Pat. 
No. 4,261,632 discloses a sleeve member with a tongue containing 
insulation piercing tines. The tongue penetrates the outer jacket of 
insulation and provides electrical connection with outer conductor of a 
coaxial cable. These types of connections often result in imperfect 
electrical connection because there is insufficient mechanical support 
behind the point of contact of the penetrating device. 
SUMMARY OF THE INVENTION 
In accordance with the present invention there is provided a terminal for 
establishing an electrical connection between a metallic shroud 
surrounding an interface bus connector and an insulated cable terminated 
on the connector having a flexible conductive shield beneath the 
insulation. In a particular embodiment, the cable has an aluminized 
Mylar.RTM. layer surrounded by the conductive shield. A ferrule which is 
preferably longitudinally split is inserted between the outer shield and 
the Mylar.RTM. and is locked in place by an insulation displacement device 
which penetrates the insulation jacket to establish an electrical 
connection with the shield. The shroud is retained by an outwardly 
projecting portion of the insulation penetrating device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1-3, a multiconductor shielded cable 10 includes a 
plurality of conductors 12 covered in turn by an aluminized Mylar.RTM. 
layer 14, a flexible conductive shield 16 and an outer layer of insulation 
18. The inner conductors 12 may be either stranded wire or single filament 
whereas the flexible conductive shield 16 is generally in the form of a 
braided screen sheath comprised of wire filaments braided together and 
concentrically arranged around the inner conductors 12 and aluminized 
Mylar.RTM. film 14. Where the inner conductors are to be terminated, the 
cable 10 is prepared by removing the outer insulation 18 and the flexible 
conduction shield 16 from a portion of the cable to leave an exposed end 
of the cable covered by the aluminized Mylar.RTM. film 14. 
The terminal connector for the exposed end of the cable is comprised of a 
ferrule 20 and a "U"-shaped insulation penetration member 30. The ferrule 
is comprised of a metallic sleeve having an outwardly projecting collar 21 
attached to one end. The ferrule has an inner diameter "d" that is 
slightly larger than the diameter D of the exposed end of the cable 10 and 
is split longitudinally at one location 23. The "U"-shaped penetration 
device 30 includes a trio of insulation piercing tines 31, 32 and 33. 
Tines 31, 32 are spaced to define a slot 34 between them, are 
substantially flat and are of a substantial width as compared to the 
thickness so that the tines 31, 32 are not easily movable apart or toward 
one another to change the width of the slot 34. Tine 33 is sharply pointed 
and has sufficient length to pierce insulation layer 18 and contact 
flexible conductive shield 16. 
The terminal connector for the exposed end of cable 10 is installed by 
sliding the ferrule onto the exposed end of the cable and forcing it 
between the aluminized Mylar.RTM. layer 14 and the shield 16. Next the 
"U"-shaped insulation penetration device 30 is pressed on cable 10 a 
specified distance from collar 22 of ferrule 20; the insulation piercing 
tines 31, 32, 33 slice or pierce insulation layer 18 to allow the tines to 
capture the shield 16 in compression and make an electrical contact 
between the shield, the ferrule and the insulation penetration device. 
When the "U"-shaped device 30 is forced over ferrule 20, the sleeve 21 of 
the ferrule which is split is compressed; it provides an additional means 
for storing energy in the system resulting in added reliability of 
contact. The sleeve 21 presents an outward force and the "U"-shaped 
penetration device presents an inward force which results in added 
reliability and contact integrity. 
The cable thus terminated is used with a connector assembly as best shown 
in FIGS. 4 and 5. The assembly consists generally of a wiring block 50 and 
an RF shroud generally designated 40 used to shield the connector assembly 
from extraneous radio frequency transmissions or to prevent such emissions 
from the assembly. 
The connector 50 is assembled by first inserting the wires 12 from the 
cable 10 into the appropriate holes 51 of the wiring block 50b. These may 
be pushed through the block and trimmed to length. The cover 50c is then 
pressed in place. The conductors are assembled on precise centers at this 
stage and are ready for mass termination. The plug 50a and receptacle 50d 
which have tined type terminations to make contact with the wires 12 are 
then pressed onto their respective sides of the wiring block 50b, 50c. 
The RF shroud 40 is assembled around the wiring block 50, the collar or 
ferrule 20 and the insulation penetrating device 30. The two halves 40a 
and 40b of the shroud telescope into one another and device 30 fits into 
recess 41 of shroud 40 contacting the shroud. The shroud is then fastened 
together by means of bolts 42, 43, 44.