Crimp assembly for connecting an optical fiber ribbon cord to a connector

A structure is provided for securing cable, which has internal working fibers and an external outer coat, to a terminal connector. Included in the structure is a crimp body which has an interior axial hole extending therethrough and an exterior surface with at least one groove and at least one ridge. The outer coat of the cable is placed around the exterior surface of the crimp body and a crimp ring is placed around the outer coat and the crimp body. The crimp ring is deformable and has an interior large enough to accommodate the crimp body and the outer coat. The crimp ring is deformable so that it can secure the outer coat between the crimp ring and the crimp body, with the groove and ridge arrangement of the crimp body further holding the outer coat in place.

BACKGROUND OF THE INVENTION 
The present invention relates to a novel method and structure for securing 
a cable to a terminal connector. More particularly, the invention is 
directed to a method and structure for securing a ribbon optical cord to a 
connector. 
Ribbon optical cords are currently widely used for a number of different 
applications in the communications industry. These ribbon optical cords 
have a central fiber, or series of fibers called a ribbon fiber, which are 
carriers of information. Surrounding the ribbon fiber is a protective 
acrylate primary fiber coating, which in turn is followed by a layer of 
strength fibers that are typically made of Kevlar. Surrounding the 
strength fibers is a protective outer coating. The ribbon cords are used 
to carry information of all kinds from one location to another. At each 
location, it is necessary to attach a terminal connector to the ribbon 
cord so that the information can properly be transferred from the ribbon 
fiber into a mating connector or communicating hardware. The ribbon fiber 
must therefore be reliably and sturdily connected to the terminal 
connector so that the information is preserved and properly transferred. 
In the past, the ribbon cord has been attached to the terminal connector 
using an adhesive, such as epoxy. In this past method, a boot is first 
placed over the terminal end of the optical cord, followed by a connecting 
ring and a push spring connector. The outer coating is then removed from 
the end of the optical cord, while preserving the strength fibers lying 
there beneath. The exposed strength fibers are bent rearwardly so that the 
primary fiber coating is fully exposed and accessible. A given length of 
the primary fiber coating is then removed so that a given length of ribbon 
fiber is exposed. Thereafter, a spring and a rubber boot are placed over 
the exposed primary fiber coating. The rubber boot and the exposed ribbon 
fiber are then coupled with a ferrule using an epoxy resin. A connector 
pin-clamp is then attached to the ferrule assembly. The pin-clamp can be 
either male or female, depending on the orientation desired. The ferrule 
assembly is then inserted into and coupled with a connector assembly. 
Thereafter, the spring is inserted into the interior of the connector 
assembly and the push spring is then coupled to the connector assembly. 
It is at this stage that the ribbon cord is secured to the connector 
assembly. In the past method, an adhesive is applied around the outer, 
rearward portion of the push spring. Before the adhesive has cured, the 
exposed strength fibers are spread over the push spring and into the 
adhesive. Thereafter, the connecting ring is inserted over the strength 
fibers and adhesive to surround the rearward end of the push spring. The 
adhesive thus secures the strength fibers of the ribbon cord to the 
connector assembly and the connector ring after the adhesive has set, or 
cured. 
This method of coupling the ribbon cord to the connector suffers from a 
number of disadvantages. First, the process of using an adhesive is time 
consuming, because the ribbon cord will not be secured to the connector 
until the adhesive has had a sufficient amount of time to set. In past 
practice, the preferred epoxy resin used to secure the strength fibers to 
the connector assembly was STYCAST 2057, catalyst 9, available from 
Emerson & Cuming, Inc. One of the problems with this epoxy is that it 
takes about one day for it to cure. Therefore, the strength of the 
connection between the ribbon cord and the connector assembly cannot be 
adequately tested or used for at least one day. 
Second, the adhesive used must be chemically compatible with the connector 
assembly and the materials used in the ribbon cord. The range of 
acceptable adhesives is therefore somewhat diminished. If an adhesive is 
used that is not chemically compatible with the connector and the 
materials of the ribbon optical cable, the strength and reliability of the 
connection therebetween may be of an unacceptable quality. 
Further, in this past method and apparatus, only the strength fibers of the 
ribbon cord are secured to the connector. The protective outer coating is 
not used to connect the ribbon cord to the connector assembly. Thus, the 
strength of the connection is somewhat weaker than it otherwise might be 
if the outer coating could be incorporated into the connection between the 
ribbon cord and the connector. 
An alternative method for coupling the connector to the ribbon cord is to 
crimp a connecting ring, having tabs, around the connector assembly. Once 
crimped, the connecting ring will generally be in the shape of a cardioid. 
In this method, therefore, the strength of the connection is reduced 
because the member that is crimped is equipped with strength reducing 
tabs. These tabs are needed to properly secure the crimped member around 
the ribbon cord and the connector but the crimp has the inherent 
possibility of opening slightly over time. In this method, therefore, the 
need for an adhesive is reduced but the strength of the connection is 
sacrificed. 
Therefore, a method and a device are needed that can be used to reliably 
and sturdily connect a ribbon cord to a terminal connector. Further, a 
method and a device are needed that can be used to connect a ribbon cord 
to a terminal connector without the need for an adhesive. Still further, a 
method and device are needed that can be used to connect a ribbon cord to 
a connector while preserving the strength of the connection over time. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an apparatus that can 
be used to reliably and sturdily connect a ribbon cord to a connector 
without the need for an adhesive so that the assembly process is made less 
cumbersome and time consuming. 
It is another object of this invention to provide an apparatus that can be 
used to connect the outer coating and strength fibers of the ribbon cord 
to the connector so that the quality of the connection is enhanced. 
It is yet another object of this invention to provide an apparatus that can 
be used to connect a ribbon cord to a connector while maintaining the 
strength of the connecting member. 
According to the present invention, the foregoing and other objects are 
obtained by a structure for securing cable, which has internal working 
fibers and an external outer coat, to a terminal connector. The structure 
includes a crimp body which is coupled to the terminal connector and which 
has an interior axial hole extending therethrough and an exterior surface 
with at least one groove and at least one ridge. The outer coat of the 
cable is placed around the exterior surface of the crimp body and a crimp 
ring is placed around the outer coat and the crimp body. The crimp ring 
has an interior large enough to accommodate the crimp body and the outer 
coat. Further, the crimp ring is deformable so that it can secure the 
outer coat between the crimp ring and the crimp body, with the groove and 
ridge arrangement of the crimp body further holding the outer coat in 
place. The deformation of the crimp ring is accomplished with a crimp tool 
which has a pair of mating jaws. The mating jaws are moved together to 
achieve the desired crimp. 
In another embodiment of the present invention, a method is provided that 
can be used to secure a ribbon cord having internal fibers and a 
protective outer coat to a terminal connector. The method includes 
separating the outer coat from the internal fibers and placing the outer 
coat around the exterior surface of a crimp body. A deformable crimp ring 
is then moved into place around the outer coat and the crimp body, with 
the internal fibers being placed through an internal axial hole of the 
crimp body. Thereafter, the crimp ring is compressed with a crimp tool so 
that the outer coat is held securely in place between the crimp ring and 
the crimp body. Additional objects, advantages, and novel features of the 
invention will be set forth in part in the description which follows, and 
in part will become apparent to those skilled in the practice of the 
invention. The objects and advantages of the invention may be realized and 
attained by means of the instrumentalities and combinations particularly 
pointed out in the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A connecting apparatus embodying the principles of this invention is 
broadly designated in the drawings by a reference numeral 10. Connecting 
apparatus at 10 is used to connect a ribbon cord 12 to a multifiber 
connector 14. Ribbon cord 12 is used to carry information from one 
location to another through one or more ribbon fibers 16. Ribbon fibers 16 
are protected by an acrylate primary fiber coating 18. Running along the 
outside of primary coating 18 is a plurality of strength fibers 20, which 
are typically made of Kevlar. A flexible outer coat 22 surrounds strength 
fibers 20 and serves to protect fibers 16, primary coating 18 and strength 
fibers 20 from moisture, dust and other debris. 
In order to properly transfer the information contained and running through 
ribbon fibers 16, it is necessary to connect ribbon cord 12 to multifiber 
connector 14 so that the information can be transferred into another 
ribbon cord 12 for further transportation, or into a piece of 
communications hardware. In the present invention, ribbon fibers 16 are 
connected to a ferrule assembly 24 as previously described and as is well 
known in the art. Ferrule assembly 24 can be of either male or female 
orientation, depending upon the orientation of the mating piece. Ferrule 
assembly 24 is surrounded by and held within a connector housing 26 which 
includes an inner-housing 28, a pair of springs 30, and an outer coupling 
32. Connector housing 26, along with ferrule assembly 24 facilitates 
connecting ribbon fibers 16 to other ribbon fibers or a piece of 
communications hardware. 
Placed behind ferrule assembly 24 within the interior of inner-housing 28 
is a compression spring 34. As can best be seen in FIG. 2, ribbon fibers 
16 extending from ferrule assembly 24 pass through the interior of 
compression spring 34. Disposed immediately behind compression spring 34 
in connecting apparatus 10 is a spring push connector 36 which has a 
connecting body 38 and a crimp body 40 separated by a medial wall 42. 
Spring push connector 36 further has an axial hole (not shown) extending 
through the center thereof which allows passage of ribbon fibers 16 
therethrough. 
Connecting body 38 is used to couple spring push 36 with connector housing 
26 and has an outer surface which includes a pair of sidewalls 44 (only 
one of which is shown in FIG. 2) along with a top wall 46 and a bottom 
wall 48. Side walls 44, top wall 46 and bottom wall 48 cooperate to form 
an outer surface that corresponds to an interior channel within inner 
housing 28. Extending outwardly from top wall 46 and bottom wall 48 are a 
pair of locking tabs 50 which prevent spring push connector 36 from axial 
movement once in place within connector housing 26. To assist locking tabs 
50 in maintaining spring push connector 36 within inner housing 28, an 
adhesive may be applied to the outer surface of connecting body 38 prior 
to placing spring push connector 36 within the interior of inner housing 
28. Spring push connector 36 is placed within inner housing 28 until 
medial wall 42 abuts a rear wall 52 of inner housing 28, as best been in 
FIGS. 2 and 3. Side walls 44 have formed therein a U-shaped relief 54 
which acts to allow top wall 46 and bottom wall 48 to be deflected 
inwardly in amounts sufficient to allow locking tabs 50 to pass over a 
locking cam (not shown) which extends from the interior of inner housing 
28. 
Extending rearwardly away from medial wall 42 is crimp body 40. Crimp body 
40 is preferably generally oval in shape, and has an exterior surface 56. 
Exterior surface 56 has formed therein an alternating series of grooves 58 
and ridges 60 which operate to form a gripping surface as is more fully 
described below. 
An additional component of connecting apparatus 10 is crimp ring 62, which 
is placed around crimp body 40 and which serves to couple ribbon cord 12 
to spring push connector 36 as is more fully discussed below. Crimp ring 
62 has a continuous wall 64 with an inner surface 66 and an outer surface 
68. Prior to crimping, inner surface 66 defines an interior passage of 
generally oval shape, through which crimp body 40 will extend. Further, 
outer surface 68 will also be oval in shape and will be a generally smooth 
surface prior to crimping. The overall length of crimp ring 62 is slightly 
less than the length of crimp body 40 so that crimp body 40 will extend 
slightly beyond crimp ring 62 when crimp ring 62 is placed over crimp body 
40. After crimping, inner surface 66 will cooperate with exterior surface 
56 of crimp body 40 to hold ribbon cord 12 securely in place. As can best 
be seen in FIG. 3, crimp ring 62 is crimped around crimp body 40 and is 
deformed during crimping so that wall 64 has an alternating series of 
indentations 69 formed therein. Thus, after crimping, the interior passage 
defined by inner surface 66 will be smaller so that outer coat 22 and 
strength fibers 20 of ribbon cord 12 are held securely against crimp body 
40. A boot 70 is placed over crimp body 40 and crimp ring 62 and is 
secured in place using an adhesive. Boot 70 protects the connection 
between ribbon cord 12 and spring push connector 36 from dust and debris. 
In use, after ferrule assembly 24 and spring push connector 36 have been 
secured within connector housing 26, outer coat 22 and strength fibers 20 
are placed around the outer surface 56 of crimp body 40. Thereafter, crimp 
ring 62 is placed around outer coat 22 and strength fibers 20. Crimp ring 
62 is then crimped in place as is more fully discussed below. After 
crimping, crimp ring 62 will be deformed such that it has a series of 
alternating extensions and indentations in a location corresponding to top 
wall 48 and bottom wall 50. When crimp ring 62 has been crimped, outer 
coat 22 and strength fibers 20 are held securely in place against crimp 
body 40. The connection thus formed with crimp ring 62 is surrounded with 
boot 70 to protect the connection thereunder. Boot 70 is held in place 
with an adhesive or other suitable attaching means. At this stage, 
connecting apparatus 10 is ready for use. Specifically, it is not 
necessary to wait for an adhesive to cure before the outer coat 22 and 
strength fibers 20 are held in place on crimp body 40. 
In order to properly deform crimp ring 62 about crimp body 40, a crimp tool 
72 is used which acts to compress crimp ring 62 about crimp body 40 and 
thereby hold outer coat 22 and strength fibers 20 securely in place. Crimp 
tool 72 includes a pair of mating jaws 74 which are similar in many 
respects, with like parts of designated by like numerals. Each mating jaw 
74 has a mounting block 76 which is formed by opposing vertical walls 78, 
top wall 80 and end walls 82. Ends walls 82 extend away from top wall 80 
at an acute angle thereto. Disposed through mounting block 76 between 
vertical walls 78 is a mounting bore 84 which is used to couple mounting 
block 76 with the mechanism used to move mating jaws 74. Mounting bore 84 
can thus be used to couple mating jaws 74 to a hand-held instrument or can 
alternatively be used to mount mating jaws 74 within automated machinery. 
Other methods of coupling mating jaws 74 to a crimping mechanism could be 
used and are well known within the art. Mounting block 76 terminates 
opposite top wall 80 at a strength support shoulder 86 which is formed 
integrally therewith. Shoulder 86 separates mounting block 76 from a 
crimping section 88 and adds structural support to mating jaws 74. 
Shoulder 86 extends outwardly from vertical walls 78 but is generally 
flush with end walls 82. 
Crimping section 88 of mating jaws 74 is located on the side of shoulder 86 
opposite mounting block 76 and provides the operative tooling to properly 
compress crimp ring 62 in place about crimp body 40. As best seen in FIG. 
7, each crimping section 88 has formed therein a set of teeth 90 and 
notches 92 which are formed so that the teeth of one crimping section 88 
mate with the notches 92 of the opposite crimping section 88. Teeth 90 and 
notches 92 are used to ensure proper alignment of mating jaws 74 during 
the crimping process as well as providing the necessary deformation of 
crimp ring 62. Each crimping section 88 has a pair of side walls 94 and 
end walls 96 which, along with a bottom surface 98, serve as the outer 
boundaries for crimping section 88. 
Extending inwardly from bottom surface 98 from one side wall 94 to the 
other, in a location slightly offset from center, is a cavity 100 which is 
used to hold and crimp ring 62. Each cavity 100 has the same dimensions, 
so that each is a mirror image of the other. Cavity 100 extends inwardly 
from bottom surface 98 beyond the depth of notches 92 and is defined at is 
lowermost point by a flat 102. Flat 102 transitions via a radius 104 to 
angled walls 106, which preferably extend at an angle of 15 degrees from 
vertical. Further, cavity 100 is sized so that when crimp ring 62 is 
placed therein and mating jaws 74 are brought together, portions of crimp 
ring 62 will be deformed by teeth 90 and notches 92. Thus, teeth 90 and 
notches 92 form indentations 69 in crimp ring 62 as mating jaws 74 are 
brought together. Outer coat 22 and strength fibers 20 of ribbon cord 12 
are thus held securely in place about crimp body 40 by crimp ring 62. 
The method of the present invention involves sliding boot 70, crimp ring 
62, spring push connector 36 and compression spring 34 over the terminal 
end of ribbon cord 12. A ferrule assembly 24 is then constructed and 
coupled with connector housing 26 as is well known in the art. Thereafter, 
spring 34 is placed within connector housing 26, and connector body 38 of 
spring push connector 36 is secured to connector housing 26, such as with 
an adhesive or other suitable attaching means. Each of these previous 
steps is accomplished using methods known to those of skill in the art. 
After spring push 36 is secured to connector housing 26, it is necessary to 
couple ribbon cord 12 to the connector housing. In past methods, this was 
accomplished by adhesively securing only strength fibers 20 to the spring 
push connector. In the method of the present invention, the need for an 
adhesive is eliminated or greatly reduced. In this method, outer coat 22 
and strength fibers 20 are separated from primary coating 18 and ribbon 
fibers 16 on the terminal end of ribbon cord 12 for a distance sufficient 
to extend slightly rearwardly of spring push connector 36. This separation 
is done prior to placing compression spring 34 about ribbon fibers 16, and 
subsequent to placing push spring 34 about ribbon cord 12. After spring 
push connector 36 has been secured to connector housing 26, the separated 
portion of strength fibers 20 and outer coat 22 are moved in place about 
crimp body 40, and crimp ring 62 is then moved in place about strength 
fibers 20 and outer coat 22. Therefore, both strength fibers 20 and outer 
coat 22 lie between crimp body 40 and crimp ring 62. Thereafter, crimp 
ring 62 is placed within cavity 100 of mating jaws 74, and mating jaws 74 
are moved together. As mating jaws 74 are moved together, crimp ring 62 is 
compressed about crimp body 40 and is deformed by cavity 100 and teeth 90 
and notches 92. Subsequent to crimping, wall 64 of crimp ring 62 is 
deformed, as best seen in FIG. 3. Thus, crimp ring 62 cooperates with 
grooves 58 and ridges 60 of crimp body 40 to securely hold outer coat 22 
and strength fibers 20 therebetween. 
As can be understood, when the more malleable crimp ring 62 is crimped 
about the rigid crimp body 40, inner surface 66 of crimp ring 62 is forced 
to undulate into grooves 58 and over ridges 60 of crimp body 40. As a 
result, the strength fiber 20 and outer coat 22 which are disposed between 
crimp body 40 and crimp ring 62 are captured along the undulating 
interface of inner surface 66 of crimp ring 62 and the grooves 58 and 
ridges 60 of the crimp body. This undulating capture of the strength 
fibers and outer coat contributes to increased retention of the strength 
fibers 20 and outer coat 20 which translates to an increase in strain 
relief at the connector. For example, were there to be an unintended axial 
force pulling ribbon cord 12 away from the connector when the connector 
was fixedly mated to a structure, such force would be relieved at the 
undulating capture of strength fibers 20 and outer coat 20 and would not 
be transferred through ribbon fibers 16 thus better protecting the 
interconnection of ribbon fibers in two connectors. 
Additionally, with reference to FIG. 6, by the time flats 102 of jaws 88 
begin acting on the outer surface of crimp ring 62, teeth 90 and notches 
92 have interleaved such that the entire circumference of crimp ring 62 is 
bound. This prevents any "squeezing" of crimp ring radially outward such 
as might occur with other crimping tools that have jaws that do not 
interleave before compressive forces are exerted on a crimp ring. Such 
"squeezing" leaves a point of leverage on the outside of the crimp that 
renders it susceptible to coming open over time. In contrast, the 
interleaved jaws 88 force the crimp ring completely inward causing it to 
actually thicken and become stronger as it radially compresses. 
From the foregoing, it will be seen that this invention is one well adapted 
to attain all the ends and objects hereinabove set forth together with 
other advantages which are obvious and which are inherent to the 
structure. It will be understood that certain features and subcombinations 
are of utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
Since many possible embodiments may be made of the invention without 
departing from the scope thereof, it is to be understood that all matter 
herein set forth or shown in the accompanying drawings is to be 
interpreted as illustrative and not in a limiting sense.