Seal for cable splice closure

A seal for use in an optical closure is formed in the general shape of a truncated cone. The seal has an aperture which extends completely through the conical shape portion of the seal and which terminates within a plug located at the larger end of the seal. A sinusoidal shaped slit is formed completely through the seal from the small end of the seal to a small distance away from the large end of the seal. The seal is placed within an angled section of a port within an optical closure and an end cap is screwed into the port thereby forcing the seal further into the angled section. The seal can be used for both sealing ports which receive optical cables and ports which do not receive any cables. For the ports that do receive an optical cable, the plug is removed from the seal and the slit is extended all he way to the rear of the seal. When the optical cable is passed through the slit into the aperture of the seal, portions of the seal on either side of the slit become separated from each other.

FIELD OF THE INVENTION 
This invention relates to a seal and, more particularly to a seal for use 
with an optical cable splice closure. 
BACKGROUND OF THE INVENTION 
A typical optical cable splice closure has a number of ports for receiving 
fiber optic cables. After being passed into a port, a fiber optic cable is 
mechanically secured to the closure, has its outer plastic and metallic 
sheath removed, and has its core tube, which encase the optical fibers, 
split and routed to one or more splice trays inside protective tubes. 
Within the splice trays, the optical fibers are removed from their 
respective protective tubes and are spliced to other fibers. The optical 
splice closure usually can accommodate a number of splice trays, with each 
splice tray holding a number of splices. For protection of the optical 
fibers which are exposed within the closure, the closure generally has a 
number of components for sealing it from the outside environment. 
In a widely used prior art lightguide closure, which will be discussed more 
fully hereinafter, sealing is achieved by means of a grommet disposed 
between the flanges of upper and lower halves of a two part closure shell, 
with the two halves being clamped together. The closure thus formed has 
openings at each end through which the cables are introduced into the 
interior of the closure. Each end of the grommet has inner and outer bored 
blocks adapted to receive and embrace the cables which are anchored in 
cable grips mounted adjacent to the cable seals just inside the closure. 
The placing of each cable within its respective bore is facilitated by 
means of a longitudinal slit within the block over each bore so that the 
bore can be opened up sufficiently to receive the cable or grommet plug 
and, when released, tightly embrace them. In those cases where a bore does 
not receive a cable, it must be independently sealed by means of, for 
example, a solid grommet plug. In addition, where a cable is to be passed 
straight through the closure without splicing, it is sometimes necessary 
to have slits formed in the cable embracing grommet to facilitate locating 
the cable within the inner and outer bored blocks of the grommet. 
The splice closures of the prior art are generally designed to accommodate 
a range of cable diameters, however, they require that the installer or 
splicer carry a corresponding range of grommets, each having different 
size bores, both split and unsplit. The grommets are, themselves, somewhat 
expensive to manufacture because of their generally unique configuration. 
It has been the accepted practice to produce them by casting them in an 
open mold process out of polyurethane, which is a relatively expensive and 
time consuming process. 
SUMMARY OF THE INVENTION 
The present invention, in a preferred embodiment thereof, is a seal for 
providing a seal between a cable and a tapered port in a closure. The seal 
has a conical shaped outer surface, and has a base defining a rear end of 
the seal and a truncated top defining a front end of the seal. An aperture 
extends completely through the seal from the front end to the rear end and 
defines a conically shaped inner surface having a base at the front end of 
the seal and a truncated top near the rear end of the seal. A slit extends 
completely through the seal from the outer surface to the inner surface 
thereof and extends from the front end toward the rear end of the seal. 
When the seal is compressed from the rear end toward the front end of the 
seal, the outer surface of the seal engages the tapered port, the inner 
surface of the seal engages the cable, and portions of the seal on either 
side of the slit are forced together, as will be more fully discussed 
hereinafter. 
Preferably, the seal of the invention is injection molded from a 
thermoplastic elastomer and can seal cables having a range of diameters. 
The slit in the seal has a generally sinusoidal shape along its length 
which assists in the recombination of the seal on either side of the slit 
as the seal is being compressed from the rear end. 
In another aspect of the invention, the seal is formed with a plug on the 
rear end of the seal and has the aperture terminating within the plug. The 
seal formed with the plug can be used to seal any tapered port which does 
not receive any cables. If the tapered port does receive a cable, then the 
plug is removed from the rear end whereby the aperture in the seal extends 
completely through the seal from the front end to the rear end thereof. 
The cable is then passed through the slit into the aperture of the seal. 
Thus, a single seal according to the invention can be used to seal either 
ports that receive cables or ports which do not receive any cables. 
With a seal according to the invention, the installer or splicer can use a 
single seal for a wide range of cable diameters. The seal according to the 
invention can also be used with ports that do not receive any optical 
cables. Consequently, the number of different seals or grommets that the 
installer or splicer must stock can be significantly reduced. 
The principles and features of the present invention will be more readily 
apparent and understood from the following detailed description, read in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
FIG. 1 illustrates an example of the sealing components used with a UCB2 
Universal Lightguide Closure.TM. 1 manufactured by AT&T. The optical 
closure 1 comprises a base 10, a cover 14, a grommet or gasket 12, and 
clamps 16. The grommet 12 is placed on top of the base 10 with side edges 
of the grommet 12 being disposed over side edges of the base 10. When the 
cover 14 and clamps 16 are mounted on top of the base 10 with the grommet 
12 therebetween, the grommet 12 seals the sides of the optical closure 1 
from the outside environment. 
The grommet 12 has an inner block 20 and an outer block 22 disposed at both 
ends and each set of inner and outer blocks 20 and 22 has a pair of 
apertures 19 for collectively defining four ports providing access to the 
interior of the optical closure 1. In order for an optical cable to pass 
into the optical closure 1 through one of the apertures 19, the blocks 20 
and 22 are formed with slits 20a and 22a, respectively, which permit an 
installer or lineman to widen the bores in the blocks sufficiently to 
receive the cable therein. 
Although the optical closure 1 can receive up to four optical cables, the 
optical closure 1 frequently receives less than four cables, such as only 
two cables as shown in FIG. 1. To seal a port which does not receive an 
optical cable, a long grommet plug 18 is inserted into the apertures 19 of 
both the inner and outer blocks 20 and 22 for that port. The grommets 18 
have ridges 18a formed on an outer surface which mate with grooves (not 
shown) in the blocks 20 and 22. When the cover 14 and clamps 16 are 
mounted to the base 10, the grommet 12 is compressed against the long 
grommet plug 18 to seal the port from the outside environment. 
An inner grommet 24 and an outer grommet 26 are used to seal each port that 
does receive an optical cable. As with the long grommet plug 18, the inner 
and outer grommets 24 and 26 have ridges 24a and 26a, respectively, which 
assist in sealing the grommets 24 and 26 to the blocks 20 and 22, 
respectively, when the cover 14 and clamps 16 are secured to the base 10. 
Each grommet 24 or 26 is cylindrically shaped and is bored through the 
center for the passage of an optical cable. The center of each of the 
grommets 24 and 26 is formed with a number of protrusions, similar to an 
O-ring, for contacting an inserted optical cable and for providing a seal 
between the grommet 24 or 26 and the optical cable. The grommets 24 and 26 
therefore seal the ends of the optical closure 1 while permitting the 
passage of optical cables into the closure 1. 
The installer or lineman must have in stock grommets 24 and 26 that are 
formed with slits into the center of the grommets 24 and 26 as well as 
grommets 24 and 26 without any slits. The grommets 24 and 26 with slits 
are necessary since some optical cables have fibers which pass completely 
through the closure 1 without being spliced to another fiber. With these 
cables, the installer or lineman must attach the grommets 24 and 26 to the 
cables by sliding the optical cables through the slits and into the 
centers of the grommets 24 and 26. 
For the cables that have all of their fibers cut for splicing, the grommets 
24 and 26 can be attached to an optical cable by passing the cable through 
the centers of the grommets 24 and 26. It is preferable to use grommets 24 
and 26 which are not formed with slits since this type of grommet provides 
a better seal between the grommet 12 and the optical cable. The installer 
or lineman must therefore maintain a supply of both split grommets 24 and 
26 and grommets 24 and 26 without any splits. 
The optical closure 1 is a "universal" optical closure 1 since it can 
accommodate fiber optic cables having a range of diameters. Since the 
inside diameter of the grommets 24 and 26 and the inner protrusions in the 
grommets 24 and 26 are designed for a specific cable diameter, separate 
sets of grommets 24 and 26 must be manufactured for each diameter of 
optical cable. Thus, in addition to supplying both split and non-split 
grommets 24 and 26, the installer or lineman must further supply grommets 
24 and 26 for each diameter of fiber optic cable. 
With reference no FIGS. 2(A), (B), and (C), a seal 30 according to a 
preferred embodiment of the invention is formed in the general shape of a 
truncated cone. The seal 30 has an outer surface 34, which defines the 
generally conical shape of the seal 30, and has a plug 36 formed at a rear 
end of the seal 30. An aperture 38 extends completely through the conical 
portion of the seal 30 and terminates within the plug 36. An inner surface 
37 of the seal 30 defines a generally conical shaped space within the seal 
30 which is inverted relative to the conical shape of the seal 30. 
The seal 30 also has a slit 32 which extends from the outer surface 34 
completely through to the inner surface 37 of the seal 30. The slit 32 
begins at the front end of the seal 30 and terminates a distance from the 
rear end of the surface 34. The slit 32 is formed in a wavelike pattern 
and generally resembles a sinusoidal waveform. The exact shape of the slit 
32 is not critical to the invention but preferably is a wave pattern 
defining at least one arcuate protrusion and a corresponding arcuate 
depression. 
The seal 30 is injection molded or compression molded formed from a 
thermoplastic elastomer, such as Santoprene.TM.. The use of a 
thermoplastic elastomer renders the seal 30 very resilient whereby the 
seal 30 can be separated along the slit 32. Additionally, the use of a 
thermoplastic elastomer permits the compression of the seal 30 along both 
its length and width. 
FIGS. 3(A), (B), and (C) illustrate the seal 30 within an optical closure 
having outer ports 40 and inner ports 41. Each port 40 or 41 has an angled 
section 42 for receiving one of the seals 30 and a threaded section 44 for 
receiving an end cap 50. While only the bottom halves of the optical 
closure, seal 30, and end cap 50 have been illustrated in FIGS. 3(A), (B), 
and (C), the appearance and functioning of the upper halves of the optical 
closure, seal 30, and end cap 50 should be apparent to one skilled in the 
art and, accordingly, will not be described in any further detail. 
To seal an optical cable, such as cable 58 shown in FIG. 3(B), the plug 36 
of the seal 30 is removed from the seal 30 so that the aperture 38 extends 
completely from the front to the rear of the seal 30. Next, the seal 30 is 
separated along its slit 32 until the slit 32 is extended all the way to 
the rear of the seal 30. The slit 32 may be extended in other ways, such 
as by cutting along the seal 30 from the end of the slit 32 to the rear 
end of the seal 30. With the slit 32 extending completely from the front 
to the rear of the seal 30, the optical cable 58 is passed through the 
slit 32 and into the aperture 38 of the seal 30. 
The seal 30 can accommodate a wide range of cable diameters. For the 
dimensions of the seal 30 shown in FIGS. 2(A), (B), and (C), the seal 30 
can accommodate optical cables having diameters at least in the range of 
0.25 of an inch to 1 inch. Since the diameter of the aperture 38 is 
approximately 0.150 of an inch at the rear end of the seal 30, the rear 
end of the seal 30 cannot extend completely around the optical cable 58. 
Consequently, the seal 30 will be separated along the slit 32 at least 
near the rear end of the seal 30 and the angle of the surface 34 will be 
increased. To better accommodate this increase in angle size, the angle of 
the section 42 is selected to be greater than the angle of the surface 34 
on the seal 30, preferably by about 3 degrees. 
After the optical cable 58 has been passed through the aperture 38 of the 
seal 30, the seal 30 is placed into the port 41 of the optical closure 
front end first so that the rear of the seal 30 is exposed to the outside 
of the optical closure. When the end cap 50 is threaded into the section 
44 of the optical closure, the end 52 of the cap 50 forces the seal 30 
further into the angled section 42. As the seal 30 is forced into the 
angled section 42, the seal 30 is compressed along its length by the end 
cap 50 on one end and the small width of the port 41 on the other end of 
the seal 30. The seal 30 is also compressed across its width since the end 
cap 50 forces the seal 30 into an area having a smaller diameter. The 
diameter at the base of the aperture 38 is larger than the diameter of the 
cable 58 whereby the seal 30 is easily compressed even though the other 
end of seal 30 may be held open by the cable 58. 
The compression of the seal 30 along its length and width causes the seal 
30 to seal the space between the optical closure and the optical cable 58. 
The compression of the seal 30 from the end by the cap 50 forces the 
portions of the seal 30 that had been separated along the slit 32 to 
recombine. The sinusoidal shape of the slit 32 assists in this 
recombination by guiding the protrusions on one side of the seal 30 into 
corresponding depressions on the other side of the seal 30. By closing the 
seal 30 along the slit 32, the seal 30 prevents moisture, dirt, or other 
contaminants from entering the optical closure. 
A second embodiment of a seal 30' is shown in FIGS. 4(A), (B), and (C). The 
seal 30' differs from the seal 30 in that it can accommodate optical 
cables with larger diameters, such as diameters in the range of 0.8 of an 
inch to 1.5 inches. The seal 30', however, is similar to seal 30 in that 
it has a slit 32', an angled outer surface 34', a plug 36', an inner 
surface 37', and an aperture 38'. The seal 30' is received within ports 40 
of the optical closure, which are larger than the ports 41. The operation 
of the seal 30' is apparent from the description of seal 30 and will 
therefore be omitted. 
In order to pass the cable 58 through the cap 50, the cap 50 is formed in 
two halves 50a and 50b which may be separated from each other. A lower 
half 50a is disclosed in FIG. 5(A) while an upper half 50b is shown in 
FIG. 5(B). The two halves 50a and 50b of the cap 50 are joined together by 
inserting the protrusions 54 on half 50a into cavities 56 in the other 
half 50b. Each of the halves 50a and 50b also has apertures 57 so that a 
screwdriver may be used to tighten the assembled cap as it is threaded 
into threaded section 44. As will be apparent to those skilled in the art, 
the two halves 50a and 50b of the cap 52 may be formed in various other 
ways. 
The foregoing has been illustrative of the features and principles of the 
present invention. Various changes or modifications to the invention may 
be apparent to workers in the art without departure from the spirit and 
scope of the invention.