Flat cable sealing element

A sealing element is provided for use on insulated flat cables of the type having opposed rounded minor surfaces and opposed substantially flat parallel major surfaces which comprises an elongated body of resilient material having an orifice extending longitudinally within said body. The orifice has a width greater than its height. Opposed involute walls extend within said orifice substantially along the width of the orifice whereby the involute walls stretch and conform to the opposed substantially flat parallel major surfaces of the flat cable when placed thereon, thus providing a secure, watertight interference fit. Depending upon usage, the orifice may extend through the body or terminate within the body. Additionally, it is preferred that sealing rings be formed in the inner wall of the orifice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In underground wiring, common practice in jointing round secondary voltage 
cable watertight is to provide interference fit sealing elements. 
Elastomeric materials, such as EPDM rubber, are commonly used to obtain 
these interference fits. FIGS. 1, 2, and 3 illustrate such useage. FIG. 1 
discloses a typical round insulated cable 11 with an outside diameter "A." 
FIG. 2 discloses a typical interference fit sealing element 13 having an 
inside diameter of "A" minus 20%. FIG. 3 illustrates sealing element 13 in 
place about cable 11. With the dimensions previously discussed, the 
configuration of FIG. 3 provides an interference fit between the cable and 
the sealing element of 20%. 
The sealing element is designed to provide constant annular pressure 
against the cable without taking a permanent set. To provide a greater 
interference fit, the inside diameter of the seal can be decreased. The 
wall thickness of the seal can also be increased to obtain a higher 
annular pressure. 
One typical use of the above type of seal is in an insulated underground 
bus which is used to terminate secondary voltage feeder cable and energize 
service cables. In one specific instance, the cable outlet covers have, at 
one end, six annular sealing rings to seal cables of various diameter. At 
their opposite end, the cable outlet covers provide interference fits with 
cylindrical insulated portions of the bus. 
Another typical use is in submersible splice kits, which include a splice 
connector and a two-piece splice cover. The same annular sealing rings 
provide watertight interference seals to the insulated cable being 
spliced. 
FIG. 4 illustrates a typical flat insulated cable 15 having two conductors 
and a ground. It is obvious that a round sealing element, such as shown in 
FIG. 2, would not be able to seal this cable in a watertight fashion. This 
is true since the round sealing element would not provide an interference 
fit against the flat sections of the cable. 
In order to provide the proper interference fit, that is a seal which would 
provide an interference fit between the cable and a seal of 20%, a seal 
configuration is required with a periphery 20% less than the cable that 
would impart radial pressure to both the radial ends of the cable and to 
the flat sides of the cable. 
FIG. 5 illustrates a seal which will provide the necessary interference 
fit, discussed above, when placed about the flat cable, such as shown in 
FIG. 4. FIG. 6 shows seal 17 in place about cable 15. 
In order to develop radial pressure about the radial ends of the cable, the 
terminal radius R2 of orifice 18 must be smaller than radius R1 of cable 
15, as shown in FIG. 4. Additionally, the centerline dimension, W2 of FIG. 
5, is decreased with respect to W1 in FIG. 4 so as to further increase 
radial pressure. Radii R3, which are the radii for involute inner walls 20 
and 22, intersect radii R2 so as to form the surface configuration as 
shown. 
At assembly, as illustrated in FIG. 6, the radial pressure from radii R3 is 
applied to the flat portions of the cable along the area of W1, as 
indicated in FIG. 4. The radii R2, as previously discussed, provide radial 
pressure about the cable radii R1. Radial pressure is, therefore, applied 
about the entire periphery of the cable. 
Pressure may be increased by increasing the dimensions H1/L1, as indicated 
in FIG. 6, and/or by reducing the periphery of the seal interface with 
respect to the periphery of the cable. Conversely, dimensions H1 and L1 
may be reduced to lessen sealing pressure. The periphery of the sealing 
interface can also be made greater with relationship to the cable 
periphery to reduce pressure. 
As previously discussed, typical applications include street lighting and 
equipment wiring. FIG. 7 illustrates a typical configuration in wiring to 
an instrument transformer or similar control device where internal wiring 
is accomplished with flat cable. Cable 19 issuing from cylindrical cable 
port 21 of housing 23 is to be spliced to flat line cable 25. This is 
accomplished by sliding sealing element 27, including flange 28, which 
includes an orifice having a configuration as described in FIG. 5, and 
housing 29 over flat line cable 25 to provide room to splice the two 
cables. The cables are then spliced with connectors and insulated with 
round splice covers 31. Housing 29 is placed over the splice assembly and 
over cylindrical cable port 21 providing a watertight interference fit at 
that juncture. Sealing element 27 is then assembled to the opposite end of 
housing 29, providing interference fit seals about flat line cable 25 and 
about the internal diameter of housing 29. FIG. 8 is an end view of FIG. 7 
at the flat cable sealing end. 
FIG. 9 illustrates a splice assembly typically used in street lighting. 
Sealing elements 37 and 39 are installed at each end over cables 33 and 
35. The assembly of this unit substantially follows that described 
relative to FIG. 7. FIG. 10 is an end view of FIG. 9 showing sealing 
element 37 in place over flat cable 33. 
FIG. 11 is an illustration of cable cap 45 having an orifice 47, similar to 
the configuration of the orifice of FIG. 5, which is used in sealing 
moisture out of the flat cable end when it is exposed. FIG. 12 is an end 
view of sealing element 45, more clearly showing orifice 47. 
FIGS. 13 and 14 illustrate the use of the sealing element of FIG. 11 with 
the flat cable 49, with FIG. 14 being an end view of sealing element 45 
about cable 49. 
Another use for flat cables is in a service entrance connection. The 
present method for assembling flat cable to a service entrance box 
requires that the installer use particular connectors which include an 
internally threaded bolt-on hub. In practice, a connector is threaded to 
the internal threads of the bolt-on hub. The cable is then assembled 
through the connector and the connector nut is tightened. By tightening 
the nut the neoprene bushing is compressed about the cable, providing a 
watertight seal. 
Using the basic concept of the present invention, as illustrated in FIGS. 
15 and 16, greatly simplifies and reduces the cost of this installation. 
FIG. 15 illustrates a typical flat cable 51 used in such installation. The 
cable includes conductors 53 and 55, ground 57 and insulation 59. 
Referring to FIG. 16, cable sealing element 68, in the form of a bushing 
which includes an orifice similar to that disclosed in FIG. 5, has an 
upper reduced section 69 and a protruding shoulder section 71. This 
bushing is placed over the end of the cable before the cable installation 
is stripped. After cable stripping and attaching the conductors and ground 
as illustrated, the bushing is pressed into hub 65 secured to cover 63 by 
belt 67, effecting a permanent seal. As indicated in FIG. 16, three 
sealing areas are provided, namely, within threads 70, against the bolt-on 
hub by shoulder 71, and against upturned flange 73 of cover 63 for housing 
61. 
The principal advantage in using the sealing elements of the present 
invention for this particular application is that the seal is always 
uniform, and is not dependent on the skill of the installer. The previous 
method used, as discussed above, requires that the connector must be 
tightened all the way to effect a seal. Another advantage is that the 
rubber sealing elements of the present invention weather much better than 
plated steel connectors, which are normally used. A final advantage is 
that the rubber sealing element, or bushing, is less expensive than the 
metalic connectors now in use. 
A further use for flat cables is in converted junction boxes. One such 
assembly is shown in FIGS. 17 and 18. 
A standard octagonal junction box 77 having knockouts for providing 
borehole 83 is shown adapted for retention of standard adapter 79 having a 
threaded portion 80 which mates with locknut 81. Sealing bushing 85 
includes cavity 87 having a dimension so as to provide an interference fit 
about adapter 79. The opposite end of the bushing contains orifice 89 
configured in accordance with FIG. 5 and extending through the bushing to 
cavity 87. 
The assembled structure is shown in FIG. 18. Adapter 79 and bushing 85 are 
passed over cable 91 and secured to junction box 77 by locknut 81. 
The construction shown in FIGS. 17 and 18 replaces conventional Romex metal 
connectors now used with standard octagonal or rectangular boxes. The 
bushing seals the cable and provides an interference fit with the 
unthreaded portion of the adapter. 
FIGS. 19 and 20 illustrate the use of sealing rings 105 in a cable cap 101 
having an orifice 103. Sealing rings 105 increase sealing capability where 
cable insulation has surface irregularities. While this feature is shown 
in a cable cap, it should be understood that this modification equally 
applies to all seal configurations described and discussed hereinabove. 
As will be obvious, the present invention provides a constant pressure 
interference fit which is watertight and may be used in various 
applications where flat cable is now in common use. 
It is to be understood that the above description and drawings are 
illustrative only, since modifications could be made without departing 
from the invention, the scope of which is to be limited only by the 
following claims.