Cable entrance module

Details Cable entrance module Cable entrance module

1999-04-23

2001-05-15

Reichard, Dean A. (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

Single duct conduits

C174S068300

Reexamination Certificate

active

06232554

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cable entrance module, and, in particular, to a cable entrance module which is applied to an optical subscriber-line network unit installed aerially.
FIG.1
roughly shows a communication system to which an optical subscriber-line network unit is applied. This communication system is proposed as a near future system for coping with multimedia use. A feature of this system is that an optical cable extends to a position near to houses.
Telephone stations
10
and
11
are connected by an optical cable
12
. From the telephone station
11
, a multi-conductor trunk-line optical cable
13
extends via branch units
30
while being installed on poles
14
. An aerially installed optical subscriber-line network unit
20
is set aerially outdoors for every ten houses, for example. In the branch unit
30
, a one-conductor drop cable
31
branches off from the trunk-line optical cable
13
, and the drop cable
31
enters the optical subscriber-line network unit
20
. The optical subscriber-line network unit
20
has an arrangement in which, in a box
32
, a light-electricity converter
21
, a multiplexer/demultiplexer
22
, and ten and several subscriber channel units
23
are contained. The extending end of the drop cable
31
is connected to the optical subscriber-line network unit
20
, and, also, a power line
17
is connected to the optical subscriber-line network unit
20
. Power is supplied to the optical subscriber-line network unit
20
through the power line
17
so that the optical subscriber-line network unit
20
may operate. One outside-line metal cable
18
extends from each of the subscriber channel units
23
, and, thus, ten and several outside-line metal cables
18
extend from the optical subscriber-line network unit
20
. Each outside-line metal cable
18
extends to a respective one of houses
15
, and is connected to a communication terminal such as a telephone, a facsimile machine or the like.
In this communication system, because the drop cable
31
extends to the position near to the houses
15
and the length of each of the outside-line metal cables
18
is short, it is possible to transmit a large amount of information in comparison to the conventional case. Further, in addition to voice transmission, image transmission is possible. Furthermore, a digital signal and so forth are transmitted.
In the above-described optical subscriber-line network unit
20
, a drop-cable entrance module
33
is attached to a side plate
32
a
of the box
32
. The drop cable
31
is inserted through the inside of the drop-cable entrance module
33
, and, then, enters the box
32
.
As shown in
FIG. 2A
, the drop cable
31
includes an optical fiber
40
at the center thereof, and piano wires
41
and
42
on both sides thereof. The entirety of the drop cable is covered by a covering portion
43
made of vinyl chloride. Further, notch grooves
44
and
45
are formed in the drop cable
31
on the top and bottom sides facing the optical fiber
40
. The drop cable
31
has an approximately figure-eight-shaped cross section, as shown in the figure. The drop cable
31
enters the box
32
through the drop-cable entrance module
33
, and, then, as shown in
FIG. 1
, is split into two by using the notch grooves
44
and
45
. Then, the optical fiber
40
is exposed, and a terminal treatment, in which the covering portion
43
is cut and removed, and the piano wires
41
and
42
are exposed, is performed. Then, the ends of the piano wires
41
and
42
are fixed to the box
32
by using fixing screws
50
and
51
. The optical fiber
40
is connected to the light-electricity converter
21
by using an optical connector.
The piano wires
41
and
42
are provided for the purpose of receiving a pulling force when the drop cable
31
is pulled and preventing the pulling force from being applied to the optical fiber
40
. The notch grooves
44
and
45
are formed for the purpose of enabling easy splitting of the drop cable
31
into two as mentioned above. The reason why the notch grooves
44
and
45
are formed on the top and bottom sides facing the optical fiber
40
is that the optical fiber
40
is exposed when the drop cable
31
is split into two at the end thereof as mentioned above.
Because the optical subscriber-line network unit
20
is set outdoors, it is demanded, in order for the optical subscriber-line network unit
20
to have a high reliability, that the drop-cable entrance module
33
is sufficiently waterproof so that rain water drops flowing on the drop cable
31
do not enter the optical subscriber-line network unit
20
in a condition in which the drop cable
31
has been inserted through the drop-cable entrance module
33
.
The waterproof structure of the drop-cable entrance module
33
should be such that the cross section of the drop cable
31
is not a circle and has a special shape as mentioned above.
2. Description of the Related Art
FIG. 3A
shows a drop-cable entrance module
60
in the related art. The drop-cable entrance module
60
includes a sleeve
62
made of rubber having a tunnel
61
, and a pressing mechanism (not shown in the figure) which presses the outer circumferential surface of the sleeve
62
as a result of screws being tightened. The cross section of the tunnel
61
has a figure-eight shape corresponding to the cross section of the drop cable
31
. Projections
63
and
64
project inwards from the top and bottom of the tunnel
61
, respectively. The projections
63
and
64
extend along the tunnel
61
. The drop-cable entrance module
60
is attached to the side plate
32
a
of the box
32
of the optical subscriber-line network unit
20
.
The drop cable
31
is inserted through the tunnel
61
of the sleeve
62
as shown in FIG.
3
A. Then, the sleeve
62
is pressed by the pressing mechanism. As a result, as shown in
FIG. 3B
, the inner wall of the tunnel
61
makes contiguous contact with the outer circumferential surface of the drop cable
31
, so that no gap is formed between the inner wall of the tunnel
61
and the outer circumferential surface of the drop cable
31
. Thus, a waterproof structure is formed. Thereby, rain water drops flowing on the drop cable
31
are prevented from entering the optical subscriber-line network unit
20
.
However, there may be a case where, as shown in
FIG. 3C
, the drop cable
31
is located at a position shifted rightward a little from the center of the tunnel
61
. When the pressing mechanism presses the sleeve
62
in this condition, as shown in
FIG. 3D
, spaces
65
may remain between the outer surface of the drop cable
31
and the inner wall of the tunnel
61
. The reason why the spaces
65
remain is that the cross section of the drop cable
31
has the special shape having the notch grooves
44
and
45
, and the notch grooves
44
and
45
are not aligned with the projections
63
and
64
, respectively. In a case where the drop cable
31
is located in a position shifted leftward a little from the center of the tunnel
61
, similar spaces may remain. When spaces remain, a completely waterproof structure cannot be provided.
Thus, the drop-cable entrance module
60
in the related art is problematic in view of reliability.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a cable entrance module in which the above-described problem is solved.
A cable entrance module according to the present invention is provided at a position of equipment at which position a cable enters the equipment from the outside. The cable is inserted through the inside of the cable entrance module. The cable entrance module comprises an entrance-side membrane, an exit-side membrane, and a viscous-matter filling portion, the inside of which portion is filled with viscous matter. The entrance-side membrane has a strength such that the entrance-side membrane is pierced by the extending end of the cable when being pushed by the extending end of the cable, the exit-side membrane has a strength such that the exit

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