Note: Descriptions are shown in the official language in which they were submitted.
CA 02287772 1999-10-29
HOUSING FOR HIGH-DENSITY
SUBSCRIBER LINE MODULES
S
Background of the Invention
The present invention relates to improvements in high-density subscriber line
repeater cases. Repeater cases have been known for years, and the technology
was well
developed for T1 communication lines. Extensive specifications for 818-/819-
type
repeater cases have been promulgated by AT&T describing the type of cases
involved.
These cases are designed to hold sensitive telecommunications equipment in
relatively
unfavorable environments. In particular, they are designed for installation in
manholes
or on telephone poles exposed to the weather. Accordingly, in order to protect
the
contents, the housings of the cases provide environmental protection and seal
the
contents from attack by environmental elements such as water and the like.
Recently, the repeater cases that were originally designed to hold T1 line
cards
have been used to hold high-density subscriber line modules. The high-density
subscriber line modules are somewhat larger than Tl modules, resulting in only
every
other one of the slots provided in the Tl case being used for the high-density
subscriber
line ("HDSL") modules.
The HDSL modules work well in the T1 repeater cases, except that it has been
found that the modules prematurely fail due to excessive heat buildup.
Premature failure
adds considerably to the cost in having to replace the modules: both from the
replacement cost of the modules themselves and the labor required to gain
access into the
casing. Furthermore, the reliability of the HDSL modules reduces dramatically
with
increases in heat buildup. Accordingly, there is a need in the art for a
solution to the heat
buildup problem in HDSL cases.
CA 02287772 1999-10-29
The inventor has previously addressed this problem in an invention described
in
U.S. Patent application Serial No. 08/909,242 filed August 1 l, 1997, the
entire
disclosure which is incorporated herein by reference. However, there have
remained
problems of installation of certain configurations of HDSL modules.
Summary of the Invention
The present invention fulfills this need in the art by providing a repeater
case for
HDSL subscriber lines including a repeater base, a repeater case housing
Forming a
sealed enclosure with the repeater base, and a module frame in tile repeater
case
housing. The module frame has a plurality of through-extending module slots
formed
by a plurality of interior walls, and each module slot configured to receive a
grooveless
high-density subscriber line module. The interior walls are configured to make
thermally conductive contact with the respective HDSL modules when the modules
are
installed into the frame. The HDSL modules are cooled through the thermal
conductivity with the interior walls of the module frame, as well as by the
convection of
cooling air.
In the preferred embodiment, the module frame is comprised of a fiberglass
composite integrally molded into the repeater case housing, which is also made
of a
fiberglass composite. The module frame may be separable from the repeater case
housing and be preferably formed of a material having the thermal conduction
properties of a metal.
An electromagnetic interference (EMI) coating may be applied to the interior
walls of the module frame enhancing the thermal conductivity of the contact
between
the HDSL module and the module frame. Alternatively, another thermally
conductive
contact could be enhanced through the application of a thermally conductive
coating
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CA 02287772 1999-10-29
applied to the interior walls of the module frame. Furthermore, the HDSL
module is
typically without a groove on its sides.
The invention also provides a method for dissipating thermal energy from the
HDSL modules, including opening a repeater case, installing a high-density
subscription
5 line module without side grooves into a slot defined by certain of interior
walls of a
module frame that is integrally molded into the repeater case such that the
high-density
subscription line module makes thermally conductive contact with certain of
interior
walls of the module frame, and closing the repeater case.
10 Brief Description of the Drawings
The invention will be better understood after a reading of the Detailed
Description of the Preferred Embodiment and a review of the drawings in which:
FIGURE 1 is a horizontal sectional view of a repeater case housing according
to
a preferred embodiment of the invention;
15 FIGURE 2 is a side perspective view of a high-density subscriber line
repeater
case according to a preferred embodiment of the invention;
FIGURE 3 is a sectional view of the case in Figure 2;
FIGURE 4 is a sectional view of the case of Figure 2, taken along lines III-
III and
looking in the direction of the arrows; and
20 FIGURE 5 is a sectional view like the view of Figure 1 for another
embodiment
of the invention.
Detailed Description of the Preferred Embodiment
Figure 1 shows a repeater case which has been modified to accommodate certain
25 designs of HDSL modules. To do so, the T1 repeater housings have been
adapted to
allow the insertion of HDSL modules that have grooves.
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CA 02287772 1999-10-29
In my prior application, Serial No. 08/909,242 referred to above, I disclosed
a
modification to printed circuit boards that support connectors to receive HDSL
modules.
The modules useable with that invention fit into a conventionally-modified
repeater case,
configured to receive the modules that have grooves in their sides. Examples
of these
5 modules are the HDU 439 Hi Gain Doubler manufactured by Pairgain and the
HRX819
HDSL Repeater made by ADC.
However, modules identified as HDSL Range Extender, model No. 1244044L1
made by Adtran, are configured differently. They do not have grooves in their
sides, and
do not fit into the repeater case as configured for the Pairgain and ADC
modules.
10 Referring to Figure 2, a repeater case 10 adapted from a T1 repeater case
of
AT&T styles 818-819 is shown. Conventional details of those cases are known to
those
of ordinary skill in the art and will not, for brevity, be expounded upon. The
repeater
housing 10 includes a molded repeater base 12 and a repeater case housing 14
having
cover portions 16 and 18. The base 12 and housing 14 are made of a fiberglass
15 composite. The cover portions 16 and 18 are held to the housing 14 with
torque bolts
20. The volume inside the cover portions 16 and 18 is generally empty to serve
as a
heat dissipating plenum. Between the base 12 and housing 14, and housing 14
and
covers 16 and 18 are gaskets 30 and 32, not visible in Figure 2, but seen in
Figure 3.
The base 12, repeater case housing 14 and its covers 16 and 18 together forth
a sealed
20 enclosure that can contain a pressurized atmosphere. The pressurized
atmosphere can
be admitted through conventional valve arrangements in the base 12, such as
pressure
relief valve 26 and air bypass valve 24. The base 12 is provided with mounting
brackets
28 to permit mounting of the casing 10 in a desired location, typically in a
manhole or
on a pole, but any suitable mounting may suffice. A stub cable 22 provides a
cable inlet
25 into the base 12 for telecommunication lines.
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The repeater case need not be configured like .AT&T repeater cases, but can be
provided in a number of shapes and sizes suitable to protect the pertinent
number of
HDSL cards to be contained. For example, the case can be configured to hold 12
cards
as seen in Figure 1, or reduced in size to hold 6 cards, with a configuration
as shown in
5 Figure 5. Other variations are also encompassed by the invention.
Referring to Figure 3, the stub cable 22 can be seen as dividing into a
plurality of
individual conductors 23. The conductors 23 pass through an opening in a
Plexiglas
acrylic plastic barrier 34 and are hard wired to the bottoms of PC boards 36.
At the top
of the PC boards 36 are mounted electrical connectors 38 suitable for
receiving HDSL
10 modules 40. The PC boards 36 are mounted to the inside of housing 14 and
thus
support the connectors 38 and modules 40. The HDSL modules 40 are vertically
inserted into the slots 50 defined by the walls 60 of the module frame 35 in
the point of
view of Figure 3. Other orientations may also be used. As can be seen, each of
the
modules 40 contacts one of the walls 52, but not others. The heat from the
modules can
15 thus be dissipated by conduction to the wall 52 and convection through the
air passing
over the modules and the walls.
Referring to Figure 4, the locations of the HDSL modules 40 in slots 50 within
the housing can be seen. The slots 50 in the module frame 35 have been widened
and
reconfigured to provide for the easy insertion of a grooveless HDSL module 40
into the
20 slots 50, while maintaining thermally conductive contact between the
grooveless HDSL
modules 40 and the interior walls 60 of the module frame 35. Preferably, the
module
frame 35 is integrally molded into the repeater case 10. However, it can also
be
provided as a separate item, perhaps of a metal like aluminum. As can be seen,
the
walls 60 are made thicker than the other walls 62 inside the case, to increase
their heat
25 capacity and thermal conductivity.
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When inserted into a conventional T1 casing, the HDSL modules 40 experience
premature failure due to overheating of the module. The inventor has found
that
cooling to substantially decrease the temperature of the HDSL module 40,
thereby
reducing the premature failure rate, may be obtained through the enhancement
of the
5 thermally conductive contact between the grooveless HDSL modules 40 and the
interior
walls 60 of the module frame 35. This thermally conductive contact is enhanced
by an
EMI coating on the surface of the interior walls 60 of the module frame 35,
and onto the
module frame itself 35. Alternatively, any suitable thermally conductive
coating may
be used to increase the conductivity of the thermal contact between the
grooveless
10 HDSL module 40 and the interior walls 60 of the module frame 35. The module
frame
60 may be made of any suitable material, but preferably has the thermal
conductive
properties of a metal. In addition, the separation of the PC board into
smaller pieces and
the provision of holes in the barrier sheet 34 adds to the cooling effect, as
noted above.
The modified case in the present invention is specifically configured to
receive
15 and maintain thermal and electrical connection with HDSL modules, providing
commercial savings in both initial fabrication and on-site repairs.
Those of ordinary skill in the art will appreciate that the invention can be
carried
out in other forms differing from as specifically outlined herein yet still
fall within the
scope of the invention, and the claims are to be read as covering such
embodiments.
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