Note: Descriptions are shown in the official language in which they were submitted.
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MULTI-WIRE TERMINAL BLOCR EMPLOYING
REMOVABhE SURGE PROTECTOR
BACKGROUND
1. Field of the Invention
The present invention relates to telecommunications
terminal blocks such as terminal bloclcs for connecting
telephone service wires to telephone exchange distribution
cables. More particularly, the present invention relates to
providing electrical surge protection for telecommunications
terminal blocks.
2. Description of Related Art
Telecommunications terminal blacks are used to provide
convenient electrical connections between telephone customer
service wires, or drop wires, (the "service" side) and
telephone exchange distribution cables (the "exchange" side).
Such terminal blocks typically connect up to 50 distribution
cable wire pairs on the exchange side, which may have several
thousand wire pairs, to up to 50 corresponding service wire
pairs on the service side. Terminal blocl~s generally are
configured as standard, multi-wire units which terminate
either 3, 5, 10, 12, 15, 25 or 50 wire pairs.
The exchange side of the terminal block is connected to
the exchange wires of the distribution cable through a stub
cable. One end of the stub cable is typically connected to
the exchange side of the terminal block within the terminal
block. The other end of the stub cable is connected to
selected wire pairs from the distribution cable. The
permanent connection between the stub cable and the exchange
side of the terminal block may be potted or provided within a
chamber which seals the exchange side from the environment and
provides a physically robust connection to withstand the
~ recurring installing and removing of connections on the
service side.
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The service side of a terminal block is used to removably
connect service wires to the distribution cable, through the
permanent connection for the terminal block, so as to allow
later disconnection and reconnection. Service wire pairs are '
typically connected to the terminal block through some type of
terminal which is easy to connect and disconnect on-site such
as a simple binding post where a stripped service wire is
connected to the binding post and then secured with some type
of cap. Another common type of terminal is an insulation
displacement terminal where the service wire need not be bared
prior to the connection to the terminal block and the
insulation is severed through a blade or other sharp surface
as the service wire is secured to the terminal. Again, in the
insulation displacement type of terminal, some type of cap is
typically employed to secure the service wire in place.
While the caps typically employed in the binding post or
insulation displacement type terminals provide some protection
from the environment, nonetheless, moisture, pollutants,
chemicals, dust and even insects may reach the terminal
connection resulting in corrosion or other degradation of the
contact. This problem is exacerbated by the fact that in
addition to the traditional aerial location of such terminal
blocks, underground and even underwater terminal block
locations are more and more frequently required for telephone
distribution applications. Accordingly, efforts have been
made to better insulate the terminal in the terminal block
from the environment to prevent such degradation. One such
approach has been to use a variety of insulating mediums, such
as greases or gels to surround the terminal where the
electrical connection is made.
Protecting telecommunications equipment against current '
and voltage surges is well known. Conventionally, the
protection systems have been designed to resist major surges,
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e. g. due to lightning strikes or accidental connection to high
voltage sources. Typically, protection provided for
telecommunications lines is comparatively large and unwieldy,
and therefore provided as a stand-alone package which is
installed in concert with the lines to be protected. Due to
their size, many of these systems are limited to protecting
individual lines in areas without space restrictions such as
telephone central offices or corporate offices which have
adequate room to house individual protection for each line.
Protection systems in this environment typically used gas
tubes and, more recently, solid state devices to provide
protection.
Increasingly, telecommunications terminal blocks connect
service applications having sensitive electronic equipment,
such as computers, directly to the telecommunication lines.
As a result, protection against surges smaller than lightning
strikes is needed. Such smaller surges may occur virtually
anywhere along a system and hence more individualized
protection for each line is needed.
Terminal blocks are available which provide protection in
addition to terminating service wires to exchange wires. A
prior art telecommunications terminal block, of the binding
post variety, provides protection by providing a substantially
larger terminal block which includes separate protection
circuits. Each binding post which is used for service wire
connections is connected to a corresponding screw-in type
protector secured within a threaded protection retainer
adapted to receive the screw-in protector. A protector may be
added as needed to provide protection to a particular line or
to permit replacement of a protector.
The prior art terminal block, as described above, is
larger than a typical terminal block because it must provide
the required room for the protection circuits. Moreover, as
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a binding post type terminal block, limited protection is
provided against the environment. Due to the substantial
space required and the limited protection against the
environment, this prior art protected terminal block may be
inadequate for installations where exposure to the environment
can be expected or where terminal block space is limited.
Terminal blocks undergo extensive development and field
testing prior to use in the field to ensure a particular
design is capable of withstanding the difficult environmental
and operational challenges inherent in terminal block use. As
a result, users tend to be faithful to terminal block designs
which have proven themselves rugged and reliable over time.
With the advent of an increasing need for protection in
terminal blocks, it would be desirable to be able to add
protection using existing terminal block designs without
requiring extensive redesign. Extensive redesign requires
additional testing, new tooling and, in the mind of the user,
could call into question the terminal block's environmental or
operational integrity.
Another issue which is raised in providing protection is
related to how often line protection is needed. In some
applications every line connected to a particular terminal
block may need to be protected. Protecting a specific line
can be costly, however, due to the components involved in
providing protection. Therefore, in some cases a particular
user may decide that certain lines do not require protection
or are not worth the cost of protection in view of the
probability that a voltage surge may occur. As a result, it
is desirable that a protected terminal block be provided in
which the user has the option to determine which lines may
need protection and add protection to those lines. Further,
it is desirable to permit the user to either add or remove the
protection, as the used of the lines involved changes. '
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For the foregoing reasons, there is a need for an
improved telecommunications terminal block having protection
against electrical surges.
5 SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and
method that satisfies the above noted needs.
In accordance with a preferred embodiment, the protected
terminal block in accordance with the present invention
comprises a housing having a test port, an access hole for
allowing a wire to be inserted into the housing, and an
electrical contact element having a test lead, the electrical
contact element configured in the housing and conductively
connected to an exchange wire. The test port provides access
to the test lead from outside the housing. The present
invention includes a means configured within the housing for
electrically connecting a service wire to a contact element.
A ground contact and a receptacle are provided which are
secured to the housing. The receptacle is attached to the
housing adjacent a test port. The present invention also
includes means, removably mounted in the receptacle and
extending into the test port, for protecting a selected
electrically conductive path. The means for protecting is
connected to the ground contact and the test lead.
The receptacle of the present invention may be provided
as a protection module retainer. The protection module
retainer is secured to a side of the housing proximate the
test ports to form a plurality of retaining cups adapted to
receive the protection module. The means for protecting a
selected electrically conductive path may be provided as a
protection module which includes a protector conductively
connected to a protection module ground connector and a pair
of terminal block contact elements . The protection module may
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employ any of the protectors known in the art including a gas
discharge tube protector; a solid state protector; or a hybrid '
solid state and gas discharge tube protector, depending on the
specific equipment to be protected.
The present invention also includes a ground contact
secured to the housing. In a preferred embodiment the ground
contact may be provided as a grounding strip conductively
secured to ground and retained between the protection module
retainer and the housing proximate the test ports, the
grounding strip having integrally formed therein a plurality
of ground connectors.
When inserted into a retaining cup, the protection module
ground connector is conductively connected to the ground
contact, providing a path to ground for the protector. The
terminal block contact elements are inserted into a pair of
test ports, providing a connection between a corresponding
pair of test leads and the protector. Therefore, when
installed in a retaining cup, a protector provides surge
protection to a pair of conductive paths through the
connection of the test leads in the test ports. The retainer
ensures the protection module is secured in place and properly
aligned with the ground connectors of the grounding strip.
The protection module may be removed if worn out or exposed to
excessive voltage surge and protection modules may be used
sparingly to save money by only protecting conductive paths
where necessary.
In another embodiment, the present invention may further
comprise a chamber within the housing and the means for
electrically connecting a service wire to a contact element
comprises a wire carrier member configured in the housing, the
wire carrier member having an opening for receiving a wire
inserted through the access hole and being movable within the
housing so as to move a service wire engaged thereby into
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contact with the electrical contact element to form an
electrically conductive path; and an actuator mechanism,
coupled to the wire carrier member and adapted to move the
wire carrier member within the housing and relative to the
actuator mechanism in a manner such that the actuator
mechanism does not change its degree of entry into the
housing. Each electrical contact element may be provided as
a metal element configured outside the chamber and having a
test lead extending into the test port, and a pair of slotted
insulation cutting blades extending into the chamber toward
the wire carrier member.
In another aspect, the present invention provides a
method for adding protection to a terminal block. The method
is adapted for use with a terminal block having a housing
having a plurality of separate chambers, a plurality of holes
for allowing service wire pairs to be inserted into the
chambers, and a test port having a test lead connected to the
conductive path between the service wire and th.e exchange
wire. In a preferred embodiment, the method for protecting a
terminal block comprises securing a ground contact to the side
of the housing of the terminal block proximate the test ports
of the terminal block. A protection module retainer is
secured to a side of the housing proximate the test ports to
form a plurality of retaining cups adapted to removably
receive a protection module. Preferably, the ground contact
may be retained between the protection module retainer and the
housing. A protection module having a protector with a
terminal block contact element and a protection module ground
connector is inserted within a selected retaining cup
corresponding to a selected electrically conductive path to
be
protected, so as to form an electrically conductive connection
between the terminal block contact element and the test lead,
and to form an electrically conductive connection between the
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protection module ground connector and the ground contact.
In accordance with an alternate embodiment, the protected
multi-wire terminal block in accordance with the present
invention comprises a housing having a plurality of separate °
chambers and a plurality of access holes for allowing service
wire pairs to be inserted into the chambers. A plurality of
electrical contact elements are respectively configured in
each of the plurality of separate chambers and conductively
connected to an exchange wire. A means for electrically
connecting each respective service wire to an electrical
contact element is configured within the housing and a ground
contact is secured to the housing. A plurality of receptacles
is attached to the housing and a means, removably mounted in
a selected receptacle and conductively connected to said
ground contact and a selected contact element, is provided for
electrical surge protection, wherein a protected electrical
path is provided between said service wire, said selected
electrical contact element and said exchange wire.
In an alternate embodiment, the electrical contact
element has an insulation displacement connector, and the
means for electrically connecting a service wire to a contact
element comprises a wire carrier member configured in the
chamber, the wire carrier member having an opening for
receiving a wire inserted through the access hole and being
movable within the chamber so as to move a service wire
engaged thereby into contact with the insulation displacement
connector to form an electrically conductive path; and an
actuator mechanism, coupled to the wire carrier member and
adapted to move the wire carrier member within the chamber and
relative to the actuator mechanism in a manner such that the
actuator mechanism does not change its degree of entry into
the chamber.
A more complete understanding of the present invention
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will be afforded to those of ordinary skill in the art, as
" well as a realization of additional advantages and objects
thereof, by a consideration of the following detailed
" description of the preferred embodiment. Reference will be
made to the appended sheets of drawings which will first be
described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a first perspective view of a preferred
embodiment of the terminal block of the present invention
showing a detached protection module.
Fig. 2 is a second perspective view of a preferred
embodiment of the terminal block of the present invention
showing an exploded view of the protection module retainer of
the present invention.
Fig. 3 is a side view taken along line 3-3 of Fig. 2
showing a cross-section of a preferred embodiment of the
terminal block of the present invention before the service
wires are connected to the IDC connectors.
Fig. 4 is a the same view as in Fig. 3 showing a cross-
section of a preferred embodiment of the terminal block of the
present invention, but after the service wires are connected
to the IDC connectors.
Fig. 5 is an exploded view of the basic components of the
protection module of the present invention.
Fig. 6 is a cross-section of a preferred embodiment of
the terminal block of the present invention with the
protection module installed in the terminal block.
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DETAILED DESCRIPTION
A detailed description of the present invention will now
be presented in conjunction with the embodiment of the present
invention illustrated in Figs. 1-6, wherein like reference
5 numbers refer to like elements. While the embodiment
illustrated in Figs. 1-6 is a preferred embodiment, it is to
be understood that the present invention is in no way limited
to the embodiment shown in the drawings.
A surge protected telecommunications terminal block in
10 accordance with a preferred embodiment of the present
invention is shown in Figs. 1 and 2. Referring to Fig. 1 a
first perspective view of a telecommunications terminal block
is illustrated showing a single detached protection module 100
for ease of illustration. Any number of protection modules
100 may be employed, up to the total number of connections of
the terminal block, allowing flexibility for the specific
application.
Prior to describing the protection system a preferred
embodiment of the unprotected terminal block will first be
discussed. Any of a variety of other terminal block designs
may be equally employed however. As illustrated, the terminal
block employs an elongated housing 10 having a plurality of
wire pair openings 12 along a front surface thereof. The
housing 1o is composed of a dielectric material, suitable for
manufacture in the desired shape. For example, any one of
several commercially available thermoplastic resins may be
readily employed due to their relatively low cost and ease of
manufacture. Other dielectric materials may be also employed,
however.
As shown in Fig. 1, the wire pair openings 12 are spaced
apart along the length direction of the housing 10 and, as
will be discussed in more detail below, provide access to
service wires into isolated internal chambers within the '
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housing 10. The number of pairs of the wire openings 12 thus
corresponds to the number of internal chambers and will vary
with the specific application of the terminal block. In
' conventional U.S. telecommunications applications for
providing service wire drop connections to telephone
distribution cables, 2 to 50 pairs of service wires are
typically connected by a single terminal block. Other
applications may require different numbers of wire pairs,
however. Also, for other types of applications, a single wire
opening instead of a pair of openings 12 may be employed for
each chamber, or additional wire openings could be provided
into each chamber if a need arose in a specific application.
Accordingly, the configuration of openings and their spacing
along the housing l0 is an illustrative embodiment only and
may be varied with the specific application as needed.
Still referring to Fig. 1, arrayed along the top of the
housing l0 are a series of terminal actuators 14 equal in
number to the number of chambers contained within the housing
10 and respectively positioned over each such isolated
chamber. Shown in Fig. 1 are the top portions of terminal
actuators 14 and, as will be discussed in more detail below,
the remainder of each actuator extends through the housing 10
into each respective chamber. The actuators 14 are inserted
into the interior of the housing 10 through matching openings
16 in the housing 10. Terminal actuators 14 are preferably
made of a dielectric material which may be the same as the
housing 10. The top of the terminal actuator 14 preferably
has a shape which may be readily engaged and turned by a hand
held wrench or other implement. Alternatively, actuator 14
may be adapted to be grasped and turned by a user of the
terminal block. Turning the actuator a fixed amount,
preferably indicated by visual markings on the housing and
actuator, effects the connection of the service wires to the
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stub cable in a manner to be discussed in more detail below.
As further illustrated in Figs. 1 and 2, the housing 10
also has a pair of test ports 18 for each internal chamber.
These test ports 18 provide ready access to test leads (not '
shown) which are conductively connected to the terminations
located within the housing 10. Thus the test ports 18 permit
testing of the conductive path formed by the termination of
the service wires and the exchange wires without opening the
housing 10 or disconnecting the service wires.
A pair of housing bosses 154 are provided on the external
side of the housing 10 proximate the test ports 18. The
housing bosses 154 may be provided as raised cylindrical
elements integrally formed with the housing 10 and formed of
the same material as the housing 10. The housing bosses 154
are also adapted to receive the bolts 152 which are used to
secure the protection module retainer 140 to the side of the
terminal block housing 10. The term "bolt" is used herein in
a broad sense to include any female/male connector where some
turning motion is involved, and includes screws and cams.
The housing bosses 154 ensure proper alignment of the
grounding strip 150 and the elements secured thereto, as will
be described further below.
Surge protection for a telecommunications terminal block
in accordance with a preferred embodiment of the present
invention is provided with an add-on protection module 100, a
protection module retainer 140 and a grounding strip 150.
The grounding strip 150 is provided as an electrically
conductive bar. The grounding strip 150 may be manufactured
from steel or aluminum or any other suitably conductive
material. The grounding strip 150 is retained proximate the
housing bosses 154 along the side of the housing 10 by
securing the grounding strip between the protection module
retainer 140 and the side of the housing 10. Preferably, the
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grounding strip includes semi-circular cut-outs which permit
the grounding strip to rest on top of the housing bosses 154.
At least one point of the grounding strip 150 is attached to
ground, using an electrically conductive connection, through
a grounding cable 156 which may be provided as a wire mesh
cable or other electrically conductive cable as is known in
the art to conductively connect telecommunications terminal
blocks to ground upon installation.
The grounding strip 150 includes a series of ground
connectors 158. Each ground connector 158 may be provided as
a conductor, integrally formed with the grounding strip 150,
which extends as a conductive loop perpendicularly from the
grounding strip to permit a connection with a protection
module ground connector 160 provided by the protection module
100 as will be described further below.
In the alternative the grounding strip 150 may be molded
in place within the terminal block wherein each ground
connector 158 protrudes from the housing 10 to permit each
ground connector 158 to connect with each protection module
ground connector 160.
A protection module retainer 140 is provided to secure
the protection module 100 to the housing 10 proximate the test
ports 18. The protection module retainer 140 is composed of
a dielectric material, suitable for manufacture in the desired
shape. For example, any one of several commercially available
thermoplastic resins may be readily employed due to their
relatively low cost and ease of manufacture. The protection
module retainer 140 is provided. with a series of retaining
cups 142. Each retaining cup may be integrally formed with
the protection module retainer 140 to form three horizontal
walls. The side of the housing 10 provides a fourth wall,
forming a four-walled cup, once the protection module retainer
has been secured to the side of the housing 10. In order to
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provide a form-fit to the side of the housing 10, the
protection module retainer 140 is provided with a longitudinal '
cut-out 146. The longitudinal cut-out 146 is formed to retain
the ground strip 150 between the outer wall of the housing 10
proximate the test ports 18 and the cut-out of the retainer
142.
In order to properly align the protection module retainer
140 and secure the protection module retainer to the housing
10, the protection module retainer may be provided with bolt
through holes formed in bosses. The bosses of the protection
module retainer 140 are adapted to receive the housing bosses
154 during installation. Similarly, the ground strip 150 is
adapted to be aligned with the housing bosses 154. The bosses
of the protection module retainer 140 are secured to the
housing bosses 154 by bolts 152. During installation of the
protection module retainer 140, the ground strip 150 is
aligned by the housing bosses 154 and retained between the
protection module retainer 140 and the housing l0.
In the alternative, the protection module retainer may be
integrally formed with the housing 10 and ground strip 150
during manufacture.
Once secured to the housing 10, each retaining cup 142 is
adapted to receive a protection module 100 in a friction fit
such that a protection module 100 may be easily inserted or
removed therefrom. Upon insertion, the retaining cup 142
provides support for the protection module 100. The housing
bosses 154 and the retainer mounting bosses 148 provide a
substantial mass to support the retainer 140 on the side of
the housing 10 during protection module 100 insertion and
removal. In addition, through the mounting bosses, the
retainer 14o ensures the protection module 100 is properly
aligned with the test ports 18 and the ground connector 158 of
the grounding strip 150. The friction fit provided by the '
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retaining cup 142 securely retains a protection module 100
against the dynamic environment where telecommunications
terminal blocks are typically employed.
The protection module 100 is provided with a protection
5 module ground connector 160 and terminal block contact
elements 110 which provide a conductive path between each test
port 18 and the protection module 100 as will be described
further below.
Referring to Figs. 3 and 4, a partially broken away
10 cross-sectional view taken along lines 3-3 in Fig. 2 is shown
illustrating the interior of a single chamber of the terminal
block. Since telephone lines employ pairs of conductors, the
terminal block will in general have one or more pairs of
contacts, etc. In the following discussion, however,
15 connection of single wires will be referred to for simplicity.
As illustrated, each internal chamber 22 is preferably
integrally formed with the tops and sides of the housing 10.
The opening 16 which receives the terminal actuator 14 and the
wire access slot 12 thus provides direct access into the
chamber 22 from outside the housing 10. Positioned within
each chamber 22 and threadedly engaged with the terminal
actuator 14 is a wire carrier member 24. More particularly,
the carrier member 24 has a threaded opening 26 in the top end
thereof for receiving the matching size threaded end of
terminal actuator 14. Wire carrier member 24 also has a wire
receiving opening 28 for receiving a service wire inserted
into the chamber through the wire access slot 12. The wire
access opening 28 extends through a flanged extension 30 of
the wire carrier 24 into the central portion of the carrier
24. A first contact blade receiving slot 32 is provided in
the carrier at a first position along the wire access opening
28 and a second contact blade receiving slot 34 is provided at
a second inner position of the wire access opening 28.
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The first and second contact blade receiving slots 32,
34, respectively, receive first and second insulation cutting
contact blades 36, 38, when the wire carrier member 24 is in
the closed position illustrated in Fig. 4. The insulation '
cutting blades 3 6 , 3 8 extend up from a double L-shaped contact
element 40 which is configured outside the chamber 22 and the
contact blades 36, 38 extend into the chamber 22 through the
slots 42, 44 in the bottom of the chamber 22. A stub cable
contact element 46 in turn extends outside of the chamber 22
and provides a connection to the stub cable (not shown). The
contact element 40, including the insulation cutting blades 36
and 38 and the stub cable contact element 46, is preferably
made of a metallic conductor to provide good electrical
contact to the service wires when the blades 36, 38 pierce the
insulation thereof. Which of the two blades 36, 38 makes
electrical contact to the wires is determined by the diameter
of the wire. That is, whether the wire is inserted to the
first slot 32 or the second slot 34 will depend on the wire
diameter. For example, a large gauge wire will only proceed
along the opening 28 far enough to reach the slot 32 and will
thus make electrical contact with the blade 36. A smaller
gauge wire in turn will reach to the second slot 34 and make
contact with the second, longer blade 38.
As shown in Figs. 3 and 4, a test lead 48 is provided as
part of the double L-shaped contact element 40. The test lead
48 extends into the test port 18. This allows ready
electrical connection to the service wire by a test lead
inserted into the test port 18. Although the test port 18 and
the test lead 48 of the contact element 40 are shown in a
separate test access opening sealed off from the chamber 22,
they may be provided in an opening into the chamber 22.
As best illustrated in Figs. 3 and 4, the top portion of
the housing 10 over the chamber 22 is provided with an annular
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groove 50 around the opening 16. The top end of the terminal
actuator 14 is provided with a matching annular flange 52
which fits within the annular groove 50. This thus prevents
vertical motion of the terminal actuator 14 during rotation
thereof.
In view of the foregoing structural description of the
terminal block, its functional features may be readily
appreciated in consideration with Figs. 3 and 4.
Prior to use of the terminal block for service wire
connection, and preferably during manufacture or assembly of
the terminal block, a suitable insulating medium is injected
into the chamber 22 so as to completely surround the carrier
24 and fill the wire opening 28 in the carrier 24. Any one of
a large number of well known commercially available greases,
gels and other insulating mediums may be employed, depending
on the specific requirements of the application. The
viscosity and adhesive qualities of the medium should be such
that wire may be inserted to and removed from the opening 28
without adhering excessively to the medium and the medium
should be sufficiently fluid so as to allow the carrier 24 to
move therethrough. The medium may be injected into the
chamber 22 through an opening extending through the actuator
14 into the chamber, which opening may be sealed by a small
plug after the medium is in the chamber. Alternatively, the
medium may be injected through the wire opening 28, test port
18 or during some intermediat.-.e assembly point in the
manufacture of the terminal block. Also, the medium may be
injected in a precured state or injected in an uncured state
and subsequently allowed to cure.
In the field, the service wire desired to be connected to
the stub cable (not shown) are inserted into opening 28 with
the wire carrier 24 configured in a first position illustrated
in Fig. 3. In this position, the wire may be readily inserted
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into the interior of wire carrier 24 displacing only a very
moderate amount of insulating medium. As may be appreciated
from Fig. 3, in the first position, the flanged extension 30
of carrier 24 blocks the portion of the wire access slot 12
below the opening 28 preventing outflow of the insulating
medium therethrough. Once the wire has been inserted into the
opening 28, the user of the terminal block rotates the
terminal actuator 14 which in turn drives the wire carrier 24
downward due to the threaded engagement of actuator 14 and the
wire carrier 24. The actuator 14 is rotated until the wire
carrier 24 is driven down to the second position illustrated
in Fig. 4. In this position, the wire has been forced into
contact with the insulation cutting blades 36, 38. The
insulation cutting blades 36, 38 slice through the insulation
on the wire providing good electrical contact to the inner
conductive core of the wire.
During the downward motion of the wire carrier 24, from
the first position shown in Fig. 3 to the second position
shown in Fig. 4, the insulating medium inside chamber 22 will
flow around the sides of the wire carrier 24 so as to be
displaced from the bottom to the top portion of the chamber
22. In this regard, vertical channels may be provided on the
wire carrier 24 to facilitate the flow of the insulting medium
around the wire carrier as it is driven from the first to
second position by rotation of the actuator 14. Thus, despite
the forcing down of the wire carrier 24 and the wire connected
thereto, the volume of insulating medium in the chamber 22
remains substantially constant, avoiding the outflow of medium
and/or the creation of any voids which could allow the entry
of moisture or contaminants from the environment.
Figure 5 illustrates an exploded view of the basic '
components of the protection module 100 of the present
invention. The protection module 100 of the present invention -
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provides protection for each of two wire connections between
the exchange side and the service side. To simplify the
description, and to avoid unnecessarily cluttering the
drawings, only those components defining a single conductive
path through the protection module 100 are described, although
the detailed description applies equally to both conductive
paths.
The protection module 100 is provided with a set of
protection contact elements 102, a protector base 104, a
protector cover 146, a protector 116, and a protection module
ground connector 160. The protector base 104 is.formed of a
plastic material having similar properties as that of the
protection module retainer 140 (as shown in Fig. 2). The
protector base 104 provides an internal area sufficient to
accept a protector 116, such as a twin gas discharge tube
protector or other type of protector as will be described
further below. The protector base 104 includes four walls
which form a friction fit with a retaining cup 142 when
inserted therein.
As illustrated in Figs. 5 and 6, a protector 216 is
provided within the housing base 104 of the protection module
100. The protector 116 may be provided as a gas discharge
tube as shown in Figs. 5 and 6 and as disclosed, for example,
in U.S. Patent No. 4,866,563, entitled "Transient Suppressor
Device Assembly,", A gas
discharge tube has three conductive rings, a first ring 120
and a second ring 120 encircling the circumference of each of
the ends of the tube and a third ring 122 encircling the
middle of the tube. Each set of protection contact elements
102 are conductively connected to the end rings, respectively,
and the protection module ground connector 160 is conductively
connected to the middle ring. Among its many functions, the
gas discharge tube and the protection module ground connector
' CA 02202658 2005-08-23
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160 perform in conjunction with protection contact elements
102 to shunt voltage to earth in the event there are voltage
spikes on the conductive path, for example. Therefore, once
the protector module 100 is properly inserted into a retaining
5 cup 142, the two primary conductive paths through a wire,pair
connection of a terminal block are protected from intermittent
destructive voltage levels. The use arid operation of the gas
discharge tube and its application in protecting signal lines
in this manner are well known in the art.
10 In the alternative, the protector 116 may be provided as
a gas discharge tube device modified to provide faster
response to voltage surges. It is commonplace to encounter
solid state protector devices, such as disclosed in U.S.
Patent No. 4,796,150, entitled "Telecommunication Protector
15 Unit With Pivotal Surge Protector,"
in use in telecommunications systems. Such solid
state devices may be increasingly sensitive to voltage surges
and may be destroyed before a typical gas discharge tube has
triggered its protection. In order, to protect such equipment;
20 the protector 116 may be provided as a hybrid device including
a gas discharge tube in combination with faster-response solid
state discrete components capable of grounding voltages to
earth faster than typical gas discharge tubes. In the
alternative, the protector 116 may be provided as a solid
state device which provides the necessary voltage protection
and response time.
The protector 116 within the protection module 100, is
connected to ground by connecting the third ring 122 to a
protector contact 162 which is integrally formed with the
protection module ground connector 160 from a metallic
electrical conductor. When the protection module 100 is
inserted into a retaining cup 142, the ground connector 160
which extends through the base 104 of the protection module
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21
100 mates with the grounding strip 150. As illustrated in
Fig. 6, the ground connector 158 integrally formed with the
grounding strip 150 is adapted to receive the ground connector
160 when the protection module 100 is snapped in place in a
retaining cup 142. Therefore the ground connector 158
provides a ground connection between the grounding strip 150
and the third ring 122 of the protector 116.
Each protection contact element 102 is formed of a
metallic, conductive material similar to that used in the
contact element 40 shown in Figs. 3 and 4. As illustrated in
Fig. 5, each protection contact element 102 is provided with
a plurality of bends forming a terminal block contact element
110, an external test contact element 112 and a protector
contact element 114. The terminal block contact element 110,
external test contact element 112 and protector contact
element 114 are integrally formed to provide a continuous
conductive path.
The terminal block contact element 110 may be provided in
an S-shape as illustrated in Figs. 5 and 6 to ensure a highly
conductive path is established between the terminal block
contact element 110 and the test lead 48 within the test port
18. The test port 18 is adapted to receive the terminal block
contact element 110 such that the terminal block contact
element 110 forms a compressive contact with the test lead 48.
The protector contact element 114 is conductively secured to
a first ring 120 of the protector 116 to provide the
connection to the protector 116. As such, once the protection
module 100 has been properly installed into the retaining cup
142, the protector 11G will be in conductive communication
with the test lead 18.
The external test contact element 112 is established as
a raised portion of the protection contact element 102 adapted
to receive a test probe or test lead such as an alligator-type
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22
clip (not shown) . Once the protection module 100 is installed
into retaining cup 142, any signal available at the test lead '
48 is available at the external test contact element 112.
As illustrated in Fig. 5, the protection module is '
provided with a cover 106. The cover is provided with a
recessed slot through which may be provided the external test
contact element 112. The recessed slot is surrounded by
raised walls. The top of the cover 106 in combination with
the raised walls provides a reservoir 118. The reservoir 118
may be filled with an insulating medium such as a grease or
gel, which medium is sufficiently deformable to allow access
of a test probe to test contact element 112.
The protector 116, the protection contacts 102 connected
to the protector 116 and the protection module ground
connector 160 may be maintained within the protection module
100 with a hard encapsulant such as a non-conductive epoxy.
The hard encapsulant itself may also serve as the bottom
surface of the protection module 100. The encapsulant
provides an environmental seal which protects the contents of
the protection module 100. Preferably, any interstitial space
between the encapsulant and the cover 106, as well as the
reservoir formed on the top surface of the cover, is filled
with an insulating media which further protects the contents
of the protection module 100 from the environment.
In view of the foregoing structural description of the
protection module, its functional features may be readily
appreciated in consideration with Fig. 6. In the field, the
service wire desired to be connected to the stub cable is
inserted into opening 28 of the housing 10 and terminated by
the actuator 14. When actuation is complete, the insulation
displacement blades 36, 38 are in conductive contact with the
service wire. This creates a single conductive path between
the service and exchange sides by terminating the service wire
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23
to the stub cable contact element 46. Moreover, the test lead
48 extending into test port 18 carries the signal from the
conductive path termination to the test part 18.
A technician may add voltage surge protection to the
conductive path by securing a grounding strip 15o and a
protection module retainer 140 to the housing 10. A
protection module 100 may be inserted into a retainer cup 142
corresponding to the conductive path to be protected. When
the protection module 100 is installed into the retainer cup
142, the protection module ground connector 160 engages the
ground connector 158 of the ground strip 150, providing a
conductive path between the third ring 122 encircling the
middle of the protector 116 and earth. During installation,
the terminal block contact element 110 engages the test lead
48 to form a conductive path between the test lead and the
first or the second end rings 120 encircling the circumference
of the end of the gas discharge tube.
When a voltage surge occurs, for example, the open
circuit between the third ring 122 and the first ring 120
closes and the voltage surge is shunted to earth, thus
protecting the telecommunications equipment conductively
connected to the conductive path. Once a voltage surge has
occurred, forcing the protector 116 to connect to earth, the
protector may be replaced by lifting it from the retaining cup
142 and replacing it with a functioning protection module 100.
The replacement occurs without disrupting the termination
between the exchange side and the service side.
Accordingly, it will be appreciated 1=hat the protection
module and retainer of the present invention provides
significantly improved protection against voltage surges and
allows a protection module to be added to or removed from the
retaining cup 142 without affecting the exchange wire or
service wire terminations. In addition, providing protection
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24
on an as-needed basis ensures the additional cost of
protection is limited to those conductive paths needing
protection. Finally, the retainer provides the needed
alignment and support needed to repeatedly install and remove
a protection module from a terminal block while securely
retaining the protection module. Furthermore, the present
invention provides a protection module which is simple to use,
easy to fabricate, and not prone to failure even after
repeated connections and reconnections.
While the foregoing description has been of a presently
preferred embodiment of the present invention, it should be
appreciated that the protection module of the present
invention may be modified in a wide variety of ways while
still remaining within the spirit and scope of the present
invention. For example, the specific configurations of the
retaining cups and the protection module may all be varied due
to specific manufacturing considerations or other reasons
without departing from the spirit and scope of the present
invention. For example, the retaining cups and the grounding
strip may be integrally formed with the terminal block
housing. Moreover, the protector may be provided as a solid
state protection device to provide enhanced speed and range of
protection. Furthermore, while the present invention has been
described as a terminal block adapted for use with an
insulated wire, the present invention may equally well be
employed with a bare wire.
Additional variations and modifications of the preferred
embodiment described above may also be made as will be
appreciated by those skilled in the art and accordingly the
above description of the present invention is only
illustrative in nature. The invention is further defined by
the following claims.
