Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Reexamination Certificate
1998-01-07
2001-01-16
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
C361S106000, C361S824000
Reexamination Certificate
active
06175483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-tap distribution apparatus, More particularly, the present invention relates to a multi-tap distribution apparatus which is suitable for use with CATV cables.
2. Description of the Related Art
In a CATV system, transmission cables are aerially strung on, for example, telephone poles or laid underground with a number of multi-tap distribution apparatuses and amplifiers interposed therein at suitable points. Secondary cables are branched out from multi-tap distribution apparatuses to subscribers' homes to distribute signals.
CATV stations transmit not only high-frequency signals, such as television signals and control signals, but also currents for operating amplifiers provided on the main lines and CATV telephones installed at subscribers' homes. Therefore, if a short circuit is caused by inappropriate installation of equipment or tampering by children, excess currents may flow through the cable to cause damage to the equipment installed in the cable.
In order to prevent such accidents, distribution apparatuses are normally provided with circuit-breakers that break the circuitry upon occurrence of a short circuit, One type of device used as a circuit-breaker is a positive thermistor (referred to as “thermistor” hereinafter), Thermistors are provided in series with respective taps (distribution output terminals) in the distribution apparatus' current transmission circuit for feeding the taps with operating currents. Any of the thermistors can interrupt the circuit upon occurrence of a short circuit as the resistance of the thermistor increases with the increase in the amperage of the current.
Where a CATV telephone system is used, each time a subscriber changes the CATV service company or cancels the subscription (which often occurs, especially in the United States), the power to the CATV telephone needs to be switched off and on. As described above, a positive thermistor or other suitable switch device can be installed in the current transmission circuit so that the circuit can be interrupted by operating the switch to stop the current supply to, and thus disable, the CATV telephone or other type of terminal.
FIG. 10
shows a conventional distribution apparatus used in a CATV system. This apparatus has an enclosure comprising a box-shaped housing
39
with one side open and a main body
38
that includes a plurality of distributing output terminals
5
and fits in the open side of the housing
39
. The housing
39
is provided with transmission cable connection terminals
6
for connection to the main line. The apparatus contains a distributing circuit, a current transmission circuit, and a branch unit
7
having a branch circuit therein. Thermistors
14
are mounted as circuit breakers inside the apparatus via connectors
42
as illustrated, so that the distribution apparatus needs to be opened to remove or mount any of the thermistors
14
.
Whenever the distribution apparatus needs to be opened to remove or mount the thermistors
14
, the shield factor of the main line is reduced to allow external noise to enter the CATV line or to cause leakage of radio waves from the apparatus. Furthermore, since a plurality of subscribers are normally served from a single distribution apparatus, signal transmission to all of the subscribers is interrupted whenever the apparatus is opened. This inconveniences the subscribers as they cannot view the CATV programs or use the CATV telephone services even if only for a short time.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an object of the present invention is to provide an improved distribution apparatus that allows making and breaking of the current transmission circuit to a specific subscriber without opening the apparatus so as not to inconvenience other subscribers served by the same distribution apparatus.
Another object of the present invention is to provide an improved distribution apparatus that passes and blocks operating currents to a specific subscriber without affecting the characteristics of the signals carried on the main line.
The above objects and other related objects are realized by providing an improved distribution apparatus for being interposed in a transmission cable. The distribution apparatus is encased in an enclosure including a box-shaped housing with one side open and a main body closing up the open side of the housing. The housing is provided with portions for connecting with the transmission cable. The distribution apparatus further includes: a modularized branch circuit detachably mounted in the enclosure; a plurality of distribution output terminals provided on the main body, for distributing signals received from the transmission cable via the branch circuit; a current transmission circuit provided between the distribution output terminals and the transmission cable; at least one operating window provided in a wall of the enclosure; and a plurality of switch means interposed in the current transmission circuit so as to pass and block currents to the respective distribution output terminals, The switch means are located in the at least one operating window, thus allowing the switch means to be operated through the at least one window from the outside of the enclosure.
According to one aspect of the present invention, the at least one operating window is formed in the main body. Furthermore, each of the switch means has an operating member and at least one operation hole through which the operating members are exposed in the operating windows is provided within the window. Therefore, only the operating members of the switch means can be operated from the outside of the enclosure.
According to another aspect of the present invention, the operating member of each switch means is an operating lever.
According to still another aspect of the present invention, connectors are placed in the current transmission circuit and the switch means are positive thermistors which are detachably mounted in the current transmission circuit via the connectors.
According to yet another aspect of the present invention, the at least one operating window is provided with a cover for sealing the at least one operating window.
In accordance with another aspect of the present invention, the cover of the at least one operating window is hinged along one edge thereof on the main body.
REFERENCES:
patent: 4850014 (1989-07-01), Gillis et al.
patent: 5637011 (1997-06-01), Meyerhoefer et al.
patent: 98585 (1997-01-01), None
patent: 955266 (1997-02-01), None
Leja Ronald W.
Maspro Denkoh Company, Ltd.
Pearson & Pearson LLP
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