Communications: electrical – Land vehicle alarms or indicators
Reexamination Certificate
2001-05-29
2003-05-06
Pope, Daryl (Department: 2635)
Communications: electrical
Land vehicle alarms or indicators
C340S426110, C340S539230, C340S937000, C340S506000, C340S003100
Reexamination Certificate
active
06559760
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a platform monitoring system which permits an operator or the like on the vehicle side such as a vehicle running on a track to monitor a situation on a platform (how passengers are getting on and off a train, and so on).
When a train stopping at a platform is to leave the platform, it is necessary to confirm the safety as to whether or not any passenger is being caught by a door of the train, and so on before the train is started. Not only that, a continuous safety check is requested in some cases as to whether or not any passenger caught by a door is being dragged in a predetermined range of running immediately after the start as well to duplicate the safety check such that neglected safety check before the start will never result in a grave accident.
While a crew has visually confirmed the safety as mentioned in the past, a platform monitoring system has been provided for permitting an operator or the like to monitor a situation on a platform as so-called one-man operated trains, without crews, have been increasingly introduced.
An example of a conventional platform monitoring system will be described with reference to FIG.
5
.
FIG. 5
is a schematic plan view generally illustrating an exemplary configuration of some components of a conventional platform monitoring system. In
FIG. 5
, reference numeral
1
designates a track;
2
, a vehicle (a train in the illustrated example) running on the track
1
;
3
, a platform; and an arrow X, a direction in which the vehicle
2
runs.
The conventional platform monitoring system illustrated in
FIG. 5
comprises television cameras
4
a
-
4
c
installed on the ground side for capturing situations on the platform
3
; an optical wireless transmission system for transmitting images captured by the television cameras
4
a
-
4
c
to the vehicle side as optical signals; and a television monitor (not shown) installed near an operator's seat in the vehicle
2
for displaying images transmitted by the optical wireless transmission system. The optical wireless transmission system comprises an optical transmitter installed on the ground side, and an optical receiver installed on the side of the vehicle
2
. The optical transmitter has a multiplicity of light emitters
5
a
-
5
e
installed on the ground side, while the optical receiver has an light receiver
6
mounted at a leading end of the vehicle
2
. The multiplicity of light emitters
5
a
-
5
e
are disposed at predetermined intervals along the track
1
, as illustrated in
FIG. 5
, such that they cover a desired vehicle position range R
1
in which signal transmission can be achieved.
The multiplicity of light emitters
5
a
-
5
e
are used in this way because each of the light emitters has a light emitting angle so narrow that a single light emitter cannot cover the desired range R
1
. In
FIG. 5
, the position of the vehicle
2
is indicated as the position of the leading end of the vehicle
2
for convenience of explanation. Since the track
1
extends in the horizontal direction in the figure, vehicle positions P
0
-P
2
in the figure are indicated at positions in the horizontal direction in the figure. Position P
0
indicates a predetermined stopping position on the platform
3
at which the vehicle
2
should be stopped. The range R
1
extends from position P
1
to position P
2
, where position P
1
is defined at a position slightly in front of stopping position P
0
in the vehicle running direction (indicated by the arrow X) (on the right side in FIG.
5
), and position P
2
is defined at a predetermined position behind stopping position P
0
in the vehicle running direction (on the left side in FIG.
5
). Position P
2
is set in accordance with the length of the vehicle
2
and a distance over which a continuous safety check is desired for checking whether or not any passenger is caught by a door and dragged after the vehicle
2
has been started from the platform
3
.
According to the conventional platform monitoring system, when the vehicle
2
is positioned within the range R
1
, images representing situations (situations of passengers getting on and off the vehicle) on the platform
3
captured by the cameras
4
a
-
4
c
are transmitted from the ground side to the side of the vehicle
2
through the light emitters
5
a
-
5
e
and the light receiver
6
, and displayed on the television monitor near the operator's seat in the vehicle
2
. Thus, the operator of the vehicle
2
, viewing the display, not only can make a safety check as to whether any passenger is caught by a door while the vehicle
2
remains stopped at position P
0
with respect to the platform
3
, but also can continue the safety check as to whether any passenger caught by a door is being dragged also in the predetermined range of running immediately after the vehicle
2
has been started.
In addition, according to the conventional platform monitoring system, the optical wireless transmission system is employed as a wireless transmission system for transmitting images from the ground side to the side of the vehicle
2
, and light is employed as a transmission medium, so that, unlike the employment of radio waves as a transmission medium, images representing situations on the platform
3
can be transmitted without fail and displayed on the television monitor in the vehicle
2
without suffering from noise which could be generated due to multiple reflection (multipath).
However, since the conventional platform monitoring system requires the multiplicity of light emitters
5
a
-
5
e
, a higher cost is inevitable, and the installation of the light emitters also requires significant time and labor. Particularly, if a portion of the track
1
behind the platform
3
in the vehicle running direction (on the left side in
FIG. 5
) is curved, a further increased number of light emitters
5
a
-
5
e
must be installed, thereby resulting in a further increase in the cost and labor for the installation.
As an alternative, it is contemplated to use a radio wave based wireless transceiver as a wireless transmission system in place of the optical wireless transmission system. In this case, since radio waves tend to be less directive and therefore propagate over a wider range as compared with the light, the number of transmitters can be reduced. It is therefore possible to greatly reduce the cost and labor for installation, as compared with the employment of the optical wireless transmission system.
However, the radio wave based wireless transceiver, if employed, is more susceptible to noise due to multiple reflection (multipath). As a result, depending on a nearby situation (existence of wall surfaces and other buildings), the vehicle
2
may be located at a position at which images available for monitoring for a safety check cannot be displayed on the television monitor at the operator's seat. Such a position may be coincident with the stopping position P
0
of the vehicle
2
with respect to the platform
3
. In this event, notwithstanding the fact that the monitoring of situations on the platform
3
is most important when the vehicle
2
remains stopped at the stopping position P
0
(i.e., when passengers are getting on and off) for ensuring the safety for the passengers, the monitoring is disabled, which is fatal as the platform monitoring system.
For the reason set forth above, it has been a matter of technical common sense in the field of a platform monitoring system that light should be used, rather than radio waves, as a transmission medium for images representing situations on a platform, and that an increase in the cost and labor for the installation resulting from the employment of the multiplicity of light emitters
5
a
-
5
e
must be regarded as acceptable.
JP-A-62-16636 discloses an optical space transmission device against a moving body, which is constituted of a plurality of optical transmitters installed on the ground side and an optical receiver installed on a moving body.
JP-A-11-331816 discloses a mobile body optical space trans
Araki Takayuki
Samejima Akitaka
Koito Industries, Ltd,
Pope Daryl
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