The present invention refers to a railroad advance starting light
signal, that is, a signal of a type similar to the conventional one known in the
railroad signalisation technique as a call signal.
The traditional call signal is constituted by means of two lamps horizontally
combined and usually fixed, on the same pole (or post, as it is called in technical
jargon) that carries the lamps for first class protection signal therebelow. The
call signal is normally off or deactivated; when activated, it projects, in the
direction of the incoming train, two milk-white blinking lights which authorize
the train to enter the station, thereby overriding the relevant protection signal
which is disposed in off-state or stop mode.
The light signals of this type have many drawbacks.
One drawback relates to the fact that in case of a burnt-out lamp,
the relevant useful signal cannot be generated; in fact, when a lamp burns out,
after a service life no longer than 700 hours for this type of signal, these known
devices are unable to supply all the same the required information, thereby compromising
both the regularity and safety of the operation.
Moreover, the known devices result subjected, in a more or less variable
extent, which depends on the constructional characteristics, to the so-called "ghost
effect". The latter is a phenomenon of essentially optical nature by which the optical
unit - intended to emit the light signal by projecting white or otherwise coloured
light - although switched off, is able all the same to project a beam of light following
the input and subsequent reflection of foreign radiations (for example, coming from
artificial sources like railroad or road lamps and lights, signs, natural sources
like sun rays) in the signal-projecting direction. Obviously, an event of such nature
would dangerously prejudice the recognition and interpretation of the signals by
the train's staff.
The main object of the present invention is to suppress or at least
greatly reduce the above said drawbacks.
This result has been achieved, according to the invention, by adopting
the idea of making an apparatus having the features disclosed in the claim 1. Further
characteristics being set forth in the dependent claims.
The present invention makes it possible to greatly increase the reliability and
thus the operation safety of this type of signal apparatus and to avoid the onset
of the "ghost effect".
Moreover, an apparatus according to the present invention is relatively simple
to make and cost-effective in relation to the its performance.
These and other advantages and characteristics of the invention will
be best understood by anyone skilled in the art from a reading of the following
description in conjunction with the attached drawings given as a practical exemplification
of the invention, but not to be considered in a limitative sense, wherein:
- Fig. 1 is an elevation front view of an apparatus according to the invention;
- Figs. 2 and 3 are, respectively, a top view and a side view of the apparatus
of Fig. 1 when in use;
- Figs. 4 and 5 show the apparatus of the preceding figures in views similar to
those of Figs. 2 and 3, and without a relevant covering guard; and
- Fig. 6 is an operational electric diagram relating to a matrix which defines
an optical group, said matrix being made up of sectors connected in parallel and
consisting of in-series LEDs.
Reduced to its basic structure, and reference being made to the figures
of the attached drawings, an apparatus 100 according to the invention comprises
a pair of optical groups, each of which is made up of a matrix 1 of luminous elements
or sectors connected electrically to each other.
In the example illustrated in the figures of the accompanying drawings,
the light advance starting signal apparatus 100 in question comprises two matrixes
of light elements disposed horizontally syde-by-side.
Advantageously, each light element or sector 1 consists of one or
more light sources 10 connected in series to each other.
The apparatus 100 provides for using two matrixes 1 with eight sectors
in the whole, five of which are made up of eleven LEDs in-series, and the other
three consisting of ten LEDs also in series, the said sectors being in turn connected
in parallel for a total of 85 LEDs.
Shown in Fig. 6 is and electric diagram of a matrix with m sectors
in parallel, each of which consists of n LEDs in series. Provided on each sector
is a relevant limiting resistance (R1, ..., Rm) and n LEDs
(D1,1 ..., Dm,n).
Each LED may be of white light-type, falling in the "Lunar White"
class indicated by the standard specification BSI 1376, with a typical light intensity
of 3.7 cd at 20 mA, and angle of emission of ±6.5° with respect to its optical axis.
The light intensity on the optical axis is higher than 100 cd.
With reference in particular to Figs. 1-5, the apparatus 100 comprises
a containment structure consisting of a base 2 and a lid 3 protruding frontally
(and sideways with wings 33) so as to define a screen or shield. The containment
structure being possibly made of foamed polycarbonate. The front part 5 of the structure
of apparatus 100 is downwardly inclined by an angle α of about 10°, so as
to avoid the reflexes of the sun light towards the train's staff. On said front
part, supported by a relevant fixing ring nut, are two plano-lenses 8 made of plastic
material and which can have the dual function of protective means and optical filter.
The base 2 is mounted on a corresponding support 4 allowing it to be fixed to a
supporting post or pole (not shown) and which provides for an inlet 6 for relevant
power cables (not shown) to be connected to a terminal block 7 inside the containment
structure of the apparatus 100.
The matrixes 1 of LEDs 10, moreover, may be supported by a heat sink
9 of finned aluminum, with consequent advantages from the thermal point of view.
In place of the above indicated LEDs of "Lunar White" class, LEDs
can be used which project white light with different trichromatic coordinates by
using coated glass or dichroic filters located in front of the LEDs so as to cause
the light to take up the desidered colour.
A light signal apparatus according to the invention is characterized,
as above mentioned, by a high reliability.
As for the reliability of a signal apparatus according to the invention, comprising
a matrix of LEDs arranged in sectors in parallel, each sector inluding one or more
LEDs in series, experimental tests have shown that this arrangement allows a significant
increase of the reliability and availability of each of the three optical groups
(equal to each other) that form the ligth signal apparatus. The particular embodiment
and technology being used actually bring about a very long average life; by way
of non limiting example, such length can be expected of over 20 years.
It should be apparent that the maintenance signal systems result therefore
economical as far as the costs and organization of the maintenance activity are
For example, while the traditional lamps are replaced about 4 times in a year,
the present invention would allow a system to be in operation for over 20 years.
By using a matrix of LEDs or equivalent light sources as above described, it is
avoided to make use of optical components like mirrors, prisms, colour filters or
others, which may alter the optical path and/or the colour of the light rays produced
by external sources and coming back to the observer ("ghost effect").