The present invention refers to a light signal, especially for use
in the railroad field.
In the railroad field, maneuver low light signals are known to control
the maneuver movements (routings) by switching-on two white lamps vertically superimposed
to indicate all-clear way, and two white lamps horizontally lined up to indicate
no admittance. These signals comprise three optical groups and three electric power
transformers disposed in a container of plastic material. The optical groups make
use of incandescent lamps or halogen lamps, with one lamp of each group.
The light signals of this type have many drawbacks among which the
fact that in case of a burnt-out lamp, the relevant useful signal cannot be generated,
the fact that overheating, and thus integrity, problems may arise due to the excess
of heat generated by the lamps, besides the fact that they may often be affected
by the so-called "ghost effect". The latter being 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 eliminate 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; to avoid the onset
of the "ghost effect"; to reduce the costs related to the inspection and maintenance
of the signal apparatus; to limit at a minimum or at least to more acceptable levels
the detrimental thermal effects due to the electrical supply of the light sources.
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 exploded perspective rear view of a light signal apparatus according
to the invention, relating to the assembly of the power supply;
- Fig. 2 ia a view similar to the preceding one, relating to the assembly of a
- Fig. 3 is a simplified wiring diagram for connection between the supply and
the luminous matrixes;
- Fig. 4 shows schematically a luminous matrix; and
- Fig. 5 is an electric diagram relating to one embodiment of the luminous matrix.
Reduced to its basic structure, and reference being made to the figures
of the attached drawings, a signal apparatus according to the invention comprises
three light units L1, L2, L3 disposed according the vertexes of a right-angled triangle
within a box-like container 1 of thermoplastic material which is provided with three
corresponding front apertures 10, preferably of circular shape. The said units L1,
L2, L3 are intended for operating in pairs: for example, in order to signal "all
clear" there are activated the units L1 and L2, whereas to signal "no admittance"
the units L1 and L2 are activated. For the sake of simplification, the rear lid
of the container 1 is not shown in the drawings. The said container 1 has an inner
base 11 on which a power supply 2 is fixed for supplying power to the light units
L1, L2, L3 via corresponding connectors C1, C2, C3.
Advantageously, each light unit L1, L2, L3 is made up of a matrix
of light sources 3 comprising a preset number of luminous groups or sectors which
are connected in parallel to each other: each luminous sector comprising a preset
number of light sources 3 connected in series to each other.
Shown in Fig. 5 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).
For example, each unit L1, L2, L3 may comprise eight sectors or groups
of thirteen light sources 3, the light sources 3 of each sector being, as above
indicated, connected in series to each other, and the sectors being connected in
parallel, thereby resulting electrically independent from each other. According
to this example, therefore, there will be one hundred and four light sources 3 for
each unit L1, L2, L3.
Each light source 3 may consist of LEDs of lunar white light with
a typical light intensity of 1.6 cd at 20 mA, and angle of emission of ±25° with
respect to its optical axis.
The light sources 3 of each unit L1, L2, L3 may be mounted on a plate
30 provided with a finned heat sink 31 and mounted on a metal support 32 which allows
the same plate to be fixed to the container 1 by screw means.
The said support 32 may be fixed to the container 1 so as to orient
the plate 30 of about 9° upwardly, and about 6° towards the rail under control,
so as to make the signal visible to the train's staff also from a very close distance.
Between the light units L1, L2, L3 and the respective aperture 10
of container 1, a piano-lens 4 may be positioned by means of a fixing ring nut commonly
used for this type of apparatus.
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 including
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 light 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, the service interventions can be limited to a simple
yearly visual inspection, in order to check the physical integrity and the efficiency
of the luminous sectors and to provide for cleaning the lenses 4, by deferring the
replacement of the whole matrix at the end of the second year.
The present apparatus is not provided with optical components like
mirrors, prisms, colour filters so that the risk of the occurrence of the so-called
"ghost effect" results practically suppressed.
The container 1 may be provided, in correspondence of the side facing
the rail under control, with a screen or shield which further contributes to reduce
the probability of the occurrence of the above said phenomenon.
In place of LEDs, equivalent light sources may be used, organized
according to a matrix scheme as above described.
Particularly positive results, from the constructional and functional
point of view have been obtained with matrixes of 8 sectors connected in parallel
and consisting of 13 LEDs in series, for a total of 104 LEDs.