Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BI~NKOUT SIGN
Field o~_the Invention
rrhis invention relates in general to illuminated
signs, and more particularly to an illuminated blankout
traffic sign.
Background of the Invention
It is a common requirement of traffic signs that
they must be visible in broad day light as well as in the
darkness of night. A number of well known non-
illuminated painted signs are available which are clearlyvisible by day. These signs typically incorporate a
ra~lective surface coating adapted to enhance visibility
at night in response to an automotive headlight beam
impinging upon and reflecting off of the sign. However,
these signs suffer from the shortcoming tha~ they are
only visible when an extarnal light source is shined
th~reon.
Another requirement for some traffic signs is that
they be visible ~at day or night) only under certain
conditions. Such signs are known as blankout signs. Fsr
example, a blankout sign may be placed at a railway
crossing to provide a no-left and no-right turn
indication during a railway pre-emption call. Thus, the
blankout sign must be completely visible in both daylight
and night csnditions, but must also blankout completely
in the absence of the pre-emption call.
A number of blankout signs are presently available.
However, none of the presently available signs provide
the desired indication on a white or colored background,
as is required under various legislated traffic acts
(e.g Ontario Highway Traffic Act (OHTA), O. Reg.
667~78). For example, 3M Canada Inc. currently sells a
blankout sign under the trade name Vari-Comm. This sign
comprises a series of horizontal louvres that operats in
thP manner of venetian blinds: when closed in one plane
they form a blankout white colour and when rotated in the
opposite direction they display the required no-left or
no-right turn indication. The 3M Vari-Comm sign is
illuminated by reflected light mounted in the sides of
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the sign so as to impinge upon the non translucent face
material of the sign. This sign suffers from mechanical
difficulties with the operation of the horizontal
louvres, particularly in climates exhibiting very low
winter temperatures.
A further prior art blankout sign is manufactured by
Ferrenti-Packard Electronics and is illuminated in the
same way as the Vari-Comm sign ~xcept that the non-
translucent face consists of a matrix of tiny disks that
are all of one colour, but when electromagnetically
flipped they display the required symbol of no-left or
no-right turn.
While both of the above-discussed known prior art
blankout signs are capable of displaying an indication on
a white or colored background, in accordance with the
required legislative provisions, the signs are front
illuminated and are of complex design and are prone to
mechanical and electrical failure.
In addition, such prior art signs have encountered
problems operating in daylight conditions. For example,
the prior art illuminated signs have been known to
succumb to a negative fade out condition when the sign
is silhouetted against counter-vailing sunlight ~ince
increased ambient light is provided in front of the sign.
In such counter-vailing light situations, the blankout
signs according to the prior art are difficult to see at
normal sight distances. In addition, it has been found
that the no-left and no-right turn indications can be
qeen in conditions of strong direct vailing sunlight when
the illumination is turned off (this is known as
"ghosting"). In some versions of the prior art
illuminated blankout signs, the ghosting effect was
reduced by making the sign background black. However, as
discussed above, a black background is not acceptable
under most gov rnmental traffic legislation~
Summary of the Invent on
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According to the present invantion, an internally
backlit illuminated blankout sign is prov.ided which
conforms to the regulatory section o~ the Manual of
Uniform Traffic Control Devices (Province of Ontario) for
turn indication on a white or colored background, yet
includes no moving parts.
According to an aspect of the invention there is
provided an internally backlit illuminated blankout sign
adapted to be exposed to ambient light, comprising:
a~ an enclosure;
b) light generating means within said
enclosure;
c) a front face for said enclosure adapted to
change from a first colour when backlit via said light
generating means to black when illuminated only by said
ambient light; and
d) indicia applied to said front face for
conveying information, whereby said indicia are visible
from outside of said enclosure with said first colour as
background when said ~ront face is backlit via said light
generating means and said indicia are not visible from
outside of said enclosure when said front ~ace is
illuminated only by said ambient light.
Brief Description of the Drawings
A preferred embodiment of the invention will be
described in greater detail below with reference to the
~ollowing drawings, in which:
Figure 1 is a perspective view of the blankout sign
according to the present invention;
Figures 2A and 2B are front elevation views o~ the
blankout sign in blankout condition and illuminated
condition, respectively;
Figure 3 is a partially exploded view o~ the
blankout sign o~ Figure 1 without hood;
Figure 4 is a cross-sectional view through IV-IV in
Figure 3;
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Figure 5 is a perspective view of the internal
structure of the blankout sign shown in Figure 3; and
Figure 6 is a cross-sectional view through VI-VI in
Figure 3.
Detailed Description of the Preferred Embodiment
Turning to the Figures, the blankout sign of the
present invention is shown comprising an enclosure 1 to
which an aluminium hood 2 is connected. The hood is
sloped downwardly for drainage and to eliminate
accumulation of snow. The hood functions in the same
fashion as a traffic light visor for shading the sign in
th~ presence of strong overhead light. The hood 2 is
preferably painted grey on the exterior with a matte
black finish on the inside.
The enclosure 1 is preferably in the form of an
aluminum box which houses illumination means which are
discussed in greater detail below with reference to
Figures 4-6. The enclosure 1 preferably includes upper
and lower ventilation louvres 3 and 4 on both sides of
the sign. A hinged frame (not shown) is provided by
which the ~ront surface 5 may be opened to reveal the
internal structure of ~igures 4-6.
The external surface or front face 5 of the sign
incorporates indicia 5A thereon for conveying such as
traffic signal information, etc. According to an
important aspect of the present invention, the front face
5 of the sign is manufactured from a Casocryl~ plexiglass
surface which changes from black (when front illuminated)
to white or colored (when back lit). The use of
CasocrylT~ plexiglass is known in commercial signs to
provide colour changes. For example, a commercial sign
using Casocryl~ plexiglass may appear as one colour with
~; front ambient illumination but may change to another
colour when illuminated from behind the plexiglass
; 35 surface. However, the use of Casocryl~ plexiglass for
the creation of blankout tra~fic signs which fade to
black in blankout condition and which exhibit a white
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background when illuminated, is not believed to be
hitherto known. Alternatively, the plexiglass surface
may exhibit a coloured background when illuminated (e.g.
this would be useful for a blank out "yield" sign with a
blank indication on a yellow ba~kground).
The required no-turn indication is applied to the
Casocryl~ plexiglass surface 5 by means of coloured vinyl
strips 6 applied to the inside surface of plexiglass face
5~
Turning now to Figures 4-6, a raceway 6 is provided
with sockets on both sides of the sign to which a
plurality of fluorescent lamps are mounted via
appropriate fixtures at each end. Preferably, each of
the lamps 7 are wired independently in order that the
sign may be dimmed at night by reducing the number of
illuminate lamps.
A pair of fans 8 are shown on each side of the sign
adjacent the top louvres 3 for forcing air through the
louvres 3. In particular, as shown best with reference
to the airflow arrows of Figure 5, air is circulated
through the enclosure for maintaining reduced temperature
by being drawn in through the louvres 4 and purged via
the ~ans 8 through louvres 3.
An electrical connection 9 is provided for powering
the lamps 7.
Although not shown, a pair of ballasts are located
at the top of the sign for controlling operation of the
lamps 7.
Drain holes 11 (not shown) are preferably provided
at the bottom of the sign to allow for the release of
condensation from within the sign, etc. Mounting
hardware (not shown) is also provided in a well known
manner for securing the raceway 6 and fluorescent lamp
sockets to the sign box.
A plurality of reflectors 10 are provided, one
reflector hehind each lamp 7, and successive reflectors
maeting intermediate each pair of fluorescent lamps 7.
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The reflectors are V-shaped and are used to amplify the
light created by the fluorescent lamps 7 in order to
minimize the number of lamps required and therefore
minimize heat generation within the sign which otherwise
can result in overheating of the ballasts. Preferably,
the reflectors 10 are fabricated from Silverlux
reflective material.
Other modifications and variations of the invention
are possible. For example, whereas fluorescent lamps
were chosen for the successful prototype, it may be
possible to use mercury vapour or other lamps. However,
fluorescent lamps are thought to be preferable due to the
immediate start up phase, long lamp life and absence of
after image when the illumination is turned off.
Furthermore, although the preferred embodiment relates to
a blankout sign for conveying a traffic signal, it is
contemplated that the principles of the present invention
may be applied to the creation of commercial,
advertising, or other types of blanXout signs where
indicia are provided on a neutral coloured background
when the sign is backlit and wherein the sign fades when
not backlit. All such modifications and variations are
believed to be possible within the scope of the invention
as defined by the claims appended hereto.
