U.S. patent number RE36,245 [Application Number 08/213,266] was granted by the patent office on 1999-07-06 for non-linear signalling device for vehicles.
This patent grant is currently assigned to Federal Signal Corporation. Invention is credited to Michael Benner, Earl Gosswiller, Edward S. Stanuch.
United States Patent |
RE36,245 |
Stanuch , et al. |
July 6, 1999 |
Non-linear signalling device for vehicles
Abstract
A light bar is provided for mounting to a roof of an emergency
vehicle such that the signalling devices comprising the light bar
are distributed across the roof to form a non-linear pattern. A
dome assembly covers the signalling devices and also forms a
non-linear pattern traversing the roof. The light bar provides for
enhanced visibility at angles approaching 90.degree. to the heading
of the vehicle. Moreover, the non-linear pattern of the signalling
devices allows the light bar to provide a signalling pattern whose
warning effect can be alternatively directionalized into different
distinct zones about the vehicle. In a preferred embodiment, each
of the signalling devices is contained in a module comprising a
base and a dome such that enhanced transmittance of light is
provided at angles approaching 90.degree. from the heading of the
vehicle.
Inventors: |
Stanuch; Edward S. (Oak Forest,
IL), Benner; Michael (Lisle, IL), Gosswiller; Earl
(Pompano Beach, FL) |
Assignee: |
Federal Signal Corporation (Oak
Brook, IL)
|
Family
ID: |
24371285 |
Appl.
No.: |
08/213,266 |
Filed: |
March 15, 1994 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
592587 |
Oct 4, 1990 |
05097397 |
Mar 17, 1992 |
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Current U.S.
Class: |
362/480;
D10/114.1; D10/114.4; 340/472; 362/284; D26/35; 362/324; 362/238;
362/240; 362/249.01 |
Current CPC
Class: |
B60Q
1/2611 (20130101) |
Current International
Class: |
B60Q
1/26 (20060101); B60Q 001/00 () |
Field of
Search: |
;340/468,471,472,473,474
;362/35,61,66,80,234,238,240,249,252,324,368,284,74,251 ;D26/35
;D10/114 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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43-22004 |
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Sep 1943 |
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48-19579 |
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Jun 1973 |
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JP |
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56-5201 |
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Feb 1981 |
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JP |
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57-59602 |
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Dec 1982 |
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JP |
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752243-1 |
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Jan 1989 |
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JP |
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752243 |
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Jan 1989 |
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JP |
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767499 |
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Aug 1989 |
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JP |
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2-1764 |
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Jan 1990 |
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JP |
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787405 |
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May 1990 |
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JP |
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2-38327 |
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Oct 1990 |
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JP |
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2-36163 |
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Oct 1990 |
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JP |
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862217 |
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Feb 1993 |
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JP |
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864872 |
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Mar 1993 |
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JP |
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1166580 |
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Oct 1969 |
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GB |
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2012037 |
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Jul 1979 |
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GB |
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Other References
Color photograph of a Hush XL Custom Pumper (Half Door)
manufactured by Emergency One, Inc., Ocala, Florida (no date
given). .
Color photograph of a 50' Teleboom manufactured by Emergency One,
Ind., Ocala, Florida (no date given). .
Color photograph of a 80' Aerial Ladder with Pump manufactured by
Emergency One, Inc., Ocala, Florida (no date given). .
Letter and Record of Invention to Federal Signal Corp. sent by
Randy Emon dated Sep. 30, 1989. .
1989 Product Catalog of Whelen Engineering Company (3 pages)
illustrating EDGE 9000 Strobe Light Bar and TOWMAN's EDGE light
bar. .
Catalogue No. 145 "Patlite", pp. 1/3-2/3, no date given. .
Catalogue "The Edge+Plus, Emergency Warning Systems", pp. 1/505/5
no date given..
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Primary Examiner: Husar; Stephen F.
Attorney, Agent or Firm: Leydig, Voit & Mayer, Ltd.
Claims
We claim:
1. A light bar for mounting to a roof of a vehicle and providing a
signalling pattern whose primary warning effect can be
alternatively directionalized into at least four distinct zones
about the vehicle, the light bar comprising:
a frame for traversing the roof of the vehicle;
means at both ends of the frame for securing the frame to opposing
edges of the roof;
a plurality of signalling devices for radiating light distributed
along the frame to form a non-linear pattern; and
a dome assembly covering the signalling devices and mounted on the
frame in such a manner that the assembly forms a non-linear pattern
traversing the roof.
2. A light bar as set forth in claim 1 wherein the dome assembly
comprises at least one continuous dome that contains two or more of
the signalling devices.
3. A light bar as set forth in claim 1 wherein the dome assembly
comprises a plurality of modules, each module covering only one of
the signalling devices.
4. A light bar as set forth in claim 3 wherein the dome assembly is
shaped to substantially maintain maximum transmittance of light
emanating from the plurality of signalling devices for light
propagating at any angle to a heading of the vehicle.
5. A light bar as set forth in claim 1 wherein the non-linear
patterns formed by the signalling devices and the dome assembly are
substantially the same.
6. A light bar as set forth in claim 1 wherein the non-linear
pattern formed by the dome assembly is symmetrical about a plane
that is parallel to a heading of the vehicle when the light bar is
mounted to the vehicle.
7. A light bar as set forth in claim 6 wherein the non-linear
pattern is approximately V-shaped.
8. A light bar as set forth in claim 4 wherein each of the modules
comprises a base section for supporting the signalling devices on
the frame and a transparent dome that provides a protective cover
and mates with the base section in order for the module to surround
and isolate the signalling device from the elements of the ambient
environment.
9. A light bar as set forth in claim 8 wherein the transparent dome
is secured to the base section for securing the dome to the base
section by a tongue-and-slot arrangement on one side of the module
and at least one threaded screw on the opposite side of the module
for completing the securing of the dome to the base section.
10. A light bar as set forth in claim 1 wherein the frame includes
means for housing microprocessor-based circuitry.
11. A light bar as set forth in claim 1 wherein the means for
securing the frame to the roof includes first and second foot pads
at each end of the frame for supporting the frame on the roof of
the vehicle where a first axis passes through each of the first
foot pads and a second axis passes through each of the second foot
pads such that a moment arm about one of the axes is significantly
greater than a moment arm about the other.
12. A light bar as set forth in claim 1 wherein the means for
securing the frame on the roof of the vehicle includes means
securing the frame to the roof only at the ends of the frame.
13. A light bar as set forth in claim 1 wherein at least one of the
signalling devices includes a reflector and a lamp and means for
rotating the reflector about the lamp such that the focal point of
the reflector is coincident with the position of the lamp and the
axis of the reflector's rotation.
14. A light bar as set forth in claim 13 including a mounting
assembly for each of the lamps associated with the reflector
wherein the mounting assembly includes means for supporting the
lamp at the focal point of the reflector and suspended above the
means for rotating the reflector.
15. A light bar as set forth in claim 14 wherein the means for
supporting the lamp and suspending it above the means for rotating
the reflector is oriented with respect to the lamp so as to present
a minimum silhouette to the light waves reflected by the
reflector.
16. A light bar for mounting to a roof of a vehicle comprising:
a frame for traversing the roof of the vehicle;
a plurality of signalling devices distributed along the frame to
form a non-linear pattern that is symmetrical about a plane that is
parallel to a heading of the vehicle when the light bar is mounted
to the roof; and
an assembly providing a protective cover for each of the signalling
devices where at least one of the covers on each side of the plane
.[.are.]. .Iadd.is .Iaddend.offset in .[.that.]. .Iadd.the
.Iaddend.direction of the heading of the vehicle with respect to
other covers on the same side of the plane.
17. A light bar as set forth in claim 16 wherein the non-linear
pattern is a particular pattern that allows selective operation of
the plurality of signalling devices to directionalize the visual
effect provided by the plurality of signalling devices.
18. A light bar as set forth in claim 16 wherein the covers are a
continuous dome on at least each side of the plane, which defines a
continuous interior space shared by all of the plurality of
signalling devices on the same side of the plane.
19. A light bar as set forth in claim 16 wherein the covers
comprise a plurality of individual modules, with each module
defining a confined interior space that contains and protects one
of the plurality of signalling devices.
20. A light bar as set forth in claim 19 wherein each of the module
includes a base section for supporting the signalling device on the
frame and a transparent dome that mates with the base section in
order for the module to surround the signalling device and isolate
it.
21. A light bar as set forth in claim 20 wherein the transparent
dome is secured to the base section by a tongue-and-slot
arrangement on one side of the module for securing the dome to the
base section on one side of the module and at least one threaded
screw on the opposite side of the module for completing the
securing of the dome to the base section.
22. A light bar as set forth in claim 21 wherein each module
includes means for mounting a color filter under the dome.
23. A light bar as set forth in claim 16 wherein the frame includes
means for housing microprocessor-based circuitry.
24. A light bar as set forth in claim 16 including means at both
ends of the frame for securing the frame to opposing edges of the
roof.
25. A light bar as set forth in claim 24 wherein the means includes
first and second foot pads for supporting the frame on the roof of
the vehicle where the first foot pad is forward of the second foot
pad when the light bar is mounted on the vehicle and the first foot
pad is significantly closer to a transverse plane including the
center of gravity of the light bar than the second foot pad.
26. A light bar as set forth in claim 25 wherein the means for
supporting the frame on the roof of the vehicle includes a pair of
the first and second foot pads and each of the two first and second
foot pads is positioned at the end of the frame so that the light
bar is supported on the roof only at its ends.
27. A light bar as set forth in claim 16 wherein the pattern formed
by the signalling devices is V-shaped when viewed from above the
bar and along the plane of symmetry.
28. A light bar as set forth in claim 16 wherein the pattern formed
by the signalling devices is U-shaped when viewed from above the
bar and along the plane of symmetry.
29. A light bar as set forth in claim 16 wherein the pattern formed
by the signalling devices is O-shaped when viewed from above the
bar and along the plane of symmetry.
30. A light bar for mounting to a vehicle comprising in
combination:
a continuous frame for traversing a roof of the vehicle;
means at both ends of the frame for securing the frame to opposing
edges of the roof;
a plurality of signalling devices distributed substantially evenly
along the frame to form a pattern that is symmetrical about a plane
that is parallel to the heading of the vehicle when the light bar
is mounted to the roof such that each signalling device on one side
of the plane is offset relative to adjacent ones of the signalling
devices in the direction of the heading of the vehicle;
a dome assembly for protecting the signalling devices and
transmitting light emanating from the signalling devices where a
portion of the assembly that transmits light from one of the
signalling devices in a direction transverse to the heading of the
vehicle is offset in the transverse direction with respect to the
similar portions of the assembly for the other signalling
devices.
31. A light bar as set forth in claim 30 wherein the dome assembly
forms a continuous housing for the signalling devices on at least
one side of the plane.
32. A light bar as set forth in claim 30 wherein the dome assembly
comprises a plurality of modules, each module surrounding one of
the signalling devices and isolating it from the elements of the
ambient environment.
33. A light bar as set forth in claim 32 wherein each of the
modules includes a base section for supporting the signalling
device on the frame and a transparent dome that mates with the base
section in order for the module to surround the signalling device
and isolate it.
34. A light bar as set forth in claim 33 wherein a tongue-and-slot
arrangement secures the transparent dome to the base section on one
side of the module and at least one threaded screw on the opposite
side of the module completes the securing of the dome to the base
section.
35. A light bar as set forth in claim 34 wherein each module
includes means for mounting a color filter under the dome.
36. A light bar as set forth in claim 30 wherein the base includes
means for housing microprocessor-based circuitry.
37. A light bar as set forth in claim 30 wherein the pattern formed
by the signalling devices is substantially V-shaped.
38. A light bar as set forth in claim 37 including a row of lights
mounted to the frame and spanning the V-shaped pattern from both
ends of the pattern and facing rearwardly with respect to the
vehicle when mounted to it.
39. A light bar as set forth in claim 30 including a row of lights
mounted to the frame spanning the pattern of the lamps from both
ends of the pattern and facing rearwardly with respect to the
vehicle when mounted to it.
40. An emergency lighting system that includes a light bar for
mounting to a roof of a vehicle .[.and providing a signalling
pattern whose primary warning effect can be alternatively
directionalized into at least four distinct zones about the
vehicle.]., the system comprising: a frame for the light bar
mounted to the roof of the vehicle; a plurality of signalling
devices for radiating light distributed along the frame .[.to form
a non-linear pattern.]. .Iadd.substantially in a common horizontal
plane; a mounting assembly for positioning each of the signalling
devices relative to adjacent signalling devices mounted on the
frame .Iaddend.such that .[.more than.]. .Iadd.any .Iaddend.two
.Iadd.or more .Iaddend.of the signalling devices are distinctly
visible .[.in each zone and at all positions within the zone.].
.Iadd.about the vehicle between a viewing position coincident with
a heading of the vehicle and a viewing position approaching a
position perpendicular to the heading.Iaddend.; and a single
electrical control system for controlling the operation of each of
the plurality of signalling devices .[.and for coordinating the
operation of each signalling device.]. in order to generate
signalling patterns employing some or all of the signalling
devices.
41. An emergency lighting system as set forth in claim 40 including
means at ends of the frame for securing the frame to opposing edges
of the roof.
42. An emergency lighting system as set forth in claim 40 wherein
each of the plurality of signalling devices comprises:
at least one lamp for radiating light;
a reflector having a focal point for reflecting light emanating
from the lamp and collimating it into a beam;
means for rotating the reflector about the focal point;
a mounting assembly for the lamp that positions the lamp at the
focal point and suspends it above the means for rotating the
reflector; and
the mounting assembly including members that interrupt the beam of
light from the reflector, but are positioned with respect to the
beam to present a minimum profile in order to minimize the
interruption.
43. An emergency lighting system as set forth in claim 40 wherein
at least part of the single electrical control system is contained
within a housing incorporated into the light bar.
44. .[.An.]. .Iadd.The .Iaddend.emergency lighting system as set
forth in claim 40 wherein the .Iadd.distribution of the plurality
of signalling devices is along the frame to form a
.Iaddend.non-linear pattern .[.is approximately V-shaped.]..
.Iadd.45. The emergency lighting system of claim 40 wherein the
signalling devices are distributed to form a V-shaped
formation having a forwardly pointing vertex. .Iaddend..Iadd.46.
The emergency lighting system of claims 40 or 45 including a
plurality of domes for covering the signalling devices, where each
dome covers only one of the signalling devices. .Iaddend..Iadd.47.
The emergency lighting system of claim 40 wherein the single
electrical control system includes programmable circuitry contained
within a housing that forms part of the light bar.
.Iaddend..Iadd.48. The emergency lighting system of claim 40
wherein at least one of the signalling devices includes a sensor
that provides a signal to the single electrical control system for
resolving a position of a light beam produced by the at least one
signalling device. .Iaddend..Iadd.49. The emergency lighting system
of claim 40 wherein the signalling patterns generated by the
signalling devices are controlled by the single electrical control
system to provide a primary warning effect that can be
alternatively directionalized into at least four distinct
zones about the vehicle. .Iaddend..Iadd.50. A light bar for
mounting to a roof or a vehicle, the light bar comprising: a frame
for traversing the roof of the vehicle; means for securing the
frame to the roof; a plurality of signalling devices for radiating
light distributed along the frame substantially in a common
horizontal plane such as that any two or more of the signalling
devices are distinctly visible about the vehicle between a viewing
position coincident with a heading of the vehicle and a viewing
position approaching a position perpendicular to the heading; and a
dome assembly covering the signalling devices and mounted on the
frame in such a manner that the assembly forms a non-linear pattern
traversing the roof. .Iaddend..Iadd.51. The light bar of claim 50
wherein the signalling devices are distributed to form a V-shaped
formation having a forwardly pointing vertex. .Iaddend..Iadd.52.
The light bar of claims 50 or 51 wherein the dome assembly covering
the signalling devices includes at least one dome that covers only
a single one of the signalling devices. .Iaddend..Iadd.53. The
light bar of claim 50 including a single electrical control system
for controlling the operation of each of the plurality of
signalling devices. .Iaddend..Iadd.54. The light bar of claim 53
wherein the single electrical control system includes programmable
circuitry contained within a housing that forms part of the light
bar. .Iaddend..Iadd.55. The light bar of claim 53 wherein at least
one of the signalling devices includes a sensor that provides a
signal to the single electrical control system for resolving a
position of a light beam produced by the at least one signalling
light. .Iaddend.
Description
TECHNICAL FIELD
The invention is generally directed to signalling systems for
emergency vehicles and more particularly, is directed to warning
light assemblies for mounting to emergency vehicles.
BACKGROUND
Although warning light assemblies for emergency vehicles are used
in many types of situations, one of the most common uses is to
provide an effective warning for the vehicles as they approach
traffic intersections. Despite the use of warning light assemblies
in this situation, often accompanied by the use of sirens,
collisions at intersections remain a serious problem for emergency
vehicles.
With the increasing popularity of air conditioning and stereo
systems in vehicles, sirens are often not heard. The sound of
conditioned air through the ducting of a vehicle coupled with a
loud stereo often means that an emergency vehicle is not identified
until its warning lights are noticed. As air conditioning and audio
systems in vehicles proliferate, it is important to maximize the
ability of warning lights for emergency vehicles to warn other
vehicles of their approach, particularly at intersections.
Traditionally, warning light assemblies for an emergency vehicle
have been mounted on a base that traverses a roof of the vehicle.
The warning lights are distributed substantially in a row across
the roof and are enclosed by one or more transparent domes that
protect the lights from the elements of the ambient environment. To
draw attention to the lights, their intensities are varied, usually
either by flashing them or focusing the lights into beams that
rotate.
The visual effect of these flashing and/or rotating warning lights
is greatest when viewed from directly in front or behind the
vehicle. At intersections, however, the greatest danger of
collision is derived from approaching vehicles in a crossing street
or highway. These vehicles view the row of warning lights on the
emergency vehicle at angles up to approximately 90.degree. to the
heading of the emergency vehicle. At such angles, the profile of
the lights is effectively narrowed, thereby reducing their
visibility. Furthermore, the domes over the warning lights are
often configured such that their transmittance at angles
approaching 90.degree. is significantly less than when the warning
lights are viewed from directly in front of or behind the vehicle.
The combination of the reduced profile and transmittance seriously
compromises the warning ability of the lights for vehicles
approaching the emergency vehicle from a side angle, as is
typically in an intersection.
SUMMARY OF THE INVENTION
It is a primary object of the invention to provide a light bar for
an emergency vehicle having enhanced transmittance in directions at
an angle to the heading of a vehicle carrying the light bar, while
providing the same or better transmittance as conventional light
bars along the heading of the vehicle. In this connection, it is a
more particular object of the invention to provide a light bar for
an emergency vehicle having increased visibility as the vehicle
enters an intersection.
It is another object of the invention to provide a light bar for an
emergency vehicle that is able to directionalize its warning
pattern into zones positioned about the vehicle.
It is a further object of the invention to provide a light bar for
an emergency vehicle that has the foregoing characteristics and is
easily assembled and serviced. In this connection, it is a more
particular object of the invention to provide a modular design for
such a light bar.
It is a further object of the invention to provide a light bar that
has the foregoing characteristics and is also aerodynamically
efficient.
It is a further object of the invention to provide the foregoing
light bar with a stable mounting that does not require the drilling
of holes in the roof of the vehicle.
Other objects and features of the present invention will become
apparent to those skilled in the art upon reading the following
detailed description and upon reference to the drawings.
In order to achieve the foregoing objects and others, the invention
provides a light bar comprising a plurality of like signalling
devices distributed on a frame that traverses a roof of a vehicle,
where the signalling devices are protected by a dome assembly that
forms a non-linear pattern. The non-linear pattern of the dome
assembly enhances the visibility of the warning pattern generated
by the signalling devices when viewed at an angle with respect to
the heading of the vehicle carrying the light bar. Moreover, the
non-linear pattern facilitates directionalizing the warning pattern
into zones about the vehicle so that the visual effect of a warning
pattern can be enhanced when viewed on one side of the vehicle with
respect to the visual effect from the vehicle's other side.
Preferably, each of the signalling devices of the light bar is
housed in a pod-like module mounted to the frame. The modules are
similarly shaped and distributed along the frame to form a
non-linear pattern when viewed from one end of the frame to the
other. In the illustrated embodiment, the non-linear pattern is a
V-shaped pattern. It will be appreciated from the following
detailed description, however, that other non-linear patterns may
also be implemented. The important factor in choosing a non-linear
pattern is its ability to enhance the visibility of the warning
pattern at angles approaching 90.degree. to the heading of the
vehicle while maintaining the same or better visibility along the
heading of the vehicle as is provided by conventional linear light
bars.
Each of the modules comprises a base section for supporting one of
the signalling devices. A dome fits over the base and combines with
it to isolate the signalling device from the elements of the
ambient environment. Each of the domes surrounds the associated
signalling device so that light emanating from the device is
incident on the inner surface of the dome at an angle that remains
close to 90 degrees. By maintaining such a relationship between the
radiated light and the dome, the modules provide a high percentage
transmittance of light in every direction, thereby further
enhancing the visibility of the warning pattern when viewed at an
angle to the heading of the vehicle.
As an alternative to the modular construction of the preferred
embodiment, the dome assembly for the signalling devices may extend
along the frame to cover more than one device. Although such a
construction does not benefit as much from enhanced transmittance
in all directions as does a modular construction, it may
nevertheless still provide enhanced transmittance at angles to the
heading of the vehicle relative to conventional linear light
bars.
Preferably, each of the signalling devices comprises a reflector
mounted to rotate about its focal point and a lamp positioned at
the focal point. It will be appreciated, however, that many other
types of visual signalling devices can be substituted for the
preferred one and the advantages of the invention will still be
realized.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an emergency vehicle incorporating
a light bar having a plurality of light modules mounted to a frame
in accordance with the invention;
FIG. 2 is a cross-sectional view of the light bar taken along the
line 2--2 of FIG. 1, showing a cross-sectional view of one of the
light modules and the frame;
FIG. 3a is a schematic plan view of the light bar mounted on a
vehicle illustrating the improved visibility provided by the light
bar for an observer positioned at an angle to the line of travel of
the emergency vehicle and also illustrating the ability of the
light bar to directionalize its warning pattern into zones;
FIG. 3b is a schematic plan view of the pattern formed by the
modules, illustrating the ability of the modules to maintain a
reasonably wide distribution of light even when viewed 90.degree.
from the heading of the vehicle;
FIG. 4a is an exemplary graph, using the Cartesian coordinate
system, illustrating variable transmittance of light from a lamp
through a transparent medium such as a dome of a light bar for
different angles of incidence, where the ordinate is the angle of
incidence of the light in degrees and the abscissa is the amount of
transmittance as a percentage of the incident light;
FIG. 4b is a schematic diagram illustrating the angles of incidence
on the dome of one of the modules for light radiating from a lamp
within the dome;
FIG. 5a is an enlarged view of the cross-section of the light
module in FIG. 2 more clearly illustrating the two major
subassemblies of the module--i.e., a base section and a dome;
FIG. 5b is an enlarged partial view of the light module in FIG. 5a,
illustrating a tongue-and-slot assembly for securing the base
section of the module to a front portion of the dome;
FIG. 5c is an enlarged partial view of the light module in FIG. 5a,
illustrating a threaded screw assembly for securing the base
section of the module to a back portion of the dome;
FIG. 6 is a plan view of the light module in FIG. 5a taken along
the line 6--6;
FIG. 7 is a cross-sectional view of the light module in FIG. 6
taken along the line 7--7;
FIG. 8 is a plan view of the light bar with all but one of the
modules removed in order to more clearly illustrate the structure
of the frame;
FIG. 9 is the same plan view of FIG. 8, except the cover for the
electronics of the light bar and the plates for mounting the
modules have been removed in order to expose the basic framework
and wiring;
FIG. 10 is a partial and enlarged view of the cross-sectional view
in FIG. 2, showing a back end of the frame and its connection to a
series of lights mounted to the end;
FIG. 11 is a side view of the light bar in FIG. 1 showing the
mounting assembly for securing the light bar to the roof of the
vehicle;
FIG. 12 is a partial perspective view of the underside of the light
bar, with the components of the mounting assembly exploded in order
to illustrate the composition of the assembly and its fastening to
the frame of the light bar; and
FIG. 13 is a perspective view of a light bar according to an
alternative embodiment of the invention.
While the invention will be described in connection with a
preferred embodiment and an alternative embodiment, there is no
intention to limit it to those embodiments. On the contrary, the
intent is to cover all alternatives, modifications, and equivalents
falling within the spirit and scope of the invention as defined by
the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning to the drawings and referring first to FIGS. 1 and 2, an
emergency signalling system according to a preferred embodiment of
the invention is installed in an exemplary emergency vehicle 11
shown in broken lines. The system 13 includes a plurality of like
modules 17(a)-17(g) housing signalling devices 20. The emergency
signalling system 13 is mounted to a roof 19 of the vehicle 11, and
the modules 17(a)-17(g) are evenly distributed across the roof.
Emergency signalling systems of the type mounted to the roof of
emergency vehicles are commonly called "light bars" because they
are typically shaped as a linear bar that traverses the roof. In
keeping with this convention, the illustrated emergency signalling
system is hereinafter referred to as a "light bar" since it is
intended to be mounted to the roof of an emergency vehicle.
In the light bar 13, each of the signalling devices 20 is contained
within one of the modules 17(a)-17(g). Each of the modules
comprises a base section 12 and a dome 14 (as best see in FIG. 2)
mounted to a frame 16 that traverses the vehicle. The frame 16
supports a housing 15 containing a portion of the circuitry for
controlling the signalling devices 20 as will be explained more
fully hereinafter. The light bar 13 is mounted to the vehicle 11 by
way of a mounting assembly 18 at each end of the frame 16.
Because each of the signalling devices within the modules
17(a)-17(g) is identical to the other, a single reference number 20
will be used for each of the devices, although separate devices are
housed in each one of the modules. In the illustrated light bar 13,
space in the housing 15 is reserved for a portion of the circuitry
that controls each of the signalling devices 20. The housing 15 is
intended to provide an RF shield for the circuitry inside the light
bar 13 since the vehicle 11 will most likely be exposed to
considerable RF noise. For example, the vehicle 11 is typically
equipped with a two-way radio (not shown) whose transmitter creates
serious noise problems for the electronics in the light bar 13 and,
therefore, requires the electronics to be adequately shielded. Of
course, the housing 15 must also protect electronics from the
elements. Techniques for electrically and physically sealing the
housing 15 are well known in the art.
The frame 16 comprises two extruded members 21a-21b (see FIG. 9)
that are secured to one another to form a V-shaped base. Each of
the members 21a and 21b forms one wing of the V and meet at a
vertex 23 formed by the two wings of the V. The housing 15 for the
circuitry controlling the signalling devices 20 spans the members
21a and 21b and also provides a base for supporting a row of
secondary lights 25 distributed across the back of the light
bar.
Each of the extruded members 21a and 21b is of identical cross
section and formed from aluminum by a conventional extrusion
process to define a channel 27, best seen in FIG. 2, for
communicating wiring emanating from the circuitry in the housing 15
to the signalling devices 20, each of which comprises a lamp 29 and
a stepper motor 31 mounted in the base section 12 of each module
17(a)-17(g) for rotating a reflector 33. For ease of assembly and
wiring of the light bar 13, the channel 27 opens at the top of each
member 21a and 21b. After the wiring has been placed in the channel
27, a top plate 35 made of aluminum is received by a recess in the
members 21a and 21b and secured by threaded screws 36 in order to
close the channel and isolate it from the elements of the ambient
environment. The top plate 35 includes a variety of holes (see FIG.
8) for securing the modules 17(a)-17(g) to the frame 16 and for
communicating wiring from the channel 27 to the signalling devices
20 as explained more fully hereinafter.
In order to form the housing 15 and secure it to the extruded
members 21a and 21b, a bottom pan 37 is secured by threaded screws
38 to the bottom side of each extruded member 21a and 21b and
extends rearwardly past the member. The bottom pan 37 is made of
aluminum and has the general shape of a triangle in order to fit
within the V-shape formed by the two extruded member 21a and 21b.
Circuit board assemblies 39a and 39b are mounted on the bottom pan
37 and preferably provide programmable circuitry (e.g.,
microprocessor-based circuitry) for controlling the stepper motor
31 and lamp 29 of each signalling device 20 in conjunction with
additional circuitry (not shown) contained within the vehicle 11. A
control system that may be used in conjunction with the illustrated
light bar 13 is disclosed in co-pending Ser. No. 07/592,557 filed
on Oct. 4, 1990, assigned to the same assignee as that of the
present invention. In this regard, any type of light radiating
device (e.g., a strobe) may be substituted for the illustrated
stepper motor 31 and incandescent lamp 29 since it is the relative
positioning of the signalling devices 20 rather than their
composition that is important to this invention. Nevertheless,
applicants prefer the use of the illustrated stepper motor 31 for
directly driving the rotation of the reflector 33 about its focal
point. Because the stepper motor 31 moves in response to discrete
pulses, it is particularly suitable for use with the
microprocessor-based control system disclosed in the aforementioned
co-pending application.
In order to complete the housing 15 and isolate the circuitry 39a
and 39b contained within it from the elements of the ambient
environment, a top pan 41 formed of aluminum is received by the
extruded members 21a and 21b and the bottom pan 37. As best seen in
FIG. 2, the top pan 41 includes a flange 41a that is received by a
mating slot in the extruded members 21a and 21b in order to join
the top pan to the members. When considered from the area of the
flange 41a backward, the cross section of the housing 15 flares as
best seen in FIG. 2. The flare provides a sufficient vertical back
portion 15a of the housing 15 for mounting the row of secondary
lights 25 while minimizing the leading profile of the housing so as
to reduce wind resistance as much as possible.
In accordance with one important aspect of the invention, the
signalling devices 20 are distributed along the frame 16 to form a
non-linear pattern that maintains a distributed light pattern when
viewed at angles to the heading of the vehicle 11 up to and
including 90.degree., thereby enhancing the ability of the light
bar 13 to attract attention when viewed at severe angles to the
heading of the vehicle. To facilitate the maintenance of the
distributed light pattern at angles to the heading of the vehicle
11, the dome assembly for covering the signalling devices 20 (e.g.,
the domes 14 of the modules in the illustrated embodiment) also
forms a non-linear pattern that traverses the vehicle. Preferably,
the non-linear pattern formed by the dome assembly is the same as
that formed by the signalling devices. In the illustrated and
preferred embodiment, the pattern is V-shaped. It will be
appreciated by those skilled in the art of designing light bars for
vehicles, however, that other shapes may also be used for the
non-linear pattern. For example, the pattern may be U-shaped or
O-shaped. Some of the signalling devices 20 could be aligned across
the roof so that only a few create the non-linear pattern. The
important consideration in selecting a shape of the pattern is that
it provides for a distribution of the signalling devices 20 along
the heading of the vehicle 11 so that a distributed light pattern
is seen when the vehicle is viewed from an angle.
In the illustrated and preferred embodiment, the dome assembly
comprises the domes 14 of the plurality of modules 17(a)-17(g),
where each dome covers only one signalling device 20. Asian
alternative embodiment, the dome assembly may be a continuous
canopy that covers more than one of the signalling devices 20. An
example of such an alternative embodiment illustrated in FIG. 13,
which is discussed in greater detail hereinafter.
Referring to FIG. 3a, the non-linear pattern of the illustrated
light bar 13 is symmetrical about a plane 43 that is orthogonal to
the drawing and parallel to the heading of the vehicle 11. Each of
the modules 17(a)-17(g) and its associated signalling device 20 are
offset in the direction of the vehicle heading on either side of
the plane 43 by a distance Z with respect to an adjacent module. In
a direction traversing the heading of the vehicle 11, each module
17(a)-17(g) is offset from an adjacent module by a distance Y.
Because each of the offsets for one of the modules 17(a)-17(g) is
substantially equal in magnitude to the similar offset of the other
modules, the resulting pattern is the illustrated V-shape. If the
offsets vary in magnitude, patterns of other shapes result.
Preferably, the ones of the modules 17(a)-17(g) on each side of the
plane 43 define a wing of the V-shaped pattern whose angle .theta.
with respect to the heading of the vehicle is approximately equal
to 45.degree..
Extending the wings formed by the modules 17(a)-17(g) on each side
of the plane 43 by drawing a dashed line 45 and 47 past the end
modules in each wing as illustrated divides the area around the
vehicle 11 into four (4) quadrants or zones 1, 2, 3 and 4. By
selectively operating the lamp 29 and reflector 33 of individual
ones of the signalling devices 20, the visual pattern collectively
generated by the devices may be directionalized into any one of
these four zones. For example, by operating only the signalling
devices 20 on the left-hand side of the plane, the visual pattern
can be directed primarily into zone 4. Similarly, by operating only
the signalling devices 20 on the right-hand side of the plane, the
visual pattern can be directed primarily into zone 3. Operating all
of the signalling devices 20 distributes the visual pattern among
all four zones. By controlling the rotation of the reflectors 33,
the visual pattern generated by the signalling devices 20 can be
directed into either zone 1 or zone 2 or simultaneously into zones
1 and 2.
An observer 49 positioned at an angle .beta. with respect to the
heading of the vehicle sees a distributed light pattern well beyond
the angle 90.degree.. As can be seen in FIG. 3a, the beams of light
from the signalling devices 20 remain visually discrete to the
observer 49 who is viewing the vehicle 11 at an angle .beta. close
to 90.degree. from the heading. The greatest enhancement in the
visibility of the visual pattern provided by the non-linear shape
of the light bar occurs at angles .beta. greater than 45.degree..
At an angle .beta. of approximately 45.degree., an observer sees a
distribution of light that is approximately the same visual
distribution offered by a conventional linear light bar. As the
angle of the observer increases past 45.degree., the distribution
of light in a linear light bar quickly shrinks and the beams blend
and eventually are reduced to virtually a single beam width at
90.degree.. In contrast to this rapid reduction in visibility, the
non-linear light bar of the invention maintains a distributed
pattern of light beams well past an angle .beta. equal to
90.degree. as indicated by the projection of the light beams 50
onto a plane 52 in FIG. 3a. In essence, the non-linear light bar of
the invention increases the visibility of the light patterns in
zones 3 and 4 illustrated in FIG. 3a while maintaining the same
degree of visibility provided by conventional linear light bars in
zones 1 and 2.
Referring briefly to FIG. 3b, the distribution of light beams from
the modules 17(a)-17(g) is viewed by an observer in the center of
zone 1 to provide a distribution of approximately the length
l.sub.1. As the observer moves away from the vehicle heading and
toward zone 3, the distribution decreases. At an angle .beta. of
45.degree., the visual distribution is across a length l.sub.2,
which is equal to l.sub.1 /.sqroot.2. As the observer moves into
zone 3 and toward an angle .beta. of 90.degree., the visual
distribution decreases to a length l.sub.3, which is equal to
l.sub.1 /2. By maintaining a substantial effective distribution of
the signalling devices at all angles of view, the light bar 13 is
significantly more visible at angles approaching 90.degree..
By providing the domed modules 17(a)-17(g) for every signalling
device 20 in the preferred embodiment, overall transmittance is
enhanced at angles .beta. to the heading of the vehicle 11, thereby
further increasing the visibility of the light pattern provided by
the non-linear distribution of the signalling devices. In
conventional linear light bars, the angle of incidence .phi. for a
beam of light emanating from a signalling device 20 approaches
90.degree. when the beam is viewed from the side of the vehicle. As
indicated in FIG. 4a, the angle of incidence is conventionally
measured from a reference that is perpendicular to the incident
surface. As is well known, as the angle of incidence .phi.
increases, the transmittance of light decreases. In the exemplary
graph of FIG. 4a, it can be seen that the value of transmittance
typically stays quite high (e.g., 90%) until the angle .phi.
exceeds some critical angle X. At angles greater than the critical
angle X, the transmittance quickly deteriorates until it reaches
zero at an angle .phi. equal to 90.degree..
In a conventional linear light bar, at least some of the light
beams from the signalling devices 20 would be transmitted through
the dome of the bar at angles greater than the critical angle X
when viewed from the side of the vehicle 11. In contrast, the
substantially teardropshaped modules 17(a)-17(g) of the illustrated
embodiment of the invention each provide a dome 14 surrounding and
protecting one of the signalling devices 20 such that the angle of
incidence remains less than the critical angle X for full rotations
of the light beams formed by the devices. Regarding the enhanced
transmittance provided by the domes of the modules 17(a)-17(g),
FIG. 4b illustrates in a schematic manner the angle of incidents
for several beams of light emanating from one of the signalling
devices 20. For beams 51 and 53 directed along the heading of the
vehicle 11, the angle of incidence .phi. is approximately
0.degree., thus maximum transmittance is provided. As the beam
sweeps through a 360.degree. rotation in response to rotation of
the reflector 33, the angle of incidence varies as illustrated by
the six beams 55-60. The three beams 55-57 are the mirror images of
the three beams 58-60 with respect to the plane of symmetry 61 of
the dome 14 illustrated in FIG. 4b. The three angles of incidents
for the six beams are .phi..sub.1, .phi..sub.2 and .phi..sub.3 of
which all are less than the critical angle X.
Referring now to the structure of the signalling devices and their
modules 17(a)-17(g), FIGS. 5-7 illustrate the detailed construction
of an exemplary one of the signalling devices 20 in the module
17(d) illustrated in FIG. 2. As previously indicated, each of the
signalling devices 20 is identical to the others. Similarly, the
modules 17(a)-17(g) are identical except for differences in their
shape necessary to accommodate their mountings on different areas
of the frame 16. Therefore, only the signalling device 20 of the
module 17(d) will be discussed in detail hereinafter. As for the
details of the construction of the modules 17(a)-17(g), the
following discussion refers to the illustration of module 17(d) in
FIGS. 5-7, but applies equally to all of the other modules as
well.
The stepper motor 31 directly drives the mounting 63 for the
reflector 33. In order to directly drive the reflector 33 and its
mounting assembly 63, the motor 31 is mounted in a cavity 65 of the
base section 12 of the module 17(d) such that the drive shaft 66 of
the motor projects along a vertical axis through a hole 68 in the
base section.
The mounting assembly 63 for the reflector 33 is fixed to the end
of the drive shaft 66 so that the assembly and reflector rotate
with the shaft. The shaft 66 of the stepper motor 31 rotates in
arcuate steps and, because the mounting assembly 63 and reflector
33 are secured to the shaft, they also rotate in arcuate steps. The
mounting assembly 63 extends horizontally in one direction to
define an extension 63a that interacts with a position sensor 67 in
order to provide a reference signal to the microprocessor-based
circuitry 39a-39b for the rotation of the reflector 33 about the
lamp 29. For the reflector 33 to orbit the lamp 29 as the shaft 66
of the stepper motor 31 rotates, the reflector is mounted to the
mounting assembly 63 at a position that is offset from the vertical
axis of rotation defined by the shaft. The amount of offset defines
the radius of the orbit for the reflector 33 and positions the
reflector so that its focal point is coincident with the position
of the lamp 29. The direction and speed of the arcuate steps
executed by the stepper motor 31, the mounting assembly 63 and the
reflector 33 are controlled by a control system including the
microprocessor-based circuitry 39a-39b in the housing 15 of the
light bar.
The mounting assembly 63 for the reflector 33 is generally L-shaped
as illustrated and formed from 0.040 inch thick C-1008 or C-1010
cold rolled steel. The reflector 33 is riveted to an upright arm
63b of the mounting assembly 63 so that the reflector is offset
from the axis of rotation as previously mentioned. The reflector 33
is made of 3003 aluminum and has a conventional surface contour of
a paraboloid. A finish is placed on the surface of the reflector 33
so that it has a beam of relatively intermediate width and
sufficient candle intensity on and off the axis of the paraboloid
such that both narrow and broad beam intensity requirements are
met. To ensure sufficient beam width, the finish of the reflector
is prepared using a conventional chemical dipping and anodizing
process, commonly called "bright dipping." With a sufficiently
broad beam width and bright light source for the lamp 29, the
signalling device is able to meet the photometric requirements
(e.g., SAE requirements) for all the patterns commonly made by
different types of conventional rotators.
The lamp 29 is suspended above the axis of rotation for the
reflector 33 by a lamp mounting assembly 69. The assembly 69
includes a conventional lamp socket 71 for receiving a 50 watt
single contact, bayonet base, halogen lamp, which is the preferred
light source. A 50 watt halogen light has sufficient intensity to
satisfy on-axis photometric requirements for any pattern the
signalling device may be asked to execute while complementing the
beam width of the reflector 33 to also meet or exceed beam width
photometric requirements for any pattern. Also, a 50 watt halogen
lamp for each of the signalling devices 20 is a practical power
level that can be supported by the electrical system of the vehicle
11, assuming that the number of signalling devices in a light bar
is not excessive.
In each of the modules 17(a)-17(g) of the seven signalling devices
20, a plate 73 in the base section 12 provides structural support
for mounting the devices. The plate 73 in turn is secured to the
base section 12 by five (5) screws 75a-75e. The stepper motor 31 is
mounted to the underside of the plate 73 by two screws 77a and 77b
and its shaft projects through the hole 68 in the plate. As an aid
in providing structural support, the plate 73 is stamped to include
raised ribs 79 best seen in FIG. 6.
To support the lamp 29 and lamp socket 71 above and along the axis
of rotation and focal point of the reflector 33, the lamp mounting
69 includes a one-piece frame comprising two legs 69a and 69b, each
supporting a cantilevered arm 69c and 69d that is joined at its end
to the other arm. The joint formed by the mating of these two arms
69c and 69d secures the lamp socket 71 over the axis of rotation.
To provide added structural strength, the arms include raised ribs
81. The mounting assembly 69 is formed from 0.059 inch thick 1008
or 1010 cold rolled steel. The legs 69a and 69b are oriented so as
to present a minimum profile to the light radiating from the lamp
28. Each of the legs 69a and 69b includes a foot 69e and 69f,
respectively, for securing the mounting 69 to the plate 73 of the
module. Each foot 69e and 69f is secured to the plate 73 by way of
an expanding nylon fastener and screw combination 83. The nylon
fastener allows the assembly 69 to be electrically common with the
lamp socket 71 in that the fasteners electrically insulate the
assembly from the plate 73. As explained in connection with FIG. 4,
the lamp 29 is energized by grounding the socket 71 and assembly
69.
The position sensor 67 is mounted to a tab 85 that is a vertically
bent portion of the plate 73. Two screws hold the sensor 67 to a
vertical face 85a of the bracket 85 so that the extension 63a of
the reflector mounting 63 passes through a gap in the sensor 67 and
breaks a light beam between a phototransistor and photodiode
comprising the sensor.
Each of the modules 17(a)-17(g) of the light bar 13 includes the
dome 14, which is made of transparent plastic material such as lens
grade polycarbonate plastic. To form one of the modules
17(a)-17(g). the dome 14 is secured to the front of the base
section 12 by way of a tongue-and-slot arrangement 87 as best seen
in FIG. 5b and secured at the back of the base by a pair of screws
89 as best seen in FIG. 5c. Tinnerman clips 91 cooperate with the
screws 89 to fasten the dome 14 to the base section 12 by way of a
vertical extension 73a of the plate 73. With the domes 14 in place,
the signalling devices 20 are isolated from the elements of the
ambient environment. A gasket 93 is fitted between a wall 12a of
the base section and the rim 14a of the dome 14 in order to seal
the junction between the two. Preferably, the gasket 93 need only
extend about the front portion of each module since it is this area
where high pressure caused by the movement of the vehicle 11 could
create a leak without the addition of the gasket. Under each of the
domes 14, a color filter 95 may be provided. These filters 95 fit
into slots formed by two pairs of opposing ribs 96 best seen in
FIGS. 5a and 6. The filters 95 are preferably each in front and
tick sections so that different colors can be projected into
different zones if desired.
A pair of cables 97a and 97b from the microprocessor-based
circuitry 39a-39b in the housing 15 of the light bar 13 feeds wires
to the motor 31 and lamp socket 71 of each signalling device 20 via
the channel 27 in the frame 16 as best seen in FIG. 8. Also, wires
in one of the cables 97a and 97b carry signals from the position
sensors 67 back to the microprocessor-based circuitry 39a-39b by
way of the channel 27. A wire 99 to the socket 71 for the lamp 29
is secured to one of the legs 69a or 69b of the lamp mounting 69
and provides power to the positive terminal in the socket. In each
of the modules, a connector 101 (FIGS. 5a and 8) mounted to the
underside of the plate 73 interfaces the wiring of the signalling
device 20 and the wiring from the microprocessor-based circuitry
39a-39b.
As can be best seen in FIG. 8, the top plate 35, which is fitted
into a recess of the extruded members 21a and 21b, is preferably
comprised of three sections 35a, 35b and 35c. Each of the sections
35a-c includes ports 103 for communicating the pair of the cables
97a and 97b from the channel 27 of the extruded members 21a and 21b
to the modules 17(a)-17(g). One of the cables 97a and 97b includes
a set of wires for controlling the motor 31, while the other cable
controls the lamp 29 of the signalling device 20. In this regard,
the module 17(g) is illustrated in FIG. 8 with its dome 14 removed
in order to show the wiring from the port 103 into the signalling
device 20. The ports communicate into the interior of the modules
17(a)-17(g) by way of holes in the base section 12 and the plates
73 that align with the ports when the modules are mounted to the
frame 16. Holes such as 105 illustrated in FIG. 8 are also provided
in the three sections 35a-c of the plate 35 in order to secure the
base section 12 of each module 17(a)-17(g) to the frame 16. The
extruded members 21a and 21b are capped at their end by face plates
107a and 107b.
Removing the top plate 35 and cover 41 of the housing 15 as shown
in FIG. 9 exposes the recess 108 for receiving the plates 35 and
the routing of the pairs of cables 97a and 97b for the seven (7)
signalling devices 20 of the illustrated embodiment. Cabling 109
from the control system (not shown) for the light bar 13
communicates the control system with the microprocessor-based
circuitry 39a-39b by way of a hole 110 in the pan 37. Sub-circuit
39a includes seven ports 111, each providing one of the cable 97a
in the pair 97a and 97b going to one of the signalling devices 20.
Each cable 97a from the subcircuit 39a controls the motor 31 of one
of the signalling devices 20. Correspondingly, a sub-circuit 39b
includes seven ports 113, each port being associated with the other
cable 97b in one of the pairs. Each cable 97b from the sub-circuit
39b controls the lamp 29 of one of the signalling devices 20. All
of the cables 97a and 97b are communicated into the channel 27
provided by each of the extruded members 21a and 21b by way of a
gap 115 separating the two extruded members 21a and 21b. The gap
115 is tapered such that the two extruded members 21a and 21b meet
at the vertex 23 of the tapered gap. A material made of closed cell
neoprene rubber fills the tapered gap in the area beyond where the
gap communicates to the channel 27.
A third sub-circuit 39c receives a portion of the cabling 109 from
the control system by way of a junction connector 117. The
sub-circuit 39c controls the operation of the assembly of secondary
lights 25 by way of a pair of cables 119a and 119b that connect to
a circuit board 121 for each light contained within a housing 123
as best illustrated in FIGS. 2 and 10. The pair of cables 119a-b
from the sub-circuit 39c enter the housing 123 by way of a hole
(not shown) in the top pan 41 of the housing 15. In order to secure
the back of the top and bottom pans 41 and 37 of the housing 15,
the bottom pan includes a pair of brackets 125a and 125b best seen
in FIG. 9 taken in conjunction with FIG. 2. The brackets 125a and
125b are an extension of the aluminum that form the bottom pan 37.
A spacer or standoff 126 is associated with each bracket 125a and
125b in order to provide the flared cross section of the housing 15
so that the back 15a of the housing has sufficient height for
supporting the secondary lights 25. The assembly of secondary light
25 is attached to an L-shaped back portion 15a of the top cover 41
by way of a plurality of threaded screws 127 as best seen in FIG.
10.
The row of secondary lights 25 is, in the illustrated embodiment, a
row of eight lamps 25a primarily intended for directing traffic
approaching the vehicle 11 from behind. The row has eight (8)
individual polycarbonate lens 129 and aluminum reflector
sub-assemblies 131 attached to a channel 133 formed by the housing
123, which is also made of aluminum. Each lamp 25a, lens 129 and
reflector assembly 131 form a light assembly that is secured to the
housing 123 by two screws (not shown). The row arrangement of the
secondary lights 25 allows them to flash in various patterns such
as sequentially left to right or right to left. By sequencing the
lamps 25 from one end to the other, the secondary lights 25
collectively function as an indicating arrow to direct vehicles to
pass the emergency vehicle 11 on either its left or right side. An
aluminum visor 135 surrounds the top and sides of the channel 133
and the light assemblies. This visor 135 is secured in place by
mounting it between the top pan 41 of the housing 15 and the
housing 123 of the secondary lights 25. The printed circuit boards
121 hold in place lamp sockets 137, and they snap into plastic
standoffs 139 mounted inside the channel 133. A type GH22, bi-pin
halogen lamps of 27 watts are preferably used in each light.
As best shown in FIG. 12, two (2) carriage bolts 141a and 141b that
slide into the bottom of the extruded members 21a and 21b and
protrude through a slot 143 in the bottom pan 37 of the housing 15
are used to secure each of the two mounting assemblies 18 to the
light bar. Each of the mounting assemblies 18 are mirror images of
the other and, therefore, only one will be described in detail
hereinafter.
Each of the assemblies 18 consists of a main mounting bracket 18a
made of cold-rolled steel. This bracket is configured so that the
top of the bracket attaches to the carriage bolts 141a and 141b
under the bottom pan 37. The side of the bracket 18a has outriggers
18b and 18c for attaching two separate mounting foot brackets 143a
and 143b, as well as an outrigger 18d to support a mounting hook
145. When each of the mounting assemblies 18 is mounted to the
light bar 13, the outrigger 18d is located approximately in line
with the center of gravity of the light bar 13. In order to make
the mounting assemblies 18 adaptable to various contours and widths
of roofs, the main mounting bracket 18a includes an extra screw
hole 147. The outriggers 18b and 18c each receive pairs of screws
149 that secure the foot brackets 143a and 143b. The foot brackets
143a and 143b are also made of cold-rolled steel. A rubber pad 151
snaps into the underside of each of the foot brackets 143a and 143b
and is used to protect the vehicle 11 from scratches and dents. The
mounting hook 145 is made of cold-rolled steel and secures the
light bar 13 to the roof 19. One end of the hook 145 is secured
under a rain gutter 153 of the vehicle 11 (FIG. 12) and the other
end is secured to the outrigger 18d by way of a bolt 155 as best
seen in FIG. 11.
The outrigger 18d and hook 145 are positioned to be in transverse
alignment across the roof 19 of the vehicle 11 with the center of
gravity of the light bar 13. Unlike conventional mounting
assemblies for light bars, however, the foot brackets 143a and 143b
are not evenly spaced from the outrigger 18d and hook 145 as can be
best seen in FIG. 11. The foot brackets 143a and 143b are separated
by a distance D in order to provide a sufficiently wide base for
the mounting assembly 18 to be stable. The moment arm 157 about the
outrigger 18d and hook 145 with reference to the forward foot
bracket 143a is relatively short compared to the moment arm 159
about the outrigger and hook with reference to the rearward foot
bracket 143b. The shorter moment arm 157 aids in ensuring the hook
and its connection to the outrigger 18d is sufficiently strong to
resist any rotational force resulting from currents of high
velocity wind passing the light bar 13. Strong rotational forces
about the outrigger 18d and hook 145 are much less likely to be
generated along the moment arm 159 of the rearward foot bracket.
Therefore, this bracket can be safely placed farther from the
outrigger 18d and hook 145 in order to ensure the mounting assembly
18 has a sufficiently wide stance to be stable on the roof 19.
The mounting assemblies 18 at each end of the light bar 13 provide
a highly rigid mounting for the light bar. The rigidity of the
light bar 13 itself is aided by the housing 15 spanning the wings
of the V-shaped frames 16. With a stable mounting and a rigid
construction for the light bar, applicants have found that a center
support for the light bar 13 is not necessary. Therefore, there is
no need for holes to be drilled into the center of the roof 19 or
other type of modifications made to the vehicle 11 in order to
support the light bar 13 on the roof. In order to ensure the light
bar 13 is leveled on the roof 11, the holes 160 in outrigger 18c
are elongated so the position of the foot bracket 143b can be
adjusted for the contours of different roofs. In contrast, the
holes 162 in the outrigger 18b are not elongated.
Finally, FIG. 13 illustrates an alternative embodiment of the
invention wherein a light bar 161 according to the invention
includes a dome 163 that forms a continuous closed canopy over the
signalling devices (not shown) mounted to a V-shaped frame 165. As
in the preferred to embodiment, a housing 167 contains
microprocessor-based circuitry for controlling the signalling
devices and a row of secondary lights 169 mounted across the back
of the housing 167.
The dome 163 may be formed of standard polycarbonate material and
pieced together from two linear dome sections 163a and 163b that
join at a vertex 171 of the V-shape. The interior of each dome
section 163a and 163b provides a continuous cavity for mounting the
signalling devices to the frame 165. The signalling devices may be
of any conventional type, or they may be the signalling devices 20
shown in the preferred embodiment.
The light bar 161 of FIG. 13 provides essentially the same enhanced
visibility when viewed at angles approaching 90.degree. to the
heading of the vehicle carrying the light bar as does the light bar
13 of the preferred embodiment. Because of the modular construction
of the domes 14 of the light bar 13, however, the percentage
transmittance of light at angles approaching 90.degree. may be
slightly less for the light bar 161 than for the light bar 13.
Nevertheless, the light bar 161 still provides significantly
improved visibility at severe angles to the heading of a vehicle
relative to that provided by a conventional linear light bar.
From the foregoing, it will appreciated that the light bars 13 and
161 provide enhanced visibility relative to conventional linear
light bars when viewed from an angle approaching 90.degree. to the
heading of the vehicles 11 to which the light bars are mounted. In
the light bar 13, the modules 17(a)-17(g) for the signalling
devices 20 provide high percentage transmittance of light radiating
from the signalling devices at severe angles to the heading of the
vehicle 11. Furthermore, the non-linear distribution of the
signalling devices 20 allows for the devices to be controlled in a
manner that can directionalize the warning signal generated by the
signalling devices into different zones surrounding the vehicle.
These advantages over conventional non-linear light bars are
achieved without sacrificing visibility of the light bar along the
heading of the vehicle 11. By providing a housing 15, the light bar
incorporates programmable circuitry 39a-39b that advantageously
utilizes the versatility offered by the use of a stepper motor 31
to drive the reflector 33 in the preferred signalling devices 20.
In this regard, the ability of the light bar 13 to directionalize
its warning signal is best realized by the signalling devices 20
driven by the programmable circuitry 39a-39b.
* * * * *