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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention involves traffic signal controllers and more particularly a
radio-activated traffic signal controller activated by an emergency
vehicle for changing the mode of operation of the traffic signal so as to
stop traffic in all directions as the emergency vehicle approaches the
intersection.
2. Description of the Prior Art
Remote control of traffic signal systems by emergency vehicles in order to
facilitate movement of emergency vehicles through traffic and reduce the
hazard to the emergency vehicle and other traffic when emergency runs are
being carried out has long been seen as a desirable feature of traffic
signals. In most of these systems a radio, ultrasonic, or
proximity-sensing-arrangement of some sort has been utilized to trigger an
emergency mode for the traffic light controller, typically turning all of
the lights red or alternatively the lights in the transverse direction to
the approach of the vehicle red to facilitate movement of the emergency
vehicles through the intersection.
Some variations of this concept have been proposed such as that disclosed
in U.S. Pat. No. 3,257,641 which discloses a radio-activated system which
triggers an emergency siren and an emergency light in conjunction with
activating all of the red lights, as long as the emergency vehicle is
within transmission range.
In U.S. Pat. No. 3,881,169 various permutations of this concept are
proposed which includes activating all of the red lights in the signals to
a flashing condition.
In another variation the cross street is activated to a blinking red
condition, while the street down which the emergency vehicle is traveling
has its amber lights activated in a flashing condition.
In U.S. Pat. No. 2,881,409, a system is disclosed in which the traffic
signal is activated so as to initially flash yellow, then to a steady red,
both in the cross street direction.
In U.S. Pat. No. 3,114,127, the radio-activated controller briefly flashes
all of the lights red, while sequencing the normal traffic signal controls
to obtain the right sense of the traffic signals to conform with the
direction of approach of the emergency vehicle. At this point, the lights
are maintained in this condition until the emergency vehicle passes.
Other typical systems are disclosed in U.S. Pat. Nos. 3,636,507, 2,203,871
and 3,209,325.
However, no such system has enjoyed widespread acceptance. It is felt that
an overriding concern in the design of any such system is that the cost be
held to a minimum and that this be done without compromising the
reliability of the system, since traffic lights must be highly reliable to
keep maintenance costs within reason and to avoid the resultant disruption
of traffic which would result from the failure of the traffic signal to
operate properly.
The systems described in these patents can all be characterized as being
relatively complex and costly in design with undue elaborateness in the
circuitry and in the control modes which would contribute, in no small
part, to relatively high manufacturing installation costs and which would
contribute to the maintenance problems described.
It is therefore an object of the present invention to provide such an
emergency vehicle activated traffic light controller which is simple in
design, while performing the essential functions required of such a
device. In connection with this object it is also an object of the present
invention to provide such a design which is readily incorporatable into
the traffic signal control systems presently in use.
SUMMARY OF THE INVENTION
These, and other objects, which will become apparent upon a reading of the
following Specification and Claims are carried out by a system including a
radio transmitter-receiver combination which activates a relay which
interacts with a second or master relay which disconnects the normal
sequencer-controller circuitry from the power supply and energizes all of
the signal red lights via timer delay relay contacts, which initially
energizes each of the red lights via a blinker device to produce a
flashing red signal, and after a predetermined adjustable delay on the
order of 5 to 8 seconds, energizes each red traffic signal steadily. After
the emergency vehicle has proceeded a sufficient distance past the
intersection, the signal received by the radio receiver is sufficiently
attenuated to cause de-energization of the control relay and resumption of
normal sequencing and timing by virtue of reconnection of the
sequencer-controller circuitry to the traffic lights.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation of the circuitry according to the
present invention and a diagrammatic representation of the traffic signal
light associated with such circuitry in the normal mode of operation.
FIG. 2 is a diagrammatic representation of the system shown in FIG. 1 in
which the emergency mode operation has been initiated.
FIG. 3 is a diagrammatic representation of a series of intersections having
traffic signals modified according to the present invention, and depicting
the sequencing of the signals from emergency to normal mode as the vehicle
proceeds through these intersections.
DETAILED DESCRIPTION
In the following Specification and Claims certain specific terminology will
be utilized for the sake of clarity and a particular embodiment described
in accordance with the requirements of 35 USC 112, but it is to be
understood that the same is not intended to be limiting and should not be
so-construed, inasmuch as the invention is susceptible of many variations
within the scope of the appended claims.
The present invention is contemplated as being incorporated into a
conventional traffic signal of the type having a plurality of colored
lights, i.e., red, amber and green which are sequenced in a
time-controlled fashion to regulate the flow of traffic.
Referring to FIG. 1, the system according to the present invention includes
a radio transmitter device 10 which would be carried within the emergency
vehicle, with a dash mounted manually operated switch 12 adapted to
control energization of the transmitter 10 by connection with the vehicle
battery 14. The transmitter 10 transmits via antenna 16 a radio rf signal
whenever the switch 12 is closed and does not transmit such signal when
switch is open, as shown in FIG. 1. The system also includes a
receiver-relay 18 carried within each traffic light signal mechanism.
The receiver-relay 18 is adapted to receive the signals emitted by the
transmitter 10 via antenna 19 and close relay contacts 20 whenever signals
are received of predetermined strength level. The contacts 20 are open, as
shown in FIG. 1, in the absence of such radio signals. Power to supply the
receiver-relay is provided by connection to G 110 V A/C source via lines
24 and 26, as shown in FIG. 1.
The transmitter 10 and receiver-relay 18, of course, would preferably
include design features adapted to prevent false triggering or triggering
by unauthorized transmitter devices, and for this purpose various
frequency or other coding arrangements are well known, such as are used in
connection with garage door openers, and other controlled access radio
activated devices, etc., but the details of the same do not form a part of
the present invention and, accordingly, are not here described. However,
it should be understood that such features would be normally included in
their design.
The receiver-relay 18 serves to control energization of a master relay 22
which in turn functions to control the connection of the 110 volt power
supply applied to lines 24 and 26 to the sequencer-controller circuit 30
and the traffic signal 28 lights. One of the lines 24 is connected to the
sequencer-controller circuit 30 and to the individual traffic signal
lights of the conventional traffic light 28. The other line 26 of the
input power supply is connected to switch contact 32 and via contact 34
and line 36 is connected to an input terminal 39 which serves to energize
the sequencer-controller circuitry 30, so that when contacts 32 and 34 are
closed, the operation of the traffic light 28 will be carried out in
normal fashion via lines 40, 42, 44, associated with the red light 46,
amber light 48 and green light 50, respectively.
As shown in FIG. 2, energization of the master relay coil 52 is controlled
by activation of the receiver-relay 18, by connection of one line 26 from
the power supply through closed contacts 20 and line 54. The other line 24
is directly connected to the coil 52 via line 56. Upon energization of the
master relay coil 52, relay armature 58 is drawn axially to the right, as
shown in FIG. 2, against a stop 60. Central shaft 62 integral with the
armature 58 has a first extension portion 64 which engages a switch leaf
66, opening contacts 32 and 34 and interrupting power to the
sequencer-controller circuit 30 to discontinue normal operation of the
traffic signal 28. At the same time, another portion 68 of the armature
shaft 62 activates a timer-relay section 70 of the master relay 22.
Timer-relay section 70 includes a pair of input terminals 72 and 74
connected to the output side of contacts 20 of the receiver-relay 18. A
first output terminal 76 is normally connected via a switch means 77 to
both input terminal 72 and to a blinker device 78. Blinker device 78 is a
conventional interrupter which serves to cyclically open and close an
input contact 80 connected to the timer-relay output terminal 76 and an
output contact 82 directly connected to the red traffic signal light 46,
so that upon energization of the receiver-relay 18, the red traffic signal
light 46 is initially caused to flash red.
After a predetermined adjustable delay period of from 5 to 8 seconds, the
timer-relay section 70 causes opening of switch means 77 and disconnection
of the output terminal 76, and at the same time closes a second switch
means 84 and connection of a second output terminal 86 to the output side
of contacts 20. Terminal 86 is directly connected to the red traffic
signal light 46, to bypass the blinker device 78, and cause a steady red
condition to exist.
Upon opening of the contacts 20 by sufficient attenuation of the rf signal
received by the receiver-relay 18, the timer-relay section 70 is reset by
a spring return (not shown) of the relay armature 58, to allow
reconnection of the normally closed switch means 77, to be in readiness
for the next activation.
Details of the master relay 22 and the timer section 70 are not here
included, since suitable commercial devices are available and at low cost
to perform the described function, and do not comprise per se the present
invention.
Referring to FIG. 3, there is depicted the operation of the control system
as an emergency vehicle proceeds through a series of intersections at
which are installed traffic signal lights incorporating controllers
according to the present invention.
In this representation, an emergency vehicle 88 is proceeding down a
thoroughfare 90, and has passed a sufficient distance from a first traffic
signal 28 A to allow resumption of normal operation.
At the same time, the emergency vehicle 88 has just passed a second traffic
signal 28 B which is thus in a steady red condition, and is approaching a
third traffic signal 28 C to trigger that signal to a flashing red
condition.
Accordingly, it can be appreciated that the system set forth above can be
characterized as extremely simple in implementation, such as to accomplish
the objects of the present invention including only conventional relays
which are commercially available at low cost and are highly reliable in
operation.
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