Communications: electrical – Pedestrian guidance
Reexamination Certificate
1999-11-08
2001-02-27
Lee, Benjamin C. (Department: 2736)
Communications: electrical
Pedestrian guidance
C200S520000, C200S341000
Reexamination Certificate
active
06195021
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to devices and systems for the actuation of traffic signals, and in particular, a pedestrian push-button actuator and associated system.
DESCRIPTION OF THE RELATED ART
Traffic signals can be classified as pre-timed, semi-actuated, or fully actuated. Pre-timed traffic signals operate without regard to vehicle or pedestrian detection on a pre-determined cycle that does not vary based on traffic volume. Semi-actuated traffic signals provide a fixed service (green) time for main street traffic and provide variable service time for minor street traffic based upon recognition of vehicle or pedestrian presence on the minor street. The minor street receives service up to a programmed maximum before the signal returns to main street service (green). Fully actuated traffic signals recognize vehicle presence on all approaches and provide variable service time dependent on demand up to a programmed maximum. Fully actuated signals are programmed to dwell in one phase until actuation occurs on another phase.
Semi-actuated and fully actuated traffic signals, as discussed above, provide variable service times for traffic based upon demand. The demand is measured by the detection of vehicles through any number of well-known methods, or by the detection of pedestrians by the push of a pedestrian push-button. The time required for one vehicle to cross an intersection is typically much less (e.g. 3-5 seconds) than the time required for one pedestrian to cross an intersection (e.g. 15-25 seconds). As such, the push of a pedestrian push-button signals the electronic traffic signal controller to provide the greater amount of time necessary for a pedestrian to cross.
Vehicle detection is accomplished through various methods such as, for example, inductive loops, microwave detectors, and magnetometers. In each case, a failure in the detector results in the reading of an “open” or broken circuit, and the controller recognizes that detection is lost. Upon recognition that detection is lost, the controller provides the maximum preset green time for that phase, assuming that there is a constant demand (i.e., the signal acts as a pre-timed signal). Likewise, the failure of a pedestrian push button must be recognized and provision of appropriate pedestrian crossing time provided until the button is repaired.
Non-functioning pedestrian push buttons are not always recognized by a traffic signal controller. This is because existing pedestrian push-buttons place a call to the traffic signal controller when a circuit is “closed” by the push of the button. The button, when pushed, contacts two terminals that complete a circuit and register a signal to the controller. Unless the button fails in this closed position, for instance by being mechanically stuck, the controller does not recognize that the button has failed and does not default to “Pedestrian Recall” phasing, where adequate pedestrian timing would be provided every cycle. Typically, the following types of common push button failures are not recognized by the traffic signal controller: rusted electrical terminals, dismantled button assembly, broken underground conduit/wire, broken internal workings of button.
FIGS. 1A and 1B
depict a conventional pedestrian push button device (
10
) which would typically be used at semi-actuated and fully actuated signalized intersections.
FIG. 1A
depicts a top plan view of the device (
10
), and
FIG. 1B
depicts a front elevation view of the device. The push button device (
10
) includes a casing (
17
) which is installed into a weather-proof push button assembly (not shown) using the installation threading (
18
). The push button device (
10
) also includes a push button (
21
), a positive terminal (
11
), a negative terminal (
12
), and a spring (
13
). The push button (
21
) is coupled to a non-conductive plate (
16
), which is in turn coupled to a non-conductive shaft (
15
) and a conductive plate (
14
).
The actuation (e.g. pressing by a pedestrian) of the push button (
21
) pushes the non-conductive plate (
16
), the non-conductive shaft (
15
), and the conductive plate (
14
) against the resistance of a spring (
13
), so that the conductive plate (
14
) contacts the positive terminal (
11
) and negative terminal (
12
) of the device (
10
) which closes the normally open circuit. The closing of the circuit sends a signal to a traffic signal coupled to the device (
10
), which indicates that a pedestrian requires time to cross the street. It should be noted that the spring (
13
) operates to return the push button (
21
) to its original position upon removal of the actuation (e.g. pedestrian discontinues pressing push button).
It should be noted that the above-described device (
10
) is in a “open” circuit configuration most of the time. In other words, the conductive plate (
14
) is not normally contacting the terminals (
11
,
12
). Only when a user depresses (actuates) the push button (
21
) are the conductive plate (
14
) and the terminals (
11
,
12
) brought into contact, thereby closing the “open” circuit. As discussed above, an “open” circuit pedestrian push button device often fails to detect certain types of failures.
Therefore, there is currently a need for an improved pedestrian push button actuator which allows more efficient detection of faults.
SUMMARY OF THE INVENTION
The present invention is an apparatus comprising an actuator including at least one terminal member, the actuator having at least a first and a second position; at least one electrical contact; and, a spring coupled to the at least one terminal member, the spring urging the terminal member against the at least one electrical contact when the actuator is in the first position.
The above and other advantages and features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention which is provided in connection with the accompanying drawings.
REFERENCES:
patent: 3582876 (1971-06-01), Carmack et al.
patent: 4187418 (1980-02-01), Harris
patent: 5735492 (1998-04-01), Pace
patent: 5767465 (1998-06-01), Fulton et al.
patent: 5920050 (1999-07-01), Tolman
Duane Morris & Heckscher LLP
Lee Benjamin C.
LandOfFree
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