US1950741A - Highway traffic signal - Google Patents

Description

March 13, 1934. W Q NElN m- AL 1,950,741

HIGHWAY TRAFFIC SIGNAL Filed May 31. 1929 Patented Mar. 13, 1934 UNITED STATES PATEN'U OFFICE HIGHWAY TRAFFIC SIGNAL William C. Nein and Thomas W. Varley, New

1 Claim.

This invention relates to the control of trame signals on highways where the main highway signals are normally indicating for clear tramo continuously, and the cross street signals are norm mally indicating for stop continuously.

To allow for cross street traffic to talee place, a vehicle on a cross street when approaching a main highway causes the traffic signals to reverse and indicate clear for the cross street and stop for the main highway. After the vehicle has passed away from its position of control, the trahie signals return to normal. devices may be used so that a second vehicle wishing to pass over the main highway, will not cause a signal change until some definite time has elapsed since a previous change.

The object of the invention is to provide 'apparatus such that the 'desired objects may be obtained when the control of the traffic signals is by the use of thermionic vacuum tubes and oscillating currents of electric energy, the desired control being effected by the change of oscillation of the currents.

In carrying out the invention, advantage is taken of the change of plate current to a tube when the electric oscillation changes in energy as a vehicle or metallic mass passes a part of the circuit carrying the oscillating currents.

A control between the vehicle and the traflic signals is thus obtained by proximity of the vehicle to a device along the highway.

In the accompanying drawing which illustrates the invention, ,Y

Figure 1 is a diagrammatic view showing a thermionic tube with its source of energy and its electric circuits together with a pair of wheels representing a vehicle or moving metallic mass.

Figure 2 shows a main highway and cross street with its traiiic signals, in this case light signals together with a part of the electric circuits carrying electric oscillations placed in the roadway of the cross street on either side of the main .highway The operation of the device is as follows: Referring to Figure 1: v A thermionic vacuum tube 4 has its filament 5 heated from a source, in the case 115-volt, 60- cycle, through a lamp 6 as a resistance.

Across filament 5 is a resistance '7 adjustable to give proper filament current.

Across filament 5 is also a resistance 8 with a center tap 9 to give a convenient return for the grid circuit of the tube. The grid 10 connects through grid leak 11 and condenser C1 to a tuning coil 12 and its condenser C2 and then to center tap 9. The plate 13 connects through choke 1i and relay 1 to the line side of lamp 6. The plate also connects to its tuning coil 3 and its condenser C3 by a by-pass condenser C5.

'With the two coils 12 and 3 tuned to the same 6U frequency, the tube 4 will cause oscillating currents to ow in the tuned coils 12 and 3. To assist this eect a condenser C4 connects grid lli to plate i3.

As the circuit currents are oscillating, the plate current through relay l is less in amount than when the currents of the tuned coils 12 and 3 are not oscillating.

The tuned coils 12 and 3 can be used at maximum oscillating value normally, and at less than 'Z0 maximum value when coil 3 for example is thrown less in tune by a passing vehicle 2 or the tuned coils 12 and 3 can be used at minimum oscillating value normally and at more than minimum value when coil 3 is thrown into better tuning 75 by a passing vehicle 2.

In the diagram shown with vehicle 2 over coil 3 which is embedded in the roadway, the tuned coils 12 and 3 are at a high value of oscillating current and the relay 1 is at 'open circuit due to 80 lowering of plate 13 current. i l

The contacts 4 and 5 of relay 1 are closed causing signal lights G2 and R2 to indicate by current from, in this case, a battery 14. G2 and Rz control signals to stop for main highway and to clear for cross street.

As vehicle 2 moves away from coil 3, current in coil 3 falls in value, plate 13 resumes normal high value of current through relay 1 causing relay 1 to open contacts 4 and 5 and close contacts 4 90 and 6 giving current to signal lamps G1 and R1, to indicate resumption of clear for main highway and stop for cross street- This construction of applicants has the feature that the control of the resonant circuit, which results in the control of the signal, is by varying the magnetic induction which is brought about by the passage of the metallic mass on the vehicle and is effective independently of any static induction and therefore provides a means for operating the devices buried in the roadway, notwithstanding the burying of the device shields it from eiect by the static induction occasioned by passing persons or other bodies than the metallic mass on a. vehicle which is capable of changing the magnetic induction as distinguished from the static induction. The device is only operated therefore, as intended, by passing vehicles and is prevented from false operation by passing pedestrians, animals and the like.

circuits including an inductance coil beneath the surface of the roadway and adapted to have its inductance varied by variation in its magnetic induction by the passage of a vehicle carrying a metallic mass in proximity thereto, thereby varying the resonant condition of the last mentioned circuit and consequently varying the oscillatory character of the tube, and means for operatively relating said tube to said signal.

WILLIAM C. NEIN. THOMAS W. VARLEY.

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