US3706098A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Railway signal system
Assignee: HARMON INDUSTRIES Inc
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Filing: 1970-10-23
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Granted: 1972-12-12
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Expires: 1990-10-23
Abstract
Abstract A railway crossing signaling system in which an audio frequency signal coupled into the tracks is affected by the presence of a train near the crossing location and utilized to control operation of a conventional crossing signal relay. A relatively high impedance amplifier is transformer coupled to a section of the tracks, the latter acting as a part of a low impedance feedback path to cause oscillations at a fixed frequency determined by a high Q resonant reed filter. In preferred embodiments of the invention, oscillation is sustained via either direct connection of the feedback loop or connection through the tracks and interrupted by the shunting effect of the train, however, one embodiment of the invention relies on the presence of a train to complete the feedback circuit to produce oscillation. In all embodiments of the invention a relatively low frequency high power signal is impressed upon the track circuit through the common amplifier both to enhance oscillation and to cause frittering or establishment of the track circuit in spite of surface contamination and the like.
Inventors
- 👤 Willard L Geiger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 13:16
CPC Classifications
B; B61; B61L; B61L29/00; B61L29/24; B61L29/28; B61L29/286
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
150 words
Apparatus for establishing an electrical island along a railroad track sensitive to the presence of a shunting medium therein and for signaling such shunting condition, comprising input and output transformers, said transformers being coupled to the track at first and second locations to establish the electrical island, an amplifier for energizing said output transformer, said amplifier having said input transformer connected at the input thereof forming an oscillator system in which oscillations are affected by a shunting medium in the electrical island, a resonant reed filter in connection at the input of said amplifier for restricting oscillation to a predetermined frequency, an oscillator coupled to said amplifier, said oscillator having a lower frequency oscillation than said predetermined frequency and producing a signal at said lower frequency, said signal being supplied to said amplifier for amplification, and means for monitoring the oscillatory state of said amplifier and for providing indications thereof.
Claim 2
Dependent Claim
150 words
Apparatus for establishing an electrical island along a railroad track sensitive to the presence of a shunting medium therein and for signaling such shunting condition, comprising input and output transformers, said transformers being coupled to the track at first and second locations to establish the electrical island, an amplifier for energizing said output transformer, said amplifier having said input transformer connected at the input thereof forming an oscillator system in which oscillations are affected by a shunting medium in the electrical island, a resonant reed filter in connection at the input of said amplifier for restricting oscillation to a predetermined frequency, an oscillator coupled to said amplifier, said oscillator having a lower frequency oscillation than said predetermined frequency and producing a signal at said lower frequency, said signal being supplied to said amplifier for amplification, and means for monitoring the oscillatory state of said amplifier and for providing indications thereof.
Claim 3
Dependent Claim
81 words
Apparatus as set forth in claim 1 wherein said monitoring means comprises a second amplifier coupled to said first amplifier, a transformer energized by said second amplifier, a bridge rectifier connected to the output of said transformer for converting the AC signal to pulsating DC, a capacitor in connection at the output of said bridge rectifier for smoothing the DC voltage, and a crossing relay in shunt connection with said capacitor, said relay being operative to control railway crossing signal devices.
Claim 4
Dependent Claim
75 words
Apparatus as set forth in claim 2 wherein said first amplifier comprises first and second stages of transistor amplifiers connected in common emitter configuration, and a third power amplifier stage having said output transformer in the collector path thereof, and further including a track power control potEntiometer in connection between said second and third stages for variation of the signal applied to the tracks, said amplifier stages being AC coupled to provide a fail-safe operation.
Claim 5
Dependent Claim
68 words
Apparatus as set forth in claim 3 wherein said second oscillator circuit comprises a unijunction transistor connected in oscillatory configuration for charging a capacitor in the base circuit thereof, and a diode connecting said capacitor and the base electrode signal circuit of said third amplifier stage for injection of the oscillatory signal, said diode providing synchronization of the signals of said oscillator circuit and said first amplifier circuit.
Claim 6
Dependent Claim
35 words
Apparatus as set forth in claim 4 wherein the output circuit and input circuit of said input and output transformers respectively include a high value capacitor connected to the tracks for isolation from DC signals.
Claim 7
Dependent Claim
42 words
Apparatus as set forth in claim 5 further including a potentiometer in the collector path of said second stage amplifier, the slider of said potentiometer being connected to the input of said relay driver circuit for varying the sensitivity of the system.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-12 | 1976-06-12 | 1976-12-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-12 | 1980-06-12 | 1980-12-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-12 | 1984-06-12 | 1984-12-12 | $7700.00 | Window Closed / Lapsed |