US3571789A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Vehicle presence loop detector
Assignee: LFE Corp
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Filing: 1968-11-21
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Granted: 1971-03-23
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Expires: 1988-11-21
Abstract
Abstract A vehicle presence detection system comprising an electrical signal generating system including a tuned circuit having a large magnetic field producing induction loop for receiving a vehicle in proximity thereto to change the field configuration and corresponding signal phase resulting therefrom, a phase comparator-detector for receiving said generated signals including the phase variations resulting from such field changes to produce a variable DC signal voltage which changes from a resting level to a second level in one direction of change in response to entrance of a vehicle into proximity to the loop and which changes in the opposite direction from the second level substantially to the resting level upon departure of the vehicle from such proximity to the loop, an in-amplifier for receiving said variable DC signal voltage to produce an output electrical signal responsive to said DC signal change of relatively rapid rate in the one direction of change, an out-amplifier for also receiving the variable DC signal voltage to produce a second output electrical signal responsive to said DC signal change in such opposite direction at a relatively rapid rate of change, a gating or latchup circuit for receiving the in-amplifier and outamplifier output signals to produce a further output signal substantially throughout the period between the first and second output electrical signals, and indicator means for receiving the gated further output signal for producing an indication of the presence of the vehicle in proximity to the inductive loop. The in-amplifier includes a time delay circuit to maintain its output electrical signal for a brief time period while a vehicle is maneuvering in proximity to the loop without departing.
Inventors
- 👤 Bernard J Midlock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 06:45
CPC Classifications
G; G08; G08G; G08G1/00; G08G1/01; G08G1/042
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
180 words
A vehicle presence detection system comprising: a. an electrical signal generating system including tuned circuit means having a large magnetic field producing induction loop for receiving said vehicle in proximity thereto to change the field configuration and corresponding signal phase resulting therefrom; b. means for receiving said generated signals including said phase variations resulting from said field changes to produce a variable DC signal; c. first amplifier means for receiving said variable DC signals to produce a first output electrical signal responsive to the initiation of said DC signal variation; d. second amplifier means for receiving said variable DC signals to produce a second output electrical signal responsive to the termination of said DC signal variations; e. gate circuit means for receiving the said first and second output electrical signals to produce an output signal responsive to said first output electrical signal and to terminate such gated output signal in response to said second output electrical signal; and f. means for receiving said gated output signal for producing an indication of the presence of said vehicle in the inductive loop.
Claim 2
Dependent Claim
180 words
A vehicle presence detection system comprising: a. an electrical signal generating system including tuned circuit means having a large magnetic field producing induction loop for receiving said vehicle in proximity thereto to change the field configuration and corresponding signal phase resulting therefrom; b. means for receiving said generated signals including said phase variations resulting from said field changes to produce a variable DC signal; c. first amplifier means for receiving said variable DC signals to produce a first output electrical signal responsive to the initiation of said DC signal variation; d. second amplifier means for receiving said variable DC signals to produce a second output electrical signal responsive to the termination of said DC signal variations; e. gate circuit means for receiving the said first and second output electrical signals to produce an output signal responsive to said first output electrical signal and to terminate such gated output signal in response to said second output electrical signal; and f. means for receiving said gated output signal for producing an indication of the presence of said vehicle in the inductive loop.
Claim 3
Dependent Claim
36 words
A vehicle presence detector system according to claim 1 and wherein said first amplifier means further comprises a resistor-capacitor input network having a long time constant for receiving and temporarily storing said DC signal and amplifier.
Claim 4
Dependent Claim
76 words
A vehicle presence detector system according to claim 2 and wherein said first amplifier means includes first and second transistor stages normally conductive in the absence of any said DC signal variation and a third normally nonconductive transistor stage driven by said first and second stage, the said three stages reversing their conductive status responsive to the presence of said DC signal variation so as to produce a first output driving voltage from said third stage.
Claim 5
Dependent Claim
85 words
A vehicle presence detector system according to claim 1 and wherein said second amplifier means further comprises a resistor-capacitor input network having a short time constant for receiving said DC signal variations, and amplifier means connected thereto and controllable thereby, the said last named amplifier means disposed to produce a quiescent voltage in the absence of and during a DC signal variation in one direction and a second driving voltage or second output signal responsive to variations of said DC signal in the opposite direction.
Claim 6
Dependent Claim
69 words
A vehicle presence detector system according to claim 4 and wherein said second amplifier means includes a first, second and third transistor stage, the first and third conductive and the second nonconductive in the absence of such DC signal variation in said first direction, and the conductive conditions reversed in response to such DC signal variation so as to produce a second output driving voltage from said third stage.
Claim 7
Dependent Claim
94 words
A vehicle presence signal detecting system according to claim 1 and wherein said gate circuit means includes first and second transistor stages each connected to provide a continuous current path when both are conducting, the first stage disposed to receive the said first and second driving voltages from said first and second amplifier means through coupling means, each coupling means being connected to the base of said first transistor stage and the said second stage being disposed to receive said first driving voltage from said first amplifier means through a coupling impedance connected thereto.
Claim 8
Dependent Claim
155 words
A vehicle presence signal detection system according to claim 6 and wherein said base coupling means includes dual diodes forward biased during the said first and second driving voltages to render the said first transistor stage conductive, and the said coupling impedance includes a current limiting resistor to drive the said second stage to conduction when the first driving voltage is applied thereto, the conduction of both stages producing a continuous current path therebetween to produce an output signal. e. out-amplifier means for receiving said variable DC voltage to produce an output voltage of relatively short duration responsive to said DC voltage variations in said opposite direction; f. gate circuit means for receiving the said in-amplifier and out-amplifier outputs for producing a gated output signal responsive to said DC voltage variations; and g. means responsive to said gated signals to produce an output indicative of the presence of absence of vehicles in the inductive loop.
Claim 9
Dependent Claim
84 words
A vehicle presence system as in claim 1 and in which said gate circuit means includes a silicon controlled rectifier and a transistor, coupled with the collector-emitter circuit of the transistor in series with the anode-cathode circuit of said rectifier to supply anode voltage to said rectifier when said transistor is forward biased, the gate of said silicon controlled rectifier being coupled to the output of said first amplifier and the base of said transistor being coupled to the output of said second rectifier.
Claim 10
Dependent Claim
25 words
A vehicle presence system as in claim 8 and including a circuit including a diode coupling said base to said output of said first amplifier.
Claim 11
Dependent Claim
184 words
A vehicle presence loop detection system for determining the long term presence of vehicles while being insensitive to vehicle movements in the area of detection comprising: a. a field frequency signal generator; b. a tuned circuit including an inductive loop for receiving said vehicle in proximity thereto; c. phase-comparator detection means for receiving signals from said generator and tuned circuit for producing an initial DC voltage variation of substantial amplitude in one direction of change responsive to the phase difference resulting from the presence of a vehicle in said loop; d. in-amplifier means for receiving said variable DC voltages to produce a sustained output voltage responsive to said initial DC voltage variation and insensitive to DC voltage variations of less amplitude in the opposite direction; means connected thereto and controllable thereby, the said last named amplifier means disposed to produce a quiescent voltage in the absence of a variable DC signal and a first driving voltage or first output signal when a vaRiable DC signal is present, said driving voltage persisting for a period of time after the termination of said variable DC signal.
Claim 12
Dependent Claim
184 words
A vehicle presence loop detection system for determining the long term presence of vehicles while being insensitive to vehicle movements in the area of detection comprising: a. a field frequency signal generator; b. a tuned circuit including an inductive loop for receiving said vehicle in proximity thereto; c. phase-comparator detection means for receiving signals from said generator and tuned circuit for producing an initial DC voltage variation of substantial amplitude in one direction of change responsive to the phase difference resulting from the presence of a vehicle in said loop; d. in-amplifier means for receiving said variable DC voltages to produce a sustained output voltage responsive to said initial DC voltage variation and insensitive to DC voltage variations of less amplitude in the opposite direction; means connected thereto and controllable thereby, the said last named amplifier means disposed to produce a quiescent voltage in the absence of a variable DC signal and a first driving voltage or first output signal when a vaRiable DC signal is present, said driving voltage persisting for a period of time after the termination of said variable DC signal.
Claim 13
Dependent Claim
52 words
A vehicle presence system according to claim 10 and wherein said gate circuit means includes interconnected sensing element means, each conductive during the presence of said in- and out-amplifier outputs and remaining conductive during the sustained in-amplifier output so as to render an output insensitive to vehicle movement within the loop confines.
References Cited (Backward Citations)
US3266028A
Cited
US3500310A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-22 | 1974-09-21 | 1975-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-22 | 1978-09-21 | 1979-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-22 | 1982-09-21 | 1983-03-23 | $7700.00 | Window Closed / Lapsed |