US3900830A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Piezoelectric traffic counter switch and associated pulse generator circuit
Assignee: Leupold and Stevens Inc
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Filing: 1974-08-15
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Granted: 1975-08-19
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Expires: 1994-08-15
Abstract
Abstract A traffic counter switch and associated pulse generator circuit is described which uses a piezoelectric transducer to convert air pressure waves produced in a pneumatic tube by vehicles crossing such tube, into corresponding electrical pulses which are supplied to a traffic counter. The piezoelectric transducer output pulses trigger a monostable multivibrator in the pulse generator circuit without amplification of such transducer pulses. The transducer and associated pulse generator circuit are mounted within a common housing which is separated into two chambers by a diaphragm supporting the transducer, such circuit being provided in a chamber separate and hermetically sealed from the chamber containing the transducer. Most of the false triggerings of the multivibrator by reflections of the air pressure wave from the end of the pneumatic tube, are prevented by connecting the equivalent circuit capacitance of such transducer to a high discharge resistance. As a result the RC time constant of the transducer capacitance is sufficiently long to prevent such reflections from producing transducer output pulses which trigger the multivibrator.
Inventors
- 👤 Henry O Peterson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 04:42
CPC Classifications
G; G08; G08G; G08G1/00; G08G1/065; G08G1/01; G08G1/02
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
89 words
A vehicle sensor apparatus in which the improvement comprises: a fluid tube means for producing a pressure wave within said tube when a vehicle contacts such tube; a piezoelectric transducer means coupled to an open end of said tube for producing an electrical output pulse in response to receipt of said pressure wave; and an electronic switch circuit including a monostable multivibrator having its input connected to said transDucer so that said multivibrator is triggered directly by the transducer output pulse without amplification to produce a multivibrator output pulse.
Claim 2
Dependent Claim
89 words
A vehicle sensor apparatus in which the improvement comprises: a fluid tube means for producing a pressure wave within said tube when a vehicle contacts such tube; a piezoelectric transducer means coupled to an open end of said tube for producing an electrical output pulse in response to receipt of said pressure wave; and an electronic switch circuit including a monostable multivibrator having its input connected to said transDucer so that said multivibrator is triggered directly by the transducer output pulse without amplification to produce a multivibrator output pulse.
Claim 3
Dependent Claim
33 words
A sensor apparatus in accordance with claim 1 in which the switching circuit is contained within a housing also containing said transducer means, said switching circuit being electrically isolated from any D.C. ground.
Claim 4
Dependent Claim
58 words
A sensor apparatus in accordance with claim 2 in which the transducer includes piezoelectric material supported on a diaphragm mounted by a mounting means within the housing and separating the housing into two chambers, one chamber containing the electrical switching circuit and pneumatically sealed from the other chamber which is connected to the open end of said tube.
Claim 5
Dependent Claim
36 words
A sensor apparatus in accordance with claim 3 in which the mounting means includes a pair of rings of resilient insulating material provided on opposite sides of a metal diaphragm forming one electrode of the transducer.
Claim 6
Dependent Claim
61 words
A sensor apparatus in accordance with claim 1 in which the monostable multivibrator includes an input transistor having its output connected to the input of an output transistor, and the transducer output signal is applied to the input electrode of said input transistor to trigger the multivibrator and produce the multivibrator output pulse on the output electrode of said output transistor.
Claim 7
Dependent Claim
25 words
A sensor apparatus in accordance with claim 5 in which the input electrode of said input transistor is connected through a diode to the transducer.
Claim 8
Dependent Claim
47 words
A sensor apparatus in accordance with claim 6 in which there is a shunt resistor connected across the output of the transducer and a shunt capacitor connected across the input of the input transistor, and the diode is connected between said shunt resistor and said shunt capacitor.
Claim 9
Dependent Claim
67 words
A sensor apparatus in accordance with claim 5 in which a timing capacitor is connected between the output electrode of said output transistor and the input electrode of said input transistor, a timing resistor is connected between the timing capacitor and a D.C. voltage terminal for charging said timing capacitor through said timing resistor, and a diode connected across the timing resistor for discharging the timing capacitor.
Claim 10
Dependent Claim
67 words
A sensor apparatus in accordance with claim 1 in which the piezoelectric transducer is connected to a resistance of a high value so that the RC time constant of the capacitance of said transducer is greater than the period of the monostable multivibrator and is sufficient to prevent spurious pressure waves within the tube from causing the transducer to produce false output pulses which trigger the multivibrator.
Claim 11
Dependent Claim
47 words
A sensor apparatus in accordance with claim 9 in which the resistance is a shunt resistor connected across the output of the transducer, a shunt capacitor is connected across the input of the multivibrator, and a diode is connected between the shunt resistor and the shunt capacitor.
Claim 12
Dependent Claim
39 words
A sensor apparatus in accordance with claim 5 which also includes an isolation resistor connected between the input electrode of said input transistor and the common connection terminal of a timing capacitor and a timing resistor in said multivibrator.
References Cited (Backward Citations)
US3699398A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-08-18 | 1979-02-17 | 1979-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-08-18 | 1983-02-17 | 1983-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-08-18 | 1987-02-17 | 1987-08-19 | $7700.00 | Window Closed / Lapsed |