Acoustic coin sensor
View Patent ↗The present subject matter relates to a capacity detector, a waveguide and a manifold for use with a coin sensor as well as methods for sensing a capacity of a coin receptacle. In one aspect, the waveguide for use with a coin sensor comprises an excitation end for receiving an acoustic signal, a horn end for disposition adjacent to a coin receptacle, and a conduit interconnecting the horn end and the excitation end. In embodiments, the horn end of the waveguide may define a horn selected from a tapered horn, an exponential horn, a tractrix horn, or a modified tractrix horn.
1. A coin storage capacity detector, the capacity detector comprising:
at least one waveguide, each waveguide further comprising:
an excitation end configured to receive a transmitted acoustic signal,
a horn end,
a tapered horn interconnected with the horn end, and
a conduit interconnecting the tapered horn and the excitation end;
a coin receptacle disposed adjacent to each horn end and configured to store a coin stack comprising at least one coin, wherein the transmitted acoustic signal is reflected by at least one surface within the coin receptacle thereby causing a reflected acoustic signal;
an acoustic sensor configured to output measurement signals in response to receiving the transmitted acoustic signal or the reflected acoustic signal; and
a processor configured to compute at least one parameter of the coin receptacle in response to receiving the measurement signals.
2. The capacity detector of claim 1 , wherein the horn end defines a horn selected from a tapered horn, an exponential horn, a tractrix horn, or a modified tractrix horn.
3. The capacity detector of claim 1 , wherein the horn end radius expands gradually to reduce the instantaneous change in acoustic impedance presented to the acoustic signal as it traverses through and exits the waveguide.
4. The capacity detector of claim 1 , further comprising
a signal generator configured to transmit an acoustic signal, and
wherein the horn end is configured to minimize internal reflection of the acoustic signal.
5. The capacity detector of claim 1 , wherein the horn end is a tractrix horn or a modified tractrix horn having a mouth end radius of about 3-20 mm.
6. The capacity detector of claim 1 , wherein the horn end defines a tractrix horn that comprises a mouth end having a radius r 0 .
7. The capacity detector of claim 1 , wherein the horn end comprises a signal cavity configured to minimize an instantaneous acoustical impedance mismatch between the waveguide impedance and the coin receptacle.
8. The capacity detector of claim 1 , wherein the horn end comprises a signal cavity, at least a portion of the cavity varying according to an exponential function.
9. The capacity detector of claim 1 , wherein the excitation end is disposed proximate to a spark gap for generating the acoustic signal.
10. The capacity detector of claim 1 , wherein the acoustic signal is generated by a spark.
11. The capacity detector of claim 1 , wherein the acoustic signal comprises a broadband pulse.
12. The capacity detector of claim 1 , wherein the waveguide is configured to couple the acoustic signal to a coin receptacle.
13. The capacity detector of claim 1 , wherein the at least one parameter comprises a height of the stack.
14. The capacity detector of claim 1 , wherein the at least one parameter comprises the available capacity of the coin receptacle.
15. The capacity detector of claim 1 , wherein said at least one parameter comprises a distance between the at least one surface of the stack and the acoustic sensor.
16. The capacity detector of claim 1 , wherein the acoustic sensor comprises a microphone.
17. The capacity detector of claim 1 , wherein the at least one surface comprises a surface of the uppermost coin in the stack.
18. The capacity detector of claim 1 , wherein the acoustic sensor comprises an analog to digital converter configured to output digital measurement signals.
19. The capacity detector of claim 1 , wherein the processor is configured to compute a time delay between the transmitted and reflected signals.
20. The capacity detector of claim 19 , wherein the computation of the at least one parameter is based upon the time delay.
21. A coin storage capacity detector, the capacity detector comprising:
at least one waveguide, each waveguide further comprising:
an excitation end configured to receive a transmitted acoustic signal,
a horn end comprising a mouth end having a radius r 0 ,
wherein the horn end radius r d at a given displacement d with respect to the mouth end is given by a formula
d
=
r
0
×
ln
(
r
0
+
r
0
2
-
r
d
2
r
d
)
-
r
0
2
-
r
d
2
,
and
a conduit interconnecting the horn end and the excitation end;
a coin receptacle disposed adjacent to each horn end and configured to store a coin stack comprising at least one coin, wherein the transmitted acoustic signal is reflected by at least one surface within the coin receptacle thereby causing a reflected acoustic signal;
an acoustic sensor configured to output measurement signals in response to receiving the transmitted acoustic signal or the reflected acoustic signal; and
a processor configured to compute at least one parameter of the coin receptacle in response to receiving the measurement signals.
22. A coin storage capacity detector, the capacity detector comprising:
at least one waveguide, each waveguide further comprising:
an excitation end configured to receive a transmitted acoustic signal,
a horn end comprising a signal cavity having a taper angle θ, a mouth end radius r 0 , and an inner radius r d which varies at a given displacement d with respect to the mouth end according to a formula given by
r
d
=
r
0
-
d
tan
θ
,
and
a conduit interconnecting the horn end and the excitation end;
a coin receptacle disposed adjacent to each horn end and configured to store a coin stack comprising at least one coin, wherein the transmitted acoustic signal is reflected by at least one surface within the coin receptacle thereby causing a reflected acoustic signal;
an acoustic sensor configured to output measurement signals in response to receiving the transmitted acoustic signal or the reflected acoustic signal; and
a processor configured to compute at least one parameter of the coin receptacle in response to receiving the measurement signals.
23. A method of sensing a capacity of a coin receptacle, the method comprising:
coupling a transmitted acoustic signal to a coin receptacle, by a waveguide, wherein the waveguide comprises: an excitation end configured to receive the transmitted acoustic signal, a horn end, a tapered horn interconnected with the horn end, and a conduit interconnecting the tapered horn and the excitation end, and wherein the coin receptacle is configured to store a coin stack comprising at least one coin;
receiving samples of the acoustic signal and a return signal, wherein the return signal is generated in response to at least one surface within the coin receptacle reflecting the transmitted acoustic signal; and
computing, via a processor, at least one parameter of the coin receptacle based upon a time delay between receiving the transmitted acoustic signal and the return signal.
24. The method of claim 23 , wherein the acoustic signal is coupled to the coin receptacle through a waveguide comprising:
an excitation end configured to receive an acoustic signal;
a horn end for disposition adjacent to a coin receptacle;
a conduit interconnecting the horn end and the excitation end.
25. The method of claim 24 , wherein the horn end defines a horn selected from a tapered horn, an exponential horn, a tractrix horn, or a modified tractrix horn.
26. The method of claim 24 , wherein the horn end radius expands gradually to reduce the instantaneous change in acoustic impedance presented to the acoustic signal as it traverses through and exits the waveguide.