Acoustic Coin Sensor Waveguide Impedance Matching
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Solution Overview
Problem
Existing methods for determining the available capacity of coin tubes in currency handling apparatuses are inaccurate due to variable coin dimensions and orientations, leading to potential jams and malfunctions, and ultrasonic pulse methods face challenges with resonance and noise issues.
Innovation Solution
A capacity detector using a waveguide with a horn end that minimizes acoustic impedance mismatch and internal reflections, coupled with an acoustic signal generator and sensor, computes the available capacity by measuring time delays between transmitted and reflected signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic pulses are used to measure coin receptacle capacity, then measurement capability is provided, but the transducer produces resonance and ringing that causes noise problems and requires large spacing from the coin stack
Solution Approach 1:
The patent extracts the harmful resonance and ringing from the ultrasonic transducer by using a different measurement approach. Instead of relying on the transducer's resonant frequency, the system uses a broadband impulse and measures the time of flight of the sound wave to the coin stack and back, eliminating the noise problems associated with resonant structures.
Solution Approach 2:
The patent introduces an intermediary measurement method using a broadband impulse generator and time-of-flight detection. This intermediary approach allows capacity measurement without direct coupling of the transducer to the coin stack, avoiding the resonance and noise issues while still enabling accurate measurement of the coin stack height or capacity.
2Strength
If ultrasonic transducer output is coupled to surrounding structure, then structural support is provided, but this results in saturation of the receiving microphone
Solution Approach 1:
The patent separates the structural support function from the acoustic measurement function. The transducer is mounted in a way that provides structural support without coupling its output to the surrounding structure, thereby preventing microphone saturation while maintaining measurement capability.
Solution Approach 2:
The patent segments the system into distinct functional components: the transducer for acoustic signal generation, the microphone for signal reception, and the processing system. This segmentation allows each component to perform its function independently, preventing interference and saturation issues.
3Adaptability or versatility
If coins are not received and stacked in pre-determined orientation, then flexibility in coin insertion is improved, but the coin tube may reach maximum capacity prior to receiving the predetermined quantity of coins
Solution Approach 1:
The patent replaces mechanical counting methods with acoustic measurement. Instead of relying on mechanical sensors to detect coin insertion and maintain a running count, the system uses acoustic pulses to measure the total height or volume of coins in the tube, providing accurate capacity detection regardless of coin orientation or insertion sequence.
Solution Approach 2:
The patent changes the measurement parameter from discrete coin counting to continuous acoustic measurement of coin stack height or volume. This parameter change allows the system to accurately determine capacity regardless of how coins are oriented or inserted, as the acoustic measurement captures the total physical dimensions rather than relying on predetermined stacking patterns.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a high-accuracy, compact, and efficient method for determining the available capacity of coin tubes, reducing the risk of jams and malfunctions by accurately measuring the coin stack height and capacity.
Implementation Method 1
a 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
Implementation Method 2
the horn end radius may expand gradually to reduce the instantaneous change in acoustic impedance presented to the acoustic signal as it traverses through and exits the waveguide. Additionally or alternatively, the horn end may be configured to minimize internal reflection of the acoustic signal
Implementation Method 3
the time delay between the emitted and reflected pulses can be measured
Data Source
AI summary
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.