Self-cleaning submerged instrumentation
Inventors
Farruggia, Guy J. • Fraser, Allan B. • Hudak, John K.
Assignees
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Publication Number
US-8473262-B2
Publication Date
2013-06-25
Expiration Date
Abstract
Techniques and apparatus inhibit, limit, or remove biofouling and certain inorganic accumulations, to increase the longevity of accurate in-situ oceanographic and other underwater measurements and transducing processes. The invention deters formation of an initial bacterial layer and other precipitation, without harming the environment. The invention integrates an ultrasonic source into a sensor or other device, or its supporting structures. The ultrasonic source vibrates one or more critical surfaces of the device at a frequency and amplitude that dislodge early accumulations, thus preventing the rest of the fouling sequence. The ultrasonic driver is activated for short periods and low duty cycles, and in some cases preferably while the device is not operating.
Core Innovation
The invention concerns self-cleaning submerged instrumentation for deterring biofouling and reducing or substantially eliminating formation of biofilm on a critical exposed window surface or on an exposed active transducing surface of a transducer. The problem is biofouling of a surface that is critical to device performance and that is operated at least partially submerged within and in direct contact with an aqueous medium outside any sealed chamber that may be associated with the device. The disclosed apparatus uses an ultrasonic cleaning system operative at a frequency or frequencies in a range of approximately twenty kilohertz to nearly four hundred kilohertz.
A key aspect is providing means for substantially directly fixing the ultrasonic cleaning system to or integrating the ultrasonic system into the critical surface so that the critical surface is vibrated while submerged and in direct contact with the aqueous medium. By vibrating the surface, the apparatus reduces or substantially eliminates biofouling, particularly formation of biofilm on such surface. The disclosure further characterizes integration and operation in terms of coupling and vibration transmission to the functional region and includes constraints such as duty cycle limits.
The invention also includes self-cleaning for undesirable chemical deposition on a critical surface by using an ultrasonic cleaning system operative at a frequency or frequencies in a range of approximately fifty kilohertz to eighty kilohertz and integrating means that vibrate the critical surface to reduce or substantially eliminate such chemical deposition. In addition, a conductivity-measuring apparatus is disclosed with a generally planar sensing-cell surface exposed in an aqueous medium, using plural ring-shaped current-drive electrodes and voltage-sensing electrodes offset toward each other in pairs from the centers of the current electrodes.
The disclosure also includes a method of designing a self-cleaning instrument that uses vibration to deter underwater biofouling or chemical deposition by defining vibration constraints applicable generally, defining an algorithm relating operating inputs to design specifications, and applying design principles including vibration transmission through a distance on the order of one centimeter or less, preferably substantially direct attachment or preferably substantially unitary construction, substantially nodeless vibration, preferred vibration order zero or one, and a duty cycle of five percent or less.
Claims Coverage
The independent claims present four main inventive areas: (1) an ultrasonic cleaning apparatus for biofouling reduction on exposed submerged critical surfaces, (2) an ultrasonic cleaning apparatus for chemical-deposition reduction on exposed submerged critical surfaces, (3) a conductivity-measuring electrode geometry for aqueous sensing, and (4) a method for designing vibration-based self-cleaning instruments using constraint inputs and an algorithm.
Ultrasonic self-cleaning for biofouling on submerged critical surfaces
An apparatus for use with a device having an exposed window surface or an exposed active transducing surface outside any sealed chamber, operated at least partially submerged in direct contact with an aqueous medium and susceptible to biofouling, comprising an ultrasonic cleaning system operative at a frequency or frequencies in a range of approximately twenty kilohertz to nearly four hundred kilohertz; and means for substantially directly fixing the system to or integrating the system into such critical surface, to vibrate such surface and thereby reduce or substantially eliminate biofouling, particularly formation of biofilm on such surface.
Ultrasonic self-cleaning for chemical deposition on submerged critical surfaces
An apparatus for use with a device having an exposed window surface or an exposed active transducing surface outside any sealed chamber, operated at least partially immersed in direct contact with a liquid and susceptible to undesirable chemical deposition, comprising an ultrasonic cleaning system operative at a frequency or frequencies in a range of approximately fifty kilohertz to eighty kilohertz; and means for substantially directly fixing the system to or integrating the system into such critical surface, to vibrate such surface and thereby reduce or substantially eliminate such chemical deposition.
Ring-electrode conductivity sensing with offset voltage electrodes
A conductivity-measuring apparatus comprising a generally planar sensing-cell surface exposed in an aqueous medium; and disposed on the generally planar surface plural ring-shaped current-drive electrodes and voltage-sensing electrodes, each disposed within a respective one of the drive electrodes, wherein the voltage electrodes are offset, toward each other in pairs, from respective centers of the current electrodes.
Algorithmic design of vibration-based self-cleaning instruments using vibration constraints
A method of designing a self-cleaning instrument that performs said cleaning by vibration to deter underwater biofouling or chemical deposition, comprising defining a set of inputs characterizing vibration constraints applicable to generally all said self-cleaning instruments; defining an algorithm generically relating the operating inputs to design specifications of said instruments; receiving a set of values of said inputs for a particular desired instrument; and based on the values, automatically performing the defined algorithm to compute and provide design-specification values used in designing the particular self-cleaning instrument, wherein the performing step comprises applying at least one of these design principles: vibration transmission through distance on the order of one centimeter or less; preferably substantially direct attachment of vibration transmitter to critical article to be cleaned; preferably substantially unitary construction of vibration transmitter with critical article to be cleaned; substantially nodeless vibration in critical areas; preferably vibration in order zero or one; and duty cycle of five percent or less.
Across the independent claims, the coverage centers on integrating an ultrasonic cleaning system into a critical exposed submerged surface to reduce or substantially eliminate biofouling/biofilm and to reduce or substantially eliminate undesirable chemical deposition, on a specific planar conductivity electrode arrangement with ring-shaped current-drive electrodes and offset voltage-sensing electrodes, and on a method that computes vibration-based self-cleaning instrument design specifications from generally applicable vibration constraints and a generic algorithm using specified design principles including low duty cycle and limited vibration transmission distance.
Stated Advantages
Reduces or substantially eliminates biofouling, particularly formation of biofilm on a critical surface.
Reduces or substantially eliminates undesirable chemical deposition on a critical surface.
Enables conductivity measurement with ring-shaped current-drive electrodes and voltage-sensing electrodes offset toward each other in pairs.
Computes and provides design-specification values for designing a self-cleaning instrument using vibration constraints and a generically relating algorithm.
Documented Applications
Self-cleaning of an exposed window surface or exposed active transducing surface that operates at least partially submerged in an aqueous medium susceptible to biofouling.
Self-cleaning of an exposed window surface or exposed active transducing surface that operates at least partially immersed in direct contact with a liquid susceptible to undesirable chemical deposition.
Conductivity measurement using a generally planar sensing-cell surface exposed in an aqueous medium.
Designing self-cleaning instruments that deter underwater biofouling or chemical deposition by vibration.
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