Patent Publication Number: US-2010126942-A1

Title: Multi-frequency ultrasonic apparatus and process with exposed transmitting head

Description:
RELATED APPLICATION 
     This application claims priority from co-pending U.S. Provisional Application No. 61/116,315, filed Nov. 20, 2008, entitled FREQUENCY SWEEP AND MULTIFREQUENCY ULTRASONIC TRANSMITTING DEVICE TO CONTROL ALGAE AND VARIOUS TYPE OF CONTAMINATION IN A LIQUID, and invented by Sebastian K. Thottathil and J. Michael Goodson. This prior application is expressly incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to ultrasonic apparatus and associated process methods for improving transmission of radial mode ultrasonic vibrations into liquids, and relates more specifically to an ultrasonic device with an exposed transmitting head and associated process for controlling algae, decontaminating liquids, and other applications. 
     2. Description of the Relevant Art 
     Algae is found through out the world and is a general nuisance in water treatment plants, drinking water supplies, irrigation reservoirs, fish ponds, water impoundments, swimming pools, cooling towers, and underwater surfaces of ships and boats. Algae can be physically removed by using raking or other devices, but this is very labor intensive and only a temporary control. Some algae types can grow as fast as they can be removed. Algae can also be treated chemically, but at the risk of potential contamination of the water and harm to the water stock. 
     Another way to remove algae is to use ultrasonic vibrations to break down the outer membranes of the algae. This method is environmentally friendly, cost effective, and chemical free. However, killing the various types of algae has not been successful using single frequency ultrasonic device. Some types of algae required low frequency ultrasonic energy to kill them and other types of algae can not be killed by low frequencies. Also low frequency devices do not have uniform coverage because of its large wave length. What is needed is a more powerful and efficient ultrasonic process for removing algae. 
     More generally, what is needed is a way to improve the transmission of ultrasonic energy into a liquid for a range of applications beyond killing algae, and including precision cleaning and liquid processing using ultrasonics. Prior ultrasonic devices typically are a stacked construction with one or more piezoelectric (PZT) devices sandwiched between a head mass and a tail mass and held together with a compression bolt. Such devices are typically attached to the outside of a tank or other container by bonding or welding the head mass to the structure of the tank or container. Alternatively, the ultrasonic device may be attached inside a sealed box that is immersed into the tank or container. These devices transmit ultrasonic energy from the PZT through the head mass and the structure of the tank, container, or immersible box. 
     SUMMARY OF THE INVENTION 
     The present invention is an ultrasonic device and related process having a transmitting head mass of one or more radial-mode ultrasonic transducers in direct contact with the liquid, with the remainder of the transducer enclosed in a watertight housing. The head mass of the transducer transmits ultrasonic energy directly to the liquid instead of an intermediate structure. An ultrasonic generator drives the one or more ultrasonic transducers at variable frequencies to maximize efficient transmission of ultrasonic energy. 
     The present invention is useful for controlling algae, decontaminating liquids, and other ultrasonic processing in liquids with multiple ultrasonic transmitters driven by a driving signal that continuously varies in frequency. The direction and orientation of each transmitter is horizontally freely adjustable in order to accommodate many treatment layouts. The multiple transmitters result in frequency super-positioning and interference between the different ultrasonic waves that are emitted by the transmitters of different orientation and different distances to the point of interference. The combination of multi-directional ultrasonic waves and continuous frequency sweeping around a center frequency enhances the interferences, resulting in a strong dB gain of the signals at any point within the reach of the transmitters. 
     By using both low frequency and high frequency ultrasonic transducers with both transducers connected to a frequency sweeping generator, the low and high frequency waves interact. Because of the interaction, peaks and valleys of the waves will be close to each other provide uniform coverage. The high frequencies lose amplitude more quickly than lower frequencies. By combining the two, the low frequency wave can carry the high frequency wave further away for large area coverage. 
     As a result, a broad range of algae can be successfully controlled and various liquids can be decontaminated or otherwise processed in a rapid and effective way. Amplitude controls on the generator allow the adjustment of the power setting to optimize for various types of algae infestations or contaminants, and to economize energy for the maintenance period following the successful control of the initial algae burden. 
     The transmitters are housed in a unit that can float on the surface of pools, reservoirs, lakes, fish and farm ponds and water and waste water management facilities. Alternatively, the transmitters can be attached to a structure and positioned with the exposed transmitting head mass immersed in the liquid. The multi-frequency ultrasonic waves disrupt and destroy the cellular structure and function of algae, and also break down contaminants in liquids. The present invention further includes an associated method of transmitting ultrasonic waves under water to control a broad range of algae species and/or break down a broad range of contaminants. More generally, the exposed transmitting head masses of the transducers can be used in any application where radial mode ultrasonic energy is supplied to a liquid. 
     The features and advantages described in the specification are not all inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification and claims hereof. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter, resort to the claims being necessary to determine such inventive subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of one embodiment of a multi-frequency ultrasonic apparatus according to the present invention. 
         FIG. 2  is a perspective view of one embodiment of a multi-frequency ultrasonic apparatus according to the present invention. 
         FIG. 3  is a side view, partially cut away, of the apparatus of  FIG. 2 . 
         FIG. 4  is a perspective view of another embodiment of a multi-frequency ultrasonic apparatus according to the present invention with multiple transmitters. 
         FIG. 5  is a side sectional view of another embodiment of a multi-frequency ultrasonic apparatus according to the present invention. 
         FIG. 6  is a schematic view of another embodiment of a multi-frequency ultrasonic apparatus according to the present invention with multiple transducers. 
         FIG. 7  is a schematic view of one embodiment of a multi-frequency ultrasonic apparatus according to the present invention with multiple transducers of different dimensions and operating frequencies. 
         FIG. 8  is a side view of an embodiment of the present invention with probes for increasing the surface area of the transmitting unit. 
         FIG. 9  is a side view of another embodiment of the present invention with multiple transmitting units attached to a pipe line. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drawings depict various preferred embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
     As shown in  FIGS. 1-3 , the ultrasonic device  10  has a unibody design that integrates the housing  12  of the device with the ultrasonic transducer  14 . The transducer  14  includes ring-shaped piezoelectric (PZT) elements  16 , a tail mass  18  on one side of the PZTs, and a transmitting head  20  (also known as a head mass or transmitting head mass) on the other side of the PZTs. The assembly is held together with a compression bolt  22 . The PZT elements  16  are preferably radial mode devices. An ultrasonic generator  24  supplies a driving signal to the PZTs through a signal cable  26 . The frequency of the driving signal is preferably swept or otherwise varied by the generator throughout a frequency range, The frequency can be various waveforms, including sine, square, triangle, saw tooth, staircase or any other wave shape. The driving frequencies are preferably in the range of about 10 KHz to 300 KHz. 
     A tube  28  is attached to the housing  12  and provides a passage for the signal cable  26  and also allows that housing to be rotated to different orientations. The housing enclosure  12  is sealed to prevent liquid from entering. The housing  12  is preferably proportioned so that it will float or attached to a separate float. The transducer  14  should be welded or bonded or otherwise fastened to the housing  12  at a node point of lowest longitudinal amplitude of the transducer to minimize transmitting energy onto the housing, in order to transmit maximum ultrasonic energy in the direction of the transducer axis to the transmitting head  20  and to the surrounding liquid. 
       FIG. 4  shows two ultrasonic devices  10  both attached to and suspended below a float  29 . Each device  10  has a transmitting head  20 , a waterproof housing  12 , and a tube  28  connecting the device to the float  29 . The transmitting heads  20  are shown oriented in the same direction, but they can be oriented in any direction by rotating them around the tube  28 . The ultrasonic generator  24  can be located inside the float  29  and powered by solar energy, or the ultrasonic generator can be placed remotely and connected to the ultrasonic devices with a cable. 
       FIG. 5  shows another embodiment of an ultrasonic device  31  with a different shaped transmitting head  33  and mounted inside a sealed housing  35 . The PZTs  37  are radial mode, which expand and contract primarily in a radial direction. The radial ultrasonic vibrations of the PZTs  37  are conveyed to the transmitting head  33 , which is located in the liquid  39  to be processed. Since there is no structure between the transmitting head and the liquid, the radial mode ultrasonic vibrations are transmitted very efficiently from the transducer to the liquid. This is in contrast to more conventional ultrasonic apparatus where the entire transducer structure is located on one side of a wall or plate, and all vibrations have to travel from the head mass and through the wall or plate to the liquid. The present invention significantly increases the surface area of the transmitting structure as compared to an intervening wall or plate. The present invention thus significantly improves the transmission of radial ultrasonic energy into the liquid. 
       FIG. 6  shows an embodiment of the present invention with multiple transducers  30 ,  32  of the same dimensions driven by a single sweep frequency generator  34 . The housing enclosure  36  can be in any shape. The transmitting heads  38  and  40  protrude outside the housing  36 . The sweep frequency waveform can be sine, square, triangle, saw tooth, staircase or any other wave shape depending on the application. The generator  34  preferably has amplitude modulation and the amplitude control. 
       FIG. 7  shows an embodiment of the present invention with multiple transducers  44 ,  46  of different dimensions simultaneously driven by separate sweep-frequency generators  48 ,  50  through separate signal cables  52 ,  54 . The smaller transducer  46  is driven at a higher frequency because it has a higher resonance frequency than the larger transducer  44 . The housing enclosure  56  can be in any shape and the transducers can be mounting on the same (as shown) or different surfaces. Each transducer  48 ,  50  has a transmitting head  58 ,  60  that protrudes outside the housing  56 . Preferably, each generator  48 ,  50  independently sweeps the frequency of its driving signal in various waveforms, such as sine, square, triangle, saw tooth, staircase or any other wave shape, and also preferably has amplitude modulation and amplitude control. 
       FIG. 8  shows an embodiment of the present invention for liquid processing with multiple probes  66  connected to a coupler  68  that is attached to the transmitting head  70  of an ultrasonic transducer  72  mounted in a housing  74  and driven by a frequency-sweeping generator  76 . The probes  66  are inserted into a container or tank  78  that contains a liquid  80  to be processed. Each probe  66  continuously changes its peaks and nodes to accelerate the liquid processing by shearing proteins and disrupting cells. 
       FIG. 9  shows an embodiment of the present invention with two transmitting units  86  and  88  attached to a pipe line  90 . Transmitting unit  86  has a lower frequency ultrasonic transducer  92  enclosed in a housing  94  and powered by a sweeping generator  96 . Transmitting unit  88  has a higher frequency ultrasonic transducer  98  enclosed in a housing  100  and powered by another sweeping generator  102 . The pipe line  90  can be, for example, a waste-water processing system line that carries a liquid  104  to be processed past the transmitting units. The lower frequency transducer  92  is used to break down large particles and the higher frequency transducer  98  is used to break smaller particles. One or more transducers of each type  86 ,  88  are connected to the pipe line  90 . 
     The present invention is characterized in that the ultrasonic transducer used has its head mass (transmitting head) located outside the housing enclosure while the PZTs and tail mass are located inside the housing enclosure. Nothing separates the vibrating head mass from the liquid, which maximizes efficient transfer of ultrasonic energy to the liquid. The exposed surface area is increased, also contributing to the efficiency. Also, immersion of the transmitting unit in the liquid helps to cool the unit. Plus, by sweeping the driving frequencies, the liquid is subjected to a wide range of ultrasonic energy, increasing the likelihood that algae and other contaminants will break down. Multiple transmitting units can be driven simultaneously to increase the ultrasonic energy supplied to the liquid. The process of the present invention can prevent biological encroachments in fresh and ocean water, and can be used to process contaminated water, swimming pools, runoff from car washing, etc. Blood, urine or other human and animal fluids can be decontaminated. More generally, the ultrasonic device of the present invention can be used in any ultrasonic process involving supplying ultrasonic energy to liquids. 
     From the above description, it will be apparent that the invention disclosed herein provides a novel and advantageous ultrasonic apparatus, and related processes. The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. As will be understood by those familiar with the art, the invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.