Ultrasonic cleaning and atomizing probe

Fluid sprinkling – spraying – and diffusing – With means to vibrate or jiggle discharge – By electric transducer

Reexamination Certificate

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Details

C239S104000

Reexamination Certificate

active

06799729

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method of cleaning and an associated device. In particular, this invention is related to the general field of ultrasonic cleaning. The invention is especially useful in cleaning dirt and oxides from electrical contacts. This invention is also related to the field of atomizing or spraying a liquid, and in particular ultrasonic atomization or spraying.
BACKGROUND
Ultrasonic devices have been utilized for several decades for such applications such as cleaning of precision instruments, atomization of liquids, disruption of biological material and bloodless removal of tissue in surgical procedures. Most of these devices have utilized a transducer constructed using one of three designs. In one design, a piezoelectric crystal resonator is bonded to the bottom of a metal dish or tray. In a second design, a transducer is manufactured from two or more crystal resonators sandwiched between a front and rear mass (known as a Langevin sandwich transducer). In a third design, a coil of wire is wound around a laminated nickel core, known as a magnetostrictive transducer. The manufacturing and operating principles of these devices are well-documented in prior art and engineering texts.
One characteristic of the transducer type device is that the minimum length is limited by the wavelength of a sound wave at the frequency of operation. The minimum length is roughly equal to a half-wavelength at the natural resonant frequency of operation. For a device operating at low ultrasound frequency, such as 20,000 Hz, this length is approximately 5.5 inches if titanium or aluminum is used as the material of the resonator. As the frequency of operation is increased, this length may be shorter, since the sound wavelength is inversely proportional to the resonant frequency. Although the device will resonate at the desired frequency and deliver significant power to the load, the transducer size limits the application of the device in situations where space is at a premium
Crystal resonators are significantly shorter than a Langevin sandwich transducer since the thickness or diameter of the resonator crystal sets the operating frequency of the system as front and rear masses are not used. However, the operating frequency is usually much higher than that of the Langevin sandwich units, generally greater than 40,000 Hz. A significant drawback of this type of construction is that the power and amplitude output of the device is severely limited by the mechanical properties of the crystal. The power and amplitude output of a crystal resonator may in fact be an order of magnitude less than that possible with the sandwich type units. Another factor in the use of the crystal resonator type of ultrasonic transducer device that electrical connections are needed on each face of the crystal faces, making isolation and sealing of the system difficult in some circumstances.
An application for ultrasonic cleaning exists in the manufacture of special integrated circuit assemblies. A device is needed to clean dirt and oxide deposits from the bottom of a printed circuit card having attached metal connector prongs or electrical contacts. This circuit card is mounted in a large automated testing machine, which makes the removal and cleaning of the card difficult. As dirt and oxides build up, the metal contacts do not make positive electrical connection with integrated circuits under test, and unreliable test results may be obtained. To maintain reliability the automated tester must be periodically removed from service and cleaned, at a significant cost in downtime and labor.
Experimentation has shown that a high power ultrasound bath is useful in removing the dirt and oxide deposits from the tester contacts. However, the automated tester does not allow for the mounting of a conventional bath type cleaner below the circuit card due to severe space constraints. In addition, high voltage must be avoided in the vicinity of the circuit card contacts in order to prevent electrical damage to the tester and associated circuits, and it is further undesirable to have liquid present in the vicinity of electronic devices under test. It is, therefore, an open question based on the prior art whether ultrasonic cleaning can be applied here.
In a further application of ultrasonic vibration, in addition to cavitation induced cleaning, it is found that ultrasonic energy injected into a fluid under some conditions may lead to rapid atomization, or conversion of the fluid into a mist or spray of small droplets. This phenomenon finds application, for example, in ultrasonic room humidifiers, which are able to thereby vastly increase the surface area of a volume of water, promoting evaporation. Spray formation, however, is generally broadcast, producing spray or droplets in an expanding cone. In some applications, it would be useful to have a tightly controlled spray, concentrated or focused to a small area, for example, in a local application of a liquid to a surface, or a localized cleaning operation.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an ultrasonic type cleaning device and/or an associated method.
It is another object of the present invention to provide such a method and/or device which facilitates rigorous surface cleaning in locations with restricted access.
It is a more particular object of this invention to provide a method and/or device facilitating cleaning of overhead surfaces in locations with restricted access.
Still a further object of the invention is to provide a method and/or cleaning device to clean electronic contacts without conducting potentially damaging voltages to a vicinity about the electrical contacts.
Another object of the invention is to provide a method and/or device for atomizing liquids into a mist or spray, which focusses the spray into a small area.
These and other objects of the invention will become clear by a study of the description and drawings contained herein.
BRIEF DESCRIPTION OF THE INVENTION
A cleaning device in accordance with the present invention possesses an extension which may be inserted into a confined area. The extension or probe is excitable in ultrasonic vibration via an attached transducer which may be disposed in an adjacent and more accessible area. The probe has no electrical connections, and essentially constitutes a passive mechanical tool. The probe may be provided with a channel extending to a cavity or recess at a distal end for filling the concavity or recess with fluid.
In particular, the instant ultrasonic cleaning device may be at least partially installed in a confined area below a circuit card of an automated tester, so that during a cleaning operation an associated probe or tool may be brought into contact with a bottom of the circuit card, filled with liquid, and excited in ultrasonic vibration in order to remove oxide and dirt buildup on the contacts of the card by ultrasonic cavitation. Following completion of the cleaning operation, the probe or tool allows the liquid to be drained from the area of the card until such time as the operation must be repeated. Such a device does not require the introduction of electrical contacts or voltages to the confined area during the cleaning operation.
The invention essentially comprises a self-filling ultrasonically excitable spoon.
Considered in abstract, spoons may be characterized by presence of an elongate handle attached at one end to a bowl-shaped or spatulate concavity for containing an aliquot of a liquid. A general embodiment of the present invention comprises a tool embodying these characteristics and further provided with a connector for coupling to a transducer excitable in ultrasonic vibration.
In parallel to comprehension as a modified use of a traditional tool shape, the invention may also be understood in the context of the ultrasonic art. It is known to produce tools of various shapes interchangeably couplable to an ultrasonic transducer. The present invention comprises such a tool in the form of a spoon. Accordingly, the present inven

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