High power ultrasonic transducers

Details High power ultrasonic transducers High power ultrasonic transducers

2000-05-24

2003-09-23

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Reciprocating

Reexamination Certificate

active

06624539

ABSTRACT:

FIELD
This invention relates generally to transducers, and, in particular, the present invention relates to ultrasonic transducers.
BACKGROUND
Ultrasonic transducers operate at frequencies of about 18 kHz or greater. Ultrasonic technology has been applied in a wide range of fields, from sonochemistry and industrial cleaning to medical tools. The largest limitation of existing technology is the inability to provide a single transducer with sufficient power to allow important laboratory processes to operate successfully. These include processes such as rubber devulcanization, polymer curing, seed sonication, and so forth. Most such units operate at a maximum effective continuous duty cycle of about 2.5 kW to 3 kW.
Conventional transducers contain a single drive rod, made from either a nickel, piezoelectric (PZT) or piezoceramic material. Although nickel is not known to deteriorate under use, conventional nickel units are heavy and bulky. Furthermore, nickel's relatively high Q (low damping) and low power density cause difficulties in achieving high power intensity. Piezoceramics also have a very high Q (narrow bandwidth). Conventional piezoceramic transducers are also subject to fail due to a variety of operating stresses. Furthermore, operating at maximum electrical, mechanical, and/or temperature stress to increase power output, causes accelerated aging, leading to early component failure. Piezoelectric materials are also not considered inherently reliable, and are known to cause failure in conventional devices. Although multiple units could be combined to produce higher-powered devices with these materials, this would result in inefficient transducers that are costly to operate and not practical for most operations.
An additional limitation of current ultrasonic transducers is the minimal target displacement obtainable, although displacement can be altered with additional horns. Conventional horns or wave-guides are typically made from aluminum alloys, titanium, titanium alloys or steel. These materials have a speed of sound of around 5000 meters/second and a relatively large Poisson's ratio of about 0.3 to 0.34. However, these properties tend to cause unwanted vibrations in large transducers, diverting energy away from the desired output. Furthermore, adding horns increases the size of the transducers, making them bulky and difficult to handle.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved ultrasonic transducer.
SUMMARY
A high power ultrasonic transducer is provided. In one embodiment, the transducer includes means for providing power in excess of three kilowatts. The transducer further includes an active element made from a magnetostrictive material and means for producing an electromagnetic field which extends through at least a portion of the active element. The active element is changeable between a first shape when in the absence of the electromagnetic field and a second shape when in the presence of the electromagnetic field.
The transducer also includes means for providing an electrical signal to the means for producing an electromagnetic field and an acoustic element connected to the transducer for channeling ultrasonic energy to perform work.
In one embodiment, an ultra-high power transducer is provided comprising a plurality of sub-motors, each containing an active element made from a smart material, wherein the sub-motors operate simultaneously to produce ultrasonic energy. The transducer in this embodiment further includes a cooling system connected to the transducers for cooling each active element, the cooling system utilizing a phase change medium. The transducer further includes a composite master wave-guide connected to the plurality of sub-motors, the master wave-guide reactive to the ultrasonic energy from the sub-motors, wherein the master wave-guide channels the ultrasonic energy to perform work.
In one embodiment, the transducer is capable of receiving approximately 30 kW of electrical power and converting it into mechanical ultrasonic power at about 20 kHz. In this embodiment, multiple ½ wavelength drive rods wave-guide sub-motor assemblies are connected to a single ½ wave length high speed of sound master wave-guide to provide a one full wave length device. In one embodiment, each drive rod is made from TERFENOL-D.
The high power and ultra-high power transducers of the present invention can be utilized in a number of sonochemical applications, including, but not limited to, rubber devulcanization, polymer curing, seed sonication, treating waste water and other waste byproducts, removing nitrates from potable water, and so forth. For the first time, ultrasonic power at 100% duty cycle can be achieved for high power operations, i.e., up to 30 kW or more, essentially allowing for a continuous operation seven days a week, 24 hours a day. Current ultrasonic transducers are incapable of operating at the requisite power levels for these commercial applications. Use of the transducers in the present invention can provide broad-based economic benefits to numerous industries. Additional benefits are achieved environmentally as a number of these processes allow for the recycling of various materials.


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