Appliance Design - October 2008 - (Page 25)

MOTORS high density, commonly in the range of 3 Tesla. That is one reason that patients with metal in their body or who have certain implantable medical devices cannot use an MRI machine. In addition, the motor’s magnets inherently generate magnetic and RF fields during operation that could result in RF arcing and cause hardware damage and degradation of image quality. Non-magnetic motors, those made from nonferrous materials and which do not generate magnetic or RF fields, are becoming the motor of choice for these applications. Most often, piezoelectric motors, using the reverse piezoelectric effect, are used, but other technologies are under development including a pneumatic motor. The piezoelectric effect is the term used to describe how a piezo crystal will generate voltage in response to an applied mechanical stress. A simple and common example is a piezo igniter on a barbecue gas grill, where pushing the igniter button releases a springloaded hammer that hits the piezo materials to generate a spark that ignites the gas. By contrast, a piezoelectric motor uses the effect in the opposite direction, using piezoelectric ceramic materials to convert electrical energy in to mechanical energy, known as the reverse piezoelectric effect. The external application of a voltage to a piezo crystal causes it to change shape, or distort by a small amount. This distortion is typically about 0.1 percent of the size of the original piezoelectric crystal. While the change is small, its cumulative effect is big. Not all piezo motors are automatically non-magnetic. While they do not generate electromagnetic fields, to be non-magnetic the motors and all their parts must be constructed from non-ferrous materials. At least two companies, New Scale Technologies, Victor, N.Y., and Nanomotion, Ronkokoma, N.Y., are using the reverse piezoelectric effect for their miniaturized piezoelectric motors. Beyond the fact that they can be non-magnetic, these motors have other useful features. They are small, for instance, smaller than even the smallest electromagnetic motor. They are also very precise, with accuracy and motion control in the nanometers. New Scale Technologies’ Squiggle motor uses the small movements of several piezo crystals to generate linear movement. Fundamentally, the motor is just a nut and a screw, says Dan Viggiano, vice president and general manager of New Scale’s OEM and Industrial Business. The motor consists of four piezoelectric plates bonded in 90 Deg spacing to a nonmagnetic metal tube — the “nut” — that has been threaded on the inside. A matching threaded screw is inserted into the tube. The linear motor uses ultrasonic standing wave vibration in the threaded nut to directly rotate the screw. The externally applied voltage pulses sequentially and bends the nut 90 Deg in one direction and 90 Deg in the other direction. The signals are synchronized so that the “nut” works its way up the “screw” in an orbital motion. The company refers to this as an orbital “hula hoop.” This action At LCR, we recognize that your application may require some different specifications than what comes out of a catalog. That's where our hard-earned experience, agile engineering and flexible manufacturing systems go to work for you. LCR can quickly and efficiently produce motor controls that fit your need, so you don't have to make your product fit the control. LCR's stock of controls are made for a wide variety of motors, including: DC Brush Brushless � AC Induction � Universal � Shaded Pole � Split Phase AC � You Name It! � � As a leader in the EMI field, our motor controls are designed "EMI-friendly" . And they can all be customized to meet your specific requirements. Let LCR build the controls you need, so you can build the product you want. Call LCR today to see how we can make your job easier. 9 South Forest Avenue Norristown, PA 19401 (800) 527-4362 sales email: sales@lcr-inc.com w w w. l c r- i n c . c o m applianceDESIGN October 2008 25 9/16/08 1:50:50 PM www.applianceDESIGN.com AD10084LCR.indd 1 http://www.lcr-inc.com http://www.lcr-inc.com http://www.applianceDESIGN.com

Table of Contents Feed for the Digital Edition of Appliance Design - October 2008

Appliance Design - October 2008 Contents Editorial Shipments/Forecasts News Watch Prototyping - Materials Play the Part Prototyping - Mix & Match Motors Electronics Coatings Design Marts Association Report: AHRI Advertiser's Index

Appliance Design - October 2008

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