Appliance Design - August 2007 - (Page 17)

Light Touch, ActiveTouch switches can be used to make vandal-resistant and contamination-proof user interfaces. SWITCHES & RELAYS Heavy Duty T ouch-type actuation devices have become increasingly popular in a wide variety of products because they are easy to use, easy to clean, and they provide environmental sealing and a broader range of aesthetic options. Resistive touch screens and glass-front capacitance controls have become more extensively used in recent years, and are well-suited for many applications. But there are many situations where rough handling, extreme environments, or the potential for vandalism demand something more rugged and resistant to abuse. Piezoelectric switches are often used in these cases, but they, too, have some limitations. To overcome the drawbacks of existing touch-actuation devices, ITW ActiveTouch, Buffalo Grove, Ill., developed a novel actuation/sensing technology that is sensitive enough to register a light touch, but tough enough to resist blows from a hammer. The division of Illinois Tool Works spent seven years researching and developing the technology, which is based on the principle of trapped acoustic resonance. Given the name ActiveTouch, the touchsensitive switch can be made from a variety of rigid materials, but when made from metal it becomes an extremely robust and durable www.applianceDESIGN.com actuator. ITW says the switch can be made from stainless steel up to 1/2-in. thick, making such a switch not only vandal-proof, but also waterproof, shockproof and even explosion-proof, as well as unaffected by hightemperature sterilization. Such switches can, therefore, be designed to operate in harsh or hazardous environments, including underwater. With no moving parts, and no ingression of water or chemicals possible, the switches offer virtually unlimited lifespan. Switch notices a fingertip, but shrugs off a hammer. How it works The principle of trapped acoustic resonance rests upon the fact that a material capable of supporting shear and torsional mechanical waves at ultrasonic frequencies can have those waves trapped, or localized, by creating specific features or geometries in the material. The cylindrical regions designated to trap the ultrasonic energy serve as resonant cavities that are set into motion by ultrasonic transducers emitting in the area of 1 MHz. The ultrasonic waves induce a twisting motion, which is called the trapped torsional mode, and confines the motion to the cylindrical cavity. In doing so, the ultrasonic vibrations initiate a resonance in the cavity, which is analogous to ringing a bell. As with a bell, by richard babyak applianceDESIGN August 2007 17 http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - August 2007

Contents Editorial Shipments/Forecasts News Watch A Reed Switch is Simople, yet Versatile, and Designers are Finding New Uses for this Time-Tested Technology A Novel Actuation and Sensing Technology can Register a Light Touch, but Resist Blows from a Hammer Tracing the Source of Noise is Made Easier with Noise Source Identification Methods Appliance Noise can be Annoying, but Designers have Many Material Choices to Help Rein in the Racket Nanocomposites are No Longer a Technology for the Future. These Plastic Materials are Already on the Job A New High-Strength, Low-Density Glass-Microsphere Additive can Improve Plastic Part and Molding Performance A New Electromagnetic Weld/Bonding Process Helps Ensure Long-Term Integrity of Joints in Plastic Parts Snap-Based Technology Eases Installation and Makes Products More Serviceable Two-Part Silicone Adhesives Provide a Rapid-Cure Alternative to Traditional One-Part Silicones Classified DesignMart Advertiser’s Index Association Report: GAMA

Appliance Design - August 2007

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