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issue: November 2005 APPLIANCE Magazine

Switches
Simple Construction, High-Performance Switch Technology


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by Tony Van Zeeland, chief technology officer, InPlay Technologies, Inc.

New switch technology is easily integrated into existing manufacturing processes, with minimal piece-parts.

Figure 1. PushFlex construction

The electronics market continues to demand cost-efficient, high performance products from its vendors. A new switch technology offers a simple switch solution that can be easily integrated into existing manufacturing processes. Two types of switches—pushbutton and rotary—are being developed using a simple, magnetic-based design, with few piece parts and making use of common materials.

Figure 2. Actuating layers for a web of switches

Magnets in Switch Design

It is the use of permanent magnets in switches that makes the new technologies unique. Although many electronic products utilize magnets—they are common and often integral parts of motors, CD-players and computers—the switch industry has not taken full advantage of the benefits magnets offer. The developments capitalize on the inherent properties of magnetism to create an elegant, robust and highly customizable user interface solution, thereby offering numerous advantages over traditional electromechanical and membrane switches.
The latest development in this area represents a low-cost refinement of the supplier’s core technology and combines a commonly available magnet sheet and a magnetically receptive actuating layer to create a unique switch construction. See Figure 1. The actuating layer includes flaps that are cut into the material, which aligns to holes cut in the magnetic layer. Together, the layers form a web of switches, as seen in Figure 2. The first layer is a single magnet sheet, which is utilized to provide the switch breakaway and return force. The second layer is an embossed, magnetically receptive rubber that is used to provide the individual flexing switch “armatures,” as well as all spacer and actuating layers as required. Actuation of the design is shown in Figure 3.
Simple to manufacture, the magnetic switch technology offers an alternative to both domes and conductive rubber keypads. The web configuration eliminates the need for individual placement of domes, keeping assembly costs down. The entire tooling, sourcing and molding process for conductive rubber keypads is eliminated.
Because the technology offers a compelling cost-per-key value proposition, development of the technology has been aimed at applications using numerous pushbuttons, like a typical keyboard. Recent magnetic switches offer several design options, including constructions for use under plastic keycaps or standard graphic overlays. Feel and travel can be customized to meet varying specifications, and normally closed key options can be incorporated.
Using this construction, only two piece parts are required to provide all of the switch contacts, regardless of the required number of switches on the panel. The obvious target for this type of technology would be keypads with numerous switches in a compact area, such as portable electronic devices, laptop computers as well as the low-cost market of appliances.

Figure 3. Basic push-button actuation demo

FlexRotor Technology

The flex rotor switch concept is shown in Figure 4. A single magnet and a flexible, magnetically receptive rubber armature are used. As the rotor rotates, the magnetic rubber armature is pulled up against the individual contacts, which are screen-printed on the bottom side of the film material. When the rotor is turned further, the rubber armature returns to its original open position. The flex slider is merely a linear version of this concept.
This product offers simple construction, with no wearing contact surfaces and electromechanically “quiet” contacts. Also, since the actuating mean is isolated from the switch, the product can be hermetically sealed, making it ideal for harsh environments.

Figure 5. Integrated transparent Push-Flex and Flex-Rotor

Integration

The magnetic switch technology allows integration of multiple switch types to allow for differing functionality and output, as well as ergonomic considerations. A concept of integration of the technologies is shown in Figure 5.
Further development of the technology opens doors to the low-cost, high-volume market. Switch manufacturers can readily adopt this technology using existing manufacturing capabilities to provide customers with a durable, inexpensive design.

About the Author

Tony Van Zeeland is chief technology officer of InPlay Technologies, a developer and licensor of proprietary technologies. InPlay was co-founded by Van Zeeland as Duraswitch to commercialize his patented “magnetically-coupled armature,” a new advancement in electronic switch design. His 30 years of experience includes several years with Oak Industries, where he conceived and developed electromechanical membrane keyboard technology used with many computers today. He later worked for Rogers Corp., working with electroluminescent technology. Van Zeeland holds a Master of Science degree in materials engineering and a Bachelor of Science degree in physics from the University of Wisconsin. If you would like to contact Mr. Van Zeeland, please e-mail: editor@appliance.com

 

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