Originally Published MPMN November 2007

BREAKTHROUGHS

Dual-Action Switch Cuts Clutter

Stephanie Steward

Reducing the size and number of components in a medical device can help lower manufacturing costs and, ultimately, make the part more user-friendly. Combining functions within a part is one way to reduce component clutter. For example, IntelliTac technology provides two electrical functions within a single low-profile switch. According to Snaptron Inc., the metal tactile-dome unit is the first dual-action dome switch in the industry.

“The real estate OEMs have is limited,” says Jon Mullett, a Snaptron marketing specialist. “They’re trying to put as much functionality into a device [as they can] without making it big and clunky.” The low profile of the IntelliTac switch can help keep a design flat and sleek. It can also replace bulky knobs or more-expensive and complex switches.

Snaptron’s switch is similar to dual-action tactile switches that activate the shutter of a camera, which typically consist of two domes in a housing with an actuator. However, according to the manufacturer, its dome contact is less complex and has a lower profile. Its size and actuation force can be customized by the supplier, and software can be used to customize the way in which it performs the two electrical functions.

The switch is a four-legged dome with three legs that sit on a flat electrical pad on the printed circuit board and a fourth, shorter leg. When light pressure is applied, the first contact is made and the first electrical function is performed. Applying further pressure causes the dome to snap and create the second electrical contact and function.

If incorporated into a surgical tool, this function combination could be used to provide short bursts of power with the first contact and sustained use with the second. Or, the light-touch function could be used to scroll on a device display, as on an insulin pump, and then the second contact could select the option the user wanted. Software can be programmed to make the switch’s second function occur only when the first has made contact for a certain amount of time. This safety feature could benefit such devices as surgical tools or the injection component on an insulin pump.

The dual-action switch can also be incorporated into devices to allow engineers to service equipment diagnostics from the front of the machine. To service equipment, a separate button is typically used, or the actual switch housing must be opened up. “Some medical devices have complicated control panels. [This switch] allows the serviceability, or at least the diagnostics, of the equipment to be accessed from the front [of the machine],” says Walter Goodrich, applications engineer for Snaptron.

Currently, the company offers the four-legged dome in diameters ranging from 6 to 30 mm, and in activation forces from 40 g to 15 lb.

Snaptron Inc., Windsor, CO
www.snaptron.com

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