Totally-sealed microswitches tolerate immersion

April 28, 2016 // By Graham Prophet
Designed to meet more demanding industrial applications, a series of Microprecision microswitches is fully dust-tight and water-sealed, and available in various configurations to meet IEC/EN 60529 ingress protection levels of IP67, and even IP68, over a temperature range from -40°C to +125°C or greater.

Dave Mellor, Managing Director of dsitributor Cyntech Components, said, "Whether it is push-button, plunger, simple lever or roller lever, Microprecision has ... microswitches that provides all the usual options for voltage/current ratings and switch contact material. What's just as important ... is robust and reliable operation, which is where Microprecision excels with its dust and water sealed designs."

Protection against dust and water (or oil) is achieved with a flexible membrane that seals the space between the moving actuator pin and the switch housing. Guaranteeing its performance over temperature extremes, however, places demands on design and the right choice of materials. Microprecision uses a pin made out of two parts with the membrane squeezed between those parts and held securely in place. The membrane is then attached to the housing with a compression ring that is held in place with ultrasonic welding. This approach ensures the membrane is tightly fitted and able to resist the effects of temperature and pressure fluctuations without impacting its flexibility.

Ultrasonic welding is also used for assembling the rest of the switch housing. This provides a superior solution to the use of adhesives or gaskets and, by not adding another material, ensures the seal supports UL61058 temperature requirements. As well as protecting the switch itself it is necessary to provide protection for the connections to the switch. While this is often left to the user, Microprecision also offers microswitches with the cable already soldered to the switch terminals and potted to meet the required IP67/68 rating.