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An AC/DC Mix ~ Appliance Manufacturer - October 1999 pg. 44
Trio of functions are built into Eureka vacuum by DNA Group
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Transferring technology from a DC to an AC application resulted in the right solution.
DNA Group, Inc. was challenged with supplying a reliable mechanical switch combined with an electronic variable speed control. With the capabilities of Defond Manufacturing Ltd., HK, this challenge was met.
This new variable speed rotary switch, created for the Eureka Company's Super Broom Vacuum, was tooled to provide three functions:
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- First, the switch serves as the main power source for the vacuum.
- As the switch is rotated into the ON position, it enters the variable-speed function of the switch. The switch remains within the variable speed through the middle travel points of the control.
- The third function is a high-speed bypass to provide full power to the unit.
Defond created this AC rotary switch, meeting the requirements of reapplying features previously designed for a DC trigger switch. Defond's patented "stepped-speed" technology produced the variable speed function. Coupled with the addition of an externally mounted power semiconductor with an external heat sink, the technology increased the reliability of the control.
The variable-speed capability of the switch is achieved by phase-controlling power delivered to the vacuum's motor. This power is half wave controlled by an SCR.
The consistency provided by the stepped speed technology allows the control to more reliably repeat the speed and power curve. The electronic control is an example of Defond's surface-mount assembly capability, making use of its miniaturization to produce a compact control.
Trio of Functions
Both the DC trigger switch and the AC variable-speed rotary switch function as a main power, variable speed control and high-speed bypass. However, further improvements were made to the rotary switch to help prevent common assembly problems. Lead wires are welded internally to provide a superior electrical connection. This connection can withstand more handling than traditional poke-in terminal connections, preventing problems associated with wire retention and handling after wire insertion.
Defond tooled the new housing of the switch and gained UL approval. Production of the units is slated for October, just 8 months after the program began. DNA and Defond, together, offered cost savings and a reliable product for Bloomington, IL-based Eureka.
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