A recent device that provides the function of conventional slip rings is said to outperform them with maintenance-free operation, low electrical resistance, low torque, and high shock tolerance. Instead of letting an arm slide on a conductive wheel, developer Diamond-Roltran (www.diamond-roltran.com) devised the system in which rings of spring copper roll between two conductive races like balls in a bearing to transfer power, signals, and data across the interface. These appropriately called Roll Rings, says the developer, work in a variety of mission-critical applications such as the International Space Station which has 16 units in service. More recently, the device has gone into a few wind turbines.

While only one Roll-Ring is installed in each groove, more grooves and more rolling rings can be added per channel to increase current handling capacity. Channels can be added to meet application requirements.

The pictured layout is said to minimize high-frequency coupling and let the device pass data at rates to 15 Mbit/s at frequencies to 30 MHz. Various insulations are available to increase voltage handling capability up to 4,000V. The developer says the unit accommodates most manufacturing tolerance variations making it possible to stack up to 70 channels and more while maintaining life and electrical performance. The interface does not require lubrication and thus is suitable for vacuum applications.

The devices have survived three-axis 180 G shock loads and have operated for over 240 million revolutions. In an aircraft gyroscope, the device allowed a 99% reduction in torque over slip rings.

The developer says its Roll-Rings can replace slip rings in a many applications but not all because they sometimes require more space than that available. As you might expect, the units are more expensive than slip rings of similar capacity. WPE