T o create motion within a vacuum chamber, typical rotary feedthrough devices use a ferrofluid or O-ring to seal the shaft, or a magnetic feed-through device. But ferrofluids are expensive and complicated, O-rings wear out, and magnetic couplings don't provide a positive connection, according to Harmonic Drive Technologies Senior Applications Engineer Alan Clements.

In contrast, ChamberLink(TM)combines a rotary feedthrough and precise harmonic drive servo actuator in one stainless steel device that seamlessly integrates the harmonic drive with the chamber wall, keeping the motor and input elements on the chamber's ambient side and the geared output shaft on the vacuum side. Because the device has no chamber-wall penetrating shafts that require seals, vacuum leakage is averted. "It reduces particle count, downtime, and maintenance costs," says Clements, "because there are no seals to wear out and fail.

Moreover, vacuum is not compromised even if the motor is removed." Two new sizes, ChamberLink 14 and ChamberLink 32, recently became available. Size 14 is rated at 40 inch-lbs continuous torque at 70-rpm output speed and can provide accurate positioning for wafers and small cassettes in load lock, transfer, and process chambers. The size 32 unit, rated at 500 inch-lbs continuous torque, is recommended for turning indexing-platens operating in vacuum process chambers.

Additional Details...Jeff Stoehr, Harmonic Drive Technologies, 247 Lynnfield St., Peabody, MA 01960; Tel: (978) 573-3420; FAX: (978) 532-9406; www.harmonic-drive.com .