Running rings around thermal growth
Stainless-steel tolerance rings recently helped Coleman Powermate Inc. run rings around potential thermal-expansion problems within its Pulse portable generators. These trunk-sized 12,000W generators employ a rotor-shaft and needle-bearing assembly mounted in a 30% glass-filled nylon housing. To secure the metal bearing assembly within the plastic housing—both axially and radially—Coleman turned to stainless-steel tolerance rings, which act as an elastic shim between components that are subject to thermal-expansion differences. And by fastening a freely rotating needle bearing, the Coleman application represents a departure for the tolerance rings that more typically secure ball bearings or plain bushings within electric-motor housings.
USA Tolerance Rings:Enter 515
A clean bond for displays
Two new pressure-sensitive adhesives target perimeter-spacer bonding in resistive touch screens and other electronic devices where cleanliness counts. With low outgassing properties and low extractable ions, these "electrically clean" adhesives combat the corrosion and fogging that can interfere with the bonding of oxide surfaces and conductive circuitry in touch screen devices. ARclean 8769 is a double-sided 3.0-mil tape with an acid-free acrylic adhesive. ARclean 8855 uses the same adhesive but comes in a 7.5-mil thickness.
Adhesives Research Inc.:Enter 516
Adhesives that stick to magnets
Who says adhesives can't have a magnetic personality? PERMABOND 581 and 681 have been formulated specifically to adhere to ferrite, alnico, and rare-earth magnets. PERMABOND 581 is a no-mix structural adhesive that works with an acrylic activator. Setting in as little as 15 minutes, it lets assemblies undergo magnetization soon after bonding. Applications include bonding permanent-magnet dc motors, flywheels, generators, and sensors. PERMABOND 681 is a two-part mixable structural adhesive that needs no activator. It can fix parts in less than 60 seconds, cures to 90% strength in one hour, and reaches full strength in eight hours. Applications include bonding permanent magnets to frames in dc and TENV electric motors, to pole pieces and baskets in speakers, and to generator housing. Neither of these new acid-free adhesives requires an oven cure.
Permabond, div. of National Starch and Chemical Co.:Enter 517