Materials

When complicated geometry proves more trouble than it’s worth, the deceptively simple function of transmitting torque can be improved by even small changes in chemical makeup. The core material and finish of a connecting device are its dominating characteristics.

Jim/Lovejoy: There is always a trade off between cost and convenience. Many times older materials have not been surpassed in terms of usefulness for a job. Rubber, for example, continues to be the best material for hysteresis damping and a leader for resilient couplings.

Tom/Climax Metals: Special high-tech platings and surface treatments are being tested for possible release in the near future.

Rob/Thomson Industries: In the linear motion industry, poor steel quality and incorrect surface finishes, as well as incorrect Rockwell hardnesses and OD tolerances can severely limit bearing and shaft life, causing premature failure. Materials must meet specific application requirements.

Andrew/R+W: As far as extending the life of a coupling, several options exist. Using a doublewalled stainless steel bellow can make for a much stronger flexible element than helical or beam cutting of one continuous piece of stock. In addition, using a welded connection between a bellow and hubs rather than a traditional swedged or bonded connection can make the coupling less likely to shear in the case of excess lateral misalignment. Beyond using stronger materials and assembly methods, other adaptations can be made on an application- specific basis.

Tom/Climax Metals: Corrosion-resistant shaft collars in Type 316 stainless steel or yellow zinc dichromate plated steel are ideal for wash down and highly corrosive environments in mining, fertilizer, construction, pharmaceutical, and food processing industries.

Rob/Thomson Industries: AISI 1566 is good for common linear bearing applications, AISI 52100 for lightweight applications (for example, running wires or coolant through a tube as in aerospace applications), 440C hardened stainless for increased corrosion resistance in medical, and 316 non-hardened stainless for very corrosive atmospheres in food packaging and processing.

Jim/Lovejoy: We see more coupling types made in powder metals as presses become more suitable for short runs; these couplings are low cost and strong. We also see more materials of the visco-elastic type for higher load carrying with resilience.

Paul/Servometer: An electrodeposited nickel bellows coupling exhibits about one quarter the windup of hydroformed bronze or stainless steel bellows; its elastic windup is typically less than 1 arc-sec per N-cm.

Jim/Lovejoy: We are always trying to increase coupling life via new materials and designs; new materials with promise include the viscoelastic urethanes and powder metal technology.

Tom/Climax Metals: Our nonmetallic shaft collars are made from USDA and FDAapproved nylon and acetal. They are ideal for washdown environments found in food processing and pharmaceutical applications because they resist solvents, chemicals, wet, and caustic environments.

Jim/Lovejoy: We see more non-lubricated high power couplings in the future. Right now the coupling with the greatest power density capability is the all-steel gear coupling. But it requires a grease lubrication to reduce tooth wear.

Maintenance

Connecting devices often function as “safety valves” in the systems where they’re used. By absorbing abnormal forces, they protect more costly components from damage. However, this puts their accessibility and interchangeability at a premium.

Andrew/R+W: When machine jams and collisions occur it can be very costly, not only in terms of damage, but also in terms of down time and lost production.

Tom/Climax Metals: Our new adjustable-width collars are designed for fluid power or robotics requirements, where linear slides are common. They provide for quick and accurate adjustments that allow the end-user to make precise stroke adjustments.

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