The Versatility of Couplings

April 24, 2017

Coupling versatility is today’s topic. There’s an extensive range of shaft connecting devices on the engineering market, chief among which is the clamping mechanism. This is a cylindrical mechanism that mates two perfectly aligned shafts. It uses screws and keying assemblies to lock two spinning drive shafts, but what happens when these two rotating rods are misaligned? Only the versatility factor, as established by different coupling types, can answer that question.

Why Do Couplings Need Versatile Designs? 

If the drive components aren’t perfectly aligned, then there’s no point resorting to a clamping coupling, not when this solution uses a fixed cylindrical form factor. A bellows mechanism will work here, for this coupling format is equipped with a torsional stiffness feature. That feature means the coupling system will work efficiently, even if the two shafts are poorly aligned. Indeed, the bellows mechanism maintains operability even when there’s an angular misalignment error.

Rated for Torsional Stiffness 

Highly versatile elastomeric designs come ready-built with a torsional stiffness rating. The bellows configuration changes this material base pairing method by adding steel plates and anodised aluminium hubs to the mix, hence the bellows moniker. That’s not to say an inflexible mechanism doesn’t have a place of prominence in this drive synchronising solution base, for these unidirectional products do handle shock loads very well. It’s just that, well, unless the power transmitting elements are perfectly aligned, the shearing force will eventually damage the motor or gearing unit’s bearings, at which point the entire power chain would grind to a halt.

Stopping Power Transmission Wear 

In point of fact, there are enough coupling solutions to occupy several datasheets. The elastomeric family and the bellows category are certainly better at handling misalignment issues than a standard clamping assembly. Granted, that standard solution synchronises perfectly with the rotating power source thanks to a series of shaft keys. Screws and/or a geometrically flattened rod profile strengthen that synchronisation factor. Unfortunately, wear is likely when this fitting is employed, especially when complex gearing units are creating a chain of power transmitting force. Simply put, even the smallest alignment error will propagate through that drive chain, which then causes system-wide gear teeth and bearing overload.

The two coupling types illustrated here represent a cross-section of this drive locking mechanism, but they should in no way be considered a complete picture. Indeed, there are chain and diaphragm connectors, plus grid and plate meshing solutions. The versatility of couplings is rooted in these types and their custom-made cousins, the drive and gearing joining mechanisms that accommodate angular and planar misalignment conditions, and in the ingrained operational characteristics of each drive element.

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