A spring coupling is a method used to ease irregularities in power sent between a drive system and a driven system. These systems rely on springs to absorb and redirect energy between two systems. When an irregularity occurs, instead of the one part of the two systems jerking the other to match its speed, the spring will absorb the majority of the impact and allow the system time to equalize. Using a spring coupling drastically reduces vibration and increases the life of both systems.
A coupling is a method of connecting two shafts. In general, using a coupling is superior to simply having a longer shaft for two reasons—it is easier to line up the shafts and modify the connection. When two systems are put into a larger machine, the shafts won’t always line up perfectly; this is especially true as the machine functions over time. In order to combat the misalignment and prevent shaft damage, the shafts are connected in ways that give slightly more freedom to the systems.
In addition to the freedom, couplings are used to modify the way the power moves from one shaft to another. In some cases, like automobiles, this allows the shaft to change the directional spin. Other systems, like a spring coupling, are used to modify the power as it moves from one system to the other.
Springs absorb and store power. As the spring tightens, it is taking in power, which it releases when it uncoils; basically, shortened springs hold power and elongated springs transfer it. For this reason, springs are used in a variety of manufacturing processes and types of machinery to store or release power at specific times. For example, the springs in a car lessen impacts caused by bumps and holes in the road by absorbing a majority of the force and then releasing it slowly.
This principle extends to the spring coupling. When a drive system turns a shaft, a spring coupling takes in power and releases it to a connected system. If everything is going correctly, the coupling is releasing power in exactly the same amount as it is taking in, meaning the coupling is simply connecting the systems rather that transferring or absorbing power.
If something goes wrong in the system, the spring coupling comes into effect. Fluctuations in the power sent from the drive system will cause its end of the coupling to move faster or slower than the end connected to the driven shaft. If the shaft slows down, the change in speed causes the spring to elongate, transferring additional power and maintaining the driven speed. If the drive shaft speeds up, the speed difference shortens the spring as it absorbs the additional power. In either case, the spring slowly returns to its normal shape as it bleeds the power out into the connected systems.