Fail-safe versus a fuse type couplings

Edited by Mike Santora

Understanding how a coupling may fail is critical during the design process. Oldham couplings are a fuse type coupling and power transmission will stop upon failure. A jaw type coupling are fail safe as the tenons will interlock and continue power transmission.

Depending on your application you may want a fuse type coupling, For example, if you have a process where a machine jamming is possible, perhaps a letter sorter. In many cases you want the coupling to break or with an oldham in particular, that disc to break and disconnect power transmission. This can protect the drive systems from the machine from further damage. With a jaw type coupling, if the spider fails the jaws on a jaw coupling will interconnect and you’ll still drive, you’ll still have power transmission, that can be advantageous.

Another example: in the semi-conductor industry in wafer manufacturing, in a Z access you’re lifting a boat of these wafers, which are tremendously expensive. In the case of a drive system, a failure of some type is not an option. If the spider fails they want the jaws to interconnect so that they don’t backdrive their system and drop a load or a boat of wafers or something valuable. Many times you’ll see the need for a fail-safe coupling where you continue to be connected. In Z access applications where if the coupling was to fail, there’s enough weight or mass to backdrive the system and drop a load.

Ruland
www.ruland.com