An automatic lubricator is a device fitted to a steam engine to supply lubricating oil to the cylinders and, sometimes, the bearingsand axle box mountings as well.[1] There are various types of automatic lubricator, which include various designs of displacement, hydrostatic and mechanical lubricators
.Elijah McCoy, a Canadian who moved to Michigan and became a U.S. citizen, received a patent for his automatic lubricator in 1872. Piping delivered oil by gravity from a central reservoir to where it was required. Later types of lubricator (from around 1887[2]), referred to as the "sight-feed" type, allowed a sight glassto be positioned in the cab where the rate of oil feed could be observed. In 1898 McCoy's further patent added a glass tube mounted below the reservoir so that the rate of delivery could be monitored, with a bypass pipe available in case the main feed was seen to be blocked.[3]