Abstract: In various embodiments, the invention provides a lubricator comprising a housing defining, a main lubricant chamber adapted to contain a fluid lubricant. A piston pump in fluid communication with the main lubricant chamber may be adapted to be driven to discharge the lubricant from a pump changer through a lubricant outlet in the housing. A check valve may be mounted on the lubricant outlet, to check the discharge of lubricant from the lubricator. The lubricator may include a motor having a drive shaft adapted to rotate a swash plate to act as a cam to drive reciprocating motion of the pump piston in the pump chamber. The drive shaft may be in axial alignment with the piston, the swash plate being set obliquely on the drive shaft to revolve when the motor is activated to give reciprocating motion to the piston in a direction parallel to the driven shaft. The piston may be biased in the pump chamber against the swash plate, so that the swash plate rides on the piston.