Question 47

The Correct Answer is C ### Why Option C (spring force) is Correct In a compression type automatic grease cup, the lubricant (grease) is held within a reservoir, usually situated above a piston or plunger. A heavy internal spring applies continuous downward pressure on this piston. As the grease is consumed or the bearing needs lubrication, the spring continuously pushes the plunger down, forcing a steady supply of lubricant into the bearing. This design ensures controlled, consistent feeding of grease over an extended period without manual intervention until the cup is empty. ### Why Other Options Are Incorrect * **A) a Zerk fitting:** A Zerk fitting is a specialized valve (grease nipple) that allows grease to be *inserted* into a bearing using an external pressure gun. It is not the mechanism that *forces* the grease into the bearing within an automatic compression cup; the cup *replaces* the need for continuous Zerk injection. * **B) gravity flow:** While gravity plays a role in some simple lubrication devices (like gravity-feed oilers), compression grease cups rely on a much stronger and consistent *force* than gravity alone to push the thick grease paste into the pressurized environment of a bearing. * **D) a pressure gun:** A pressure gun (or grease gun) is an external tool used for *recharging* the automatic grease cup or servicing fittings like Zerks. It is not the internal mechanism that dispenses the grease into the bearing during the cup's normal operation.