Patent ID: 7811039

Claim:
A screw loosening prevention structure, comprising: a first member that is formed with a container space filled with gas, and includes a first threaded portion; a second member that includes a second threaded portion threadedly engaged with the first threaded portion; and a spring member provided between the first and second members, wherein the first member includes a first spring seat for supporting one end portion of the spring member, and the second member includes a second spring seat for supporting the other end portion of the spring member such that the spring member exerts equal and opposite forces on each of the first and second spring seats, and such that the first and second spring seats constrain radial movement of the respective end portions of the spring member; wherein the spring member is supported by the first spring seat and the second spring seat in a deformed and compressed state, the spring member initially being deformed and compressed with an initial displacement from an unloaded state when the second member is threadedly coupled with the first member by threadedly engaging the first threaded portion of the first member with the second threaded portion of the second member; and wherein the spring member is compressed with the initial displacement that is greater than a displacement of the spring member caused by a relative displacement between the first member and second member in a direction in which the second member moves back from the first member due to a screw loosening factor including a pressing force against the second member received by the pressure from the gas in the container space, such that the screw loosening prevention structure maintains a tightened state in which the first and second threaded portions are inhibited from disengagement with each other due to spring force acting on the first and second spring seats by the spring member that is maintained deformed and compressed after said relative displacement.