| 摘要 |
A plumb device includes a direction determination unit suspended on an upper, movable, convexed portion of a universal joint. A lower, fixed, concaved portion of the movable joint is rigidly connected to a stand by means of a housing. The lower joint part has a lubricant supply line through which a lubricant can be introduced to a groove located on the upper joint part and positioned so as to be between the upper and lower joint parts.
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