| 摘要 |
An aid apparatus for level surveying instrument comprises a housing having a receiving chamber therein, two channels at opposite ends of the receiving chamber respectively, a window at one side of the receiving chamber, and a socket opening at the side wall of the housing connecting to receiving chamber via the channel. A controlling member is slidable received in the housing. The controlling member has a movable bar, two seal block disposed at opposite ends of the movable bar for sealing the channel, and a driving member is provided at the housing for driving the controlling to shift, whereby the sealing block being driven by the driving member to seal the channel and to depart from the channel to prevent bubbles formed in liquid.
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