| 摘要 |
A vehicle wash boom apparatus includes a fixed journalling tube for journalling a boom-supporting tube for reciprocal and rotational movement about a vertical axis. The journalling tube carries a cam and the boom-supporting tube carries a cam follower. A pair of torsion springs at all times bias the cam follower in an upward direction against a cam surface of the cam which is inclined relative to the vertical axis. Thus, as the boom is rotated, the interaction between the cam and the cam follower effects a vertical movement of the boom-supporting member which allows the boom while being used to by-pass a like boom of an identical apparatus when in its home or parked position.
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