| 摘要 |
The inner, plastic, tube (1) is cylindrical, with an axial groove (9) in the outer wall in which slide two tabs (20) projecting from the outer tube (2), thus preventing relative rotation. The outer tube's diameter gradually increases towards the lower end, where a pivoted spring-loaded lever (1716) has a catch (18) engaging in recesses (19) regularly spaced along the inner tube, allowing different extension lengths. An annular seal fitted inside the outer tube, near the catch, has a flexible skirt which wipes the outside of the inner tube during extension. A bearing ring (3) fitted in the latter surface near its upper end prevents jamming and undue friction in intermediate positions, and forms an airtight joint with the sealing ring (6) in the fully extended position. When fully retracted, chamfered surfaces (12,14) mutually locate and seal the two tube ends. The outer tube is connected at the top, through a cranked section, to the flexible hose, while the inner tube ends in the suction head.
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