Bag-Full indicator for a vacuum cleaner has a piston normally held clear of the sight window until a vacuum on one side is generated when it becomes visible

摘要

The piston (4) is held against a projection (6) in the housing (1) by a helical compression spring (5) when both sides of the piston are equal. When the cleaner is activated a reduced pressure is generated on one side (7) of the piston moving it beneath the viewing lens (3) and window (2).