Liq. filled timer of hour-glass type - has two different density liquids replacing granular material normally employed and has two holes in central partition

摘要

A timer or 'hourglass' is based on the use of two liquids rather than the orthodox granular material normally employed. The two liquids (2, 3) are of different colours and densities and are contained within a transparent enclosure (1) which has a central membrane (4). This membrane has two holes to allow passage of the liquids in both directions, the hole size and volume determining the time period being measured. The accuracy of the instrument is greater than that of granule types and can be used as a kitchen egg-timer or in offices to indicate the duration of telephone calls. The two holes allow flows to be established in opposite directions with the light liquid flowing up through one hole and the heavy liquid flowing down through the other hole.