| 摘要 |
This invention relates to a novel means for detecting a low level of liquid in a reservoir. One application for the invention is to provide a way to indicate when the level of windshield washer fluid for a vehicle is at a low level. According to one of its broad aspects, the windshield washer fluid noticeably changes colour on the windshield, when it is running low in the reservoir; for example, changing from very light blue to an intense red. There are known electrical and mechanical means for indicating the level of a fluid in a reservoir. However, these indicators of fluid level rely on special equipment such as floats and electrical contacts. An advantage of the present invention, is that it can be used with existing windshield washer reservoirs without the need for additional equipment and/or gauges in the interior of the vehicle. According to one aspect of this invention, the windshield washer reservoir contains a first liquid which usually would be ordinary windshield washer fluid, normally of a light blue or light green colour and normally comprising a mixture of water, methyl alcohol and a dye. Added to this first liquid in the reservoir is a second liquid having a specific gravity different from and floating on top of the first liquid such that when the first liquid is exhausted, the windshield washer delivery system will then pump, on to the windshield, the second liquid. This provides an advance warning the windshield fluid is running low; however the second liquid will continue to be available to clean the windshield for as long as previously planned. The second liquid has a colour that is noticeably different from that of the first liquid so that it is apparent that the first liquid has been consumed. Hexyl alcohol is one example of a second liquid that is relatively immiscible with, and works well with ordinary windshield washer fluid as a first liquid. The hexyl alcohol based second liquid can be coloured bright red, for example, with a dye that is relatively insoluble in the ordinary windshield washer fluid.
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