Liquid level gauge

Claim 1

A liquid level gauge comprising an elongate support member, a plurality of optical fibres carried by the support member, said fibres extending on the support member generally lengthwise thereof and generally parallel to each other, and a light source disposed at one end of the support member, each of said fibres having one end adjacent said one end of the support member and communicating with the light source to receive light therefrom, said fibres being spaced apart from each other circumferentially of the support member and each fibre being divided at a point along the length of the support member by a gap so arranged that the transmission of light from said source across the gap from one part of the fibre to the other part thereof is determined by the presence or absence in the gaps of the liquid being gauged, the gaps of the fibres being spaced lengthwise of the support member, and the faces of each fibre presented to one another across the gap of the fibre being parallel and lying at an angle to the length of the fibre such that, in the absence of liquid to be gauged in the gap, light from said source passing along the fibre and striking a face will be totally internally reflected, whereas, when liquid to be gauged fills the gap, light from one part of the fibre can be conducted across the gap by the liquid to the other part of the fibre.