Railroad crossing signal lamp

Claim 1

An improved signal lamp for use at railroad crossings to warn pedestrians and vehicle operators approaching the railroad track along the crossing highway of the approach of a train, comprising: a housing positioned adjacent said highway at said crossings, said housing defining an interior volume and a frontal opening; parabolic reflector means located in said housing for projecting through said frontal opening essentially parallel light rays from a light source located essentially at the focus of the parabola defined by said reflector means; a light transmitting closure attached to said housing, said closure defining a first hollow portion for passing said rays projected by said light source and having a translucent, distinctively colored lens oriented across said first hollow portion to intercept said rays, said lens having an essentially flat exterior face oriented at an angle to said rays with the top of said lens being further from said focus than the bottom of said lens, whereby said lens is rendered relatively free from phantom signals due to ambient light rays and from accumulation of snow, ice and grime on said exterior face, said lens having: a first plurality of prism elements extending from the top to the bottom of said lens on the inside surface thereof for dispersing said rays laterally preferantially toward said crossing highway so that light from said source is directed to areas along said highway distant from said signal and to areas progressively closer to said signal whereby said signal may be easily viewed at points both distant from and close to said railroad; each of said prism elements comprising a first essentially convex surface facing said first hollow portion, said first convex surface being made up of a first plurality of essentially flat facets extending along said first convex surface, each facet being set at an angle relative to said rays each angle being chosen to disperse rays incident thereon laterally to a preselected area spaced from said signal; a second plurality of segmented prism elements interspersed among said first plurality of prism elements and also extending from top to bottom of said lens, said segmented prism element having first spaced segments with faceted, convex surfaces of the type found in said first plurality of prism elements and second spaced segments interspersed among said first spaced segments, each of said second spaced segments comprising a second essentially convex surface facing into said first hollow portion, said second convex surface being made up of a second plurality of essentially flat facets, said facets being oriented transversely to said first plurality of essentially flat facets, each facet of said second plurality being set at an angle relative to said rays, each angle being chosen to disperse rays incident thereon vertically, whereby said lens provides a minimum brightness to observers in front of said lens.