Retroreflective protective helmet

Abstract

Protective helmets that give a distinctive retroreflective signal under wet or dry conditions at night or in other darkened environments are provided by disposing a retroreflective layer covered by a transparent layer over at least a major portion of the outer surface of the helmet.

What is claimed is: 
     
       1. A protective helmet comprising a protective shell adapted to be worn on a person's head; a retroreflective layer disposed over substantially all of the outer surface of the protective shell, comprising a layer of binder material and a monolayer of transparent glass microspheres that are partially embedded in the layer of binder material and have a coating of specular reflective material on their embedded surfaces; and a transparent sheet having the shape of the protective shell disposed directly over the retroreflective layer, said sheet being in tight frictional engagement with said retroreflective layer but without optical contact to the exposed surfaces of the microspheres and being attached to the protective shell at least around the periphery of the retroreflective layer so as to provide an airtight sealed pocket between the retroreflective layer and the transparent sheet, whereby the retroreflective layer retroreflects light shined at the helmet under either wet or dry conditions. 
     
     
       2. A protective helmet of claim 1 in which the retroreflective layer is carried on a support sheet that has the shape of the protective shell and is attached over the exterior of the protective shell. .Iadd. 3. A protective helmet comprising a protective shell adapted to be worn on a person's head; a support sheet that has the shape of the protective shell disposed over the exterior of the protective shell; a retroreflective layer carried on said support sheet and disposed over substantially all of the outer surface of the protective shell and comprising a layer of binder material and a monolayer of transparent glass microspheres that are partially embedded in the layer of binder material and have a coating of specular reflective material on their embedded surfaces; and a transparent sheet having the shape of the protective shell disposed directly over the retroreflective layer, said sheet being in tight frictional engagement with said retroreflective layer but without optical contact to the exposed surfaces of the microspheres and being attached to the support sheet at least around the periphery of the retroreflective layer so as to provide an airtight sealed pocket between the retroreflective layer and the transparent sheet, whereby the retroreflective layer retroreflects light shined at the helmet under either wet or dry conditions. .Iaddend.