Safety Helmet

Abstract

A safety helmet includes an outer shell configured for surrounding a head of a user, and an infrared reflective layer disposed in an interior of the outer shell. The infrared reflective layer is configured for reflecting at a least a portion of incident infrared radiation transmitted through the outer shell. The infrared reflective layer has infrared reflectivity of at least 40%. A method of manufacturing a safety helmet with an infrared reflective layer is also disclosed. The method may further produce a safety helmet having an evaporative cooling pad positioned within a cavity defined by the inner surface of the outer shell.

What is claimed is: 
     
         1 . A safety helmet comprising:
 an outer shell configured for surrounding a head of a user; and   an infrared reflective layer disposed in an interior of the outer shell, the infrared reflective layer being configured for reflecting at least a portion of incident infrared radiation transmitted through the outer shell,   wherein the infrared reflective layer has infrared reflectivity of at least 40%.   
     
     
         2 . The safety helmet of  claim 1 , wherein the infrared reflective layer has infrared reflectivity in a range of 83% to 89%. 
     
     
         3 . The safety helmet of  claim 1 , wherein the infrared reflective layer has a hemispherical emissivity of less than 0.2. 
     
     
         4 . The safety helmet of  claim 1 , wherein the infrared reflective layer has an optical density of at least 2.0. 
     
     
         5 . The safety helmet of  claim 1 , wherein the infrared reflective layer comprises at least one of the following: aluminum, gold, silver, copper, or any combination thereof. 
     
     
         6 . The safety helmet of  claim 1 , wherein the infrared reflective layer comprises at least one of the following: doped titanium dioxide, doped or undoped indium tin oxide, doped cerium oxide, doped manganese oxide, iron (III) oxide, cadmium sulfide, chromium trioxide, or any combination thereof. 
     
     
         7 . The safety helmet of  claim 1 , wherein a thickness of the infrared reflective layer is 20 nm to 5 μm. 
     
     
         8 . The safety helmet of  claim 1 , wherein the infrared reflective layer is applied on an insert that is removably or non-removably connected to the outer shell. 
     
     
         9 . The safety helmet of  claim 8 , wherein the insert comprises a substrate made from a thermoplastic film. 
     
     
         10 . A method of manufacturing a safety helmet comprising:
 molding an outer shell of the safety helmet out of a thermoplastic material; and   applying an infrared reflective layer onto at least a portion of an inner surface of the outer shell or applying the infrared reflective layer onto an insert that is connectable to the outer shell.   
     
     
         11 . The method of  claim 10 , wherein the insert having the infrared reflective layer is integrally formed with the outer shell during molding of the outer shell. 
     
     
         12 . The method of  claim 10 , further comprising connecting the insert having the infrared reflective layer to the outer shell by at least one of the following: adhesive, one or more mechanical clips or fasteners, press fit, ultrasonic bonding, or any combination thereof. 
     
     
         13 . The method of  claim 10 , further comprising inserting an evaporative cooling pad inside a cavity of the outer shell defined by the inner surface, wherein the evaporative cooling pad comprises:
 a top waterproof, vapor permeable layer and a bottom waterproof, vapor permeable layer with a cavity defined therebetween;   a liquid absorbing layer positioned within the cavity; and   an opening in at least one of the top and bottom layers.   
     
     
         14 . The method of  claim 13 , wherein the liquid absorbing layer is configured to become saturated with a cooling liquid added to the cavity through the opening. 
     
     
         15 . The method of  claim 14 , wherein the top waterproof, vapor permeable layer and the bottom waterproof, vapor permeable layer are configured to allow passage of the cooling liquid in a direction out of the cavity in vapor form but not allow passage of the cooling liquid in liquid form. 
     
     
         16 . The method of  claim 14 , wherein the evaporative cooling pad is configured to allow heat to be transferred from the head of the user to the evaporative cooling pad, thereby evaporating the cooling liquid in the cavity. 
     
     
         17 . The method of  claim 10 , wherein the infrared reflective layer comprises at least one of the following: aluminum, gold, silver, copper, or any combination thereof. 
     
     
         18 . The method of  claim 10 , wherein the infrared reflective layer comprises at least one of the following: doped titanium dioxide, doped or undoped indium tin oxide, doped cerium oxide, doped manganese oxide, iron (III) oxide, cadmium sulfide, chromium trioxide, or any combination thereof. 
     
     
         19 . The method of  claim 10 , wherein the infrared reflective layer has an optical density of at least 2.0. 
     
     
         20 . The method of  claim 10 , wherein the infrared reflective layer has a hemispherical emissivity of less than 0.2.