Patent Description:
When an electric current passes through air between ungrounded conductors, or between ungrounded conductors and grounded conductors, the temperatures can reach <NUM>,<NUM> (<NUM>,<NUM>°F). Exposure to the arc flash thermal energy from these extreme temperatures both burns the skin directly and causes ignition of conventional work clothing, which adds to the severity of burn injury. The majority of hospital admissions due to electrical accidents are from arc flash burns, not from shocks. Each year more than <NUM>,<NUM> people are admitted to burn centers with severe arc flash burns. Arc flash events can and do severely injure and kill workers even at distances of <NUM> (10ft).

Arc flash hazard exposure level is a function of a variety of factors, including but not limited to fault clearing time, magnitude of the arc current, the type of equipment in which the arc is initiated and a worker's distance from the arc flash event. Multiple techniques can be employed to limit risks related to such exposures. Arc flash injuries, for instance, are particularly prevalent among electricians. A myriad of solutions have been proposed to minimize such injuries.

One such method is through the use of Personal Protective Equipment (PPE) by electricians, electric utility workers and others at risk, including protective eyewear, faceshields, hoods, shirts, pants, coveralls and arc flash suits. One of the common ways to prevent eye and face injuries from an arc flash is interposing a lens or transparent window between the wearer and the arcing source. One such problem with PPE, however, is the restrictions in movement and perception which they place upon such workers. In the case of protective arc flash PPE eyewear, faceshields and hood windows, it may be essential for such workers to have full visual perception (including color acuity) in order to perceive and conduct work on energized electrical equipment as may be needed in the use of color coded electrical wiring and the like. Working on an incorrect conductor due to the worker not being able to perceive the correct color for color coded wires can be a contributing cause for an arc flash event. As a result, there is a need for arc flash PPE eyewear, faceshields and hood windows which provides optical clarity, and in particular color acuity to the user.

One example of a prior art approach <CIT>purports to disclose compositions that block electric-arc energy. Specifically, Paulson claims to disclose a composition and process for manufacturing electric-arc resistant objects that are at least partially transparent. As that patent defines the term, however "substantially transparent" means a composition which allows the passage of a sufficient amount of light to allow a person looking through the material to view objects under normal working conditions. It does not, however, teach or suggest color acuity for a user. Put another way, there is a difference between transparency, i.e., being able to see objects, as opposed to color acuity, i.e., seeing objects without alteration in color versus the distortion in color perceived looking through the material used.

<CIT>teaches a plastic optical filter related to the stabilization of infrared absorbing organic dyes in plastic substrates. A problem arises due to the degradation of the infrared dyes in sunlight and the fact that the Donoian device is simply an optical filter and not an arc shield.

A further approach is known to be offered through BSD Bildungs- und Servicezentrum GmbH. BSD has offered a Bayer Plastics product typically used in architectural or automotive applications to protect against sun light. BSD's product, however, is a faceshield with a laminate of protective film over the faceshield.

Still another publication is shown in <CIT>), which discloses an arc shielding lens or a laminate for such a lens with a mixture of nanoparticles for thermal negation and absorption. However, nothing in this application teaches or suggests the need for color acuity to enable the wearer to better identify potential arc flash hazards while still being protected from an arc flash occurrence.

A further reference regarding to charring of eye and face PPE during arc flash exposure relates to polycarbonate faceshields and is described in, <NPL>. The paper describes a reduction of arc flash thermal energy transmitted through clear polycarbonate faceshields at exposures of <NUM> to <NUM> cal/cm2 but the authors note that at the exposure level needed to generate charring, sufficient energy has already been transmitted through the faceshield to cause burn injury.

<CIT> relates to a transparent electric-arc resistant composition is produced by preparing crystalline tungsten bronze nanoparticles and homogenously dispersing the nanoparticles in a transparent plastic matrix. The crystalline tungsten bronze nanoparticles are prepared by homogeneously mixing an aqueous solution of soluble tungsten and cesium salts and then drying the solution. The dried solution is then heated in a reducing gas or inert gas atmosphere to form crystalline tungsten bronze nanoparticles. Thereafter, a dispersion agent is added and the nanoparticles are dispersed in a liquid solvent medium by wet milling to form a dispersion mixture. The dispersion mixture is then mixed with polymer pellets to form a polymer mixture, and the polymer mixture is then extruded to yield polymer pellets containing highly homogeneously dispersed inorganic nanoparticles. During or after dispersion, additional particles, dyes, heat stabilizers or UV absorbers, may be added. A lens or shield is then molded from the polymer pellets.

<CIT> relates to an arc shielding lens formed of plastic and a plurality of additives such as saturation absorbing dye and reverse saturation absorbing dye having enhanced reaction times to protect a user from arc flash energy.

<CIT> relates to laminates having interlayers containing an infrared absorbing amount of lanthanum hexaboride (LaB6) coated on or dispersed in a thermoplastic polymeric matrix. Preferably, the LaB6 is combined with other materials, such as indium tin oxide, antimony tin oxide, organic dyes or pigments in a polymeric matrix of polyvinyl butyral (PVB). Alternatively, LaB6 is coated on a sheet of polyethylene terephthalate and encapsulated with one or more sheets of PVB. The interlayers having LaB6 dispersed therein or coated thereon are advantageously combined with encapsulation layers, reflective layers, dyed layers and/or pigmented layers.

<CIT> relates to the use of IR-radiation-absorbing particles of the composition ZnSb2O6 having a ZnO/Sb2O5 ratio of <NUM>-<NUM> and to the dispersion thereof in plasticized polyvinyl butyral films using non-ionic surfactants, preferably ethoxylated nonylphenols having a degree of ethoxylation of <NUM>-<NUM>, which have an HLB greater than <NUM>.

In sum, the prior art fails to teach the use of a composition for a PPE eyewear, faceshields or hood windows which enables color acuity by a wearer during use.

The following terms are used in the claims of the patent as filed and are intended to have their broadest plain and ordinary meaning consistent with the requirements of the law.

"Arc flash thermal energy" means all forms of energy created by an arc flash event including but not limited to infrared radiation, ultraviolet radiation, visible light spectrum radiation, convective energy due to hot gases and plasma, and conductive energy due to molten metal and other heated debris.

"Color acuity" means the ability to discern and distinguish between colors in the visible light spectrum.

"Eyewear" means spectacles and goggles used for protection of the eyes.

"Hood window" means a faceshield that is fitted into a hood to provide protection for the eyes, face, neck and head.

"Faceshield" means a device that protects the face and eyes and is generally attached to a hard cap or hard hat.

Eye and face PPE consists of eyewear, faceshields and hood windows.

"Optically neutral" means the near absence of any color shift in the visible light spectrum.

"Charring" means the creation of a black porous material on the surface of eye and face PPE which reduces light transmission and heat transmission through the eye and face PPE.

Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims set forth below are intended to be used in the normal, customary usage of grammar and the English language.

The present invention is defined in appended independent claim <NUM> to which reference should be made.

The apparatus the present invention generally include eyewear, a faceshield or a hood window for blocking or absorbing infrared radiation emanating from an arc flash event. The eyewear, faceshield and hood window are comprised of an infrared absorber including but not limited to particulates of antimony doped tin oxide, indium doped tin oxide, lanthanum boride or cesium tungstate mixed with an optically clear plastic material for providing a grey lens or shield which permits color acuity. The eyewear further includes a frame or similar support structure for the lens comprised of polycarbonate or similar non-conductive material. The faceshield is mounted on a hard cap or hard hat, and the hood window is inserted into a sewed pocket in the front of a hood and secured with a grommet or the like.

The combination of a polycarbonate optically clear plastic material and the selected particulate of the invention provides blocking of infrared radiation by the particulate at lower exposure levels that are insufficient to generate charring and provides a significantly increased level of charring which very effectively blocks higher exposure levels of arc flash thermal energy at or above the level needed to generate the charring phenomenon. In addition, the charring process removes heat from the polycarbonate lens or shield material during the formation of the char, i.e. the heated polycarbonate near the surface is removed from the surface as it undergoes pyrolysis and is converted into a thick char on the surface that very effectively blocks arc flash thermal energy. Consequently, once the charring process is initiated, the level of heat transmitted by the eye and face PPE surprisingly decreases even as the infrared radiation is increased. The concentration of particulate used in the polycarbonate optically clear plastic material must be properly set to block infrared radiation at lower exposure levels in order to avoid burn injury up to the exposure levels at which the charring process is initiated. The combination of infrared radiation blocking by the infrared absorbing particulate at low exposure levels, the removal of heat from the polycarbonate lens or shield surface and the blocking of arc flash thermal energy at higher exposure levels by the charring process permits the use of reduced levels of infrared absorbing particulate which in turn provides higher visible light transmission and consequently higher visual acuity and color acuity for the user of the eye and face PPE of this invention.

The immediate application of the present invention will be seen in providing personal protective equipment for electricians and electrical workers exposed to a wide range of arc flash conditions whereby the workers have color acuity to recognize wire color coding.

Thus it can be seen that one object of the present invention is to provide electricians and electrical workers with eyewear, faceshields or hood windows for preventing injury due to arc flash thermal energy while at the same time providing workers with color acuity in order to reduce the likelihood of working on an incorrect wire or circuit part due to color distortion.

A further object of the present invention is to provide eyewear, a faceshield and a hood window which inhibits the tinting or discoloration of objects being viewed therethrough.

Still another object of the present invention is to provide eyewear and a faceshield which can block and dissipate up to <NUM> cal/cm<NUM> and a hood window which can block and dissipate up to <NUM> cal/cm<NUM> of arc flash thermal energy.

Yet another object of the present invention is to provide eyewear, a faceshield and a hood window which includes an infrared absorber for blocking infrared radiation.

Still another object of the present invention is to provide eyewear, a faceshield and a hood window which provides an electrical worker protection from arc flash events combined with a superior ability to detect and address potential arc flash conditions over prior faceshield compositions.

Yet another object of the present invention is to provide eyewear, a faceshield and a hood window which includes a very thin gold coating on the surface to reflect radiant heat in prolonged exposures such as experienced by firefighters and some industrial workers who deal with molten metals or other molten substances. The gold coating reflects a substantial portion of the radiant heat exposure and the grey eyewear, faceshield and hood window absorbs a substantial portion of the remaining infrared radiation that is not reflected by the thin gold surface coating.

It should be noted that not every embodiment of the claimed invention will accomplish each of the objects of the invention set forth above. In addition, further objects of the invention will become apparent based the summary of the invention, the detailed description of preferred embodiments, and as illustrated in the accompanying drawings. Such objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, and as illustrated in the accompanying drawings.

Set forth below is a description of what is currently believed to be the preferred embodiment or best examples of the invention claimed. Future and present alternatives and modifications to this preferred embodiment are contemplated. Any alternatives or modifications which make insubstantial changes in function, in purpose, in structure or in result are intended to be covered by the claims in this patent.

<FIG> shows a first preferred embodiment of a faceshield <NUM> constructed in accordance with the present invention. The faceshield <NUM> is attached to a hard hat <NUM> or other type of headgear and protects users from electric arcs while at the same time allowing the user to view objects with color acuity. The optically clear plastic material for this product is preferably polycarbonate, but may also include acrylics, cellulose propionates, cellulose acetates and cellulose acetate butyrate or similar optically clear plastics known to those of skill in the art. Similarly, a face shield <NUM> in accordance with the present invention may be fitted into a hood <NUM> (as shown in <FIG>), or eyewear, like spectacles or goggles may be constructed in accordance with the present invention.

In order to provide the necessary user protection for the optically neutral faceshield <NUM> of the present invention, the invention should further include a particulate comprised of antimony doped tin oxide particles coated with a dispersant for blocking infrared radiation associated with arc flashes and similar events. Such particulate may be of a nanoparticle size. Such a particulate for use with the present invention typically consists of nanoparticles of antimony doped tin oxide that are coated with a dispersant to provide a dispersible powder with dimensions in a range of about <NUM>-<NUM> microns, and most preferably about <NUM> microns.

A coating on substantially each antimony doped tin oxide particle is important for it to disperse in the optically clear plastic material, such coating being applied by fluidized bed, sol-gel, sputtering, evaporation or other methods known to those of skill in the art. Without the coating in the practice of the present invention, the particles are difficult to disperse evenly in the processing of the particles in mixing with the optically clear plastic material and the molding of the plastic part. In the absence of such a coating, the faceshield will have a haze that will affect the visibility through the optical part (shield or lens) and prevent or diminish the color acuity provided by the present invention.

In an attempt to quantify the advantage of the present invention, the following table compares several different models of face shields in their ability to transmit the visible light spectrum therethrough. That is, a goal of the present invention is to provide both: <NUM>) a higher level of transmission of visible light across the visible light spectrum; and <NUM>) a substantially consistent transmission of light across the visible light spectrum (i.e., so as to maintain color acuity). Specifically, the following comparison shows: <NUM>) a conventional green IR arc flash shield, <NUM>) a range of concentration of particulate plus dispersants as a weight per <NUM> (<NUM> pound) of optically clear polycarbonate material manufactured in accord with the present invention, and <NUM>) a "clear" face shield:.

Claim 1:
A faceshield (<NUM>) for blocking arc flash thermal energy, the faceshield comprising: a lens providing color acuity within the visible light spectrum, wherein the lens provides at least <NUM> % <NUM>% light transmission across the visible light spectrum, the lens comprised of a particulate consisting of antimony doped tin oxide that blocks infrared radiation, and a optically clear polycarbonate, the optically clear polycarbonate and the particulate chosen and blended in proportion so that the faceshield will block a range from <NUM> to <NUM> cal/cm<NUM> of arc flash thermal energy, the lens further comprising the particulate of antimony doped tin oxide coated with a dispersant dispersed within the optically clear polycarbonate.