Facemask for abrasive service
This invention relates to a face protective mask with a respirator employed in heavy duty industrial uses, and in particular to a new durable sealed viewing lens cartridge assembly. 
     BACKGROUND OF THE INVENTION 
     In many industrial activities, workers require full facemasks mounted in hoods which rely on a separate air supply for respiration for protection. Many of these workers also require a full field vision to carry out their work effectively. Typical applications are with spray painters (deleterious solvents employed), welders (gas fuel and eyeburn risks from arc filtering) and surface blasters (sanders), who prepare corroded surfaces for recoating, painting, and the like. 
     In applications such as jet blasting, workman require both physical and respiratory protection from the particulate sanding material and loosened scale. The typical protective mask with its air intake passages and the outer viewing facepiece become clogged and obstructed. Practical operation requires that the pitted viewing lens be replaced with a new lens while working in the contaminated atmosphere. Protective upper body hoods, whether waist or shoulder length, are available to accomodate facemasks and their integrated breathing tubes and exhalation equipment. 
     One of the problems encountered in use of these protective masks is the difficulty in replacing the lens retainment under field conditions. Other problems include the inability to obtain a good seal to minimize grit ingestion and keeping the lens in place during use. 
     It is, therefore, an object of the invention to provide a lens and cartridge assembly for use with a standard protective facemask and associated abrasive blast hoods. It is another object to provide a lens cartridge assembly which can be replaced with a different configuration of lenses in the facepiece component with considerable ease when the existing unit has reached its limits of usefulness or specific service. It is still another object to provide a novel lens assembly which provides superior sealing against the invasion of grit from the outside into the breathing components of the external protective assembly. 
     SUMMARY OF THE INVENTION 
     Generally, the present invention provides a lens cartridge assembly which can be readily mated with any one of a variety of lens housing adaptors. These adaptors are tailored for specific field uses. The lens cartridge of the present invention is sealably mounted on the face opening of a head or facemask. The lens of the cartridge assembly can be substituted or exchanged to accommodate the particular work environment, such as sand blasting, welding, or the like. With the invention, the chance for grit being forced between the lens assembly and its surrounding adaptor is minimized. Also, when grit infiltration does occur, the lens assembly is handily removed, the lenses refurbished, or replaced for another type of service, and then quickly restored to the facepiece housing adaptor. 
     The present invention is particularly well adapted for use with a facemask having means for respiration, including a head buckle assembly, a mask exhalation valve, and an inhalation tube assembly. These masks also have a sealable but transparent front facepiece, a lens opening to receive a viewing lens, lens ring, and a lens housing adaptor operatively connected to the facepiece for viewing. The lens holder itself is of a generally rectangular shaped configuration thereby facilitating full field vision. It is preferably molded of any one of a variety of thermoplastic materials, which are known as castable (moldable) resins, have high elastic modulus and good electrical resistance. Rigid or flexible thermoplastics can be used depending on the environmental conditions. Flexible polyurethane foams are well suited to the present invention, since they can be fabricated to a formed configuration but are deformable with minimal pressure by the lenses, yet have memory which returns them to their initial fabricated configuration upon lens removal. 
    
    
     The present invention also provides a retainer element adapted to releasably support the lens assembly comprising a first rigid planar panel with a substantial opening in its face that defines a first open frame portion, a similarly configured and spaced apart second planar panel, means to provide a hingeable mating along one edge of the aligned panels and means to permit interruptable latching of the panels. The retainer facilitates the removal and replacement of lens cartridges. Other advantages of the invention will become apparent from a perusal of the following detailed descriptions taken in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, perspective view of the major components of a mask, lens, facepiece and eyes protective lens assembly, including the multi-lens assembly cartridge of the present invention; 
     FIG. 2 shows the assembly in perspective of FIG. 1 in an operating mode with a breathing tube; 
     FIG. 3 is a perspective view of the reverse side of holder 39 shown in FIG. 1; 
     FIG. 4 is a side plan view, in full section of the housing adaptor assembly tailored for use in abrasion blasting of surfaces and adapted to receive the lens cartridge assembly of the present invention; 
     FIG. 5 is a front elevational, in partial section, of the novel lens assembly and holder ready for mounting on the housing adaptor assembly of FIG. 3; and 
     FIG. 6 is a side elevational view, in full section, of the multi-lens cartridge assembly of the invention, taken along line VI--VI of FIG. 5. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a conventional face protective mask facepiece 11 is shown, with respiration accessories and provision for wearer viewing in an industrial setting. A harness 12 is tensioned against the back of the head (not seen) by the use of buckle assemblies 13a, 13b and 13c. A nose cup assembly 14 is dispose within the mask to rest sealingly on the wearer&#39;s nose bridge. Cup 14 has bilateral valve spiders 15a and 15b. In the lower section of flexible mask 11 are laterally opposing exhalation valve assemblies 16a and 16b, and consisting of a fitted valve body 17a and 17b, a flapper valve 18a and 18b, and the externally facing valve cover 19a and 19b, respectively. 
     Centrally located in the lower section of the mask is mask port 21 which accomodates breathing tube 22 (shown in FIG. 2). Positioned between port 21 and tube 22 for securing them together are clamp 23, retainer ring 24, speaking diaphram 25, O ring 26, inlet housing 27, disk valve 28, combined gasket and valve spider 29, tube adapter assembly 31 and gasket 32. Clamp 33 and threaded insert 34 (shown in FIG. 2) which slips over tube rigid end 35 serve to couple breathing tube 22 to mask port 21. 
     With respect to the support of protective lenses assembly there is provided a generally concave ring 36 deferring lens frames 36u and 36l, which serve as a peripheral ring that slips over the ovular channeled opening 37 centrally located on the front of mask 11. Faceplate lens adapter 38 includes a narrow peripheral edge or rim 38R which is adapted to engage channeled opening 37 and is secured therein by half-rings 36u and 36l, as is shown in U.S. Pat. No. 3,968,793, which is incorporated herein by reference. Lens adapter 38 is preferably made of a plastic, such as from a polycarbonate resin. Lens adapter 38 includes a planar lens face 38F which is transparent. Positioned adjacent to and matable therewith is to hinged, preferably bottom-hinged, lens assembly retainer 39 which will be described in connection with FIGS. 3 and 4. 
     Positionable within retainer 39, is the lens cartridge assembly 40 of the present invention to be described in detail in relation to FIGS. 5 and 6. Faceplate lens adaptor 38 is preferably used on masks by persons engaged in abrasive blasting operations. The severity of the blasting operation is compensated for by the specific choice of multi-lens assemblies, variable numbers of lenses, thicknesses and tempering which are possible to employ. 
     Lens adaptor 38 includes a first narrow peripheral edge or Rim 38R which is adapted to engage channeled half-rings 36u and 36l. The reverse side of ring 36 is also channeled (not seen) and is adapted to mate with frame 37 of the mask opening, for example, as shown in U.S. Pat. No. 3,968,793, which is incorporated herein by reference. Lens adapter 38 is preferably made of a plastic, such as from a polycarbonate resin. Lens adapter 38 includes a planar lens face 38F which is transparent. 
     Cartridge retainer 39 is provided with an open frame 46 in face plate 41, as is best seen in FIG. 3. The edge of plate 41 is further provided with a flange 42 that mates with shoulder 43 of lens adapter 38. Cartridge retainer 39 is mounted, preferably by sonic bonding or by adhesive, to lens adapter 38 and is configured to receive lens cartridge 40. Lens adapter 38 has a flared bilateral configuration, of which its Rim 38R peripherally engages with channeled ring 36, as described above. 
     In FIG. 4, lens adaptor 38 has its opposing planar face 38f, which is stepped downward near its periphery, provided with raised shoulder 43 that receives and locks with the flanged outwardly, ringlike, ridge 42 of retainer 39. The inner surface of face panel 41 has a substantially rectangular cut out 46 to create a vision path 46p through the body of the housing. The lowest point of the circumference of frame edge 44 is provided with at least one a radially disposed rib 47 which has an axial passage (not seen) serving to permit the rib to be hinged by a metal pin 48 to the outwardly hinged, frame face 49a which is also provided with an axial passage (not seen). 
     Front panel 49 of frame 44 is provided with an inwardly facing horizontal strip 51, which is preferably pliable, having a downwardly depending bead 52 that overlaps the outwardly flanged upper detent 53 of frame 44. A rectangular recess 54 is defined by panel 49, frame 44 and adaptor face 38f, which serves to receive lens assembly 40. Rectangular opening 55 in panel 49 is of a substantially identical dimension to that of opening 46 of plate 41. When a lens cartridge assembly 40 is to be installed (not seen in FIG. 3), the bead latch 52 can be released by a minimum effort exerted at upper edge of frame 44 to access the lens assembly chamber 54, and thus to replace a marred or gritted assembly 39. Vertical flange 56 extends above frame edge 44 and is contiguous with panel 49. 
     Referring to FIG. 5, a front view (as loaded into retainer 39) of cartridge lens assembly 40 is shown, comprising cartridge frame 57, preferably made from an elastomeric material. Cartridge frame 57 includes a supporting shoulder 58 shown (shows broken out portion), for supporting the peripheral edges of the most outwardly positioned, removable lens 59A. The lenses have a pair of oppositely positioned end tapes 61L and 61R facilitating removal of the individual lenses. Each of such lenses are of a preferably rectangular shape configuration and so oriented with their longer edges being horizontal, providing maximum peripheral vision for the user. 
     With a reference to FIG. 6, lens cartridge frame 57 is preferably molded from a deformable elastomeric material, such as flexible polyurethane foam. The outer periphery 61 of assembly 40 is adapted to snugly engage the inner chamber 54 of retainer 39. The inner periphery 63 is sized to sealingly engage the edges 64A through 64D of a plurality of lenses 59A to 59D to provide a dust-free seal. 
     Supporting shoulder 58 (abutting innermost lens 59D) of holder 40 is flanged inwardly to provide a sealable shoulder 66 to support the periphery of innermost lens 59D when it is placed in snug abutment thereto. Transparent lens 59D is positioned within frame 57 of cartridge 40, and sealed, edge-wise, by surface 63, asurface 66. Abutting first lens plate 59D are a plurality of lenses, 59A-59C, sized to engage their edges 64A through 64C in a airtight seal, with the inner periphery 63 of the deformable cartridge 40. Lense 59 may be made from glass or other transparent material. The selection of material is based upon the intended operating environment. 
     The replaceable lenses are removable by manual manipulation which is preferably facilitated by using one or more flexible strips, 61L and 61R (FIG. 5). These strips are preferably bonded along one extremity of the strip to the surfaces of each of the removable glass lenses. The other free end of the strip extends outwardly (while retained within cartridge 40) but its of a sufficient length to permit manual grasping to serve for removal of its attached single lens from its compressive peripheral retention (and the vacuum between lens surfaces) by the holder inner surface 63. The strips are made quite thin so as to cause only minimal spacing apart of the adjacent lenses when they are aligned for use. In the preferred embodiment, the innermost lens 59D is adhesively bonded on its periphery to the abutting holder flange 66. Also preferably, the two strips, such as 61L and 61R, are bonded to each of the removable lens 59A, 59B and 59C. They are conveniently positioned on the vertical periphery of each lens so as to minimize any visual distortion. 
     An assembly of lenses as shown in FIG. 6 are prepackaged in varying dimensions and uses, and containerized to be ordered as needed for a particular service, such as those described above. 
     In another embodiment, removable lens 59A and 59B are laminated to one another where stress forces are anticipated. Alternatively, the removable lenses 59A to 59C may be of tempered or untempered glass, and may vary from two that are laminated to four which are merely arranged face to face to form the lens package. 
     While in the foregoing, preferred embodiments of the invention has been described, it should be understood to one skilled in the art that various modifications and changes can be made without departing from the true spirit and scope of the invention as recited in the appended claims.