fig1 and 2 illustrate an earplug 10 of the invention which is of simple construction and which seals well to ear canals of different diameters . the earplug includes a stem 12 and a main flange 14 that each extends rearward r along an axis 16 of the earplug from a front end part 20 of the earplug . the main flange has a progressively greater diameter at progressively more rearward locations . the main flange has an inside 22 that joins to the stem at a location 24 , and the main flange has an outside 30 that merges with the front end part to form a smooth convexly curved earplug front end outside surface 32 . the earplug is symmetric about the axis 16 . the ear canal a shown in fig4 has an entrance with a diameter b such as 0 . 30 inch . most people have ear canals with an entrance diameter of between about 0 . 33 inch ( 8 . 4 mm ) and 0 . 27 inch ( 6 . 86 mm ). there is also variation in the cross - sectional shape of the ear canal ( slightly elliptical instead of round ) and the axes of many ear canals are curved . the rear end 48 of the main flange 14 of fig1 has an initial diameter d of about 0 . 48 inch ( 12 . 2 mm ) and is expected to be radially compressed ( with respect to axis 16 ) to press firmly against the internal surface of the ear canal . the earplug is molded of an elastomeric material such as silicone having a durometer a of about 30 . it is desirable that the total expansion force of the flange against the walls of the ear canal be about two ounces . this assures sufficient radially inward deflection of the flange rear portion 40 so the flange presses firmly against the ear canal at all locations around the flange to prevent the passage of sound around the flange . this also avoids large forces that can bring discomfort to the wearer . the single long flange 14 has high resilience because of its length . as a result , the flange rear portion 40 applies a primarily constant force against the ear canal despite the flange bearing against walls of a small ear canal ( e . g . diameter b of 0 . 27 inch ) or a large ear canal ( e . g . diameter b of 0 . 33 inch ). it is desirable that the flange bear with about the same force ( e . g . 2 ounces , or 54 grams ) against small and large diameter ear canal walls . if the flange had a smaller length l , such as about half its maximum undeflected diameter d , then the force of the flange rear portion against the ear canal walls would vary more with variation of the ear canal diameter . prior earplug flanges , such as those shown in u . s . pat . nos . 4 , 867 , 149 and 6 , 241 , 041 had flange lengths no more than 62 % of their largest diameters , resulting is less resilience and therefore a greater change in force with ear canal diameter . applicant prefers to use a main flange length l that is at least 80 %, of the undeflected main flange largest diameter d , that is preferably at least 90 % of the diameter d , and that is more preferably at least 100 % of the diameter d . the flange 14 has a thickness t that varies along its length . the thickness is greatest at the front end 44 of the flange and gradually decreases towards the rear of the flange . the thinner flange rear portion allows better conforming of the flange rear portion to irregularities in the ear canal walls , while the thicker flange front portion provides greater resistance to deflection that balances the smaller force of the thin flange front portion . it is desirable that there be substantial radially inward deflection of the rear of the flange , to assure that it presses firmly against the surface of the ear canal . the stem 12 is used to insert the earplug into the ear and to withdraw it . the stem usually extends rearward of the main flange , and its diameter does not have much effect on the earplug . applicant has constructed earplugs of the construction shown in fig1 - 4 . the earplugs had a main flange outside diameter d of 0 . 48 inch and a main flange length l of 0 . 53 inch , for a diameter - to - length ratio of 110 %. the entire length g of the earplug front portion ( not including the stem ) between the extreme front end 46 of the front end part and the rear end 48 of the main flange was 0 . 63 inch . the diameter d of the earplug rearmost flange , which is the main flange 14 , is at least 55 %, preferably at least 65 % and most preferably at least 75 % of the entire length g of the earplug front portion , that is , up to the rear end 48 of the main flange ( which is the flange of greatest length ). the angle c between the main flange outside surface and a line 49 that is parallel to the axis 16 , varies from about 25 ° at the flange front end 44 to about 5 ° at the flange rear end 48 . the main flange rear end diameter should be between 0 . 35 inch and 0 . 60 inch , and the main flange axial length should be at least 0 . 45 inch . fig5 though 7 illustrate an earplug 50 that is similar to that of fig1 , except that it includes internal flanges 52 , 54 that radially - outwardly bias a location 55 ( a ring - shaped location ) on the main flange 56 . the rearward internal flange 52 has a rear end 62 that merges with the stem , a front end 64 that bears against the inside 58 of the main flange , and a middle portion 66 . the rearward internal flange 52 biases the middle 55 of the main flange radially outward . this results in the main flange rear portion 72 pressing more firmly against the ear canal without requiring a thicker flange , so a thin main flange can be used that conforms to local irregularities in the ear canal . the rearward internal flange has a considerable length j and thin walls especially at its front end 64 so it is highly resilient . the forward internal flange 54 is thin and of length k . its rear end 80 urges the middle of the rearward internal flange radially outwardly . the combination of the main flange with one or both of the internal flanges , results in resilient outwardly biasing of the main flange . fig7 shows how the one - piece molded earplug 50 of fig5 and 6 can be molded , with the main flange 56 initially opening forwardly and the two umbrella - shaped internal flanges 52 , 54 opening rearwardly . after molding , the rear end portion 64 of the rear internal flange 52 is deflected to “ snap ” it in reverse so it opens forwardly as in fig5 . then the main flange 56 is “ snapped ” in reverse so it opens rearwardly as in fig5 . although the earplugs with the long main flange 14 of fig1 and the long main flange 56 of fig5 can provide good sound sealing , they lack a “ backup ”, or second location where the earplug seals to the walls of the ear canal . such a backup location has an advantage in providing a sound seal in the event that there is an irregularity in the ear canal , such as a small bump where the main flange rear portion presses against the ear canal and where an air gap might be left , or where the earplug is inserted only a small part of the total designed insertion distance into the ear canal . fig8 illustrates an earplug 90 that includes a main flange 92 and a backup flange 94 that “ piggybacks ” on the main flange . the main flange 92 is similar to those of the prior two embodiments of the invention , with a length m along the earplug axis 100 that is over at least 75 %, preferably at least 90 %, and more preferably at least 100 % of the main flange maximum outside diameter n . the backup flange 94 has a front end 102 that lies slight forward of the main flange and merges with an earplug front part 104 . the backup flange has a rear end 106 that has about the same diameter as the rear of the main flange . however , the backup flange has an average thickness p that is about half the average thickness q of the main flange and slightly more sound can penetrate the backup flange . in most cases , the main flange seals well against the ear canal walls and the backup flange seals also , though not quite as well . however , when the main flange does not seal well , the moderately good sealing of the backup flange protects the hearing of the worker from damage . applicant prefers to mold the earplug of a “ solid ” ( not foam ) elastomeric material such as silicone . however , it is possible to mold the earplug of a foam material , preferably one of a high density foam . in either case , the earplug is a one - piece molded article . thus , the invention provides an earplug of a type that has a stem and that has a flange that extends at a rearward and radially outward ( with respect to the axis ) incline as seen in a sectional view , wherein the flange has an especially high resilience so it can provide a force on the order of magnitude of two ounces against the ear canal despite variation in the diameter of the ear canal . this is accomplished by using a main flange that extends along most of the length of the earplug other than the stem , with the main flange length being at least 80 % ( more than 75 %), 90 % or 100 % of the largest diameter of the main flange . the resilience of the main flange can be enhanced by providing an internal flange that extends from the stem , preferably at an average incline of no more than 30 ° to the axis , and that presses against the inside surface of the main flange to resiliently bias it radially outward . a second internal flange can bias the first internal flange outward . the earplug can be provided with a backup flange that has about the same or slightly smaller rear portion diameter but a smaller length and thickness than the main flange . such backup flange assures a moderate sound seal in the event that the main flange does not provide a good sound seal . although particular embodiments of the invention have been described and illustrated herein , it is recognized that modifications and variations may readily occur to those skilled in the art , and consequently , it is intended that the claims be interpreted to cover such modifications and equivalents .
an earplug of the type that is molded of elastomeric material and that has a flange that seals to the walls of a person &# 39 ; s ear canal as a stem is pushed forward into the ear canal . instead of using three or four flanges , applicant &# 39 ; s earplug has a single very long main flange with a maximum diameter that is at least 80 % of the length of the main flange , and at least 55 % of the entire length of the earplug except for the stem . this allows the outside of the long flange to extend at a very small angle to the axial direction , and apply a constant force against the walls of the ear canal , for good and comfortable sealing to the ear canal .