Energy-absorbing earcup assembly

Abstract: An energy-absorbing sound-attenuating earcup (10) compris­ es a rigid shell (12) of an ABS terpolymer that is about 0.090 inch thick so as to crush upon impact at an applied force less than that required to crush the skull of the wearer. The shell (12) has an inner coating (60) of a sound-deadening rubber material to compensate for the reduced sound-attenuating capability of the thinner-than-normal shell (12). Spaced flanges defining a peripheral channel for receiving a cord (32) of a helmet suspension (34) are formed as staggered series of (16,18,20,22,24,26,28,30) tabs rather than as circumferentially continuous members to facilitate crushing of the shell (12) upon impact. Resilient earseals (62) disposed between the shells and the wearer's ears comprise first thicknesses (66) of standard polyurethane foam and second thicknesses (64) of slow-­ recovery polyurethane foam to provide additional impact absorp­ tion while permitting the earseals (62) to conform to the wearer's head in cold weather when the helmet is first put on. The earcup (10) may alternatively be releasably secured to the helmet by means of mating hook and loop fastener strips (36) rather than being secured through the staggered tabs.

Description: This invention relates to a sound-absorbing sound-attenuating earcup assembly of the type adapted to be received and retained in an opening in a suspension carried by the wearer's head, said earcup assembly insulating the ear of the wearer from ambient sound, said assembly being of the type in which a discrete hollow cup-shaped rigid plastic shell forming a cavity for receiving the wearer's ear has a periphery carrying an earseal which engages the wearer's head around his ear when the shell is mounted on the wearer's head by said suspension with the wall of the shell spaced from the wearer's ear to form a sound-attenuating chamber around the ear. A sound-absorbing earcup assembly of this general type is known from DE-A-2 000 933. The known earcup assembly is provided with means for mounting the same in a protective helmet and comprises a rigid plastic shell especially consisting of a high impact thermoplastic styrene-type resin. Further, earcup assemblies for attenuating ambient sound in noisy environments, such as in or around military helicopters or other aircraft, are also known in the art. Such assemblies are shown, for example, in US-A's 3,190,973, 3,470,564, 3,875,592 and 3,943,572. As shown in the first US patent identified above, the earcups of such assemblies may house earphones to allow communication or monitoring of the ambient sound. Generally, in such assemblies the earcup shells, which comprise a rigid plastic, are about 6.35 mm (0.25 inch) thick to provide the necessary sound attenuation. As will be apparent from the above description, not only are such assemblies heavy, and thus uncomfortable after extended use, but the rigid plastic shell transmits lateral impact forces, such as might be sustained if the wearer falls against a hard object, almost without attenuation. It is the object of this invention to provide an earcup assembly which minimizes the transmission of impact forces to the head. This object is accomplished by means of an earcup assembly of the type indicated at the outset, which is characterized in that said shell is provided with two spaced rows of discrete circumferentially spaced tabs forming a channel for receiving the portion of said suspension around said opening, that said shell comprises a plastic material of a low-impact grade and that the thickness of the shell is selected so that the shell is crushed upon impact at an applied force less than that required to crush the skull of the wearer. Thus, the present invention contemplates an earcup assembly comprising a rigid shell of such a thickness as to crush upon impact at an applied force less than that required to crush the skull of the wearer. By crushing upon impact, the shell absorbs much of the energy of the impact rather than simply transmitting it to the wearer's skull. Preferably, the earcup shell comprises a acrylonitrile-butadiene-styrene (ABS) terpolymer having a thickness of about 2.3 mm (0.09 inch) to provide the desired crushability. In accordance with another aspect of our invention, the earcup shell is provided with the desired sound-attenuating capability by coating its inner surface with a layer of sound-deadening material, preferably a flexible vinyl rubber coating of about 0.25 to 0.38 mm (0.010-0.015 inch). As indicated above, this invention contemplates an earcup-mounting means in which a channel extending circumferentially along the outer surface of the shell is formed by respective pluralities of circumferentially spaced, outwardly extending tabs defining the sides of the channel. The channel thus formed receives a cord carried by the helmet suspension to secure the earcup to the suspension and therefore the helmet. Forming the channel in this manner improves the crushability of the earcup over what it would have been if the channel had been formed with continuous circumferential flanges as in the prior art. Preferably, the tabs are rounded so as to be shorter at their ends, thereby avoiding sharp corners which might otherwise catch on parts of the helmet. Still another aspect of our invention contemplates a resilient earseal comprising an energy-absorbing material for sealing the region between the earcup and the wearer's head. Preferably the energy-absorbing material comprises an annular layer of slow-recovery polyurethane foam. The inclusion of the slow-recovery foam layer contributes to the overall impact-absorbing capability of the earcup assembly, as well as to its sound attenuation and conformability with the wearer's head. At the same time, the retention of the normal-recovery foam layer allows the earseal to conform to the wear's head when the assembly is donned at temperatures below 40°F and the slow-recovery layer is initially stiff. In the accompanying drawings to which reference is made in the instant specification and which are to be read in conjunction therewith and in which like reference characters are used to indicate like parts in the various views: FIGURE 1 is a left side elevation of a right earcup assembly constructed according to our invention, with parts broken away. FIGURE 2 is a section of the earcup assembly of FIGURE 1, taken along line 2-2. FIGURE 3 is an enlarged fragmentary section of the earseal of the assembly of FIGURE 1 as it appears when removed from the earcup. FIGURE 4 is a right side elevation of the earcup assembly of FIGURE 1 with the earseal and earcup flange removed. FIGURE 5 is a rear elevation of the earcup assembly of FIGURE 1 with the earseal removed, showing one form of mounting in a helmet assembly. FIGURE 6 is a rear elevation of the earcup assembly of FIGURE 1 with the earseal removed, showing an alternative form of mounting in a helmet assembly. FIGURE 7 is a right side elevation of one of the spacer pads of the mounting shown in FIGURE 6. FIGURES 1 to 5 show a right earcup assembly, indicated generally by the reference numeral 10, constructed according to our invention. The corresponding left earcup assembly is a mirror image of the right earcup assembly 10 and therefore has not been shown. Earcup assembly 10 includes a generally elliptical cup-shaped rigid shell 12 having an opening for receiving the ear of the wearer. Shell 12 preferably comprises a low-impact grade of plastic such as the acrylonitrile-butadiene-styrene (ABS) terpolymer sold under the trademark CYCOLAC. In accordance with one aspect of our invention, shell 12 has a thickness of 2.23 mm (0.090 inch) so as to crush upon impact at applied force less than that required to crush the skull of the wearer. The disclosed shell 12, when used in combination with the helmet shell to be described, absorbs impact accelerations of to 175 times that of gravity at an impact velocity of 6 m/s (19.7 feet per second). A flange indicated generally by the reference numeral 14 extends inwardly from the periphery of the shell 12 to define an opening for receiving the ear of the wearer. Preferably, flange 14 is formed from the same ABS terpolymer as shell 12, but somewhat thinner (e.g. 1.57 mm (0.062 inch)). Referring particularly to FIGURE 2, flange 14 is formed with a peripheral portion 38 which is generally in register with the periphery of shell 12 and which is formed with a stepped shoulder portion 40 for receiving said periphery of the shell. Flange 14 also has a portion 42 extending inwardly away from peripheral portion 38 to define a smaller-circumference aperture for receiving the wearer's ear as well as to provide a support for the earseal to be described. Preferably the surface of portion 42 of flange 38 is contured in a manner complementary to that of the adjacent portion of the wearer's head as described in US-A-3,875,592, the disclosure of which is incorporated herein by reference. Inwardly extending portion 42 of flange 38 in turn has a portion 44 extending in the direction of shell 12 and away from the wearer's ear. Flange 38 is secured to shell 12 by any suitable means such as a layer of cement (not shown) applied along the interface between shoulder 40 and the periphery of shell 12. Earcup assembly 10 contains an earphone element 46 of any suitable type known to the art. Earphone element 46 fits within a complementary cutout 54 formed in an earphone pad 48 preferably comprising polyurethane foam. A circular aperture 52 formed in the front of earphone pad 48 provides a direct acoustical coupling between earphone element 46 and the wearer's ear. A spacer pad 50 fills the interior of earcup shell 12 behind pad 48. Pads 48 and 50, shown in a compressed state in FIGURE 2, are of uniform thickness when uncompressed and substantially of the shape of flange 14 as viewed in FIGURE 1. In addition to locating earphone element 46, pads 48 and 50 enhance the impact-absorbing capability of assembly 10 by relieving the shell 12 of some of the impact force. Preferably pads 48 and 50 comprise high-porosity polyurethane foam to allow unrestricted transmission of sound from earphone element 46 to the wearer. Referring to FIGURES 4 and 5, a multiple-conductor cord 56 from earphone element 46 is passed through a grommet 58, received in an aperture (not shown) formed in shell 12, for coupling to an external communication system (not shown). In accordance with our invention, shell 12 is provided on its inner surface with a coating 60 of sound-deadening material, preferably a heavy-duty flexible vinyl rubber coating available from Abbeon Cal, Inc. under the trademark PLASTIDIP. Preferably, two coats are applied by brush to form a layer 60 of 0.25 to 0.38 mm (0.010-0.015 inch). A plurality of tabs 16, 18, 20, 22, 24, 26, 28 and 30 extending outwardly from earcup shell 12 at circumferentially spaced locations about the periphery thereof define a circumferentially extending, outwardly opening channel for receiving a helmet suspension to be described. Tabs 16, 20, 24 and 28 are on the side of the channel adjacent to the wearer, while tabs 18, 22, 26 and 30 are on the side remote from the wearer. As shown in FIGURES 1 and 4, tabs 16, 20, 24 and 28 are offset from tabs 18, 22, 26 and 30 so as not to overlap about the periphery of earcup shell 12. Forming the sides of the channel as series of tabs in this manner rather than as circumferentially continuous flanges improves the crushability of the earcup 12, since the solid rings formed by such flanges would tend to resist crushing. Preferably, the tabs 16 to 30 are rounded so as to be shorter at their ends, as shown in FIGURES 1 and 4, so as not to present any sharp corners that might catch on other equipment. Tabs 16 to 30 are preferably about 1.57 mm (0.062 inch) thick and formed of the same ABS terpolymer as shell 12 and flange 14. Any suitable means such as cement (not shown) is used to secure tabs 16 to 30 on earcup shelf 12. Referring to FIGURE 5, the channel formed by tabs 16 to 30 receives a fabric loop 31 surrounding an opening 33 in the side panel of a helmet suspension 34 such as shown, for example, in US-A-3,470,564, the specification of which is incorporated herein by reference. A cord 32 disposed in the loop 31 is adapted to be tightened to hold the suspension 34 in engagement with the outer surface of earcup shell 12, as shown in the above-identified patent. Referring to FIGURES 2, 4 and 5, earcup shell 12 also carries a strip 36 of pile fastener material, such as that sold under the trademark VELCRO, to permit assembly 10 alternatively to be releasably secured to the mounting shown in FIGURES 6 and 7. Strip 36 may be omitted if earcup assembly 10 is only intended for mounting in helmet suspensions, such as the suspension 34 shown in FIGURE 5, that engage tabs 16 to 30. An earseal indicated generally by the reference character 62 resiliently seals the region between the wearer's head and earcup 12 and flange 14. Earseal 62, which has the elongated annular shape of flange 14, contains superposed layers of polyurethane foam 64 and 66, each about 0.25 inch thick. Foam layers 64 and 66 area encased in an envelope formed from a base 70 and an outer cover 68 of 0.015-inch polyurethane film. Cover 68 is preformed in the shape shown in FIGURES 2 and 3 and is bonded to base 70 along the inner and outer peripheries thermally or ultrasonically. An annular lip 72 bonded in a similar manner to the outer periphery of base 70 on the other side from cover 68 is stretched over the periphery of flange 14 to retain earseal 62 on the earcup-flange subassembly. To facilitate assembly of the earseal 62 onto the flange 14, lip 72 is formed with a bead 74 on its inner surface as shown in FIGURE 3. Perforations 76 formed at regular intervals about cover 68 vent the interior of earseal 62 to allow air to escape from the interior in response to external pressure. Four 0.635 mm (0.025-inch) holes 76 are provided in the embodiment shown. Layer 66, which is nearest the wearer's head, comprises standard polyurethane foam, while layer 64, which is nearest flange 14, comprises an energy-absorbing slow-recovery foam, such as the foam known as Temper Foam Type T-38. The inclusion of energy-absorbing layer 64 in earseal 62 contributes to the impact-absorbing capability of assembly 10 and, in addition, improves sound attenuation and the ability of earseal 62 to conform to the head at skin temperature. The layer of standard foam 66 is also included, however, this energy-absorbing layer stiffens at temperatures below 4.44°C (40°F), and takes one to two minutes to soften in response to body heat when the assembly 10 is first donned. Helmet suspension 34 supports a helmet, indicated generally by the reference number 78, having a hard outer shell 80 extending over the earcup assembly 10 as shown in FIGURE 5. Shell 80 may comprise an suitable material, such as 1.52 mm (0.060-inch) fiberglass or a 1 to 1.27 mm (0.040- to 0.050-inch) laminate of resin-impregnated layers of aramid cloth sold under the trademark KEVLAR. Shell 80 may optionally carry a polyurethane foam pad 82 opposite earcup assembly 10. Helmet shell 80 enhances the impact absorption of earcup assembly by distributing impact forces over a larger area of the earcup shell 12 than would be the case if the helmet shell were absent. FIGURES 6 and 7 show an alternative earcup mounting using hook-and-loop fastener strips rather than the means shown in FIGURE 5. More particularly, a modified helmet shell 84 carries on its inner surface a strip 98 of hook-type fastener material, such as that sold under the trademark VELCRO, that releasably adheres to the pile material of strip 36. Earcup 10 may be secured to fastener strip 98 directly or, as shown in FIGURE 6, through one or more spacer pads 86 and 92 which are preferably of different thicknesses to maximize the number of possible spacings. Spacer pad 86, also shown in FIGURE 7, carries complementary strips 88 and 90 of hook and pile material similar to that of strips 98 and 36, respectively. Spacer pad 92, which is similar to pad 86 but twice as thick, carries strips 94 and 96 similar to strips 88 and 90, respectively. If desired, there may also be interposed, between earcup 10 and helmet shell 84, the side panel (not shown) of an inner helmet suspension that is similarly provided with hook and pile fastener strips on its opposite surfaces. Such an arrangement is shown in US-A's-4,231,117 and 3,943,572, the disclosures of which are incorporated herein by reference. If the earcup assembly is intended solely for use in helmets such as helmet 84 having hook and pile fasteners, tabs 16 to 30 may be omitted. Preferably, the external dimensions of earcup assembly 10 are identical to those of the earcup, such as shown in US-A's-3,470,564 or 3,875,592, that it is intended to replace. However, because the shell 12 is thinner, the internal dimensions of the shell will be greater. It will be seen that we have accomplished the objects of our invention. Our earcup assembly minimizes the transmission of impact forces while at the same time satisfactorily attenuating ambient sounds. Our earcup assembly is relatively lightweight and conforms to the contours of a wearer's head. Our earcup assembly also operates satisfactorily in cold weather. Finally, our assembly is compatible with existing helmets. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Claims: A sound-attenuating earcup assembly (10) of the type adapted to be received and retained in an opening in a suspension (34) carried by the wearer's head, said earcup assembly insulating the ear of the wearer from ambient sound, said assembly being of the type in which a discrete hollow cup-shaped rigid plastic shell (12) forming a cavity for receiving the wearer's ear has a periphery carrying an earseal (62) which engages the wearer's head around his ear when the shell is mounted on the wearer's head by said suspension (34) with the wall of the shell (12) spaced from the wearer's ear to form a sound-attenuating chamber around the ear, characterized in that said shell (12) is provided with two spaced rows of discrete circumferentially spaced tabs (16, 20, 24, 28 and 18, 22, 26, 30) forming a channel for receiving the portion of said suspension (34) around said opening, that said shell comprises a plastic material of a low-impact grade and that the thickness of the shell (12) is selected so that the shell is crushed upon impact at an applied force less than that required to crush the skull of the wearer. An earcup as in Claim 1 in which said shell (12) comprises an acrylonitrile-butadiene-styrene terpolymer. An earcup as in Claim 1 in which said shell (12) has a thickness of about 2.9 mm (0.09 inch). An earcup as in Claim 1 in which said shell (12) has a coating (60) of sound-deadening material on the inside surface thereof. An earcup as in Claim 4 in which said coating (60) comprises a rubber material. An earcup as in Claim 4 in which said coating (60) has a thickness of from about 0.254 to 0.38 mm (0.010 to 0.015 inch). An earcup as in Claim 1 in which said first and second pluralities of tabs are offset relative to each other. An earcup as in Claim 1 in which said first and second pluralities of tabs are nonoverlapping. An earcup as in Claim 1 in which said tabs are of reduced height at their ends. An earcup as in Claim 9 in which said tabs are rounded. An earcup as in Claim 1 including a resilient earseal (62) comprising an energy-absorbing material for sealing the region between said shell (12) and the wearer's head. An earcup as in Claim 11 in which said earseal (62) comprises two superimposed layers (64, 66) of material, one of said layers are comprising said energy-absorbing material and the other of said layers comprising a substantially non-energy-absorbing material. An earcup as in Claim 12 in which said energy-absorbing layer (64) is relatively adjacent to said shell (12) and said substantially non-energy-absorbing layer (66) is relatively adjacent to the wearer's head. An earcup as in Claim 11 wherein said energy-absorbing material is a resilient material. An earcup as in Claim 14 in which said material comprises a slow-recovery foam. An earcup as in Claim 14 in which said material comprises a polyurethane foam. An earcup as in Claim 12 including means (68, 70) for securing said layers (64, 66) to said shell (12). An earcup as in Claim 12 in which said energy-absorbing layer (64) comprises a slow-recovery polyurethane foam and said non-energy-absorbing layer (66) comprises a normal-recovery polyurethane foam. An earcup as in Claim 14 including an envelope (68, 70) encasing said material. An earcup as in Claim 19 in which said envelope (68, 70) has an annular lip (72) adapted to be stretched over the periphery of said shell (12).

Inventors: AILEO JACKSON A, LONG RICHARD J, AILEO, JACKSON A., LONG, RICHARD J.
Applicants: GENTEX CORP, GENTEX CORPORATION
Application year: 1989
Main classification: A42B3
IPC codes: A42B3, A61F11