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DESCRIPTION JP2014030277

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DESCRIPTION JP2014030277
Abstract: An audio transmissive cover assembly is disclosed that protects a transducer, such as a
microphone, a loudspeaker, a buzzer, a ringer, etc., from the surrounding environment. A cover
assembly has a microporous protective membrane. This protective membrane is captured
between the two adhesive support systems in the outer area near the edge. The protective
membrane is displaceable or movable in response to the acoustic pressure wave, as a noncoupled inner area is formed, which is surrounded by the coupled outer area. The construction of
the protective membrane, coupled with the shape, allows acoustic energy to pass through the
protective membrane with very low attenuation, while being able to withstand prolonged
exposure to liquid penetration. The cover assembly configuration includes an attached acoustic
gasket to provide a sealing effect and to focus the acoustic energy into the opening of the
housing. [Selected figure] Figure 2
Acoustic protective cover assembly
[0001]
The present invention relates generally to acoustic protective covers for transducers (eg,
microphones, ringers or speakers) employed in electronic devices. More specifically, the present
invention relates to an acoustic protective cover assembly that includes a microporous protective
membrane that provides both low acoustic loss and the ability to withstand prolonged exposure
to liquid penetration.
[0002]
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1
Modern electronic devices such as radios and cell phones have transducers such as microphones,
ringers, speakers, buzzers and the like. These electronic devices often have a housing with small
openings or holes located above the transducer, which allows the transducer to transmit and
receive audio signals from inside the housing . However, while such a structure protects the
transducer from accidental exposure to water (eg, raindrops), it significantly attenuates the
transducer's efficiency and sound quality. Furthermore, such a structure can not prevent the
ingress of a large amount of water. Accordingly, acoustic protection covers have been utilized
between the transducer and the housing to protect the transducer from damage due to the inflow
of water or other liquids.
[0003]
Conventional acoustic protective covers are typically made of porous fiber material, which is
constructed solely on the basis of reducing the resistance of the material to air flow. The large
effective pore size of this material, which results in thickening of the material, has been a means
to achieve high vent flow parameters. In this case, the sound attenuation of the material is
inversely proportional to the size of the hole. That is, as the hole diameter increases, the sound
attenuation decreases. However, the pore size adversely affects the water resistance of the
material. Materials with or without extremely small pores have high water resistance.
[0004]
Thus, prior art acoustic protective covers are focused on having large voids for advanced voice
transmission and sound quality, or having significantly smaller voids and a relatively dense
structure for high water resistance. It has Focusing on the former, acoustic protective covers
provide, at best, electronic devices with minimal protection against water exposure. Focusing on
the latter will protect electronic devices from a large amount of water, but the loud sound
attenuation will degrade the sound quality. Even if the porous material is treated to be water
repellent, the large pore structure does not allow to immerse the electronic device to a
considerable depth.
[0005]
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The prior art patents that accompany the scientific principles described above are described
below. The environmental protection cover system taught in U.S. Pat. No. 4,949,386 to the
"Speaker System" entitled: "Speaker System" is based in part on a woven or non-woven material
of polyester, and microporous polytetrafluoroethylene ( It consists of a two-layer laminate
structure, consisting of a "PTFE" membrane. The hydrophobic nature of the microporous PTFE
membrane prevents liquid from passing through the environmental barrier system. However,
although such a laminated cover system may be effective in preventing the inflow of liquid into
the electronic device, the laminate significantly attenuates the sound. Such attenuation is
unacceptable in modern communication electronic devices that require excellent sound quality.
Furthermore, the laminated cover system is effective in preventing instantaneous liquid flow, but
prolonged exposure to the liquid is limited as the adhesive / membrane interface is possibly
destroyed.
[0006]
U.S. Pat. No. 4,987,597, entitled "Apparatus For Closing Openings Of A Hearing Aid Or An Ear
Adaptor For Hearing Aids", is used as a cover for an electronic transducer. It teaches using a
porous PTFE membrane. The membrane restricts the passage of fluid through the membrane
without significantly attenuating the audio signal. However, although this patent generally
describes parameters related to porosity and permeability, which material of the membrane to
achieve both low sound loss and prolonged exposure to liquid infiltration It does not teach in
particular whether the parameter is required.
[0007]
U.S. Pat. No. 5,420,570 entitled "Manually Actuable Wrist Alarm Having A High-Intensity Sonic
Alarm Signal with High-Intensity Acoustic Alarm Signal" discloses an electronic device from liquid
infiltration. Teaches the use of non-porous films as a protective layer to protect the As mentioned
above, although non-porous films have excellent liquid permeation resistance, such non-porous
films suffer from relatively high sound transmission losses which significantly distort the sound
signal. Transmission losses are increased by the relatively high mass associated with non-porous
films.
[0008]
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U.S. Pat. No. 4,071,040 entitled "Water-Proof Air Pressure Equalizing Valve" teaches the
placement of a thin microporous membrane between two sintered stainless steel disks. There is.
Such a structure may have been effective for use in military-type outdoor robust telephone sets,
but is not desirable for use in modern telecommunication electronic devices. Because sintered
metal disks are relatively thick and heavy. Furthermore, by placing the microporous membrane
between the two stainless steel disks, the membrane is physically constrained, which limits the
membrane's ability to vibrate. This degrades the sound quality by attenuating and distorting the
transmitted audio signal.
[0009]
In order to overcome some of the above-mentioned drawbacks associated with the abovementioned US Pat. Nos. 4,949,386, 4,987,597, 5,420,570 and 4,071,040, the title of the
invention "Protective cover assembly with advanced acoustical properties The sound transmitting
acoustic cover assembly taught in U.S. Pat. No. 5,828,012 to (Protective Cover Assembly Having
Enhanced Acoustical Characteristics) has a protective membrane coupled to a porous support
layer, thereby providing an outer An inner, unbonded area is formed that is surrounded by the
bonded area. With such a structure, the membrane layer and the support layer can freely vibrate
or move independently in response to acoustic energy passing therethrough, thereby minimizing
acoustic energy attenuation. . However, although the cover assembly reduces acoustical
attenuation, the degree of acoustical attenuation is limited. This is because the mass and
thickness of the material through which the acoustic energy has to pass is increased (i.e. the
acoustic energy must first pass through the membrane and then through the support layer).
[0010]
Lastly, Japanese Patent Application Laid-Open No. 10-165787, entitled "Porous
polytetrafluoroethylene film and method for producing the same (Porous Polytetrafluoroethylene
Film And Manufacturing Process For Same)", disclosed an electronic device from the inflow of
liquid while maintaining voice permeability. The use of porous PTFE to protect the device is
disclosed. A thermoplastic resin that functions as both a reinforcement and a shape stabilizer is
reticulated on one or both sides of the longitudinally stretched PTFE membrane. Using this
method, the pore size of the film is uniformly expanded, and the sound transmission is improved
by thinning the membrane without impairing the water resistance of the film. Such porous PTFE
films exhibit an audio attenuation of 1 dB or less and a hydrostatic resistance of 30 cm or more
at frequencies of 300-3000 Hz (i.e., the frequency range known as the "telephony range").
However, although PTFE film coatings provide relatively low sound attenuation, the overall sound
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transmission loss is excessive and is considered unacceptable in modern communication
electronic devices. In addition to this, PTFE films lack the ability to withstand prolonged water
penetration at high pressure.
[0011]
As the prior art patents mentioned above focus only on the porosity of the membrane, the voice
transmission loss of the high ventilated membrane taught in these specifications is low, but the
International Electrotechnical Commission ( It is not possible to comply with the IP-57 level
waterproof (1 meter dive in 30 minutes) specified by IEC). The IEC is a related organization of the
International Organization for Standardization (ISO), and has published an IP code entitled
"Degrees of Protection Provided by Enclosures", among which the closure of electrical equipment
Describes a system for classifying the degree of protection provided by One of the goals listed in
this standard is to protect the equipment inside the enclosure against the harmful effects of
water ingress. The IP-57 standard is described in the IEC publication 529, second publication,
1992.
[0012]
The consumer market desires to use electronic devices in harsh environmental and working
conditions, such as exposure to liquid and particulate ingress over time, and so to durable water
resistant electronic devices with high sound quality. Demand has increased significantly.
Therefore, there is a need for an acoustic protective cover that has high ventilation flow enabling
low (i.e. less than 3 dB) sound attenuation and allows IP-57 level protection. The acoustic
protective cover should also be lightweight and have sufficient rigidity to provide quick and
accurate installation.
[0013]
In addition to the foregoing, it is desirable for the acoustic gasket to eliminate bypass and
structural vibrations and to focus acoustic energy at the housing opening. More specifically,
without an acoustic gasket between the sound transducer (loudspeaker, ringer, microphone, etc.)
and the housing, acoustic energy may leak into other areas of the housing. This causes the
acoustic energy entering and exiting the housing to be attenuated and distorted. Such acoustic
energy leakage can attenuate and distort the sound emitted from the housing by transducers
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such as loudspeakers, ringers, etc., or the sound that enters the housing to activate the
microphone. Without the provision of acoustic gaskets, these acoustic losses reduce the battery
life of the communication electronic device and the high power levels of the transducer. The
acoustic gasket can enhance its effectiveness by isolating the loudspeaker from the housing,
which can convert more mechanical energy of the loudspeaker directly into acoustic energy.
Acoustic gaskets and materials are well known to those skilled in the art, however, they are
usually incorporated into the device as separate components, which adds to the cost and
complexity of manufacturing the device.
[0014]
The foregoing illustrates the known limitations present in existing acoustic protective covers and
gasket systems of communication electronic devices. Thus, it is apparent that it would be
advantageous to provide an improved protection system to overcome one or more of the above
limitations. Thus, suitable alternatives are described, including the features disclosed in more
detail below.
[0015]
In conjunction with the foregoing, a sound transmissive acoustic protection cover assembly that
protects electronic devices from prolonged liquid ingress while providing equivalent or better
sound attenuation than conventional acoustic covers Disclose. The assembly meets the
requirements of IP-57 with low voice loss by recognizing that the key parameters to focus on
when constructing the membrane are moving mass and thickness, not vent flow. It has a
microporous protective membrane. Reducing both the movable mass and thickness of the
membrane effectively reduces voice transmission losses within the telephone area.
[0016]
According to one aspect of the invention, the assembly consists of a microporous protective
membrane trapped between two adhesive support systems. The first adhesive support system
may be a single-sided or double-sided adhesive, but the main function of this adhesive support
system is to secure the membrane to the opposing adhesive support system. The second adhesive
support system is a double sided adhesive, which serves as a gasket for the transducer or
housing depending on the application. Since both adhesive support systems are connected to the
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membrane, an inner, unbonded area surrounded by the outer, bonded area is formed in the
membrane. In the unbonded area, the combination of the two adhesive support systems causes
the sound pressure wave on the upstream side to vibrate the membrane, causing the solid borne
energy (mechanical vibration) of the membrane to propagate air downstream of the acoustic
protective cover assembly It is possible to convert it into energy (pressure wave). This reduces
acoustic loss / attenuation. In addition to minimizing transmission losses, the acoustic cover
assembly provides IP-57 level waterproofing for the membrane, as described above. Such
waterproof levels are achieved because the membrane is provided with additional stiffness and
anchoring. The opposing adhesive support system prevents structural failure of the assembly by
peeling the membrane from the adhesive.
[0017]
According to another aspect of the present invention, the first adhesive support system is a
double-sided adhesive further incorporating a gasket, allowing voice to pass through the opening
provided in the housing of the electronic device, acoustic leakage, and further of the device. Fill
the gap between the acoustic protection cover assembly and the device port that can cause
increased transmission loss.
[0018]
According to yet another aspect of the invention, the protective membrane is coupled only to the
second adhesive support system.
According to yet another aspect of the invention, the protective membrane is injection molded in
the cap. The apparatus and method of the present invention can be more readily understood
from the following detailed description of the invention and the claims, in conjunction with the
accompanying drawings.
[0019]
FIG. 1 shows the exterior of the front housing cover of a conventional mobile phone employing a
sound protection cover assembly. It is a figure which shows the inside of the front housing cover
of the mobile telephone of FIG. FIG. 7 is a top view of an aspect of the “captive structure”
(capture structure) acoustic protection cover assembly of the present invention. FIG. 4 is a crosssectional view of the sound protection cover assembly of FIG. 3 along line XX. FIG. 7 is a bottom
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view of an embodiment of a sound protection cover assembly having a single adhesive support
system. FIG. 6 is a cross-sectional view of the acoustic protection cover assembly of FIG. 5 along
line XX. FIG. 5 is a top view of an aspect of a sound protection cover assembly with a gasket
attached. FIG. 8 is a cross-sectional view of the acoustic protection cover assembly of FIG. 7 along
line XX. FIG. 7 is a top view of an embodiment of a sound protection cover assembly having a
protection membrane injection molded to a cap. FIG. 10 is a cross-sectional view of the acoustic
protection cover assembly of FIG. 9 along line XX. FIG. 6 is a top view of an embodiment of a
sound protection cover assembly having a protective membrane with a supplemental bond
designed for a central support. FIG. 12 is a cross-sectional view of the acoustic protection cover
assembly of FIG. 11 along line XX. FIG. 10 is a top view illustrating an aspect of a sound
protection cover assembly having a protective membrane with another supplemental bonding
point designed to improve the bonding support. FIG. 14 is a cross-sectional view of the acoustic
protection cover assembly of FIG. 13 along line XX. FIG. 1 is a perspective view of an apparatus
used to measure acoustic transmission loss.
[0020]
Referring to the drawings, corresponding parts are indicated by the same reference numerals
throughout the several drawings, and the sound transmitting acoustic protection cover assembly
and gasket system of the present invention are generally indicated in various structures, It is also
dimensioned for use to cover typical electronic devices, such as transducers provided in mobile
phones. The present invention is not limited to the embodiments herein, these embodiments are
merely exemplary, and modifications or adaptations may be made to these embodiments without
departing from the scope of the present claims. It is obvious that you can do it.
[0021]
As used herein, the term "captive (capture) structure" refers to the bonding of the protective
membrane between two adhesive support systems. As used herein, the term "microporous
membrane" refers to a minimum 50% porosity where 50% or more of the pores have a nominal
diameter of about 5 μm or less (ie, a pore volume of 50% or more) ) Means continuous sheet
material. As used herein, the term "oleophobic" generally refers to the property of the material to
repel oil or not absorb oil while permitting the passage of gas. As used herein, the term
"hydrophobic" generally refers to the property of the material to repel water or not absorb water
while allowing the passage of gas.
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[0022]
As used herein, the term "acoustic gasket" and its derivatives mean a material that has the
property of absorbing or reflecting sonic energy when compressed between two surfaces to form
a seal. An acoustic gasket may be used in a conventional manner between the transducer and the
housing surface, or between surfaces within the housing, to acoustically isolate and damp
vibrations in selected areas.
[0023]
FIG. 1 is a view showing the outside of a front housing cover 10 of a conventional mobile phone
having a small opening 11. The number, size and shape of the openings can be widely varied.
Alternative aperture configurations include narrow slots or various numbers of circular
apertures.
[0024]
FIG. 2 is an inside view of the front housing cover 10 showing the microphone installation
position 12, the speaker installation position 13, and the alert installation position 15. FIG. 2
generally illustrates a typical installation location for the acoustic protective cover assembly 14
provided at the microphone installation location 12, the speaker installation location 13 and the
alert installation location 15.
[0025]
3 and 4 illustrate the acoustically transparent "captive structure" aspect of the protective cover
assembly 14 of the present invention. As mentioned above, “captive structure” refers to the
shape of the protective cover assembly 14 in which the microporous protective membrane 20
generally comprises the first adhesive support system 22 and the second adhesive support
system 22. And the adhesive support system 24 in the "captive" state.
[0026]
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Adhesive support systems 22 and 24 are connected such that an inner, unbonded area of
protective membrane 22 surrounded by an outer, bonded area is formed. In the unbonded area,
the combination of the two adhesive support systems 22 and 24 constrains the edge of the
protective membrane 20 so that the upstream sound pressure wave vibrates the protective
membrane 20 and the solid-borne energy of the protective membrane 20 It allows the
(mechanical vibrations) to be converted to airborne energy (pressure waves) downstream of the
acoustic protection cover assembly 14, resulting in low acoustic loss / attenuation.
[0027]
Protective membrane 20 serves to provide a barrier to dust and other particles, is resistant to
penetration by water or other aqueous fluids, and to minimize voice loss through the membrane.
In addition, it is porous. The protective membrane 20 is preferably microporous, which reduces
the membrane weight among other things compared to non-porous materials. Protective
membrane 20 may be made of one of many polymeric materials. Such materials include, but are
not limited to, for example, polyamides, polyesters, polyolefins such as polyethylene and
polypropylene, or fluoropolymers. Polyvinylidene fluoride ("PVDF"), tetrafluoroethylenehexafluoropropylene copolymer ("FEP"), tetrafluoroethylene- (perfluoroacrylic) vinyl ether
copolymer ("PFA"), polytetrafluoroethylene ("PTFE"), etc. Such fluoropolymers are preferred for
their inherent hydrophobicity, chemical inertness, temperature resistance and processing
properties. If the porous protective membrane is not essentially made of a hydrophobic material,
the pores are treated with a fluorine-containing, water repellent and lipophobic material well
known to those skilled in the art. It can have the imparted hydrophobic nature without giving a
noticeable loss in rate. For example, water and oil repelling materials and methods disclosed in
US Pat. Nos. 5,116,650, 5,286,279, 5,342,434, 5,376,441 and other patents may be used.
[0028]
The protective membrane 20 is desirably subjected to an oleophobic treatment in order to
improve the resistance to leakage with a low surface tension liquid. This treatment is usually a
coating of a fluorinated polymer, such as, for example, dioxol / TFE copolymers as taught in US
Pat. Nos. 5,385,694 and 5,460,872, US Pat. No. 5,462,586. Perfluoroalkyl acrylates and
perfluoroalkyl methacrylates that are taught, and fluoroolefins, fluorosilicones, and the like, but
are not limited thereto. A particularly preferred liquid impermeable and gas permeable
membrane is a microporous membrane consisting of expanded PTFE ("ePTFE") treated with a
dioxol / TFE copolymer and a perfluoroalkyl acrylate polymer.
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[0029]
The protective membrane 20 should have the following properties: thickness in the range of
about 3-150 μm, preferably in the range of 3-33 μm; in the range of 0.05-5 μm, preferably
about 0.05 Nominal pore size in the range of 1 μm; pore volume in the range of 20 to 99
percent, preferably 50 to 95 percent; range of 0.15 to 50 Gurley seconds, preferably 1 to 10
Gurley seconds Air permeability within the range of 5 to 200 psi, preferably within the range of
20 to 150 psi; resistance to water pressure within the range of about 1 to 40 grams / m <2>,
preferably 1 to 30 grams / m <2 And a long pressure resistance duration longer than 0.5 hours
at a water pressure of 1 meter, preferably longer than 4 hours at a water pressure of 1 meter.
[0030]
In one aspect of the invention, the protective membrane 20 consists at least partially of
microporous PTFE.
Microporous PTFE may be incorporated into the PTFE resin by any of a number of well known
processes, such as drawing or stretching processes, papermaking processes, fillers, etc., and then
removing the fillers leaving a porous structure. It may be prepared by a process, or a powder
firing process. The microporous PTFE material is coupled to the interconnected nodes as
described in US Patent Nos. 3953566, 4187390 and 4110392, respectively, which are
incorporated herein by reference. It is preferable that it is microporous ePTFE which has the
microstructure which consists of fibrils. In these specifications, preferred materials and processes
for making microporous PTFE materials are well described. The microporous PTFE material may
contain a pigment, such as carbon black, or a dye used for coloring to improve appearance.
[0031]
The adhesive support systems 22 and 24 are preferably formed entirely in the form of a system
consisting of a substrate with an adhesive, for example an adhesive tape. Examples of suitable
substrates include web materials and mesh materials. The adhesive is, for example, a liquid or
solid, thermoplastic type, thermosetting type or reactive curing type, selected from the class
including acrylic, polyamide, polyacrylamide, polyester, polyolefin, polyurethane, polysilicon etc.
There may be, but is not limited to. Adhesive support systems 22 and 24 may be substrateless
adhesives and may be applied directly to membrane 20 by screen printing, gravure printing,
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spray coating, powder coating, and the like.
[0032]
Protective membrane 20 and adhesive support systems 22 and 24 are generally superimposed
and positioned generally such that their edges are coextensive. However, such a need does not
always occur. The protective membrane 20 and the adhesive support systems 22 and 24 are
connected to each other at least in the peripheral area near these edges, whereby one or more
inner unbonded areas are formed in the outer connected area. Form and surround. For acoustic
cover assemblies 14 where the span defined by the inner edge of the bonded area is less than or
equal to about 38 millimeters (one and a half), the addition of adhesive support systems 22 and
24 to protective membrane 20 generally Binding is not necessary. Where there is a span greater
than about 38 millimeters, it may be desirable to provide additional bonding points at discrete
discrete points. There are two goals. The first purpose is that the upstream sound pressure wave
vibrates the membrane 20 and converts the solid borne energy (mechanical vibration) of the
membrane 20 to air borne energy (pressure wave) downstream of the acoustic protection cover
assembly 14 By reducing the acoustic distortion across the assembly 14. The second objective is
to reduce the point load of the membrane in conjunction with a large area exposed to high
hydraulic pressure. For very large acoustic protective cover assemblies 14, it is more convenient
to use bond lines that are widely separated from one another, instead of discrete bond points.
Whether additional layers of the acoustic protection cover assembly 14 need to be coupled is
related to the shape of the area or device to be covered as well as the size of the assembly 14.
Thus, some experimentation may be required to establish the best method and pattern of
additional bonding to optimize the acoustic performance of the cover assembly 14. Generally, in
all sizes, the area of the bonded area is minimized and the area of the unbonded area is
maximized to the extent permitted by the mechanical and acoustical requirements of the
assembly 14 preferable.
[0033]
The purpose of the first and second adhesive support systems 22 and 24 is to mechanically
support the protective membrane 20 when the protective membrane 20 is subjected to an
accidental force. For example, when the device to which the assembly 14 is attached can be
raised, for example when the mobile phone is immersed in water, such as dropping it to a
swimming pool or dropping it from the boat into the water, the acoustic protective cover
assembly 14 against hydrostatic pressure. The captive structure further provides the advantage
of allowing the use of thinner and possibly weak protective membranes 20. This improves the
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sound transmission through the sound protection cover assembly 14. The captive structure in
combination with the two adhesive support systems 22 and 24 completes a rigid acoustic
protection cover assembly 14. The handling during the manufacturing and assembly process of
this assembly is significantly simpler than in the case of the individual parts. As mentioned above,
in the prior art, a layer structure is suggested to satisfy such a requirement. However, such a
structure excessively attenuates and distorts the sound energy passing through it. Because the
stack adds mass. In addition, the captive structure enables a thicker, more robust assembly 14
inside the electronic device that requires harsh environmental conditions without significantly
compromising the acoustic performance.
[0034]
Furthermore, the captive structure allows acoustic energy to pass through the acoustic protective
cover assembly 14 with minimal attenuation while still obtaining support and handling
advantages. The protective membrane 20 and the adhesive support systems 22 and 24 are
bonded together only in selected areas or areas, so that a large area not bonded between the
adhesive support systems 22 and 24 can be obtained. Thus, the protective membrane 20
constrained by the adhesive support systems 22 and 24 can freely move or vibrate in the
uncoupled area in response to the acoustic energy.
[0035]
Referring now to FIGS. 5 and 6, another view of the acoustic protection cover assembly 14 is
shown. This aspect is identical in all aspects to the aspect of the captive structure described
above, except that it does not have the first adhesive support system 22. In other words, the
protective membrane 20 is not bonded at all on one side and is thus more likely to peel off the
adhesive support system 24. Thus, for such a construction, the adhesive of adhesive support
system 24 must be extremely strong. Some experimentation may be required to find an adhesive
that adheres well to the protective membrane 20 and prevents the protective membrane 20 from
peeling off the adhesive support system 24.
[0036]
Figures 7 and 8 illustrate aspects of the "captive structure" acoustic protection cover assembly
14 as shown in Figures 3 and 4. An acoustic gasket 34 is coupled to the first adhesive support
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system 22. In such an embodiment, the first adhesive support system 22 is a double sided
adhesive. The acoustic gasket 34 is mounted to allow independent movement of the protective
membrane 20 in the unbonded area.
[0037]
Conventional, commercially available materials are known to those skilled in the art and are
suitable for use as acoustic gaskets. For example, flexible elastomeric materials or foamed
elastomers such as silicone rubber and silicone rubber foam can be used. The preferred gasket
material is a microporous PTFE material, and more preferably, with interconnected nodes as
described in U.S. Pat. Nos. 3,953,566, 4,187,390 and 4,110,392. Microporous ePTFE having a
microstructure composed of fibrils, the matters of which are incorporated herein by reference.
More preferably, the acoustic gasket comprises a matrix of microporous ePTFE which can be
partially filled with an elastomeric material. Acoustic gasket 34 may be bonded to the cover
material using methods and materials for bonding protective membrane 20 and adhesive support
systems 22 and 24 together.
[0038]
In the embodiment of the acoustic protective cover assembly 14 shown in FIGS. 9 and 10, the
protective membrane 20 is injection molded into a plastic capsule or cap 36. Vulcanizable
plastics, such as silicone or natural rubber, and thermoplastics, such as polypropylene,
polyethylene, polycarbonate or polyamide, and preferably thermoplastic elastomers, such as
SantopreneTM or HytrelTM, are plastic capsules 36 It is particularly suitable as a material for All
these plastics can be used in the so-called insert molding injection molding process. An
advantage of the insert molding injection molding process is that injection molding of the plastic
capsule 36 into the microporous membrane 20 is possible in a single step. Specifically, the
thermoplastic elastomer has a property that it can be processed by an insert molding injection
molding process and a property that the property of the elastomer is maintained when
performing such processing.
[0039]
Although the protective membrane 20 is illustrated as being molded in the center of the cap 36,
the membrane 20 can be molded in a vertical position of the cap 36, for example in a groove
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formed in the top or bottom. The cover assembly 14 can be used to protect transducers located
in rigid closures or housings, such as cell phones, portable radios, pagers, closures such as
loudspeakers, etc. Thus, the assembly 14 must first be configured in relation to the sound
transmission aperture of the housing, taking into account the dimensional and acoustical
properties of the transducer. This is particularly important in sizing the unbonded areas of
assembly 14. A precise relationship is not required, but it is preferable that the unbonded area be
significantly larger than the area of the opening provided in the housing near the cover assembly
14.
[0040]
11 and 12 illustrate another "captive structure" embodiment. These aspects are similar to those
described above in all respects except that the complementary bonding points 38, 39 provided in
the adhesive support systems 22 and 24 extend across the protective membrane 20. The
supplemental attachment points 38, 39, as described above, support a cover assembly having a
relatively large unjoined inner region.
[0041]
Figures 13 and 14 illustrate yet another "captive structure" aspect. These aspects are as shown in
FIGS. 11 and 12 in all respects except that the alternative arrangement of supplemental
attachment points 38, 39 in adhesive support systems 22 and 24 extend across protective
membrane 20. Is the same as
[0042]
-Test method-(1) Sound transmission loss ASTM E 1050-90 (Standard test method for impedance
and absorption of acoustic material); ASTM C 384 (Standard test method for impedance and
absorption of acoustic material by impedance tube method) Samples are tested using a
combination of the analytical procedures and methods described in Leo L. Beranek (acoustic
characteristics); AF Seybert (two-sensor method for measurement of sound intensity and acoustic
characteristics in ducts) It was evaluated.
[0043]
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The apparatus 40 used to test the sample is shown in FIG.
The device generally consists of an impedance measuring tube 42 housing a mounting plate 44,
speakers 46 and semi-animous terminations 48 located at opposite ends of the tube 42. The
mounting plate 44 has an opening 16 mm in diameter. The first pair of microphones 50 and 52
is located on the speaker side of the mounting plate 44 and the second pair of microphones 54
and 56 is located on the semi-echoless end of the mounting plate 44 . Microphones 50, 52, 54
and 56 are disposed on the side of tube 42 in a penetrating manner. By using a microphone pair
both upstream and downstream of the sample, it is possible to concentrate the analysis on the
waves incident in the sample and the waves transmitted from the sample. The speaker 46 is
directly connected to an FFT analyzer (FFT ANALYZER) 60, while the microphone is electrically
connected to the FFT analyzer 60 via an amplifier (AMPLIFIER) 58. The FFT analyzer 60 is
electrically connected to a post processor (POST-PROCESSOR) 62.
[0044]
Using the apparatus 40, measurements are made as follows. As shown in FIG. 15, the sample 66
is placed on the mounting plate 44 in the tube 42. The FFT analyzer 60 generates a white noise
sound wave 64 formed from the speaker 46. Sound pressure levels (SPL) generated from incident
waves on the PTFE membrane sample 66 are measured from the upstream microphone pair 50
and 52. The incident pressure wave then excites the PTFE membrane sample 66 and transmits
an acoustic wave 68 downstream of the sample. The transmitted sound waves 68 are measured
from the microphone pairs 54 and 56. Both microphone pairs are phase aligned to obtain
accurate results. The post processor 62 then measures the active intensity level (IL) at 50 Hz
increments from 300 Hz to 3000 Hz for the microphone pairs 50 and 52 and for the microphone
pairs 54 and 56. Post processor 62 further calculates transmission loss (TL) using the following
equation:
[0045]
TL (dB) = 10 log10 (IL50, 52 / IL54, 56) The total TL is calculated using individual TL
measurements across the telephone frequency range (300-3000 Hz). The total TL is calculated as
follows: TLoverall (dB) = 10 log 10 (Σ10 <(TL when increasing by 50 Hz at 300 to 3000 Hz) /
10>) For example: TLoverall (dB) = 10 log 10 (10 <(TL) @ 300 Hz) / 10> +10 <(TL @ 350 Hz) /
10> +10 <(TL @ 400 Hz) / 10> + ... +10 <([email protected] Hz) / 10>)
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[0046]
Such a procedure for measurement provides an accurate and simple measurement to compare
material transmission losses across the frequency range corresponding to a given application. In
addition, transmission loss calculations may be plotted relative to frequency to assess the
acoustic transmission efficiency across the spectrum.
[0047]
(2) Water pressure resistance ("WEP") Water pressure resistance ("WEP") provides a test method
for water ingress into membranes. WEP can be measured as an instantaneous WEP or as a long
time WEP. Long term WEP measures the ability of the sample to function as a water repellant or
water barrier over time. This is an important property to consider when considering the
hydrophobic venting of electronic devices. The IP-57 standard is based on WEP over time.
[0048]
To measure the instantaneous WEP, the test sample is clamped between a pair of test plates. The
lower plate has the ability to compress a portion of the sample with water. The pH paper is
placed at the top of the sample between the non-compressed plate as an indicator of evidence of
water influx. The sample is then gradually compressed until the color change of the pH paper
shows the first sign of water influx. The water pressure at the time of penetration or inflow of
water is recorded as instantaneous WEP.
[0049]
To measure WEP over time, water pressure is gradually increased to 1 meter (1.4 psig) and held
for 30 minutes. After 30 minutes, if no evidence of water infiltration is observed, this sample has
passed the IP-57 test. If there is a sign of water ingress, the sample will fail. If the sample
continues to hold pressure after 30 minutes, the sample test time can be extended to determine
the maximum time to failure for a given water pressure.
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[0050]
(3) Air Permeability The resistance of the sample to air flow was measured according to the
procedure described in ASTM test method D 726-58, W. & L. E. Measured by Gurley
Densonometer manufactured by Gurley & Sons. Results are recorded in Gurley numbers or
Gurley seconds. Gurley Seconds is the time in seconds for 100 cubic centimeters of air to pass
one square inch of test sample during a pressure drop of 4.88 inches of water.
[0051]
(4) Particle Collection Efficiency Measure the particle collection efficiency using a Model 8160 of
TSI manufacture, Automatic Filter Tester ("AFT"). AFT is an automated filter that measures the
filter efficiency, transmission to particle size, and air flow resistance of air filtration media. AFT
measures particle collection efficiency using two condensed particle counters placed both
upstream and downstream of the sample under test. The particle size used in the efficiency test
of the following example is 0.055 μm.
[0052]
Comparative Example 1-Hydrophobic Porous Membrane Having a Bonded Structure This
example is described in W. L. Gore & Associates, Inc. GORE ALL-WEATHERTM VENT, a protective
cover material commercially available under the tradename GORE ALL-WEATHERTM. This
product is manufactured by W. L. Gore & Associates, Inc. Non-woven polyester fabric (0.015
"thickness, 1.0 oz / yd <2>,. NEXUSTM 32900005, Precision Fabrics Group Co. It is made of The
membrane bound to the support had the following properties: mass 57.473 g / m <2>; thickness
0.0133 ′ ′ (338 μm); air permeability 8.6 gurley seconds; air flow 107. 76 ml / min-cm <2>;
instantaneous water pressure resistance 138 psi (951.5 kPa); particle efficiency 99.999994%.
[0053]
According to the teachings of US Pat. No. 5,828,012, two discs of 30 mm diameter were cut out,
one from the non-woven polyester fabric and the other from the porous PTFE membrane. The
disks were aligned and bonded together by an adhesive layer. A first adhesive support system
with an outer diameter of 30 mm with an inner diameter of 16 mm removed was cut from the
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double-sided adhesive tape. Double-sided adhesive tape is 50 μm thick MylarTM polyester film
(DFM-200-clear V-156, Flexcon Corp. And a layer of 19 μm thick acrylic pressure sensitive
adhesive provided on each side of The first adhesive support system was aligned and bonded to
the surface of the porous PTFE membrane, and this combination was attached to the non-woven
polyester fabric.
[0054]
A second adhesive support system having an outer diameter of 30 mm, with an inner diameter of
16 mm removed, was cut from the double sided adhesive tape described above. The second
adhesive support system was aligned with the porous PTFE membrane layer and adhered to this
layer. The outer surface of the second adhesive support system was centrally bonded to the
mounting plate with an inner diameter of 16 mm centered and the mounting plate assembly was
placed in the acoustic measurement device. Voice transmission loss of samples and long term
WEP were tested as described above. The test results are shown in Table 1.
[0055]
-Example 1-Hydrophobic porous membrane with "captive" structure An expanded PTFE
membrane is provided with the following properties: mass 18.347 g / m <2>; thickness 0.0013
"(33 μm); air Permeability 8.6 Gurley seconds; Aeration 107.71 ml / min-cm <2>; Instant water
pressure 138 psi (951.5 kPa); Particle efficiency 99.999994%. A 30 mm diameter disc was cut
from the membrane. A second adhesive support system having an outer diameter of 30 mm, with
an inner diameter of 16 mm removed, was cut from the double sided adhesive tape described
above. Double-sided adhesive tape is 50 μm thick MylarTM polyester film (DFM-200-clear V156, Flexcon Corp. And a layer of 19 μm thick acrylic pressure sensitive adhesive provided on
each side of The second adhesive support system was aligned and bonded to the surface of the
porous PTFE membrane.
[0056]
A first adhesive support system having an outer diameter of 30 mm, with an inner diameter of
16 mm removed, was cut from the single-sided adhesive tape. One sided adhesive tape is 50 μm
thick MylarTM polyester film (DFM-200-clear V-156, Flexcon Corp. And a layer of 19 μm thick
acrylic pressure sensitive adhesive provided on one side of The first adhesive support system was
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aligned with and adhered to the porous PTFE membrane surface opposite the second adhesive
support system. The exposed adhesive of the second support system was glued centrally to the
mounting plate with the 16 mm internal diameter centered, and the mounting plate assembly
was placed in the acoustic measurement device. Voice transmission loss of samples and long
term WEP were tested as described above. The test results are shown in Table 1.
[0057]
Comparative Example 2 Hydrophobic Porous Black Membrane Having Stretched Laminated
Structure This example is described in Nitto Denko, Inc. Is a protective cover material marketed
under the tradename MICRO-TEXTM N-Series. The product consists of a polyolefin network
laminated to one or both sides of a porous ePTFE membrane. The material had the following
properties: mass 38.683 g / m <2>; thickness 0.009 ′ ′ (228.6 μm); air flow 6078.4 ml / mincm <2>; instantaneous water pressure resistance 0 .4 psi (3.0 kPa); particle efficiency-NA (not
applicable). No particle efficiency test was done. Because the available sample material was
smaller than the required test size. A disc with a diameter of 30 mm was cut from the above
mentioned material.
[0058]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0059]
Comparative Example 3-Hydrophobic porous membrane having "captive" structure This example
is described in Nitto Denko, Inc. Is a protective cover material marketed under the trade name
MICRO-TEXTM Advantec 0.2. The product consists of a porous ePTFE membrane. This material
had the following properties: mass 47.5 g / m <2>; thickness 0.0036 ′ ′ (91.4 μm); air
permeability 24.2 Gurley seconds; air flow 38.43 ml / min Instantaneous pressure resistance 120
psi (827.4 kPa); particle efficiency 99.989%. A disc with a diameter of 30 mm was cut from this
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material.
[0060]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0061]
Comparative Example 4 Hydrophobic Porous Membrane Having a “Captive” Structure This
example is described by Nitto Denko, Inc. Is a protective cover material marketed under the trade
name MICRO-TEXTM NTF1033. The product consists of a porous ePTFE membrane with a pore
size of 0.2 μm. This material had the following properties: mass 4.421 g / m <2>; thickness
0.0007 '' (17.8 μm); air permeability 0.15 gurley second; air rate 6413.81 ml / min
Instantaneous pressure resistance 1.8 psi (12.1 kPa); particle efficiency 74%. A disc with a
diameter of 30 mm was cut from this material.
[0062]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0063]
-Example 2-Hydrophobic porous black membrane with "captive" structure This product is
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commercially available from W. L. Gore & Associates, Inc. 3.0 weight percent carbon black
(KETJENBLACKTM EC-300J, Akzo Corp., manufactured by And obtained from porous expanded
PTFE. The membrane had the following properties: mass 8.731 g / m <2>; thickness 0.0012 ′
′ (29.7 μm); air permeability 3.0 Gurley seconds; air permeability 314.72 ml / min− cm <2>;
instantaneous water pressure 45.6 psi (314.4 kPa); particle efficiency 99.999996%. Discs having
a diameter of 30 mm were cut from the described material.
[0064]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0065]
Comparative Example 5- An oleophobic porous membrane product having a "captive structure"
consisted of a modified acrylic copolymer cast on a non-woven nylon substrate. This product was
oleophobically manufactured by Pall Corp (VERSAPORTM 5000TR membrane). The membrane
had the following properties: mass 41.4 g / m <2>; thickness 0.037 ′ ′ (94.0 μm); air
permeability 0.8 Gurley second; air flow 1207.8 ml / min− Instant water pressure 7.9 psi (54.5
kPa); particle efficiency 80.4%. Discs having a diameter of 30 mm were cut from the described
material.
[0066]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
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[0067]
Comparative Example 6 An oleophobic porous membrane product having a “captive structure”
is made of polyvinylidene fluoride (PVDF) which is oleophobic processed and has a pore diameter
of 0.22 μm, manufactured by Millipore Corporation (DURAPEL® 0.22 μm membrane). The
membrane had the following properties: mass 67.4 g / m <2>; thickness 0.0044 "(111.3 μm); air
permeability 41.8 Gurley seconds; air flow 22.25 ml / min- cm <2>; instantaneous water
pressure> 50 psi (345.0 kPa). Particle efficiency and discontinuous pressure resistance levels
were not measured. However, according to the Millipre brochure, the water pressure resistance
corresponding to the test membrane is expected to be 62 psi (427.5 kPa). No particle efficiency
test was done. Because the available sample material was smaller than the required test size.
Discs having a diameter of 30 mm were cut from the described material.
[0068]
The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0069]
Example 3 An oleophobic porous membrane product having a "captive structure" is described in
W. L. Gore & Associates, Inc. No. 5,376,441 and made of a porous ePTFE membrane which has
been subjected to an oleophobic process according to US Pat. No. 5,376,441. The membrane had
the following properties: mass 12.1 g / m <2>; thickness 0.0009 ′ ′ (22.1 μm); air
permeability 2.6 Gurley seconds; air flow 362.10 ml / min− cm <2>; instantaneous water
pressure 73.7 psi (508.1 kPa); particle efficiency 99.999996%. Discs having a diameter of 30
mm were cut from the described material.
[0070]
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The disks were aligned with the second adhesive support system and the first adhesive support
system as described in Example 1 and coupled to these adhesive support systems to form a
sample assembly. The exposed adhesive was glued to the mounting plate at the center with the
16 mm inner diameter centered and the mounting plate assembly was placed in the acoustic
measurement device. Voice transmission loss of samples and long term WEP were tested as
described above. The test results are shown in Table 1.
[0071]
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