U.S. patent number RE29,487 [Application Number 05/666,364] was granted by the patent office on 1977-12-06 for earplugs.
This patent grant is currently assigned to Cabot Corporation. Invention is credited to Ross Gardner, Jr..
United States Patent |
RE29,487 |
Gardner, Jr. |
December 6, 1977 |
Earplugs
Abstract
There are disclosed earplugs composed of certain polymeric foam
materials. The earplugs are of generally cylindrical shape and of
somewhat larger diameter than the human ear canal. The earplugs are
composed of a foamed plasticized polymeric material having a
sufficiently high concentration of plasticizer to provide the
earplug with a reduced rate of recovery from compression.
Inventors: |
Gardner, Jr.; Ross (Stoughton,
MA) |
Assignee: |
Cabot Corporation (Boston,
MA)
|
Family
ID: |
22709352 |
Appl.
No.: |
05/666,364 |
Filed: |
March 12, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
192366 |
Oct 26, 1971 |
03811437 |
May 21, 1974 |
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Current U.S.
Class: |
128/864 |
Current CPC
Class: |
A61F
11/08 (20130101); A61F 11/10 (20130101) |
Current International
Class: |
A61F
11/08 (20060101); A61F 11/10 (20060101); A61F
11/00 (20060101); A61F 011/02 () |
Field of
Search: |
;128/152,151
;181/23,33,126,135 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Yasko; John D.
Attorney, Agent or Firm: Schuman; Jack Blaker; Barry R.
Chaletsky; Lawrence A.
Claims
What is claimed is:
1. An earplug of generally cylindrical shape having a diameter of
between 3/8 and 3/4 inch, a length .[.to.]. .Iadd.of
.Iaddend.between 1/2 and 1 inch and composed of a resilient
plasticised polymeric foam having a sufficiently high concentration
of organic plasticizer therein as to provide said foam with a rate
of recovery .[.of.]. .Iadd.from .Iaddend.60 percent compression
thereof to 40 percent compression .Iadd.thereof .Iaddend.of from 1
to 60 seconds and an equilibrium pressure .[.of.]. .Iadd.at
.Iaddend.40 percent compression thereof of from 0.2 to 1.3
p.s.i.
2. The earplug of claim 1 wherein said polymeric foam has a rate of
recovery of from 2 to 20 seconds.
3. The earplug of claim 1 wherein said polymeric foam has an
equilibrium pressure at 40 percent compression of between 0.35 and
1.0 p.s.i.
4. The earplug of claim 1 wherein the polymeric constituent of said
foam is a polymer of vinyl chloride.
5. The earplug of claim 1 wherein the polymeric constituent of said
foam is a homopolymer of vinyl chloride.
6. The earplug of claim 1 having a diameter of between 9/16 and
11/16 inch.
7. The earplug of claim 1 having a length of between 7/16 and 3/4
inch.
8. The earplug of claim 1 wherein said polymeric foam is formed
from a polyvinylchloride plastisol.
9. The earplug of claim 1 having a truncated cone shape.
10. The earplug of claim 1 having a substantially longitudinal bore
therethrough said bore being adapted to receive the tip portion of
a sound conducting tube. .Iadd. 11. An earplug having a size and
shape adapted to be compressed and inserted into the human ear
canal and there allowed to expand and obturate the ear canal, said
earplug comprising a resilient plasticized polymeric foam having a
sufficiently high concentration of organic plasticizer therein as
to provide said foam with a rate of recovery from 60 percent
compression thereof to 40 percent compression thereof of from 1 to
60 seconds and an equilibrium pressure at 40 percent compression
thereof of from 0.2 to 1.3 p.s.i. .Iaddend..Iadd. 12. An earplug as
in claim 11 having a generally cylindrical shape. .Iaddend..Iadd.
13. An earplug as in claim 11 wherein said polymeric foam has a
rate of recovery from 60 percent compression thereof to 40 percent
compression thereof from 2 to 20 seconds. .Iaddend..Iadd. 14. An
earplug as in claim 11 wherein said polymeric foam has an
equilibrium pressure at 40 percent compression thereof from 0.35 to
1.0 p.s.i. .Iaddend..Iadd. 15. An earplug as in claim 11 wherein
the polymeric constituent of said foam is a polymer of vinyl
chloride. .Iaddend..Iadd. 16. An earplug as in claim 11 wherein
said polymeric foam is formed from a polyvinylchloride plastisol.
.Iaddend..Iadd. 17. An earplug as in claim 11 having a truncated
conical shape. .Iaddend..Iadd. 18. An earplug as in claim 11 having
a bore therethrough, said bore being adapted to receive a sound
conducting tube. .Iaddend..Iadd. 19. An earplug as in claim 18,
further comprising a sound conducting tube mounted in said bore.
.Iaddend.
Description
The present invention relates generally to earplug constructions
and more particularly to earplug constructions adapted for
insertion into the ear canal.
Many devices are known which are adapted for insertion into the
human ear canal in order to suppress or attenuate the transmission
of dangerous noise and thus confer a measure of protection to the
anatomical hearing apparatus. Such devices have taken many forms.
For instance, perhaps the simplest earplug is formed of wadded
cotton. While blessed with the benefit of simplicity, such earplugs
are not normally greatly effective as acoustic barriers. In another
embodiment of this simple earplug, a fibrous material, such as
cotton wadding, is impregnated with a compliant waxy substance. Yet
another form of earplug is composed of a shapeless, compliant,
"dead soft" mineral-filled waxy substance. These ear-plugs are
normally deficiant due to a lack of sufficient resiliency; thus,
when deformed or compressed in order to enter the ear canal such
earplugs do not normally recover or expand sufficiently so as to
effectively obturate the ear canal. Still other earplugs are known
which take the form of molded elastomeric structures, natural
rubber being a common material of construction. Included within
this class are earplugs having molded therein check valves and
other substructures designed to allow normal voice tones to be
transmitted therethrough while cancelling or preventing
transmission of injurious overpressures. Such molded elastomer
earplugs suffer from the fact that their size and shape is
preordained and fixed in the molding thereof. Thus, they must
initially be carefully fitted to the wearer in order to provide
security, comfort and effective sound attenuation properties.
Unfortunately, the size and shape of the human ear canal is quite
variable amongst persons; indeed, bilateral symmetry in a single
individual is often lacking. Accordingly, it is not possible to
manufacture molded elastomeric earplugs of a universally useful
size and shape.
In recent years there have come into extensive usage lightweight
earphones or headphones comprising generally a miniature speaker
having tubular member(s) extending therefrom the tips of which
members are adapted for insertion in the external auditory meatus.
Said tips are generally comprised of a foamed or unfoamed polymeric
material such as neoprene or sponge rubber. In the case of the
unfoamed polymeric tip members major deficiencies usually reside in
the facts that the tip members (1) tend to slip out of the ear
canal, and (2) the relatively non-compliant character of the
polymeric material does not lend itself to complete obturation of
the ear canal. Thus, bothersome external ambient noise can often
by-pass such unfoamed tip members. In the case of sponge rubber tip
members the resiliency of the sponge materials is generally
excessively rapid and mitigates against actual insertion of the tip
member into the ear canal proper. Such tip members are usually
worn, therefore, in a manner such as to urge the respective members
inwardly against the external auditory meatus. This is often found
uncomfortable and, in any case, is not ordinarily efficient in
blocking the ear canal.
In accordance with the present invention, however, there are
provided earplug structures which substantially ameliorate or
overcome the aforedescribed problems.
OBJECTS OF THE INVENTION
It is a principal object of the invention to provide novel
earplugs.
It is another object of the invention to provide earplugs adapted
for insertion into the ear canals with substantially complete
obturation thereof.
It is another object of the invention to provide earplugs having
excellent sound barrier properties.
It is another object of the invention to provide earplugs adapted
for insertion into the ear canals wherein bone conduction of sound
(such as through the plug and into the mastoid process) is
substantially completely avoided.
It is still another object of the invention to provide novel ear
insertable earpieces for lightweight earphone devices.
Other objects and advantages of the invention will in part be
obvious and will in part appear hereinafter.
GENERAL DESCRIPTION OF THE INVENTION
In accordance with the present invention there are provided
earplugs of generally cylindrical shape and of somewhat larger
diameter than that of the human ear canal. Said earplugs are
composed of a foamed polymeric material having a rate of recovery
from 60 percent compression to 40 percent compression thereof of
from 1 to 60 seconds and an equilibrium pressure at 40 percent
compression thereof of from 0.2 to 1.3 p.s.i.
THE DRAWINGS
FIG. 1 is a perspective view of one embodiment of an earplug of the
invention.
FIG. 2 is a perspective, partially sectioned view of an earpiece
portion of an earphone bearing a modified foamed polymeric earplug
of the invention as the external ear insertable tip member.
.Iadd.FIG. 3 is a perspective view of another embodiment of the
invention having a truncated cone shape. .Iaddend.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1 it will be seen that the earplug of the
invention is of generally cylindrical shape and has a diameter
somewhat greater than that of the average adult human ear canal.
For instance, a diameter of between about 3/8 inch and about 3/4
inch is generally acceptable. Optimally, the diameter of the
earplug will be between 9/16 inch and 11/16 inch. Further, it
should be noted and understood that the term "cylindrical" as
employed herein includes within its scope structures having a
relatively shallow truncated cone shape or a substantially
spherical shape. Where the earplug takes the form of a truncated
cone, the above diameter criteria may be employed taken at the
midpoint of the cone. Where the earplug is spherical, the above
criteria may be applied to the diameter of said sphere.
The length of the earplug can generally be between about 1/2 inch
to about 1 inch. At lengths substantially greater than about 1
inch, for instance, sufficient material can overhang the external
ear so as to be bothersome to the wearer. Desirably, the length of
the earplug will be between 7/16 and about 3/4 inch.
Any flexible polymeric material which can be foamed so as to result
in an ultimately formed earplug structure meeting the recovery rate
and pressure criteria set forth hereinabove constitutes a
satisfactory material of construction in the earplugs of the
invention. Accordingly, polymers of ethylene, propylene, vinyl
chloride, vinyl acetate, diisocyanate, cellulose acetate or
isobutylene can all be generally employed. In particular, however,
I much favor vinyl chloride homopolymers and copolymers comprising
at least 85 percent by weight of vinyl chloride and up to 15
percent by weight of other monomers such as vinylidene chloride,
vinyl esters of carboxylic acids, e.g., vinyl acetate, vinyl
propionate, vinyl butyrate and vinyl benzoate, esters of
unsaturated acids, e.g., alkyl acrylates such as methyl acrylate,
ethyl acrylate, propyl acrylate, butyl acrylate, allyl acrylate,
and the corresponding esters of methacrylic acid; vinyl aromatic
compounds, e.g., styrene, ortho-chlorostyrene, para-chlorostyrene,
2,5-dichlorostyrene, 2,4-dichlorostyrene, paraethylstyrene, vinyl
naphthalene and .alpha.-methyl tyrene, dienes such as butadiene and
chlorobutadiene, unsaturated amides such as acrylic acid amide and
acrylic acid anilide; unsaturated nitriles such as acrylic acid
nitrile; and esters of .alpha.,.beta.-unsaturated carboxylic acids,
e.g., the methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl,
allyl, methallyl, and phenyl esters of maleic, crotonic and fumaric
acids and the like. Such vinyl chloride based polymers, and
particularly the vinyl chloride homopolymers, can normally be
compounded into plastisol form with a blowing agent and a high
concentration of a suitable organic plasticizer so as to result in
stabilized foams having the rate of recovery and pressure
characteristics necessary in the compositions from which the
earplugs of the invention are fabricated.
With respect to said characteristics, it is clear that the
relatively slow recovery rate in returning from 60 percent
compression to 40 percent compression of the foamed materials
employed in the earplug construction of the invention confers to
the user the ability to initially compress or otherwise deform the
earplug and provide sufficient time for insertion thereof into the
ear canal. Subsequent to said insertion, the compressed or deformed
earplug slowly recovers and attempts to regain its original shape.
By so doing, the recovering polymeric material conforms to the
structure of the ear canal and establishes substantially complete
obturation thereof. In a preferred embodiment of the invention, the
recovery rate of the foamed polymer composition will be between 2
and about 20 seconds.
The manner in which the recovery rate of the foamed polymer
composition is determined for the purposes of the present invention
is as follows:
Plugs of the polymeric foam composition are cut with a hollow tube
borer, the dimensions of the plugs being about 0.630-0.640 inch in
diameter and having a length of between 0.495 and 0.615 inch. A
parallel plate gauge is employed having a spacing of 0.375 inch
between the opposing plate surfaces. Said 0.375 inch spacing
between plates thus corresponds to about 40 percent compression of
the original plug diameter. A plug specimen is twirled lengthwise
between the fingers for 15 to 30 seconds with an ultimate
compression of the plug to about 0.25 inch in diameter,
corresponding to about 60 percent reduction in the original
diameter thereof. The plug is then inserted lengthwise and released
between the parallel plates, the time from said release to contact
of 75 percent of the linear surface of the plug with both plates
being determined by stopwatch measurement. In order to maximize the
relative precision of the test, a number of test specimens taken
from the same sample foam are employed and the results
averaged.
The 40 percent compression equilibrium pressure testing of the
polymeric foam is accomplished employing the test plugs produced
and employed in the above recovery rate testing procedure. In
pressure testing, however, there is employed an Instron Universal
Testing Instrument, Model TTC, having a parallel plate specimen
holder in which the parallel plates are spaced 0.375 inch apart.
The Instron is further equipped with a 1 pound load cell. Test
plugs of the foamed polymeric composition are finger twirled in the
manner described previously for a 30 second period and are placed
lengthwise between the plates of the parallel specimen holder. When
the load cell reading attains a 40 to 80 percent full scale
deflection, no further specimens are added. The instrument and
specimens are allowed to stand for 10 minutes in order to attain
substantial equilibrium and the number of plugs and the measured
total pressure are recorded. Since the contact area of each plug
with the plates of the specimen holder corresponds to about 0.25
in..sup.2, the average pressure exerted by each plug specimen is
determined by the equation: ##EQU1##
The pressure criteria established hereinbefore for the foamed
polymeric compositions employed in the fabrication of the earplugs
of the invention is also important in that the achievement of such
pressure characteristics insures that the completed earplug will
bear in obturating relationship against the ear canal but with
insufficient pressure as to cause discomfort to the wearer. In a
preferred embodiment, the foamed polymeric compositions employed in
the fabrication of the earplugs of the invention will have a 40
percent compression equilibrium pressure of between 0.35 and 1.0
p.s.i.
Taken together, the pressure and recovery rate criteria of the
foamed polymeric compositions also define a composition having the
further characteristic of relative "deadness." Thus, while form
stable in the sense that the earplug, when deformed, will tend to
recover its original shape and size, the slow rate of recovery
thereof and the very small overall pressure exerted by the plug
surfaces on the constraining ear canal further insure the fact that
little sound will be transmitted through the material and into the
bony structure of the canal. This, too, is highly advantageous
since substantial undesirable sound transmission by way of bone
conduction through the mastoid process can occur with solid
earplugs.
There follow a number of non-limiting illustrative Examples:
EXAMPLE 1
A vinyl chloride plastisol formulation was compounded employing the
following ingredients:
______________________________________ Parts by Weight
______________________________________ Opalon 440, a general
purpose homopolymer of vinyl 115 chloride produced by Monsanto Co.,
St. Louis, Missiouri Admex 523, an aromatic polyester plasticizer
95 produced by Archer-Daniels-Midland Co., Minneapolis, Minnesota
Estynox 203, an epoxidized soya bean oil 5 stabilizer/plasticizer
produced by The Baker Castor Oil Co., Bayonne, New Jersey Estynox
203, an epoxidized soya bean oil 5 stabilizer/plasticizer produced
by The Baker Castor Oil Co., Bayonne, New Jersey Kempore 200, an
azodicarbonamide foaming agent 8 produced by National
Polychemicals, Inc. Wilmington, Massachusetts Antimony Trioxide
flame retardant 8 Advastab T-150, organometallic stabilizer
produced 2 by Advance Division, Carlisle Chemical Works, Inc., New
Brunswick, New Jersey Houdry FS-100, a polymeric surfactant
produced by 2 Air Products and Chemicals, Inc., Philadelphia,
Pennsylvania Vanstay 8014, stabilizer produced by R.T. 3 Vanderbilt
Co., Inc., New York, New York
______________________________________
The resulting plastisol was cast on release paper and doctor bladed
to a thickness of about 77 mils. The cast plastisol was
continuously conducted through an oven heated to a nominal
temperature of about 420.degree. F at a nominal residence time of
about 5 minutes. The resulting foamed sheet composition had a
density of about 7 lbs/ft.sup.3, a rate of recovery from 60 percent
compression to 40 percent compression of about 4 seconds and a 40
percent compression equilibrium pressure of about 0.78 p.s.i. When
examined under 75x magnification, the foamed polymer appeared to be
of predominantly closed-celled structure.
When cut into cylindrical plugs of about 5/8 inch diameter by about
5/8 inch length, the resulting structures could be finger
compressed and inserted into the ear canals without difficulty. The
compressed plugs thereafter recovered to substantially completely
and comfortably obturate the ear canals and were found to be highly
effective in attenuating the transmission of 15-15,000 Hz/sec
frequencies therethrough.
Referring now to FIG. 2, several of the earplugs are coaxially
bored throughout their lengths with a central corer having a
diameter of about 1/8 inch. The resulting structures are then
employed as a covering 3 over tubular tip portion 5 of a
lightweight headphone set (partially shown). Again, it is found
that the foamed polymeric structures are compressible to below the
dimensions of the ear canal and can be comfortably inserted therein
with subsequent slow recovery thereof to substantially completely
fill the cross-section of the ear canal. The headphone set is
adjudged to be superior in wearer comfort and is highly effective
in selectively conducting sound only through the tubular sound
conductor 7 thereof.
EXAMPLE 2
A foamable polyvinyl chloride plastisol composition was formulated
employing the following ingredients:
______________________________________ Parts by Weight
______________________________________ Opalon 440 100 Admex 523 95
Estynox 203 5 Kempore 200 4 Antimony trioxide flame retardant 10
Surfex MM, a precipitated calcium carbonate filler produced by
Diamond Alkali Co., Cleveland, Ohio 15 Advastab T-150 2 Houdry
FS-100 2 Vanstay 8014 3 ______________________________________
The resulting plastisol composition was cast on release paper and
doctor bladed to a thickness of about 114 mils. The cast sheet was
then continuously fed through an oven as in Example 1. The
resulting foamed polyvinylchloride sheet had a density of about 13
lbs/ft.sup.3, a rate of recovery from 60 percent compression to 40
percent compression of about 1 second and a 40 percent compression
equilibrium pressure of about 1.32.
When cut into cylindrical structures of about 5/8 inch diameter and
5/8 inch length, the resulting wares were found to be acceptable as
earplugs and could be inserted into the ear canals. However, due
principally to the substantially more rapid recovery rate than the
composition of Example 1, the wearer was required to insert the
plugs with considerably more rapidity following compression thereof
and certain of the test subjects were aware of the pressure exerted
by the plugs on the ear canal.
EXAMPLE 3
Two polyvinylchloride formulations having substantially similar
ingredients as employed in Examples 1 and 2 but different relative
concentrations were produced. Upon testing, one of the resulting
polyvinylchloride foams had a density of about 4 lbs/ft.sup.3, a
recovery rate from 60 percent compression to 40 percent compression
of about 106 seconds and an exerted equilibrium pressure at 40
percent compression of about 0.19 p.s.i. Earplugs formed of this
material were found to be deficient in that the recovery rate was
excessively slow and the exerted pressure upon the ear canal was
slightly below that required to completely obturate the ear canal
with the foamed polymeric shape. The other foamed polyvinylchloride
sheet composition was found to have an apparent density of about 6
lbs/ft.sup.3, a recovery rate (60 to 40 percent compression) of
about 13 seconds and an exerted equilibrium pressure at 40 percent
compression of about 0.37 p.s.i. Cylindrical (including truncated
cone shapes) earplugs formed of this material were found to be of
excellent quality in terms of facile insertion, wearer comfort and
sound attenuation properties.
While there are above described a number of specific embodiments of
the present invention, it is obviously possible to produce other
embodiments and various equivalent modifications thereof without
departing from the spirit of the invention.
Having set forth the general nature and several preferred
embodiments of the present invention, the true scope thereof is now
particularly pointed out in the appended claims.
* * * * *