Earplug

Details Earplug Earplug

1998-10-14

2001-07-24

Silbaugh, Jan H. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

To produce composite, plural part or multilayered article

C264S222000, C264S271100, C264S279000, C264S279100, C264S328800

Reexamination Certificate

active

06264870

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to earplugs of the type having an elongate core or body part and a sealing part connected therewith, and to the manufacture of such plugs.
BACKGROUND ART
Many different kinds of earplugs of the above-mentioned type have been known for a long time. For a long time, use has been made of a core or body part having the character of a stem, at the front part of which a substantially softer sealing part was attached in some suitable manner.
Recently, earplugs of the type mentioned by way of introduction have been manufactured, completely made of elastic polymeric material of a suitable hardness, the sealing part as a rule comprising transversely protruding flange or collar portions, which extend circumferentially and are adapted to engage sealingly with the wall of the auditory canal. In this context, it has been indicated that the core or body part could be made of a material having a higher hardness than the material of the sealing part, but owing to manufacturing difficulties, use has been made of a single polymeric material for the entire plug. This has necessarily resulted in a compromise between axial rigidity (which should be high in order to facilitate insertion) and radial rigidity (which should be low for good adaptation to the auditory canal with maintained comfort).
OBJECTS OF THE INVENTION
An object of the present invention is to provide an earplug, by means of which the above-mentioned compromise can be obviated.
A further object is to provide an earplug which can be manufactured in different designs with maintained excellent sealing and comfort properties.
One more object is to provide a method that renders it possible to manufacture earplugs of the type at issue in an efficient and economic manner.
SUMMARY OF THE INVENTION
The above-mentioned objects are achieved by an earplug, a method and a use having the distinguishing features as defined in the appended claims.
The invention thus is based on the insight that multimaterial-injection moulding can be utilised to manufacture earplugs with different degrees of hardness of the material of the core or body part and the material of the sealing part. As materials, use is preferably made of elastic polymeric material, especially a thermoplastic elastomeric material, so-called TPE material.
It has surprisingly been found possible to multi-material-injection mould, for the manufacture of earplugs, such materials also having a very low Shore A Durometer hardness of the one material. Thus, the sealing part can be quite easily injection-moulded of a material having a Shore A Durometer hardness of less than about 10, while the core or body part can be injection-moulded of a material having a many times higher hardness, typically a Shore A Durometer hardness of between about 40 and about 80, preferably of between about 50 and about 60.
For the sealing part, it has been found advantageous to have a material hardness Shore A Durometer of between about 2 and about 6, preferably of between about 3 and about 5.
Excellent “physical” binding has been achieved between the main parts of the earplug, that is to say the sealing part obtains the desired good connection with the core or body part through the actual injection moulding. No additional connecting steps are required, although it is, of course, also possible to configuratively perform additional form-fit locking.
The multimaterial-injection moulding in combination with the possibility of selecting different, well-balanced degrees of material hardness for the sealing part and the core or body part, respectively, has been found to afford possibilities of applying the invention to many different plug configurations while maintaining extremely good sealing and comfort properties.
Thanks to very low hardness, the sealing part can adapt to and fill essentially all axial and radial sectional forms of the auditory canal, at the same time as the necessary axial rigidity is available, which has been found to make the insertion of the earplug extremely safe and easy.
Studies have demonstrated that a multimaterial-injection-moulded earplug according to the invention contributes to the user of the earplug spontaneously applying the plug in the ear in a fully correct fashion, i.e. the applied earplug obtains in a natural manner extremely good adaptation to the auditory canal, thereby achieving in a group of users an attenuation effect which is in average essentially improved.
The good connection between the sealing part and the core or body part which is obtained according to the invention besides guarantees that the core or body part is not “pressed through” during insertion (which could hurt the ear) and that the sealing part safely leaves the ear when pulling out the earplug.
The combination of a very soft sealing part and an essentially harder core or body part has also been found extremely advantageous when the sealing part comprises laterally or transversely protruding sealing portions, such as flange portions. These are circumferentially of annular configuration and, as a rule, of an increasing diameter from the pointed part of the earplug and backward. These flange portions are comparatively thin to yield good adaptation to the wall of the auditory canal.
In one embodiment according to the invention with a Shore A Durometer hardness of less than about 20, preferably less than about 10, of the flange material it has been found that the protruding portions easily yield or bend in relation to the core or body part. Expressed in a different manner, this means that the core or body part obtains a certain clear axial movability or resilience relative to the sealing portions, which further improves the comfort properties. Moreover, it has been found that said resilience affects the resonance frequency of the earplug. In other words, it becomes possible to control the resonance frequency by the changing of parameters, such as the rigidity of the sealing portions and/or the weight of the core or body part, said parameters directly affecting said resonance frequency. It would be preferable to change said weight, which can be easily achieved, for instance, by insertion of a special material in the core or body part.
In this context it should be pointed out that multi-material-injection moulding quite simply permits that, for instance, the core or body part is injection-moulded of more than one material and/or that special inserts are arranged therein. Weight-controlling materials and/or materials permitting later detection of the earplug may be involved, such detection being per se known.
It should also be mentioned that the skilled person realises that in connection with multimaterial-injection moulding, it is possible to mould integrally with the core or body part or attach thereto an end of a band, a headband or the like, which is adapted to hold two inventive earplugs together.
When the sealing part according to the invention comprises a number of circumferential, transversely protruding sealing flange portions or the like, especially when these protrude essentially perpendicular to the core or body part, it has been found that there will be a substantially decreased tendency toward wrinkling of the flange portions when inserting the earplug. This means that a considerable problem has been obviated, which problem is frequent in connection with flanged plugs according to prior art technique.
According to the invention, multimaterial-injection moulding suitably takes place in a single multimaterial-injection moulding machine, which can be designed according to per se known principles. It has been found advantageous first to injection mould the core or body part and then the outer sealing part. Use is preferably made of a machine of the type having a rotatable table or mould. As a result, the manufacture will be very rational at the same time as good physical binding is ensured owing to good temperature conditions and a short space of time between the different injection moulding steps.


REFERENCES:
patent: 3897376 (1975-07-01), Lampe
patent:

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