Music – Instruments – Combined
Reexamination Certificate
2002-07-01
2004-01-20
Hsieh, Shi-Yung (Department: 2837)
Music
Instruments
Combined
C084S172000, C084S173000, C084S174000
Reexamination Certificate
active
06680430
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a speaker edge disposed around a vibration plate (viz., conical body) of the speaker and adjoined to the inner periphery of a frame so as to hold the vibration plate in its correct position where it is not hindered from freely vibrating. In particular, the present invention relates to a speaker edge that is produced using a thermosetting composition and a mechanically foaming means, and also relates to foam-molding method and system and a foam-molding apparatus, all being designed to manufacture the speaker edge.
PRIOR ART
Usually, each speaker has a main vibration plate
7
whose periphery is connected by a speaker edge
7
a
to a frame
16
, as shown in FIG.
1
. The main vibration plate
7
taking this position is not hindered from vibrating in an axial direction. The speaker edge
7
a
has in cross section an arcuate portion (viz., corrugation)
115
that is curved upward or downward between its outer and inner peripheries, lest the vibration plate
7
should suffer any difficulty when vibrating transversely.
In some cases, the prior art speaker edges
7
a
have been formed of a vulcanized rubber foam. In other cases, a thermoplastic resin such as an acrylic polymer, a polycarbonate, a polyurethane, a polyester, a polyolefin or the like has been molten and injection molded around the periphery of each vibration plate
7
. Alternatively, a foamed polyurethane block has been severed into slabs, each being subsequently sliced into thin sheets of a given thickness so as to be heated and pressed in a mold to give the speaker edge
7
a.
The molten thermoplastic resin will be kept at an elevated temperature from about 200° C. to 300° C. when injection molding the speaker edge
7
a
. Thus, the vibration plate
7
being bonded to and made integral with this edge within a couple of mold segments
41
and
42
is likely to suffer from thermal deterioration.
It is a further problem that the vulcanized foam rubber has failed to provide a sufficiently high ratio of foaming, thus increasing overall weight of the speaker edge and vibration plate bonded thereto. In such an event, the frequency-to-sound pressure property will be rendered inferior to those which have been made lighter. In addition, the speaker edge of such a vulcanized foam rubber has to be adhered to the vibration plate, using a highly sophisticated adhesion technology and nevertheless encountering difficulties in adhesion process.
FIG. 10
illustrates a speaker edge
7
a
′ (hereinafter called ‘thermally compressed article of polyurethane foam slab/sheets’) whose arcuate portion has basal ends
7
b
. The rear (convex) corner of each basal end
7
b
is thermally stretched to have a lower density, during the pressing process within a mold. Consequently, the front (concave) corner of each basal end
7
b
is rendered higher in density, due to compression. Such an unevenness in density produced between the front and rear corners or surface layers has undesirably impaired strength and durability. The inner periphery of such a speaker edge
7
a
′ vibrates in unison with the periphery of vibration plate
7
, but with the outer periphery of said edge
7
a
′ being retained in place by the frame
16
. As a result, fatigue of material will proceed exclusively in one of those basal ends
7
b
, adjacent to the frame
16
. The thinned region
7
c
of each arcuate portion basal end has not necessarily been satisfactory in strength.
Each slab of polyurethane foam is not free from unevenness from region to region, due to the foaming process itself. The sheets sliced from such a slab for forming the thermally compressed article
7
a
′ of polyurethane foam do inevitably differ in density, corresponding to the regions in said slab. Thus, speakers
1
comprising the thermally compressed speaker edges
7
a
′ each composed of those slab sheets will show a considerable variation in their minimum resonance frequency f
o
, varying quality or performance of them. For example, variation of f
o
measured for 100 samples was found ±15 Hz.
FIG. 18
is an enlarged cross-sectional scheme of the thermally compressed speaker edge
7
a
′ made of the slab sheets
117
shown in FIG.
10
. As seen in
FIG. 18
, a surface layer has been depressed during the thermally compressing molding process so that void cells in said layer are collapsed to give a harder and denser skin
68
. An apparent boundary will be recognized between this skin and an inner regularly foamed core. Physical properties change sharply across the boundary, increasing amplitude of the resonance and causing a distortion in tone quality.
An internal texture of the thermally compressed slab/sheets article
7
a
′ will be seen in
FIG. 3
, that is a photo taken using a microscope of 60 magnifications. There will be observed a surprising visual difference between this photo and
FIG. 2
that is another microscopic photo of the same magnifications showing the speaker edge
7
a
of the resent invention.
Speakers built in automobile car doors or the like must be waterproof, whereas polyurethane slabs absorb water from their outer surface. The prior art speaker edges
7
a
′ that are polyurethane slab sheets thermally compressed are therefore not waterproof to a sufficient degree. In order to resolve this drawback, it has been proposed to coat the surfaces of speaker edges with a fluoride resin. However, in view of the open-cell structure of those prior art speaker edges, any excessively thick coating that will clog the cell openings with the fluoride resin should be avoided. Thus, any satisfactory waterproofing finish has not been available, despite a noticeably raised manufacture cost.
The preceding Japanese patent application No. 11-61879 discloses an improvement in the described prior art speaker edges. According to this proposal, a two-fluid reactive composition comprising an isocyanate and a polyol will be fed into a pair of male and female segments of a mold, through a stirring mixer. Within the mold, the two ingredients will react one with another to foam and solidify, for example at about 60° C. Due to such a low temperature, each cycle of molding the speaker edge will necessitate an undesirably long time, for example 2 minutes. Further, the two-fluid ingredients once blended together will solidify so soon that the mixer is jammed with them, unless immediately transferred to the mold. Process management, including process control of interrupted operation, will thus be rendered intricate and troublesome. The tow-liquid type raw material is so susceptible to ambient condition such as humidity that the foaming ratio tends to vary between batches or lots, making it difficult to ensure uniform quality.
DISCLOSURE OF THE INVENTION
The present invention was made in view of the drawbacks inherent in the prior art speaker edges and the prior art method of making same. A novel speaker edge provided herein is made of a thermosetting composition that is a mixture of main ingredients, wherein the main ingredients are a polyurethane prepolymer and a latent hardener, and the latent hardener is an inactivated solid polyamine. In manufacture of the speaker edge, a gas will be dispersed in the thermosetting composition, prior to feed thereof into a female mold segment heated to a temperature below the critical thermosetting temperature. Subsequently, a male mold segment that has previously been heated to a higher temperature above the critical temperature will be pressed and fitted in the female segment so that the ingredients react with each other to solidify within the mold. In other words, the thermosetting composition in the invention is of the one-liquid type and capable of self-foaming by virtue of the gas mechanically dispersed in said composition, whereby it can be molded directly around the main vibration plate so as to foam and solidify surrounding the periphery hereof.
Such a one-liquid type thermosetting composition of the invention can be injected into a mold either continuously or intermitt
Ikeda Kiyoshi
Mizone Shinya
Okuda Shinji
Tabata Shinya
Takada Masaharu
Hsieh Shi-Yung
Jordan and Hamburg LLP
Matsushita Electric - Industrial Co., Ltd.
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