(19)
(11) EP 0 944 292 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
02.03.2005 Bulletin 2005/09

(43) Date of publication A2:
22.09.1999 Bulletin 1999/38

(21) Application number: 99105479.2

(22) Date of filing: 17.03.1999
(51) International Patent Classification (IPC)7: H04R 7/00, H04R 7/12
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 19.03.1998 JP 7101198

(71) Applicants:
  • PIONEER ELECTRONIC CORPORATION
    Meguro-ku, Tokyo (JP)
  • TOHOKU PIONEER ELECTRONIC CORPORATION
    Tendo-shi, Yamagata-Ken (JP)

(72) Inventors:
  • Sato, Masatoshi c/oTOHOKU PIONEER ELECTRONIC CORP.
    Tendo-shi, Yamagata-ken 994-0012 (JP)
  • Mitobe, Kunio c/oTOHOKU PIONEER ELECTRONIC CORP.
    Tendo-shi, Yamagata-ken 994-0012 (JP)

(74) Representative: Sajda, Wolf E., Dipl.-Phys. et al
MEISSNER, BOLTE & PARTNER Postfach 86 06 24
81633 München
81633 München (DE)

   


(54) Loadspeaker diaphram of an injection foam molded body


(57) An inorganic or organic filler in an amount of 3 to 30 % by weight is added to a resin containing a foaming agent. The resulting resin mixture material is injection molded into a loudspeaker diaphragm (1) having a three-layer structure in which a foamed layer (3) is covered with unfoamed skin layers (2). For forming the three-layer structure, a resin mixture material of polypropylene containing a foaming agent is injected into a cavity of a mold (20). Immediately after the injection and the completion of forming the skin layers (2), the mold (20) is separated so that the material may start foaming at its inside to form the foamed layer (3). Since the surfaces of the resin mixture material are in contact with the inner surfaces of the mold in the injection, the surfaces of the resin mixture material have solidified before the foaming takes place, so as to form the unfoamed skin layers (2). By adjusting the filler to the appropriate content, the loudspeaker diaphragm (1) is improved in appearance quality while keeping the other physical properties with favourable characteristics.






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