(19)
(11) EP 1 387 012 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
07.04.2004 Bulletin 2004/15

(43) Date of publication A2:
04.02.2004 Bulletin 2004/06

(21) Application number: 03254641.8

(22) Date of filing: 23.07.2003
(51) International Patent Classification (IPC)7: E02F 3/38, E02F 9/14
(84) Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR
Designated Extension States:
AL LT LV MK

(30) Priority: 09.09.2002 JP 2002262198
02.08.2002 JP 2002226256

(71) Applicant: KOBELCO CONSTRUCTION MACHINERY CO., LTD.
Hiroshima-shi, Hiroshima 731-0138 (JP)

(72) Inventors:
  • Eita, A. c/o Kobelco Construction Machinery Co.Ltd
    Hiroshima-shi Hiroshima 731-0138 (JP)
  • Fujiwara, A c/o Okubo Plant Kobelco Co. Ltd.
    Akashi-shi Hyogo 674-0063 (JP)
  • Yamaguchi, T c/o Kobe Corporate Research Labs.
    Kobe-shi Hyogo 651-2271 (JP)

(74) Representative: Bailey, David Martin 
Brookes Batchellor LLP, 102-108 Clerkenwell Road
London EC1M 5SA
London EC1M 5SA (GB)

   


(54) Boom structure of construction machine and manufacturing method


(57) This invention provides with a boom structure (1) comprising a first straight portion (2a), a curvilinear portion (2b) positioned contiguously to the first straight portion, and a second straight portion (2c) positioned contiguously to the curvilinear portion in a direction of the boom, characterized in that a tubular member (9a,9b) forms one or more of corners (8a-8d) of a generally rectangular cross-section in the curvilinear portion (2b), wherein the tubular member (9a,9b) has a closed cross-section, whereby capable of improving the fatigue strength of the boom and attain a reduction of its weight.






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