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[51]Int.cl.7 E01B 7/14[11]授权公告号 CN 2389912Y[21]申请号99249381.1 专利号 ZL 99249381.1[22]申请日 1999.11.1[24]颁证日 2000.7.14[45]授权公告日 2000.8.1[7
[51] Int. cl. 7 E01B 7/14 [11] Authorization Bulletin No. CN 2389912Y [21] Application No. 99249381.1 Patent No. ZL 99249381.1 [22] Date of Application 1999.11.1 [24] Date of Certification 2000.7.14 [45 ] Authorized announcement day 2000.8.1 [7