Document Type and Number:
Japanese Patent JPH02144096
Kind Code:
U
Application Number:
JP5267289U
Publication Date:
December 06, 1990
Filing Date:
May 08, 1989
Export Citation:
International Classes:
E21B1/28; E21B1/00; E21B1/26; (IPC1-7): E21C3/22
Domestic Patent References:
| JP61075981B | ||||
| JPS5722543B2 | 1982-05-13 |