Document Type and Number:
Japanese Patent JPS5031731
Kind Code:
B1
Application Number:
JP663269A
Publication Date:
October 14, 1975
Filing Date:
January 31, 1969
Export Citation:
International Classes:
E01H1/08; E01H1/00; (IPC1-7): E01H1/00
Foreign References:
| US2529993A | 1950-11-14 | |||
| US3007191A | 1961-11-07 |