| 摘要 |
999,950. Trench excavators. W. EBERHARDT, D. EBERHARDT, A. EBERHARDT, I. M. CLARK and S. H. SCOTTWATSON (Legal representatives of R. E. Eberhardt). Oct. 31, 1961 [Nov. 10, 1960], No. 38998/61. Addition to 910,818. Heading E1F. The electrical control circuits of the trench excavator of the referred to parent Specification are modified by the incorporation in each relay circuit for operating an associated valve controlling an hydraulic jack of the jack system positioning the boom to datum lines of an electronic impulse control unit 42a, 42b whereby the direct current for energizing the relay of the associated valve is transmitted to the relay as being of a predetermined characteristic form created over a given period of time in order to prevent surging and shunting of the hydraulic jack system of the excavator. |
