| 摘要 |
1,139,728. Earth-grading equipment. UNITED AIRCRAFT CORP. 17 March, 1967 [25 March, 1966, 28 Dec., 1966], No. 12650/67. Heading E1F. [Also in Divisions G1 and G3] The speed of travel of an earth scraping machine is maintained at a set value by comparison of the actual speed, from a tachogenerator 22, with a reference and using any error to adjust the depth of cut. The error is derived as a D.C. voltage whose magnitude and polarity controls a hydraulic or cable and winch actuator 40. In one embodiment (Fig. 3, not shown) the gain of the system is increased with increasing quantity of earth loaded by applying the error signal to a "compensator" circuit (82) responsive to a measurement of the load. The "compensator" , also adds a differential of error term to the proportional error signal. The load is in any case measured and when the bowl 12 is full an alarm is sounded and the scraper is fully raised. The load may be determined by measurement of the pressure in the lower half of the hydraulic actuator 40, (Fig. 4; not shown), or by a strain gauge in the supporting cable if used (Fig. 5 not shown), or is derived by integrating a measurement of the rate of loading, this measurement being effected by energising a depth' of cut transducer 43 connected to a skid or wheel with the output of the or another tachogenerator. This measuring system may be A.C. or D.C., the depth of cut transducer may be a linear potentiometer or movable core transformer, and the rate of loading itself displayed on an electrical instrument. The "full load" point is set as a reference signal which is automatically reduced if the machine is on a cross gradient by a damped pendulum operated potentiometer (48). |
