GB1294901A - - Google Patents

Abstract

1294901 Automatic speed control A JOVIS 24 Jan 1970 3540/70 Heading G3R In a pile driving system the energy delivered at each stroke is controlled by maintaining constant the rate of action of the pile driver. By sensing the displacement of the pile at each stroke, the operation of the driver may also be automatically stopped when a certain driving resistence is achieved. In the system described, an accelerometer 11 secured to a pile produces a pulse at each stroke of the driver. These pulses produce a square wave output from a multivibrator 13, and this is converted by a low-pass filter 14 into a D.C. voltage proportional to the driving rate. The voltage is then compared with that from a reference 16 using a differential amplifier 15 whose output is connected to a throttle 17 on the pile driver, which may be operated by steam or compressed air. In this way, the rate of driver action is kept constant despite changes in resistance and bounce of the hammer, and as a consequence the imparted energy per stroke is also maintained constant. The pulses from the accelerometer 11 are also fed to two integrators 18,19, so that the output from the second of these gives a measure of the distance moved by the pile at each stroke. These distances are added for a number, say five, of successive strokes until a gate 24 causes the total distance to be compared with a reference 22 in a comparator 23. If the actual distance moved exceeds the reference, the circuits are reset and the procedure repeated for subsequent strokes. If, on the other hand, the actual distance falls below the reference, the comparator 23 operates to close throttle 17 and stop piling, see Fig.8 (not shown). The movement at each stroke may be recorded on a strip chart recorder 21, and the pile may be marked after each stroke, Figs.9,10 (not shown).