PILE DRIVER

PROBLEM TO BE SOLVED: To provide a rack pinion type pile driver for allowing a work device (an auger) having multistage pinion gears in the vertical direction to be easily removed from a leader.SOLUTION: In a pile driver 1, in the state that upper-, middle- and lower-stage pinion gears 61L-63R engage with a rack gear 22, operating oil is supplied into upper-, middle- and lower-stage brake flow paths 84a, 84b, 84c to cancel the rotation restriction of hydraulic motors 71L-73R by negative brakes 91L-93R. With the operating oil supplied to lifting-side flow paths 81a, 81b, 81c formed between a hydraulic pump 74 and each of the hydraulic motors, an auger 30 can be lifted up relative to a leader 20. In a hydraulic circuit of the pile driver 1, the brake flow paths are formed out of which the upper-stage brake flow path 84a and the middle-stage brake flow path 84b excluding the lower-stage brake flow path 84c are provided with an upper-stage open/closed cock 85a and a middle-stage open/closed cock 85b for restricting the flow of the operating oil with the operation of a worker.