Image Number 4 for United States Patent #5811741.
An apparatus for placing geophones beneath the surface of the earth includes a machine frame that supports an elongated probe rod. The probe rod is dimensioned to reach a selected subterranean earth layer. The rod has upper and lower end portions. A geophone holder is positioned at the lower end of the rod for holding a geophone and its cable. A plurality of drive wheels carried by the frame transport the rod between the upper and lower positions. The drive rollers include at least an opposed pair of upper wheels and an opposed pair of lower wheels. The wheels are loaded with an adjustable spring pusher so that extensive pressure can be applied from the drive wheels to the pipe for gripping and driving the pipe even when muddy. A gear train interconnects all of the driving wheels so that all of the wheels rotate at the same rotational speed. A gear train preferably includes six gears including a pair of upper gears, a pair of lower gears, and a pair of intermediate drive gears. The intermediate drive gears are intermeshed so that a single motor rotates one of the intermediate gears and thereby drives all six of the gears of the drive train.