An ultrasonic sensor control unit for a road finishing machine for generating a height control signal for a vertically adjustable beam, the ultrasonic sensor control unit including at least three ultrasonic sensors which are arranged at a considerable distance from the beam in the direction of motion of the road finishing machine. The ultrasonic sensor signals determine the distances between each ultrasonic sensor and a reference surface, the values which lie more than a predetermined distance outside of a plane which is determined by the measuring points associated with the other distances being rejected as faulty measurement. On the basis of the height signals, the mutual distances of the sensors, and the distance between a sensor and the rear edge of the beam, the evaluation means calculates the projected height at the rear edge of the beam. This height is compared with a selectable desired thickness value. The evaluation means controls the tie points of the beam so that an adequate layer thickness will be created.

A sonic grade control device for maintaining a leveling instrument of a paver at a constant distance from a datum. The device transmits and receives a sonic signal to provide first and second time periods corresponding to the round trip travel time of a sonic signal to the datum and a target, respectively. A distance indicating signal, corresponding to the distance between the control device and the datum, is provided in response to the first and second time periods and a stored target distance, such target distance corresponding to the distance between the control device and the target. The grade control device includes an operator actuable control for modifying the stored target distance to calibrate the control device. A reference signal is compared to the distance indicating signal to provide a control signal. The reference signal is adjustable by a predetermined increment and the control device includes an operator actuable control for modifying the predetermined increment. The position of the leveling instrument is changed in response to the control signal being greater than a predetermined, or deadband value. The control device includes a display for indicating such predetermined value and an operator actuable control for modifying such value.

Apparatus for controlling the cutting depth of a road grooving machine by vertical adjustment of both the front and rear travelling gear on the basis of a cutting depth control signal, which is generated by a tracer ski by sampling a reference plane, including at least three ultrasonic sensors arranged one behind the other in the direction of movement of the cutter, and an evaluation means for determining the distances between the ultrasonic sensors and a reference plane to derive therefrom an inclination signal as well as an averaged distance signal. The evaluation means controls the height of the two travelling gears such that the average distance of the cutter drum as well as the position of the machine relative to the reference plane are adjusted.

A roller is equipped with a pair of crawlers. Each crawler includes a driving wheel detachably attached to a driving shaft. Each crawler also includes a set of driven wheels. Both sets of driven wheels are supported by a connecting member that is detachably attached on a bottom of a body. A roll, which is vibrated only in the perpendicular direction with respect to the ground surface, is attached to the body.

An attachment device for laying two surface layers which may also consist of different materials in a road way. The device should be economical to produce and suitable for laying multilayer road surfaces or for simply laying a conventional single layer surface. To this end, the inventive attachment contains elements for simultaneously laying two layers, hot on hot. The elements are mounted on a frame to be detachably connected to the finisher, the frame having fixing points for detachably connecting the attachment and the finisher and the attachment and the driver's cab.