A dual paver is composed of the tractors of a pair of typical single pavers, the tractors being linked in spaced side-by-side relation and fitted across their rear with a single-screed assembly of the floating type. Two types of the screed assembly are shown, one, an elongated rigid screed formed from the two individual screeds and a special rigid center section with a central crowning mechanism, and the other a "split" screed, also formed from the two individual screeds but with a center section made up of two standard screed extensions resiliently secured to each other. The controls of each tractor are tied into a dual control console mounted on one tractor so that both can be conjointly operated as a unit. Various applications of automatic screed-leveling devices are also disclosed in combination with both types of screed assemblies.
A mobile paving machine which may, with minor modification, be employed either to distribute material along the path of movement of the machine or in a region which is laterally offset to one side of the motion path. In order to spread material in a laterally offset region, which may correspond to a break-down lane being formed along the side of a travel lane, a tiltable secondary skip is installed above the primary skip to which paving material is normally supplied. A scraper is mounted from an extension of the distribution beam of the machine to controllably disperse material discharged through an end of the secondary skip when the loaded secondary skip is angularly inclined to cause gravity induced flow of material into the lateral region.
Two feed conveyors and two spreader augers are independently driven, each by its own drive motor. The control means for each feed conveyor includes a sensor at the discharge end of the feed conveyor and means responsive to changes in the level of the paving material at the sensor for proportionally increasing the drive speed of the conveyor as the level drops and proportionally decreasing the drive speed of the conveyor as the level rises. The control means for each auger includes a sensor adjacent the discharge end of the auger and means responsive to changes in the level of the paving material at the sensor for proportionally increasing the drive speed of the auger as the level drops and proportionally decreasing the drive speed of the auger as the level rises.
Two feed conveyors and two spreader augers are independently driven, each by its own drive motor. The control means for each feed conveyor includes a sensor at the discharge end of the feed conveyor and means responsive to changes in the level of the paving material at the sensor for proportionally increasing the drive speed of the conveyor as the level drops and proportionally decreasing the drive speed of the conveyor as the level rises. The control means for each auger includes a sensor adjacent the discharge end of the auger and means responsive to changes in the level of the paving material at the sensor for proportionally increasing the drive speed of the auger as the level drops and proportionally decreasing the drive speed of the auger as the level rises. The paving material compartment, which includes the feed conveyors and spreader augers, is enclosed. Fumes are pumped out from the enclosed feed path and into a pollution control device.
A self-propelled apparatus and method are disclosed for screeding placed and/or poured, uncured concrete or like loose, spreadable materials without use of prepositioned guides or rails. The apparatus includes a frame supported on hydraulically drive, steerable wheels, a cantilevered boom mounted on the frame, and a hydraulically driven, auger-type, vibratory screed either fixedly mounted or mounted for movement along the boom to spread and smooth the concrete as the screed is moved toward the vehicle. Screed control means are included for automatically adjusting the elevation of the screed relative to a laser beacon reference plane positioned off the apparatus such that the finished height of the concrete or other material is controlled within close tolerances. Preferably, the boom is rotatably mounted on the frame and also may be extended and retracted to properly position the screed and ease movement of the vehicle around fixed obstacles. The boom may also be pivoted vertically for screeding sloped surfaces. The method includes propelling the vehicle through uncured concrete or like material while screeding behind the vehicle. Also encompassed is the method of screeding by moving the screed toward the vehicle at a controlled rate.
An apparatus and method are disclosed for pivoting a screed assembly during screeding of placed and/or poured, uncured concrete or like loose, spreadable materials to maintain proper screeding contact by the screeding assembly with the concrete or like material by counteracting the force of concrete or other like material acting against the screed assembly as it is moved along the concrete. The apparatus includes a support, preferably of the self-propelled type, a boom and boom mount, and a pivot between the boom and the screed assembly. The axis of the pivot extends generally perpendicularly to the screeding direction in which the screed sassmblyis moved. A power source, such as a pair of fluid cylinders, rotates the screed about the pivot axis, preferably in response to an electro-hydraulic leveling sensor mounted on the screed. The lateral incline of the screed perpendicular to the screeding direction may be controlled about additional pivot axes orthogonal to the first. A power operated elevation control is preferably responsive to a fixed laser beam reference plane positioned externally of the screed assembly. The boom is telescoping and has multiple sections for extending and retracting the screeding assembly with respect to the support. The screed preferably includes a vibration assembly vibrationally isolated from the remainder of the screed for smoothing the concrete.
