Automatic control of elevator height in scraper with manual setting and

Abstract

An elevating type scraper for earth moving purposes having an open-fronted bowl with rear supporting wheels and with a scraper blade at the front of the bowl. The bowl is pivotally supported on a pair of draft members forming a part of a tractor-supported draft frame. A bowl hoist actuator interposed between the draft frame and the front end of the bowl determines the degree of tilt of the bowl and hence the depth of cut of the blade. An elevator of the endless conveyor type is positioned at the front end of the bowl in sweeping engagement with the undisturbed ground and inclined upwardly and rearwardly so that the soil loosened by the blade is conveyed into the bowl. The elevator is mounted on the bowl for upward and downward swinging movement and is supported in operating position by an elevator-supporting actuator. For engaging the actuator, a bracket at the front of the elevator frame provides a point of connection, and the actuator extends upwardly and rearwardly from the tractor draft frame to such point of connection, so that when fluid is locked in the actuator the elevator is maintained at a desired sweeping height automatically and in spite of changes in degree of tilt of the bowl and depth cut of the blade. Means including a control valve are provided for the elevator supporting actuator for creating a closed loop between the ends of the actuator for establishing a 'free float' condition in which the elevator is free to rise and fall upon encountering an obstruction. The valve means further includes a check valve in the loop to establish an alternative 'checked float' condition in which the elevator can rise to meet an obstruction but in which the elevator is temporarily held in such operating position until intentionally lowered.