| 摘要 |
<p>A conveyor assembly (10) includes an endless conveyor (16) having ends supported by a drive drum/ sprocket (12) and an idler drum/sprocket (14) mounted on respective portions of a split conveyor frame. The frame portions (24, 26) are movable with respect to each other. Dual tensioning cylinders (28, 30) control the movement of the portions and thus the tensioning force acting on the conveyor (10). A hydraulic circuit (40) for the tensioning cylinders (28, 30) provides a first level of tensioning force to said conveyor upon initial start-up of the conveyor apparatus (10) and a second reduced level of tensioning force after a predetermined time. The first level of tensioning force is sufficient to overcome the breakaway friction between the frame portions (24, 26) while the second level of tensioning force is sufficient for proper and sustained tension during normal operation of the conveyor. A time delay control valve (60) in the circuit includes a movable valve element (72) actuable by a differential hydraulic force through a combination of restrictive orifices (81, 82), an accumulator (84), a return spring (68) and operating faces (88). <IMAGE></p> |
