| 摘要 |
An expandable and retractable conveyor system which comprises a main spiral-type tube conveyor which includes a cylindrical shell containing a screw element which is integral with the cylindrical shell and extends radially from said shell toward the center thereof and at least one additional spiral-type tube conveyor which includes a cylindrical shell containing a screw element which is integral with the cylindrical shell and extends radially from said shell toward the center thereof, said additional spiral-type tube conveyor being slightly smaller than the main spiral-type tube conveyor, with the screw element thereof being in screw-engaging relationship with the screw element of the main spiral-type tube conveyor. |
