EXPANSION AND CONTRACTION TYPE STEEL TUBE PROP FOR OUTDOOR MEGAPHONE SLAVE STATION INSTALLATION OF MUNICIPALITY DISASTER-PREVENTIVE ADMINISTRATION RADIO SYSTEM

摘要

PROBLEM TO BE SOLVED: To save the space for transportation, to save the space for storage, and to make assembling operation simple and safe as to the installation of the steel tube prop used for the outdoor megaphone slave station of the municipality disaster- preventive administration radio system. SOLUTION: This prop consists of steel tube props which are combined in a multistage nesting state. The outermost steel tube prop 1 has a projection 4a on its inner peripheral side, and the intermediate steel tube prop 2 has a vertically extending groove 2 in its outer peripheral part and also has a projection groove 2 projecting to the right and left nearby its lower end. Further, this prop has a projection at the upper part of the inner peripheral part of the vertical groove 2 as well as the outermost steel tube prop. To extend the prop, the intermediate steel tube prop 2 is drawn out and rotated to the right or left where the projection 4a of the external steel tube prop 1 comes to the same position in the extension groove 2c and the projection 4a of the external steel tube prop 1 is engaged with the projection groove 2c of the intermediate steel tube prop 2 and fixed.