| 摘要 |
PROBLEM TO BE SOLVED: To prevent concrete material force-fed by pump via piping from being separated and prevent coarse aggregate from falling preliminarily by providing a plurality of spherical bodies and an elastically deformable connecting body connecting the respective spherical bodies in a plunger inserted in the pipe in force-feeding the concrete. SOLUTION: A plunger 10 is constituted of two spherical bodies formed by molding hard rubber into a sphere and a coil spring connected thereto. In force-feeding concrete by pump, this plunger 10 is arranged in the tip of the concrete 20 in a concrete force-feed pipe 30 and moved in the concrete force-feed pipe 30. One spherical body 11 resists to the pressure of the concrete 20 without any deformation and the coil spring 12 is contracted so that the pressure of the concrete 20 is weakened and then transmitted to the other spherical body 11b. This constitution can suppress the pumping speed of the concrete 20 so as to prevent the materials of the concrete from being separated and the coarse aggregate from falling preliminarily.
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