As shown in Figure 2, the piston corer is prepared in the sea, and when it is lowered to the seafloor, the mud sampling part is detached from the balance trigger and thrust into the seafloor surface. Figure 7 shows the sequence of this operation.
As the piston corer set on the balance is lowered to the seafloor, the pilot weight reaches the bottom before the mud sampling section (Figure 7-①). When the pilot weight is unloaded, the balance trigger is activated, and the mud sampler is free-fallen toward the seafloor (Figure 7-2). Eventually, the mud sampling pipe reaches the seafloor surface and begins to penetrate, while the piston remains near the seafloor surface. This is because the length of the main wire is adjusted so that the piston is positioned just above the seafloor (Figure 7-3). (Figure 7-3). The piston rises relative to the mud sampler as the mud sampler tube penetrates into the seafloor, generating a suction force that does not destroy the sedimentary layer. The weight of the mud sampler and this suction force cause the mud sampling pipe to penetrate into the seafloor (Figure 7-④). The winch is slowly wound up and the mud sampling pipe is pulled out from the seafloor (Figure 7-5). The suction force generated by the piston acts as a lid for the mud sampling pipe, preventing the sample from falling out during lifting.
The sequence of operations shown in Figure 7 is shown in Figure 8 as an animated sequence. In actual operation, the penetration of the sampling tube is completed within a few seconds after the start of free fall.
