The new type of core retainer described here uses two in ternal curved gates cut from cylindrical sections. The radius of curvature of the gates is identical to the inside diameter of the sampling tube. Small levers connect from gates to an external sliding sleeve that moves up and down on the outside of the cutting head attachment. The external sleeve remains in its up-position during penetration and the internal curve gates are held open.
Sanders, John E.. 1962. "A new internal curved-gate core retainer." Journal of Marine Research 20, (3). https://elischolar.library.yale.edu/journal_of_marine_research/988