A. Kermabon; Note on an article by Andre M. Rosfelder entitled 'A tubular spring valve used as a tight and thin-walled core retainer' 1966. Journal of Sedimentary Research ; 38 (2): 688. doi: https://doi.org/10.2110/jsr.38.688
Kermabon expresses his doubts that strong torque is not needed in the valve described by Rosfelder (ibid., v. 36, no. 4, p. 973-976, 1966). To be useful and economical, the "sphincter' type core catchers must be used to close in rather compact layers when, consequently, a rather large amount of energy is required. To operate properly, the lever system used by Rosfelder must be surrounded by sediments presenting some comparison.