Key lock cylinder for possibly contaminated environments

A cylinder lock of the rotatable disc tumbler type provided with contaminant accommodating spaces to minimize foreign matter contaminant jamming of relatively movable lock components for use in contaminated environment installations and the like, comprising a stationary lock casing member having a cylindrical cavity therein for accommodating a rotatable core assembly, a rotatable cylinder lock core assembly in said cavity including a tubular cylindrical shell member rotatable in the cavity and having a hollow bore closed by a rear wall, a plurality of rotary locking disc tumblers with a spacer member interposed between each pair of disc tumblers forming a stacked array of tumblers and spacers encircled within said shell member and rotatable about a common axis therein, an elongated locking bar partially lying in a slot in said shell member arranged parallel to the axis of rotation of said disc tumblers adjacent the periphery thereof normally restrained by the disc tumblers in a position traversing the shear line between the shell member and the casing for locking the shell member against rotation relative to the casing, the disc tumblers being formed with substantially circular body portions having gate recesses of appropriate depth aligned with and adapted to receive the locking bar to accommodate radial inward movement of the locking bar relative to the disc tumblers to positions rotation of the shell member relative to the casing and said tumblers having key openings therein collectively defining a forwardly opening keyway and shaped to be engaged and angularly moved by a key having substantially semicircular cross-section portions inserted therein for aligning the gate recesses with the locking bar, said spacer members having a cylindrical center opening therethrough of predetermined larger radius than the radius of the substantially semicircular key portions providing space therebetween for accommodation of foreign matter contaminants and the spacer members having a substantially circumferentially spaced outer peripheral formation to bear against the walls of said hollow bore and having periphery portions therebetween spaced from the walls of said hollow bore providing foreign matter contaminant accommodating spaces.