Screw with filler-receiving head

Claim 1

A lock member in combination with a screw-type fastener having a threaded shank and a head integral therewith, and adapted to be driven into a structure by axial rotation about its longitudinal central axis in a driving direction such that the head is countersunk, said head being formed with at least two ribs protruding from the surface of the head thereof and extending radially outward from said central axis, said ribs defining a corresponding number of sector-shaped cavities adapted to receive means for engaging said ribs so as to prevent said fastener from axially rotating in a direction opposite said driving direction and to thereby secure said fastener against loosening, wherein said lock member comprises a resilient plate element having on a side thereof facing the structure into which said fastener is driven at least two sector-shaped protuberances arranged in spaced-apart relationship to define a corresponding number of channels adapted to receive the ribs of the head of said fastener with said sector-shaped protuberances fitting into said sector-shaped cavities of said fastener head thereby forming said means for engaging said ribs for locking said fastener in place, and a single pivot means for securing said plate element to said structure, said plate element being sufficiently resilient to permit said plate element to be first bent in a direction away from said structure and clearing said channels and then rotated laterally about said pivot means to allow access to said fastener, and permitting reengagement with said channels by the resilient force exerted by said plate element.