Abstract: A mechanism for locking a cover to a housing of medium and high speed laboratory centrifuges. The locking mechanism includes an axially moveable locking member which has at least one locking portion adapted to be moved in locking engagement with a locking hole of the cover. The axially moveable locking member is rotatably mounted in the housing and connected with a rotary drive. An advancing mechanism transforms the rotary movement of the locking member into an advancing movement thereof. Preferably said advancing mechanism includes a threaded portion provided on the locking member and in engagement with a projection provided on the housing. The locking member has a portion of reduced cross section which may pass through a slot into the locking hole when the cover is moved to its closed position.