Abstract: A lock mechanism for a rotatable stub such as the operating shaft of a fluid flow control valve has a main body 10 connected to a drive member 12 adapted for mounting on the rotatable stub. A locking sleeve 17 is adapted to fit closely to the machine (e.g. valve) on which the mechanism is fitted so as to be held against rotation, and mounted in the body are two key-operated lock members 25 engageable with the sleeve 17 to lock the body against rotation. Associated with each lock member 25 is a control plate 56, movement of which can be blocked by a stop member 53 so preventing operation of the associated lock member 25. The two stop members 53 are threaded on studs 55 fixed in the body 10, and are moved linearly on being rotated by respective toothed wheels 46, driven by a peg 62 on sleeve 17 as the body 10 is rotated.

Abstract: A security device for a rotatable member of a machine element, such as the spindle or nut of a fluid-flow control valve, to prevent the unauthorized operation thereof. A turning member having a cylindrical surface is fitted to the valve spindle and a shroud is rotatably mounted on the member, the shroud having lugs which engage parts of the valve to prevent rotation of the shroud when the device is fitted to the valve. Projections upstand from the cylindrical surface and the turning member can be operated only by a key able to fit within the shroud and over the cylindrical surface, with recesses appropriately positioned to accommodate the projections, such that torque can be imparted to the turning member through the interengagement of at least one projection with a wall of the key defining the associated recess.A locking device including a pin spring-urged out of a bore in the base of the shroud may engage an appropriate recess in the turning member, further to enhance security.