Abstract: A tamperproof cap assembly for a hydrant having a valve stem rod which in one embodiment is displaceable in elevation within the hydrant housing without rotation of the valve stem rod about its axis. The assembly includes a cap adapted to cover the outlet port in the hydrant housing. The cap is provided with a stem. A locking means secured to the valve stem rod engages the cap stem when the valve stem rod is in a first position and the cap stem is displaced toward the valve stem rod. The locking means releases the cap stem when the valve stem rod is displaced in elevation from the first position to a second position without rotation of the valve stem rod about its axis. The cap is provided with a pair of unthreaded facing annular walls which define an annular channel for receiving the hydrant nozzle.

Abstract: A tamperproof hydrant lock with a controlled shock absorber. Power transmitting means are mounted on an operating rod extending within a chamber in the hydrant housing. A spring is mounted between the power transmitting means and the hydrant housing. First and second hydraulic means operatively associated with the power transmitting means control gradual opening and closing of the hydrant valve over first and second delay intervals of time respectively.

Abstract: A tamperproof lock for a fire hydrant. A spring is mounted at one end on the fire hydrant housing. Power transmitting means are mounted on a threaded operating rod extending within the housing chamber. The power transmitting means transmit power to the threaded rod against the spring. A swivel plate is freely mounted on the power transmitting means for rotational movement thereon. The swivel plate has a contoured hub portion adapted to fit within an aperture within the fire hydrant bonnet. The hub portion is exposed to the exterior of the bonnet. Power means for applying power substantially along the axis of the threaded rod to move the rod against the spring are removably mounted on the bonnet. Means for preventing axial and rotational movement of the power means is pivotably connected thereto by means of a double pivot joint.