Abstract: A helmet is constructed with a hard surfaced, limitedly flexible shell lined with an energy absorbing material having an inner conforming liner adapted to the shape of the head or skull of a wearer for maximum comfort and safety. There may also be provided a transfer layer on the interior surface of the energy absorbing liner and formed of a flexible layer of incompressible fluid for dispersing impact forces.

Abstract: A precision machine vise having fixed and movable jaws, the movable jaw being actuated by a traveling nut having a lug which extends into a recess formed in the movable jaw. The lug and movable jaw having opposed force-transmitting surfaces which are angled downwardly and which have a preloaded spring interposed between them so that force is resiliently applied both to a work piece between the jaws and to the horizontal way surfaces which support the movable jaw. The spring provides slight articulation of the movable jaw with respect to the traveling nut permitting self-alignment of the jaw with the engaged surface of the work piece. The spring, because of its preload, causes the movable jaw to bear resiliently against the horizontal way surfaces even prior to engagement of the work piece. The preloaded spring serves, in addition, to preclude any play between the lug and the movable jaw or any looseness in the drive system which might develop during the life of the device.