Abstract: A device for distributing oil under pressure including a head (2) within which, inside a chamber (24), a shuttle (5) slides provided with a shank (5a) sealingly sliding within an end cap (6) and on whose head surface (19) oil at the feed pressure acts coming from a switch duct (18). The head (2) is provided with a feed hole (8) connected to the chamber (24) and is closed at the other end by a shutter (7) connected to a drain hole (9), while the shuttle (5) is provided with an inner cavity (26) and end ducts (25) and it is shaped so as to have in the chamber (24) opposite transverse surfaces (22, 23) whose difference of area in favour of the surface (23) at the end where the shank (5a) is located is smaller than the area of the head (19) of the latter. A hydraulic hammer including the device is provided with a pair of outflow orifices (17, 20) located so that the first orifice (17) is uncovered by the ram (4) at the end of the return travel and the second orifice (20) at the end of the descending travel.

Abstract: A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.