Abstract: A drilling arrangement is provided having a reciprocating piston hammer which hammers a drill bit for hydraulic down-the-hole piston hammer drilling. The drilling arrangement uses a liquid for driving the reciprocating piston hammer with respective impacting facing surfaces between the hammer and the drill. The respective impacting facing surfaces are formed such that at the moment of impact some of the liquid is forced between the impacting surfaces. This substantially reduces if not eliminating altogether the cavitation which might otherwise develop.

Abstract: A heat engine including a closed case having a cylindrical chamber with circumferential heat transfer surfaces in the form of radially projecting ribs. A displacer having complementary ribs around the outer surface is rotatably mounted within the chamber. Some of the displacer ribs are removed leaving a working space containing working fluid. A cylinder in the displacer opens into the working space and a piston reciprocates within the cylinder as the displacer rotates so as to alter the volume of the working space. Different parts of the circumference of the case are maintained at different temperatures during operation so that the working fluid is subjected to changes of temperature and pressure during operation. Apart from the basic sinusoidal movement of the piston a superimposing lower amplitude oscillation may be applied to provide control of the thermodynamic operating cycle.

Abstract: A heat exchanger for use with a source of heat in the form of a burner arrangement. The heat exchanger includes a relatively high flow resistance main passage for collecting combustion products from directly above the burner and a low flow resistance secondary passage opening forwardly of the main passage inlet and conveying any combustion products not collected by the main passage relatively directly to the flue. Flue downdraft principally affects flow in the secondary passage. The main passage may include a plurality of chambers to increase the heat exchange surface area. Water condensing in the main passage can be collected and drained to an evaporator rear the burner.

Abstract: A control system for heating installations which is responsive to a pre-selected target air temperature and a pre-selected radiant heat output.