Abstract: A rotary hammer which comprises a tool holder (2), an air cushion hammering mechanism which comprises a piston (9) and a beat piece (21) slideably located in a cylinder (8′) so that reciprocation of the piston in the cylinder will cause the beat piece to hit a tool located in the tool holder; and means for causing the cylinder to rotate in addition to, or instead of, reciprocation of the piston in order to cause a tool located in the tool holder to rotate. The piston (9) is formed from a plastics material and is sealed in the cylinder (8′) by means of an annular seal (27) that is located within an annular groove (26) in the piston. The annular seal has an inner diameter that is greater than the diameter of the radially outwardly directed surface of the groove, and the groove has an axial dimension that is greater than that of the annular seal, so that when the cylinder rotates about the piston (without reciprocation of the piston) the seal (26) will rotate with the cylinder (8′).

Abstract: A rotary hammer which comprises a tool holder (2), an air cushion hammering mechanism which comprises a piston (9) and a beat piece (21) slideably located in a cylinder (8′) so that reciprocation of the piston in the cylinder will cause the beat piece to hit a tool located in the tool holder; and means for causing the cylinder to rotate in addition to, or instead of, reciprocation of the piston in order to cause a tool located in the tool holder to rotate. The piston (9) is formed from a plastics material and is sealed in the cylinder (8′) by an annular seal (27) that is located within an annular groove (26) in the piston. The annular seal has an inner diameter that is greater than the diameter of the radially outwardly directed surface of the groove, and the groove has an axial dimension that is greater than that of the annular seal, so that when the cylinder rotates about the piston (without reciprocation of the piston) the seal (26) will rotate with the cylinder (8′).

Abstract: A system for removal of oxides of nitrogen from the waste gas produced by various combustion processes discloses thoroughly mixing the waste gas with ammonia by means of a static mixing element and then passing the resultant mixture through a catalytic reactor. The ammonia may be supplied by reacting a portion of the waste gas with natural gas in the presence of a catalyst.

Abstract: A system for removal of oxides of nitrogen from the waste gas produced by various combustion processes discloses thoroughly mixing the waste gas with ammonia by means of a static mixing element and then passing the resultant mixture through a catalytic reactor. The ammonia may be supplied by reacting a portion of the waste gas with natural gas in the presence of a catalyst.

Abstract: A method and system for neutralizing various toxic and explosive gases, described particularly with respect to those gases which escape during the drilling of oil and gas wells, including heating the gases to reacting temperature, desulfurizing the gases with a suitable catalyst, and reacting hydrocarbon gases to form inert gases. In one embodiment exhaust gases from existing energy sources are utilized to accomplish heating and these gases are also rendered inert. A means is also disclosed for disposing of large volumes of natural gas produced in "kicks" during the drilling of oil wells.