Abstract: A crown-like structure sits atop a chimney or smokestack as a specially formed chimney cap wherein passing air is required to take a somewhat convoluted path, providing a Bernoulli effect to improve smoke emission draft. Like at least two of its predecessors, the crown has two roof-like canopies, one within the other, each having a series of curved, bent strips separated to permit the wind-flow to pass through. As a departure from the past, the number of sets of strips, or leaves, within each canopy is raised to optimize performance, the preferred number thereof being three.

Abstract: In a high temperature seal between a closure member and a rim with interengaging hard metal rings, the ring on the rim rests on a conical shoulder and the underside of the ring is complimentary shaped, so that as the shoulder expands circumferentially the ring slides down the conical surface and remains bedded on the shoulder.

Abstract: A machine for cutting a slot in hard rock uses a percussive drill to slot the rock, the drill being so mounted that the tool has an obtuse angle to the base of the slot in the direction of advance, which angle is for optimum effect between 120.degree. and 145.degree. and preferably between 130.degree. and 140.degree.. The drill is oscillated and cuts on the forward stroke and free wheels on the return stroke. The drill may be adjusted to vary the angle and the angle of inclination to the horizontal.

Abstract: A rock boring machine of the kind consisting of a rotatable headplate on the front face of which is mounted a plurality of rotatable disc cutters, each disc cutter comprising an annular body, a plurality of cutting segments located on and substantially encircling the annular body around the periphery thereof, and removable clamping means for securing the cutting segments to the annular body. Each cutting segment is provided with a suitable formation adapted to engage with a complemental formation on the annular body to prevent peripheral movement of the segments around the annular body.

Abstract: A rock-boring machine of the type comprising a rotatable headplate having a plurality of disc cutting units mounted on the front face of the headplate. Each disc cutting unit includes an annular rotatable body having a continuous recess extending around its periphery and a plurality of cutting segments located in the recess. The segments are secured in the recess by means of removable clamping means.