Abstract: A rotary drill bit for use in drilling holes in subsurface earth formations comprises a bit body having a shank at one end for connection to a drill string and an operating end face at the other end. A plurality of first cutting structures, each comprising a preform cutting element, is mounted in the bit body at the end face thereof, and each has a superhard front cutting face. The bit body includes a plurality of protuberances projecting outwardly from the adjacent portions of the end face, the protuberances forming a plurality of second cutting structures disposed in generally trailing relation, respectively, to at least some of the first cutting structures. Each of the protuberances is impregnated with superhard particles through a significant depth measured from the outermost extremity of the protuberance.

Abstract: A pneumatically operated impact drilling tool for earth drilling, includes a reciprocating hammer, an anvil positioned under the hammer and a feeder tube extending through the hammer. The drilling tool is connected to a string of drilling pipe and high pressure compressed air or other pneumatic fluid is introduced to operate the tool. The feeder tube directs the flow of fluid through ports in the hammer to alternate pressure on opposite sides of the hammer to move the same upward and downward relative to the anvil. An elastomeric check valve is positioned inside the upper end of the feeder tube. The air inlet end of the tube is also provided with air jet passages extending upward and outwardly and having check valves operated in the outflow direction. A flow controlling washer may also be provided at the inlet to the check valve in the feeder tube.

Abstract: A pneumatically operated impact drilling tool for earth drilling, includes a reciprocating hammer, an anvil positioned under the hammer and a feeder tube extending through the hammer and at least partially through the anvil. The drilling tool is connected to a string of drilling pipe and high pressure compressed air or other pneumatic fluid is introduced to operate the tool. The feeder directs the flow of fluid through ports in the hammer to alternate pressure on opposite sides of the hammer to move the same upward and downward relative to the anvil. A venturi arrangement in the feeder tube functions to produce a vacuum which is applied to the opposite end of the hammer from the end at which pressure is being applied for moving the same.

Abstract: In one type of pneumatic percussion drilling tool, the pneumatic motor has an anvil-bit which is slidable in the forward end of the motor casing between a normal working position and an abnormal advanced position when the tool is hanging off bottom and the pneumatic fluid is caused to bypass the hammer-piston and blow continuously through the anvil-bit. In order to prevent tapping or chattering of the hammer-piston at such time, as a result of leakage of the pneumatic fluid into the forward working chamber, this chamber is vented by means of one or more passages formed in the surface of the anvil-bit member which are open while the tool is blowing and which are closed in the normal operating position of the anvil-bit member. Since the passages are only in the surface of the anvil-bit member, the structure eliminates the need for special configurations of parts to provide interconnecting recesses and passages as in certain of the prior art.