Compact, Non-Pneumatic Rock-Powder Samplers
- Thursday, 26 June 2008
Tool bits for ultrasonic/sonic drill/corers are modified to trap small particles.
Tool bits that automatically collect powdered rock, permafrost, or other hard material generated in repeated hammering action have been invented. These tool bits are intended primarily for use as parts of ultrasonic/sonic drill corers (USDCs) and related apparatuses, which have been reported in numerous prior NASA Tech Briefs articles. A USDC is based on the concept of a miniature, lightweight, low-power, piezoelectrically driven hammering mechanism that is excited with a combination of ultrasonic and sonic vibrations that enable its tool bit to bore into rock or other hard, brittle material with very little applied force. There are numerous potential applications for such apparatuses in geological exploration on Earth and on remote planets. Typically, in such an exploration, the purpose served by a USDC is to cut samples of fragmented rock from one or more depth(s).
The present invention pertains to the special case in which it is desired to collect samples in powder form for analysis by x-ray diffraction and possibly other techniques. In one prior approach, rock fragments generated by a USDC or other apparatus were first collected by some independent means, then placed into a chamber in the same or a different USDC or USDC-like apparatus, wherein the fragments were crushed into powder. In another prior approach, powder generated at the cutting face of a USDC tool bit was blown into a collection chamber by a pulse of pressurized gas. The present invention eliminates the need for both the mechanical collection equipment and the crushing chamber of the first-mentioned prior approach and the pneumatic collection equipment of the second-mentioned prior approach, so that it becomes possible to make the overall sample-acquisition apparatus more compact.
A tool bit according to the present invention (see figure) is hollow and includes holes at or near its cutting tip. Some of the powder kicked up during cutting enters the interior of the tool through the holes. To make the tool more effective in trapping the powder that enters, the holes are tapered (e.g., stepped as in the figure, or else conical), with narrow openings leading to wider inside holes. The narrow openings prevent the entry of wider rock fragments. The collected powder is retained in the tool until needed for analysis. To dispense the powder for analysis, the USDC actuator is simply turned on to shake the powder out through the holes into a suitable receptacle. Experiments have shown that the powdered rock generated by use of a tool bit of this type has essentially the same particle-size distribution, suitable for x-ray diffraction studies, as does powdered rock generated by a commercially available laboratory rock-crushing mill.