The figure depicts selected aspects of the rapid and quiet drill (RAQD), which is a prototype apparatus for drilling concrete or bricks. The design and basic principle of operation of the RAQD overlap, in several respects, with those of ultrasonic/sonic drilling and coring apparatuses described in a number of previous NASA Tech Briefs articles. The main difference is that whereas the actuation scheme of the prior apparatuses is partly ultrasonic and partly sonic, the actuation scheme of the RAQD is purely ultrasonic. Hence, even though the RAQD generates considerable sound, it is characterized as quiet because most or all of the sound is above the frequency range of human hearing.
The ultrasonic transducer in the RAQD consists of a stack of piezoelectric disks, their electrodes, and a backing layer, all held in compression by a bolt that also holds them in place on a horn. During operation, the piezoelectric stack is driven at a frequency of 24.8 kHz. A drill bit is attached to the horn by means of a simple threaded connection: for this purpose, the proximal end of the drill bit is threaded and widened, and the thread on the drill bit matches the thread in a hole on the tip of the horn. The drill bit is tipped with a crown having a cutting edge (which could be toothed) chosen to suit the specific application. The crown is attached to the bolt by brazing and, hence, can be replaced when it is worn out. The bolt, horn, drill bit, and crown are all hollow so that, optionally, air can be blown through them to remove dust from the drilled hole.
This work was done by Stewart Sherrit, Mircea Badescu, Yoseph Bar-Cohen, Zensheu Chang, and Xiaoqi Bao of Caltech for NASA's Jet Propulsion Laboratory.
This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, NASA Management Office–JPL. Refer to NPO-42131.