US 3672454 A
A means for improving the drilling rate of sonic and ultrasonic drills. Specifically, a sonic transducer, a tool, and a mechanical spring are used in combination to increase the amplitude of gross motion of the tool to better remove the particles and dust taken from the work surface. Reference is made to the claims for a legal definition of the invention.
Claims available in
Description (OCR text may contain errors)
United States Patent Likins 51 June 27, 1972 [541 SONIC TOOL APPARATUS  Inventor: Keith L. Likins, Columbus, Ohio  Assignee: The Ohio State University, Columbus,
 Filed: June 13, 1969  App]. No.: 833,131
 US. Cl ..175/56, 173/132  Int. Cl ..B06b l/02  Field ofSearch ..l75/56,203,2l1, 122;
 References Cited UNITED STATES PATENTS 3,485,307 12/1969 Riley et al "173/117 895,228 8/1908 Bartlett ..l75/2l l X 1,124,605 l/1915 2,774,193 12/1956 2,991,838 7/1961 3,194,326 7/1965 Primary Examiner-Marvin A. Champion Assistant Examiner-Richard E. Favreau Attorney-Anthony D. Cennamo [5 7] ABSTRACT A means for improving the drilling rate of sonic and ultrasonic drills. Specifically, a sonic transducer, a tool, and a mechanical spring are used in combination to increase the amplitude of gross motion of the tool to better remove the particles and dust taken from the work surface. Reference is made to the claims for a legal definition of the invention.
7 Claims, 2 Drawing Figures PATENTEnJum m2 3, 72 ,454
KEITH LIKINS ATTORNEY INVENTOR.
SONIC TOOL APPARATUS CROSS REFERENCES RELATES TO APPLICATIONS There is disclosed in US Pat. No. 3,368,085, for Sonic Transducer" by Robert C. McMaster and Bemdt B. Dettloff, a resonant-structure transducer capable of delivering highpower energy in an acoustical range. This transducer provides a continuous high mechanical output with an exceptionally high efficiency of energy transformation. The transducer is rugged, very simple in design, and capable of repetitive manufacture. Further, the transducer is readily adaptable for use as a hand tool. The disclosure of patent application, Ser. No. 713,031, filed May 20, 1968, now Ser. No. 14,777, filed Feb. 27, 1970, as a continuation application for Sonic Transducer Assembly by Robert C. McMaster, Charles C. Libby, and Keith Likins illustrates how the aforementioned transducer may be used as a hand tool.
There is further disclosed in US. Pat. No. 3,396,285, for Electromechanical Transducer" by I-Iildegard M. Minchenko, a resonant structure transducer capable of delivering extremely high power, i.e., measurable in horsepower (or kilowatts) at an acoustical frequency range. The principle un derlying the high-power output is in the structural arrangement of the components immediately associated with the piezoelectric driving elements. In theory and practice the piezoelectric elements are under radial and axial pressure that assure that they do not operate in tension even under intense sonic action. Significantly, the structural design of this transducer, that permits the extraordinary power output from the driving elements, resides in the novel method of clamping the piezoelectric elements both radially and longitudinally (axially). In this way the acoustic stresses in the piezoelectric elements are always compressive, never tensile, even under maximum voltage excitation.
The transducer disclosed in the last mentioned patent is intended, and therefore utilized, to deliver a steady state signal. That is, the piezoelectric assembly is a component of a resonant structure that will produce a mechanical vibratory output at the frequency of the driving electrical signal and vice versa.
There is disclosed in US. Pat. No. 3,475,628 impact means for efficiently coupling a high-power transducer, such as that aforementioned, to drive a load, i.e., to drive a tool in a work environment. The tool does not become a part of the transducer resonant structure, thereby permitting the transducer to develop full power capability at its resonant frequency. This is accomplished by maintaining a nonrestrictive intermittent engagement of the tool to the workpiece at a rate less than the frequency of the resonant structure, thereby permitting freedom of movement between said transducer and the workpiece.
Stated in another way, the tool is not fastened, such as by welding or threading, to the transducer tip. In theory there may be no coupling just free space; in actual practice, however, the tool is secured" to the transducer to restrict the lateral motion. There is no restriction between the tool and transducer.
It is seen, therefore, that this patent teaches a manner of coupling the tool to a transducer wherein there is intermittent impact therebetween there is not a continuous contact.
BACKGROUND A high-power electromechanical sonic or ultrasonic transducer can be utilized to provide vibratory-mechanical energy to drive a drilling tool into a refractory material. The electromechanical transducer transforms electrical energy into vibratory-mechanical energy manifested by motion at the tip of the transducer in the axial direction. lnterrnittent static force applied to the transducer is transmitted to the drilling tool through the tip of the transducer. In this way the intermittent static force in conjunction with the vibratory-mechanical energy concentrated at the tip of the transducer causes the refractory material under the drilling tool to be fractured and pulverized. Since the movement of the drilling tool is restrained to movement in the axial direction which is substantially perpendicular to the surface of the refractory material, only the refractory material directly under the tool is pulverized thereby enabling the tool to drill straight into the refractory material.
SUMlvlARY The present invention relates to a means for improving the drilling rate of a high-power, high-frequency electromechanical transducer. The drilling rate of such a transducer is greatly influenced by the presence of chips, particles, and pulverized material in the hole which is being drilled.
A spring is utilized to move the drilling tool away from the surface of the work material after every impact with the work surface. This has the effect of removing the particles and dust from the drilled hole. By eliminating the buildup of waste material from the hole, the'drilling rate with the transducer is substantially increased.
OBJECTS Accordingly it is a principal object of the present invention to provide an improved electromagnetic transducer drilling apparatus.
A further object of the invention is to provide an electromagnetic transducer drilling apparatus which removes the particles and dust from the drilled hole.
Still another object of the invention is to provide an electromagnetic transducer drilling apparatus which has a substantially improved drilling rate.
For a complete understanding of the invention, together with other objects and advantages thereof, reference may be made to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of the preferred embodiment of the invention having the spring retaining means fixedly attached to the tool; and,
FIG. 2 is a diagrammatic illustration of the preferred embodiment of FIG. 1 illustrating the spring fully extended and the tool removed from the work surface.
DETAILED DESCRIPTION OF THE DRAWINGS Referring now to FIG. 1 there is illustrated the preferred embodiment of the invention. The preferred embodiment consists of an electromechanical transducer 2 to which is attached a tool retainer 4. Secured in the tool retainer 4 is the tool 8 which is utilized to drill into the refractory material 12. The retainer 4 does not fixedly attach the tool 8 to the transducer tip 2 and may be of a configuration of any one of the embodiments shown in the aforementioned US. Pat. No. 3,475,628. In other words, the tool 8 is impact coupled to the transducer tip; the number of impacts with the tool being less than that of the resonant frequency of the transducer.
The electromechanical transducer 2 transforms an alternating-polarity input current into mechanical energy, the mechanical energy being concentrated at the tip of the electromechanical transducer 2 and being manifested by motion colinear with the axial direction of the transducer 2 (the axis referred to is the axis of symmetry of the electromechanical transducer 2). The energy so concentrated at the tip of the electromechanical transducer 2). The energy so concentrated at the tip of the electromechanical transducer 2 is, then vibratory in nature. It is this vibratory-mechanical energy transmitted from the tip of the transducer 2 to the drilling tool 8, which is the energizing force which drives the drilling tool 8 into the refractory material 12 thereby making a hole.
The electromechanical transducer 2 and drilling tool 8 are positioned over and substantially perpendicular to the refractory material 12 to be drilled. The tip of the drilling tool 8 is positioned against the refractory material 12 at the point to be drilled. A static force F is applied to the transducer 2 in the direction shown in the figures. This static force F is transmitted through the tip of the structure of the electromechanical transducer 2 to the drilling tool 8.
When an alternating-polarity input current at the resonant frequency of the electromechanical transducer 2 is fed into the electromechanical transducer 2, the resulting vibratorymechanical energy concentrated at the tip of the electromechanical transducer 2 is transmitted to the drilling tool 8. The static force F which was initially applied to the drilling tool 8 through the structure of the electromechanical transducer 2 is relaxed momentarily after the drilling tool 8 has become excited with the vibratory-mechanical energy. Static force F is intermittently applied to the drilling tool 8 through the electromechanical transducer 2. Intermittent application of static force F increases the rate at which a hole is drilled in refractory material 12.
The operation described above produces a quantity of particles and dust in the hole being drilled. This waste material greatly impedes the drilling of a hole by the use of vibratorymechanical energy. Removal of this waste material substantially increases the rate at which the hole is drilled.
As pointed out above, the number of impacts between the transducer and the tool is less than the resonant frequency. The actual number of impacts is dependent on the tool, the workpiece material, the material of the tool, etc., and as pointed out in U.S. Pat. No. 3,485,307, is the spring rate ofthe tool. Simply, how well does it bounce back.
It was found that with certain materials, i.e., lead or masonry, the spring rate is very poor. Therefore, with the application of a static force and a poor spring rate there would result an almost continuous contact. This, of course, defeats the principle of U.S. Pat. No. 3,475,628.
The improvement disclosed in this application operates to facilitate the removal of the waste material. Referring again to FIG. I there is shown attached to the drilling tool 8 a retaining means 6. In the constructed embodiment of the invention the drilling tool 8 comprised a standard commercial twist drill and the retaining means 6 was a washer which had been braised to the drill. The drilling tool 8 is not to be limited to a standard twist drill. The drilling too] 8 may, in fact, consist of an ordinary hex head bolt, a screw, or any other implement having a substantially planar surface which can be utilized as the cutting surface.
To improve the spring rate, i.e., the rate of return of the tool 8 to the transducer 2 after each impact, there is located between the retaining means 6 and the refractory surface 12 a spring 10. The spring surrounds the drilling tool 8. The spring 10 works to apply a vertical force F against the apparatus after each impact between the tool and the transducer 6 in a direction that is opposite the static force F. In operation when the intermittently impact is relaxed the spring is also allowed to relax which pushes the retaining means 6 away from the refractory surface 12. This causes the drilling tool 8 to be removed away from the bottom of the hole drilled as shown in FIG. 2.
This impact (application of static force F) removal (relaxation of static force F) cycle is repeated at an optimum rate which may be determined for each different combination of tool 8 and refractory material 12. When the tool 8 is removed from the hole (see FIG. 2) it brings with it substantially all the particles and dust that resulted from the previous impact. This makes the impact more effective and the total result is a greatly increased rate of drilling in a highly efficient system.
Generally an increase in the quantity of static force F is required to compensate for the presence of the spring 10 in order to optimize the drilling rate. However, in the experimental embodiment an increase of approximately two to one was achieved without any increase in the static force F.
Although certain and specific embodiments have been illustrated, it is to be understood that modifications may be made without departing from the true spirit and scope of the invention.
What is claimed is:
1. In combination with a resonant high-power, high Q electromechanical transducer, as a source of vibratory-mechanical energy, and a workpiece, the improvement of a tool for impacting said workpiece, means for nonrestrictive intermittent impact coupling of said tool to said transducer at a rate less than the frequency of the resonant structure; means for applying static force to said tool in a direction collinear with the longitudinal axis of said transducer, said tool in turn impacting said workpiece during the time said static force is applied, and at an impact rate less than the frequency of said resonant transducer, and means for mechanically removing said tool from said workpiece after each impact between said tool and said workpiece.
2. A combination as set forth in claim 1 wherein said resonant transducer includes a horn having a point of maximum amplitude, and wherein said intermittent contact between said tool and said transducer is at said point of maximum amplitude.
3. A combination as set forth in claim 1 wherein said tool is a drilling tool having a substantially planar surface which contacts said workpiece.
4. A combination as set forth in claim 1 wherein said coupling means comprises a chuck.
S. A combination as set forth in claim 1 wherein said mechanical removal means comprises a spring and means to retain said spring, said spring positioned around said tool and between said spring retaining means and said workpiece.
6. A combination as set forth in claim 5 wherein said spring retaining means comprises a substantially planar disc.
7. A combination as set forth in claim 6 wherein said disc is fixedly attached to said tool with said discs planar surface parallel to the surface of said workpiece.