U.S. patent number 3,683,470 [Application Number 05/102,609] was granted by the patent office on 1972-08-15 for sonic apparatus for drilling and stub setting.
Invention is credited to Charles C. Libby, Keith Likins, Robert C. McMaster.
United States Patent |
3,683,470 |
McMaster , et al. |
August 15, 1972 |
SONIC APPARATUS FOR DRILLING AND STUB SETTING
Abstract
This invention is a method and apparatus for facilitating the
driving and anchoring of a tool, bolt, or fastening device in a
refractory material or other material with the result that the
tool, bolt or fastening device is firmly fastened in the material.
Reference is made to the claims for a legal definition of the
invention.
Inventors: |
McMaster; Robert C. (Delaware,
OH), Libby; Charles C. (Columbus, OH), Likins; Keith
(Columbus, OH) |
Family
ID: |
26799556 |
Appl.
No.: |
05/102,609 |
Filed: |
December 30, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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819914 |
Apr 28, 1969 |
3588996 |
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Current U.S.
Class: |
29/33K;
228/111.5; 451/165; 156/73.1; 156/580.2; 228/245; 968/686; 29/432;
156/303.1; 227/67 |
Current CPC
Class: |
B24B
1/04 (20130101); G04D 3/0002 (20130101); B25C
1/06 (20130101); F16B 13/00 (20130101); Y10T
29/49833 (20150115); Y10T 29/5191 (20150115) |
Current International
Class: |
B24B
1/04 (20060101); B25C 1/00 (20060101); B25C
1/06 (20060101); F16B 13/00 (20060101); G04D
3/00 (20060101); B23p 011/00 () |
Field of
Search: |
;29/33R,432,525,470.3,402 ;227/67,68 ;408/700 ;156/73,580,303.1
;51/59SS |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Juhasz; Andrew R.
Assistant Examiner: Bilinsky; Z. R.
Parent Case Text
CROSS REFERENCES RELATED TO APPLICATIONS
Claims
What is claimed is:
1. A combination for drilling a hole in a refractory material and
anchoring the drilling tool therein comprising an electromechanical
transducer as a source of vibratory-mechanical energy, means for
positioning said transducer to produce oscillatory motion
substantially perpendicular to the surface of said refractory
material, a drilling tool for drilling said hole, means for
transferring said vibratory-mechanical energy to said drilling
tool, means for guiding said drilling tool, means for positioning a
metal alloy in said hole, and means for simultaneously applying
constant static force and vibratory-mechanical energy to said tool
causing high-velocity friction and causing mechanical hysteresis to
occur in said tool for a predetermined time thereby causing said
tool to heat and melt said metal alloy to anchor said tool in said
hole.
2. A combination as set forth in claim 1 wherein said drilling tool
is a tool having a substantially planar surface which contacts said
refractory material to be drilled.
3. A combination as set forth in claim 2 wherein said tool has an
upper threaded portion.
4. A combination as set forth in claim 2 wherein the cross section
of said planar surface perpendicular to the longitudinal axis of
said drilling tool is a preselected geometry.
5. A combination as set forth in claim 4 wherein said cross section
of said drilling tool is a circle.
6. A combination as set forth in claim 4 wherein said cross section
of said drilling tool is a rectangle.
7. A combination as set forth in claim 4 wherein said cross section
of said drilling tool is a triangle.
8. A combination as set forth in claim 4 wherein said cross section
of said drilling tool is a hexagon.
9. A combination as set forth in claim 4 wherein said cross section
of said drilling tool is a trapezoid.
10. A combination as set for in claim 4 wherein said cross section
of said drilling tool is irregular.
11. A combination as set forth in claim 2 wherein the longitudinal
cross section of said drilling tool is an inverted T shape.
12. A combination as set forth in claim 11 wherein a cylinder of
metal alloy is positioned over the upper portion of said inverted
T-shaped tool.
13. A combination as set forth in claim 1 wherein said means for
transferring said vibratory-mechanical energy to said drilling tool
is impact means.
14. A combination as set forth in claim 1 wherein said means for
guiding said drilling tool is a linear-motion bearing assembly.
15. A combination as set forth in claim 14 wherein said means for
guiding said drilling tool further comprises means for securing
said linear-motion bearing assembly to the node of said
electromechanical transducer.
16. A combination as set forth in claim 13 wherein said means for
transferring said vibratory-mechanical energy by said impact means
to said drilling tool further comprises positioning one end of said
drilling tool through the aperture of said linear-motion bearing
and against the transducer tip thereby constraining the motion of
said drilling tool to motion substantially colinear with that
motion produced at the tip of said electromechanical transducer.
Description
There is disclosed in U.S. Pat. No. 3,368,085, for "Sonic
Transducer" by Robert C. McMaster and Berndt B. Dettloff, a
resonant-structure transducer capable of delivering high power
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, for "Sonic Transducer Assembly" by Robert C. McMaster,
Charles C. Libby, and Keith Likins illustrates how the
aforementioned transducer may be adapted for use as a hand
tool.
There is further disclosed in U.S. Pat. No. 3,396,285, for
"Electromechanical Transducer" by Hildegard 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 underlying 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 aforementioned 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.
In the copending patent application, Ser. No. 713,035, filed Mar.
14, 1968, now U.S. Pat. No. 3,534,574 for "Hot Rolling and
Deformation of Metals Using Sonic Power," by Robert C. McMaster,
vibratory energy from an electromechanical sonic transducer is
applied to the work material. Vibratory energy is transmitted
efficiently through the material where the stresses resulting from
the vibrational energy are less than the elastic limit of the
material. Where the vibrational energy input from an
electromechanical sonic transducer creates stresses which exceed
the elastic limit of the material the vibrational energy is no
longer efficiently transmitted; rather, a large amount of the
vibrational energy is transformed into heat by mechanical
hysteresis. By this process enough heat can be generated to soften
steel and melt other metals and alloys.
In the copending patent application for "Sonic Transducer
Apparatus," Ser. No. 605,284, filed Dec. 28, 1966, now U.S. Pat.
No. 3,475,628 by Robert C. McMaster, Charles C. Libby, and
Hildegard M. Minchenko, there is disclosed means of utilizing the
aforementioned high-power, high Q electromechanical transducer in a
work environment. The apparatus consists of impact coupling the
high-power electromechanical transducer to a tool in a work
environment. The significant feature of the invention of the
last-mentioned patent application is that the tool does not form a
part of the transducer resonant structure. This feature permits the
transducer to develop full-power capability at its resonant
frequency.
BACKGROUND OF INVENTION, PRIOR ART
In the conventional type of refractory anchor several operations
are required to set an anchor. A standard anchor, for instance the
Rawl Sabor-tooth, requires the following operations to set: insert
sabor-tooth in chuck, drill sabor-tooth to proper depth, clean
sabor-tooth and hole, insert expander plug, re-insert sabor-tooth
assembly in hole, hammer till sabor-tooth anchor assumes proper
depth again, remove hammer, break off taper with sharp blow, eject
taper from chuck. This reasonably complicated procedure has eight
separate operations.
In conventional practice, lead is sometimes used to anchor bolts
into refractory materials. The bolt is merely placed into a hole in
the refractory and lead is cast into the hole. When the lead
solidifies, the anchor is well set. Lead, though, as certain
disadvantages because of its softness and can result in loosening
of the bolt should much vibration be present in the anchoring
system. Alloys that expand on cooling are useful for forming a
tight bond between a refractory material and an anchor set in said
refractory material. Low melting alloys of bismuth are useful in
this regard in that they expand on cooling.
SUMMARY OF INVENTION
The present invention is a process and apparatus which utilizes a
high-power electromechanical sonic or ultrasonic transducer to
provide vibratory-mechanical energy to drive a drilling tool (which
can be a simple bolt or stud) 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. Intermittent 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.
It is significant that the apparatus and process of the present
invention permits a hole to be drilled in refractory material with
a drilling tool that does not rotate. This feature of the present
invention enables holes of irregular shapes to be drilled in
refractory material. Holes of irregular shape are useful to solidly
anchor a stud or other implement in a refractory material by
causing a metal alloy to melt and surround the tool. This is due to
the fact that the irregular shape of the hole militates against the
anchor or stud turning.
After the drilling tool has bored into the refractory material to
the desired depth, the tool is removed and a metal alloy,
preferably a low-melting alloy such as a Bismuth alloy or a zinc
alloy, is inserted in the cavity. The drilling tool is positioned
against the metal alloy in the cavity, a constant static force is
then exerted on the transducer which is transmitted through the
transducer tip to the drilling tool, and the electromechanical
transducer is activated. The combination of the constant static
stress in the tool and the dynamic stresses created by the
vibratory-mechanical energy cause mechanical hysteresis to occur in
the tool thereby liberating heat in the tool. This phenomenon in
conjunction with frictional heating causes the metal alloy to at
least partially melt and the vibratory-mechanical energy agitates
the melted metal alloy as the applied constant static force
squeezes the drilling tool past the metal alloy to the bottom of
the hole. Agitation of the melted metal alloy due to the action of
the vibratory-mechanical energy transmitted to the alloy through
the drilling tool facilitates penetration of the melted metal alloy
into the interstices of the refractory material making an excellent
bond therewith. Further, any dust which remained in the hole from
the drilling operation is agitated and mixed with the melted metal
alloy thereby eliminating the deleterious "lubricating" effect
which the dust could have on the alloy-refractory or alloy-tool
interfaces. Removal of the electromechanical transducer from
contact with the drilling tool prevents further heating action and
allows the drilling tool to cool. Upon cooling, the solidification
and expansion (in the case of Bismuth alloys) of the melted alloy
firmly affixes the drilling tool in the refractory material.
OBJECTS
The present invention has for its principal object a system and
method for setting a stud in refractory materials.
Another object of the invention is to reduce the number of
operations necessary to set a stud in refractory materials.
Another object of the invention is to provide a system and method
to increase the speed and facility with which holes can be drilled
in refractory and other materials.
Another object of the invention is to provide a system and method
which may use any of a variety of implements of preselected
geometries as the working tool.
Another object of the invention is to provide a system and method
for sonically melting metal alloy to set a stud in a hole in
refractory materials.
A further object of the invention is to eliminate the need for
separate facilities for melting metal alloy.
Still another object of the invention is to provide a system and
method which will agitate melted metal alloy and facilitate
penetration thereof into the refractory making a secure
alloy-masonry bond.
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 illustrates the preferred embodiment of the masonry stud
setting device in position to drive a drilling tool, in this case
an ordinary hex head bolt, into a block of refractory material;
FIG. 2 illustrates the positioning of the planar surface of a
drilling tool, in this case an ordinary hex head bolt, head
positioned against the surface of a refractory material with an
electromechanical sonic or ultrasonic transducer assembly
positioned to drive the hex head bolt into the refractory material
thereby making a hole;
FIG. 2a illustrates the drilling tool, here an ordinary hex head
bolt, with a hollow cylinder of metal alloy fitted around its
shank;
FIG. 3 illustrates a drilling tool, here an ordinary hex head bolt,
driven into the refractory material to a desired depth;
FIG. 3a illustrates the drilling tool, here an ordinary hex head
bolt, having a hollow cylinder of metal alloy around its shank,
driven into the refractory material to the desired depth;
FIG. 4 illustrates a hollow cylinder of metal alloy placed in the
hole drilled using the drilling tool, here an ordinary hex head
bolt, and electromechanical transducer, the transducer positioned
to sonically excite the bolt, generate heat and melt the metal
alloy;
FIG. 5 illustrates the bolt set in the refractory after the metal
alloy has been sonically melted, sonically agitated, and
solidified;
FIG. 6 is an illustration of how the drilling rate varies with tool
length;
FIG. 7 is an illustration of the oscillatory action of various
elements of the sonic drilling system; and,
FIG. 8 illustrates the physical relationship of the elements of the
drilling system, not including the gross motion of the
transducer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring generally to FIG. 1 there is illustrated the preferred
embodiment of the present invention. The apparatus of the present
invention is used to effect a novel drilling and anchoring process
for securely affixing a stud or other implement in a refractory
material. The apparatus comprises an electromechanical transducer 1
which is supported by nodal supports 15 attached to the node point
16 of the electromechanical transducer 1. A linear-motion bearing
assembly 3 is securely attached to the structure 15. The assembly 3
is secured to the nodal support 15 by means comprising snap rings
17 attached to the linear-motion bearing assembly 3 and the nodal
support 15. A bushing 6 in the linear-motion bearing assembly 3 is
a guide for the drilling tool 4 which is shown positioned against
the refractory material 5 to be drilled.
Details concerning the electromechanical transducer utilized in the
present invention are disclosed in U.S. Pat. No. 3,368,085, for
"Sonic Transducer" by Robert C. McMaster, and Berndt B. Dettloff.
The adaptation of the sonic transducer for use as a hand-held tool
is facilitated by a shroud which is designed to enclose the
transducer, support the transducer, and eliminate any electrical
shock hazard associated with the transducer.
The electromechanical transducer 1 transforms an
alternating-polarity input current into mechanical energy, the
mechanical energy being concentrated at the tip of the
electromechanical transducer 1 and being manifested by motion
colinear with the axial direction of the transducer 1 (the axis
referred to is the axis of symmetry of the electromechanical
transducer 1). The energy so concentrated at the tip of the
electromechanical transducer 1 is, then, vibratory in nature. It is
this vibratory-mechanical energy transmitted from the tip of the
transducer 1 to the drilling tool 4, which is the energizing force
which drives the drilling tool 4, into the refractory material 5
thereby making a hole. The structure of the electromechanical
transducer is resonant, or nearly so, at the frequency of the
alternating-polarity input current. Of significance in the
operation of the electromechanical transducer 1 is the fact that no
direct coupling of the tip of the electromechanical transducer to
either the drilling tool 4 or to the refractory material 5 occurs.
There is substantial freedom of movement by the drilling tool
between the tip of the electromechanical transducer and the
refractory material 5. Accordingly, the drilling tool 4 and the
refractory material (workpiece) do not constitute added structure
to the electromechanical transducer 1 and, therefore, have no
effect on the resonant length and frequency of the
electromechanical transducer 1.
The bushing 6 of the linear-motion bearing assembly 3 is a guide
for the drilling tool 4. One end of the drilling tool 4 is fitted
through the cylindrical aperture in the bushing 6 of the
linear-motion bearing assembly 3; that end of the drilling tool 4
contacts the tip of the transducer. The drilling tool 4 and the
bushing 6 make a sliding fit. The sliding fit arrangement restrains
the drilling tool 4 from shifting position or canting. That is, the
linear-motion bearing assembly 3 constrains the movement of the
tool to movement coincidental with the axial movement of the tip of
the electromechanical transducer 1. Restraining the movement of the
drilling tool 4 to movement in the axial direction is very
important as this is a key factor in maintaining dimensional
accuracy while drilling a hole in refractory materials and other
materials. Restraining the drilling tool to axial movement prevents
the drilling tool 4 from "wandering."
In the system and method of the present invention it is significant
that the configurations of the drilling tool 4 that are most
efficient are those configurations which have a substantially
planar surface contacting the refractory material 5 to be drilled.
That is, the drilling tool 4 of the system of the present invention
operates much better with a drilling tool 4 that has blunt
(substantially planar) cutting surface as opposed to conventional
implements which are used for drilling refractory material. Most
conventional drilling implements have a pointed cutting surface or
a cutting edge which drills or cuts with a rotary motion. The
system and process of the present invention, however, is not
dependent on a drilling implement with a pointed cutting surface or
a cutting edge. Further, the drilling tool 4 of the system and the
process of the present invention does not even rotate.
Advantages may be derived from the last-mentioned feature of the
present invention. The fact that the drilling tool 4 need not
rotate in order to drill a hole in a refractory material enables
the system and process of the present invention to be used to bore
holes of irregular shapes in refractory material. For example,
holes can be drilled which have a perimeter geometry of not only a
circle but also a triangle, a rectangle, a hexagon, a trapezoid, or
any conceivable irregular shape. The drilling tool 4 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. In the case of the hex head bolt,
FIGS. 1 through 5 illustrate how a hex head bolt 4 can be
positioned to perform the drilling operation. The substantially
planar surface of the hex head bolt is positioned against the
refractory material 5 to be drilled, the threaded end of the hex
head bolt being fitted through the cylindrical aperture of the
bushing 6. In fact, the hex head bolt 4 makes a convenient and
inexpensive drilling tool 4 while doubling as a stud which can be
anchored in the refractory material 5. After a hole is drilled with
the hex head bolt 4 it is secured in the hole in the refractory
material 5 by melting and flowing (after removal of bolt 4 from the
hole) a metal alloy around the bolt 4. The hexagonally shaped hole
acts essentially as a wrench on the hex head of the hex head bolt
thereby militating against the hex head bolt turning in the
refractory material 5. This feature gives added utility and
permanence to a stud installation using the system and method of
the present invention. Of course, the invention is not limited to
anchoring a hex head bolt in refractory material. Other implements
of special design for performing specialty jobs can readily be
adapted for use with the system and method of the present
invention.
Examples of only a few of the manifold configurations which
specialty drilling tools or implements might take would be
implements for securing female threads in a refractory material,
securing a hanging hook in a refractory material, or securing any
implement in refractory material which is now secured using
conventional means. Further, the ability to drill irregularly
shaped holes with the system and process of the present invention
can be of importance in utilizing some specialty implement. An
irregularly shaped hole is, in and of itself, of utilitarian
significance for many applications.
In operation, the drilling tool 4 is fitted into the bushing 6 as
described hereinabove. The electromechanical transducer 1 and
drilling tool 4 are positioned over and substantially perpendicular
to the refractory material 5 to be drilled. The substantially
planar surface of the drilling tool 4 is positioned against the
refractory material 5 at the point to be drilled. A static force F
is exerted on the electromechanical transducer 1 at the node 16
thereof. This static force F is transmitted through the tip of the
structure of the electromechanical transducer 1 to the drilling
tool 4 thereby "trapping" the drilling tool 4 between the tip and
the refractory material 5. The end of the drilling tool 4 which is
fitted through the bushing 6 in in contact with the transducer tip.
When an alternating-polarity input current at the resonant
frequency of the electromechanical transducer 1 is fed into the
electromechanical transducer 1, the resulting vibratory-mechanical
energy concentrated at the tip of the electromechanical transducer
1 is transmitted to the drilling tool 4. The static force F which
was initially applied to the drilling tool 4 through the structure
of the electromechanical transducer 1 is relaxed momentarily after
the drilling tool 4 has become excited with the
vibratory-mechanical energy. Static force F is intermittently
applied to the drilling tool 4 through the electromechanical
transducer 1. Intermittent application of static force F increases
the rate at which a hole is drilled in refractory material 5.
After the drilling operation has been completed in accordance with
the aforedescribed apparatus and method or otherwise, the drilling
tool 4 or conventional drilling implement is removed from the hole.
Refractory particles remaining in the hole may be removed or not at
the option of the operator. It has been found that holes drilled
using the apparatus and method of the present invention contain few
particles and little dust as compared with the holes drilled with
conventional equipment. The vibratory-mechanical agitation of the
drilling tool 4 during the drilling operation utilizing the present
invention tends to expel the particles and dust from said hole.
Refer to FIG. 3 for an illustration of the elements of the
apparatus and their positions when the drilling operation has been
completed and prior to removal of the drilling tool 4 from the
hole.
With the apparatus as illustrated in FIG. 3, the drilling tool 4
must be removed from the hole. A metal alloy slug 13 is then placed
in the hole in the refractory material 5. The metal alloy slug 13
may be any alloy but is preferably an alloy of Bismuth, a metal
which expands on cooling. The metal alloy slug 13 may be either a
hollow cylinder as shown or may be solid or assume any convenient
geometry. The drilling tool 4 and electromechanical transducer 1
are positioned over the metal alloy slug 13, the substantially
planar surface of the drilling tool 4 contacting the metal alloy
slug 13. A constant static force is applied to the
electromechanical transducer 1 and thereby transmitted through the
tip of the electromechanical transducer 1 to the drilling tool 4.
The electromechanical transducer is activated by feeding an
alternating-polarity input current into the electromechanical
transducer 1 at its resonant frequency thereby generating
vibratory-mechanical energy manifested by axial motion at the tip
of the electromechanical transducer 1; the axial motion is
oscillatory in nature and substantially perpendicular to the
surface of the metal alloy 13. The vibratory-mechanical energy
generated by the electromechanical transducer 1 is transmitted to
the drilling tool 4 via the tip of the electromechanical transducer
1. The electromechanical energy so transmitted to the drilling tool
4 establishes dynamic stresses within the drilling tool 4.
Likewise, the constant static force applied to the
electromechanical transducer 1 and transmitted to the drilling tool
4 creates a constant stress level in the drilling tool 4. The
constant stress combines with the dynamic stress created in the
drilling tool 4 resulting in mechanical hysteresis and the
liberation of heat. Heat is also generated by high-velocity
friction attributable to the rapid cyclic acceleration of the tool
4 against the metal alloy 13 and the refractory material 5.
The constant stress and vibratory-mechanical energy are applied to
the drilling tool 4 for a sufficient time to allow enough heat to
build up in the drilling tool 4 to melt or partially melt the metal
alloy 13 with which the drilling tool 4 is in contact. When the
drilling tool 4 reaches the requisite temperature the metal alloy
13 in contact with the drilling tool 4 melts. The constant static
force which is applied to the electromechanical transducer 1 and
transmitted to the drilling tool 4 forces the drilling tool 4 past
the melted or partially melted metal alloy 13 until the drilling
tool 4 reaches the bottom of the hole. The melted or partially
melted metal alloy 13 is agitated by the vibratory-mechanical
energy which is applied to the drilling tool 4 and then transmitted
to the melted metal alloy 13. The agitation flows the melted or
partially melted metal alloy and mixes any residual dust in the
hole with the melted metal alloy 13. The agitation facilitates the
flow and penetration of the melted metal alloy 13 into the
interstices of the refractory material 5.
The electromechanical transducer 1 is removed from contact with the
drilling tool 4 leaving the drilling tool 4 in place surrounded by
the melted metal alloy 13. Upon removal of the constant static
force and the source of the vibratory-mechanical energy the
electromechanical transducer 1, mechanical hysteresis,
high-velocity friction, and, hence, the liberation of heat in the
drilling tool 4 ceases to occur. This allows the melted metal alloy
13 to cool and solidify thereby solidly locking the drilling tool 4
in place. Reference is made to FIG. 5 which illustrates the
drilling tool 4 secured in the refractory material 5.
The same result, anchoring a drilling tool 4 in a refractory
material 5, may be achieved by an alternative method. Reference is
made to FIG. 2a where a hollow cylindrical slug 13 of low-melting
alloy 13 is shown positioned over the upper portion of an inverted
T-shaped drilling tool 4, a common hex head bolt 4. The metal alloy
may be cast about the drilling tool 4 or may be so positioned by
using a prefabricated hollow cylinder making a press fit or a
sliding fit with the drilling tool 4. By using the drilling tool 4,
13, as illustrated in FIG. 2a, the need for removing the drilling
tool 4, 13 after the drilling operation has produced a hole in the
refractory material 5 of the desired depth is eliminated. FIG. 3a
illustrates a hole which has been completed using the drilling tool
4, 13 illustrated in FIG. 2a. The drilling operation is
accomplished as in the first-described method by applying an
intermittent static force to the electromechanical transducer 1 and
transmitting the intermittent static force to the drilling tool 4.
Simultaneously, the electromechanical transducer 1 is excited by an
alternating-polarity current which produces vibratory-mechanical
energy in the electromechanical transducer 1, the
vibratory-mechanical energy likewise being transmitted to the
drilling tool 4.
Since the metal alloy 13 is already in position in the hole when
the drilling tool 4, 13 of FIGS. 2a and 3a is used to drill a hole
in refractory material 5, it is not necessary to remove the
drilling tool 4, 13 from the completed hole in order to complete
the anchoring operation. Once the hole has been drilled to the
desired depth as illustrated in FIG. 3a, constant static force is
applied to the electromechanical transducer 1 in lieu of the
intermittent static force. Replacing the intermittent static force
used in the drilling operation with the constant static force
causes the resultant constant stress created in the drilling tool
4, 13, to be combined with the dynamic stresses in the drilling
tool 4,13. This combination of stresses produces mechanical
hysteresis thereby liberating heat in the tool 4, 13. The heat
generated in the drilling tool 4, 13 by the mechanical hysteresis
and by high-velocity friction melts the metal alloy 13 which
surrounds the drilling tool 4. The metal alloy 13 is melted or
partially melted and agitated by the vibratory-mechanical energy
which flows the melted metal alloy 13 and facilitates penetration
of the metal alloy 13 into the interstices of the refractory
material 5. The electromechanical transducer 1 is then removed from
contact with the drilling tool 4 leaving the drilling tool 4 in its
position in the hole. With the removal of the constant static
stress and the source of vibratory-mechanical energy, the
electromechanical transducer 1, heat ceases to be liberated in the
drilling tool 4. Hence, the melted metal alloy 13 is allowed to
cool and solidify thereby locking the drilling tool 4 securely in
the hole in the refractory material 5. Reference is made to FIG. 5
for an illustration of the drilling tool 4 permanently secured in
the hole in the refractory material 5 after the melted or partially
melted metal alloy 13 has solidified upon cooling. The end result
as illustrated in FIG. 5 is the same for either of the described
methods of melting and flowing the metal alloy 13 around the
drilling tool 4 to affix the drilling tool 4 securely in the
hole.
It should be noted that the foregoing description has referred to
drilling and setting an anchor, stud, or other implement in a
refractory material. In order to utilize the method of melting the
metal alloy 13 as aforedescribed, the drilling tool 4 or implement
must be set in a material of a refractory nature, i.e., a material
that does not absorb a substantial amount of heat. Materials which
are not of a refractory nature act as heat sinks and prevent the
metal alloy from attaining its melting point. It should be noted
that with appropriate modifications, the present invention can be
used for other applications such as to facilitate the driving of
nails into hard wood by generating heat and thereby burning or
charring said wood in lieu of drilling a pilot hole.
The drilling operation of the present invention is analogous to the
drilling operations performed with conventional apparatus and
processes. An analogy may be drawn between the present invention
and a conventional pneumatic hammer for breaking pavement or to a
common hammer for manually impacting a star-drill to penetrate a
refractory material such as a masonry wall. In the case of the
hammer and star-drill, the star-drill is impacted with a single
blow per cycle of motion of said hammer. Each time the star-drill
is impacted by the hammer the refractory material is in turn
impacted by the star-drill. In the system of the present invention
the tip of the electromechanical transducer 1 and the axial motion
thereof is analogous to the conventional hammer and the cycle of
motion of said hammer, respectively. Distinctive of the process for
drilling with the system of the present invention is the fact that
the "hammer" or electromechanical transducer 1 tip does not strike
the work a single blow per cycle of motion of the electromechanical
transducer 1 tip. Further, while the cycle of motion of a
conventional hammer may be readily measurable in inches, the cycle
of axial motion of the electromechanical transducer 1 tip measures
only about 0.0035 inch at a typical resonant frequency of
approximately 10,000 cycles per second. During the drilling process
of the present invention the drilling tool 4 is impacted at a rate
of up to 10,000 blows per second for brief intervals.
The energy of the hammer and star-drill system is the gross motion
of the hammer as supplied by the craftsman holding and swinging the
hammer. The system and method of the present invention utilizes
electrical energy to produce axial motion at the tip of the
electromechanical transducer 1 which is the source of mechanical
energy used for driving the drilling tool 4 of the present
invention into the refractory material 5. The drilling process of
the present invention is essentially a "spring-mass" system
comprising the oscillatory (gross) motion of the transducer mass 1,
the mass of its supporting structure 15, enclosure, and the
drilling tool 4. The "spring" of the spring-mass system is the
resilient action of the impacted drilling tool 4 as it rapidly
oscillates in free flight between the resonant electromechanical
transducer 1 tip and the refractory material surface 5. Since
static force is intermittently applied to the electromechanical
transducer 1, the drilling tool 4 is not in contact with the tip of
the electromechanical transducer 1 for relatively long periods of
time. That is, while the tip of the electromechanical transducer 1
typically strikes said drilling tool 4 approximately 50 times per
second, the drilling tool 4 spends a greater period of time in free
flight between the tip of the electromechanical transducer 1 and
the refractory material 5 surface than it does in contact with the
tip.
Hereinabove, in conjunction with the drilling operation, the
drilling tool 4 was "trapped" between the electromechanical
transducer 1 tip and the refractory material 5 to be drilled. The
trapping of the drilling tool 4 between the electromechanical
transducer 1 is important in achieving proper drilling action. The
drilling action consists of the manner in which the drilling tool 4
performs work on the refractory material 5. The drilling tool 4
moves between the refractory material 5 and the tip of the
electromechanical transducer 1. The forward and return motion is
taken up by the drilling tool 4. That is, the drilling tool 4
bounces back and forth within the confined region with each impact.
The impacts of the drilling tool 4 relative to the refractory
material 5 do not necessarily occur with each forward movement of
the tip of the electromechanical transducer 1. The relative motion
between the drilling tool 4 and the tip of said electromechanical
transducer 1 may occur (1) due to the compression of the drilling
tool 4 at the instant of the impact or (2) due to this compression
plus a gross motion of the mass of the drilling tool 4. In either
case the motion of the drilling tool 4 causes the drilling tool 4
to disconnect from the tip of the electromechanical transducer 1.
Referring again to the drilling action, there are several motions
occurring at different frequencies. Certain of the motions are
intermittent; some motions are vibratory or oscillatory in nature,
a gross movement of the drilling tool 4 (all molecules of a
structure moving together) being detectable; and, some motions of
the drilling tool 4 are of a resonant type, nodes being observable
(parts of the structure not in motion). These various motions are
all closely interrelated and derive their energy from a single
source, the electromechanical transducer 1.
FIG. 8 schematically illustrates the physical relationship of the
various elements of the present invention. As shown in FIG. 8,
distance 14 is the total displacement of the tip of the
electromechanical transducer 1 during each cycle of axial motion at
the resonant frequency of the transducer 1. Distances 11 and 12 are
equal and represent the displacement of the drilling tool 4 while
the drilling tool 4 is in free flight. When static force is applied
to the electromechanical transducer 1 making the tip of the
electromechanical transducer 1 contact the drilling tool 4 thereby
driving the drilling tool 4 against the refractory material 5, an
"interference" between the drilling tool 4 and the tip of the
electromechanical transducer 1 occurs. That is, the drilling tool 4
is in contact with the refractory material and the tip of the
electromechanical transducer 1 is in contact with the drilling tool
4. This interference initiates and sustains the aforementioned
spring-mass oscillatory motion of the system of the present
invention. That is, the vibratory energy of the electromechanical
transducer 1 initiates the spring-mass oscillatory motion when the
drilling tool 4 initially interferes with the electromechanical
transducer 1 tip motion. The spring-mass oscillatory motion is
maintained by periodic interference which occurs at the extreme
downward (toward the refractory material 5) position of the tip of
the electromechanical transducer and when intermittent static force
is being applied to the electromechanical transducer 1, thereby
forcing the electromechanical transducer 1 tip into momentary
intimate contact with the drilling tool 4.
Resonant vibration is initiated in the drilling tool 4 itself. The
resonant vibration is caused by the periodic pulses of high
frequency impacts (up to 10,000 per second) with the tip of the
electromechanical transducer 1. The periodic pulses occur once each
cycle of gross motion of the electromechanical transducer 1. It has
been found that the resonant frequency of the electromechanical
transducer 1. The periodic pulses occur once each cycle of gross
motion of the electromechanical transducer 1. It has been found
that the resonant frequency of the drilling tool 4 is at least four
times that of the electromechanical transducer 1 for typical
lengths of the drilling tool 4. The resonant vibration of the
drilling tool 4 probably lasts little longer than the brief
interval of 10-KC impacts between the drilling tool 4 and the tip
of the electromechanical transducer 1 (in the case of 10-KC
electromechanical transducer).
FIG. 7 illustrates data from measurements of a typical drilling
cycle indicating that, in the case of a 10-KC electromechanical
transducer 1, the drilling tool 5 is impacted at a rate varying
from 3.5-KC to 10-KC during approximately one-third of a cycle of
oscillation 9 of the spring-mass system, or 1/150 second in a 50
cps oscillation. During the other two-thirds of the cycle, the
drilling tool 4 is not impacted by the tip of the electromechanical
transducer 1.
Referring again to FIG. 7, it can be seen that there is illustrated
the frequencies of the various elements of the present invention.
FIG. 7, Section A, illustrates the gross motion of the
electromechanical transducer 1 and supporting structure as measured
at the node 16 or the supporting structure 15 of the
electromechanical transducer 1. This gross motion is related to the
motion associated with the application of the intermittent static
force to the electromechanical transducer 1 during the operation of
the transducer during the drilling process. FIG. 7, Section B,
illustrates the axial motion of the tip of the electromechanical
transducer 1 as superimposed on the gross motion of the
electromechanical transducer 1 and its supporting structure 2 (see
FIG. 7, Section A). FIG. 7, Section C, illustrates the period
during which the drilling tool 4 is impacted. The drilling tool 4
is impacted during approximately one-third of the gross motion
oscillatory cycle of said electromechanical transducer 1 as
illustrated by the distance 9 in the figure. This impacting occurs
at a rate of approximately 10-KC when the drilling tool 4 is forced
against the tip of the electromechanical transducer 1 and the
refractory material 5. As illustrated, contact occurs approximately
one-third of the time and no contact occurs two-thirds of the time,
the period during which the drilling tool 4 is in free flight.
It has been found that the drilling rate using the system and
method of the present invention varies with the dimensions of the
drilling tool 4. It has been found that variation in the dimensions
of the drilling tool 4 can have a substantial effect on the gross
motion of the drilling tool 4. Alteration of the gross motion of
the drilling tool 4 in turn affects the number of times the
drilling tool 4 strikes the refractory material 5 per second. In
the drilling process of the present invention, the length of the
drilling tool 4 affects the resonant frequency of the drilling tool
4. This affects the drilling rates by as much as 3:1. This is
attributable to the vibration of the drilling tool which effects
removal of dust from the hole as it is being drilled in the
refractory material 5. Reference is made to FIG. 6 which
illustrates the manner with which the drilling rate varies with
tool length.
Differences between conventional drilling tools and processes and
the system and process of the present invention involve the nature
of the respective tool geometries and the nature or form of the
material removed during the drilling operation. The following table
illustrates the difference between the conventional drilling
operations and the system and process of the present invention:
Conventional Drilling Electromechanical Drilling 1. Sharp ended
tools. Flat or planar tools. 2. Chips and dust formed. Powder
formed. 3. Chips and dust tend to Powder usually ejected remain in
hole. from hole. 4. Tool length of little signi- Tool length
affects ficance. drilling rate.
Although certain and specific embodiments of the present invention
have been illustrated, modifications may be made to said invention
to perform related functions without departing from the true spirit
and scope thereof.
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