U.S. patent application number 13/854440 was filed with the patent office on 2014-09-18 for ballistic polycrystalline mining tool and method for making the same.
This patent application is currently assigned to Guilin Color Engineered Diamond Technology (EDT) Co., LTD. The applicant listed for this patent is Ashwin B. CHOKSI, Chen HONGYAO, Navin Chandra PARSANA. Invention is credited to Ashwin B. CHOKSI, Chen HONGYAO, Navin Chandra PARSANA.
Application Number | 20140262541 13/854440 |
Document ID | / |
Family ID | 51500900 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140262541 |
Kind Code |
A1 |
PARSANA; Navin Chandra ; et
al. |
September 18, 2014 |
BALLISTIC POLYCRYSTALLINE MINING TOOL AND METHOD FOR MAKING THE
SAME
Abstract
A cutting element for a mining or drilling tool provides a body
that provides a recess for receiving a ballistic insert. The
ballistic insert provides a top portion having a shape
characterized by a first radius (R1) and a second radius (R2), and
R1 and R2 have a tangential relationship. A sleeve may be
positioned on the body to protect the body from erosion.
Inventors: |
PARSANA; Navin Chandra;
(Mumbai, IN) ; CHOKSI; Ashwin B.; (Mumbai, IN)
; HONGYAO; Chen; (Guilin, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PARSANA; Navin Chandra
CHOKSI; Ashwin B.
HONGYAO; Chen |
Mumbai
Mumbai
Guilin |
|
IN
IN
CN |
|
|
Assignee: |
Guilin Color Engineered Diamond
Technology (EDT) Co., LTD
Guilin
CN
|
Family ID: |
51500900 |
Appl. No.: |
13/854440 |
Filed: |
April 1, 2013 |
Current U.S.
Class: |
175/428 |
Current CPC
Class: |
E21C 35/1837 20200501;
E21C 35/183 20130101; E21B 10/567 20130101 |
Class at
Publication: |
175/428 |
International
Class: |
E21B 10/567 20060101
E21B010/567 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2013 |
CN |
201310078101.6 |
Claims
1. A cutting element for mining a formation, the cutting element
comprising: a ballistic insert that provides a top portion
comprising a first section forming a tip of the ballistic insert
and a second section below said first section, wherein the first
section has a shape characterized by a first radius (R1), the
second section has a shape characterized by a second radius (R2),
and R1 and R2 have a tangential relationship, and a bottom portion
supporting the top portion.
2. The cutting element of claim 1, further comprising a body
providing a recess for receiving said ballistic insert.
3. The cutting element of claim 2, further comprising a sleeve that
is positioned on the body, wherein the sleeve protects the body
from erosion.
4. The cutting element of claim 2, wherein the body is steel.
5. The cutting element of claim 1, wherein the ballistic insert is
solid body comprising a mixture of polycrystalline diamond (PCD)
and cubic boron nitride (CBN).
6. The cutting element of claim 1, wherein the ballistic insert is
polycrystalline diamond (PCD), cubic boron nitride (CBN), cobalt,
carbide, tungsten, or a combination thereof.
7. The cutting element of claim 1, wherein the top portion of said
ballistic insert is polycrystalline diamond (PCD), cubic boron
nitride (CBN), or a combination thereof.
8. The cutting element of claim 1, wherein the bottom portion of
said ballistic insert is a carbide substrate.
9. The cutting element of claim 3, wherein the sleeve is a
carbide.
10. The cutting element of claim 1, wherein a tip of the top
portion of said ballistic insert provides a concave apex.
11. The cutting element of claim 1, wherein R2 is between 0.02 to
0.30 inches or 0.5 to 7.6 mm.
12. The cutting element of claim 1, wherein R1 is between 1.2 to 10
inches or 30.5 to 254 mm.
13. The cutting element of claim 1, wherein a ratio of R1 to R2
(R1/R2) is equal to or greater than 18.
14. The cutting element of claim 1, wherein the ballistic insert
provides one or more depressions for receiving an insert.
15. The cutting element of claim 2, wherein the body provides one
or more openings for receiving an insert.
16. The cutting element of claim 1, wherein a height of said top
portion is equal to or greater than 1 inch.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of Chinese Patent
Application No. 201310078101.6, filed on Mar. 12, 2013 which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a mining tool and method. More
particularly, to a mining tool or method that utilizes
polycrystalline cutting elements.
BACKGROUND OF INVENTION
[0003] Cutting elements are used in earth boring bits or the like
for drilling and excavating earth formations. Degradation of
cutting structure during the excavation process often leads to down
time of expensive machinery used in underground mining or road
repair applications. Consequently, extension of life of cutting
structures is very important to performance of mining tools. U.S.
Pat. Nos. 6,102,486 and 4,944,559 describe body of tool that have
as steel body in which hard material such as cemented carbide
cutting structure is embedded. Attempts to apply super hard
material such as polycrystalline diamond on the cutting tip is
described in U.S. Pat. No. 8,136,887 on a substantially conical
surface with aside forming a 35 to 55 degree angle with the central
axis of the tool and having apex of 0.050 to 0.125 inch radius.
[0004] The performance of such super hard conical tools has had
limited viability since the outer layer tends to fracture
prematurely due to the geometry and composition of the working
layer, which makes it highly brittle. These tools have not been
very cost effective in mining and concrete milling
applications.
SUMMARY OF THE INVENTION
[0005] In one embodiment, a cutting element includes a
ballistic-shaped insert. In some embodiment, the ballistic-shaped
insert may provide a substrate comprising an end surface that is
attached to two layers of a tough grade of polycrystalline diamond
(PCD) material layers. The PCD material layer is formed by mixing
cobalt, tungsten carbide and diamond crystals together with a
sandwich layer that acts as shock absorbing layer. The sandwich
layer may be formed from a mixture of diamond, cobalt or carbide of
elements of periodic table Group IV and/or V, or a combination
thereof. In some embodiments, the sandwich layer may include cubic
boron nitride (CBN) in addition to the materials previously
mentioned. The various layers of the ballistic-shaped insert may be
secured on a carbide or cermet substrate. In another embodiment,
the ballistic-shaped insert may be a mixture of polycrystalline
diamond and cubic boron nitride. In other embodiments, the
ballistic-shaped insert is polycrystalline diamond (PCD), cubic
boron nitride (CBN), cobalt, carbide, cobalt or carbides of Group
IV and/or Group V, tungsten, or a combination thereof. In some
embodiments, the ballistic-shaped insert is secured to a body
having an opening to receive the ballistic-shaped insert. In some
embodiments, a sleeve may be positioned on the body to protect the
steel body from erosion and wear. In some embodiments, the body may
be a steel body. In some embodiments, the sleeve may be a
carbide.
[0006] In some embodiments, a top portion of the ballistic-shaped
insert may be defined by radius R1 and R2. In some embodiments, R1
and R2 may have a tangential relationship. In some embodiments, the
ratio of R1 to R2 (R1/R2) is equal to or greater than 18. In other
embodiments, the ratio of R1 to R2 is between approximately 18 to
23. In some embodiments, R2 is between approximately 0.02 to 0.30
inches or 0.5 to 7.6 m. In some embodiments, R1 is between
approximately 1.2 to 10 inches or 30.5 to 254 mm. In some
embodiments, the ratio of R1 to R2 is 4 or greater.
[0007] The foregoing has outlined rather broadly various features
of the present disclosure in order that the detailed description
that follows may be better understood. Additional features and
advantages of the disclosure will be described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a more complete understanding of the present disclosure,
and the advantages thereof, reference is now made to the following
descriptions to be taken in conjunction with the accompanying
drawings describing specific embodiments of the disclosure,
wherein:
[0009] FIGS. 1A-1D are an illustrative implementation of a cutting
element with a ballistic insert, steel body, and sleeve;
[0010] FIG. 2 is an illustrative implementation of a finite element
model showing stress on the insert of a ballistic PCD insert;
[0011] FIG. 3 is an illustrative implementation of a finite element
model showing stress on the insert of a conical PCD insert;
[0012] FIGS. 4A-4B are an illustrative implementation of a
ballistic insert with a radii R1 and R2;
[0013] FIGS. 5A-5B are an illustrative implementation of a
ballistic insert with a concave apex; and
[0014] FIGS. 6A-6B are an illustrative implementation of a
ballistic insert with a round top.
DETAILED DESCRIPTION
[0015] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0016] Referring to the drawings in general, it will be understood
that the illustrations are for the purpose of describing particular
implementations of the disclosure and are not intended to be
limiting thereto. While most of the terms used herein will be
recognizable to those of ordinary skill in the art, it should be
understood that when not explicitly defined, terms should be
interpreted as adopting a meaning presently accepted by those of
ordinary skill in the art.
[0017] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only, and are not restrictive of the invention, as
claimed. In this application, the use of the singular includes the
plural, the word "a" or "an" means "at least one", and the use of
"or" means "and/or", unless specifically stated otherwise.
Furthermore, the use of the term "including", as well as other
forms, such as "includes" and "included", is not limiting. Also,
terms such as "element" or "component" encompass both elements or
components comprising one unit and elements or components that
comprise more than one unit unless specifically stated
otherwise.
[0018] Improved mining tools and methods are discussed herein.
Mining tools utilized to drill and excavate earth formations may
provide components that abrade, impact, shear, and/or the like a
desired region of a formation. For example, a mining tool may be
used for removal of earth formations, asphalt, concrete and/or
surface removal. A mining tool may comprise at least one tooling
element. These mining tools may provide a tooling element that
rotates and/or impacts the formation, such as a bit or the like.
The tooling element may provide at least one cutting element that
is designed to abrade, impact, shear, and/or the like.
[0019] A tooling element may provide a body that has several
recesses for receiving one or more cutting elements. FIGS. 1A-1D
are an illustrative implementation of a cutting element 200 with a
ballistic insert 210, body 220, and sleeve 230. A cutting element
200 for use in a bit or the like may provide a cutting layer formed
from tough grade material(s) that are able to withstand the
stresses imparted on the cutting element during mining or drilling.
Ballistic insert 210 may be shaped to withstand stresses exerted
during mining or drilling. Steel body 220 may provide an opening or
recess for receiving ballistic insert 210. In some embodiments,
ballistic insert 210 may be brazed to the steel body 220. A sleeve
230 may be positioned on the body 220 and ballistic insert 210 to
protect a portion of the body from erosion. In some embodiments,
sleeve 230 may be bonded to the body 220 with a high strength
epoxy. In some embodiments, the cutting layer surface may be a
polycrystalline diamond (PCD) characterized by a mixture of diamond
crystals, cobalt or carbides of group IV and/or group V and
tungsten carbide particles; a cubic boron nitride (CBN) mixture; or
a combination thereof.
[0020] In an exemplary embodiment, a cutting element 200 is
provided where ballistic insert 210 made of PCD is used to form a
cutting layer. In the exemplary embodiment, the PCD material
extends along a section of the ballistic insert 210 so as to make
contact with the earth formations during mining or drilling. The
various embodiments of ballistic inserts discussed herein may be
formed from diamond crystals, a catalyst for forming diamond
crystals, a group IV and/or V, cobalt, carbide, tungsten carbide,
cubic boron nitride (CBN), combinations thereof, and/or any other
suitably tough material(s). As non-limiting example, the ballistic
insert may be made from a mixture of diamond crystals and CBN.
Another non-limiting example is a ballistic insert that provides a
mixture of diamond and catalysts, such as cobalt, which is bonded
to a tungsten carbide substrate. In some embodiments, the ballistic
insert may be a solid body of material(s), and, in other
embodiments, the ballistic insert may include two or more layers.
In some embodiments, a sandwich layer may be provided as a shock
absorbing layer. In some embodiments, the sandwich layer may
comprise a mixture of diamond, a catalyst for forming diamond
crystals, a group IV or group V material, cobalt, carbide, tungsten
carbide, cubic boron nitride (CBN), or a combination thereof. In
some embodiments, the sandwich layer may comprise 70-80% (by
weight) carbide, 0-5% cobalt, and 8-18% diamond. Further, in
another embodiment, the sandwich layer may provide material
percentages in the same ranges and may also include 0-3.5% (by
weight) CBN 0-3.5.
[0021] In some embodiments, ballistic inserts may comprise a single
solid body made of one or more material(s) or a solid insert. For
example, in an exemplary embodiment, a ballistic insert may be a
solid PCD, as opposed to a PCD bonded to a carbide substrate. In
other embodiments, the solid body may be CBN, a mixture of PCD and
cobalt, or a mixture of CBN and PCD. In some embodiments, the
ballistic inserts may be thermally stable or treated to prevent
damage from thermal expansion. For example, a PCD and catalyst
mixture may be acid leached to remove catalyst material that
expands at a greater rate than the PCD when heated. In some
embodiments, a ballistic insert may comprise multiple layers of
materials, such as diamond and catalyst layers bonded to a tungsten
carbide substrate. In some embodiments, ballistic inserts may be
graded to provide different concentrations of the material(s). For
example, a cutting layer provided by a top layer of a ballistic
insert may be the toughest layer with a high ratio of diamond
crystals to catalyst, whereas subsequent layers of diamond and
catalyst below the top cutting layer have increasing percentages of
catalyst.
[0022] Body 220 of the cutting element may provide a bottom portion
shaped to allow the body to be secured to a mining tool. A braze
material may be utilized to secure the ballistic insert 210 and
body 220 together. Body 220 may be steel, titanium and its alloys,
cermets or any other suitable material. In some embodiments, body
220 may also have openings or grooves positioned at specific
locations that are subject to high stresses. Segments of hard
materials, such as cemented carbide, segments of diamond and CBN,
boron carbide, silicon carbide segments, may be either brazed or
bonded by high temperature epoxy into the openings. To protect body
220 from erosion, sleeve 230 is secured onto ballistic insert 210
and body 220. Sleeve 230 may have a thickness between approximately
0.040 to 0.500 inch or approximately 0.1 mm to 12.7 mm. Sleeve 230
may be a cemented carbide or any other suitable material. In some
embodiments, the sleeve 230 is bonded to the body 220 by means of
high strength epoxy having strength of approximately 5000 psi or
greater. The epoxy may be a high temperature epoxy. Alternatively,
cemented carbide sleeve can be bonded to the body 220 by means of
braze material. In some embodiments, the sleeve may be conically
shaped. However, in other embodiments, the sleeve may have any
shape.
[0023] FIG. 2 is an illustrative embodiment of a finite element
model of a ballistic PCD insert. FIG. 3 is an illustrative
embodiment of a finite element model of a conical PCD insert. The
conical PCD insert may experience 14.4.times.10.sup.6 PSI of stress
(von Mises), whereas the ballistic PCD dip may experience
610.times.10.sup.3 PSI of stress (von Mises). In the embodiments
above, the ballistic insert reduces stresses by a factor of 10 over
the conical insert.
[0024] FIG. 4A-4B are an illustrative embodiment of a ballistic
insert 300. Ballistic insert 300 provides a base 310 and a top
portion 320. In some embodiments, top portion 320 may be bonded to
base 310 and the interface between base 310 and top portion 320 may
be planar. Base 310 provides a portion of ballistic insert 300 that
may be secured by a body. In the embodiment shown, base 310 may be
a cylindrically-shaped body with a diameter (D) and a base height
(BH). However, in other embodiments, the base 310 may be any other
suitable shape. Top portion 320 provides a portion of ballistic
insert 300 that may contact a formation during mining or drilling.
While some mining tools utilize conically-shaped inserts, it is
apparent from FIG. 4 that such conical inserts are subjected to
significant stress. In order to reduce stress, top portion 320 is
curved like a ballistic projectile, such as a bullet. In some
embodiments, a ballistic insert 300 may provide a top portion
defined by two radii, R1 and R2. Top portion 320 has a total height
(H). H1 defines the height of a first section comprising the tip of
top portion 320, and the first section is defined by radius R2. H2
defines the height of a second section of top portion 320 below the
tip or first section, and the second section is defined by radius
R1. It should be apparent that a circle or sphere providing a
radius R2 would have a center positioned along the central axis of
ballistic insert 300. The total height (H) of top portion 320 is
equal to the sum of H1 and H2. R1 and R2 form a tangential
relationship with one another. In other words, where R1 and R2
meet, R1 and R2 share the same tangent line. It should be
recognized that the total height (H) of the top portion 320 is
large in comparison to other prior art devices. In some
embodiments, the total height (H) is 1 inch or greater. In some
embodiments, the ratio of R1 to R2 is 4 or greater. In other
embodiments, the ratio of R1 to R2 is 18 or greater. In other
embodiments, the ratio of R1 to R2 (R1/R2) is between 18 to 23. In
some embodiments, top portion 320 has a radius R2 between
approximately 0.020 to 0.300 inches (or approximately 0.5 to 7.6
mm). In some embodiments, top portion 320 has a radius R1 between
approximately 1.2 to 10 inches (or approximately 30.5 to 254 mm).
In some embodiments, top portion 320 has a radius R2 between
approximately 0.020 to 0.300 inches (or approximately 0.5 to 7.6
mm) and a radius R1 between approximately 1.2 to 10 inches (or
approximately 30.5 to 254 mm).
[0025] FIG. 5A-5C are an illustrative embodiment of a ballistic
insert 400 with a concave apex 430. Base 410 is a
cylindrically-shaped base. Similar to the top portion 310 discussed
in the prior embodiment, top portion 420 is defined by two radii,
R1 and R2. Top portion 410 may provide a concave apex 430. Concave
apex 430 is disposed on a central axis of the ballistic insert 400.
Concave apex 430 is concave-shaped depression provided at the apex
of ballistic insert 400. The apex or tip of a cutting element may
be point at which the cutting element experiences the highest
stresses. By providing a concave apex 430, the stresses may be
spread out over the edge of concave apex 430. In conical tipped
inserts, the tip may potentially be cracked, broken, or damaged
during manufacturing. The ballistic insert 400 has a rounded top
portion that avoids this risk of damage during manufacturing.
[0026] In an alternate embodiment, further PCD layers may be bonded
to grooves or pockets formed on the cutting element. For example,
the element may be formed with two or more pockets which may be
equidistantly spaced and each of which supports a separate PCD
layer. In this regard if PCD layer wears out, the cutting element
may be rotated within a pocket of a bit exposing another PCD layer
for cutting the earth formations.
[0027] FIGS. 6A-6B are an illustrative embodiment of a ballistic
insert 500. Ballistic insert 500 provides a base 510 and a top
portion 520. Similar to the top portion 310 discussed in the prior
embodiment, top portion 520 is defined by two radii, R1 and R2.
Further, base 510 provides a rounded bottom 530, which may more
evenly distribute stress to a body the ballistic insert 500 is
secured in.
[0028] In another embodiment, a ballistic insert may provide a
material layer bonded to a substrate. The material layer may be a
mixture of one or more of PCD, cobalt, carbide, CBN, or any other
tough material that is suitable for mining or drilling. In some
embodiments, the material layer may be a combination of PCD and
catalyst such as cobalt. Further, to prevent potential damage from
thermal expansion, said material layer or a portion of the material
layer may be leached to remove said catalyst. The substrate may be
any suitable material, such as carbide, tungsten carbide, or the
like.
[0029] The ballistic inserts or inserts described herein may be
formed as ballistic substrates using conventional methods. In some
embodiments, the ballistic substrates may then be cut or machined
to achieve a desired shape using various known methods such as
electrical discharge machining (EDM). In some embodiments, the
ballistic substrates may be cut or machined to define groove(s) or
depression(s) to accommodate inserts of a desired material at
particular locations of ballistic inserts. For example, PCD inserts
may be placed in grooves position at locations of ballistic insert
that experience high stress. In another exemplary embodiment, the
substrates are molded with the appropriate grooves or depressions.
This may be accomplished by using mold materials which can be
easily removed to define the appropriate cut-outs or depressions to
accommodate the PCD layer(s). One such mold material may be
sand.
[0030] In a further exemplary embodiment, the cutting elements may
be strategically positioned at different locations on a bit
depending on the required impact and abrasion resistance. This
allows for the tailoring of the cutting by the bit for the earth
formation to be drilled. For example, the cutting elements furthest
away from the rotational axis of the bit may have more PCD material
at their cutting edge. The cutting elements closer to the
rotational axis of the bit may have narrower portions of PCD
material occupying the cutting edge. In other words, in an
exemplary embodiment, the cutting elements furthest from rotational
axis of the bit which travel at a higher speed will require greater
abrasion resistance and may be made to include more PCD material at
their cutting edge, whereas the cutting elements closer to the
rotational axis of the bit which travel at a slower speed will
require more impact resistance and less abrasion resistance. Thus,
the latter cutting elements will require more ultra hard material
at their cutting edge making contact with the earth formations. The
amount of PCD material forming the cutting edge of a cutting
element may be varied as necessary for the task at hand.
[0031] In other exemplary embodiments, inserts incorporating PCD
materials may be used in rotary cone bits which are used in
drilling earth formations.
[0032] The PCD utilized for the ballistic inserts may be
substantially free of the problems associated with the use of
Period 4 elements or their compounds for the purpose of sintering
diamond particles on to a cemented carbide substrate. Naturally
available polycrystalline diamond, called Carbonados, is commonly
known as "Black Diamond" and can be found in alluvial deposits in
the Central African Republic and Brazil. Its natural color is black
or gray depending upon the level of impurities such as nitrogen or
boron. It is believed that boron and nitrogen atoms can diffuse
into the diamond lattice and provide means of bonding diamond
crystals together.
[0033] Cubic boron Nitride (CBN) is a very hard material
synthesized by the same process as industrial diamond. Its hardness
is second to diamond and its chemical elements, boron and nitrogen,
can diffuse into the diamond crystals and provide bonding not only
among diamond crystals but also among CBN and diamond crystals.
Coefficient of thermal expansion of CBN is very close to diamond
(1.2.times.10.sup.-6 compared to diamond 1.0.times.10.sup.-6) and
this substantially eliminates local tensile stresses generated due
to mismatch of thermal expansion characteristics encountered
otherwise in use of group IV and V elements of periodic table or
their compounds during the sintering of PCD layer. Since hardness
of CBN crystals is much higher than cemented carbide, the resulting
hardness of PCD layer synthesized using CBN will be much higher
than PCD layer synthesized using Period 4 elements or their
compounds.
[0034] Although the present invention has been described and
illustrated to respect to multiple embodiments thereof, it is to be
understood that it is not to be so limited, since changes and
modifications may be made therein which are within the full
intended scope of this invention as hereinafter claimed.
Experimental Example
[0035] The following examples are included to demonstrate
particular aspects of the present disclosure. It should be
appreciated by those of ordinary skill in the art that the methods
described in the examples that follow merely represent illustrative
embodiments of the disclosure. Those of ordinary skill in the art
should, in light of the present disclosure, appreciate that many
changes can be made in the specific embodiments described and still
obtain a like or similar result without departing from the spirit
and scope of the present disclosure.
[0036] Diamond crystals of approximately 4 to 8 micron were mixed
with cobalt powder and cemented carbide powder. The weight percent
of diamond varied from approximately 40 to 60%, cobalt powder
approximately 8 to 15% and cemented carbide powder approximately 25
to 40% by weight. This powder was milled and treated in a vacuum
hydrogen system and assembled with a cemented carbide substrate.
The inner layer has substantially less amount of diamond crystal.
Both layers were assembled with a cemented carbide substrate. The
assembly was subjected to a pressure exceeding 88 KBar at
temperatures of more than 1400.degree. C. for 10 minutes. The
resulting mass was removed and ground to a precise dimensions.
[0037] A steel body of suitable geometry was used to braze the
ballistic cutting insert described above. In particular, a steel
body commonly used in mining and road applications was utilized. A
carbide sleeve of conical shape was used to envelop the outer steel
body for the purpose of protecting it from erosion. The cemented
carbide sleeve was bonded to the steel body by means of a high
strength epoxy.
[0038] Implementations described herein are included to demonstrate
particular aspects of the present disclosure. It should be
appreciated by those of skill in the art that the implementations
described herein merely represent exemplary implementation of the
disclosure. Those of ordinary skill in the art should, in light of
the present disclosure, appreciate that many changes can be made in
the specific implementations described and still obtain a like or
similar result without departing from the spirit and scope of the
present disclosure. From the foregoing description, one of ordinary
skill in the art can easily ascertain the essential characteristics
of this disclosure, and without departing from the spirit and scope
thereof, can make various changes and modifications to adapt the
disclosure to various usages and conditions. The implementations
described hereinabove are meant to be illustrative only and should
not be taken as limiting of the scope of the disclosure.
* * * * *