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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for introducing fine solid particles
into fluid streams under accurate control. The solid particles are
contained in a foam for mixture with a fluid jet stream. This invention
can be advantageously used to generate abrasive fluid jet streams having
material-cutting capabilities heretofore unobtainable.
2. Description of the Prior Art
Many materials encountered in industry are very hard and tough making
cutting, drilling and shaping of these materials difficult with the
requirements of special tools, techniques and skills. Tools and methods
currently available for cutting these materials have shortcomings and
limitations that need to be reduced or eliminated. Further, the present
consideration of energy consumption and efficiency places new emphasis on
improved tools and methods for cutting such materials.
The usual method for cutting steel plate involves the use of mechanical or
thermal tools that have undesirable characteristics such as slow speed,
tool wear, poor edge quality, alterations of metallurgical properties, and
fire hazards.
Concrete, rock and minerals are also difficult to cut, drill or break
because of their mineral compositions and abrasive nature. The presence of
steel reinforcing rods in reinforced concrete further increases the
difficulties. Currently, saws and drills equipped with carbide or
diamond-studded cutting edges are the only workable tools for cutting or
drilling these materials. These tools have recognized limitations, such as
rapid wear of cutting edges; ability to cut only shapes and patterns
allowed by the geometry of the cutting edges; expense of diamond-studded
edges; necessity to maintain a large tool inventory to meet the
requirements of various jobs; slow operation due to hardness and
abrasiveness of material to be cut; and the cutting can be very noisy,
dusty and fatiguing to operating personnel. Breaking concrete and rock is
usually achieved by use of the commonly available jackhammers which are
grossly inadequate. Thus, removing a large volume of concrete or rock
without using explosives can be a slow, expensive and energy consuming
operation.
There are also difficulties associated with cutting high strength plastics
and composites in production plants. For example, graphite and Kevlar
fiber reinforced laminates are difficult to cut because of the abrasive
nature of these fibers and the need to avoid delamination in cutting. In
some operations, the work pieces are three dimensional wherein cutting or
trimming must follow the surface contours and the work pieces must be
rigid enough and/or fastened to withstand the cutting forces. The
development of new engineering materials has imposed new requirements for
cutting tools and techniques. The need for new and more effective cutting
methods has become very urgent and continuous efforts have been devoted in
recent years to the development of better cutting methods.
One of the relatively new methods for cutting and breaking materials
utilizes a stream of water traveling at high velocity in a water jet. The
water jet is already being employed to cut a wide variety of materials,
including synthetic polymers, leather, paper products, fiberglass,
asbestos and textiles. Description of the water jet apparatus and its
applications are found in the following publications: H. D. Harris and W.
H. Brierley, "Application of Water Jet Cutting", Paper G-1, 1st
International Symposium on Jet Cutting Technology, Coventry, U.K., April
1972; E. N. Leslie, "Application of the Water Jet to Automated Cutting in
the Shoe Industry", Paper F-3, 3rd International Symposium on Jet Cutting
Technology, Chicago, May 1976; and T. J. Labus, "Cutting and Drilling of
Composites Using High Pressure Water Jets", Paper G-2, 4th International
Symposium on Jet Cutting Technology, Canterbury, U.K., April 1978. In the
apparatus and methods described, water is pressurized to a level as high
as 60,000 psi and ejected through a small orifice to generate a high
velocity, substantially coherent water jet. Such a water jet possesses
high kinetic energy and can cleanly cut many materials. There are many
advantages for using a water jet to cut materials, including absence of
tool wear, absence of direct tool contact with the target material, and
minimum dust problems. In some applications, the speed of cutting is also
increased and the quality of cut improved by employing the water jet
method.
The water jet cutting method has not been used widely due primarily to its
high equipment cost resulting from the high fluid pressure involved, high
energy consumption and the inability to satisfactorily cut hard and tough
materials, such as concrete, rock, glass, hard plastics and metals.
Attempts have been made to cut such materials with a water jet by
increasing the water pressure and thus the power input to a very high
level. These attempts have not been satisfactory due to the cost of the
equipment escalating drastically with the increased pressure and power
while the quality of cutting has not been improved proportionally. For
example, attempts to cut concrete with a water jet having power input in
excess of 200 hp and water pressure greater than 50,000 psi have not been
a complete success as concrete and aggregates tend to spall rather than
being cut cleanly and the debris generated by the high pressure water jet
settles in the cut volume hampering the cutting process. The application
of high pressure water jets to cut rock and concrete has been discussed in
many publications including: L. H. McCurrich and R. D. Browne,
"Application of Water Jet Cutting Technology to Cement Grouts and
Concrete", Paper G-7, 1st International Symposium on Jet Cutting
Technology, Coventry, U.K., April 1972; A. G. Norsworthy, U. H. Mohaupt
and D. J. Burns, "Concrete Slotting with Continuous Water Jets at
Pressures up to 483 MPa", Paper G-3, 2nd International Symposium on Jet
Cutting Technology, Cambridge, U.K., April 1974; and T. J. Labus and J. A.
Hilaris, "Highway Maintenance Application of Jet Cutting Technology",
Paper G-1, 4th International Symposium on Jet Cutting Technology,
Canterbury, U.K., April, 1978. A high pressure pulsed water jet apparatus
and process is taught by U.S. Pat. No. 4,074,858.
Abrasive particles propelled by compressed air have been used to cut many
hard materials. This method can be quite effective when the abrasive
particles are accelerated to high velocity and ejected through a suitable
nozzle. However, the difficulty in containing the particles and dust
during cutting operation prohibits its use in large scale material
cutting. Currently, air-propelled abrasive powders are used for deburring
metals and for surface preparation of materials where a hood or an
enclosure can be employed to contain the dust. A wide variety of abrasive
powders, such as silicon carbide, aluminum oxide, garnet, glass beads and
silica sand are used for such applications.
The combination of solid particles with a fluid jet has been employed for
several uses. For example, U.S. Pat. No. 2,821,396 teaches solid particles
in an air or steam injector as an attrition impact pulverizer; U.S. Pat.
No. 3,424,386 teaches mixing of granular solids with a liquid for use in
sandblasting; U.S. Pat. Nos. 3,972,150 and 3,994,097 teach water jets of
particulate abrasive for cleaning with water pressures under 5,000 psi;
U.S. Pat. No. 4,080,762 teaches a fluid-abrasive jet for paint removal
with fluid pressures up to 30,000 psi; and U.S. Pat. No. 4,125,969 teaches
a wet abrasion blast cleaning apparatus and method utilizing soluble
abrasive materials. These patents show that combining abrasive particles
with water jets have not produced an abrasive water jet capable of cutting
hard materials. The jets generated by the devices taught by these patents
can at best clean and blast the surface of hard materials. The prior
devices fail in achieving cutting capability of hard materials primarily
because the devices fail to generate a sufficiently high velocity and
sufficiently coherent water jet; and fail to mix the abrasive particles
with the high velocity water stream in sufficient quantity.
U.S. Pat. Nos. 3,424,386, 3,972,150, 4,080,762 and 4,125,969 all teach the
abrasive (sand) stream to be in the central portion of the nozzle while
the pressurized fluid is introduced into the peripheral area surrounding
the central sand stream. A ring orifice plate or disk such as employed in
the U.S. Pat. Nos. 3,424,386, 4,080,762 and 4,125,969 to provide the fluid
jets around the sand stream has many disadvantages including: the
introduction of pressurized fluid tangentially into a nozzle a short
distance above the orifice disk is not conducive to the generation of a
coherent fluid jet due to flow disturbances upstream of the orifices; sand
in the central portion of a nozzle creates an abrasive environment that
can weaken the interior wall of the annular fluid chamber without being
detected; pressurized fluid in the outer annular space results in a nozzle
that is very large in dimensions as both interior and exterior walls must
be sized to accommodate the fluid pressure; and sealing the annular
orifice disk can be very troublesome. The U.S. Pat. No. 3,994,097 teaches
a centrally located water jet while sand is fed into a nozzle chamber
through a single sand passageway. The sand is forced into the water jet by
passage through a conical nozzle. This patent recognizes abrasion problems
within the nozzle and the necessity of exact alignment. These problems
would be intensified at higher pressures. All of these patents teach
mixing abrasive into water by (1) intercepting an abrasive stream with
water jets, and (2) forcing abrasives, water and air through a conical
nozzle, without concern of fluid actions.
The prior art devices have generally utilized compressed air to deliver the
abrasive particles to a nozzle in which the particles are mixed with the
water stream. It is desirable, however, for the particles to be wetted by
water before they are to be most effectively mixed with the water.
Further, if the water stream is coherent and is traveling at high speed,
the conditions are not favorable for the air propelled particles to be
mixed into the water stream. At best, some particles are carried away by
the water droplets formed around the coherent core of the water stream.
The introduction of abrasive particles would be significantly improved if
the water jet is made to disperse into droplet form, however, the
resultant abrasive water jet would be weak and incapable of cutting hard
materials.
The transporting of abrasive particles by compressed air or gas also has
other undesirable characteristics. Since abrasive particles are generally
heavy, the air flow must be sufficiently turbulent to move the particles,
otherwise the particles will settle and block the passage. The air or gas
must be dry to avoid agglomeration of particles and resulting blockage of
the passage. Further, erosion of tubings, hoses and fittings by the
abrasive particles is a common problem. The air or gas used to propel the
abrasive particles can interfere with the formation of a coherent abrasive
water jet and result in a dust problem as some abrasive particles will
escape with the air or gas without being mixed with the water.
A possible alternative approach of transporting abrasive particles to the
nozzle is to convert the abrasives to a slurry as taught by U.S. Pat. No.
3,972,150. This abrasive slurry is then pumped into a nozzle and mixed
with the water jet. One problem of this approach is that the slurry must
be mixed into the water jet, the mixing of which can consume a significant
amount of the water jet's kinetic energy as the slurry rather than the
individual abrasive particles must be accelerated to the water jet
velocity. Such loss of water jet energy can be particularly severe if the
abrasive slurry is viscous. These problems are increased by the fact that
high viscosity may be necessary in formulating such an abrasive slurry, if
settlement of the particles is to be avoided.
SUMMARY OF THE INVENTION
This invention provides a process suited for introducing heavy abrasive
particles into high velocity fluid jets, such as water jets, without the
above problems. This invention provides a process to generate fluid jets,
such as water jets, having unique material cutting capabilities. This
invention also provides a process which is applicable to introduce fine
solid particles, abrasive or otherwise, into a fluid jet, which could be
liquid or gas.
The particulate-fluid mixing processes of this invention provide
pressurized fluid flow through the central portion of a nozzle and
particulate introduction peripherally. Thus, the fluid flow is not
disturbed and the peripheral portion of the nozzle may be readily adapted
to accommodate a wide variety of particulate requirements, such as volume.
The processes of this invention provide improved fluid jet quality and
preferably utilize multiple fluid jets and flow shaping construction to
provide a conical volume of reduced pressure in the central portion of the
fluid jet to readily entrain and accelerate the particulates in the fluid
jet stream. A coherent, well mixed particulate-fluid jet is provided by
the process of this invention.
One important feature of the process of this invention is to provide the
solid particles contained in a foam for mixture with a fluid jet stream.
As the foam containing the solid particles contacts the fluid stream, the
gaseous bubbles dispersed throughout the foam will collapse and the solid
particles dispersed in the bubble film throughout the foam will be carried
away by the fluid stream. The foam containing the solid particles provides
a particle of wetted surface to the fluid stream and presents little
intereference to the fluid stream as the foam is largely gaseous bubbles
in a much lesser amount of liquid than experienced with prior particulate
containing slurries. Therefore, the energy loss of the fluid jet in
principally accelerating the solid particulates is much less than the
prior art devices wherein slurries of particulates were introduced. The
transport of the solid particulates in foam is advantageous since the foam
containing solids can be readily released under pressure or pumped through
tubing over a long distance without settling of the solids and with
reduced wear or abrasion problems when the solids are abrasive
particulates. The transport of solid particles by foam in accordance with
this invention also provides much better control over introduction of
solid particulates into the fluid stream since more precise control over
the pumping range or regulation of rate of release of pressurized foam may
be readily achieved. In accordance with the introduction of abrasive solid
particulates to a fluid stream according to this invention, high amounts
of abrasive particles may be introduced into the fluid jet stream and the
resultant particulate containing jet stream has cutting capabilities not
previously attainable. Further, the manner of introduction of solid
particles into the fluid stream by a foam avoids dust and reduces
consumption of solid particulates. The properties of the foam used for
wetting, carrying and introduction of solid particulates into the fluid
stream can be readily adjusted to meet special needs by varying
formulations, such as to obtain control of bubble size, solids content,
rheological properties, freezing temperatures, abrasion capabilities, and
the like.
Apparatus to generate solid particulate entrained fluid jets suitable for
cutting hard materials, such as plastics, glass, ceramics, metals,
concrete and rock are specifically disclosed in the following description.
The same apparatus may be used for lower pressure particulate entrained
fluid jets for use in surface alteration or cleaning, fuel introduction
into combustion chambers and other uses which will be apparent. For such
low pressure uses it may not always be advantageous to introduce the
solids in a foam.
BRIEF DESCRIPTION OF THE DRAWING
Specific embodiments of apparatus suitable for use in this invention are
shown in the drawing wherein:
FIG. 1 is a cross-sectional view of a particulate-fluid jet nozzle assembly
according to one embodiment of this invention;
FIG. 2 is a cross-sectional view showing another particulate-fluid jet
nozzle of this invention with an integrated orifice cone;
FIGS. 3 and 4 are cross-sectional views showing different embodiments of
orifice cones of this invention;
FIGS. 5, 6 and 7 are top views of different embodiments of orifice cones;
FIG. 8 is a cross-sectional view showing another embodiment of a
particulate-fluid jet nozzle according to this invention;
FIG. 9 is a cross-sectional view showing another embodiment of a
particulate-fluid jet nozzle according to this invention with a different
orifice cone;
FIG. 10 is a cross-sectional view showing another particulate-fluid jet
nozzle according to this invention used in conjunction with a drill;
FIGS. 11A and 11B are sectional views of different embodiments along the
line 11--11 shown in FIG. 10;
FIG. 12 is a side view of the apparatus shown in FIG. 10;
FIG. 13 is a cross-sectional view showing another embodiment of a nozzle
suitable for the particulate-fluid jet according to this invention
utilizing compressed air to form a shroud around the particulate-fluid
jet; and
FIG. 14 is a diagrammatic showing of the principal components of a system
using this invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Generally the process of this invention involves producing a fluid jet
stream comprising solid particulates by forming at least one fluid jet
stream, introducing solid particulates through multiple orifices at an
angle to and peripheral to the fluid jet stream, mixing the solid
particulates with the fluid jet stream, and passing the mixed solid
particulate-fluid jet stream through a converging flow shaping nozzle. The
throat of the flow shaping nozzle confines the output of the mixed solid
particulate-fluid jet stream.
One embodiment of this invention involves producing a fluid jet stream
comprising solid particulates by introducing the solid particules into the
fluid stream in a foam carrying the solid particulates. The foam carrying
solid particulates may be prepared and stored away from the apparatus for
forming the fluid jet and for introducing the particulate solids into the
fluid stream.
A wide range of solid particles may be used in the process of this
invention, most suitably those having average diameters from about 2
microns to about 0.05 inches, preferably particles from about 10 microns
to about 200 microns. Further, due to the maintenance of the solid
particulates in a foam, particles having high densities may be used
according to this invention. Especially suitable solids for use in this
invention include abrasives such as silicon carbide, aluminum oxide,
garnet, silica sand, metallic slag, glass beads, and the like. The process
and apparatus of this invention may be used for mixing solid particulates
with a fluid stream of liquid or gas for any desired purpose. For example,
the solid particles may be ground coal and the fluid may be natural gas or
fuel oil, and the nozzle used to generate a jet of the solid-fluid mixture
for combustion purposes.
The solid particulates may be introduced in dry condition through multiple
orifices into a fluid jet stream, but are preferably introduced in the
form of a foam. To form the foam the solid particulates are first mixed
with the desired liquid to form a slurry. A wide variety of organic or
inorganic liquids may be used, such as water, ethylene glycol, diethylene
glycol, and other liquids for special purposes to form the slurry. The
solid particulates may be accurately measured into a pre-measured amount
of liquid to form a slurry by mixing. The solid particulates may be wetted
prior to forming the slurry by first mixing the solid particles with the
slurry liquid or other wetting liquid to obtain desired properties. Such
wetting may be enhanced by mixing a wetting and/or dispersing agent with
the solid particles or the wetting and/or dispersing agent may be added to
the wetting and/or slurry liquid. For example, some solids may not be
wetted well by water, which is the desired slurry liquid in a particular
case. In such case, the solids can be wetted first with a small amount of
oil or other liquid that is known to wet the solids well and subsequently,
surfactant that is compatible with the wetting liquid and with water may
be added to the wetted solids. The selected wetting liquid may not be
miscible with water, but the addition of a selected surfactant enables
each wetted solid particle to be coated with the surfactant molecules and
the coated particles can then be suspended in water to form a slurry.
Suitable surfactants are well known in the art to be useful as wetting
and/or dispersing agents in a wide variety of systems. Specific
surfactants offer certain desired properties and advantages with certain
liquid-gas or liquid-liquid or liquid-solid interfaces. The selection of a
surfactant is determined by the solid particles involved, the liquid used
in making the slurry, the gas used in generating the foam, and the desired
amount of foam and foam stability. For example, suitable surfactants
include sodium stearate, potassium stearate, stearic acids, sulfonic
acids, alkyl sulfates, alkylolamides, alkyl sulfoacetates, alkyl aryl
polyetheralcohols, and the like. Surfactants which are non-ionic, anionic
or cationic may be used depending upon the materials used and desired
properties, such as polyethylene oxides, sodium lauryl sulfates, and cetyl
pyridinium chlorides, respectively. Settlement of the solid particulates
in the slurry, especially high density materials, can be avoided by adding
a thickening agent. Especially suitable thickening agents are thixotropic
agents. Suitable thickeners or thixotropic agents are well known in the
art and common materials include sodium silicate, carboxy methyl
cellulose, hydroxy ethyl cellulose, sodium carboxy methyl cellulose,
polyethylene oxide, attapulgite clay, sepiolite clay, sodium bentonite,
polyacrylamides, natural or modified polyssacharides such as guar gum,
xanthum gum bipolymer and starch based polymers. Some of the chemicals
referred to as thickening or thixotropic agents also act as foam
stabilizers to prevent collapse of the foam bubbles sooner than desired
and some also act as lubricating agents.
In the practice of this invention, it is suitable for the slurry to
comprise about 100 to about 800 grams/liter of solids, preferably about
300 to about 500 grams/liter.
The slurry comprising solid particulates is then formed into a foam by any
suitable method. In one embodiment, the slurry comprising solid
particulates and at least one surfactant acting as a foaming agent may be
placed in a pressure vessel with a propellent. Release of the mixture from
the pressure vessel instantly generates the desired foam which may then be
readily transported. Various propellents are well known to the art and
suitable for use in the process of this invention, such as air, carbon
dioxide, propane, butane, and fluorinated hydrocarbons. Another means of
forming a suitable foam is by mixing a stream of the slurry containing a
foaming agent with a stream of gas, such as air, to generate a foam. This
method is widely used in various spraying processes. In both of the above
described methods for forming the foam, the foam is generated as a result
of the action of the foaming agent or surfactant with the gas.
In another embodiment of forming foam according to the process of this
invention, an in situ blowing agent may be added to the slurry and
activated as desired. The activation of the blowing agent is usually
accomplished by heat or by a catalyst. The bubbles produced by such
blowing agents include nitrogen, carbon dioxide or other gases, depending
upon the blowing agent used. Blowing agents are well known such as sodium
bicarbonate and many blowing agents used in the manufacture of foam rubber
and plastics including p-toluene sulfonyl hydrazide, marketed by Uniroyal,
Inc. under the term Celogen TSH and azoalkenes, such as those marketed by
Penwalt Corporation under the name Lucel. The amount of gas produced by
each type of blowing agent is precisely known and thus the bubble size
generated can be well controlled.
In one preferred embodiment of the process of this invention, abrasive
water jets are formed which are capable of cutting hard and aggregate
containing materials. In such cases, commonly used abrasives, such as
silicon carbide, aluminum oxide, garnet and fine sand are all readily
wetted with water and a wide variety of surfactants suitable for forming
thixotropic slurries and for use as foaming agents are well known for
water based systems. Such an aqueous abrasive slurry can be stored, easily
handled and easily transported. Propellents can be added to the slurry
which will provide instant generation of aqueous abrasive foam by either
being stored in pressurized vessels or by pressurizing the vessel at time
of use with compressed air. Releasing of the pressure results in the foam.
In another embodiment, the aqueous abrasive slurry can be pumped to the
fluid jet apparatus as a slurry and mixed with a gas stream to generate
the foam just prior to mixing with the fluid jet. In either case, the
abrasive solid particulates are in the form of a stable slurry or a stable
foam, the particles being homogeneous throughout the system and greatly
reducing erosion problems as compared with prior systems which used
gaseous streams to transport the solids.
An important aspect of this invention is the provision of nozzles suitable
for proper mixing of solid particulates with fluid jet streams and
particularly mixing foam containing abrasives with a high pressure fluid
jet stream to form and maintain the desired shape high velocity
particulate containing fluid jet stream. The nozzles disclosed herein also
can be advantageously used in the formation of high velocity particulate
containing fluid jet streams utilizing dry particulate materials, such as
abrasives. While the apparatus described herein is primarily apparatus for
cutting hard and aggregate containing materials, the process of this
invention for producing a fluid jet stream comprising solid particulates
by introducing the solid particulates contained in a foam into a fluid jet
stream is useful for various lower pressure jet streams for surface
cleaning and treating uses as well.
In one embodiment, the apparatus for use in this invention is a fluid-solid
mixing nozzle generally shown in FIG. 1 as 10 comprising nozzle body 20
defining pressurized fluid chamber 21 and capable of withstanding internal
fluid pressures used; an orifice support cone 60 and orifice plate 70 as
shown in FIG. 1, or an orifice cone 75 as shown in FIG. 2; a flow shaping
cone 50 for facilitating the combination of the solids in the fluid stream
and shaping the fluid stream; pressurized fluid inlet means 11; solids
feed means 35; and a nozzle assembly means 40 permitting disassembly of
the support cone or orifice cone and flow shaping cone for cleaning and/or
replacement.
Referring specifically to FIG. 1, nozzle body 20 forms pressurized fluid
chamber 21 capable of maintaining desired high fluid pressures. The
pressurized fluid is introduced into pressurized fluid chamber 21 through
pressurized fluid inlet tube 11 forming inlet tube through passage 18 and
maintained in communication with pressurized fluid chamber 21 by being
threadedly engaged with collar 15 which is held in position by gland nut
12 which is threadedly engaged to nozzle body 20. Pressure release chamber
23 is provided with pressure relief conduit 24 to the atmosphere. Upon
reading this disclosure it is apparent that any pressurized fluid inlet
means which provides pressurized fluid to pressurized fluid chamber 21 is
suitable.
As shown in FIG. 1, pressurized fluid chamber 21 is larger in cross section
than inlet tube through passage 18 which reduces the fluid velocity
through chamber 21. It is also preferred that the walls of fluid chamber
21 have smooth surfaces to minimize fluid turbulence. Orifice plate 70
having orifice 71 shaped for generating a substantially coherent fluid jet
is mounted on top of support cone 60. Orifice plate 70 is preferably made
from a hard material, such as hardened steel, hard ceramics, tungsten
carbide, diamond, ruby or sapphire. Orifices of such materials have a long
lifetime, withstand high fluid pressures, and can be made by methods known
to the art to very high precision standards. Materials such as hardened
steel and tungsten carbide are suitable for lower pressures and less
critical applications. Support cone 60 has through passage 61 aligned with
orifice 71. Support cone 60 is held tightly against nozzle body 20 by
nozzle cap 30 being threadedly engaged with the lower portion of nozzle
body 20. A tapered fit between support cone 60 and nozzle body 20 centers
support cone 60. Wrench flats 25 and 33 permit tightening of nozzle cap 30
upon nozzle body 20. Nozzle nut 40 with through passage 42 is threadedly
engaged with the lower end of nozzle cap 30 and holds loosely fitting flow
shaping cone 50. In the embodiment shown in FIG. 1, abrasive feed means 35
with abrasive feed passage 36 provides abrasive to mixing chamber 55 above
flow shaping cone 50. Flow shaping cone 50 has through passage 51 which is
a tapered bore in which the solid particles are mixed with the fluid jet.
The exit of through passage 51 is sized according to the diameter of the
fluid jet at that location, the threaded nozzle nut 40 allowing some
adjustment to the size relationship between the fluid jet and the
cross-sectional area of flow shaping cone 50. Having the loose fit, flow
shaping cone 50 will align itself with the fluid jet so that it is
properly centered. The high velocity particulate containing fluid jet 80
leaves the apparatus through nozzle nut through passage 42.
FIG. 2 shows another embodiment of an apparatus for use in this invention
using an orifice cone for mixing of the solid particulates with the fluid
stream. The high velocity particulate containing fluid jet apparatus shown
in FIG. 2 shows orifice cone 75 with multiple fluid orifices 76 which may
generate substantially parallel jets or converging fluid jets which are
particularly advantageous for mixing with foam containing particulates
introduced by multiple abrasive orifices 77. Various embodiments of
orifice cone 75 are further disclosed in FIGS. 3-7 and the more detailed
description to follow. As shown in FIG. 2, the abrasive enters through
abrasive supply hose 85 into abrasive chamber 87 an annular cavity
surrounding nozzle body 20 and defined by outer tube 86. Protective sleeve
82 is shown surrounding nozzle body 20 to avoid erosion of the nozzle body
by the abrasive particles. Cross linked polyethylene or other suitable
materials may be used for such a protective sleeve as well as for abrasive
supply hose 85. Abrasive chamber 87 may be sealed at its lower end by
O-ring seal 67. In the embodiment shown in FIG. 2, mounting block 83 and
tube hose transition member 63 are engaged with nozzle body 20 by gland
nut 12 and collar 15. Hose fitting 28 is provided for pressurized fluid
input. Orifice cone 75 is tightly engaged against the end of nozzle body
20 by orifice cone retaining nut 68 threadedly engaged with nozzle cap 30.
In a manner as described with respect to FIG. 1, flow shaping cone 50 is
retained by nozzle nut 40 screwedly engaged with nozzle cap 30.
FIG. 2 also shows shroud 81 which may be situated around the nozzle
generally and extend to the surface to be cut. Not shown is a suitable
vacuum system in communication with the interior of the volume defined by
shroud 81 for removing cuttings and for collecting fluid. Such a shroud is
particularly useful in applications such as cutting concrete.
FIG. 3 is an enlarged cross-sectional view of one embodiment of an orifice
cone suitable for use in this invention. In this embodiment, multiple
fluid orifices 76 and fluid orifice outlets 78 are drilled directly
through the top of cone 75. Two or more converging fluid orifices may be
used. Abrasive orifices 77 are drilled directly through the orifice cone
tapered walls. Tapered side walls 79 are suitably tapered in the portion
between abrasive orifices 77 and fluid orifices 76 to seat tightly against
the tapered bottom of nozzle body 20. The inlet to abrasive orifices 77 is
in communication with abrasive chamber 34 which is supplied abrasive by
abrasive chamber 87 as shown in FIG. 2 or directly by abrasive feed means
35 as shown in FIG. 8. The center lines of the individual fluid orifices
76 converge at a point P which is on the center line of the orifice cone.
The angle of the converging fluid orifices 76 with the center line of
orifice cone 75 is suitably about 3.degree. to about 10.degree.. Fluid
orifices 76 are shaped such that the length of the flow restriction, L, is
about 1 to about 4 times the diameter of the restricted portion, D. The
lower portion of the fluid orifice has an enlarged portion 78 having a
diameter, d, sufficiently large so as to not interfere with the fluid jet
formed in the fluid jet portion 76.
FIG. 4 shows another embodiment of an orifice cone for use in this
invention wherein the center lines of multiple fluid orifices 76 are
parallel to the center line of orifice cone 75. As shown in FIG. 4,
separate orifice plates 69 may be mounted in recesses in the top of
orifice cone 75 providing replacement of orifice plates and easier
fabrication by avoidance of precision drilling of the orifice cone. The
orifice cones useful in this invention may be drilled directly to provide
fluid orifices 76 or may have separate orifice plates set in retaining
receptacles in orifice cones. The orifice cone 75 may have abrasive
orifices directly drilled through the side of the orifice cone, as shown
in FIG. 4, or have the abrasive orifices drilled through the nozzle cap
30, as shown in FIG. 1.
FIGS. 5 through 7 show top views of various embodiments of orifice cones
useful in this invention. Particularly suitable orifice cones are those
having two or more fluid orifices and two or more abrasive orifices for
better mixing of the abrasive particulates with the fluid jet. Any number
and combination of orifices for enhancing the desired mixing may be used,
dictated primarily by the diameter of orifices and the orifice cone at the
top, preferably from 2 to | | |
