[0001] The present invention relates to a method for cutting and an apparatus for the application
thereof. More particularly, the present invention relates to a method for jet cutting
and an apparatus for the application thereof, which are excellent in cutting efficiency
with a uniform cut surface and permit inhibition of production of burrs.
[0002] For cutting a metal object, a high temperature gas flame melting-cutting method using
gas combustion and a liquid jet cutting method adopted under conditions which do not
permit use of flame e.g. in a tank for storage of an oily material, have conventionally
been known.
[0003] For example, the liquid jet cutting method is popularly known as a water jet cutting
method using high pressure water, and is widely applied for cutting steel sheet. This
method is employed also in building sites where powder cannot be used for cutting
or breaking rocks and concrete.
[0004] A typical jet nozzle used for the liquid jet cutting method is illustrated in Fig.
3. High pressure water is introduced from a high-pressure water inlet (B) toward a
nozzle exit (A), while introducing hard particles from a cutting particles inlet (C)
provided transversely, and cutting is conducted by means of a jet flow ejected from
the nozzle exit (A). Hard cutting particles may be omitted in this case.
[0005] While the jet cutting method is very useful as a cutting method applicable under
conditions making it difficult to use fire, the conventional method and apparatus
have several points to be improved.
[0006] More specifically, in the conventional method, the jet flow ejected from the nozzle
exit (A) shown in Fig. 3 rapidly diffuses so that it is difficult to concentrate the
jet flow onto the portion to be cut. Furthermore, a cut surface is apt to be ununiform
and production of burrs is inevitable. When using hard cutting particles, the nozzle
inner wall suffers seriously from being worn.
[0007] These defects are inevitable in the generation of a jet flow based on the introduction
of high-pressure water, and this naturally limits the applicability of the liquid
jet cutting method. There has, therefore, been a strong demand for improvement of
cutting efficiency, homogenization of a cut surface, inhibition of occurrence of burrs,
and reduction of nozzle wear.
[0008] SU-A-1 245 349 discloses a nozzle which produces a spiral jet flow which offers some
improvements and the preambles of claims 1 and 5 are based on this document.
[0009] The present invention has an object to provide a novel jet cutting method based on
a jet flow which avoids at least some of the aforementioned defects in the conventional
method.
[0010] Furthermore, the present invention has another object to provide a new apparatus
for the application of said jet cutting method.
[0011] Viewed from one aspect the present invention provides a method of jet cutting performed
by ejecting a fluid, comprising: transporting hard cutting particles by means of a
first pressurised fluid flowing through a conduit having a conical nozzle at the downstream
end thereof, the diameter of the nozzle decreasing in the downstream direction and
the nozzle having an axially directed opening at its downstream end for the ejection
of cutting fluid; and characterized in that it further comprises: introducing pressurised
fluid flowing initially towards the nozzle axis into the nozzle around the periphery
of an upstream end of the nozzle to introduce a tangential component to the flow of
the first pressurised fluid, whereby a Coanda spiral flow of fluid having a high velocity
in the downstream direction with the maximum downstream velocity on the axis, together
with a Coanda layer near the nozzle inner wall, is produced.
[0012] Preferably the pressurised fluid is introduced through an annular slit in the nozzle
and the inner wall of the nozzle is convexly curved at least from where the pressurised
fluid is introduced towards the nozzle exit.
[0013] In a preferred embodiment the pressurised fluid is water and the ejected fluid contains
hard cutting particles.
[0014] Viewed from another aspect the present invention provides jet cutting apparatus comprising
a conical nozzle having an axially directed opening for the ejection of cutting fluid
at its downstream end, through which fluid carrying cutting particles can flow, the
nozzle diameter decreasing in the downstream direction; and characterized in that:
means for introducing a pressurised fluid which flows initially towards the axis of
the nozzle into the fluid flowing in use through the nozzle to introduce a tangential
component to the flow of fluid flowing in use through the nozzle is provided around
the periphery of an upstream end of the nozzle, thereby to generate a Coanda spiral
flow of fluid having a high velocity in the downstream direction with the maximum
downstream velocity on the axis in said fluid flowing through said nozzle, together
with a Coanda layer near the nozzle inner wall.
[0015] Preferably, the nozzle has an annular slit for introducing the pressurized fluid
transversely to the nozzle ejecting port and a curved wall running from said slit
to said ejecting port.
[0016] In a preferred embodiment, the upstream end of the nozzle is attached to a conduit
for conveying the fluid, and the nozzle is movable and rotatable about the downstream
end of the conduit, such that the ejected fluid can be directed.
[0017] The Coanda spiral flow used in the present invention was discovered by the present
inventor as a state of movement different from a turbulent flow while being under
the conditions of movement of a fluid belonging the turbulent region, unlike the laminar
flow or a turbulent flow known as the conventional concept of fluid movement. A method
for forming the Coanda spiral flow has already been proposed also by the present inventor.
[0018] More particlarly, the Coanda spiral flow as defined herein is a flow of a fluid which
runs at a high velocity in the pipe direction while forming a spiral, and can be formed
by adding a vector in the pipe radial direction to the flow vector of the fluid introduced
in the pipe direction. In this case, a negative pressure having a strong sucking force
is formed on the side opposite to the running direction of the Coanda sprial flow,
and high velocity Coanda layer based on the spiral flow near the pipe inner wall is
formed.
[0019] The present invention may perform cutting of a metal, an inorganic material, cement
or other solids by the use of the features of such a Coanda spiral flow. One of the
most important things in using the present method and apparatus is to concentrate
velocity distribution on the running axis relative to the running direction of the
Coanda sprial flow. This concentration is never observed in a conventional jet flow
based on a turbulent flow. This concentration of velocity distribution permits improvement
of cutting efficiency with a uniform cut surface and inhibition of burr occurrence.
[0020] An embodiment of the invention will now be described, by way of example only, with
reference to the accompanying drawings wherein:-
Fig. 1 is a sectional view illustrating an embodiment of a nozzle of an apparatus
of the present invention;
Fig. 2 (a) and (b) are drawings illustrating velocity distributions of the jet flow
in an embodiment of a method of the present invention and the conventional method,
respectively; and
Fig. 3 is a sectional view illustrating a conventional water jet cutting nozzle.
[0021] Fig. 1 illustrates an embodiment of the present invention as a Coanda spiral flow
generating nozzle which has been developed for use in efficient mixing of abrasive
and for improved focusing of water jet streams in high pressure abrasive water jet
cutting applications. The development of the nozzle was based on the spiral flow theory.
To obtain a focused jet flow, the nozzle is designed with an annular slit connected
to a generally conical tube. Pressurized fluid is supplied through this slit and the
fluid, passing through the generally conical tube, is deformed to the spiral flow
with the maximum axial flow on the axis, caused by Coanda effect and the instability
of turbulence.
[0022] In the embodiment shown in Fig. 1 there is an annular slit (3) for pressurizing and
introducing a fluid such as water on a main tube (2) directed toward a nozzle exit
(1), and this slit (3) is provided with a supply pipe (7) for supplying a pressurized
fluid.
[0023] The main cylinder (2) has a diameter becoming similarly and gradually larger from
the nozzle exit (1) toward the slit (3) and a wall surface (5) of the main cylinder
(2) is formed to be smoothly curved. The end opposite to the nozzle exit (1) is provided
with an auxiliary cylinder (4) with an inlet (6) for a mixed flow of a fluid, or a
fluid and hard cutting particles. At the opposite side of the wall surface (5) opposite
to the slit (3), a wall surface (8) of the auxiliary cylinder (4) is bent at right
angles or at an acute angle.
[0024] The interval of the slit (3) may be adjustable. There is no particular limitation
on the structure of the supply pipe (7) supplying a pressurized fluid. Furthermore,
a distribution chamber (9), for example, may be provided for the purpose of ensuring
uniform supply.
[0025] For the main cylinder (2), the inclination angle (ϑ) should preferably be such that
tan ϑ is about 1/3 to 1/10.
[0026] In a Coanda spiral flow generating nozzle, such as has been described above, pressurized
water as a pressurized fluid may be introduced from the slit (3) into the main cylinder
(2). This permits synthesis of the motion vector of the pressurized water and the
motion vector of the fluid such as water and air from the inlet (6), thus forming
a spiral motion (10). This spiral motion (10) brings about concentration of fluid
velocity in the running axis direction. forming a high velocity concentrated flow,
Since a Coanda layer is formed in the main cylinder (2), wear of the nozzle inner
wall is inhibited even when hard cutting particles are mixed in a pressurized fluid.
When mixing particles such as alumina, SiC, Si₃N₄, BN, WC, etc., their dispersion
is homogenized.
[0027] The nozzle has been developed in at least preferred embodiments for use in efficient
mixing of abrasive and for improved focusing of water jet streams in high pressure
abrasive water jet cutting applications.
[0028] In at least preferred embodiments the jet stream is more stable and concentrates
the particles to the axial area of the jet flow caused by the characteristics of a
spiral jet. That is the maximum axial flow on the axis and a rotational flow around
the axis.
[0029] In at least preferred embodiments, in cutting, the pressure of the fluid such as
water can be appropriately set, and any of metals, inorganic materials such as alumina
garnet, or the like may be used appropriately as hard cutting particles. It may not
always be necessary to use those hard cutting materials.
[0030] Pressurized fluid may be water or other fluid or a mixed liquid. The object to be
cut may be any of metals, inorganic materials and other solids.
[0031] Embodiments of the present invention are further illustrated by means of the following
examples:-
EXAMPLE 1
[0032] The nozzle shown in Fig. 1 was used. An exit diameter of the nozzle was 19 mm.
[0033] A distance of 50 mm was provided between the nozzle exit and a sample, and a concrete
wall as the sample was cut. In this case, water pressurized at 400 kgf/cm² was ejected,
without the use of hard cutting particles.
[0034] The sample was cut to a depth of 18 cm. Cutting was conducted by the conventional
water jet method under the same conditions. The sample was cut only to a depth of
10 cm. The cut surface was rough with innumerous fine burrs occurring on it. The cut
width was more than twice as large as in the cutting by the Coanda spiral flow of
the present embodiment.
[0035] Additionally, when mixing in alumina particles, the cut depth increased even to about
26 cm.
EXAMPLE 2
[0036] Velocity distribution of a jet flow from a nozzle of 8 mm was evaluated.
[0037] A velocity of 43 m/sec was set at a position of 4 cm from the nozzle tip, and comparison
was made with the conventional water jet.
[0038] Velocity distributions of an embodiment of the Coanda jet with pressurized water
of 4.8 kgf/cm² and the conventional water jet are shown in Figs. 2 (a) and (b).
[0039] As is clear from the comparison of velocity distribution of 20 m/sec, i.e., expanses
(ℓ) of the velocity, velocity concentration is far higher in the Coanda jet of the
present embodiment than the conventional jet.
[0040] According to at least preferred embodiments of the present invention, as describe
above, the following effects are available when performing cutting with the use of
a jet flow based on a Coanda spiral flow:
1) Since diffusion of the jet is smaller and the energy exerts its effect concentrically
in the running direction, the cutting efficiency may be largely improved.
2) Wear resistance of the nozzle may be excellent.
3) Hard cutting particles may be uniformly dispersed throughout the fluid.
[0041] For these advantages, it may be possible to achieve far more useful method and apparatus
for cutting than the conventional ones.
1. A method of jet cutting performed by ejecting a fluid, comprising:
transporting hard cutting particles by means of a first pressurised fluid flowing
through a conduit (4) having a conical nozzle at the downstream end thereof, the diameter
of the nozzle decreasing in the downstream direction and the nozzle having an axially
directed opening (1) at its downstream end for the ejection of cutting fluid; and
characterized in that it further comprises:
introducing pressurised fluid flowing initially towards the nozzle axis into the
nozzle around the periphery of an upstream end of the nozzle to introduce a tangential
component to the flow of the first pressurised fluid, whereby a Coanda spiral flow
of fluid having a high velocity in the downstream direction with the maximum downstream
velocity on the axis, together with a Coanda layer near the nozzle inner wall, is
produced.
2. A method as claimed in claim 1, wherein the pressurised fluid flowing initially towards
the nozzle axis is introduced by means of an annular slit (3) in the wall (5) of the
nozzle.
3. A method as claimed in claim 1 or 2, wherein the pressurised fluid is water and hard
cutting particles are ejected.
4. Jet cutting apparatus comprising a conical nozzle having an axially directed opening
(1) for the ejection of cutting fluid at its downstream end through which fluid carrying
cutting particles can flow, the nozzle diameter decreasing in the downstream direction;
and characterized in that:
means (3) for introducing a pressurised fluid which flows initially towards the
axis of the nozzle into the fluid flowing in use through the nozzle to introduce a
tangential component to the flow of fluid flowing in use through the nozzle is provided
around the periphery of an upstream end of the nozzle, thereby to generate a Coanda
spiral flow of fluid having a high velocity in the downstream direction with the maximum
downstream velocity on the axis in said fluid flowing through said nozzle, together
with a Coanda layer near the nozzle inner wall.
5. Apparatus as claimed in claim 4, wherein the means (3) for introducing a pressurised
fluid comprises an annular slit through which said pressurised fluid can be introduced
into said fluid flow.
6. Apparatus as claimed in claim 4 or 5, wherein the nozzle is attached to a conduit
(4) which conveys the fluid flowing in use through the nozzle to the upstream end
of the nozzle, the nozzle being movable and rotatable about the downstream end of
the conduit, whereby the ejected fluid can be directed.
1. Verfahren zum Strahlschneiden, durchgeführt durch Ausstoßen eines Fluids, umfassend:
Fördern harter Schneidpartikel mittels eines ersten Druckfluids, das durch eine Leitung
(4) mit einer konischen Düse an ihrem stromabwärtigen Ende fließt, wobei der Durchmesser
der Düse in die stromabwärtige Richtung abnimmt und die Düse an ihrem stromabwärtigen
Ende eine axial gerichtete Öffnung (1) zum Ausstoßen des Schneidfluids aufweist; und
dadurch gekennzeichnet, daß es weiter umfaßt:
Einführen von Druckfluid, das anfänglich um den Umfang eines stromaufwärtigen Endes
der Düse zu der Düsenachse in die Düse fließt, um eine Tangentialkomponente zu dem
Fluß des ersten Druckfluids einzuführen, wodurch ein Coandaspiralfluß aus Fluid mit
einer hohen Geschwindigkeit in der stromabwärtigen Richtung mit der maximalen Stromabwärtsgeschwindigkeit
auf der Achse zusammen mit einer Coandaschicht nahe der Düseninnenwand erzeugt wird.
2. Verfahren nach Anspruch 1, in dem das anfänglich zu der Düsenachse fließende Druckfluid
mittels eines Ringschlitzes (3) in der Wand (5) der Düse eingeführt wird.
3. Verfahren nach Anspruch 1 oder 2, in dem das Druckfluid Wasser ist und harte Schneidpartikel
ausgestoßen werden.
4. Strahlschneidvorrichtung, umfassend eine konische Düse mit einer axial gerichteten
Öffnung (1) zum Ausstoßen eines Schneidfluids an ihrem stromabwärtigen Ende, durch
die Schneidpartikel führendes Fluid fließen kann, wobei der Düsendurchmesser in die
stromabwärtige Richtung abnimmt, und dadurch gekennzeichnet, daß:
um den Umfang eines stromaufwärtigen Endes der Düse ein Mittel (3) zum Einführen eines
Druckfluids vorgesehen ist, welches anfänglich zu der Achse der Düse in das bei Verwendung
durch die Düse fließende Fluid fließt, um zu dem Fluß des bei Verwendung durch die
Düse fließenden Fluids eine Tangentialkomponente einzuführen, um hierdurch einen Coandaspiralfluß
von Fluid mit einer hohen Geschwindigkeit in der stromabwärtigen Richtung mit der
maximalen Stromabwärtsgeschwindigkeit auf der Achse in dem durch die Düse fließenden
Fluid zusammen mit einer Coandaschicht nahe der Düseninnenwand zu erzeugen.
5. Vorrichtung nach Anspruch 4, in der das Mittel (3) zum Einführen eines Druckfluids
einen Ringschlitz aufweist, durch den das Druckfluid in den Fluidfluß eingeführt werden
kann.
6. Vorrichtung nach Anspruch 4 oder 5, in dem die Düse an einer Leitung (4) angebracht
ist, die das bei Verwendung durch die Düse fließende Fluid zu dem stromaufwärtigen
Ende der Düse fördert, wobei die Düse um das stromabwärtige Ende der Leitung beweglich
und drehbar ist, wodurch das ausgeworfene Fluid ausgerichtet werden kann.
1. Procédé de coupe au jet exécuté en éjectant un fluide, comprenant:
-- le transport de particules de coupe dures au moyen d'un premier fluide sous pression
s'écoulant à travers un conduit (4) ayant un ajutage conique à son extrémité avale,
le diamètre de l'ajutage diminuant dans le sens aval et l'ajutage ayant une ouverture
à orientation axiale (1) à sort extrêmité avale pour l'éjection du fluide de coupe,
et
caractérisé en ce qu'il comprend en outre :
-l'introduction de fluide sous pression s'écoulant initialement vers l'axe de l'ajutage,
à l'intérieur de l'ajutage autour de la périphérie d'une extrêmité d'amont de l'ajutage
pour introduire une composante tangentielle à l'écoulement du premier fluide sous
pression, de telle sorte qu'un débit de fluide en spirale à effet Coanda ayant une
grande vitesse dans le sens aval, avec la vitesse maximale en aval sur l'axe, ainsi
qu'une couche à effet Coanda près de la paroi interne de l'ajutage, est produit.
2. Procédé selon la revendication 1, dans lequel le fluide sous pression s'écoulant initialement
vers l'axe de l'ajutage, est introduit au moyen d'une fente annulaire (3) pratiquée
dans la paroi (5) de l'ajutage.
3. Procédé selon la revendication 1 ou 2, dans lequel le flluide sous pression est l'eau,
et dans lequel sont éjectées des particules de coupe dures.
4. Appareil de coupe au jet comprenant un ajutage conique ayant une ouverture à orientation
axiale (1) pour l'éjection du fluide de coupe a son extrêmité avale, à travers laquelle
le fluide transportant es particules de coupe peut s'écouler, le diamètre de l'ajutage
diminuant dans le sens aval; et caractérisé en ce que:
un moyen (3) pour introduire un fluide sous pression qui s'écoule initialement
vers l'axe de l'ajutage dans le fluide s'écoulant, en service, à travers l'ajutage
pour introduire une composante tangentielle au débit de fluide s'écoulant, en service,
à travers l'ajutage, est prévu autour de la périphérie d'une extrêmité d'amont de
l'ajutage, pour engendrer ainsi un débit de fluide en spirale a effet Coanda ayant
une grande vitesse dans le sens aval, avec la vitesse d'aval maximale sur l'axe dans
ledit fluide s'écoulant à travers ledit ajutage, ainsi qu'une couche à effet Coanda
près de la paroi interne de l'ajutage.
5. Appareil selon la revendication 4, dans lequel le moyen (3) pour introduire un fluide
sous pression comprend une fente annulaire à travers laquelle ledit fluide sous pression
peut être introduit dans ledit écoulement de fluide.
6. Appareil selon la revendication 4 ou 5, dans lequel l'ajutage est rattaché à un conduit
(4) qui transporte le fluide s'écoulant, en service, à travers l'ajutage vers l'extrêmité
amont de l'ajutage, l'ajutage étant mobile et rotatif autour de l'extrêmité avale
du conduit, de telle sorte que le fluide éjecté peut être dirigé.