U.S. patent application number 12/450827 was filed with the patent office on 2010-11-04 for apparatus and method for particle radiation by frozen gas particles.
Invention is credited to Eckart Uhlmann, Robert Veit.
Application Number | 20100279587 12/450827 |
Document ID | / |
Family ID | 39540619 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100279587 |
Kind Code |
A1 |
Veit; Robert ; et
al. |
November 4, 2010 |
APPARATUS AND METHOD FOR PARTICLE RADIATION BY FROZEN GAS
PARTICLES
Abstract
The invention relates to a device for pressure blasting by means
of a mixed jet made of particles of a frozen gas and a carrier gas,
comprising a nozzle housing, which encloses an outer cavity and an
inner cavity, wherein the inner cavity forms an expansion space,
which comprises an inlet at its upstream longitudinal end for
inducting a liquefied gas into the expansion space, and comprises
an outlet opening at its downstream longitudinal end, wherein the
outlet opening comprises a much larger cross section than the
inlet, and wherein the outer cavity envelops the inner cavity at
least partially in the portion of the outlet opening, at least one
liquid gas supply, which is connected to the inlet of the expansion
space, a support gas supply, which is connected with the outer
cavity, and an acceleration nozzle having a nozzle outlet
downstream of the outlet opening of the expansion space, the
acceleration nozzle initially contracts in flow direction, wherein
a carrier gas defined laterally from the outlet opening and has
cross section which is variably adjustable.
Inventors: |
Veit; Robert; (Graz, AT)
; Uhlmann; Eckart; (Kibitzreihe, DE) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS & ADOLPHSON, LLP
BRADFORD GREEN, BUILDING 5, 755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Family ID: |
39540619 |
Appl. No.: |
12/450827 |
Filed: |
April 14, 2008 |
PCT Filed: |
April 14, 2008 |
PCT NO: |
PCT/EP2008/054466 |
371 Date: |
April 26, 2010 |
Current U.S.
Class: |
451/39 ;
451/75 |
Current CPC
Class: |
B24C 1/003 20130101 |
Class at
Publication: |
451/39 ;
451/75 |
International
Class: |
B24C 1/00 20060101
B24C001/00; B24C 3/00 20060101 B24C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2007 |
DE |
10 2007 018 338.2 |
Claims
1. A device for pressure blasting by means of a mixed jet made of
particles of a frozen gas and a carrier gas, comprising: a nozzle
housing, which encloses an outer cavity and an inner cavity,
wherein the inner cavity forms an expansion space, which comprises
an inlet at its upstream longitudinal end for inducting a liquefied
gas into the expansion space, and comprises an outlet opening at
its downstream longitudinal end, wherein the outlet opening
comprises a much larger cross section than the inlet, and wherein
the outer cavity envelops the inner cavity at least partially in
the portion of the outlet opening, at least one liquid gas supply
connected to the inlet of the expansion space, a carrier gas supply
connected with the outer cavity; and an acceleration nozzle having
a nozzle outlet downstream of the outlet opening of the expansion
space, the acceleration nozzle initially contracts in flow
direction, wherein a carrier gas inlet is defined laterally from
the outlet opening and has a cross section which is variably
adjustable.
2. A device according to claim 1, wherein the cross-sectional area
of the carrier gas inlet can be varied through relative movement of
the inner cavity with respect to the acceleration nozzle.
3. A device according to claim 2, wherein moving the expansion
space is performed in axial direction with reference to the
longitudinal axis of the acceleration nozzle.
4. A device according to claim 1, wherein the inner diameter of the
expansion space continuously expands in flow direction from its
upstream longitudinal end to its downstream longitudinal end.
5. A device according to claim 1, wherein the outer cavity and the
inner cavity have substantially circular cross sections.
6. A device according to claim 1, further comprising a dosing
device having an inner diameter defining the inlet into the
expansion space, the dosing device is an expansion nozzle with a
substantially smaller diameter than the inner diameter of the
expansion space.
7. A device according to claim 1, wherein the carrier gas inlet
comprises a variably adjustable distance between 0 mm and 2 mm,
transversal to the longitudinal axis of the device between the
outer edge of the outlet opening of the inner cavity and the inner
wall of the outer cavity or of the acceleration nozzle.
8. A device according to claim 1, wherein the expansion space
comprises an inner diameter of the outlet opening between 5 mm and
70 mm.
9. A device according to claim 1, wherein the volume flow of the
liquefied gas and also of the carrier gas can be varied.
10. A device according to claim 1, comprising a variably adjustable
volume of the expansion space.
11. A device according to claim 10, wherein the volume of the
expansion space is configured variably adjustable by moving the
dosage device, which is disposed in the transition portion between
the supply of the liquefied gas and the expansion space, in the
transition portion and parallel to the flow direction, so that the
length or the volume of the expansion space changes.
12. A method for cleaning or treating surfaces comprising the steps
of: (a) providing a device for pressure blasting by means of a
mixed jet made of particles of a frozen gas and a carrier gas,
comprising: a nozzle housing, which encloses an outer cavity and an
inner cavity, wherein the inner cavity forms an expansion space,
which comprises an inlet at its upstream longitudinal end for
inducting a liquefied gas into the expansion space, and comprises
an outlet opening at its downstream longitudinal end, wherein the
outlet opening comprises a much larger cross section than the
inlet, and wherein the outer cavity envelops the inner cavity at
least partially in the portion of the outlet opening, at least one
liquid gas supply connected to the inlet of the expansion space, a
carrier gas supply connected with the outer cavity; and an
acceleration nozzle having a nozzle outlet downstream of the outlet
opening of the expansion space, the acceleration nozzle initially
contracts in flow direction, wherein a carrier gas inlet is defined
laterally from the outlet opening and has a cross section which is
variably adjustable; (b) generating a mixed jet made of frozen
CO.sub.2 particles and a carrier gas using the device; and (c)
cleaning or treating at least one surface with the mixed jet.
Description
[0001] The invention relates to a device and a method for pressure
blasting by means of a mixed jet made of frozen gas particles and a
carrier gas. The invention relates in particular to a device and a
method for CO.sub.2 snow blasting by means of a mixed jet made of
frozen CO.sub.2 gas particles and a carrier gas.
[0002] Frozen gas particles are particles made of a substance,
which is gaseous at normal ambient temperature and normal ambient
pressure.
[0003] Blasting with solid carbon dioxide became popular in recent
years in different fields of application. When sensitive surfaces
need to be uncoated or cleaned, or a secondary contamination
through blasting media is undesirable, this technology can play out
its advantages.
[0004] The low hardness of solid carbon dioxide facilitates
treating a large spectrum of materials without damaging them. Due
to the sublimation of the blasting media only the removed pure
coating or contamination has to be disposed of.
[0005] When blasting by means of frozen gas particles, the blasting
media is pneumatically accelerated and applied to the surface to be
treated. Contrary to the purely mechanical effect of other blasting
media, blasting with frozen gas particles is based on three
different effects. Through the low temperature of the blasting
media, a thermal tension between the coating and contamination of
the substrate is created. Furthermore, the kinetic energy of the
frozen gas particles leads to a mechanical separation which is
supported by the third effect, the pressure shock due to the
instantaneous sublimation of the frozen gas particles.
[0006] Such devices and methods are known in principle and there is
a multitude of different configurations, which give the mixed jet
made of frozen gas particles and the carrier gas different
properties with respect to e.g. velocity, volume flow, size, number
and characteristics of the frozen gas particles, so that a desired
effect can be created on the work piece or the surface during
operation.
[0007] Thus, in particular a differentiation is made between two
basic configuration principles. The first configuration, which is
also designated as dry ice blaster differs from the second
configuration which is also designated as snow blaster, in that the
first type generates the mixed jet from the solid phase and the
second type generates the mixed jet from the liquid phase. For dry
ice blasting, the blasting media is provided in a separate process
in the form of pellets or blocks, and subsequently added to the
compressed airflow in a blasting apparatus.
[0008] Since it is an object of the present invention, to provide a
device for pressure blasting with frozen particles, which device is
small in size and can thus be integrated in machinery and equipment
easily, the present invention relates to a device for pressure
blasting by means of a mixed jet comprised of frozen gas particles
and a carrier gas according to the second configuration.
Accordingly, the blasting medium, in particular CO.sub.2, is stored
under pressure in liquid phase in the devices described herein.
[0009] Also for this configuration, which is also designated as a
snow blaster, two configurations are differentiated in turn: the
two-material ring nozzle and the blasting nozzle with an
agglomeration chamber.
[0010] In the two-material ring nozzle, the liquid gas is expanded
to ambient pressure at the exit of the nozzle. The snow particles
created are focused and accelerated by an enveloping jet made of
supersonic compressed air.
[0011] The frozen gas particles formed in the two-material ring
nozzle have a lower diameter compared to the ones formed in the
blasting nozzle with agglomeration chamber, and thus have lower
kinetic energy at the same velocity. Therefore, the particles which
are generated according to said configuration have little abrasive
effect, and such devices are therefore used primarily for cleaning
highly sensitive components with a fine structure. Such a device is
described in DE 199 26 119 C2.
[0012] In a device of the type with the second configuration,
liquefied gas is inducted into an agglomeration chamber together
with the carrier gas flow and expanded. Thus, larger snow particles
are created compared to the two-material ring nozzle, which are
then accelerated through the compressed air in a subsequent nozzle
and cause a significantly stronger abrasive effect. Such a method
and such a device are described in DE 102 43 693 B3.
[0013] While the first configuration with two-material ring nozzle
has the disadvantage of a low abrasive effect, the second variant
of the pressure blasting device with agglomeration chamber has the
disadvantage that a high pressure drop occurs during operation.
Furthermore, frozen gas particles accumulate in the interior of the
agglomeration chamber at the outer walls and disengage from the
outer walls in uneven time intervals and with undefined size. Thus,
the materials removal rate increases in pulses, which creates an
inhomogeneous blasting pattern.
[0014] A CO.sub.2 cold gas jet for pressure blasting by means of a
mixed jet comprised of CO.sub.2 particles and compressed air is
known from DE 202 14 063 U1.
[0015] Thus, it is the object of the present invention to provide a
mixed jet technology which is not provided by the known
configurations and variants.
[0016] The deficiency of the prior art solutions is that they
cannot provide a strong abrasiveness of the mixed jet while
consuming a small amount of compressed air. Such a device can also
be connected to typical compressed air lines in shops, while
providing the required strong abrasiveness.
[0017] Furthermore, it is the object of the present invention to
configure the abrasiveness, this means in particular the size of
the frozen gas particles and their volume adjustable and thus to
make their abrasiveness variable.
[0018] This object is accomplished by a device for particle
blasting with frozen particles, which stores the blasting medium in
liquid form. Thus, the device is among the group of snow blasting
devices.
[0019] The device according to the invention comprises a nozzle
housing which encloses an outer and an inner cavity.
[0020] Thus, the inner cavity forms an expansion--or agglomeration
space, which comprises an inlet connected to the supply for
liquefied gas for inducting a liquefied gas at a longitudinal end
disposed upstream, and an outlet opening at its longitudinal end
disposed downstream. The outlet opening thus comprises a much
larger cross section than the inlet.
[0021] This inner cavity is enveloped by an outer cavity at least
in the portion of the outlet of the inner cavity, which outer
cavity is connected to at least one carrier gas supply.
[0022] The inner cavity and the outer cavity preferably comprise
circular cross sections.
[0023] An initially converging acceleration nozzle connects in flow
direction to the outlet opening of the expansion space and to the
outer cavity, which acceleration nozzle comprises a lateral carrier
gas inlet as an outlet for the outer cavity, which carrier gas
inlet is in particular disposed on all sides of the outlet
opening.
[0024] Since it is an object of the present invention as described
supra to configure the abrasiveness, this means in particular the
size of the frozen gas particles and their volume, adjustable, and
thus to configure their abrasiveness variable, the cross section of
the carrier gas inlet is variably adjustable according to the
invention.
[0025] In a transition portion between the supply for the liquefied
gas and the expansion space, there is a dosage device which forms
the inlet for the expansion space and which is configured
preferably as an expansion--or needle valve nozzle preferably with
a variably adjustable interior diameter. In the flow direction
behind the dosage device, the flow diameter instantaneously expands
from the inner diameter of the dosage device to the inner diameter
of the expansion space. This expands the liquefied gas in the
expansion space which forms a mixture made from frozen gas
particles and gas.
[0026] During the flow of the mixture of frozen gas particles and
gas through the expansion space, particular particles agglomerate
with one another, so that an increase of the particle size occurs
downstream in the expansion space, or also in the agglomeration
space.
[0027] Preferably, the diameter of the expansion space is
configured, so that the cross section of the expansion space
continuously increases downstream.
[0028] Said cross section expansion of the expansion space towards
the nozzle exhaust provides a continuous flow and thus a safe
removal of the snow particles created. With a constant cross
section, accretion and accumulation of solid gas particles occurs
in the so-called "dead spaces" directly after jetting in the
liquefied gas. These accretions come off in uneven time intervals,
so that an inhomogeneous and pulsating blasting pattern of the
nozzle is created, which is also designated "coughing" in the art.
The comparatively large particle agglomerations have a higher
kinetic energy and thus impact the blasted surface more strongly.
This effect is negative for reproducible application of the snow
blasting technique. Furthermore, the accumulation of frozen gas
particles can create a plugging of the blasting nozzle.
[0029] In order to configure the abrasiveness, this means in
particular the size of the frozen gas particles and their volume
adjustable, the volume flow of the liquefied gas flowing into the
expansion space and also the carrier gas flow flowing into the
outer cavity is variably adjustable.
[0030] Since the abrasiveness substantially is a function of the
particle size, which is also a function of the length or the volume
of the expansion space or the agglomeration space according to a
preferred embodiment of the invention, the volume of the
agglomeration space is also variably adjustable according to a
preferred embodiment of the invention.
[0031] Preferably, the volume of the agglomeration space can be
varied in that the dosage device which is disposed in the
transition portion between the supply for the liquefied gas and the
expansion space can be moved in the transition portion and parallel
to the flow direction, so that the length or the volume of the
agglomeration space changes.
[0032] According to another embodiment of the invention, also the
agglomeration space can be configured movable in the direction of
the longitudinal axis, so that also here the relative position of
the dosage device is movable in the transition portion so that the
volume of the agglomeration space is variable.
[0033] The volume of the expansion space can also be configured
variable through a variably adjustable inner diameter of the
expansion space according to another embodiment of the
invention.
[0034] Through the variably adjustable volume flows of liquid gas
supply and carrier gas supply and furthermore also through the
variable length of the agglomeration space, the flow properties and
the size of the frozen gas particles can also be quite different in
the portion of the inlet of the acceleration nozzle. When these
flow properties are disadvantageous, it can occur, that the frozen
gas particles sublimate while being mixed with the carrier gas and
before they can impart the desired effect upon the work piece. In
order to prevent this, an essential feature of the invention is
comprised in that the outlet cross section of the carrier gas inlet
which is formed between the outer contour of the expansion space
and the inner contour of the inlet of the acceleration nozzle is
configured variably adjustable.
[0035] Preferably, the device for pressure blasting by means of a
mixed jet made of frozen gas particles and a carrier gas is
configured, so that the outlet cross section can be varied in that
the expansion space can be moved in axial direction relative to the
acceleration nozzle with reference to the longitudinal axis of the
acceleration nozzle. According to other embodiments of the
invention, said outlet cross section is configured variably
adjustable in that the expansion space is movable in orthogonal
direction relative to the longitudinal axis of the acceleration
nozzle. According to another embodiment of the invention, the
outlet cross section at said location can be varied in that the
inner contour of the acceleration nozzle and/or the outer contour
of the outlet of the expansion space can be configured variably at
least on a partial portion of its circumference.
[0036] Additional features and advantages of the present invention
are described infra with reference to the appended drawing
figure.
[0037] The singular FIG. 1 shows a preferred embodiment of the
invention in a cross sectional view.
[0038] The illustrated device for pressure blasting comprises a
nozzle housing 4 which encloses an outer cavity 6 and an inner
cavity 2.
[0039] The inner cavity 2 is connected to a supply 7 for inducting
liquefied gas into the inner cavity 2. The outer cavity 6 in turn
is connected with a supply 3 for inducting pressurized carrier gas
into the outer cavity 6.
[0040] The inner cavity 2 is defined by an inlet 8 at one
longitudinal end, which inlet 8 is defined by the inner diameter of
a dosage device 1 according to the illustrated embodiment. The
dosage device 1 is disposed in a transition portion between the
supply 7 and the inner cavity 2. The dosage device 1 is configured
as a needle valve nozzle in the illustrated preferred embodiment
and preferably has a diameter between 0.1 mm and 2 mm. After the
dosage device 1 operating as an inlet 8 for the inner cavity 2, the
inner cavity 2 itself is connected, which comprises a much larger
diameter of 3 mm to 50 mm. Due to the instantaneous diameter
increase directly behind the inlet 8 to the diameter of the inner
cavity 2, the liquefied gas instantaneously evaporates when
entering the inner cavity 2 while generating coldness, and a
portion of the liquefied gas freezes into small particles.
Therefore, the inner cavity 2 is also designated as expansion
space.
[0041] The inner cavity 2 is defined by an outlet opening 9 at its
other longitudinal end, which outlet opening is disposed
downstream. From the inlet 8 of the inner cavity 2 to the outlet
opening 9, the diameter of the expansion space 2 continuously
expands in flow direction, and preferably has a dimension between 5
mm and 70 mm at the outlet opening 9. While flowing through the
inner cavity 2, particular particles agglomerate with other
particles. Therefore, the inner cavity 2 which forms the expansion
space is also designated as agglomeration space.
[0042] Directly after the outlet opening 9 of the expansion space 2
and after the outer cavity 6, an acceleration nozzle 5 is
connected, which initially contracts in flow direction and which
protrudes into the outlet opening 9 of the expansion space 2. The
acceleration nozzle 5 has a diameter of preferably between 2 mm and
20 mm at its tightest location. Since the outer contour of the
expansion space 2 comprises a smaller diameter in the portion of
its outlet opening 9, than the diameter of the inner contour in the
transition portion between the inner contour of the outer cavity 6
and the inlet of the acceleration nozzle 5, an annular carrier gas
inlet 10 into the acceleration nozzle 5 is created, which annular
carrier gas inlet simultaneously forms the outlet of the outer
cavity 6.
[0043] The inner cavity 2 is configured movable in axial direction
with respect to the longitudinal axis of the acceleration nozzle 5
and leads into the acceleration nozzle 5 which contracts at this
location. Thereby, the cross section of the carrier gas inlet 10
into the acceleration nozzle 5 can be varied through longitudinal
movement of the inner cavity 2. The carrier gas inlet 10 preferably
comprises a variably adjustable offset between 0 mm and 2 mm,
transversal to the longitudinal axis of the device as a function of
the position of the nozzle opening 9 within the device between the
outer edge of the nozzle opening 9 of the inner cavity 2 and the
inner wall of the outer cavity 6 or of the acceleration nozzle
5.
* * * * *