DE102008037089A1 - Apparatus and method for cleaning objects by means of dry snow - Google Patents

Abstract

The device has an expansion channel for producing carbon dioxide crystals from liquid carbon dioxide, and a venturi nozzle (7) for discharging the crystals, where the nozzle mixes the crystals with abrasive additives. The crystals and the additives are fed into a section (25) of small cross section of the nozzle, and the channel is partially spiral shaped around a compression part (23) of the nozzle. The additives are selected from a group consisting of lava granules, oil emulsive core e.g. cherry stone, glass beads and plastic granules e.g. polyethylene, polyamide and polycarbonate. An independent claim is also included for a method for cleaning surfaces of an object using dry snow.

Description

The The present invention relates to an apparatus and a method for cleaning objects with dry snow.

To the Cleaning the surfaces of objects in industrial Range are various chemical and physical cleaning methods and possibilities known.

Dry Cleaning procedures often require due to the used there aggressive means and due to legal regulations one high expenditure on safety and disposal facilities. Therefore It is the physical cleaning processes in which the Impurities usually by bombardment or irradiation of the surface to be cleaned with sand, metal or glass particles to be removed, it is necessary that the cleaning itself in separate Cabins is performed. This has to be done for this cleaning component first from the corresponding machine be expanded and placed in such a cabin.

A Another alternative is to use components by means of bombardment To clean dry ice. The dry ice is in the solid state and transferred to at least -78.5 ° C. cooled carbon dioxide. Dry ice goes under atmospheric pressure directly from the solid state of matter into the gaseous state, where no molten liquid is formed. This can be up particularly simple way, namely with normal compressed air, both the bombardment with dry ice and the suction and removal the dirt particles take place.

Dry ice is present during production in the form of snow. The generation of CO ₂ snow locally by means of a nozzle of liquid CO ₂ and the direct irradiation of a surface with this snow, possibly with the assistance of compressed air, is procedurally comparatively easy to handle and easy to automate.

However, the cleaning effect of CO ₂ snow is limited. To remove more stubborn soils, it is compressed into granules or pellets or the like by pressing them through dies. The mass density of the pellets is about 1000 kg / m ³ . They have the form of pins with a length of about 5 mm to 30 mm and a diameter of about 3 mm.

To further increase the cleaning effect of CO ₂ particles suggests the FR-A-2 837 122 to provide the cryogenic CO ₂ with an additive of synthetic or mineral particles. The CO ₂ particles are preferably around 150-250 microns, the synthetic or mineral particles by 50 microns in size. The synthetic additives may be formed, for example, from tallow or resin-coated recycling waste. With this method, coatings such. As paint, anti-corrosion paint, dust or sanding dust and natural impurities such as fats are removed.

Cryotechnics, NL offers a similar process called CryoAdd, which uses dry ice (CO ₂ ) in the form of pellets, nuggets or blocks to clean objects, this dry ice material being blown onto the surface to be cleaned in a stream of compressed air. To increase the cleaning effect, abrasive or non-abrasive material can be added to this compressed air / dry ice mixture. Non-abrasive particles penetrate into the soil layer and allow for increased effect of explosive sublimation of the dry ice particles, while abrasive particles are used to mechanically remove hard surface layers.

However, the use of CO ₂ pellets also has disadvantages. For CO ₂ pellets, a special silo must be provided. If the pellets are stored too long in the silo, they clump together. The cleaning function of the pellets depends strongly on the storage time.

There are various devices (eg., Cold Jet, Micro Clean) are known in which provided CO ₂ pellets or block ice in a separate device such. As a rasp mechanism o. Ä. To shred again and then supply a nozzle of the device. This comminution requires a lot of energy and thus leads to higher cleaning costs.

In the DE 2005 005 638 B3 A method and apparatus for cleaning, activating or pretreating workpieces by means of carbon dioxide snow blasting is described. By means of the device carbon dioxide snow is produced from pressurized CO ₂ fluids and at least one carrier pressure gas. An outlet nozzle is provided which accelerates the mixture, producing a two-phase carbon dioxide gas and carbon dioxide particles in an agglomeration chamber by agglomeration and densification of carbon dioxide snow crystals and radially admixing the carrier gas into a multi-stage mixing chamber. The mixing chamber is arranged in front of the outlet nozzle. In this way, a turbulent gas flow of high energy is provided for machining the workpiece. The apparatus may include a feed system which supplies solid abrasive particles in a first region or second region of the mixing chamber in order to improve the blasting performance.

From the EP 1 501 655 B1 goes forth a blasting method and a blasting device. In this device, liquid CO _{2 is} supplied via a feed line to a relaxation space expanded in cross-section. By relaxing the liquid CO _{2 is converted} into dry snow and fed together with a carrier gas under pressure to a jet nozzle. In this device can be provided to allow solid or liquid blasting agent via lateral feeds in the jet line upstream or downstream of a branch, which is arranged in front of the jet nozzle, or possibly also open in an even more downstream relaxation space.

The WO 03/022525 A2 discloses a blasting method and apparatus. Here, a stream of a blasting medium, which carries an abrasive blasting agent provided. With the help of an adapter, an additional jet medium is supplied from a pressure source. The supply of the additional radiation medium takes place immediately before a jet nozzle, which has a bottleneck. It can be provided via the second blasting system to perform a radiation agent with higher abrasiveness, for example, granules.

The The object of the present invention is a device and to create a process that improves the efficiency of cleaning can be further increased with dry snow.

Especially The object of the invention is to provide a method and a for Implementation of the method to provide suitable device for cryogenic cleaning of objects by means of dry snow at the same time high cleaning efficiency and good handling and automation.

The Task is achieved by a device according to claim 1 or a method according to claim 8 solved.

According to the invention, a mixture of CO ₂ snow and abrasive additive is produced and directed to the object to be cleaned, wherein the mixture is preferably applied with compressed air.

According to the invention, a device for cleaning objects by means of dry snow is provided. The apparatus comprises an expansion channel for generating CO ₂ snow from liquid CO ₂ , a nozzle for discharging the CO ₂ snow, and means for mixing the CO ₂ snow with an abrasive additive, wherein the means for mixing the additive is the nozzle is.

The combination of CO ₂ snow and abrasive additive can clean surfaces considerably more than CO ₂ snow alone and therefore compensates well for the energetic weaknesses of the snow blasting process. On the other hand, the disadvantages of pellets do not occur. In particular, it is possible to accurately meter the cleaning effect and provide consistent. In contrast to the handling of CO ₂ pellets, this method of production is easy to control in terms of process technology and can be easily automated.

By applying compressed air, the resulting material flow can be ideally conditioned and the consumption of CO ₂ or additive can be limited.

Thereby, that the additive is first added in the nozzle the additive with the dry snow only immediately before blasting in contact.

The Solid additives have a high heat capacity and compared to dry snow, a high temperature. By the Addition of the additive in the nozzle is the residence time of the Additive in dry snow short. This will ensure that no appreciable heat transfer from the additive the dry snow takes place. As a result, the dry snow in almost unchanged quality together with the additive delivered to the object to be cleaned.

One Another significant advantage is that the abrasive additive only comes into contact with the nozzle. As a result, no finds the additive caused increased wear the nozzle upstream components instead.

According to one embodiment, liquid CO _{2 is} supplied to an expansion channel and relaxed in it in such a way that CO ₂ snow and preferably additionally CO ₂ gas are produced therefrom. The CO ₂ snow is then fed to a Venturi nozzle. In such a construction, the dry snow produced is used without intermediate steps as it is produced. The handling and storage of liquid carbon dioxide is well and safely manageable.

The CO ₂ snow is preferably supplied in the section of the narrowest cross section of the Venturi nozzle or on the negative pressure side of the Venturi nozzle.

The abrasive additive is also in the section of the narrowest cross section the Venturi nozzle or on the negative pressure side of the Venturi nozzle be added.

The feed to the Venturi nozzle may be at least partially helically guided around the compression part of the Venturi nozzle. The addition at the narrowest point or the point of the smallest cross-section is advantageous because of the prevailing high flow velocity and the well-defined and stable flow conditions. Due to the helical arrangement, the supply for the CO ₂ snow, which requires a specific line length, can be realized in a space-saving manner.

Alternatively, the abrasive additive may be added at the mouth of the venturi, with the abrasive additive preferably being introduced by suction into the mass flow of CO ₂ snow and air.

• – Sande (z. B. Quarz-, Muschel-, Lava-, Granitsand)
• – Lavagranulat oder dergleichen,
• – Calciumcarbonat,
• – Calciumbicarbonat,
• – Natriumhydrogencarbonat,
• – Glasperlen oder dergleichen,
• – Glasbruch, vorzugsweise aus Glasperlen oder dergleichen
• – Metallpulver und/oder Metallstaub, vorzugsweise aus Eisen, einer Eisenlegierung, Aluminium, Kupfer oder Messing oder dergleichen,
• – Korund oder dergleichen,
• – Nuss-Schalen und/oder Bruchstücke davon,
• – ölhaltige Kerne wie etwa Kirschkerne und/oder Bruchstücke davon,
• – Kunststoffgranulat, vorzugsweise aus PE, PA, oder PC oder dergleichen.

The abrasive additive preferably comprises at least one of the following substances:

• - sands (eg quartz, shell, lava, granite sand)
• - lava granules or the like,
• Calcium carbonate,
• Calcium bicarbonate,
• Sodium bicarbonate,
• - glass beads or the like,
• - Glass breakage, preferably from glass beads or the like
• Metal powder and / or metal dust, preferably of iron, an iron alloy, aluminum, copper or brass or the like,
• - corundum or the like,
• - nutshells and / or fragments thereof,
• Oily kernels such as cherry pits and / or fragments thereof,
• - Plastic granules, preferably made of PE, PA, or PC or the like.

Further Objects, features and advantages of the present invention from the description of the exemplary embodiments, which are illustrated in the accompanying drawings.

1 shows a basic operation of the invention.

2 shows a first embodiment of the invention.

3 shows a second embodiment of the invention.

4 shows a third embodiment of the invention.

5 shows a modification of the third embodiment.

First, the principle of operation of the present invention will be described with reference to a schematic representation in FIG 1 explained.

As shown in 1 is a device for cleaning 1 via a supply line 2 Carbon dioxide (CO ₂ ), via an abrasive pipe 3 an abrasive additive (A) and a compressed air line 4 Compressed air (DL) supplied.

Inside the device 1 From these ingredients, a mixture of dry snow, abrasive and compressed air is generated and used as a cleaning jet 5 issued. The cleaning jet 5 is on an object to be cleaned 6 directed. Any devices for shutting off and regulating the mass flows of carbon dioxide, the compressed air and the additive and for keeping or generating the respective substances are not shown in detail in the figure; their execution will be adapted by the skilled person to the conditions and properties of the substances.

It should be noted that the addition of compressed air is optional. It can, for. B. the CO _{2 are} already supplied under high pressure or the abrasive material are supplied from reaching flow rate in a gaseous carrier to in the device 1 to be mixed together.

For the purposes of the invention, the device comprises a device for mixing CO ₂ snow with an abrasive additive, which is designed as a nozzle, preferably under the action of compressed air, wherein the resulting mixture is dispensed onto the object to be cleaned.

The addition of abrasive material or of abrasive substances produces a mixture whose cleaning effect is superior to that of CO ₂ snow alone. The cleaning effect must be precisely metered and consistently provided. The combination of CO ₂ snow and the abrasive additive is easy to automate and is easy to control in terms of process engineering, eliminating the annoying handling of dry ice pellets.

2 shows an embodiment of an apparatus according to the present invention. A venturi 7 is a connection piece 8th upstream and an ejection funnel 9 downstream. The Venturi nozzle 7 , the connection piece 8th and the discharge funnel 9 can be integrated in a pistol grip (not shown) or in a tool holder of a machine (not shown in detail).

Via the supply line 2 is the on circuit-piece 8th with a container 10 connected. The container 10 contains liquid carbon dioxide (LCO ₂ ). A pump 11 and a solenoid valve 12 are intended to regulate the mass flow. The solenoid valve 12 is shown in the figure as on / off valve (shut-off valve), but can also be designed as a control valve. The solenoid valve 12 can be controlled by a control device (not shown) with a predetermined duty cycle to control the opening and closing times. A pressure tank 13 is provided to the container 10 to pressurize with a predetermined pressure. The container 10 is cold-insulated.

About the only indicated compressed air line 4 becomes the connection piece 8th Also supplied compressed air. The connection piece 8th is designed as an expansion channel. The LCO ₂ stream becomes in the expansion channel 8th relaxed. In this way, a dry snow stream is generated which is mixed with the compressed air as the connecting piece continues to move.

In the section of the smallest cross-section of the Venturi nozzle 7 is via the abrasive pipe 3 supplied an abrasive. This is entrained by the high flow velocity in the section of the smallest cross-section and is distributed in the compressed air / dry snow stream to a mixture that passes through the discharge funnel 9 as a cleaning jet 5 is delivered.

For the purposes of the invention, the venturi serves as a means for mixing the CO ₂ snow with an abrasive additive, preferably under pressurized air. The discharge funnel 9 serves as a means for directing the resulting mixture on the object to be cleaned, while the connecting piece serves as a means for supplying dry snow.

In 3 a second embodiment of the present invention is shown. A venturi 14 a compressed air / dry snow stream generated in an expansion channel is supplied and at the outlet cross section 15 the Venturi nozzle issued.

The Venturi nozzle 14 is coaxial within a pipe wall 16 arranged where they are from a stream of abrasive material as a sheath flow 17 is flowed around. At the outlet cross-section 15 the Venturi nozzle 14 the Abrasivstoffstrom is sucked by the compressed air / dry snow stream and entrained and a mixture 20 mixed in a drain pipe 19 the further use is performed as a cleaning jet. In one area 18 the cross section of the pipe wall tapers 16 to that of the discharge pipe 19 , whereby an additional acceleration effect is achieved.

By means of a bore 21 In the area of the smallest cross-section of the Venturi nozzle on the one hand a balance of pressure fluctuations can be achieved, on the other hand, the bore 21 be designed so that a partial flow of Abrasivstoffstroms is already supplied here to the premix.

4 shows the third, preferred embodiment of the invention. The device for cleaning comprises a nozzle 7 in which all the essential parts in a housing 22 are incorporated. The nozzle is z. B. as Venturi 7 educated. In the case 22 upstream is a tapered compression part 23 and downstream an expanding expansion part 24 brought in. The compression part 23 and the expansion part 24 meet inside the case 22 on top of each other and together form the venturi nozzle with a section of small diameter (narrowest nozzle area) 25 out.

Upstream of the compression part 23 is fed from a source not shown compressed air DL. In the section of the smallest cross section 25 is via a CO ₂ supply 26 CO ₂ snow fed from pre-relaxation. Likewise, there is an abrasive feed 27 an abrasive A supplied. The CO ₂ feed 26 can as an expansion channel 8th be formed in which the CO ₂ snow is generated from liquid CO ₂ . Due to the high flow velocity in the section of the smallest cross section 25 CO ₂ snow and abrasive are entrained and together with the compressed air as cleaning jet 5 downstream of the expansion part 24 issued.

5 shows a modification of the third embodiment. While in the latter both feeds 26 and 27 as straight holes along the compression part 23 are formed, in the modification, the CO ₂ supply 26 ' or the expansion channel 8th helical around the compression part 24 guided around. This allows the CO ₂ supply 26 ' , which can have a considerable run length (eg 500 mm-800 mm), compared to a straight design in a space-saving manner in the housing 22 ' be housed.

at In all embodiments, the abrasive additive may be any be solid substance that has an abrasive action and is in can be promoted desired shape. He will based on the circumstances, in particular the desired Intensity of the abrasive effect, but also of the procurement possibilities, of price, storage and promotion features and other properties and effects selected.

• – Sande (z. B. Quarz-, Muschel-, Lava-, Granitsand)
• – Lavagranulat oder dergleichen,
• – Calciumcarbonat,
• – Calciumbicarbonat,
• – Natriumhydrogencarbonat (Backpulver),
• – Glasperlen oder dergleichen,
• – Glasbruch, vorzugsweise aus Glasperlen oder dergleichen
• – Metallpulver und/oder Metallstaub, vorzugsweise aus Eisen, einer Eisenlegierung, Aluminium, Kupfer oder Messing oder dergleichen,
• – Korund oder dergleichen,
• – Nuss-Schalen und/oder Bruchstücke davon,
• – ölhaltige Kerne wie etwa Kirschkerne und/oder Bruchstücke davon,
• – Kunststoffgranulat, vorzugsweise aus PE, PA, oder PC oder dergleichen.

The following substances are available as abrasive additives:

• - sands (eg quartz, shell, lava, granite sand)
• - lava granules or the like,
• Calcium carbonate,
• Calcium bicarbonate,
• Sodium bicarbonate (baking powder),
• - glass beads or the like,
• - Glass breakage, preferably from glass beads or the like
• Metal powder and / or metal dust, preferably of iron, an iron alloy, aluminum, copper or brass or the like,
• - corundum or the like,
• - nutshells and / or fragments thereof,
• Oily kernels such as cherry pits and / or fragments thereof,
• - Plastic granules, preferably made of PE, PA, or PC or the like.

It is also possible to use several additive substances in a selected mass or volume ratio. In this case, separate lines and feed points can be provided for different additives. For example, an additive in the section of least cross section 25 , another may be added in the outlet section of the Venturi nozzle. There may also be several feed points in the region of the smallest cross section 25 be provided.

additionally to abrasive additives can also binders, antimicrobial, disinfecting, surface-active (surfactant) or odorizing Substances are added as further additives. Here are also further supply points into consideration. So can a liquid Additive can be given directly in the cleaning jet or already a liquid carbon dioxide before its relaxation be added.

Instead of The Venturi nozzle can also be provided with a Laval nozzle be.

The inventive method and apparatus for cleaning objects by means of dry ice are characterized by the use of a mixture of CO ₂ snow, compressed air and an abrasive additive for cleaning articles.

1

contraption for cleaning

2

Supply line for CO ₂

3

management for abrasive

4

management for compressed air

5

mass flow

6

to cleansing object

7

venturi

8th

Union joint

9

discharge hoppers

10

Container for liquid CO ₂

11

pump

12

magnetic valve

13

pressure tank

14

venturi

15

exit plane

16

pipe wall

17

bowl channel

18

mixing area

19

drain pipe

20

mixture

21

drilling

22 22 '

casing

23

compression part

24

expansion part

25

section of the smallest cross section

26 26 '

CO ₂ feed

27

Abrasive supply

A

abrasive

DL

compressed air

LCO ₂

liquid CO ₂

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• FR 2837122 A [0007]
• - DE 2005005638 B3 [0011]
• - EP 1501655 B1 [0012]
• WO 03/022525 A2 [0013]

Claims (14)

Device for cleaning objects by means of dry snow, having an expansion channel for generating CO ₂ snow from liquid CO ₂ , a nozzle for emitting CO ₂ snow, a device for mixing CO ₂ snow with an abrasive additive, characterized in that the means for mixing the additive is the nozzle. Apparatus according to claim 1, characterized in that the CO ₂ snow in the section of the smallest cross-section 25 the Venturi nozzle is supplied. Apparatus according to claim 2, characterized in that the means for supplying the CO ₂ snow to the Venturi nozzle at least partially helically around the compression part of the Venturi nozzle. Device according to one of claims 1 to 3, characterized in that the abrasive additive in the region of the smallest cross-section 25 the Venturi nozzle is added. Device according to one of claims 1 to 4, characterized in that the abrasive additive is added at the mouth of the venturi, wherein the abrasive additive is preferably introduced by suction into the mass flow of CO ₂ snow and air. Apparatus according to claim 5, characterized characterized in that the Venturi nozzle within a tube wall is arranged and the abrasive additive the Venturi nozzle flows around the shell wall in the form of a jacket. Device according to one of the claims 1 to 6, characterized, that the abrasive additive at least one of the following substances: - lava granules or similar, Calcium carbonate, Calcium bicarbonate, Sodium bicarbonate, - Glass beads or similar, - Glass breakage, preferably of glass beads or similar Metal powder and / or metal dust, preferably of iron, an iron alloy, aluminum, copper or Brass or the like, - corundum or the like, - nut shells and / or fragments thereof, - oily Kernels such as cherry pits and / or fragments thereof, - plastic granules, preferably made of PE, PA, or PC or the like. A process for cleaning objects by means of dry ice, wherein in a nozzle, a mixture of CO ₂ snow and abrasive additive is generated and directed to the object to be cleaned, wherein the mixture is preferably applied with compressed air. A method according to claim 8, characterized in that the CO ₂ snow is supplied in the region of the smallest cross section of the venturi. A method according to claim 9, characterized in that the CO ₂ snow before being fed to the Venturi nozzle is at least partially helically guided around the compression part of the Venturi nozzle. Method according to one of the claims 9 to 10, characterized in that the abrasive additive in the range of the smallest cross-section of the Venturi nozzle is added. A method according to any one of claims 10 to 11, characterized in that the abrasive additive is added at the mouth of the venturi, wherein the abrasive additive is preferably introduced by suction into the mass flow of CO ₂ snow and air. A method according to claim 12, characterized characterized in that the abrasive additive is the Venturi nozzle flows around jacket-shaped. Method according to one of the claims 8 to 13, characterized, that the abrasive additive at least one of the following substances: - sands (eg quartz, shell, lava, granite sand) - lava granules or similar, Calcium carbonate, Calcium bicarbonate, Sodium bicarbonate, - Glass beads or similar, - Glass breakage, preferably of glass beads or similar Metal powder and / or metal dust, preferably of iron, an iron alloy, aluminum, copper or Brass or the like, - corundum or the like, - nut shells and / or fragments thereof, - oily Kernels such as cherry pits and / or fragments thereof, - plastic granules, preferably made of PE, PA, or PC or the like.