EP3096591B1 - Method and device for reducing an electrostatic charge during the machining, joining or coating of areas using vacuum suction blasting - Google Patents

Method and device for reducing an electrostatic charge during the machining, joining or coating of areas using vacuum suction blasting Download PDF

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Publication number
EP3096591B1
EP3096591B1 EP16001093.0A EP16001093A EP3096591B1 EP 3096591 B1 EP3096591 B1 EP 3096591B1 EP 16001093 A EP16001093 A EP 16001093A EP 3096591 B1 EP3096591 B1 EP 3096591B1
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EP
European Patent Office
Prior art keywords
blasting
workpiece
workpiece holder
voltage source
tube
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Not-in-force
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EP16001093.0A
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German (de)
French (fr)
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EP3096591A1 (en
Inventor
Marcel Heeger-Renaud
Jörg Renaud
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Gp Anlagenbau GmbH
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Gp Anlagenbau GmbH
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Publication of EP3096591A1 publication Critical patent/EP3096591A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C3/00—Abrasive blasting machines or devices; Plants
    • B24C3/32—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks
    • B24C3/322—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks for electrical components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C5/00—Devices or accessories for generating abrasive blasts
    • B24C5/02—Blast guns, e.g. for generating high velocity abrasive fluid jets for cutting materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C9/00—Appurtenances of abrasive blasting machines or devices, e.g. working chambers, arrangements for handling used abrasive material
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
    • H05F1/00—Preventing the formation of electrostatic charges

Definitions

  • the invention relates to a method for reducing an electrostatic charge when machining, bonding or coating surfaces by means of vacuum suction, in which a blasting agent held under reduced pressure in a reservoir, transported by this via a hose feed line to a jet lance with jet pipe, through this a stream of blasting agent predetermined acceleration generated and this is directed to a processing surface located in a set under negative pressure blasting chamber or blasting hood, held by a workpiece holder workpiece, then sucked and returned via a hose discharge into the reservoir.
  • the invention further relates to a device for carrying out the method, with at least one reservoir for receiving blasting agent, a Separating unit for cleaning the blasting agent, a suction unit connected to the separation unit for generating a negative pressure in the reservoir, a hose connected to the reservoir hose for transporting the blasting agent in a set under negative blast chamber or blasting hood via a jet lance, the jet a stream of abrasive on a workpiece holder directs fixed workpiece, and connected to the blasting chamber / jet hood hose outlet for sucking the blasting agent from the blasting chamber / blasting hood in the separation unit.
  • the beam processing in particular the removal, compression, coating or joining of solid surfaces of a workpiece is known ( DE 197 47 838 A1 . DE 101 02 924 C1 . DE 102 57 241 A1 . DE 10 2010 020 691 A1 ). All these known solutions work in the vacuum suction, in which a blasting agent held under negative pressure in a reservoir, transported by this via a hose feed line to a jet, generated by this a blasting medium predetermined acceleration and this on a working surface of a set in a negative pressure blasting chamber or blasting hood directed, held by a workpiece holder workpiece, then sucked and returned by a hose discharge via a separator in the reservoir.
  • the blasting agents used are sodium bicarbonate, plastic particles, preferably thermoset particles, ash, Crushed fine-grained slag, corundum, quartz, metallic particles with a round or angular habit, glass beads, organic granules, carbides, alumina, silicates or mixtures thereof in particle sizes of a few microns up to 2000 microns depending on the application used.
  • These blasting materials belong to the category of bulk solids, which are known to have an electrostatic charge and whose ignitability increases with decreasing grain size (TRBS 2153 "Prevention of Ignition Hazards due to Electrostatic Charges, 6.
  • Electrostatic Charges when Handling Bulk Materials http: www.bgbau-medien .com / tr / trbs2153 / 6.htm). Such charges can reach potentials of a few kilovolts to megavolts, which easily exceed the minimum ignition energy and, when discharged, also endanger the operating personnel. Thereafter, the electrostatic charging by increasing the conductivity of the bulk material or the plant parts, for example by coating, increasing the humidity or ionization, reducing fine particles, eg abrasion in bulk, restriction on the plug conveying, reducing the conveying speed, the mass flow or the air velocity Avoiding large bulk heaps, Preventing the Schwellasttransportes and the use of conductive hoses counteracted.
  • the present invention seeks to improve a method and an apparatus of the type mentioned so that the risk of static discharge in the vacuum suction while maintaining the procedural and economic advantages of the vacuum suction while simplifying the plant technical effort significantly reduced becomes.
  • the solution according to the invention is based on the surprising finding that a potential difference existing between the jet pipe and the workpiece holder or workpiece leads to a significant reduction in the risk of static discharge. This is achieved in that the jet pipe and the workpiece or the workpiece holder separated from each other and electrostatically maintained during the application of the workpiece with the blasting agent permanently under a potential difference of 1.5 to 4 V of a DC voltage source, the negative terminal of the DC voltage source on the jet pipe and the positive pole of the DC voltage source is applied to the workpiece / workpiece holder.
  • a further preferred embodiment of the method according to the invention provides that a battery, an accumulator or power supply or a combination thereof is used as the DC voltage source. This ensures that no major interference with the existing system configuration is required and existing systems can be easily retrofitted.
  • the polarity of the jet pipe and workpiece / workpiece holder is temporarily reversed for cleaning by a pulsed DC voltage source. This allows contamination of the radiant tube to be removed by abrasion and dust after a long jet time.
  • the jet pipe and / or the workpiece holder can be grounded with a static discharge, so that any remaining on the jet pipe and / or the workpiece holder charging potentials are safely derived.
  • the jet pipe and the workpiece holder can be provided with a highly conductive coating, preferably Co-Cr-Ni coating, to dissipate the electrostatic charge.
  • conductive pneumatic hoses are used as Schlauchzu- and -abtechnisch, so that a potential build-up between the abrasive flow and the inner tube wall is effectively counteracted.
  • the object is further achieved by a device in that the jet pipe and the workpiece holder and the workpiece are electrostatically separated from each other and the workpiece holder with the workpiece are electrostatically connected to each other, and that the jet pipe a terminal for a negative pole and the workpiece holder / the workpiece Terminal for a positive pole of a DC voltage source, wherein the potential difference between the negative pole and the positive pole is 1.5 to 4 V.
  • the connection of the jet tube as a negative terminal and the workpiece holder / workpiece as a positive pole ensures a current flow from the jet tube to the workpiece holder / workpiece when applying a DC voltage, so that existing charging potentials on the jet tube and workpiece holder / workpiece compensate each other.
  • the DC voltage source can be a battery or a rechargeable battery or a power supply or a combination thereof so that the device according to the invention can be easily and easily integrated into existing systems.
  • the battery or the accumulator or the power supply is controlled by a controller so that the potential difference is always applied to the jet pipe and the workpiece holder / workpiece when the blasting process begins and is turned off when the blasting process is completed.
  • the jet pipe and the workpiece holder can be provided with a static Erdabtechnisch, so that existing charging potentials safely the soil can be derived.
  • the beam tube and the workpiece holder are provided with a high-performance coating, preferably Cu-Cr-Ni coating, whereby it is possible to dissipate the electrostatic voltage.
  • the hose supply and discharge it has also proved to be advantageous for the hose supply and discharge to be conductive pneumatic hoses, so that charging between the blasting agent and the hose inner wall can be effectively counteracted.
  • the filled in the reservoir 7 blasting agent 8 for example, corundum, glass breakage, zircon sand, slag, cast steel, steel, ceramics, alumina, welding powder, etc., is present in a loose bed 9, from which via a metering 10 Strahlkarteilchen with the carrier air flow TML in a Hose supply line 11 are conveyed to a jet lance 12.
  • the jet lance 12 has a jet pipe 13, which extends over a pressure-tight passage 14 in the set under negative pressure blasting chamber 3.
  • a suction nozzle 15 is connected, which is connected to a recirculating to the reservoir 7 hose outlet 16, wherein the suction nozzle 15 is disposed at a significant distance and below the impingement of the blasting agent on the workpiece 1, so that spent blasting agent drops by gravity and creates a closed circuit for the carrier air flow, which ensures that in the metering tube 10, in the hose inlet 11, in the jet lance 12, in the blasting chamber 3 and the hose outlet 16 equally prevails the pressure prevailing in the reservoir 7 negative pressure.
  • triboelectric charging achieves values of a few kilovolts to megavolt, which endanger the operating personnel when discharged.
  • the height and the polarity of this charge depend on the substance-specific properties of the body involved in the charging process and the external influencing factors.
  • Such parameters include electrical properties such as electrical resistance and dielectric constant of the body, atmospheric conditions such as relative humidity, temperature, pressure and number of ions in the air, contact conditions such as charge type and intensity, contact count and contact duration as well as the surface shape and nature of the contacting bodies. From these influencing factors exemplified it becomes clear that the triboelectric charging not only remains limited to electrically conductive materials, but also covers non-conductive materials such as plastics, welding powder, carbon, soot or other organic particles or agricultural products. Basically, only two different substances have to come into frictional contact with each other.
  • the blasting chamber 3 is fixed in a table top 17 of a support frame 18 in a suspended position. It is designed to be closed and has a cover plate 19 associated with the top wall 19, side walls 20 and a bottom wall 21.
  • the passage 2 In the top wall 19 is the passage 2 for the workpiece 1, so that the workpiece 1 can be inserted into the interior 22 of the blasting chamber 3 ,
  • the passage 2 comprises a hose seal which can be inflated by compressed air and which ensures a vacuum-tight seal and at the same time enables corresponding workpiece operations such as rotation or displacement of the workpiece 1, if required.
  • the workpiece 1 is held by a mounted on one of the side walls 20 workpiece holder 23 within the blasting chamber 3 in a receptacle 24, whereby the outlet end 25 of the jet pipe 13 of the jet lance 12 assumes a defined position to the processing location on the workpiece 1.
  • the workpiece 1 and the workpiece holder 23 are thus connected electrostatically.
  • an angle arm 26 is fixed, which holds the jet lance 12 in a defined position with respect to a arranged in the bottom wall 21 vacuum-tight passage for the jet pipe 13, which extends with its outlet end 25 to the processing on the workpiece 1.
  • a terminal 28 At the freely accessible portion 27 of the jet pipe 13 is located a terminal 28 which is connected via a connecting cable 29 to the negative terminal 30 of a DC voltage source 31.
  • the workpiece holder 23, which is in contact with the workpiece 1, has a terminal 32 fixed to the side wall 20, which is connected via a connecting cable 33 to the positive pole 34 of the DC voltage source 31.
  • the DC voltage source 31 is attached to the support frame 18 and is switched by a controller not shown on the terminal 28 of the negative terminal 30 on the beam tube 13 and the terminal 32 of the positive pole 34 on the workpiece holder 23, so that the negative triboelectric charges the Strahlstoffteilchen can balance over the beam tube 13 and the positive triboelectric charges on the workpiece 1 via the current flow.
  • this may be provided with a conductivity-increasing coating, preferably a Cu-Cr-Ni layer of a few microns.
  • a conductivity-increasing coating preferably a Cu-Cr-Ni layer of a few microns.
  • the process according to the invention proceeds as follows.
  • the jet tube 13 of the jet lance 12 and the workpiece holder 23 holding the workpiece 1 are arranged in the jet chamber 3 separated by a sufficient distance from each other electrostatically:
  • a DC voltage in the amount of 1.5 to 4 V, preferably 2.5 V applied and maintained until the blasting process is completed.
  • batteries accumulators or power supplies can be used.
  • the polarity between the jet tube 13 and the workpiece holder 23 can be reversed, resulting in a repulsion of the particles on the jet tube.
  • pulsed DC voltage sources have proven to be suitable.
  • the triboelectric charging always occurs when surfaces of two bodies come into contact and rub against each other, so that this phenomenon occurs not only with electrically conductive substances but also with non-conductors.
  • the method according to the invention can therefore be based on materials made of metal, non-metal, plastic, ceramic, composite and abrasives susceptible to triboelectric charging, such as sodium bicarbonate, plastic parts, preferably duroplastic particles, ash, comminuted fine-grained slag, corundum quartz, metallic particles with a round or angular habit, glass beads, organic granules, carbides, alumina, silicates or mixtures thereof.

Description

Die Erfindung betrifft ein Verfahren zum Reduzieren einer elektrostatischen Aufladung beim Bearbeiten, Verbinden oder Beschichten von Flächen mittels Vakuumsaugstrahlen, bei dem ein Strahlmittel unter Unterdruck in einem Vorratsbehälter bereitgehalten, von diesem über eine Schlauchzuleitung zu einer Strahllanze mit Strahlrohr befördert, durch diese ein Strahlmittelstrom vorgegebener Beschleunigung erzeugt und dieser auf eine Bearbeitungsfläche eines in einer unter Unterdruck gesetzten Strahlkammer oder Strahlhaube befindlichen, von einem Werkstückhalter gehaltenen Werkstücks gelenkt, danach abgesaugt und über eine Schlauchableitung in den Vorratsbehälter zurückbefördert wird.The invention relates to a method for reducing an electrostatic charge when machining, bonding or coating surfaces by means of vacuum suction, in which a blasting agent held under reduced pressure in a reservoir, transported by this via a hose feed line to a jet lance with jet pipe, through this a stream of blasting agent predetermined acceleration generated and this is directed to a processing surface located in a set under negative pressure blasting chamber or blasting hood, held by a workpiece holder workpiece, then sucked and returned via a hose discharge into the reservoir.

Die Erfindung betrifft weiterhin eine Vorrichtung zum Durchführen des Verfahrens, mit mindestens einem Vorratsbehälter zur Aufnahme von Strahlmittel, einer Abscheideeinheit zum Reinigen des Strahlmittels, einem an die Abscheideeinheit angeschlossenen Saugaggregat zum Erzeugen eines Unterdrucks im Vorratsbehälter, einer mit dem Vorratsbehälter verbundenen Schlauchzuleitung zum Transport des Strahlmittels in eine unter Unterdruck gesetzte Strahlkammer oder Strahlhaube über eine Strahllanze, deren Strahlrohr einen Strahlmittelstrom auf ein auf einem Werkstückhalter fixiertes Werkstück lenkt, und einer an die Strahlkammer/Strahlhaube angeschlossenen Schlauchableitung zum Absaugen des Strahlmittels aus der Strahlkammer/Strahlhaube in die Abscheideeinheit.The invention further relates to a device for carrying out the method, with at least one reservoir for receiving blasting agent, a Separating unit for cleaning the blasting agent, a suction unit connected to the separation unit for generating a negative pressure in the reservoir, a hose connected to the reservoir hose for transporting the blasting agent in a set under negative blast chamber or blasting hood via a jet lance, the jet a stream of abrasive on a workpiece holder directs fixed workpiece, and connected to the blasting chamber / jet hood hose outlet for sucking the blasting agent from the blasting chamber / blasting hood in the separation unit.

Stand der TechnikState of the art

Das Strahlbearbeiten, insbesondere das Abtragen, Verdichten, Beschichten oder Verbinden von festen Flächen eines Werkstücks ist bekannt ( DE 197 47 838 A1 , DE 101 02 924 C1 , DE 102 57 241 A1 , DE 10 2010 020 691 A1 ).
Alle diesen bekannten Lösungen arbeiten im Vakuumsaugstrom, bei dem ein Strahlmittel unter Unterdruck in einem Vorratsbehälter bereitgehalten, von diesem über eine Schlauchzuleitung zu einer Strahllanze befördert, durch diese ein Strahlmittelstrom vorgegebener Beschleunigung erzeugt und dieser auf eine Bearbeitungsfläche eines in einer unter Unterdruck gesetzten Strahlkammer oder Strahlhaube befindliches, von einem Werkstückhalter gehaltenen Werkstücks gelenkt, danach abgesaugt und durch eine Schlauchableitung über einen Abscheider in den Vorratsbehälter zurückbefördert wird.
Als Strahlmittel kommen Natriumhydrogencarbonat, Kunststoffteilchen, vorzugsweise Duroplasteteilchen, Asche, Zerkleinerte feinkörnige Schlacke, Korund, Quarz, Metallische Teilchen mit rundem oder kantigem Habitus, Glasperlen, organische Granulate, Carbide, Aluminiumoxid, Silikate oder Gemische daraus in Korngrößen von einigen µm bis zu 2000 µm je nach Anwendung zum Einsatz.
Diese Strahlmittel gehören in die Kategorie der Schüttgüter, die bekanntlich zu elektrostatischen Aufladungen neigen und deren Zündempfindlichkeit mit abnehmender Korngröße ansteigt (TRBS 2153 "Vermeidung von Zündgefahren infolge elektrostatischer Aufladungen, 6. Elektrostatische Aufladungen beim Umgang mit Schüttgütern", http:www.bgbau-medien.de/tr/trbs2153/6.htm). Derartige Aufladungen können Potenziale von einigen Kilovolt bis Megavolt erreichen, die ohne Weiteres die Mindestzündenergie übersteigen und bei Entladung auch zu einer Gefährdung des Bedienpersonals führen.
Danach wird den elektrostatischen Aufladungen durch ein Erhöhen der Leitfähigkeit des Schüttgutes oder der Anlagenteile, beispielsweise durch Beschichtung, dem Erhöhen der Feuchte oder Ionisierung, Verringern von Feinteilchen, z.B. Abrieb im Schüttgut, Beschränkung auf die Pfropfenförderung, Verringern der Fördergeschwindigkeit, des Massedurchflusses oder der Luftgeschwindigkeit, Vermeiden großer Schüttguthaufen, Bevorzugen des Schwellasttransportes und dem Einsatz leitfähiger Schläuche entgegengewirkt.
Alle diese Maßnahmen lassen sich jedoch beim Vakuumsaugstrahlen nicht realisieren, weil das Verfahren dann nicht mehr anwendbar ist.
Aus der DE :102 57 241 , die ein Verfahren gemäß dem Oberbegriff des Anspruchs 1 und eine Vorrichtung gemäß dem Oberbegriff des Anspruchs 8 offenbart, ist bekannt, die Strahllanze oder Strahlhaube mit einer statischen Ableitung zu versehen, die die durch das Strahlgut hervorgerufene statische Aufladung ableitet und Spannungsüberschläge verhindert.The beam processing, in particular the removal, compression, coating or joining of solid surfaces of a workpiece is known ( DE 197 47 838 A1 . DE 101 02 924 C1 . DE 102 57 241 A1 . DE 10 2010 020 691 A1 ).
All these known solutions work in the vacuum suction, in which a blasting agent held under negative pressure in a reservoir, transported by this via a hose feed line to a jet, generated by this a blasting medium predetermined acceleration and this on a working surface of a set in a negative pressure blasting chamber or blasting hood directed, held by a workpiece holder workpiece, then sucked and returned by a hose discharge via a separator in the reservoir.
The blasting agents used are sodium bicarbonate, plastic particles, preferably thermoset particles, ash, Crushed fine-grained slag, corundum, quartz, metallic particles with a round or angular habit, glass beads, organic granules, carbides, alumina, silicates or mixtures thereof in particle sizes of a few microns up to 2000 microns depending on the application used.
These blasting materials belong to the category of bulk solids, which are known to have an electrostatic charge and whose ignitability increases with decreasing grain size (TRBS 2153 "Prevention of Ignition Hazards due to Electrostatic Charges, 6. Electrostatic Charges when Handling Bulk Materials", http: www.bgbau-medien .com / tr / trbs2153 / 6.htm). Such charges can reach potentials of a few kilovolts to megavolts, which easily exceed the minimum ignition energy and, when discharged, also endanger the operating personnel.
Thereafter, the electrostatic charging by increasing the conductivity of the bulk material or the plant parts, for example by coating, increasing the humidity or ionization, reducing fine particles, eg abrasion in bulk, restriction on the plug conveying, reducing the conveying speed, the mass flow or the air velocity Avoiding large bulk heaps, Preventing the Schwellasttransportes and the use of conductive hoses counteracted.
However, all these measures can not be realized in the vacuum suction blasting, because the process is then no longer applicable.
From the DE: 102 57 241 discloses a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 8, it is known to provide the jet lance or jet hood with a static discharge, which dissipates the charge caused by the blasting static charge and prevents flashovers.

Aufgabenstellungtask

Bei diesem Stand der Technik liegt der Erfindung die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung der eingangs genannten Gattung so zu verbessern, dass die Gefahr einer statischen Entladung beim Vakuumsaugstrahlen unter Beibehaltung der verfahrenstechnischen und wirtschaftlichen Vorteile des Vakuumsaugstrahlens bei gleichzeitiger Vereinfachung des anlagentechnischen Aufwandes deutlich reduziert wird.In this prior art, the present invention seeks to improve a method and an apparatus of the type mentioned so that the risk of static discharge in the vacuum suction while maintaining the procedural and economic advantages of the vacuum suction while simplifying the plant technical effort significantly reduced becomes.

Diese Aufgabe wird durch ein Verfahren und eine Vorrichtung der eingangs genannten Art mit den Merkmalen des Anspruches 1 und durch eine Vorrichtung mit den Merkmalen des Anspruches 8 gelöst.This object is achieved by a method and a device of the type mentioned above with the features of claim 1 and by a device having the features of claim 8.

Vorteilhafte Ausgestaltungen des erfindungsgemäßen Verfahrens und der erfindungsgemäßen Vorrichtung sind den Unteransprüchen entnehmbar.Advantageous embodiments of the method according to the invention and the device according to the invention can be taken from the subclaims.

Die erfindungsgemäße Lösung geht von der überraschenden Erkenntnis aus, dass eine zwischen dem Strahlrohr und dem Werkstückhalter bzw. Werkstück bestehende Potenzialdifferenz zu einer deutlichen Reduzierung der Gefahr einer statischen Entladung führt.
Dies wird dadurch erreicht, dass das Strahlrohr und das Werkstück bzw. der Werkstückhalter voneinander elektrostatisch getrennt und während der Beaufschlagung des Werkstücks mit dem Strahlmittel permanent unter einer Potenzialdifferenz von 1,5 bis 4 V einer Gleichspannungsquelle gehalten werden, wobei der Minuspol der Gleichspannungsquelle am Strahlrohr und der Pluspol der Gleichspannungsquelle am Werkstück/Werkstückhalter angelegt wird.The solution according to the invention is based on the surprising finding that a potential difference existing between the jet pipe and the workpiece holder or workpiece leads to a significant reduction in the risk of static discharge.
This is achieved in that the jet pipe and the workpiece or the workpiece holder separated from each other and electrostatically maintained during the application of the workpiece with the blasting agent permanently under a potential difference of 1.5 to 4 V of a DC voltage source, the negative terminal of the DC voltage source on the jet pipe and the positive pole of the DC voltage source is applied to the workpiece / workpiece holder.

Eine weitere bevorzugte Ausgestaltung des erfindungsgemäßen Verfahrens sieht vor, dass als Gleichspannungsquelle eine Batterie, ein Akkumulator oder Netzteil bzw. eine Kombination daraus verwendet wird.
Dies gewährleistet, dass kein großer Eingriff in die vorhandene Anlagenkonfiguration erforderlich ist und auch bereits vorhandene Anlagen einfach nachgerüstet werden können.A further preferred embodiment of the method according to the invention provides that a battery, an accumulator or power supply or a combination thereof is used as the DC voltage source.
This ensures that no major interference with the existing system configuration is required and existing systems can be easily retrofitted.

In einer weiteren bevorzugten Ausführungsvariante des erfindungsgemäßen Verfahrens wird die Polung von Strahlrohr und Werkstück/Werkstückhalter zum Reinigen durch eine gepulste Gleichspannungsquelle kurzzeitig umgepolt. Dies ermöglicht, dass eine Verschmutzung des Strahlrohrs durch Abrieb und Staub nach einer langen Strahldauer beseitigt werden kann.In a further preferred embodiment variant of the method according to the invention, the polarity of the jet pipe and workpiece / workpiece holder is temporarily reversed for cleaning by a pulsed DC voltage source. This allows contamination of the radiant tube to be removed by abrasion and dust after a long jet time.

In einer weiteren vorteilhaften Ausführungsform des erfindungsgemäßen Verfahrens kann das Strahlrohr und/oder der Werkstückhalter mit einer statischen Ableitung geerdet werden, so dass eventuell auf dem Strahlrohr und/oder dem Werkstückhalter verbleibende Aufladungspotenziale gefahrlos abgeleitet werden.
Zweckmäßigerweise kann das Strahlrohr und der Werkstückhalter mit einer hochleitfähigen Beschichtung, vorzugsweise Co-Cr-Ni-Beschichtung, versehen werden, um die elektrostatische Aufladung abzuleiten.
Weiterhin hat es sich auch als vorteilhaft erwiesen, wenn leitfähige Pneumatikschläuche als Schlauchzu- und -ableitung verwendet werden, so dass einem Potenzialaufbau zwischen Strahlmittelstrom und Schlauchinnenwand wirksam entgegengewirkt wird.In a further advantageous embodiment of the inventive method, the jet pipe and / or the workpiece holder can be grounded with a static discharge, so that any remaining on the jet pipe and / or the workpiece holder charging potentials are safely derived.
Conveniently, the jet pipe and the workpiece holder can be provided with a highly conductive coating, preferably Co-Cr-Ni coating, to dissipate the electrostatic charge.
Furthermore, it has also proved to be advantageous if conductive pneumatic hoses are used as Schlauchzu- and -ableitung, so that a potential build-up between the abrasive flow and the inner tube wall is effectively counteracted.

Die Aufgabe wird weiterhin durch eine Vorrichtung dadurch gelöst, dass das Strahlrohr und der Werkstückhalter bzw. das Werkstück elektrostatisch voneinander getrennt und der Werkstückhalter mit dem Werkstück elektrostatisch miteinander verbunden sind, und dass das Strahlrohr eine Abschlussklemme für einen Minuspol und der Werkstückhalter/ das Werkstück eine Anschlussklemme für einen Pluspol einer Gleichspannungsquelle aufweist, wobei die Potenzialdifferenz zwischen dem Minuspol und dem Pluspol 1,5 bis 4 V beträgt. Die Schaltung des Strahlrohrs als Minuspol und des Werkstückhalters/Werkstücks als Pluspol stellt beim Anlegen einer Gleichspannung einen Stromfluss vom Strahlrohr zum Werkstückhalter/Werkstück sicher, so dass sich vorhandene Aufladungspotenziale am Strahlrohr und Werkstückhalter/ Werkstück ausgleichen.The object is further achieved by a device in that the jet pipe and the workpiece holder and the workpiece are electrostatically separated from each other and the workpiece holder with the workpiece are electrostatically connected to each other, and that the jet pipe a terminal for a negative pole and the workpiece holder / the workpiece Terminal for a positive pole of a DC voltage source, wherein the potential difference between the negative pole and the positive pole is 1.5 to 4 V. The connection of the jet tube as a negative terminal and the workpiece holder / workpiece as a positive pole ensures a current flow from the jet tube to the workpiece holder / workpiece when applying a DC voltage, so that existing charging potentials on the jet tube and workpiece holder / workpiece compensate each other.

Die Gleichspannungsquelle kann nach einer weiteren bevorzugten Ausführungsform der Erfindung eine Batterie oder ein Akkumulator oder ein Netzteil bzw. eine Kombination daraus sein, s o dass die erfindungsgemäße Vorrichtung einfach und problemlos in vorhandene Anlagen integrierbar ist.
Zweckmäßigerweise wird die Batterie oder der Akkumulator oder das Netzteil von einer Steuerung so angesteuert, dass die Potenzialdifferenz immer dann am Strahlrohr und am Werkstückhalter/Werkstück anliegt, wenn der Strahlvorgang beginnt und abgeschaltet wird, sobald der Strahlvorgang beendet ist.According to a further preferred embodiment of the invention, the DC voltage source can be a battery or a rechargeable battery or a power supply or a combination thereof so that the device according to the invention can be easily and easily integrated into existing systems.
Conveniently, the battery or the accumulator or the power supply is controlled by a controller so that the potential difference is always applied to the jet pipe and the workpiece holder / workpiece when the blasting process begins and is turned off when the blasting process is completed.

In einer weiteren vorteilhaften Ausgestaltung der erfindungsgemäßen Vorrichtung können das Strahlrohr und der Werkstückhalter mit einer statischen Erdableitung versehen sein, so dass vorhandene Aufladungspotenziale gefahrlos in das Erdreich abgeleitet werden können.In a further advantageous embodiment of the device according to the invention, the jet pipe and the workpiece holder can be provided with a static Erdableitung, so that existing charging potentials safely the soil can be derived.

Von Vorteil ist des Weiteren, wenn das Strahlrohr und der Werkstückhalter mit einer hochleistungsfähigen Beschichtung, vorzugsweise Cu-Cr-Ni-Beschichtung, versehen ist, wodurch es möglich ist, die elektrostatische Spannung abzuleiten.
Weiterhin hat es sich auch als vorteilhaft erwiesen, dass die Schlauchzu- und -ableitung leitfähige Pneumatikschläuche sind, so dass einer Aufladung zwischen Strahlmittel und Schlauchinnenwand wirksam entgegengewirkt werden kann.Furthermore, it is advantageous if the beam tube and the workpiece holder are provided with a high-performance coating, preferably Cu-Cr-Ni coating, whereby it is possible to dissipate the electrostatic voltage.
Furthermore, it has also proved to be advantageous for the hose supply and discharge to be conductive pneumatic hoses, so that charging between the blasting agent and the hose inner wall can be effectively counteracted.

Weitere Vorteile und Einzelheiten ergeben sich aus der nachfolgenden Beschreibung unter Bezugnahme auf die beigefügten Zeichnungen.Further advantages and details will become apparent from the following description with reference to the accompanying drawings.

Ausführungsbeispielembodiment

Die Erfindung soll nachstehend an einem Ausführungsbeispiel näher erläutert werden.The invention will be explained in more detail below using an exemplary embodiment.

Es zeigen

  • Fig. 1 eine schematische Darstellung des Vakuumsaugstrahlens nach dem Stand der Technik und
  • Fig. 2 eine Seitenansicht in Schnittdarstellung einer Strahlkammer mit Integration der erfindungsgemäßen Vorrichtung.
  • Die Fig. 1 zeigt das Arbeitsprinzip des Vakuumsaugstrahlens nach dem Stand der Technik bei der Bearbeitung eines Werkstücks 1 in Form einer langgestreckten Welle, die durch eine Durchführung 2 in die Strahlkammer 3 geführt ist.
Mit einem Saugaggregat 4 werden ein Trägerluftstrom von etwa 20 m3/h bis 300 m3/h und zugleich ein Unterdruck, beispielsweise von 30 bis 350 mbar, erzeugt. Das Saugaggregat 4 ist über eine Schlauchleitung 5 an eine Abscheideeinheit 6 angeschlossen, die einen Vorratsbehälter 7 für Strahlmittel 8 druckdicht verschließt, so dass der vom Saugaggregat 4 erzeugte Unterdruck von beispielsweise 200 mbar im Vorratsbehälter 7 anliegt.Show it
  • Fig. 1 a schematic representation of the vacuum suction jet according to the prior art and
  • Fig. 2 a side view in a sectional view of a blasting chamber with integration of the device according to the invention.
  • The Fig. 1 shows the working principle of the vacuum suction jet according to the prior art in the Machining a workpiece 1 in the form of an elongated shaft which is guided through a passage 2 in the blasting chamber 3.
With a suction unit 4, a carrier air flow of about 20 m 3 / h to 300 m 3 / h and at the same time a negative pressure, for example from 30 to 350 mbar, generated. The suction unit 4 is connected via a hose 5 to a separation unit 6, which closes a reservoir 7 for blasting agent 8 pressure-tight, so that the vacuum generated by the suction unit 4, for example, 200 mbar in the reservoir 7 is applied.

Das im Vorratsbehälter 7 eingefüllte Strahlmittel 8, beispielsweise Korund, Glasbruch, Zirkonsand, Schlacke, Stahlguss, Stahl, Keramik, Aluminiumoxid, Schweißpulver usw., liegt in einer losen Schüttung 9 vor, aus der über ein Dosierrohr 10 Strahlmittelteilchen mit dem Trägerluftstrom TML in einer Schlauchzuleitung 11 zu einer Strahllanze 12 befördert werden. Die Strahllanze 12 besitzt ein Strahlrohr 13, das über eine druckdichte Durchführung 14 in die unter Unterdruck gesetzte Strahlkammer 3 reicht. An die Strahlkammer 3 ist ein Absaugstutzen 15 angeschlossen, der mit einer zum Vorratsbehälter 7 zurückführenden Schlauchableitung 16 verbunden ist, wobei der Absaugstutzen 15 im deutlichen Abstand und unterhalb der Auftrefffläche des Strahlmittels auf das Werkstück 1 angeordnet ist, so dass verbrauchtes Strahlmittel durch die Schwerkraft absinkt und ein geschlossener Kreislauf für den Trägerluftstrom entsteht, der dafür sorgt, dass im Dosierohr 10, in der Schlauchzuleitung 11, in der Strahllanze 12, in der Strahlkammer 3 und der Schlauchableitung 16 gleichermaßen der im Vorratsbehälter 7 herrschende Unterdruck anliegt.The filled in the reservoir 7 blasting agent 8, for example, corundum, glass breakage, zircon sand, slag, cast steel, steel, ceramics, alumina, welding powder, etc., is present in a loose bed 9, from which via a metering 10 Strahlmittelteilchen with the carrier air flow TML in a Hose supply line 11 are conveyed to a jet lance 12. The jet lance 12 has a jet pipe 13, which extends over a pressure-tight passage 14 in the set under negative pressure blasting chamber 3. To the blasting chamber 3, a suction nozzle 15 is connected, which is connected to a recirculating to the reservoir 7 hose outlet 16, wherein the suction nozzle 15 is disposed at a significant distance and below the impingement of the blasting agent on the workpiece 1, so that spent blasting agent drops by gravity and creates a closed circuit for the carrier air flow, which ensures that in the metering tube 10, in the hose inlet 11, in the jet lance 12, in the blasting chamber 3 and the hose outlet 16 equally prevails the pressure prevailing in the reservoir 7 negative pressure.

Beim Transport des feinkörnigen Strahlmittels durch die Schlauchzuleitung 11 und die turbulente Strömung des hochbeschleunigten Trägerluft-Strahlmittelgemisches entsteht eine triboelektrische Aufladung an den Strahlmittelteilchen und am Werkstück 1 bzw. Werkstückhalter 23, da die Strahlmittelteilchen untereinander und mit den inneren Wandabschnitten des Strahlrohrs 13 Kontakt haben und somit der Reibung unterworfen sind. Die triboelektrische Aufladung erreicht Werte von einigen Kilovolt bis Megavolt, die bei Entladung das Bedienpersonal gefährden.
Bekanntlich hängen die Höhe und die Polarität dieser Aufladung von den stoffspezifischen Eigenschaften der am Ladevorgang beteiligten Körper und den äußeren Einflussfaktoren ab. Solche Parameter sind die elektrischen Eigenschaften wie elektrischer Widerstand und die Dielektrizitätszahl der Körper, die atmosphärischen Bedingungen beispielsweise die relative Luftfeuchtigkeit, die Temperatur, der Druck und die Anzahl der Ionen in der Luft, die Kontaktbedingungen wie die Aufladungsart und -intensität, Kontaktanzahl und die Kontaktdauer sowie die Oberflächenform und -beschaffenheit der kontaktierenden Körper.
Aus diesen beispielhaft aufgeführten Einflussfaktoren wird deutlich, dass die triboelektrische Aufladung nicht nur auf elektrisch leitende Werkstoffe beschränkt bleibt, sondern auch nichtleitenden Werkstoffe wie Kunststoffe, Schweißpulver, Kohlen, Ruß oder sonstige organische Teilchen Oder landwirtschaftliche Produkte erfasst. Grundsätzlich müssen nur zwei unterschiedliche Stoffe miteinander in reibenden Kontakt treten.During transport of the fine-grained blasting agent through the hose feed line 11 and the turbulent flow of the highly accelerated carrier air-blasting agent mixture creates a triboelectric charge to the blasting agent and the workpiece 1 and workpiece holder 23, since the blasting agent particles have contact with each other and with the inner wall portions of the jet pipe 13 and thus subject to friction. The triboelectric charging achieves values of a few kilovolts to megavolt, which endanger the operating personnel when discharged.
As is known, the height and the polarity of this charge depend on the substance-specific properties of the body involved in the charging process and the external influencing factors. Such parameters include electrical properties such as electrical resistance and dielectric constant of the body, atmospheric conditions such as relative humidity, temperature, pressure and number of ions in the air, contact conditions such as charge type and intensity, contact count and contact duration as well as the surface shape and nature of the contacting bodies.
From these influencing factors exemplified it becomes clear that the triboelectric charging not only remains limited to electrically conductive materials, but also covers non-conductive materials such as plastics, welding powder, carbon, soot or other organic particles or agricultural products. Basically, only two different substances have to come into frictional contact with each other.

Überraschenderweise wurde gefunden, dass eine solche Aufladung wesentlich reduziert werden kann, wenn eine Potenzialdifferenz von mindestens 1,5 bis 4 V zwischen dem zu bearbeitenden Werkstück 1 und den aus dem Strahlrohr 13 austretenden triboelektrisch aufgeladenen Strahlmittel 9 besteht.Surprisingly, it has been found that such a charge can be substantially reduced if a Potential difference of at least 1.5 to 4 V between the workpiece 1 to be machined and the exiting from the jet pipe 13 triboelectrically charged blasting agent 9 is.

Es wird jetzt auf die Fig. 2 Bezug genommen, die eine Schnittdarstellung der Strahlkammer 3 zeigt.
Die Strahlkammer 3 ist in eine Tischplatte 17 eines Traggestells 18 in hängender Lage befestigt. Sie ist geschlossen ausgeführt und besitzt eine der Tischplatte 17 zugeordnete Deckwand 19, Seitenwände 20 und eine Bodenwand 21. In der Deckwand 19 befindet sich die Durchführung 2 für das Werkstück 1, so dass das Werkstück 1 in den Innenraum 22 der Strahlkammer 3 eingeschoben werden kann. Zweckmäßigerweise umfasst die Durchführung 2 eine durch Druckluft aufblasbare Schlauchdichtung, die eine vakuumdichte Abdichtung gewährleistet und zugleich, wenn erforderlich, entsprechende Werkstückoperationen wie eine Rotation oder eine Verschiebung des Werkstücks 1 ermöglicht. Das Werkstück 1 ist von einem an einer der Seitenwände 20 befestigten Werkstückhalter 23 innerhalb der Strahlkammer 3 in einer Aufnahme 24 gehalten, wodurch das Austrittsende 25 des Strahlrohrs 13 der Strahllanze 12 eine definierte Lage zum Bearbeitungsort am Werkstück 1 einnimmt.
Das Werkstück 1 und der Werkstückhalter 23 sind somit elektrostatisch verbunden.
An der Bodenwand 21 ist ein Winkelarm 26 befestigt, der die Strahllanze 12 in definierter Position in Bezug auf eine in der Bodenwand 21 angeordnete vakuumdichte Durchführung für das Strahlrohr 13 hält, welches mit seinem Austrittsende 25 bis zum Bearbeitungsart am Werkstück 1 reicht.
Am frei zugänglichen Abschnitt 27 des Strahlrohrs 13 befindet sich eine Anschlussklemme 28, die über ein Verbindungskabel 29 an den Minuspol 30 einer Gleichspannungsquelle 31 angeschlossen ist. Der Werkstückhalter 23, der in Kontakt mit dem Werkstück 1 steht, hat eine an der Seitenwand 20 befestigte Anschlussklemme 32, welche über ein Verbindungskabel 33 mit dem Pluspol 34 der Gleichspannungsquelle 31 verbunden ist. Die Gleichspannungsquelle 31 ist am Traggestell 18 befestigt und wird von einer nicht weiter dargestellten Steuerung mit Beginn des Strahlvorganges auf die Anschlussklemme 28 des Minuspols 30 am Strahlrohr 13 und auf die Abschlussklemme 32 des Pluspols 34 am Werkstückhalter 23 zugeschaltet, so dass sich die negativen triboelektrischen Aufladungen der Strahlmittelteilchen über das Strahlrohr 13 und die positiven tribolelektrischen Aufladungen am Werkstück 1 über den Stromfluss ausgleichen können.It is now on the Fig. 2 Reference is made, which shows a sectional view of the blasting chamber 3.
The blasting chamber 3 is fixed in a table top 17 of a support frame 18 in a suspended position. It is designed to be closed and has a cover plate 19 associated with the top wall 19, side walls 20 and a bottom wall 21. In the top wall 19 is the passage 2 for the workpiece 1, so that the workpiece 1 can be inserted into the interior 22 of the blasting chamber 3 , Expediently, the passage 2 comprises a hose seal which can be inflated by compressed air and which ensures a vacuum-tight seal and at the same time enables corresponding workpiece operations such as rotation or displacement of the workpiece 1, if required. The workpiece 1 is held by a mounted on one of the side walls 20 workpiece holder 23 within the blasting chamber 3 in a receptacle 24, whereby the outlet end 25 of the jet pipe 13 of the jet lance 12 assumes a defined position to the processing location on the workpiece 1.
The workpiece 1 and the workpiece holder 23 are thus connected electrostatically.
On the bottom wall 21, an angle arm 26 is fixed, which holds the jet lance 12 in a defined position with respect to a arranged in the bottom wall 21 vacuum-tight passage for the jet pipe 13, which extends with its outlet end 25 to the processing on the workpiece 1.
At the freely accessible portion 27 of the jet pipe 13 is located a terminal 28 which is connected via a connecting cable 29 to the negative terminal 30 of a DC voltage source 31. The workpiece holder 23, which is in contact with the workpiece 1, has a terminal 32 fixed to the side wall 20, which is connected via a connecting cable 33 to the positive pole 34 of the DC voltage source 31. The DC voltage source 31 is attached to the support frame 18 and is switched by a controller not shown on the terminal 28 of the negative terminal 30 on the beam tube 13 and the terminal 32 of the positive pole 34 on the workpiece holder 23, so that the negative triboelectric charges the Strahlmittelteilchen can balance over the beam tube 13 and the positive triboelectric charges on the workpiece 1 via the current flow.

Zur Verbesserung der Leitfähigkeit des Strahlrohrs 13 kann dieses mit einer leitfähigkeitserhöhenden Beschichtung, vorzugsweise einer Cu-Cr-Ni-Schicht von wenigen µm, versehen sein. Ebenso werden innen leitfähige Schläuche als Schlauchzu- und -ableitung verwendet, um eine verbesserte Ableitung der triboelektrischen Aufladung zwischen Schlauchinnenwand und Strahlmittelteilchen zu erreichen.To improve the conductivity of the jet pipe 13, this may be provided with a conductivity-increasing coating, preferably a Cu-Cr-Ni layer of a few microns. Likewise conductive hoses are used as Schlauchzu- and -ableitung inside to achieve an improved dissipation of the triboelectric charging between the inner tube wall and Strahlmittelteilchen.

Das erfindungsgemäße Verfahren läuft wie folgt ab. Das Strahlrohr 13 der Strahllanze 12 und der das Werkstück 1 haltende Werkstückhalter 23 sind in der Strahlkammer 3 durch einen ausreichenden Abstand voneinander elektrostatisch getrennt angeordnet.: Während der Beaufschlagung des Werkstücks 1 mit dem Strahlmittel 8 wird an das Strahlrohr 13 und den Werkstückhalter 23 eine Gleichspannung in Höhe von 1,5 bis 4 V, vorzugsweise 2,5 V, angelegt und solange aufrechterhalten bis der Strahlvorgang beendet ist.
Als Gleichspannungsquelle 31 können Batterien, Akkumulatoren oder auch Netzteile eingesetzt werden.
Um zu verhindern, dass sich nach einer langen Betriebsdauer am Strahlrohr 13 durch Abrieb oder Staub Beeinträchtigungen in der Leitfähigkeit einstellen, kann die Polung zwischen Strahlrohr 13 und Werkstückhalter 23 umgekehrt werden, so dass sich eine Abstoßung der Teilchen am Strahlrohr ergibt. Für einen derartigen Einsatz haben sich gepulste Gleichspannungsquellen als geeignet erwiesen.The process according to the invention proceeds as follows. The jet tube 13 of the jet lance 12 and the workpiece holder 23 holding the workpiece 1 are arranged in the jet chamber 3 separated by a sufficient distance from each other electrostatically: During the application of the workpiece 1 with the blasting agent 8 to the jet pipe 13 and the workpiece holder 23 is a DC voltage in the amount of 1.5 to 4 V, preferably 2.5 V applied and maintained until the blasting process is completed.
As a DC voltage source 31 batteries, accumulators or power supplies can be used.
In order to prevent deterioration in the conductivity due to attrition or dust after a long period of operation at the jet tube 13, the polarity between the jet tube 13 and the workpiece holder 23 can be reversed, resulting in a repulsion of the particles on the jet tube. For such an application, pulsed DC voltage sources have proven to be suitable.

Die triboelektrische Aufladung tritt immer dann auf, wenn Oberflächen zweier Körper in Kontakt treten und aneinander reiben, so dass dieses Phänomen nicht nur bei elektrisch leitfähigen Stoffen, sondern auch bei Nichtleitern auftritt. Daher kann das erfindungsgemäße Verfahren auf Werkstoffe aus Metall, Nichtmetall, Kunststoff, Keramik, Composite und zu triboelektrische Aufladungen neigende Strahlmittel wie Natriumhydrogencarbonat, Kunststoffteilen, vorzugsweise Duroplasteteilchen, Asche, zerkleinerte feinkörnige Schlacke, Korund Quarz, metallische Teilchen mit rundem oder kantigem Habitus, Glasperlen, organische Granulate, Carbide, Aluminiumoxid, Silikate oder Gemische daraus eingesetzt werden. Bezugszeichenliste Werkstück 1 Durchführung 2 Strahlkammer 3 Saugaggregat 4 Schlauchleitung 5 Abscheideeinheit 6 Vorratsbehälter 7 Strahlmittel 8 Schüttung 9 Dosierrohr 10 Schlauchzuleitung 11 Strahllanze 12 Strahlrohr 13 Durchführung für 12 14 Abzugsstutzen 15 Schlauchableitung 16 Tischplatte 17 Traggestell 18 Deckwand von 3 19 Seitenwände von 3 20 Bodenwand 21 Innenraum von 3 22 Werkstückhalter 23 Aufnahme in 23 24 Austrittsende von 12 25 Winkelarm 26 Abschnitt von 13 27 Anschlussklemme 28 Verbindungskabel 29 Minuspol 30 Gleichspannungsquelle 31 Anschlussklemme für 23 32 Verbindungskabel 33 Pluspol 34 Tragluftstrom TML The triboelectric charging always occurs when surfaces of two bodies come into contact and rub against each other, so that this phenomenon occurs not only with electrically conductive substances but also with non-conductors. The method according to the invention can therefore be based on materials made of metal, non-metal, plastic, ceramic, composite and abrasives susceptible to triboelectric charging, such as sodium bicarbonate, plastic parts, preferably duroplastic particles, ash, comminuted fine-grained slag, corundum quartz, metallic particles with a round or angular habit, glass beads, organic granules, carbides, alumina, silicates or mixtures thereof. LIST OF REFERENCE NUMBERS workpiece 1 execution 2 blasting chamber 3 suction unit 4 hose 5 separation unit 6 reservoir 7 blasting agent 8th fill 9 dosing 10 flexible supply line 11 jet lance 12 lance 13 Execution for 12 14 draw stub 15 tube drainage 16 tabletop 17 supporting frame 18 Top wall of 3 19 Sidewalls of 3 20 bottom wall 21 Interior of 3 22 Workpiece holder 23 Recording in 23 24 Exit end of 12 25 angle arm 26 Section of 13 27 terminal 28 connection cable 29 minuspol 30 DC voltage source 31 Terminal for 23 32 connection cable 33 positive pole 34 Supporting air stream TML

Claims (13)

  1. A method for reducing electrostatic charging during the machining, joining or coating of areas using vacuum suction blasting, in which a blasting medium (8) is held ready under a vacuum in a reservoir (7), is conveyed from the latter via a hose feed line (11) to a blasting lance (12) with a blasting tube (13), a blasting medium stream of a specified acceleration is produced by said lance and said stream is directed onto a machining surface of a workpiece (1), which is located in a blasting chamber (3) or blasting hood placed under a vacuum and is held by a workpiece holder (23), after which it is exhausted and conveyed back into the reservoir (7) via a hose discharge line (16), characterised in that the blasting tube (13) and the workpiece (1) or workpiece holder (23) are electrostatically isolated from one another and, during exposure of the workpiece (1) to the blasting medium (8), permanently kept at a potential difference of 1.5 to 4 V from a DC voltage source (31), wherein the negative terminal (30) of the DC voltage source (31) is applied to the blasting tube (13) and the positive terminal (34) of the DC voltage source (31) is applied to the workpiece/workpiece holder (1, 23).
  2. A method according to claim 1, characterised in that the DC voltage source (31) used is a battery, a storage battery or power supply unit resp. a combination thereof.
  3. A method according to claim 1, characterised in that, for cleaning, the polarity of the blasting tube (13) and workpiece/workpiece holder (1, 23) is briefly reversed by a pulsed DC voltage source.
  4. A method according to claim 1, characterised in that the blasting tube (13) and the workpiece holder (23) are earthed with a static discharge line.
  5. A method according to claim 1, characterised in that the blasting tube (13) and workpiece holder (23) are used with a coating to increase their conductivity.
  6. A method according to claim 1, characterised in that hoses with an internal conductive wall are used as the hose feed line (11) and hose discharge line (16).
  7. A method according to claim 1, characterised in that workpieces made of metal, non-metal, plastics, ceramics or composites are used, as are blasting media susceptible to triboelectric charging such as sodium hydrogencarbonate, plastics particles, preferably thermoset particles, ash, comminuted finely divided slag, corundum, quartz, metallic particles with a round or angular habit, glass beads, organic granules, carbides, aluminium oxide or mixtures thereof.
  8. An apparatus for carrying out the method according to claim 1, with at least one reservoir (7) for accommodating blasting medium (8), a separation unit (6) for cleaning the blasting medium, a suction unit (4) connected to the separation unit (6) for generating a vacuum in the reservoir (7), a hose feed line (11) connected to the reservoir (7) for conveying the blasting medium (8) into a blasting chamber (3) or blasting hood placed under a vacuum via a blasting lance (12), the blasting tube (13) of which directs a blasting medium stream onto a workpiece (1) fixed to a workpiece holder (23), and a hose discharge line (126) connected to the blasting chamber/blasting hood (3) for exhausting the blasting medium from the blasting chamber/blasting hood (3) into the separation unit (6), characterised in that the blasting tube (13) and the workpiece holder (23) or the workpiece (1) are electrostatically isolated from one another, and the workpiece holder (23) and workpiece (1) are electrostatically connected together, and in that the blasting tube (13) comprises a terminal clamp (28) for a negative terminal (30) of a DC voltage source (31) and the workpiece holder/workpiece (23, 1) comprises a terminal clamp (32) for a positive terminal (34) of the DC voltage source (31), wherein the potential difference between the negative terminal (30) and the positive terminal (34) amounts to 1.5 to 4 V.
  9. An apparatus according to claim 8, characterised in that the DC voltage source (31) is a battery or a storage battery or a power supply unit or a combination thereof.
  10. An apparatus according to claim 8, characterised in that the DC voltage source (31) is a pulsed voltage source which, for cleaning, briefly reverses the polarity of the blasting tube (13) and workpiece/workpiece holder (1, 23) after blasting.
  11. An apparatus according to claim 8, characterised in that the blasting tube (13) and the workpiece holder (23) are provided with a static earth discharge line.
  12. An apparatus according to claim 8, characterised in that the blasting tube (13) and the workpiece holder (23) are provided with a coating to increase their conductivity.
  13. An apparatus according to claim 8, characterised in that the hose feed line (11) and the hose discharge line (16) are internally conductive.
EP16001093.0A 2015-05-22 2016-05-13 Method and device for reducing an electrostatic charge during the machining, joining or coating of areas using vacuum suction blasting Not-in-force EP3096591B1 (en)

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DE102015006504.1A DE102015006504B4 (en) 2015-05-22 2015-05-22 Method and apparatus for reducing electrostatic charge when machining, bonding or coating surfaces by vacuum suction blasting

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CN106625287B (en) * 2017-01-03 2018-11-09 无锡天旭机械科技有限公司 A kind of roller movement rotating vane type sand shaker
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DE9317921U1 (en) * 1993-11-23 1994-01-20 Siemens Ag Particle jet nozzle
US5837064A (en) 1996-10-04 1998-11-17 Eco-Snow Systems, Inc. Electrostatic discharge protection of static sensitive devices cleaned with carbon dioxide spray
DE19747838C2 (en) 1997-10-19 2001-07-12 Gp Granulate Pneumatic Geraete Method and device for the dry removal of coatings, graffiti or other surface contaminants
DE10102924C1 (en) 2001-01-23 2002-06-13 Pieper Innovationsgmbh Blasting treatment process for hard surfaces involves applying at least one auxiliary energy pulse to blasting medium
DE10257241B4 (en) 2001-01-23 2006-08-17 Pieper Innovationsgesellschaft Mbh Device, in particular workshop and / or Hobbysystem for processing, in particular vacuum suction of surfaces
WO2005096699A2 (en) * 2004-04-06 2005-10-20 Craig Randall H Control of liquid droplet stream with electro-nebulizer
DE102010020691B4 (en) * 2010-05-17 2014-09-04 Pieper Innovationsgesellschaft Mbh Method and device for conveying and metering bulk material during vacuum suction blasting

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