USRE28394E - Point apparatus for testing electrical contact between metallic objects - Google Patents

Point apparatus for testing electrical contact between metallic objects Download PDF

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Publication number
USRE28394E
USRE28394E US37866973A USRE28394E US RE28394 E USRE28394 E US RE28394E US 37866973 A US37866973 A US 37866973A US RE28394 E USRE28394 E US RE28394E
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United States
Prior art keywords
spark
charge
electrical contact
electrical
metallic objects
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
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English (en)
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Publication of USRE28394E publication Critical patent/USRE28394E/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/10—Arrangements for supplying power, e.g. charging power
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/053—Arrangements for supplying power, e.g. charging power
    • B05B5/0533—Electrodes specially adapted therefor; Arrangements of electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/087—Arrangements of electrodes, e.g. of charging, shielding, collecting electrodes

Definitions

  • a device for preventing risks of fire or explosion due to electric sparks which may be produced at the attachment or suspension contacts of metal objects on which an electrostatic coating is intended to be applied comprising means for inducing an electric charge on said metal object, and also means for [giving an information] detecting a spark when said electric charge reaches a predetermined dangerous value.
  • the chargeinducing means may utilize the existing high-tension source employed for the electrostatic coating, acting from a distance, and [may comprise a variable-threshold charge-detection device adapted to trip a safety, alarm or indicator means.
  • the device] can be used in automatic electrostatic painting and powder-applying installations.
  • the present invention relates to a device for preventing risk of fire or explosion due to electric sparks which may be produced at the attachment contacts of metallic objects intended to be covered with an electrostatic coating.
  • Electrostatic coating installations generally comprise one or more electrodes which are brought up to a high potential, of about a hundred kilovolts for example, and also metallic objects to be coated, fixed on a conveyor by means of hooks, the said conveyor being connected to earth.
  • the coating product divided into fine particles may constitute an inflammable mixture with air, and a spark can effectively set fire to or cause the explosion of this mixture.
  • a resistive protection element is added to these latter, placed in series between the electrode itself and the high-tension supply.
  • the object to be coated at the moment of its passage close to the electrodes brought up to high tension, acquires electric charges which accumulate on the object until the latter has a potential sufficiently high to cause the breakdown of the insulating crust between the object and the hook by which it is attached, the said breakdown being accompanied by a spark capable of developing sufficient energy to ignite the mixture constituted by the air and the finely divided coating product.
  • a first measure consists of utilizing hooks provided with sharp points or edges in contact with the objects which are suspended by these hooks, so that the pressure due to the actual weight of the object has a tendency to pierce the insulating crust.
  • a second measure consists, when this is possible, of ensuring the hooking contact at a masked area of the object, the said area not being intended to be covered.
  • a third solution consists of the application by the user of maintenance rules for the systematic cleaning of the hooks. It will readily be understood that these measures, which are solely preventive, cannot be considered as infallible and do not prevent any accidental risk of fire or explosion.
  • Another solution would consist of ensuring the maintenance of good electrical contact between the object and the conveyor by means of an instrument for measuring the electrical resistance between these latter before the parts pass into the coating cabin.
  • This device necessitates the use of brushes in rubbing contact with the object, which has the drawback that they may scratch the object.
  • measurement of the resistance is not feasible if the part is already covered with a first layer of a coating product, for example a priming coat.
  • the device forming the object of the invention acts without the use of members in mechanical contact with the object to be coated, so as to verify systematically that the contact is sutficiently well made between the object and its suspension hook on the conveyor, in order to avoid any dangerous sparks. It is characterized by the fact that it comprises means for electrically charging the object, located upstream of the electrostatic coating cabin, the said charge being detected when it has reached a dangerous value, for example by a device for detecting any spark produced at the bad hooking contact.
  • the figure shows a transverse section of a metallic object 3 suspended by a metal hook 2 from a conveyor 1 made entirely of metal and connected to earth. As shown, the object is assumed to be placed in a position on the conveyor in front of the entrance to the electrostatic coating cabin.
  • a safety device comprising a hightension generator 5 connected to one or a plurality of ionizers 4, placed at a short distance from the object 3, together with a spark detector constituted by an antenna 6 connected to a detector-amplifier 7.
  • the detectoramplifier 7 is connected to a safety device 8 arranged to trip an alarm device, a stopping device or any other information recorder.
  • the object 3 receives electrical charges conveyed by the ionized air. If the electrical contact between the object 3 and the hook 2 is satisfactory, these charges are naturally evacuated to earth without causing sparks. If the electric contact between the object 3 and the hook 2 is poor, these charges accumulate on the part until this latter is brought up to a potential capable of creating a breakdown spark capable of piercing the insulating layer which creates the bad contact between the object 3 and the hook 2.
  • the signal emitted by the breakdown spark is received by the antenna 6, and transmitted to the detectoramplifier 7 which itself transmits the information to a safety device 8 permitting either a warning to be given to the staff by a light or audible signal, or the chain to be stopped or the projection to be stopped inside the cabin when the part having the defective electrical hooking contact passes into the cabin.
  • the detector-amplifier may advantageously be provided with a means for adjusting the sensitivity of detection so as to react only to sparks which exceed a level of energy previously defined as dangerous.
  • the value chosen for the voltage of the generator is a function of the characteristics of the installation, and in particular of the capacity of the object 3. In certain cases, it is advantageously possible to utilize the hightension source supplying the electrostatic coating cabin itself for also supplying the ionizers 4 of the safety device.
  • the safety device is mounted upstream of the coating cabin. It is preferably enclosed in a small chamber, the interior of which does not offer any danger of fire or explosion.
  • the invention is not limited to the use of a spark detector, and any other device for detecting a high voltage charge accumulated on the part which passes in front of the ionizers 4 may also be utilized without departing from the scope of the invention]
  • the device forming the object of the invention may be employed in all cases where, in an installation for coating objects by electrostatic painting or powdering, there exists a risk of fire or explosion in the vicinity of the objects to be painted, this fire or this explosion being [possibly] caused by a spark produced at a point of bad electrical contact.
  • a device for testing the electrical contact between a metallic object and a grounded support on which said object is to be subjected to an electrostatic coating process comprising means for imparting an electrical charge to said object [and means for indicating whether said charge is conducted away from said object through said grounded support or a suflicient charge accurriulates on said object to generate a spark between said object and support] just before it is to be subjected to said coating process, and a spark detector positioned to detect any spark resulting from the imparting of said electrical charge.
  • a device as claimed in claim 1 in which said indicating means comprises a spark detector] 5.
  • a device as claimed in claim 1 in which said [indicating means] spark detector produces a signal when a charge sufiicient to generate a spark accumulates on said object, and comprising a safety device connected to be actuated by said signal.
  • a testing device as claimed in claim 3 and an electrostatic coating installation comprising a high voltage generator, said generator being connected to supply said ionizing means as well as said coating installation] [9.

Landscapes

  • Electrostatic Spraying Apparatus (AREA)
  • Coating Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
US37866973 1971-05-21 1973-07-12 Point apparatus for testing electrical contact between metallic objects Expired USRE28394E (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7118740A FR2138368B1 (forum.php) 1971-05-21 1971-05-21

Publications (1)

Publication Number Publication Date
USRE28394E true USRE28394E (en) 1975-04-15

Family

ID=9077545

Family Applications (1)

Application Number Title Priority Date Filing Date
US37866973 Expired USRE28394E (en) 1971-05-21 1973-07-12 Point apparatus for testing electrical contact between metallic objects

Country Status (5)

Country Link
US (1) USRE28394E (forum.php)
DE (1) DE2224660C3 (forum.php)
FR (1) FR2138368B1 (forum.php)
GB (1) GB1383104A (forum.php)
NL (1) NL147957B (forum.php)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4042971A (en) 1974-09-30 1977-08-16 Hermann Brennecke Electrostatic charge neutralization
US4546400A (en) 1983-06-03 1985-10-08 Robert Bosch Gmbh Method and apparatus of protecting a coating plant against explosion
USH330H (en) 1984-07-02 1987-09-01 The United States Of America As Represented By The Secretary Of The Navy Personnel grounding system tester
WO1997000730A1 (en) * 1995-06-22 1997-01-09 Fire Sentry Systems Inc. System and process for coincidence detection of ungrounded parts with detectors located within and outside a production coating area
US5949235A (en) 1995-06-22 1999-09-07 Fire Sentry Corporation System and method for detection and control of ungrounded parts in a production coating line

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH542663A (de) * 1972-03-22 1973-10-15 Gema Ag App Bau Anordnung an einer Einrichtung zum elektrostatischen Beschichten von geerdeten Gegenständen, zum Messen des Erdungswiderstandes derselben
DE3207402C2 (de) * 1982-03-02 1985-04-25 Robert Bosch Gmbh, 7000 Stuttgart Verfahren zur Überwachung einer Pulverbeschichtungsanlage gegen Explosionsgefahr
NO317999B3 (no) * 2002-06-28 2010-07-05 Sts Gruppen As Anordning for sikring av driften av et habitat

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2045678A1 (de) * 1969-09-17 1971-04-22 Ransburg Electro Coating Corp Verfahren und Vorrichtung zum Anzei gen der Fähigkeit eines Gegenstandes, Ener gie zu speichern
US3601694A (en) * 1968-12-09 1971-08-24 Eastman Kodak Co Apparatus for electrically checking the continuity of a coating
US3611122A (en) * 1969-09-17 1971-10-05 Henry D Pahl Jr Testing of wire insulation by corona discharge

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3601694A (en) * 1968-12-09 1971-08-24 Eastman Kodak Co Apparatus for electrically checking the continuity of a coating
DE2045678A1 (de) * 1969-09-17 1971-04-22 Ransburg Electro Coating Corp Verfahren und Vorrichtung zum Anzei gen der Fähigkeit eines Gegenstandes, Ener gie zu speichern
US3611122A (en) * 1969-09-17 1971-10-05 Henry D Pahl Jr Testing of wire insulation by corona discharge

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4042971A (en) 1974-09-30 1977-08-16 Hermann Brennecke Electrostatic charge neutralization
US4546400A (en) 1983-06-03 1985-10-08 Robert Bosch Gmbh Method and apparatus of protecting a coating plant against explosion
USH330H (en) 1984-07-02 1987-09-01 The United States Of America As Represented By The Secretary Of The Navy Personnel grounding system tester
WO1997000730A1 (en) * 1995-06-22 1997-01-09 Fire Sentry Systems Inc. System and process for coincidence detection of ungrounded parts with detectors located within and outside a production coating area
US5598099A (en) * 1995-06-22 1997-01-28 Fire Sentry Systems, Inc. System and method for coincidence detection of ungrounded parts with detectors located within and outside a production coating area
US5949235A (en) 1995-06-22 1999-09-07 Fire Sentry Corporation System and method for detection and control of ungrounded parts in a production coating line

Also Published As

Publication number Publication date
FR2138368B1 (forum.php) 1975-01-17
DE2224660A1 (de) 1972-12-07
DE2224660C3 (de) 1976-08-26
NL7203696A (forum.php) 1972-11-23
FR2138368A1 (forum.php) 1973-01-05
GB1383104A (en) 1975-02-05
NL147957B (nl) 1975-12-15
DE2224660B2 (de) 1976-01-15

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