DE1490867A1 - Special high voltage cables for electrostatic systems - Google Patents

Description

High-voltage special cable for electrostatic systems t-> The!; Invention, refers to a high-voltage, -GI special cable for electrostatic systems.

Otatic iliac tension, #, swell with relatively low levels of itromic strength Time in an ever-increasing scope are very different recently Two industries are needed. In particular, four are needed to build up electrostatic ones Fields such as those used by Vir electrostatic spraying, flocking, Coating or dusting are required.

Because these systems are often operated with voltages of Mber 100 kV, are special ichutzmaßnahmen not # vendi, - "efährd'en This applies especially to the operator not to g ortsverUnderliche systems to, for example on the electrostatic Ilandspritzpistole where. it is often unavoidable that the contact with non-stressed parts is not possible without further ado.

The known arrangements of an electrostatic manual spray gun 3, as shown schematically together with a low voltage energizer 1 in Pi r 1 , are the charging and atomization of the Parbe on a stationary or rotating edge 3e , for example on the edge of a bell or disc. The high voltage is conducted via a corresponding cable 2 from the generator 1 to 1.) the spray electrode 3b , which, as a result of its free availability, is carried by the operator in the event of careless handling of the land -Lne more can be asked. Together with the spray electrode 3b , which is made of conductive laturial, the air turbine '3e' or an electric motor, or at least certain bearing parts, which are required to drive the bell and are embedded in the gun barrel made of non-conductive material 3f, are also connected to high voltage. In strong Lz #, 3e iiiit ausE # chla, - die Berii * liriitl-L; -, iclic-r- Such a facility is the. t - Icsalilte a U'-. Loaded, .a ur z- Pacityt (Ue, sic "1) rin-iPicll '-, Wil-Z # i 2 in JiL Gerc.ratoi-- the k 0 - have, # lkapazit-t C tn 'in U L'ie elektrodenlic.pp, zi # t "; t CLpr aul, # ipaltet. becomes Fn, -, ecitrebt, the. #, - named quote. «, # ite.ii so kluin" -iie -In -, estalten, -Liiii ein lin-.111 * Z £ 3, # "i-, Large Lner ._, - iespeicl.ierun .- # - in the daVir components to prevent, for their part, viieder bc - ii., i i # rdschluss at the ß'Jprillielr - lctrode a Jwiken- bildun. # The internal resistance of ipannun.,; squellc.-ii becomes den, 're "eri,' ber se'ir -roß; cv.j * :, ilt, uLi ilIrLn au to limit a woolly linen. 2 U Despite Cieser unconcerned # Lin -, t (#urc '-, izuf;, t_Iirenden Laßnahi-Jen iot cinc : 3e, r, ii - .. run over £, 16ktrode in faot allen len -efahrlos kauiii rjiö .-; lic.li, also vienn the K-short circuit current C. er L ner!, - iequellE- under Cen Wvrt of 1 mA be.rL-n - t vierden can. The cause liL -..- t is that the -, enaniitrcn hapazit-Uten not- * it Lo far reduced vierden ..- can to them trot-- 1,1er -9ei-Lr high ipannun #; without '-jle-drive to escape the human body load. : #, it is usually not the case that the generation : -ani a, because dieoe can be small enough ', okapa-it77t C switched but the largest part of the "# xesamtkapazi-LL" at #i almost always has (read the connecting cable 2 between the high- fi annungsgenerato.- 1 and the spray electrode 3. p (J l #> For voltage reasons, the known arrangement Now the connecting line 2 is a coaxial cable Poly.Ut'r, ylen-Dieleliztrilzum and Lrdmantel are used, but that a relatively large capacity, depending on the structure in the order of 10 2 pL "/ i, i lie, -, t. The principal The structure of such an i # abel is shown in 2 - i-ur 3 . Denmach consists of a coaxial cable from a protective .ii; Ilse 2ag the outer conductor 2b, (3em mostly made of polyithylene, low dielectric 2c and (leil inner conductor 2d.

In the case of conventional, portable colored wire systems according to figures 1 and 2, in spite of the use of a coaxial cable just described, contact security is now achieved by preventing the cable and generator output capacitance from being released suddenly when a ground fault is initiated at the spray electrode 3b, but rather For this purpose, as already indicated in Pigur 1 , a concentrated Olunscher resistor R 3d is arranged inside the spray gun, which is connected between the volumetric capacitance C k and the sprinkler electrode capacitance C spr and only a delayed release of energy is permitted. The size of the resistor R depends on the level of the capacitance Ga and C k9 capable of being discharged The spray electrode 1: apazitnt C 01) r wiA, however, sc; lir be small, so here only one very, ee rinl-, e energy can be stored, the yes of which is not influenced by d a resistance R-.

., and the installation of such a limitation The production resistance q in a small space within the gun body, however, causes great difficulties. It must be ensured that the * # Iiderstand R genilgt the specific characteristics of the generator, in particular its maximum possible voltage and Leistun, csabgabe. In particular, such a resistor must be designed to be extremely voltage-resistant, because when a ground fault occurs at the prill electrode 3b , the full working voltage U a is in the order of magnitude of 60 to 100 kV , which then corresponds to the time constant except for a stationary fourth U. The latter is determined by the st "abe the generator when loaded with said Stromabt- Be.rPrenzungswiderstand R. A basic representation of this voltage waveform at the resistor R in AbhUngigkeit of the Zeiti the FTIR also proportional the current load of the resistance is significantly" is used in Figure 5 made, The requirement for a good heat dissipation from this protective resistor, its voltage-proof design and a p., edr ** r47, th a construction can, however, only be realized with great difficulty and certain concessions ) To replace the resistor with a special cable, which, due to its great attenuation capacity, ensures a delayed release of energy when a ground fault is initiated at the Sprttho electrode and thus a limitation of the first current impulse when discharging * The special cable according to the invention is characterized by the well-known Me Features a) that the cable is in the form of a coaxial cable with protective sleeve and b) has a dielectric and an earth sheath as the outer conductor and the new feature e) that a special inner conductor is arranged with a sufficiently high specific resistance homogeneously distributed over the entire length of the cable.

The inner conductor has a differential resistance of 2 to 10 MOhm per meter.

Since such a high line resistance cannot be achieved by means of a conventional metal wire, a strand of plastic or rubber is used as the inner conductor. To reduce resistance and to maintain the required differential resistance of -2 to 10 MOhm, the plastic mixture, consisting of polyethylene or PM, or the rubber mixture, a proportion of conductive substances, * carbon black, graphite or metal powder of 15 to 45 % of the total mixture is added and incorporated into the high polymer organic materials in the usual way. The mode of operation of the cable according to the invention is shown in the diagram shown in FIG. 6. It can be seen from it that the total cable capacitance 0 is divided into theoretically infinitely k many # differentially small partial capacitances Gi, which are separated from one another by corresponding length resistances 11 1.

When using such a cable for electrostatic systems is the guarantee of contact safety with sufficiently high longitudinal resistance given without further ado, since the charged generator output capacitance C a and the theoretically consisting of an infinite number of differentially small parts C not suddenly, but only in a relatively "" -essen time constant can discharge, at the same time the occurring discharge current through the high Ohmic series resistance of the cable is limited in such a way that it does not damage any Effect for the Isienschen # represents.

In order to increase the discharge time constant, the cable can also be designed in such a way that the earthed metal jacket is replaced by a layer that is similar in terms of material and specific resistance to the inner conductor. This outer layer causes an increase in the longitudinal resistance effective for the discharge time.-With the design according to the invention, the difficult problem of heat dissipation from the otherwise required voltage-proof protective resistors is solved at the same time, since the heat radiation that results from the current flow through the longitudinal resistance both during operation and especially in the event of a short circuit, the result is that the entire cable length is distributed from 8 to 15 m and thus a locally concentrated W-Irmestau is not possible at all.

In addition to guaranteeing operation safety with electrostatic paint spraying systems, the inventive .Auef'tIhruhg of the connection cable between generator and spray electrode the risk of laplosion in the presence of solvent-air C2 Mixtures reduced, because with a possible A.inkenbil (lun -; -, #J #i the suddenly freed L-nerjie diminishes vjird "or only can still be delayed, -, given, -, - given. The insert of the in the preceding Auk3ffllirun - # - t, # n invention # -s, -eriißen Vorrichtun, - to the Gevi ": ilirleiEltun ## der Berillirungs- With all such systems, there is therefore no security a transfer of direct voltage is possible for your parts. PatenLq.lIoprftclle: 1, '.L'Iocilspannw1iT0Special cable for electrostatic systems, the .i U between the Günerator generating the high voltage and the U #i Same as annunj, -Lri, - # iirende electrode one vorzu, -ONvei £ 3e from p Hand züi betdti, #, renLIen Vorrichtuni; --ur.1 On dust or On "pri, ion von Llberz" r, en -, eschaltet iut, 13 - denoted by Liie known features, a) (let the cable (2) have the same shape as a coaxial cable iutzlilIlle (2a), b) a 4, rCiaaiitel (IC-b) as an outer conductor and a dielectric ooviie den, nu.ueii Lierkiaal, c) that a special inner conductor (2d) with an Ilber the -esamte lilabc-11 * in # -e homojen distributed -large 2 zil 2 1-> 1 - *> U specific resistance is arranged. 2. 'Ioclispalliiuii # -s'apezialliabel according to claim 1, thereby --ekenn- shows that the inner conductor (2d) is made of a plastic or Giiiiimi "-c-.iaiocii, which has a proportion of 15 to 45 ., Liquor, graphite or lethal powder in the geoamt mixture, to- , is decomposed. 3. Iloch tension special cable according to claim 1 and 2, characterized U , # eI indicates that the inner conductor (2d) has a different Has a target resistance of 2 to 10 L.Ohms per liter. 4. High-voltage special cable according to claim 1 to 3, characterized that the outer conductor (2b) has a similar one has a specific resistance like the inner conductor (2d) . 5. High-voltage special cable according to claim 1 to 4, characterized , - indicates that the outer conductor (2b) with the L'rdpotential of the generator (1) and the handle Oa) of the spray gun stole (3) galvanically connected.