DE1628208A1 - Multi-stage vacuum pump, especially rotary lobe pump - Google Patents

Description

Rudolf Brand, Gl & finstrumenten- und Thermometerfabrik

Wertheim / Main ^ ÖXashütte-

"Multi-stage vacuum pump, especially rotary lobe pump ¹ *

The invention relates to two-stage or multi-stage vacuum pumps, in particular rotary piston vacuum pumps. These pumps are known to be widely used as two-stage rotary vane or locking vane pumps in the vacuum unit because they are used by all Vaktiuiäpumpön, which on atmospheric spheres #? UG : k compress * | can mize, the greatest IJruQkUjfitersQhied: Overwhelming _r The [ compression ratio is in these fum | i # it ^ o to to . : Significantly high to achieve this Kompressiorisverhälfnisses 1st using Qk, not only for lubricating 4 ^he moving parts, but BeFore age for Ab ^ 0i5alieb ''. \ between the suction and pressure side of the pumping chambers is used »In the pressure-side 3 stage, in which the extracted gases / to atmospheric _; pressure are compressed, the oil also has the important task of filling the harmful tree, which can not be disturbed, and lifting the outlet valve if a high F®Huum is reached on the suction side, so that Άμψ still "extremely ? low sftfmettgen geÄföwt -trerden, which ^ never go out, dss.; discharge valve dureli DruoiibaÄufgchlsgung © iaauheösm *, this can only be achieved by a constantia ÖlHmlsüf in öer 4i? uakseittgtn

■ - ■■ ^-:.: '- ■■ .. - - 2 - ■ ■■ ".

can be achieved. Often the two pump stages are also complete built into an oil bath · to keep them from. outside safe against to seal the atmosphere.

However, the oil in these pumps has »one major disadvantage, While namely the compression ratio in two-stage Pumps for the pumped permanent gases Io to Io is what

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corresponds to a final vacuum of Ιο · to Io Torr, is the

- · / ■ * ■■
Oil vapor pressure of the oil approx. lo ~ Torr. The total or total pressure is thus at least a factor of 100 higher, and the compression ratio based on the total pressure is correspondingly smaller.

The pressure by the oil vapor erheblieh- deteriorated Biidvakuum is not * Much has-the serious fact that, as a result, the high vapor pressure constantly oil vapor against the Pumprlchtunie from the suction port of the Öliu ^ tpumpen to be evacuated Vfikuumapparatui * J flows the only drawback and there may even be condensed, after longer periods of operation there may therefore be considerable amounts of oil-collecting oil * oil vapor [and even more kohdensie ?? " However, in most processes of vacuum technology * especially high vacuum and tlltralkoehyakuumtechnik, oil is an extremely effective contamination that must be pre-reddened. Many of these procedures are carried out in the presence of

Aucii beito is used as backing pumps for high vacuum pumps hohf ^ idarapfdrucsk and the strong & krtiökstr8mun $ d * r Brihkoibenöl air pumps Husserst sewn. Β «. all main vacuum pumps first with eiriem certain pre-vacuum pressure: be set in Bötritb the angular gust vacuum apparatus first

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with the backing pump to the required backing vacuum. During the pre-evacuation, every high vacuum apparatus " Immediately contaminated by oil vapor from the backing pump ^. Äfoer even after commissioning the high vacuum pump, the Oil vapor from the backing pump still noticeable disadvantageously *.

Another harmful effect of the oil vapor coming from rotary piston oil-air pumps is of considerable importance. For almost all vacuum measuring and testing devices, this oil vapor represents an extremely disadvantageous contamination, Di «; In many cases, measured values are thereby significantly falsified. With some measuring and testing methods, the measuring transducer is destroyed or unusable even after a short period of operation. V

A large number of measures have already been proposed to eliminate the negative effect of the operating oil of rotary piston oil air pumps.

In the first group, these measures deal with reducing the oil vapor pressure in the pump itself. For example it was proposed that the operating oil of the vacuum-side stage be completely separated from that of the pressure-side stage

hold and arrange so that during operation of the pump it is under the fore-vacuum generated by the 'pressure-side stage represents. This causes the oil of the vacuum-side stage · _. · constantly degassed and freed from components with high vapor pressure, In the BstriefespauaeiSeiS, this oil is then turned into one against the AbsoooiaXossenen 'atmosphere promoted container where there are hardly any gases or can absorb vapors suxs d-sr atmosphere. In this way

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■ the effective vapor pressure can be reduced by a factor of 3-4 will.

- A decisive reduction in the oil vapor pressure and only These measures do not allow the oil to be recirculated reach. '·

In the second group, known measures deal with the removal of the oil vapor by means of suitable devices, which in the suction line between rotary lobe pumps and downstream equipment. With deep-frozen condensers In the suction line, for example, the oil vapor can be completely frozen out. In adsorption cases, those with activated charcoal or recently loaded with sodium aluminum silicates of high porosity oil vapor is also largely bound.

However, both measures represent an additional effort.

Another known measure for removing oil vapor is the so-called ion baffle. In it, the oil molecules are split by means of an electrical discharge, producing gaseous and solid fission products; the gaseous are pumped out by the pump, the solid ones are deposited on the walls of the ion baffle. This arrangement allows continuous operation over a longer period of time and requires little maintenance. The oil vapor pressure is effectively reduced to approx. 1%. However, this measure also represents an additional effort. The expense for the ion baffle is in the same order of magnitude as for the rotary lobe pump itself.

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The invention "is therefore based on the object of decisively reducing the oil vapor pressure and the oil return flow of multistage rotary lobe vacuum pumps, the various disadvantages ---, -; " _ .. of the previously known measures for the same purpose being reduced.

According to the invention, this is done in that in the vacuum stages in particular a multi-stage rotary lobe vacuum pump, the components that form the pump chamber and the displacement ' cause effect, in case of direct mutual contact 'slide against each other with dry friction without liquid lubrication.

In an advantageous embodiment of the invention, the upstream pump stage on the pressure side, a rotary piston oil air pump, '

To a. To report sticking of the moving parts, according to a further feature of the invention, each metallic sliding surface is paired in a known manner with a counter surface which has dry lubricating properties. . In a multi-stage rotary piston vacuum pump with erfindungsgemässön vacuum stages in '■ rotary vane type, for example, pass the separating slide which |

i Front surfaces of the port and the contact point of the pump cylinder

the other with the rotor circumference made of a material with dry lubrication 1

^ ₃ properties.

ω In a particularly advantageous way, the smooth surfaces with

^ Dry lubrication properties from metal-impregnated charcoal

In Ainet .anösen epfinteigegejBässen;. 'Construction 4ia sliding fötstehen ·

- ,, The erfindurigsgemäß dry running vacuum stages a Multi-stage rotary lobe vacuum pumps have the advantage that their Components' to generate the displacement effect practical can be moved against each other without play. From this it follows a significantly higher compression ratio than, for example, a Roots pump. This has the consequence that at most traces of oil vapor from the upstream oil air ~ ' pump on the suction side of the vacuum stage according to the invention can kick. Even if after a long period of operation due to frictional wear, there is little play between the surfaces sliding on top of each other, hardly any oil vapor can pass through the narrow gaps that form occur, as gaps in size

-2 ^: -2

Order of Iq mm in the pressure range of; e.g. Io Torr in which turn pumps according to the invention used, a very high;

Flow resistance for oil sumps pictures ^ *

Practical investigations on an initial pump arrangement with a rear / stage eiriettfeliclie single-stage oil-sealed rotary shaft pump 4ieH & € u have shown that at pressures below 1 Torr, the increased digestion reaches the value of the vacuum stage is the same throw as the well-known two-stage Drefikoibeii oil air pumps achieve in the oil-lubricated vacuum stage. 3 |) he end partiaXdruok of the inventions ^ rotary valve> Eümpena arrangement in ssvreistitifigsr execution achieved'therefore also the equally good «, Werfe file two-stage oil-air pumps, In comparison; In relation to these, however, the oil inoculation is about a factor of 2q smaller. The Ö is $ Qgar so small that aie with the evil kanji are seldom shown nooh tiaah.

A two-stage pump arrangement according to the invention therefore has the same compression ratio and thus the same performance characteristics as known two-stage oil-air pumps, but can in contrast to these, create a practically steam-free vacuum, which represents a decisive step forward. Multi-stage pump arrangements according to the invention can be known Unreservedly replace multi-stage rotary lobe oil air pumps » They also make the previously known devices and measures to reduce the oil vapor pressure from oil air pumps and the oil return flow superfluous. : '

Multi-stage pump arrangements according to the invention, however, have other advantages. For example, a... Arrangement of lirafig be performed with a single-stage ^{Drehkolben'-:} oil pump as a backing pump and inventiveness two ge§chaitete in row _n. according to vacuum levels. This enables a further improvement in the belt vacuum and a considerable improvement in the delivery rate at low intake values.

In the known "multi-stage rotary piston oil air pumps / .is is * · as is known, a more than two-stage arrangement does not make sense. The oil used in these pumps gives off at low pressures constantly emitting so much gases and vapors * that e.g. a three-stage oil air pump no better ultimate vacuum and no better

• ■ _; ; _ © ine '/ - :. .- ^;:; · ,. ' - - ..: · '■ has characteristic "-.-.- ,.; as / corresponding two | stage pump;'

In addition, the multistage pump arrangement according to the invention can be used the well-known advantage of the boat pump combination-the "

high pumping speed in the pressure range between 1 and Io "^ iorr -. ·

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'Can also be used with small pump outputs below 50 m / h , with the advantage that no protective measures against excessive pirfferenz pressure in the vacuum stages are necessary, as is the case with boat pumps.

Further features and advantages of the invention are based on the The drawing explains in more detail the exemplary embodiments represent. It shows: ■

E ¹ Ig. 1 according to the invention. trained rotary vane pump, _- "" ■ .. .Fig. "2 a slide valve pump designed according to the invention, and
FIG. 3 shows a section along the line AB in FIG. 1.

In the exemplary embodiment according to FIG. 1, pressure stage 1 is

designed as a known rotary vane oil air pump * Here .., 'spring-loaded

A rotor 2 with vanes 3 and 4 is arranged in a pump housing 1. The lower part of the outlet channel 5 with outlet nozzle 6 is filled with oil. In a known manner, an outlet valve 8 is provided Connection line Io with the outlet side 11 of the vacuum stage II in connection. This pump stage is also designed in the form of a "slide valve pump" in which a rotor 1> with spring-loaded 35peiinschiebern 14 and I.5 rotates in a housing 12 Suction nozzle 6 ¹ is the connection to the room to be evacuated.

According to the invention, the slide gate 14 and 15 are for Gätize, .Preferably at the contact edges, at least at the leading ends Edges made of material with dry lubricant properties » For example, from metal-coated synthetic material or from

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.1-62 * 20 «

a plastic molybdenum disulphite mixture »further- is in the housing

12 at the point of separation between suction and pressure side as well a sliding surface 16 with dry lubricating property is provided.

From Figure 3 it can be seen that the end faces of the rotor

13 are designed with self-lubricating sliding surfaces 17 ¹ , 17 "and I8 ^f , 18", preferably in the form of a sliding ring. The rotor itself is mounted in the housing 12 in a manner known per se by means of ball bearings 19 and 20. Furthermore, a bearing seal 21, which is also known, is provided.

In the embodiment according to FIG. 2, gate valve pumps are used. In this embodiment runs in a cylindrical interior 22 of a housing 21 or; 23 in the housing 24 an eccentrically mounted piston 25 or 26 around such that the contact point between the inner wall of the housing 22 and the outer wall of the piston 23 or housing 24 and piston 26 runs in a circle. Two periodically changing parts of the working space are formed by a slide 27 or 28 between inlet channel 29 or 3o and outlet space 31 or 32, respectively. The piston 27 or 26 carries out an oscillating movement between the rotary piston 25 or and the respective housing. The pistons 27 and 28 are guided in pivot bearings 32 and £ 3 so that they can be displaced longitudinally. The pressure stage I ¹ again has an oil fill Jj4 in the discharge chamber 31. An exhaust valve 35 is also provided. The connection between the pressure level I ¹ and the vacuum level II ^! takes place via a

36. »

- Io -

According to the invention, ^{no oil is used in the vacuum stage II 1.} Rather, the rotor 26 and the bearing Z6 are made of material with drying properties. Here, too, two oil guide surfaces work together, one of which is made of material with dry lubrication properties.

e invention is not shown on the schematic Embodiments limited. It also includes all partial and sub-combinations of those described and / or shown Characteristics*

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Stehmann * Dr. Shitzerland «(

Claims (5)

Claims (l) Multi-stage vacuum pump, especially rotary lobe pump, characterized in that the components at the vacuum stages which form the scoop chamber and which cause the displacement effect, with direct mutual contact without liquid absorption slide dry rubbing against each other. 2. Pump according to claim 1, characterized in that a rotary piston oil air pump is used as the upstream pump stage on the pressure side. ^: 3. Pump according to claim 1 or claim 2, characterized in that each metallic sliding surface is paired with an opposing surface * has the anti-friction lubrication properties. . ■ ■ ". ■ ■ '-f Λ ■ -, -?' _ ^',' .-> ϊ ν.. 4. Pump according to claim J, characterized in that, the Sliding surfaces with dry lubrication properties made of metal-impregnated Charcoal are formed. ; '"-, 5. Pump according to claim j, characterized in that the Sliding surfaces made from a mixture of plastic and molybdenum disulphite exist. , 0098 31/0546 BATH Stöhmann - Dr, Schweinzer