Two-stage pump, in particular a vacuum pump

Aug. 21, 1956 μ. auwArter 2,759,664

TWO-STAGE PUMP, IN PARTICULAR A VACUUM PUMP

Filed May 6, 1950

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United States Patent Office _P , ²’⁷⁵⁹’⁶⁶⁴

Patented Aug. 21, 1956 ranged concentrically of the stator casing 1 and has a diameter selected so that its outside wall contacts the inside wall of the rotor 2 at one point thereof. Thus the cylindrical stator space located between the outer 5 stator casing 1 and the inner stator part or extension chamber 4 is subdivided by the rotor 2 into two interspace chambers or pump spaces which are crescentshaped at A and B as seen in Fig. 2. Supported in the guiding slots of the rotor 2, are two slides 5 and 6 1θ which are disposed radially of the rotor and are arranged for radial displacement. The slides 5 and 6 extend from the inside wall of the stator 1 through the outside wall of the rotor 2 and subdivide each of the two pump spaces into two delivery chambers. The end surfaces ¹⁰ of the slides 5 and 6 which rest against the stator walls are rounded off into circular-cylindrical surfaces. As illustrated in Fig. 2 the two end surfaces of each one slide are defined by one and the same circular cylinder, the radius of which is equal to half the difference of the 20 radii of the inner and the outer wall of the cylindricalannular stator space.

If tl^e rotor is adapted for rotation in the direction of the arrow 7, the outer pump is provided with a suction inlet opening 8 which is connected to a suction 25 pipe by means of a connecting pipe 9, whereas its delivery outlet 10 is in connection with an interspace 11 which is formed above the cover wall 3 by means of an insert 12 forming a transverse wall also connected to stator housing as is transverse cover wall 3. The ³⁸ inner pump has a suction inlet 13 which leads into the afore-mentioned interspace 11, whereas the delivery outlet 14 leads into an ejection space or chamber 15 provided above the insert or transverse wall 12 through a valve 23. The interspace 11 is similarly connected to ³³ this ejection space through a valve 16. A drip pipe 17 passes through transverse wall 12 and the cover wall 3 and further into the interior of the inner stator extension chamber or part 4 in which a flat pan or reservoir 18 is provided. Ducts 25 connect reservoir 18 with the 40 space of the outer pump. An orifice or overflow 19 leads from the interior of the hollow-cylindrical r-.bamber 4 to the suction side of the inner pump.

The ejection space 15 is partly filled with an oil bath 20 serving for sealing and lubricating the pump, said 45 oil bath covering the two ejection valves 16 and 23 held in place by means of screws 16' and 23'. Through conduit means in the form of drip pipe 17 oil drips slowly into the reservoir 18 and from here through ducts 25 into the outer pump space (due to centrifugal 50 force past the fine gap between stator 1 and rotor 2). During operation the outer pump sucks the fluid to be pumped through pipe 9 and the suction inlet 8 and forces the quantity of fluid conveyed through the ejection outlet 10 into the interspace 11 and from there through ₅₅ the valve 16 into the ejection space 15. If the suction pipe 9 is connected to a container to be evacuated the discharge pressure of the aforesaid quantity of gas or fluid progressively decreases with the increase of the vacuum in the container until this vacuum becomes GO insufficient to contribute to a discharge pressure to open the ejection valve 16. Now the inner pump sucks off the gas from the interspace 11 through its suction inlet 13 and forces it through the ejection valve 23 into the ejection space 15. Together with the gas the two pumps θ5 simultaneously convey the oil contained therein, said oil reaching the ejection space 15 by passing from the outer pump through the inner pump and returning from there by way of the pipe 17 and the reservoir 18 back to the outer pump space.

₇₀ The reservoir 18 located in the inner stator extension part 4 serves as a degasifying and regenerating device for the oil which in a thin layer in the tank is subjected

2,759,664

TWO-STAGE PUMP, IN PARTICULAR A VACUUM PUMP

Max Auwarter, Iramalinstrasse, Balzers, Liechtenstein, assignor to Dr. Alois Vogt, Vaduz, Liechtenstein

Application May 6,1950, Serial No. 160,562

Claims priority, application Switzerland May 7,1949

Claims. (CI. 230—152)

This invention relates to pumps, and more particularly to a high speed two-stage pump.

Vacuum pumps heretofore known as circular piston pumps have a cylindrical or slightly elliptical stator part in which an eccentrically mounted rotor operates. Depending on the particular type of circular piston pump, either vane-shaped slides are arranged in the rotor or the stator, or additional roller rings are provided which are rolled past along the wall of the stator and the slide.

In either case, the rotary parts of such pumps are never balanced with respect to the mass of the slides. For this reason the speed of the pumps cannot be increased at will and accordingly there is a practically constant ratio between the output of the pump on the one hand and the volumetric capacity and the speed on the other hand which cannot be improved by an increase of the speed.

It is an object of the present invention to provide means rendering it possible to increase the output of a circular piston pump by increasing the speed at which the pump is driven.

It is another object of the present invention to provide means facilitating the automatic guiding of slides in a pump of the aforesaid type whereby said pump is balanced with respect to the mass of the slides thereof.

It is a further object of the present invention to provide means facilitating the construction of a pump having an exceptionally high output capacity in comparison to its overall dimensions.

According to the present invention there is provided a pump which does not have the disadvantages mentioned and is in particular characterized in that a cylindrical stator space is subdivided in two pump spaces arranged in series by a cylindrically shaped annular rotor arranged eccentrically to said stator space, said rotor contacting simultaneously the inner and the outer wall of said stator space at one point each, said pump spaces in their turn being subdivided into delivery chambers by means of slides arranged in said rotor and bearing against the walls of said stator space.

By way of example an embodiment of the present invention is illustrated in the drawing accompanying and forming part of this specification, in which:

Fig. 1 shows a vertical longitudinal section through a two-stage vacuum pump with vertical rotary shaft according to the present invention, the section being taken along lines I—I of Fig. 2 and

Fig. 2 is a horizontal cross-section taken along lines II—II of Fig. 1.

Disposed within the inner space of a drum-shaped stator casing 1 and supported on a lower bottom or transverse wall thereof is a cup-shaped rotor 2 which is eccentrically mounted so that its outer cylindrical surface contacts the stator casing 1 at one point on its inner cylindrical surface. Traversing the stator 1 is a transverse cover wall 3 which dependingly carries a hollowcylindrical extension chamber or sleeve 4. The sleeve 4 extends into the interior of the rotor 2 and is ar2,759,664 ing communication through said ducts provided in said SecondTransverse wall with said mterspace chambers, arid normally closed valve means on said third transverse wall regulating the passage of a medium from said intake opening through said interspace chambers, said passage means and said ducts to said exhaust opening, said slides defining pressure and suction spaces during rotation of said rotor relative to said stator housing and said extension chamber, whereby the Outer wall surface of said rotor chamber contacts the inner wall surface of said stator housing and said outer wall surface of said extension chamber contacts said inner wall surface of said rotor chamber during said rotation.

2. A multi-stage vacuum pump comprising, in combination, a hollow cylindrical stator housing provided with intake opening for connection with a receptacle and exhaust opening, first, second, and third transverse walls, respectively, extending substantially across the axis of said Stator housirig, a rotor provided with a cylindrical chamber, said rotor being disposed in spaced relation to the inner Wall srirface Of said stator housing therewithin and being eccentrically journalled on said first transverse wall With respect tb the axis of said stator housing, said second transverse wall retaining said rotor within said stator housing and being provided with a cylindrical extension chamber projecting into and spaced from said rotor charilber to thereby provide respective interspace chambers between upright walls defining, respectively, said stator housing, said rotor chamber, and said extension chamber, a plurality bf slide means having cylindrical end faces arid disposed ih slots passing through the upright wall of said rotor charilber and in contact with the inner cylindrical Wall surface of said stator housing arid the outer cylinder surface Of said wall of said extension chamber, to thereby transform said interspace chambers to pressure arid suction spaces, respectively, said second arid said third transverse Walls being provided With respective passageways interconnecting one of said interspace chambers between said stator housing and said rotor bn one side Of the latter and another of said interspace chambers between said extension chamber and said rOtor oil the other side of the latter, and normally closed Valve mearis positioned on said third transverse wall for controlling said passageways during rotation of said rotor thereby establishing direct connection of said one interspace chamber through said exhaust opening with the atmosphere at predetermined pressure in said one interspace chamber.

3. A mtilti-stage vacuum pump comprising, in combination, a hollow cylindrical stator housing provided with inlet means for cohnectiori With a receptacle and exhaust means, first, second, and third transverse walls, respectively, extending substantially across the axis of said stator housing, a rotor provided with a cylindrical chamber, said rotor being disposed in spaced relation to the inner wall surface Of said stator housing therewithin and being eccentrically journalled On said first transverse wall with respect to the axis bf said stator housing, said second transverse wall retaining said rotor in position within said Stator housing and supportirig a cylindrical extension chamber projecting into arid spaced from said rotor chamber tb thereby provide respective interspace chambers betWeeri upright walls defining, respectively, said stator housing, said rotor chamber, arid said extension chamber, a plurality of slide means having cylindrical end faces arid disposed in slots passing through the upright wall of said rotor chamber and in linear contact with the inner cylindrical wall surface Of said stator housing and the outer cylindrical surface of said wall of said extension chamber, to thereby transform said interspace chambers to pressure and suction compartments, respectively, said second and said third transverse walls being provided with respective passageways interconnecting one of said interspace chambers between said stator housing and said rotor on one -side of the latter and another Of said interspace to the vacuum of the inner atmospheric-sided pump as ‘the interior space of the part 4 is in connection with the suction side of this pump by means of the aperture 19. This vacuum is sufficient to evacuate the gas particles from the heated oil, the heating of the oil being 5 achieved automatically by the friction prevailing iii the pump. As this degasifying and regenerating device is located in the center of the pump a higher temperature prevails at this point than in the remaining parts of the pump arid aids in the degasifying and regeneration of 10 the oil and lessens the diffusing effect in the outer pump.

The vacuum pump shown is designed for a vertical rotary shaft, and the rotor 2 can be coupled with the shaft of a motor by means of the shaft 21 or can actually be the motor shaft. In the latter case the shaft 21 is 15 vactium-'tightly mounted in the pump casing by means Of a seal 22. In this vertical position the described vacuum puinp is suitable for being fitted together with a diffusion pump located vertically below it under the boiler. ²θ

With the embodiment of the pump according to the present invention the slides 5 and 6 arranged in the rotor are guided automatically by the constant contact with the inner and the outer wall defining the stator space in such a manner that no centrifugal moments 25 can cause a sudden reversal of movement bf the slides regardless of the speed at which the pump is driven. Thus for the first time it has become possible to increase the output of the pump by increasing the speed thereof and by coupling the rotor of the pump directly to ah 30 electric motor. Furthermore a two-stage pump is obtained by the present invention which is formed by one and the same stator and one and the sariie rotor Which is a decided improvement and simplification as compared to other known devices. In particular this puinp has 35 an exceptionally high output capacity in relation to its Overall dimensions. The sealing-off of the pump spaces towards the atmosphere is exceptionally simple in the pump described for the reason that the cover wall 3 and the insert or transverse wall 12 of the stator casing 40 respectively, are located below the oil bath of the ejection space. On the other hand the overhung construction of the rotor demands only a single shaft seal 22.

Although only one specific embodiment of the invention has been described and shown in the drawing, it 45 should be noted that the invention may be realized in modified form and adaptations of the arrangement herein disclosed may be made as may readily occur to persons skilled in the art without constituting a departure from the spirit and scope of the invention as defined in the 50 objects and in the appended claims.